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Neurological effects of inorganic arsenic exposure: altered cysteine/glutamate transport, NMDA expression and spatial memory impairment.

Ramos-Chávez LA, Rendón-López CR, Zepeda A, Silva-Adaya D, Del Razo LM, Gonsebatt ME - Front Cell Neurosci (2015)

Bottom Line: In humans, As species cross the placenta and are found in cord blood.Also, the expression of the glutamate receptor N-methyl-D-aspartate (NMDAR) subunits NR2A and B as well as the presence of As species in cortex and hippocampus were investigated.Behavioral tasks showed significant spatial memory impairment in males while the effect was marginal in females.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Medicina Genómica, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México Mexico, DF, Mexico.

ABSTRACT
Inorganic arsenic (iAs) is an important natural pollutant. Millions of individuals worldwide drink water with high levels of iAs. Chronic exposure to iAs has been associated with lower IQ and learning disabilities as well as memory impairment. iAs is methylated in tissues such as the brain generating mono and dimethylated species. iAs methylation requires cellular glutathione (GSH), which is the main antioxidant in the central nervous system (CNS). In humans, As species cross the placenta and are found in cord blood. A CD1 mouse model was used to investigate effects of gestational iAs exposure which can lead to oxidative damage, disrupted cysteine/glutamate transport and its putative impact in learning and memory. On postnatal days (PNDs) 1, 15 and 90, the expression of membrane transporters related to GSH synthesis and glutamate transport and toxicity, such as xCT, EAAC1, GLAST and GLT1, as well as LAT1, were analyzed. Also, the expression of the glutamate receptor N-methyl-D-aspartate (NMDAR) subunits NR2A and B as well as the presence of As species in cortex and hippocampus were investigated. On PND 90, an object location task was performed to associate exposure with memory impairment. Gestational exposure to iAs affected the expression of cysteine/glutamate transporters in cortex and hippocampus and induced a negative modulation of NMDAR NR2B subunit in the hippocampus. Behavioral tasks showed significant spatial memory impairment in males while the effect was marginal in females.

No MeSH data available.


Related in: MedlinePlus

Cystine/cysteine and glutamate transporters expression in control and gestational exposed mice on PND 15. Confocal images of (A) xCT and (B) EAAC1 expression in control and PND 15 CA1 hippocampal cells. Neuron marker anti-MAP2 (green), xCT (red) or EAAC1 (red). Nucleus were counterstained with DAPI (blue). Scale bar, 30 μm. The cortex and hippocampus regions were removed from males and females and processed for western blotting as described in Materials and Methods for (C) xCT; (D) EAAC1;(E) NMDAR NR2A and; (F) NMDAR NR2B subunits. Densitometric evaluation of the blot images was performed using β-tubulin as loading control. Bars represent mean ± SE relative to control values, n = 4–6. Data were analyzed using Student’s t-test. (*) Significantly different from controls,*P < 0.05, **P < 0.01,***P < 0.001. Representative blot images are shown.
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Figure 4: Cystine/cysteine and glutamate transporters expression in control and gestational exposed mice on PND 15. Confocal images of (A) xCT and (B) EAAC1 expression in control and PND 15 CA1 hippocampal cells. Neuron marker anti-MAP2 (green), xCT (red) or EAAC1 (red). Nucleus were counterstained with DAPI (blue). Scale bar, 30 μm. The cortex and hippocampus regions were removed from males and females and processed for western blotting as described in Materials and Methods for (C) xCT; (D) EAAC1;(E) NMDAR NR2A and; (F) NMDAR NR2B subunits. Densitometric evaluation of the blot images was performed using β-tubulin as loading control. Bars represent mean ± SE relative to control values, n = 4–6. Data were analyzed using Student’s t-test. (*) Significantly different from controls,*P < 0.05, **P < 0.01,***P < 0.001. Representative blot images are shown.

Mentions: Changes in GSH could be due to the modulation of cysteine and glutamate transporters. Western blot analysis was performed to explore the expression of xCT, EAAC1 and LAT1 transporters in the whole brain on PND 1 and in the cortex and hippocampus on PND 15 and 90. The expression of xCT, EAAC1 and LAT1 transporters (Figures 3A–C respectively) was significantly increased in the brains of pups at PND 1. This up-regulation continued at PND 15 for xCT and EAAC1 (Figures 4C,D) but not for LAT1 (data not shown) in gestationally exposed male and female mice. The expression of xCT and EAAC1 was observed mainly in hippocampal neurons (Figures 4A,B). Increased extracellular levels of glutamate have been associated with modulation of NMDAR subunits. At the same time, iAs exposure down-regulated the NR2A NMDA receptor subunits in the male hippocampus in PND 15 pups (Figure 4E), while the NR2B subunit was down-regulated in both the male and female cortex and hippocampus (Figure 4F).


