Resveratrol protects primary cortical neuron cultures from transient oxygen-glucose deprivation by inhibiting MMP-9

It was recently shown that resveratrol exerts neuroprotective effects against cerebral ischemia in mice. The aim of the present study was to further confirm these effects in in vitro primary cortical neuron cultures with transient oxygen-glucose deprivation (OGD), and to investigate whether these effects are due to the inhibition of matrix metalloproteinase-9 (MMP-9) and of cell apoptosis. Neuronal primary cultures of cerebral cortex were prepared from BALB/c mice embryos (13-15 days). Cells from 14- to 16-day cultures were subjected to OGD for 3 h, followed by 21 h of reoxygenation to simulate transient ischemia. Different doses of resveratrol were added into the culture medium during the simulation of transient ischemia. The effect of the extracellular signal-regulated kinase (ERK) inhibitor U0126 was studied by adding U0126 (5 μg/μl, 4 μl) into the culture medium during transient ischemia; as a control, we used treatment of cells with 50 μM of resveratrol. Cell viability was investigated using the 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) reduction assay. Cell apoptosis was assessed by flow cytometry. The effects of resveratrol on the expression of MMP-9 were analyzed by western blotting and reverse transcription-polymerase chain reaction (RT-PCR), while the levels of ERK, phosphorylated (p)-ERK, cleaved caspase-3, Bax and Bcl-2 were measured by western blotting. The results of the MTT assay showed that cell viability is significantly reduced by transient OGD. OGD induced cell apoptosis, the expression of Bax and the activation of caspase-3 and ERK, inhibited the expression of Bcl-2 and increased the expression of MMP-9, while these effects were reversed by treatment with resveratrol. The therapeutic efficacy of resveratrol was shown to be dose-dependent, with the most suitable dose range determined at 50-100 μM. Treatment with U0126 inhibited MMP-9 and Bax expression and caspase-3 activation, while it further promoted the expression of the anti-apoptotic molecule Bcl-2, suggesting that resveratrol inhibits MMP-9 expression and cell apoptosis by attenuating the activation of ERK1/2. In conclusion, OGD can induce apoptosis through canonical apoptotic signals and by regulating the expression of MMP-9; the anti-apoptotic activity of resveratrol and its inhibitory effect on MMP-9 expression contribute in the reduced activation of ERK.