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BACKGROUND: Immunotherapy-based combinations have emerged as standard therapies for patients with metastatic renal cell carcinoma (mRCC). Pembrolizumab, a PD-1 inhibitor, combined with epacadostat, an indoleamine 2,3-deoxygenase 1 selective inhibitor, demonstrated promising antitumor activity in a phase 1 study in advanced solid tumors, including mRCC. METHODS: KEYNOTE-679/ECHO-302 was a randomized, open-label, parallel-group, multicenter, phase 3 study (NCT03260894) that compared pembrolizumab plus epacadostat with sunitinib or pazopanib as first-line treatment for mRCC. Eligible patients had histologically confirmed locally advanced or metastatic clear cell RCC and had not received systemic therapy. Patients were randomly assigned 1:1 to pembrolizumab 200 mg IV every 3 weeks plus epacadostat 100 mg orally twice daily versus sunitinib 50 mg orally once daily (4 weeks on treatment followed by 2 weeks off treatment) or pazopanib 800 mg orally once daily. Original dual primary end points were progression-free survival and overall survival. Enrollment was stopped when a phase 3 study in melanoma of pembrolizumab plus epacadostat compared with pembrolizumab monotherapy did not meet its primary end point. This protocol was amended, and primary end point was changed to investigator-assessed objective response rate (ORR) per RECIST 1.1. RESULTS: One-hundred-twenty-nine patients were randomly assigned to receive pembrolizumab plus epacadostat (n = 64) or sunitinib/pazopanib (n = 65). Median (range) follow-up, defined as time from randomization to data cutoff, was 10.3 months (2.2-14.3) and 10.3 months (2.7-13.8) in the pembrolizumab plus epacadostat and sunitinib/pazopanib arms, respectively. ORRs were similar between pembrolizumab plus epacadostat (31.3% [95% CI 20.2-44.1] and sunitinib/pazopanib (29.2% [18.6-41.8]). Grade 3-5 treatment-related adverse events occurred in 34.4% and 42.9% of patients in the pembrolizumab plus epacadostat and sunitinib/pazopanib arms, respectively. One patient in the sunitinib/pazopanib arm died of septic shock (not treatment-related). Circulating kynurenine levels decreased in the pembrolizumab plus epacadostat arm, but not to levels observed in healthy subjects. CONCLUSIONS: ORRs were similar between pembrolizumab plus epacadostat and sunitinib/pazopanib as first-line treatment in patients with mRCC. Safety and tolerability appeared similar between treatment arms; no new safety concerns were identified. Antitumor responses observed in patients with RCC receiving pembrolizumab plus epacadostat may be driven primarily by pembrolizumab. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov; NCT03260894 .

Kehua Jiang,1 Qing Wang,1 Xiao-Long Chen,1 Xiaodong Wang,1 Xiaoya Gu,1 Shuangshuang Feng,1 Jian Wu,2 Haojie Shang,2 Xiaozhuo Ba,2 Yanlong Zhang,1 Kun Tang2 1Department of Urology, Guizhou Provincial People’s Hospital, Guiyang, Guizhou, People’s Republic of China; 2Department of Urology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, People’s Republic of ChinaCorrespondence: Yanlong Zhang, Department of Urology, Guizhou Provincial People’s Hospital, Guiyang, Guizhou, People’s Republic of China, Email ylzhang3030@163.com Kun Tang, Department of Urology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, No. 1095, Jiefang Avenue, Qiaokou District, Wuhan, 430030, People’s Republic of China, Email tangsk1990@163.comAbstract: Tryptophan (Trp) metabolism plays a vital role in cancer immunity. Indoleamine 2.3-dioxygenase 1 (IDO1), is a crucial enzyme in the metabolic pathway by which Trp is degraded to kynurenine (Kyn). IDO1-mediated Trp metabolites can inhibit tumor immunity and facilitate immune evasion by cancer cells; thus, targeting IDO1 is a potential tumor immunotherapy strategy. Recently, numerous IDO1 inhibitors have been introduced into clinical trials as immunotherapeutic agents for cancer treatment. However, drawbacks such as low oral bioavailability, slow onset of action, and high toxicity are associated with these drugs. With the continuous development of nanotechnology, medicine is gradually entering an era of precision healthcare. Nanodrugs carried by inorganic, lipid, and polymer nanoparticles (NPs) have shown great potential for tumor therapy, providing new ways to overcome tumor diversity and improve therapeutic efficacy. Compared to traditional drugs, nanomedicines offer numerous significant advantages, including a prolonged half-life, low toxicity, targeted delivery, and responsive release. Moreover, based on the physicochemical properties of these nanomaterials (eg, photothermal, ultrasonic response, and chemocatalytic properties), various combination therapeutic strategies have been developed to synergize the effects of IDO1 inhibitors and enhance their anticancer efficacy. This review is an overview of the mechanism by which the Trp-IDO1-Kyn pathway acts in tumor immune escape. The classification of IDO1 inhibitors, their clinical applications, and barriers for translational development are discussed, the use of IDO1 inhibitor-based nanodrug delivery systems as combination therapy strategies is summarized, and the issues faced in their clinical application are elucidated. We expect that this review will provide guidance for the development of IDO1 inhibitor-based nanoparticle nanomedicines that can overcome the limitations of current treatments, improve the efficacy of cancer immunotherapy, and lead to new breakthroughs in the field of cancer immunotherapy.Keywords: indoleamine 2, 3-dioxygenase 1, IDO1, IDO1 inhibitors, nanodrugs, nanodelivery, cancer immunotherapy, combination therapy

Objective To observe the effect of Lactobacillus casei(L.casei) on the depression-like behaviors of offspring rats induced by maternal separation (MS), and explore the potential action mechanism of probiotics to improve central nervous inflammation in depression-like behaviors. Methods MS stress was used to establish a depressed animal model in offspring.Female SD rats were randomly divided into control group (CON), MS group, and MS+L.casei group, with 8 animals in each group.The female rats and their offspring in the control group did not undergo MS intervention after delivery, while those in the MS group were separated 3 h each day, for 14 consecutive days after normal delivery.The offspring of the MS+L.casei group was given intervention of 8×108 CFU/(kg·d)L.casei gavage for 4 weeks.Source preference test (SPT) and forced swimming test (FST) were used to evaluate the changes in depressive behaviors of the offspring rats.ELISA was employed to determine the levels of TNF-α, IL-6, IL-1 β and IL-10 in serum and hippocampus tissue.Real-time fluorescence quantitative PCR was applied to detect the mRNA expression levels of indoleamine 2, 3-dioxygenase-1(IDO1) and 5-HT mRNA in hippocampus. Results Compared with the CON group, the offspring in the MS group had significantly reduced percentage of source preference (P < 0.05), prolonged immobility time during forced swimming (P < 0.05), and decreased number of grid crossings in spontaneous activity test (though no statistical difference), indicating that the offspring rats had obvious depression-like behaviors after MS.L.casei treatment improved the behavioral changes of offspring rats caused by MS stress, with significantly increased percentage of source preference (P < 0.05) and shortened immobility time of forced swimming (P < 0.05).Compared with the conditions in the MS group, L.casei reduced the levels of IL-6, IL-1 β and TNF-α(P < 0.01) and increased that of IL-10(P < 0.05) in the hippocampus and peripheral blood, and decreased mRNA level of IDO1 and enhanced 5-HT mRNA level in hippocampus (P < 0.01) in the offspring rats of the MS+L.casei group. Conclusion MS stress induces depression-like behavior in offspring rats.L.casei inhibits the hippocampal expression of IDO1 and enhances that of 5-HT by regulating inflammatory factors in hippocampus and peripheral blood, and thus, improves depression-like behavior.

Celiac Disease (CeD) is an autoimmune disorder with various symptoms upon gluten exposure. Dendritic cells (DCs) play a crucial role in gliadin-induced inflammation. Vitamin A (retinol; Ret) and its metabolite, retinoic acid (RA), along with tryptophan (Trp) and its metabolite, kynurenic acid (KYNA), are known to influence the immune function of DCs and enhance their tolerogenicity. This research aims to assess the impact of gliadin on DC maturation and the potential of vitamin A and tryptophan to induce immune tolerance in DCs. The monocyte cells obtained from peripheral blood mononuclear cells (PBMCs) of celiac disease patients were differentiated into DCs in the absence or presence of Ret, RA, Trp, KYNA, and then stimulated with peptic and tryptic (PT) digested of gliadin. We used flow cytometry to analyze CD11c, CD14, HLA-DR, CD83, CD86, and CD103 expression. ELISA was carried out to measure TGF-β, IL-10, IL-12, and TNF-α levels. qRT-PCR was used to assess the mRNA expression of retinaldehyde dehydrogenase 2 (RALDH2) and integrin αE (CD103). The mRNA and protein levels of Indoleamine 2, 3-dioxygenase (IDO) was analyzed by qRT-PCR and Western blot assays, respectively. Our findings demonstrate that PT-gliadin enhances the expression of maturation markers, i.e. CD83, CD86 and HLA-DR and promote the secretion of TNF-α and IL-12 in DCs. Interestingly, vitamin A, tryptophan, and their metabolites increase the expression of CD103, while limiting the expression of HLA-DR, CD83, and CD86. They also enhance RALDH2 and IDO expression and promote the secretion of TGF-β and IL-10, while limiting IL-12 and TNF-α secretion. These findings suggest that vitamin A and tryptophan have beneficial effects on PT-gliadin-stimulated DCs, highlighting their potential as therapeutic agents for celiac disease. However, further research is needed to fully understand their underlying mechanisms of action in these cells. [ABSTRACT FROM AUTHOR]

