A critical role of the Toll-like receptor(TLR) and its downstream molecules, including IL-1 receptor-associated kinase 1(IRAK1) and tumor necrosis factor receptor– associated factor 6(TRAF6), in the pathogenesis of liver ischemia/reperfusion (I/R) injury has been documented. Recently a microRNA, miR-146a, was identified as a potent negative regulator of the TLR signaling pathway. In this study, we investigated the role of miR-146a to attenuate TLR signaling and liver I/R injury in vivo and in vitro. miR-146a was decreased in mice Kupffer cells following hepatic I/R, whereas IRAK1 and TRAF6 increased. Overexpression of miR-146a directly decreased IRAK1 and TRAF6 expression and attenuated the release of proinflammatory cytokines through the inactivation of NF-κB P65 in hypoxia/reoxygenation (H/R)-induced macrophages, RAW264.7 cells. Knockdown experiments demonstrated that IRAK1 and TRAF6 are two potential targets for reducing the release of proinflammatory cytokines. Moreover, co-culture assays indicated that miR-146a decreases the apoptosis of hepatocytes after H/R. In vivo administration of Ago-miR-146a, a stable version of miR-146a in vivo, protected against liver injury in mice after I/R via inactivation of the TLR signaling pathway. We conclude that miR-146a ameliorates liver ischemia/reperfusion injury in vivo and hypoxia/reoxygenation injury in vitro by directly suppressing IRAK1 and TRAF6.

Ischemia-reperfusion and chronic injuries associated with small-for-size liver transplantation (SFSLT) impair the regeneration of liver graft and induce liver fibrosis. Mesenchymal stem cells (MSCs) can prevent the development of liver fibrosis, and hepatocyte growth factor (HGF) can also attenuate liver cirrhosis. Our previous studies have demonstrated that higher occurrence of liver fibrosis existed in rats post-SFSLT, and that implantation of HGF/MSCs, the human HGF (hHGF)-expressing MSCs, can improve liver regeneration, reduce mortality of rats, as well as have the potent antifibrotic effect in this SFSLT model. In the present study, we implanted HGF/MSCs into liver grafts via the portal vein and investigated their role in antifibrosis effect, using a 30% SFSLT rat model. Fibrosis indexes, including laminin (LN), hyaluronic acid (HA) levels in serum and hydroxyproline (Hyp) content in the liver grafts, the expression of transforming growth factor-beta1 (TGF-beta(1)), rat HGF (rHGF), alpha-smooth muscle actin (alpha-SMA) in hepatic stellate cells (HSCs), alanine aminotransferase (ALT), total bilirubin (BIL), and albumin (ALB) levels in serum, in rats in different treatment groups were assessed at different time points. We found that HGF/MSCs significantly inhibited the formation of liver fibrosis in rats undergoing SFSLT, while MSCs and HGF had synergistic effects in the process. The antifibrosis effect of HGF/MSCs may have contributed in modulating the activation and apoptosis of HSCs, elevating the rHGF expression level, and decreasing the TGF-beta(1) secretion of activated HSCs. These studies suggest that HGF/MSCs may be a novel therapeutic option for the treatment of liver fibrosis after SFSLT.

Background/Aims: The present study aimed to evaluate the effects as well as the underlying mechanisms of bone marrow-derived dendritic cells (BMDCs) and exosomes produced by BMDCs (DEXs) on hepatic ischemia-reperfusion (I/R) injury (IRI). Methods: Primary hepatocytes were isolated and used to mimic the liver IR microenvironment. BMDCs were induced and characterized both biochemically with a flow cytometer (FCM) and biophysically with a microscope. Then, we exposed BMDCs to the supernatants from primary hepatocytes and evaluated the maturation of BMDCs by FCM. BMDCs were systemically injected into mice before liver IR via the tail vein, and the therapeutic effects were evaluated. The serum levels of transaminases (aspartate aminotransferase (AST) and alanine aminotransferase (ALT), inflammatory cytokines, and histological changes were respectively examined by ELISA, RT-qPCR and microscopy. Furthermore, we isolated DEXs by ultracentrifugation, characterized DEXs by transmission electron microscopy (TEM) and nanosight tracking analysis (NTA) and western blotting (WB), and then we co-cultured BMDCs/DEXs and naïve T cells and performed FCM, ELISA and confocal imaging. Moreover, we injected DEXs into mice prior to liver IR via the tail vein and examined its therapeutic effects by microscopy and ELISA. Finally, inhibitors of HSP70 (cmHSP70.1), PI3K (BKM120) and mTOR (Rapamycin) were used to investigate the role of HSP70 and the PI3K/mTOR axis in the effects of DEXs on naïve T cells by WB and FCM. Results: Bone marrow cells were efficiently induced into dendritic cells (DCs) with typical DC characteristics. The supernatants from primary hepatocytes exposed to H/R upregulated DC maturation markers. After DC administration, liver IR injury was improved with histopathological scores and serum transaminases. Additionally, we found that the anti-inflammatory cytokines TGF-β, Foxp3 and interleukin (IL)-10 were upregulated and that IL-17 was downregulated. Furthermore, confocal imaging revealed that the uptake of H/R-DEXs by naïve T cells was greater than that of DEXs derived from the control or negative group of BMDCs, and this increase was correlated with a significantly greater degree of differentiation of Tregs and Th17 cells. Moreover, H/R-DEXs administration improved liver function in mice after IR. Finally, the inhibition of HSP70, PI3K and mTOR completely abolished the effect of DEXs on naïve T cells. Conclusion: These results demonstrated that BMDCs and DEXs could alleviate hepatic I/R injury via modulating the balance between Tregs and Th17 cells. DEXs transported HSP70 into naïve T cells and stimulated the PI3K/mTOR axis to modulate the balance between Tregs and Th17 cells and protect the liver from IR injury.