Long-term behavioural effects of developmental exposure to

organophosphates

Ora KofmanDepartment of Psychology

Zlotowski Centre for Neuroscience Ben-Gurion University of the Negev

Beer-Sheva

Why is pesticide exposure in children different from exposure in adults?

Neurotransmitters and related enzymeshave neurotrophic roles.

Cholinergic markers appear at the same time that synaptogenesis, pruning, thalamic and cortical stratification occur in the developing brain. The high level of AChE prior to the development of cholinergic projections, suggests that it has a role inneuronal growth .

migration

Formation of synapses continues after birth and is influenced by sensory stimulation and learning, drugs and toxins .

Cerebral Cortex 1998 8:142-155

Neonatal rats injected unilaterally with basal forebrainNeonatal rats injected unilaterally with basal forebrainACh neuronal toxin on day of birth and postnatal day 2ACh neuronal toxin on day of birth and postnatal day 2show reduced cortical thicknessshow reduced cortical thickness..

Neonatal rats injected with ACh neuronal toxin onNeonatal rats injected with ACh neuronal toxin on P0 and P2 show reduced number of dendrites (A vs B)P0 and P2 show reduced number of dendrites (A vs B)dendritic spines (C vs D) and axons (E vs F)dendritic spines (C vs D) and axons (E vs F)..

Control LesionedControl Lesioned ControlControl Lesioned Lesioned

Robertson et al. Cerebral Cortex 1998 8:142-155

Prenatal exposure to OP pesticide alters cortical thickness and gene expression

Exposure

Accidental poisoning

Chronic low dose exposure

Plants

Mush-rooms

Rat poison

Cleaning agents

Medicine and drugs

PesticidePesticideKerosene

Sri Lanka

Over age 30

includes

suicide attemptsSenanayake & Karalliedde, Forensic Sci Int 1988

88515112

Trinidad

Children <16Pillai, Boland, Jagdeo and Persad, West Indian Med J. 2004

9.421.815.915.919.5

India

Children 1-3Sarker, Ghosh, Barik Indian J Public Health 1990

96.720.920.942.5

% %cases recordedcases recorded

Who is at risk? Who is at risk? •In urban and rural areas high levels ofpesticides have been found in bloodof pregnant women and cord blood at birth.

•Children in agricultural communities:Drift from fieldsPesticides on clothes, shoes of parents

•Inner city children have higher exposurethan children in the suburbs.

Dilworth Bart and Moore, Child Development, 2006Castorina et al. Env Health Perspect 2003Whyatt et al. Toxicol Appl Pharmacol 2005Curwin et al. Environmental Health 2007

Young et al. Neurotoxicology 2005 :

Exposure during pregnancy

Total metabolite levels of OP pesticides associated with abnormal reflexes on the Brazelton assessment.

Abnormal reflexes: RootingPassive Leg ResistanceIncurvationMoro

Eskenazi et al. Env Health Perspect 2007

Exposure during pregnancy

Followup of children exposed in utero to OPs at6, 12 and 24 months.

•Association between OP metabolites and lowerscores on Mental Development Index of Bayley.

•Association between OP metabolites and PDD(Pervasive Developmental Disorder) scaleof CBCL (Child Behavioral Checklist) at 24 months.

•No effects on attention deficit scale of CBCL.

Grandjean et al., Pediatrics 2006Impaired visual memory (Stanford Binet drawings) and copyingdrawings (visuo-constructive, visuo-spatial). Rauh et al. , Pediatrics 2006

Inner city children followed from birth

36 monthsPsychomotor development index lower in group with high prenatal chlorpyrifos (CPF) exposure: cognitive and psychomotor delays.CBLC: Attention disorder associate with prenatal CPF exposure .

Exposure during pregnancy

Grandjean et al., Pediatrics 2006

Participants: Children in Ecuador whose mother work in floriculture.Simple reaction time is slower in children with higher levels of urinary OP metabolites.

