Reduction in extracellular superoxide dismutase activity in African-American patients with hypertension.
Superoxide anions react with nitric oxide to form peroxynitrite and hence reduce the bioavailability of nitric oxide in the arteries. Extracellular superoxide dismutase (EC-SOD) is a major superoxide scavenger in human plasma and vascular tissues. The objective of this study is to assess whether essential hypertension is associated with an alteration in EC-SOD activity. In this report, blood samples were obtained from hypertensive (n=39) and normotensive (n=37) African-Americans. Plasma EC-SOD activity was measured using in-gel activity staining and spectrophotometric assays, EC-SOD protein level was measured using Western blotting, nitrotyrosine was measured using slot blotting, 8-isoprostane was measured with an enzyme immunoassay, and plasma copper and zinc concentrations were measured using an atomic absorption assay. Our data demonstrate that the copper, zinc, and plasma EC-SOD protein concentrations in the hypertensive and normotensive subjects are indistinguishable. Compared to normotensive controls, hypertensive patients have significantly reduced plasma EC-SOD activity. Plasma nitrotyrosine and 8-isoprostane levels are significantly higher in the hypertensive patients than in normotensive controls. Results from this study suggest that a reduction in EC-SOD activity in hypertensive patients is not due to a down-regulation of the SOD3 gene (encoding EC-SOD) or deficiency in mineral cofactors. Furthermore, the reduced EC-SOD activity might be at least partially responsible for the increased oxidative stress, as reflected by increased plasma nitrotyrosine and 8-isoprostane, in hypertensive subjects.
Zhou
LiChun
L
Division of Cardiovascular Biology, Department of Biomedical Sciences, Meharry Medical College, Nashville, TN 37208, USA.
Xiang
Wei
W
Potts
James
J
Floyd
Michael
M
Sharan
Chakradhari
C
Yang
Hong
H
Ross
Joan
J
Nyanda
Alfred M
AM
Guo
ZhongMao
Z
D000328:Adult; D001741:Black or African American; D001786:Blood Glucose; D002784:Cholesterol / Q000097:blood; D003300:Copper / Q000032:analysis; D015237:Dinoprost / Q000031:analogs & derivatives / Q000378:metabolism; D005260:Female; D006801:Humans; D006973:Hypertension / Q000097:blood / Q000201:enzymology* / Q000208:ethnology; D008297:Male; D008875:Middle Aged; D013482:Superoxide Dismutase / Q000097:blood / Q000378:metabolism*; D014280:Triglycerides / Q000097:blood; D015032:Zinc / Q000032:analysis
D001786:Blood Glucose; D014280:Triglycerides; C075750:8-epi-prostaglandin F2alpha; D003300:Copper; D002784:Cholesterol; D015237:Dinoprost; C441642:SOD3 protein, human; D013482:Superoxide Dismutase; D015032:Zinc