Tissue-specific regulation of ACE/ACE2 and AT1/AT2 receptor gene expression by oestrogen in apolipoprotein E/oestrogen receptor-alpha knock-out mice

Abstract

Angiotensin-converting enzyme (ACE) and ACE2 and the AT1 and AT2 receptors are pivotal points of regulation in the renin-angiotensin system. ACE and ACE2 are key enzymes in the formation and degradation of angiotensin II (Ang II) and angiotensin-(1-7)(Ang-(1-7)). Ang II acts at either the AT1 or the AT2 receptor to mediate opposing actions of vasoconstriction or vasodilatation respectively. While it is known that oestrogen acts to downregulate ACE and the AT(1) receptor, its regulation of ACE2 and the AT2 receptor and the involvement of a specific oestrogen receptor subtype are unknown. To investigate the role of oestrogen receptor-alpha (ERalpha) in the regulation by oestrogen of ACE/ACE2 and AT1/AT2 mRNAs in lung and kidney, ovariectomized female mice lacking apolipoprotein E (ee) with the ERalpha (AAee) or without the ERalpha (alphaalphaee) were treated with 17beta-oestradiol (6 microg day(-1)) or placebo for 3 months. ACE, ACE2, AT1 receptor and AT2 receptor mRNAs were measured using reverse transcriptase, real-time polymerase chain reaction. In the kidney, 17beta-oestradiol showed 1.7-fold downregulation of ACE mRNA in AAee mice, with 2.1-fold upregulation of ACE mRNA in alphaalphaee mice. 17beta-Oestradiol showed 1.5- and 1.8-fold downregulation of ACE2 and AT1 receptor mRNA in AAee mice; this regulation was lost in alphaalphaee mice. 17beta-Oestradiol showed marked (81-fold) upregulation of the AT(2) receptor mRNA in AAee mice. In the lung, 17beta-oestradiol treatment had no effect on AT1 receptor mRNA in AAee mice, but resulted in a 1.5-fold decreased regulation of AT1 mRNA in alphaalphaee mice. There was no significant interaction of oestrogen with ERalpha in the lung for ACE, ACE2 and AT2 receptor genes. These studies reveal tissue-specific regulation by 17beta-oestradiol of ACE/ACE2 and AT1/AT2 receptor genes, with the ERalpha receptor being primarily responsible for the regulation of kidney ACE2, AT1 receptor and AT2 receptor genes.

Figure 1

ACE, ACE2, AT₁ receptor and AT₂ receptor mRNAs (n=7-8/group) in the kidney of ovariectomized ApoE knock-mice (ee) with (AA) (solid bar) and without (αα) (crosshatch bar) the ERα receptor and either treated with placebo (white bar) or 17-β estradiol (grey bar). Values expressed as mean ± SEM. Statistical analysis using the 2-way ANOVA revealed a significant interaction of estrogen (p < 0.05) with ER for ACE, ACE2, AT₁ receptor and AT₂ receptor mRNA. Fisher LSD multiple comparisons are indicated by * p < 0.05 vs placebo; ** p < 0.01 vs placebo; ***p < 0.001 vs placebo.

Figure 2

ACE, ACE2, AT₁ receptor and AT₂ receptor mRNAs (n=7-8/group) in the lung of ovariectomized apoE knock-out mice (ee) with (AA) and without (αα) the ERα receptor and either treated with placebo (white bar) or 17-β estradiol (grey bar). Values are expressed as mean ± SEM. Statistical analysis using the 2-way ANOVA revealed a significant interaction of estrogen (p < 0.05) with ER for AT₁ receptor mRNA, whereas there was only an effect of 17-β estradiol that was localized to ααee for ACE and ACE2 mRNA. * p<0.05 vs placebo.