Rohitukine Down-regulates Expression Of LPL And Lipid Accumulation Via PI3k/m TOR/PPARY Pathways In Macrophages

[Objective] Atherosclerosis(As), the underlying cause of heart attacks, stroke and other cardiovascular diseases. Lipid metabolism disorder, especially foam cell formation resulted from macrophage lipid accumulation plays an important role in the occurrence and development of AS. Lipoprotein lipase(LPL), a key enzyme in lipid metabolism, hydrolyzes triglycerides in lipoproteins. However, LPL in aorta produced by macrophages exerts a pro-atherogenic effect by acting as a structural cofactor facilitating cellular lipid uptake. Rohitukine(RH), a chromone alkaloid isolated from Dysoxylum binectariferum Hook, has various biological activities, such as anti-cancer and immunomodulatory properties. Latest study shows that it possesses an anti-adipogenic activity in vitro and an anti-dyslipidemic activity in vivo.We conducted this study to explore the impact of rohitukine on macropage LPL expression, so as to macropage cellular lipid accumulation.[Methods] RAW 264.7 macropageswere treated with RH(0, 5,10,20 u M) for 24 h or with 20 u M RH for 0, 12,24,48 h, then LPL protein level were detected by Western blot, LPL m RNA level were detected by RT-PCR and LPL activity level were detected by special kit. After incubation of RAW 264.7 with 20 u M RH and 50mg/ml LDL for 24 h, cellular level of TG and TC was tested by standard enzymc process, and lipid droplets in macrophage was observed by oil Red O staining. After incubation of RAW264.7 with 20 u M RH for 24 h,protein level of p-PI3K、p-m TOR and PPARγ were detected by Western Blot. Then, LPL expression and activity were measured after treatment with agonist of PI3 K, m TOR and PPARγ respectively. At last, the bonding between macropage LDLR and LPL were measured by co-immunoprecipitation.[Results] RH downregulated macrophage LPL expression(protein and m RNA level) and its activity in a dose-dependent and time-dependent manner, leading to decreases of cellular cholesterol and triglyceride level as well as cellular lipid droplets. At the same time, RH inhibit phosphorylation of PI3 K and m TOR and expression of PPARγ. Moreover, addition of PI3 K, m TOR and PPARγ agonist abolished the decreases of LPL expression and activity induced by RH. Binding of Macrophage LDLR and LPL also decreased after RH treatment.[Conclusions] RH down-regulated macrophage LPL expression and activity through PI3K/m TOR/PPARγ pathway and decreased the binding between macrophage LDLR and LPL, thus inhibiting cellular lipid accumulation mediated by macrophage LPL.