Zinc Finger Protein Tristetraprolin Interacts with CCL3 mRNA and Regulates Tissue Inflammation

Center for Molecular Medicine, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA.
The Journal of Immunology (Impact Factor: 4.92). 09/2011; 187(5):2696-701. DOI: 10.4049/jimmunol.1101149
Source: PubMed


Zinc finger protein tristetraprolin (TTP) modulates macrophage inflammatory activity by destabilizing cytokine mRNAs. In this study, through a screen of TTP-bound mRNAs in activated human macrophages, we have identified CCL3 mRNA as the most abundantly bound TTP target mRNA and have characterized this interaction via conserved AU-rich elements. Compared to the wild-type cells, TTP(-/-) macrophages produced higher levels of LPS-induced CCL3. In addition, the plasma level of CCL3 in TTP(-/-) mice was markedly higher than that in wild-type mice. To determine the in vivo significance of TTP-regulated CCL3, we generated CCL3(-/-)TTP(-/-) double-knockout mice. Along with decreased proinflammatory cytokines in their paw joints, there were significant functional and histologic improvements in the inflammatory arthritis of TTP(-/-) mice when CCL3 was absent, although cachexia, reflecting systemic inflammation, was notably unaffected. Furthermore, the marked exacerbation of aortic plaque formation caused by TTP deficiency in the APOE(-/-) mouse model of atherosclerosis was also rescued by disrupting CCL3. Taken together, our data indicate that the interaction between TTP and CCL3 mRNA plays an important role in modulating localized inflammatory processes in tissues that are dissociated from the systemic manifestations of chronic inflammation.

