Calcium/calmodulin signaling elicits release of cytochrome c during 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced apoptosis in the human lymphoblastic T-cell line, L-MAT.
We have reported previously that 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induces apoptosis in the human lymphoblastic T-cell line L-MAT, although these cells do not express the aromatic hydrocarbon receptor (AhR). The AhR-dependent pathway for the induction of immunotoxicity by TCDD has been studied extensively, but the AhR-independent pathway is not understood. Several studies have reported that TCDD elevates the concentration of free intracellular calcium ([Ca(2+)](i)) in various types of cells. However, the precise mechanism of the increase in [Ca(2+)](i) that occurs during apoptosis induced by TCDD has not been elucidated. Upon treatment of L-MAT cells with 20nM TCDD, we observed an early increase in [Ca(2+)](i), within 30min of the addition of TCDD, which was followed by an additional increase at 90min, after which the increase in [Ca(2+)](i) was sustained until 3h after the addition of TCDD. A chelator of intracellular calcium, 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetra(acetoxymethyl ester) (BAPTA-AM), blocked the induction of apoptosis by TCDD in L-MAT cells, but EGTA, a chelator of extracellular calcium, did not. An antagonist of calcium-dependent calmodulin (CaM), W-7, inhibited the induction of apoptosis by TCDD in L-MAT cells. Moreover, W-7 suppressed the mitochondrial release of cytochrome c to the cytosol. These results demonstrate that activated Ca(2+)/CaM could transmit apoptotic signal(s) to mitochondria. The results suggest that Ca(2+)/CaM signals may play an important role in the induction of apoptosis in L-MAT cells by TCDD.
Kobayashi
Daisuke
D
Science of Bioresources, United Graduate School of Agricultural Sciences, Iwate University, Morioka 020-8551, Japan. tougarashi_karai1234@yahoo.co.jp
Ahmed
Sohel
S
Ishida
Masato
M
Kasai
Shuya
S
Kikuchi
Hideaki
H
D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D020013:Calcium Signaling / Q000187:drug effects*; D002147:Calmodulin / Q000037:antagonists & inhibitors / Q000378:metabolism*; D053148:Caspase 3 / Q000378:metabolism; D002458:Cell Fractionation; D045744:Cell Line, Tumor; D002614:Chelating Agents / Q000494:pharmacology; D045304:Cytochromes c / Q000378:metabolism*; D053938:DNA Fragmentation / Q000187:drug effects; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D000072317:Polychlorinated Dibenzodioxins / Q000633:toxicity*; D018336:Receptors, Aryl Hydrocarbon / Q000378:metabolism; D013449:Sulfonamides / Q000494:pharmacology; D013601:T-Lymphocytes / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology
D002147:Calmodulin; D002614:Chelating Agents; D000072317:Polychlorinated Dibenzodioxins; D018336:Receptors, Aryl Hydrocarbon; D013449:Sulfonamides; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D004533:Egtazic Acid; C017967:W 7; D045304:Cytochromes c; D053148:Caspase 3