Deregulated Expression of IL-37 in Patients with Bladder Urothelial Cancer: The Diagnostic Potential of the IL-37e Isoform

IL-37 Isoform A Prevents Collagen-Induced Arthritis in Mice by Modulating the Th17/Treg Balance via IL1R8 Receptors

Cytokines play a complex and pivotal role in modulating synovitis in rheumatoid arthritis. Interleukin (IL)-37 is known for its extensive anti-inflammatory properties that set it apart from the majority of other IL-1 family members. However, IL-37a, a member of the IL-37 family, lacks research into rheumatoid arthritis. This research aims to explore the role of IL-37a in regulating T-cell homeostasis in rheumatoid arthritis using the Collagen-Induced Arthritis(CIA) model. IL-37atg mice, a genetically altered strain carrying the human IL-37a gene, were used to test the influence of this cytokine on the progression of arthritis. The results show that IL-37atg mice demonstrated a notable reduction in both the incidence and severity of arthritis relative to WT mice. The protective effect was accompanied by lower levels of cytokines in plasma and synovial tissues (such as IL-17A and IL1β) that drive the inflammatory response. The ratio of Th17/Treg decreased in the lymph nodes of IL-37atg mice. However, the knockout of IL1R8 in IL37atg mice eliminated the effects of IL-37a. Additionally, transcriptomic analysis revealed that Th17 cell differentiation is a key pathway through which IL-37a exerts its protective effects, and experiments confirmed that IL-37a suppresses Th17-polarizing in vitro.

Agree to disagree: The contradiction between IL-18 and IL-37 reveals shared targets in cancer

IL-37 is a newly discovered member of the IL-1 cytokine family which plays an important role in regulating inflammation and maintaining physiological homeostasis. IL-37 showed a close relationship with IL-18, another key cytokine in inflammation regulation and cancer development. IL-37 affects the function of IL-18 either by binding to IL-18Rα, a key subunit of both IL-37 and IL-18 receptor, or by drastically neutralizing the IL-18 protein expression of IL-18 binding protein, an important natural inhibitory molecule of IL-18. Moreover, as another subunit receptor of IL-37, IL-1R8 can suppress IL-18Rα expression, functioning as a surveillance mechanism to prevent overactivation of both IL-18 and IL-37 signaling pathways. While IL-18 and IL-37 share the same receptor subunit, IL-18 would in turn interfere with IL-37 signal transduction by binding to IL-18Rα. It is also reported that IL-18 and IL-37 demonstrated opposing effects in a variety of cancers, such as glioblastoma, lung cancer, leukemia, and hepatocellular cancer. Although the mutual regulation of IL-18 and IL-37 and their diametrically opposed effects in cancers has been reported, IL-18 has not been taken into consideration when interpreting clinical findings and conducting mechanism investigations related to IL-37 in cancer. We aim to review the recent progress in IL-18 and IL-37 research in cancer and summarize the correlation between IL-18 and IL-37 in cancer based on their expression level and underlying mechanisms, which would provide new insights into elucidating the conflicting roles of IL-18 and IL-37 in cancer and bring new ideas for translational research related to IL-18 and IL-37.

The nuclear cytokine IL-37a controls lethal cytokine storms primarily via IL-1R8-independent transcriptional upregulation of PPARγ

Cytokine storms are crucial in the development of various inflammatory diseases, including sepsis and autoimmune disorders. The immunosuppressive cytokine INTERLEUKIN (IL)-37 consists of five isoforms (IL-37a-e). We identified IL-37a as a nuclear cytokine for the first time. Compared to IL-37b, IL-37a demonstrated greater efficacy in protecting against Toll-like receptor-induced cytokine hypersecretion and lethal endotoxic shock. The full-length (FL) form of IL-37a and the N-terminal fragment, which is processed by elastase, could translocate into cell nuclei through a distinctive nuclear localization sequence (NLS)/importin nuclear transport pathway. These forms exerted their regulatory effects independent of the IL-1R8 receptor by transcriptionally upregulating the nuclear receptor peroxisome proliferator-activated receptor (PPARγ). This process involved the recruitment of the H3K4 methyltransferase complex WDR5/MLL4/C/EBPβ and H3K4me1/2 to the enhancer/promoter of Pparg. The receptor-independent regulatory pathway of the nuclear IL-37a-PPARγ axis and receptor-dependent signaling by secreted IL-37a maintain homeostasis and are potential therapeutic targets for various inflammatory diseases, including sepsis.