Regulation of inflammatory responses by dynamic subcellular localization of RNA-binding protein Arid5a

Benproperine reduces IL-6 levels via Akt signaling in monocyte/macrophage-lineage cells and reduces the mortality of mouse sepsis model induced by lipopolysaccharide

Benproperine (BNP) is a nonnarcotic antitussive drug that is used to treat bronchitis. In the present study, we examined the anti-inflammatory effects of BNP in vitro and in vivo. BNP was found to reduce the secretion of pro-inflammatory cytokines, such as interleukin (IL)-6, in lipopolysaccharide (LPS)-treated RAW264.7 monocyte/macrophage-lineage cells in vitro. As IL-6 is a biomarker for sepsis and has been suggested to exacerbate symptoms, we used an animal model to determine whether BNP reduces IL-6 levels in vivo and improves sepsis symptoms. Notably, BNP reduced IL-6 levels in the lungs of LPS-treated mice and improved LPS-induced hypothermia, one of the symptoms of sepsis. BNP reduced the mortality of septic mice administered a lethal dose of LPS. To reveal the mechanisms underlying the anti-inflammatory function of BNP, we assessed intracellular signaling in LPS-treated RAW264.7 cells. BNP induced the phosphorylation of protein kinase B (Akt) in RAW264.7 cells with/without LPS treatment. Wortmannin, an inhibitor of phosphoinositide 3-kinase reduced the phosphorylation levels of Akt. Wortmannin also obstructed the reduction of IL-6 secretion caused by BNP. Altogether, BNP was found to exhibit an anti-inflammatory function via Akt signaling. Therefore, BNP could be a drug candidate for inflammatory diseases, including sepsis.

The RNA binding protein Arid5a drives IL-17-dependent autoantibody-induced glomerulonephritis

Autoantibody-mediated glomerulonephritis (AGN) arises from dysregulated renal inflammation, with urgent need for improved treatments. IL-17 is implicated in AGN and drives pathology in a kidney-intrinsic manner via renal tubular epithelial cells (RTECs). Nonetheless, downstream signaling mechanisms provoking kidney pathology are poorly understood. A noncanonical RNA binding protein (RBP), Arid5a, was upregulated in human and mouse AGN. Arid5a-/- mice were refractory to AGN, with attenuated myeloid infiltration and impaired expression of IL-17-dependent cytokines and transcription factors (C/EBPβ, C/EBPδ). Transcriptome-wide RIP-Seq revealed that Arid5a inducibly interacts with conventional IL-17 target mRNAs, including CEBPB and CEBPD. Unexpectedly, many Arid5a RNA targets corresponded to translational regulation and RNA processing pathways, including rRNAs. Indeed, global protein synthesis was repressed in Arid5a-deficient cells, and C/EBPs were controlled at the level of protein rather than RNA accumulation. IL-17 prompted Arid5a nuclear export and association with 18S rRNA, a 40S ribosome constituent. Accordingly, IL-17-dependent renal autoimmunity is driven by Arid5a at the level of ribosome interactions and translation.

Arid5a uses disordered extensions of its core ARID domain for distinct DNA- and RNA-recognition and gene regulation

AT-rich interacting domain (ARID)-containing proteins, Arids, are a heterogeneous DNA-binding protein family involved in transcription regulation and chromatin processing. For the member Arid5a, no exact DNA-binding preference has been experimentally defined so far. Additionally, the protein binds to mRNA motifs for transcript stabilization, supposedly through the DNA-binding ARID domain. To date, however, no unbiased RNA motif definition and clear dissection of nucleic acid-binding through the ARID domain have been undertaken. Using NMR-centered biochemistry, we here define the Arid5a DNA preference. Further, high-throughput in vitro binding reveals a consensus RNA-binding motif engaged by the core ARID domain. Finally, transcriptome-wide binding (iCLIP2) reveals that Arid5a has a weak preference for (A)U-rich regions in pre-mRNA transcripts of factors related to RNA processing. We find that the intrinsically disordered regions flanking the ARID domain modulate the specificity and affinity of DNA binding, while they appear crucial for RNA interactions. Ultimately, our data suggest that Arid5a uses its extended ARID domain for bifunctional gene regulation and that the involvement of IDR extensions is a more general feature of Arids in interacting with different nucleic acids at the chromatin-mRNA interface.

