miR-449a ameliorates acute rejection after liver transplantation via targeting procollagen-lysine1,2-oxoglutarate5-dioxygenase 1 in macrophages.

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.

Fisetin mitigates hepatic ischemia-reperfusion injury by regulating GSK3ß/AMPK/NLRP3 inflammasome pathway.

BACKGROUND: Hepatic ischemia-reperfusion (I/R) injury (IRI) represents a crucial challenge in liver transplantation. Fisetin has anti-inflammatory, anti-aging and anti-oxidative properties. This study aimed to examine whether fisetin mitigates hepatic IRI and examine its underlying mechanisms. METHODS: Sham or warm hepatic I/R operated mice were pretreated with fisetin (5, 10 or 20 mg/kg). Hepatic histological assessments, TUNEL assays and serum aminotransferase measurements were performed. An in vitro hypoxia/reoxygenation (H/R) model using RAW264.7 macrophages pretreated with fisetin (2.5, 5 or 10 µmol/L) was also used. Serum and cell supernatant concentrations of interleukin-1ß (IL-1ß), IL-18 and tumor necrosis factor-α (TNF-α) were determined by enzyme-linked immunosorbent assay (ELISA). Protein levels of p-GSK3ß, p-AMPK and NLR family pyrin domain-containing 3 (NLRP3)-associated proteins were detected by Western blotting. RESULTS: Compared with the I/R group, fisetin pretreatment reduced pathological liver damage, serum aminotransferase levels, serum concentrations of IL-1ß, IL-18 and TNF-α in the murine IRI model. Fisetin also reduced the expression of NLRP3 inflammasome-associated proteins (NLRP3, cleaved caspase-1, IL-1ß and IL-18) in I/R-operated liver. The experiments in vitro showed that fisetin decreased the release of IL-1ß, IL-18 and TNF-α, and reduced the expression of NLRP3 inflammasome-associated proteins in H/R-treated RAW264.7 cells. Moreover, fisetin increased the expressions of p-GSK3ß and p-AMPK in both models, indicating that its anti-inflammatory effects were dependent on GSK3ß/AMPK signaling. The anti-inflammatory effects of fisetin were partially inhibited by the AMPK specific inhibitor compound C. CONCLUSIONS: Fisetin showed protective effects against hepatic IRI, countering inflammatory responses through mediating the GSK3ß/AMPK/NLRP3 inflammasome pathway.