Evidence of functional modulation of mitogenic cascades by PTH in intestinal cells: Effect of ageing.

BUZZI, NATALIA SOL; RICARDO BOLAND,; RUSSO DE BOLAND, ANA

Pinamar

Congreso; XLI Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2005

PABMB, SAIB, SAN

EVIDENCE OF FUNCTIONAL MODULATION OF MITOGENIC CASCADES BY PTH IN INTESTINAL CELLS: EFFECT OF AGEING Natalia Buzzi, Ricardo Boland and Ana Russo de Boland.. Depto. Biología, Bioquímica y Farmacia, Universidad Nacional del Sur. 8000 Bahia Blanca, Argentina nbuzzi@criba.edu.ar In the present study we examined the role of PTH on members of the MAPK family as it relates to ageing by measuring hormone-induced changes in the activity of JNK 1/2 and p38 MAPK in enterocytes isolated from young (3 month-old) and aged (24 month-old) rats. Our results show that, PTH induces a transient activation of JNK1/2, with the greater response achieved at 2 min (+3 fold). The hormone also stimulates JNK1/2 tyrosine phosphorylation, in a dose-dependent fashion, being maximal at 10 nM. PTH-induced JNK1/2 phosphorylation was effectively suppressed by its selective inhibitor SP600125 (20 M). Moreover, hormone-dependent tyrosine phosphorylation and activation of JNK1/2 was dependent on intracellular calcium, since the pretreatment of cells with BAPTA-AM (5 M), an intracellular Ca2+ chelator, blocked PTH effects. With ageing, the response to PTH was signifincantly reduced. However, the amount of basal protein expression determined by Western blot analysis for JNK was not different in the enterocytes from young and aged rats. PTH does not stimulate p38 MAK in intestinal cells; furthermore, the hormone decreases, within 15 to 30 min, the basal phosphorylation and activity of p38 MAPK. PTH increased enterocyte DNA synthesis. The response is dose-dependent and decreases (-40%) with ageing. Of physiological significance, in agreement with the mitogenic role of the MAPK cascades, this effect was blocked by the specific inhibitors of ERK1/2 and JNK1/2. The results obtained in this work expand our knowledge on the mechanism of action of PTH in duodenal cells, revealing that activation of JNK1/2 and ERK1/2 is linked to PTH regulation of intestinal cell proliferation, and that this mechanism is impaired with ageing.