Decoding Toll-like receptors: Recent insights and perspectives in innate immunity

Toll-like receptors (TLRs) are an evolutionarily conserved family in the innate immune system and are the first line of host defense against microbial pathogens by recognizing pathogen-associated molecular patterns (PAMPs). TLRs, categorized into cell surface and endosomal subfamilies, recognize diverse PAMPs, and structural elucidation of TLRs and PAMP complexes has revealed their intricate mechanisms. TLRs activate common and specific signaling pathways to shape immune responses. Recent studies have shown the importance of post-transcriptional regulation in TLR-mediated inflammatory responses. Despite their protective functions, aberrant responses of TLRs contribute to inflammatory and autoimmune disorders. Understanding the delicate balance between TLR activation and regulatory mechanisms is crucial for deciphering their dual role in immune defense and disease pathogenesis. This review provides an overview of recent insights into the history of TLR discovery, elucidation of TLR ligands and signaling pathways, and their relevance to various diseases.

Novel ratio-expressions of genes enables estimation of wound age in contused skeletal muscle

Given that combination with multiple biomarkers may well raise the predictive value of wound age, it appears critically essential to identify new features under the limited cost. For this purpose, the present study explored whether the gene expression ratios provide unique time information as an additional indicator for wound age estimation not requiring the detection of new biomarkers and allowing full use of the available data. The expression levels of four wound-healing genes (Arid5a, Ier3, Stom, and Lcp1) were detected by real-time polymerase chain reaction, and a total of six expression ratios were calculated among these four genes. The results showed that the expression levels of four genes and six ratios of expression changed time-dependent during wound repair. The six expression ratios provided additional temporal information, distinct from the four genes analyzed separately by principal component analysis. The overall performance metrics for cross-validation and external validation of four typical prediction models were improved when six ratios of expression were added as additional input variables. Overall, expression ratios among genes provide temporal information and have excellent potential as predictive markers for wound age estimation. Combining the expression levels of genes with ratio-expression of genes may allow for more accurate estimates of the time of injury.

RNA Metabolism Governs Immune Function and Response

Inflammation is a complex process that protects our body from various insults such as infection, injury, and stress. Proper inflammation is beneficial to eliminate the insults and maintain organ homeostasis, however, it can become detrimental if uncontrolled. To tightly regulate inflammation, post-transcriptional mechanisms governing RNA metabolism play a crucial role in monitoring the expression of immune-related genes, such as tumor necrosis factor (TNF) and interleukin-6 (IL-6). These mechanisms involve the coordinated action of various RNA-binding proteins (RBPs), including the Regnase family, Roquin, and RNA methyltransferases, which are responsible for mRNA decay and/or translation regulation. The collaborative efforts of these RBPs are essential in preventing aberrant immune response activation and consequently safeguarding against inflammatory and autoimmune diseases. This review provides an overview of recent advancements in our understanding of post-transcriptional regulation within the immune system and explores the specific roles of individual RBPs in RNA metabolism and regulation.

Fates and functions of RNA-binding proteins under stress

Exposure to stress activates a well-orchestrated set of changes in gene expression programs that allow the cell to cope with and adapt to the stress, or undergo programmed cell death. RNA-protein interactions, mediating all aspects of post-transcriptional regulation of gene expression, play crucial roles in cellular stress responses. RNA-binding proteins (RBPs), which interact with sequence/structural elements in RNAs to control the steps of RNA metabolism, have therefore emerged as central regulators of post-transcriptional responses to stress. Following exposure to a variety of stresses, the dynamic alterations in the RNA-protein interactome enable cells to respond to intracellular or extracellular perturbations by causing changes in mRNA splicing, polyadenylation, stability, translation, and localization. As RBPs play a central role in determining the cellular proteome both qualitatively and quantitatively, it has become increasingly evident that their abundance, availability, and functions are also highly regulated in response to stress. Exposure to stress initiates a series of signaling cascades that converge on post-translational modifications (PTMs) of RBPs, resulting in changes in their subcellular localization, association with stress granules, extracellular export, proteasomal degradation, and RNA-binding activities. These alterations in the fate and function of RBPs directly impact their post-transcriptional regulatory roles in cells under stress. Adopting the ubiquitous RBP HuR as a prototype, three scenarios illustrating the changes in nuclear-cytoplasmic localization, RNA-binding activity, export and degradation of HuR in response to inflammation, genotoxic stress, and heat shock depict the complex and interlinked regulatory mechanisms that control the fate and functions of RBPs under stress. This article is categorized under: RNA Interactions with Proteins and Other Molecules > Protein-RNA Interactions: Functional Implications.

