INVESTIGADORES
RONDA Ana Carolina
congresos y reuniones científicas
Título:
17beta-Estradiol and Testosterone Exert Antiapoptotic Effects in Skeletal Muscle Cells Involving AR, ER, ERK, MnSOD and COXIV
Autor/es:
ANABELA LA COLLA; PRONSATO LUCIA; ANA CAROLINA RONDA; LORENA MILANESI; ANDREA VASCONSUELO; BOLAND RICARDO
Lugar:
Baltimore
Reunión:
Congreso; Thirsty fifth Annual Meeting of American Society for Bone and Mineral Research; 2013
Resumen:
17beta-Estradiol (E2) and Testosterone (T) have effects in several tissues including skeletal muscle. In aged skeletal muscle both a deficit of sex hormones and prominent apoptosis are observed contributing to the pathogenesis of sarcopenia. We previously showed that E2 and T inhibit H2O2 - induced apoptosis in C2C12 muscle cells. Here we demonstrate that E2 has a relevant role in muscle mitochondria, up-regulating the expression and activity of manganese superoxide dismutase (MnSOD) and increasing the activity of cytochrome c oxidase IV (COXIV), through ERK signaling. Pharmacological and immunological assays employing the estrogen receptor (ER) antagonist fulvestrant indicate that ER mediates these events. In addition, MnSOD expression and COXIV activity decrease when cells are treated with H2O2, effects that are reversed with E2 pretreatment. Experiments with the androgen receptor (AR) antagonist flutamide involved the AR in the antiapoptotic action of T. Competitive binding assays, immunocytochemistry and Western blots supported a non-classical localization of the AR in C2C12 cells. Thus, AR was detected by immunoblots using specific antibodies after subcellular fractionation, not only in nucleus and cytosol, but also in mitochondria and microsomes. [3H] T binding characteristics were established in total homogenates and subcellular fractions. Specific and saturable [3H] T binding sites were detected in mitochondria and microsomes. Immunolocalization of the non-classical AR was also confirmed using confocal microscopy. Sucrose gradient fractionation demonstrated the presence of the AR in lipid rafts and caveolae. These results point to an active role of the AR during the antiapoptotic effect of T at different levels: nuclear (in the genomic response), mitochondrial (in the intrinsic pathway) and microsomal (in the response mediated by membrane proteins). Besides, coimmunoprecipitation assays indicated that the AR physically interacts with caveolin-1, association which was lost after T treatment at the same time that a decrease of AR expression was observed in the microsomal fraction, suggesting translocation of the membrane AR to inner cellular compartments. Our studies contribute to elucidate the mechanism by which these hormones regulate signaling cascades throwing light on the molecular basis of myopathies associated with deregulation of apoptosis by sex hormone deficiency states.