[Effects of PM_(2. 5) exposure on synaptic plasticity and Wnt/β-catenin pathway in rat hippocampus].

OBJECTIVE To investigate the effects of PM_(2. 5) exposure on the development of synaptic plasticity and Wnt/β-catenin pathway in hippocampus of offspring rats. METHODS Healthy 7-week-old SPF SD rats(n=36) mated with a male to female ratio of 2∶1. Pregnant rats were randomly divided into three groups, including control group, low PM_(2. 5) group, and high PM_(2. 5) group, with eight rats in each group. The low and high PM_(2. 5) concentrations in dynamic exposure cabinet were approximately two times and four times higher than the annual average PM_(2. 5) concentration in Tangshan city respectively. The exposure started from pregnant day 0, until postnatal day 21(PND21) of offspring rats. After weaning, the offspring rats continued to be exposed to PM_(2. 5) until PND42. PND21 and PND42 pups were subjected to Morris water maze and new object recognition experiments. Western blot was used to detect post synaptic density-95(PSD-95), synaptophysin(SYN), growth associated protein(GAP-43), glycogen synthase kinase 3β(GSK-3β), β-catenin protein levels and phosphorylation levels of GSK-3β and β-catenin in the hippocampus of offspring rats. RESULTS Compared with the control group, the learning and memory abilities of the pups of each PM_(2. 5) group were significantly decreased with a dose dependent manner. Compared with the control group, the protein level of SYN, GAP-43 and PSD-95 in hippocampus of PND0 rats of each PM_(2. 5)groups were decreased(P<0. 05), and the protein level of SYN of each PM_(2. 5)group and PSD-95 of high PM_(2. 5) group in PND21 and PND42 were decreased(P<0. 05), and the level of GAP-43 of low PM_(2. 5) group in PND42 were decreased(P<0. 05). Compared with the low PM_(2. 5) group, the level of PSD-95 of high PM_(2. 5) group in PND0 and PND21, the level of PSD-95 of high PM_(2. 5) group in PND0 and PND42 were decreased(P<0. 05). Compared with the control group, the level of p-GSK-3β in hippocampus of each PM_(2. 5)group in PND0, PND21 and PND42 was decreased(P<0. 05), and with the increase of PM_(2. 5) exposure dose, the trend is more obvious. The protein level of p-β-catenin in hippocampus of high PM_(2. 5) group in PND0 and PND42 was significantly increased(P<0. 05). The level of p-β-catenin in high-dose PND21 pups compared with the control group was significantly reduced(P<0. 05). CONCLUSION Exposure to PM_(2. 5) in early life can damage the synaptic plasticity and decrease the protein levels of β-catenin and p-GSK-3β in the Wnt/β-catenin pathway of hippocampus in offspring rats.