CyA and OxLDL cause endothelial dysfunction in isolated arteries through endothelin-mediated stimulation of O(2)(-) formation.
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.


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.
Galle
J
J
Department of Medicine, Division of Nephrology, University Hospital of Würzburg, Würzburg, Germany.
Lehmann-Bodem
C
C
Hübner
U
U
Heinloth
A
A
Wanner
C
C
D000818:Animals; D001011:Aorta / Q000187:drug effects* / Q000503:physiopathology; D016572:Cyclosporine / Q000494:pharmacology*; D004357:Drug Synergism; D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1 / Q000494:pharmacology; D016232:Endothelins / Q000502:physiology*; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000503:physiopathology; D005260:Female; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D066298:In Vitro Techniques; D008077:Lipoproteins, LDL / Q000494:pharmacology*; D010456:Peptides, Cyclic / Q000494:pharmacology; D011817:Rabbits; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism*; D044022:Receptor, Endothelin A; D014664:Vasodilation / Q000187:drug effects
D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1; D016232:Endothelins; D007166:Immunosuppressive Agents; D008077:Lipoproteins, LDL; D010456:Peptides, Cyclic; D017382:Reactive Oxygen Species; D044022:Receptor, Endothelin A; C099252:oxidized low density lipoprotein; D016572:Cyclosporine; C072247:cyclo(Trp-Asp-Pro-Val-Leu)