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Objective: Abdominal aortic aneurysm (AAA) is a common age-related vascular disease characterized by progressive weakening and dilatation of the aortic wall. Microfibrillar-associated protein 4 (MFAP4) is an extracellular matrix (ECM) protein involved in the induction of vascular remodeling. This study aimed to investigate if MFAP4 facilitates the development of AAA and characterize the underlying MFAP4-mediated mechanisms. Approach and Results: Double apolipoprotein E- and Mfap4 -deficient ( ApoE -/- Mfap4 -/- ) and control apolipoprotein E-deficient ( ApoE -/- ) mice were infused subcutaneously with angiotensin II (Ang II) for 28 days. Mfap4 expression was localized within the adventitial and medial layers and was upregulated after Ang II treatment. While Ang II-induced blood pressure increase was independent of Mfap4 genotype, ApoE -/- Mfap4 -/- mice exhibited significantly lower AAA incidence and reduced maximal aortic diameter compared to ApoE -/- littermates. The ApoE -/- Mfap4 -/- AAAs were further characterized by reduced macrophage infiltration, matrix metalloproteinase (MMP)-2 and MMP-9 activity, proliferative activity, collagen content, and elastic membrane disruption. MFAP4 deficiency also attenuated activation of integrin- and TGF-β-related signaling within the adventitial layer of AAA tissues. Finally, MFAP4 stimulation promoted human monocyte migration and significantly upregulated MMP-9 activity in macrophage-like THP-1 cells. Conclusion: This study demonstrates that MFAP4 induces macrophage-rich inflammation, MMP activity, and maladaptive remodeling of the ECM within the vessel wall, leading to an acceleration of AAA development and progression. Collectively, our findings suggest that MFAP4 is an essential aggravator of AAA pathology that acts through regulation of monocyte influx and MMP production., Competing Interests: AS and GS are inventors of patents owned by the University of Southern Denmark WO2014114298 and EP17199552.5. PH is employed by Astra Zeneca. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Pilecki, de Carvalho, Kirketerp-Møller, Schlosser, Kejling, Dubik, Madsen, Stubbe, Hansen, Andersen, Moeller, Marcussen, Azevedo, Hvidsten, Baun, Shi, Lindholt and Sorensen.)

Objective: To explore the associations of common mitochondrial DNA polymorphisms with chronic kidney disease (CKD). Methods: Data from 286 longevous individuals aged 95 years or older from the longevity arm from the Rugao Longevity and Ageing Study (RuLAS) were used. Twenty-eight common haplogroups defined by 33 single nucleotide polymorphisms were genotyped using SNaPshot minisequencing reaction assays. The creatinine-based estimated glomerular filtration rate (eGFR) was calculated using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation. Results: The prevalence of CKD was 23.6% among the longevous participants aged 95 years and older. The D haplogroup (67.37 ± 14.72 vs. 70.65 ± 11.07, p  = 0.045), the D5 haplogroup (60.86 ± 18.36 vs. 70.34 ± 11.53, p  = 0.002), and the 5178A allele (67.23 ± 14.48 vs. 70.75 ± 11.10, p  = 0.029) were associated with lower eGFR levels compared with noncarriers. The D5 haplogroup (13.8% vs. 3.6%, p  = 0.005) was significantly higher, while D haplogroup (35.4% vs. 24%, p  = 0.067) and the 5178A allele (36.9% vs. 24.9%, p  = 0.056) were borderline significantly higher in CKD individuals than those without CKD. Further, after adjusting for multiple covariates, the D haplogroup, the D5 haplogroup, and the 5178A allele were associated with increased odds of CKD with odds ratios of 1.93 (95% confidence interval [CI]: 1.00-3.72, p  = 0.050), 4.76 (95% CI: 1.49-15.22, p  = 0.009) and 2.04 (95% CI: 1.05-3.96, p  = 0.035), respectively. Conclusions: The D and D5 haplogroups, as well as the 5178A allele are associated with decreased eGFR levels and an increased risk of CKD in a longevous population.

Pressure overload and heart failure are among the leading causes of cardiovascular morbidity and mortality. Accumulating evidence suggests that inflammatory cell activation and release of inflammatory mediators are of vital importance during the pathogenesis of these cardiac diseases. Yet, the roles of innate immune cells and subsequent inflammatory events in these processes remain poorly understood. Here, we outline the possible underlying mechanisms of innate immune cell participation, including mast cells, macrophages, monocytes, neutrophils, dendritic cells, eosinophils, and natural killer T cells in these pathological processes. Although these cells accumulate in the atrium or ventricles at different time points after pressure overload, their cardioprotective or cardiodestructive activities differ from each other. Among them, mast cells, neutrophils, and dendritic cells exert detrimental function in experimental models, whereas eosinophils and natural killer T cells display cardioprotective activities. Depending on their subsets, macrophages and monocytes may exacerbate cardiodysfunction or negatively regulate cardiac hypertrophy and remodeling. Pressure overload stimulates the secretion of cytokines, chemokines, and growth factors from innate immune cells and even resident cardiomyocytes that together assist innate immune cell infiltration into injured heart. These infiltrates are involved in pro-hypertrophic events and cardiac fibroblast activation. Immune regulation of cardiac innate immune cells becomes a promising therapeutic approach in experimental cardiac disease treatment, highlighting the significance of their clinical evaluation in humans., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Liu, Shi and Guo.)

Background: We aimed to investigate the mechanisms of renal fibrosis and explore the effect of CD4+CD25+Foxp3+ regulatory T cells (Treg) on renal fibrosis after the obstruction was removed., Methods: Fifty-five C57BL/6 mice were randomly divided into three groups: the unilateral ureteral obstruction (UUO) group, the relief for unilateral ureteral obstruction (RUUO) group, and the RUUO+Treg group. Renal fibrosis indexes of RUUO mice were evaluated using hematoxylin and eosin (HE) and, Masson staining and immunohistochemistry after CD4+CD25+Treg cells were injected into the tail vein at the moment of recanalization. We detected the levels of Treg, M1, and M2 markers by flow cytometry, and the levels of transforming growth factor (TGF)-β1, interleukin (IL)-1β, IL-6 and IL-10 using ELISA., Results: The tubular necrosis score, AO value of α-SMA (smooth muscle actin), and collagen area on the 3rd and 14th days post RUUO were up-regulated compared with the 7th day post RUUO (P<0.05). After injection of Treg via tail vein, the tubular necrosis score, AO value of α-SMA, TGF-β1 level, and collagen area in the RUUO+Treg group on the 14th day were down-regulated compared with the RUUO group (P<0.05). Moreover, Treg could transform M1 macrophages into M2 macrophages, manifesting as up-regulated expression of CD206 compared with the RUUO group (P<0.05). Treg could also down-regulate the secretion of IL-6 and IL-1β while up-regulating the secretion of IL-10 in vitro compared with the M1 group (P<0.05)., Conclusions: The kidney could deteriorate into a state of injury and fibrosis after the obstruction was removed, and Treg could effectively protect the kidney function., Competing Interests: Declaration of Competing Interest The authors declare that they have no conflict of interest., (Copyright © 2021 Southern Society for Clinical Investigation. Published by Elsevier Inc. All rights reserved.)

Dysregulation of circular RNAs (circRNAs) is involved in various human diseases. Fibroblast-like synoviocytes (FLSs), which form the lining of the joint, are epigenetically imprinted with an aggressive phenotype and contribute to joint destruction in rheumatoid arthritis (RA). In the present study, we identified a novel circRNA, Circ&#95;0088194, which was upregulated in RA fibroblast-like synoviocytes (RA-FLSs) and correlated with the disease activity score in 28 joints. Overexpression of Circ&#95;0088194 promoted RA-FLS migration and invasion, while inhibition of Circ&#95;0088194 had the opposite effect. Mechanistically, Circ&#95;0088194 acted as a miR-766-3p sponge to relieve the repressive effect of miR-766-3p on its target, MMP2 (encoding matrix metalloproteinase 2), thereby promoting migration and invasion. The expression level of Circ&#95;0088194 was inversely correlated with that of miR-766-3p in RA-FLSs. Importantly, overexpression of miR-766-3p partially blocked the migration and invasion induced by Circ&#95;0088194 overexpression. Collectively, this study identified a novel circRNA Circ&#95;0088194 that promotes RA-FLS invasion and migration via the miR-766-3p/MMP2 axis. Circ&#95;0088194 might represent a novel therapeutic target to prevent and treat RA., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Cai, Liang, Xiao, Huang, Zhu, Shi, Ouyang and Yang.)

