Shenqi formula delayed Alzheimer's disease-like symptoms by skn-1 pathway in Caernorhabditis elegans

Abstract

Ethnopharmacological relevance: Shenqi formula is composed of Codonopsis pilosula (Cp) and Lycium barbarum (Lb), and it is traditionally used for promoting qi and nourishing the spleen, liver and kidney. Cp and Lb have been reported to improve cognitive performance in APP/PS1 mice, prevent the accumulation of Aβ, and reduce the neurotoxicity of Aβ to achieve the anti-Alzheimer's disease (AD) effect.

Aim of the study: Shenqi formula was explored the therapeutic effect on Caenorhabditis elegans AD pathological model and the underlying mechanism of action.

Materials and methods: Paralysis assay and serotonin sensitivity assay was used to detect whether Shenqi formula can alleviate AD paralysis phenotype, and then DPPH, ABTS, NBT and Fenton methods were applied to investigate the scavenging capacity to free radical, ROS, ·O₂^- and ·OH of Shenqi formula in vitro. H₂DCF-DA and MitoSOX™ Red were employed to measure ROS and ^.O₂^- accumulation, respectively. RNAi was used to knock down the expression of skn-1 and daf-16 related to oxidative stress resistance signalling pathway. Fluorescence microscopy was used to record the expression of SOD-3::GFP, GST-4::GFP, SOD-1::YFP, and the nuclear translocation of SKN-1 and DAF-16. Western blot assay was carried out to test Aβ monomers and oligomers.

Results: Shenqi formula delayed the AD-like pathological characteristics in C. elegans, and the complete Shenqi formula was more effective than Cp or Lb alone. The effect of Shenqi formula on delaying worm paralysis was partially eliminated by skn-1 RNAi, but not daf-16 RNAi. Shenqi formula significantly inhibited the abnormal deposition of Aβ protein, decreased Aβ protein monomers and oligomers. It increased the expressions of gst-4, sod-1, and sod-3 similar to paraquat, companied by rise then fall of ROS and ^.O₂^- in AD worms.

Conclusions: Shenqi formula at least partially depended on SKN-1 signalling pathway to exert its anti-AD effect, and it is potential to be used as a kind of health food to prevent the progress of AD.

Keywords: AD; Anti-oxidative stress; C. elegans; Pro-oxidant agent; SKN-1; Shenqi formula.