Estrogen regulation of cardiac cAMP-L-type Ca2+ channel pathway modulates sex differences in basal contraction and responses to β2AR-mediated stress in left ventricular apical myocytes

Abstract

Backgrounds/Aim Male and female hearts have many structural and functional differences. Here, we investigated the role of estrogen (E2) in the mechanisms of sex differences in contraction through the cAMP-L-type Ca 2+ channel pathway in adult mice left ventricular (LV) apical myocytes at basal and stress state. Methods Isolated LV apical myocytes from male, female (Sham) and ovariectomised mice (OVX) were used to investigate contractility, Ca 2+ transients and L-type Ca 2+ channel (LTCC) function. The levels of β 2 AR, intracellular cAMP, phosphodiesterase (PDE 3 and PDE 4), RyR2, PLB, SLN, and SERCA2a were compared among the experimental groups. Results We found that (1) intracellular cAMP, I CaL density, contraction and Ca 2+ transient amplitudes were larger in Sham and OVX + E2 myocytes compared to male and OVX. (2) The mRNA expression of PDE 3 and 4 were lower in Sham and OVX + E2 groups compared with male and OVX groups. Treatment of myocytes with IBMX (100 μM) increased contraction and Ca 2+ transient amplitude in both sexes and canceled differences between them. (3) β 2 AR-mediated stress decreased cAMP concentration and peak contraction and Ca 2+ transient amplitude only in male and OVX groups but not in Sham or OVX + E2 groups suggesting a cardioprotective role of E2 in female mice. (4) Pretreatment of OVX myocytes with GPR30 antagonist G15 (100 nM) abolished the effects of E2, but ERα and ERβ antagonist ICI 182,780 (1 μM) did not. Moreover, activation of GPR30 with G1 (100 nM) replicated the effects of E2 on cAMP, contraction and Ca 2+ transient amplitudes suggesting that the acute effects of E2 were mediated by GPR30 via non-genomic signaling. (5) mRNA expression of RyR2 was higher in myocytes from Sham than those of male while PLB and SLN were higher in male than Sham but no sex differences were observed in the mRNA of SERCA2a. Conclusion Collectively, these results demonstrate that E2 modulates the expression of genes related to the cAMP-LTCC pathway and contributes to sex differences in cardiac contraction and responses to stress. We also show that estrogen confers cardioprotection against cardiac stress by non-genomic acute signaling via GPR30.

Female Heart Health: Is GPER the Missing Link?

“…The ability of G1 to restore these parameters suggest that chronic GPER activation re-sensitizes cardiac β-AR regulation in this HFpEF model (68). These data also mirror those reported in a study of the apical myocardium, in which expression of the Ca v 1.2α subunit and I Ca,L were lower in apical myocytes from male or OVX mice compared with sham female mice, and E 2 treatment of myocytes from OVX animals corrected these differences (72). The reduction in the amplitude of electrically stimulated Ca 2+ transients in myocytes isolated from OVX female mice were restored by G1, to an extent similar to that achieved with E 2 treatment.…”

Estrogen and calcium handling proteins: new discoveries and mechanisms in cardiovascular diseases

“…High levels of catecholamines during stress impair left ventricular systolic function, which may lead to Takotsubo cardiomyopathy (TTC) (96,118). Along with other researchers, we found that E2/ERs reversed the decreased Ca 2ϩ transient amplitude in ventricular myocytes stimulated by high concentration of catecholamine, which restored myocardial contractility (17,54,69,135). Furthermore, Ma et al (68) reported that estrogen improved cardiac contractility and intracellular Ca 2ϩ transient amplitude in OVX rat models of ischemia-reperfusion treated with Iso.…”

“…In female rabbit hearts, E2 upregulated I CaL and Ca v 1.2␣ protein levels through ER␣ via a regional genomic mechanism (144). In our recent study, we found that estrogen supplementation significantly increased I CaL , Ca v 1.2␣ mRNA, and protein levels in OVX mice cardiomyocytes compared with male and sham female cardiomyocytes (69). Elsewhere, estrogen increased I CaL and prolonged the plateau period of action potential, leading to a longer QT interval, an effect that increased the risk of LQT2 arrhythmia phenotype (19,27,53,84,94,115,144,145).…”

“…Other studies have demonstrated that OVX rat cardiomyocytes have reduced SERCA2a protein expression and PLB phosphorylation levels compared with sham groups, which reduces the recovery of Ca 2ϩ (2,16). Estrogen supplementation in OVX animals enhanced SERCA2a activity and PLB phosphorylation levels, thereby increasing the Ca 2ϩ uptake rate into the SR (20,69,105,125).…”

(Sex differences in cardiac tolerance to ischemia-reperfusion injury - the role of mitochondria)

“…18 Údaje o pohlavních rozdílech v kontraktilitě myokardu se liší a byly nedávno shrnuty Machukim a spol. 19 Zatímco Schwertz a spol. 20,21 a Machuki a spol.…”