Transcript The Neurotoxicology of attention deficits

The Neurotoxicology of
attention deficits: Dietary
Manganese Exposure as a
Particular Case
Sabrina E.B. Schuck, Ph.D., Melody Yi,
Ph.D. & Francis M. Crinella, Ph.D.
The Child Development Center
University of California, Irvine
Everyone knows what attention is.
It is the taking possession in the
mind, in clear and vivid form, of
one out of what seem several
simultaneous object or trains of
thought.
William James [The Principles of
Psychology, 1890]
ATTENTION HELPS US TO MANAGE
CONFLICTING PERCEPTUAL INPUTS
ATTENTION ALLOWS US TO
PERSIST IN TASK PERFORMANCE
ATTENTION HELPS US FOCUS ON
THE TASK AT HAND
ATTENTION ENABLES US TO PERFORM
TASKS THAT REQUIRE PLANNING AND
WORKING MEMORY
ATTENTION ENABLES US TO MAINTAIN
VIGILANCE WHEN MONITORING SIGNALS
ATTENTION ENABLES US TO AVOID
COSTLY ERRORS
HOWEVER: ATTENTION IS THE MOST
FRAGILE OF ALL MENTAL FUNCTIONS
1. ATTENTION CAN BE ADVERSELY AFFECTED BY ANY
NUMBER OF INTERNAL AND EXTERNAL INFLUENCES
2. ALL NEURODEVELOPMENTAL AND
NEUROPSYCHIATRIC DISORDERS ARE ACCOMPANIED
BY ATTENTION DEFICITS
3. ADHD IS BUT ONE OF MANY DIAGNOSABLE
CONDITIONS IN WHICH ATTENTION IS AFFECTED
DSM-IV SYMPTOMS OF ADHD
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•
INATTENTION
HYPERACTIVITY/IMPULSIVITY
CAN’T ATTEND TO DETAILS
CAN’T SUSTAIN ATTENTION
DOESN’T LISTEN
FAILS TO FINISH
CAN’T ORGANIZE TASKS
AVOIDS SCHOOLWORK
LOSES THINGS
EASILY DISTRACTED
FORGETFUL
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FIDGETS
CAN’T STAY SEATED
RUN ABOUT AND CLIMBS
CAN’T PLAY QUIETLY
IS OFTEN ON THE GO
TALKS TOO MUCH
BLURTS OUT ANSWERS
CAN’T WAIT TURN
INTERRUPTS OR INTRUDES
BIOLOGICAL BASIS OF
ADHD
I. PSYCHOPHARMACOLOGY
II. MOLECULAR BIOLOGY
III.BRAIN IMAGING
IV.ELECTROPHYSIOLOGY
V. NEUROPSYCHOLOGY
I. PSYCHOPHARMACOLOGY
TREATMENT WITH CNS STIMULANTS
BENZEDRINE (Bradley, 1937)
DEXTROAMPHETAMINES (e.g., Dexedrine, Adderall)
METHYLPHENIDATES (e.g., Ritalin, Concerta)
THE DOPAMINE HYPOTHESIS
Wender P. Minimal brain dysfunction in children. Wiley-Liss, New York (1971).
Levy F. The dopamine theory of attention deficit hyperactivity disorder (ADHD).
Aust. N. Z. J. Psychiatry 25, 277-83 (1991).
Grady D, Moyzis R, Swanson JM. Molecular genetics and attention in ADHD. Clin.
Neurosci. Res. 5, 265-272 (2005).
BIOLOGICAL BASIS OF ADHD II:
MOLECULAR BIOLOGY
• DOPAMINE D4 RECEPTOR GENE POLYMORPHISM
ASSOCIATED WITH ADHD (Lahoste, Swanson et al., 1996,
Molecular Psychiatry)
• ASSOCIATION OF THE DOPAMINE RECEPTOR D4 (DRD4)
GENE WITH A REFINED PHENOTYPE OF ADHD (Swanson,
Sunohara, Kennedy et al., 1998, Molecular Psychiatry)
• MOLECULAR GENETICS AND ATTENTION IN ADHD (Grady,
Moyzis & Swanson, 2005, Clinical Neuroscience Research)
From Grady, Moyzis & Swanson, (2005), Clinical Neuroscience Research, 5, 265-272
From Grady, Moyzis & Swanson (2005), Clinical Neuroscience Research, 5, 265-272.
