#4967 GASDERMIN D IS REQUIRED FOR CONTROL OF NECROPTOTIC CELL DEATH IN AKI

Abstract Background and Aims Contradicting previous reasoning, it is now established that necrotic rather than apoptotic cell death pathophysiologically drives acute tubular necrosis during AKI. Whereas involvement of necroptosis and ferroptosis has been demonstrated by various groups, the role of pyroptosis, a highly immunogenic form of cell death requiring proteolytic activation of gasdermin protein family members, remains uncertain upon AKI. Thus, we aimed to investigate the role of pyroptosis and its mechanism of action in AKI. Method We set to detect gasdermin D (GSDMD) expression in murine renal samples after ischemia/reperfusion injury (AKI) by immunohistochemistry. Furthermore, we investigated GSDMD-deficient mice in IRI and cisplatin-induced AKI. To conclude on mechanisms, we isolated fresh murine renal tubules and measured LDH release over time. We generated MLKL/GSDMDdko mice to investigate the interplay of these caspase-dependent forms of regulated necrosis in AKI. Results After IRI, we detected a specific GSDMD signal in areas surrounding necrotic tubules, whereas no such signal could be detected within necrotic areas. Whereas interference with other forms of regulated necrosis leads to reduced injury, GSDMD-deficient mice demonstrated higher levels of serum creatinine and urea as well as more severe tubular injury compared to wildtypes. In line with the findings of immunohistochemistry, we only found GSDMD protein expression in whole kidney lysates but not isolated renal tubules; and no difference in spontaneous cell death propagation was detectable. Co-deletion of MLKL (effector protein of necroptosis) reversed the sensitization to AKI by GSDMD-deficiency. These results could be reproduced in cisplatin-induced AKI. Conclusion Here, we found an unexpected protective role for GSDMD, the effector protein of pyroptosis, in two different models of AKI. Mechanistically, our studies indicate the effect of GSDMD to function outside the tubular compartment, specifically surrounding areas of tubular necrosis. These infiltrating innate immune cells appear to interfere with tubular necroptosis in a non-cell autonomous manner. Alongside with these mechanistic insights, our data urge caution when inhibition of pyroptosis is therapeutically considered.