IL-38-mediated NLRP3/caspase-1 inhibition is a disease-modifying treatment for TMJ inflammation

Role of IL-1 Family Cytokines IL-36, IL-37, IL-38 in Osteoarthritis and Rheumatoid Arthritis: A Comprehensive Review

Inflammatory cytokines, interleukin-36 (IL-36), IL-37, IL-38 belong to IL-1 family. The IL-36 subfamily obtains pro- and anti-inflammatory effects on various immune responses. Cytokine IL-37, has anti-inflammatory functions in immunity, and the recently identified IL-38 negatively associated with disease pathogenesis. To date, expression of IL-36, IL-37, IL-38 is reported dysregulated in osteoarthritis (OA) and rheumatoid arthritis (RA), and may be disease markers for arthritis-related diseases. Interestingly, expression of IL-38 was different either in OA patients or animal models, and expression of IL-36Ra in synovium was different in OA and RA patients. Moreover, functional studies have demonstrated significant role of these cytokines in OA and RA progress. These processes were related to immune cells and non-immune cells, where the cytokines IL-36, IL-37, IL-38 may regulate downstream signalings in the cells, and then involve in OA, RA development. In this review, we comprehensively discuss recent advancements in cytokines and the development of OA, RA. We hope that targeting these cytokines will become a potential treatment option for OA and RA in the future.

Mechanisms of NLRP3 inflammasome in rheumatoid arthritis and osteoarthritis and the effects of traditional Chinese medicine

ETHNOPHARMACOLOGICAL RELEVANCE

It has been widely reported that various anti-rheumatic traditional Chinese medicines (TCMs) ameliorate rheumatoid arthritis (RA) and osteoarthritis (OA) through regulating the abnormal production, assembly, and activation of the NOD-like receptor thermal protein domain-associated protein 3 (NLRP3) inflammasome. These TCMs include monomers isolated from Chinese herbs, extracts of Chinese herbs, and Chinese medical formulae with a lengthy application history.

AIM OF THE STUDY

This review aimed to summarize and analyze the published articles about the NLRP3 inflammasome and its role in the pathogenesis of RA and OA. We also reviewed existing knowledge on the therapeutic mechanism of TCMs in RA and OA via the regulation of the NLRP3 inflammasome.

MATERIALS AND METHODS

We searched for relevant articles with the keywords "NLRP3 inflammasome", "traditional Chinese medicine," "Chinese herbal drugs," "rheumatoid arthritis," and "osteoarthritis." The information retrieval was conducted in medical Chinese and English databases from the date of construction to April 19, 2023, including PubMed, MEDLINE, Web of Science, Scopus, Ovid, China National Knowledge Infrastructure (CNKI), Chinese Biomedicine Literature Database (CBM), Chinese Science and Technology Periodicals Database (VIP), and China Online Journals (COJ).

RESULTS

According to retrieval results, 35 TCMs have been demonstrated to relieve RA by targeting the NLRP3 inflammasome, including six traditional Chinese prescriptions, seven extracts of Chinese herbs, and 22 monomers extracted from traditional Chinese herbs and formulae. Additionally, 23 TCMs have shown anti-OA effects with abilities to modulate the NLRP3 inflammasome, including five traditional Chinese prescriptions, one extract of Chinese herbs, and 17 monomers from Chinese herbs.

CONCLUSIONS

We summarized mechanism research about the pivotal roles of the NLRP3 inflammasome in the pathogenesis of RA and OA. Moreover, a review of TCMs with targets of the NLRP3 inflammasome in RA and OA treatment was also conducted. Our work is conducive to a better application of TCMs in complementary and alternative therapies in RA and OA.

Resatorvid alleviates experimental inflammatory TMJOA by restraining chondrocyte pyroptosis and synovial inflammation

OBJECTIVES

Innate immunity plays a significant role in the pathogenesis of temporomandibular joint osteoarthritis (TMJOA), which is characterized by synovial inflammation and condylar cartilage degradation. We are urged to investigate the impact of Resatorvid, a preventative drug that inhibits Toll-like receptor 4 (TLR4), on experimental inflammatory TMJOA pathology.

METHODS

An intra-articular injection of complete Freund's adjuvant (CFA) was used to induce an experimental inflammatory mouse TMJOA model, and TLR4 expression was identified by immunofluorescent labeling. Intraperitoneal injections of Resatorvid were administered to CFA-induced TMJOA mice, and the pathology of TMJOA animals with and without Resatorvid treatment was examined by H&E, Safranin-O/Fast Green, and TRAP staining, as well as micro-CT, immunohistochemistry, and immunofluorescence. The impact of Resatorvid on chondrocyte pyroptosis and macrophage inflammation was further investigated using ATDC5 chondrocytes and RAW264.7 macrophages pretreated with relevant antagonists.