BIOLOGICAL BASIS OF
ADHD III: STRUCTURAL
IMAGING
LONGITUDINAL MAPPING OF CORTICAL
THICKNESS AND CLINICAL OUTCOME IN
CHILDREN AND ADOLESCENTS WITH
ATTENTION-DEFICIT/HYPERACTIVITY
DISORDER. Shaw, Lerch, Greenstein et al. (2006),
Archives of Genetic Psychiatry, 63, 540-549.
IV. ELECTROPHYSIOLOGY
Early studies of analog EEG:
Satterfield, J.H., & Schell, A.M. (1984). Childhood brain
function differences in delinquent and non-delinquent
hyperactive boys. Electroencephalography and Clinical
Neurophysiology, 57, 199-207.
Finding: Abnormal maturational effects of auditory eventrelated potential differentiated ADHD from non-ADHD subjects
Recent brain mapping studies:
Pliszka, S.R., Liotti, M., & Woldorff, M.G. (2000). Inhibitory
control in children with attention-deficit/hyperactivity
disorder. Biological Psychiatry, 48,238-46.
Finding: Event related potentials identify the processing
component and timing of an impaired right-frontal responseinhibition mechanism.
V: NEUROPSYCHOLOGICAL
EVIDENCE
• ADHD conceptualized as “frontal lobe” disorder
(e.g., Douglas, 1980; Chelune et al., 1986)
• ADHD conceptualized as disorder of “executive
function” (Pennington et al., 1990; Barkley 1997;
Schuck & Crinella, 2000)
Brief Definitions of Executive
Function
• Appropriate set maintenance to achieve a future
goal (Pennington, Welsh & Grossier, 1990)
• A process that alters the probability of
subsequent responses to an event, thereby
altering the probability of later consequences
(Barkley, 1997).
• A process which enables the brain to function as
many machines in one, setting and resetting itself
dozens of times in the course of a day, now for
one type of operation, now for another (Sperry,
1955)
EXECUTIVE FUNCTIONS CAN BE
ADVERSELY AFFECTED BY ANY
NUMBER OF NEUROTOXINS
FOR EXAMPLE:
• PESTICIDES
• LEAD (Pb)
• CNS STIMULANTS
Odds Ratio of Detectable Pesticide in Serum
Children 8-12 Years Old (n = 167)
Oahu vs. Neighbor Islands
5
4
3.8
3
2
1.7
1.4
1.0
1
0
Heptachlor
Epoxide
pp'-DDE
Oxychlordane
trans-Nonachlor
From Baker, Yang & Crinella, 2004, Neurotoxicology, 25, 700-701
STANDARD SCORES ON NEUROBEHAVIORAL TESTS
FOR SUBJECTS BORN ON OAHU (n = 332) vs.
SUBJECTS BORN ELSEWHERE (n = 112)
140
120
100
80
BORN ELSEWHERE
OAHU BORN
60
40
20
0
RAVEN
WRAML
HRTMT
STROOP
WCST
CPT HIT REACTION TIMES FOR CHILDREN (AGES 7—10),
STIMULANT-EXPOSED IN UTERO AND AGE-MATCHED CONTROLS
BY ISI INTERVALS
800
750
1 SEC
2 SEC
4 SEC
700
MILLISECONDS
650
600
550
500
450
400
350
300
1
2
3
4
5
6
7
----------STIMULANT EXPOSED
-----------CONTROLS
8
9
10
11
12
BLOCKS OF TRIALS
13
14
15
16
17
18
19
20
HYPERACTIVITY RATINGS AS A FUNCTION OF Pb LEVELS IN
TIJUANA CHILDREN
12
10
HYPERACTIVITY RATING
8
6
4
2
0
<5
5--8
9--12
13--16
Pb LEVELS IN µG/DL
17--22
>22
STUDIES ASSOCIATING HAIR
MANGANESE [Mn] LEVELS WITH ADHD
Pihl, R.O. & Parks, M. (1977). Hair element content in learning
disabled children. Science, 198, 204-206.
