ABSTRACT
Acute rejection (AR) is an important factor that leads to poor prognosis after liver transplantation (LT). Macrophage M1-polarization is an important mechanism in AR development. MicroRNAs play vital roles in disease regulation; however, their effects on macrophages and AR remain unclear. In this study, rat models of AR were established following LT, and macrophages and peripheral blood mononuclear cells were isolated from rats and humans, respectively. We found miR-449a expression to be significantly reduced in macrophages and peripheral blood mononuclear cells. Overexpression of miR-449a not only inhibited the M1-polarization of macrophages in vitro but also improved the AR of transplant in vivo. The mechanism involved inhibiting the noncanonical nuclear factor-kappaB (NF-κB) pathway. We identified procollagen-lysine1,2-oxoglutarate5-dioxygenase 1 (PLOD1) as a target gene of miR-449a, which could reverse miR-449a's inhibition of macrophage M1-polarization, amelioration of AR, and inhibition of the NF-κB pathway. Overall, miR-449a inhibited the NF-κB pathway in macrophages through PLOD1 and also inhibited the M1-polarization of macrophages, thus attenuating AR after LT. In conclusion, miR-449a and PLOD1 may be new targets for the prevention and mitigation of AR.
Subject(s)
Liver Transplantation , MicroRNAs , Animals , Humans , Rats , Leukocytes, Mononuclear/metabolism , Macrophages/metabolism , MicroRNAs/genetics , NF-kappa B/metabolism , Procollagen/metabolism , Procollagen/pharmacologyABSTRACT
Liver ischemia/reperfusion injury (IRI) is an inevitable pathological process exacerbating the occurrence of rejection in liver transplantation. At present, there is still a lack of sufficient cognition for the mechanism as well as effective clinical strategies. F-box/WD repeat-containing protein 5 (FBXW5), a key modulator of stress signalling, was recently reported to participate in hepatic immunity. However, the role of FBXW5 in liver IRI is still unclear. In the present study, we found expression of FBXW5 was increased in liver IRI both in vivo and in vitro. Inhibition of FBXW5 significantly alleviated both mitogen-activated protein kinase (MAPK) and inhibitor of nuclear factor kappa-B kinase (IKK) pathways, thus resulting in cytokine release, hepatic pathological injury and apoptosis. Over-expression of FBXW5 achieved an opposite effect. Investigations on the mechanism showed that FBXW5 intensified hepatic inflammation by promoting phosphorylation of ASK1, while blockade of TRAF6 could abolish this process. Moreover, reinforce of mTOR amplified the anti-inflammatory efficacy derived from inhibition of FBXW5, indicating the function of FBXW5/ASK1/TRAF6 axis in hepatic IRI might be relatively independent of mTOR-guided M2 polarization of Kupffer cell. Taken together, FBXW5 could be a key accelerator in liver IRI by enhancing activation of ASK1 in a TRAF6-dependent manner. The joint intervention towards both FBXW5 and mTOR might be a promising strategy to protect liver from IRI.
Subject(s)
F-Box Proteins/metabolism , Intracellular Signaling Peptides and Proteins/metabolism , MAP Kinase Kinase Kinase 5/metabolism , Reperfusion Injury/metabolism , Animals , Anti-Inflammatory Agents/chemistry , Anti-Inflammatory Agents/pharmacology , Apoptosis , Cytokines/metabolism , Enzyme Inhibitors/metabolism , F-Box Proteins/genetics , Gene Expression Regulation , Humans , Kupffer Cells , Liver , MAP Kinase Signaling System , Male , Mice , Mice, Inbred C57BL , Mitogen-Activated Protein Kinases/metabolism , Models, Animal , Phosphorylation , Phosphotransferases/antagonists & inhibitorsABSTRACT
Hepatic ischemia/reperfusion injury (IRI) is an inevitable pathological process in liver resection, shock and transplantation. However, the internal mechanism of hepatic IRI, including inflammatory transduction of multiple signaling pathways, is not fully understood. In the present study, we identified pleckstrin homology-like domain family member 1 (PHLDA1), suppressed by microRNA (miR)-194, as a critical intersection of dual inflammatory signals in hepatic IRI. PHLDA1 was upregulated in hepatic IRI with a concomitant downregulation of miR-194. Overexpression of miR-194 diminished PHLDA1 and inhibitors of the nuclear factor kappa-B kinase (IKK) pathway, thus leading to remission of hepatic pathological injury, apoptosis and release of cytokines. Further enrichment of PHLDA1 reversed the function of miR-194 both in vivo and in vitro. For an in-depth query, we verified PHLDA1 as a direct target of miR-194. Notably, inflammatory signal transduction of PHLDA1 was induced by activating TNF receptor-associated factor 6 (TRAF6), sequentially initiating IKK and mitogen-activated protein kinase (MAPK), both of which aggravate stress and inflammation in hepatic IRI. In conclusion, the miR-194/PHLDA1 axis was a key upstream regulator of IKK and MAPK in hepatic IRI. Targeting PHLDA1 might be a potential strategy for hepatic IRI therapy.
