“Modulation of Intracellular Calcium and MAPK Activation by ATP in Osteoblasts and Breast Cancer Cells”

KATZ SEBASTIÁN,; SCODELARO BILBAO, PAOLA GABRIELA; BOLAND, RICARDO; SANTILLÁN GRACIELA

Philadelphia, Pennsylvania, USA

Congreso; 28TH American Society for Bone and Mineral Research Annual Meeting; 2006

American Society for Bone and Mineral Research

The aim of this study was to compare the modulation of mitogen-activated protein kinase (MAPK) signaling pathways and its relationship to changes in intracellular calcium concentration ([Ca2+]i) induced by ATP in osteoblast-like osteosarcoma (ROS-A 17/2.8) and human breast cancer (MCF-7) cell lines. ATP, UTP and ADP (10 µM) induced an increase in [Ca2+]i by cation release from inner stores as determined by spectrofluorometry measurements in a calcium free medium (+0.5 mM EGTA). This response was similar for ATP and UTP whereas a smaller [Ca2+]i increase was observed in the case of ADP. When measurements were performed in medium containing 1.5 mM Ca2+, the Ca2+ response did not differ respect to calcium free medium. We found that mechanical stimulation of the cells after ATP or UTP but not ADP treatment induced a transient Ca2+ influx, thus suggesting that P2Y2 receptor activation is required for this mechanical stress-activated Ca2+ (SAC) influx. Moreover, preincubation of the cells with 5 mM Gd3+ inhibited ATP-dependent SAC influx. In addition, western blot analysis revealed that ERK 1/2 and p38 MAPKs were activated by ATP in a dose- and time-dependent manner in both cell types. The use of 0.5 mM EGTA or 5 mM Gd3+ reduced MAPK activation by ATP in osteoblastic ROS-A 17/2.8 cells, whereas in MCF-7 cells this effect was only suppressed by the use of 150 mM 2-APB, which completely inhibited intracellular calcium release induced by ATP. These results suggest the presence of SAC influx in both cell lines, which is involved in the activation of ERK 1/2 and p38 MAPK by ATP only in ROS-A 17/2.87 cells, while in MCF-7 cells this effect is only dependent on intracellular calcium.