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The human innate immune system recognizes dsRNA as a pathogen‐associated molecular pattern that induces a potent inflammatory response. The primary source of pathogenic dsRNA is cells infected with replicating viruses, but can also be released from uninfected necrotic cells. Here, we show that the dsRNA poly(I:C) challenge in human macrophages activates the p38 MAPK‐MK2 signalling pathway and subsequently the phosphorylation of tristetraprolin (TTP/ZFP36). The latter is an mRNA decay‐promoting protein that controls the stability of AU‐rich mRNAs (AREs) that code for many inflammatory mediators. Hydroxychloroquine (HCQ), a common anti‐malaria drug, is used to treat inflammatory and autoimmune disorders and, controversially, during acute COVID‐19 disease. We found that HCQ reduced the dsRNA‐dependent phosphorylation of p38 MAPK and its downstream kinase MK2. Subsequently, HCQ reduced the abundance and protein stability of the inactive (phosphorylated) form of TTP. HCQ reduced the levels and the mRNA stability of poly (I:C)‐induced cytokines and inflammatory mRNAs like TNF, IL‐6, COX‐2, and IL‐8 in THP‐1 and primary blood monocytes. Our results demonstrate a new mechanism of the anti‐inflammatory role of HCQ at post‐transcriptional level (TTP phosphorylation) in a model of dsRNA activation, which usually occurs in viral infections or RNA release from necrotic tissue. [ABSTRACT FROM AUTHOR]

Abstract Immune evasion of Mycobacterium tuberculosis (Mtb) facilitates intracellular bacterial growth. The mechanisms of immune evasion, however, are still not fully understood. In this study, we reveal that tristetraprolin (TTP), one of the best characterized RNA‐binding proteins controlling the stability of targeted mRNAs, mediates innate immune evasion of mycobacteria. We found that TTP knockout mice displayed reduced bacterial burden in the early stage after Mtb aerosol challenge. Macrophages deficient in TTP also showed an inhibition in intracellular mycobacterial growth. Live mycobacteria induced TTP protein expression in macrophages, which was blocked by the mTOR inhibitor rapamycin. Rapamycin and AZD8055 specifically blocked 4EBP1 phosphorylation in infected macrophages and suppressed intracellular BCG growth. Rapamycin promoted TTP protein degradation through the ubiquitination pathway, whereas the proteasome inhibitor MG‐132 blocked rapamycin function and thus stabilized TTP protein. TTP induction suppressed the expression of iNOS/TNF‐α/IL‐12/IL‐23, and weakened protective immune responses in macrophages, whereas rapamycin enhanced the bactericidal effects through TTP inhibition. Moreover, blocking TTP binding increased the expression of TNF‐α and iNOS and suppressed intracellular mycobacterial growth. Overall, our study reveals a novel role for RNA‐binding protein TTP in Mtb immune evasion mechanisms and provides a potential target for host‐directed therapy against tuberculosis (TB).

Immune evasion of Mycobacterium tuberculosis (Mtb) facilitates intracellular bacterial growth. The mechanisms of immune evasion, however, are still not fully understood. In this study, we reveal that tristetraprolin (TTP), one of the best characterized RNA‐binding proteins controlling the stability of targeted mRNAs, mediates innate immune evasion of mycobacteria. We found that TTP knockout mice displayed reduced bacterial burden in the early stage after Mtb aerosol challenge. Macrophages deficient in TTP also showed an inhibition in intracellular mycobacterial growth. Live mycobacteria induced TTP protein expression in macrophages, which was blocked by the mTOR inhibitor rapamycin. Rapamycin and AZD8055 specifically blocked 4EBP1 phosphorylation in infected macrophages and suppressed intracellular BCG growth. Rapamycin promoted TTP protein degradation through the ubiquitination pathway, whereas the proteasome inhibitor MG‐132 blocked rapamycin function and thus stabilized TTP protein. TTP induction suppressed the expression of iNOS/TNF‐α/IL‐12/IL‐23, and weakened protective immune responses in macrophages, whereas rapamycin enhanced the bactericidal effects through TTP inhibition. Moreover, blocking TTP binding increased the expression of TNF‐α and iNOS and suppressed intracellular mycobacterial growth. Overall, our study reveals a novel role for RNA‐binding protein TTP in Mtb immune evasion mechanisms and provides a potential target for host‐directed therapy against tuberculosis (TB). [ABSTRACT FROM AUTHOR]

Early brain injury (EBI) following subarachnoid hemorrhage (SAH) can lead to inflammation and neuronal dysfunction. There is a need for effective strategies to mitigate these effects and improve the outcome of patients who experience SAH. The mRNA-destabilizing protein tristetraprolin (TTP) is an anti-inflammatory factor that induces the decay of cytokine transcripts and has been implicated in diseases such as glioma. However, the mechanism of action of TTP in EBI after SAH is unclear. The present study investigated the effects of TTP regulation via phosphorylation in a rat model of SAH by protein phosphatase (PP)2A, which is a pleiotropic enzyme complex with multiple substrate phospho-proteins. We hypothesized that inhibitory phosphorylation of TTP by PP2A would reduce neuroinflammation and apoptosis. To evaluate the function of each factor, the PP2A agonist FTY720, short interfering (si)RNAs targeting TTP and PP2A were administered to rats by intracerebroventricular injection 24 h before SAH. Rats were evaluated with SAH grade, neurological score, brain water content and by western blotting, and terminal deoxynucleotidyltransferase dUTP nick-end labeling. We found that endogenous PP2A and TTP levels were increased after SAH. FTY720 induced PP2A activation would lead to dephosphorylation and activation of TTP and decreased production of tumor necrosis factor (TNF)-a, interleukin (IL)-6, and IL-8. SiRNA-mediated TTP knockdown abolished anti-inflammatory effects of FTY720 treatment, indicating that PP2A was associated with TTP activation in vivo. Decreased TNF-a, IL-6, and IL-8 levels were associated with improvement of neurological function, reduction of brain edema, suppression of caspase-3, and up-regulation of B cell lymphoma-2. These results demonstrated that PP2A activation could enhance the anti-inflammatory and anti-apoptotic effects of TTP, by which it might shed light on the development of an effective therapeutic strategy against EBI following SAH. [ABSTRACT FROM AUTHOR]

Cellular metabolism is tightly regulated by growth factor signaling, which promotes metabolic rewiring to support growth and proliferation. While growth factor-induced transcriptional and post-translational modes of metabolic regulation have been well defined, whether post-transcriptional mechanisms impacting mRNA stability regulate this process is less clear. Here, we present the ZFP36/L1/L2 family of RNA-binding proteins and mRNA decay factors as key drivers of metabolic regulation downstream of acute growth factor signaling. We quantitatively catalog metabolic enzyme and nutrient transporter mRNAs directly bound by ZFP36 following growth factor stimulation-many of which encode rate-limiting steps in metabolic pathways. Further, we show that ZFP36 directly promotes the mRNA decay of Enolase 2 (Eno2), altering Eno2 protein expression and enzymatic activity, and provide evidence of a ZFP36/Eno2 axis during VEGF-stimulated developmental retinal angiogenesis. Thus, ZFP36-mediated mRNA decay serves as an important mode of metabolic regulation downstream of growth factor signaling within dynamic cell and tissue states.

Objective To investigate the role and mechanism of zinc finger protein 281 (ZNF281) in high glucose (HG)-induced epithelial-mesenchymal transition (EMT) and extracellular matrix (ECM) synthesis in renal tubular epithelial cells (RTECs). Methods HG induced RTECs were used to construct a diabetic kidney disease cell model, and cells were divided into the control group, the HG group and the mannitol group. Cell proliferation viability was detected by CCK-8. The expression of ZNF281 was knocked down in HG-treated RTECs using small interfering RNA (siRNA). HG-induced RTECs after knockdown of ZNF281 were divided into the control group, the HG group, the HG+ZNF281 siRNA group and the HG+ ZNF281 vector group. Adenosine monophosphate-activated protein kinase (AMPK) was activated using AMPK agonist, acadexin (AICAR), and then cells were divided into the control group, the HG group, the HG+AICAR group and the HG+ dimethyl sulfoxide group. The expression levels of ZNF281, EMT and ECM synthesis-related indexes were detected by qPCR and Western blot assay. Results Compared with the control group, the protein and mRNA expression levels of vimentin, α-smooth muscle actin (α-SMA), fibronectin (FN) and collagen Ⅰ (Col Ⅰ) were significantly higher, and the expression of E-cadherin was significantly lower in the HG group. Compared with the HG group, the protein and mRNA expression levels of EMT and ECM synthesis-related indexes were significantly changed in the HG+ZNF281 siRNA group and the HG+AICAR group. The protein and mRNA expression levels of ZNF281 were significantly reduced in the HG+ AICAR group compared with the HG group. In cells co-treated with AICAR and transfected with ZNF281 plasmid, the expression levels of vimentin, α -SMA, FN and Col Ⅰ were significantly higher in the AICAR+ZNF281 group, and E-cadherin was significantly lower compared with that of the vector group. Conclusion AMPK inhibits EMT and ECM synthesis in HG-treated RTECs by negatively regulating the expression level of ZNF281. [ABSTRACT FROM AUTHOR]

Abstract Objective Tristetraprolin (TTP/ZFP36) family proteins exhibit antiinflammatory effects by destabilizing proinflammatory mRNAs. Previous studies showed that bacterial endotoxin lipopolysaccharides (LPS) stimulated TTP and tumor necrosis factor (TNF) gene expression, but less was known about LPS effects on TTP homologues and other proinflammatory gene expression in macrophages. The objective was to investigate LPS regulation of TTP family gene and TTP-targeted gene expression in mouse RAW264.7 macrophages using much higher concentrations of LPS and much longer treatment time than previous studies. Results MTT assay showed that LPS was not toxic to the cells under LPS treatment up to 1000 ng/mL for 2–24 h. LPS mildly affected the soluble protein content in the cells. qPCR assay showed that LPS stimulated TTP mRNA rapidly but not sustainably with 40, 10, and 3 fold of the DMSO control after 2, 8 and 24 h treatment, respectively. Immunoblotting confirmed qPCR results on LPS stimulation of TTP gene expression in the mouse macrophages. LPS exhibited minimal effects on ZFP36L1, ZFP36L2 and ZFP36L3 mRNA levels. LPS increased mRNA levels of TNF, COX2, GM-CSF, INFγ and IL12b up to 311, 418, 11, 9 and 4 fold, respectively. This study demonstrated that LPS did not affect macrophage viability, dramatically increased antiinflammatory TTP gene expression as well as proinflammatory TNF and COX2 gene expression but had only mild effects on TTP homologues and other proinflammatory cytokine gene expression in the mouse macrophages.

