thiourea and Diabetic-Angiopathies

Hyperglycemia is the major cause of diabetic angiopathy. The aim of our study was to evaluate the impact of KB-R7943, an inhibitor of Na+/Ca2+ exchanger (NCX) on cell growth and function of human "diabetic" endothelial cells (EC). Intercellular adhesion molecule-1 (ICAM-1) expression and NCX activity were determined after EC were exposed to high glucose in the absence and presence of KB-R7943. Coincubation of EC with high glucose for 24 h resulted in a significant increase of monocyte-endothelial cell adhesion and the expression of ICAM-1. These effects were abolished by KB-R7943 and KB-R7943 significantly decreased the activation of NCX induced by high glucose. These findings suggested that KB-R7943 may play a role in inhibiting expression of adhesion molecules by inhibiting the reverse activation of NCX.

Topics: Blood Glucose; Cell Adhesion; Cells, Cultured; Diabetic Angiopathies; Endothelium, Vascular; Humans; Hyperglycemia; Intercellular Adhesion Molecule-1; Monocytes; Sodium-Calcium Exchanger; Thiourea

Diabetes mellitus is a disease characterised by hyperglycaemia and associated with several cardiovascular disorders, including angiopathy and platelet hyperactivity, which are major causes of morbidity and mortality in type 2 diabetes mellitus. In type 2 diabetic patients, homocysteine levels are significantly increased compared with healthy subjects. Hyperhomocysteinaemia is an independent risk factor for macro- and microangiopathy and mortality. The present study is aimed to investigate the effect of homocysteine on platelet apoptosis. Changes in cytosolic or intraluminal free Ca(2+) concentration were determined by fluorimetry. Caspase activity and phosphorylation of the eukaryotic initiation factor 2alpha (eIF2alpha) were explored by Western blot. Our results indicate that homocysteine releases Ca(2+) from agonist sensitive stores, enhances eIF2alpha phosphorylation at Ser(51) and activates caspase-3 and -9 independently of extracellular Ca(2+). Homocysteine induced activation of caspase-3 and -9 was abolished by salubrinal, an agent that prevents endoplasmic reticulum (ER) stress-induced apoptosis. Homocysteine-induced platelet effects were significantly greater in type 2 diabetics than in healthy subjects. These findings demonstrate that homocysteine induces ER stress-mediated apoptosis in human platelets, an event that is enhanced in type 2 diabetic patients, which might be involved in the pathogenesis of cardiovascular complications associated with type 2 diabetes mellitus.

Topics: Apoptosis; Blood Donors; Blood Platelets; Calcium Signaling; Caspase 3; Caspase 9; Cells, Cultured; Cinnamates; Diabetes Mellitus, Type 2; Diabetic Angiopathies; eIF-2 Kinase; Endoplasmic Reticulum; Enzyme Activation; Homocysteine; Humans; Hyperhomocysteinemia; Stress, Physiological; Thiourea

The vasoactive responses of renal arteries from diabetic and control rats were compared in vitro in arteriograph assemblies. Diabetes was established by an iv injection of streptozotocin (55 mg/kg) in Wistar-Kyoto rats. Endothelium-dependent relaxations mediated by nitric oxide (EDNO) were impaired in arteries from the diabetic rats; the impairment in endothelial function increased with duration of the diabetic state. After 6 and 16 wk, the concentrations of acetylcholine required to produce 50% relaxation of norepinephrine preconstriction were 3.2 and 25 microM for arteries from diabetic rats and 0.4 microM in control arteries, representing 8- and 62-fold decreases in sensitivity to the endothelium-dependent vasodilator in the diabetic arteries. After 6 wk of diabetes, renal arteries also became 20-fold less sensitive to relaxation induced by histamine, another agonist that induces EDNO-mediated relaxations. The inhibition of EDNO production with L-NG-nitroarginine produced greater impairments in acetylcholine relaxations in arteries from diabetic rats than from control rats. Relaxations in response to acetylcholine were impaired in arteries from diabetic rats because of increased production of factors that opposed the vasorelaxant effects of EDNO, rather than from decreased production of EDNO. Pretreatment of the diabetic arteries with the hydroxyl radical scavenger dimethylthiourea normalized relaxations in response to acetylcholine. The blockade of prostaglandin H2-thromboxane A2 receptors with SQ 29548 also improved relaxations in response to acetylcholine in diabetic arteries. These data indicate that endothelial dysfunction in the renal arteries of diabetic rats may be mediated by the increased production of free radicals and of prostaglandin endoperoxides, which oppose the vasorelaxant effects of EDNO.

Topics: Animals; Arginine; Arterioles; Bridged Bicyclo Compounds, Heterocyclic; Diabetes Mellitus, Experimental; Diabetic Angiopathies; Endothelium, Vascular; Fatty Acids, Unsaturated; Free Radical Scavengers; Free Radicals; Hydrazines; In Vitro Techniques; Male; NG-Nitroarginine Methyl Ester; Nitric Oxide; Prostaglandin Endoperoxides; Rats; Rats, Inbred WKY; Receptors, Thromboxane; Renal Artery; Superoxide Dismutase; Thiourea; Vasodilation