Ischemic preconditioning prevents free radical production and mitochondrial depolarization in small-for-size rat liver grafts.
BACKGROUND
Ischemic preconditioning (IP) renders tissues more tolerant to subsequent longer episodes of ischemia. This study tested whether IP attenuates injury of small-for-size liver grafts by preventing free radical production and mitochondrial dysfunction.


METHODS
IP was induced by clamping the portal vein and hepatic artery for 9 min. Livers were harvested 5 min after releasing the clamp. Mitochondrial polarization and cell death were assessed by intravital confocal/multiphoton microscopy of rhodamine 123 (Rh123) and propidium iodide. Free radicals were trapped with alpha-(4-pyridyl 1-oxide)-N-tert-butylnitrone and measured using electron spin resonance.


RESULTS
After quarter-size liver transplantation, alanine aminotransferase, serum bilirubin, necrosis, and apoptosis all increased. IP blocked these increases by more than 58%. 5-Bromo-2'-deoxyuridine labeling and increases of graft weight were only approximately 3% and 0.2% in quarter-size grafts without IP, respectively, but increased to 32% and 60% in ischemic-preconditioned grafts, indicating better liver regeneration. Eighteen hours after implantation, viable cells with depolarized mitochondria in quarter-size grafts were 15 per high power field, and dead cells were less than 1 per high power field, indicating that depolarization preceded necrosis. A free radical adduct signal was detected in bile from quarter-size grafts. IP decreased this free radical formation and prevented mitochondrial depolarization. IP did not increase heat shock proteins 10, 27, 32, 60, 70, 72, 75 and Cu/Zn-superoxide dismutase (SOD) but increased heat shock protein-90, a chaperone that facilitates protein import into mitochondria, and mitochondrial Mn-SOD.


CONCLUSIONS
Taken together, IP decreases injury and improves regeneration of small-for-size liver grafts, possibly by increasing mitochondrial Mn-SOD, thus protecting against free radical production and mitochondrial dysfunction.
Rehman
Hasibur
H
Department of Pharmaceutical Sciences, Medical University of South Carolina, Charleston, SC 29425, USA.
Connor
Henry D
HD
Ramshesh
Venkat K
VK
Theruvath
Tom P
TP
Mason
Ronald P
RP
Wright
Gary L
GL
Lemasters
John J
JJ
Zhong
Zhi
Z
D000410:Alanine Transaminase / Q000097:blood; D000447:Aldehydes / Q000032:analysis; D000818:Animals; D001663:Bilirubin / Q000097:blood; D005609:Free Radicals / Q000009:adverse effects; D006499:Hepatic Artery; D019194:Ischemic Preconditioning / Q000379:methods; D016031:Liver Transplantation / Q000379:methods*; D008297:Male; D023421:Models, Animal; D011169:Portal Vein; D018809:Proliferating Cell Nuclear Antigen / Q000032:analysis; D051381:Rats; D011917:Rats, Inbred Lew; D014185:Transplantation, Isogeneic
D000447:Aldehydes; D005609:Free Radicals; D018809:Proliferating Cell Nuclear Antigen; D000410:Alanine Transaminase; C027576:4-hydroxy-2-nonenal; D001663:Bilirubin