Fenton Reaction-Induced Oxidative Damage to Membrane Lipids and Protective Effects of 17β-Estradiol in Porcine Ovary and Thyroid Homogenates

Abstract

The Fenton reaction (Fe2++H2O2→Fe3++•OH+OH-) results in strong oxidative damage to macromolecules when iron (Fe) or hydrogen peroxide (H2O2) are in excess. This study aims at comparing Fe2++H2O2-induced oxidative damage to membrane lipids (lipid peroxidation, LPO) and protective effects of 17β-estradiol (a potential antioxidant) in porcine ovary and thyroid homogenates. Iron, as one of the Fenton reaction substrates, was used in the highest achievable concentrations. Thyroid or ovary homogenates were incubated in the presence of: (1st) FeSO4+H2O2 with/without 17β-estradiol (1 mM; 100, 10.0, 1.0 µM; 100, 10.0, 1.0 nM; 100, 10.0, 1.0 pM); five experiments were performed with different FeSO4 concentrations (2400, 1200, 600, 300, 150 µM); (2nd) FeSO4 (2400, 1200, 600, 300, 150 µM)+H2O2 with/without 17β-estradiol; three experiments were performed with three highest 17β-estradiol concentrations; (3rd) FeSO4 (2400, 1200, 1100, 1000, 900, 800, 700, 600, 300, 150, 75 µM)+H2O2 (5 mM). LPO level [MDA+4-HDA/mg protein] was measured spectrophotometrically. The basal LPO level is lower in ovary than in thyroid homogenates. However, experimentally-induced LPO was higher in the former tissue, which was confirmed for the three highest Fe2+ concentrations (2400, 1200, 1100 µM). Exogenous 17β-estradiol (1 mM, 100, and 10 µM) reduced experimentally-induced LPO independently of iron concentration and that protective effect did not differ between tissues. The ovary, compared to the thyroid, reveals higher sensitivity to prooxidative effects of iron, however, it showed similar responsivity to protective 17β-estradiol activity. The therapeutic effect of 17β-estradiol against iron overload consequences should be considered with relation to both tissues.

Pro-Oxidative Effect of KIO3 and Protective Effect of Melatonin in the Thyroid—Comparison to Other Tissues

“…The basal level of LPO was lower in the ovary than in the thyroid homogenates, which was confirmed also in our previous studies [ 44 ]; and observations from two different studies [ 45 , 46 ]. On the other hand, LPO induced by KIO 3 , similar to LPO induced by Fenton reaction substrates [ 44 ], was higher in the ovary than in the thyroid homogenates.…”

“…The basal level of LPO was lower in the ovary than in the thyroid homogenates, which was confirmed also in our previous studies [ 44 ]; and observations from two different studies [ 45 , 46 ]. On the other hand, LPO induced by KIO 3 , similar to LPO induced by Fenton reaction substrates [ 44 ], was higher in the ovary than in the thyroid homogenates. This observation also confirms the hypothesis, that in physiological conditions oxidative stress in the thyroid (resulting mostly from oxidative reactions indispensable for thyroid hormone synthesis) is at a substantially higher level than in other tissues.…”

Melatonin and Indole-3-Propionic Acid Reduce Oxidative Damage to Membrane Lipids Induced by High Iron Concentrations in Porcine Skin

“…In most studies published previously, iron was used in concentrations not exceeding the value of 300 µM to induce oxidative damage in vitro [ 9 , 10 , 11 , 14 , 15 , 22 ]. This work is the second in which we applied ferrous in extremely high concentrations, i.e., as high as 2400 µM; the first study was performed on other tissues, namely porcine thyroid and ovary [ 12 ].…”

“…During this reaction, the most harmful free radical, the hydroxyl radical ( • OH), is produced. The model of Fenton reaction-induced oxidative damage to macromolecules has been widely used in laboratories [ 9 , 10 , 11 , 12 , 13 , 14 , 15 ]. Both substrates of the Fenton reaction, i.e., iron, used as a ferrous ion (Fe 2+ ), and hydrogen peroxide (H 2 O 2 ) are natural and essential elements for the proper functioning of organisms, with iron serving as a micronutrient and (H 2 O 2 ) being an important ROS indispensable for certain biochemical reactions.…”

Membrane Lipids in the Thyroid Comparing to Those in Non-Endocrine Tissues Are Less Sensitive to Pro-Oxidative Effects of Fenton Reaction Substrates

“…Until now, Fenton reaction substrates were used very commonly to experimentally induce oxidative damage to macromolecules in different tissues (e.g., ovary, thyroid, and skin) with very high Fe 2+ concentrations (Rynkowska et al, 2020(Rynkowska et al, , 2021, equal to these used in the present study.…”