Darryl B. Hood, Ph.D.

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Molecular Dysfunction Following Environmental
Intoxication During Gestation
Darryl B. Hood, Ph.D. Department of Neurobiology
and Neurotoxicology Center for Molecular and
Behavioral Neuroscience
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(No Transcript)
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Benzo(a)Pyrene
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Benzo(a)pyrene

• Polycyclic Aromatic Hydrocarbon (prototype)
• Released as a result of combustion processes
• AhR Agonist
• 1º exposure routes are oral and inhalation
• Peripheral neuropathies
• Neurobehavioral deficits
• Decline in MDI- Perera et al., 2006
• Dysregulates MET temporal developmental
  expression

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For the first time, results presented demonstrate
that in utero exposure to PAH affects early
cognitive development
Perera, et al., Environ Health Perspect
1141287-1292 (2006)
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HYPOTHESIS Prenatal exposure to B(a)P produces
behavioral learning and memory deficits mediated
through downregulation of developmental
glutamatergic receptor subunit expression at a
time when synapses are being formed for the first
time.
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Approach Susceptibility-Exposure Paradigm
GD 0
GD 5
GD 10
GD 15
GD 20
GD 21
Insemination
Birth-Rat
Birth-Mice
Entorhinal /Dentate Gyrus, Cortical Neurogenesis
Neuronal Differentiation
Down-regulation of Early Developmental
Glutamatergic Receptor Subunit Expression Hood et
al., 2006 Brown et al., 2007 McCallister et
al., 2008
Behavioral Deficit Phenotypes Wormley et al.,
2004 Sheng et al., 2008
Onset of Hearing
Eye Opening
PND 70
PND 0
PND 10
PND 20
PND 30
PND 60
PND 65
Weaning
Cortical Synapse Consolidation
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Exposed Cpr Dam and Offspring have a Similar
Composition of B(a)P Metabolites
Total Metabolites ()
Dam Pup PND3 (microsomes) (whole brain)
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Learning and Memory Correlate (LTP) Deficits in
Offspring Plasticity Mechanisms- Hippocampal





Wormley et al., (2004) Tox. Appl. Pharm. 197 (1)
49-65.
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Schedule-Controlled Operant Task(Behavioral
Learning)
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Correlate Deficits in Offspring Learning Behavior







Wormley et al., (2004) Tox. Appl. Pharm. 197 (1)
49-65.
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Behavioral Correlate2-Choice Novel Object
Recognition Task

• A test of executive function and requires more
  cognitive skills from the animal.
• Task measures exploration of novel environments
  or a single novel object.
• In order to discriminate between a novel and a
  familiar object, the animal must first attend to
  two identical objects and keep the two objects in
  working memory.
• Upon replacement of one of the familiar objects
  with a novel object, the animal should display
  differential behavior directed towards the novel
  object.

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B(a)P-exposed Cpr offspring exhibit robust
deficits in executive function
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B(a)P-exposed offspring mice exhibit robust
deficits in executive function
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Learning and Memory Correlate (Whisker-to-S1
Cortex)
Hood et al., (2006) NeuroToxicology
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Deficits in Offspring Cortical Neuronal Activity
150mg/kg BW B(a)P
S1 Cortex Control Offspring
NMDA Dependent Responses
Short Latency AMPA Dependent Responses
S1 Cortex B(a)P-Exposed Offspring
McCallister et al., 2008
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Reduced Expression of Glutamatergic Markers in
Primary Cortical Neuronal Cultures from
B(a)P-exposed Cpr Offspring
Exposure during Neurogenesis Analysis during
Synaptogenesis
c
c
c
a
a
a
b
e
b
e
e
Control Primary Mouse Cortical Neuronal Cultu
re (D7)
c
a
b
d
a
b
b
d
c
e
g
e
g
e
f
h
f
h
f
h
ex vivo B(a)P-exposed Primary
Mouse Cortical Neuronal Culture (D7)
e
f
g
h
e
g
f
h
MAP2
GluR1
NR2B
Co-localization
Sheng et al., (2008) In Preparation
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MET is a pleiotropic receptor and contributes to
cortical development
In mature cortical neurons, MET
signaling augments NMDA currents, enhances
synaptic long-term potentiation and contributes
to glutamatergic synapse formation.
MET and NMDA Co-localize at Synapses
Tyndall Walikonis. 2006. Cell Cycle
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HGF induces increased expression of NR2B and
GluR1 during cortical development

• In mature cortical neurons, MET signaling
• augments NMDA currents,
• enhances synaptic LTP and
• contributes to glutamatergic synapse formation.
• Therefore, the regulation of MET expression in
  development is critical.

