Effect of GSDMD-mediated pyroptosis on the myocardial injury induced by PD-1 inhibitor combined with x-ray radiation.

e14631 Background: Radiation in combination with programmed cell death 1 (PD-1) antibodies greatly enhanced the anti-tumor activity by reactivating T lymphocytes. Whether it will produce the superposition of toxic side effects and the underlying mechanism remains elusive. Pyroptosis is a novel type of programmed cell death associated with the pathogenesis of many inflammatory diseases. We hypothesized that GSDMD plays a pathogenic role in PD-1 inhibitor combined with radiation-induced myocardial injury (RIMI) and that GSDMD gene knockout (KO) or blockade the caspase-1/GSDMD pathway will alleviate RIMI. Methods: GSDMD-KO mice and their wildtype (WT) C57BL/6J were used to investigate whether PD-1 inhibitor aggravated RIMI through pyroptosis pathway. Myocardial contractile functions, myocardial inflammation and fibrosis, and myocardial injury were assessed. Pyroptosis-related proteins and inflammatory cytokines were evaluated. Flow cytometry was used to detect the level of lymphocyte in myocardium. To further confirm the presence of pyroptosis in cardiomyocyte, double-immunostaining was performed. We verified the effect of radiotherapy combined with PD-1 inhibitor on pyroptosis in cell experiments. Results: Compared with irradiation or anti-PD-1 alone, PD-1 inhibitor could aggravate RIMI, increase the infiltration of CD8+T cells in the myocardium, and aggravate inflammatory reactions. The expressions of pyroptosis-related proteins and inflammatory cytokines were upregulated. Immunofluorescence also indicated that pyroptosis cells were increasing. While GSDMD-KO or caspase-1GSDMD inhibitor, myocardial injury and pyroptosis-related proteins were significantly reduced. Conclusions: We speculate that PD-1 inhibitors activate CD8+T cells and mediate cardiomyocyte pyroptosis. GSDMD-triggered immune-inflammatory response plays a key role in the aggravation of myocardial injury.