Arid5a controls IL-6 mRNA stability, which contributes to elevation of IL-6 level in vivo

AT-rich interaction domain 5A regulates the transcription of interleukin-6 gene in prostate cancer cells

BACKGROUND

Interleukin-6 (IL-6) is a pleiotropic cytokine that confers androgen-independence and aggressiveness in prostate cancer (PCa); however, the molecular mechanisms regulating IL-6 expression remain unclear. The expression of ARID5A, an AT-rich interaction domain (ARID) DNA-binding motif-containing transcription factor is positively correlated with IL-6 expression in human PCa. We, therefore, hypothesized that ARID5A could regulate IL-6 expression in PCa.

METHODS

The relationship between ARID5A and IL-6 in PCa patients was analyzed using statistical analyses of multiple clinical microarray data sets. To investigate whether ARID5A regulates IL-6 expression, CRISPR-driven ARID5A knockout clones were established in DU145 and PC-3 cells.

RESULTS

Analysis of three microarray data sets showed a positive correlation between ARID5A and IL-6 expression. The expression of IL-6 in ARID5A knockout clones was significantly reduced compared with control clones in both PCa cell lines. Knockout of ARID5A did not result in any loss of IL-6 mRNA stability. Instead, we observed a significant decrease in the occupancy of both active RNA Polymerase II and the active histone mark, H3K4me3 at the IL-6 transcriptional start site in ARID5A knockout PCa cells, suggesting a role for transcriptional regulation.

CONCLUSIONS

Our study demonstrated that loss of ARID5A downregulates the expression of IL-6 at the transcriptional level.

The RNA binding protein IMP2 drives a stromal-Th17 cell circuit in autoimmune neuroinflammation

Stromal cells are emerging as key drivers of autoimmunity, partially because they produce inflammatory chemokines that orchestrate inflammation. Chemokine expression is regulated transcriptionally but also through posttranscriptional mechanisms, the specific drivers of which are still incompletely defined. CCL2 (MCP1) is a multifunctional chemokine that drives myeloid cell recruitment. During experimental autoimmune encephalomyelitis (EAE), an IL-17–driven model of multiple sclerosis, CCL2 produced by lymph node (LN) stromal cells was essential for immunopathology. Here, we showed that Ccl2 mRNA upregulation in human stromal fibroblasts in response to IL-17 required the RNA-binding protein IGF-2 mRNA-binding protein 2 (IGF2BP2, IMP2), which is expressed almost exclusively in nonhematopoietic cells. IMP2 binds directly to CCL2 mRNA, markedly extending its transcript half-life, and is thus required for efficient CCL2 secretion. Consistent with this, Imp2^−/− mice showed reduced CCL2 production in LNs during EAE, causing impairments in monocyte recruitment and Th17 cell polarization. Imp2^–/– mice were fully protected from CNS inflammation. Moreover, deletion of IMP2 after EAE onset was sufficient to mitigate disease severity. These data showed that posttranscriptional control of Ccl2 in stromal cells by IMP2 was required to permit IL-17–driven progression of EAE pathogenesis.

Sequence determinants as key regulators in gene expression of T cells

T cell homeostasis, T cell differentiation, and T cell effector function rely on the constant fine-tuning of gene expression. To alter the T cell state, substantial remodeling of the proteome is required. This remodeling depends on the intricate interplay of regulatory mechanisms, including post-transcriptional gene regulation. In this review, we discuss how the sequence of a transcript influences these post-transcriptional events. In particular, we review how sequence determinants such as sequence conservation, GC content, and chemical modifications define the levels of the mRNA and the protein in a T cell. We describe the effect of different forms of alternative splicing on mRNA expression and protein production, and their effect on subcellular localization. In addition, we discuss the role of sequences and structures as binding hubs for miRNAs and RNA-binding proteins in T cells. The review thus highlights how the intimate interplay of post-transcriptional mechanisms dictate cellular fate decisions in T cells.

Conceptual Advances in Control of Inflammation by the RNA-Binding Protein Tristetraprolin

Regulated changes in mRNA stability are critical drivers of gene expression adaptations to immunological cues. mRNA stability is controlled mainly by RNA-binding proteins (RBPs) which can directly cleave mRNA but more often act as adaptors for the recruitment of the RNA-degradation machinery. One of the most prominent RBPs with regulatory roles in the immune system is tristetraprolin (TTP). TTP targets mainly inflammation-associated mRNAs for degradation and is indispensable for the resolution of inflammation as well as the maintenance of immune homeostasis. Recent advances in the transcriptome-wide knowledge of mRNA expression and decay rates together with TTP binding sites in the target mRNAs revealed important limitations in our understanding of molecular mechanisms of TTP action. Such orthogonal analyses lead to the discovery that TTP binding destabilizes some bound mRNAs but not others in the same cell. Moreover, comparisons of various immune cells indicated that an mRNA can be destabilized by TTP in one cell type while it remains stable in a different cell linage despite the presence of TTP. The action of TTP extends from mRNA destabilization to inhibition of translation in a subset of targets. This article will discuss these unexpected context-dependent functions and their implications for the regulation of immune responses. Attention will be also payed to new insights into the role of TTP in physiology and tissue homeostasis.

Identification of a Five-Gene Prognostic Signature Related to B Cells Infiltration in Pancreatic Adenocarcinoma

Background

Pancreatic adenocarcinoma (PAAD) is an extremely malignant cancer. Immunotherapy is a promising avenue to increase the survival time of patients with PAAD.

Methods

RNA sequencing and clinical data for PAAD were downloaded from the TCGA database. The ssGSEA method and weighted gene co-expression network analysis were used to calculate the relative abundance of tumor-infiltrating immune cells and identify the related modules. Least absolute shrinkage and selection operator (LASSO) and Cox regression analyses were used to construct a prognostic model. MCPcounter and EPIC were also used to assess immune cell components using gene expression profiles.

Results

The B cells closely related module was identified, and five genes, including ARID5A, CLEC2B, MICAL1, MZB1, and RAPGEF1, were ultimately selected to establish a prognostic signature to calculate the risk scores of PAAD patients. Kaplan–Meier curves showed worse survival in the high-risk patients (p < 0.05), and the area under the receiver operating characteristic (ROC) curves of risk score for 1-year and 3-year survival were 0.78 and 0.80, respectively, based on the training set. Similar results were verified using the validated and combined sets. Interestingly, the low-risk group presented significantly elevated immune and stromal scores, proportion of B cells, and associations between these five genes and B cells were identified using multiple methods including ssGSEA, MCPcounter, and EPIC.

Conclusion

This is the first attempt to study a B cells-related prognostic signature, which is instrumental in the exploration of novel prognostic biomarkers in PAAD.

Regnase-1-related endoribonucleases in health and immunological diseases

Dynamic changes in gene expression are key factors in the development and activation of immune cells. RNA metabolism is one of the critical steps for the control of gene expression. Together with transcriptional regulation, mRNA decay by specific ribonucleases (RNases) plays a vital role in shaping gene expression. In addition to the canonical exoribonuclease-mediated mRNA degradation through the recognition of cis-elements in mRNA 3' untranslated regions by RNA-binding proteins (RBPs), endoribonucleases are involved in the control of mRNAs in immune cells. In this review, we gleam insights on how Regnase-1, an endoribonuclease necessary for regulating immune cell activation and maintenance of immune homeostasis, degrades RNAs involved in immune cell activation. Additionally, we provide insights on recent studies which uncover the role of Regnase-1-related RNases, including Regnase-2, Regnase-3, and Regnase-4, as well as N4BP1 and KHNYN, in immune regulation and antiviral immunity. As the dysregulation of immune mRNA decay leads to pathologies such as autoimmune diseases or impaired activation of immune responses, RNases are deemed as essential components of regulatory feedback mechanisms that modulate inflammation. Given the critical role of RNases in autoimmunity, RNases can be perceived as emerging targets in the development of novel therapeutics.