Objective To analyze the influence of cyclic RNA homologous domain interacting protein kinase 3 (circ_HIPK3) on function and morphology of myloid β-protein (Aβ) induced hippocampal neurons by targeting miR-381-3p/ zinc finger protein 217 (ZNF217) axis. Methods Hippocampal neurons of neonatal rats were prepared and divided into the control group, the Aβ group, the si NC1 group, the si HIPK3 group, the si HIPK3+inhibitor NC group, the si HIPK3+miR381-3p inhibitor group, the si HIPK3+miR-381-3p inhibitor+si NC2 group and the si HIPK3+miR-381-3p inhibitor+si ZNF217 group. Except the control group, all the other groups were modeled by 40 µmol/L Aβ1~42. qRT-PCR was used to determine the circ of hippocampal neurons circ_HIPK3, miR-381-3p and ZNF217 mRNA levels. Cell morphology was observed by transmission electron microscope, and the survival rate of hippocampal neurons was measured by CCK-8 method. Hochesst 33342 method was used to measure apoptosis of hippocampal neurons. The intracellular Ca2+ fluorescence intensity of hippocampal neurons was detected by flow cytometry. The expression levels of P-Tau, B-cell lymphoma-2 (Bcl2), Bcl-2-associated X protein (Bax), Caspase-3 and ZNF217 proteins in hippocampal neurons were measured by Western blot assay. Double luciferase reporter genes were used to analyze the targeting relationship between miR-381-3p and circ_HIPK3, ZNF217. Results In the control group, the structure of hippocampal neurons was normal, the morphology of nucleus was normal, and there were no pathological changes in mitochondria and endoplasmic reticulum. In the Aβ group, hippocampal neurons showed degenerative changes, abnormal nuclear morphology, membrane invagination, a large number of mitochondria swelling and a large number of lipid droplets vacuoles in cytoplasm. Compared with the Aβ group, the hippocampal neuronal structure was partially restored in the si HIPK3 group. Compared with the si HIPK3 group, the hippocampal neuronal structure was severely damaged in the si HIPK3+miR-381-3p inhibitor group. Compared with the si HIPK3+miR-381-3p inhibitor group, the damage of hippocampal neurons in the si HIPK3+miR-381-3p inhibitor+si ZNF217 group was reduced. Compared with the control group, the circ_HIPK3, ZNF217 mRNA and ZNF217 protein levels, apoptosis rate, Ca2+ fluorescence intensity, P-Tau, Bax, Caspase-3 protein expression of hippocampal neurons were increased in the Aβ group, and the miR-381-3p level, survival rate and Bcl-2 protein expression decreased (P＜0.05). Compared with the Aβ group, the circ_HIPK3, ZNF217 mRNA and ZNF217 protein levels, apoptosis rate, Ca2+ fluorescence intensity, P-Tau, Bax and Caspase-3 protein expression of hippocampal neurons were decreased in the si HIPK3 group, and miR-381-3p level, survival rate and Bcl-2 protein expression increased (P＜0.05). Compared with the si HIPK3 group, the circ_HIPK3, ZNF217 mRNA and ZNF217 protein levels, apoptosis rate, Ca2+ fluorescence intensity, P-Tau, Bax and Caspase-3 protein expression of hippocampal neurons in the si HIPK3+miR-381-3p inhibitor group were increased, and the miR-381-3p level, survival rate and Bcl-2 protein expression decreased (P＜0.05). Compared with the si HIPK3+miR381-3p inhibitor group, the ZNF217 mRNA and ZNF217 protein levels, apoptosis rate, Ca2+ fluorescence intensity, P-Tau, Bax and Caspase-3 protein expression of hippocampal neurons in the si HIPK3+miR-381-3p inhibitor+si ZNF217 group were decreased, and the survival rate and Bcl-2 protein expression increased (P＜0.05). miR-381-3p targeted and combined with HIPK3 and ZNF217. Conclusion circ_HIPK3 silencing may ameliorate Aβ -induced damage of hippocampal neuronal structure and function by regulating miR-381-3p/ZNF217 axis. [ABSTRACT FROM AUTHOR]

Tristetraprolin (TTP), encoded by Zfp36 in mice, is one of the best-characterized tandem zinc-finger mRNA binding proteins involved in mRNA deadenylation and decay. TTPΔARE mice lack an AU-rich motif in the 3′-untranslated regions of TTP mRNA, leading to increased TTP mRNA stability and more TTP protein, resulting in elevated mRNA decay rates of TTP targets. We examined the effect of TTP overexpression on the hematopoietic system in both young and middle-aged mice using TTPΔARE mice and found alterations in blood cell frequencies, with loss of platelets and B220 cells and gains of eosinophils and T cells. TTPΔARE mice also have skewed primitive populations in the bone marrow, with increases in myeloid-biased hematopoietic stem cells (HSCs) but decreases in granulocyte/macrophage-biased multipotent progenitors (MPP3) in both young and middle-aged mice. Changes in the primitive cells' frequencies were associated with transcriptional alterations in the TTP overexpression cells specific to age as well as cell type. Regardless of age, there was a consistent elevation of transcripts regulated by TNFα and TGFβ signaling pathways in both the stem and multipotent progenitor populations. HSCs with TTP overexpression had decreased reconstitution potential in murine transplants but generated hematopoietic environments that mitigated the inflammatory response to the collagen antibody-induced arthritis (CAIA) challenge, which models rheumatoid arthritis and other autoimmune disorders. This dampening of the inflammatory response was even present when there was only a small frequency of TTP overexpressing cells present in the middle-aged mice. We provide an analysis of the early hematopoietic compartments with elevated TTP expression in both young and middle-aged mice which inhibits the reconstitution potential of the HSCs but generates a hematopoietic system that provides dominant repression of induced inflammation. [ABSTRACT FROM AUTHOR]

Tristetraprolin (TTP; also known as NUP475, GOS24, or TIS11), encoded by Zfp36, is an RNA‐binding protein that regulates target gene expression by promoting mRNA decay and preventing translation. Although previous studies have indicated that TTP deficiency is associated with systemic inflammation and a catabolic‐like skeletal phenotype, the mechanistic underpinnings remain unclear. Here, using both TTP‐deficient (TTPKO) and myeloid‐specific TTPKO (cTTPKO) mice, we reveal that global absence or loss of TTP in the myeloid compartment results in a reduced bone microarchitecture, whereas gain‐of‐function TTP knock‐in (TTPKI) mice exhibit no significant loss of bone microarchitecture. Flow cytometry analysis revealed a significant immunosuppressive immune cell phenotype with increased monocytic myeloid‐derived suppressor cells (M‐MDSCs) in TTPKO and cTTPKO mice, whereas no significant changes were observed in TTPKI mice. Single‐cell transcriptomic analyses of bone marrow myeloid progenitor cell populations indicated a dramatic increase in early MDSC marker genes for both cTTPKO and TTPKO bone marrow populations. Consistent with these phenotypic and transcriptomic data, in vitro osteoclastogenesis analysis of bone marrow M‐MDSCs from cTTPKO and TTPKO displayed enhanced osteoclast differentiation and functional capacity. Focused transcriptomic analyses of differentiated M‐MDSCs showed increased osteoclast‐specific transcription factors and cell fusion gene expression. Finally, functional data showed that M‐MDSCs from TTP loss‐of‐function mice were capable of osteoclastogenesis and bone resorption in a context‐dependent manner. Collectively, these findings indicate that TTP plays a central role in regulating osteoclastogenesis through multiple mechanisms, including induction of M‐MDSCs that appear to regulate skeletal phenotype. [ABSTRACT FROM AUTHOR]

Inhibition of apoptosis is one of the hallmarks of cancer and is a target of various therapeutic interventions. BIRC5 is an inhibitor of apoptosis that is aberrantly expressed in cancer leading to sustained growth of tumours. Post-transcriptional control mechanisms involving RNA-binding proteins and AU-rich elements (AREs) are fundamental to many cellular processes and changes in the expression or function of these proteins can promote an aberrant and pathological phenotype. BIRC5 mRNA has an ARE in its 3' UTR making it a candidate for regulation by the RNA binding proteins tristetraprolin (TTP) and HuR (ELAVL1). In this study, we investigated the binding of TTP and HuR by RNA-immunoprecipitation assays and found that these proteins were associated with BIRC5 mRNA to varying extents. Consequently, BIRC5 expression decreased when TTP was overexpressed and apoptosis was induced. In the absence of TTP, BIRC5 mRNA was stabilized, protein expression increased and the number of apoptotic cells declined. As an ARE-mRNA stabilizing protein, recombinant HuR led to upregulation of BIRC5 expression, whereas HuR silencing was concomitant with downregulation of BIRC5 mRNA and protein and increased cell death. Survival analyses demonstrated that increased TTP and low BIRC5 expression predicted an overall better prognosis compared to dysregulated TTP and high BIRC5. Thus, the results present a novel target of ARE-mediated post-transcriptional regulation. [ABSTRACT FROM AUTHOR]

