Background and Purpose Angiotensin II produces oxidative stress and endothelial dysfunction in cerebral arteries, and angiotensin II type I receptors may play a role in longevity and vascular aging. Angiotensin converting enzyme type 2 (ACE2) converts angiotensin II to angiotensin (1–7) and thus may protect against effects of angiotensin II. We hypothesized that ACE2 deficiency increases oxidative stress and endothelial dysfunction in cerebral arteries, and examined the role of ACE2 in age-related cerebrovascular dysfunction. Methods Endothelial function, expression of angiotensin system components, NADPH oxidase subunits, and proinflammatory cytokines were examined in cerebral arteries from adult [12 mo old] and old [24 mo old] ACE2 knockout (KO) and wild type (WT) mice. The superoxide scavenger tempol was used to examine the role of oxidative stress on endothelial function. Results Vasodilatation to acetylcholine was impaired in adult ACE2 KO [24±6% (mean +/− SE)] compared to WT mice [52±7%, p<0.05]. In old mice, vasodilatation to acetylcholine was impaired in WT mice [29±6%] and severely impaired in ACE2 KO mice [7±5%]. Tempol improved endothelial function in adult and old ACE2 KO and WT mice. Aging increased mRNA for TNFα in WT mice, and significantly increased mRNA levels of Nox2, p47phox, and Rcan1 in both ACE2 KO and WT mice. mRNA levels of angiotensin system components did not change during aging. Conclusions ACE2 deficiency impaired endothelial function in cerebral arteries from adult mice and augmented endothelial dysfunction during aging. Oxidative stress plays a critical role in cerebrovascular dysfunction induced by ACE2 deficiency and aging.

Carotid and cerebrovascular disease increase markedly with age contributing to stroke and cognitive impairment. Inflammation is a key element of vascular disease. In these studies, we tested the hypothesis that interleukin-10 (IL-10), a potent anti-inflammatory cytokine, protects against aging-induced endothelial dysfunction. Responses of carotid arteries from adult (5 ± 1 months) and old (22 ± 1 months) wild-type and IL-10-deficient mice were examined in vitro. Acetylcholine (an endothelium-dependent agonist) produced relaxation in arteries from adult wild-type that was not altered in old mice. In contrast, relaxation to acetylcholine in arteries from old IL-10-deficient mice was reduced by ∼50% (P < 0.05). Tempol, a scavenger of superoxide, did not affect responses in adult or old wild-type mice, but restored vasodilation to acetylcholine to normal in old IL-10-deficient mice. Responses of the carotid artery to nitroprusside (an endothelium-independent agonist) were not altered in any group. Vascular expression of IL-6 (a proinflammatory mediator of vascular disease) and components of NADPH oxidase (a major source of superoxide) was increased in old IL-10-deficient mice compared with wild-type (P < 0.05). These findings provide the first evidence that age-related and superoxide-mediated endothelial dysfunction occurs earlier with IL-10 deficiency. Our findings suggest a novel role for IL-10 to protect against age-related increases in expression of IL-6, oxidative stress, and endothelial dysfunction.

Angiotensin II (Ang-II) stimulates vascular inflammation, oxidative stress, and formation and rupture of intracranial aneurysms in mice. Because angiotensin 1-7 (Ang-1-7) acts on Mas receptors and generally counteracts deleterious effects of Ang-II, we tested the hypothesis that Ang-1-7 attenuates formation and rupture of intracranial aneurysms. Intracranial aneurysms were induced in wild type and Mas receptor deficient mice using a combination of Ang-II-induced hypertension and intracranial injection of elastase in the basal cistern. Mice received elastase+Ang-II alone, or a combination of elastase+Ang-II+Ang-1-7. Aneurysm formation, prevalence of subarachnoid hemorrhage, mortality, and expression of molecules involved in vascular injury were assessed. Systolic blood pressure was similar in mice receiving elastase+Ang-II (148±5 mmHg, mean ±SE) or elastase+Ang-II+Ang-1-7 (144±5 mmHg). Aneurysm formation was also similar in mice receiving elastase+Ang-II (89%) or elastase+Ang-II+Ang-1-7 (84%). However, in mice that received elastase and Ang II, Ang-1-7 reduced mortality (from 64 to 36%, p<0.05) and prevalence of subarachnoid hemorrhage (from 75 to 48%, p<0.05). In cerebral arteries, expression of the inflammatory markers, Nox2 and catalase increased similarly in elastase+Ang-II or elastase+Ang-II+Ang-1-7 groups. Ang-1-7 increased expression of cyclooxygenase-2, and decreased expression of metalloproteinase 9 induced by elastase+Ang-II (p<0.05). In Mas receptor deficient mice, systolic blood pressure, mortality, and prevalence of subarachnoid hemorrhage were similar (p>0.05) in groups treated with elastase+Ang-II or elastase+Ang-II+Ang-1-7. Expression of Mas receptor was detected by immunohistochemistry in samples of human intracranial arteries and aneurysms. In conclusion, without attenuating Ang-II-induced hypertension, Ang-1-7 decreased mortality and rupture of intracranial aneurysms in mice, through a Mas receptor-dependent pathway.