Defining the RBPome of primary T helper cells to elucidate higher-order Roquin-mediated mRNA regulation

Post-transcriptional gene regulation in T cells is dynamic and complex as targeted transcripts respond to various factors. This is evident for the Icos mRNA encoding an essential costimulatory receptor that is regulated by several RNA-binding proteins (RBP), including Roquin-1 and Roquin-2. Here, we identify a core RBPome of 798 mouse and 801 human T cell proteins by utilizing global RNA interactome capture (RNA-IC) and orthogonal organic phase separation (OOPS). The RBPome includes Stat1, Stat4 and Vav1 proteins suggesting unexpected functions for these transcription factors and signal transducers. Based on proximity to Roquin-1, we select ~50 RBPs for testing coregulation of Roquin-1/2 targets by induced expression in wild-type or Roquin-1/2-deficient T cells. Besides Roquin-independent contributions from Rbms1 and Cpeb4 we also show Roquin-1/2-dependent and target-specific coregulation of Icos by Celf1 and Igf2bp3. Connecting the cellular RBPome in a post-transcriptional context, we find contributions from multiple RBPs to the prototypic regulation of mRNA targets by individual trans-acting factors.

An extensive RNA binding protein atlas (RBPome) for primary T cells would be a useful resource. Here the authors use two different methods to characterise the mouse and human T cell RBPome and show regulation of Roquin-1/2 dependent and independent pathways.

Unravelling the broader complexity of IL-6 involvement in health and disease

The classification of interleukin-6 (IL-6) as a pro-inflammatory cytokine undervalues the biological impact of this cytokine in health and disease. With broad activities affecting the immune system, tissue homeostasis and metabolic processes, IL-6 displays complex biology. The significance of these involvements has become increasingly important in clinical settings where IL-6 is identified as a prominent target for therapy. Here, clinical experience with IL-6 antagonists emphasises the need to understand the context-dependent properties of IL-6 within an inflammatory environment and the anticipated or unexpected consequences of IL-6 blockade. In this review, we will describe the immunobiology of IL-6 and explore the gamut of IL-6 bioactivity affecting the clinical response to biological drugs targeting this cytokine pathway.

Gut Microbiota and Development of Vibrio cholerae-Specific Long-Term Memory B Cells in Adults after Whole-Cell Killed Oral Cholera Vaccine

Cholera is a diarrheal disease caused by Vibrio cholerae that continues to be a major public health concern in populations without access to safe water. IgG- and IgA-secreting memory B cells (MBC) targeting the V. cholerae O-specific polysaccharide (OSP) correlate with protection from infection in persons exposed to V. cholerae and may be a major determinant of long-term protection against cholera. Shanchol, a widely used oral cholera vaccine (OCV), stimulates OSP MBC responses in only some people after vaccination, and the gut microbiota is a possible determinant of variable immune responses observed after OCV. Using 16S rRNA sequencing of feces from the time of vaccination, we compared the gut microbiota among adults with and without MBC responses to OCV. Gut microbial diversity measures were not associated with MBC isotype or OSP-specific responses, but individuals with a higher abundance of Clostridiales and lower abundance of Enterobacterales were more likely to develop an MBC response. We applied protein-normalized fecal supernatants of high and low MBC responders to THP-1-derived human macrophages to investigate the effect of microbial factors at the time of vaccination. Feces from individuals with higher MBC responses induced significantly different IL-1β and IL-6 levels than individuals with lower responses, indicating that the gut microbiota at the time of vaccination may "prime" the mucosal immune response to vaccine antigens. Our results suggest the gut microbiota could impact immune responses to OCVs, and further study of microbial metabolites as potential vaccine adjuvants is warranted.

The novel long noncoding RNA AU021063, induced by IL-6/Arid5a signaling, exacerbates breast cancer invasion and metastasis by stabilizing Trib3 and activating the Mek/Erk pathway

Interleukin (IL-6) is a pleotropic cytokine with both tumor-promoting and -inhibitory effects on breast cancer growth. However, the mechanisms governing the outcome of IL-6 on cancer progression remain to be clarified. Our study unraveled a novel long noncoding RNA (lncRNA) AU021063 downstream of IL-6 signaling. We found that IL-6 induced the expression of AU021063 predominantly in breast cancer compared to other cancer types. Mechanistically, IL-6 induced AT-rich interactive domain 5a (Arid5a) expression, which promotes the transcription of AU021063. In turn, AU021063 promotes breast cancer metastasis through stabilizing tribbles homolog 3 (Trib3) and activating Mek/Erk signaling pathway. Genetic ablation of either Arid5a, AU021063 or Trib3 abolished breast cancer metastasis in vitro and in vivo. Overall, our study highlights the importance of IL-6-Arid5a-AU021063 axis in regulating breast cancer invasiveness and metastasis, which may provide potential novel therapeutics for breast cancer.

Investigation of Fascin1, a Marker of Mature Dendritic Cells, Reveals a New Role for IL-6 Signaling in CCR7-Mediated Chemotaxis

Migration of mature dendritic cells (DCs) to lymph nodes is critical for the initiation of adaptive immunity. CCR7, a G-protein-coupled receptor for CCL19/21 chemokines, is known to be essential for chemotaxis of mature DCs, but the molecular mechanism linking inflammation to chemotaxis remains unclear. We previously demonstrated that fascin1, an actin-bundling protein, increases chemotaxis of mature mouse DCs. In this article, we demonstrated that fascin1 enhanced IL-6 secretion and signaling of mature mouse DCs. Furthermore, we demonstrated that IL-6 signaling is required for chemotaxis. Blockage of IL-6 signaling in wild-type DCs with an anti-IL-6 receptor α (IL-6Rα) Ab inhibited chemotaxis toward CCL19. Likewise, knockout of IL-6Rα inhibited chemotaxis of bone marrow-derived DCs. The addition of soluble IL-6Rα and IL-6 rescued chemotaxis of IL-6Rα knockout bone marrow-derived DCs, underscoring the role of IL-6 signaling in chemotaxis. We found that IL-6 signaling is required for internalization of CCR7, the initial step of CCR7 recycling. CCR7 recycling is essential for CCR7-mediated chemotaxis, explaining why IL-6 signaling is required for chemotaxis of mature DCs. Our results have identified IL-6 signaling as a new regulatory pathway for CCR7/CCL19-mediated chemotaxis and suggest that rapid migration of mature DCs to lymph nodes depends on inflammation-associated IL-6 signaling.

Post-transcriptional regulation of immunological responses by Regnase-1-related RNases

Regulation of messenger RNA (mRNA) decay plays a crucial role in the control of gene expression. Canonical mRNA decay pathways are initiated by deadenylation and decapping, and are followed by exonucleolytic degradation. However, recent studies revealed that endoribonucleolytic cleavage also mediates mRNA decay, and both exoribonucleolytic and endoribonucleolytic decay pathways are important for the regulation of immune responses. Regnase-1 functions as an endoribonuclease to control immunity by damping mRNAs. Particularly, Regnase-1 controls cytokines and other inflammatory mediators by recognizing their mRNAs via stem-loop structures present in the 3' untranslated regions. Regnase-1 was found to be critical for human inflammatory diseases such as ulcerative colitis and idiopathic pulmonary fibrosis. Furthermore, a set of Regnase-1-related RNases contribute to immune regulation as well as antiviral host defense. In this review, we provide an overview of recent findings as to immune-related RNA-binding proteins (RBPs) with an emphasis on stem-loop-mediated mRNA decay via Regnase-1 and related RNases and discuss how the function of these RBPs is regulated and contributes to inflammatory disorders.

