Gα12 Regulates Interleukin-8 Expression after Epithelial Cell Injury

Acute kidney injury (AKI) is common in hospitalized patients and is strongly correlated with increased morbidity, mortality, and prolonged hospitalization. However, signals that determine whether injured tissues following AKI will repair or fibrose and lead to chronic kidney disease (CKD) are not well defined. Numerous cytokines are activated at various times after injury and recruit inflammatory cells. Interleukin-8 (IL-8) is upregulated following activation of Gα12 by H2O2, a reactive oxygen species (ROS). Herein, we study this occurrence in vitro and in vivo. IL-8 was measured by ELISA in Gα12-silenced (si-Gα12) and inducible QLα12 (constitutively active Gα12) Madin-Darby Canine Kidney (QLα12-MDCK) cell lines after H2O2/catalase cell injury. QLα12- and si-Gα12 MDCK cells showed time-, agonist- and Gα12-dependent increases in IL-8 mRNA and protein. Gα12-silenced MDCK cells demonstrated lower IL-8 expression and blunted IL-8 increases. In transgenic mice (QLα12γGTCre+, proximal tubule Qα12 expression) ischemia reperfusion injury led to significant upregulation of CXCL-1 (IL-8 homologue) at 48 hours that was not observed in Gα12 knockout mice. Macrophages in renal cells from these mice were imaged by immunofluorescent microscopy and QLα12γGTCre+ showed increased macrophage infiltration. We demonstrate that IL-8 is a critical link between H2O2 stimulated Gα12 and renal injury. Gα12 activation led to increased IL-8 expression, a potent mediator of inflammation after injury. Future studies targeting Gα12 for inhibition after injury may blunt the IL-8 response and allow for organ recovery.