title: Distinct mechanisms of cardiomyocyte apoptosis induced by doxorubicin and hypoxia converge on mitochondria and are inhibited by Bcl-xL.
abstract: Hypoxia and doxorubicin can cause cardiotoxicity and loss of myocardial function. These effects are due, in part, to an induction of apoptosis. Herein we identify the apoptotic pathways activated in H9c2 cells in response to hypoxia (O(2)/N(2)/CO(2), 0.5:94.5:5) and doxorubicin (0.5 muM). Although the apoptosis induced was accompanied by induction of Fas and Fas ligand, the death receptor pathway was not critical for caspase activation by either stimulus. Hypoxia induced the expression of endoplasmic reticulum (ER) stress mediators and processed ER-resident pro-caspase-12 whereas doxorubicin did not induce an ER stress response. Most importantly, both stimuli converged on mitochondria to promote apoptosis. Accumulation of cytochrome c in the cytosol coincided with the processing of pro-caspase-9 and -3. Increasing the expression of the anti-apoptotic protein Bcl-x(L), either by dexamethasone or adenovirus-mediated transduction, protected H9c2 cells from doxorubicin- and hypoxia-induced apoptosis. Bcl-x(L) attenuated mitochondrial cytochrome crelease and reduced downstream pro-caspase processing and apoptosis. These data demonstrate that two distinct cardiomyocyte-damaging stimuli converge on mitochondria thus presenting this organelle as a potentially important therapeutic target for anti-apoptotic strategies for cardiovascular diseases.
authors.affiliation: Department of Biochemistry, National Centre for Biomedical Engineering Science, National University of Ireland, Galway, Ireland.
authors.forename: Janice L V
authors.initials: JL
authors.lastname: Reeve
authors.forename: Eva
authors.initials: E
authors.lastname: Szegezdi
authors.forename: Susan E
authors.initials: SE
authors.lastname: Logue
authors.forename: Tríona
authors.initials: T
authors.lastname: Ní Chonghaile
authors.forename: Timothy
authors.initials: T
authors.lastname: O'Brien
authors.forename: Thomas
authors.initials: T
authors.lastname: Ritter
authors.forename: Afshin
authors.initials: A
authors.lastname: Samali
mesh_terms: D000256:Adenoviridae; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D053453:Caspase 9 / Q000378:metabolism; D015687:Cell Hypoxia / Q000187:drug effects; D002460:Cell Line; D045304:Cytochromes c / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology; D004317:Doxorubicin / Q000494:pharmacology*; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000473:pathology; D053222:Fas Ligand Protein / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D008928:Mitochondria / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000166:cytology* / Q000187:drug effects*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D051020:bcl-X Protein / Q000378:metabolism*; D019014:fas Receptor / Q000235:genetics / Q000378:metabolism
chemical_list: D053222:Fas Ligand Protein; D012333:RNA, Messenger; D051020:bcl-X Protein; D019014:fas Receptor; D003907:Dexamethasone; D004317:Doxorubicin; D045304:Cytochromes c; D053453:Caspase 9