Hepatoprotective effect of syringin combined with costunolide against LPS-induced acute liver injury in L-02 cells via Rac1/AKT/NF-κB signaling pathway

Acute liver injury (ALI) leads to abnormal liver function and damage to liver cells. Syringin (syr) and costunolide (cos) are the major extracts from Dolomiaea souliei (Franch.) C.Shih (D. souliei), showing diverse biological functions in various biological processes. We explored the underlying hepatoprotective effects of syr+cos against LPS-induced ALI. Cell viability and proliferation were assessed using an MTT assay and immunofluorescence staining. Flow cytometry analysis was used to detect cell cycle distribution and apoptosis. ELISA was utilized to measure liver function and antioxidant stress indexes. qRT-PCR and western blotting was performed to determine mRNA and protein levels respectively. Using shRNA approach to Rac1 analyzed transcriptional targets. The results showed that syr+cos promoted L-02 cell proliferation, inhibiting the cell apoptosis and blocking cell cycle in G1 and G2/M phase. Syr+cos decreased the production of ALT, AST, LDH, MDA and ROS while increased SOD and CAT activities. Pretreated with syr+cos may decrease expressions of caspase-3,7,9, NF-κB, TNF-α proteins, Cyclin B, CDK1 and p-IκB proteins while p-IκB increased. Silencing of Rac-1 may protect the liver by increasing AKT, S473, T308 and reducing p-AKT proteins. Syr+cos exhibits anti-ALI activity via Rac1/AKT/NF-κB signaling pathway which might act as an effective candidate drug for the treatment of ALI.