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    • "Also, in rheumatoid arthritis upregulated TTP is found in cells involved in pathogenesis [52] and may be a marker of severe disease [53], in part because of production stimulated by the TTP target TNF. Although the complete absence of TTP (knockout mice) is associated with uncontrolled inflammatory responses [20,54-56] and TTP influences cytokine levels in cell culture models, there are conflicting reports on whether TTP and TNF levels are correlated in rheumatoid arthritis patient samples [34,53]. Exposure of mouse brain to hypertonic insult resulted in upregulation of both TTP and TNF [57]. "
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    ABSTRACT: The RNA-binding protein tristetraprolin (TTP) participates in normal post-transcriptional control of cytokine and chemokine gene expression, dysregulation of which contributes to the HIV-associated neurocognitive disorders. Transcriptional and post-transcriptional regulation of TTP has been described, including regulation by microRNA-29a. In the simian immunodeficiency virus (SIV) model of HIV CNS disease, control of cytokine/chemokine expression coincides with the end of acute phase infection. This control is lost during progression to disease. In this study, we assessed TTP regulation and association with cytokine regulation in the brain during SIV infection. Quantitation of TTP expression over the course of SIV infection revealed downregulation of TTP during acute infection, maintenance of relatively low levels during asymptomatic phase, and increased expression only during late-stage CNS disease, particularly in association with severe disease. The ability of miR-29a to regulate TTP was confirmed, and evidence for additional miRNA targeters of TTP was found. However, increased miR-29a expression in brain was not found to be significantly negatively correlated with TTP. Similarly, increased TTP during late-stage disease was not associated with lower cytokine expression. TTP expression is regulated during SIV infection of the CNS. The lack of significant negative correlation of miR-29a and TTP expression levels suggests that while miR-29a may contribute to TTP regulation, additional factors are involved. Reduced TTP expression during acute infection is consistent with increased cytokine production during this phase of infection, but the increases in TTP observed during late-stage infection were insufficient to halt runaway cytokine levels. While antisense inhibitors of the post-transcriptional targeters of TTP identified here could conceivably be used further to augment TTP regulation of cytokines, it is possible that high levels of TTP are undesirable. Additional research is needed to characterize members of the miRNA/TTP/cytokine regulatory network and identify nodes that may be best targeted therapeutically to ameliorate the effects of chronic inflammation in retrovirus-associated CNS disease.
    Full-text · Article · Sep 2013 · Molecular Brain
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    • "Tristetraprolin (TTP; encoded by Zfp36) is one of the best-characterized ARE-binding protein . TTP limits the production of several TLR-induced cytokines , including TNF, IL6, GM-CSF, and CCL3 (Lai et al., 1999; Carballo et al., 2000; Kang et al., 2011; Van Tubergen et al., 2011). Recently, transcriptome analyses indicate that out of 546 LPS-inducible transcripts in macrophages, 138 were found to be unstable. "
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    ABSTRACT: Interleukin (IL) 12 and IL23 are two related heterodimeric cytokines produced by antigen-presenting cells. The balance between these two cytokines plays a crucial role in the control of Th1/Th17 responses and autoimmune inflammation. Most studies focused on their transcriptional regulation. Herein, we explored the role of the adenine and uridine-rich element (ARE)-binding protein tristetraprolin (TTP) in influencing mRNA stability of IL12p35, IL12/23p40, and IL23p19 subunits. LPS-stimulated bone marrow-derived dendritic cells (BMDCs) from TTP(-/-) mice produced normal levels of IL12/23p40. Production of IL12p70 was modestly increased in these conditions. In contrast, we observed a strong impact of TTP on IL23 production and IL23p19 mRNA stability through several AREs in the 3' untranslated region. TTP(-/-) mice spontaneously develop an inflammatory syndrome characterized by cachexia, myeloid hyperplasia, dermatitis, and erosive arthritis. We observed IL23p19 expression within skin lesions associated with exacerbated IL17A and IL22 production by infiltrating γδ T cells and draining lymph node CD4 T cells. We demonstrate that the clinical and immunological parameters associated with TTP deficiency were completely dependent on the IL23-IL17A axis. We conclude that tight control of IL23 mRNA stability by TTP is critical to avoid severe inflammation.
    Full-text · Article · Aug 2013 · Journal of Experimental Medicine
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    • "We have previously reported that apoA-I inhibits the mRNA expression of various proinflammatory cytokines via activation of STAT3 and that apoA-I upregulates the cytokine mRNA-destabilizing protein tristetraprolin (TTP) in both THP-1 macrophages and human primary macrophages18. TTP has been reported to be expressed in human atherosclerotic lesions19, and it has been implicated in the prevention of atherosclerosis plaque formation in ApoE−/− mice20. However, the potential role of apoA-I-mediated antiinflammatory activity and modulation via either STAT3 or TTP signaling during LPS-induced atherosclerosis has not yet been investigated. "
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    ABSTRACT: Aim: To investigate the effects of the major component of high-density lipoprotein apolipoprotein A-I (apoA-I) on the development of atherosclerosis in LPS-challenged ApoE−/− mice and the underlying mechanisms. Methods: Male ApoE-KO mice were daily injected with LPS (25 μg, sc) or PBS for 4 weeks. The LPS-challenged mice were intravenously injected with rAAV-apoA-I-GFP or rAAV-GFP. After the animals were killed, blood, livers and aortas were collected for biochemical and histological analyses. For ex vivo experiments, the abdominal cavity macrophages were harvested from each treatment group of mice, and cultured with autologous serum, then treated with LPS. Results: Chronic administration of LPS in ApoE−/− mice significantly increased the expression of inflammatory cytokines (TNF-α, IL-1β, IL-6, and MCP-1), increased infiltration of inflammatory cells, and enhanced the development of atherosclerosis. In LPS-challenged mice injected with rAAV-apoA-I-GFP, viral particles and human apoA-I were detected in the livers, total plasma human apoA-I levels were grammatically increased; HDL-cholesterol level was significantly increased, TG and TC were slightly increased. Furthermore, overexpression of apoA-I significantly suppressed the expression of proinflammatory cytokines, reduced the infiltration of inflammatory cells, and decreased the extent of atherosclerotic lesions. Moreover, overexpression of apoA-I significantly increased the expression of the cytokine mRNA-destabilizing protein tristetraprolin (TTP), and phosphorylation of JAK2 and STAT3 in aortas. In ex vivo mouse macrophages, the serum from mice overexpressing apoA-I significantly increased the expression of TTP, accompanied by accelerated decay of mRNAs of the inflammatory cytokines. Conclusion: ApoA-I potently suppresses LPS-induced atherosclerosis by inhibiting the inflammatory response possibly via activation of STAT3 and upregulation of TTP.
    Preview · Article · Apr 2013 · Acta Pharmacologica Sinica
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