Astragalus membranaceus Root Concentration and Exposure Time: Role in Heat Stress Diminution in C. elegans

Astragalus membranaceus (AM) root modulates polyglutamine aggregation in adult C. elegans via the DAF-16/IIS pathway. The effects of AM root on stress response in larval C. elegans through the HSF-1/IIS pathway are unknown. Herein, this study aims to elucidate AM root effects on heat-induced paralysis of first larval stage (L1) C. elegans during short-term and long-term heat shock. Wild-type (N2) C. elegans (n=100 per plate) were synchronized to the L1 stage to eliminate age-based variability, exposed to 0 mg/mL (control) or 2 mg/mL, 4 mg/mL, or 8 mg/mL AM root extract (experimental), and heat shocked at 37°C for either ten or twenty minutes. A harsh touch sensitivity assay was performed, and C. elegans responses were recorded. Paralysis rate after ten-minute heat shock decreased as AM root extract concentration increased, indicating that AM root may enhance HSF-1 activity in L1 C. elegans after short-term stress. Unexpectedly, longer periods of heat shock resulted in a lower percentage of worms becoming paralyzed in the control condition, possibly due to habituation to stress. Exposure to low concentrations of AM root extract promoted paralysis during long-term stress (p<0.05), possibly due to AM root interference in the habituation of C. elegans. Further investigations will be necessary to explore the role of AM root in C. elegans habituation and in other laboratory organisms. Deeper insight into molecular pathways altered by AM root during stress responses will not only help to elucidate such pathways in C. elegans, but will also have implications in the modulation of stress-response pathways in humans.