Chloroquine and Rapamycin Augment Interleukin-37 Expression via the LC3, ERK, and AP-1 Axis in the Presence of Lipopolysaccharides

Anti-Inflammatory Effect of Atorvastatin and Rosuvastatin on Monosodium Urate-Induced Inflammation through IL-37/Smad3-Complex Activation in an In Vitro Study Using THP-1 Macrophages

Objective: The pleiotropic effect of hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) is responsible for potent defense against inflammatory response. This study evaluated the inhibitory effects of HMG-CoA reductase inhibitors on the monosodium urate (MSU)-induced inflammatory response through the regulation of interleukin-37 (IL-37) expression. Methods: Serum was collected from patients with gout (n = 40) and from healthy controls (n = 30). The mRNA and protein expression of the target molecules IL-1β, IL-37, caspase-1, and Smad3 were measured in THP-1 macrophages stimulated with MSU, atorvastatin, or rosuvastatin using a real-time quantitative polymerase chain reaction and Western blot assay. Transfection with IL-1β or Smad3 siRNA in THP-1 macrophages was used to verify the pharmaceutical effect of statins in uric-acid-induced inflammation. Results: Serum IL-37 levels in gout patients were significantly higher than in controls (p < 0.001) and was associated with the serum uric acid level (r = 0.382, p = 0.008). THP-1 cells stimulated with MSU markedly induced IL-37 mRNA expression and the transition of IL-37 from the cytoplasm to the nucleus. Recombinant IL-37 treatment dose-dependently inhibited activation of caspase-1 and IL-1β in MSU-induced inflammation. Atorvastatin and rosuvastatin attenuated caspase-1 activation and mature IL-1β expression but augmented translocation of IL-37 from the cytoplasm to the nucleus. Atorvastatin and rosuvastatin induced phosphorylation of Smad3 in THP-1 cells treated with MSU crystals. Statins potently attenuated translocation of IL-37 from the cytoplasm to the nucleus in THP-1 macrophages transfected with Smad3 siRNA compared to cells with negative control siRNA. Conclusions: This study revealed that statins inhibit the MSU-induced inflammatory response through phosphorylated Smad3-mediated IL-37 expression in THP-1 macrophages.

Bioactive Molecules against Rheumatoid Arthritis by Suppressing Pyroptosis

Rheumatoid arthritis is an inflammatory disease, and pyroptosis is a form of death associated with an inflammatory response. Pyroptosis, which occurs in synovial and osteoblastic cells, can exacerbate the development of rheumatoid arthritis. The inhibition of pyroptosis of these cells can, therefore, clearly be used as a therapeutic strategy against rheumatoid arthritis. Here, we have summarized the current status of progress in the treatment of rheumatoid arthritis by targeting cellular pyroptosis. We have identified seven compounds, including a cyclic RNA, a microRNA, a peptide, and a cytokine (protein), that may influence the progression of rheumatoid arthritis by regulating the initiation of pyroptosis. All of these compounds have been shown to have anti-rheumatoid effects in vitro and/or in vivo and have the potential to be developed as anti-rheumatoid agents. These findings may help to accelerate the development of anti-rheumatoid arthritis drugs.

IL-37 alleviates TNF-α-induced pyroptosis of rheumatoid arthritis fibroblast-like synoviocytes by inhibiting the NF-κB/GSDMD signaling pathway

OBJECTIVE

Pyroptosis is crucial to rheumatoid arthritis (RA) by inducing and aggravating inflammation. TNF-α is abundant in fibroblast-like synoviocytes of RA (RA-FLSs) and plays a key role in pyroptosis by inducing nuclear factor (NF)-κB activation. Additionally, interleukin (IL)-37 is involved in autoimmune diseases as an anti-inflammatory cytokine and innate and acquired immune response inhibitor. However, the effect of IL-37 on pyroptosis in RA-FLSs remains unclear. Therefore, this study investigated the effects and mechanism of IL-37 on RA-FLS pyroptosis induced by TNF-α.

