Expression of bcl-2 homologue mRNAs in rat liver allograft: rejection-induced cell apoptosis is associated with upregulation of bax and bcl-xs expression

Abstract Apoptosis is considered to play an important role in rejection of organ transplants, although the precise mechanism has not been elucidated. In this study, we screened for the expression of bcl-2 homologues (bcl-2, bax, bcl-xl, and bcl-xs) and Fas ligand (FasL) by RT-PCR method in grafts during acute rejection in rats following liver transplantation. Both bax and bcl-xs (inducers of apoptosis) mRNA levels increased steadily in the allografted group from postoperative day (POD) 2 to 8, while no remarkable changes of bcl-2 and bcl-xl expression (inhibitors of apoptosis) were recognized. Significant induction of FasL gene expression was observed in the allografted group on POD 4 and expression gradually decreased thereafter, although minimal FasL mRNA expression was seen in isografts. Our results indicated, for the first time, that rejection-induced cell apoptosis is closely associated with upregulation of bax and bcl-xs expression besides FasL, but not with down-regulation of bcl-xl.