Objectives: Kynurenine is the breakdown product of tryptophan. The tryptophan metabolic pathway increases in COVID-19 infection. This study was designed to reveal the relationship between tryptophan and kynurenine levels and disease severity. Our study also aimed to explore the relationship between tryptophan-kynurenine levels and patient survival, need for mechanical ventilation, and length of hospital stay. Methods: All 82 COVID-19 patients were grouped as severe and mild cases. Serum tryptophan and kynurenine levels were measured by the ELISA method. Receiver operating characteristic curves were generated to plot the KYN/TRP ratio and other variables. Multivariate logistic regression analyses were used to assess the strength of associations between risk factors and patient status. Categorical variables were compared. Results: The kynurenine/tryptophan level was significantly higher (p<0.001), and the tryptophan level was signifi- cantly lower (p=0.008) in the severe group. With a cutoff point of 14.2, the kynurenine/tryptophan ratio had 56.1% sensitivity and 80.49% specificity in predicting COVID-19 severity. In the multivariate logistic regression analysis using age, troponin, platelet count, ferritin, and kynurenine/tryptophan levels, with a cut-off value of 0.34, the sensitivity and specificity were 92.6% and 87.8%, respectively. There was no significant difference in tryptophan and kynurenine levels in terms of patient survival, need for mechanical ventilation, and length of hospital stay. Conclusion: The kynurenine/tryptophan ratio is valuable in evaluating clinical outcomes of COVID-19 patients, especially when used in conjunction with age, troponin, platelet count, and ferritin. It is useful in predicting the clinical course at the time of admission to the emergency department. To our knowledge, the kynurenine/tryptophan ratio, together with age, troponin, platelet count, and ferritin parameters, is the best model with the highest AUC that can be used to show early prediction of clinical outcomes in COVID-19. [ABSTRACT FROM AUTHOR]

Objective: To investigate whether IL-6 using in early pregnancy can improve the pregnancy outcome of recurrent spontaneous abortion （RSA） mice and its relevant mechanism, providing new ideas for RSA clinical treatment. Methods: CBA/J×DBA/2 RSA model mice were constructed, and randomly divided the pregnant mice into five groups: control group, 0.1 ng/ml IL-6 group, 1 ng/ml IL-6 group, 10 ng/ml IL-6 group and 100 ng/ml IL-6 group. IL-6 was not injected in control group, while different concentrations of IL-6 were respectively injected into other groups on the 0.5 day of pregnancy. Pregnant rats were killed at 13.5 d and the embryo loss rate was calculated, the placental tissue was taked out, and expressions of IL-6 and indoleamine 2, 3-dioxygenase （IDO） in tissues were detected by Western blot. Results: Embryo absorption rates of 0.1 ng/ml IL-6 group, 1 ng/ml IL-6 group, 10 ng/ml IL-6 group and 100 ng/ml IL-6 group were obviously lower than that in control group （P=0.002 4, P=0.007 0, P=0.027 0, P=0.031 0）. IL-6 of exogenous injection was positive correlated with that expressed in mice placental tissue（r=0.791, P=0.000 052）. IL-6 concentration of exogenous injection was between 0~1 ng/ml, which was positively correlated with IDO expression in placental tissue（r=0.868, P<0.000 1）, IL-6 was positively correlated with IDO expressed in placental tissue （r=0.982, P<0.000 1）. IL-6 concentration of exogenous injection was between 1~100 ng/ml, which was inversely correlated with IDO expression（r=-0.725, P=0.002）, and IL-6 was inversely correlated with IDO expressed in placental tissue（r=-0.972, P<0.000 1）. Conclusion: A single intraperitoneal injection of specific concentration of exogenous IL-6 to RSA mice can reduce embryo absorption rate of mice and modify their pregnancy outcome, which possible mechanism is the exogenous IL-6 induces expressions of IL-6 and IDO for a long term. Whether the IDO expression in placental tissue increase or not can be regarded as a mark for whether the specific concentration IL-6 can protect the pregnancy or not. [ABSTRACT FROM AUTHOR]

Background and Aim: Induction of experimental autoimmune encephalomyelitis (EAE) is associated with an overexpression of indoleamine 2,3-dioxygenase 1 (IDO1) and exacerbation of clinical symptoms. This study aimed to investigate the effect of physical activity on the gene expression of IDO1 and arylalkylamine N-acetyltransferase (AANAT) in the cerebellum of the mice with EAE. Materials and Methods: 30 C57BL/6 mice were randomly divided into three groups of 10: healthy control, EAE control, and physical activity in the enriched environment. Mice were placed in an enriched environment after induction of EAE with MOG35-55 for 4 weeks and then the cerebellum tissue was dissected and the expression of IDO1 and AANAT genes were measured by real time-PCR method in all three groups. Analysis of variance test was used for data analysis at a significance level of less than 0.05. Results: The group with physical activity in an enriched environment showed significant reduction in the gene expression of IDO1 (P = 0.02) and AANAT (P = 0.04) genes, and also significantly reduced the clinical score (P = 0.001) compared to the EAE group. Conclusion: Changing the environment and lifestyle in the enriched environment can prevent the progression of the autoimmune diseases such as MS, through downregulation of the expression of the IDO1 and AANAT genes.

Abnormal tryptophan (Trp) metabolism disrupts the 5-hydroxytryptamine (5-HT) system, contributing to clinical depression. However, the link between altered Trp metabolism and post-stroke depression remains unclear. This study investigates Trp metabolism in rats exhibiting depression-like behavior after middle cerebral artery occlusion (MCAO). Male Sprague-Dawley rats were divided into three groups: sham operation (sham), MCAO, and MCAO + 1-methyltryptophan (1-MT) treatment groups. The MCAO + 1-MT group received daily subcutaneous injections of 1-MT (60 mg/Kg/day), an indoleamine 2,3-dioxygenase (IDO) inhibitor. Sucrose preference and marble burying tests assessed depressionlike behavior. Brain tissue was analyzed for Trp, 5-HT, kynurenine (KYN), and other metabolites. Immunohistochemistry was used to detect 5-HT, IDO, and tryptophan hydroxylase (TPH) expression in the hippocampus and frontal cortex. MCAO reduced sucrose preference and increased marble burying, indicating depression-like behavior. Treatment with 1-MT improved neurological scores and reversed these behavioral changes. The MCAO group showed elevated KYN levels and KYN/Trp ratios, which decreased with 1-MT treatment. No significant differences were observed in 5-HT levels or 5-HT/Trp ratios across the groups. The sham group exhibited more 5-HT-positive cells in the hippocampus than the MCAO group, while IDO-positive cells were higher in the frontal cortex of the MCAO group compared to the MCAO + 1-MT group. These results concluded that subcutaneous 1-MT, an IDO inhibitor, enhances neurological function and reduces depression-like behavior in rats after ischemic stroke. Clinical trials with bigger samples are required to further validate these findings. [ABSTRACT FROM AUTHOR]

The indoleamine-2,3-dioxygenase (IDO) enzyme causes immunosuppressive consequences in the tumor microenvironment (TME). In addition, the role of aryl hydrocarbon receptor (AHR) in the TME is under discussion. The current study evaluated the role of the IDO and AHR blockers on cell migration, clonogenic, and IDO expression of murine breast cancer cells. The cell migration and clonogenic abilities of breast cancer cells are evaluated by wound‑healing assay (cell migration assay) and Colony formation assay (clonogenic assay). Also, flow cytometry analysis was used to detect the IDO-positive breast cancer cells. The results showed that treating cells with a combination of IDO and AHR blockers dramatically reduced breast cancer cells' migration and clonogenic capacities. Treating cells with only AHR blockade suppressed the clonogenic rate. Since both IDO and AHR are involved in their complex molecular networks, blocking both IDO and AHR might cause alterations in their molecular networks resulting in diminishing the migration and clonogenic abilities of breast cancer cells. However, further investigations are required to confirm our findings within in vivo models as a novel therapy for breast cancer. [ABSTRACT FROM AUTHOR]

Objective: The objective of this study was to observe the changes in the levels of indoleamine 2, 3-dioxygenase (IDO) and tryptophan-2, 3-dioxygenase (TDO) in patients with major depressive disorder (MDD) and investigate their potential role as novel biomarkers for diagnosing MDD. Methods: A total of 55 MDD patients and 55 healthy controls (HC) were enrolled in the study. The severity of MDD was assessed using the 24-item Hamilton Depression Rating Scale (HAMD-24) before and after treatment. The serum concentrations of IDO and TDO were measured at baseline and after treatment. The correlations between the serum levels of IDO and TDO and HAMD-24 scores were evaluated using Pearson's correlation test. Receiver operating characteristic (ROC) curve analysis was used to evaluate the area under the curve (AUC) of serum levels of IDO and TDO for discriminating MDD patients from HC. Results: The serum IDO and TDO concentrations were significantly higher in patients with MDD at baseline than in healthy controls, and decreased significantly after 2 weeks or 1 month of treatment. The levels of IDO and TDO were significantly positively correlated with HAMD-24 scores. Furthermore, the AUC values for IDO and TDO were 0.999 and 0.966, respectively. Conclusion: The study suggests that serum IDO and TDO may serve as novel biomarkers for diagnosing MDD. These findings may lead to a better understanding of the pathogenesis of MDD and the development of new therapeutic targets. [ABSTRACT FROM AUTHOR]

"Objective To investigate the correlation between cerebral hemodynamics, serum indoleamine 2,3-dioxygenase (IDO) and post-stroke cognitive impairment (PSCI), and to explore the predictive value of IOD for PSCI. Methods A total of 50 patients with acute ischemic stroke who were diagnosed and the onset being not more than 7 days in the Department of Neurology of the 900th Hospital of PLA Joint logistics Support Force from July 2020 to June 2021 were selected as the case group. According to the presence or absence of PSCI, the patients were divided into PSCI group (n=30) and non-PSCI (PSNCI) group (n=20), and 50 healthy individuals during the same period were selected as the control group (n=50). ELISA was used to detect the serum IDO levels of the enrolled population. Transcranial color Doppler ultrasound (TCCD) breath-holding test was performed and relevant data was recorded, breath holding index (BHI) was calculated as an evaluation index of cerebral hemodynamics. ROC curve was used to analyze the predictive efficacy of IDO level on PSCI. Results There were statistically significant differences in serum levels of D-dimer and N-terminal pro-brain natriuretic peptide (NT-proBNP) among the three groups (P＜0.05). The serum IDO levels in the control group, PSNCI group, and PSCI group were (0.23±0.05), (0.25±0.02), and (0.31±0.03) ng/mL, respectively, with statistically significant differences among the three groups (F=41.092, P＜0.01). Compared with the PSNCI group, the PSCI group showed an increase in IDO levels (P＜0.05), while there was no statistically significant difference in D-dimer and NT-proBNP levels (P＞0.05). There was no significant difference in BHI among the three groups (P＞0.05). No significant difference was found in lesion location between the PSCI group and the PSNCI group (χ2=15.478, P=0.113). The predictive efficacy was highest when the IDO level cutoff value was 0.277 ng/mL, with a area under the ROC curve (AUC) of 0.938, sensitivity of 83.3%, and specificity of 95.0%. Conclusion There is a significant correlation between serum IDO levels and PSCI, but the relationship between hemodynamic indicators and the occurrence of PSCI is still unclear. Early detection of IDO levels after acute ischemic stroke is helpful for the early identification and diagnosis of PSCI."

