PROTECTIVE ACTIONS OF ESTRADIOL INVOLVE MITOCHONDRIAL MEMBRANE POTENTIAL AND BAX REGULATION IN SKELETAL MUSCLE CELLS

ANA CAROLINA RONDA; RICARDO BOLAND; ANDREA VASCONSUELO

Puerto Madryn, Argentina

Congreso; SAIB XLVI REUNION ANUAL; 2010

Sociedad Argentina de Investigaciones Biológicas

We have previously demonstrated that 17b-estradiol (E2), at physiological concentrations, abrogates apoptosis induced by oxidative stress (H2O2) in murine skeletal muscle cells. We have shown that PI3K/Akt and MAPKs pathways are involved in these events in C2C12 cells. In order to deepen our investigations, here we study the role of the proapoptotic protein Bax. By coimmunoprecipitation analyses, we show that Bax binds to the cytoplasmic protein 14-3-3 and ERK. When cells were treated with E2 increased levels of Bax/14-3-3 interaction was observed. On the other hand, incubation of the cultures with E2 diminished Bax/ERK complex, according with E2 induced-ERK translocation to mitochondria. Apoptotic stimulation with hydrogen peroxide disrupts Bax/14-3-3 association and increases Bax/ERK interaction and these effects are reversed by E2 pretreatment. Moreover, we have investigated the mitochondrial membrane depolarization by flow cytometry. Results show that the apoptotic stimulus with H2O2 induces a decrease in mitochondrial membrane potential, which is prevented by preincubation with E2. When the cells were preincubated with the ERK inhibitor U0126, the hormone was unable to avoid the effect of the oxidative stress suggesting a role for ERK in this event. These findings suggest that Bax, 14-3-3 and ERK are involved in negative regulation of muscle apoptosis by E2 affecting mitochondrial function.