Background & objective: The kidneys are vital and complex organs responsible for maintaining normal body functions. Kidney disease or a loss of kidney function and, in severe cases, complete kidney failure disrupt whole of the body systems. Tristetraprolin (TTP ZFP36) is an RNA-binding proteins (RBP), that regulates cytokine mRNAs by specific binding of its two conserved ZF domains to adenylate-uridylate-rich elements (AREs) at the untranslated region (UTR), leading to degradation of the RNA. Recently, it was suggested that S100 A8/A9 and TTP were involved in pathogenesis of renal diseases. However, the protective roles of S100 A8/A9 and TTP in renal disease is still unclear. The primary objective of this study was to explore the involvement of S100 A8/A9 and TTP in the inflammatory response among different groups of kidney diseases. These factors may hold therapeutic value in the treatment of these diseases by targeting and modulating the inflammatory response. Methodology: The study was performed between October 2022 to April 2023. We included 150 subjects, including 30 patients with chronic kidney disease (CKD), (Female = 16, Male = 14) with mean age (58.33 ± 18.33 y), 30 patients with acute kidney injury (AKI), (Female = 15, Male = 15), with mean age (54.48 ± 18.10 y), 30 patients with diabetic nephropathy (DN), (Female = 18, Male = 12), with mean age (60.84 ± 12.38 y), 30 patients with nephrotic syndrome (NS), (Female = 13, Male = 17), with mean age (52.54 ± 14.02 y), and 30 healthy persons as a control group. NLR analysis was performed directly using the hematology analyzer CBC (Sysmex, Japan) technique, serum S100 A8/A9 were measured by ELISA, and TTP gene expression was measured by Quantitative Real Time-Polymerase Chain Reaction (RT-qPCR). Results: In comparison to the healthy control group, all patient groups exhibited a significant increase in the NLR (P < 0.05). Furthermore, the findings clearly demonstrated elevated levels of S100 A8/A9 in all patient groups when compared to the control group (P ≤ 0.05). The results also demonstrated a significant down regulation in the expression of TTP in DN and nephrotic syndrome (NS) groups compared to the control (P ≤ 0.01). AKI showed highly significant increase in TTP expression in comparison to control and other patient groups (P ≤ 0.01). Non-significant decrease in TTP gene expression was indicated in CKD compared to healthy group (P ≥ 0.05). Conclusions: The activation of Ca2+ -binding protein S100A8/A9 is involved in the renal damage; thus, targeting it could have a therapeutic value in the treatment of kidney diseases. Tristetraprolin is contributed to the regulation of inflammatory events in kidney diseases especially in AKI group due to a rapid and robust inflammatory response that contributes to the pathogenesis of this disease. [ABSTRACT FROM AUTHOR]

The 3′ untranslated regions (UTRs) of Ebola virus (EBOV) mRNAs are enriched in their AU content and therefore represent potential targets for RNA binding proteins targeting AU-rich elements (ARE-BPs). ARE-BPs are known to fine-tune RNA turnover and translational activity. We identified putative AREs within EBOV mRNA 3′ UTRs and assessed whether they might modulate mRNA stability. Using mammalian and zebrafish embryo reporter assays, we show a conserved, ARE-BP-mediated stabilizing effect and increased reporter activity with the tested EBOV 3′ UTRs. When coexpressed with the prototypic ARE-BP tristetraprolin (TTP, ZFP36) that mainly destabilizes its target mRNAs, the EBOV nucleoprotein (NP) 3′ UTR resulted in decreased reporter gene activity. Coexpression of NP with TTP led to reduced NP protein expression and diminished EBOV minigenome activity. In conclusion, the enrichment of AU residues in EBOV 3′ UTRs makes them possible targets for cellular ARE-BPs, leading to modulation of RNA stability and translational activity. [ABSTRACT FROM AUTHOR]

Objective To investigate the correlation between circrNa-Zinc finger protein 532 (ZNF532), circrNahomologous domain interaction protein kinase-3 (HIPK3) and diabetic retinopathy (DR). Methods A total of 109 patients with DR (DR group), 110 patients with simple diabetes (DM group) and 65 healthy volunteers (control group) were selected from our hospital from October 2020 to October 2022. Serum circRNA-ZNF532 and circRNA-HIPK3 expression levels were detected by real-time quantitative polymerase chain reaction (RT-PCR), and serum vascular endothelial growth factor (VEGF), interleukin (IL) -1β, tumor necrosis factor (TNF) - α and IL-6 levels were detected by enzyme-linked immunosoradsorption assay. The correlation between serum circRNA-ZNF532 and circRNA-HIPK3 expression and serum levels of VEGF, IL-1β, TNF-α and IL-6 were analyzed by Pearson method. Univariate Logistic regression analysis and multivariate Logistic regression analysis were used for DR risk factors, and receiver operating characteristic curve (ROC) was used for analysis of circRNA-ZNF532 and circRNA-HIPK3 diagnostic value of DR. Results Serum expressions of circRNA-ZNF532 and circRNA-HIPK3 and levels of VEGF, IL-1β, TNF-α and IL-6 were significantly higher in the DR group than those in the DM group and the control group (P＜0.05). Serum circRNA-ZNF532 and circRNA-HIPK3 expression were positively correlated with levels of VEGF, IL-1β, TNF-α and IL-6 in the DR group (P＜0.05). Multivariate Logistic regression analysis showed that high levels of VEGF, circRNA-ZNF532 and circRNA-HIPK3 were risk factors for developing DR in diabetic patients (P＜0.05). The areas under the curve of circRNA-ZNF532, circRNA-HIPK3 and VEGF in the diagnosis of DR in diabetic patients were 0.736, 0.740 and 0.864. Combined diagnosis was higher than that of circRNA-ZNF532, circRNA-HIPK3 and VEGF alone (P＜0.05). Conclusion The up-regulated expression levels of circRNA-ZNF532 and circRNA-HIPK3 in serum of diabetic patients are related to the occurrence of DR, and both circRNA-ZNF532 and circRNA-HIPK3 can be used as potential indicators for the auxiliary diagnosis of DR. [ABSTRACT FROM AUTHOR]

ABSTRACT Zika virus (ZIKV) is a mosquito-borne Flavivirus that persistently infects patients; enters protected brain, placental, and testicular compartments; is sexually transmitted; and causes fetal microcephaly in utero. ZIKV persistently infects human brain microvascular endothelial cells (hBMECs) that form the blood-brain barrier and Sertoli cells that form testicular barriers, establishing reservoirs that enable viral dissemination. ZIKV persistence requires inhibiting interferon (IFN) responses that direct viral clearance. We found that ZIKV induces IFNβ and IFNλ in hBMECs but post-transcriptionally inhibits IFNβ/IFNλ expression. IFNβ/IFNλ mRNAs contain AU-rich elements (AREs) in their 3′ untranslated regions which regulate protein expression through interactions with ARE-binding proteins (ARE-BPs). We found that ZIKV infection of primary hBMECs induces the expression of the ARE-BP tristetraprolin (TTP) and that TTP is a novel regulator of endothelial IFN secretion. In hBMECs, TTP knockout (KO) increased IFNβ/IFNλ mRNA abundance and IFNβ/IFNλ secretion in response to ZIKV infection and inhibited viral persistence. In contrast, TTP expression dramatically reduced IFNβ/IFNλ secretion in hBMECs. IFNβ/IFNλ mRNA stability was not significantly altered by TTP and is consistent with TTP inhibition of IFNβ/IFNλ translation. TTP is similarly induced by ZIKV infection of Sertoli cells, and like hBMECs, TTP expression or KO inhibited or enhanced IFNβ/IFNλ mRNA levels, respectively. These findings reveal a mechanism for ZIKV-induced TTP to promote viral persistence in hBMECs and Sertoli cells by post-transcriptionally regulating IFNβ/IFNλ secretion. Our results demonstrate a novel role for virally induced TTP in regulating IFN secretion in barrier cells that normally restrict viral persistence and spread to protected compartments. IMPORTANCE Our findings define a novel role for ZIKV-induced TTP expression in regulating IFNβ/IFNλ production in primary hBMECs and Sertoli cells. These cells comprise key physiological barriers subverted by ZIKV to access brain and testicular compartments and serve as reservoirs for persistent replication and dissemination. We demonstrate for the first time that the ARE-binding protein TTP is virally induced and post-transcriptionally regulates IFNβ/IFNλ secretion. In ZIKV-infected hBMEC and Sertoli cells, TTP knockout increased IFNβ/IFNλ secretion, while TTP expression blocked IFNβ/IFNλ secretion. The TTP-directed blockade of IFN secretion permits ZIKV spread and persistence in hBMECs and Sertoli cells and may similarly augment ZIKV spread across IFNλ-protected placental barriers. Our work highlights the importance of post-transcriptional ZIKV regulation of IFN expression and secretion in cells that regulate viral access to protected compartments and defines a novel mechanism of ZIKV-regulated IFN responses which may facilitate neurovirulence and sexual transmission.