Exposure during childhood

Ruckart et al. Env Health Perspect 2004 1-2 years after exposure to methyl parathion:Increased impulsivity and conduct disorders Sanchez Lizardi et al. J. Pediatric Psychol 2008 High OP metabolites associated with more errors inWisconsin Card Sorting but BETTER concept formation.

Rohlman et al., Neurotoxicology 2005

Slower motor performance (tapping)

Exposure during childhood

Summary: Exposure to OPs during early development:from birth to childhood

Foetus -InfantLower gestational age

Abnormal neonate reflexes

Impaired psychomotordevelopment

Impaired mental development Social skill deficit (PDD)

Child

Visuospatial impairment

Attention deficit

Motor deficit

Motor Inhibition and Learning Impairments in School-AgedChildren Following Exposure to Organophosphate Pesticides in

InfancyORA KOFMAN, ANDREA BERGER, ALI MASSARWA, ALON FRIEDMAN, AND ABED

ABU JAFFAR Pediatr Res 60: 88–92, 2006

Hospitalizations under age 3 with acute poisoning at Soroka University Medical

Center. More than 90% of poisonings reported were in children from the Bedouin

sector.

Statue and Knock-Tap tests from NEPSY battery.

Inhibition and ability to ignore distraction

Stand like a statue with eyes closed with one hand up as if holding a flag (75 seconds) while experimenter makes different noises.Lose points for movements, eye opening, talking and other rule breaks .

Knock – Tap. Experimenter sits opposite child and performshand movements: strike table with palm down, or fist .

Child has to perform the alternate movement and in some cases no movement at all .Inhibition of pre-potent response .

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Children with OP poisoning had lower scores than age and sexmatched controls. No effect on Knock-Tap test.

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OP

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Control K

Kerosene

Verbal listlearning andrecall

Children fromboth poisoninggroups hadpoorer recallin acquisition phase BUTthere was nodifference in delayed recallor recognition.

AChE I inhibitors or stress induce alternate splicing of the enzyme AChE to its rare readthrough form

AChE –R (Soreq and colleagues).

DFP – Kaufer et al. 1998; Meshorer et al. 2002 Soman- Perrier et al. 2005Diazinon– Jameson et al. 2007

Restraint, but not swim stress – Perrier et al. 2005Swim stress – Kaufer et al. 1998

Future Directions Exploring Gene x exposure interactions in rodents

Forced swim test- prolonged immobility is

regarded as enhanced depression (helplessness)

Stages of brain development dependent on induction of genesat different stages. Development is influenced by substances such as neurotransmitters and enzymes.

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1

AChER CTX RQ PCR

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The greater the AChER levels in cortex, the less immobility depression) is found.

Elevated plus maze: Rodent test for anxiety

The less time in the open arms of the maze, the more anxious the mouse is.

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Entries open arms

r=-.21 ,p<.05

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Future Directions Exploring Gene x Exposure Interactions in rodents

Injection of DFP in mice at age 4-10 or 14-20 days

•Increased learned anxiety on 2nd exposure to the elevated plus maze.

•Females but not males show poor passive avoidance despite evidence of good retention.

•Females but not males are impaired in complexdiscrimination learning involving set shifting.

•Male but not females show anhedonia (reduced preference of a sweet solution) and this effect seemsto be strain dependent.

THANKSTHANKS

Israel Science FoundationIsrael Science Foundation

National Institute for Psychobiology in IsraelNational Institute for Psychobiology in Israel

Ali MassarwaAli Massarwa

Amneh AtamnehAmneh Atamneh Andrea Berger, PhDAndrea Berger, PhD

Alon Friedman, MD PhDAlon Friedman, MD PhD

Abd Abu Jaffar, MDAbd Abu Jaffar, MD

Amir Dori, MD PhDAmir Dori, MD PhD

Guy Ben BashatGuy Ben Bashat

Uri LivnehUri Livneh

Tamar LinTamar Lin

Or DuekOr Duek