27.07.2013 Views

The Toxicologist - Society of Toxicology

The Toxicologist - Society of Toxicology

The Toxicologist - Society of Toxicology

SHOW MORE
SHOW LESS

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

lower anxiety levels. We have previously reported induction <strong>of</strong> excessive cell death in<br />

various fetal brain areas with different sensitivity to BrdU exposure. However, at this<br />

stage, we could not clarify the effects <strong>of</strong> BrdU on the olfactory bulb (OB).<br />

<strong>The</strong>refore, to examine the effects <strong>of</strong> BrdU on OB development, we conducted a<br />

histopathological examination <strong>of</strong> the OB on later brain stages, GD20 fetal brain<br />

and postnatal day (PD)11 neonatal brain in rat developmental disorder model. In<br />

the BrdU over control group, results revealed a thinner mitral cell layer and fewer<br />

distributions <strong>of</strong> tyrosine hydroxylase (TH) immunoreactive cells in glomerular layer<br />

<strong>of</strong> GD20 fetal brain. In PD11 neonatal group, disruption <strong>of</strong> the mitral cell layer<br />

structure was seen. Neurites <strong>of</strong> TH-positive cells in the glomerular layer showed abnormal<br />

spindle extension, suggesting induction <strong>of</strong> disturbances in synaptogenesis.<br />

Furthermore, fewer distributions <strong>of</strong> parbalbumin (PV), a Ca-binding protein coexisting<br />

with GABA neurons, and presence <strong>of</strong> underdeveloped neurites in external<br />

plexiform layer <strong>of</strong> TH-immunoreactive cells was also observed in the BrdU group.<br />

Using PD11 neonatal brains, we previously reported that BrdU affects GABAergic<br />

neurons in the cerebral and limbic cortex (the hippocampus, amygdale and entorhinal<br />

area). <strong>The</strong> present findings reinforce the idea that abnormal GABAergic neurons<br />

may contribute to BrdU-induced abnormal behaviors in rat.<br />

2596 PHENCYCLIDINE-INDUCED APOPTOSIS AND<br />

CHANGES IN GENE EXPRESSION IN POSTNATAL<br />

RAT PUPS.<br />

N. V. Sadovova 1 , F. Liu 2 , X. Zhang 2 , L. Shi 3 , L. Guo 3 , F. Quan 4 , Z. Wen 4 , C.<br />

Wang 2 , T. A. Patterson 5 , J. P. Hanig 2 , M. G. Paule 2 and W. Slikker 2 . 1 Toxicologic<br />

Pathology Associates, Jefferson, AR, 2 Division <strong>of</strong> Neurotoxicology, NCTR/FDA,<br />

Jefferson, AR, 3 Division <strong>of</strong> System <strong>Toxicology</strong>, NCTR/FDA, Jefferson, AR, 4 Z-Tech,<br />

ICF International Company, Jefferson, AR and 5 CDER/FDA, Silver Spring, MD.<br />

Repeated administration <strong>of</strong> phencyclidine (PCP), an N-methyl-D-aspartate<br />

(NMDA) receptor antagonist, during development, may result in neuronal damage<br />

that leads to behavioral deficits in adulthood. <strong>The</strong> present study examined the potential<br />

neurotoxic effects <strong>of</strong> PCP exposure (10 mg/kg) in rats on postnatal days<br />

(PNDs) 7, 9 and 11 and the possible underlying mechanism(s) for neurotoxicity.<br />

Brain tissue was harvested for RNA extraction and morphological assessments.<br />

Elevated neuronal cell death was observed in layers II and III <strong>of</strong> the frontal cortex in<br />

PCP treated group, using Fluoro-Jade C staining. More active caspase-3 positive<br />

neurons in PCP treated group further confirmed the neurotoxic effects <strong>of</strong> PCP, indicating<br />

PCP induced rat neuron death is apoptosis in nature. RNA was collected<br />

from the frontal cortex for DNA microarray analysis and quantitative RT-PCR.<br />

Gene expression pr<strong>of</strong>iling was determined using Illumina Rat Ref-12 Expression<br />