Rationale: Blood eosinophil count and ECP (eosinophil cationic protein) associate with human cardiovascular diseases. Yet, whether eosinophils play a role in cardiovascular disease remains untested. The current study detected eosinophil accumulation in human and murine abdominal aortic aneurysm (AAA) lesions, suggesting eosinophil participation in this aortic disease., Objective: To test whether and how eosinophils affect AAA growth., Methods and Results: Population-based randomized clinically controlled screening trials revealed higher blood eosinophil count in 579 male patients with AAA than in 5063 non-AAA control (0.236±0.182 versus 0.211±0.154, 10 9 /L, P <0.001). Univariate (odds ratio, 1.381, P <0.001) and multivariate (odds ratio, 1.237, P =0.031) logistic regression analyses indicated that increased blood eosinophil count in patients with AAA served as an independent risk factor of human AAA. Immunostaining and immunoblot analyses detected eosinophil accumulation and eosinophil cationic protein expression in human and murine AAA lesions. Results showed that eosinophil deficiency exacerbated AAA growth with increased lesion inflammatory cell contents, matrix-degrading protease activity, angiogenesis, cell proliferation and apoptosis, and smooth muscle cell loss using angiotensin-II perfusion-induced AAA in Apoe -/- and eosinophil-deficient Apoe -/- ΔdblGATA mice. Eosinophil deficiency increased lesion chemokine expression, muted lesion expression of IL (interleukin) 4 and eosinophil-associated-ribonuclease-1 (mEar1 [mouse EOS-associated-ribonuclease-1], human ECP homolog), and slanted M1 macrophage polarization. In cultured macrophages and monocytes, eosinophil-derived IL4 and mEar1 polarized M2 macrophages, suppressed CD11b + Ly6C hi monocytes, and increased CD11b + Ly6C lo monocytes. mEar1 treatment or adoptive transfer of eosinophil from wild-type and Il13 -/- mice, but not eosinophil from Il4 -/- mice, blocked AAA growth in Apoe -/- ΔdblGATA mice. Immunofluorescent staining and immunoblot analyses demonstrated a role for eosinophil IL4 and mEar1 in blocking NF-κB (nuclear factor-κB) activation in macrophages, smooth muscle cells, and endothelial cells., Conclusions: Eosinophils play a protective role in AAA by releasing IL4 and cationic proteins such as mEar1 to regulate macrophage and monocyte polarization and to block NF-κB activation in aortic inflammatory and vascular cells.

Clinical studies reveal changes in blood eosinophil counts and eosinophil cationic proteins that may serve as risk factors for human coronary heart diseases. Here we report an increase of blood or heart eosinophil counts in humans and mice after myocardial infarction (MI), mostly in the infarct region. Genetic or inducible depletion of eosinophils exacerbates cardiac dysfunction, cell death, and fibrosis post-MI, with concurrent acute increase of heart and chronic increase of splenic neutrophils and monocytes. Mechanistic studies reveal roles of eosinophil IL4 and cationic protein mEar1 in blocking H 2 O 2 - and hypoxia-induced mouse and human cardiomyocyte death, TGF-β-induced cardiac fibroblast Smad2/3 activation, and TNF-α-induced neutrophil adhesion on the heart endothelial cell monolayer. In vitro-cultured eosinophils from WT mice or recombinant mEar1 protein, but not eosinophils from IL4-deficient mice, effectively correct exacerbated cardiac dysfunctions in eosinophil-deficient ∆dblGATA mice. This study establishes a cardioprotective role of eosinophils in post-MI hearts.

Background and Aims: This study aimed at investigating whether depression symptoms are associated with prevalent and incident physical frailty in Chinese older population., Methods: We analyzed data of 1168 older Chinese adults aged 70 and above in the aging arm of the Rugao Longevity and Aging Study (RuLAS). Depressive symptoms (Geriatric Depression Scale ≥ 6) were assessed by the Geriatric Depression Scale. Frailty was defined using Fried phenotype criteria at baseline and 3-year survey., Results: At baseline, 8.9% of the participants had depression symptoms. The prevalence of pre-frailty and frailty were 34.5% and 5.9%, respectively. The percentages of depressive symptoms increase from robust (5.3%) to pre-frail (11.2%), and then to frail (31.9%) groups. After adjustments of multiple covariates, depressive symptoms were associated with both prevalent pre-frailty (OR = 1.75, 95% CI 1.08-2.84) and prevalent frailty (OR = 5.64, 95% CI 2.85-11.14) at baseline. At 3-year survey, 9.3% participants reported the development of frailty. After multiple adjustments, depressive symptoms were associated with a 2.79-fold (95% CI 1.09-7.10) increased risk of 3-year incident frailty., Conclusion: Depressive symptoms are associated with prevalent and incident frailty in Chinese older population. Together with the observations of the European populations, depressive symptoms may be a candidate risk factor of frailty.

Competing Interests: Declaration of Competing Interest The author declares no conflicts of interest.

Background: To explore the cross-sectional and longitudinal associations between frailty and incident depressive symptoms in a Chinese elderly sample., Methods: We analysed data of 1264 older Chinese elders aged 70-87 years in the Rugao Longevity and Ageing Study. The frailty phenotype was assessed using the Fried criteria and depression symptoms was measured by the Geriatric Depression Scale., Results: At baseline, 10.6% of participants had depressive symptoms and 9.0% had frailty. In cross-sectional analysis, both pre-frailty (odds ratio (OR) = 2.18, 95% CI 1.35-3.51) and frailty (OR = 4.64, 95% CI 2.49-8.66) were associated with depressive symptoms. In longitudinal analyses, frailty (OR = 2.12, 95% CI 1.17-3.83), instead of pre-frailty, was associated with 1.5-year incident depressive symptoms in a full-adjusted model among participants free of baseline depressive symptoms. In the components of frailty, lower grip strength was associated with increased risk of depressive symptoms onset (OR = 1.56, 95% CI 1.06-2.29)., Conclusions: Frailty and lower grip strength were associated with incident depressive symptoms in a Chinese elderly sample. Interventions designed to prevent depressive symptoms may be useful by utilising physical aspects of the elderly population., (© 2020 Japanese Psychogeriatric Society.)

The widespread coronavirus SARS-CoV-2 has already infected over 4 million people worldwide, with a death toll over 280,000. Current treatment of COVID-19 patients relies mainly on antiviral drugs lopinavir/ritonavir, arbidol, and remdesivir, the anti-malarial drugs hydroxychloroquine and chloroquine, and traditional Chinese medicine. There are over 2,118 on-going clinical trials underway, but to date none of these drugs have consistently proven effective. Cathepsin L (CatL) is an endosomal cysteine protease. It mediates the cleavage of the S1 subunit of the coronavirus surface spike glycoprotein. This cleavage is necessary for coronavirus entry into human host cells, virus and host cell endosome membrane fusion, and viral RNA release for next round of replication. Here we summarize data regarding seven CatL-selective inhibitors that block coronavirus entry into cultured host cells and provide a mechanism to block SARS-CoV-2 infection in humans. Given the rapid growth of the SARS-CoV-2-positive population worldwide, ready-to-use CatL inhibitors should be explored as a treatment option. We identify ten US FDA-approved drugs that have CatL inhibitory activity. We provide evidence that supports the combined use of serine protease and CatL inhibitors as a possibly safer and more effective therapy than other available therapeutics to block coronavirus host cell entry and intracellular replication, without compromising the immune system., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Nonalcoholic steatohepatitis (NASH) is a severe form of nonalcoholic fatty liver disease characterized by fat accumulation and inflammation in liver. Yet, the mechanistic insight and diagnostic and therapeutic options of NASH remain incompletely understood. This study tested the roles of cysteine protease cathepsin B (CatB) in mouse NASH development. Immunoblot revealed increased liver CatB expression in NASH mice. Fructose-palmitate-cholesterol diet increased body weight gain, liver to body weight ratio, blood fasting glucose, plasma total cholesterol and alanine transaminase levels, and liver triglyceride, but decreased plasma high-density lipoprotein in wild-type mice. All these changes were blunted in CatB-deficient (Ctsb -/- ) mice. In parallel to reduced expression of genes involved in liver lipid transport and lipogenesis, liver CD36, FABP4, and PPARγ protein levels were also significantly decreased in Ctsb -/- mice, although CatB deficiency did not affect liver gluconeogenesis and fatty acid beta-oxidation-associated gene expression. Mechanistic studies showed that CatB deficiency decreased liver expression of adhesion molecules, inflammatory cytokine, and chemokine, along with reduced liver inflammatory cell infiltration. CatB deficiency also promoted M2 macrophage polarization and reduced liver TGF-β1 signaling and fibrosis. Together, CatB deficiency improves liver function in NASH mice by suppressing de novo lipogenesis and liver inflammation and fibrosis., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Background: Chronic psychological stress (CPS) is linked to cardiovascular disease initiation and progression. Given that cysteinyl cathepsin K (CatK) participates in vascular remodeling and atherosclerotic plaque growth in several animal models, we investigated the role of CatK in the development of experimental neointimal hyperplasia in response to chronic stress., Methods and Results: At first, male wild-type (CatK) mice that underwent carotid ligation injury were subjected to chronic immobilization stress. On postoperative and stressed day 14, the results demonstrated that stress accelerated injury-induced neointima hyperplasia. On day 4, stressed mice showed following: increased levels of monocyte chemoattractant protein-1, gp91phox, toll-like receptor-2 (TLR2), TLR4, and CatK mRNAs or/and proteins, oxidative stress production, aorta-derived smooth muscle cell (SMC) migration, and macrophage infiltration as well as targeted intracellular proliferating-related molecules. Stressed mice showed increased matrix metalloproteinase-2 (MMP-2) and MMP-9 mRNA expressions and activities and elastin disruption in the injured carotid arteries. Second, CatK and CatK deficiency (CatK) mice received ligation injury and stress to explore the role of CatK. The stress-induced harmful changes were prevented by CatK. Finally, CatK mice that had undergone ligation surgery were randomly assigned to one of two groups and administered vehicle or CatK inhibitor for 14 days. Pharmacological CatK intervention produced a vascular benefit., Conclusion: These data indicate that CatK deletion protects against the development of experimental neointimal hyperplasia via the attenuation of inflammatory overaction, oxidative stress production, and VSMC proliferation, suggesting that CatK is a novel therapeutic target for the management of CPS-related restenosis after intravascular intervention therapies.

