title: Antiapoptotic action of prolactin is associated with up-regulation of Bcl-2 and down-regulation of Bax in HC11 mouse mammary epithelial cells.
abstract: The effect of prolactin on apoptosis and the expression of bcl-2 and bax in HC11 mouse mammary epithelial cells were investigated. Flow cytometric analysis of Bcl-2 level (FITC-conjugated monoclonal anti-Bcl-2 antibody and FITC-conjugated monoclonal anti-IgG1 antibody as a negative control), number of apoptotic cells and cell cycle phases (DNA stained with DAPI) was performed. Bax transcript was measured using the RT-PCR method with GAPDH serving as a reference gene. Administration of prolactin (5 microg/ml) in the presence of insulin stimulated differentiation of mammary epithelial cells, which manifested in stopping cells at G0/G1 phase, cell swelling and increase of cell number with enhanced protein content. Moreover, prolactin highly significantly reduced the extent of apoptosis of HC11 cells during 48 h of incubation. Nevertheless, the apoptotic cell number rose with increased time length of cell culture, probably due to the resulting high cell density and EGF withdrawal from t he incubation medium. The antiapoptotic effect of prolactin was associated with up-regulation of bcl-2 expression, shown as an increase in cell numbers expressing this protooncogene and elevated Bcl-2 content in these cells. A negative relationship (r=-0.87, p< or =0.001) between the number of apoptotic cells and those expressing bcl-2 was also found. Prolactin administration lowered Bax transcript by 68.8% and 70.7% after 3 and 6h, respectively. In conclusion, the results presented indicate that stimulation of bcl-2 expression with simultaneous suppression of bax may be key events in the mechanism of antiapoptotic action of prolactin in HC11 mammary epithelial cells.
authors.affiliation: Department of Animal Physiology, Faculty of Veterinary Medicine, Warsaw Agricultural University, Nowoursynowska 166, 02-787 Warsaw, Poland.
authors.forename: T
authors.initials: T
authors.lastname: Ploszaj
authors.forename: T
authors.initials: T
authors.lastname: Motyl
authors.forename: A
authors.initials: A
authors.lastname: Orzechowski
authors.forename: W
authors.initials: W
authors.lastname: Zimowska
authors.forename: P
authors.initials: P
authors.lastname: Wareski
authors.forename: J
authors.initials: J
authors.lastname: Skierski
authors.forename: L
authors.initials: L
authors.lastname: Zwierzchowski