Viral Subversion of the Chromosome Region Maintenance 1 Export Pathway and Its Consequences for the Cell Host

In eukaryotic cells, the spatial distribution between cytoplasm and nucleus is essential for cell homeostasis. This dynamic distribution is selectively regulated by the nuclear pore complex (NPC), which allows the passive or energy-dependent transport of proteins between these two compartments. Viruses possess many strategies to hijack nucleocytoplasmic shuttling for the benefit of their viral replication. Here, we review how viruses interfere with the karyopherin CRM1 that controls the nuclear export of protein cargoes. We analyze the fact that the viral hijacking of CRM1 provokes are-localization of numerous cellular factors in a suitable place for specific steps of viral replication. While CRM1 emerges as a critical partner for viruses, it also takes part in antiviral and inflammatory response regulation. This review also addresses how CRM1 hijacking affects it and the benefits of CRM1 inhibitors as antiviral treatments.

Blockade of the Arid5a/IL-6/STAT3 axis underlies the anti-inflammatory effect of Rbpjl in acute pancreatitis

Background

The microarray data analysis predicted that Rbpjl is poorly expressed in acute pancreatitis (AP). Activated IL-6/STAT3 signaling is further known to contribute to the progression of AP through immune regulation, and both IL-6 and STAT3 were bioinformatically predicted to interact with Arid5a. Accordingly, we aimed to investigate the potential involvement of the Arid5a/IL-6/STAT3 axis in the regulatory role of Rbpjl in the inflammation of AP.

Methods

Pancreatic acinar cells were exposed to lipopolysaccharide (LPS) to induce the pancreatic cell damage, and mice were subjected to supramaximal cerulein stimulation to induce AP. Expression patterns of Rbpjl and the Arid5a/IL-6/STAT3 axis were measured in mouse and cell models. Their expression was further manipulated to explore their effects on pancreatic cell injury and inflammation, as reflected by cell viability and apoptosis as well as reactive oxygen species (ROS) accumulation and proinflammatory cytokine secretion. Moreover, ChIP, EMSA, and dual-luciferase reporter assays were carried out to identify the interactions between Rbpjl and Arid5a.

Results

Rbpjl was found to be down-regulated in pancreatic tissues of AP mice and LPS-induced pancreatic acinar cells, while re-expression of Rbpjl led to enhanced cell viability, suppressed LPS-induced inflammation and ROS accumulation, and alleviation of AP-induced damage. Mechanistically, Rbpjl could bind to the promoter region of Arid5a and down-regulated its expression, thus repressing the activation of the IL-6/STAT3 signal axis. Furthermore, Rbpjl impaired Arid5a-dependent IL-6/STAT3 activation, hence alleviating pancreatic acinar cell inflammation. Furthermore, these effects were validated with in vivo experiments.

Conclusion

Collectively, our findings highlight that Rbpjl attenuates AP by down-regulating Arid5a and inactivating the IL-6/STAT3 pathway.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13578-022-00819-1.

Roles of RNA-binding proteins in immune diseases and cancer

Genetic information that is transcribed from DNA to mRNA, and then translated from mRNA to protein, is regulated by complex and sophisticated post-transcriptional mechanisms. Recently, it has become clear that mRNA degradation not only acts to remove unnecessary mRNA, but is also closely associated with the regulation of translation initiation, and is essential for maintaining cellular homeostasis. Various RNA-binding proteins (RBPs) have been reported to play central roles in the mechanisms of mRNA stability and translation initiation through various signal transduction pathways, and to modulate gene expression faster than the transcription process via post-transcriptional modifications in response to intracellular and extracellular stimuli, without de novo protein synthesis. On the other hand, inflammation is necessary for the elimination of pathogens associated with infection, and is tightly controlled to avoid the overexpression of inflammatory cytokines, such as interleukin 6 (IL-6) and tumor necrosis factor (TNF). It is increasingly becoming clear that RBPs play important roles in the post-transcriptional regulation of these immune responses. Furthermore, it has been shown that the aberrant regulation of RBPs leads to chronic inflammation and autoimmune diseases. Although it has been recognized since the time of Rudolf Virchow in the 19th century that cancer-associated inflammation contributes to tumor onset and progression, involvement of the disruption of the balance between anti-tumor immunity via the immune surveillance system and pro-tumor immunity by cancer-associated inflammation in the malignant transformation of cancer remains elusive. Recently, the dysregulated expression and activation of representative RBPs involved in regulation of the production of pro-inflammatory cytokines have been shown to be involved in tumor progression. In this review, we summarize the recent progress in our understanding of the functional roles of these RBPs in several types of immune responses, and the involvement of RBP dysregulation in the pathogenesis of immune diseases and cancer, and discuss possible therapeutic strategies against cancer by targeting RBPs, coupled with immunotherapy.

