15d-prostaglandin J2 protects cortical neurons against oxygen-glucose deprivation/reoxygenation injury: involvement of inhibiting autophagy through upregulation of Bcl-2.

We have previously shown that PPAR-γ agonist 15d-PGJ2 inhibited neuronal autophagy after cerebral ischemia/reperfusion injury. However, the underlying mechanism of its regulatory role in neuronal autophagy remains unclear. This study was designed to test the hypothesis that 15d-PGJ2 upregulated Bcl-2 which binds to Beclin 1, and thereby inhibits autophagy. We performed cell viability assay, cytotoxicity assay, western blot, and co-immunoprecipitation to analyze autophagy activities in vitro model of oxygen-glucose deprivation/reoxygenation (OGD/R). OGD/R induced autophagy in cultured cortical neurons. 15d-PGJ2 treatment significantly decreased LC3-II/LC3-I ratio and Beclin 1 expression, but increased p62 expression. Autophagic inhibitor 3-methyladenine decreased LC3-II levels, increased neuronal cell viability, and mimicked some protective effect of 15d-PGJ2 against OGD/R injury. OGD/R-induced autophagy coincided with decreases in Bcl-2 expression and increases in Beclin 1 expression. 15d-PGJ2 treatment upregulated Bcl-2 expression and decreased Beclin 1 expression, and inhibit the dissociation of Beclin1 from Bcl-2 significantly. Bcl-2 siRNA abrogated the effect of 15d-PGJ2 on Beclin 1, LC3-II and p62, and influence cell viability and LDH level, while scRNA did not. PPAR-γ agonist 15d-PGJ2 exerts neuroprotection partially via inhibiting neuronal autophagy after OGD/R injury. The inhibition of autophagy by 15d-PGJ2 is mediated through upregulation of Bcl-2.