Expression and Regulation of Interleukin-37 in Pathogenesis of Nasal Polyps

Enhanced IL-37-IL-1R8 axis is negatively associated with inflammatory and clinical severity of chronic rhinosinusitis with nasal polyps

Background

The importance of IL-37 and downstream signal in the pathogenesis of chronic rhinosinusitis with nasal polyps (CRSwNP) demanding further investigation.

Objective

We sought to address the potential importance of the IL-37-IL-1R8 axis in regulating inflammatory response in patients with CRSwNP.

Methods

Nasal polyp (NP) tissues and control sinonasal tissues were obtained from adult CRSwNP, chronic rhinosinusitis without nasal polyps patients and healthy control subjects. The mRNA and protein levels of IL-37 and IL-1R8 in nasal tissues were examined by using quantitative PCR, immunohistochemical staining, and immunoblotting. In addition, the regulation of IL-1R8 expression was evaluated in human nasal epithelial cells (HNECs) in the presence of different stimuli.

Results

The mRNA and protein levels of IL-37 and IL-1R8 were significantly elevated in nasal polyps compared with that in control tissues. IL-37 and IL-1R8 were mainly distributed in the epithelial layer and lamina propria of tissues. IL-1R8 mRNA level in nasal polys was negatively associated with eosinophil and neutrophil infiltration, as well as endoscopic score and computed tomography score. Moreover, the mRNA expression of IL-1R8 in HNECs was significantly increased by toll-like receptor agonists, but significantly inhibited by proinflammatory cytokines, which can be rescued by using steroid (DEX).

Conclusion

Our findings showed that enhanced IL-37-IL-1R8 axis in NP tissues was negatively associated with inflammatory and clinical severity of CRSwNP patients, which could be considered as a future therapeutic target in CRSwNP patients.

Suppression of innate inflammation and immunity by interleukin-37

IL-37 is unique in the IL-1 family in that unlike other members of the family, IL-37 broadly suppresses innate immunity. IL-37 can be elevated in humans with inflammatory and autoimmune diseases where it likely functions to limit inflammation. Transgenic mice expressing human IL-37 (IL37-tg) exhibit less severe inflammation in models of endotoxin shock, colitis, myocardial infarction, lung, and spinal cord injury. IL37-tg mice have reduced antigen-specific responses and dendritic cells (DCs) from these mice exhibit characteristics of tolerogenic DCs. Compared to aging wild-type (WT) mice, aging IL37-tg mice are protected against B-cell leukemogenesis and heart failure. Treatment of WT mice with recombinant human IL-37 has been shown to be protective in several models of inflammation and injury. IL-37 binds to the IL-18 receptor but then recruits the orphan IL-1R8 (formerly TIR8 or SIGIRR) in order to function as an inhibitor. Here, we review the discovery of IL-37, its production, release, and mechanisms by which IL-37 reduces inflammation and suppresses immune responses. The data reviewed here suggest a therapeutic potential for IL-37.