Calcium homeostasis in vascular smooth muscle cells is altered in type 2 diabetes by Bcl-2 protein modulation of InsP3R calcium release channels.
This study examines the extent to which the antiapoptotic Bcl-2 proteins Bcl-2 and Bcl-x(L) contribute to diabetic Ca(2+) dysregulation and vessel contractility in vascular smooth muscle cells (VSMCs) through their interaction with inositol 1,4,5-trisphosphate receptor (InsP(3)R) intracellular Ca(2+) release channels. Measurements of intracellular ([Ca(2+)](i)) and sarcoplasmic reticulum ([Ca(2+)](SR)) calcium concentrations were made in primary cells isolated from diabetic (db/db) and nondiabetic (db/m) mice. In addition, [Ca(2+)](i) and constriction were recorded simultaneously in isolated intact arteries. Protein expression levels of Bcl-x(L) but not Bcl-2 were elevated in VSMCs isolated from db/db compared with db/m age-matched controls. In single cells, InsP(3)-evoked [Ca(2+)](i) signaling was enhanced in VSMCs from db/db mice compared with db/m. This was attributed to alterations in the intrinsic properties of the InsP(3)R itself because there were no differences between db/db and db/m in the steady-state [Ca(2+)](SR) or InsP(3)R expression levels. Moreover, in permeabilized cells the rate of InsP(3)R-dependent SR Ca(2+) release was increased in db/db compared with db/m VSMCs. The enhanced InsP(3)-dependent SR Ca(2+) release was attenuated by the Bcl-2 protein inhibitor ABT-737 only in diabetic cells. Application of ABT-737 similarly attenuated enhanced agonist-induced [Ca(2+)](i) signaling only in intact aortic and mesenteric db/db vessels. In contrast, ABT-737 had no effect on agonist-evoked contractility in either db/db or db/m vessels. Taken together, the data suggest that in type 2 diabetes the mechanism for [Ca(2+)](i) dysregulation in VSMCs involves Bcl-2 protein-dependent increases in InsP(3)R excitability and that dysregulated [Ca(2+)](i) signaling does not appear to contribute to increased vessel reactivity.
Department of Physiology and Biophysics, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois 60064, USA.
Gopal V
GV
Velmurugan
Carl
C
White
D000818:Animals; D001013:Aorta, Thoracic / Q000378:metabolism / Q000503:physiopathology; D001713:Biphenyl Compounds / Q000494:pharmacology; D001786:Blood Glucose / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D002478:Cells, Cultured; D003924:Diabetes Mellitus, Type 2 / Q000150:complications* / Q000378:metabolism / Q000503:physiopathology; D003925:Diabetic Angiopathies / Q000209:etiology* / Q000378:metabolism / Q000503:physiopathology; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D006706:Homeostasis; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000378:metabolism*; D008297:Male; D051379:Mice; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism* / Q000503:physiopathology; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism*; D009596:Nitrophenols / Q000494:pharmacology; D010879:Piperazines / Q000494:pharmacology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D013449:Sulfonamides / Q000494:pharmacology; D013997:Time Factors; D015854:Up-Regulation; D014661:Vasoconstriction; D051020:bcl-X Protein / Q000378:metabolism
C501332:ABT-737; C494812:Bcl2l1 protein, mouse; D001713:Biphenyl Compounds; D001786:Blood Glucose; D053496:Inositol 1,4,5-Trisphosphate Receptors; D009596:Nitrophenols; D010879:Piperazines; D019253:Proto-Oncogene Proteins c-bcl-2; D013449:Sulfonamides; D051020:bcl-X Protein; D015544:Inositol 1,4,5-Trisphosphate; D002118:Calcium