Inhibitory effect of polyphenol cyanidin on TNF-α-induced apoptosis through multiple signaling pathways in endothelial cells

The aim of this study was to investigate the inhibitory effect of non-aglycone cyanidin on TNF-α-induced endothelial cell apoptosis and its mechanism through enhancing expression of thioredoxin in endothelial cells. We found that exposure of the serum-starved BAECs to TNF-α increased significantly the number of dead cells, the cleaved caspase-3 and cleaved poly(ADP-ribose)polymerase (RARP)assayed by Western blot, whereas supplementation with cyanidin considerably suppressed these events. Inhibitors of the Akt, ERK1/2, Src kinase and transfection with a dominant-negative Akt cDNA blocked the inhibitory effect of cyanidin on cleaved caspase-3. Cyanidin significantly elevated expression of endothelial nitric oxide synthase (eNOS) and thioredoxin (Trx). The increased Trx expression was blocked by siRNA transfection of cGMP-dependent protein kinase (PKG) and by using a PKG inhibitor, KT5823. Cyanidin also ameliorated TNF-α-induced decrease of Trx S-nitrosylation and intracellular glutathione and elevation of 4-hydroxynonenal (4-HNE), a major aldehydic product of lipid peroxidation. Furthermore, cyanidin also restored S-nitrosylation of caspase-3 and reduced the rise in expression and acetylation of tumor suppression gene p53. However, KT5823 or L-NAME, an inhibitor of eNOS, removed the preventive effects of cyanidin. Our data show that inhibitory effect of cyanidin on TNF-α-induced apoptosis involves multiple pathways, such as Akt activation, eNOS and thioredoxin expression in endothelial cells.