1alpha,25(OH)2D3 and parathyroid hormone (PTH) signaling in rat intestinal cells: activation of cytosolic PLA2.
In the current study, we have probed the role of cytosolic phospholipase A2 (cPLA2) activity in the cellular response to the calciotropic hormones, 1alpha,25,dihydroxy-vitamin D(3) [1alpha,25(OH)(2)D(3)] and PTH. Stimulation of rat enterocytes with either hormone, increased release of arachidonic acid (AA) 3H-AA] one-two fold in a concentration and time-dependent manner. The effect of either hormone on enterocytes was totally reduced by preincubation with the intracellular Ca(2+) chelator BAPTA-AM (5 microM), suggesting that the release of AA following cell exposure to the calciotropic hormones occurs mainly through a Ca(2+)-dependent mechanism involving activation of Ca(2+)-dependent cPLA2. Calciotropic homone stimulation of rat intestinal cells increases cPLA2 phosphorylation (three to four fold). This effect was decreased by PD 98059 (20 microM), a MAP kinase inhibitor, indicating that this action is, in part, mediated through activation of the MAP kinases ERK 1 and ERK2. Enterocytes exposure to 1alpha,25(OH)(2)D(3) (1nM) or PTH (10 nM) also resulted in P-cPLA2 translocation from cytosol to nuclei and membrane fractions, where phospholipase subtrates reside. Collectively, these data suggest that PTH and 1alpha,25(OH)(2)D(3) activate in duodenal cells, a Ca(2+)-dependent cytosolic PLA2 and attendant arachidonic acid release and that this activation requieres prior stimulation of intracellular ERK1/2. 1alpha,25(OH)(2)D(3) and PTH modulation of cPLA2 activity may change membrane fluidity and permeability and thereby affecting intestinal cell membrane function.
Gentili
Claudia
C
Department of Biologia, Bioquimica and Farmacia, Universidad Nacional del Sur, San Juan 670, Bahia Blanca 8000, Argentina.
Morelli
Susana
S
de Boland
Ana Russo
AR
D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D002117:Calcitriol / Q000502:physiology*; D003600:Cytosol / Q000201:enzymology*; D004386:Duodenum / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D008297:Male; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors; D010281:Parathyroid Hormone / Q000502:physiology*; D010741:Phospholipases A / Q000378:metabolism*; D054467:Phospholipases A2; D010766:Phosphorylation; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000502:physiology*
D004791:Enzyme Inhibitors; D005419:Flavonoids; D010281:Parathyroid Hormone; D016718:Arachidonic Acid; D020928:Mitogen-Activated Protein Kinases; D010741:Phospholipases A; D054467:Phospholipases A2; D002117:Calcitriol; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one