Activation of Na(+), K(+), Cl(-)-cotransport mediates intracellular Ca(2+) increase and apoptosis induced by Pinacidil in HepG2 human hepatoblastoma cells.
The role of Na(+), K(+), Cl(-)-cotransport (NKCC) in apoptosis of HepG2 human hepatoblastoma cells was investigated. Pinacidil (Pin), an activator of ATP-sensitive K(+) (K(ATP)) channels, induced apoptosis in a dose- and time-dependent manner in HepG2 cells. Pin increased intracellular K(+) concentration ([K(+)](i)). Bumetanide and furosemide, NKCC inhibitors, significantly inhibited the Pin-induced increased [K(+)](i) and apoptosis, whereas K(ATP) inhibitors (glibenclamide and tolbutamide) had no effects. The Pin-induced [K(+)](i) increase was significantly prevented by reducing extracellular Cl(-) concentration, and Pin also increased intracellular Na(+) concentration ([Na(+)](i)), further indicating that these effects of Pin may be due to NKCC activation. In addition, Pin induced a rapid and sustained increase in intracellular Ca(2+) concentration ([Ca(2+)](i)), which was completely prevented by the NKCC inhibitors. Treatment with EGTA or BAPTA/AM markedly inhibited the Pin-induced apoptosis. Inhibitors of Na(+), Ca(2+)-exchanger, bepridil, and benzamil significantly prevented both [Ca(2+)](i) increase and apoptosis induced by Pin. Taken together, these results suggest that Pin increases [Na(+)](i) through NKCC activation, which leads to stimulation of reverse-mode of Na(+), Ca(2+) exchanger, resulting in [Ca(2+)](i) increase, and in turn, apoptosis. These results further suggest that NKCC may be a good target for induction of apoptosis in human hepatoma cells.
Kim
J A
JA
College of Pharmacy, Yeungnam University, Kyongsan 712-749, Korea.
Kang
Y Y
YY
Lee
Y S
YS
D000255:Adenosine Triphosphate / Q000502:physiology; D000584:Amiloride / Q000031:analogs & derivatives / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D015764:Bepridil / Q000494:pharmacology; D002034:Bumetanide / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002352:Carrier Proteins / Q000187:drug effects* / Q000502:physiology; D053938:DNA Fragmentation / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D005665:Furosemide / Q000494:pharmacology; D005905:Glyburide / Q000494:pharmacology; D018197:Hepatoblastoma / Q000378:metabolism / Q000473:pathology*; D006801:Humans; D020110:Pinacidil / Q000494:pharmacology*; D011188:Potassium / Q000378:metabolism; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000502:physiology; D012964:Sodium / Q000378:metabolism; D019831:Sodium-Calcium Exchanger / Q000037:antagonists & inhibitors / Q000378:metabolism; D028021:Sodium-Potassium-Chloride Symporters; D013997:Time Factors; D014044:Tolbutamide / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D002352:Carrier Proteins; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D019831:Sodium-Calcium Exchanger; D028021:Sodium-Potassium-Chloride Symporters; C013407:benzamil; D002034:Bumetanide; D015764:Bepridil; D020110:Pinacidil; D000584:Amiloride; D005665:Furosemide; D000255:Adenosine Triphosphate; D014044:Tolbutamide; D012964:Sodium; D011188:Potassium; D005905:Glyburide; D002118:Calcium