The m6A reader IMP2 directs autoimmune inflammation through an IL-17- and TNFα-dependent C/EBP transcription factor axis

Excessive cytokine activity underlies many autoimmune conditions, particularly through the interleukin-17 (IL-17) and tumor necrosis factor-α (TNFα) signaling axis. Both cytokines activate nuclear factor κB, but appropriate induction of downstream effector genes requires coordinated activation of other transcription factors, notably, CCAAT/enhancer binding proteins (C/EBPs). Here, we demonstrate the unexpected involvement of a posttranscriptional "epitranscriptomic" mRNA modification [N6-methyladenosine (m6A)] in regulating C/EBPβ and C/EBPδ in response to IL-17A, as well as IL-17F and TNFα. Prompted by the observation that C/EBPβ/δ-encoding transcripts contain m6A consensus sites, we show that Cebpd and Cebpb mRNAs are subject to m6A modification. Induction of C/EBPs is enhanced by an m6A methylase "writer" and suppressed by a demethylase "eraser." The only m6A "reader" found to be involved in this pathway was IGF2BP2 (IMP2), and IMP2 occupancy of Cebpd and Cebpb mRNA was enhanced by m6A modification. IMP2 facilitated IL-17-mediated Cebpd mRNA stabilization and promoted translation of C/EBPβ/δ in response to IL-17A, IL-17F, and TNFα. RNA sequencing revealed transcriptome-wide IL-17-induced transcripts that are IMP2 influenced, and RNA immunoprecipitation sequencing identified the subset of mRNAs that are directly occupied by IMP2, which included Cebpb and Cebpd Lipocalin-2 (Lcn2), a hallmark of autoimmune kidney injury, was strongly dependent on IL-17, IMP2, and C/EBPβ/δ. Imp2-/- mice were resistant to autoantibody-induced glomerulonephritis (AGN), showing impaired renal expression of C/EBPs and Lcn2 Moreover, IMP2 deletion initiated only after AGN onset ameliorated disease. Thus, posttranscriptional regulation of C/EBPs through m6A/IMP2 represents a previously unidentified paradigm of cytokine-driven autoimmune inflammation.

Terminal uridyltransferase 7 regulates TLR4-triggered inflammation by controlling Regnase-1 mRNA uridylation and degradation

Different levels of regulatory mechanisms, including posttranscriptional regulation, are needed to elaborately regulate inflammatory responses to prevent harmful effects. Terminal uridyltransferase 7 (TUT7) controls RNA stability by adding uridines to its 3′ ends, but its function in innate immune response remains obscure. Here we reveal that TLR4 activation induces TUT7, which in turn selectively regulates the production of a subset of cytokines, including Interleukin 6 (IL-6). TUT7 regulates IL-6 expression by controlling ribonuclease Regnase-1 mRNA (encoded by Zc3h12a gene) stability. Mechanistically, TLR4 activation causes TUT7 to bind directly to the stem-loop structure on Zc3h12a 3′-UTR, thereby promotes Zc3h12a uridylation and degradation. Zc3h12a from LPS-treated TUT7-sufficient macrophages possesses increased oligo-uridylated ends with shorter poly(A) tails, whereas oligo-uridylated Zc3h12a is significantly reduced in Tut7^-/- cells after TLR4 activation. Together, our findings reveal the functional role of TUT7 in sculpting TLR4-driven responses by modulating mRNA stability of a selected set of inflammatory mediators.

Terminal uridyltransferase 7 (TUT7) adds U-tails on diverse RNAs to promote degradation. Here the authors show that TUT7 is induced upon LPS treatment in macrophages and promotes decay of Regnase-1, thereby regulating the expression of a subset of cytokines, including IL-6.

The mRNA-destabilizing protein Tristetraprolin targets "meiosis arrester" Nppc mRNA in mammalian preovulatory follicles

C-natriuretic peptide (CNP) and its receptor guanylyl cyclase, natriuretic peptide receptor 2 (NPR2), are key regulators of cyclic guanosine monophosphate (cGMP) homeostasis. The CNP-NPR2-cGMP signaling cascade plays an important role in the progression of oocyte meiosis, which is essential for fertility in female mammals. In preovulatory ovarian follicles, the luteinizing hormone (LH)-induced decrease in CNP and its encoding messenger RNA (mRNA) natriuretic peptide precursor C (Nppc) are a prerequisite for oocyte meiotic resumption. However, it has never been determined how LH decreases CNP/Nppc In the present study, we identified that tristetraprolin (TTP), also known as zinc finger protein 36 (ZFP36), a ubiquitously expressed mRNA-destabilizing protein, is the critical mechanism that underlies the LH-induced decrease in Nppc mRNA. Zfp36 mRNA was transiently up-regulated in mural granulosa cells (MGCs) in response to the LH surge. Loss- and gain-of-function analyses indicated that TTP is required for Nppc mRNA degradation in preovulatory MGCs by targeting the rare noncanonical AU-rich element harbored in the Nppc 3' UTR. Moreover, MGC-specific knockout of Zfp36, as well as lentivirus-mediated knockdown in vivo, impaired the LH/hCG-induced Nppc mRNA decline and oocyte meiotic resumption. Furthermore, we found that LH/hCG activates Zfp36/TTP expression through the EGFR-ERK1/2-dependent pathway. Our findings reveal a functional role of TTP-induced mRNA degradation, a global posttranscriptional regulation mechanism, in orchestrating the progression of oocyte meiosis. We also provided a mechanism for understanding CNP-dependent cGMP homeostasis in diverse cellular processes.

Therapeutic targeting of IL-6 trans-signaling

Interleukin-6 (IL-6) is a cytokine, which is involved in innate and acquired immunity, in neural cell maintenance and in metabolism. IL-6 can be synthesized by many different cells including myeloid cells, fibroblasts, endothelial cells and lymphocytes. The synthesis of IL-6 is strongly stimulated by Toll like receptors and by IL-1. Therefore, IL-6 levels in the body are high during infection and inflammatory processes. Moreover, IL-6 is a prominent growth factor of tumor cells and plays a major role in inflammation associated cancer. On target cells, IL-6 binds to an IL-6 receptor, which is not signaling competent. The complex of IL-6 and IL-6 receptor associate with a second receptor subunit, glycoprotein gp130, which dimerizes and initiates intracellular signaling. Cells, which do not express the IL-6 receptor are not responsive to IL-6. They can, however, be stimulated by the complex of IL-6 and a soluble form of the IL-6 receptor, which is generated by limited proteolysis and to a lesser extent by translation from an alternatively spliced mRNA. This process has been named IL-6 trans-signaling. This review article will explain the biology of IL-6 trans-signaling and the specific inhibition of this mode of signaling, which has been recognized to be fundamental in inflammation and cancer.

Expression and Prognostic Value of ARID5A and its Correlation With Tumor-Infiltrating Immune Cells in Glioma

AT-rich interaction domain 5A (ARID5A) is a member of the ARID family with a function that has been linked to autoimmune as well as inflammatory diseases. Some ARID family members are involved in the initiation and progression of human cancers. However, the function of ARID5A in glioma remains unknown. In this study, ARID5A expression levels were analyzed using the Gene Expression Profiling Interactive Analysis (GEPIA) database. Subsequently, the relationship between ARID5A expression and the clinical characteristics of glioma patients was evaluated using the Chinese Glioma Genome Atlas (CGGA) database and The Cancer Genome Atlas (TCGA) database. The prognostic value of ARID5A in glioma was estimated by Kaplan-Meier analysis and the receiver operating characteristic (ROC) curve analysis. Gene ontology (GO) analysis and gene set enrichment analysis (GSEA) were performed for functional prediction. The Tumor Immune Estimation Resource (TIMER) database was used to analyze the relationship between ARID5A and immune cell infiltration in glioma. Our results demonstrate that the expression of ARID5A was upregulated in glioma compared with that in nontumor brain tissues. High expression of ARID5A is associated with poor prognosis in glioma. We found that the expression of ARID5A was significantly upregulated with an increase in tumor malignancy. GO analysis revealed that co-expression genes of ARID5A are significantly involved in some important functions in glioma, and GSEA showed that multiple cancer-associated and immune-associated signaling pathways are enriched in the high ARID5A expression group. TIMER database indicated that ARID5A is correlated with tumor-infiltrating immune cells in glioma. Collectively, these findings indicate that ARID5A may be a potential prognostic biomarker and is correlated with immune infiltration in glioma.