Arid5a Mediates an IL-17-Dependent Pathway That Drives Autoimmunity but Not Antifungal Host Defense

IL-17 contributes to the pathogenesis of certain autoimmune diseases, but conversely is essential for host defense against fungi. Ab-based biologic drugs that neutralize IL-17 are effective in autoimmunity but can be accompanied by adverse side effects. Candida albicans is a commensal fungus that is the primary causative agent of oropharyngeal and disseminated candidiasis. Defects in IL-17 signaling cause susceptibility to candidiasis in mice and humans. A key facet of IL-17 receptor signaling involves RNA-binding proteins, which orchestrate the fate of target mRNA transcripts. In tissue culture models we showed that the RNA-binding protein AT-rich interaction domain 5A (Arid5a) promotes the stability and/or translation of multiple IL-17-dependent mRNAs. Moreover, during oropharyngeal candidiasis, Arid5a is elevated within the oral mucosa in an IL-17-dependent manner. However, the contribution of Arid5a to IL-17-driven events in vivo is poorly defined. In this study, we used CRISPR-Cas9 to generate mice lacking Arid5a. Arid5a -/- mice were fully resistant to experimental autoimmune encephalomyelitis, an autoimmune setting in which IL-17 signaling drives pathology. Surprisingly, Arid5a -/- mice were resistant to oropharyngeal candidiasis and systemic candidiasis, similar to immunocompetent wild-type mice and contrasting with mice defective in IL-17 signaling. Therefore, Arid5a-dependent signals mediate pathology in autoimmunity and yet are not required for immunity to candidiasis, indicating that selective targeting of IL-17 signaling pathway components may be a viable strategy for development of therapeutics that spare IL-17-driven host defense.

Interleukin-6 cytokine: An overview of the immune regulation, immune dysregulation, and therapeutic approach

Several studies have shown that interleukin 6 (IL-6) is a multifunctional cytokine with both pro-inflammatory and anti-inflammatory activity, depending on the immune response context. Macrophages are among several cells that secrete IL-6, which they express upon activation by antigens, subsequently inducing fever and production of acute-phase proteins from the liver. Moreover, IL-6 induces the final maturation of B cells into memory B cells and plasma cells as well as an adaptive role for short-term energy allocation. Activation of IL-6 receptors results in the intracellular activation of the JAK/STAT pathway with resultant production of inflammatory cytokines. Several mechanisms-controlled IL-6 expression, but aberrant production was shown to be crucial in the pathogenesis of many diseases, which include autoimmune and chronic inflammatory diseases. IL-6 in combination with transforming growth factor β (TGF-β) induced differentiation of naïve T cells to Th17 cells, which is the cornerstone in autoimmune diseases. Recently, IL-6 secretion was shown to form the backbone of hypercytokinemia seen in the Coronavirus disease 2019 (COVID-19)-associated hyperinflammation and multiorgan failure. There are two classes of approved IL-6 inhibitors: anti-IL-6 receptor monoclonal antibodies (e.g., tocilizumab) and anti-IL-6 monoclonal antibodies (i.e., siltuximab). These drugs have been evaluated in patients with rheumatoid arthritis, juvenile idiopathic arthritis, cytokine release syndrome, and COVID-19 who have systemic inflammation. JAK/STAT pathway blockers were also successfully used in dampening IL-6 signal transduction. A better understanding of different mechanisms that modulate IL-6 expression will provide the much-needed solution with excellent safety and efficacy profiles for the treatment of autoimmune and inflammatory diseases in which IL-6 derives their pathogenesis.

Emerging roles for RNA-binding proteins in T lymphocytes

RNA-binding proteins (RBPs) are essential effectors in defining and regulating gene expression, and as such their function underlies all cellular processes. Within the immune system in general, and in T lymphocytes in particular, RBPs have been shown to crucially modulate almost every aspect of T cell biology, including differentiation, inflammatory responses and effector functions. However, questions remain regarding the function of many RBPs that have been recently discovered, their regulation, and in general their role within gene regulatory networks that control immune responses. Here, I will focus on unconventional RBPs with an emerging role in T lymphocytes, including proteins with unusual or unknown mode of binding, and proteins displaying enzymatic or regulatory roles in addition to their RNA-binding feature. I will also discuss how in the future distinguishing RBP:mRNA interactions that are functional and biologically relevant from those that have only limited impact will be crucial to fully dissect the intricacies of RBP-mediated regulation in the immune system.

