THE POTENTIAL ROLE OF ALLOGRAFT INFLAMMATORY FACTOR 1 (AIF-1) IN MACROPHAGE ACTIVATION IN SMALL-FOR-SIZE LIVER TRANSPLANTATION

Abstract

P967 Aims: Our previous study demonstrated that early macrophage activation was related to inflammatory and acute rejection processes in small-for-size allografts. However, the mechanisms that lead to early macrophage activation in the small-for-size liver grafts remain unclear. The present study aims to identify the potential role of allograft inflammatory factor 1 (AIF-1) in mediating macrophage activation in small-for-size liver transplantation. Methods: An orthotopic liver transplantation model was performed. Male DA (RT1a) and LEW (RT1l) rats, weighing 250-300 g, were used as donors and recipients, respectively. Grafts were either 40% of recipients’ livers or whole grafts. Experimental groups included: 1) whole isograft; 2) 40% isograft; 3) whole allograft; and 4) 40% allograft. No treatment was given to all the groups. Tissue samples were collected at 1, 6, 24, and 72 hr after reperfusion. The expression of AIF-1 was detected at both mRNA (by RT-PCR) and protein (by Western blot) levels. In the in vitro study, the expression of AIF-1 in macrophage cell lines was measured after the animals were treated with pro-inflammatory cytokines IL-1β, TNF-α, and anti-inflammatory drug sodium salicylate. In addition, the macrophage cell lines were transfected with PCDNA3.1/AIF-1 (to enhance AIF-1 expression) or short interference RNA (siRNA to block AIF-1 expression). The expression of AIF-1 and iNOS in macrophages was detected, and cell migration assay was performed. Results: The expression of AIF-1 was significantly increased at both mRNA and protein levels in the small-for-size liver grafts in both isogeneic and allogeneic settings, starting from 1 hr to 72 hr after reperfusion. Immunohistochemical staining revealed that at 1 and 6 hr after reperfusion, the majority of AIF-1 positive cells were Kupffer cells, and at 72 hr after reperfusion, AIF-1 was also expressed in some infiltrating cells in the peri-portal area of liver allografts. Pro-inflammatory cytokines IL-1β and TNF-α could stimulate AIF-1 upregulation, whereas anti-inflammatory treatment by sodium salicylate could downregulate the expression of AIF-1. Transfection of AIF-1 to macrophage cell lines significantly enhanced AIF-1 expression. At the same time, the level of iNOS was also upregulatd and the number of migrated macrophages was increased. Blocking the expression of AIF-1 by siRNA significantly decreased the level of iNOS and inhibited the migration of macrophages. Conclusions: The expression of AIF-1 is upregulated in the small-for-size liver grafts during early phase after reperfusion; the expression of AIF-1 is related to iNOS production and migration activities of macrophages.