Introduction: Diffuse large B-cell lymphoma (DLBCL) is an aggressive malignancy of B-cells frequently encountered among people living with HIV. Immunological abnormalities are common in immunocompetent individuals with DLBCL, and are often associated with poorer outcomes. Currently, data on derangements of immunological proteins, such as cytokines and acute phase reactants, and their impact on outcomes in HIV-associated DLBCL (HIV-DLBCL) is lacking. This study assessed the levels and prognostic relevance of interleukin (IL)-6, IL-10 and Transforming Growth Factor Beta (TGFb), the acute phase proteins C-reactive protein (CRP) and ferritin; serum free light chains (SFLC) (elevation of which reflects a prolonged pro-inflammatory state); and the activity of the immunosuppressive enzyme Indoleamine 2,3-dioxygenase (IDO)in South African patients with DLBCL. Methods: Seventy-six patients with incident DLBCL were enrolled, and peripheral blood IL-6, IL-10, TGFb, SFLC and IDO-activity measured in selected patients. Additional clinical and laboratory findings (including ferritin and CRP) were recorded from the hospital records. Results: Sixty-one (80.3%) of the included patients were people living with HIV (median CD4-count = 148 cells/ul), and survival rates were poor (12-month survival rate 30.0%). The majority of the immunological proteins, except for TGFb and ferritin, were significantly higher among the people living with HIV. Elevation of IL-6, SFLC and IDO-activity were not associated with survival in HIV-DLBCL, while raised IL-10, CRP, ferritin and TGFb were. On multivariate analysis, immunological proteins associated with survival independently from the International Prognostic Index (IPI) included TGFb, ferritin and IL-10. Conclusion: Derangements of immunological proteins are common in HIVDLBCL, and have a differential association with survival compared to that reported elsewhere. Elevation of TGFb, IL-10 and ferritin were associated with survival independently from the IPI. In view of the poor survival rates in this cohort, investigation of the directed targeting of these cytokines would be of interest in our setting. [ABSTRACT FROM AUTHOR]

• • Preeclampsia (PE) and depression (MDD) increase risk bi-directionally for each other. • • One potential intermediate mechanism is immunovascular dysfunction. • • Indoleamine 2,3 dioxygenase (IDO) regulates immunovascular function in PE and MDD. • • Vascular stiffness and depression symptoms increase with decreased IDO in pregnancy. • • Decreased IDO may be a target for improved psycho-obstetric health. Preeclampsia and depression in pregnancy are among the most prevalent obstetric disorders with no known cures. While depression and preeclampsia each increase risk for the other, shared mechansisms are unclear. One possibility is low levels of Indoleamine 2,3 dioxygenase (IDO), which links immune dysregulation and oxidative arterial damage resulting in poor vascular function in both preeclampsia and depression. We hypothesized low circulating IDO activity levels in pregnancy would correspond to poor vascular function and depression symptoms. In this nested case-control study, clinical, demographic, and biologic data from a cohort of pregnant women recruited to longitudinal studies measuring noninvasive vascular function and circulating factors were analyzed. IDO activity across all three trimesters of pregnancy was measured using a colorimetric assay. Carotid-femoral pulse wave velocity (cfPWV), a measure of arterial stiffness, was also assessed throughout gestation by non-invasive applanation tonometry. Depression symptoms were assessed in pregnancy via the validated patient health questionnaire 9 (PHQ9). Participants with low second and third trimester IDO activity had significantly decreased cfPWV. This association remained statistically significant when controlled for confounders such as BMI and chronic hypertension in the third but not second trimester. While PHQ9 scores were not associated with cfPWV differences, IDO activity was lower in moderate and severely depressed relative to non-depressed pregnant individuals. Conclusion: These results implicate IDO in arterial stiffness and depression symptoms, suggesting that decreased IDO may be a central target for improved psycho-obstetric health. [ABSTRACT FROM AUTHOR]

Chikungunya virus (CHIKV) infection causes intense cytokine/chemokine inflammatory responses and debilitating joint pain. Indoleamine2,3-dioxygenase 1 (IDO-1) is an enzyme that initiates the tryptophan degradation that is important in initial host innate immune defense against infectious pathogens. Besides that, IDO-1 activation acts as a regulatory mechanism to prevent overactive host immune responses. In this study, we evaluated IDO-1 activity and cytokine/chemokine patterns in CHIKV patients. Higher IDO-1 (Kyn/Trp ratio) activation was observed during the early acute phase of CHIKV infection and declined in the chronic phase. Importantly, increased concentrations of Tumor Necrosis Factor-α (TNF-α), Interleukin-6 (IL-6), Interferon γ (IFN-γ), C-C motif chemokine ligand 2/Monocyte Chemoattractant Protein-1 (CCL2/MCP-1) and C-X-C motif chemokine ligand 10/Interferon Protein-10 (CXCL10/IP-10) were found in the acute phase of infection, while C-C motif chemokine ligand 4/Macrophage Inflammatory Protein 1 β (CCL4/MIP-1β) was found at increased concentrations in the chronic phase. Likewise, CHIKV patients with arthritis had significantly higher concentrations of CCL4/MIP-1β compared to patients without arthritis. Taken together, these data demonstrated increased IDO-1 activity, possibly exerting both antiviral effects and regulating exacerbated inflammatory responses. CCL4/MIP-1β may have an important role in the persistent inflammation and arthritic symptoms following chikungunya infection.

Indoleamine 2,3-dioxygenase (IDO) is a tryptophan-degrading enzyme belonging to the kynurenine pathway. IDO activity has been suggested as a biomarker for diagnosis of chronic kidney disease. The aim of the study was to estimate the level of IDO, urea, creatinine, uric acid, phosphate, calcium, albumin, MDA, GSH, and activity of peroxidase, catalase, arylesterase in the serum of chronic renal failure (CRF) patients treated with dialysis compared to the healthy control group. The results showed a significant increment in IDO level in patients compared with the control. Linear regression analysis using the Pearson correlation coefficient showed that increased IDO level correlates positively with urea, creatinine, uric acid, phosphate, MDA level and peroxidase activity whereas negatively with albumin, calcium, glutathione level, catalase activity and glomerular filtration rate. We concluded that IDO level might be a possible marker of oxidative stress and inflammation in patients with CRF.

Immunoregulation and indoleamine 2,3-dioxygenase 1 (IDO1) play pivotal roles in the rejection of allogeneic organ transplantation. This study aims to elucidate the immune-related functional mechanisms of exosomes (Exos) derived from bone marrow–derived mesenchymal stem cells (BMSCs) overexpressing IDO1 in the context of allogeneic heart transplantation (HTx) rejection. A rat model of allogeneic HTx was established. Exos were extracted after transfection with oe-IDO1 and oe-NC from rat BMSCs. Exos were administered via the caudal vein for treatment. The survival of rats was analyzed, and reverse transcription qualitative PCR (RT-qPCR) and immunohistochemistry (IHC) were employed to detect the expression of related genes. Histopathological examination was conducted using hematoxylin and eosin (HE) staining, and flow cytometry was utilized to analyze T-cell apoptosis. Proteomics and RNA-seq analyses were performed on Exos. The data were subjected to functional enrichment analysis using the R language. A protein interaction network was constructed using the STRING database, and miRWalk, TargetScan, and miRDB databases predicted the target genes, differentially expressed miRNAs, and transcription factors (TFs). Exos from BMSCs overexpressing IDO1 prolonged the survival time of rats undergoing allogeneic HTx. These Exos reduced inflammatory cell infiltration, mitigated myocardial damage, induced CD4 T-cell apoptosis, and alleviated transplantation rejection. The correlation between Exos from BMSCs overexpressing IDO1 and immune regulation was profound. Notably, 13 immune-related differential proteins (Anxa1, Anxa2, C3, Ctsb, Hp, Il1rap, Ntn1, Ptx3, Thbs1, Hspa1b, Vegfc, Dcn, and Ptpn11) and 10 significantly different miRNAs were identified. Finally, six key immune proteins related to IDO1 were identified through common enrichment pathways, including Thbs1, Dcn, Ptpn11, Hspa1b, Il1rap, and Vegfc. Thirteen TFs of IDO1-related key miRNAs were obtained, and a TF-miRNA-mRNA-proteins regulatory network was constructed. Exosome miRNA derived from BMSCs overexpressing IDO1 may influence T-cell activation and regulate HTx rejection by interacting with mRNA. [ABSTRACT FROM AUTHOR]

