P050 Paneth cell retinoid X receptor alpha drives metabolic gut inflammation

Abstract

Abstract Background The rising incidence of inflammatory bowel diseases throughout the western world could be partially explained by changes in dietary behaviour such as an increased consumption of polyunsaturated fatty acids (PUFA). In previous projects we demonstrated that PUFA induce a Crohn’s disease (CD) like gut inflammation in mice lacking antioxidant GPX4 in their intestinal epithelial cells. Cellular stress within Paneth cells has been shown to drive enteritis in mice. In this project we investigated the role of the PUFA receptor and transcription factor RXRα as driver of PUFA induced metabolic gut inflammation. Methods We generated mice lacking GPX4 (GPX4ΔPC) and GPX4 as well as RXRα (GPX4/RXRαΔPC) specifically in Paneth cells and fed them and littermate controls a Western-style diet enriched with PUFA (PUFA-WD). Mice were treated with 9-cis retinoic acid, HX531 or a neutralizing CXCL1 antibody. MODE-K cells (murine IECs) were stimulated with PUFA and were analysed by biochemical methods including ELISA, qPCR, ChIP and RNA sequencing for mechanistical workup in vitro. Results When stimulated with PUFA, GPX4 deficient IECs showed an increased activation of RXRα as well as an increased transcription and production of neutrophil attracting chemokine CXCL1, the murine homologue of IL-8. This could be attenuated by ablation of RXRα or treatment with HX531, an RXRα antagonist. By using ChIP we can demonstrate that RXRα is directly binding to the promoter region of CXCL1 upon PUFA stimulation, thereby regulating its transcription. GPX4ΔPC mice develop a CD like enteritis with mucosal to submucosal infiltration of neutrophils, macrophages, B and T cells. GPX4/RXRαΔPC mice were protected from PUFA induced enteritis and gut inflammation could be significantly ameliorated by treatment of GPX4ΔPC mice with RXRα antagonist HX531 or a neutralizing CXCL1 antibody after a PUFA-WD challenge. Moreover 9-cis retinoic acid treatment dose dependently blunted CXCL1 response and attenuated PUFA induced intestinal inflammation in GPX4ΔPC mice, thus indicating a competitive binding of PUFA to RXRα. Conclusion Our findings reveal, that PUFA binding to RXRα within Paneth cells regulates the transcription of cytokines and is crucially involved in the development of diet induced metabolic gut inflammation. Future studies are now warranted to prove if RXRα could be a promising new druggable target in human CD patients.