Annals of Occupational and Environmental Medicine

Original Article

Effect of Developmental Lead Exposure on the Expression of Hippocampal NMDA Receptor Subunit mRNA: Tae Wan Kim, In Sung Chung, Jae Hoon Bae, Dong Hoon Shin, Mi Young Lee, Joon Sik Kim; Korean Journal of Occupational and Environmental Medicine 2005;17(4):278-287. Published online December 31, 2005; DOI: https://doi.org/10.35371/kjoem.2005.17.4.278

Abstract PDF: OBJECTIVES
The purpose of the present study was to examine the differential effects of lead (Pb) exposure on the expression of specific NMDA receptor subunit mRNAs on the hippocampal cells depending on the neuronal developmental stage.
METHODS
Expression of the NR2A and NR2B subunits of the NMDA receptors mRNA on the hippocampal neurons was measured by in situ hybridization in the control and Pb treated groups. Pb-treated and NMDA cytotoxicity was assessed by morphological examination and LDH measurements.
RESULTS
Hippocampal NR2A subunit mRNA expression was gradually increased with increasing age, and was significantly decreased after Pb exposure. The expression of NR2B subunit mRNA was not changed during development in the rat hippocampus and the developmental effect of Pb exposure on NR2B expression was minimal. These results indicate that chronic Pb exposure may decrease the levels of NR2A-containing NMDA receptors and may thereby alter normal synaptic signal transmission. Pb or NMDA-induced cytotoxicity in vitro differed significantly between the immature and the mature hippocampal cells.
CONCLUSIONS
This study demonstrates that chronic Pb exposure during brain development alters the levels of specific NMDA receptor subunit mRNA in the rat hippocampus. These results suggest that chronic Pb exposure may attenuate the precise neuronal synaptic transmission through the differential alteration of the composition of the NMDA receptor subunit on the hippocampus depending on neuronal developmental stage.

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Original Article

Apoptosis of Neuronal Cells Induced by Lead: Seon Hee Yang, Dong Hoon Shin, Won Ki Baek; Korean Journal of Occupational and Environmental Medicine 1999;11(2):254-263. Published online June 30, 1999; DOI: https://doi.org/10.35371/kjoem.1999.11.2.254

Lead is a major environmental and occupational neurotoxicant. It has been shown that long-term exposure to a low level of lead impairs the development of brain. For example, it was reported that lead exposure during the childhood causes a learning difficulty and a memory deficit of children. Neurotoxic agents including the lead are believed to cause neuronal death in developing brain by two mechanisms: apoptosis and necrosis. However, the exact mechanism of neuronal death caused by lead exposure is still not known explicitly. In this study, we conducted a study to clarify a mechanism of hippocampal neuronal cell death caused by lead acetate. Hippocampal neurons were cultured for 14-16 days and treated with lead acetate of 1. 10, 100 1 microM concentrations for 12 hours. With the MTT(methyl tetrazolium test) kit, the viability of neuronal cells was measured. Next, in order to examine apoptosis caused by lead acetate, TUNEL (TdT-mediated d-UTP Nick End Labelling) assay was performed. It has been shown that lead acetate reduced the viability of neuronal cells in a dose dependent manner, especially at the concentration of 100 ~M lead acetate. TUNEL immunostain showed brownish signals in the nucleus of apoptotic cells. The proportions of apoptotic cells in the lead?acetate treated group were more higher than those in the controls and increased as lead acetate concentration increased. From above results, it may be concluded that lead in the hippocampal neuronal cells reduced cell viability and one of mechanisms in neuronal cell death by lead appears to be apoptosis.

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Teratogenic Effects of Lead in the Developing Chick Embryos
Aqsa Shafiq, . Mahnoor, Mirza Fahad Baig, Yashal Fatima, Arooj Haer, Shakila Parveen, Muhammad Akram Tariq, Muhammad Khalil Ahmad Khan
MARKHOR (The Journal of Zoology).2023; : 16. CrossRef

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