BeadChips containing 22,226 probes. Based on criteria <strong>of</strong> a fold change greater<br />

than 1.4 and a P-value less than 0.05, 19 genes including NMDAR1 (N-methyl-Daspartate<br />

receptor) and four pro-apoptotic genes were up-regulated, and 25 genes<br />

including four anti-apoptotic genes were down-regulated, in the PCP-treated<br />

group. Quantitative RT-PCR confirmed the microarray results. <strong>The</strong>se findings support<br />

the hypothesis that neurodegeneration caused by PCP occurs, at least in part,<br />

through the up-regulation <strong>of</strong> NMDA receptors, which makes neurons possessing<br />

these receptors more vulnerable to endogenous glutamate. Supported by<br />

NCTR/NTP IAG # 244-07-0007 (E-2155).<br />

2597 GENE EXPRESSION IN KETAMINE-EXPOSED RAT<br />

BRAIN.<br />

C. Wang1 , Q. Shi2 , L. Guo3 , T. A. Patterson1 , S. Dial2 , Q. Li4 , N. Sadovova5 ,<br />

X. Zhang1 and J. P. Hanig6 . 1Division <strong>of</strong> Neurotoxicology, National Center for<br />

Toxicological Research/FDA, Jefferson, AR, 2Division <strong>of</strong> Systems <strong>Toxicology</strong>, National<br />

Center for Toxicological Research/FDA, Jefferson, AR, 3Division <strong>of</strong> Biomedical<br />

<strong>Toxicology</strong>, National Center for Toxicological Research/FDA, Jefferson, AR,<br />

4Microarray Core Facility, UTSW Medical Center, Dallas, TX, 5Toxicologic Pathology Associates, Jefferson, AR and 6Center for Drug Evaluation and<br />

Research/FDA, Silver Spring, MD.<br />

Ketamine, a non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist,<br />

is associated with accelerated neuronal apoptosis in the developing rodent brain.<br />

Here, postnatal day (PND) 7 rats were treated with 20 mg/kg ketamine or saline in<br />

six successive doses (sc) at 2-h intervals. Brain frontal cortical areas were collected 6<br />

h after the last dose and RNA isolated and hybridized to the Illumina Rat Ref-12<br />

Expression BeadChip with 22,226 probes. Many <strong>of</strong> the differentially expressed<br />

genes were associated with cell death or differentiation and receptor activity.<br />

Ingenuity Pathway Analysis s<strong>of</strong>tware identified perturbations in NMDA-type glutamate,<br />

GABA and dopamine receptor signaling. Q-PCR confirmed that NMDA<br />

receptor subunits were significantly up-regulated. Up-regulation <strong>of</strong> NMDA receptor<br />

mRNA signaling was further confirmed by in situ hybridization. <strong>The</strong>se observations<br />

support our working hypothesis that prolonged ketamine exposure produces<br />

up-regulation <strong>of</strong> NMDA receptors and subsequent over-stimulation <strong>of</strong> the glutamatergic<br />

system by endogenous glutamate, triggering enhanced apoptosis in developing<br />

neurons.<br />

556 SOT 2011 ANNUAL MEETING<br />

2598 MIDAZOLAM-INDUCED CHANGES IN GENE<br />

EXPRESSION IN POSTNATAL RAT PUP BRAIN.<br />

F. Liu 1 , S. W. Rainosek 2 , J. Zhang 3 , L. Guo 4 , L. Shi 5 , N. Sadovova 6 , M. G.<br />

Paule 1 and W. Slikker 1 . 1 Division <strong>of</strong> Neurotoxicology, National Center for<br />

Toxicological Research, Jefferson, AR, 2 UAMS College <strong>of</strong> Medicine, Little Rock, AR,<br />

3 Z-Tech, an ICF International Company at NCTR, Jefferson, AR, 4 Division <strong>of</strong><br />

Biomedical <strong>Toxicology</strong>, NCTR/FDA, Jefferson, AR, 5 Division <strong>of</strong> System <strong>Toxicology</strong>,<br />

NCTR/FDA, Jefferson, AR and 6 Toxicologic Pathology Associates, Jefferson, AR.<br />

Midazolam is a short-acting drug in the benzodiazapine class, <strong>of</strong>ten used for induction<br />

and maintenance <strong>of</strong> anesthesia in combination with either N-methyl-D-aspartate<br />

(NMDA) receptor antagonists or other γ-Aminobutyric acid (GABA) receptor<br />

agonists in pediatric anesthesia. Little is known regarding its effects on the developing<br />

brain. In the present study, postnatal day (PND) 7 rats were treated subcutaneously<br />

with 9 mg/kg midazolam or saline at 2-h intervals for 3 times. Brain frontal<br />

cortical areas were collected 6 h after the last dose and RNA was isolated for gene<br />

expression analysis. Gene expression pr<strong>of</strong>iling was determined using a whole<br />

genome-wide expression array, Illumina Rat Ref-12 Expression BeadChip with<br />

22,523 probes. <strong>The</strong> differentially expressed genes (DEGs) were selected using the<br />

criteria <strong>of</strong> a fold change greater than 1.4 and a P-value less than 0.05 comparing the<br />

treatment group to the control group. Based on these criteria, 93 genes were up-regulated,<br />

and 121 genes were down-regulated in midazolam-treated animals. <strong>The</strong>se<br />

