Ischemic postconditioning attenuates liver warm ischemia-reperfusion injury through Akt-eNOS-NO-HIF pathway.
BACKGROUND
Ischemic postconditioning (IPO) has been demonstrated to attenuate ischemia/reperfusion (I/R) injury in the heart and brain, its roles to liver remain to be defined. The study was undertaken to determine if IPO would attenuate liver warm I/R injury and its protective mechanism.


METHODS
Mice were divided into sham, I/R, IPO+I/R (occlusing the porta hepatis for 60 min, then treated for three cycles of 10 sec brief reperfusion consecutively, followed by a persistent reperfusion); L-NAME+ sham (L-NAME, 16 mg/kg, i.v., 5 min before repefusion); L-NAME+I/R; and L-NAME+ IPO. Blood flow of caudate and left lobe of the liver was blocked. Functional and morphologic changes of livers were evaluated. Contents of nitric oxide, eNOS and iNOS in serum were assayed. Concentration of eNOS, iNOS, malondialdehyde (MDA) and activity of superoxide dismutase (SOD) in hepatic tissue were also measured. Expressions of Akt, p-Akt and HIF-1α protein were determined by western blot. Expressions of TNF-α and ICAM-1 were measured by immunohistochemistry and RT-PCR.


RESULTS
IPO attenuated the dramatically functional and morphological injuries. The levels of ALT was significantly reduced in IPO+I/R group (p < 0.05). Contents of nitric oxide and eNOS in serum were increased in the IPO+I/R group (p < 0.05). IPO also up-regulated the concentration of eNOS, activity of SOD in hepatic tissue (p < 0.05), while reduced the concentration of MDA (p < 0.05). Moreover, protein expressions of HIF-1α and p-Akt were markedly enhanced in IPO+I/R group. Protein and mRNA expression of TNF-α and ICAM-1 were markedly suppressed by IPO (p < 0.05). These protective effects of IPO could be abolished by L-NAME.


CONCLUSIONS
We found that IPO increased the content of NO and attenuated the overproduction of ROS and I/R-induced inflammation. Increased NO contents may contribute to increasing HIF-1α level, and HIF-1α and NO would simultaneously protect liver from I/R injury. These findings suggested IPO may have the therapeutic potential through Akt-eNOS-NO-HIF pathway for the better management of liver I/R injury.
Key Laboratory of Transplant Engineering and Immunology of Health Ministry of China, West China Hospital, Sichuan University, Chengdu, Sichuan Province, P.R. China.
Jia Y
JY
Guo
Tong
T
Yang
Xiang G
XG
Sun
Ni Y
NY
Zhou
Fu S
FS
Li
Dan
D
Long
Tao
T
Lin
Ping Y
PY
Li
Li
L
Feng
D000410:Alanine Transaminase / Q000097:blood; D000818:Animals; D005786:Gene Expression Regulation; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism*; D018799:Intercellular Adhesion Molecule-1 / Q000235:genetics / Q000378:metabolism; D057775:Ischemic Postconditioning / Q000379:methods*; D008099:Liver / Q000473:pathology*; D008315:Malondialdehyde / Q000097:blood; D051379:Mice; D008807:Mice, Inbred BALB C; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000097:blood*; D019001:Nitric Oxide Synthase / Q000097:blood / Q000378:metabolism*; D009195:Peroxidase / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D015427:Reperfusion Injury / Q000517:prevention & control*; D013482:Superoxide Dismutase / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism
C497443:Hif1a protein, mouse; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D014409:Tumor Necrosis Factor-alpha; D018799:Intercellular Adhesion Molecule-1; D009569:Nitric Oxide; D008315:Malondialdehyde; D009195:Peroxidase; D019001:Nitric Oxide Synthase; D013482:Superoxide Dismutase; D000410:Alanine Transaminase; D051057:Proto-Oncogene Proteins c-akt; D019331:NG-Nitroarginine Methyl Ester