LY294002, but not wortmannin, increases intracellular calcium and inhibits calcium transients in bovine and human airway smooth muscle cells.
To characterize the effect that a phosphatidylinositol 3-kinase (PI3-kinase) inhibitor, LY294002, has on cytosolic calcium concentrations ([Ca2+]i), bovine airway smooth muscle cells (BASMC) and cultured human bronchial smooth muscle cells (HBSMC) were loaded with fura 2-AM, imaged as single cells and [Ca2+]i measured ratiometrically. LY294002 (50 microM) increased [Ca2+]i by 294+/-76 nM (P<0.01, n=13) and 230+/-31 nM (P<0.001, n=10) in BASMC and HBSMC, respectively, and increases occurred in the absence of extracellular calcium. In contrast, after pre-treatment with thapsigargin, LY294002 no longer increased [Ca2+]i. This calcium mobilization by LY294002 was associated with a significant functional effect since LY294002 also inhibited calcium transients to carbachol (45+/-23 nM), caffeine (45+/-32 nM), and histamine (20+/-22 nM), with controls of 969+/-190, 946+/-156, and 490+/-28 nM, respectively. Wortmannin, a different PI3-kinase inhibitor, neither increased [Ca2+]i nor inhibited transients. Also, LY294002 increased [Ca2+]i in the presence of wortmannin, U-73122, and xestospongin C. We concluded that LY294002 increased [Ca2+]i, at least in part, by mobilizing intracellular calcium stores and inhibited calcium transients. The effects of LY294002 on [Ca2+]i were not dependent on wortmannin-sensitive PI3-kinases, phospholipase C, or inositol trisphosphate receptors (IP3R). For BASMC and HBSMC, LY294002 has effects on calcium regulation that could be important to recognize when studying PI3-kinases.
Department of Medicine, UMass Medical School, NRB Floor #3, 364 Plantation Street, Worcester, MA 01605-2324, USA.
M F
MF
Ethier
J M
JM
Madison
D000730:Androstadienes / Q000494:pharmacology*; D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002417:Cattle; D002867:Chromones / Q000494:pharmacology*; D004357:Drug Synergism; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006801:Humans; D009025:Morpholines / Q000494:pharmacology*; D009130:Muscle, Smooth / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D014132:Trachea / Q000166:cytology; D000077191:Wortmannin
D000730:Androstadienes; D002867:Chromones; D004791:Enzyme Inhibitors; D009025:Morpholines; D010726:Phosphodiesterase Inhibitors; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D002110:Caffeine; D002118:Calcium; D000077191:Wortmannin