Converged Rab37/IL-6 trafficking and STAT3/PD-1 transcription axes elicit an immunosuppressive lung tumor microenvironment

Background: Increased IL-6 level, M2 macrophages and PD-1⁺CD8⁺ T cells in tumor microenvironments (TME) have been identified to correlate with resistance to checkpoint blockade immunotherapy, yet the mechanism remains poorly understood. Rab small GTPase-mediated trafficking of cytokines is critical in immuno-modulation. We have previously reported dysregulation of Rab37 in lung cancer cells, whereas the roles of Rab37 in tumor-infiltrating immune cells and cancer immunotherapy are unclear.

Methods: The tumor growth of the syngeneic mouse allograft in wild type or Rab37 knockout mice was analyzed. Imaging analyses and vesicle isolation were conducted to determine Rab37-mediated IL-6 secretion. STAT3 binding sites at PD-1 promoter in T cells were identified by chromatin immunoprecipitation assay. Multiplex fluorescence immunohistochemistry was performed to detect the protein level of Rab37, IL-6 and PD-1 and localization of the tumor-infiltrating immune cells in allografts from mice or tumor specimens from lung cancer patients.

Results: We revealed that Rab37 regulates the secretion of IL-6 in a GTPase-dependent manner in macrophages to trigger M2 polarization. Macrophage-derived IL-6 promotes STAT3-dependent PD-1 mRNA expression in CD8⁺ T cells. Clinically, tumors with high stromal Rab37 and IL-6 expression coincide with tumor infiltrating M2-macrophages and PD1⁺CD8⁺ T cells that predicts poor prognosis in lung cancer patients. In addition, lung cancer patients with an increase in plasma IL-6 level are found to be associated with immunotherapeutic resistance. Importantly, combined blockade of IL-6 and CTLA-4 improves survival of tumor-bearing mice by reducing infiltration of PD1⁺CD8⁺ T cells and M2 macrophages in TME.

Conclusions: Rab37/IL-6 trafficking pathway links with IL-6/STAT3/PD-1 transcription regulation to foster an immunosuppressive TME and combined IL-6/CTLA-4 blockade therapy exerts potent anti-tumor efficacy.

Anti-Inflammatory Effects of a Polyphenol, Catechin-7,4'-O-Digallate, from Woodfordia uniflora by Regulating NF-κB Signaling Pathway in Mouse Macrophages

Inflammation is a defense mechanism that protects the body from infections. However, chronic inflammation causes damage to body tissues. Thus, controlling inflammation and investigating anti-inflammatory mechanisms are keys to preventing and treating inflammatory diseases, such as sepsis and rheumatoid arthritis. In continuation with our work related to the discovery of bioactive natural products, a polyphenol, catechin-7,4′-O-digallate (CDG), was isolated from Woodfordia uniflora, which has been used as a sedative and remedy for skin infections in the Dhofar region of Oman. Thus far, no study has reported the anti-inflammatory compounds derived from W. uniflora and the mechanisms underlying their action. To investigate the effects of CDG on the regulation of inflammation, we measured the reduction in nitric oxide (NO) production following CDG treatment in immortalized mouse Kupffer cells (ImKCs). CDG treatment inhibited NO production through the downregulation of inducible nitric oxide synthase expression in lipopolysaccharide (LPS)-stimulated ImKCs. The anti-inflammatory effects of CDG were mediated via the inhibition of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) activation, an important inflammatory-response-associated signaling pathway. Moreover, CDG treatment has regulated the expression of pro-inflammatory cytokines, such as IL-6 and IL-1β. These results suggested the anti-inflammatory action of CDG in LPS-stimulated ImKCs.

Interleukin-6: From arthritis to CAR-T cell therapy and COVID-19

Blockade of interleukin (IL)-6 function by an anti-IL-6 receptor (IL-6R) antibody (tocilizumab, trade name Actemra) has been shown to be effective for the treatment of chronic autoimmune inflammatory diseases including rheumatoid arthritis. Interestingly, treatment with tocilizumab has also been found to alleviate the cytokine storm induced by chimeric antigen receptor (CAR)-T cell therapy. Patients with serious cases of coronavirus disease 2019 (COVID-19) exhibit cytokine release syndrome (CRS), which suggested that tocilizumab might be an effective therapeutic for serious cases of COVID-19. In the first part of this short review, the therapeutic effect of tocilizumab for the disease induced by IL-6 overproduction is described. CRS induced by CAR-T cell therapy and COVID-19 is then discussed.

IL-6 in inflammation, autoimmunity and cancer

IL-6 is involved both in immune responses and in inflammation, hematopoiesis, bone metabolism and embryonic development. IL-6 plays roles in chronic inflammation (closely related to chronic inflammatory diseases, autoimmune diseases and cancer) and even in the cytokine storm of corona virus disease 2019 (COVID-19). Acute inflammation during the immune response and wound healing is a well-controlled response, whereas chronic inflammation and the cytokine storm are uncontrolled inflammatory responses. Non-immune and immune cells, cytokines such as IL-1β, IL-6 and tumor necrosis factor alpha (TNFα) and transcription factors nuclear factor-kappa B (NF-κB) and signal transducer and activator of transcription 3 (STAT3) play central roles in inflammation. Synergistic interactions between NF-κB and STAT3 induce the hyper-activation of NF-κB followed by the production of various inflammatory cytokines. Because IL-6 is an NF-κB target, simultaneous activation of NF-κB and STAT3 in non-immune cells triggers a positive feedback loop of NF-κB activation by the IL-6-STAT3 axis. This positive feedback loop is called the IL-6 amplifier (IL-6 Amp) and is a key player in the local initiation model, which states that local initiators, such as senescence, obesity, stressors, infection, injury and smoking, trigger diseases by promoting interactions between non-immune cells and immune cells. This model counters dogma that holds that autoimmunity and oncogenesis are triggered by the breakdown of tissue-specific immune tolerance and oncogenic mutations, respectively. The IL-6 Amp is activated by a variety of local initiators, demonstrating that the IL-6-STAT3 axis is a critical target for treating diseases.

Control of RNA Stability in Immunity

Posttranscriptional control of mRNA regulates various biological processes, including inflammatory and immune responses. RNA-binding proteins (RBPs) bind cis-regulatory elements in the 3' untranslated regions (UTRs) of mRNA and regulate mRNA turnover and translation. In particular, eight RBPs (TTP, AUF1, KSRP, TIA-1/TIAR, Roquin, Regnase, HuR, and Arid5a) have been extensively studied and are key posttranscriptional regulators of inflammation and immune responses. These RBPs sometimes collaboratively or competitively bind the same target mRNA to enhance or dampen regulatory activities. These RBPs can also bind their own 3' UTRs to negatively or positively regulate their expression. Both upstream signaling pathways and microRNA regulation shape the interactions between RBPs and target RNA. Dysregulation of RBPs results in chronic inflammation and autoimmunity. Here, we summarize the functional roles of these eight RBPs in immunity and their associated diseases.

Expression and prognostic values of ARID family members in breast cancer

The ARID family is a superfamily of 15 members containing a domain that interacts with AT-rich DNA elements. However, the expression and prognostic roles of each ARID in breast cancer are still elusive.

We used the TCGA and Kaplan-Meier plotter databases to assess the expression and prognostic values of ARID mRNA levels in breast cancer respectively. In the present study, 6 members were significantly lower in tumor tissues than those in the normal tissues, while 6 members were significantly higher. Further assessment of ARID expression in breast cancer with different molecular subtypes, 3 members were significantly higher in no-luminal molecular subtype than those in the luminal molecular subtype, and 6 members were significantly higher. In regard to prognostic values, high expression of ARID1A, ARID2, ARID3B, ARID4A, ARID5A, ARID5B, JARID1A were associated with favorable outcome, while ARID4B and JARID1B were correlated to a worse outcome. We further analyzed the prognostic value of ARID in different intrinsic subtypes and clinicopathological features of breast cancer. We found many meaningful ARID family biomarkers in breast cancer. The relevant results will expound the role of ARID in breast cancer and may further provide new insight to explore the ARID-targeting reagents for treating breast cancer patients.

