Intestinal Phospholipid Disequilibrium Initiates an ER Stress Response That Drives Goblet Cell Necroptosis and Spontaneous Colitis in Mice

BACKGROUND & AIMS: Patients with ulcerative colitis have low concentrations of the major membrane lipid phosphatidylcholine (PC) in gastrointestinal mucus, suggesting that defects in colonic PC metabolism might be involved in the development of colitis. To determine the precise role that PC plays in colonic barrier function, we examined mice with intestinal epithelial cell (IEC)-specific deletion of the rate-limiting enzyme in the major pathway for PC synthesis: cytidine triphosphate: phosphocholine cytidylyltransferase-alpha (CT alpha(IKO) mice). METHODS: Colonic tissue of CT alpha(IKO) mice and control mice was analyzed by histology, immunofluorescence, electron microscopy, quantitative polymerase chain reaction, Western blot, and thin-layer chromatography. Histopathologic colitis scores were assigned by a pathologist blinded to the experimental groupings. Intestinal permeability was assessed by fluorescein isothiocyanate-dextran gavage and fecal microbial composition was analyzed by sequencing 16s ribosomal RNA amplicons. Subsets of CT alpha(IKO) mice and control mice were treated with dietary PC supplementation, antibiotics, or 4-phenylbutyrate. RESULTS: Inducible loss of CT alpha in the intestinal epithelium reduced colonic PC concentrations and resulted in rapid and spontaneous colitis with 100% penetrance in adult mice. Colitis development in CT alpha(IKO) mice was traced to a severe and unresolving endoplasmic reticulum stress response in IECs with altered membrane phospholipid composition. This endoplasmic reticulum stress response was linked to the necroptotic death of IECs, leading to excessive loss of goblet cells, formation of a thin mucus barrier, increased intestinal permeability, and infiltration of the epithelium by microbes. CONCLUSIONS: Maintaining the PC content of IEC membranes protects against colitis development in mice, showing a crucial role for IEC phospholipid equilibrium in colonic homeostasis.

Automated summary

The study found that the loss of CT alpha in intestinal epithelial cells leads to decreased colonic PC concentrations and rapid, spontaneous colitis development in adult mice, which is linked to an endoplasmic reticulum stress response. These results highlight the crucial role of IEC phospholipid equilibrium in colonic homeostasis.