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Abstract
The present study aimed to test whether, beyond the known antioxidant effect of estradiol, such a property is also possessed by estrone and estriol. For this purpose, an in vitro investigation of the effect of estrone and estriol on superoxide anion production by human neutrophil granulocytes was carried out. Blood samples were obtained from healthy volunteers and neutrophil granulocytes were separated for measurement of superoxide anion generation after incubation with estrone, estriol (10^sup -7^, 10^sup -6^ and 10^sup -5^ M) and 17β-estradiol (10^sup -7^ M). Superoxide anion production of isolated neutrophil granulocytes was quantified by photometry and using the reduction of ferricytochrome-C. When adding estrone and estriol to neutrophil granulocyte suspensions, the production of superoxide anion fell (10^sup -5^ M: 84.17 ± 3.14% and 88.77 ± 1.98% of control production, p < 0.01 and p < 0.05, respectively). Estradiol produced an antioxidant effect at lower concentration (10^sup -7^ M: 72.91 ± 7.94% of control production, p < 0.001). The weak estrogens estrone and estriol, similarly to estradiol, are also able to reduce the superoxide anion release in our experimental model. This may have importance in the antioxidant defense of biological systems.
Keywords: superoxide anion, estradiol, weak estrogens, antioxidant effect, pre-eclampsia
Introduction
The most important reactive oxygen species is the superoxide anion, which can exert effects on cellular function itself or be converted into other more reactive radicals. Although the superoxide anion free radical is reactive to only a limited degree, by cooperating with hydrogen peroxide, on the other hand, it can produce hydroxyl radical and singlet oxygen, which are the proximate causes of lipid peroxidation. Beyond this role, superoxide anion is a vasoconstrictor, significantly stimulates vascular smooth muscle cell proliferation in aortic explants of rats, and activates adhesion molecules and fibrosis. By neutralizing the vasodilator nitric oxide, superoxide anion produces peroxynitrite, which also oxidizes lipoproteins and decomposes into highly reactive species.
Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase has been shown to be the main source of superoxide anion [1]. Some types of oxidative stress (e.g. hypercholesterolemia) are able to increase this enzyme [1]. The structure and function of NADPH oxidase were first described and characterized in neutrophils, but it can also be found in the elements (endothelium, smooth muscle cells, fibroblasts) of...