Non- genomic mechanism involved in the antiapoptotic actin of 17beta-estradiol in skeletal muscle cells¡±.

RICARDO BOLAND; LORENA MILANESI; RONDA, ANA C; ANDREA VASCONSUELO

Faculty of Biological Sciences, University of Concepci¨®n. Concepci¨®n, Chile. .Concepci¨®n, Chile.

Congreso; Second Workshop of Signal Transduction Mechanisms mediating Steroid Non- Genomic Acti; 2008

NON-GENOMIC MECHANISM INVOLVED IN THE ANTIAPOPTOTIC ACTION OF 17b-ESTRADIOL IN SKELETAL MUSCLE CELLS Ricardo Boland*, Lorena Milanesi, Ana Ronda, Andrea Vasconsuelo Departamento de Biolog¨ªa, Bioqu¨ªmica y Farmacia, Universidad Nacional del Sur,         8000 Bah¨ªa Blanca, Argentina. rboland@criba.edu.ar In this study we report that 17b-estradiol, through estrogen receptors with non-nuclear localization, e.g. mitochondria, endoplasmic reticulum and Golgi, can regulate apoptosis in mouse skeletal muscle C2C12 cells. 17b-estradiol, at physiological concentrations, abrogates DNA damage, PARP cleavage and cytochrome c release induced by H2O2 or etoposide. This protective action of the steroid involves fast activation of the PI3K/Akt/Bad pathway. Within the same short time interval 17b-estradiol increases phosphorylation of ERK 1/2 and p38 MAPK. Interestingly the main localization of phosphorylated ERK 1/2 is mitochondrial. In addition the effect of the hormone on cytochrome c release was blocked in presence of inhibitors of MAPKs. Evidence was obtained suggesting that the ERK 1/2 and PI3K/Akt/Bad pathways play a role in the antiapoptotic effects of 17b-estradiol at the level of mitochondria. Blocking experiments with specific antibodies and siRNAs against the estrogen receptors a (ER a) and ¦Â (ER ¦Â) isoforms, revealed that ER ¦Â mediates to a greater extent than ER a the antiapoptotic effects of 17b-estradiol in mitochondria. Furthermore, it was shown that the protective role of the hormone requires the participation of heat shock protein 27 (HSP27). 17¦Â-estradiol rapidly induced phosphorylation of HSP27. Immunocytochemistry and co-immunoprecipitation assays demonstrated co-localization and interaction of the chaperone with ER ¦Â in mitochondria. Altogether, these results suggest that the antiapoptotic signal triggered by 17¦Â-estradiol in muscle cells involves a non-genomic mechanism mediated by ER ¦Â and rapid activation of Akt and MAPKs, and the participation of HSP27.