Pinosylvin at a high concentration induces AMPK-mediated autophagy for preventing necrosis in bovine aortic endothelial cells

Pinosylvin is a known functional compound of the Pinus species. Pinosylvin at low concentrations (∼pmol/L) was reported to promote cell proliferation in endothelial cells. However, this study found that pinosylvin at a high concentration (100 μmol/L) induces cell death in bovine aortic endothelial cells. Therefore, we examined how pinosylvin was associated with apoptosis, autophagy, and necrosis. Pinosylvin at a high concentration appeared to promote caspase-3 activation, nuclear condensation, and the “flip-flop” of phosphatidylserine, indicating that pinosylvin induces apoptosis. However, based on flow cytometry data obtained from double-staining with annexin V and propidium iodide, pinosylvin was shown to inhibit necrosis, a postapoptotic process. Pinosylvin induced LC3 conversion from LC3-I to LC3-II and p62 degradation, which are important indicators of autophagy. In addition, AMP-activated protein kinase (AMPK) appeared to be activated by pinosylvin, and an AMPK inhibitor was markedly shown to reduce the LC3 conversion. The inhibitory effect of an AMPK inhibitor was reversed by pinosylvin. These results suggest that pinosylvin induces autophagy via AMPK activation. Further, necrosis was found to be promoted by an autophagy inhibitor and then restored by pinosylvin, while the caspase-3 inhibitor had no effect on necrosis. These findings indicate that pinosylvin-induced autophagy blocks necrotic progress in endothelial cells.