Effects Of Prenatal And Postnatal PFOS Exposure On IGF-Ⅰ,IGF-ⅠR, IGFBP-2 MRNA And NR2B MRNA And Protein Levels In Brain Of Rat Pups

IntroductionPerfluorooctane sulfonate(PFOS) has been utilized in a wide variety of industrial and household products and possesses chemical stability toward degradation, long-distance migration,biological accumulation and development toxicity, reproductive toxicity,immunotoxicity,neurotoxicity and potential multi-organ toxicity. The neurotoxicities of PFOS that have been reported main include increase of Ca²⁺ concentration in hippocampus neuron,and change of amino acids neurotransmitter contents and increasing activities of protein kinase A(PKA) and protein kinase C(PKC) and interfering synaptic transmission and synaptogenesis in brain.Prenatal and postnatal PFOS exposure resulted in significant prolongation in the escape latency of rat pups,and significant increase in the number of errors in water maze experiment. There was spatial learning and memory damage to some extent.Embryonic period and earlier postnatal period are the critical periods of brain development,and brain functions are imcomplete.The PFOS exposure probably induces irreversible effects on the proceeding of brain development and maturity.It is urgent to probe the mechanism of neural development toxicity and learning and memory damage induced by PFOS and relative sensitive period of its toxicity effects,and provid science evidence to know the toxicity characteristics of PFOS and other perfluorine compounds more generally and progress health risk assessment.The aim of this study was to explore the mechanism of developmental neurotoxicity and learning and memory damage induced by PFOS through observing the effects of prenatal and postnatal PFOS exposure on IGF-I,IGF-I R,IGFBP-2 mRNA and NR2B mRNA and protein levels in brain of rat pups.Materials and Methods 1.Animals and treatmentTwenty-eight pregnant rats were randomly divided into three groups in proportion of 3:2:2,including control group(C),low dose group(L) and high dose group(H), which respectively received 0,7.2,14.4mg PFOS/kg feed from pregnancy day 0 to postnatal day 28(PD28) by free feeding.The animal models of prenatal and postnatal non-exposure(CC),prenatal exposure(LC and HC),postnatal exposure(CL and CH), and prenatal and postnatal exposure(LL and HH) to PFOS were established by cross-fostering method.The pups were feed using the same feed as their foster rats after weaning until PD28.Seven to eight pups were sacrificed by decapitation in CC,LC,HC groups at PD1 and each group at PD14 and PD28.Brain was removed quickly on ice.Three samples for paraffin section were fixed by 4%paraformaldehyde.The rest samples were stored at -70℃.2.MethodsThe IGF- I,IGF- I R,IGFBP-2 and NR2B mRNA levels in frontal cortex of rat pups was determined with semi-quantitative RT-PCR.NR2B protein express in frontal cortex and hippocampus(CA1,CA3 and DG regions) of rat pups was detected by immunohistochemistry.3.Statistical analysisStatistical analysis was performed using SPSS 13.0 software.All data were presented as mean±SD.Normality of data was verified through the Kolmogorov-Smirnov test,and homogeneity of variances was checked using Levene's test. Differences from control values were determined by one-way ANOVA,and the later followed by a Fisher's LSD or Dunnett's T3 test with the level of statistical significance set at p＜0.05.If the analysis of normal distribution was not appropriate,the Kruskal-Wsllis test was used to identify the statistical significance of the individual groups.Results1.Effects of PFOS on IGF-I,IGF-I R,IGFBP-2 mRNA and NR2B mRNA and protein express levels in frontal cortex of rat pupsAt PD1,IGF- I,IGF- I R and IGFBP-2 mRNA levels of exposure groups increased in comparison with that in control group significantly(p＜0.01).At PD14, IGF- I,IGF- I R and IGFBP-2 mRNA levels of the other exposure groups were significantly lower than control(p＜0.05) excepted for the IGF- I R mRNA level of LC group which was higher than control significantly.At PD28,IGF- I and IGF- I R mRNA levels of exposure groups were significantly lower than control(p＜0.01). However,there was no significance in the differences of IGFBP-2 mRNA levels between exposure groups and control.NR2B mRNA levels in frontal cortex of pups were significantly lower than control in HC group at PD1 and LC,HC and HH group at PD14(p＜0.05).But there was no change at PD28.NR2B protein levels in frontal cortex of rat pups were significant lower than control group at PD14(p＜0.01).2.Effects of PFOS on NR2B protein express level in hippocampus of rat pupsIn the pernotal exposure group,NR2B protein express of the hippocampus CA1 region of pups in LC group showed significant lower than control at PD1(p＜0.05).At PD14,the effect of PFOS extended to all of the hippocampus regions.At PD28,the NR2B protein express in hippocampus CA1 region was significant decrease barely in HC group(p＜0.05).In the postnatal exposure and prenatal and postnatal exposure group,the NR2B protein express in CA3 and DG regions of pups were significantly lower in comparison with that in control group at PD14(p＜0.01).At PD28,the NR2B protein express in hippocampus CA1 and CA3 regions of pups decreased significantly compared with control(p＜0.05).Conclusions1.Prenatal exposure to PFOS resulted in the significant increases of IGF- I,IGF-I R, IGFBP-2 mRNA levels in frontal cortex of rat pups comparing with control groups at PD1.Significant decreases were showed at later development stage.The mRNA levels of them were lower than control in the postnatal exposure and prenatal and postnatal exposure groups.2.NR2B mRNA and protein levels in frontal cortex of rat pups decreased at early development stage.3.NR2B protein levels in hippocampal formation regions were significant decrease.