Introduction: Asthma is the most common chronic inflammatory disease of the airways. The airway epithelium is a key driver of the disease, and numerous studies have established genome-wide differences in mRNA expression between health and asthma. However, the underlying molecular mechanisms for such differences remain poorly understood. The human TTP family is comprised of ZFP36, ZFP36L1 and ZFP36L2, and has essential roles in immune regulation by determining the stability and translation of myriad mRNAs encoding for inflammatory mediators. We investigated the expression and possible role of the tristetraprolin (TTP) family of RNA binding proteins (RBPs), poorly understood in asthma.Methods: We analysed the levels of ZFP36, ZFP36L1 and ZFP36L2 mRNA in several publicly available asthma datasets, including single cell RNA-sequencing. We also interrogated the expression of known targets of these RBPs in asthma. We assessed the lung mRNA expression and cellular localization of Zfp36l1 and Zfp36l2 in precision cut lung slices in murine asthma models. Finally, we determined the expression in airway epithelium of ZFP36L1 and ZFP36L2 in human bronchial biopsies and performed rescue experiments in primary bronchial epithelium from patients with severe asthma.Results: We found ZFP36L1 and ZFP36L2 mRNA levels significantly downregulated in the airway epithelium of patients with very severe asthma in different cohorts (5 healthy vs. 8 severe asthma; 36 moderate asthma vs. 37 severe asthma on inhaled steroids vs. 26 severe asthma on oral corticoids). Integrating several datasets allowed us to infer that mRNAs potentially targeted by these RBPs are increased in severe asthma. Zfp36l1 was downregulated in the lung of a mouse model of asthma, and immunostaining of ex vivo lung slices with a dual antibody demonstrated that Zfp36l1/l2 nuclear localization was increased in the airway epithelium of an acute asthma mouse model, which was further enhanced in a chronic model. Immunostaining of human bronchial biopsies showed that airway epithelial cell staining of ZFP36L1 was decreased in severe asthma as compared with mild, while ZFP36L2 was upregulated. Restoring the levels of ZFP36L1 and ZFP36L2 in primary bronchial epithelial cells from patients with severe asthma decreased the mRNA expression of IL6, IL8 and CSF2.Discussion: We propose that the dysregulation of ZFP36L1/L2 levels as well as their subcellular mislocalization contributes to changes in mRNA expression and cytoplasmic fate in asthma.

The p38MAPK-MK2 signaling axis functions as an initiator of inflammation. Targeting the p38MAPK-MK2 signaling axis represents a direct therapeutic intervention of inflammatory diseases. We described here a novel role of andrographolide (AG), a small-molecule ent-labdane natural compound, as an inhibitor of p38MAPK-MK2 axis via MK2 degradation. AG was found to bind to the activation loop of MK2, located at the interface of the p38MAPK-MK2 biomolecular complex. This interaction disrupted the complex formation and predisposed MK2 to proteasome-mediated degradation. We showed that AG induced MK2 degradation in a concentration- and time-dependent manner and exerted its anti-inflammatory effects by enhancing the mRNA-destabilizing activity of tristetraprolin, thereby inhibiting pro-inflammatory mediator production (e.g., TNF-α, MCP-1). Administration of AG via intratracheal (i.t.) route to mice induced MK2 downregulation in lung alveolar macrophages, but not lung tissues, and prevented macrophage activation. Our study also demonstrated that the anti-inflammatory effects achieved by AG via MK2 degradation were more durable and sustained than that achieved by the conventional MK2 kinase inhibitors (e.g., PF-3644022). Taken together, our findings illustrated a novel mode of action of AG by modulating the p38MAPK-MK2 signaling axis and would pave the way for the development of a novel class of anti-inflammatory agents targeting MK2 for degradation by harnessing the privileged scaffold of AG.

Egg granuloma formation in the liver is the main pathological lesion caused by Schistosoma japonicum infection, which generally results in liver fibrosis and may lead to death in advanced patients. MicroRNAs (miRNAs) regulate the process of liver fibrosis, but the putative function of miRNAs in liver fibrosis induced by S. japonicum infection is largely unclear. Here, we detect a new miRNA, miR-182-5p, which shows significantly decreased expression in mouse livers after stimulation by soluble egg antigen (SEA) of S. japonicum or S. japonicum infection. Knockdown or overexpression of miR-182-5p in vitro causes the increased or decreased expression of tristetraprolin (TTP), an important immunosuppressive protein in the process of liver fibrosis. Furthermore, knockdown of miR-182-5p in vivo upregulates TTP expression and significantly alleviates S. japonicum-induced hepatic fibrosis. Our data demonstrate that downregulation of miR-182-5p increases the expression of TTP in mouse livers following schistosome infection, which leads to destabilization of inflammatory factor mRNAs and attenuates liver fibrosis. Our results uncover fine-tuning of liver inflammatory reactions related to liver fibrosis caused by S. japonicum infection and provide new insights into the regulation of schistosomiasis-induced hepatic fibrosis.

Gossypol is a complex plant polyphenol reported to be cytotoxic and anti-inflammatory, but little is known about its effect on gene expression in macrophages. The objective of this study was to explore gossypol's toxicity and its effect on gene expression involved in the inflammatory response, glucose transport and insulin signaling pathways in mouse macrophages. Mouse RAW264.7 macrophages were treated with multiple concentrations of gossypol for 2–24 h. Gossypol toxicity was estimated by MTT assay and soluble protein content. qPCR analyzed the expression of anti-inflammatory tristetraprolin family (TTP/ZFP36), proinflammatory cytokine, glucose transporter (GLUT) and insulin signaling genes. Cell viability was greatly reduced by gossypol, accompanied with a dramatic reduction in soluble protein content in the cells. Gossypol treatment resulted in an increase in TTP mRNA level by 6–20-fold and increased ZFP36L1, ZFP36L2 and ZFP36L3 mRNA levels by 26–69-fold. Gossypol increased proinflammatory cytokine TNF, COX2, GM-CSF, INFγ and IL12b mRNA levels up to 39–458-fold. Gossypol treatment upregulated mRNA levels of GLUT1, GLUT3 and GLUT4 genes as well as INSR, AKT1, PIK3R1 and LEPR, but not APP genes. This study demonstrated that gossypol induced macrophage death and reduced soluble protein content, which was accompanied with the massive stimulation of anti-inflammatory TTP family and proinflammatory cytokine gene expression, as well as the elevation of gene expression involved in glucose transport and the insulin signaling pathway in mouse macrophages. [ABSTRACT FROM AUTHOR]

Aging can increase the risk of various hepatic diseases, especially non-alcoholic fatty liver disease (NAFLD). Although the mechanisms underlying the pathogenesis of age-related disorders such as NAFLD remain incompletely understood, recent studies have implicated the accumulation of senescent cells as a contributing factor. Here, we show that tristetraprolin (TTP) deficiency accelerates NAFLD during aging by enhancing the senescence-associated secretory phenotype (SASP) as well as several hallmarks of senescence. The sequestration of plasminogen activator inhibitor (PAI)-1, a mediator of cellular senescence, in stress granules, (SGs) inhibits cellular senescence. In our previous report, we have shown that carbon monoxide (CO), a small gaseous mediator, can induce the assembly of SGs via an integrated stress response. Here, we show that CO treatment promotes the assembly of SGs which can sequester PAI-1, resulting in the inhibition of etoposide (ETO)-induced cellular senescence. Notably, CO-induced TTP activation enhances PAI-1 degradation, leading to protection against ETO-induced cellular senescence. CO-dependent Sirt1 activation promotes the inclusion of TTP into SGs, leading to decreased PAI-1 levels. Therefore, our findings highlight the importance of TTP as a therapeutic target in age-related NAFLD and offer a potential new strategy to reduce the detrimental effects of senescent cells in hepatic disorders. [ABSTRACT FROM AUTHOR]

Tristetraprolin (TTP) is a nonclassical CCCH zinc finger (ZF) that plays a crucial role in regulating inflammation. TTP regulates cytokine mRNAs by specific binding of its two conserved ZF domains (CysX8CysX5CysX3His) to adenylate-uridylate-rich sequences (AREs) at the 3ʹ-untranslated region, leading to degradation of the RNA. Dysregulation of TTP in animal models has demonstrated several cytokine-related syndromes, including chronic inflammation and autoimmune disorders. Exposure to Pb(II), a prevalent environmental toxin, is known to contribute to similar pathologies, in part by disruption of and/or competition with cysteine-rich metalloproteins. TTP's role during stress as a ubiquitous translational regulator of cell signaling (and dysfunction), which may underpin various phenotypes of Pb(II) toxicity, highlights the importance of understanding the interaction between TTP and Pb(II). The impact of Pb(II) binding on TTP's fold and RNA-binding function was analyzed via UV–Vis spectroscopy, circular dichroism, X-ray absorption spectroscopy, nuclear magnetic resonance spectroscopy, and fluorescence anisotropy. A construct containing the two ZF domains of TTP (TTP-2D) bound to Pb(II) with nanomolar affinity and exhibited a different geometry and fold in comparison to Zn2-TTP-2D. Despite the altered secondary structure, Pb(II)-substituted TTP-2D bound a canonical ARE sequence more selectively than Zn2-TTP-2D. Taken together, these data suggest that Pb(II) may interfere with proper TTP regulation and hinder the cell's ability to respond to inflammation. [ABSTRACT FROM AUTHOR]

Tristetraprolin (TTP) is a critical negative immune regulator. It binds AU-rich elements in the untranslated-regions of many mRNAs encoding pro-inflammatory mediators, thereby accelerating their decay. A key but poorly understood mechanism of TTP regulation is its timely proteolytic removal: TTP is degraded by the proteasome through yet unidentified phosphorylation-controlled drivers. In this study, we set out to identify factors controlling TTP stability. Cellular assays showed that TTP is strongly lysine-ubiquitinated, which is required for its turnover. A genetic screen identified the ubiquitin E3 ligase HUWE1 as a strong regulator of TTP proteasomal degradation, which we found to control TTP stability indirectly by regulating its phosphorylation. Pharmacological assessment of multiple kinases revealed that HUWE1-regulated TTP phosphorylation and stability was independent of the previously characterized effects of MAPK-mediated S52/S178 phosphorylation. HUWE1 function was dependent on phosphatase and E3 ligase binding sites identified in the TTP C-terminus. Our findings indicate that while phosphorylation of S52/S178 is critical for TTP stabilization at earlier times after pro-inflammatory stimulation, phosphorylation of the TTP C-terminus controls its stability at later stages.

Iron is an indispensable micronutrient for all eukaryotic organisms due to its participation as a redox cofactor in many metabolic pathways. Iron imbalance leads to the most frequent human nutritional deficiency in the world. Adaptation to iron limitation requires a global reorganization of the cellular metabolism directed to prioritize iron utilization for essential processes. In response to iron scarcity, the conserved Saccharomyces cerevisiae mRNA-binding protein Cth2, which belongs to the tristetraprolin family of tandem zinc finger proteins, coordinates a global remodeling of the cellular metabolism by promoting the degradation of multiple mRNAs encoding highly iron-consuming proteins. In this work, we identify a critical mechanism for the degradation of Cth2 protein during the adaptation to iron deficiency. Phosphorylation of a patch of Cth2 serine residues within its amino-terminal region facilitates recognition by the SCFGrr1 ubiquitin ligase complex, accelerating Cth2 turnover by the proteasome. When Cth2 degradation is impaired by either mutagenesis of the Cth2 serine residues or deletion of GRR1, the levels of Cth2 rise and abrogate growth in iron-depleted conditions. Finally, we uncover that the casein kinase Hrr25 phosphorylates and promotes Cth2 destabilization. These results reveal a sophisticated posttranslational regulatory pathway necessary for the adaptation to iron depletion.IMPORTANCE Iron is a vital element for many metabolic pathways, including the synthesis of DNA and proteins, and the generation of energy via oxidative phosphorylation. Therefore, living organisms have developed tightly controlled mechanisms to properly distribute iron, since imbalances lead to nutritional deficiencies, multiple diseases, and vulnerability against pathogens. Saccharomyces cerevisiae Cth2 is a conserved mRNA-binding protein that coordinates a global reprogramming of iron metabolism in response to iron deficiency in order to optimize its utilization. Here we report that the phosphorylation of Cth2 at specific serine residues is essential to regulate the stability of the protein and adaptation to iron depletion. We identify the kinase and ubiquitination machinery implicated in this process to establish a posttranscriptional regulatory model. These results and recent findings for both mammals and plants reinforce the privileged position of E3 ubiquitin ligases and phosphorylation events in the regulation of eukaryotic iron homeostasis.

The metabolic state of a cell is influenced by cell-extrinsic factors, including nutrient availability and growth factor signaling. Here, we present extracellular matrix (ECM) remodeling as another fundamental node of cell-extrinsic metabolic regulation. Unbiased analysis of glycolytic drivers identified the hyaluronan-mediated motility receptor as being among the most highly correlated with glycolysis in cancer. Confirming a mechanistic link between the ECM component hyaluronan and metabolism, treatment of cells and xenografts with hyaluronidase triggers a robust increase in glycolysis. This is largely achieved through rapid receptor tyrosine kinase-mediated induction of the mRNA decay factor ZFP36, which targets TXNIP transcripts for degradation. Because TXNIP promotes internalization of the glucose transporter GLUT1, its acute decline enriches GLUT1 at the plasma membrane. Functionally, induction of glycolysis by hyaluronidase is required for concomitant acceleration of cell migration. This interconnection between ECM remodeling and metabolism is exhibited in dynamic tissue states, including tumorigenesis and embryogenesis.

Global transcriptional silencing is a highly conserved mechanism central to the oocyte-to-embryo transition. We report the unexpected discovery that global transcriptional silencing in oocytes depends on an mRNA decay activator. Oocyte-specific loss of ZFP36L2 an RNA-binding protein that promotes AU-rich element-dependent mRNA decay prevents global transcriptional silencing and causes oocyte maturation and fertilization defects, as well as complete female infertility in the mouse. Single-cell RNA sequencing revealed that ZFP36L2 downregulates mRNAs encoding transcription and chromatin modification regulators, including a large group of mRNAs for histone demethylases targeting H3K4 and H3K9, which we show are bound and degraded by ZFP36L2. Oocytes lacking Zfp36l2 fail to accumulate histone methylation at H3K4 and H3K9, marks associated with the transcriptionally silent, developmentally competent oocyte state. Our results uncover a ZFP36L2-dependent mRNA decay mechanism that acts as a developmental switch during oocyte growth, triggering wide-spread shifts in chromatin modification and global transcription.

The mRNA destabilizing factor tristetraprolin (TTP) functions as a tumor suppressor by down-regulating cancer-associated genes. TTP expression is significantly reduced in various cancers, which contributes to cancer processes. Enforced expression of TTP impairs tumorigenesis and abolishes maintenance of the malignant state, emphasizing the need to identify a TTP inducer in cancer cells. To search for novel candidate agents for inducing TTP in cancer cells, we screened a library containing 1019 natural compounds using MCF-7 breast cancer cells transfected with a reporter vector containing the TTP promoter upstream of the luciferase gene. We identified one molecule, of which the enantiomers are betamethasone 21-phosphate (BTM-21-P) and dexamethasone 21-phosphate (BTM-21-P), as a potent inducer of TTP in cancer cells. We confirmed that BTM-21-P, DXM-21-P, and dexamethasone (DXM) induced the expression of TTP in MDA-MB-231 cells in a glucocorticoid receptor (GR)-dependent manner. To identify potential pathways linking BTM-21-P and DXM-21-P to TTP induction, we performed an RNA sequencing-based transcriptome analysis of MDA-MB-231 cells at 3 h after treatment with these compounds. A heat map analysis of FPKM expression showed a similar expression pattern between cells treated with the two compounds. The KEGG pathway analysis results revealed that the upregulated DEGs were strongly associated with several pathways, including the Hippo signaling pathway, PI3K-Akt signaling pathway, FOXO signaling pathway, NF-κB signaling pathway, and p53 signaling pathway. Inhibition of the FOXO pathway using a FOXO1 inhibitor blocked the effects of BTM-21-P and DXM-21-P on the induction of TTP in MDA-MB-231 cells. We found that DXM enhanced the binding of FOXO1 to the TTP promoter in a GR-dependent manner. In conclusion, we identified a natural compound of which the enantiomers are DXM-21-P and BTM-21-P as a potent inducer of TTP in breast cancer cells. We also present new insights into the role of FOXO1 in the DXM-21-P- and BTM-21-P-induced expression of TTP in cancer cells. [ABSTRACT FROM AUTHOR]

Aging results in enhanced myelopoiesis, which is associated with an increased prevalence of myeloid leukemias and the production of myeloid-derived suppressor cells (MDSCs). Tristetraprolin (TTP) is an RNA binding protein that regulates immune-related cytokines and chemokines by destabilizing target mRNAs. As TTP expression is known to decrease with age in myeloid cells, we used TTP-deficient (TTPKO) mice to model aged mice to study TTP regulation in age-related myelopoiesis. Both TTPKO and myeloid-specific TTPKO (cTTPKO) mice had significant increases in both MDSC subpopulations MMDSCs (CD11b+Ly6ChiLy6G-) and PMN-MDSCs (CD11b+Ly6CloLy6G+), as well as macrophages (CD11b+F4/80+) in the spleen and mesenteric lymph nodes; however, no quantitative changes in MDSCs were observed in the bone marrow. In contrast, gain-of-function TTP knock-in (TTPKI) mice had no change in MDSCs compared with control mice. Within the bone marrow, total granulocyte-monocyte progenitors (GMPs) and monocyte progenitors (MPs), direct antecedents of M-MDSCs, were significantly increased in both cTTPKO and TTPKO mice, but granulocyte progenitors (GPs) were significantly increased only in TTPKO mice. Transcriptomic analysis of the bone marrow myeloid cell populations revealed that the expression of CC chemokine receptor 2 (CCR2), which plays a key role in monocyte mobilization to inflammatory sites, was dramatically increased in both cTTPKO and TTPKO mice. Concurrently, the concentration of CC chemokine ligand 2 (CCL2), a major ligand of CCR2, was high in the serum of cTTPKO and TTPKO mice, suggesting that TTP impacts the mobilization of M-MDSCs from the bone marrow to inflammatory sites during aging via regulation of the CCR2-CCL2 axis. Collectively, these studies demonstrate a previously unrecognized role for TTP in regulating age-associated myelopoiesis through the expansion of specific myeloid progenitors and M-MDSCs and their recruitment to sites of injury, inflammation, or other pathologic perturbations. [ABSTRACT FROM AUTHOR]