Aims: Obesity is a risk factor of abdominal aortic aneurysm (AAA). Inflammatory cytokine interleukin-18 (IL18) has two receptors: IL18 receptor (IL18r) and Na-Cl co-transporter (NCC). In human and mouse AAA lesions, IL18 colocalizes to its receptors at regions rich in adipocytes, suggesting a role of adipocytes in promoting IL18 actions in AAA development., Methods and Results: We localized both IL18r and NCC in human and mouse AAA lesions. Murine AAA development required both receptors. In mouse AAA lesions, IL18 binding to these receptors increased at regions enriched in adipocytes or adjacent to perivascular adipose tissue. 3T3-L1 adipocytes enhanced IL18 binding to macrophages, aortic smooth muscle cells (SMCs), and endothelial cells by inducing the expression of both IL18 receptors on these cells. Adipocytes also enhanced IL18r and IL18 expression from T cells and macrophages, AAA-pertinent protease expression from macrophages, and SMC apoptosis. Perivascular implantation of adipose tissue from either diet-induced obese mice or lean mice but not that from leptin-deficient ob/ob mice exacerbated AAA development in recipient mice. Further experiments established an essential role of adipocyte leptin and fatty acid-binding protein 4 (FABP4) in promoting IL18 binding to macrophages and possibly other inflammatory and vascular cells by inducing their expression of IL18, IL18r, and NCC., Conclusion: Interleukin-18 uses both IL18r and NCC to promote AAA formation. Lesion adipocyte and perivascular adipose tissue contribute to AAA pathogenesis by releasing leptin and FABP4 that induce IL18, IL18r, and NCC expression and promote IL18 actions., (Published on behalf of the European Society of Cardiology. All rights reserved. © The Author(s) 2019. For permissions, please email: journals.permissions@oup.com.)

Regulatory T cells (Tregs) play essential roles in obesity and diabetes. Here, we report a role of Tregs in enhancing β3-adrenergic receptor agonist CL316243 (CL)-stimulated thermogenic program in subcutaneous adipose tissue (SAT), but not in visceral fat. CL treatment for 7 days increased SAT adipocyte beiging and thermogenic gene expression in male or female mice. Adoptive transfer of Tregs enhanced this CL activity. Such Treg activity lost in male epididymal white adipose tissue (eWAT) and female gonadal gWAT. Adipocyte culture yielded the same conclusion. Tregs enhanced the expression of CL-induced thermogenic genes in SAT from male and female mice. This activity of Tregs reduced or disappeared in adipocytes from eWAT or gWAT. Both CL and Tregs induced much higher UCP-1 (uncoupling protein-1) expression in SAT from females than that from males. A mechanistic study demonstrated a role of Tregs in suppressing the expression of M1 macrophage markers (Tnfa, Il6, iNos, Ip10) and promoting the expression of M2 macrophage markers (Mrc1, Arg1, Il10) in bone-marrow-derived macrophages or in SAT from male or female mice. In female mice with pre-established obesity, Treg adoptive transfer reduced the gWAT weight in 2 weeks. Together with CL treatment, Treg adoptive transfer reduced the SAT weight and further improved CL-induced glucose metabolism and insulin sensitivity in female obese mice, but did not affect CL-induced body weight loss in male or female obese mice. This study revealed a predominant role of Tregs in female mice in promoting adipocyte beiging and thermogenesis in SAT, in part by slanting M2 macrophage polarization., (© 2020 Federation of American Societies for Experimental Biology.)

IgE-mediated activation of Nhe1 (Na + -H + exchanger-1) induces aortic cell extracellular acidification and promotes cell apoptosis. A pH-sensitive probe pHrodo identified acidic regions at positions of macrophage accumulation, IgE expression, and cell apoptosis in human and mouse abdominal aortic aneurysm (AAA) lesions. Ang II (angiotensin II)-induced AAA in Nhe1-insufficient Apoe -/- Nhe1 +/- mice and Apoe -/- Nhe1 +/+ littermates tested Nhe1 activity in experimental AAA, because Nhe1 -/- mice develop ataxia and epileptic-like seizures and die early. Nhe1 insufficiency reduced AAA incidence and size, lesion macrophage and T-cell accumulation, collagen deposition, elastin fragmentation, cell apoptosis, smooth muscle cell loss, and MMP (matrix metalloproteinase) activity. Nhe1 insufficiency also reduced blood pressure and the plasma apoptosis marker TCTP (translationally controlled tumor protein) but did not affect plasma IgE. While pHrodo localized the acidic regions to macrophage clusters, IgE expression, and cell apoptosis in AAA lesions from Apoe -/- Nhe1 +/+ mice, such acidic areas were much smaller in lesions from Apoe -/- Nhe1 +/- mice. Nhe1-FcεR1 colocalization in macrophages from AAA lesions support a role of IgE-mediated Nhe1 activation. Gelatin zymography, immunoblot, and real-time polymerase chain reaction analyses demonstrated that Nhe1 insufficiency reduced the MMP activity, cysteinyl cathepsin expression, IgE-induced apoptosis, and NF-κB activation in macrophages and blocked IgE-induced adhesion molecule expression in endothelial cells. A near-infrared fluorescent probe (LS662) together with fluorescence reflectance imaging of intact aortas showed reduced acidity in AAA lesions from Nhe-1-insufficient mice. This study revealed extracellular acidity at regions rich in macrophages, IgE expression, and cell apoptosis in human and mouse AAA lesions and established a direct role of Nhe1 in AAA pathogenesis.

Cysteinyl cathepsins are lysosomal/endosomal proteases that mediate bulk protein degradation in these intracellular acidic compartments. Yet, studies indicate that these proteases also appear in the nucleus, nuclear membrane, cytosol, plasma membrane, and extracellular space. Patients with cardiovascular diseases (CVD) show increased levels of cathepsins in the heart, aorta, and plasma. Plasma cathepsins often serve as biomarkers or risk factors of CVD. In aortic diseases, such as atherosclerosis and abdominal aneurysms, cathepsins play pathogenic roles, but many of the same cathepsins are cardioprotective in hypertensive, hypertrophic, and infarcted hearts. During the development of CVD, cathepsins are regulated by inflammatory cytokines, growth factors, hypertensive stimuli, oxidative stress, and many others. Cathepsin activities in inflammatory molecule activation, immunity, cell migration, cholesterol metabolism, neovascularization, cell death, cell signaling, and tissue fibrosis all contribute to CVD and are reviewed in this article in memory of Dr. Nobuhiko Katunuma for his contribution to the field., Competing Interests: Declaration of Competing Interest None., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Objective: By binding to its high-affinity receptor FcεR1, IgE activates mast cells, macrophages, and other inflammatory and vascular cells. Recent studies support an essential role of IgE in cardiometabolic diseases. Plasma IgE level is an independent predictor of human coronary heart disease. Yet, a direct role of IgE and its mechanisms in cardiometabolic diseases remain incompletely understood. Approach and Results: Using atherosclerosis prone Apoe -/- mice and IgE-deficient Ige -/- mice, we demonstrated that IgE deficiency reduced atherosclerosis lesion burden, lesion lipid deposition, smooth muscle cell and endothelial cell contents, chemokine MCP (monocyte chemoattractant protein)-1 expression and macrophage accumulation. IgE deficiency also reduced bodyweight gain and increased glucose and insulin sensitivities with significantly reduced plasma cholesterol, triglyceride, insulin, and inflammatory cytokines and chemokines, including IL (interleukin)-6, IFN (interferon)-γ, and MCP-1. From atherosclerotic lesions and peritoneal macrophages from Apoe -/- Ige -/- mice that consumed an atherogenic diet, we detected reduced expression of M1 macrophage markers (CD68, MCP-1, TNF [tumor necrosis factor]-α, IL-6, and iNOS [inducible nitric oxide synthase]) but increased expression of M2 macrophage markers (Arg [arginase]-1 and IL-10) and macrophage-sterol-responsive-network molecules (complement C3, lipoprotein lipase, LDLR [low-density lipoprotein receptor]-related protein 1, and TFR [transferrin]) that suppress macrophage foam cell formation. These IgE activities can be reproduced in bone marrow-derived macrophages from wild-type mice, but muted in cells from FcεR1-deficient mice, or blocked by anti-IgE antibody or complement C3 deficiency., Conclusions: IgE deficiency protects mice from diet-induced atherosclerosis, obesity, glucose tolerance, and insulin resistance by regulating macrophage polarization, macrophage-sterol-responsive-network gene expression, and foam cell formation.

Background and Aims: To explore whether frailty, defined by frailty index (FI), is associated with the risk of elevated B-type natriuretic peptide (BNP), a surrogate endpoint of cardiovascular events., Methods: Data of 1382 community-dwelling elders who had no documented cardiovascular diseases aged 70-84 years from the ageing arm of the Rugao Longevity and Ageing Study was used. Traditional risk factor index (TI) was constructed using eight established cardiovascular-related risk factors. FI was constructed using 36 health deficits. Elevated BNP was defined as BNP ≥ 100pg/mL. Cardiovascular events include incident major cardiovascular events and cardiovascular death., Results: During a 3-year follow-up period, 97 participants had cardiovascular events. TI was not associated with the risk of elevated BNP, but was associated with cardiovascular events (HR = 1.16, 95% CI 1.01-1.34). Frailty index was not only associated with cardiovascular events (HR = 1.32, 95% CI 1.06-1.64), but also associated with elevated BNP with an OR of 1.22 (95% CI 1.02-1.47) for each 0.1 increment. Further, both frailty (OR = 1.93, 95% CI 1.67-3.17) and pre-frailty (OR = 1.54, 95% CI 1.06-2.25) were associated with increased risk of elevated BNP., Conclusion: FI is associated with increased risks of both cardiovascular events and surrogated endpoint of cardiovascular disease-elevated BNP. Frailty may be a non-traditional risk factor of cardiovascular diseases and frailty index may be a measurement for early identifying high risk elderly individuals of cardiovascular abnormities.