RanBP2/Nup358 enhances miRNA activity by sumoylating Argonautes

Mutations in RanBP2 (also known as Nup358), one of the main components of the cytoplasmic filaments of the nuclear pore complex, contribute to the overproduction of acute necrotizing encephalopathy (ANE1)-associated cytokines. Here we report that RanBP2 represses the translation of the interleukin 6 (IL6) mRNA, which encodes a cytokine that is aberrantly up-regulated in ANE1. Our data indicates that soon after its production, the IL6 messenger ribonucleoprotein (mRNP) recruits Argonautes bound to let-7 microRNA. After this mRNP is exported to the cytosol, RanBP2 sumoylates mRNP-associated Argonautes, thereby stabilizing them and enforcing mRNA silencing. Collectively, these results support a model whereby RanBP2 promotes an mRNP remodelling event that is critical for the miRNA-mediated suppression of clinically relevant mRNAs, such as IL6.

Cell-intrinsic mechanisms to restrain inflammatory responses in T lymphocytes

A mechanistic understanding of the regulatory circuits that control the effector responses of memory T helper lymphocytes, and in particular their ability to produce pro-inflammatory cytokines, may lead to effective therapeutic interventions in all immune-related diseases. Activation of T lymphocytes induces robust immune responses that in most cases lead to the complete eradication of invading pathogens or tumor cells. At the same time, however, such responses must be both highly controlled in magnitude and limited in time to avoid unnecessary damage. To achieve such sophisticated level of control, T lymphocytes have at their disposal an array of transcriptional and post-transcriptional regulatory mechanisms that ensure the acquisition of a phenotype that is tailored to the incoming stimulus while restraining unwarranted activation, eventually leading to the resolution of the inflammatory response. Here, we will discuss some of these cell-intrinsic mechanisms that control T cell responses and involve transcription factors, microRNAs, and RNA-binding proteins. We will also explore how the same mechanisms can be involved both in anti-tumor responses and in autoimmunity.

Differential modulation of Ahr and Arid5a: A promising therapeutic strategy for autoimmune encephalomyelitis

Multiple sclerosis (MS) is an autoimmune disease that involves demyelination of axons in the central nervous system (CNS) and affects patients worldwide. It has been demonstrated that ligand-activated aryl hydrocarbon receptor (Ahr) ameliorates experimental autoimmune encephalomyelitis (EAE), a murine model of MS, by increasing CD4⁺FoxP3⁺ T cells. Recent evidence indicates that AT-rich interactive domain-containing protein 5a (Arid5a) is required for EAE pathogenesis by stabilizing Il6 and OX40 mRNAs. However, the differential modulation of Ahr and Arid5a in autoimmunity as a therapeutic strategy is unexplored. Herein, an in silico, in vitro and in vivo approach identified Flavipin (3,4,5-trihydroxy-6-methylphthalaldehyde) as an Ahr agonist that induces the expression of Ahr downstream genes in mouse CD4⁺ T cells and CD11b⁺ macrophages. Interestingly, Flavipin inhibited the stabilizing function of Arid5a and its counteracting effects on Regnase-1 on the 3′ untranslated region (3′UTR) of target mRNAs. Furthermore, it inhibited the stabilizing function of Arid5a on Il23a 3′UTR, a newly identified target mRNA. In EAE, Flavipin ameliorated disease severity, with reduced CD4⁺IL-17⁺ T cells, IL-6 and TNF-α and increased CD4⁺FoxP3⁺ T cells. Moreover, EAE amelioration was concomitant with reduced CD4⁺OX40⁺ and CD4⁺CD45⁺ T cells in the CNS. RNA interference showed that the modulatory effects of Flavipin on pro- and anti-inflammatory mediators in CD4⁺ T cells and macrophages were Ahr- and/or Arid5a-dependent. In conclusion, our findings reveal differential modulation of Ahr and Arid5a as a new therapeutic strategy for MS.

Historical overview of the interleukin-6 family cytokine

Interleukin-6 (IL-6) has been identified as a 26-kD secreted protein that stimulates B cells to produce antibodies. Later, IL-6 was revealed to have various functions that overlap with other IL-6 family cytokines and use the common IL-6 signal transducer gp130. IL-6 stimulates cells through multiple pathways, using both membrane and soluble IL-6 receptors. As indicated by the expanding market for IL-6 inhibitors, it has become a primary therapeutic target among IL-6 family cytokines. Here, we revisit the discovery of IL-6; discuss insights regarding the roles of this family of cytokines; and highlight recent advances in our understanding of regulation of IL-6 expression.

Structural basis for the recognition of transiently structured AU-rich elements by Roquin

Adenylate/uridylate-rich elements (AREs) are the most common cis-regulatory elements in the 3′-untranslated region (UTR) of mRNAs, where they fine-tune turnover by mediating mRNA decay. They increase plasticity and efficacy of mRNA regulation and are recognized by several ARE-specific RNA-binding proteins (RBPs). Typically, AREs are short linear motifs with a high content of complementary A and U nucleotides and often occur in multiple copies. Although thermodynamically rather unstable, the high AU-content might enable transient secondary structure formation and modify mRNA regulation by RBPs. We have recently suggested that the immunoregulatory RBP Roquin recognizes folded AREs as constitutive decay elements (CDEs), resulting in shape-specific ARE-mediated mRNA degradation. However, the structural evidence for a CDE-like recognition of AREs by Roquin is still lacking. We here present structures of CDE-like folded AREs, both in their free and protein-bound form. Moreover, the AREs in the UCP3 3′-UTR are additionally bound by the canonical ARE-binding protein AUF1 in their linear form, adopting an alternative binding-interface compared to the recognition of their CDE structure by Roquin. Strikingly, our findings thus suggest that AREs can be recognized in multiple ways, allowing control over mRNA regulation by adapting distinct conformational states, thus providing differential accessibility to regulatory RBPs.

The glutathione peroxidase 8 (GPX8)/IL-6/STAT3 axis is essential in maintaining an aggressive breast cancer phenotype

One of the emerging hallmarks of cancer illustrates the importance of metabolic reprogramming, necessary to synthesize the building blocks required to fulfill the high demands of rapidly proliferating cells. However, the proliferation-independent instructive role of metabolic enzymes in tumor plasticity is still unclear. Here, we provide evidence that glutathione peroxidase 8 (GPX8), a poorly characterized enzyme that resides in the endoplasmic reticulum, is an essential regulator of tumor aggressiveness. We found that GPX8 expression was induced by the epithelial-mesenchymal transition (EMT) program. Moreover, in breast cancer patients, GPX8 expression significantly correlated with known mesenchymal markers and poor prognosis. Strikingly, GPX8 knockout in mesenchymal-like cells (MDA-MB-231) resulted in an epithelial-like morphology, down-regulation of EMT characteristics, and loss of cancer stemness features. In addition, GPX8 knockout significantly delayed tumor initiation and decreased its growth rate in mice. We found that these GPX8 loss-dependent phenotypes were accompanied by the repression of crucial autocrine factors, in particular, interleukin-6 (IL-6). In these cells, IL-6 bound to the soluble receptor (sIL6R), stimulating the JAK/STAT3 signaling pathway by IL-6 trans-signaling mechanisms, so promoting cancer aggressiveness. We observed that in GPX8 knockout cells, this signaling mechanism was impaired as sIL6R failed to activate the JAK/STAT3 signaling pathway. Altogether, we present the GPX8/IL-6/STAT3 axis as a metabolic-inflammatory pathway that acts as a robust regulator of cancer cell aggressiveness.

