The Science on Autism, Mitochondria, and Mercury

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 (Photo credit: Patrick Hoesly)

From  Safe Minds (http://www.safeminds.org/research/science-autism-mitochondria-mercury.html)

The U.S government has conceded a case in the Vaccine Injury Court. The case is a child diagnosed with autism who has a mitochondrial disorder. The child’s vaccinations triggered an adverse effect that led to her autism. David Kirby, author of Evidence of harm, has written an extensive article on the Huffington Post about the case and its implications.

Kirby mentions that mercury, including thimerosal, can trigger mitochondrial dysfunction. Mercury can also lead to oxidative stress (OS) and calcium (Ca2+) dysregulation, both of which are key features of mitochondrial dysfunction. Several studies have linked increased OS, Ca2+ imbalance, and mitochondrial dysfunction to autism.

Also, read David Kirby’s interview with Imus on WABC Radio.

To help readers understand the science relevant to this court case, SafeMinds has posted an assortment of research articles (in full or the abstracts) that pertain to mitochondria function, related physiology (that is, calcium homeostasis and oxidative stress), mercury (including thimerosal) and autism.

Dr. Jon Poling to Dr. Steven Novella on Age of Autism

By Dr. Jon Poling, father of Hannah Poling.

OPEN LETTER TO DR. STEVEN NOVELLA IN RESPONSE TO
“Has the Government Conceded Vaccines Cause Autism?”

Dr. Novella,
Thank you for generating interesting discussion regarding my little girl, Hannah Poling.  I would like to give you additional information in order to generate further productive discussions on this matter amongst the neurology community.  This information should assist you, Dr. DiMauro, and Dr. Trevethan, who have also commented publicly, to formulate better theories as to the significance of Hannah’s mitochondrial dysfunction in relation to her autism.
1. Mito Dysfunction or Mito Disease?  Chicken or Egg?

READ THE ENTIRE LETTER

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Uncoupling of ATP-Mediated Calcium Signaling and Dysregulated Interleukin-6 Secretion in Dendritic Cells by Nanomolar Thimerosal
Samuel R. Goth,1,2 Ruth A. Chu,2 Jeffrey P. Gregg,1,3,4 Gennady Cherednichenko,2 and Isaac N. Pessah1,2,4

1National Institute of Environmental Health Sciences Center for Children’s Environmental Health, 2Department of Veterinary Molecular Biosciences, and 3Department of Medical Pathology, University of California-Davis, Davis, California, USA; 4MIND (Medical Investigation of Neurodevelopmental Disorders) Institute, University of California-Davis, Sacramento, California, USA

Abstract
Dendritic cells (DCs) , a rare cell type widely distributed in the soma, are potent antigen-presenting cells that initiate primary immune responses. DCs rely on intracellular redox state and calcium (Ca2+) signals for proper development and function, but the relationship between these two signaling systems is unclear. Thimerosal (THI) is a mercurial used to preserve vaccines and consumer products, and is used experimentally to induce Ca2+ release from microsomal stores. We tested adenosine triphosphate (ATP) -mediated Ca2+ responses of DCs transiently exposed to nanomolar THI. Transcriptional and immunocytochemical analyses show that murine myeloid immature DCs (IDCs) and mature DCs (MDCs) express inositol 1,4,5-trisphosphate receptor (IP3R) and ryanodine receptor (RyR) Ca2+ channels, known targets of THI. IDCs express the RyR1 isoform in a punctate distribution that is densest near plasma membranes and within dendritic processes, whereas IP3Rs are more generally distributed. RyR1 positively and negatively regulates purinergic signaling because ryanodine (Ry) blockade a) recruited 80% more ATP responders, b) shortened ATP-mediated Ca2+ transients > 2-fold, and c) produced a delayed and persistent rise (≥ 2-fold) in baseline Ca2+. THI (100 nM, 5 min) recruited more ATP responders, shortened the ATP-mediated Ca2+ transient (≥ 1.4-fold) , and produced a delayed rise (≥ 3-fold) in the Ca2+ baseline, mimicking Ry. THI and Ry, in combination, produced additive effects leading to uncoupling of IP3R and RyR1 signals. THI altered ATP-mediated interleukin-6 secretion, initially enhancing the rate of cytokine secretion but suppressing cytokine secretion overall in DCs.DCs are exquisitely sensitive to THI, with one mechanism involving the uncoupling of positive and negative regulation of Ca2+ signals contributed by RyR1. Key words: calcium, calcium channel, dendritic cell, ethyl mercury, immunotoxicity, interleukin-6, organic mercury, redox, thimerosal. Environ Health Perspect 114:1083-1091 (2006) . doi:10.1289/ehp.8881 available via http://dx.doi.org/ [Online 21 March 2006]

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Pharmacol Res. 2005 Oct;52(4):328-33.
Thimerosal-induced cytosolic Ca2+ elevation and subsequent cell death in human osteosarcoma cells.
Chang HTLiu CSChou CTHsieh CHChang CHChen WCLiu SIHsu SSChen JS, Jiann BPJan CR.
Department of Surgery, Kaohsiung Veterans General Hospital, Kaohsiung 813, Taiwan.

