The Regulation Of SREBPs And VEGF On Vascular Smooth Muscle Cell Affected By Simvastatin

Objective: To investigate the effect of low and high dose simvastatin on the proliferation and migration of VSMCs and the regulation of simvastatin on the expression of SREBPs and VEGF in vivo and in vitro. To infer the biphasic effect of Statins and it's possible mechanism, which can supply the further experimental evidence for the clinical application of Statins.Methods: 1. Use primary VSMCs culture in vitro to investigate the effect of Simvastatin on the proliferation (Detected by ELISA) and migration (Scratch Wound Assay method ) of VSMCs, and the mRNA expression of SREBP-1, SREBP-2 and VEGF (Measured by RT-PCR). 2. Establish the atherosclerotic vessel injured model and divide Male Sprague-Dawley rats into four groups randomly: Normal Control group (NC, n=8), Atherosclerotic Injured group (AI, n=6), Low-dose Simvastatin group (LS, n=6), and High-dose Simvastatin group (HS, n=6). The rats were administered Simvastatin orally once a day: LS group (0.5 mg·kg-1·d-1 ), HS group (3.0 mg·kg-1·d-1 ), NC group and AI group (normal saline). The rats were put to death after 4 weeks. We detected the serum lipid by enzyme method, detected the ratio of intima/ (intima + tunica media) of thoracic aorta and left common carotid artery, identified the type of vascular intima cells, determined the expression of VEGF on blood vessel by immunohistochemistory and measured the mRNA expression of SREBP-1, SREBP-2 and VEGF of blood vessel by RT-PCR method.Results: 1. Compared with control group (0.00μmol/L), the proliferation of VSMCs didn't show any statistics difference in low concentration Simvastatin group (0.01μmol/L, 0.05μmol/L, 0.25μmol/L and 0.50μmol/L). High concentration Simvastatin group (10.0μmol/L, 25.0μmol/L, 50.0μmol/L and 100μmol/L) showed time and concentration dependent inhibitive effect on VSMCs'proliferation except 10.0μmol/L simvastatin group. 2. Compared with control group (0.00μmol/L), the migration of VSMCs didn't show any statistics difference in low concentration simvastatin (0.50μmol/L) group while high concentration simvastatin (50.0μmol/L) group significantly inhibited the migration of VSMCs (P<0.01). 3. Compared with control group (0.00μmol/L), the SREBP-1 and SREBP-2 mRNA expression of VSMCs in low concentration simvastatin (0.50μmol/L) group increased 16.87% and 5.62% (P>0.05) while high concentration simvastatin (50.0μmol/L) group increased 52.80% and 39.13% (P<0.01). 4. Compared with control group (0.00μmol/L), the VEGF mRNA expression of VSMCs in low concentration simvastatin (0.50μmol/L) group increased 6.11% (P>0.05) while high concentration simvastatin (50.0μmol/L) group decreased 22.32% (P<0.05). Animal experiment: 1. After treated by simvastatin for four weeks, rats'serum lipid (TG and HDL-C) didn't show any statistics difference between each group. Compared with NC group, the level of LDL-C and TC increased in AI group (P<0.05). Compared with AI group, the level of LDL-C and TC decreased in HS group, but showed no statistics difference (P>0.05).There were no difference between LS group and AI group about the level of LDL-C and TC. 2. The ratio of intima/ (intima + tunica media): Compared with NC group, thoracic aorta and left common carotid artery in AI group and LS group increased 54.01%, 49.97% and 173.29%, 134.96% (P<0.01). Compared with AI group, thoracic aorta and left common carotid artery in LS group decreased (P>0.05) while HS group obviously decreased 32.18% and 33.16% (P<0.01). 3. After we identified the type of vascular intima cells, we found that most of the cells were VSMCs (α-SMA stains showed positive reaction). 4. Compared with NC group, the SREBP-1 and SREBP-2 mRNA expression of blood vessel decreased 38.67% and 24.28% (P<0.05) in AI group and LS group. Compared with AI group, the SREBP-1 and SREBP-2 mRNA expression show no statistics difference (increased 23.46% and -2.19%) in LS group while showed significant statistics difference (increased 90.38% and 49.10%) in HS group. 5. VEGF expressed in vascular intima and medial VSMCs. Compared with NC group, VEGF's expression significantly increased in AI group and LS group. Compared with AI group, VEGF's expression decreased obviously in HS group and didn't show any statistics difference in LS group. 6. Rats'thoracic aorta VEGF mRNA expression: AI group and LS group increased 32.27% and 38.71% (P<0.01) compared with NC group. LS group didn't show any statistics difference while HS group significantly decreased 33.83% (P<0.01) compared with AI group.Conclusion: 1. Simvastatin didn't show biphasic effect on the proliferation and migration of VSMCs. Low dose simvastatin didn't promote the proliferation and migration of VSMCs, while high dose simvastatin showed inhibition effect on the proliferation and migration of VSMCs which was dose-dependent and independent of lipid decreased. 2. The mechanism of the effect explained above might be that simvastatin could activate and increase the mRNA expression of SREBPs and decrease the expression of VEGF in VSMCs. Simvastatin might exert the effect via activating and increasing the expression of SREBPs at first, and then supressing the expression of VEGF in VSMCs.