Estrogens are potentially the only steroids with an antioxidant role in pregnancy: in vitro evidence

Background. Pregnancy is a condition that favors oxidative stress by reactive oxygen species. Oxidative stress is involved in the etiopathogenesis of disorders of pregnancy such as pre-eclampsia. An antioxidant effect of estrogens has been described and a putative role of them as antioxidants has been proposed. The aim of this work was to evaluate in vitro the antioxidant properties of dehydroepiandrosterone sulfate, estradiol, estriol, progesterone, and testosterone, five steroid hormones present in the maternofetal circulation. Methods. The antioxidant properties of the hormones were evaluated by two methods: 1. their antioxidant effect on the auto-oxidation of linoeic acid, a hydrogen atom transfer reaction; 2. diphenylpicrylhydrazil-scavenging capacity, a single electron transfer reaction. Results. Of the five hormones tested, only estradiol and estriol at 10 μM concentration exerted a strong antioxidant effect of 81.73 and 70.97% respectively on linoleic acid auto-oxidation, at the end-point of the reaction. Likewise, only these two hormones showed radical-scavenging activity on diphenylpicrylhydrazil, noticeable only at supraphysiological concentrations of 1 mM. Conclusions. Estradiol and estriol could play a role as antioxidants for maternofetal autoprotection in addition to their hormonal activity, but this role could be preferentially exerted by estriol due to its higher concentrations exhibited during pregnancy. In vivo studies are necessary to shed light on this issue.