The Effects Of Atorvastatin On Expression Of Osteopontin In Liver Of ApoE Gene Knockout Mice With Hypercholesterolemia And Its Molecular Mechanism

Objective: To study the effects of atorvastatin on expression of osteopontin in liver of the ApoE gene knockout mice with hypercholesterolemia and its molecular mechanism.Methods: 18 ApoE knockout mice of 4 weeks were randomly divided into 3 groups, normal,high-cholesterol and high-cholesterol+atorvastatin group,and fed high-cholesterol diet for 12 weeks in SPF keeping room. When high-cholesterol+atorvastatin group were given atorvastatin 5 mg / (kg.d). The blood and liver were obtained after 12 weeks . Serum cholesterol and low-density lipoprotein(LDL) were analyzed. HE stain and PV immunohistochemistry were applied to observe liver organizational changes and detect OPN expression and distribution in liver of each group. When western blot was applied to test the change of osteopontin expression in liver of the three groups. Firstly,the human hepatoma cells (HepG2) was stitulated with different rabbit high cholesterol serum(0,5%,10%),after that, it was observed that change of OPN expression and ERK, p38 phosphorylation levels,and then high cholesterol serum concentration was selected which obviouly induced OPN expression and p38,ERK phosphorylation in HepG2 cells, at the same time with different concentrations of atorvastatin to stimulate HepG2 cells for 24h, analying the changes of OPN expression and p38,ERK phosphorylation. Results: The ApoE knockout mouse with hypercholesterolemia model was established successfully. The high-cholesterol diet after 12 weeks, compared with normal group, cholesterol and LDL in serum significantly increased ( P <0.05, P <0.05);While high-cholesterol diet + atorvastatin group, compared to high-cholesterol diet group, cholesterol and LDL in serum significantly decreased (P <0.05, P <0.05). Compared with normal, HE staining showed that the liver of high-cholesterol diet group appeared diffuse fatty degeneration which was better obvious around central vein, liver cell volume of which increased , a circular size of vacuoles were found in cytoplasm and nucleus was edge;While liver cell of high-cholesterol diet + atorvastatin group was cord disorder, but no vacuoles, nuclear center. Immunohistochemistry and Western blot both showe that the OPN expression in liver of high-cholesterol groups increase compared with the normal control group, while the expression of OPN was decreased in high-cholesterol diet + atorvastatin group. In vitro HepG2, 0,5% and 10% rabbit high cholesterol serum were selected to stimulate HepG2 for 24h, compared with normal control, OPN expression and phosphorylation levels of p38 and ERK have increased. 10% rabbit high cholesterol serum was selected to stimulate HepG2, simultaneously with different concentrations of atorvastatin stimulation (0uM, 2uM, 4uM, 8uM, 16uM) for 24h, OPN expression and phosphorylation level of ERK was inhabited at 2uM atorvastatin, and gradually weaked along with the concentration of atorvastatin increased; but p38 phosphorylation levels increase at 2uM atorvastatin, when the level of p38 phosphorylation did not significantly change with the concentrations of atorvastatin increased. Conclusions: Atorvastatin can not only low ApoE knockout mice with hypercholesterolemia serum cholesterol concentration and inhibit hepatic steatosis, but also low the expression of OPN in liver; Rabbit high cholesterol serum can induce OPN expression in HepG2 cells, but atorvastatin can inhabit the role that rabbit high cholesterol serum enhance OPN expression in HepG2 cells,the role may be related with the phosphorylation levels of the p38 and ERK .