Collip, P.J., Chen, S.Y. & Maitinsky, S. (1983). Manganese in infant
formulas and learning disability. Annals of Nutrition and
Metabolism, 27, 488-494.
Marlowe, M. & Bliss, L. (1993). Hair element concentrations and
young children's behavior at school and home. Journal of
Orthomolecular Medicine, 9, 1-12.
Cordova, E.J., Ericson, J., Swanson, J.M., & Crinella, F.M. (1997).
Head hair manganese as a biomarker for ADHD. Proceedings of
the 15th Annual Conference on Neurotoxicology.
HEAD HAIR Mn LEVEL
0.14
0.12
0.1
0.08
PPM
0.06
0.04
0.02
0
ADHD
CONTROL
IS MN EXPOSURE AN ETIOLOGIC
AGENT IN ADHD?
1. CHILDREN WITH ADHD HAVE HIGH LEVELS OF
HEAD HAIR MN
2. MN IS A KNOWN NEUROTOXIN
3. MN TOXICITY AFFECTS BRAIN DOPAMINE
SYSTEMS
4. ADHD IS A PRIMARILY DOPAMINERGIC DISORDER
Critical Observations Regarding
Mn in infants and children
Manganese in head hair of children with ADHD
may be the result of soy-based infant formulas
(Collip et al., 1983)
Term infants fed soy formula have significantly
higher blood Mn than breast-fed infants
(Kirchgessner et al., 1981)
High, positive retention of Mn from formula, but
not breast milk in preterm infants (Lonnerdal,
1994)
INFANT DIETARY MN INTAKE
HYPOTHESES
Since Mn is well absorbed from
infant diets, and absorbed Mn is
retained by the body, it will
accumulate in brain, resulting in:
1. Depleted striatal DA
2. Neuromotor delay
3. Executive function deficits
Tissue Mn Assays
an
d1
d6
d10
d14
d20
d35
d58
d60
Control (0)
50 µg Mn/d
250 µg Mn/d
500 µg Mn/d
Righting
(d6) Homing
(d10)
Other measurements
Hb and Wt
Passive Avoidance
(d35) Digging latency
running time (d58)
Passive Avoidance
(60-64)
Concentrations of Mn in brain of
rats killed at day 14, 21 and 35
Brain
4
3
0
250
500
2
1
0
d14
d21
d35
DA
(ng/10 mg wet tissue)
Striatal Dopamine in Animals
Killed at d35
30
*
20
*
10
0
0
50
250
500
Mn dose (ug/day)
*Significant difference between control and low Mn exposure
PASSIVE AVOIDANCE TEST
Results of Passive Avoidance Test at d32
No. of Footshocks
7.5
5.0
2.5
0.0
control
50 ug
250 ug
Mn (ug/day)
500 ug
Results of Burrowing Detour Test d55
Digging Latency
500
Time (sec)
400
300
200
100
0
Control
50
250
Mn ( g/day)
500
STRIATAL DOPAMINE LEVELS AT d65
2
1.8
DA LEVEL (ng/mg)
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
0
50
250
TREATMENT LEVEL (ug/l)
500
NONHUMAN PRIMATE MODELS
ADVANTAGES OVER RODENT MODEL
– Maturity of brain development at birth
– Prolonged period of postnatal brain
development
– Complexity of behavioral repertoire
– Assessments similar to humans
Study Design
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•
•
Subjects: Male newborn rhesus
monkeys
Treatment: Exclusively formula fed
freom 0-4 months of age
Groups (n = 8):



Cow’s milk based infant formula, 0.03 µg
Mn /ml
Soy based infant formula, 0.3 µg Mn/ml
Soy + Mn; soy based infant formula with