Brassinin, a phytochemical in cruciferous vegetables, is an indoleamine 2,3‐dioxygenase inhibitor and possesses a therapeutic opportunity in cancer immunotherapy. Here, we have developed and validated a novel, specific, and rapid bioanalytical method in rat plasma that is unavailable in the literature for preclinical studies. The method development involved single‐step protein precipitation as an extraction method using acetonitrile with an absolute and relative mean recovery of 79.32% and 93.59%, respectively. The method is accurate and precise over the linearity range of 1.0–50.0 μg/mL with a retention time of 5.3 and 3.5 min of brassinin and telmisartan, an internal standard. The intra‐day and inter‐day precision of the method expressed as a %coefficient of variation, ranging from 0.03% to 2.82% and 0.39% to 5.82%, whereas intra‐day and inter‐day accuracy ranged from 99.75% to 103.40% and 99.76% to 104.25%, respectively. The high‐performance liquid chromatography bioanalytical method was successfully validated as per Food and Drug Administration guidelines, and it can be applied in routine bioanalysis and pharmacokinetic studies. [ABSTRACT FROM AUTHOR]

ObjectiveTo determine the expression and functional roles of indoleamine 2,3-dioxygenase 1 (IDO1) and tryptophan 2,3-dioxygenase (TDO2) in leiomyoma.DesignExperimental study.SettingAcademic research laboratory.Patient(s)Women undergoing hysterectomy for leiomyoma.Intervention(s)Blockade of IDO1 and TDO2.Main outcome measure(s)Expression of IDO1 and TDO2 in leiomyoma and the effects of their inhibitors on the extracellular matrix.Result(s)Leiomyoma expressed significantly higher levels of IDO1 and TDO2 messenger ribonucleic acid (mRNA; 60.3%, 35/58 pairs and 98.3%, 57/58 pairs, respectively) and protein (54%, 27/50 pairs and 92%, 46/50 pairs, respectively) as well as the enzyme activity marker kynurenine (78.3%, 36/46 pairs for IDO1/TDO2) compared with levels in matched myometrium. The expression of TDO2 but not IDO1 mRNA was significantly higher in fibroids from African American compared with that in Caucasian and Hispanic patients. The TDO2 but not the IDO1 protein and mRNA levels were more abundant in fibroids bearing the MED12 mutation compared with results in wild-type leiomyomas. Treatment of leiomyoma smooth muscle cell and myometrial smooth muscle cell spheroids with the TDO2 inhibitor 680C91 but not the IDO1 inhibitor epacadostat significantly repressed cell proliferation and the expression of collagen type I (COL1A1) and type III (COL3A1) in a dose-dependent manner; these effects were more pronounced in leiomyoma smooth muscle cells compared with myometrial smooth muscle cell spheroids.Conclusion(s)These results underscore the physiological significance of the tryptophan degradation pathway in the pathogenesis of leiomyomas and the potential utility of anti-TDO2 drugs for treatment of leiomyomas.

BackgroundPregnant women with HIV (PWWH) have high postpartum morbidity and mortality from infections like tuberculosis. Immunologic changes during pregnancy and postpartum periods may contribute to these risks, particularly the immunoregulatory kynurenine pathway of tryptophan catabolism, which contributes to both HIV and tuberculosis pathogenesis and increases in the early postpartum period.MethodsWomen with HIV initiating antiretroviral therapy (ART) in the Uganda AIDS Rural Treatment Outcomes (UARTO) cohort who were pregnant at enrollment or became pregnant during observation were studied (n = 54). Plasma kynurenine/tryptophan (KT) ratio, soluble CD14 (sCD14), sCD163, sCD27, interferon-inducible protein 10 (IP-10), D-dimer, interleukin-6, and intestinal fatty-acid binding protein levels were assessed through the first year of ART and at 3-month intervals throughout pregnancy and 1 year postpartum. Biomarker changes were assessed with linear mixed models adjusted for ART duration. Hemoglobin concentration changes were used to estimate pregnancy-related changes in plasma volume.ResultsThe median pre-ART CD4 count was 134. D-dimer increased through the third trimester before returning to baseline postpartum, while most other biomarkers declined significantly during pregnancy, beyond what would be expected from pregnancy-associated plasma volume expansion. IP-10 and sCD14 remained suppressed for at least 12 months postpartum. KT ratio was the only biomarker that increased above prepregnancy baseline postpartum (mean + 30%; P

BackgroundDespite early antiretroviral therapy (ART), ART-suppressed people with human immunodeficiency virus (HIV) (PWH) remain at higher risk for infections and infection-related cancers than the general population. The immunologic pathways that remain abnormal in this setting, potentially contributing to these complications, are unclear.MethodsART-suppressed PWH and HIV-negative controls, all cytomegalovirus seropositive and enriched for HIV risk factors, were sampled from an influenza vaccine responsiveness study. PWH were stratified by timing of ART initiation (within 6 months of infection [early ART] vs later) and nadir CD4+ T-cell count among later initiators. Between-group differences in kynurenine-tryptophan (KT) ratio, interferon-inducible protein 10, soluble CD14 and CD163, soluble tumor necrosis factor receptor 2, interleukin 6, and soluble urokinase plasminogen activator receptor were assessed after confounder adjustment.ResultsMost participants (92%) were male, reflecting the demographics of early-ART initiators in San Francisco. Most biomarkers were higher among later-ART initiators. Participants in the early-ART group achieved near-normal soluble tumor necrosis factor receptor 2, interleukin 6, and soluble urokinase plasminogen activator receptor levels, but substantially higher KT ratio than those without HIV after confounder adjustment (P = .008). Soluble CD14, soluble CD163, and interferon-inducible protein 10 trended similarly.ConclusionsWhile early-ART initiators restore near-normal levels of many inflammatory markers, the kynurenine pathway of tryptophan catabolism remains abnormally high. Because this pathway confers adaptive immune defects and predicts tuberculosis and cancer progression, this it may contribute to persistent risks of these complications in this setting.

Kashif Asghar,1 Shaarif Bashir,2 Iftikhar Ali Rana,2 Muhammad Abu Bakar,3 Asim Farooq,1 Muhammad Hassan,1 Zukhruf Asif,1 Mahnoor Afzal,1 Iqra Masood,4 Muhammad Ishaq,2 Muhammad Tahseen,2 Sundus Bilal,5 Shafqat Mehmood,5 Nosheen Kanwal,6 Islah Ud Din,6 Asif Loya2 1Department of Basic Sciences Research, Shaukat Khanum Memorial Cancer Hospital and Research Centre, Lahore, Punjab, Pakistan; 2Department of Pathology, Shaukat Khanum Memorial Cancer Hospital and Research Centre, Lahore, Punjab, Pakistan; 3Department of Cancer Registry and Clinical Data Management, Shaukat Khanum Memorial Cancer Hospital and Research Centre, Lahore, Punjab, Pakistan; 4Department of Clinical Research, Shaukat Khanum Memorial Cancer Hospital and Research Centre, Lahore, Punjab, Pakistan; 5Department of Internal Medicine (Gastroenterology), Shaukat Khanum Memorial Cancer Hospital and Research Centre, Lahore, Punjab, Pakistan; 6Department of Radiology, Shaukat Khanum Memorial Cancer Hospital and Research Centre, Lahore, Punjab, PakistanCorrespondence: Kashif Asghar, Department of Basic Sciences Research, Shaukat Khanum Memorial Cancer Hospital and Research Centre, 7-A Block R-3, Johar Town, Lahore, Punjab, 54000, Pakistan, Tel +92-42-35905000, Fax +92-42-35945206, Email kashifasghar@skm.org.pkBackground/Aim: Hepatocellular carcinoma (HCC) is one of the most common forms of liver cancer that is modulated by the immune system. Programmed cell death ligand-1 (PD-L1) has emerged as a novel therapeutic target in various cancers. Indoleamine 2,3-dioxygenase (IDO) is an immunosuppressive enzyme that is associated with poor prognoses in various cancer types. The aim of this study was to investigate the PD-L1 expression, and clinicopathological features of non-HCV and non-HBV-associated HCC patients, including IDO expression.Patients and Methods: In this study, immunohistochemical analysis was performed to analyze the expression of PD-L1 and IDO. Formalin-fixed paraffin-embedded HCC tumor tissues (n=50) were obtained from the pathology department, at Shaukat Khanum Memorial Cancer Hospital and Research Centre (SKMCH&RC) in Lahore, Pakistan between 2005 and 2022. All the patients were HBV and HCV negative. Furthermore, it was a rare group of patients with no previous history of any viral hepatitis. In addition, for categorical and continuous variables chi-square or Fisher exact test and Mann–Whitney U-test was performed.Results: Of 50 tissue specimens, PD-L1+ was observed in 21 [high: 12 (24%), low: 9 (18%)] and PD-L1- was observed in 29 HCC patients. IDO+ was observed in all 50 specimens [high: 42 (84%), low: 8 (16%)]. Additionally, both PD-L1 and IDO had high expression in 11 (22%) patients. While both PD-L1 and IDO had low expression in 2 (4%) patients. Furthermore, in IDO+/PD-L1- group, 20 (69%) out of 29 patients died while in the IDO+/PD-L1+ group, 9 (43%) out of 21 patients died.Conclusion: Evaluation of IDO and PD-L1 expression may add therapeutic advantage in non-HCV and non-HBV-associated HCC patients that overexpress IDO. Further validation in a larger cohort is warranted.Keywords: programmed cell death ligand-1, indoleamine 2, 3-dioxygenase, non-HCV HCC, non-HBV HCC, immune checkpoint molecules

ABSTRACTIndoleamine 2,3 dioxygenase 1 (IDO1), a leader tryptophan-degrading enzyme, represents a recognized immune checkpoint molecule. In neoplasia, IDO1 is often highly expressed in dendritic cells infiltrating the tumor and/or in tumor cells themselves, particularly in human melanoma. In dendritic cells, IDO1 does not merely metabolize tryptophan into kynurenine but, after phosphorylation of critical tyrosine residues in the non-catalytic small domain, it triggers a signaling pathway prolonging its immunoregulatory effects by a feed-forward mechanism. We here investigated whether the non-enzymatic function of IDO1 could also play a role in tumor cells by using B16-F10 mouse melanoma cells transfected with either the wild-type Ido1 gene (Ido1WT) or a mutated variant lacking the catalytic, but not signaling activity (Ido1H350A). As compared to the Ido1WT-transfected counterpart (B16WT), B16-F10 cells expressing Ido1H350A (B16H350A) were characterized by an in vitro accelerated growth mediated by increased Ras and Erk activities. Faster growth and malignant progression of B16H350A cells, also detectable in vivo, were found to be accompanied by a reduction in tumor-infiltrating CD8+ T cells and an increase in Foxp3+ regulatory T cells. Our data, therefore, suggest that the IDO1 signaling function can also occur in tumor cells and that alternative therapeutic approach strategies should be undertaken to effectively tackle this important immune checkpoint molecule.

