The Effects Of Nonylphenol On Depression-like Behaviors And Neure Synaptic Plasticity In Rats

The prevalence of depression has increased dramatically over the last decade.Environmental endocrine disruptors(EDCs)can pass blood-brain barrier to induce neurodevelopmental retardation,alterations of neuron,and synaptic plasticity,as well as depression-like behaviors.Nonylphenol(NP)is one of the typical representatives of EDCs.Our previous study showed that short-term exposure to high-dose NP during gestation could lead to neural reflex retardation in offspring,and futher decline in learning and memory in their adulthood.However,whether chronic exposure to NP at environmental concentration could cause depression-like behaviors,which has not been elucidated.Therefore,in the current study,rats were exposed to NP which was designed to mimic human exposure to observe whether NP could induce depression-like behaviors,and further alterations of synaptic plasticity.In vivo and in vitro were conducted in this study: in vivo study,the depression-like behaviors of rats was explored by behavior test(e.g.,sucrose-preference test,and forced swimming test).The effects of NP on the neurotoxicity by the detection of serum neurotransmitters and corticosterone(CORT)in rats.The effects of NP on the morphological changes of neuron and synaptic plasticity in rats were tesified by hematoxylin-eosin(HE)staining,Golgi staining and electron microscope.In vitro study,the effects of NP on the neuronal morphology and expression levels of synapse related proteins(PSD-95 and Synapsin I)in HT22 cells were further to explore the mechanism of synaptic plasticity alterations induced by NP.PartⅠ Effects of nonylphenol chronic exposure on depression-like behaviors and synaptic plasticity in ratsObjective: To investigate the effects of nonylphenol(NP)chronic exposure on the depression-like behaviors,and synaptic plasticity alterations in rats.Methods: One hundred 4-week-old male SD rats were randomly divided into 5 groups(n=20 per group): control group(C,corn oil),low(L,NP 0.4mg/kg),middle(M,NP 4mg/kg),high(H,NP 40mg/kg)dose group and depression model group(CORT 20mg/kg).At 90 and 180 days after rats exposed to NP,the depression behavior was detected by sugar-preference and forced swimming;Serum neurotransmitters(5-hydroxytryptamine(5-HT),dopamine(DA),and noradrenaline(NE))were measured by γ radioimmunoassay;Serum CORT level was detected by ELISA assay;morphological and ultrastructure changes of prefrontal cortex and hippocampus were observed by HE staining,Golgi staining,and electron microscopy,respectively.Western blot was conducted to detect the expression levels of synapse related proteins(PSD-95,Synapsin I);RT-PCR was conducted to detect the expression levels of synapse related m RNA(PSD-95,Synapsin I).Results: 1.With an increase of NP exposure dose and time,sugar-preference index deceased and forced swimming immobility time increased(P < 0.05).NP accumulation in brain increased with an increase in NP exposure dose in a dose response manner(P < 0.05).2.Compared with the control,serum DA level decreased in both middle and high NP groups(P < 0.05),while serum CORT level increased(P < 0.05)in the NP treatment group.3.(1)There were cell slightly shrinkage and nucleus pyknosis of neurons in both middle and high NP groups;(2)In the prefrontal cortex,the number of neurocyte and dendritic spines density in both middle and high NP groups decreased(P < 0.05).(3)Compared with the control,with an increase of NP exposure dose and time,synaptic cleft width increased(P < 0.05),and postsynaptic density thickness and synaptic interface curvature decreased(P < 0.05).(4)Compared with the control,the protein expression of PSD-95 decreased with an increase of NP exposure dose(P < 0.05).The expression levels of PSD-95 and synapsin I m RNA decreased with an increase of NP exposure dose,respectively(P < 0.05).Conclusion: Chronic exposure to NP could induce depression-like behaviors and synaptic plasticity alterations in rats.PartⅡ Effects of nonylphenol on the expression of synapse related proteins in HT22 cellsObjective: To investigate the effects of NP on the expression of NMDAR2 B,PSD-95 and Synapsin I in HT22 cells.Methods: CCK-8 was conducted to detect the absorbance value of HT22 cells.Half maximal inhibitory concentration(IC50)for HT22 cells and the lowest toxic concentration of NP were calculated,which based on the absorbance value,to determine the concentration of NP exposure in this study.Our experiment was divided into four groups: control group(C),NP group(NP,20 μ M),NMDAR inhibitor group(MK-801,10 μ M),NMDAR inhibitor + NP group(MK-801 + NP).HT22 cells were treated with MK-801 + NP for 30 minutes before NP exposure.The expressions of PSD-95 and Synapsin I were observed by immunofluorescence for 24 hours.The protein expressions of PSD-95 and Synapsin I were detected by Western blot.Results: 1.NP exposure inhibited the growth of HT22 cells.The IC50 of NP was 200 μM.The lowest toxic concentration of NP for HT22 cells was 20 μM.2.NP exposure could change the cell morphology(e.g.,shrinkage).3.The fluorescence expressions of Synapsin I decreased in both the NP and MK-801 + NP groups(P < 0.001).4.Compare with the control,the protein expression levels of NMDAR2 B,PSD-95 and Synapsin I in the NP,MK-801 and MK-801 + NP groups decreased(P < 0.001).The protein expression in the NP group was lower than that in the MK-801 + NP group(P < 0.001).Conclusion: NP could reduce the expression levels of synapse related proteins(NMDAR2B,PSD-95,Synapsin I).Its can reduce the effects of the expression levels of such synapse related proteins when inhibite NMDA receptor.