Imperatorin Alleviates Intestinal Fibrosis by Suppressing AIM2-mediated GSDMD Pyroptosis in Macrophages

Abstract

Background & aims: Over-activation of pyroptosis, recently reidentified as Gasdermin D (GSDMD)-mediated proinflammatory cell death, results in severe inflammation-related disorders. Intestinal fibrosis, an inflammation-related disorder, remains one of the most common and intractable complications of Crohn's disease (CD). However, it is unknown whether excessive pyroptosis contributes to the development of intestinal fibrosis in CD.

Methods: Immunofluorescence costaining of CD11b and the pyroptosis-inducing fragment GSDMD-N terminal (GSDMD-NT) was performed in stenotic ileocecal valve tissues from patients with CD. A 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced mouse CD model was established. J744a.1 macrophages pretreated with imperatorin (IMP) were transfected with lipopolysaccharides (LPS) plus poly (dA: dT) to explore potential regulatory mechanisms controlling GSDMD-mediated pyroptosis in vitro.

Results: GSDMD-NT⁺ CD11b⁺ macrophages were significantly increased in stenotic ileocecal valve tissues from patients with CD compared with that in normal ileocecal valve tissues, reflecting that GSDMD-mediated pyroptosis in macrophages is excessively activated in CD-associated intestinal fibrosis. In the TNBS-induced model, Gsdmd^-/- mice had decreased intestinal fibrosis compared with their wild-type littermates. We also found that imperatorin (IMP), a natural furocoumarin, not only alleviated TNBS-induced intestinal fibrosis, but also inhibited TNBS-induced increase of AIM2 expression, Caspase-1 activation, and GSDMD cleavage in the colon. In vitro, we revealed IMP acting as a new regulatory factor that negatively controlled the AIM2 inflammasome via downregulating AIM2 expression, thereby avoiding excessive GSDMD-mediated pyroptosis in J744a.1 macrophages.

Conclusions: IMP negatively controls GSDMD-mediated pyroptosis via inhibiting the AIM2 pathway in macrophages. Thus, IMP enema may be a potential therapeutic approach for CD-associated intestinal fibrosis.

Keywords: Crohn’s disease; Imperatorin; Intestinal fibrosis; Pyroptosis.