Tyndall Walikonis. 2006. Cell Cycle
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Offspring MET Developmental Protein Expression is
Downegulated in B(a)P-exposed Cpr offspring
MET
b-Actin
1.4
MET/b-Actin
WT Cpr 150mg/kg Cpr 300mg/kg Cpr
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Prenatal insult during cortical neurogenesis
GluR1 subunit
NR2B subunit
MET
B(a)P Metabolites
XRE
E14-17 Synapse in S1 Cortex
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leads to postnatal deficits in
in vivo Neuronal
Activity and Behavior
MET NR2B and GluR11 mRNA and protein
NR2B subunit
GluR1 subunit
Postnatal Synaptogenesis in Layer 3 S1 Cortex
MET
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CONCLUSIONS

• Prenatal exposure to environmental contaminants
  causes modulation of developmental glutamate
  receptor subunit expression.
• Prenatal exposure to these environmental
  contaminants causes decrements neuronal activity.
  
• Prenatal exposure to environmental contaminants
  causes behavioral deficits.
• Current studies are directed at selective
  knockdown of upstream targets to produce
  offspring with phenotypes that exhibit robust
  behavioral deficits.

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Acknowledgements

• Meharry Vanderbilt
• Tultul Nayyar Ford Ebner
• Jie Wu Letha Woods
• Tianxiang Tu Mark Maguire
• Deanna Wormley Bill Valentine
• SaLynn Johnson K. Amernath
• LaNissa Brown
• Anthony Archibong Miki Aschner
• Aramandla Ramesh Dan Campbell
• Sheng Liu FP Guengerich
• Habibeh Khoshbouei Pat Levitt
• Lee E. Limbird RRO3032 (NCRR)
• ES014156 (NIEHS)
• Clivel G. Charlton NS041071 (NINDS)

Center for Molecular and Behavioral Neuroscience
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Acknowledgements
Alliance for Research Training in Neuroscience
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Gestational Toxicant Exposure
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Short Latency AMPA Dependent Response
Deficits in Offspring Cortical Neuronal
Activity (700ng/kg BW TCDD)
NMDA Dependent Responses
Evoked Activity




Hood et al., (2006) Neurotoxicology
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Translational Research
Bench
Bedside
Therapeutics
Environmental Toxicology
Translational Research
Epidemiology (Impacted Communities)
Bench
Use epidemiology studies to inform design of
molecular studies of neurological dysfunction
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Recording from the Hippocampus
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Mechanistic Model of Prenatal B(a)P Exposure
Effects on Offspring Neuronal Activity and
Behavior
Deficits in in vivo Neuronal Activity and
Behavior
AMPA
Glu
Glu
Glu
NMDA
Glu
Glu
Glu
Glu
MET NR2B and GluR1 mRNA and protein
Glu
siRNAMET
ARNT
Glu
Glu
Glu
B(a)P Metabolites
B(a)P
AhR
Glu
XRE
WT Cpr (brain/liver-Cpr-null)
Glial Cell
E14-17 Synapse
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Prenatal Exposure Effects on Postnatal (PND15)
MET Protein Expression in WT and B(a)P-exposed
Cpr offspring
MET
1.4
b-Actin
1.2
1.0
MET/b-Actin
1.4
0.7
0.35
0.0
WTCpr 150mg/kg Cpr 300mg/kg Cpr
COntrol
Sheng et al.,(2008) in preparation
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B(a)P-induced Reductions in the Magnitude of
Inward Currents in ex vivo Primary Cortical
Neuronal Cultures
Control ex vivo Primary Mouse Cortical Neur
onal Culture (Day 3)
a
20
-100
-80
-60
-40
-20
20
(mV)
MAP2
-20
-40
(pA)
B(a)P-exposed ex vivo Primary
Mouse Cortical Neuronal Culture (Day 3)
e
MAP2

Offspring control cortical neuronal culture

B(a)P-exposed offspring cortical neuronalculture
Sheng et al., 2008, in preparation
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Schedules of Reinforcement
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Schedules of Reinforcement, Las Vegas Style
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ARCH Meharry Medical College-Vanderbilt University Advanced Research Cooperation in Environmental Health (ARCH) Consortium A Research Program in the Center for Molecular and Behavioral Neuroscience Department of Neurobiology and Neurotoxicology
Prenatal Environmental Exposures and Early
Childhood Development
Autism Spectrum Disorder
PAH Exposure ETS