Maitotoxin-induced calcium entry in human lymphocytes: modulation by yessotoxin, Ca(2+) channel blockers and kinases.
We have studied the effect of the ciguatera-related toxin maitotoxin (MTX) on the cytosolic free calcium concentration ([Ca(2+)]i) of human peripheral blood lymphocytes loaded with the fluorescent probe Fura2 and the regulation of MTX action by different drugs known to interfere in cellular Ca(2+) signalling mechanisms and by the marine phycotoxin yessotoxin (YTX). MTX produced a concentration-dependent elevation of [Ca(2+)]i in a Ca(2+)-containing medium. This effect was stimulated by pretreatment with YTX 1 microM and NiCl(2) 15 microM. The voltage-independent Ca(2+) channel antagonist 1-[beta-[3-(4-methoxyphenyl)propoxyl]-4-methoxyphenyl]-1H-imidazole hydrochloride (SKF96365) blocked the MTX-induced [Ca(2+)]i elevation, while the L-type channel blocker nifedipine had no effect. Pretreatment with NiCl(2) or nifedipine did not modify YTX-induced potentiation of MTX effect, and SKF96365-induced inhibition was reduced in the presence of YTX, which suggest different pathways to act on [Ca(2+)]i. Preincubation with N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide.2HCl (H-89) or genistein (10 microM) also had no effect on the MTX-induced [Ca(2+)]i increment. In contrast, the PKC inhibitor bisindolilmaleimide I (GF109203X 1 microM) potentiated the MTX effect, whereas phosphatidylinositol (PI) 3-kinase inhibition with wortmannin (10 nM) reduced the MTX-elicited Ca(2+) entry. In summary, MTX produced Ca(2+) influx into human lymphocytes through a SKF96365-sensitive, nifedipine-insensitive pathway. The MTX-induced [Ca(2+)]i elevation was stimulated by the marine toxin YTX through a mechanism insensitive to SKF96365, nifedipine or NiCl(2). It was also stimulated by the divalent cation Ni(2+) and PKC inhibition and was partially inhibited by PI 3-kinase inhibition.
de la Rosa
L A
LA
Department of Pharmacology, Faculty of Veterinary, University of Santiago de Compostela, Lugo 27002, Spain.
Alfonso
A
A
Vilariño
N
N
Vieytes
M R
MR
Yasumoto
T
T
Botana
L M
LM
D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D002478:Cells, Cultured; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004988:Ethers, Cyclic / Q000494:pharmacology*; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D007700:Kinetics; D008214:Lymphocytes / Q000187:drug effects / Q000378:metabolism*; D008387:Marine Toxins / Q000494:pharmacology*; D008978:Mollusk Venoms; D009532:Nickel / Q000494:pharmacology; D009543:Nifedipine / Q000494:pharmacology; D035964:Oxocins; D010770:Phosphotransferases / Q000037:antagonists & inhibitors*; D000095702:Polyether Toxins
D002118:Calcium; D002121:Calcium Channel Blockers; D004791:Enzyme Inhibitors; D004988:Ethers, Cyclic; D007093:Imidazoles; D008387:Marine Toxins; D008978:Mollusk Venoms; D009532:Nickel; D009543:Nifedipine; D035964:Oxocins; D010770:Phosphotransferases; C022838:nickel chloride; C020394:maitotoxin; D000095702:Polyether Toxins; C063159:1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole; C066632:yessotoxin