Different mechanisms underlie IL-6 release in chemosensitive and chemoresistant ovarian carcinoma cells

Interleukin (IL)-6 has been detected in serum and ascites from patients affected by epithelial ovarian cancers, and also in some human ovarian cancer cell lines. To investigate the role of IL-6 in ovarian lesions, we first measured its levels in serum samples of 24 healthy donors and in 17 and 9 patients affected by ovarian carcinomas and ovarian benign cysts respectively. IL-6 levels were significantly higher than healthy donors in serum samples from ovarian cancer patients, but not in benign ovarian cysts. We then investigated the mechanism of IL-6 production in two cell lines obtained from the same patient with high grade serous ovarian carcinoma before (PEA1) and after (PEA2) development of cisplatinum resistance. The levels of intracellular IL-6, analysed by western blotting, did not relevantly differ in the two cell lines, and they did not change after the cell treatment with an AKT inhibitor. Although the interleukin was present in supernatants from both cell lines, its concentration in the supernatant of chemoresistant cells was significantly higher than chemosensitive cells. Interestingly, exposure to the AKT inhibitor resulted in a reduced IL-6 release in PEA1, but not in PEA2 cells. These results let infer different mechanisms of IL-6 release in chemoresistant and chemosensitive cell lines, and contribute new insights in ovarian cancer biology that suggest more in depth studies about the role of AKT in IL-6 release and in development of chemoresistance.

RNA Recognition and Immunity-Innate Immune Sensing and Its Posttranscriptional Regulation Mechanisms

RNA acts as an immunostimulatory molecule in the innate immune system to activate nucleic acid sensors. It functions as an intermediate, conveying genetic information to control inflammatory responses. A key mechanism for RNA sensing is discriminating self from non-self nucleic acids to initiate antiviral responses reliably, including the expression of type I interferon (IFN) and IFN-stimulated genes. Another important aspect of the RNA-mediated inflammatory response is posttranscriptional regulation of gene expression, where RNA-binding proteins (RBPs) have essential roles in various RNA metabolisms, including splicing, nuclear export, modification, and translation and mRNA degradation. Recent evidence suggests that the control of mRNA stability is closely involved in signal transduction and orchestrates immune responses. In this study, we review the current understanding of how RNA is sensed by host RNA sensing machinery and discuss self/non-self-discrimination in innate immunity focusing on mammalian species. Finally, we discuss how posttranscriptional regulation by RBPs shape immune reactions.

Origin and Function of Stress-Induced IL-6 in Murine Models

Acute psychological stress has long been known to decrease host fitness to inflammation in a wide variety of diseases, but how this occurs is incompletely understood. Using mouse models, we show that interleukin-6 (IL-6) is the dominant cytokine inducible upon acute stress alone. Stress-inducible IL-6 is produced from brown adipocytes in a beta-3-adrenergic-receptor-dependent fashion. During stress, endocrine IL-6 is the required instructive signal for mediating hyperglycemia through hepatic gluconeogenesis, which is necessary for anticipating and fueling "fight or flight" responses. This adaptation comes at the cost of enhancing mortality to a subsequent inflammatory challenge. These findings provide a mechanistic understanding of the ontogeny and adaptive purpose of IL-6 as a bona fide stress hormone coordinating systemic immunometabolic reprogramming. This brain-brown fat-liver axis might provide new insights into brown adipose tissue as a stress-responsive endocrine organ and mechanistic insight into targeting this axis in the treatment of inflammatory and neuropsychiatric diseases.

No Significant Effects of IL-6 and IL-13 Gene Variants on Tuberculosis Susceptibility in the Chinese Population

Tuberculosis (TB) is an intricate infectious disease that causes a large number of deaths in the population. Interleukin (IL)-6 and IL-13 play functional roles in host resistance to Mycobacterium tuberculosis infection. Our aim in this study was to explore the association of IL-6 and IL-13 polymorphisms with TB susceptibility in the Western Chinese Han population. The case and control groups comprised 900 TB patients and 1534 healthy controls, respectively, and four single-nucleotide polymorphisms (SNPs) were genotyped in IL-6 and five SNPs in IL-13 through the improved multiplex ligation detection reaction method. We found no genetic variants in the IL-6 or IL-13 genes that were related to TB susceptibility in the analysis of alleles, genotypes, genetic models, and TB clinical subtypes, except for a trend toward low pulmonary tuberculosis and extrapulmonary tuberculosis susceptibility for the SNPs rs1295686 and rs20541. Our study did not find a link between IL-6 and IL-13 polymorphisms and TB susceptibility in the Western Chinese Han population. Therefore, our present data revealed the challenge of applying IL-6 and IL-13 SNPs as genetic markers for TB and that increased sample sizes and additional races are needed for further studies.

Analysis of the nucleocytoplasmic shuttling RNA-binding protein HNRNPU using optimized HITS-CLIP method

RNA-binding proteins (RBPs) control many types of post-transcriptional regulation, including mRNA splicing, mRNA stability, and translational efficiency, by directly binding to their target RNAs and their mutation and dysfunction are often associated with several human neurological diseases and tumorigenesis. Crosslinking immunoprecipitation (CLIP), coupled with high-throughput sequencing (HITS-CLIP), is a powerful technique for investigating the molecular mechanisms underlying disease pathogenesis by comprehensive identification of RBP target sequences at the transcriptome level. However, HITS-CLIP protocol is still required for some optimization due to experimental complication, low efficiency and time-consuming, whose library has to be generated from very small amounts of RNAs. Here we improved a more efficient, rapid, and reproducible CLIP method by optimizing BrdU-CLIP. Our protocol produced a 10-fold greater yield of pre-amplified CLIP library, which resulted in a low duplicate rate of CLIP-tag reads because the number of PCR cycles required for library amplification was reduced. Variance of the yields was also reduced, and the experimental period was shortened by 2 days. Using this, we validated IL-6 expression by a nuclear RBP, HNRNPU, which directly binds the 3’-UTR of IL-6 mRNA in HeLa cells. Importantly, this interaction was only observed in the cytoplasmic fraction, suggesting a role of cytoplasmic HNRNPU in mRNA stability control. This optimized method enables us to accurately identify target genes and provides a snapshot of the protein-RNA interactions of nucleocytoplasmic shuttling RBPs.

β2-adrenergic stimulation induces interleukin-6 by increasing Arid5a, a stabilizer of mRNA, through cAMP/PKA/CREB pathway in cardiac fibroblasts

BACKGROUND AND PURPOSE

In cardiovascular diseases, cardiac fibroblasts (CFs) participate in the myocardial inflammation by producing pro-inflammatory cytokines, worsening the prognosis. β2-adrenergic receptor (AR) and β3AR are expressed in CFs, and β-adrenergic stimulation promotes CFs to produce pro-inflammatory cytokines. However, the mechanism of the expression of pro-inflammatory cytokines in response to β-adrenergic stimulation remains to be fully elucidated.

EXPERIMENTAL APPROACH

CFs were isolated from adult wild-type or AT-rich interactive domain-containing protein 5A (Arid5a) knockout mice. The expression of mRNA was measured by real-time RT-PCR. Interleukin (IL)-6 protein was measured by ELISA. The activity of nuclear factor-κB (NF-κB) and cyclic AMP (cAMP) response element binding protein (CREB) was assessed by ELISA-like assay or Western blotting.

KEY RESULTS

The β-adrenergic stimulation remarkably induced IL-6 mRNA and protein through β2AR in CFs. The activation of adenylate cyclase and the enhancement of intracellular cAMP resulted in the upregulation of IL-6 mRNA expression. The induction of IL-6 transcript by β2AR signaling was independent of NF-κB. Concomitant with IL-6, the expression of Arid5a, an IL-6 mRNA stabilizing factor, was enhanced by β2-adrenergic stimulation and by cAMP increase. Importantly, β2AR signaling-mediated IL-6 induction was suppressed in Arid5a knockout CFs. Finally, β2AR stimulation phosphorylated CREB via PKA pathway, and the activation of CREB was essential for the induction of Arid5a and IL-6 mRNA.

