Effect of gossypol on intracellular Ca2+ regulation in human hepatoma cells.
Gossypol is a natural toxicant present in cottonseeds, and is hepatotoxic to animals and human. The effect of gossypol on cytosolic free Ca2+ levels ([Ca2+]i) in HA22/VGH human hepatocytes was explored using fura-2 as a fluorescent Ca2+ indicator. Gossypol increased [Ca2+]i in a concentration-dependent manner with an EC50 value of 2 microM. The Ca2+ signal was reduced by removing extracellular Ca2+ or by 10 microM La3+, but was not affected by nifedipine, verapamil or diltiazem. Pretreatment with 1 microM thapsigargin (an endoplasmic reticulum Ca2+ pump inhibitor) to deplete the endoplasmic reticulum Ca2+ partly reduced 10 microM gossypol-induced Ca2+ release; and conversely pretreatment with gossypol abolished thapsigargin-induced Ca2+ release. The Ca2+ release induced by 10 microM gossypol was not changed by inhibiting phospholipase C with 2 microM U73122 or by depleting ryanodine-sensitive Ca2+ stores with 50 microM ryanodine. Together, the results suggest that in human hepatocytes, gossypol induced a [Ca2+]i increase by causing store Ca2+ release from the endoplasmic reticulum in a phospholipase C-independent manner, and by inducing Ca2+ influx.
Cheng
Jin-Shiung
JS
Department of Medicine, Kaohsiung Veterans General Hospital, Kaohsiung 813, Taiwan.
Lo
Yuk-Keung
YK
Yeh
Jeng-Hsien
JH
Cheng
He-Hsiung
HH
Liu
Chun-Peng
CP
Chen
Wei-Chuan
WC
Jan
Chung-Ren
CR
D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects; D006528:Carcinoma, Hepatocellular; D045744:Cell Line, Tumor; D003272:Contraceptive Agents, Male / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006072:Gossypol / Q000494:pharmacology*; D022781:Hepatocytes / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D008113:Liver Neoplasms; D019284:Thapsigargin / Q000494:pharmacology
D002121:Calcium Channel Blockers; D003272:Contraceptive Agents, Male; D004791:Enzyme Inhibitors; D019284:Thapsigargin; D006072:Gossypol; D002118:Calcium