1,25(OH)2-VITAMIN D3 AND PTH PROMOTE APOPTOSIS IN THE HUMAN COLONIC Caco-2 CELLS

CALVO N; GENTILI C; RUSSO DE BOLAND A

Rosario, Santa Fe

Congreso; Reunion anual de la Sociedad Argentina de Investigacion en Bioquimica y Biologia Molecular; 2006

Sociedad Argentina de Investigacion en Bioquimica y Biologia Molecular (SAIB)

Apoptosis plays a critical role in maintaining homeostasis of the intestinal epithelium. The objective of this study was to delineate the role of PTH and 1,25(OH)2-vitamin D3 [1,25(OH)2D3] in intestinal apoptosis using the human colonic Caco-2 cells. We first demonstrated the presence of the PTH and 1,25(OH)2D3 receptors (R) in Caco-2 cells by immunoblot analysis and immunocitochemistry. Following hormone interaction with its R, PTH (10 nM) rapidly (3 min) and transiently stimulates the serine 473 phosphorylation of AKT and of the pro-apoptotic protein Bad in Ser 136, while 1,25(OH)2D3 (100 nM)  causes a transient phosphorylation of  Bad (1-5 min) and has no effects on AKT. In addition, the steroid hormone, opposite to PTH, activates the extracellular signal-regulated kinase ERK 1/2 (+2 fold). Analysis by DAPI staining and, evaluation of the cell survival, reveal that PTH and 1,25(OH)2D3 treatment for longer time-intervals (24 h) increase the number of apoptotic nuclei (+190 % and  +260%, respectively) and diminishes the number of cells (-58% and -52%, respectively). Both hormones also induce the expression of cleaved forms of Caspase-3. This apoptosis is associated with reduced levels of phosphorylation of AKT. Taken together, our results indicate that both hormones promote the apoptosis of Caco-2 intestinal cells and may be potentially useful in the therapy of human colon cancer.