Efficacy of a Low Dose of Estrogen on Antioxidant Defenses and Heart Rate Variability

Abstract

This study tested whether a low dose (40% less than the pharmacological dose of 17-β estradiol) would be as effective as the pharmacological dose to improve cardiovascular parameters and decrease cardiac oxidative stress. Female Wistar rats (n = 9/group) were divided in three groups: (1) ovariectomized (Ovx), (2) ovariectomized animals treated for 21 days with low dose (LE; 0.2 mg), and (3) high dose (HE; 0.5 mg) 17-β estradiol subcutaneously. Hemodynamic assessment and spectral analysis for evaluation of autonomic nervous system regulation were performed. Myocardial superoxide dismutase (SOD) and catalase (CAT) activities, redox ratio (GSH/GSSG), total radical-trapping antioxidant potential (TRAP), hydrogen peroxide, and superoxide anion concentrations were measured. HE and LE groups exhibited an improvement in hemodynamic function and heart rate variability. These changes were associated with an increase in the TRAP, GSH/GSSG, SOD, and CAT. A decrease in hydrogen peroxide and superoxide anion was also observed in the treated estrogen groups as compared to the Ovx group. Our results indicate that a low dose of estrogen is just as effective as a high dose into promoting cardiovascular function and reducing oxidative stress, thereby supporting the approach of using low dose of estrogen in clinical settings to minimize the risks associated with estrogen therapy.

Combined Catalase and ADH Inhibition Ameliorates Ethanol-Induced Myocardial Dysfunction Despite Causing Oxidative Stress in Conscious Female Rats

“…The present study further supports the role of catalase in our model system because reported studies, including ours, show that E 2 enhances catalase catalytic activity in the heart of female rats (Campos et al., ; El‐Mas and Abdel‐Rahman, ; Ibrahim et al., ; Yao and Abdel‐Rahman, ). Further, acute EtOH causes additional increase in cardiac catalase activity in the presence of E 2 receptor‐alpha activation along with myocardial oxidative stress and dysfunction (Yao and Abdel‐Rahman, ).…”

Estrogen Receptors α and β Play Major Roles in Ethanol‐Evoked Myocardial Oxidative Stress and Dysfunction in Conscious Ovariectomized Rats

“…It is important to consider the underlying biochemical environment following the regaining of each individual ER subtype function in OVX rats to understand the basis for their relative contribution to EtOH‐evoked biochemical and hemodynamic effects. While reported studies including ours (Campos et al., ; Ibrahim et al., ; Yao and Abdel‐Rahman, ) showed that E 2 enhances myocardial catalase and mitALDH2 activities in OVX rats, the present study is the first to show that these biochemical effects were only replicated following regaining ERα function (Fig. ).…”

“…The catalytic activity of catalase and ALDH2, which serve antioxidant roles (Ma et al., ; Ren et al., ), and catalyze EtOH metabolism (Kinoshita et al., ; Soffia and Penna, ), is enhanced in the presence of E 2 (Campos et al., ), but the ER subtype that mediates these effects in the absence or presence of EtOH is not known. Therefore, these ex vivo studies were conducted to elucidate the effect of selective activation of each of the 3 ER subtypes on myocardial alcohol‐metabolizing enzymes (ADH, CYP2E1, and catalase), antioxidative enzymes (catalase and mitALDH2), and mediators of oxidative stress (MAKs) in the absence or presence of EtOH.…”

Estrogen receptor α activation enhances its cell surface localization and improves myocardial redox status in ovariectomized rats

“…These current findings are important because enhancement of cardiac catalase activity alleviates myocardial oxidative in E 2 treated OVX rats [52], and changes in cellular ER subtype ratios are linked to oxidative stress and antioxidant enzyme activity [53, 54]. Further, similar E 2 beneficial effects on the redox status were reported in female aortas and cardiac tissues [55, 56], and catalase supplementation is linked to improvements in functional recovery of globally ischemic and perfused isolated hearts [57].…”