CONCLUSION AND IMPLICATIONS

β2-adrenergic stimulation post-transcriptionally upregulates the expression of IL-6 by the induction of Arid5a through cAMP/PKA/CREB pathway in adult CFs. β2AR/Arid5a/IL-6 axis could be a therapeutic target against cardiac inflammation.

Noncanonical STAT1 phosphorylation expands its transcriptional activity into promoting LPS-induced IL-6 and IL-12p40 production

The lipopolysaccharide (LPS)–induced endocytosis of Toll-like receptor 4 (TLR4) is an essential step in the production of interferon-β (IFN-β), which activates the transcription of antiviral response genes by STAT1 phosphorylated at Tyr701. Here, we showed that STAT1 regulated proinflammatory cytokine production downstream of TLR4 endocytosis independently of IFN-β signaling and the key proinflammatory regulator NF-κB. In human macrophages, TLR4 endocytosis activated a noncanonical phosphorylation of STAT1 at Thr749, which subsequently promoted the production of interleukin-6 (IL-6) and IL-12p40 through distinct mechanisms. STAT1 phosphorylated at Thr749activated the expression of the gene encoding ARID5A, which stabilizesIL6mRNA. Moreover, STAT1 phosphorylated at Thr749directly enhanced transcription of the gene encoding IL-12p40 (IL12B). Instead of affecting STAT1 nuclear translocation, phosphorylation of Thr749facilitated the binding of STAT1 to a noncanonical DNA motif (5′-TTTGANNC-3′) in the promoter regions ofARID5AandIL12B. The endocytosis of TLR4 induced the formation of a complex between the kinases TBK1 and IKKβ, which mediated the phosphorylation of STAT1 at Thr749. Our data suggest that noncanonical phosphorylation in response to LPS confers STAT1 with distinct DNA binding and gene-regulatory properties that promote bothIL12Bexpression andIL6mRNA stabilization. Thus, our study provides a potential mechanism for how TLR4 endocytosis might regulate proinflammatory cytokine production.

Role of Signal Transduction Pathways and Transcription Factors in Cartilage and Joint Diseases

Osteoarthritis and rheumatoid arthritis are common cartilage and joint diseases that globally affect more than 200 million and 20 million people, respectively. Several transcription factors have been implicated in the onset and progression of osteoarthritis, including Runx2, C/EBPβ, HIF2α, Sox4, and Sox11. Interleukin-1 β (IL-1β) leads to osteoarthritis through NF-ĸB, IκBζ, and the Zn²⁺-ZIP8-MTF1 axis. IL-1, IL-6, and tumor necrosis factor α (TNFα) play a major pathological role in rheumatoid arthritis through NF-ĸB and JAK/STAT pathways. Indeed, inhibitory reagents for IL-1, IL-6, and TNFα provide clinical benefits for rheumatoid arthritis patients. Several growth factors, such as bone morphogenetic protein (BMP), fibroblast growth factor (FGF), parathyroid hormone-related protein (PTHrP), and Indian hedgehog, play roles in regulating chondrocyte proliferation and differentiation. Disruption and excess of these signaling pathways cause genetic disorders in cartilage and skeletal tissues. Fibrodysplasia ossificans progressive, an autosomal genetic disorder characterized by ectopic ossification, is induced by mutant ACVR1. Mechanistic target of rapamycin kinase (mTOR) inhibitors can prevent ectopic ossification induced by ACVR1 mutations. C-type natriuretic peptide is currently the most promising therapy for achondroplasia and related autosomal genetic diseases that manifest severe dwarfism. In these ways, investigation of cartilage and chondrocyte diseases at molecular and cellular levels has enlightened the development of effective therapies. Thus, identification of signaling pathways and transcription factors implicated in these diseases is important.

Arid5a, an RNA-Binding Protein in Immune Regulation: RNA Stability, Inflammation, and Autoimmunity

AT-rich interactive domain 5A (ARID5A/Arid5a) is a known cofactor of transcription factors (TFs) that contributes to cell growth and differentiation. It has recently been recognized for its unique function in the stabilization of mRNA, which is associated with inflammatory autoimmune diseases. Studies have revolutionized our understanding of the post-transcriptional regulation of inflammatory genes by revealing the fundamental events underpinning novel functions and activities of Arid5a. We review current research on Arid5a, which has focused our attention towards the therapeutic potential of this factor in the putative treatment of inflammatory and autoimmune disorders, including experimental autoimmune encephalomyelitis and sepsis in mice.

Exercise as an anti-inflammatory therapy for cancer cachexia: a focus on interleukin-6 regulation

Cancer cachexia is a complicated disorder of extreme, progressive skeletal muscle wasting. It is directed by metabolic alterations and systemic inflammation dysregulation. Numerous studies have demonstrated that increased systemic inflammation promotes this type of cachexia and have suggested that cytokines are implicated in the skeletal muscle loss. Exercise is firmly established as an anti-inflammatory therapy that can attenuate or even reverse the process of muscle wasting in cancer cachexia. The interleukin IL-6 is generally considered to be a key player in the development of the microenvironment of malignancy; it promotes tumor growth and metastasis by acting as a bridge between chronic inflammation and cancerous tissue and it also induces skeletal muscle atrophy and protein breakdown. Paradoxically, a beneficial role for IL-6 has also been identified recently, and that is its status as a “founding member” of the myokine class of proteins. Skeletal muscle is an important source of circulating IL-6 in people who participate in exercise training. IL-6 acts as an anti-inflammatory myokine by inhibiting TNFα and improving glucose uptake through the stimulation of AMPK signaling. This review discusses the action of IL-6 in skeletal muscle tissue dysfunction and the role of IL-6 as an “exercise factor” that modulates the immune system. This review also sheds light on the main considerations related to the treatment of muscle wasting in cancer cachexia.

Arid5a Regulation and the Roles of Arid5a in the Inflammatory Response and Disease

Abnormal gene expression patterns underlie many diseases that represent major public health concerns and robust therapeutic challenges. Posttranscriptional gene regulation by RNA-binding proteins (RBPs) is well-recognized, and the biological functions of RBPs have been implicated in many diseases, such as autoimmune diseases, inflammatory diseases, and cancer. However, a complete understanding of the regulation mediated by several RBPs is lacking. During the past few years, a novel role of AT-rich interactive domain-containing protein 5a (Arid5a) as an RBP is being investigated in the field of immunology owing to binding of Arid5a protein to the 3' untranslated region (UTR) of Il-6 mRNA. Indeed, Arid5a is a dynamic molecule because upon inflammation, it translocates to the cytoplasm and stabilizes a variety of inflammatory mRNA transcripts, including Il-6, Stat3, Ox40, T-bet, and IL-17-induced targets, and contributes to the inflammatory response and a variety of diseases. TLR4-activated NF-κB and MAPK pathways are involved in regulating Arid5a expression from synthesis to degradation, and even a slight alteration in these pathways can lead to intense production of inflammatory molecules, such as IL-6, which may further contribute to the development of inflammatory diseases such as sepsis and experimental autoimmune encephalomyelitis. This review highlights the regulation of the Arid5a expression and function. Additionally, recent findings on Arid5a are discussed to further our understanding of this molecule, which may be a promising therapeutic target for inflammatory diseases.

Post-transcriptional regulation of inflammation by RNA-binding proteins via cis-elements of mRNAs

In human genome, there are approximately 1,500 RNA-binding proteins (RBPs). They can regulate mRNA stability or translational efficiency via ribosomes and these processes are known as 'post-transcriptional regulation'. Accumulating evidences indicate that post-transcriptional regulation is the determinant of the accurate levels of cytokines mRNAs. While transcriptional regulation of cytokines mRNAs has been well studied and found to be important for the rapid induction of mRNA and regulation of the acute phase of inflammation, post-transcriptional regulation by RBPs is essential for resolving inflammation in the later phase, and their dysfunction may lead to severe autoimmune diseases such as rheumatoid arthritis or systemic lupus erythematosus. For post-transcriptional regulation, RBPs recognize and directly bind to cis-regulatory elements in 3' untranslated region of mRNAs such as AU-rich or constitutive decay elements and play various roles. In this review, we summarize the recent findings regarding the role of RBPs in the regulation of inflammation.