Background: Indoleamine 2,3-dioxygenase (IDO), an enzyme in the first step of tryptophan catabolism, plays a role in the pathogenesis of various malignancies and inflammatory diseases. Although its pathogenesis is unclear, vascular dysregulation and chronic inflammation are the most common culprits for rosacea. Objectives: The aim of this study is to evaluate the relationship between IDO and rosacea and whether there is a correlation with disease severity. Methods: Fifty-two patients with rosacea and 29 healthy volunteers were recruited. The patients were grouped according to severity stage, period, and subtype of the disease. Serum IDO levels were measured with enzyme-linked immunosorbent assay. Results: Serum IDO levels were significantly higher in the patients with rosacea compared to the healthy controls (P < 0.001) and were significantly higher in the patients in remission period and with papulopustular type rosacea compared to the controls (P = 0.002 and P = 0.001, respectively). The serum IDO levels of the female rosacea patients were higher than those of the healthy female controls (P < 0.001). When the diagnostic value of the parameter was investigated, it was observed that the serum IDO level has high sensitivity (83.3%) and specificity (76.1%), with a cutoff value of 47.1 ng/mL for female rosacea patients. Conclusion: IDO was found to increase in rosacea patients. With the high specificity and sensitivity observed, especially in female patients, IDO may be a supporting parameter in the diagnosis of rosacea.

Magdalena Massalska,1 Marzena Ciechomska,1 Ewa Kuca-Warnawin,1 Tomasz Burakowski,1 Anna Kornatka,1 Anna Radzikowska,1 Dariusz Pawlak,2 Barbara Muz,3 Adrianna Loniewska-Lwowska,4 Andrzej Palucha,5 Pawel Maldyk,6,7 Wlodzimierz Maslinski1 1Department of Pathophysiology and Immunology, National Institute of Geriatrics, Rheumatology, and Rehabilitation (NIGRiR), Warsaw, 02-637, Poland; 2Department of Pharmacodynamics, Medical University of Bialystok, Bialystok, 15-222, Poland; 3Department of Radiation Oncology, Cancer Biology Division, Washington University School of Medicine, St. Louis, MO, 63108, USA; 4Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, 02-106, Poland; 5Genomed S.A. Ponczowa 12, Warsaw, 02-971, Poland; 6Department of Rheumoorthopaedic Surgery, National Institute of Geriatrics, Rheumatology, and Rehabilitation (NIGRiR), Warsaw, 02-637, Poland; 7Clinical Department of Orthopaedic and Traumatology of Locomotor System, Enfant-Jesus Clinical Hospital, Warsaw, 02-005, PolandCorrespondence: Magdalena Massalska, Department of Pathophysiology and Immunology, National Institute of Geriatrics, Rheumatology, and Rehabilitation, Spartanska 1, Warsaw, 02-637, Poland, Tel/Fax +48 22 670 94 94, Email magdalena.massalska@spartanska.plBackground: Rheumatoid arthritis (RA) is a chronic autoimmune disease with systemic inflammation finally resulting in damaged joints. One of the RA development models suggests bone marrow (BM) as a place of inflammation development further leading to disease progression. We aimed to investigate the potential of CTLA-4-Fc molecule in inducing tolerogenic milieu in BM measured as indoleamine 2,3-dioxygenase (IDO) expression, CD4+Foxp3+ Treg induction, and T cell activation control. The expression of IDO-pathway genes was also examined in monocytes to estimate the tolerogenic potential in the periphery.Methods: Bone marrow mononuclear cells (BMMC) were stimulated by pro-inflammatory cytokines and CTLA-4-Fc. Next IDO expression, CD4+CD69+ and CD4+Foxp3+ percentage were estimated by PCR and FACS staining, respectively. Enzymatic activity of IDO was confirmed by HPLC in BM plasma and blood plasma. Genes expressed in IDO-pathway were analyzed by NGS in peripheral monocytes isolated from RA patients and healthy controls.Results: We found that CTLA-4-Fc and IFN-γ stimulation results in IDO production by BMMC. CTLA-4-Fc induced tryptophan catabolism can inhibit mitogen-induced CD4+ T cells activation without influencing CD8+ cells, but did not control CD25 nor Foxp3 expression in BM cells. Significantly higher expression of selected IDO-pathway genes was detected on peripheral monocytes isolated from RA as compared to healthy controls.Conclusion: This study sheds light on some immunosuppression aspects present or induced in BM. The potential of IDO-mediated pathways were confirmed in the periphery, what may represent the promising candidates for therapeutic strategies in RA.Keywords: rheumatoid arthritis, bone marrow, CTLA-4-Fc, indoleamine 2,3- dioxygenase, CD4+Foxp3+, monocytes

Context: Implantation of fertilised eggs and survival of a semi-allogenic embryo rely on the interactions between the cells and molecules preparing the uterus. We investigated the effect of regulatory T cell (Treg) therapy on the mechanism of local immune tolerance of mice prone to spontaneous abortion. Methods: Naive T cells were stimulated in vitro with 17β-oestradiol (E2), progesterone (P4) and TGF-β1 for 96 h to generate induced Tregs (iTreg). The iTregs were injected into DBA/2-mated pregnant CBA/J female mice (abortion prone model). On day 14 of pregnancy, mice were killed and decidual and placental tissues were collected for cellular composition analysis. Results: Abortion prone mice (PBS treated) showed significantly lower survival rates (P < 0.0001), increased CD3+CD8+ (P < 0.05), lower IDO+ (P < 0.05) and increased natural killer cells (uNK) cell numbers (P < 0.001) in the uterus, as well increased NK cells in the placenta (P < 0.05) than in normal pregnant mice (CBA/J × BALB/c). Adoptive transfer of iTregs increased fetal survival in abortion-prone mice (P < 0.01) and histopathological evaluation revealed a significantly decreased number of uNK cells in the uterus of TGF-β1-, E2- and P4-iTregs (P < 0.05, P < 0.0001 and P < 0.05, respectively) than in the PBS treated group. In the placenta, we found significantly lower numbers of uNK cells from TGF-β1-, E2- and P4-iTregs than in the PBS treated group (P < 0.05, P < 0.05 and P < 0.01, respectively). Conclusions: We propose that modulation of uterine NK cell activity through immunotherapy using Treg cells should be given more attention as an immunological strategy in the treatment of recurrent miscarriage. Recurrent spontaneous abortion has been associated to imbalanced cellular immunological status. Adoptive transfer of induced regulatory T cells promoted survival rate and corrected dysregulated uterine natural killer cells. Induced regulatory T cells might have potential therapeutic benefits in women with recurrent spontaneous abortion. [ABSTRACT FROM AUTHOR]

In parallel with the genetic and epigenetic changes that accumulate in tumor cells, chronic tumor-promoting inflammation establishes a local microenvironment that fosters the development of malignancy. While knowledge of the specific factors that distinguish tumor-promoting from nontumor-promoting inflammation remains inchoate, nevertheless, as highlighted in this series on the 'Hallmarks of Cancer', it is clear that tumor-promoting inflammation is essential to neoplasia and metastatic progression making identification of specific factors critical. Studies of immunometabolism and inflamometabolism have revealed a role for the tryptophan catabolizing enzyme IDO1 as a core element in tumor-promoting inflammation. At one level, IDO1 expression promotes immune tolerance to tumor antigens, thereby helping tumors evade adaptive immune control. Additionally, recent findings indicate that IDO1 also promotes tumor neovascularization by subverting local innate immunity. This newly recognized function for IDO1 is mediated by a unique myeloid cell population termed IDVCs (IDO1-dependent vascularizing cells). Initially identified in metastatic lesions, IDVCs may exert broader effects on pathologic neovascularization in various disease settings. Mechanistically, induction of IDO1 expression in IDVCs by the inflammatory cytokine IFNg blocks the antagonistic effect of IFNg on neovascularization by stimulating the expression of IL6, a powerful pro-angiogenic cytokine. By contributing to vascular access, this newly ascribed function for IDO1 aligns with its involvement in other cancer hallmark functionalities, (tumor-promoting inflammation, immune escape, altered cellular metabolism, metastasis), which may stem from an underlying role in normal physiological functions such as wound healing and pregnancy. Understanding the nuances of how IDO1 involvement in these cancer hallmark functionalities varies between different tumor settings will be crucial to the future development of successful IDO1-directed therapies. [ABSTRACT FROM AUTHOR]

