The Effects Of Maternal Lead Exposure On Learning & Memory And The Expression Of IL-1β And TNF-α Of Offspring

Lead (Pb), is a ubiquitous environmental pollutant. Numerous studies on lead neurotoxicity have indicated this metal to be a dangerous toxin, particularly during developmental stages of higher animals. In spite of striving to reduce lead levels in the ecosystem all the time, people have been unable to completely get rid of low-dose lead exposure. Toxic effects of this metal are principally manifested in the central nervous system (CNS), such as destruction of the blood-brain barrier (BBB), loss of neurons, and gliosis. Extensive studies have revealed that perinatal exposure to even low doses of lead is extremely dangerous and leads neurological disturbances.Astrocytes are responsible for sequestration of this metal in brain tissue. Activation of astroglia may often lead to loss of the buffering function and contribute to pathological processes. This phenomenon is accompanied by death of neuronal cells and may be connected with inflammatory events arising from the production of a wide range of cytokines and chemokines, such as IL-1βand TNF-α.OBJECTIVEThe study established animal model of mice's perinantal lead exposure at different levels and measused the concentration of lead in the blood and hippocampus of offsprings, explore the poisoning effects of lead on learning and memory, the changs of hippocampal IL-1βand TNF-αat mRNA level. The goal was to find the relationship between hippocampal IL-1βand TNF-αand neurological impairment.METERIALA S AND METHODS1 AnimalsTo set up the animal models, the pregnant mice were randomly divided into four groups provided with distilled water,0.3g/L, 1.0g/L,3.0g/L lead acetate solution via drinking water respectively from the pregnancy until weaning period.2 Sample collectionOn the postnatal day 7,14 and 21, blood was collected from the mice pup tail. Ten mice from each of the groups were killed by decapitation. Then the hippocampus was separated and stored at-20℃for future use. 3 Determination of the lead concentration in blood and hippocampusThe content of lead in offspring blood and hippocampus were measured by using Z-5000 graphite furnace atomic absorption spectrometer.4 Water maze testOn the postnatal day 7,14 and 21, ten mice from each groups were evaluated for their learning and memory function by water maze test.5 Determination of IL-1βmRNA, TNF-a mRNA expression and protein content of IL-1βin the hippocampusOn the day 7th,14th and 21st days after offspring produced, the IL-1βand TNF-a expression level in hippocampus of offspring were determined by RT-PCR.The IL-1βlevel in hippocampus of offspring was determined by a double-antibody with filling ELISA assay.7 Data analysisThe behavior testing and biochemistry measuring results were analysed using SPSS 12.0. One way ANOVA method was used. The significant level was set at 0.05.RESULTS1 Lead levels in blood and hippocampusOn the same time point, the offsprings'lead levels in blood and hippocampus were different (P＜0.05). On the different days, within the same group, the blood lead level was lowest on the 14th day, and highest on the 21st day (P＜0.05); the hippocampus lead level was highest on the 14th day (P＜0.05).2 Water maze testThe escape latency was longer in the lead-exposed groups, the longer and higher dosage exposure, the poorer learning performance (P＜0.05)3 The effects of perninatal lead expose on the expression of IL-1βmRNA, TNF-a mRNA and IL-1βprotein in the hippocampus of offsprings3.1 The effects of perinatal lead expose on the IL-1βmRNA expression in the hippocampus.The IL-1βmRNA expression in the hippocampus of offsprings was increased with the maternal exposure dosage (P<0.05).3.2 The effects of perinatal lead expose on the TNF-αmRNA expression in the hippocampus.The TNF-a mRNA expression in the hippocampus of offsprings was increased with the maternal exposure dosage (P＜0.01).3.3 The effects of perinatal lead expose on the IL-1βprotein expression in the hippocampus.The IL-1βprotein expression in the hippocampus of offsprings was increased with the maternal exposure dosage (P＜0.05).5 Correlation analysisThe expression of IL-1βmRNA and TNF-a mRNA in offsprings'hippocampus were positive correlation with the lead level of blood and hippocampus and the escape latency on the 21st day (P＜0.01).CONCLUSIONS1 The perinatal lead exposure may increases the lead level in blood and hippocampus.2 The perinatal lead exposure may damage the learning and memory function; and it was not appearance until the dosage of lead was up to a certain level, and then the damage increased with the maternal lead expose during pregnancy.3 The maternal pregnancy exposure to lead may increase the expression of IL-1βand TNF-αin hippocampus of offsprings, is likely to be correlated with the lead neurotoxicology.