Acrylamide Exposure Induced Locomotor Defects And Neurotoxicity In Caenorhabditis Elegans

Acrylamide (AA) is a common industrial raw material; however it was firstly detected in fried starchy foods in 2002, in which its content was higher than the maximal limit of drinking water for more than 500 times. In recent years, the possible health risks and biological toxicity of acrylamide have been widely concerned. Previous studies have shown that acrylamide presents neurotoxicity and genotoxicity; however chronic effects of acrylamide on the nervous system and their mechanisms have not been fully elucidated. In Caenorhabditis elegans, this study aims to illustrate the neurotoxic effect of acrylamide and its potential mechanisms on the whole animal level, neuron level and the related gene and protein level, in order to provide new evidences for revealing the neurotoxicity of acrylamide.After assay for LC50S, L3-stage wild-type (N2) worms were respectively exposed to 3,30, or 300 mg/L acrylamide for 48 h. Then multi-indexes of worms were measured including growth, reproduction, embryo hatching and other aspects. Using WormLab software, changes in basic motion behaviors, crawling movement characteristics and the chemotaxis learning behavior were respectively recorded and analyzed for illustrating its neurotoxicity. Using transgenic strains, morphological changes of dopamine neurons were measured for checking the neural degeneration; expression of a-synuclein and relative genes were also assayed after exposure.The main results are as followings:1. Acrylamide presented obvious lethal effects to C. elegans, the median lethal dose (LC50) were respectively 2296.8,897.8, or 243.1 mg/L for 24,48 or 72 h exposure.48 h exposure to 3 mg/L or higher concentration acrylamide significantly inhibited the growth of worms; body length and width were significantly shortened. After exposure, numbers of worm eggs were significantly decreased, which shows the reproductive toxicity of acrylamide. Exposure to worm embryos resulted in the significant inhibition of hatching rates, and caused growth delay, dead embryo or cracking, which shows the developmental toxicity of acrylamide.2. Acrylamide exposure resulted in significant decrease of spontaneous movement of C. elegans, including head thrashes, body bends and pharyngeal pumping frequency. After exposure to 30 mg/L acrylamide, the chemotaxis index was significantly increased in comparison to the control group, which shows the decrease of learning ability of worms. After exposure, colony contact rates were significantly decreased, which indicates the reducing of active exploration movement of nematode. Compared to control animals, crawling distance of the exposed worms were shortened; crawling speed peak was decreased; the peak of bending angles become smaller, which shows the reducing of crawling ability, unbalance disorders of body and other characteristics of behavioral deficits of nematodes.3. By fluorescence detection in transgenic animals, we found that acrylamide exposure showed no obvious influence on the synaptic vesicle protein expression in the nervous system of worms. In contrast,250 mg/L or higher concentration of acrylamide exposure caused decreasing expression of Pdat-1; the dopaminergic neurons showed degenerative characteristics including atrophy of cell body and lose of dendrite. We further found that acrylamide exposure resulted in up-regulation of unc-54 gene and acceleration of a-synuclein protein aggregation.These results indicate that:1. Chronic exposure to acrylamide significantly affects the growth and development of C. elegans, and reduces reproductive capacity, which indicates that acrylamide shows extensive health hazards and risks.2. Chronic exposure to acrylamide caused decrease of the spontaneous movement diminished, and reducing of predation ability and chemotaxis learning ability. After acrylamide exposure, crawling speeds of worms were decreased; bending angles become small and obtuse which show balance ability was weakened. Together, these results indicate that acrylamide exposure can induce Parkinsonian-like movement impairment including bradykinesia, hypokinesia and unbalance.3. Cellular and molecular level results indicates that acrylamide exposure can cause degeneration of dopaminergic neurons and promote a-synuclein protein aggregation, and thus trigger dysfunction of neuromotor modulation system, and eventually lead to behavior deficits of the animal. Acrylamide-induced locomotor defects were closely associated with neurotoxicity to dopaminergic neurons.In the present study, we investigated the neurotoxicity of acrylamide in C. elegans in detail. It was found that chronic exposure to acrylamide can result in Parkinsonian-like locomotor defects. We found that acrylamide induced aggregation of a-synuclein protein, and caused a selective degeneration of dopaminergic neurons, which induced dysfunction of movement regulation in Parkinsonian-like locomotor defects. With diversification of diets, acrylamide from food processing may cause health risks, which should be widely concerned. Our study suggests that acrylamide may be associated with Parkinson’s disease. Along with the increasing trend of population aging in China, prevention and treatment of Parkinson’s disease has become an important social issue. Our results suggest the neurotoxicity risk of long-term intake of acrylamide, which provides an important reference for prevention of Parkinson’s disease.