Rosiglitazone and PPAR-γ overexpression protect mitochondrial membrane potential and prevent apoptosis by upregulating anti-apoptotic Bcl-2 family proteins

To determine the involvement of peroxisome proliferator‐activated receptor‐γ (PPAR‐γ) in cytoprotection, we subjected N2‐A cells to oxygen–glucose deprivation followed by reoxygenation (H‐R). Following H‐R insults, H2O2 production was increased while cell viability declined, which was accompanied by loss of mitochondrial membrane potential (MMP), cytochrome c release, caspases 9 and 3 activation, poly(ADP‐ribose)polymerase (PARP) cleavage and apoptosis. Rosiglitazone up to 5 µM protected cell viability, normalized MMP, and prevented apoptotic signals. The protective effect of rosiglitazone was abrogated by GW9662, a PPAR‐γ antagonist, or a specific PPAR‐γ small interference RNA (siRNA) but not a control scRNA. PPAR‐γ overexpression alone was effective in maintaining MMP and preventing apoptosis and its protective effect was also abrogated by PPAR‐γ siRNA or GW9662. To elucidate the mechanism by which PPAR‐γ protects MMP and prevents apoptosis, we analyzed Bcl‐2, Bcl‐xl, and phosphorylated Bad (p‐Bad). H‐R suppressed them. Rosiglitazone or PPAR‐γ overexpression restored them via PPAR‐γ. Rosiglitazone or PPAR‐γ overexpression preserved phosphorylated Akt and 3‐phosphoinositide‐dependent kinase‐1 (PDK‐1) in a PPAR‐γ dependent manner. These results indicate that ligand‐activated PPAR‐γ protects N2‐A cells against H‐R damage by enhancing Bcl‐2/Bcl‐xl and maintaining p‐Bad via preservation of p‐Akt. J. Cell. Physiol. 220: 58–71, 2009. © 2009 Wiley‐Liss, Inc.