Mitochondrial RNA/RIG-I promotes Caspase-1/GSDMD-mediated inflammation in sepsis-associated acute kidney injury

Abstract

Mitochondria play a decisive role in the pathological mechanisms of acute kidney injury (AKI). However, the specific mechanisms by which mitochondria regulate inflammation in AKI remain elusive. We aimed to investigate the role of mitochondrial RNA (mtRNA) and retinoic acid-inducible gene I (RIG-I) in sepsis-induced renal injury. To establish an AKI mouse model, intraperitoneal injection of lipopolysaccharide was used. Meanwhile, NRK-52E cells were treated with lipopolysaccharide, ATP, and Nigericin (LAN). Western blotting and immunohistochemistry analyses revealed an upregulation of RIG-I expression in AKI samples. Depolarization of mitochondrial membrane potential and elevation of cytoplasmic mtRNA were observed after LAN treatment. RNA immunoprecipitation demonstrated a direct binding interaction between mtRNA and RIG-I. Additionally, mtRNA was shown to induce mitochondrial membrane potential depolarization, an effect that could be mitigated by RIG-I knockdown. It was observed that Caspase-1 and ASC associating with RIG-I through co-immunoprecipitation. The mitochondrial damage induced by LAN, along with the upregulation of caspase-1, cleaved caspase-1, GSDMD, and cleaved GSDMD, were mitigated by the knockdown of RIG-I. Additionally, GSDMD knockout attenuates lipopolysaccharide-induced renal injury and reduces the level of IL-1β and TNF-α in murine models. Our research indicates that the pathological processes of AKI are driven by mtRNA/RIG-I-mediated Caspase-1/GSDMD, leading to inflammation.