BackgroundAngotensin converting enzyme 2 (ACE2) is a newly discovered monocarboxypeptidase that counteracts the vasoconstrictor effects of angiotensin II (Ang II) by converting Ang II to Ang-(1-7) in the kidney and other tissues.MethodsACE2 activity from renal homogenates was investigated by using the fluorogenic peptide substrate Mca-YVADAPK(Dnp)-OH, where Mca is (7-methoxycoumarin-4-yl)-acetyl and Dnp is 2,4-dinitrophenyl.ResultsWe found that ACE2 activity expressed in relative fluorescence units (RFU) in the MF1 mouse is higher in the male (M) compared to the female (F) kidney [ACE2 (RFU/min/μg protein): M 18.1 ± 1.0 versus F 11.1 ± 0.39; P < 0.0001; n = 6]. Substrate concentration curves revealed that the higher ACE2 activity in the male was due to increased ACE2 enzyme velocity (Vmax) rather than increased substrate affinity (Km). We used the four core genotypes mouse model in which gonadal sex (ovaries versus testes) is separated from the sex chromosome complement enabling comparisons among XX and XY gonadal females and XX and XY gonadal males. Renal ACE2 activity was greater in the male than the female kidney, regardless of the sex chromosome complement [ACE2 (RFU/min/μg protein): intact-XX-F, 7.59 ± 0.37; intact-XY-F, 7.43 ± 0.53; intact-XX-M, 12.1 ± 0.62; intact-XY-M, 12.7 ± 1.5; n = 4-6/group; P < 0.0001, F versus M, by two-way ANOVA]. Enzyme activity was increased in gonadectomized (GDX) female mice regardless of the sex chromosome complement whereas no effect of gonadectomy was observed in the males [ACE2 (RFU/min/μg protein): GDX-XX-F, 12.4 ± 1.2; GDX-XY-F, 11.1 ± 0.76; GDX-XX-M, 13.2 ± 0.97; GDX-XY-M, 11.6 ± 0.81; n = 6/group]. 17β-oestradiol (E2) treatment of GDX mice resulted in ACE2 activity that was only 40% of the activity found in the GDX mice, regardless of their being male or female, and was independent of the sex chromosome complement [ACE2 (RFU/min/μg protein): GDX+E2-XX-F, 5.56 ± 1.0; GDX+E2-XY-F, 4.60 ± 0.52; GDX+E2-XX-M, 5.35 ± 0.70; GDX+E2-XY-M, 5.12 ± 0.47; n = 6/group].ConclusionsOur findings suggest sex differences in renal ACE2 activity in intact mice are due, at least in part, to the presence of E2 in the ovarian hormone milieu and not to the testicular milieu or to differences in sex chromosome dosage (2X versus 1X; 0Y versus 1Y). E2 regulation of renal ACE2 has particular implications for women across their life span since this hormone changes radically during puberty, pregnancy and menopause.

Studies suggest T cells modulate arterial pressure. Since robust sex differences exist in the immune system and in hypertension, we investigated sex differences in T cell modulation of angiotensin II (Ang II)-induced increases in mean arterial pressure (MAP) in male (M) and female (F) wild type (WT) and recombination-activating-gene-1-deficient (Rag1−/−) mice. Sex-differences in peak MAP in WT were lost in Rag1−/− mice [mmHg: WT-F, 136±4.9 vs. WT-M, 153±1.7; P<0.02; Rag1−/−-F, 135±2.1 vs. Rag1−/−-M, 141±3.8]. Peak MAP was 13 mmHg higher after adoptive transfer of male (CD3M→Rag1−/−-M) vs. female (CD3F→Rag1−/−-M) T-cells. CD3M→Rag1−/−-M mice exhibited higher splenic frequencies of pro-inflammatory interleukin-17A (2.4-fold) and tumor-necrosis factor-α (2.2-fold)-producing T cells and lower plasma levels (13-fold) and renal mRNA expression (2.4-fold) of interleukin-10 while CD3F→Rag1−/−-M mice displayed a higher activation state in general and T-helper 1-biased renal inflammation. Greater T cell infiltration into perivascular adipose tissue and kidney associated with increased pressor responses to Ang II if the T cell donor was male but not female and these sex differences in T cell subset expansion and tissue infiltration were maintained for 7–8 weeks within the male host. Thus, the adaptive immune response and role of pro- and anti-inflammatory cytokine signaling in hypertension is distinct between the sexes and needs to be understood to improve therapeutics for hypertension-associated disease in both men and women.

Abstract-Sex differences in mean arterial pressure (MAP) are reported in many experimental models of hypertension and are ascribed to gonadal sex based on studies showing that gonadectomy and gonadal hormone replacement affect MAP. The interpretation of these studies, however, has been confounded by differences in the sex chromosome complement (XX versus XY). To investigate the sex chromosome complement independent of gonadal sex, we used the 4 core genotype mouse model in which gonadal sex is separated from the sex chromosome complement enabling comparisons among XX and XY females and XX and XY males. We found that, in the gonadectomized (GDX) 4 core genotype, MAP after 2 weeks of angiotensin II infusion (200 ng/kg per minute) was greater in XX than XY (MAP [in millimeters of mercury]: GDX-XX-female, 148Ϯ4.5; GDX-XY-female, 133Ϯ4.4; GDX-XX-male, 149Ϯ9.4; GDX-XY-male, 138Ϯ5.5; PϽ0.03, XX versus XY; nϭ8 to 9 per group). In contrast, no sex chromosome effects were found on heart rate, body weight, or plasma angiotensin II 2 weeks after angiotensin II infusion. This study suggests that, in addition to effects of gonadal hormones on blood pressure, X-or Y-linked genes, parental imprinting, or X mosaicism contributes to sex differences in hypertension. Furthermore, the finding that MAP was greater in XX mice compared with XY mice in the GDX state suggests that adverse sex chromosome effects encoded within the XX sex chromosome complement could contribute to hypertension in women with ovarian hormone deficiency, such as postmenopausal women and women with premature ovarian failure. (Hypertension. 2010;55:1275-1282.)Key Words: hypertension Ⅲ angiotensin II Ⅲ sex differences Ⅲ sex chromosomes Ⅲ 4 core genotype C ompared with aged-matched men, young adult women are protected from the development of hypertension and its deleterious consequences in the kidney and cardiovascular system. 1,2 Furthermore, studies have shown that the sexual dimorphism in the incidence of hypertension becomes apparent during adolescence and persists throughout adulthood. 3 Sex differences in blood pressure (BP) control have also been observed in numerous animal models of hypertension, including spontaneously hypertensive rats, 4,5 deoxycorticosteronesalt hypertensive rats, 6 Dahl salt-sensitive rats, 7 New Zealand genetically hypertensive rats, renal wrap hypertensive rats, 8 and angiotensin II (Ang II)-infused mice. 9 Sex differences in physiology and pathophysiology arise from direct effects of gonadal hormones and sex chromosome genes. 10 Gonadal hormone effects in hypertension have been widely studied because of the ease of manipulating gonadal steroids in adulthood. For example, a study in C57BL/6 mice demonstrated that infusion of Ang II increases mean arterial pressure (MAP) to a greater extent in male compared with female mice and that gonadectomy attenuates Ang II-induced hypertension in male mice while augmenting hypertension in the females. 11Although much evidence suggests that gonadal steroids play an important role in the developm...