HIF1α inhibits LPS-mediated induction of IL-6 synthesis via SOCS3-dependent CEBPβ suppression in human dental pulp cells

Hypoxia-inducible factor 1 alpha (HIF1α) is a transcriptional factor that plays a key role in the regulation of various molecules expressed in hypoxic conditions. Ischemic/hypoxic conditions are regarded as a distinct characteristic of dental pulp inflammation due to the encasement of pulp tissue within the rigid tooth structure. This study was performed to examine the role of HIF1α in the regulation of interleukin (IL)-6, a proinflammatory cytokine expressed in inflamed dental pulp, in lipopolysaccharide (LPS)-stimulated human dental pulp cells (hDPCs). LPS stimulation promoted the expression of IL-6 in hDPCs, while HIF1α suppressed the expression of IL-6. Moreover, HIF1α induced suppressor of cytokine signaling 3 (SOCS3) expression in LPS-stimulated hDPCs, and SOCS3 activity led to downregulate expression of CCAAT enhancer-binding protein beta (CEBPβ), an inducer of IL-6. LPS stimulation promoted HIF1α expression in hDPCs and mouse pulp tissue explants cultured under hypoxic conditions. These findings suggest that HIF1α negatively regulates IL-6 synthesis in LPS-stimulated hDPCs via upregulation of SOCS3 and subsequent downregulation of CEBPβ.

The Splicing Factor hnRNP M Is a Critical Regulator of Innate Immune Gene Expression in Macrophages

While transcriptional control of innate immune gene expression is well characterized, almost nothing is known about how pre-mRNA splicing decisions influence, or are influenced by, macrophage activation. Here, we demonstrate that the splicing factor hnRNP M is a critical repressor of innate immune gene expression and that its function is regulated by pathogen sensing cascades. Loss of hnRNP M led to hyperinduction of a unique regulon of inflammatory and antimicrobial genes following diverse innate immune stimuli. While mutating specific serines on hnRNP M had little effect on its ability to control pre-mRNA splicing or transcript levels of housekeeping genes in resting macrophages, it greatly impacted the protein's ability to dampen induction of specific innate immune transcripts following pathogen sensing. These data reveal a previously unappreciated role for pattern recognition receptor signaling in controlling splicing factor phosphorylation and establish pre-mRNA splicing as a critical regulatory node in defining innate immune outcomes.

The IL-17 Family of Cytokines in Health and Disease

The interleukin 17 (IL-17) family of cytokines contains 6 structurally related cytokines, IL-17A through IL-17F. IL-17A, the prototypical member of this family, just passed the 25^th anniversary of its discovery. Although less is known about IL-17B-F, IL-17A (commonly known as IL-17) has received much attention for its pro-inflammatory role in autoimmune disease. Over the past decade, however, it has become clear that the functions of IL-17 are far more nuanced than simply turning on inflammation. Accumulating evidence indicates that IL-17 has important context- and tissue-dependent roles in maintaining health during response to injury, physiological stress, and infection. Here, we discuss the functions of the IL-17 family, with a focus on the balance between the pathogenic and protective roles of IL-17 in cancer and autoimmune disease, including results of therapeutic blockade and novel aspects of IL-17 signal transduction regulation.

Targeting Interleukin-6 Signaling in Clinic

Interleukin-6 (IL-6) is a pleiotropic cytokine with roles in immunity, tissue regeneration, and metabolism. Rapid production of IL-6 contributes to host defense during infection and tissue injury, but excessive synthesis of IL-6 and dysregulation of IL-6 receptor signaling is involved in disease pathology. Therapeutic agents targeting the IL-6 axis are effective in rheumatoid arthritis, and applications are being extended to other settings of acute and chronic inflammation. Recent studies reveal that selective blockade of different modes of IL-6 receptor signaling has different outcomes on disease pathology, suggesting novel strategies for therapeutic intervention. However, some inflammatory diseases do not seem to respond to IL-6 blockade. Here, we review the current state of IL-6-targeting approaches in the clinic and discuss how to apply the growing understanding of the immunobiology of IL-6 to clinical decisions.

Feedback regulation of Arid5a and Ppar-γ2 maintains adipose tissue homeostasis

Immune cells infiltrate adipose tissues and provide a framework to regulate energy homeostasis. However, the precise underlying mechanisms and signaling by which the immune system regulates energy homeostasis in metabolic tissues remain poorly understood. Here, we show that the AT-rich interactive domain 5A (Arid5a), a cytokine-induced nucleic acid binding protein, is important for the maintenance of adipose tissue homeostasis. Long-term deficiency of Arid5a in mice results in adult-onset severe obesity. In contrast, transgenic mice overexpressing Arid5a are highly resistant to high-fat diet-induced obesity. Inhibition of Arid5a facilitates the in vitro differentiation of 3T3-L1 cells and fibroblasts to adipocytes, whereas its induction substantially inhibits their differentiation. Molecular studies reveal that Arid5a represses the transcription of peroxisome proliferator activated receptor gamma 2 (Ppar-γ2) due to which, in the absence of Arid5a, Ppar-γ2 is persistently expressed in fibroblasts. This phenomenon is accompanied by enhanced fatty acid uptake in Arid5a-deficient cells, which shifts metabolic homeostasis toward prolipid metabolism. Furthermore, we show that Arid5a and Ppar-γ2 are dynamically counterregulated by each other, hence maintaining adipogenic homeostasis. Thus, we show that Arid5a is an important negative regulator of energy metabolism and can be a potential target for metabolic disorders.

An integrative computational approach for a prioritization of key transcription regulators associated with nanomaterial-induced toxicity

A rapid increase of new nanomaterial products poses new challenges for their risk assessment. Current traditional methods for estimating potential adverse health effect of nanomaterials (NMs) are complex, time consuming and expensive. In order to develop new prediction tests for nanotoxicity evaluation, a systems biology approach and data from high-throughput omics experiments can be used. We present a computational approach that combines reverse engineering techniques, network analysis and pathway enrichment analysis for inferring the transcriptional regulation landscape and its functional interpretation. To illustrate this approach, we used published transcriptomic data derived from mice lung tissue exposed to carbon nanotubes (NM-401 and NRCWE-26). Because fibrosis is the most common adverse effect of these NMs, we included in our analysis the data for bleomycin (BLM) treatment, which is a well-known fibrosis inducer. We inferred gene regulatory networks for each NM and BLM to capture functional hierarchical regulatory structures between genes and their regulators. Despite the different nature of the lung injury caused by nanoparticles and BLM, we identified several conserved core regulators for all agents. We reason that these regulators can be considered as early predictors of toxic responses after NMs exposure. This integrative approach, which refines traditional methods of transcriptomic analysis, can be useful for prioritization of potential core regulators and generation of new hypothesis about mechanisms of nanoparticles toxicity.

Post-transcriptional control of immune responses and its potential application

Inflammation is the host response against stresses such as infection. Although the inflammation process is required for the elimination of pathogens, uncontrolled inflammation leads to tissue destruction and inflammatory diseases. To avoid this, the inflammatory response is tightly controlled by multiple layers of regulation. Post-transcriptional control of inflammatory mRNAs is increasingly understood to perform critical roles in this process. This is mediated primarily by a set of RNA binding proteins (RBPs) including tristetraprolin, Roquin and Regnase-1, and RNA methylases. These key regulators coordinate the inflammatory response by modulating mRNA pools in both immune and local nonimmune cells. In this review, we provide an overview of the post-transcriptional coordination of immune responses in various tissues and discuss how RBP-mediated regulation of inflammation may be harnessed as a potential class of treatments for inflammatory diseases.