Intracellular oxygenation and cytochrome oxidase C activity in ischemic preconditioning of steatotic rabbit liver.
BACKGROUND
Mild to moderate steatotic livers are used as marginal donors in liver transplantation. Very little is known about the mechanisms of ischemia reperfusion (IR) injury (IRI) in fatty liver. This study aimed to establish whether cytochrome oxidase C (COX) activity is compromised by IRI in fatty liver and whether ischemic preconditioning (IPC) can protect COX activity.


METHODS
New Zealand rabbits were fed on a high-cholesterol diet for 8 weeks to induce moderate hepatic steatosis. Three groups were tested. The IR group underwent 60 minutes of ischemia, followed by 7 hours of reperfusion. The IPC group (IPC + IR) underwent 5 minutes of ischemia, followed by 10 minutes of reperfusion and then 60 minutes of ischemia and 7 hours of reperfusion. The control group (sham) underwent the same surgical procedure, but ischemia was not induced. Deoxyhemoglobin, oxyhemoglobin, and change in the redox state of COX was continuously monitored in vivo by near-infrared spectroscopy. COX and citrate synthase (CS) activity assays were carried out on liver biopsy specimens in vitro. Bile was collected continuously during the procedure and analyzed using proton nuclear magnetic resonance spectroscopy.


RESULTS
The IR group had decreased COX activity and tissue oxygenation represented by deoxyhemoglobin, oxyhemoglobin, COX, and elevated redox ratios of lactate/pyruvate and β-hydroxybutarate/acetoacetate in vivo and a decrease in COX and CS activity in vitro. The IPC + IR group showed higher levels of all measured parameters in vivo and showed a smaller decrease in COX and CS activity in vitro.


CONCLUSIONS
This study shows that IRI affects COX activity in fatty livers. This is attenuated by IPC.
Hafez
Tariq S
TS
UCL Division of Surgery and Interventional Science, University College London, London, United Kingdom.
Glantzounis
George K
GK
Fusai
Guiseppe
G
Taanman
Jan-Willem
JW
Wignarajah
Primeera
P
Parkes
Harry
H
Fuller
Barry
B
Davidson
Brian R
BR
Seifalian
Alexander M
AM
D000818:Animals; D004195:Disease Models, Animal; D003576:Electron Transport Complex IV / Q000378:metabolism*; D005234:Fatty Liver / Q000378:metabolism* / Q000473:pathology; D006454:Hemoglobins / Q000378:metabolism; D007424:Intracellular Fluid / Q000378:metabolism*; D019194:Ischemic Preconditioning / Q000379:methods*; D010101:Oxygen Consumption / Q000502:physiology*; D010108:Oxyhemoglobins / Q000378:metabolism; D011379:Prognosis; D011817:Rabbits; D015427:Reperfusion Injury / Q000378:metabolism / Q000517:prevention & control*; D012720:Severity of Illness Index
D006454:Hemoglobins; D010108:Oxyhemoglobins; C100003:deoxyhemoglobin; D003576:Electron Transport Complex IV