Polyunsaturated fatty acids fuel intestinal inflammation in GPX4 deficient hosts

Introduction:

A single nucleotide polymorphism next to glutathione peroxidase 4 (GPX4) was associated with the development of Crohn's disease in a GWAS study. GPX4 is the central regulatory enzyme in a form of regulated cell death termed ferroptosis, that is characterised by an iron dependent accumulation of lipidperoxides (LPO). The prime substrates for LPO are polyunsaturated fatty acids (PUFAs) in cellular biomembranes, one of which is arachidonic acid (AA). The increased consumption of PUFAs during the last decades is paralleled with an increase in inflammatory bowel disease. However, the role played by increased PUFA/AA uptake in intestinal inflammation remains elusive.

Materials and Methods:

In this study we aimed to investigate the influence of PUFAs on intestinal epithelial cells with reduced GPX4 expression evoked by siRNA silencing. For in vivo analysis we crossed Gpx4 ^flox/flox mice with Villin-Cre ^+/- mice to obtain Gpx4^flox/wt; Villin-Cre^+/- (Gpx4 ^+/-IEC) mice. We investigated an inflammatory phenotype in Gpx4-deficient murine MODE-K small intestinal epithelial cells (IEC) upon PUFA treatment.

Results:

PUFAs fuelled cell death and LPO in IECs with reduced GPX4 activity, which was paralleled by the production of IL-6 and the IL-8 homologue CXCL1. Cytokine production and LPO were both governed by ferric iron. Moreover, Gpx4 ^+/-IEC mice fed a PUFA enriched western style diet developed a small intestinal inflammation while wildtype mice were unaffected. Similar, Gpx4 ^+/-IEC mice that were orally challenged with AA and ferric maltol developed a neutrophilic inflammation. Treatment with α-tocopherol ameliorated PUFA induced small intestinal inflammation in Gpx4 ^+/-IEC mice.

Conclusion:

PUFAs promote cytokine release and LPO in GPX4-deficient IECs which trigger small intestinal inflammation in mice with reduced levels of GPX4 in the intestinal epithelium. Our study identified a dietary derived component as an environmental trigger that instigates intestinal inflammation in susceptible hosts.