Sarilumab Administration in COVID-19 Patients: Literature Review and Considerations

Two years have passed since WHO declared a pandemic state for SARS-CoV-2 infection. COVID-19 pathogenesis consists of a first viral phase responsible for early symptoms followed by an inflammatory phase, cytokine-mediated, responsible for late-onset manifestations up to ARDS. The dysregulated immune response has an outstanding role in the progression of pulmonary damage in COVID-19. IL-6, through the induction of pro-inflammatory chemokines and cytokines, plays a key role in the development and maintenance of inflammation, acting as a pioneer of the hyperinflammatory condition and cytokine storm in severe COVID-19. Therefore, drugs targeting both IL-6 and IL-6 receptors have been evaluated in order to blunt the abnormal SARS-CoV-2-induced cytokine release. Sarilumab, a high-affinity anti-IL-6 receptor antibody, may represent a promising weapon to treat the fearsome hyperinflammatory phase by improving the outcome of patients with moderate-to-severe COVID-19 pneumonia. Further prospective and well-designed clinical studies with larger sample sizes and long-term follow-up are needed to assess the efficacy and the safety of this therapeutic approach to achieve improved outcomes in COVID-19.

Structures and nucleic acid-binding preferences of the eukaryotic ARID domain

The DNA-binding AT-rich interactive domain (ARID) exists in a wide range of proteins throughout eukaryotic kingdoms. ARID domain-containing proteins are involved in manifold biological processes, such as transcriptional regulation, cell cycle control and chromatin remodeling. Their individual domain composition allows for a sub-classification within higher mammals. ARID is categorized as binder of double-stranded AT-rich DNA, while recent work has suggested ARIDs as capable of binding other DNA motifs and also recognizing RNA. Despite a broad variability on the primary sequence level, ARIDs show a highly conserved fold, which consists of six α-helices and two loop regions. Interestingly, this minimal core domain is often found extended by helices at the N- and/or C-terminus with potential roles in target specificity and, subsequently function. While high-resolution structural information from various types of ARIDs has accumulated over two decades now, there is limited access to ARID-DNA complex structures. We thus find ourselves left at the beginning of understanding ARID domain target specificities and the role of accompanying domains. Here, we systematically summarize ARID domain conservation and compare the various types with a focus on their structural differences and DNA-binding preferences, including the context of multiple other motifs within ARID domain containing proteins.

Recent Advances in the Role of Arid5a in Immune Diseases and Cancer

AT-rich interactive domain 5a (Arid5a) is a nucleic acid binding protein. In this review, we highlight recent advances in the association of Arid5a with inflammation and human diseases. Arid5a is known as a protein that performs dual functions. In in vitro and in vivo studies, it was found that an inflammation-dependent increase in Arid5a expression mediates both transcriptional and post-transcriptional regulatory effects that are implicated in immune regulation and cellular homeostasis. A series of publications demonstrated that inhibiting Arid5a augmented several processes, such as preventing septic shock, experimental autoimmune encephalomyelitis, acute lung injury, invasion and metastasis, immune evasion, epithelial-to-mesenchymal transition, and the M1-like tumor-associated macrophage (TAM) to M2-like TAM transition. In addition, Arid5a controls adipogenesis and obesity in mice to maintain metabolic homeostasis. Taken together, recent progress indicates that Arid5a exhibits multifaceted, both beneficial and detrimental, roles in health and disease and suggest the relevance of Arid5a as a potential therapeutic target.