Xuerun Peng,1,&ast; Zhipeng Zhao,1,&ast; Liwen Liu,2 Lan Bai,1 Rongsheng Tong,1 Hao Yang,3 Lei Zhong1 1Department of Pharmacy, Personalized Drug Therapy Key Laboratory of Sichuan Province, Sichuan Provincial People’s Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, Sichuan, 610072, People’s Republic of China; 2Department of Obstetrics and Gynecology, Fengrun District People’s Hospital, Tangshan, Hebei, 063000, People’s Republic of China; 3POWERCHINA Chengdu Engineering Corporation Limited, Chengdu, Sichuan, 610072, People’s Republic of China&ast;These authors contributed equally to this workCorrespondence: Lei Zhong, Department of Pharmacy, Personalized Drug Therapy Key Laboratory of Sichuan Province, Sichuan Provincial People’s Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, Sichuan, 610072, People’s Republic of China, Email zhl7235301@163.com Hao Yang, POWERCHINA Chengdu Engineering Corporation Limited, Chengdu, 610072, Sichuan, People’s Republic of China, Email yanghao@chidi.com.cnAbstract: Indoleamine 2.3-dioxygenases (IDO1/2) and tryptophan 2.3-dioxygenase (TDO) are the initial and rate-limiting enzymes in tryptophan metabolism, which play an essential role in mediating immunosuppression in tumor microenvironment. Accumulating evidence has indicated that both IDO1 and TDO are highly expressed in many malignant tumors, and their expression is generally associated with reduced tumor-infiltrating immune cells, increased regulatory T-cell infiltration, as well as cancer progression and poor prognosis for malignancies. A large number of IDO1 and TDO inhibitors have been screened or synthesized in the last two decades. Thus far, at least 12 antagonists targeting IDO1 and TDO have advanced to clinical trials. In this account, we conducted a comprehensive review of the development of IDO1 and TDO inhibitors in cancer immunotherapy, particularly their clinical research progress, and presented the current challenges and corresponding solutions.Keywords: indoleamine 2, 3-dioxygenase, tryptophan-2, 3-dioxygenase, tryptophan metabolism, cancer immunotherapy, immune tolerance

Indoleamine 2,3-dioxygenase 1 (IDO1) is an enzyme participating in tryptophan metabolism that has been implicated in numerous cancers. In the present study, a series of novel 5/6-amino indazole derivatives having amide linker were designed, synthesized, and evaluated for IDO1 inhibitory activity. The compounds were initially designed based on the known structural feature of IDO1 active site, and the important role of the indazole scaffold in interaction with IDO1 active site. Thirteen compounds exibited the moderate to excellent inhibitory activity (49% to 100% at the concentration of 1.0 mM). One of them, compound, 2-(6-amino-1H-indazol-1-yl)-N-(4-chlorophenyl) acetamide (19d), with chloro substituents group at para- position increased the activity upto 100%, equal to that value of the positive control, IDO5L. This research suggests that 5/6-amino indazole moiety combined with amide template is a potential scaffold for IDO1 inhibition as anti-cancer agents. [ABSTRACT FROM AUTHOR]

AIM: To explore the effect of indoleamine 2,3-dioxygenase (IDO) on recruitment and chemotaxis function of neutrophils in Aspergillus fumigatus (A. fumigatus) keratitis. METHODS: C57BL/6 mice models of A. fumigatus keratitis were established by inoculating hyphae of A. fumigatus evenly on the corneas. The clinical scores and inflammatory cytokines expression were measured respectively on the 1st, 3rd, 5th day after infection. The 1-MT (1 mg/mL) was administered by gavage to exert an inhibitory effect on IDO during infection. The mice were divided into control group, 1-MT group, A. fumigatus (A.F.) group, and 1-MT+A.F. groups. The corneas were monitored by slit lamp microscopy, and recorded disease scores in 3d after infection. Myeloperoxidase (MPO) assay was done to evaluate the neutrophils infiltration. Immunofluorescence staining was used to detect the recruitment of neutrophils in murine corneas. The mRNA of inflammatory cytokines was measured with reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: The corneal inflammation and the clinical score reached the peak on the 3rd day after the corneal infection. The mRNA of inflammatory cytokines of the A.F. group reached the highest on the 3rd day after the infection accordingly. Meanwhile, the results of slit light photography indicated that inhibitors of IDO made inflammation more serious contrasted with the A.F. group on the 3rd day. Besides, imunofluorescence staining and MPO indicated that 1-MT enhanced the recruitment, infiltration and chemotaxis of neutrophils obviously in contrast to the A.F. group. RT-PCR indicated that 1-MT increased the expression of CXCL-1, ICAM-1, IL-1β, and IL-8 significantly. CONCLUSION: IDO participates in the pathogenesis of A. fumigatus keratitis and plays an important role in inducing immune protection by inhibiting neutrophils-related inflammatory reaction and suppressing recruitment and chemotaxis of the neutrophils.

IntroductionChitinase, Indoleamine 2,3-dioxygenesae-1 (IDO-1) and heme oxygenase-1 (HO-1) are candidate diagnostic biomarkers for tuberculosis (TB). Whether these immune markers could also serve as predictive biomarkers of unfavorable treatment outcomes in pulmonary TB (PTB) is not known.MethodsA cohort of newly diagnosed, sputum culture-positive adults with drug-sensitive PTB were recruited. Plasma chitinase protein, IDO protein and HO-1 levels measured before treatment initiation were compared between 68 cases with unfavorable outcomes (treatment failure, death, or recurrence) and 108 control individuals who had recurrence-free cure.ResultsPlasma chitinase and IDO protein levels but not HO-1 levels were lower in cases compared to controls. The low chitinase and IDO protein levels were associated with increased risk of unfavourable outcomes in unadjusted and adjusted analyses. Receiver operating characteristic analysis revealed that chitinase and IDO proteins exhibited high sensitivity and specificity in differentiating cases vs controls as well as in differentiating treatment failure vs controls and recurrence vs controls, respectively. Classification and regression trees (CART) were used to determine threshold values for these two immune markers.DiscussionOur study revealed a plasma chitinase and IDO protein signature that may be used as a tool for predicting adverse treatment outcomes in PTB.

Indoleamine 2,3 dioxygenase 1 (IDO1), a leader tryptophan-degrading enzyme, represents a recognized immune checkpoint molecule. In neoplasia, IDO1 is often highly expressed in dendritic cells infiltrating the tumor and/or in tumor cells themselves, particularly in human melanoma. In dendritic cells, IDO1 does not merely metabolize tryptophan into kynurenine but, after phosphorylation of critical tyrosine residues in the non-catalytic small domain, it triggers a signaling pathway prolonging its immunoregulatory effects by a feed-forward mechanism. We here investigated whether the non-enzymatic function of IDO1 could also play a role in tumor cells by using B16-F10 mouse melanoma cells transfected with either the wild-type Ido1 gene (Ido1WT) or a mutated variant lacking the catalytic, but not signaling activity (Ido1H350A). As compared to the Ido1WT-transfected counterpart (B16WT), B16-F10 cells expressing Ido1H350A (B16H350A) were characterized by an in vitro accelerated growth mediated by increased Ras and Erk activities. Faster growth and malignant progression of B16H350A cells, also detectable in vivo, were found to be accompanied by a reduction in tumor-infiltrating CD8+ T cells and an increase in Foxp3+ regulatory T cells. Our data, therefore, suggest that the IDO1 signaling function can also occur in tumor cells and that alternative therapeutic approach strategies should be undertaken to effectively tackle this important immune checkpoint molecule. [ABSTRACT FROM AUTHOR]

Background: Indoleamine 2,3-dioxygenase (IDO), an enzyme in the first step of tryptophan catabolism, plays a role in the pathogenesis of various malignancies and inflammatory diseases. Although its pathogenesis is unclear, vascular dysregulation and chronic inflammation are the most common culprits for rosacea. Objectives: The aim of this study is to evaluate the relationship between IDO and rosacea and whether there is a correlation with disease severity. Methods: Fifty-two patients with rosacea and 29 healthy volunteers were recruited. The patients were grouped according to severity stage, period, and subtype of the disease. Serum IDO levels were measured with enzyme-linked immunosorbent assay. Results: Serum IDO levels were significantly higher in the patients with rosacea compared to the healthy controls (P < 0.001) and were significantly higher in the patients in remission period and with papulopustular type rosacea compared to the controls (P = 0.002 and P = 0.001, respectively). The serum IDO levels of the female rosacea patients were higher than those of the healthy female controls (P < 0.001). When the diagnostic value of the parameter was investigated, it was observed that the serum IDO level has high sensitivity (83.3%) and specificity (76.1%), with a cutoff value of 47.1 ng/mL for female rosacea patients. Conclusion: IDO was found to increase in rosacea patients. With the high specificity and sensitivity observed, especially in female patients, IDO may be a supporting parameter in the diagnosis of rosacea. [ABSTRACT FROM AUTHOR]

Preconditioning of mesenchymal stem/stromal cells (MSCs) with the inflammatory cytokine IFN-γ enhances not only their immunosuppressive activity but also their expression of HLA and proinflammatory genes. We hypothesized that prevention of the upregulation of inflammatory cytokines and HLA molecules in IFN-γ-primed MSCs would render these cells more immunosuppressive and less immunogenic. In this study, we discovered the following findings supporting this hypothesis: (1) activated human T cells induced the expression of IDO1 in MSCs via IFN-γ secretion and those MSCs in turn inhibited T-cell proliferation in an AHR-dependent fashion; (2) there was no difference in the expression of IDO1 and HLA-DR in MSCs after priming with a low dose (25 IU/mL) versus a high dose (100 IU/mL) of IFN-γ; (3) the transient addition of bortezomib, a proteasome inhibitor, to culture MSCs after IFN-γ priming decreased the expression of HLA-DR, inflammatory cytokine genes and Vcam1 while increasing the expression of IDO1 and the production of L-kynurenine; finally, MSCs primed with a combination of a low dose of IFN-γ and bortezomib were more effective in inhibiting Th17-mediated idiopathic pneumonia syndrome (IPS) and chronic colitis than unprimed MSCs. Our results suggest that bortezomib significantly eliminates the unfavorable effects of IFN-γ priming of MSCs (increased expression of MHC molecules and inflammatory cytokines and cell aggregation genes) and simultaneously increases their immunosuppressive activity by upregulating IDO1. Taken together, our newly established MSC priming method may contribute to MSC-based cell therapy for inflammatory diseases. Graphical Abstract [ABSTRACT FROM AUTHOR]

