Ce(4+) induced down-regulation of ERK-like MAPK and activation of nucleases during the apoptosis of cultured Taxus cuspidata cells.
Ce(4+) (Ce(NH(4))(2)(NO(3))(6)) at 1mM induces apoptosis of suspension cultures of Taxus cuspidata cells; however, the underlying signal mechanisms are unknown. We show here that a 46-kDa ERK (extracellular signal-regulated kinase)-like MAPK appears to be down-regulated at 4h, and remains at low levels for up to 48 h. An inhibitor of superoxide anions (O(2)(-)) generation, diphenyl iodonium (DPI) successfully blocks down-regulation of ERK-like MAPK and degradation of DNA. Moreover, a 41-kDa p38-like MAPK activity remains unchanged from 0.5 to 48 h. The p38 inhibitor SB202190 effectively inhibits p38-like MAPK activity, however, SB202190 fails to modify the apoptotic rate at concentrations up to 100 microM. Three nuclease (34-kDa, 22-kDa and 20-kDa) activities are profoundly enhanced in Ce(4+)-induced T. cuspidata cells. They have an optimum pH at 6.8, and are stimulated by Ca(2+)/Mg(2+). Caspase-3 inhibitor, Ac-DEVD-CHO, does not attenuate the 34-kDa nuclease activity, but inhibits the 22-kDa and the 20-kDa nuclease activities. In addition, inhibition of O(2)(-) generation by DPI significantly reduces the three nuclease activities. In conclusion, the present study suggests that down-regulation of ERK-like MAPK, burst of O(2)(-), activation of caspase-3-like and induction of three nucleases as the key signaling events mediating apoptosis in Ce(4+)-induced cultured T. cuspidata cells.
Ge
Zhi-Qiang
ZQ
Department of Pharmaceutical Engineering, School of Chemical Engineering and Technology, Tianjin University, P.O. Box 6888, Tianjin 300072, PR China.
Yang
Song
S
Yuan
Ying-Jin
YJ
D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D002563:Cerium / Q000494:pharmacology*; D015536:Down-Regulation / Q000187:drug effects; D004720:Endonucleases / Q000187:drug effects / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000187:drug effects; D016877:Oxidants / Q000494:pharmacology; D013481:Superoxides / Q000378:metabolism / Q000494:pharmacology; D020946:Taxus / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology*
D016877:Oxidants; D013481:Superoxides; D002563:Cerium; D048049:Extracellular Signal-Regulated MAP Kinases; D004720:Endonucleases