RESUMO
The underlying mechanism behind age-induced wastage of the human ovarian follicle reserve is unknown. We identify impaired ATM (ataxia-telangiectasia mutated)-mediated DNA double-strand break (DSB) repair as a cause of aging in mouse and human oocytes. We show that DSBs accumulate in primordial follicles with age. In parallel, expression of key DNA DSB repair genes BRCA1, MRE11, Rad51, and ATM, but not BRCA2, declines in single mouse and human oocytes. In Brca1-deficient mice, reproductive capacity was impaired, primordial follicle counts were lower, and DSBs were increased in remaining follicles with age relative to wild-type mice. Furthermore, oocyte-specific knockdown of Brca1, MRE11, Rad51, and ATM expression increased DSBs and reduced survival, whereas Brca1 overexpression enhanced both parameters. Likewise, ovarian reserve was impaired in young women with germline BRCA1 mutations compared to controls as determined by serum concentrations of anti-Müllerian hormone. These data implicate DNA DSB repair efficiency as an important determinant of oocyte aging in women.
Assuntos
Envelhecimento/metabolismo , Proteína BRCA1/metabolismo , Senescência Celular , Quebras de DNA de Cadeia Dupla , Reparo do DNA , Oócitos/metabolismo , Ovário/metabolismo , Adolescente , Adulto , Fatores Etários , Envelhecimento/genética , Envelhecimento/patologia , Animais , Hormônio Antimülleriano/sangue , Proteína BRCA1/genética , Proteína BRCA2/genética , Proteína BRCA2/metabolismo , Criança , Pré-Escolar , Feminino , Fertilidade , Regulação da Expressão Gênica , Humanos , Camundongos , Camundongos Transgênicos , Mutação , Oócitos/patologia , Ovário/patologia , Ovário/fisiopatologia , Interferência de RNA , Adulto JovemRESUMO
BACKGROUND AND PURPOSE: Antagonists of angiotensin AT(1) receptors elicit beneficial vascular effects in diabetes mellitus. We hypothesized that diabetes induces sustained availability of AT(1) receptors, causing enhanced arterial constriction to angiotensin II. EXPERIMENTAL APPROACH: To assess functional availability of AT(1) receptors, constrictions to successive applications of angiotensin II were measured in isolated skeletal muscle resistance arteries (â¼150 µm) of Zucker diabetic fatty (ZDF) rats and of their controls (+/Fa), exposed acutely to high glucose concentrations (HG, 25 mM, 1 h). AT(1) receptors on cell membrane surface were measured by immunofluorescence. KEY RESULTS: Angiotensin II-induced constrictions to first applications were greater in arteries of ZDF rats (maximum: 82 ± 3% original diameter) than in those from +/Fa rats (61 ± 5%). Constrictions to repeated angiotensin II administration were decreased in +/Fa arteries (20 ± 6%), but were maintained in ZDF arteries (67 ± 4%) and in +/Fa arteries vessels exposed to HG (65 ± 6%). In ZDF arteries and in HG-exposed +/Fa arteries, Rho-kinase activities were enhanced. The Rho-kinase inhibitor, Y27632 inhibited sustained constrictions to angiotensin II in ZDF arteries and in +/Fa arteries exposed to HG. Levels of surface AT(1) receptors on cultured vascular smooth muscle cells (VSMCs) were decreased by angiotensin II but were maintained in VSMCs exposed to HG. In VSMCs exposed to HG and treated with Y27632, angiotensin II decreased surface AT(1) receptors. CONCLUSIONS AND IMPLICATIONS: In diabetes, elevated glucose concentrations activate Rho-kinase which inhibits internalization or facilitates recycling of AT(1) receptors, leading to increased functional availability of AT(1) receptors and sustained angiotensin II-induced arterial constriction.