Paracrine effects of endothelial cells in a diabetic mouse model: capacitative calcium entry stimulated thromboxane release.
Augmented vasoconstriction contributes to arterial stiffness associated with diabetes. It has been shown that capacitative calcium entry induced by sarcoplasmic-endoplasmic reticulum calcium ATPase blocker cyclopiazonic acid (CPA) in endothelial cells stimulates production of constrictor prostaglandins, which causes contractions of vascular smooth muscle cells. The aim of the work was to study the effect of diabetes on the vasoconstrictor response induced by calcium entry into endothelial and smooth muscle cells. Force was measured in isolated aortae of diabetic ob/ob and control C57BL/6J mice under isometric conditions. Contractions caused by 10 micromol/l CPA in diabetic mouse aortae featured higher amplitudes and longer durations in comparison with nondiabetic aortae. These contractions were abolished by a COX inhibitor indomethacin (10 micromol/l) or a specific thromboxane A2 receptor blocker SQ 29548 (1 micromol/l) and were not observed in denuded aortae. The contractions were sensitive to extracellular Ca (2+) and store-operated channel blockers. All together this suggests that vasoconstriction was caused by thromboxane A2 synthesis in endothelial cells induced by Ca (2+) entry through store-operated channels. Higher concentrations of CPA (30 micromol/l) or thapsigargin (1 micromol/l) elicited indomethacin-resistant tonic contractions of aortae with 2-fold amplitude in diabetic mice compared to their nondiabetic littermates, which were sensitive to store-operated channel blockers, but not to indomethacin, SQ 29548, or denudation. In conclusions, increases in intracellular Ca (2+) cause augmented vasoconstriction in diabetic vasculature through endothelial synthesis of contractile prostaglandins. In addition capacitative Ca (2+) entry is enhanced in diabetic vascular smooth muscle. These mechanisms indicate possible targets for clinical applications.
Okon
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EB
Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, 2176 Health Sciences Mall, Vancouver, Canada. okon@icord.org
Golbabaie
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A
Breemen
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Cv
D000818:Animals; D001011:Aorta / Q000187:drug effects / Q000503:physiopathology; D020013:Calcium Signaling / Q000187:drug effects; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism* / Q000473:pathology*; D004195:Disease Models, Animal; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology*; D066298:In Vitro Techniques; D007211:Indoles / Q000494:pharmacology; D007213:Indomethacin / Q000494:pharmacology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008820:Mice, Obese; D008954:Models, Biological; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D019899:Paracrine Communication / Q000187:drug effects; D013931:Thromboxanes / Q000378:metabolism*; D014661:Vasoconstriction / Q000187:drug effects
D007211:Indoles; D013931:Thromboxanes; D019331:NG-Nitroarginine Methyl Ester; C000543:cyclopiazonic acid; D007213:Indomethacin