Study On Neurotoxicity Effects Of Joint Exposure To Formaldehyde And Trichloroethylene In Mice

Objective:The decoration of indoor air pollution has resulted series of health problems which is closely related to our lives, has become a hot spot in today’s society. There are many different kinds and sources of indoor decoration pollution.This study aimed to explore the neurotoxicity effects of formaldehyde and trichloroethylene in mice, and determine the type of the joint action. Not only to providing experimental basis for the future related research, but also to the theory reference for better health standard.Methods:Using Morris water maze test sieve out108Kunming mice (healthy and clean level), and then divide male and female mice into A, B two groups,3X3factorial design was used in the experiment, The mice of each group were randomly assigned into9groups. Poisonous dose is divided into:the control group (inhaled clean air), formaldehyde group (1,5mg/m3) trichloroethylene group (1000,5000mg/m3), combined group (1mg+1000mg/m3,5mg+5000mg/m3;1mg+5000mg/m3;5mg+1000mg/m3).The test used static inhaling type. Two hours per day and last for14days. On the15th day, their behaviors of learning memory were tested by Morris water maze and open field test (OFT). At the end, executed the mice, and separated brain tissue into cortex and hippocampus. Which hippocampal tissues were used to detect cell apoptosis rate, the cortical part is used to idetermine the oxidation index of MDA and glutathione GSH’s content, the activity of NOS and SOD.Results:1. Formaldehyde and trichloroethylene exposure could reduce the ability of learning and memory in mice:(1) Morris water maze test:in space training, with the time of training’s increasing, the escape latency showed a trend of decrease, there is a high degree of correlation between5days’ repeated measurement results (P<0.001). The escape latency of all groups increased as the exposure dose increased, and the combined group is more obviously.Training days, the influence on escape latency of formaldehyde and trichloroethylene were statistically significant (P0.001), and there is interaction effect on escape latency in mice of the two toxicant (P<0.05). In space exploration experiment, compared with the control group, the first time of crossing the platform presented an ascend tendency. In each dose group, with the increase of the exposure dose.the time spent in target quadrant showing a decease trend.the percentage of swimming distance in target quadrant presented a descend tendency, and high dose group is the most obviously in all groups. The differences above have statistical significance (P<0.05). There was interaction between formaldehyde and trichloroethylene in the time of finding the platform and the percentage of swimming distance in target quadrant (P<0.05). Through the comparison of male and female mice, there are few differences in the individual groups.(2) Open-field test:Comparing with control group, with the exposure does of formaldehyde and trichloroethylene’s increasing, the times of standing showed a trend of decrease, the activity in central and the percentage of central distance in total distance presented a ascend tendency. There have a synergy effect between the two toxicants. In each exposure dose of male and female mice, the time spent in central only in the high and low dose group of trichloroethylene show a significant difference (P<0.05), the percentage of central distance in total distance have difference in formaldehyde low dose group (P<0.05), while the the number of standing in Open-field (OF) have no statistically significant difference in female and male mice.2. Formaldehyde and trichloroethylene can cause brain lipid peroxidation:The twe toxicant could increase the brain tissue of MDA content and NOS activity, and decrease SOD activity and GSH content. Comparing with control group, most of the infected group have statistical significance (P<0.05) except trichlorethylene low-dose group. There have interactions between formaldehyde and trichloroethylene.Except for SOD indicators, NOS, MDA and GSH in the combined exposure of formaldehyde and trichlorethylene showed synergistic effects. And in each dose, female, male mice have differences in most dose levels except control group.3. Formaldehyde and trichlorethylene exposure can increased apoptosis rate of hippocampus in mice:Comparing with the control group, with the twe toxicant’s exposure dose increasing, the brain cells apoptosis rate showed a trend of increase in mice and the differences were statistically significant (P<0.001). Combined exposure on apoptosis in mice’s hippocampus have interaction (P<0.001), and showed synergy. The combined effect showed a stronger toxic effect. Through comparing with the female and male, there are differences in most dose levels between the two, except for control group.Conclusion:Formaldehyde and trichloroethylene have neurotoxic effect in mice, and they can degrade the learning and memory abilities, reduce the activity of Alertness, excitability and etc. cause brain tissue of lipid peroxidation in mice; also increased apoptosis rate of hippocampus. There are interactionsins in their combination of nervous behavior, brain tissue lipid peroxidation and the effect of brain cells apoptosis, the joint toxicity effect showed synergy.