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Medical AI Inquiry: You was designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.  Labels: BACKGROUND, RESULTS. Meshes: Alkaloids, Benzophenanthridines, Bosentan, Caveolin 1, Cell Membrane, Cells, Cultured, Endothelial Cells, Endothelin-1, Endothelium, Vascular, Enzyme Activation, Enzyme Induction, Homeostasis, Isoenzymes, Naphthalenes, Nitric Oxide, Nitric Oxide Synthase Type II, Nitric Oxide Synthase Type III, Phenanthridines, Protein Kinase C, Protein Kinase C-alpha, Protein Kinase C-delta, Protein Transport, Saphenous Vein, Sulfonamides, Tetradecanoylphorbol Acetate.
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Do elevated endothelin-1 levels impair nitric oxide homeostasis through a PKC-dependent pathway? Context: Endothelin-1 (ET-1) plays an important role in the maintenance of vascular tone and pathological states such as ischemia/reperfusion (I/R) injury, coronary vasospasm, and cardiac allograft vasculopathy. We assessed the effects of elevated ET-1 levels as seen after I/R to determine if ET-1 modulates nitric oxide (NO) production via the translocation of specific protein kinase C (PKC) isoforms. Human saphenous vein endothelial cells (HSVECs) (n=8) were incubated with ET-1 or phosphate-buffered saline (PBS) for 24 hours. NO production was determined in the supernatant by measuring nitrate/nitrite levels. Protein expression of endothelial nitric oxide synthase (eNOS), inducible NOS (iNOS), caveolin-1 and PKC were determined. Lastly, PKC translocation and activity were assessed after exposure to the drug of interest. HSVECs exposed to ET-1 displayed decreased NO production. PKC inhibition reduced NO production, whereas PKC activation increased production. NO production was maintained when HSVECs exposed to ET-1 were treated with the PKC agonist, PMA. eNOS protein expression was reduced after ET-1 treatment. PKC inhibition also downregulated eNOS protein expression, whereas PMA upregulated expression. ET-1 exposure led to a significant increase in PKCdelta and PKCalpha translocation compared with control, whereas translocation of PKClambda was inhibited. ET-1 exposure significantly reduced overall PKC activity compared with control.
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Our study demonstrates that high levels of ET-1 impair endothelial NO production via an isoform-specific PKC-mediated inhibition of eNOS expression. ET-1 antagonism with bosentan stimulates translocation of PKClambda and leads to increased PKC activity and NO production. ET-1 antagonism may provide a novel therapeutic strategy to improve vascular homeostasis. Final Decision: yes