RESULTS

CFA-induced TMJOA mice revealed remarkable synovial inflammation, together with a time course of cartilage degradation and bone destruction, with TLR4 elevated in the synovium and condylar cartilage. Prophylactic treatment with Resatorvid mitigated synovial inflammation, cartilage degeneration, and bone destruction in CFA-induced TMJOA mice and downregulated MyD88/NF-κB expression. Ex vivo studies demonstrated that Resatorvid treatment alleviated NOD-like receptor protein 3 (NLRP3)-mediated chondrocyte pyroptosis and degeneration and relieved macrophage inflammation by preventing reactive oxygen species (ROS) production through NLRP3 signaling.

CONCLUSION

Prophylactic treatment with Resatorvid alleviates TMJOA pathology by inhibiting chondrocyte pyroptosis and degeneration, as well as ROS-induced macrophage inflammation, through TLR4/MyD88/NF-κB/NLRP3.

IL-38 suppresses macrophage M1 polarization to ameliorate synovial inflammation in the TMJ via GLUT-1 inhibition

OBJECTIVES

Interleukin (IL)-38 was discovered as an anti-inflammatory factor. However, IL-38's role in M1 macrophage polarization in the temporomandibular joint (TMJ) and the related mechanism are still unclear. We aimed to explore the effect and the mechanism of IL-38 on synovial inflammation in the TMJ in this study.

METHODS

The expression of IL-38 in the TMJ synovium and macrophages was determined using immunohistochemistry (IHC) and Western blotting (WB). M1 macrophage polarization was induced by LPS, the macrophages were pre-treated with IL-38, and the levels of inflammatory markers associated with M1 macrophages were measured. To assess the mechanism of IL-38, small-interfering RNA (siRNA)-GLUT-1 and STF31 were administered to macrophages, and the affected pathways were identified by WB. The effect of macrophage-conditioned medium (CM) on chondrocyte function was also determined. Finally, a mouse model of CFA-induced TMJ inflammation was established. Histological staining and IHC were used to determine the effect of IL-38.

RESULTS

IL-38 was detected at high levels in macrophages after lipopolysaccharide (LPS)challenge, and IL-38 downregulated M1 macrophage-related proinflammatory markers (iNOS, IL-6, TNF-α, and COX-2) in vitro. IL-38 suppressed M1 polarization by inhibiting GLUT-1 expression, NF-κB signaling, and MAPK signaling. Intriguingly, CM from macrophages that were pretreated with IL-38 and STF31 decreased inflammatory protein expression in chondrocytes. In addition, intra-articular injection of recombinant IL-38 ameliorated synovial inflammation in the TMJ by inhibiting M1 macrophage polarization and suppressing cartilage inflammation in vivo.

CONCLUSIONS

IL-38 is a novel anti-inflammatory factor that contributes to alleviating TMJ inflammation by inhibiting macrophage M1 polarization, thereby ameliorating chondrocyte inflammation and restoring TMJ homeostasis.

The emerging role of IL-38 in diseases: A comprehensive review

INTRODUCTION

Interleukin-38 (IL-38) is a new type of anti-inflammatory cytokine, which is mainly expressed in the immunity-related organs and is involved in various diseases including cardiovascular and cerebrovascular diseases, lung diseases, viral infectious diseases and autoimmune diseases.

AIM

This review aims to detail the biological function, receptors and signaling of IL-38, which highlights its therapeutic potential in related diseases.

CONCLUSION

This article provides a comprehensive review of the association between interleukin-38 and related diseases, using interleukin-38 as a keyword and searching the relevant literature through Pubmed and Web of science up to July 2023.

Progress of Research into the Interleukin-1 Family in Cardiovascular Disease

Inflammatory factors, such as the IL-1 family, are generally acknowledged to be involved in systemic diseases and IL-1α and IL-1β, in particular, have been linked to cardiovascular disease with IL-18, IL-33, IL-36, IL-37 and IL-38 yet to be explored. The current review aims to summarize mechanisms of IL-18, IL-33, IL-36, IL-37 and IL-38 in myocardial infarction, hypertension, arrhythmia, valvular disease and aneurysm and to explore the potential for cardiovascular disease treatment strategies and discuss future directions for prevention and treatment.

Interleukin 38 alleviates aortic valve calcification by inhibition of NLRP3

Calcific aortic valve disease (CAVD) is common in people over the age of 65. Progressive valvular calcification is a characteristic of CAVD and due to chronic inflammation in aortic valve interstitial cells (AVICs) resulting in CAVD progression. IL-38 is a naturally occurring anti-inflammatory cytokine; here, we report lower levels of endogenous IL-38 in AVICs isolated from patients' CAVD valves compared to AVICs from non-CAVD valves. Recombinant IL-38 suppressed spontaneous inflammatory activity and calcium deposition in cultured AVICs. In mice, knockdown of IL-38 enhanced the production of inflammatory mediators in murine AVICs exposed to the proinflammatory stimulant matrilin-2. We also observed that in cultured AVICs matrilin-2 stimulation activated the NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasome with procaspase-1 cleavage into active caspase-1. The addition of IL-38 to matrilin-2-treated AVICs suppressed caspase-1 activation and reduced the expression of intercellular adhesion molecule-1, vascular cell adhesion molecule-1, runt-related transcription factor 2, and alkaline phosphatase. Aged IL-38-deficient mice fed a high-fat diet exhibited aortic valve lesions compared to aged wild-type mice fed the same diet. The interleukin-1 receptor 9 (IL-1R9) is the putative receptor mediating the anti-inflammatory properties of IL-38; we observed that IL-1R9-deficient mice exhibited spontaneous aortic valve thickening and greater calcium deposition in AVICs compared to wild-type mice. These data demonstrate that IL-38 suppresses spontaneous and stimulated osteogenic activity in aortic valve via inhibition of the NLRP3 inflammasome and caspase-1. The findings of this study suggest that IL-38 has therapeutic potential for prevention of CAVD progression.

