Effects of Panax notoginseng saponins on liver graft rejection in rats and the mechanisms

Abstract

To investigate the effects of Panax notoginseng saponins (PNS) on the functional status of Kupffer cells (KCs) and immune environment after liver transplantation and explore the possible mechanisms. KCs were isolated from rats and assessed for phagocytic activity and viability using ink and Trypan blue staining. The cells were exposed to lipopolysaccharide (LPS) alone or in combination with PNS treatment at 0, 10 or 20 μmol/L. The expressions of the inflammatory factors and the oxidative stress products in the cells and the supernatant were assayed with Western blotting and ELISA; the expression of CD206 was detected using immunofluorescence assay, and the expressions of NF-κB and Keap1-Nrf2-ARE pathway proteins were detected using Western blotting. We established an orthotopic liver transplantation (LT) model in rats and assessed the effect of 200 mg/kg PNS on the graft function, inflammatory factors, pathology of the liver tissue, hepatocyte apoptosis and survival time of the rats in comparison with those in rats receiving a sham operation or PBS treatment following LT. Treatment with PNS significantly lowered the levels of inflammatory factors and oxidative stress products and increased the levels of interleukin-10 (IL-10) and SOD in a concentration-dependent manner in the KCs (P < 0.05). Immunofluorescence assay showed that PNS treatment obviously increased the expression of CD206 in the KCs. PNS treatment also significantly reduced the expressions of IRAK4, p-IKKα, p-IκBα, p-p65 and Keap1 proteins and increased the expression levels of Nrf2 and ARE proteins in the KCs (P < 0.05). In the rat models of LT, PNS treatment significantly improved the liver graft function, lowered the expression of the pro-inflammatory factors, and reduced hepatocyte apoptosis as compared with PBS treatment. PNS treatment obviously alleviated pathological changes in the liver graft and significantly prolonged the survival time of the rats following LT (P < 0.05). In addition, injection of GdCl3 to block KC function resulted in severe acute graft rejection in the rats regardless of PNS treatment (P > 0.05). PNS can reduce inflammatory response and oxidative stress in activated KCs by inhibiting NF-κB and Keap1-Nrf2-ARE pathways and promote the polarization of KCs into M2 phenotype to prolong the survival time of rats after LT.