Protection of hepatic cells from apoptosis induced by ischemia/reperfusion injury by protein therapeutics

Aim: Apoptosis is involved in hepatic ischemia/reperfusion injury. The protein FNK, constructed from an anti-apoptotic protein Bcl-x(L), exhibits the stronger anticell death activity. We evaluated the effect of FNK on apoptosis after hepatic ischemia and reperfusion, using FNK-overexpressing transgenic mice and the HIV/Tat protein-transduction-domain (PTD) that mediates the introduction of FNK into cells when fused with FNK (PTD-FNK). Methods: Mice were given hepatic ischemic insult for 90 min followed by reperfusion for 3 h. FNK overexpression was determined by immunohistochemistry and Western blot. PTD-FNK was intraperitoneally injected into wild mice 3 h before the insult. Liver injury was determined by the caspase activation, DNA fragmentation, and hematoxylin-eosin and terminal deoxynucleotidyl transferase-mediated dUTP- digoxigenin nick-end labelling (TUNEL) stainings. Results: In FNK-transgenic mice, FNK overexpression inhibited the activation of caspase 3/caspase 3-like activity and DNA fragmentation caused by the injury. In wild mice preinjected with PTD-FNK, PTD-FNK significantly inhibited the caspase activation and DNA fragmentation, reduced the area of liver vacuolization, and protected hepatic cells surrounding blood vessels, irrespective of central or portal veins, from the ischemia/reperfusion damage. Conclusions: FNK inhibits apoptotic death due to the ischemia/reperfusion injury. Our results provide the reasonable expectation of therapeutic protein PTD-FNK for clinical applications, such as transplantation, to protect against ischemia/reperfusion injury.