Allergic asthma with high plasma IgE levels is a significant risk factor of human abdominal aortic aneurysm (AAA). This study tests a direct role of IgE in angiotensin-II (Ang-II) perfusion- and peri-aortic CaCl 2 injury-induced AAA in mice. In both models, IgE-deficiency in Apoe -/- Ige -/- mice blunts AAA growth and reduces lesion accumulation of macrophages, CD4 + and CD8 + T cells, and lesion MHC class-II expression, CD31 + microvessel growth, and media smooth muscle cell loss, compared with those from Apoe -/- control mice. Real time-PCR reveals significant reductions in expression of neutrophil chemoattractants MIP-2α and CXCL5 in AAA lesions or macrophages from Apoe -/- Ige -/- mice, along with reduced lesion Ly6G + neutrophil accumulation. Consistent with reduced lesion inflammatory cell accumulation, we find significant reductions of plasma and AAA lesion IL6 expression in Apoe -/- Ige -/- mice. Immunofluorescent staining and FACS analysis show that AAA lesion neutrophils express FcεR1. Mechanistic study demonstrates that IgE induces neutrophil FcεR1 expression, activates MAPK signaling, and promotes IL6 production. This study supports a direct role of IgE in AAA by promoting lesion chemokine expression, inflammatory cell accumulation, MAPK signaling, and cytokine expression. IgE inhibition may represent a novel therapeutic approach in AAA management., (© 2020 Federation of American Societies for Experimental Biology.)

Objectives: To explore the associations of TNF-α -308 G>A (rs1800629) and TNF-β 252 A>G (rs909253) with physical function and plasma B-type natriuretic peptide (BNP)., Methods: Data of 1747 community-dwelling elders from the ageing arm of the Rugao Longevity and Ageing Study was used. Physical function was measured by handgrip strength, Timed Up and Go (TUG) test and 5-meter walking test (5MWT)., Results: AA genotype of the TNF-α -308 G>A was associated with higher mean time of TUG test and 5MWT (multivariable adjusted β=5.75 and 5.70, respectively, p<0.05), compared with GG genotype. For the TNF-β 252 A>G polymorphism, GG genotype was associated with higher mean time of TUG test and 5MWT (multivariable adjusted β=1.55 and 0.83, respectively, p<0.05) and lower handgrip strength (multivariable adjusted β=-0.69, p<0.05), compared with AA genotype. Further, GG was associated with greater odds of low handgrip strength (OR=1.47, 95% CI=1.06-2.04), low speed of TUG test (OR=1.87, 95% CI=1.20-2.01) and elevated BNP (OR=1.30, 95% CI=1.08-1.84). GG also interacted with elevated BNP to be associated with greater odds of low handgrip strength and 5MWT., Conclusions: TNF-β 252 A>G was associated with physical function measurements, plasma BNP level, and odds of elevated BNP in an elderly population. TNF-β 252 A>G also interacted with elevated BNP to be associated with greater odds of physical function measurements., Competing Interests: The authors declare that they have no conflict of interest.

Background Although apoptosis and cell proliferation have been extensively investigated in atherosclerosis and restenosis postinjury, the communication between these 2 cellular events has not been evaluated. Here, we report an inextricable communicative link between apoptosis and smooth muscle cell proliferation in the promotion of vascular remodeling postinjury. Methods and Results Cathepsin K-mediated caspase-8 maturation is a key initial step for oxidative stress-induced smooth muscle cell apoptosis. Apoptotic cells generate a potential growth-stimulating signal to facilitate cellular mass changes in response to injury. One downstream mediator that cathepsin K regulates is PLF-1 (proliferin-1), which can potently stimulate growth of surviving neighboring smooth muscle cells through activation of PI3K/Akt/p38MAPK (phosphatidylinositol 3-kinase/protein kinase B/p38 mitogen-activated protein kinase)-dependent and -independent mTOR (mammalian target of rapamycin) signaling cascades. We observed that cathepsin K deficiency substantially mitigated neointimal hyperplasia by reduction of Toll-like receptor-2/caspase-8-mediated PLF-1 expression. Interestingly, PLF-1 blocking, with its neutralizing antibody, suppressed neointima formation and remodeling in response to injury in wild-type mice. Contrarily, administration of recombinant mouse PLF-1 accelerated injury-induced vascular actions. Conclusions This is the first study detailing PLF-1 as a communicator between apoptosis and proliferation during injury-related vascular remodeling and neointimal hyperplasia. These data suggested that apoptosis-driven expression of PLF-1 is thus a novel target for treatment of apoptosis-based hyperproliferative disorders.

CLCA1 is a member of the CLCA (calcium-activated chloride channel regulator) family and plays an essential role in goblet cell mucus production from the respiratory tract epithelium. CLCA1 also regulates Ca 2+ -dependent Cl - transport that involves the channel protein transmembrane protein 16A (TMEM16A) and its accessary molecules. CLCA1 modulates epithelial cell chloride current and participates in the pathogenesis of mucus hypersecretory-associated respiratory and gastrointestinal diseases, including asthma, chronic obstructive pulmonary disease, cystic fibrosis, pneumonia, colon colitis, cystic fibrosis intestinal mucous disease, ulcerative colitis, and gastrointestinal parasitic infection. Most studies have been focused on the expression regulation of CLCA1 in human specimens. Limited studies used the CLCA1-deficient mice and CLCA1 blocking agents and yielded inconsistent conclusions regarding its role in these diseases. CLCA1 not only regulates mucin expression, but also participates in innate immune responses by binding to yet unidentified molecules on inflammatory cells for cytokine and chemokine production. CLCA1 also targets lymphatic endothelial cells and cancer cells by regulating lymphatic cell proliferation and lymphatic sinus growth in the lymphatic organs and controlling cancer cell differentiation, proliferation, and apoptosis, all which depend on the location of the lymphatic vessels, the type of cancers, the presence of Th2 cytokines, and possibly the availability and type of CLCA1-binding proteins. Here we summarize available studies related to these different activities of CLCA1 to assist our understanding of how this secreted modifier of calcium-activated chloride channels (CaCCs) affects mucus production and innate immunity during the pathogenesis of respiratory, gastrointestinal, and malignant diseases., Competing Interests: The authors declare no conflicts of interest and agree to publish the work., (© 2019 The Authors.)

Background: Cathepsin L and some other cathepsins have been implicated in the development of obesity in humans and mice. The functional inactivation of the proteases reduces fat accumulation during mammalian adipocyte differentiation. However, beyond degrading extracellular matrix protein fibronectin, the molecular mechanisms by which cathepsins control fat accumulation remain unclear. We now provide evidence from Caenorhabditis elegans and mouse models to suggest a conserved regulatory circuit in which peripheral cathepsin L inhibition lowers fat accumulation through promoting central serotonin synthesis., Results: We established a C. elegans model of fat accumulation using dietary supplementation with glucose and palmitic acid. We found that nutrient supplementation elevated fat storage in C. elegans, and along with worm fat accumulation, an increase in the expression of cpl-1 was detected using real-time PCR and western blot. The functional inactivation of cpl-1 reduced fat storage in C. elegans through activating serotonin signaling. Further, knockdown of cpl-1 in the intestine and hypodermis promoted serotonin synthesis in worm ADF neurons and induced body fat loss in C. elegans via central serotonin signaling. We found a similar regulatory circuit in high-fat diet-fed mice. Cathepsin L knockout promoted fat loss and central serotonin synthesis. Intraperitoneal injection of the cathepsin L inhibitor CLIK195 similarly reduced body weight gain and white adipose tissue (WAT) adipogenesis, while elevating brain serotonin level and WAT lipolysis and fatty acid β-oxidation. These effects of inhibiting cathepsin L were abolished by intracranial injection of p-chlorophenylalanine, inhibitor of a rate-limiting enzyme for serotonin synthesis., Conclusion: This study reveals a previously undescribed molecular mechanism by which peripheral CPL-1/cathepsin L inhibition induces fat loss in C. elegans and mice through promoting central serotonin signaling.

Background: Given that cathepsin S (CatS) gained attention due to its enzymatic and non-enzymatic functions in signaling, the role of CatS in ischemia-induced angiogenesis of aged mice was explored., Methods and results: To study the role of CatS in the decline in aging-related vascular regeneration capacity, a hindlimb ischemia model was applied to aged wild-type (CatS +/+ ) and CatS-deficient (CatS -/- ) mice. CatS -/- mice exhibited impaired blood flow recovery and capillary formation and increased levels of p-insulin receptor substrate-1, Wnt5a, and SC35 proteins and decreased levels of phospho-endothelial nitric oxide synthase (p-eNOS), p-mTOR, p-Akt, p-ERK1/2, p-glycogen synthase kinase-3α/β, and galatin-3 proteins, as well as decreased macrophage infiltration and matrix metalloproteinase-2/-9 activities in the ischemic muscles. In vitro, CatS knockdown altered the levels of these targeted essential molecules for angiogenesis. Together, the results suggested that CatS -/- leads to defective endothelial cell functions and that CatS -/- is associated with decreased circulating endothelial progenitor cell (EPC)-like CD31 + /c-Kit + cells. This notion was reinforced by the study finding that pharmacological CatS inhibition led to a declined angiogenic capacity accompanied by increased Wnt5a and SC35 levels and decreased eNOS/Akt-ERK1/2 signaling in response to ischemia., Conclusions: These findings demonstrated that the impairment of ischemia-induced neovascularization in aged CatS -/- mice is due, at least in part, to the attenuation of endothelial cell/EPC functions and/or mobilization associated with Wnt5a/SC35 activation in advanced age.