added manganese, 1 µg Mn/ml
Behavior testing schedule
APOMORPHINE
DRUG
CHALLENGE
FORMULA FEEDING
IMPULSIVITY TESTS:
NON-MATCH TO SAMPLE
CPT
POSITION REVERSAL
DIURNAL ACTIVITY
MOTOR MATURATION
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16 17 18
Gross Motor Maturation
14
12
10
8
6
Walk
4
2
0
20
18
16
14
12
10
8
6
4
2
0
30
Climb
25
20
15
10
5
0
5
4
20
18
16
14
12
10
8
6
4
2
0
Manual
10
8
3
6
2
4
1
2
0
0
Control
Soy
Soy + Mn
1
2
3
4
5
6
Session
7
8
9 10 11 12
Amount of activity
Number of counts/ 2 min
WAKE
120
100
80
60
40
20
0
SLEEP
Cow’s milk
14
Soy
12
10
8
Soy + Mn
*.01
6
4
2
0
4 months
8 months
WGTA
One-way mirror
Sliding test
board
Door on pulley
Delayed nonmatch to sample
Test board 1
Test board 2
.12
.
Cow’s milk
.08
.
Soy
.06
.
.04
.
Percent
.1
.02
0
Balks-no sample choice made
.
Soy + Mn
Position reversals
Test board
sessions to criterion for learning
Cow’s milk
8
7
Soy
Sessions
6
5
4
3
2
1
0
6
Soy + Mn
Test board
Food reward
Sliding
opaque cover
MOTOR
IMPULSIVITY
TEST
Impulsivity-response inhibition
average number of trials (of 40) on which the monkey responded at each interval
25
22.5
Cow’s milk
20
17.5
15
number of trials
12.5
Soy
*.04
Soy + Mn
10
7.5
*.03
5
2.5
0
0
1-6
7
interval
balk
CANTAB
Fixed interval;dopamine challenge
Continuous performance test
Change in response rate from vehicle injection
Dopamine drug challenge
Fixed interval responding
Cow’s milk
100
Soy
75
50
Soy + Mn
25
*.01
0
-25 0.1 mg/kg
-50
0.2 mg/kg .0.3 mg/kg
amphetamine
-------apomorphine-----
-75
-100
haloperidol
-125
-150
apomorphine, dopamine agonist, response rate
haloperidol, dopamine antagonist,  response rate
*.02
haloperidol+
apomorphine
Social Interaction Study
• Method-videotape of dyadic interaction
• Familiar same group, unfamiliar same
group, unfamiliar opposite group
• Social buffering
• Used previously to compare field cage
with nursery reared males
dyadic interactions during round robin
socialization (16 sessions)
40
*.01
number of occurrences
35
30
*.03
25
control
20
*.003*.003
15
10
Soy
.06
Soy+Mn
*.003
5
0
Chase play
Rough play
cling
Age and formula effects on
CSF catecholamine metabolites
5HIAA
160
140
120
control
450
low mn
400
350
hi mn
100
Cell Mean
Cell Mean
HVA
500
80
60
300
250
200
150
40
100
20
50
0
0
3
10
12
Months of age
3
10
12
Early responses
Relationship between CSF catecholamine
metabolites and impulsivity
45
40
35
30
25
20
15
10
5
5HIAA- 10 months of age
10
20
30
40
R2 = 0.156
50
60
70
80
90 100
45
40
35
30
25
20
15
10
5
HVA- 10 months of age
150 200 250 300 350 400 450 500 550
R2 = 0.19
THE “TOOTH FAIRY” STUDY
• Participants: 27 children (11 boys) from the NICHD
Study of Early Child Care and Youth Development
• Procedures:
•
– Shed molars collected from 400 children (ages 11-13); 27
teeth randomly selected
– Measures of children’s behavioral disinhibition collected
from ages 3 to 9 years.