Neurological effects of inorganic arsenic exposure: altered cysteine/glutamate transport, NMDA expression and spatial memory impairment.

Ramos-Chávez LA, Rendón-López CR, Zepeda A, Silva-Adaya D, Del Razo LM, Gonsebatt ME - Front Cell Neurosci (2015)

Cystine/cysteine and glutamate transporters expression in control and gestational exposed mice on PND 15. Confocal images of (A) xCT and (B) EAAC1 expression in control and PND 15 CA1 hippocampal cells. Neuron marker anti-MAP2 (green), xCT (red) or EAAC1 (red). Nucleus were counterstained with DAPI (blue). Scale bar, 30 μm. The cortex and hippocampus regions were removed from males and females and processed for western blotting as described in Materials and Methods for (C) xCT; (D) EAAC1;(E) NMDAR NR2A and; (F) NMDAR NR2B subunits. Densitometric evaluation of the blot images was performed using β-tubulin as loading control. Bars represent mean ± SE relative to control values, n = 4–6. Data were analyzed using Student’s t-test. (*) Significantly different from controls,*P < 0.05, **P < 0.01,***P < 0.001. Representative blot images are shown.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4321597&req=5

Figure 4: Cystine/cysteine and glutamate transporters expression in control and gestational exposed mice on PND 15. Confocal images of (A) xCT and (B) EAAC1 expression in control and PND 15 CA1 hippocampal cells. Neuron marker anti-MAP2 (green), xCT (red) or EAAC1 (red). Nucleus were counterstained with DAPI (blue). Scale bar, 30 μm. The cortex and hippocampus regions were removed from males and females and processed for western blotting as described in Materials and Methods for (C) xCT; (D) EAAC1;(E) NMDAR NR2A and; (F) NMDAR NR2B subunits. Densitometric evaluation of the blot images was performed using β-tubulin as loading control. Bars represent mean ± SE relative to control values, n = 4–6. Data were analyzed using Student’s t-test. (*) Significantly different from controls,*P < 0.05, **P < 0.01,***P < 0.001. Representative blot images are shown.
Mentions: Changes in GSH could be due to the modulation of cysteine and glutamate transporters. Western blot analysis was performed to explore the expression of xCT, EAAC1 and LAT1 transporters in the whole brain on PND 1 and in the cortex and hippocampus on PND 15 and 90. The expression of xCT, EAAC1 and LAT1 transporters (Figures 3A–C respectively) was significantly increased in the brains of pups at PND 1. This up-regulation continued at PND 15 for xCT and EAAC1 (Figures 4C,D) but not for LAT1 (data not shown) in gestationally exposed male and female mice. The expression of xCT and EAAC1 was observed mainly in hippocampal neurons (Figures 4A,B). Increased extracellular levels of glutamate have been associated with modulation of NMDAR subunits. At the same time, iAs exposure down-regulated the NR2A NMDA receptor subunits in the male hippocampus in PND 15 pups (Figure 4E), while the NR2B subunit was down-regulated in both the male and female cortex and hippocampus (Figure 4F).

Bottom Line: In humans, As species cross the placenta and are found in cord blood.Also, the expression of the glutamate receptor N-methyl-D-aspartate (NMDAR) subunits NR2A and B as well as the presence of As species in cortex and hippocampus were investigated.Behavioral tasks showed significant spatial memory impairment in males while the effect was marginal in females.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Medicina Genómica, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México Mexico, DF, Mexico.

ABSTRACT
Inorganic arsenic (iAs) is an important natural pollutant. Millions of individuals worldwide drink water with high levels of iAs. Chronic exposure to iAs has been associated with lower IQ and learning disabilities as well as memory impairment. iAs is methylated in tissues such as the brain generating mono and dimethylated species. iAs methylation requires cellular glutathione (GSH), which is the main antioxidant in the central nervous system (CNS). In humans, As species cross the placenta and are found in cord blood. A CD1 mouse model was used to investigate effects of gestational iAs exposure which can lead to oxidative damage, disrupted cysteine/glutamate transport and its putative impact in learning and memory. On postnatal days (PNDs) 1, 15 and 90, the expression of membrane transporters related to GSH synthesis and glutamate transport and toxicity, such as xCT, EAAC1, GLAST and GLT1, as well as LAT1, were analyzed. Also, the expression of the glutamate receptor N-methyl-D-aspartate (NMDAR) subunits NR2A and B as well as the presence of As species in cortex and hippocampus were investigated. On PND 90, an object location task was performed to associate exposure with memory impairment. Gestational exposure to iAs affected the expression of cysteine/glutamate transporters in cortex and hippocampus and induced a negative modulation of NMDAR NR2B subunit in the hippocampus. Behavioral tasks showed significant spatial memory impairment in males while the effect was marginal in females.

No MeSH data available.


Related in: MedlinePlus