Pancreatic ductal adenocarcinoma (PDAC) represents one of the deadliest malignancies. Elevated regulatory T cell (Treg) infiltration has a potent immunosuppressive function in tumor biology, which contributes to low survival in PDAC. Nonetheless, the crosstalk between malignant cells and tumor-infiltrating Tregs in PDAC is not well understood. Here, clinical data demonstrates that the insulin-like growth factor binding protein 2 (IGFBP2) is associated with Treg accumulation in the microenvironment of PDAC in humans. Additionally, IGFBP2 increases Treg infiltration in the tumor microenvironment and promotes disease progression in mouse PDAC. Bioinformatic analysis and mechanistic assessment reveals IGFBP2 upregulated indoleamine 2, 3-dioxygenase (IDO) by activating signal transducer and activator of transcription 3 (STAT3) signaling in PDAC cells, thus inducing Treg differentiation and an immunosuppressive tumor microenvironment. These findings provide mechanistic insights into an important molecular pathway that promotes an immunosuppressive microenvironment, which suggests the IGFBP2 axis as a potential target for improved immune response in PDAC. [ABSTRACT FROM AUTHOR]

Background: Rheumatoid arthritis (RA) is a chronic autoimmune disease with systemic inflammation finally resulting in damaged joints. One of the RA development models suggests bone marrow (BM) as a place of inflammation development further leading to disease progression. We aimed to investigate the potential of CTLA-4-Fc molecule in inducing tolerogenic milieu in BM measured as indoleamine 2,3-dioxygenase (IDO) expression, CD4+Foxp3+ Treg induction, and T cell activation control. The expression of IDO-pathway genes was also examined in monocytes to estimate the tolerogenic potential in the periphery. Methods: Bone marrow mononuclear cells (BMMC) were stimulated by pro-inflammatory cytokines and CTLA-4-Fc. Next IDO expression, CD4+CD69+ and CD4+Foxp3+ percentage were estimated by PCR and FACS staining, respectively. Enzymatic activity of IDO was confirmed by HPLC in BM plasma and blood plasma. Genes expressed in IDO-pathway were analyzed by NGS in peripheral monocytes isolated from RA patients and healthy controls. Results: We found that CTLA-4-Fc and IFN-γ stimulation results in IDO production by BMMC. CTLA-4-Fc induced tryptophan catabolism can inhibit mitogen-induced CD4+ T cells activation without influencing CD8+ cells, but did not control CD25 nor Foxp3 expression in BM cells. Significantly higher expression of selected IDO-pathway genes was detected on peripheral monocytes isolated from RA as compared to healthy controls. Conclusion: This study sheds light on some immunosuppression aspects present or induced in BM. The potential of IDO-mediated pathways were confirmed in the periphery, what may represent the promising candidates for therapeutic strategies in RA. [ABSTRACT FROM AUTHOR]

L-tryptophan metabolism is involved in the regulation of many important physiological processes, such as, immune response, inflammation, and neuronal function. Indoleamine 2, 3-dioxygenase 1 (IDO1) is a key enzyme that catalyzes the first rate-limiting step of tryptophan conversion to kynurenine. Thus, inhibiting IDO1 may have therapeutic benefits for various diseases, such as, cancer, autoimmune disease, and depression. In the search for potent IDO1 inhibitors, natural quinones were the first reported IDO1 inhibitors with potent inhibitory activity. Subsequently, natural compounds with diverse structures have been found to have anti-IDO1 inhibitory activity. In this review, we provide a summary of these natural IDO1 inhibitors, which are classified as quinones, polyphenols, alkaloids and others. The overview of in vitro IDO1 inhibitory activity of natural compounds will help medicinal chemists to understand the mode of action and medical benefits of them. The scaffolds of these natural compounds can also be used for further optimization of potent IDO1 inhibitors. [ABSTRACT FROM AUTHOR]

Hepatitis B virus-related acute-on-chronic liver failure (HBV-ACLF) results in high susceptibility to infection. Although granulocytic myeloid-derived suppressor cells (gMDSC) are elevated in patients with HBV-ACLF, their role in HBV-ACLF pathogenesis is unknown. To elucidate the mechanism of gMDSC expansion and susceptibility to infection in HBV-ACLF patients, we analyzed the proportion of gMDSC in the peripheral blood and organ tissues of patients with HBV-ACLF and an ACLF mouse model established by continuous injection (eight times) of Concanavalin by flow cytometry and immunohistochemistry. We found that the proportion of gMDSC increased significantly in the blood and liver of patients with HBV-ACLF. This increase was positively correlated with disease severity, prognosis, and infection. gMDSC percentages were higher in peripheral blood, liver, spleen, and bone marrow than control levels in the ACLF mouse model. Immunofluorescence revealed that the gMDSC count increased in the liver of patients with HBV-ACLF as well as in the liver and spleen of ACLF mice. We further exposed peripheral blood monocyte cells from healthy donors to plasma from HBV-ACLF patients, recombinant cytokines, or their inhibitor, and found that TNF-α led to gMDSC expansion and significant upregulation of indoleamine 2, 3-dioxygenase (IDO), while blocking TNF-α signaling decreased gMDSC. Moreover, we detected proliferation and cytokine secretion of T lymphocytes when purified gMDSC was co-cultured with Pan T cells or IDO inhibitor and found that TNF-α-induced gMDSC inhibited T cell proliferation and interferon-γ production through the IDO signaling pathway. Lastly, the ability of gMDSC to phagocytose bacteria was low in patients with HBV-ACLF. Our findings elucidate HBV-ACLF pathogenesis and provide potential therapeutic targets.

Janus kinase Tyk2 is implicated in cancer immune surveillance, but its role in solid tumors is not well defined. We used Tyk2 knockout mice (Tyk2Δ/Δ) and mice with conditional deletion of Tyk2 in hematopoietic (Tyk2ΔHem) or intestinal epithelial cells (Tyk2ΔIEC) to assess their cell type-specific functions in chemically induced colorectal cancer. All Tyk2-deficient mouse models showed a higher tumor burden after AOM-DSS treatment compared to their corresponding wild-type controls (Tyk2+/+ and Tyk2fl/fl), demonstrating tumor-suppressive functions of Tyk2 in immune cells and epithelial cancer cells. However, specific deletion of Tyk2 in hematopoietic cells or in intestinal epithelial cells was insufficient to accelerate tumor progression, while deletion in both compartments promoted carcinoma formation. RNA-seq and proteomics revealed that tumors of Tyk2Δ/Δ and Tyk2ΔIEC mice were immunoedited in different ways with downregulated and upregulated IFNγ signatures, respectively. Accordingly, the IFNγ-regulated immune checkpoint Ido1 was downregulated in Tyk2Δ/Δ and upregulated in Tyk2ΔIEC tumors, although both showed reduced CD8+ T cell infiltration. These data suggest that Tyk2Δ/Δ tumors are Ido1-independent and poorly immunoedited while Tyk2ΔIEC tumors require Ido1 for immune evasion. Our study shows that Tyk2 prevents Ido1 expression in CRC cells and promotes CRC immune surveillance in the tumor stroma. Both of these Tyk2-dependent mechanisms must work together to prevent CRC progression.

Background: Poor sleep is associated with human immunodeficiency virus (HIV), particularly among women with HIV (WWH), although mechanisms are unclear. We explored cross-sectional associations between sleep disruption and tryptophan-kynurenine (T/K) pathway activation, measured by the kynurenine-to-tryptophan ratio (K:T).Methods: HIV-uninfected women (HIV-) and WWH aged 35-70 years and on stable antiretroviral therapy were included. Sleep metrics were measured using wrist actigraphy. Plasma T/K pathway metabolites were measured using liquid chromatography-tandem mass spectrometry. Multivariate linear regression models examined relationships between K:T and actigraphy-based sleep metrics by HIV status.Results: WWH (n = 153) and HIV- women (n = 151) were demographically similar. Among WWH, median CD4 was 751 cells/µL; 92% had undetectable HIV RNA. Compared to HIV- women, WWH had higher K:T (P < .001) and kynurenine (P = .01) levels but similar tryptophan levels (P = .25). Higher K:T was associated with more wake bouts (P = .001), more time awake after sleep onset (P = .01), and lower sleep efficiency (P = .03) in WWH only.Conclusions: HIV infection was associated with T/K pathway activation; this activation was associated with poorer sleep efficiency and more fragmented sleep. While longitudinal studies are needed to elucidate the directionality of these associations, these findings may help identify treatments to reduce sleep disruption in WWH by targeting residual inflammation and T/K pathway activation. [ABSTRACT FROM AUTHOR]

Glioblastoma multiforme (GBM) is a fatal brain tumor in adults with a bleak diagnosis. Expansion of immunosuppressive and malignant CD4 + FoxP3 + GITR + regulatory T cells is one of the hallmarks of GBM. Importantly, most of the patients with GBM expresses the tryptophan-degrading enzyme indoleamine 2,3-dioxygenase (IDO). While IDO1 is generally not expressed at appreciable levels in the adult central nervous system, it is rapidly stimulated and highly expressed in response to ongoing immune surveillance in cancer. Increased levels of immune surveillance in cancer are thus related to higher intratumoral IDO expression levels and, as a result, a worse OS in GBM patients. Conversion of the important amino acid tryptophan into downstream catabolite known as kynurenines is the major function of IDO. Decreasing tryptophan and increasing the concentration of immunomodulatory tryptophan metabolites has been shown to induce T-cell apoptosis, increase immunosuppressive programming, and death of tumor antigen-presenting dendritic cells. This observation supported the immunotherapeutic strategy, and the targeted molecular therapy that suppresses IDO1 activity. We review the current understanding of the role of IDO1 in tumor immunological escape in brain tumors, the immunomodulatory effects of its primary catabolites, preclinical research targeting this enzymatic pathway, and various issues that need to be overcome to increase the prospective immunotherapeutic relevance in the treatment of GBM malignancy. [ABSTRACT FROM AUTHOR]

