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Background & Aims A critical role of the Toll-like receptor ( TLR)-4 and its downstream mediators in the pathogenesis of small-for-size liver graft injury has been documented. Recently, the micro RNA-146 (miR-146) was identified as a potent negative regulator of the TLR4 signalling pathway. In this study, the role of miR-146a and miR-146b in the attenuation of TLR-4 signalling and small-for-size liver graft injury was investigated. Methods The expression levels of miR-146a and miR-146b during small-for-size liver graft injury were studied in vivo. In addition, the effects of miR-146a and miR-146b on the expression of IRAK1 and TRAF6 in the rat macrophage cell line NR8383 and rat liver kupffer cells were studied in vitro. The in vivo effect of miR-146a and miR-146b on small-for-size liver graft injury was studied by the tail vein injection of miR-146a mimics and miR-146b mimics. Results The levels of miR-146a and miR-146b decreased with a small-for-size liver graft. MiR-146a and miR-146b inhibited IRAK1 and TRAF6 expression by binding to the 3′ UTR of IRAK1 or TRAF6, respectively, in the rat macrophage cell line NR8383. The administration of miR-146a mimics and miR-146b mimics prevented liver graft injury in small-for-size liver graft injury via the inactivation of IRAK1 and TRAF6 in vivo. Conclusions miR-146a and miR-146b prevent liver injury in small-for-size liver graft injury via the inactivation of IRAK1 and TRAF6. [ABSTRACT FROM AUTHOR]