Study On Neurotoxicity Of Formaldehyde In Mice

Objective: In recent years, with the development of society and the continuous improvement of people's living standards, indoor decorating becomes the trend of fashion, finally the condition of indoor air pollution becomes increasingly serious. As the numerous application of FA resin adhesives and urea foamed plastics, formaldehyde becomes the main pollutants of indoor air. Formaldehyde can cause numerous toxic actions to exposed population, create great harm to human, including the effects on irritating to eyes and respiratory tract,sensitization,immunotoxicity,genetoxic,reproduction toxicity,neurotoxicity and so on. There are less reports on the neurotoxic effect at present, and the study focused primarily on the investigation of the exposed population in the past. This study is to explore the neurotoxicity and its mechanism in mice exposed to formaldehyde, to provide scientific basis for the synthetic evaluation of the security of formaldehyde, and provide theory references for the researches on indoor pollution.Methods: Four groups of Kunming mice were exposed to different concentrations(0 mg/m3,1mg/m3,3mg/m3,5mg/m3) of formaldehyde, 2h/day, for 14 days consecutively. 12 mice for each group, and 6 mice for each closet. Selected 6 mice of each group, their behavior of learning and memory were detected by step-down test,passive avoidance test and Morris water maze experiment. Then the rest of mice were killed by infusing the heart with ice normal saline, to ensure that there was no blood in the body of mouse, then took out of the brain quickly. At the end, the pathological changes of brain tissue and the apoptosis rate of brain cells could be observed, the activities of SOD,the contents of MDA in brains could be determined and DNA damages in brain cells could be observed.Results: 1,Formaldehyde could degrade the learning and memory abilities of mice. (1)Step-down test showed that, mice in groups of 3mg/m3 and 5mg/m3 formaldehyde exposure made notable errors(P<0.05), and the incubation period significantly reduced(P<0.05); (2)Passive avoidance test showed the same consequence as the Step-down test did; (3)Morris water maze test indicated that the incubation period of finding platform significantly extended in group of 5mg/m3 formaldehyde exposure(P<0.05), there was no significant difference of the space memory ability in each group(P>0.05). 2,Some pathological damages existed in brain tissues of mice exposed to formaldehyde, and the damages became obviously with the increasing of doses. 3,A notable decline tendency of the activities of SOD was showed with increasing of doses, there was significant difference in 3mg/m3 and 5mg/m3 formaldehyde inhalation groups compared with the control group(P<0.05); The contents of MDA were significantly increased with increasing of doses, 3mg/m3 and 5mg/m3 formaldehyde inhalation groups showed notable difference with the control group(P<0.05). 4,Formaldehyde could cause damages to brain cells, the comet assay indicated that the length of comet tail,Tail DNA% and Tail moment were significantly increased in each formaldehyde inhaling group(P<0.01). 5,Formaldehyde could induce apoptosis of brain cells, the rate of apoptosis were increased with increasing of doses, but there was no significantly difference between each group(P>0.05).Conclusion: Formaldehyde had neurotoxicity in mice, it could degrade the learning and memory abilities of mice, induce pathological damages in brains of mice, result in lipid peroxide in brains and the DNA damage in brain cells of mice, raise the apoptosis rate of brain cells. Lipid peroxide and DNA damage might be the important mechanisms of central nervous system function damage in mice induced by formaldehyde.