Renal ischemia/reperfusion injury triggers proximal tubular apoptosis and NHE3 dysfunction via p38MAPK/ezrin signaling pathway.

Acute kidney injury (AKI) induced by ischemia/reperfusion (IR) contributes to a high rate of morbidity and mortality in many clinical settings. We hypothesized that IR-induced proximal tubule (PT) injury is associated with inflammation and apoptosis and that PT cell injury may impair Na⁺/H⁺ exchanger isoform 3 (NHE3) activity. This study aimed to investigate the relationship between PT injury and NHE3 activity, analyzing the contribution of the p38MAPK/ezrin signaling pathway. To this end, we used in vivo and in vitro models of IR. For the in vivo approach, eight-week-old C57BL/6J mice were subjected to bilateral kidney IR and compared with the sham group. In vitro, TKPTS cells (mouse proximal tubular cell line) were subjected to IR by treatment with antimycin A (5 μM) and/or SB203580 (1 μM, p38MAPK inhibitor) or NSC305787 (3.2 μM, ezrin phosphorylation inhibitor) and compared with respective controls. Renal IR in mice resulted in PT injury, severe inflammation, increased p38MAPK activation, reduced p-ezrin immunostaining, and decreased colocalization of NHE3 with both villin and p-ezrin. Similarly, in vitro IR caused cell apoptosis, increased p38MAPK activation, induced translocation of ezrin from the membrane to the cytosol, and reduced NHE3 activity. Thus, these findings suggest that in ischemic AKI, tubulointerstitial injury is driven by inflammation and apoptosis, mediated through p38MAPK activation and altered ezrin function, ultimately impairing NHE3 activity and exacerbating cell injury.