Obstructive nephropathy is a common cause for chronic kidney disease. Surgery, which is adopted to promptly relieve the obstruction, is the most important method to save damaged kidneys. However, earlier studies have shown that renal function will continue to deteriorate until the terminal stage after the obstruction' relief. The aim of this study is to explore the renal fibrosis and investigate the effect of losartan on renal fibrosis after the obstruction' relief using an improved mouse model of relief for unilateral ureteral obstruction (RUUO). Experiments carried out using C57BL/6 mice (n = 30) were randomly divided into RUUO + Losartan group, RUUO group and sham group. Using an improved mouse RUUO model, this study revealed that the mouse kidney for 3- or 7-day unilateral ureteral obstruction undergoing the RUUO surgery was still in a state of injury and fibrosis, while losartan could effectively ameliorate renal fibrosis by upregulating the expression of CD4 + CD25 + Foxp3 + regulatory T cells (Tregs) in kidney after the surgery of RUUO.

Transforming growth factor beta (TGF-β) signaling contributes to tissue fibrosis. Here we demonstrate that TGF-β enhances CatS and CatK expression but reduces CatB and CatL expression in mouse kidney tubular epithelial cells (TECs). CatS- and CatK deficiency reduces TEC nuclear membrane importer importin-β expression, Smad-2/3 activation, and extracellular matrix (ECM) production. Yet CatB- and CatL-deficiency displays the opposite observations with reduced nuclear membrane exporter RanBP3 expression. CatS and CatK form immunocomplexes with the importin-β and RanBP3 more effectively than do CatB and CatL. On the plasma membrane, CatS and CatK preferentially form immunocomplexes with and activate TGF-β receptor-2, whereas CatB and CatL form immunocomplexes with and inactivate TGF-β receptor-1. Unilateral ureteral obstruction-induced renal injury tests differential cathepsin activities in TGF-β signaling and tissue fibrosis. CatB- or CatL-deficiency exacerbates fibrosis, whereas CatS- or CatK-deficiency protects kidneys from fibrosis. These cathepsins exert different effects in the TGF-β signaling cascade independent of their proteolytic properties., (Copyright © 2019 The Author(s). Published by Elsevier Inc. All rights reserved.)

The pH in atherosclerotic lesions varies between individuals. IgE activates macrophage Na + -H + exchanger (Nhe1) and induces extracellular acidification and cell apoptosis. Here, we show that the pH-sensitive pHrodo probe localizes the acidic regions in atherosclerotic lesions to macrophages, IgE, and cell apoptosis. In Apoe -/- mice, Nhe1-deficiency or anti-IgE antibody reduces atherosclerosis and blocks lesion acidification. Reduced atherosclerosis in Apoe -/- mice receiving bone marrow from Nhe1- or IgE receptor FcεR1-deficient mice, blunted foam cell formation and signaling in IgE-activated macrophages from Nhe1-deficient mice, immunocomplex formation of Nhe1 and FcεR1 in IgE-activated macrophages, and Nhe1-FcεR1 colocalization in atherosclerotic lesion macrophages support a role of IgE-mediated macrophage Nhe1 activation in atherosclerosis. Intravenous administration of a near-infrared fluorescent pH-sensitive probe LS662, followed by coregistered fluorescent molecular tomography-computed tomography imaging, identifies acidic regions in atherosclerotic lesions in live mice, ushering a non-invasive and radiation-free imaging approach to monitor atherosclerotic lesions in live subjects.

Severe haemorrhagic transformation (HT), a common complication of recombinant tissue plasminogen activator (rtPA) treatment, predicts poor clinical outcomes in acute ischaemic stroke. The search for agents to mitigate this effect includes investigating biomolecules involved in neovascularization. This study examines the role of Cathepsin K (Ctsk) in rtPA-induced HT after focal cerebral ischaemia in mice. After knockout of Ctsk, the gene encoding Ctsk, the outcomes of Ctsk +/+ and Ctsk -/- mice were compared 24 h after rtPA-treated cerebral ischaemia with respect to HT severity, neurological deficits, brain oedema, infarct volume, number of apoptotic neurons and activated microglia/macrophage, blood-brain barrier integrity, vascular endothelial growth factor (VEGF) expression and Akt-mTOR pathway activation. We observed that haemoglobin levels, brain oedema and infarct volume were significantly greater and resulted in more severe neurological deficits in Ctsk -/- than in Ctsk +/+ mice. Consistent with our hypothesis, the number of NeuN-positive neurons was lower and the number of TUNEL-positive apoptotic neurons and activated microglia/macrophage was higher in Ctsk -/- than in Ctsk +/+ mice. Ctsk knockout mice exhibited more severe blood-brain barrier (BBB) disruption, with microvascular endothelial cells exhibiting greater VEGF expression and lower ratios of phospo-Akt/Akt and phospo-mTOR/mTOR than in Ctsk +/+ mice. This study is the first to provide molecular insights into Ctsk-regulated HT after cerebral ischaemia, suggesting that Ctsk deficiency may disrupt the BBB via Akt/mTOR/VEGF signalling, resulting in neurological deficits and neuron apoptosis. Ctsk administration has the potential as a novel modality for improving the safety of rtPA treatment following stroke.

Background Exposure to chronic psychosocial stress is a risk factor for atherosclerosis-based cardiovascular disease. We previously demonstrated the increased expressions of cathepsin S (CatS) in atherosclerotic lesions. Whether CatS participates directly in stress-related neointimal hyperplasia has been unknown. Methods and Results Male wild-type and CatS-deficient mice that underwent carotid ligation injury were subjected to chronic immobilization stress for morphological and biochemical studies at specific times. On day 14 after stress/surgery, stress enhanced the neointima formation. At the early time points, the stressed mice had increased plaque elastin disruption, cell proliferation, macrophage accumulation, mRNA and/or protein levels of vascular cell adhesion molecule-1, angiotensin II type 1 receptor, monocyte chemoattractant protein-1, gp91 phox , stromal cell-derived factor-1, C-X-C chemokine receptor-4, toll-like receptor-2, toll-like receptor-4, SC 35, galectin-3, and CatS as well as targeted intracellular proliferating-related molecules (mammalian target of rapamycin, phosphorylated protein kinase B, and p-glycogen synthase kinase-3α/β). Stress also increased the plaque matrix metalloproteinase-9 and matrix metalloproteinase-2 mRNA expressions and activities and aorta-derived smooth muscle cell migration and proliferation. The genetic or pharmacological inhibition of CatS by its specific inhibitor (Z- FL -COCHO) ameliorated the stressed arterial targeted molecular and morphological changes and stressed aorta-derived smooth muscle cell migration. Both the genetic and pharmacological interventions had no effect on increased blood pressure in stressed mice. Conclusions These results demonstrate an essential role of CatS in chronic stress-related neointimal hyperplasia in response to injury, possibly via the reduction of toll-like receptor-2/toll-like receptor-4-mediated inflammation, immune action, and smooth muscle cell proliferation, suggesting that CatS will be a novel therapeutic target for stress-related atherosclerosis-based cardiovascular disease.

Adipose tissue browning and systemic energy expenditure provide a defense mechanism against obesity and associated metabolic diseases. In high-cholesterol Western diet-fed mice, mast cell (MC) inactivation ameliorates obesity and insulin resistance and improves the metabolic rate, but a direct role of adipose tissue MCs in thermogenesis and browning remains unproven. Here, we report that adrenoceptor agonist norepinephrine-stimulated metabolic rate and subcutaneous adipose tissue (SAT) browning are enhanced in MC-deficient Kit w-sh/w-sh mice and MC-stabilized wild-type mice on a chow diet. MC reconstitution to SAT in Kit w-sh/w-sh mice blocks these changes. Mechanistic studies demonstrate that MC inactivation elevates SAT platelet-derived growth factor receptor A (PDGFRα + ) adipocyte precursor proliferation and accelerates beige adipocyte differentiation. Using the tryptophan hydroxylase 1 (TPH1) inhibitor and TPH1-deficient MCs, we show that MC-derived serotonin inhibits SAT browning and systemic energy expenditure. Functional inactivation of MCs or inhibition of MC serotonin synthesis in SAT promotes adipocyte browning and systemic energy metabolism in mice., (Copyright © 2019 The Author(s). Published by Elsevier Inc. All rights reserved.)