– IMS analyses of teeth performed by CAMECA IMS 1270
– Concentration of manganese in the molar cusp tip (formed
at approximately the 20th gestational week) used as an
indication of prenatal Mn absorption
Tooth Enamel Biomarker
• Tooth enamel layers, like tree rings, provide a
temporal record of mineral absorption
• Absorbed minerals, as reflected in the tooth enamel
record, may be associated with embryogenetic
variations
• Depending on corresponding embryological
developments in CNS, Mn absorption, as reflected in
tooth enamel record, may be associated with specific
variation in behavioral outcomes
Human Tooth Enamel
• As tooth develops over rime, incremental
growth rings of enamel are deposited
• Oldest enamel is found at the incisal tip
• Mature enamel is a metabolic isolate
• Mn is stable in calcium hydroxyapatite
Analytical Measurements
•
•
•
•
•
•
ion microprobe mass spectrometer (ims)
10 - 35 um spot resolution
auger & sputter sample
measurement of Mn concentration
detection <30 ppb
90% accuracy
Behavior Battery
• Data base of NICHD Early Childhood
Study
• Administered Age 3, Grade 1 and Grade 3
• Teachers, mothers, and standardize tests
of subjects
• 21 behavior measures (disinhibition,
intelligence and depression) over 5 years
• Same subjects maintain position
RESULTS
Mn LEVELS WERE POSITIVELY CORRELATED
WITH:
 Increased play with “Forbidden Toy” (36 mo.)
 More impulsive errors on CPT (54 mo.)
 More impulsive errors on Stroop Test (54 mo.)
 Higher ratings on externalizing behavior and
attentional problems (teachers and mothers; 1st and
3rd grades)
 Higher incidence of disruptive disorders (ADHD,
hyperactivity/impulsivity, and inattention (teachers, 1st
and 3rd grades)
MULTIPLE REGRESSION ANALYSIS
(Predicting Mn Level With Behavioral Measures)
CPT (54 months)
Stroop (54 months)
CBCL Inattention (1st grade)
DBD3 HYPERACTIVITY (3RD GRADE)
R2 = 0.62; df = 4, 26; P < .001
Adjustment for socioeconomic confounds did not
increase significance
• Mother’s education
• Income
• Ethnicity
(F of change = .13, p = .97)
DISCUSSION
• A link was demonstrated between prenatal
Mn absorption and measures of behavioral
disinhibition in later childhood
• The source of Mn was unknown, but may
have been due to maternal gestational
anemia, a common occurrence during
pregnancy that results in overabsorption of
Mn.
CONCLUSIONS
• Attention deficits are observed in almost all
neuropsychiatric disorders, including ADHD
• ADHD symptoms may are associated with a number
of genetic, epigenetic and environmental influences,
including toxic exposures
• Mn serves as an example of a toxic exposure that
can produce ADHD-like symptoms in rodents, nonhuman primates, and humans
• The Mn-ADHD link is likely to be mediated by toxic
effects on DRD4 and DAT genes.
CONCLUSIONS (CONT’D)
• The Mn-ADHD link is likely to be mediated by
toxic effects on DRD4 and DAT genes.
• A DAT1 40bp VNTR 9/10 polymorphism was
reliably associated with greater symptoms of
ADHD.
Barkley, Smith, Fischer & Bradford, (2006), American Journal of
Medical Genetics. 141B, 487-498.
• And, there is persistent evidence that DAT
can be adversely impacted by Mn.
Kern, Stanwood & Smith, (2010), Synapse, 64, 363-378.
CONTRIBUTORS
University of California, Irvine
Aleksandra Chicz-DeMet
Louis Le
Mike Parker
Jonathon E. Ericson
K. Alison Clarke-Stewart
Virginia D. Allhusen
Tony Chan
Richard T. Robertson
University of California, Davis
Bo Lonnerdal
Mari Golub
Winyoo Chowanadisai
Stacey Germann
Casey Hogrefe
University of California, San Francisco
Trinh Tran
City University of New York
Joey Trampush