The Effects of Astragalus treatment on Caenorhabditis elegans stress and antimicrobial response pathways and longevity

Abstract

The Chinese medicinal herb, Astragalus, has been shown to contain immune stimulating polysaccharides; treatment with Astragalus has been shown to increase killer cell activity and tumor cell lysis rates. In this study, C. elegans were used to measure the effects of Astragalus treatment on stress and antimicrobial response pathways. C. elegans do not have a complex adaptive immune system including T cells and B cells, however, they do have a robust innate immune system involving inflammation, antimicrobial peptides, and pathogen recognition receptors. Astragalus treatment was given to C. elegans in increasing concentrations (0 μg/ml, 100 μg/ml, 200 μg/ml) through ingestion to observe its effects on the worm's lifespan as well as on the stress and antimicrobial response pathways. We hypothesized that an increase in concentration of the Astragalus treatment would produce an increase in C. elegan's lifespan along with an increase in transcript levels of intermediate genes involved in the worm's stress and antimicrobial response pathways. Survival assays performed in triplicate indicate that Astragalus treatment produces no significant increase in lifespan. To observe the stress response pathway, worms exposed to the Astragalus treatment for twenty‐four hours were heat shocked for two hours. RNA extraction was performed and transcript levels of mek‐1 and jkk‐1 were measured by qRT‐PCR. Stress levels were also examined using a wild type worm strain treated with DCFDA to examine expression of reactive oxygen species (ROS) and a CL2070 worm strain to examine expression of HSP‐16.2 GFP in the heat‐shock treated worms with and without prior Astragalus exposure. Corrected Total Worm Fluorescence (CTWF) values were calculated with Image J software for both worm strains and it was found that Astragalus treatment caused no significant effect on either ROS or HSP‐16.2 expression levels. To observe the antimicrobial response pathway, worms exposed to the Astragalus treatment for 24 hours were then exposed to Pseudomonas bacteria for four hours. RNA extraction was performed and transcript levels of mek‐1 and sek‐1 were measured with qRT‐PCR. A wild‐type strain of worms given this treatment were also treated with DCFDA to examine expression of ROS levels and CTWF values again showed Astragalus treatment had no significant effect on the worms, but did show an upward trend with increasing concentration of treatment. The results of both qRT‐PCR studies are inconclusive but an upward trend in transcript level to concentration of treatment can be observed in each as well. In the future, more trials and RNA extractions must be performed to produce viable data and conclusive results as to whether Astragalus has a significant effect on C. elegan's stress and antimicrobial response pathways. This work was supported by APS IOSP Undergraduate Research Fellowship.Support or Funding InformationAPS IOSP Undergraduate Research FellowshipThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.