Shaping the Innate Immune Response Through Post-Transcriptional Regulation of Gene Expression Mediated by RNA-Binding Proteins

Innate immunity is the frontline of defense against infections and tissue damage. It is a fast and semi-specific response involving a myriad of processes essential for protecting the organism. These reactions promote the clearance of danger by activating, among others, an inflammatory response, the complement cascade and by recruiting the adaptive immunity. Any disequilibrium in this functional balance can lead to either inflammation-mediated tissue damage or defense inefficiency. A dynamic and coordinated gene expression program lies at the heart of the innate immune response. This expression program varies depending on the cell-type and the specific danger signal encountered by the cell and involves multiple layers of regulation. While these are achieved mainly via transcriptional control of gene expression, numerous post-transcriptional regulatory pathways involving RNA-binding proteins (RBPs) and other effectors play a critical role in its fine-tuning. Alternative splicing, translational control and mRNA stability have been shown to be tightly regulated during the innate immune response and participate in modulating gene expression in a global or gene specific manner. More recently, microRNAs assisting RBPs and post-transcriptional modification of RNA bases are also emerging as essential players of the innate immune process. In this review, we highlight the numerous roles played by specific RNA-binding effectors in mediating post-transcriptional control of gene expression to shape innate immunity.

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.

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.

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.

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.

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.

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.

Physiological heating augments the anti-inflammatory reactions during granulocyte/monocyte apheresis: A in vitro study

Granulocyte and monocyte adsorptive apheresis (GMA), an effective therapy for inflammatory disorders, exerts an anti-inflammatory influence by utilizing the biological reaction between blood and cellulose acetate (CA) beads, which are the carriers of the GMA column. Although the biological reaction has an optimum temperature, blood contacts the CA beads below body temperature as GMA is performed in an extracorporeal circulation system. We investigated various soluble factors in blood treated with CA beads at 25°C and 37°C. Here, the optimal temperature for IL-1 receptor antagonist (IL-1ra) release induced by CA beads was 37°C, and IL-6 production from monocytic cells was inhibited by the addition of plasma prepared from the CA bead-treated blood at 37°C, rather than at 25°C. These results indicated that physiological heating of the apheresis carrier augmented the anti-inflammatory reaction in vitro. Thus, heating during GMA may be a new approach for augmenting clinical efficacy.

Novel insights into wound age estimation: combined with "up, no change, or down" system and cosine similarity in python environment

Wound age estimation is a complex, multifactorial issue. It is considered to have great practical significance that combining multi-biomarkers and multi-methods for injury time estimation. We optimized our earlier "up, no change, or down" model by adding data on the expression levels of mRNAs encoding ABHD2, MAD2L2, and ARID5A, and we converted the relative quantitative expression levels of seven genes into a vector rather than a color model. We used Python to derive the cosine similarity (CS) between a test set and the vector matrix; the highest similarity most accurately reflected the injury time. For the optimized model, the internal and external verifications were approximately 0.71 and 0.66, respectively. The good double-blinded results indicated that the model was stable and reliable. In summary, we used a vector matrix and cosine similarities derived by Python to mine the levels of genes expressed in contused skeletal muscle. We are the first to combine several biomarkers and methods for wound age estimation.

Plasticity of nuclear and cytoplasmic stress responses of RNA-binding proteins

Cellular stress causes multifaceted reactions to trigger adaptive responses to environmental cues at all levels of the gene expression pathway. RNA-binding proteins (RBP) are key contributors to stress-induced regulation of RNA fate and function. Here, we uncover the plasticity of the RNA interactome in stressed cells, differentiating between responses in the nucleus and in the cytoplasm. We applied enhanced RNA interactome capture (eRIC) analysis preceded by nucleo-cytoplasmic fractionation following arsenite-induced oxidative stress. The data reveal unexpectedly compartmentalized RNA interactomes and their responses to stress, including differential responses of RBPs in the nucleus versus the cytoplasm, which would have been missed by whole cell analyses.

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.

Post-transcriptional regulation of C-C motif chemokine ligand 2 expression by ribosomal protein L22 during LPS-mediated inflammation

Monocyte infiltration to the site of pathogenic invasion is critical for inflammatory response and host defence. However, this process demands precise regulation as uncontrolled migration of monocytes to the site delays resolution of inflammation and ultimately promotes chronic inflammation. C-C motif chemokine ligand 2 (CCL2) plays a key role in monocyte migration, and hence, its expression should be tightly regulated. Here, we report a post-transcriptional regulation of CCL2 involving the large ribosomal subunit protein L22 (RPL22) in LPS-activated, differentiated THP-1 cells. Early events following LPS treatment include transcriptional upregulation of RPL22 and its nuclear accumulation. The protein binds to the first 20 nt sequence of the 5'UTR of ccl2 mRNA. Simultaneous nuclear translocation of up-frameshift-1 protein and its interaction with RPL22 results in cytoplasmic degradation of the ccl2 mRNA at a later stage. Removal of RPL22 from cells results in increased expression of CCL2 in response to LPS causing disproportionate migration of monocytes. We propose that post-transcriptional regulation of CCL2 by RPL22 fine-tunes monocyte infiltration during a pathogenic insult and maintains homeostasis of the immune response critical to resolution of inflammation. DATABASES: Microarray data are available in NCBI GEO database (Accession No GSE126525).

