17β-Estradiol enhances sulforaphane cardioprotection against oxidative stress

The lower incidence of ischemic heart disease in female with respect to male gender suggests the possibility that female sex hormones could have specific effects in cardiovascular protection. 17β-Estradiol is the predominant premenopausal circulating form of estrogen and has a protective role on the cardiovascular system. Recent evidences suggest that gender can influence the response to cardiovascular medications; therefore, we hypothesized that sex hormones could also modulate the cardioprotective effects of nutraceutical compounds, such as the isothiocyanate sulforaphane, present in Brassica vegetables. This study was designed to explore the protective effects of sulforaphane in the presence of 17β-estradiol against H₂O₂-induced oxidative stress in primary cultures of rat cardiomyocytes. Interestingly, 17β-estradiol enhanced sulforaphane protective activity against H₂O₂-induced cell death with respect to sulforaphane or 17β-estradiol alone as measured by 3-(4,5-dimethylthiazol-2-yl)-2,5diphenyl-tetrazolium bromide and lactate dehydrogenase assays. Moreover, 17β-estradiol boosted sulforaphane ability to counteract oxidative stress, reducing intracellular reactive oxygen species and 8-hydroxy-2'-deoxyguanosine levels and increasing the expression of phase II enzymes. Using specific antagonists of estrogen receptor α and β, we observed that these effects are not mediated by estrogen receptors. Otherwise, ERK1/2 and Akt signaling pathways seem to be involved, as the presence of specific inhibitors of these kinases reduced the protective effect of sulforaphane in the presence of 17β-estradiol. Sulforaphane and 17β-estradiol co-treatment counteracted cell morphology alterations induced by H₂O₂ as evidenced by transmission electron microscopy. Our results demonstrated, for the first time, that estrogens could enhance sulforaphane protective effects, suggesting that nutraceutical efficacy might be modulated by sex hormones.