[Protective functions of recombinant protein targeted at RANKL against hepatic ischemia/reperfusion injury transfected by retrovirus in mice]

Abstract

Objective: To explore the protective functions of recombinant protein RANK-Fc against hepatic ischemia/reperfusion injury and clarify its possible mechanism.

Methods: Sixty male Balb/c mice were randomly divided into 3 groups according to different treatments: serum-free medium control (Sham) group, target gene retrovirus (RANK-Fc) group and empty vector retrovirus (eGFP) group. All mice were injected with 2.5 ml solution (with or without retrovirus) within 6 seconds via tail vein. After 3 days, the model of 70% hepatic ischemia/reperfusion was induced under warm conditions for 90 minutes after different periods of reperfusion in RANK-Fc and eGFP groups; Sham group underwent the same procedure without the occlusion of blood supply. Blood and liver samples were obtained at different time points (1, 3, 6 and 24 h; n = 5 in each). Reverse transcription-polymerase chain reaction (RT-PCR) was used for the evaluation of eGFP mRNA expression. RANK-Fc was assessed by Western blot. Liver transaminases and histopathological changes were used for the evaluation of hepatic injury. The activity of NF-κB in liver nucleus was analyzed by Western blot and immunohistochemistry. The activation level of JNK was also assessed by Western blot. Liver homogenate levels of tumor necrosis factor (TNF)-α and interleukin (IL)-6 were detected by enzyme-linked immunosorbent assay (ELISA). Apoptosis was identified by the terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) analysis. The differences between three treatment groups at each time point were detected by the one-way ANOVA. Statistical analysis for inter-comparison was performed by Student's t test.

Results: RANK-Fc and eGFP were successfully expressed in liver after hydrodynamics-based transfection. Compared with eGFP group, RANK-Fc significantly improved liver functions at the same time point (P < 0.01), decreased NF-κB nuclear translocation (t = 6.726, P < 0.01)and JNK phosphorylation (t = 6.713, P < 0.01)and obviously suppressed the release of pro-inflammatory cytokine TNF-α (t = 4.779, P < 0.01) and IL-6 (t = 5.482, P < 0.01). Morphological injuries were markedly alleviated while the expressions of immunohistochemical positive cells and TUNEL staining positive cells decreased in RANF-Fc group.

Conclusion: RANK-Fc has protective functions against hepatic ischemia/reperfusion injury in mice. Its mechanism is at least partially related with the suppressions of proinflammatory NF-κB and proapoptotic JNK signaling pathways.