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Effects of simulated hyperglycemia, insulin, and glucagon on endothelial nitric oxide synthase expression. Am J Physiol Endocrinol Metab 279: E11-E17, 2000.--Diabetes is associated with endothelial dysfunction and increased risk of hypertension, cardiovascular disease, and renal complications. Earlier studies have revealed that hyperglycemia impairs nitric oxide (NO) production and diabetes causes endothelial dysfunction in humans and experimental animals. This study was designed to test the effects of altered concentrations of glucose, insulin, and glucagon, the principal variables in types I and II diabetes, on NO production and endothelial NO synthase (eNOS) expression in cultured human coronary endothelial cells. Cultured endothelial cells were incubated in the presence of glucose at either normal (5.6 mM) or high (25 mM) concentrations for 7 days. The rates of basal and bradykinin-stimulated NO production (nitrate + nitrite) and eNOS protein expression (Western blot) were then determined at the basal condition and in the presence of insulin ([10.sup.-8] and [10.sup.-7] M), glucagon ([10.sup.-8] and [10.sup.-7 M), or both. Incubation with a high-glucose concentration for 7 days significantly downregulated, whereas insulin significantly upregulated, basal and bradykinin-stimulated NO production and eNOS expression in cultured endothelial cells. The stimulatory action of insulin was mitigated by high-glucose concentration and abolished by cotreatment of cells with glucagon. Thus hyperglycemia, insulinopenia, and hyperglucagonemia, which frequently coexist in diabetes, can work in concert to suppress NO production by human coronary artery endothelial cells. endothelial cells; diabetes; coronary artery; hypertension; arteriosclerosis; endothelium-derived relaxation

Bassa, Babu V., Daeyoung D. Roh, Nosratola D. Vaziri, Michael A. Kirschenbaum, and Vaijinath S. Kamanna. Lysophosphatidylcholine activates mesangial cell PKC and MAP kinase by PLC[Gamma]-1 and tyrosine kinase-Ras pathways. Am. J. Physiol. 277 (Renal Physiol. 46): F328-F337, 1999.--Although lysophosphatidylcholine (LPC)-mediated cellular responses are attributed to the activation of protein kinase C (PKC), relatively little is known about the upstream signaling mechanisms that regulate the activation of PKC and down-stream mitogen-activated protein (MAP) kinase. LPC activated p42 MAP kinase and PKC in mesangial cells. LPC-mediated MAP kinase activation was inhibited (but not completely) by PKC inhibition, suggesting additional signaling events. LPC stimulated protein tyrosine kinase (PTK) activity and induced Ras-GTP binding. LPC-induced MAP kinase activity was blocked by the PTK inhibitor genistein. Because LPC increased PTK activity, we examined the involvement of phospholipase C[Gamma]-1 (PLC[Gamma]-1) as a key participant in LPC-induced PKC activation. LPC stimulated the phosphorylation of PLC[Gamma]-1. PTK inhibitors suppressed LPC-induced PKC activity, whereas the same had no effect on phorbol 12-myristate 13-acetate-mediated PKC activity. Other lysophospholipids [e.g., lysophosphatidylinositol and lysophosphatidic acid (LPA)] also induced MAP kinase activity, and only LPA-induced MAP kinase activation was sensitive to pertussis toxin. These results indicate that LPC-mediated PKC activation may be regulated by PTK-dependent activation of PLC[Gamma]-1, and both PKC and PTK-Ras pathways are involved in LPC-mediated downstream MAP kinase activation. atherogenic lipoproteins; oxidatively modified lysophosphati-dylcholine; intracellular signaling; atherosclerosis; glomerulo-sclerosis; protein kinase C; mitogen-activated protein kinase; phospholipase C[Gamma]-1