The hepatoprotective effects of Salvia plebeia R. Br. extract in zebrafish (Danio rerio)

Salvia plebeia R. Br. is a traditional Chinese medicinal herb that has been widely used for the treatment of many inflammatory diseases such as hepatitis. However, the underlying molecular mechanism about the hepatoprotective effects of S. plebeia remains largely unknown. Here, we investigated the antioxidant activities and anti-inflammatory effects of ethanol extracts of S. plebeia (SPEE) in the zebrafish model. Firstly, we determined the chemical compositions of SPEE and identified three major constituents by using GC-MS analysis. After that, SPEE exhibited significantly antioxidant properties in the LPS-induced zebrafish embryos, and the enzyme activities of ROS, CAT and SOD were obviously inhibited in a dose-dependent manner. Secondly, SPEE greatly reduced fat vacuoles (HE staining), lipid accumulation (Oil O staining) and hepatocyte fibrosis (Gemori staining) in the thioacetamide (TAA)-induced hepatocyte injury of adult zebrafish. Meanwhile, the NO contents and lipid metabolism-related genes were substantially down-regulated after SPEE exposure. Thirdly, we used RNA-Seq analysis to identify the differentially expressed genes (DEGs) after SPEE exposure in adult zebrafish liver. The results showed that 1289 DEGs including 558 up-regulated and 731 down-regulated were identified between the TAA + SPEE and TAA groups. KEGG pathway and GO functional analysis revealed that steroid biosynthesis, oxidation-reduction and innate immunity were significantly enriched. Mechanistically, SPEE can considerably reduce the cell apoptosis of hepatocytes and promote the translocation of Nrf2 protein from the nucleus to the cytoplasm in TAA-induced zebrafish. Moreover, SPEE can modulate various inflammatory cytokines and immune genes both in the control and H₂O₂-stimulated conditions. The pro-inflammatory cytokines such as IL-1β and TNF-α was markedly up-regulated but the anti-inflammatory cytokines such as TGF-β was greatly down-regulated after SPEE treatment. In addition, some key genes in the TLR signaling were also activated in the H₂O₂-stimulated conditions. In summary, our results suggested that SPEE had an important role in the antioxidant and anti-inflammatory effects in zebrafish. Some of the components identified in this study may be served as potential sources of new hepatoprotective compounds for the treatment of inflammatory diseases.