[Effects of puerarin on proliferation of vascular smooth muscle cells induced by thrombin].

Objective: To investigate the effects of puerarin on the proliferation of vascular smooth muscle cells (VSMC) induced by thrombin and the mechanism thereof.

Methods: VSMCs were isolated from the thoracic aorta of a SD rat and cultured, then co-cultured with thrombin of the concentration 0.1, 0.3, 1.0, 3.0, and 10 U/L for 24 h, thrombin of the concentration of 1 U/L for 0, 6, 12, 24, 36, and 48 h respectively, or thrombin of the concentration of 1 U/L combined with puerarin of the concentrations of 1.5 x 10(-5), 1.5 x 10(-4), or 1.5 x 10(-3) mol/L for 24 h. Flow cytometry was used to detect the cell number and cell cycle. Western blotting was used to indicate the protein expression of the oncogenes c-fos and bcl-2 RT-PCR was used to evaluate the thrombin receptor (TR) mRNA expression.

Results: he numbers of the groups of VSMCs stimulated by 0.1, 0.3, 1.0, 3.0, and 10 U/L thrombin for 24 hours were 4.82 x 10(4)/ml +/- 0.11 x 10(4)/ml, 6.37 x 10(4)/ml +/- 0.09 x 10(4)/ml, 8.78 x 10(4)/ml +/- 0.08 x 10(4)/ml, 7.37 x 10(4)/ml +/- 0.07 x 10(4)/ml, and 5.28 x 10(4)/ml +/- 0.12 x 10(4)/ml respectively, all significantly higher than that of the control group (4.08 +/- 0.054 x 10(4)/ml, all P < 0.05). The effect of thrombin was in a dose-dependent manner within a concentration range of 0.1 - 1.0 U/L. The suppression rates of VSMC proliferation in the combination groups with puerarin of the concentrations of 1.5 x 10(-5), 1.5 x 10(-4), and 1.5 x 10(-3) mol/L were 10.9% +/- 1.6%, 32.1% +/- 3.3%, and 42.6% +/- 5.2% respectively in comparison with the thrombin group (all P < 0.05). The c-fos protein expression of the VSMCs after thrombin stimulation for 24 h increased by 156.0% +/- 11.3% (P < 0.05), and the bcl-2 protein expression of the VSMCs pretreated with puerarin of the concentrations of 1.5 x 10(-5), 1.5 x 10(-4), and 1.5 x 10(-3) mol/L, and then stimulated by thrombin was significantly lower than that of the VSMCs only stimulated by thrombin with the suppression rates of 20.7% +/- 2.1%, 31.6% +/- 5.2%, and 44.5% +/- 7.5% respectively (all P < 0.05). The bcl-2 protein expression of the VSMCs after thrombin stimulation for 24 h increased by 96.7% +/- 8.3% (P < 0.05), and the bcl-2 protein expression of the VSMCs pretreated with puerarin of the concentrations of 1.5 x 10(-5), 1.5 x 10(-4), and 1.5 x 10(-3) mol/L, and then stimulated by thrombin was significantly lower than that of the VSMCs only stimulated by thrombin with the suppression rates of 7.1% +/- 0.8%, 18.8% +/- 1.2%, and 39.6% +/- 6.4% respectively (all P < 0.05). The stimulation of thrombin increased the TR mRNA expression by 183.9% +/- 9.4%. The puerarin of the concentrations of 1.5 x 10(-5) mol/L and 1.5 x 10(-4) mol/L decreased the increase of TR mRNA expression induced by thrombin, however, without significant differences (both P > 0.05), and puerarin of the concentration of 1.5 x 10(-3) mol/L significantly suppressed the increase of TR mRNA expression induced by thrombin by 17.6% +/- 1.7% (P < 0.05).

Conclusion: Puerarin suppresses the proliferation and DNA synthesis of VSMC induced by thrombin. The inhibitory effect of puerarin is closely related with the suppression of the protein expression of c-fos and bcl-2n, and partly related with the suppression of the TR mRNA expression.