The regulation of the mRNA decay activator Tristetraprolin (TTP) by the p38 mitogen-activated protein kinase (MAPK) pathway during the mammalian inflammatory response represents a paradigm for the control of mRNA turnover by signaling. TTP activity is regulated through multiple phosphorylation sites, including an evolutionary conserved serine in its CNOT1 Interacting Motif (CIM) whose phosphorylation disrupts an interaction with CNOT1 of the CCR4-NOT deadenylase complex. Here we present evidence that the TTP CIM recruits the CCR4-NOT deadenylase complex and activates mRNA degradation cooperatively with the conserved tryptophan residues of TTP, previously identified to interact with CNOT9. Surprisingly, the TTP CIM remains unphosphorylated and capable of promoting association with the CCR4-NOT complex and mRNA decay upon activation of p38-MAPK-activated kinase MK2, a well-established regulator of TTP activity. The CIM is instead targeted by other kinases including PKCα. These observations suggest that signaling pathways regulate TTP activity in a cooperative manner and that the p38 MAPK-MK2 kinase pathway relies on the activation of additional kinase pathway(s) to fully control TTP function. [ABSTRACT FROM AUTHOR]

The abundance of mRNA is mainly determined by the rates of RNA transcription and decay. Here, we present a method for unbiased estimation of differential mRNA decay rate from RNA-sequencing data by modeling the kinetics of mRNA metabolism. We show that in all primary human tissues tested, and particularly in the central nervous system, many pathways are regulated at the mRNA stability level. We present a parsimonious regulatory model consisting of two RNA-binding proteins and four microRNAs that modulate the mRNA stability landscape of the brain, which suggests a new link between RBFOX proteins and Alzheimer's disease. We show that downregulation of RBFOX1 leads to destabilization of mRNAs encoding for synaptic transmission proteins, which may contribute to the loss of synaptic function in Alzheimer's disease. RBFOX1 downregulation is more likely to occur in older and female individuals, consistent with the association of Alzheimer's disease with age and gender."mRNA abundance is determined by the rates of transcription and decay. Here, the authors propose a method for estimating the rate of differential mRNA decay from RNA-seq data and model mRNA stability in the brain, suggesting a link between mRNA stability and Alzheimer's disease."

Aging results in enhanced myelopoiesis, which is associated with an increased prevalence of myeloid leukemias and the production of myeloid-derived suppressor cells (MDSCs). Tristetraprolin (TTP) is an RNA binding protein that regulates immune-related cytokines and chemokines by destabilizing target mRNAs. As TTP expression is known to decrease with age in myeloid cells, we used TTP-deficient (TTPKO) mice to model aged mice to study TTP regulation in age-related myelopoiesis. Both TTPKO and myeloid-specific TTPKO (cTTPKO) mice had significant increases in both MDSC subpopulations M-MDSCs (CD11b+Ly6ChiLy6G-) and PMN-MDSCs (CD11b+Ly6CloLy6G+), as well as macrophages (CD11b+F4/80+) in the spleen and mesenteric lymph nodes; however, no quantitative changes in MDSCs were observed in the bone marrow. In contrast, gain-of-function TTP knock-in (TTPKI) mice had no change in MDSCs compared with control mice. Within the bone marrow, total granulocyte-monocyte progenitors (GMPs) and monocyte progenitors (MPs), direct antecedents of M-MDSCs, were significantly increased in both cTTPKO and TTPKO mice, but granulocyte progenitors (GPs) were significantly increased only in TTPKO mice. Transcriptomic analysis of the bone marrow myeloid cell populations revealed that the expression of CC chemokine receptor 2 (CCR2), which plays a key role in monocyte mobilization to inflammatory sites, was dramatically increased in both cTTPKO and TTPKO mice. Concurrently, the concentration of CC chemokine ligand 2 (CCL2), a major ligand of CCR2, was high in the serum of cTTPKO and TTPKO mice, suggesting that TTP impacts the mobilization of M-MDSCs from the bone marrow to inflammatory sites during aging via regulation of the CCR2-CCL2 axis. Collectively, these studies demonstrate a previously unrecognized role for TTP in regulating age-associated myelopoiesis through the expansion of specific myeloid progenitors and M-MDSCs and their recruitment to sites of injury, inflammation, or other pathologic perturbations.

Abstract Background Tristetraprolin (TTP) family proteins contain conserved tandem CCCH zinc-finger binding to AU-rich elements and C-terminal NOT1-binding domain. TTP is phosphorylated extensively in cells, and its mRNA destabilization activity is regulated by protein phosphorylation. Methods We generated an antibody against phospho-Serine316 located at the C-terminal NOT1-binding site and examined TTP phosphorylation in LPS-stimulated RAW264.7 cells. Knockout of TTP was created in RAW264.7 cells using CRISPR/Cas9 gene editing to explore TTP functions. Results We demonstrated that Ser316 was phosphorylated by p90 ribosomal S6 kinase 1 (RSK1) and p38-activated protein kinase (MK2) and dephosphorylated by Protein Phosphatase 2A (PP2A). A phosphorylation-mimic mutant of S316D resulted in dissociation with the CCR4-NOT deadenylase complex through weakening interaction with CNOT1. Furthermore, Ser316 and serines 52 and 178 were independently contributed to the CCR4-NOT complex recruitment in the immunoprecipitation assay using phosphor-mimic mutants. In RAW264.7 macrophages, TTP was induced, and Ser316 was phosphorylated through RSK1 and MK2 by LPS stimulation. Knockout of TTP resulted in TNFα mRNA increased due to mRNA stabilization. Overexpression of non-phosphorylated S316A TTP mutant can restore TTP activity and lead to TNFα mRNA decreased. GST pull-down and RNA pull-down analyses demonstrated that endogenous TTP with Ser316 phosphorylation decreased the interaction with CNOT1. Conclusions Our results suggest that the TTP-mediated mRNA stability is modulated by Ser316 phosphorylation via regulating the TTP interaction with the CCR4-NOT deadenylase complex.

Rheumatoid arthritis (RA) is an autoimmune disorder of unknown etiology with aberrant immunological responses leading to inflammation, swelling and pain of the joints. CD8+ T cells have been known to be one of the major immune modulators in the progression of RA and the presence of toll-like receptors (TLRs) on these cells further accentuate their role in RA. Herein, we report an increased expression of TLR7 in the endosomes of CD8+ T cells of RA patients correlating with disease severity. The stimulation of TLR7 with Imiquimod (IMQ) in these CD8+ T cells drives the signalling cascade via NFkB and pERK activation and hence an increase in the mRNA transcripts of signature cytokines and cytolytic enzymes. However, a parallel synthesis of Tristetraprolin (TTP), an mRNA destabilizing protein prevents the translation of the mRNA transcripts, leading to a rapid degeneration of the target mRNA. We thus report that a direct TLR7 ligation by its agonist increases cytokine transcript signature but not an equivalent protein surge. [ABSTRACT FROM AUTHOR]

Diabetic foot ulcers (DFUs) are classified as chronic wounds and are one of the most common complications of diabetes. In chronic wounds, management of inflammation is a key step in treatment. Nutrition plays an important role in managing and controlling inflammation. This study evaluated the effects of nutrition supplementation and education on inflammatory biomarkers in patients with DFUs. Eligible patients with foot ulcers were randomly assigned to either a treatment (n = 15) or control group (n = 14). Both groups received standard care for wound treatment from the clinic; however, the treatment group was also provided with nutritional supplementation and education. Plasma concentrations of inflammatory biomarkers, namely C-reactive protein (CRP), interleukin 6 (IL6), interleukin 10 (IL10), and tristetraprolin (TTP), were evaluated at baseline and every four weeks, until complete wound closure had occurred or up to 12 weeks. The mean plasma concentration of IL6 significantly decreased in the treatment group (p = 0.001). The interaction between time and group was not statistically significant for the mean plasma concentrations of CRP, IL10, and TTP during the 12 weeks of the study. The results of this study showed the positive effects of nutritional intervention on controlling inflammation in DFU patients. More clinical trials with a larger population and longer duration of time are needed to confirm our results. [ABSTRACT FROM AUTHOR]

The zinc finger protein tristetraprolin (TTP) promotes translation repression and degradation of mRNAs containing AU-rich elements (AREs). Although much attention has been directed toward understanding the decay process and machinery involved, the translation repression role of TTP has remained poorly understood. Here we identify the cap-binding translation repression 4EHP-GYF2 complex as a cofactor of TTP. Immunoprecipitation and in vitro pull-down assays demonstrate that TTP associates with the 4EHP-GYF2 complex via direct interaction with GYF2, and mutational analyses show that this interaction occurs via conserved tetraproline motifs of TTP. Mutant TTP with diminished 4EHP-GYF2 binding is impaired in its ability to repress a luciferase reporter ARE-mRNA. 4EHP knockout mouse embryonic fibroblasts (MEFs) display increased induction and slower turnover of TTP-target mRNAs as compared to wild-type MEFs. Our work highlights the function of the conserved tetraproline motifs of TTP and identifies 4EHP-GYF2 as a cofactor in translational repression and mRNA decay by TTP.

