Rol de PTH en la apoptosis de células intestinales

CALVO NATALIA; GENTILI CLAUDIA; RUSSO DE BOLAND ANA

Rosario, Santa Fe

Congreso; XXIII Reunión Anual de la Asociación Argentina de Osteología y Metabolismo Mineral (AAOMM); 2006

Asociación Argentina de Osteología y Metabolismo Mineral (AAOMM)

PTH is a hormone functioning as a major mediator of bone remodeling and as an essential regulator of calcium homeostasis. Depending on the cell type involved, PTH also inhibits or promotes the apoptosis (programmed cell death). However, at this moment, the role of PTH in the apoptosis of intestinal cells remains understood. In this work we demonstrated, for the first time, the presence of the PTH receptor (R) in Caco-2 cells (epithelial cells isolated from a primary colonic tumor) by inmunoblot analysis and immunocitochemistry with a specific anti-PTH R antibody. The R, a 66 Kda protein, is mainly present in plasma membrane and nuclear membrane. Following PTH interaction with its R, the hormone (10-8 M) rapidly (3 min) and transiently stimulates the serine phosphorylation of AKT (PKB), an enzyme implicated in the regulation of the cell cycle, apoptosis and cell survival. PTH also stimulates the serine phosphorylation of Bad. This protein is a pro-apoptotic factor that interacts with and inhibits the anti-apoptotic protein Bcl-2. Once activated by phosphorylation, Akt induces the phosphorylation of Bad and inhibits its pro-apoptotic functions. With more time of PTH treatment (1, 2 and 9 hs) the serine phosphorylation of Akt and Bad are not altered. The apoptotic program is characterized by the condensation of the nucleus. In Caco-2 cells, analysis of the reduction in the nuclear size by the nuclear-specific colorant DAPI and evaluation of the cell survival reveal that PTH treatment (10 hs) increases the number of apoptotic nuclei (+190 %) and diminishes the number of cells ( 58% respect to control). In addition, in these cells, analysis by western blot shows that PTH induces the expression of cleaved forms (pro-apoptotic) of Caspase-3 (protease that proteolytically activates other caspases, leading to morphological features of apoptosis). These results suggest that the prolonged PTH action could promote the apoptosis of the intestinal cells Caco-2 and that the hormone can be used in medicine for possible new directions in the therapy of human colon cancer.