Mast cell (MC) deficiency in Kit W-sh/W-sh mice and inhibition with disodium chromoglycate (DSCG) or ketotifen reduced obesity and diabetes in mice on a high-cholesterol (1.25%) Western diet. Yet, Kit-independent MC-deficient mice and mice treated with DSCG disproved MC function in obesity and diabetes when mice are fed a high-fat diet (HFD) that contains no cholesterol. This study reproduced the obesity and diabetes inhibitory activities of DSCG and ketotifen from mice on a Western diet. Yet, such inhibitory effects were diminished in mice on the HFD. DSCG and ketotifen MC inhibitory activities were recovered from mice on the HFD supplemented with the same amount of cholesterol (1.25%) as that in the Western diet. DSCG and ketotifen effectively blunted the high-cholesterol diet-induced elevations of blood histamine and adipose tissue MC degranulation. Pearson's correlation test demonstrated significant and positive correlations between plasma histamine and total cholesterol or low-density lipoprotein-cholesterol (LDL). In cultured bone marrow-derived MCs, plasma from mice following a Western diet or a cholesterol-supplemented HFD, but not those from HFD-fed mice, induced MC degranulation and the release of β-hexosaminidase, histamine, and serotonin. IgE, LDL, very low-density lipoprotein, and high-density lipoprotein also induced MC activation, which can be inhibited by DSCG and ketotifen depending on the doses and types of MC inhibitors and cholesterol, and also the MC granule molecules of interest. DSCG or ketotifen lost their activities in inhibiting LDL-induced activation of MCs from LDL receptor-deficient mice. These results indicate that dietary cholesterol critically influences the function of mouse MCs., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Mast cells (MCs) have been implicated in the pathogenesis of cardiometabolic diseases by releasing pro-inflammatory mediators. Patients and animals with diabetic cardiomyopathy (DCM) also show inflammatory cell accumulation in the heart. Here, we detected MCs in mouse heart after streptozotocin (STZ)-induced DCM. DCM production caused significant systole and diastole interventricular septum and left ventricular (LV) posterior wall thinning, and systolic LV internal dilation in wild-type (WT) mice. DCM production also led to significant reductions of fractional shortening percentage, heart rate, body weight, heart weight, and significant increases of kidney, pancreas, and lung weight to body weight ratios, and blood hemoglobin HbA1c and glucose levels in WT mice. All these changes were improved or disappeared in MC-deficient Kit W-sh/W-sh mice. In the myocardium from WT DCM mice, we detected significant decrease of cardiac cell proliferation and increases of cardiac cell death, chemokine expression, macrophage infiltration, inflammatory cytokine expression, and collagen deposition. These changes were also improved or disappeared in Kit W-sh/W-sh DCM mice. Adoptive transfer of bone marrow-derived MCs (BMMCs) from WT mice fully or partially reversed these cardiac functional and morphologic changes in Kit W-sh/W-sh DCM recipient mice. Yet, adoptive transfer of BMMCs from Il6 -/- and Tnf -/- mice failed to make these corrections or at much less extent than the WT BMMCs. Mechanistic studies demonstrated a role of MC and MC-derived IL6 and TNF-α in promoting cardiomyocyte death and cardiac fibroblast TGF-β signaling, and collagen synthesis and deposition. Therefore, MC inhibition may have therapeutic potential in attenuating DCM progression., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Mouse mast cell protease-4 (mMCP4) is a chymase that has been implicated in cardiovascular diseases, including myocardial infarction (MI). This study tested a direct role of mMCP4 in mouse post-MI cardiac dysfunction and myocardial remodeling. Immunoblot and immunofluorescent double staining demonstrated mMCP4 expression in cardiomyocytes from the infarct zone from mouse heart at 28 day post-MI. At this time point, mMCP4-deficient Mcpt4 -/- mice showed no difference in survival from wild-type (WT) control mice, yet demonstrated smaller infarct size, improved cardiac functions, reduced macrophage content but increased T-cell accumulation in the infarct region compared with those of WT littermates. mMCP4-deficiency also reduced cardiomyocyte apoptosis and expression of TGF-β1, p-Smad2, and p-Smad3 in the infarct region, but did not affect collagen deposition or α-smooth muscle actin expression in the same area. Gelatin gel zymography and immunoblot analysis revealed reduced activities of matrix metalloproteinases and expression of cysteinyl cathepsins in the myocardium, macrophages, and T cells from Mcpt4 -/- mice. Immunoblot analysis also found reduced p-Smad2 and p-Smad3 in the myocardium from Mcpt4 -/- mice, yet fibroblasts from Mcpt4 -/- mice showed comparable levels of p-Smad2 and p-Smad3 to those of WT fibroblasts. Flow cytometry, immunoblot analysis, and immunofluorescent staining demonstrated that mMCP4-deficiency reduced the expression of proapoptotic cathepsins in cardiomyocytes and protected cardiomyocytes from H 2 O 2 -induced apoptosis. This study established a role of mMCP4 in mouse post-MI dysfunction by regulating myocardial protease expression and cardiomyocyte death without significant impact on myocardial fibrosis or survival post-MI in mice., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Objective- Inflammation occurs during the progression of abdominal aortic aneurysm (AAA). IL (interleukin)-33 is a pleiotropic cytokine with multiple immunomodulatory effects, yet its role in AAA remains unknown. Approach and Results- Immunoblot, immunohistochemistry, and immunofluorescent staining revealed increased IL-33 expression in adventitia fibroblasts from mouse AAA lesions. Daily intraperitoneal administration of recombinant IL-33 or transgenic IL-33 expression ameliorated periaorta CaPO 4 injury- and aortic elastase exposure-induced AAA in mice, as demonstrated by blunted aortic expansion, reduced aortic wall elastica fragmentation, enhanced AAA lesion collagen deposition, attenuated T-cell and macrophage infiltration, reduced inflammatory cytokine production, skewed M2 macrophage polarization, and reduced lesion MMP (matrix metalloproteinase) expression and cell apoptosis. Flow cytometry analysis, immunostaining, and immunoblot analysis showed that exogenous IL-33 increased CD4 + Foxp3 + regulatory T cells in spleens, blood, and aortas in periaorta CaPO 4 -treated mice. Yet, ST2 deficiency muted these IL-33 activities. Regulatory T cells from IL-33-treated mice also showed significantly stronger activities in suppressing smooth muscle cell inflammatory cytokine and chemokine expression, macrophage MMP expression, and in increasing M2 macrophage polarization than those from vehicle-treated mice. In contrast, IL-33 failed to prevent AAA and lost its beneficial activities in CaPO 4 -treated mice after selective depletion of regulatory T cells. Conclusions- Together, this study established a role of IL-33 in protecting mice from AAA formation by enhancing ST2-dependent aortic and systemic regulatory T-cell expansion and their immunosuppressive activities.

Background: Extracellular matrix metabolism and cardiac cell death participate centrally in myocardial infarction (MI). This study tested the roles of collagenolytic cathepsin K (CatK) in post-MI left ventricular remodeling., Methods and Results: Patients with acute MI had higher plasma CatK levels (20.49 ± 7.07 pmol/L, n = 26) than those in subjects with stable angina pectoris (8.34 ± 1.66 pmol/L, n = 28, P = .01) or those without coronary heart disease (6.63 ± 0.84 pmol/L, n = 93, P = .01). CatK protein expression increases in mouse hearts at 7 and 28 days post-MI. Immunofluorescent staining localized CatK expression in cardiomyocytes, endothelial cells, fibroblasts, macrophages, and CD4 + T cells in infarcted mouse hearts at 7 days post-MI. To probe the direct participation of CatK in MI, we produced experimental MI in CatK-deficient mice (Ctsk -/- ) and their wild-type (Ctsk +/+ ) littermates. CatK-deficiency yielded worsened cardiac function at 7 and 28 days post-MI, compared to Ctsk +/+ littermates (fractional shortening percentage: 5.01 ± 0.68 vs. 8.62 ± 1.04, P < .01, 7 days post-MI; 4.32 ± 0.52 vs. 7.60 ± 0.82, P < .01, 28 days post-MI). At 7 days post-MI, hearts from Ctsk -/- mice contained less CatK-specific type-I collagen fragments (10.37 ± 1.91 vs. 4.60 ± 0.49 ng/mg tissue extract, P = .003) and more fibrosis (1.67 ± 0.93 vs. 0.69 ± 0.20 type-III collagen positive area percentage, P = .01; 14.25 ± 4.12 vs. 6.59 ± 0.79 α-smooth muscle actin-positive area percentage, P = .016; and 0.82 ± 0.06 vs. 0.31 ± 0.08 CD90-positive area percentage, P = .008) than those of Ctsk +/+ mice. Immunostaining demonstrated that CatK-deficiency yielded elevated cardiac cell death but reduced cardiac cell proliferation. In vitro studies supported a role of CatK in cardiomyocyte survival., Conclusion: Plasma CatK levels are increased in MI patients. Heart CatK expression is also elevated post-MI, but CatK-deficiency impairs post-MI cardiac function in mice by increasing myocardial fibrosis and cardiomyocyte death., (Copyright © 2018. Published by Elsevier Ltd.)

