Stat3 confers resistance against hypoxia/reoxygenation-induced oxidative injury in hepatocytes through upregulation of Mn-SOD.
OBJECTIVE
Hypoxia/reoxygenation (H/R) causes oxidative stress to the cell and induces apoptotic cell death. Signal transducer and activator of transcription-3 (Stat3) is one of the most important molecules involved in the initiation of liver development and regeneration, and has recently been shown to protect cells against various pathogens. In order to investigate the hepatoprotective effects of Stat3, we examined whether it protects against H/R-induced injury in primary hepatocytes.


METHODS
Primary cultured hepatocytes were prepared from SD rats. Adenoviruses and cytokines were added 2 days and 1h prior to the H/R insult, respectively. Hepatocytes and culture media were harvested for the assays before and after H/R insult.


RESULTS
Interleukin-6 and cardiotropin-1, which may function mainly through Stat3 activation, protected cells from H/R-induced apoptosis. Adenoviral overexpression of the constitutively activated form of Stat3 (Stat3-C) reduced H/R-induced apoptosis as well as generation of reactive oxygen species (ROS) in hepatocytes. Interestingly, Stat3-C induced Mn-SOD, but not Cu/Zn-SOD, both at the protein and mRNA levels. Overexpression of Mn-SOD significantly reduced H/R-induced ROS and apoptosis by inhibiting redox-sensitive activation of caspase-3 activity.


CONCLUSIONS
Stat3 protects hepatocytes from H/R-induced cell injury at least partly by upregulating Mn-SOD and inactivating caspase-3.
Terui
Keita
K
Bioengineering Laboratory, Department of Innovative Surgery, National Research Institute for Child Health and Development, 2-10-1, Okura, Setagaya, Tokyo 157-8535, Japan.
Enosawa
Shin
S
Haga
Sanae
S
Zhang
Hui Qi
HQ
Kuroda
Hiroaki
H
Kouchi
Katsunori
K
Matsunaga
Tadashi
T
Yoshida
Hideo
H
Engelhardt
John F
JF
Irani
Kaikobad
K
Ohnuma
Naomi
N
Ozaki
Michitaka
M
D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D017209:Apoptosis; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D016207:Cytokines / Q000494:pharmacology; D019610:Cytoprotection; D004268:DNA-Binding Proteins / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D018014:Gene Transfer Techniques; D005822:Genetic Vectors; D022781:Hepatocytes / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology*; D000860:Hypoxia / Q000473:pathology*; D015850:Interleukin-6 / Q000494:pharmacology; D051379:Mice; D010100:Oxygen / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000037:antagonists & inhibitors; D050796:STAT3 Transcription Factor; D013482:Superoxide Dismutase / Q000378:metabolism*; D015534:Trans-Activators / Q000494:pharmacology*; D015854:Up-Regulation
D061945:Caspase Inhibitors; D016207:Cytokines; D004268:DNA-Binding Proteins; D015850:Interleukin-6; D017382:Reactive Oxygen Species; D050796:STAT3 Transcription Factor; C494087:Stat3 protein, mouse; C494088:Stat3 protein, rat; D015534:Trans-Activators; C092073:cardiotrophin 1; D013482:Superoxide Dismutase; C505409:Casp3 protein, mouse; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases; D010100:Oxygen