AMP-activated protein kinase confers protection against TNF-{alpha}-induced cardiac cell death.
OBJECTIVE
Although a substantial role for 5' adenosine monophosphate-activated protein kinase (AMPK) has been established in regulating cardiac metabolism, a less studied action of AMPK is its ability to prevent cardiac cell death. Using established AMPK activators like dexamethasone (DEX) or metformin (MET), the objective of the present study was to determine whether AMPK activation prevents tumour necrosis factor-alpha (TNF-alpha) induced apoptosis in adult rat ventricular cardiomyocytes.


RESULTS
Cardiomyocytes were incubated with DEX, MET, or TNF-alpha for varying durations (0-12 h). TNF-alpha-induced cell damage was evaluated by measuring caspase-3 activity and Hoechst staining. Protein and gene estimation techniques were employed to determine the mechanisms mediating the effects of AMPK activators on TNF-alpha-induced cardiomyocyte apoptosis. Incubation of myocytes with TNF-alpha for 8 h has increased caspase-3 activation and apoptotic cell death, an effect that was abrogated by DEX and MET. The beneficial effect of DEX and MET was associated with stimulation of AMPK, which led to a rapid and sustained increase in Bad phosphorylation. This event reduced the interaction between Bad and Bcl-xL, limiting cytochrome c release and caspase-3 activation. Addition of Compound C to inhibit AMPK reduced Bad phosphorylation and prevented the beneficial effects of AMPK against TNF-alpha-induced cytotoxicity.


CONCLUSIONS
Our data demonstrate that although DEX and MET are used as anti-inflammatory agents or insulin sensitizers, respectively, their common property to phosphorylate AMPK promotes cardiomyocyte cell survival through its regulation of Bad and the mitochondrial apoptotic mechanism.
Kewalramani
Girish
G
Division of Pharmacology and Toxicology, Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, BC, Canada.
Puthanveetil
Prasanth
P
Wang
Fang
F
Kim
Min Suk
MS
Deppe
Sylvia
S
Abrahani
Ashraf
A
Luciani
Dan S
DS
Johnson
James D
JD
Rodrigues
Brian
B
D055372:AMP-Activated Protein Kinases / Q000502:physiology*; D000818:Animals; D017209:Apoptosis; D002118:Calcium / Q000378:metabolism; D054729:Calcium-Calmodulin-Dependent Protein Kinase Type 1 / Q000378:metabolism; D053148:Caspase 3 / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology; D008297:Male; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000473:pathology; D010766:Phosphorylation; D019859:Proto-Oncogene Proteins c-met / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D014409:Tumor Necrosis Factor-alpha / Q000633:toxicity*; D051025:bcl-Associated Death Protein / Q000378:metabolism
C494821:Bad protein, rat; D014409:Tumor Necrosis Factor-alpha; D051025:bcl-Associated Death Protein; D003907:Dexamethasone; D045304:Cytochromes c; D019859:Proto-Oncogene Proteins c-met; D054729:Calcium-Calmodulin-Dependent Protein Kinase Type 1; C517599:Camk1 protein, rat; D055372:AMP-Activated Protein Kinases; D053148:Caspase 3; D002118:Calcium