Effect of heme oxugenase-1 on delayed xenograft rejection: experiment of guinea pig-to-rat liver xenotransplantation

Abstract

To investigate the effects and mechanism of heme oxygenase-1 (HO-1) in liver xenotransplantation and mechanism thereof. Thirty male guinea-pigs used as donors were injected intravenously with cobra venom factor (CVF) and then randomly divided into 3 groups 24 hours after: Group A injected intraperineally with NaCl, Group B injected intraperineally with cobalt-protoporphyrin (CoPP), heme oxygenase-1 inducer, and Group C injected intraperineally with CoPP and zinc protoporphyrin (ZnPP), HO-1 inhibitor zinc before their livers were harvested. Thirty male SD rats used as recipients underwent the above-mentioned treatment 24 hours before receiving the xenografts. Five pairs of guinea pigs and rats in each group underwent collection of blood and liver tissues 3 hours after the recovery of blood perfusion in the transplanted livers for detection of serum enzymes by biochemical methods and expression of HO-1 mRNA and protein in the transplanted livers by RT-PCR and Western blotting respectively. The other 5 pairs in each group were used to observe the survival time. The survival time of Group B was 15.5 h +/- 3.8 h, significantly longer than those of Group A (7.3 h +/- 2.1 h) and Group C (6.7 h +/- 2.9 h, both P < 0.01). The values of ALT and LDH of Group B were significantly lower than those of Group A and C (all P < 0.05). HOI-1 mRNA expression was not detected or only expressed in trace amount in the livers of normal guinea pigs, expressed in a small amount in the transplanted livers of Group A. The expression of HO-1 mRNA and that of HO-1 protein in the transplanted livers of Group B were significantly higher than those of Group A (both P < 0.01), and the expression of HO-1 mRNA and that of HO-1 protein in the transplanted livers of Group C were not significantly different from those of Group A (both P > 0.05). Remarkable NF-kB band was detected in Groups A and C, and only weak NF-kB band was seen in Group B. The E-selectin expression was significantly lower in the transplanted livers of Group B than in those of Group A and C (both P < 0.05). HO-1 delays the occurrence of delayed xenograft rejection in liver xenotransplantation. This effect depends, at least in part, on HO-1-mediated inhibition of endothelium activation in xenografts.