Multiple effects of econazole on calcium signaling: depletion of thapsigargin-sensitive calcium store, activation of extracellular calcium influx, and inhibition of capacitative calcium entry.
The effect of econazole on intracellular calcium levels ([Ca2+]i) in Madin Darby canine kidney cells was investigated using fura-2 fluorimetry. Econazole increased [Ca2+]i dose-dependently at 5-50 microM. The Ca2+ signal consisted of an initial rise, a gradual decay and a sustained plateau. Extracellular Ca2+ removal partially reduced the econazole response. Mn2+ quench of fura-2 fluorescence confirmed econazole-induced Ca2+ influx. The econazole-sensitive intracellular Ca2+ store overlaps with that sensitive to thapsigargin, an inhibitor of the endoplasmic reticulum Ca2+ pump, because 25 microM econazole depleted the thapsigargin-sensitive store, and conversely, thapsigargin abolished the econazole response. Econazole (25-50 microM) partially inhibited capacitative Ca2+ entry induced by cyclopiazonic acid, another endoplasmic reticulum Ca2+ pump inhibitor, measured by depleting internal Ca2+ store in Ca(2+)-free medium followed by adding 10 mM CaCl2. Econazole induced capacitative Ca2+ entry itself. Pretreatment with La3+ (100 microM) partially inhibited 25 microM econazole-induced Mn2+ quench of fura-2 fluorescence, and La3+ immediately reduced 20 microM econazole-induced Ca2+ signal when added at the peak of the signal, suggesting that econazole induced Ca2+ influx via two separate pathways: one is sensitive to La3+, the other is not. La3+ enlarged 25 microM econazole-induced [Ca2+]i transient during the decay phase. The econazole response was not altered when the cytosolic level of inositol 1,4,5-trisphosphate was inhibited by the phospholipase C inhibitor U73122.
Jan
C R
CR
Department of Medical Education and Research, Veterans General Hospital-Kaohsiung, Taiwan. crjan@isca.vghks.gov.tw
Ho
C M
CM
Wu
S N
SN
Tseng
C J
CJ
D000818:Animals; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D002460:Cell Line; D004285:Dogs; D004464:Econazole / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004963:Estrenes / Q000494:pharmacology; D005110:Extracellular Space / Q000378:metabolism; D015544:Inositol 1,4,5-Trisphosphate / Q000096:biosynthesis; D007424:Intracellular Fluid / Q000378:metabolism; D007811:Lanthanum / Q000494:pharmacology; D011760:Pyrrolidinones / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors