The role of mercury in the pathogenesis of autism

Bernard, Sallie; Enayati, Albert; Roger, H; Binstock, Teresa; Redwood, Lyn

doi:10.1038/sj.mp.4001177

Cited by 104 publications

(38 citation statements)

References 17 publications

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“…30 Some investigators postulate that it is the mercury-based preservative thimerosal in vaccines, rather than the vaccines themselves, that poses a risk to the developing infant. 31 This theory has also met with significant criticism. 32 Epilepsy has the highest association with autism, reported in up to a third of individuals with an ASD by adulthood.…”

Section: Defined Nongenetic and Genetic Medical Conditions Associatedmentioning

confidence: 99%

The Genetics of Autism

2004

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ABSTRACT. Autism is a complex, behaviorally defined, static disorder of the immature brain that is of great concern to the practicing pediatrician because of an astonishing 556% reported increase in pediatric prevalence between 1991 and 1997, to a prevalence higher than that of spina bifida, cancer, or Down syndrome. This jump is probably attributable to heightened awareness and changing diagnostic criteria rather than to new environmental influences. Autism is not a disease but a syndrome with multiple nongenetic and genetic causes. By autism (the autistic spectrum disorders [ASDs]), we mean the wide spectrum of developmental disorders characterized by impairments in 3 behavioral domains: 1) social interaction; 2) language, communication, and imaginative play; and 3) range of interests and activities. Epidemiologic studies indicate that environmental factors such as toxic exposures, teratogens, perinatal insults, and prenatal infections such as rubella and cytomegalovirus account for few cases. These studies fail to confirm that immunizations with the measles-mumps-rubella vaccine are responsible for the surge in autism. Epilepsy, the medical condition most highly associated with autism, has equally complex genetic/nongenetic (but mostly unknown) causes. Autism is frequent in tuberous sclerosis complex and fragile X syndrome, but these 2 disorders account for but a small minority of cases. Currently, diagnosable medical conditions, cytogenetic abnormalities, and single-gene defects (eg, tuberous sclerosis complex, fragile X syndrome, and other rare diseases) together account for <10% of cases. There is convincing evidence that "idiopathic" autism is a heritable disorder. Epidemiologic studies report an ASD prevalence of ϳ3 to 6/1000, with a male to female ratio of 3:1. This skewed ratio remains unexplained: despite the contribution of a few well characterized X-linked disorders, male-to-male transmission in a number of families rules out X-linkage as the prevailing mode of inheritance. The recurrence rate in siblings of affected children is ϳ2% to 8%, much higher than the prevalence rate in the general population but much lower than in single-gene diseases. Twin studies reported 60% concordance for classic autism in monozygotic (MZ) twins versus 0 in dizygotic (DZ) twins, the higher MZ concordance attesting to genetic inheritance as the predominant causative agent. Reevaluation for a broader autistic phenotype that included communication and social disorders increased concordance remarkably from 60% to 92% in MZ twins and from 0% to 10% in DZ pairs. This suggests that interactions between multiple genes cause "idiopathic" autism but that epigenetic factors and exposure to environmental modifiers may contribute to variable expression of autism-related traits. The identity and number of genes involved remain unknown. The wide phenotypic variability of the ASDs likely reflects the interaction of multiple genes within an individual's genome and the existence of distinct genes and gene combinations among those affec...

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Section: Defined Nongenetic and Genetic Medical Conditions Associatedmentioning

confidence: 99%

The Genetics of Autism

2004

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“…One important example is represented by thimerosal, an ethyl-mercury compound used as a preservative in vaccines. 59,60 Thimerosal has drawn attention following initial anecdotal reports by some parents linking vaccinations to behavioral regression and to the onset of autism in their child within a matter of days or few weeks. Thimerosal is a Ca 2 þ -mobilizing agent, capable of releasing Ca 2 þ from intracellular stores and increasing Ca 2 þ entry.…”

Section: à1688mentioning

confidence: 99%

Altered calcium homeostasis in autism-spectrum disorders: evidence from biochemical and genetic studies of the mitochondrial aspartate/glutamate carrier AGC1

et al. 2008

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Autism is a severe developmental disorder, whose pathogenetic underpinnings are still largely unknown. Temporocortical gray matter from six matched patient-control pairs was used to perform post-mortem biochemical and genetic studies of the mitochondrial aspartate/glutamate carrier (AGC), which participates in the aspartate/malate reduced nicotinamide adenine dinucleotide shuttle and is physiologically activated by calcium (Ca(2+)). AGC transport rates were significantly higher in tissue homogenates from all six patients, including those with no history of seizures and with normal electroencephalograms prior to death. This increase was consistently blunted by the Ca(2+) chelator ethylene glycol tetraacetic acid; neocortical Ca(2+) levels were significantly higher in all six patients; no difference in AGC transport rates was found in isolated mitochondria from patients and controls following removal of the Ca(2+)-containing postmitochondrial supernatant. Expression of AGC1, the predominant AGC isoform in brain, and cytochrome c oxidase activity were both increased in autistic patients, indicating an activation of mitochondrial metabolism. Furthermore, oxidized mitochondrial proteins were markedly increased in four of the six patients. Variants of the AGC1-encoding SLC25A12 gene were neither correlated with AGC activation nor associated with autism-spectrum disorders in 309 simplex and 17 multiplex families, whereas some unaffected siblings may carry a protective gene variant. Therefore, excessive Ca(2+) levels are responsible for boosting AGC activity, mitochondrial metabolism and, to a more variable degree, oxidative stress in autistic brains. AGC and altered Ca(2+) homeostasis play a key interactive role in the cascade of signaling events leading to autism: their modulation could provide new preventive and therapeutic strategies. Molecular Psychiatry (2010) 15, 38-52; doi: 10.1038/mp.2008.63; published online 8 July 200

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“…Developmental exposure to transition metals such as mercury is causes cognitive impairment [2,3,14]. Organic mercury (methyl or ethyl) are much more potent neurotoxicants than metallic mercury, but metallic mercury (HgCl 2 ) has neurotoxic effects as well.…”

Section: Introductionmentioning

confidence: 99%

Mercury-induced cognitive impairment in metallothionein-1/2 null mice

Eddins

Petro

Pollard

et al. 2008

Neurotoxicology and Teratology

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Metallothioneins are central for the metabolism and detoxification of transition metals. Exposure to mercury during early neurodevelopment is associated with neurocognitive impairment. Given the importance of metallothioneins in mercury detoxification, metallothioneins may be a protective factor against mercury-induced neurocognitive impairment. Deletion of the murine metallothionein-1 and metallothionein-2 genes causes choice accuracy impairments in the 8-arm radial maze. We hypothesize that deletions of metallothioneins genes will make metallothionein-null mice more vulnerable to mercury-induced cognitive impairment. We tested this hypothesis by exposing MT1/MT2-null and wildtype mice to developmental mercury (HgCl 2 ) and evaluated the resultant effects on cognitive performance on the 8-arm radial maze. During the early phase of learning metallothionein-null mice were more susceptible to mercury-induced impairment compared to wildtype. Neurochemical analysis of the frontal cortex revealed that serotonin levels were higher in metallothionein-null mice compared to wildtype mice. This effect was independent of mercury exposure. However, dopamine levels in mercury exposed metallothionein-null mice were lower compared to mercury-exposed wildtype mice. This work shows that deleting metallothioneins increase the vulnerability to developmental mercury-induced neurocognitive impairment. Metallothionein effects on monoamine transmitters may be related to this cognitive effect.

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The role of mercury in the pathogenesis of autism

Cited by 104 publications

References 17 publications

The Genetics of Autism

The Genetics of Autism

Altered calcium homeostasis in autism-spectrum disorders: evidence from biochemical and genetic studies of the mitochondrial aspartate/glutamate carrier AGC1

Mercury-induced cognitive impairment in metallothionein-1/2 null mice

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