Heat stress prevents mitochondrial injury in ATP-depleted renal epithelial cells.
The events that precipitate cell death and the stress proteins responsible for cytoprotection during ATP depletion remain elusive. We hypothesize that exposure to metabolic inhibitors damages mitochondria, allowing proapoptotic proteins to leak into the cytosol, and suggest that heat stress-induced hsp72 accumulation prevents mitochondrial membrane injury. To test these hypotheses, renal epithelial cells were transiently ATP depleted with sodium cyanide and 2-deoxy-D-glucose in the absence of medium dextrose. Recovery from ATP depletion was associated with the release into the cytosol of cytochrome c and apoptosis-inducing factor (AIF), proapoptotic proteins that localize to the intermitochondrial membrane space. Concomitant with mitochondrial cytochrome c leak, a seven- to eightfold increase in caspase 3 activity was observed. In controls, state III mitochondrial respiration was reduced by 30% after transient exposure to metabolic inhibitors. Prior heat stress preserved mitochondrial ATP production and significantly reduced both cytochrome c release and caspase 3 activation. Despite less cytochrome c release, prior heat stress increased binding between cytochrome c and hsp72. The present study demonstrates that mitochondrial injury accompanies exposure to metabolic inhibitors. By reducing outer mitochondrial membrane injury and by complexing with cytochrome c, hsp72 could inhibit caspase activation and subsequent apoptosis.
Li
F
F
Renal Section, Department of Medicine, Boston Medical Center, Boston University, Massachusetts 02118-2518, USA.
Mao
H P
HP
Ruchalski
K L
KL
Wang
Y H
YH
Choy
W
W
Schwartz
J H
JH
Borkan
S C
SC
D000255:Adenosine Triphosphate / Q000172:deficiency / Q000378:metabolism*; D000818:Animals; D051033:Apoptosis Inducing Factor; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D003574:Cytochrome c Group / Q000032:analysis / Q000378:metabolism; D003600:Cytosol / Q000737:chemistry / Q000378:metabolism; D003847:Deoxyglucose / Q000494:pharmacology; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D005420:Flavoproteins / Q000378:metabolism; D005456:Fluorescent Dyes; D050884:HSP72 Heat-Shock Proteins; D006360:Heat-Shock Proteins / Q000378:metabolism; D018869:Heat-Shock Response / Q000502:physiology*; D007668:Kidney / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D009893:Opossums; D011485:Protein Binding / Q000502:physiology; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology; D012966:Sodium Cyanide / Q000494:pharmacology
D051033:Apoptosis Inducing Factor; D003574:Cytochrome c Group; D005420:Flavoproteins; D005456:Fluorescent Dyes; D050884:HSP72 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D008565:Membrane Proteins; D000255:Adenosine Triphosphate; D003847:Deoxyglucose; D053148:Caspase 3; D020169:Caspases; D012966:Sodium Cyanide