Background: To explore the associations of frailty phenotype and frailty index (FI) defined frailty and pre-frailty with mortality in a Chinese elderly population., Methods: Data of 1788 community-dwelling elders aged 70-84 years from the ageing arm of Rugao Longevity and Ageing Study, a prospective cohort study, were used. Frailty phenotype was defined using modified Fried's phenotype (FP) criteria and FI was constructed using 45 health deficits. Mortality was ascertained using the Death Registry of Rugao's Civil Affairs Bureau., Results: During 3-year follow-up, 149 (8.3%) of the 1788 elderly subjects died. For frailty phenotype, about 9.5% of the elderly were frail and 43% were pre-frail. For FI, frail (FI > 0.21) was approximately 27.5%, and pre-frail (FI: 0.1-0.21) was approximately 51.3%. Highest mortality was observed among frail participants defined by both FP and FI criteria (all Log Rank P < 0.05). Frailty defined by the frailty index was associated with a 2.31 fold (95% CI 1.16-4.6) risk of all-cause death compared with robust elderly. Compared with the robust elderly, not only frailty (HR 2.24, 95% CI 1.31-3.83) defined by frailty phenotype but also pre-frailty (HR 1.51, 95% CI 1.03-2.21) was associated with risk of all-cause mortality., Conclusions: Frailty, defined by either phenotype or index, is associated with increased risks of mortality in elderly Chinese community population., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Objective/background: The development of an abdominal aortic aneurysm (AAA) involves extensive extracellular matrix remodelling, leading to aortic wall weakening. This process is mediated by proteases, including cysteinyl cathepsins. Cystatins are their endogenous inhibitors. This study tested whether plasma cystatin B levels in patients with AAA differed from those of healthy controls., Methods: Plasma samples from patients with AAA and age matched controls were selected from the Viborg Vascular (VIVA) screening trial for AAA. Enzyme linked immunosorbent assay determined plasma cystatin B. T-test, logistic regression, Pearson's correlation and Cox regression tested whether plasma cystatin B correlates with AAA size and growth rate, or serves as a marker for AAA., Results: Plasma cystatin B levels were significantly higher in patients with AAA than in controls (p < 0.001). Logistic regression analysis showed that cystatin B tertile at baseline was associated with the presence of AAA before (odds ratio [OR] 1.656; p < 0.001) and after adjustment for peripheral arterial disease (PAD), chronic obstructive pulmonary disease (COPD), and previous ischaemic events (OR 1.526; p < 0.001). A t-test showed a significant association between cystatin B and PAD at screening, hospital diagnosis of COPD, previous atherosclerotic events, and use of low dose aspirin. Pearson's correlation test showed positive and significant associations between cystatin B and AAA size (r = 0.15; p < 0.001). Cox regression test showed that plasma cystatin B tertile at baseline was associated with later AAA surgical repair before (hazard ratio [HR] 1.387; p < 0.001) and after adjustment for PAD, COPD, previous ischaemic event, and maximum infrarenal aortic diameter (HR 1.523; p < 0.001)., Conclusion: In contrast to prior studies that showed that cystatin C is negatively associated with AAA development, this study demonstrated a positive association between cystatin B and AAA size and associations between cystatin B tertile at baseline and AAA presence and need for later surgical repair. It is possible that these two cystatins inhibit cathepsin activity and participate in AAA with different mechanisms., (Copyright © 2018 European Society for Vascular Surgery. Published by Elsevier B.V. All rights reserved.)

This study aimed to determine the expression of circRNAs in plasma from lupus nephritis (LN) patients to identify novel biomarkers for LN screening. We initially performed microarray screening of circRNA changes in plasma from 5 L N patients, 5 systemic lupus erythematosus (SLE) patients without LN, and 5 healthy controls. We then confirmed the selected circRNA changes in plasma from 59 SLE patients (30 with LN and 29 without LN), 26 rheumatoid arthritis (RA) patients, and 27 age- and sex-matched controls using real-time quantitative reverse transcription-polymerase chain reaction. Spearman's correlation test was performed to assess the correlation of circRNAs and clinical variables. The receiver operating characteristic (ROC) curve was created to evaluate the diagnostic value. We confirmed that plasma circRNA&#95;002453 was significantly elevated in LN patients when compared with SLE patients without LN, RA patients, and healthy controls. Plasma circRNA&#95;002453 was also found to be upregulated in SLE patients when compared with RA patients and healthy controls. Among these LN patients, we detected no significant correlation between plasma circRNA&#95;002453 and disease activity, including complement 3 (C3), complement 4 (C4), and SLE disease activity index 2000 (SLEDAI-2 K) score. However, its expression level was significantly and positively correlated with 24-hour proteinuria (r = 0.571, p = 0.001) and renal SLEDAI score (r = 0.640, p < 0.001). ROC analysis showed that plasma circRNA&#95;002453 had an area under the curve of 0.906 (95% CI 0.838-0.974, p < 0.001) to discriminate LN patients from controls (SLE patients without LN, RA patients, and healthy controls) with sensitivity of 0.900 and specificity of 0.841. The highest Youden index was 0.741 and the corresponding optimal cut-off value was 0.001. This study suggests that upregulated plasma circRNA&#95;002453 level in LN patients is associated with the severity of renal involvement and may also serve as a potential biomarker for LN patient diagnosis., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Interleukin (IL)-22 regulates tissue inflammation and repair. Here we report participation of the liver in IL-22-mediated cardiac repair after acute myocardial infarction (MI). Methods: We induced experimental MI in mice by ligation of the left ascending artery and evaluated the effect of IL-22 on post-MI cardiac function and ventricular remodeling. Results: Daily subcutaneous injection of 100 µg/kg mouse recombinant IL-22 for seven days attenuated adverse ventricular remodeling and improved cardiac function in mice at 28 days after left anterior descending coronary artery ligation-induced MI. Pharmacological inhibition of signal transducer and activator of transcription (STAT3) muted these IL-22 activities. While cardiomyocyte-selective depletion of STAT3 did not affect IL-22 activities in protecting post-MI cardiac injury, hepatocyte-specific depletion of STAT3 fully muted these IL-22 cardioprotective activities. Hepatocyte-derived fibroblast growth factor (FGF21) was markedly increased in a STAT3-dependent manner following IL-22 administration and accounted for the cardioprotective benefit of IL-22. Microarray analyses revealed that FGF21 controlled the expression of cardiomyocyte genes that are involved in cholesterol homeostasis, DNA repair, peroxisome, oxidative phosphorylation, glycolysis, apoptosis, and steroid responses, all of which are responsible for cardiomyocyte survival. Conclusions: Supplementation of IL-22 in the first week after acute MI effectively prevented left ventricular dysfunction and heart failure. This activity of IL-22 involved crosstalk between the liver and heart after demonstrating a role of the hepatic STAT3-FGF21 axis in IL-22-induced post-MI cardiac protection., Competing Interests: Competing Interests: Recombinant mouse IL-22 was provided by Generon (Shanghai, China) Corporation Ltd in the present study.

Cysteine protease cathepsins have traditionally been considered as lysosome-restricted proteases that mediate proteolysis of unwanted proteins. However, studies from the past decade demonstrate that these proteases are localized not only in acidic compartments (endosomes and lysosomes), where they participate in intracellular protein degradation, but also in the extracellular milieu, plasma membrane, cytosol, nucleus, and nuclear membrane, where they mediate extracellular matrix protein degradation, cell signalling, and protein processing and trafficking through the plasma and nuclear membranes and between intracellular organelles. Studies in experimental disease models and on cathepsin-selective inhibitors, as well as plasma and tissue biomarker data from animal models and humans, have verified the participation of cysteinyl cathepsins in the pathogenesis of many cardiovascular diseases, including atherosclerosis, myocardial infarction, cardiac hypertrophy, cardiomyopathy, abdominal aortic aneurysms, and hypertension. Clinical trials of cathepsin inhibitors in chronic inflammatory diseases suggest the utility of these inhibitors for the treatment of cardiovascular diseases and associated complications. Moreover, development of cell transfer technologies that enable ex vivo cell treatment with cathepsin inhibitors might limit the unwanted systemic effects of cathepsin inhibition and provide new avenues for targeting cysteinyl cathepsins. In this Review, we summarize the available evidence implicating cysteinyl cathepsins in the pathogenesis of cardiovascular diseases, discuss their potential as biomarkers of disease progression, and explore the potential of cathepsin inhibitors for the treatment of cardiovascular diseases.

Objective: To examine the associations of the actinin alpha 3 gene (ACTN3) R577X polymorphism with physical performance and frailty in an older Chinese population., Methods: Data from 1,463 individuals (57.8% female) aged 70-87 years from the Rugao Longevity and Ageing Study were used. The associations between R577X and timed 5-m walk, grip strength, timed Up and Go test, and frailty index (FI) based on deficits of 23 laboratory tests (FI-Lab) were examined. Analysis of variance and linear regression models were used to evaluate the genetic effects of ACTN3 R577X on physical performance and FI-Lab., Results: The XX and RX genotypes of the ACTN3 R557X polymorphism accounted for 17.1 and 46.9%, respectively. Multivariate regression analysis revealed that in men aged 70-79 years, the ACTN3 577X allele was significantly associated with physical performance (5-m walk time, regression coefficient (β) = 0.258, P = 0.006; grip strength, β = -1.062, P = 0.012; Up and Go test time β = 0.368, P = 0.019). In women aged 70-79 years, a significant association between the ACTN3 577X allele and the FI-Lab score was observed, with a regression coefficient of β = 0.019 (P = 0.003). These findings suggest an age- and gender-specific X-additive model of R577X for 5-m walk time, grip strength, Up and Go Test time, and FI-Lab score., Conclusion: The ACTN3 577X allele is associated with an age- and sex-specific decrease in physical performance and an increase in frailty in an older population.