DEGs were then searched in the Kyoto Encyclopedia <strong>of</strong> Genes and Genomes<br />

(KEGG) for pathway identification. Twelve pathways were significantly altered by<br />

treatment with midazolam. Functionally, these signaling pathways belong to the<br />

following 4 categories: 1) metabolism, 2) transcription/genetic information processing,<br />

3) cell death and growth/cellular processes, and 4) neurodegenerative diseases/human<br />

diseases. This gene expression analysis provides novel molecular insights<br />

into the effects <strong>of</strong> midazolam in the developing brain.<br />

2599 DIFFERENT APOPTOTIC RESPONSE IN MOUSE<br />

BRAIN AFTER NEONATAL EXPOSURE TO DIFFERENT<br />

FLAME RETARDANTS.<br />

H. Viberg. Department Environmental <strong>Toxicology</strong>, Uppsala University, Uppsala,<br />

Sweden.<br />

Polybrominated diphenyl ethers (PBDEs) and tetrabromo bisphenol A (TBBPA)<br />

are used as flame retardants and are detected in environment, wildlife species and<br />

human tissues. Earlier studies have shown that exposure to PBDEs during the brain<br />

development in the neonatal period affects behavior, learning and memory in adult<br />

life, while exposure to TBBPA during the neonatal period did not affect behavioral<br />

variables in the adult mouse. PBDE 99, but not TBBPA, has also been shown to affect<br />

proteins important for normal brain development neonatally, for example<br />

CaMKII, GAP-43 and synaptophysin. <strong>The</strong>re are indications that one <strong>of</strong> the neurotoxic<br />

mechanisms <strong>of</strong> PBDEs can be apoptosis and therefore we investigated apoptotic<br />

markers in neonatal mouse brain. Mouse pups, age 10 days, were exposed to<br />

PBDE 99 (12 mg/kg bw, po), TBBPA (11.5 mg/kg bw, po) or ketamine (50 mg/kg<br />

bw, sc) and sacrificed 24 or 48 hours after exposure. <strong>The</strong> brains were sliced and immunohistochemical<br />

analysis <strong>of</strong> caspase-3, caspase-9 and p53 were performed. After<br />

slicing the whole brain, a screening analysis were done for caspase-3 and 3 different<br />

levels were chosen for semi-quantitative analysis <strong>of</strong> caspase-3, caspase-9 and p53. So<br />

far these analysis have shown that the number <strong>of</strong> caspase-3 activated cells are significantly<br />

increased 24 h after PBDE 99 exposure (100%) and 24 h after ketamine exposure<br />

(600%) in two different structures in the neonatal mouse brain. 48 hours<br />

after exposure to PBDE 99 or ketamine, there were no significant differences seen.<br />

TBBPA did not increase the number <strong>of</strong> caspase-3 activated cells at any time. <strong>The</strong>se<br />

results confirm that PBDE 99 and ketamine can act as neurotoxicants, possibly by<br />

inducing apoptosis and altering the levels <strong>of</strong> proteins important for normal brain<br />

development, which may be related to the behavioral and cognitive alterations earlier<br />

seen after neonatal exposure to PBDE 99 and ketamine. <strong>The</strong> lack <strong>of</strong> effect <strong>of</strong><br />

TBBPA on caspase-3 activation further strengthen previous results, where TBBPA<br />

have been shown not to induce neurotoxic effects on behavior and protein levels<br />

after neonatal exposure.<br />

2600 SEX SPECIFIC EFFECTS ON NEUROGLIAL<br />

DEVELOPMENT FOLLOWING DEVELOPMENTAL<br />

EXPOSURE TO PCBs: IMPLICATIONS FOR ADHD RISK<br />

IN MALES.<br />

R. F. Seegal 1, 2 , K. Andrews 1 , S. Sanchez-Morrissey 1 , K. O. Brosch 1 and V. M.<br />

Miller 1, 2 . 1 Wadsworth Center, New York State Department <strong>of</strong> Health, Albany, NY<br />

and 2 School <strong>of</strong> Public Health, University at Albany, Albany, NY.<br />

Developmental exposure to environmental toxicants, including polychlorinated<br />

biphenyls (PCBs), is associated with an increased risk <strong>of</strong> ADHD which is four-fold<br />

more likely in boys. Hypothyroidism is also a risk factor for ADHD and PCBs sig-

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!