Characterization of the Cardiac Renin Angiotensin System in Oophorectomized and Estrogen-Replete mRen2.Lewis Rats

Abstract

The cardioprotective effects of estrogen are well recognized, but the mechanisms remain poorly understood. Accumulating evidence suggests that the local cardiac renin-angiotensin system (RAS) is involved in the development and progression of cardiac hypertrophy, remodeling, and heart failure. Estrogen attenuates the effects of an activated circulating RAS; however, its role in regulating the cardiac RAS is unclear. Bilateral oophorectomy (OVX; n = 17) or sham-operation (Sham; n = 13) was performed in 4-week-old, female mRen2.Lewis rats. At 11 weeks of age, the rats were randomized and received either 17 β-estradiol (E2, 36 µg/pellet, 60-day release, n = 8) or vehicle (OVX-V, n = 9) for 4 weeks. The rats were sacrificed, and blood and hearts were used to determine protein and/or gene expression of circulating and tissue RAS components. E2 treatment minimized the rise in circulating angiotensin (Ang) II and aldosterone produced by loss of ovarian estrogens. Chronic E2 also attenuated OVX-associated increases in cardiac Ang II, Ang-(1–7) content, chymase gene expression, and mast cell number. Neither OVX nor OVX+E2 altered cardiac expression or activity of renin, angiotensinogen, angiotensin-converting enzyme (ACE), and Ang II type 1 receptor (AT1R). E2 treatment in OVX rats significantly decreased gene expression of MMP-9, ACE2, and Ang-(1–7) mas receptor, in comparison to sham-operated and OVX littermates. E2 treatment appears to inhibit upsurges in cardiac Ang II expression in the OVX-mRen2 rat, possibly by reducing chymase-dependent Ang II formation. Further studies are warranted to determine whether an E2-mediated reduction in cardiac chymase directly contributes to this response in OVX rats.

GPR30 decreases cardiac chymase/angiotensin II by inhibiting local mast cell number

“…Immunohistochemical staining of formalin-fixed and paraffin-embedded heart sections was performed as we described before [10,11,13,15]. Tissue sections were incubated with antibodies against chymase (1:1000, Bioss, Inc.) or Ang II (1:2000, IgG Corp, Nashville, TN, USA) overnight at 4°C, rinsed with PBS, and incubated with biotinylated secondary IgG (Vector Laboratories, Burlingame, CA) for 3 hours at 4°C.…”

“…Mounting evidence indicates that estrogen regulates all components of the renin-angiotensin-system (RAS) [2,12,13]. In the OVX mRen2.Lewis rat, an established rodent model that mimics the cardiac phenotype of women following surgical or natural cessation of ovarian hormone production, estrogen replacement reduces plasma levels of angiotensin (Ang) II and increases circulating Ang-(1-7), as well as corrects the increase in circulating activities of renin and angiotensin-converting enzyme (ACE) [14].…”

“…In the OVX mRen2.Lewis rat, an established rodent model that mimics the cardiac phenotype of women following surgical or natural cessation of ovarian hormone production, estrogen replacement reduces plasma levels of angiotensin (Ang) II and increases circulating Ang-(1-7), as well as corrects the increase in circulating activities of renin and angiotensin-converting enzyme (ACE) [14]. Our data using the same animal model showed that 17β-estradiol (E2) treatment attenuates OVX-associated increases in cardiac Ang II and diastolic dysfunction [13,15]. E2 regulation of local cardiac Ang II might occur through its effects on cardiac chymase, rather than ACE [13,16].…”

“…Our data using the same animal model showed that 17β-estradiol (E2) treatment attenuates OVX-associated increases in cardiac Ang II and diastolic dysfunction [13,15]. E2 regulation of local cardiac Ang II might occur through its effects on cardiac chymase, rather than ACE [13,16]. Chymase, which is found mainly in the secretory granules of mast cells, plays an important role in cardiac tissue formation of Ang II, particularly under pathophysiological conditions [17,18].…”

Estrogen Signaling in the Adrenal Cortex

“…29 Estrogens also stimulate renin release from the juxtaglomerular cells through estrogen receptor-α (ERα), 30 whereas endogenous estrogens exert inhibitory effects on the RAAS. 28,29 Experimental studies have shown that circulating levels of aldosterone increase after menopause and that estrogen therapy blunts this increase [31][32][33][34][35] ; however, corresponding data in humans are lacking.…”