Background: Risk factors for heart rate-corrected QT interval (QTc) proglongation should be explored to stratify high-risk individuals to aid the prevention of incident cardiovascular events and mortality. The diversity of risk factors for QTc prolongation suggests that use of the frailty index (FI), indicating general health deficits, may be an effective approach, especially in the elderly, to identify the risk of QTc prolongation., Methods: We used the data of 1,780 individuals aged 70-87 years from the Rugao Longevity and Ageing Study (RuLAS), a community-based longitudinal study. The FI was constructed using 20 routine laboratory tests, plus the body mass index and measures of systolic and diastolic blood pressures (FI-Lab)., Results: The mean FI-Lab value was 0.24±0.09. The mean heart rate-corrected QT interval (QTc) was 407±38 ms. The prevalence of QTc prolongation was 5.2% in elderly community populations aged 70-87 years. A higher FI-Lab value was associated with a higher risk for QTc prolongation. Each 10% increase in the FI-Lab value increased the odds ratio (OR) by 33% (OR: 1.33; 95% CI: 1.07-1.64). Compared with the lowest quartile, the top quartile FI-Lab score was associated with a 2.50-fold QTc prolongation risk in elderly individuals (95% CI: 1.21-5.19)., Conclusion: An FI based on routine laboratory data can identify older adults at increased risk for QTc prolongation. The FI approach may therefore be useful for the risk stratification of QTc prolongation., Competing Interests: Disclosure The authors report no conflicts of interest in this work.

Background: Cathepsin K (CatK) is a widely expressed cysteine protease that has gained attention because of its enzymatic and non-enzymatic functions in signalling. Here, we examined whether CatK-deficiency (CatK -/- ) would mitigate injury-related skeletal muscle remodelling and fibrosis in mice, with a special focus on inflammation and muscle cell apoptosis., Methods: Cardiotoxin (CTX, 20 μM/200 μL) was injected into the left gastrocnemius muscle of male wild-type (CatK +/+ ) and CatK -/- mice, and the mice were processed for morphological and biochemical studies., Results: On post-injection Day 14, CatK deletion ameliorated muscle interstitial fibrosis and remodelling and performance. At an early time point (Day 3), CatK -/- reduced the lesion macrophage and leucocyte contents and cell apoptosis, the mRNA levels of monocyte chemoattractant protein-1, toll-like receptor-2 and toll-like receptor-4, and the gelatinolytic activity related to matrix metalloproteinase-2/-9. CatK deletion also restored the protein levels of caspase-3 and cleaved caspase-8 and the ratio of the BAX to the Bcl-2. Moreover, CatK deficiency protected muscle fibre laminin and desmin disorder in response to CTX injury. These beneficial muscle effects were mimicked by CatK-specific inhibitor treatment. In vitro experiments demonstrated that pharmacological CatK inhibition reduced the apoptosis of C2C12 mouse myoblasts and the levels of BAX and caspase-3 proteins induced by CTX., Conclusions: These results demonstrate that CatK plays an essential role in skeletal muscle loss and fibrosis in response to CTX injury, possibly via a reduction of inflammation and cell apoptosis, suggesting a novel therapeutic strategy for the control of skeletal muscle diseases by regulating CatK activity., (© 2017 The Authors. Journal of Cachexia, Sarcopenia and Muscle published by John Wiley & Sons Ltd on behalf of the Society on Sarcopenia, Cachexia and Wasting Disorders.)

Background: MicroRNAs (miRNAs) can play important roles in inflammation and infection, which are common manifestations of acute respiratory distress syndrome (ARDS). We assessed if whole blood miRNAs were potential diagnostic biomarkers for human ARDS., Methods: This nested case-control study (N = 530) examined a cohort of ARDS patients and critically ill at-risk controls. Whole blood miRNA profiles and logistic regression analyses identified miRNAs correlated with ARDS. Stratification analysis also assessed selected miRNA markers for their role in sepsis and pneumonia associated with ARDS. Receiver operating characteristic (ROC) analysis evaluated miRNA diagnostic performance, along with Lung Injury Prediction Score (LIPS)., Results: Statistical analyses were performed on 294 miRNAs, selected from 754 miRNAs after quality control screening. Logistic regression identified 22 miRNAs from a 156-patient discovery cohort as potential risk or protective markers of ARDS. Three miRNAs-miR-181a, miR-92a, and miR-424-from the discovery cohort remained significantly associated with ARDS in a 373-patient independent validation cohort (FDR q < 0.05) and meta-analysis (p < 0.001). ROC analyses demonstrated a LIPS baseline area-under-the-curve (AUC) value of ARDS of 0.708 (95% CI 0.651-0.766). Addition of miR-181a, miR-92a, and miR-424 to LIPS increased baseline AUC to 0.723 (95% CI 0.667-0.778), with a relative integrated discrimination improvement of 2.40 (p = 0.005) and a category-free net reclassification index of 27.21% (p = 0.01)., Conclusions: miR-181a and miR-92a are risk biomarkers for ARDS, whereas miR-424 is a protective biomarker. Addition of these miRNAs to LIPS can improve the risk estimate for ARDS.

Background: Coronary heart disease (CHD) is characterized by arterial wall inflammation and matrix degradation. Matrix metalloproteinase (MMP)-22 and -29 and pro-inflammatory cytokine interleukin-18 (IL18) are present in human hearts. IL18 may regulate MMP-22 and -29 expression, which may correlate with CHD progression., Methods and Results: Immunoblot analysis showed that IL18 induced MMP-22 expression in human aortic smooth muscle cells. The Mann Whitney test from a prospective study of 194 CHD patients and 68 non-CHD controls demonstrated higher plasma levels of IL18, MMP-22 and -29 in CHD patients than in the controls. A logistic regression test suggested that plasma IL18 (odds ratio (OR)=1.131, P=0.007), MMP-22 (OR=1.213, P=0.040), and MMP-29 (OR=1.198, P=0.033) were independent risk factors of CHD. Pearson's correlation test showed that IL18 (coefficient (r)=0.214, P=0.045; r=0.246, P=0.031) and MMP-22 (r=0.273, P=0.006; r=0.286, P=0.012) were associated with the Gensini score before and after adjusting for potential confounding factors. The multivariate Pearson's correlation test showed that plasma MMP-22 levels correlated positively with high-sensitive-C-reactive protein (hs-CRP) (r=0.167, P=0.023), and MMP-29 levels correlated negatively with triglyceride (r=-0.169, P=0.018). Spearman's correlation test indicated that plasma IL18 levels associated positively with plasma MMP-22 (r=0.845, P<0.001) and MMP-29 (r=0.548, P<0.001)., Conclusions: Our observations suggest that IL18, MMP-22 and -29 serve as biomarkers and independent risk factors of CHD. Increased systemic IL18 in CHD patients may contribute to elevated plasma MMP-22 and -29 levels in these patients.

Toll-like receptor 7 (TLR7) mediates autoantigen and viral RNA-induced cytokine production. Increased TLR7 expression in human atherosclerotic lesions suggests its involvement in atherogenesis. Here we demonstrated TLR7 expression in macrophages, smooth muscle cells (SMCs), and endothelial cells from mouse atherosclerotic lesions. To test a direct participation of TLR7 in atherosclerosis, we crossbred TLR7-deficient (Tlr7 -/- ) mice with apolipoprotein E-deficient (Apoe -/- ) mice and produced Apoe -/- Tlr7 -/- and Apoe -/- Tlr7 +/+ littermates, followed by feeding them an atherogenic diet to produce atherosclerosis. Compared to Apoe -/- Tlr7 +/+ mice, Apoe -/- Tlr7 -/- mice showed reduced aortic arch and sinus lesion areas. Reduced atherosclerosis in Apoe -/- Tlr7 -/- mice did not affect lesion macrophage-positive area and CD4 + T-cell number per lesion area, but reduced lesion expression of inflammatory markers major histocompatibility complex-class II and IL6, lesion matrix-degrading proteases cathepsin S and matrix metalloproteinase-9, and systemic serum amyloid A levels. TLR7 deficiency also reduced aortic arch SMC loss and lesion intima and media cell apoptosis. However, TLR7 deficiency did not affect aortic wall elastin fragmentation and collagen contents, or plasma lipoproteins. Therefore, TLR7 contributes to atherogenesis in Apoe -/- mice by regulating lesion and systemic inflammation. A TLR7 antagonist may mitigate atherosclerosis.

CD74 mediates MHC class-II antigenic peptide loading and presentation and plays an important role in the pathogenesis of autoimmune diseases, including systemic lupus erythematosus. C57BL/6 Fas lpr mice that develop spontaneous lupus-like autoimmunity and pathology showed elevated CD74 expression in the inflammatory cell infiltrates and the adjacent tubular epithelial cells (TECs) in kidneys affected by lupus nephritis but negligible levels in kidneys from age-matched wild-type mice. The inflammatory cytokine IFN-γ or IL-6 induced CD74 expression in kidney TECs in vitro. The presence of kidney TECs from Fas lpr mice, rather than from wild-type mice, produced significantly stronger histones, dsDNA, and ribonucleoprotein-Smith Ag complex-induced CD4 + T cell activation. Splenocytes from CD74-deficient Fas lpr Cd74 -/- mice had muted responses in a MLR and to the autoantigen histones. Compared with Fas lpr Cd74 +/+ mice, Fas lpr Cd74 -/- mice had reduced kidney and spleen sizes, splenic activated T cells and B cells, serum IgG and autoantibodies, urine albumin/creatinine ratio, kidney Periodic acid-Schiff score, IgG and C3 deposition, and serum IL-6 and IL-17A levels, but serum IL-2 and TGF-β levels were increased. Study of chronic graft-versus-host C57BL/6 mice that received donor splenocytes from B6.C- H2 bm12 /KhEg mice and those that received syngeneic donor splenocytes yielded similar observations. CD74 deficiency reduced lupus-like autoimmunity and kidney pathology in chronic graft-versus-host mice. This investigation establishes the direct participation of CD74 in autoimmunity and highlights a potential role for CD74 in kidney TECs, together with professional APCs in systemic lupus erythematosus., (Copyright © 2017 by The American Association of Immunologists, Inc.)