title: Apoptosis induced by cadmium in human lymphoma U937 cells through Ca2+-calpain and caspase-mitochondria- dependent pathways.
abstract: Apoptosis induced by cadmium has been shown in many tissues in vivo and in cultured cells in vitro. However, its molecular mechanism is not fully understood. When the human histiocytic lymphoma cell line U937 was treated with cadmium for 12 h, evidence of apoptotic features, including change in nuclear morphology, DNA fragmentation, formation of DNA ladder in agarose gel electrophoresis, and phosphatidylserine externalization, were obtained. Moreover, loss of the mitochondrial membrane potential (Deltapsi(m)) was observed in the cadmium-treated cells and was inhibited by a broad caspase inhibitor (Z-VAD-FMK). Caspase inhibitors suppressed the DNA fragmentation in the order of Z-VAD-FMK > caspase-8 inhibitor > caspase-3 inhibitor. Expression of Bcl-x(L) and Bid decreased significantly in the cadmium-treated cells, although no apparent change in Bcl-2 and Bax expression was found. Tetrakis-(2-pyridylmethyl) ethylendiamine, a cell-permeable heavy metal chelator, partially reversed the increase of fluorescence of Fura-2 in the cadmium-treated cells. In addition, verapamil (70 microm), a voltage-dependent Ca(2+) channel blocker, inhibited the DNA fragmentation induced by cadmium less than 100 microm and decreased the fluorescence of Fura-2. Cadmium up-regulated the expression of type 1 inositol 1,4,5-trisphosphate receptor (IP(3)R) but not type 2 or type 3 IP(3)R. Calpain inhibitors I and II partially prevented DNA fragmentation. No effects of Z-VAD-FMK on the expression of type 1 IP(3)R or of calpain inhibitors on the loss of Deltapsi(m) were observed. These results suggest that cadmium possibly induced apoptosis in U937 cells through two independent pathways, the Ca(2+)-calpain-dependent pathway and the caspase-mitochondria-dependent pathway.
authors.affiliation: Department of Public Health, the Department of Radiological Sciences, Faculty of Medicine, Toyama Medical and Pharmaceutical University, Toyama, 930-0194, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Li
authors.forename: T
authors.initials: T
authors.lastname: Kondo
authors.forename: Q L
authors.initials: QL
authors.lastname: Zhao
authors.forename: F J
authors.initials: FJ
authors.lastname: Li
authors.forename: K
authors.initials: K
authors.lastname: Tanabe
authors.forename: Y
authors.initials: Y
authors.lastname: Arai
authors.forename: Z C
authors.initials: ZC
authors.lastname: Zhou
authors.forename: M
authors.initials: M
authors.lastname: Kasuya
mesh_terms: D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D051023:BH3 Interacting Domain Death Agonist Protein; D015153:Blotting, Western; D002104:Cadmium / Q000378:metabolism* / Q000494:pharmacology*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism; D002154:Calpain / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism*; D002467:Cell Nucleus / Q000187:drug effects; D002614:Chelating Agents / Q000494:pharmacology; D053938:DNA Fragmentation / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D005029:Ethylenediamines / Q000494:pharmacology; D006801:Humans; D053496:Inositol 1,4,5-Trisphosphate Receptors; D008223:Lymphoma / Q000378:metabolism*; D008564:Membrane Potentials; D008928:Mitochondria / Q000378:metabolism*; D008954:Models, Biological; D010718:Phosphatidylserines / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D013997:Time Factors; D020298:U937 Cells; D015854:Up-Regulation; D014700:Verapamil / Q000494:pharmacology; D051020:bcl-X Protein
chemical_list: D000590:Amino Acid Chloromethyl Ketones; C494811:BCL2L1 protein, human; D051023:BH3 Interacting Domain Death Agonist Protein; C494814:BID protein, human; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D002352:Carrier Proteins; D061945:Caspase Inhibitors; D002614:Chelating Agents; D005029:Ethylenediamines; C506926:ITPR1 protein, human; C506927:ITPR2 protein, human; D053496:Inositol 1,4,5-Trisphosphate Receptors; D010718:Phosphatidylserines; D019253:Proto-Oncogene Proteins c-bcl-2; D018160:Receptors, Cytoplasmic and Nuclear; D051020:bcl-X Protein; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D002104:Cadmium; D014700:Verapamil; C505407:CASP3 protein, human; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D002154:Calpain; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases; C044387:N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine