Nitro-Oleic Acid Attenuates OGD/R-Triggered Apoptosis in Renal Tubular Cells via Inhibition of Bax Mitochondrial Translocation in a PPAR-γ-Dependent Manner

Abstract

Background: Nitroalkene derivatives of oleic acid (OA-NO₂) serve as high-affinity ligand for PPAR-γ, which regulates apoptosis, oxidation and inflammation and plays a central role in ischemia-reperfusion injury. In the present study, we elucidated the protective mechanisms of OA-NO₂ against renal ischemia-reperfusion injury. Methods: HK-2 cells were subjected to oxygen and glucose deprivation followed by re-oxygenation (OGD/R) to mimic renal ischemia-reperfusion injury. Cell apoptosis was analyzed by flow cytometry. Bax mitochondrial translocation, cytochrome c and apoptosis-inducing factor (AIF) cytosolic leakage and Akt/Gsk 3β phosphorylation were evaluated by Western blotting. Bax activation was visualized by immunocytochemistry. GW9662 and siRNA transfection were employed to examine the involvement of PPAR-γ. Results: OGD/R injury promoted mitochondrial translocation and activation of Bax, leakage of cytochrome c and AIF, subsequent caspase-3 activation, and eventually cell apoptosis. Pre-incubation with OA-NO₂ (1.25 µM, 45min) inhibited Bax activation and blocked apoptotic cascade, while the protective effects were negated by GW9662 or PPAR-γ siRNA. Moreover, OA-NO₂ restored Akt and Gsk 3β phosphorylation in a PPAR-γ-dependent way. Conclusion: These findings suggest that OA-NO₂ attenuates OGD/R-induced apoptosis by inhibiting Bax translocation and activation and the subsequent mitochondria-dependent apoptotic cascade in a PPAR-γ dependent manner.

Protective Effect of Nicotinamide Adenine Dinucleotide Phosphate on Renal Ischemia-Reperfusion Injury

“…Oxidative stress may lead to apoptosis, which has been shown to participate in induced IRI [38-40]. In the kidneys, the link between apoptosis inhibition and improved renal function is not obvious.…”

The Key Roles of GSK-3β in Regulating Mitochondrial Activity

“…Mcl-1, an anti-apoptotic member of Bcl-2 family, stabilizes mitochondrial outer membrane permeabilization through sequestering Bak- or Bax-activating proteins Bim and Bid. Mcl-1 can be phosphorylated at S159 by GSK-3β and recognized for ubiquination and degradation [74, 75]. …”

Mitogen-Activated Protein Kinases and Hypoxic/Ischemic Nephropathy

“…However, the precise roles of MAPKs in renal I/R injury are not straightforward and are influenced by many factors and signaling pathways such as p53 [59], PI3K/Akt signaling pathways [49,73], as well as NF-kappaB signaling pathways [61]. Thus, the further investigation for the function of MAPK in renal I/R injury is necessary before finding a correct direction toward clinical targets for the treatment of renal injury.…”