Elucidation of Ageing on Low Dose Exposure to Neurotoxicant Dichlorvos in Invertebrate Model Caenorhabditis Elegans

Abstract

Ageing is a complex process and understanding the factors affecting ageing and end points of study design are complicated and needs to be addressed through various strategies. In this study we have evaluated the ageing process on exposure to low doses of dichlorvos an organophosphorous insecticide used in controlling crop pests and also used in warfare agent and elucidated the various degrees of end points during the life time of an invertebrate model nematode Caenorhabditis elegans. This organism dwells in moist soils and it gets exposed to the various toxicants during its life time and this strategy has been modulated in lab conditions by exposing these worms to low doses without affecting the ability of feeding which is essential for survival. The low concentration residues of dichlorvos remain in the water, soil and sprayed areas. The concentrations of dichlorvos 250 and 500nM affected normal feeding as tested by exposing the worms and this induced cessation in feeding at 24h of experimentation. Hence the worms fed at normal rate at 5,100 and 200nM doses were selected for the evaluation of ageing parameters. Synchronized 2d old worm were used for the experiment. Control worms, the AChE activity increased up to 5d and then decreased after 10 d. A similar trend was also evident in worms exposed to dichlorvos concentration. The inhibition due to exposure to dichlorvos was evident and maximum inhibition was recorded on day 10. The organophosphorous insecticide inhibits acetylcholinesterase in irreversible manner hence low dosage exposure also inhibited the acetylcholinesterase levels on exposure. The range of inhibition on comparison between 100 and 200nM exposure to dichlorvos in relation to non exposed controls were clearly evident. Similarly, increase in carboxylesterase activity was evident in control worms up to day 5, beyond which the enzyme activity decreased drastically. Quantitation of lipofuscein ageing marker content was increasing with the exposure dose and duration of age and qualitative localization was evident. Our study clearly demonstrates the low dose affect of dichlorovs on ageing process quantitatively and qualitatively in model system.