Gpx4 regulates iNKT cell homeostasis and function by preventing lipid peroxidation and ferroptosis

Invariant natural killer T (iNKT) cells are a group of innate like T cells that plays important roles in immune homeostasis and activation. We found that iNKT cells, compared to CD4+ T cells, have significantly higher levels of lipid peroxidation in both mice and humans. Proteomic analysis also demonstrated that iNKT cells express higher levels of Glutathione peroxidase 4 (Gpx4), a major antioxidant enzyme that reduces lipid peroxidation and prevents ferroptosis. T cell specific deletion of Gpx4 reduces iNKT cell population, most prominently the IFNg producing NKT1 subset. RNAseq analysis revealed IFNg signaling, cell cycle regulation, as well as mitochondrial function are perturbed by Gpx4 deletion in iNKT cells. Consistently, we detected impaired cytokine production, elevated cell proliferation and cell death, and accumulation of lipid peroxides and mitochondrial ROS in Gpx4 KO iNKT cells. Ferroptosis inhibitor, iron chelator, vitamin E and vitamin K2 can prevent ferroptosis induced by Gpx4 deficiency in iNKT cells and ameliorate the impaired function of iNKT cells due to Gpx4 inhibition. Lastly, vitamin E rescued iNKT cell population in Gpx4 KO mice. Altogether, our findings reveal the critical role of Gpx4 in regulating iNKT cell homeostasis and function, through controlling lipid peroxidation and ferroptosis.