BACKGROUND: Cyclosporin A (CyA) and oxidized low-density lipoprotein (OxLDL) cause endothelial dysfunction, partly through stimulation of O(2)(-) formation (which can inactivate nitric oxide). We investigated whether CyA and OxLDL potentiate their influence on oxidative stress, whether endothelin (ET) is a mediator of CyA- and OxLDL-induced O(2)(-) formation, and whether enhanced oxidative stress results in further attenuation of endothelium-dependent vasodilation. METHODS AND RESULTS: Human LDL was oxidized by Cu(++). O(2)(-) formation of isolated rat aortic rings was measured using a chemiluminescence assay. Incubation (60 min) of aortic rings with CyA (10 ng-10 microg/ml) or with OxLDL (300 microg/ml) caused a significant, dosedependent increase of the basal O(2)(-) formation. Pretreatment of the aortic rings with CyA (10 ng/ml) further enhanced the OxLDL-induced O(2)(-) formation by factor 1.9. The enhancement of the OxLDL-induced stimulation of O(2)(-) formation by CyA could be completely blocked by BQ123, a selective endothelin-1 (ET-1) receptor antagonist. Likewise, exogenously applied ET-1 (1 nM) potentiated the OxLDL-induced O(2)(-) formation by factor 1.8. Endothelium-dependent dilation was measured in isolated rings of rabbit aorta superfused with physiological salt solution in an organ bath. Incubation of the aortic rings with CyA (10 microg/ml, 60 min) or with OxLDL (300 microg/ml, 60 min) alone did not attenuate endothelium-dependent dilations. However, coincubation of the aortic rings with CyA+OxLDL in the presence of diethyl-dithio-carbamate, an inhibitor of the endogenous superoxide dismutase, caused a 60% inhibition of acetylcholine-induced dilator responses. CONCLUSIONS: Coincubation of isolated aortic rings with CyA and OxLDL causes a potent enhancement of vascular O(2)(-) formation. ET-1 seems to be mediator of the CyA-induced O(2)(-) formation. Enhanced oxidative stress results in further attenuation of endothelium dependent vasodilation.
BACKGROUND:Cyclosporin A (CyA) and oxidized low-density lipoprotein (OxLDL) cause endothelial dysfunction, partly through stimulation of O(2)(-) formation (which can inactivate nitric oxide). We investigated whether CyA and OxLDL potentiate their influence on oxidative stress, whether endothelin (ET) is a mediator of CyA- and OxLDL-induced O(2)(-) formation, and whether enhanced oxidative stress results in further attenuation of endothelium-dependent vasodilation. METHODS AND RESULTS:Human LDL was oxidized by Cu(++). O(2)(-) formation of isolated rat aortic rings was measured using a chemiluminescence assay. Incubation (60 min) of aortic rings with CyA (10 ng-10 microg/ml) or with OxLDL (300 microg/ml) caused a significant, dosedependent increase of the basal O(2)(-) formation. Pretreatment of the aortic rings with CyA (10 ng/ml) further enhanced the OxLDL-induced O(2)(-) formation by factor 1.9. The enhancement of the OxLDL-induced stimulation of O(2)(-) formation by CyA could be completely blocked by BQ123, a selective endothelin-1 (ET-1) receptor antagonist. Likewise, exogenously applied ET-1 (1 nM) potentiated the OxLDL-induced O(2)(-) formation by factor 1.8. Endothelium-dependent dilation was measured in isolated rings of rabbit aorta superfused with physiological salt solution in an organ bath. Incubation of the aortic rings with CyA (10 microg/ml, 60 min) or with OxLDL (300 microg/ml, 60 min) alone did not attenuate endothelium-dependent dilations. However, coincubation of the aortic rings with CyA+OxLDL in the presence of diethyl-dithio-carbamate, an inhibitor of the endogenous superoxide dismutase, caused a 60% inhibition of acetylcholine-induced dilator responses. CONCLUSIONS: Coincubation of isolated aortic rings with CyA and OxLDL causes a potent enhancement of vascular O(2)(-) formation. ET-1 seems to be mediator of the CyA-induced O(2)(-) formation. Enhanced oxidative stress results in further attenuation of endothelium dependent vasodilation.
Authors: G Hetet; B Grandchamp; C Bouchier; V Nicaud; L Tiret; G Roizès; M Desnos; K Schwartz; R Dorent; M Komajda Journal: Heart Date: 2001-12 Impact factor: 5.994