Apoptosis of intestinal epithelial cells restricts Clostridium difficile infection in a model of pseudomembranous colitis

Pedro H V Saavedra,Peter Vandenabeele,Farzaneh Ghazavi,Nozomi Takahashi,Tom Vanden Berghe,Stephanie Kourula,Linyan Huang,Mohamed Lamkanfi

doi:10.1038/s41467-018-07386-5

Abstract

Clostridium difficile is the leading cause of pseudomembranous colitis in hospitalized patients. C. difficile enterotoxins TcdA and TcdB promote this inflammatory condition via a cytotoxic response on intestinal epithelial cells (IECs), but the underlying mechanisms are incompletely understood. Additionally, TcdA and TcdB engage the Pyrin inflammasome in macrophages, but whether Pyrin modulates CDI pathophysiology is unknown. Here we show that the Pyrin inflammasome is not functional in IECs and that Pyrin signaling is dispensable for CDI-associated IEC death and for in vivo pathogenesis. Instead, our studies establish that C. difficile enterotoxins induce activation of executioner caspases 3/7 via the intrinsic apoptosis pathway, and demonstrate that caspase-3/7-mediated IEC apoptosis is critical for in vivo host defense during early stages of CDI. In conclusion, our findings dismiss a critical role for inflammasomes in CDI pathogenesis, and identify IEC apoptosis as a host defense mechanism that restricts C. difficile infection in vivo.

Highlights

Clostridium difficile is the leading cause of pseudomembranous colitis in hospitalized patients
Intestinal organoids from Mefv−/− mice incorporated propidium iodide (PI) and displayed cell death features with kinetics resembling that of wild-type intestinal epithelial cells (IECs) organoids (Fig. 1a), indicating that Pyrin signaling is dispensable for TcdA-induced cytotoxicity of IECs
These results demonstrate that unlike in monocytes and macrophages, Pyrin inflammasome activation and inflammasome-induced pyroptosis are dispensable for IEC cytotoxicity induced by C. difficile toxins TcdA and TcdB

Summary

Introduction

Clostridium difficile is the leading cause of pseudomembranous colitis in hospitalized patients. Our studies establish that C. difficile enterotoxins induce activation of executioner caspases 3/7 via the intrinsic apoptosis pathway, and demonstrate that caspase-3/7-mediated IEC apoptosis is critical for in vivo host defense during early stages of CDI. Our findings dismiss a critical role for inflammasomes in CDI pathogenesis, and identify IEC apoptosis as a host defense mechanism that restricts C. difficile infection in vivo. We identified C. difficile toxin-induced activation of the apoptotic executioner proteases caspases 3 and 7 by the intrinsic apoptosis pathway as a critical mechanism driving IEC death. We established that the Pyrin inflammasome is dispensable in vivo for host defense against CDI, whereas selective deletion of caspases 3 and 7 in IECs exacerbated bacterial burdens and clinical parameters of CDI during early stages of infection

Methods

Results

Conclusion