Inhibition of NADPH Oxidase Attenuates Hyperhomocysteinemia‐induced NALP3 Inflammasome Activation in Mouse Glomeruli

Abstract

Our previous studies have shown that NALP3 inflammasome activation is importantly involved in podocyte dysfunction and glomerular sclerosis induced by hyperhomocysteinemia (hHcys). The present study was designed to test whether in vivo inhibition of NADPH oxidase (Nox)‐mediated redox signaling by administration of a gp91ds‐tat peptide attenuates hHcys‐induced NALP3 inflammasome activation in mouse glomeruli. Uninephrectomized C57BL/6J WT mice were fed normal chow or a folate free (FF) diet for 4 weeks to produce hHcys. Confocal microscopy showed increased inflammasome formation, demonstrated by increased colocalization between the 3 major inflammasome components NALP3, ASC and caspase‐1. Associated with such colocalization, hHcys also increased both renal caspase‐1 activity (1.5 folds) and IL‐1β production (2.1 folds) compared to the control mice. All of these hHcys‐induced changes were significantly blocked when mice were administered a gp91ds‐tat peptide. hHcys‐induced superoxide production was also considerably inhibited with the peptide by 57.3%. Furthermore, gp91ds‐tat treatment demonstrated in vivo renal protective effects, preventing proteinuria, albuminuria, and glomerular morphological changes induced by the hHcys. In addition, immunohistochemical staining showed that hHcys promoted glomerular infiltration of macrophages and T‐cells; however, this effect was not observed in mice simultaneously receiving gp91ds‐tat. These results confirm that Nox redox signaling may trigger hHcys‐induced NALP3 inflammasome activation and that inhibition of Nox indeed prevents the inflammatory response as shown by decreased immune cell infiltration in glomeruli (supported by NIH grants HL057244 and DK54927).