Mechanisms of inhibiting proliferation of vascular smooth muscle cells by serum of rats treated with Dahuang Zhechong pill

Dahuang Zhechong pill (DHZCP), a famous and classical Chinese herbal prescription, consists of twelve traditional Chinese drugs: Eupolyphaga sinensis Walker., Rheum officinale Baill., Scutellaria baicalensis Georgi., Glycyrrhiza uralensis Fisch., Prunus persica Batsch., Prunus armeniaca L., Paeonia lactiflora Pall., Rehmannia glutinosa Libosch., Toxicodendron vernicifluum F.A. Barkl., Tabanus bivittatus Mats., Hirudo nipponica Whitman. and Holotrichia diomphalia Bates., and is clinically used to treat hepatic diseases, gynecopathy and atherosclerosis in China. Our previous studies confirm that DHZCP is able to significantly inhibit proliferation of vascular smooth muscle cells (VSMCs) in vivo and in vitro. Aim of the study: To investigate the mechanisms of inhibition of VSMCs proliferation by DHZCP with the method of Serum Pharmacology. Materials and methods: VSMCs proliferation of rat was assayed by measuring the cell viability with the MTT method, and platelet-derived growth factor (PDGF) expression in VSMCs was examined by the immunocytochemical method. Cycle and apoptosis of VSMCs were evaluated with flow cytometry. Results: The serum of DHZCP-treated rats not only inhibited endothelin-1 (ET-1) stimulated cell proliferation and PDGF expression in VSMCs, but also promoted apoptosis of the proliferated VSMCs. Meanwhile, the serum of rats containing DHZCP interfered with the cycle of PDGF-stimulated VSMCs, increasing proportion of the cells in G₀/G₁ phases and decreasing proportion of the cells in S and G₂/M phases. Conclusion: These suggest that the inhibitory effect of DHZCP on VSMCs proliferation is partially attributed to depressing PDGF expression in VSMCs, retarding the cell cycle and to promoting apoptosis of VSMCs.