Contributions of Rho-kinase and AMP-related kinase (AMPK) Signaling Pathways to Endothelium-Derived Contracting Factors (EDCF)-mediated Responses in Diabetic Rat Aorta.

Diabetes-induced endothelium damage leads to vascular dysfunction. The current study was designed to determine the effects of short-term (4-week) streptozotocin (STZ)-induced diabetes on endothelium-derived contracting factors (EDCF)-mediated responses with possible contributions of Rho-kinase and AMP-activated kinase (AMPK) signaling pathways. The effects of STZ-diabetes on vascular functions were examined in isolated thoracic aorta preparations of 30-week-old rats. The diabetes-associated changes in vascular function were studied with calcium ionophore A23187, acetylcholine, Rho-kinase inhibitor Y27632 and AMPK activator AICAR. The phosphorylation of acetyl-CoA carboxylase (ACC), AMPK and phospholamban (PLN) and protein levels of sarcoplasmic/endoplasmic Ca2+-ATPase 2 (SERCA2) and Rho-associated protein kinase (ROCKII) were investigated in aortic preparations. Although the acetylcholine-mediated relaxation responses were preserved in 4-week-STZ-diabetes, the increased activation of Rho-kinase pathway was demonstrated with 2-fold enhancement in A23187-mediated contractile responses and significantly augmented protein levels of ROCKII. AICAR-activated AMPK-mediated relaxation response was also augmented by approximately 4-fold in diabetics without any alteration in PLN phosphorylations and suppressed the A23187-mediated contraction in both groups. AICAR-induced AMPK-mediated vasorelaxation was found to be increased in diabetes in addition to 2.5-fold-elevation of diabetes-induced phosphorylated AMPK levels. These results indicated a possible compensation between hyperglycemia-induced endothelium-dependent hypercontractility and AMPK-mediated vasorelaxation in diabetes.