Effects of exercise training on cellular mechanisms of endothelial nitric oxide synthase regulation in coronary arteries after chronic occlusion

Abstract

-Exercise training enhances agonist-mediated relaxation in both control and collateral-dependent coronary arteries of hearts subjected to chronic occlusion, an enhancement that is mediated in part by nitric oxide. The purpose of the present study was to elucidate exercise training-induced adaptations in specific cellular mechanisms involved in the regulation of endothelial nitric oxide synthase (eNOS) in coronary arteries of ischemic hearts. Ameroid constrictors were surgically placed around the proximal left circumflex coronary artery (LCX) of adult female Yucatan miniature swine. Eight weeks postoperatively, animals were randomized into sedentary (pen-confined) or exercise training (treadmill run; 5 days/ wk; 14 wk) protocols. Coronary artery segments (ϳ1.0 mm luminal diameter) were isolated from collateral-dependent (LCX) and control (nonoccluded left anterior descending) arteries 22 wk after ameroid placement. Endothelial cells were enzymatically dissociated, and intracellular Ca 2ϩ responses (fura 2) to bradykinin stimulation were studied. Immunofluorescence and laser scanning confocal microscopy were used to quantify endothelial cell eNOS and caveolin-1 cellular distribution under basal and bradykinin-stimulated conditions. Immunoblot analysis was used to determine eNOS, phosphorylated (p)-eNOS, protein kinase B (Akt), pAkt, and caveolin-1 protein levels. Bradykinin-stimulated nitrite plus nitrate (NOx; nitric oxide metabolites) levels were assessed via HPLC. Exercise training resulted in significantly enhanced bradykinin-mediated increases in endothelial Ca 2ϩ levels, NOx levels, and the distribution of eNOS-to-caveolin-1 ratio at the plasma membrane in endothelial cells of control and collateral-dependent arteries. Exercise training also significantly increased total eNOS and phosphorylated levels of eNOS (pSer 1179 ) in collateral-dependent arteries. Total eNOS protein levels were also significantly increased in collateral-dependent arteries of sedentary animals. These data provide new insights into exercise traininginduced adaptations in cellular mechanisms of nitric oxide regulation in collateral-dependent coronary arteries of chronically occluded hearts that contribute to enhanced nitric oxide production. coronary artery disease; coronary circulation; nitrate; nitrite; porcine CORONARY ARTERY DISEASE is associated with progressive impairment of endothelial function, including changes in endo-

Exercise training enhances multiple mechanisms of relaxation in coronary arteries from ischemic hearts

“…However, recent reports confirmed the specificity of fluorescence signal produced by DAF-FM DA as representative of nitric oxide, demonstrating complete blockade of the signal by NOS inhibition (8, 37, 43). Furthermore, in support of our current findings with DAF-FM DA, using HPLC, we previously reported enhanced bradykinin-mediated nitrite/nitrate production in nonoccluded and collateral-dependent coronary arteries of exercise-trained pigs (49).…”

“…Visual examination of the ameroid occluder during dissection of the LCX artery indicated complete occlusion in all animals that were included in the study. We previously published coronary angiograms that document that the occluded LCX artery in our model is completely occluded and dependent on collateral vessels for its blood supply (49). Previous studies also documented that blood flow to the chronically occluded main artery is maintained via collateral circulation to this vessel (10,39,40); thus we refer to the LCX as a collateral-dependent artery.…”

“…There were no significant differences. dent coronary arteries, resulting in enhanced nitric oxide production (49). Other studies have shown increased eNOS mRNA and protein levels after exercise training in control animals (26,41) and in numerous animal models of disease (15,16,20,44).…”

“…Previous studies have shown that exercise training enhances endothelial nitric oxide synthase (eNOS) mRNA expression in coronary arteries (41) and eNOS protein levels in coronary arterioles (26) of control animals. Exercise training also has been shown to increase nitric oxide generation, eNOS (15,16,44), and phosphorylated (Ser 1179 ) eNOS gene expression in animal models of disease (20,49), as well as phosphorylated (Ser 1177 ) eNOS gene expression in human coronary artery disease patients (17).…”

Alternative Non-Medical, Non-Surgical Therapies for the Treatment of Angina Pectoris

“…Exercise training in stable CAD leads to an improved agonist-mediated endothelium-dependent vasodilatory capacity. (42-45) Exercise training induces adaptations in cellular mechanisms of nitric oxide regulation in collateraldependent coronary arteries of chronically occluded vessels that contribute to enhanced nitric oxide production (46). Also arterial production of reactive oxygen species could significantly reduced by exercise training.…”