Mechanism of endothelial dysfunction in apolipoprotein E-deficient mice.
Endothelium-dependent relaxations mediated by NO are impaired in a mouse model of human atherosclerosis. Our objective was to characterize the mechanisms underlying endothelial dysfunction in aortas of apolipoprotein E (apoE)-deficient mice, treated for 26 to 29 weeks with a lipid-rich Western-type diet. Aortic rings from apoE-deficient mice showed impaired endothelium-dependent relaxations to acetylcholine (10(-)(9) to 10(-)(5) mol/L) and Ca(2+) ionophore (10(-)(9) to 10(-)(6) mol/L) and endothelium-independent relaxations to diethylammonium (Z)-1-(N,N-diethylamino)diazen-1-ium-1,2-diolate (DEA-NONOate, 10(-)(10) to 10(-)(5) mol/L) compared with aortic rings from C57BL/6J mice (P<0.05). By use of confocal microscopy of an oxidative fluorescent probe (dihydroethidium), increased superoxide anion (O(2)(-)) production was demonstrated throughout the aortic wall but mainly in smooth muscle cells of apoE-deficient mice. CuZn-superoxide dismutase (SOD) and Mn-SOD protein expressions were unaltered in the aorta exposed to hypercholesterolemia. A cell-permeable SOD mimetic, Mn(III) tetra(4-benzoic acid) porphyrin chloride (10(-)(5) mol/L), reduced O(2)(-) production and partially normalized relaxations to acetylcholine and DEA-NONOate in apoE-deficient mice (P<0.05). [(14)C]L-Citrulline assay showed a decrease of Ca(2+)-dependent NOS activity in aortas from apoE-deficient mice compared with C57BL/6J mice (P<0.05), whereas NO synthase protein expression was unchanged. In addition, cGMP levels were significantly reduced in the aortas of apoE-deficient mice (P<0.05). Our results demonstrate that in apoE-deficient mice on a Western-type fat diet, impairment of endothelial function is caused by increased production of O(2)(-) and reduced endothelial NO synthase enzyme activity. Thus, chemical inactivation of NO with O(2)(-) and reduced biosynthesis of NO are key mechanisms responsible for endothelial dysfunction in aortas of atherosclerotic apoE-deficient mice.
d'Uscio
L V
LV
Departments of Anesthesiology and Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic and Foundation, Rochester, MN 55905, USA.
Baker
T A
TA
Mantilla
C B
CB
Smith
L
L
Weiler
D
D
Sieck
G C
GC
Katusic
Z S
ZS
D000818:Animals; D001011:Aorta / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology; D001057:Apolipoproteins E / Q000235:genetics*; D001161:Arteriosclerosis / Q000378:metabolism / Q000503:physiopathology*; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D046508:Culture Techniques; D000242:Cyclic AMP / Q000096:biosynthesis; D006152:Cyclic GMP / Q000096:biosynthesis; D004730:Endothelium, Vascular / Q000378:metabolism*; D008297:Male; D008665:Metalloporphyrins / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D019001:Nitric Oxide Synthase / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D013482:Superoxide Dismutase / Q000276:immunology / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism; D014661:Vasoconstriction; D014664:Vasodilation
D001057:Apolipoproteins E; D008665:Metalloporphyrins; C097284:manganese(III)-tetrakis(4-benzoic acid)porphyrin; D013481:Superoxides; D000242:Cyclic AMP; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; C496315:Nos3 protein, mouse; D013482:Superoxide Dismutase; D006152:Cyclic GMP; D002118:Calcium