Epigallocatechin-3-gallate increases intracellular [Ca2+] in U87 cells mainly by influx of extracellular Ca2+ and partly by release of intracellular stores.
Green tea has been receiving considerable attention as a possible preventive agent against cancer and cardiovascular disease. Epigallocatechin-3-gallate (EGCG) is a major polyphenol component of green tea. Using digital calcium imaging and an assay for [3H]-inositol phosphates, we determined whether EGCG increases intracellular [Ca2+] ([Ca2+]i) in non-excitable human astrocytoma U87 cells. EGCG induced concentration-dependent increases in [Ca2+]i. The EGCG-induced [Ca2+]i increases were reduced to 20.9% of control by removal of extracellular Ca2+. The increases were also inhibited markedly by treatment with the non-specific Ca2+ channel inhibitors cobalt (3 mM) for 3 min and lanthanum (1 mM) for 5 min. The increases were not significantly inhibited by treatment for 10 min with the L-type Ca2+ channel blocker nifedipine (100 nM). Treatment with the inhibitor of endoplasmic reticulum Ca2+-ATPase thapsigargin (1 micro M) also significantly inhibited the EGCG-induced [Ca2+]i increases. Treatment for 15 min with the phospholipase C (PLC) inhibitor neomycin (300 micro M) attenuated the increases significantly, while the tyrosine kinase inhibitor genistein (30 micro M) had no effect. EGCG increased [3H]-inositol phosphates formation via PLC activation. Treatment for 10 min with mefenamic acid (100 micro M) and flufenamic acid (100 micro M), derivatives of diphenylamine-2-carboxylate, blocked the EGCG-induced [Ca2+]i increase in non-treated and thapsigargin-treated cells but indomethacin (100 micro M) did not affect the increases. Collectively, these data suggest that EGCG increases [Ca2+]i in non-excitable U87 cells mainly by eliciting influx of extracellular Ca2+ and partly by mobilizing intracellular Ca2+ stores by PLC activation. The EGCG-induced [Ca2+]i influx is mediated mainly through channels sensitive to diphenylamine-2-carboxylate derivatives.
Kim
Hee Jung
HJ
Department of Physiology, College of Medicine, The Catholic University of Korea, 505 Banpo-dong, Socho-gu, 137-701 Seoul, Korea.
Yum
Keun Sang
KS
Sung
Jong-Ho
JH
Rhie
Duck-Joo
DJ
Kim
Myung-Jun
MJ
Min
Do Sik
DS
Hahn
Sang June
SJ
Kim
Myung-Suk
MS
Jo
Yang-Hyeok
YH
Yoon
Shin Hee
SH
D002118:Calcium / Q000378:metabolism*; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology*; D004789:Enzyme Activation; D005439:Flufenamic Acid / Q000737:chemistry / Q000494:pharmacology; D019833:Genistein / Q000494:pharmacology; D007295:Inositol Phosphates / Q000096:biosynthesis; D007473:Ion Channels / Q000037:antagonists & inhibitors; D008528:Mefenamic Acid / Q000737:chemistry / Q000494:pharmacology; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D013662:Tea / Q000737:chemistry; D014407:Tumor Cells, Cultured; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism; D062367:ortho-Aminobenzoates / Q000737:chemistry
D007295:Inositol Phosphates; D007473:Ion Channels; D013662:Tea; D062367:ortho-Aminobenzoates; D008528:Mefenamic Acid; D005439:Flufenamic Acid; D002392:Catechin; C001209:fenamic acid; C045651:epigallocatechin gallate; D019833:Genistein; D011505:Protein-Tyrosine Kinases; D010738:Type C Phospholipases; D002118:Calcium