Nitro-oleic acid ameliorates oxygen and glucose deprivation/re-oxygenation triggered oxidative stress in renal tubular cells via activation of Nrf2 and suppression of NADPH oxidase

Nitroalkene derivative of oleic acid (OA-NO₂), due to its ability to mediate revisable Michael addition, has been demonstrated to have various biological properties and become a therapeutic agent in various diseases. Though its antioxidant properties have been reported in different models of acute kidney injury (AKI), the mechanism by which OA-NO₂ attenuates intracellular oxidative stress is not well investigated. Here, we elucidated the anti-oxidative mechanism of OA-NO₂ in an in vitro model of renal ischemia/reperfusion (I/R) injury. Human tubular epithelial cells were subjected to oxygen and glucose deprivation/re-oxygenation (OGD/R) injury. Pretreatment with OA-NO₂ (1.25 μM, 45 min) attenuated OGD/R triggered reactive oxygen species (ROS) generation and subsequent mitochondrial membrane potential disruption. This action was mediated via up-regulating endogenous antioxidant defense components including superoxide dismutase (SOD1), heme oxygenase 1 (HO-1), and γ-glutamyl cysteine ligase modulatory subunits (GCLM). Moreover, subcellular fractionation analyses demonstrated that OA-NO₂ promoted nuclear translocation of nuclear factor-E2- related factor-2 (Nrf2) and Nrf2 siRNA partially abrogated these protective effects. In addition, OA-NO₂ inhibited NADPH oxidase activation and NADPH oxidase 4 (NOX4), NADPH oxidase 2 (NOX2) and p22^phox up-regulation after OGD/R injury, which was not relevant to Nrf2. These results contribute to clarify that the mechanism of OA-NO₂ reno-protection involves both inhibition of NADPH oxidase activity and induction of SOD1, Nrf2-dependent HO-1, and GCLM.