Maternal low-level lead exposure reduces the expression of PSA-NCAM and the activity of sialyltransferase in the hippocampi of neonatal rat pups

Abstract

Highly polysialylated neural cell adhesion molecule (PSA-NCAM) is transiently expressed specifically in newly generated cells, and is important for cell migration and neurite outgrowth. Developmental lead (Pb) exposure has been considered to affect the expression of PSA-NCAM, which contributes to the neurotoxicity of Pb exposure. However, the effect of maternal low-level Pb exposure on the expression of PSA-NCAM in neonatal rat pups has not been reported. In the present study, female Wistar rats were exposed to vehicle or different dosages of lead chloride (0.5–4 mM PbCl 2) 2 weeks before and during pregnancy. This exposure protocol resulted in neonatal rat pups blood Pb levels up to 12.12 ± 0.38 μg/dl, and hippocampal Pb levels up to 9.22 ± 0.81 μg/g at postnatal day 1 (PND 1). Immunohistochemistry analysis and Western blot analysis revealed that the expressions of PSA-NCAM and NCAM in the hippocampi of neonatal rat pups at PND 1 were significantly reduced by the maternal low-level Pb exposures. Furthermore, the mRNA levels of NCAM and polysialyltransferases (STX and PST), measured by the fluorescent real-time quantitative RT-PCR, dosage-dependently and significantly decreased by 13.26–37.62%, 25.17–59.67%, and 10.78–47.81%, respectively. In addition, the sialyltransferase activity in neonatal rat pups was significantly reduced by 6.23–32.50% in the presence of the low-level Pb exposure, too. Taken together, these results suggest that maternal low-level Pb exposure reduces the expression of PSA-NCAM, NCAM, and the activity of sialyltransferase in the hippocampi of neonatal rat pups, which might contribute to the learning and memory impairments in the developmental pups following maternal low-level Pb exposure.