Hypoxia/reoxygenation up-regulated the expression of death receptor 5 and enhanced apoptosis in human hepatocyte line.
OBJECTIVE
Ischemia-reperfusion injury (IRI) is a key factor that contributes to early and late dysfunction of liver graft. Although we have known that hepatocytes express death receptors for tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), the effects of TRAIL on hypoxia/reoxygenation (H/R)-mediated apoptosis are unclear. This study sought to examine the effects of H/R on TRAIL cytotoxicity, as a cause of primary hepatic graft dysfunction, delayed graft refunction, and chronic graft dysfunction.


METHODS
Using an hepatocyte H/R model in vitro to mimic IRI in the grafted liver, normal human hepatocytes HL-7702 were exposed to hypoxia for 5 hours then reoxygenated for 0, 2, 4, 6, or 20 hours. In another experiment, hepatocytes were exposed to hypoxia for 0, 2, 4, 8, or 20 hours. Expressions of TRAIL-R2/Death receptor 5 (DR5) mRNA were measured by semiquantitative reverse-transcriptase polymerase chain reactions. After 16 hours of hypoxia, human hepatocytes were treated with TRAIL in different concentrations for 5 hours. The death of hepatocytes was confirmed by flow cytometer and methyl thiazolyl tetrazolium analysis.


RESULTS
After 5-hour hypoxia, the expressions of DR5 mRNA increased at all times of reoxygenation. DR5 mRNA was up-regulated from 0 hour after reoxygenation, reaching a peak value at 2 hours after reoxygenation compared with the normoxia cultured cells. Moreover, DR5 mRNA was up-regulated gradually following prolonged hypoxia. TRAIL-mediated cell killing was concentration-dependent being greater in the hypoxia treatment group compared to the normoxia group.


CONCLUSIONS
H/R up-regulated the expression of DR5 and enhanced TRAIL-mediated apoptosis in an human hepatocyte line. The TRAIL pathway might play a critical role in hepatocyte apoptosis induced by IRI.
Cao
L
L
Lab of Transplant Engineering and Immunology, West China Hospital, Sichuan University, Guoxuexiang 37, Chengdu 610041, People's Republic of China.
Li
Y
Y
Cheng
F
F
Li
S
S
Long
D
D
D017209:Apoptosis; D018929:Cell Culture Techniques; D015687:Cell Hypoxia; D002460:Cell Line; D002470:Cell Survival; D005786:Gene Expression Regulation; D022781:Hepatocytes / Q000166:cytology / Q000502:physiology*; D006801:Humans; D012333:RNA, Messenger / Q000235:genetics; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000235:genetics*; D015427:Reperfusion Injury / Q000503:physiopathology; D020133:Reverse Transcriptase Polymerase Chain Reaction
D012333:RNA, Messenger; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; C505639:TNFRSF10B protein, human