Hypoxia-induced cell death of HepG2 cells involves a necrotic cell death mediated by calpain.
To elucidate mechanism of cell death in response to hypoxia, we attempted to compare hypoxia-induced cell death of HepG2 cells with cisplatin-induced cell death, which has been well characterized as a typical apoptosis. Cell death induced by hypoxia turned out to be different from cisplatin-mediated apoptosis in cell viability and cleavage patterns of caspases. Hypoxia-induced cell death was not associated with the activation of p53 while cisplatin-induced apoptosis is p53 dependent. In order to explain these differences, we tested involvement of micro-calpain and m-calpain in hypoxia-induced cell death. Calpains, especially micro-calpain, were initially cleaved by hypoxia, but not by cisplatin. Interestingly, the treatment of a calpain inhibitor restored PARP cleavage that was absent during hypoxia, indicating the recovery of activated caspase-3. The inhibition of calpains prevented proteolysis induced by hypoxia. In addition, hypoxia resulted in a necrosis-like morphology while cisplatin induced an apoptotic morphology. The calpain inhibitor prevented necrotic morphology induced by hypoxia and converted partially to apoptotic morphology with nuclear segmentation. Our result suggests that calpains are involved in hypoxia-induced cell death that is likely to be necrotic in nature and the inhibition of calpain switches hypoxia-induced cell death to apoptotic cell death without affecting cell viability.
Kim
Min-Ju
MJ
Department of Biochemistry, College of Medicine, Hallym University, 1 Okchon-dong, Chuncheon, Gangwon-do 200-702, Korea.
Oh
Soo-Jin
SJ
Park
Seong-Hoon
SH
Kang
Hong-Jun
HJ
Won
Moo-Ho
MH
Kang
Tae-Cheon
TC
Hwang
In Koo
IK
Park
Jae-Bong
JB
Kim
Jong-Il
JI
Kim
Jaebong
J
Lee
Jae-Yong
JY
D000590:Amino Acid Chloromethyl Ketones / Q000378:metabolism; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D002154:Calpain / Q000037:antagonists & inhibitors / Q000378:metabolism*; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D016923:Cell Death / Q000502:physiology*; D045744:Cell Line, Tumor / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D048430:Cell Shape; D002945:Cisplatin / Q000494:pharmacology; D015853:Cysteine Proteinase Inhibitors / Q000378:metabolism; D006801:Humans; D000860:Hypoxia; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
D000590:Amino Acid Chloromethyl Ketones; D000970:Antineoplastic Agents; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D011065:Poly(ADP-ribose) Polymerases; D002154:Calpain; D020169:Caspases; D002945:Cisplatin