Aim: Chronic inflammation is closely associated with tryptophan (TRP)-kynurenine (KYN) metabolic pathway. However, TRP-KYN pathway has not been fully elucidated in psoriasis, a systemic inflammatory disease with skin lesions and extracutaneous manifestations. Herein, we studied comprehensively serum profiles of TRP-KYN pathway metabolites in psoriatic patients (PSOs) to clarify the involvement of this pathway in the pathophysiology of psoriasis and to evaluate serum biomarkers reflecting systemic inflammation in PSOs. Methods: The concentrations of main TRP metabolites, TRP, KYN, 3-hydroxykynurenine (3HK), kynurenic acid (KYNA), 3-hydroxyanthranilic acid (3HAA), and anthranilic acid (AA), were determined by high-performance liquid chromatography in the sera from 65 PSOs and 35 healthy controls (HCs). The levels of these metabolites and the ratios of metabolites were compared between these subjects. The correlations between these values and the psoriasis area severity index (PASI) scores were analyzed. Skin samples from PSOs and HCs were subjected to immunohistochemical staining for kynureninase, catabolic enzyme from KYN or 3HK to downstream. Cytokine concentrations were comprehensively measured in the same samples and the correlations between the cytokine levels and TRP-KYN pathway metabolite levels were examined. Results: Serum TRP, KYN, and KYNA concentrations were lower and the 3HAA concentrations were higher in PSOs than in HCs. The ratios of 3HK/KYN, 3HAA/3HK, and 3HK/AA were higher in PSOs than in HCs. The AA levels and the ratio of AA/KYN were weakly positively correlated, and TRP, KYNA, and 3HK levels and the ratios of KYNA/KYN and 3HAA/AA were weakly negatively correlated with the PASI scores. The AA, KYN, and KYNA levels were positively correlated with the interferon gamma-induced protein 10 (IP-10) concentrations. Kynureninase expression was enhanced in the epidermis, both involved and uninvolved skin. Conclusions: Serum profiles of TRP-KYN pathway metabolites differed between PSOs and HCs. TRP-KYN pathway-associated processes, including kynureninase activation, may be involved in the pathogenesis of psoriasis, and thus serve as targets for psoriasis therapy.

Purpose: Host immunity influences the impact of cancer therapy but the effect of immune status in radioiodine (RAI)-treated differentiated thyroid cancer (DTC) remains obscure. Here we investigated indoleamine 2,3-dioxygenase (IDO) activity as a biomarker of response to RAI in patients with distant metastatic DTC (dmDTC). Methods: Patients with dmDTC receiving RAI were evaluated for serum IDO activity (kynurenine and kynurenine:tryptophan ratio) at baseline and 3 months after RAI. The optimal cut-off value for these biomarkers to predict response was established by receiver operating characteristic analysis. The relationship between disease outcomes, overall survival (OS) and progression-free survival (PFS), and IDO activity levels was studied. Results: Higher baseline kynurenine:tryptophan ratio (>2.46) was correlated with poorer RAI response as well as shorter median PFS (45 mo versus not reached, p=0.002) and OS (78 mo versus not reached, p=0.035). High baseline kynurenine:tryptophan ratio was also correlated with a reduced number of tumor-infiltrating lymphocytes. Higher post/prekynurenine ratio (>1.69) was associated with survival endpoints: shorter median PFS (48 mo versus not reached, p=0.002) and OS (68 mo versus not reached, p=0.010). Favorable baseline and favorable change corresponded with better PFS and OS. Conclusions: Our results suggest that RAI also alters IDO activity in dmDTC patients. IDO activity could predict progression and survival outcomes for advanced dmDTC patients. Serum IDO biomarker levels could be used to select dmDTC likely to benefit from RAI therapy, although further studies are necessary. [ABSTRACT FROM AUTHOR]

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In this study, we synthesized a molecule GA-1MT (GM) composed of indoleamine 2,3-dioxygenase (IDO) inhibitor (1-methyl-d-tryptophan, 1MT) called NLG8189 and gallic acid (GA) and verified its therapeutic effect on B16F10 melanoma cells and an orthotopic tumor-bearing mouse model. The synthesized molecule GM was analyzed by 1H NMR and mass spectrometry (MS). In addition, we confirmed that GM could mediate the immune response in the B16F10 cell tumor model by flow cytometry and immunofluorescence. The synthesized GM molecule could increase the solubility of 1MT to enhance the drug efficacy and lower costs. Moreover, GM could inhibit melanoma growth by combining 1MT and GA. In vivo experiments showed that GM could effectively inhibit the expression of tyrosinase, regulate the proportion of CD4+ T cells, CD8+ T cells, and regulatory T cells (Treg cells) in tumors, and significantly suppress melanoma growth. The newly synthesized drug GM could more effectively inhibit melanoma than GA and 1MT alone or in combination.

The immunomodulatory activity of mesenchymal stem/stromal cells (MSCs) to suppress innate and adaptive immune responses offers a potent cell therapy for modulating inflammation and promoting tissue regeneration. However, the inflammatory cytokine milieu plays a critical role in stimulating MSC immunomodulatory activity. In particular, interferon-γ (IFN-γ)-induced expression of indoleamine 2,3-dioxygenase (IDO) is primarily responsible for MSC suppression of T-cell proliferation and activation. Although pretreatment with IFN-γ is commonly used to prime MSCs for immunomodulatory activity prior to transplantation, the transient effects of pretreatment may limit the potential of MSCs to potently modulate immune responses. Therefore, the objective of this study was to investigate whether microparticle-mediated presentation of bioactive IFN-γ within three-dimensional spheroidal MSC aggregates could precisely regulate and induce sustained immunomodulatory activity. Delivery of IFN-γ via heparin-microparticles within MSC aggregates induced sustained IDO expression during 1 week of culture, whereas IDO expression by IFN-γ-pretreated MSC spheroids rapidly decreased during 2 days. Furthermore, sustained IDO expression induced by IFN-γ-loaded microparticles resulted in an increased and sustained suppression of T-cell activation and proliferation in MSC cocultures with CD3/CD28-activated peripheral blood mononuclear cells. The increased suppression of T cells by MSC spheroids containing IFN-γ-loaded microparticles was dependent on induction of IDO and supported by affecting monocyte secretion from pro- to anti-inflammatory cytokines. Altogether, microparticle delivery of IFN-γ within MSC spheroids provides a potent means of enhancing and sustaining immunomodulatory activity to control MSC immunomodulation after transplantation and thereby improve the efficacy of MSC-based therapies aimed at treating inflammatory and immune diseases. Stem Cells Translational Medicine 2017;6:223-237.

: The immunomodulatory activity of mesenchymal stem/stromal cells (MSCs) to suppress innate and adaptive immune responses offers a potent cell therapy for modulating inflammation and promoting tissue regeneration. However, the inflammatory cytokine milieu plays a critical role in stimulating MSC immunomodulatory activity. In particular, interferon-γ (IFN-γ)-induced expression of indoleamine 2,3-dioxygenase (IDO) is primarily responsible for MSC suppression of T-cell proliferation and activation. Although pretreatment with IFN-γ is commonly used to prime MSCs for immunomodulatory activity prior to transplantation, the transient effects of pretreatment may limit the potential of MSCs to potently modulate immune responses. Therefore, the objective of this study was to investigate whether microparticle-mediated presentation of bioactive IFN-γ within three-dimensional spheroidal MSC aggregates could precisely regulate and induce sustained immunomodulatory activity. Delivery of IFN-γ via heparin-microparticles within MSC aggregates induced sustained IDO expression during 1 week of culture, whereas IDO expression by IFN-γ-pretreated MSC spheroids rapidly decreased during 2 days. Furthermore, sustained IDO expression induced by IFN-γ-loaded microparticles resulted in an increased and sustained suppression of T-cell activation and proliferation in MSC cocultures with CD3/CD28-activated peripheral blood mononuclear cells. The increased suppression of T cells by MSC spheroids containing IFN-γ-loaded microparticles was dependent on induction of IDO and supported by affecting monocyte secretion from pro- to anti-inflammatory cytokines. Altogether, microparticle delivery of IFN-γ within MSC spheroids provides a potent means of enhancing and sustaining immunomodulatory activity to control MSC immunomodulation after transplantation and thereby improve the efficacy of MSC-based therapies aimed at treating inflammatory and immune diseases.This study demonstrates that biomaterial-based presentation of cytokines within spheroidal mesenchymal stem/stromal cell (MSC) aggregates provides a means of locally concentrating and sustaining presentation of cytokines to potentiate MSC immunomodulatory activity. Overall, this approach could aid in overcoming the limitations of transient pretreatment strategies by continuously presenting cytokines within the MSC microenvironment and thereby maximizing the immunomodulatory potential of transplanted MSCs. Furthermore, this approach provides a means of inducing potent MSC immunomodulation, irrespective of unknown or ill-defined environmental inflammatory milieu, such as in chronic inflammation or when administered with immunosuppressants. Altogether, biomaterial-based engineering of the MSC microenvironment provides a means of controlling the function of transplanted cells to specifically direct their therapeutic activity and may improve MSC-based therapies aimed at treating a number of inflammatory and immune diseases.