Effect Of DI(2-Ethylhexyl) Phthalate On Neurobehavioral Development Of Mice And Its Molecular Mechanism

The plasticizer Di-(2-ethylhexyl) phthalate(DEHP) has been identified as environmental endocrine disruptor that possesses weak estrogenic and anti-androgenic activity. Currently, neurodevelopmental toxicity of DEHP is a lack of understanding though the developmental and reproductive toxicity of DEHP in wildlife and human has caused widespread concern. Perinatal DEHP exposure can interfere with the effect of estrogen on brain development through sex-specifically changing the activities of aromatase enzyme. In additionly,in early life exposure to low doses of DEHP the levels of serum testosterone decreased significantly in male rat. In vitro cultured hepatocytes DEHP shows the effect of estrogen. And in vitro studies have also shown before, according to different concentration, DEHP can activate Estrogen receptor(ER) and show the effects of estrogen, can adersely affect17beta-estradiol combination with Estrogen receptor(ER) shows anti-estrogen effect. However, sex hormones not only effect on the development of animals and humans, research has shown that pregnancy and neonatal period is particularly sensitive to estrogen-like activity material. Therefore, if the regulation of of sex hormones on brain development in pregnancy and early birth period interferes with endocrine disruptors may cause animals neurobehavioral abnormalities.In addition the hippocampus is not only the DEHP sensitive brain areas are also part of the brain is related to the neurobehavioral, Endogenous estrogen can affect the growth of the brain by effect of NMDA receptor. Previous studies of our laboratory found that perinatal period exposure to BPA which possesses weak estrogenic and anti-androgenic activity, injury rats learning and memory, increase anxiety behavior, with the decrease of hippocampal NMDA receptor expression. Recently, a large number of studies have shown that ERK signal transduction pathways (ERK1/2) participate in LTP formation in the brain and related to learning, memory and other cognitive function.Moreover, activation of ERK in area CA1in vitro through either the protein kinase C or protein kinase A pathways, biochemical events known to be involved in long term memory formation. Study shows the ER beta can adjust the activation of hippocampal synaptic plasticity and enhance cognitive function related to the hippocampus. ER beta knockout mice showed synaptic loss, LTP weaker and impair of memory. Estrogen receptor can be decreased by estrogen itself. Considering the glutamate neurotransmitter system closely related with anxiety and depression behavior. We conceive of DEHP exposure affect learning and memory, anxiety and depression behaviors may be associated with the hippocampus neurotransmitter glutamate system, ERK1/2signaling pathways may also be involved in the regulation of this process. It has been reported that T and its5a reduced metabolite, dihydrotestosterone, as well as the systemic administration of anabolic steroids reduce anxiety-like behavior in rodents. Administration of The AR antagonist flutamide to newborn male rat pups resulted in increased depressive-like behavior in the forced swim and sucrose preference tests prior to puberty.The research content:Therefore, this research explores the perinatal period(gestation and lactation) mothers DEHP exposure, the effects of DEHP exposure on the adolescence and adulthood offspring on spontaneous activity behavior, exploratory behavior, anxiety behavior, spatial learning and memory behavior, and explored the molecular mechanisms of animal behavior after exposure to DEHP.The research methods:In this study, The dams were weighed every day to calculate the dosing volume of0.5ml/kg bw and they were gavaged with blank control(water), bvehicle or10,50,200mg DEHP/kgbw/day(mg/kg)From GD7to PND21respectively, the adolescence and adulthood offspring spontaneous activity behavior, exploratory behavior, anxiety behavior, spatial learning and memory behavior, were tested on PND42and PND84, using open field, elevated plus maze; forced swim, and Morris water maze. According to the requirements of separation of the hippocampus tissue samples. Western blot to detect the expression of NMDA receptor subunit NR2B and estrogen receptor beta(ERP), androgen receptor(AR), ERK1/2and ERK1/2phosphorylation level in hippocampus. Record the average litter size, measure the length of young mice on PND3At the same time, body weight and the weight of reproductive organs were measured. Radiommunoassay to detect the serum levels of estrogen in female mice and the serum levels of testosterone in male mice.The results of the study:1) During perinatal period exposure to10-200(mg/kg/day) DEHP does not affect mothers litter size and the length of offspring mice on PND3, does not change the body weight and the weight of reproductive organs of adolescence male mice while increase10mg/kg/day and200mg/kg/day body weight (p<0.001) of adolescence female mice. Adult mice Just50mg/kg/day male mice observed body weight increase no change of the weight reproductive organs was observed. The serum hormones detected found that10-200mg/kg/day low dose level DEHP expose make hormone decline to some extent but compared with the solvent control group had no significant effect.2) Perinatal period DEHP exposure significantly decreased exploratory behavior and locomotion activity of the adolescence female, impaired spatial learning and memory of the males, and increased depression-like behaviors of both sexes. The anxiety-like state was reduced in the males but enhanced in the females by DEHP. In all of behavior model the extent of the damage of adult is lighter than puberty. DEHP exposure mainly inhibition of adulthood female activity, the psychological conflicts increased, but have less effect on the male. Aggravate depressive state of male and female, but was not observed for both male and female of anxiety state or learning and memory behavior.3)Western blot analysis revealed that DEHP exposure in the perinatal period significantly lowered the adolescent male mice NMDA receptor NR2B subunits expression in hippocampal, the expression of female and adulthood male and female have no effect. Estrogen receptor beta (ER(3) expression effect in adolescence and adulthood is difference, results show DEHP exposure decrease the expression of beta estrogen receptor (ERβ) in both male and female in adolescence while in adulthood females only. Inhibition of6-week-old male and female offspring while the12-week-old male and female offspring expressing no significant of AR in hippocampus. Inhibit the phosphorylation levels of ERK1/2of adolescence male and female mice no change was observed in adult mice.Conclusion:Perinatal DEHP exposure can affect behavior in many kinds of adolescence and adulthood mice and affect gender differences in behavioral.Different behavior of the sensitive degree of DEHP, among them with learning and memory behavior is the most sensitive and anxiety depression.DEHP affect neurobehavioral development in mice may be mediated by estrogen and androgen eceptor, activation of ERK1/2letter transduction pathway of NMDA receptor NR2B subunits expression to participate in the regulation of this process.