Members of the tristetraprolin (TTP) family of RNA binding proteins (RBPs) regulate the metabolism of a variety of mRNA targets. In mammals, these proteins modulate many physiological processes, including immune cell activation, hematopoiesis, and embryonic development. Regulation of mRNA stability by these proteins requires that the tandem zinc finger (TZF) domain binds initially and directly to target mRNAs, ultimately leading to their deadenylation and decay. Proteins of this type throughout eukarya possess a highly conserved TZF domain, suggesting that they are all capable of high-affinity RNA binding. However, the mechanism of TTP-mediated mRNA decay is largely undefined. Given the vital role that these TTP family proteins play in maintaining RNA homeostasis throughout eukaryotes, we focused here on the first, key step in this process: recognition and binding of the TZF domain to target RNA. For these studies, we chose a primitive plant, the spikemoss Selaginella moellendorffii, which last shared a common ancestor with humans more than a billion years ago. Here we report the near complete backbone and side chain resonance assignments of the spikemoss TZF domain, including: (1) the assignment of the RNA-TZF domain complex, representing one of only two data sets currently available for the entire TTP family of proteins; and (2) the first NMR resonance assignments of the entire TZF domain, in the RNA-free form. This work will serve as the basis for further NMR structural investigations aimed at gaining insights into the process of RNA recognition and the mechanisms of TTP-mediated mRNA decay. [ABSTRACT FROM AUTHOR]

Tristetraprolin (TTP) is an RNA-binding protein that negatively regulates its target mRNAs and has been shown to inhibit tumor progression and invasion. Tumor invasion requires precise regulation of cytoskeletal components, and dysregulation of cytoskeleton-associated genes can significantly alter cell motility and invasive capability. Several genes, including SH3PXD2A, SH3PXD2B, CTTN, WIPF1, and WASL, are crucial components of the cytoskeleton reorganization machinery and are essential for adequate cell motility. These genes are also involved in invasion processes, with SH3PXD2A, SH3PXD2B, WIPF1, and CTTN being key components of invadopodia-specialized structures that facilitate invasion. However, the regulation of these genes is not well understood. This study demonstrates that ectopic expression of TTP in MDA-MB-231 cells leads to decreased mRNA levels of CTTN and SH3PXD2A, as well as defects in cell motility and actin filament organization. Additionally, doxorubicin significantly increases TTP expression and reduces the mRNA levels of cytoskeleton-associated genes, enhancing our understanding of how doxorubicin may affect the transcriptional profile of cells. However, doxorubicin affects target mRNAs differently than TTP ectopic expression, suggesting it may not be the primary mechanism of doxorubicin in breast cancer (BC) treatment. High TTP expression is considered as a positive prognostic marker in multiple cancers, including BC. Given that doxorubicin is a commonly used drug for treating triple-negative BC, using TTP as a prognostic marker in this cohort of patients might be limited since it might be challenging to understand if high TTP expression occurred due to the favorable physiological state of the patient or as a consequence of treatment., (© 2024 The Author(s). Cytoskeleton published by Wiley Periodicals LLC.)

Skeletal muscle satellite cells in their niche are quiescent and upon muscle injury, exit quiescence, proliferate to repair muscle tissue, and self-renew to replenish the satellite cell population. To understand the mechanisms involved in maintaining satellite cell quiescence, we identified gene transcripts that were differentially expressed during satellite cell activation following muscle injury. Transcripts encoding RNA binding proteins were among the most significantly changed and included the mRNA decay factor Tristetraprolin. Tristetraprolin promotes the decay of MyoD mRNA, which encodes a transcriptional regulator of myogenic commitment, via binding to the MyoD mRNA 3' untranslated region. Upon satellite cell activation, p38α/β MAPK phosphorylates MAPKAP2 and inactivates Tristetraprolin, stabilizing MyoD mRNA. Satellite cell specific knockdown of Tristetraprolin precociously activates satellite cells in vivo, enabling MyoD accumulation, differentiation and cell fusion into myofibers. Regulation of mRNAs by Tristetraprolin appears to function as one of several critical post-transcriptional regulatory mechanisms controlling satellite cell homeostasis.

Members of the tristetraprolin (TTP) family of CCCH tandem zinc finger proteins bind to AU-rich regions in target mRNAs, leading to their deadenylation and decay. Family members in Saccharomyces cerevisiae influence iron metabolism, whereas the single protein expressed in Schizosaccharomyces pombe, Zfs1, regulates cell-cell interactions. In the human pathogen Candida albicans, deep sequencing of mutants lacking the orthologous protein, Zfs1, revealed significant increases (> 1.5-fold) in 156 transcripts. Of these, 113 (72%) contained at least one predicted TTP family member binding site in their 3'UTR, compared with only 3 of 56 (5%) down-regulated transcripts. The zfs1Δ/Δ mutant was resistant to 3-amino-1,2,4-triazole, perhaps because of increased expression of the potential target transcript encoded by HIS3. Sequences of the proteins encoded by the putative Zfs1 targets were highly conserved among other species within the fungal CTG clade, while the predicted Zfs1 binding sites in these mRNAs often 'disappeared' with increasing evolutionary distance from the parental species. C. albicans Zfs1 bound to the ideal mammalian TTP binding site with high affinity, and Zfs1 was associated with target transcripts after co-immunoprecipitation. Thus, the biochemical activities of these proteins in fungi are highly conserved, but Zfs1-like proteins may target different transcripts in each species.

To observe and evaluate the correlation between single-nucleotide polymorphisms (SNPs) and messenger RNA (mRNA) level related to tristetraprolin (TTP) in Chinese rheumatoid arthritis (RA). TapMan SNP was used for genotyping analysis in 580 RA patients and 554 healthy people. Association between TTP gene polymorphisms (rs251864 and rs3746083) and RA was obtained. Quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) technology was applied for the detection of TTP mRNA level in peripheral blood mononuclear cells (PBMCs) in 36 RA patients and 37 healthy people. We observed that the allele T of TTP rs3746083 increased RA susceptibility (p = 0.019). A significant difference was found under the dominant model of rs3746083 (p = 0.037). Further analysis showed the allele distribution of rs3746083 was nominally correlated with RF phenotype of RA patients (p = 0.045). Nevertheless, the association between TTP rs251864 and the incidence of RA was no statistically significant (p > 0.05). The TTP expression level in PBMCs of RA patients was significantly reduced (p < 0.001). In conclusion, the results of this experiment support that TTP may be involved in the pathogenesis of RA.

To clarify the mechanism of semicarbazide-modified α-lactalbumin (SEM-LA)-mediated cytotoxicity, we investigated its effect on human U937 leukemia cells and MCF-7 breast cancer cells in the current study. SEM-LA induced apoptosis in U937 cells, which showed increased NOX4 expression, procaspase-8 degradation, and t-Bid production. FADD depletion inhibited SEM-LA-elicited caspase-8 activation, t-Bid production, and cell death, indicating that SEM-LA activated death receptor-mediated apoptosis in U937 cells. SEM-LA stimulated Ca2+-mediated Akt activation, which in turn increased Sp1- and p300-mediated NOX4 transcription. The upregulation of NOX4 expression promoted ROS-mediated p38 MAPK phosphorylation, leading to protein phosphatase 2A (PP2A)-regulated tristetraprolin (TTP) degradation. Remarkably, TTP downregulation increased the stability of TNF-α mRNA, resulting in the upregulation of TNF-α protein expression. Abolishment of Ca2+-NOX4-ROS axis-mediated p38 MAPK activation attenuated SEM-LA-induced TNF-α upregulation and protected U937 cells from SEM-LA-mediated cytotoxicity. The restoration of TTP expression alleviated the effect of TNF-α upregulation and cell death induced by SEM-LA. Altogether, the data in this study demonstrate that SEM-LA activates TNF-α-mediated apoptosis in U937 cells through the NOX4/p38 MAPK/PP2A axis. We think that a similar pathway can also explain the death of MCF-7 human breast cancer cells after SEM-LA treatment. • Semicarbazide-modified α-lactalbumin (SEM-LA) shows cytotoxicity. • SEM-LA promotes NOX4 transcription via Ca2+/Akt-induced Sp1 and p300 upregulation. • NOX4 induces ROS/p38MAPK/PP2A axis-mediated TTP degradation. • TTP degradation reduces TNF-α mRNA turnover, thereby increasing TNF-α expression. • SEM-LA induces TNF-α-mediated apoptosis in leukemia and breast cancer cells. [ABSTRACT FROM AUTHOR]

To observe and evaluate the correlation between single-nucleotide polymorphisms (SNPs) and messenger RNA (mRNA) level related to tristetraprolin (TTP) in Chinese rheumatoid arthritis (RA). TapMan SNP was used for genotyping analysis in 580 RA patients and 554 healthy people. Association between TTP gene polymorphisms (rs251864 and rs3746083) and RA was obtained. Quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) technology was applied for the detection of TTP mRNA level in peripheral blood mononuclear cells (PBMCs) in 36 RA patients and 37 healthy people. We observed that the allele T of TTP rs3746083 increased RA susceptibility (p = 0.019). A significant difference was found under the dominant model of rs3746083 (p = 0.037). Further analysis showed the allele distribution of rs3746083 was nominally correlated with RF phenotype of RA patients (p = 0.045). Nevertheless, the association between TTP rs251864 and the incidence of RA was no statistically significant (p > 0.05). The TTP expression level in PBMCs of RA patients was significantly reduced (p < 0.001). In conclusion, the results of this experiment support that TTP may be involved in the pathogenesis of RA. [ABSTRACT FROM AUTHOR]

Post-transcriptional regulation is involved in the regulation of many inflammatory genes. Zinc finger protein 36 (ZFP36) family proteins are RNA-binding proteins involved in messenger RNA (mRNA) metabolism pathways. The ZFP36 family is composed of ZFP36 (also known as tristetraprolin, TTP), ZFP36L1, ZFP36L2, and ZFP36L3 (only in rodents). The ZFP36 family proteins contain two tandemly repeated CCCH-type zinc-finger motifs, bind to adenine uridine-rich elements in the 3’-untranslated regions (3’ UTR) of specific mRNA, and lead to target mRNA decay. Although the ZFP36 family members are structurally similar, they are known to play distinct functions and regulate different target mRNAs, probably due to their cell-type-specific expression patterns. For instance, ZFP36 has been well-known to function as an anti-inflammatory modulator in murine models of systemic inflammatory diseases by down-regulating the production of various pro-inflammatory cytokines, including TNF-α. Meanwhile, ZFP36L1 is required for the maintenance of the marginal-zone B cell compartment. Recently, we found that ZFP36L2 reduces the expression of Ikzf2 (encoding HELIOS) and suppresses regulatory T cell function. This review summarizes the current understanding of the post-transcriptional regulation of immunological responses and inflammatory diseases by RNA-binding ZFP36 family proteins.

