Depletion of gut microbiota suppresses spontaneous ileitis in mice driven by mitochondrial dysfunction induced by Phb1 deficiency

Dysbiosis in gut microbiota is associated with inflammatory bowel diseases (IBD), such as Crohn’s disease. Prohibitin 1 (PHB1) is a mitochondrial protein important in optimal mitochondrial respiration and is decreased in biopsies from IBD patients. Intestinal epithelial mitochondrial dysfunction is emerging as an underlying contributor to inflammation in IBD. Previous studies from our laboratory have demonstrated that mice with Phb1 ‐deficiency in the intestinal epithelium ( Phb1 iΔIEC ) manifest mitochondrial dysfunction, Paneth cell defects, and spontaneous inflammation in the ileum with a penetrance of 87% at 12 weeks after inducing Phb1 deletion. This inflammation is associated with a reduction in the abundance of short chain acid (SCFA)‐producing bacteria, such as Blautia , Roseburia , Ruminococcus , and Coprococccus . However, little is known whether gut dysbiosis is a driver or consequence of ileitis during intestinal epithelial mitochondrial dysfunction. In the present study, we hypothesized that the gut microbiota is necessary to induce intestinal inflammation during epithelial cell mitochondrial dysfunction. Methods Phb1 iΔIEC mice and control Phb1 fl/fl littermates were co‐housed and treated with broad spectrum antibiotics (ABX) (1 g/L ampicillin sodium salt, 1 g/L neomycin sulfate, 1 g/L metronidazole, and 500 mg/L vancomycin) in autoclaved drinking water for 4 weeks beginning 8 weeks after the induction of Phb1 deletion. Ileal stools were collected for 16S rRNA sequencing and quantification of SCFAs by liquid chromatography‐mass spectrometry. Ileum was collected for histological (inflammation) scoring after H&E staining and for immunofluorescent staining of lysozyme and Muc2 to quantitate Paneth cell defects (lysozyme allocation patterns, increase of lysozyme+/Muc2+ staining, and crypts devoid of lysozyme+ cells). Spleen weight was also measured at the time of sacrifice. Results Ileal stool from Phb1 iΔIEC mice exhibited a significant reduction in the SCFA butyrate compared to Phb1 fl/fl littermates. 16S rRNA sequencing showed that ABX treatment abolished the ileal bacterial population in both Phb1 fl/fl and Phb1 iΔIEC mice. ABX treatment ameliorated enlarged spleen weights, histological inflammation, and Paneth cell defects characteristic of Phb1 iΔIEC mice to measurements noted in Phb1 fl/fl mice. Conclusions These results suggest that mitochondrial dysfunction in IECs on its own is not sufficient to cause inflammation, but triggers disease when coupled with gut microbiota interaction. This is especially relevant to IBD given the prevalence of epithelial mitochondrial dysfunction in these patients.