Lab Anim Res.  2011 Sep;27(3):219-225. 10.5625/lar.2011.27.3.219.

Inorganic lead (Pb)- and mercury (Hg)-induced neuronal cell death involves cytoskeletal reorganization

• Choi WS
• Kim SJ
• Kim JS

• KMID: 1850049
• DOI: http://doi.org/10.5625/lar.2011.27.3.219

Abstract

Inorganic lead and mercury are widely spread xenobiotic neurotoxicants threatening public health. The exposure to inorganic lead and mercury results in adverse effects of poisoning including IQ deficit and peripheral neuropathy. Additionally, inorganic neurotoxicants have even more serious impact on earlier stages of embryonic development. This study was therefore initiated in order to determine the cytotoxic effects of lead and mercury in earlier developmental stages of chick embryo. Administration of inorganic lead and mercury into the chick embryo resulted in the prolonged accumulation of inorganics in the neonatal brain, with detrimental cytotoxicity on neuronal cells. Subsequent studies demonstrated that exposure of chick embryo to inorganic lead and mercury resulted in the reorganization of cytoskeletal proteins in the neonatal brain. These results therefore suggest that inorganics-mediated cytoskeletal reorganization of the structural proteins, resulting in neurocytotoxicity, is one of the underlying mechanisms by which inorganics transfer deleterious effects on central nervous system.

Keyword

Lead; mercury; neurotoxicity; tubulin; tau; chick embryo

MeSH Terms

Animals
Brain
Cell Death
Central Nervous System
Chick Embryo
Cytoskeletal Proteins
Embryonic Development
Female
Neurons
Peripheral Nervous System Diseases
Pregnancy
Proteins
Public Health
Tubulin
Cytoskeletal Proteins
Proteins
Tubulin

Figure

• 

  Figure 1 Administered lead (Pb) and mercury (Hg) in early developmental stage of chick embryo were still detectable in the brain of adult stage. (A) Schematic diagram of experimental design for AAS analysis. The prepared solution [0, 50 (25 µg/500 µL) and 100 ppm (50 µg/500 µL) of Pb; and 0, 50 (25 µg/500 µL) and 80 ppm (40 µg/500 µL) of Hg] was injected into each yolk sac of 6-ED chick embryos. On 20-ED, the collected chick embryo brains were digested for Atomic Absorption Spectrometry analysis. (B-C) Accumulated Pb (B) and Hg (C) in neonatal brain. Indicated concentration of inorganic Pb or Hg were injected into yolk sac on 6-ED. On day 20, the accumulated concentration of Pb (B) and Hg (C) in neonatal brain were determined by F-AAS as described in Materials and Methods. All data represent three independent experiments, each carried out in triplicate, and significance was tested using ANOVA with a Newman-Keuls post-hoc test, where ** represents P<0.05 vs control. ND represents non-detectable.

• 

  Figure 2 Lead and mercury induces cytotoxicity of neuronal cells. A-B. Decreased cell viability with the treatment of Pb (A) and Hg (B). Neuronal cells were treated with Pb (7 mM) and Hg (23 µM) for overnight, and MTT colorimetric assay was performed as described in Materials and Methods. All data represent three independent experiments, each carried out in triplicate, and significance was tested using ANOVA with a Newman-Keuls post-hoc test, where ** represents P<0.05 vs control.

• 

  Figure 3 Lead and mercury modulate cytoskeletal reorganization in neonatal brain. (A-B) Effect of lead and mercury on tubulin (A) and tau (B) expression. Indicated concentration of inorganic lead or mercury were injected into yolk sac on 6-ED. On day 20, total cellular extracts were isolated from neonatal brain and Western blot analyses performed with antibodies against tubulin or tau. Western blots were quantified using densitometric analysis, and values expressed relative to control. Western blots are representative of n=3, and significance was tested using ANOVA with a Newman-Keuls post-hoc test, where ** represents P<0.05 vs control.

• 

  Figure 4 Lead and mercury modulate cytoskeletal reorganization in neuronal cells. Neuronal cells were treated with Pb (4.8 and 7 mM for 50 and 100 ppm groups, respectively) and Hg (2.4 and 23 µM for 50 and 80 ppm groups, respectively) for overnight, and immunocytochemical staining was performed using antibody against tubulin (A-E) or tau (F-J).

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