| The recent studies showed that the 'fatty streak' lesion began to form from fetal period and lasted several decades and many risk factors participate in atherogenesis. As atherosclerosis is a chronic disease requring lifetime preventive therapy, new antiatherogenic drugs should meet the criteria of being safe, palatable, inexpensive and of broad role against several causes. Platelet activating factor (PAF) and intracellular free calcium ion [Ca2+]j level are reported to be correlated with atherogenesis. In addition, the resourses of PAF receptor antagonist ginkgolide B (GB) and Ca2+ entry blocker praeruptorin (pra-C) are very abundant in China. To explore the value of GB and pra-C on the prevention and therapy against atherosclerosis, their roles on cattle aortic smooth muscle cells (SMC) proliferation and foam cell formation was investigated.After pretreating with GB, the mixture of ginkgolide A and B(GA:GB), pra-C or enalaprilat (Ena) at 37癈 for 0.5 h, the VSMC were treated with or without angiotensin II (Ang II) for 24 h. The proliferation of SMC was evaluated by 3H-thymidine incorporation and the cell cycle phase was measured by flow cytometry. Cytotoxicity was reflected by MTT and lactate dehydrogenase (LDH)activity of superfatant. It was shown that GB and GA:GB suppressed Angiotensin II (Ang II)-induced SMC proliferation in concentration-dependent fashion at concentrations ranging from 10"9 mol-L" to 10" mol-L"1. The most inhibitory ratio of GB and GA:GB was 54.6 % and 69.4 % respectively and their inhibitory role on SMC proliferation had no statistically significant difference at the same concentrations. 10"7 mol-L"1 GB and GA:GB also reduced the cell proliferation index from 45.0 % (Ang II group) to 40.5 % and 41.9 % separately. In addition, GB and GA:GB were shown to inhibit the synthesis of cell DNA and mitochondrial succinate dehydrogenase activity of cattle aortic SMC in a dose-dependent way in the absence of Ang II, while the LDH activity of superfatant had not any change. The results suggest that the inhibitory effects of GB appeared to relate to a G1-籗 block in cell cycle traverse and had nothing to do with cytotoxicity. The suppression of SMC proliferation by GB might not only be contributed by blockage of the PAF receptor activity. Whether or not treated with Ang II, SMC proliferation was suppressed by pra-C in a concentration-dependent manner. The inhibitory ratio could reach 63.1 % or 59.0% in the absence or presence of Ang II. Simultaneously, the ratio of S phase cells was reduced while the LDH activity of superfatant did not change dramatically. So we conclude that pra-C can suppress cell mitogenesis through blockade of Ca2+ influx. As a positive control drug, Ena, the angiotensin tranferase inhibitor (ACEI), obviously inhibited the Ang II-induced SMC proliferation and the most inhibitory ratio was 74.9 %. However, the treatment with Ena could elevate the LDH activity in cell cultivated medium. The aboveresults indicate that though the effects of GB and pra-C are not stronger than Ena, however, they are safer than the latter, suggesting GB and pra-C may have broader perspective for the prevention and therapy against vascular hyperplastic diseases.After treated with 50 M g ?ml"1 heavily modified oxidized low density lipoprotein (heavy-ox-LDL) at 37癈for 48 h, the mass of total cholesterol (TC) in the mouse peritoneal macrophages (MPM) was increased to 2 times of that at 0 h. The results proved that foam cell model was convincing. GB inhibited intracellular TC and cholesterol ester (CE) accumulation in concentration-dependent manner at concentrations ranging from lO^mol-L"1 to 10"5 mol-L"1, while the percentage of CE in TC was not influenced by GB. The results suggest that GB prevent intracellular cholesterol accumulation and retard foam cell formation, but it does not change the activity of tissue acetyl coenzyme A cholesterol acetyl transferase (ACAT).When MPM were cultivated with GB, their abilities to take up heavily, moderately and mildly modified 125I-ox-LDL...
|
PDF Full Text Request