PROTECTION OF VASCULAR ENDOTHELIAL-CELLS FROM HYDROGEN PEROXIDE-INDUCED OXIDANT INJURY BY GYPENOSIDES, SAPONINS OF GYNOSTEMMA-PENTAPHYLLUM

Lipid peroxidation and toxicity associated with oxygen radicals have b een suggested as major causes of cancer, atherosclerosis and the aging process. Damage of endothelial cells may lead to cardiovascular and c erebrovascular diseases. Endothelial cells are susceptible to oxidant insult. In the present study, the antioxidant effect of a Chinese medi cinal herb, Gynostemma pentaphyllum Makino (Chinese name, Jiaogulan), was investigated in vitro using vascular endothelial cells. Confluent monolayers of bovine pulmonary artery endothelial cells (PAEC) were pr eincubated with different concentrations of gypenosides (GP, total sap onins of Gynostemma pentaphyllum) for 16 h, then washed and incubated with hydrogen peroxide (H2O2) for 4 h. Cell injury was assessed by mea suring the release of intracellular lactate dehydrogenase (LDH), and c ell viability with tetrazolium (MTT) assay. Lipid peroxidation product s of PAEC were monitored as thiobarbituric acid-reactive substances (T BARS) with a fluorometric assay. The results showed that 62.5 mum H2O2 incubated with PAEC for 4 h increased the percentage of LDH release, decreased cell viability manifested by MTT absorbance at 620 nm, and e levated TBARS. Preincubation of GP (25-150 mug/mL) with PAEC for 16 h before H2O2 exposure significantly declined LDH release, increased cel l viability, and reduced TBARS. These results demonstrate that gypenos ides can protect vascular endothelial cells from oxidant injury. The d ata thus suggest that gypenosides may be beneficial for the prevention and treatment of atherosclerosis and for retardation of the aging pro cess.