Arsenic induces transgenerational behavior disorders in Caenorhabditis elegans and its underlying mechanisms.

The present study aimed to identify the effects of arsenic on behaviors in Caenorhabditis elegans (C. elegans) and the transgenerational effects. The synchronized C. elegans (P generation) were exposed to 0, 0.2, 1.0, and 5.0 mM NaAsO2 and the subsequent generations (F1 and F2) were maintained on fresh nematode growth medium (NGM). The behaviors and growth were recorded at 0, 12, 24, 36, 48, 60, and 72 h post synchronization. The results demonstrated that arsenic affected various indicators regarding the behavior (head thrash, body bend, movement speed, wavelength, amplitude and so on) and in general the effects started to accumulate from 24 h and lasted throughout the exposure. The behavior impairments were transgenerational with varying patterns, amongst the head thrash and body bend responded most sensitively though the responses gradually declined across generations. Arsenic exposure inhibited the growth (body length, body width, and body area) in P C. elegans from 24 h to 60 h, however there was no difference between treatments groups and the control at 72 h. Arsenic led to a dose-dependent degeneration of dopaminergic neurons in C. elegans, and inhibition of BAS-1 and CAT-2 expressions. The expressions of GCS-1, GSS-1, and SKN-1 were induced by arsenic exposure. Overall, chronic arsenic exposure impaired the behaviors and there were transgenerational effects. The head thrash and body bend responded most sensitively. Arsenic induced behavioral disorders might be attributed to degeneration of dopaminergic neurons which was associated with oxidative stress.

Chlorpyrifos exposure reduces reproductive capacity owing to a damaging effect on gametogenesis in the nematode Caenorhabditis elegans.

Previous studies have revealed that chlorpyrifos exposure adversely affects the reproductive capacity of male rodents. The present study investigated the reproductive toxicity of chlorpyrifos exposure and possible related mechanisms using the nematode Caenorhabditis elegans. L4 nematode larvae were exposed to chlorpyrifos at concentrations of 0.003, 0.03, 0.3 and 3.0 mg l(-1) for different durations. In addition to decreased brood size, reduced spermatid size, increased percentage of abnormal spermatids, suppressed spermatid activation and motility of sperm, damaged oocyte morphology, increased numbers of apoptotic cells and unfertilized oocytes were observed in nematodes exposed to various concentrations of chlorpyrifos. Moreover, expression patterns of the genes spe-10, spe-15, fer-1, prg-1, glp-1, mlh-1, cyb-3, ced-3, ced-4 and ced-9 (which are associated with spermatid size, spermatid activation and morphology, oocyte morphology, oocyte function, and apoptosis) were altered after chlorpyrifos exposure. Therefore, chlorpyrifos exposure may adversely affect fertility in nematodes by influencing both spermatogenesis and oogenesis. Alterations in the expression patterns of genes involved in gametogenesis may explain the corresponding changes in gametogenesis in nematodes exposed to chlorpyrifos. Hence, the model organism Caenorhabditis elegans is recommended for assessment of reproductive toxicity relating to gametogenesis.

Evaluation of pesticide toxicities with differing mechanisms using Caenorhabditis elegans.

The aim of this study was to (1) determine whether model organism Caenorhabditis elegans was sensitive to pesticides at the maximum concentration limits regulated by national agency standards, and (2) examine the multi-biological toxicities occurring as a result of exposure to pesticides. Five pesticides, namely, chlorpyrifos, imibacloprid, buprofezin, cyhalothrin, and glyphosate, with four different mechanisms of action were selected for the investigation. In accordance with national agency requirements, 4 exposed groups were used for each tested pesticide with the concentration scales ranging from 1.0 x 10(-3) to 1 mg/L. L4 larvae were exposed for 24 and 72 h, respectively. Endpoints of locomotion, propagation, and development were selected for the assay as parameters of toxicity. After exposure for 24 h, both the body bend frequency and head thrash frequency of nematodes exposed to chlorpyrifos, imibacloprid, and cyhalothrin decreased in a concentration-dependent manner, and there were significant differences between exposed groups at maximum concentration level (MCL) compared to control. The generation time of nematodes exposed to buprofezin 24 h significantly increased in a concentration-dependent manner in the highest exposed group. When exposed for 72 h, the body bend frequency and head thrash frequency of nematodes exposed to cyhalothrin markedly decreased at MCL. The generation time and brood size of nematodes exposed to buprofezin were reduced in a concentration-dependent manner. The behavior of nematodes was sensitive to pesticides with neurotoxic properties, while pesticides affecting insect growth modified the reproductive system. The effects of pesticides on nematodes exposed for 24 h appeared more sensitive than with exposure for 72 h. Caenorhabditis elegans may thus be used for assessing the adverse effects of pesticide residues in aquatic environment.