Combination of hypoxic preconditioning and postconditioning does not induce additive protection of ex vivo human skeletal muscle from hypoxia/reoxygenation injury.
We previously demonstrated that hypoxic preconditioning (HPreC) or postconditioning (HPostC) protected ex vivo human skeletal muscle from hypoxia/reoxygenation injury. Here, we investigated if combined HPreC and HPostC could convey additive protection. Human rectus abdominis muscle strips were cultured in normoxic Krebs buffer for 5 hours (control) or in 3 hours hypoxic/2 hours normoxic buffer (treatment groups). HPreC and HPostC were induced by 1 cycle of 5 minutes hypoxia/5 minutes reoxygenation immediately before or after 3 hours hypoxia, respectively. Muscle injury, viability, and adenosine triphosphate (ATP) synthesis were assessed by measuring lactate dehydrogenase release, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide reduction, and ATP content, respectively. Hypoxia/reoxygenation caused lactate dehydrogenase to increase and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide reduction and ATP content to decrease (P < 0.05; n = 7). HPreC, HPostC, and combination of both were equally effective in protection of muscle from hypoxia/reoxygenation injury. Atractyloside (5 × 10 M), a mitochondrial permeability transition pore opener, abolished the protective effect of HPreC or HPostC. We conclude that HPreC and HPostC protect ex vivo human skeletal muscle against hypoxia/reoxygenation injury by closing the mitochondrial permeability transition pore. For that reason, they are equally effective and do not demonstrate an additive effect. Moreover, the potent effect of HPostC indicates ischemic postconditioning as an effective clinical intervention against reperfusion injury in autogenous skeletal muscle transplantation and replantation surgery.
Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada.
Andreas
A
Naparus
Homa
H
Ashrafpour
Ning
N
Huang
Stefan O P
SO
Hofer
Toni
T
Zhong
Christopher R
CR
Forrest
Cho Y
CY
Pang
D000255:Adenosine Triphosphate / Q000378:metabolism; D000368:Aged; D001278:Atractyloside / Q000494:pharmacology; D005260:Female; D006801:Humans; D057775:Ischemic Postconditioning / Q000379:methods*; D019194:Ischemic Preconditioning / Q000379:methods*; D008875:Middle Aged; D033681:Mitochondrial Membrane Transport Proteins / Q000378:metabolism*; D000083162:Mitochondrial Permeability Transition Pore; D017568:Rectus Abdominis / Q000473:pathology; D015427:Reperfusion Injury / Q000503:physiopathology*; D013997:Time Factors
D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D001278:Atractyloside; D000255:Adenosine Triphosphate