IL-38 Gene Deletion Worsens Murine Colitis

IL-38 is a recently discovered cytokine and member of the IL-1 Family. In the IL-1 Family, IL-38 is unique because the cytokine is primarily a B lymphocyte product and functions to suppress inflammation. Studies in humans with inflammatory bowel disease (IBD) suggest that IL-38 may be protective for ulcerative colitis or Crohn’s disease, and that IL-38 acts to maintain homeostasis in the intestinal tract. Here we investigated the role of endogenous IL-38 in experimental colitis in mice deficient in IL-38 by deletion of exons 1-4 in C57 BL/6 mice. Compared to WT mice, IL-38 deficient mice subjected to dextran sulfate sodium (DSS) showed greater severity of disease, more weight loss, increased intestinal permeability, and a worse histological phenotype including increased neutrophil influx in the colon. Mice lacking IL-38 exhibited elevated colonic Nlrp3 mRNA and protein levels, increased caspase-1 activation, and the concomitant increased processing of IL-1β precursor into active IL-1β. Expression of IL-1α, an exacerbator of IBD, was also upregulated. Colonic myleloperoxidase protein and Il17a, and Il17f mRNA levels were higher in the IL-38 deficient mice. Daily treatment of IL-38 deficient mice with an NLRP3 inhibitor attenuated diarrhea and weight loss during the recovery phase. These data implicate endogenous IL-38 as an anti-inflammatory cytokine that reduces DSS colitis severity. We propose that a relative deficiency of IL-38 contributes to IBD by disinhibition of the NLRP3 inflammasome.

IL-38 in modulating hyperlipidemia and its related cardiovascular diseases

Hyperlipidemia is confirmed to be associated with several health problems that include the combination of diabetes mellitus, obesity, and hypertension, ie, metabolic syndrome. Although the lipid-lowering therapy is an effective treatment in hyperlipidemia and its related cardiovascular diseases (CVDs), the persistence of high atherosclerotic risk is notable which could not be simply explained as a phenomenon of hyperlipidemia. Concerning on this notion, it is imperative to identify novel biomarkers which could monitor treatment and predict adverse cardiovascular events. It is demonstrated that the chronic inflammatory response caused by immune cells is a characteristic of hyperlipidemia and atherosclerosis. Notably, among several inflammatory related cytokines, interleukin 38 (IL-38), as a member of the IL-1 family, plays an important role in anti-inflammatory response by binding with its receptor which inhibits the downstream signaling pathways. In addition, IL-38 suppresses the expression of inflammatory factors mainly through the mitogen-activated protein kinase (MAPK). At the cellular level, IL-38 could inhibit the CD4 positive T lymphocyte into T-helper 17 (Th-17) lymphocyte which further enhances the immunosuppressive activity of the T-regulatory lymphocyte (T-reg) to inhibit the inflammatory response. Consistently, IL-38 is shown to be strongly correlated to development of hyperlipidemic related CVDs. In this review, the roles of IL-38 in the development of hyperlipidemia are fully summarized. Furthermore, a theoretical basis for further in-depth research of IL-38 for treatment of hyperlipidemia is also provided.

IL-38 Alleviates Inflammation in Sepsis in Mice by Inhibiting Macrophage Apoptosis and Activation of the NLRP3 Inflammasome

Interleukin- (IL-) 38 is an emerging cytokine with multiple functions involved in infection and immunity. However, the potential role of IL-38 in the host immune response during sepsis remains elusive. Herein, we investigated if macrophages in septic mice express IL-38, the molecular mechanisms behind its expression, and the downstream effects of its expression. In mouse peritoneal macrophages, lipopolysaccharide (LPS) upregulated IL-38 and its receptor IL-36R, and the resulting IL-38 shifted macrophages from a M1 to M2 phenotype. Moreover, exposure to IL-38 alone was sufficient to inhibit macrophage apoptosis and LPS-driven activation of the NOD-, LRR-, and pyrin domain-containing 3 (NLRP3) inflammasome. These effects were partly abrogated by IL-38 downregulation. In septic mice, IL-38 markedly lowered serum concentrations of proinflammatory cytokines and greatly improved survival. Conversely, IL-38 blockade aggravated their mortality. Collectively, these findings present IL-38 as a potent immune modulator that restrains the inflammatory response by suppressing macrophage apoptosis and activation of the NLRP3 inflammasome. IL-38 may help protect organs from sepsis-related injury.