The hepatoprotective effects of Sedum sarmentosum extract and its isolated major constituent through Nrf2 activation and NF-κB inhibition

Abstract

BackgroundSedum sarmentosum, which is recorded in Chinese Pharmacopoeia, has been applied clinically to treat liver and gallbladder diseases. PurposeThis study aimed to explore the hepatoprotective effect of S. sarmentosum less polar extract (SSE) against ANIT-induced liver injury in rats, and the protective activity and mechanism of one major constituent isolated from this extract on D-GalN-induced human hepatic QSG7701 cell damage. MethodsRats were divided into groups and then administrated intragastrically with SSE at doses of 100, 200 and 400 mg/kg for 7 days. They were modeled in the experiments with ANIT (70 mg/kg) to induce liver injury after the sixth day administration. The levels of serum biochemical markers ALT, AST, ALP, GGT/γ-GT, DBiL, TBiL, ALB, TP, and bile flow rate, as well as the histopathology of the liver tissue were used as indices of liver damage and measured. The inflammatory response and oxidative stress were thought to be key contributors to ANIT-induced liver injury in rats. Therefore, the inflammatory mediators (TNF-α, IFN-γ, IL-4) and oxidative stress (ROS, SOD, GSH-PX) were measured in the serum and liver homogenates, respectively. Next, phytochemical research was performed to produce the main component, and the isolated compound was evaluated for its hepatoprotective activity against QSG7701 cell injured by D-GalN through the measurement of cell viabilities, ALT, AST, IL-1β, TNF-α, IL-6, ROS, GSH-PX and SOD productions. Furthermore, the protein expression of the Nrf2 and NF-κB pathways were analyzed by western blotting. ResultsSSE had an obvious effect on the decreases of ALT, AST, ALP, GGT/γ-GT, DBiL and TBiL levels, the increases of ALB and TP levels in serum, and the ANIT-induced deceleration in bile flow for liver injury. Meanwhile, SSE pretreatment alleviated ANIT-induced liver pathological injuries exhibited by HE stain of the liver. Moreover, SSE significantly suppressed levels of pro-inflammatory cytokines TNF-α and IFN-γ, and elevated level of anti-inflammatory cytokine IL-4 in serum. SSE also attenuated oxidative stress by reducing ROS level and by enhancing antioxidative enzymes (SOD and GSH-PX) activities after ANIT administration in liver tissue. Further, the major compound shown in HPLC was isolated from SSE. Its structure was identified by the spectroscopic data analysis and comparison with literature values. The principal constituent had potent protective effect on D-GalN-induced QSG7701 cells damage in a dose dependent manner with survival rates of 58.2% and 69.5% at 10 μM and 20 μM, respectively. Its cytoprotective effect was associated with the reduction of ALT, AST, IL-1β, TNF-α, IL-6 and ROS levels, and the elevation of GSH-PX and SOD productions in QSG7701 cells induced by D-GalN. Western blotting showed that this compound enhanced the expression of Nrf2, HO1, NQO1 and GCLC, and inhibited D-GalN-induced IκBα and NF-κB p65 phosphorylation. ConclusionsCurrent study showed that SSE treatment exerted a protective effect on ANIT-induced liver injury. The main compound δ-amyrone isolated from the extract was characterized as the effective component with hepatoprotective activity by promoting Nrf2 antioxidant defense and suppressing NF-κB inflammatory response.