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.

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.

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.

Sleep fragmentation, microglial aging, and cognitive impairment in adults with and without Alzheimer's dementia

Sleep disruption is associated with cognitive decline and dementia in older adults; however, the underlying mechanisms are unclear. In rodents, sleep disruption causes microglial activation, inhibition of which improves cognition. However, data from humans are lacking. We studied participants in two cohort studies of older persons-the Rush Memory and Aging Project and the Religious Orders Study. We assessed sleep fragmentation by actigraphy and related this to cognitive function, to neocortical microglial marker gene expression measured by RNA sequencing, and to the neocortical density of microglia assessed by immunohistochemistry. Greater sleep fragmentation was associated with higher neocortical expression of genes characteristic of aged microglia, and a higher proportion of morphologically activated microglia, independent of chronological age- and dementia-related neuropathologies. Furthermore, these were, in turn, associated with worse cognition. This suggests that sleep fragmentation is accompanied by accelerated microglial aging and activation, which may partially underlie its association with cognitive impairment.

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.

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.

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.

Recent advances in gut Microbiota mediated therapeutic targets in inflammatory bowel diseases: Emerging modalities for future pharmacological implications

The inflammatory bowel diseases (IBDs) are chronic inflammatory conditions, which are increasing in prevalence worldwide. The IBDs are thought to result from an aberrant immune response to gut microbes in genetically susceptible individuals. Dysbiosis of the gut microbiome, both functional and compositional, promotes patient susceptibility to colonization by pathobionts. Manipulating gut microbial communities and gut microbiota-immune system interactions to restore gut homeostasis or reduce inflammation are appealing therapeutic models. We discuss the therapeutic potential of precision microbiota editing, natural and engineered probiotics, the use of gut microbiota-derived metabolites in colitogenic phenotypes, and intestinal stem cells, in maintaining gut microbiota balance, restoring the mucosal barrier, and having positive immunomodulatory effects in experimental IBD. This review highlights that we are only just beginning to understand the complexity of the microbiota and how it can be manipulated for health benefits, including treatment and prevention of the clinical IBDs in future.

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.

Cardiovascular inflammation: RNA takes the lead

Inflammation has recently gained tremendous attention as a key contributor in several chronic diseases. While physiological inflammation is essential to counter a wide variety of damaging stimuli and to improve wound healing, dysregulated inflammation such as in the myocardium and vasculature can promote cardiovascular diseases. Given the high severity, prevalence, and economic burden of these diseases, understanding the factors involved in the regulation of physiological inflammation is essential. Like other complex biological phenomena, RNA-based processes are emerging as major regulators of inflammatory responses. Among such processes are cis-regulatory elements in the mRNA of inflammatory genes, noncoding RNAs directing the production or localization of inflammatory cytokines/chemokines, or pathogenic RNA driving inflammatory responses. In this review, we describe several specific RNA-based molecular mechanisms by which physiological inflammation pertaining to cardiovascular diseases is regulated. These include the role of AU-rich element-containing mRNAs, long non-coding RNAs, microRNAs, and viral RNAs.

Functional proteomic atlas of HIV infection in primary human CD4+ T cells

Viruses manipulate host cells to enhance their replication, and the identification of cellular factors targeted by viruses has led to key insights into both viral pathogenesis and cell biology. In this study, we develop an HIV reporter virus (HIV-AFMACS) displaying a streptavidin-binding affinity tag at the surface of infected cells, allowing facile one-step selection with streptavidin-conjugated magnetic beads. We use this system to obtain pure populations of HIV-infected primary human CD4+ T cells for detailed proteomic analysis, and quantitate approximately 9000 proteins across multiple donors on a dynamic background of T cell activation. Amongst 650 HIV-dependent changes (q < 0.05), we describe novel Vif-dependent targets FMR1 and DPH7, and 192 proteins not identified and/or regulated in T cell lines, such as ARID5A and PTPN22. We therefore provide a high-coverage functional proteomic atlas of HIV infection, and a mechanistic account of host factors subverted by the virus in its natural target cell.