METHODS

In this study, the serum cytokines in patients with RA and healthy controls were detected using ELISA. The RA-FLSs were then cultured with TNF-α, with or without various IL-37 concentrations, to test the cytokine levels in the cell supernatant. 5-Ethynyl-2'-Deoxyuridine (EdU) assay assessed the effects of IL-37 on RA FLS proliferation. RA-FLS apoptosis was assessed using flow cytometry and mitochondrial membrane potential (MMP) measurement. In addition, transmission electron microscopy (TEM) was used to examine cell pyroptosis. We selected the optimal concentration for the following experiments and detected the signal pathway of IL-37 on pyroptosis of RA FLSs by quantitative reverse-transcription polymerase chain reaction (qRT-PCR) and Western blotting. Finally, we validated the therapeutic effects of IL-37 on CIA rat model in vivo.

RESULTS

IL-37 inhibited inflammation in vitro and in vivo and reduced pyroptosis-related protein expression in RA FLSs. Furthermore, we determined that nuclear factor κB (NF-κB) signaling is required for GSDMD-mediated pyroptosis in RA FLSs.

CONCLUSION

IL-37 alleviates TNF-α-induced pyroptosis of RA FLSs by inhibiting NF-κB/GSDMD signaling. Additionally, our data revealed a novel mechanism for IL-37 in RA FLSs, suggesting a new potential therapy for IL-37 to treat RA.

In-vitro immunomodulatory effects of nicotine on Nitric Oxide, interleukin 1β and interleukin 37 production in human peripheral blood mononuclear cells (PBMC) from patients with Behçet disease

Behçet's disease is a chronic systemic inflammatory disorder associated with a cytokine profile disruption and increased nitric oxide levels. In our current study we sought to evaluate the in-vitro modulatory effect of nicotine, the principal alkaloid of tobacco, on nitric oxide (NO), interleukin 1β (IL-1β) and interleukin 37 (IL-37) production during Behçet's disease. Peripheral blood mononuclear cells cultures were performed with or without nicotine (200 μg/ml). Culture supernatants were harvested after 24 h of incubation. NO, IL-1β and IL-37 measurements were, respectively, performed by modified Griess method and ELISA sandwich. Our results showed that nicotine significantly reduced NO and IL-1β levels in patients with Behçet's disease, while it increased IL-37 production. Our results showed no sex differences in the effects of nicotine on the production of nitric oxide and IL-1β nor IL-37 in PBMC of patients. Our findings suggest that nicotine may provide a potential therapeutic strategy targeting inflammation during Behçet's disease.

Current Understanding of IL-37 in Human Health and Disease

IL-37 is a recently discovered cytokine in the IL-1 family exerting broad protective effects on inflammatory diseases, autoimmune diseases, and cancer. Immune and non-immune cells produce the IL-37 precursor upon pro-inflammatory stimuli. Intracellularly, caspase-1 cleaves and activates IL-37, and its mature form binds to Smad3; this complex translocates into the nucleus where it suppresses cytokine production, consequently reducing inflammation. Extracellularly, IL-37 forms a complex with IL-18Rα and IL-1R8 (formerly TIR8 or SIGIRR) that transduces anti-inflammatory signals by the suppression of NF-κB and MAPK and the activation of Mer-PTEN-DOK pathways. During inflammation, IL-37 suppresses the expression of several pro-inflammatory cytokine in favor to the expression of the anti-inflammatory ones by the regulation of macrophage polarization, lipid metabolism, inflammasome function, TSLP synthesis and miRNAs function. Moreover, IL-37 not only regulates the innate and acquired immunity, but also improves aging-associated immunosenescence. Furthermore, IL-37 exerts an inhibitory effect on tumor angiogenesis and metastasis, and progression. Finally, IL-37 may have a potential ability to reduce excessive inflammation since it is aberrantly expressed in patients with inflammatory diseases, autoimmune diseases, and cancer, thus, it may be used as a marker for different types of diseases. Therefore, this review provides an updated view of the role of IL-37 in human health and disease, and discusses the potential of IL-37 as a therapeutic target and biomarker in inflammatory diseases, autoimmune diseases, and cancer.