nitrophenols and Diabetic-Angiopathies

People with diabetes are at a significantly higher risk of cardiovascular disease, in part, due to accelerated atherosclerosis. Diabetic subjects have increased number of platelets that are activated, more reactive, and respond suboptimally to antiplatelet therapies. We hypothesized that reducing platelet numbers by inducing their premature apoptotic death would decrease atherosclerosis. Approach and Results: This was achieved by targeting the antiapoptotic protein Bcl-x. These studies suggest that selectively reducing circulating platelets, by targeting Bcl-x

Topics: Animals; Apoptosis; Atherosclerosis; Biphenyl Compounds; Blood Platelets; Diabetes Mellitus, Experimental; Diabetic Angiopathies; Female; Humans; Leukocytes; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Nitrophenols; Piperazines; Platelet Count; Receptors, LDL; Risk Factors; Sulfonamides

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.

Topics: Animals; Aorta, Thoracic; bcl-X Protein; Biphenyl Compounds; Blood Glucose; Calcium; Calcium Signaling; Cells, Cultured; Diabetes Mellitus, Type 2; Diabetic Angiopathies; Disease Models, Animal; Dose-Response Relationship, Drug; Homeostasis; Inositol 1,4,5-Trisphosphate; Inositol 1,4,5-Trisphosphate Receptors; Male; Mice; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Nitrophenols; Piperazines; Proto-Oncogene Proteins c-bcl-2; Sarcoplasmic Reticulum; Sulfonamides; Time Factors; Up-Regulation; Vasoconstriction