Interleukin-6 is prone to be a candidate biomarker for predicting incomplete and IVIG nonresponsive Kawasaki disease rather than coronary artery aneurysm

Kawasaki disease (KD) is an acute, systemic vasculitis and occurs mainly in childhood. Interleukin-6 (IL-6) is a pleiotropic cytokine synthesized predominantly by neutrophils and monocytes/macrophages and plays an important role in systemic inflammatory disease. However, a little information is currently available on the relationship of serum IL-6 with conventional inflammatory mediators, clinical classification, IVIG response and coronary artery aneurysm (CAA). 165 Chinese children with KD were enrolled and divided into six subgroups, including complete KD, incomplete KD, IVIG-responsive KD, IVIG-nonresponsive KD, coronary artery noninvolvement KD and coronary artery involvement KD. Blood samples were collected from all subjects within 24-h pre- and 48-h post-IVIG therapy, respectively. Serum IL-6 and conventional inflammatory mediators were detected. (1) Serum IL-6 markedly increased in the acute phase of KD, whereas declined to normal after IVIG therapy; it was positively correlated with C-reactive protein and erythrocyte sedimentation rate. (2) Serum IL-6 was significantly elevated in patients with incomplete KD when compared with their complete counterparts. The area under receiver operating characteristic curve (AUC) value for serum IL-6 in prediction of incomplete KD was 0.596, and the estimated sensitivity and specificity were 77.80% and 54.40% with a cutoff of IL-6 > 13.25 pg/ml, respectively. (3) Serum IL-6 was significantly elevated in patients with IVIG-nonresponsive KD when compared with their IVIG-responsive counterparts; the AUC value for serum IL-6 in prediction of IVIG-nonresponsive KD was 0.580, and the estimated sensitivity and specificity were 60.00% and 66.30% with a cutoff of IL-6 > 26.40 pg/ml, respectively. (4) No significant differences in IL-6 were found between KD patients with and without CAA. IL-6 is prone to be a candidate biomarker for predicting incomplete and IVIG nonresponsive KD rather than CAA.

The Two-Faced Cytokine IL-6 in Host Defense and Diseases

Interleukein-6 (IL-6), is produced locally from infectious or injured lesions and is delivered to the whole body via the blood stream, promptly activating the host defense system to perform diverse functions. However, excessive or sustained production of IL-6 is involved in various diseases. In diseases, the IL-6 inhibitory strategy begins with the development of the anti-IL-6 receptor antibody, tocilizumab (TCZ). This antibody has shown remarkable effects on Castleman disease, rheumatoid arthritis and juvenile idiopathic arthritis. In 2017, TCZ was proven to work effectively against giant cell arteritis, Takayasu arteritis and cytokine releasing syndrome, initiating a new era for the treatment of these diseases. In this study, the defensive functions of IL-6 and various pathological conditions are compared. Further, the diseases of which TCZ has been approved for treatment are summarized, the updated results of increasing off-label use of TCZ for various diseases are reviewed and the conditions for which IL-6 inhibition might have a beneficial role are discussed. Given the involvement of IL-6 in many pathologies, the diseases that can be improved by IL-6 inhibition will expand. However, the important role of IL-6 in host defense should always be kept in mind in clinical practice.

IL-17 integrates multiple self-reinforcing, feed-forward mechanisms through the RNA binding protein Arid5a

Interleukin-17A (IL-17A) not only stimulates immunity to fungal pathogens but also contributes to autoimmune pathology. IL-17 is only a modest activator of transcription in experimental tissue culture settings. However, IL-17 controls posttranscriptional events that enhance the expression of target mRNAs. Here, we showed that the RNA binding protein (RBP) Arid5a (AT-rich interactive domain-containing protein 5a) integrated multiple IL-17-driven signaling pathways through posttranscriptional control of mRNA. IL-17 induced expression of Arid5a, which was recruited to the adaptor TRAF2. Arid5a stabilized IL-17-induced cytokine transcripts by binding to their 3' untranslated regions and also counteracted mRNA degradation mediated by the endoribonuclease MCPIP1 (Regnase-1). Arid5a inducibly associated with the eukaryotic translation initiation complex and facilitated the translation of the transcription factors (TFs) IκBζ (Nfkbiz ) and C/EBPβ (Cebpb). These TFs in turn transactivated IL-17-dependent promoters. Together, these data indicated that Arid5a orchestrates a feed-forward amplification loop, which promoted IL-17 signaling by controlling mRNA stability and translation.