Aim: The effect of ginsenoside Rb2 purified from Panax ginseng on fibrinolytic activity of bovine aortic endothelial cells (BAEC) was investigated.
Methods: Cellular plasminogen activator (PA) level of the lysates was measured by the chromogenic substrate S-2403. Fibrin underlay technique was carried out to observe fibrinolysis by growing endothelial cells in the culture medium. Cell viability was then determined by measurement of the activity of mitochondrial dehydrogenase. The ability of Rb2 of potentiating cellular PA activity was investigated by measuring the amounts of PA and PA inhibitor-1 (PAI-1) in the culture medium using zymography and reverse zymography. Changes in the expression of urokinase-type PA (uPA), uPA receptor, and PAI-1 mRNA in BAEC after treatment with Rb2 were analyzed by Northern blot.
Results: Rb2 enhanced cellular PA activity in a concentration-and time-dependent manner. Treatment of BAEC with Rb2 10 mg/L for 9 h resulted in a 3.5-fold increase of PA activity without a marked cytotoxic effect, as shown by LDH levels in culture. Increased PA levels caused the increase in surface plasmin levels as observed by fibrin underlay technique. Rb2 greatly or moderately increased the amount of urokinase-type PA (uPA) or its inhibitor (PAI-1), present in the culture medium, whereas saponin did not influence mRNA levels of uPA, its surface receptor, and PAI-1, suggesting that Rb2 may stimulate the secretion of uPA without enhancing its gene expression. The enhancement of PA levels by retinoic acid alone, a stimulator of PA synthesis, was potentiated by the simultaneous addition of ginsenoside Rb2 1 mg/L. Therefore, Rb2 might exert a strong synergism in the synthesis of cellular PA in BAEC.
Conclusion: Ginsenoside Rb2 enhanced the PA activity levels in BAEC as well as the surface plasmin activity of BAEC. Rb2 may stimulate the secretion of uPA without enhancing the gene expression of uPA, uPA receptor (uPAR), and PAI-1.