Post-transcriptional regulation is involved in the regulation of many inflammatory genes. Zinc finger protein 36 (ZFP36) family proteins are RNA-binding proteins involved in messenger RNA (mRNA) metabolism pathways. The ZFP36 family is composed of ZFP36 (also known as tristetraprolin, TTP), ZFP36L1, ZFP36L2, and ZFP36L3 (only in rodents). The ZFP36 family proteins contain two tandemly repeated CCCH-type zinc-finger motifs, bind to adenine uridine-rich elements in the 3'-untranslated regions (3' UTR) of specific mRNA, and lead to target mRNA decay. Although the ZFP36 family members are structurally similar, they are known to play distinct functions and regulate different target mRNAs, probably due to their cell-type-specific expression patterns. For instance, ZFP36 has been well-known to function as an anti-inflammatory modulator in murine models of systemic inflammatory diseases by down-regulating the production of various pro-inflammatory cytokines, including TNF-α. Meanwhile, ZFP36L1 is required for the maintenance of the marginal-zone B cell compartment. Recently, we found that ZFP36L2 reduces the expression of Ikzf2 (encoding HELIOS) and suppresses regulatory T cell function. This review summarizes the current understanding of the post-transcriptional regulation of immunological responses and inflammatory diseases by RNA-binding ZFP36 family proteins. [ABSTRACT FROM AUTHOR]

Background: Tristetraprolin (TTP) family proteins contain conserved tandem CCCH zinc-finger binding to AU-rich elements and C-terminal NOT1-binding domain. TTP is phosphorylated extensively in cells, and its mRNA destabilization activity is regulated by protein phosphorylation. Methods: We generated an antibody against phospho-Serine316 located at the C-terminal NOT1-binding site and examined TTP phosphorylation in LPS-stimulated RAW264.7 cells. Knockout of TTP was created in RAW264.7 cells using CRISPR/Cas9 gene editing to explore TTP functions. Results: We demonstrated that Ser316 was phosphorylated by p90 ribosomal S6 kinase 1 (RSK1) and p38-activated protein kinase (MK2) and dephosphorylated by Protein Phosphatase 2A (PP2A). A phosphorylation-mimic mutant of S316D resulted in dissociation with the CCR4-NOT deadenylase complex through weakening interaction with CNOT1. Furthermore, Ser316 and serines 52 and 178 were independently contributed to the CCR4-NOT complex recruitment in the immunoprecipitation assay using phosphor-mimic mutants. In RAW264.7 macrophages, TTP was induced, and Ser316 was phosphorylated through RSK1 and MK2 by LPS stimulation. Knockout of TTP resulted in TNFα mRNA increased due to mRNA stabilization. Overexpression of non-phosphorylated S316A TTP mutant can restore TTP activity and lead to TNFα mRNA decreased. GST pull-down and RNA pull-down analyses demonstrated that endogenous TTP with Ser316 phosphorylation decreased the interaction with CNOT1. Conclusions: Our results suggest that the TTP-mediated mRNA stability is modulated by Ser316 phosphorylation via regulating the TTP interaction with the CCR4-NOT deadenylase complex. [ABSTRACT FROM AUTHOR]

Tristetraprolin (TTP) is a nucleocytoplasmic 326 amino acid protein whose sequence is characterized by possessing two CCCH-type zinc finger domains. In the cytoplasm TTP function is to promote the degradation of mRNAs that contain adenylate/uridylate–rich elements (AREs). Mechanistically, TTP promotes the recruitment of poly(A)-specific deadenylases and exoribonucleases. By reducing the half-life of about 10% of all the transcripts in the cell TTP has been shown to participate in multiple cell processes that include regulation of gene expression, cell proliferation, metabolic homeostasis and control of inflammation and immune responses. However, beyond its role in mRNA decay, in the cell nucleus TTP acts as a transcriptional coregulator by interacting with chromatin modifying enzymes. TTP has been shown to repress the transactivation of NF -κB and estrogen receptor suggesting the possibility that it participates in the transcriptional regulation of hundreds of genes in human cells and its possible involvement in breast cancer progression. In this review, we discuss the cytoplasmic and nuclear functions of TTP and the effect of the dysregulation of its protein levels in the development of human diseases. We suggest that TTP be classified as a moonlighting tumor supressor protein that regulates gene expression through two different mechanims; the decay of ARE-mRNAs and a transcriptional coregulatory function. [ABSTRACT FROM AUTHOR]

BackgroundConventional p38α inhibitors have limited efficacy in rheumatoid arthritis, possibly because p38 blockade suppresses the counter-regulatory mechanisms that limit inflammation. In contrast, targeting the upstream MAP kinase kinases, MKK3 and MKK6, partially maintains p38-mediated anti-inflammatory responses in bone marrow-derived macrophages (BMDM). In this study, we explored the mechanisms that preserve anti-inflammatory gene expression by evaluating differential regulation of IL-10 and p38-dependent anti-inflammatory genes in MKK3-/-, MKK6-/-, and p38 inhibitor-treated wildtype cells.MethodsBMDM from wild type (WT), MKK3-/-, and MKK6-/- mice were pre-treated with p38 inhibitor SB203580 (SB), JNK inhibitor SP600125 (SP), and/or ERK inhibitor PD98059 (PD) and stimulated with LPS. Supernatant protein levels were measured by multiplex bead immunoassay. mRNA expression was determined by qPCR and protein expression by Western blot analysis. De novo IL-10 mRNA synthesis was quantified in cells treated with ethynyl-uridine and LPS followed by reverse transcription and qPCR. mRNA half-life was measured in LPS-treated cells that were then incubated with actinomycin D ± SB203580.ResultsPre-treatment of WT BMDM with p38 inhibitor significantly reduced IL-10 production in the three groups, while ERK and JNK inhibitors had minimal effects. IL-10 production was significantly decreased in MKK3-/- BMDM compared with either WT or MKK6-/- cells. IL-10 mRNA expression was modestly reduced in MKK3-/- BMDM but was preserved in MKK6-/- cells compared with WT. De novo IL-10 mRNA synthesis was inhibited in MKK3-/- and p38 inhibitor pre-treated cells, but not MKK6-/- cells compared with WT. IL-10 mRNA half-life was markedly reduced in p38 inhibitor-treated WT cells while MKK-deficiency had minimal effect. DUSP1 mRNA levels were preserved in MKK-deficient cells but not in p38 inhibitor-treated WT cells. Tristetraprolin mRNA and protein levels were reduced in p38 inhibitor-treated WT cells compared with MKK6-/- cells.ConclusionUnlike p38-inhibition, the absence of MKK6 mostly preserves IL-10 and TTP protein expression in BMDM. MKK6-deficiency also spares DUSP1 and IL-1RA, which are key negative regulators of the inflammatory response. Together, these data suggest that MKK6 is a potential therapeutic target in RA.

The tristetraprolin (TTP) family of zinc-finger proteins, TTP, BRF1 and BRF2, regulate the stability of a subset of mRNAs containing 3'UTR AU-rich elements (AREs), including mRNAs coding for cytokines, transcription factors, and proto-oncogenes. To better understand the mechanism by which TTP-family proteins control mRNA stability in mammalian cells, we aimed to identify TTP- and BRF1-interacting proteins as potential TTP-family co-factors. This revealed hnRNP F as a prominent interactor of TTP and BRF1. While TTP, BRF1 and hnRNP F are all RNA binding proteins (RBPs), the interaction of hnRNP F with TTP and BRF1 is independent of RNA. Depletion of hnRNP F impairs the decay of a subset of TTP-substrate ARE-mRNAs by a mechanism independent of the extent of hnRNP F binding to the mRNA. Taken together, these findings implicate hnRNP F as a co-factor in a subset of TTP/BRF-mediated mRNA decay and highlight the importance of RBP cooperativity in mRNA regulation.

Tristetraprolin (TTP), an mRNA binding and decaying protein, plays a significant role in controlling inflammation by decaying mRNAs encoding inflammatory cytokines such as TNFalpha. We aimed to test a hypothesis that TTP in bone marrow (BM) cells regulates atherogenesis by modulating inflammation and lipid metabolism through the modulation of oxidative stress pathways by TTP target genes. In a BM transplantation study, lethally irradiated atherogenic LDLR−/− mice were reconstituted with BM cells from either wild type (TTP+/+) or TTP knockout (TTP−/−) mice, and fed a Western diet for 12 weeks. We made the following observations: (1) TTP−/− BM recipients display a significantly higher systemic and multi-organ inflammation than TTP+/+ BM recipients; (2) BM TTP deficiency modulates hepatic expression of genes, detected by microarray, involved in lipid metabolism, inflammatory responses, and oxidative stress; (3) TTP−/− BM derived macrophages increase production of mitochondrial reactive oxygen species (mtROS); (4) BM-TTP−/− mice display a significant reduction in serum VLDL/LDL levels, and attenuated hepatic steatosis compared to controls; and (5) Reduction of serum VLDL/LDL levels offsets the increased inflammation, resulting in no changes in atherosclerosis. These findings provide a novel mechanistic insight into the roles of TTP-mediated mRNA decay in bone marrow-derived cells in regulating systemic inflammation, oxidative stress, and liver VLDL/LDL biogenesis.