HMG-CoA reductase inhibitor enhances inducible nitric oxide synthase expression in rat vascular smooth muscle cells; Involvement of the Rho/Rho kinase pathway
ABSTRACT Little is known about the mechanism by which HMG-CoA reductase inhibitors affect inducible nitric oxide synthase (iNOS) expression. We investigated the effect of HMG-CoA reductase inhibitor cerivastatin on iNOS expression in cultured rat vascular smooth muscle cells (VSMCs). Quiescent VSMCs were incubated with or without various concentrations of drugs as follows: cerivastatin, C3 exoenzyme or Y-27632. Then, pretreated VSMCs were stimulated by a vehicle or interleukin (IL)-1beta (10 ng/ml). Treatment of VSMCs with cerivastatin (10(-7)-10(-5) mol/l), which inhibits isoprenylation of Rho and other small G proteins, significantly increased nitrite/nitrate (NOx) production and upregulated the expression of iNOS mRNA in IL-1beta-stimulated VSMCs. This effect of cerivastatin was abolished by cotreatment with mevalonate (2x10(-4) mol/l) or geranylgeranyl-pyrophosphate (GGPP) (10(-5) mol/l), but not by farnesyl-pyrophosphate (10(-5) mol/l). Furthermore, C3 exoenzyme (50 microg/ml), an inactivator of Rho protein, and Rho kinase inhibitor Y-27632 (10(-5) mol/l) also enhanced NOx production and the expression of iNOS mRNA in IL-1beta-stimulated VSMCs. Immunocytochemical study revealed that cerivastatin, C3 exoenzyme and Y-27632 did not affect the nuclear translocation of nuclear factor-kappaB in IL-1beta-stimulated VSMCs. Our study suggests that cerivastatin stimulates iNOS expression in IL-1beta treated VSMCs by its inhibitory effect on Rho/Rho kinase pathway. In addition, this effect of cerivastatin, by enhancing iNOS expression, may contribute to the prevention of restenosis after percutaneous coronary intervention and protect against atherothrombosis.
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ABSTRACT: Numerous epidemiological studies indicate that flavonoid intake as part of a balanced diet confers beneficial health effects in man, including improved cardiovascular function, reduced incidence of cancer and amelioration of symptoms associated with inflammatory disorders (Boots et al., 2008). A recent area of interest that may be fruitful is the study of anti-inflammatory effects of flavonoids in combination with statins. Porcine coronary artery (PCA) segments were incubated overnight at 37°C in modified Krebs-Henseleit solution with or without 1µg mL -1 lipopolysaccharides (LPS), with either (0.1–10µM) quercetin, or 10µM quercetin 3′-suphate and 10µM quercetin-3-glucuronide, or with (0.01-10µM) epicatechins, 10µM catecchin and10µM epigallocatechin gallate. (0.03-3µM) simvastatins and 10µM pravastatin are also used in this study. In addition, since many quercetin-rich foods also contain significant amounts of myricetin, this flavonoid has also been examined.
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ABSTRACT: In rat glial cells the lipopolysaccharide (LPS)-induced inducible nitric oxide synthase (iNOS) gene expression was enhanced by extracellular glucose concentration in a dose-dependent manner. On the other hand, 2-deoxy-d-glucose decreased the LPS-induced iNOS gene expression even in the presence of glucose (6 gm/l), suggesting that glucose metabolism is linked to the regulation of iNOS gene expression. The intracellular NADPH/NADP+ directly correlated with the extracellular glucose concentration, and the reduction of NADPH generation via a block of glucose-6-phosphate dehydrogenase (G6PD) by treatment with dehydroepiandrosterone or the antisense DNA oligomer of G6PD mRNA resulted in the inhibition of iNOS gene expression. Gel shift assays showed that CAAT/enhancing binding protein (C/EBP), rather than AP-1 or NF-kappaB, correlated better with a glucose-dependent increase in iNOS gene expression. The induction of C/EBP DNA binding activity by LPS and glucose was attributable mainly to the increase in C/EBP-delta protein. The cotransfection with wild-type C/EBP-delta increased the iNOS promoter activity to the level achieved with a higher glucose concentration in the presence of LPS. Therefore, our results suggest that C/EBP-delta may be a critical mediator in glucose-mediated regulation of iNOS gene expression.The Journal of Neuroscience : The Official Journal of the Society for Neuroscience 09/2003; 23(20):7470-8. · 6.34 Impact Factor
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ABSTRACT: These studies demonstrate that treatment of macrophages with lovastatin, a cholesterol-lowering drug that blocks farnesylation and geranylgeranylation of target proteins, increases LPS-induced TNF-alpha production. This is reversed by the addition of mevalonate, which bypasses the lovastatin block. Examination of membrane localization of RhoA, Cdc42, Rac1, and Ras demonstrated decreased membrane localization of the geranylgeranylated Rho family members (RhoA, Cdc42, and Rac1) with no change in the membrane localization of farnesylated Ras. LPS-induced TNF-alpha production in the presence of the Rho family-specific blocker (toxin B from Clostridium difficile) was significantly enhanced consistent with the lovastatin data. One intracellular signaling pathway that is required for TNF-alpha production by LPS is the extracellular signal-regulated kinase (ERK). Significantly, we found prolonged ERK activation after LPS stimulation of lovastatin-treated macrophages. When we inhibited ERK, we blocked the lovastatin-induced increase in TNF-alpha production. As a composite, these studies demonstrate a negative role for one or more Rho family GTPases in LPS-induced TNF-alpha production.The Journal of Immunology 10/2003; 171(5):2625-30. DOI:10.4049/jimmunol.171.5.2625 · 4.92 Impact Factor