The effect of the oxidizing agent thimerosal on cytosolic free Ca(2+) concentration ([Ca(2+)]i) and proliferation has not been explored in human osteoblast-like cells. This study examined whether thimerosal alters Ca(2+) levels and causes cell death in MG63 human osteosarcoma cells. [Ca(2+)]i and cell death were measured using the fluorescent dyes fura-2 and WST-1, respectively. Thimerosal at concentrations above 5 microM increased [Ca(2+)]i in a concentration-dependent manner. The Ca(2+) signal was reduced by 80% by removing extracellular Ca(2+). The thimerosal-induced Ca(2+) influx was sensitive to blockade of La(3+), and dithiothreitol (50 microM) but was insensitive to nickel and several L-type Ca(2+) channel blockers. After pretreatment with 1 microM thapsigargin (an endoplasmic reticulum Ca(2+) pump inhibitor), thimerosal failed to induce [Ca(2+)]i rises. Inhibition of phospholipase C with 2 microM U73122 did not change thimerosal-induced [Ca(2+)]i rises. At concentrations of 5, 10 and 20 microM thimerosal killed 33, 55 and 100% cells, respectively. The cytotoxic effect of 5 microM thimerosal was reversed by 54% by prechelating cytosolic Ca(2+) with BAPTA. Collectively, in MG63 cells, thimerosal induced a [Ca(2+)]i rise by causing Ca(2+) release from endoplasmic reticulum stores and Ca(2+) influx from extracellular space. Furthermore, thimerosal can cause Ca(2+)-related cytotoxicity in a concentration-dependent manner.

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Toxicology. 2004 Jan 15;195(1):77-84.
Effect of thimerosal, a preservative in vaccines, on intracellular Ca2+ concentration of rat cerebellar neurons.
Ueha-Ishibashi TOyama YNakao HUmebayashi CNishizaki YTatsuishi TIwase KMurao KSeo H.
Laboratory of Cellular Signaling, Faculty of Integrated Arts and Sciences, The University of Tokushima, Tokushima 770-8502, Japan.

The effect of thimerosal, an organomercurial preservative in vaccines, on cerebellar neurons dissociated from 2-week-old rats was compared with those of methylmercury using a flow cytometer with appropriate fluorescent dyes. Thimerosal and methylmercury at concentrations ranging from 0.3 to 10 microM increased the intracellular concentration of Ca2+ ([Ca2+]i) in a concentration-dependent manner. The potency of 10 microM thimerosal to increase the [Ca2+]i was less than that of 10 microM methylmercury. Their effects on the [Ca2+]i were greatly attenuated, but not completely suppressed, under external Ca(2+)-free condition, suggesting a possibility that both agents increase membrane Ca2+ permeability and release Ca2+ from intracellular calcium stores. The effect of 10 microM thimerosal was not affected by simultaneous application of 30 microM L-cysteine whereas that of 10 microM methylmercury was significantly suppressed. The potency of thimerosal was similar to that of methylmercury in the presence of L-cysteine. Both agents at 1 microM or more similarly decreased the cellular content of glutathione in a concentration-dependent manner, suggesting an increase in oxidative stress. Results indicate that thimerosal exerts some cytotoxic actions on cerebellar granule neurons dissociated from 2-week-old rats and its potency is almost similar to that of methylmercury.

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Curr Opin Neurobiol. 2007 Feb;17(1):112-9. Epub 2007 Feb 1.
Molecular mechanisms of autism: a possible role for Ca2+ signaling.
Krey JFDolmetsch RE.
Autism spectrum disorders (ASDs) are a group of developmental disorders characterized by social and emotional deficits, language impairments and stereotyped behaviors that manifest in early postnatal life. The molecular mechanisms that underlie ASDs are not known, but several recent developments suggest that some forms of autism are caused by failures in activity-dependent regulation of neural development. Mutations of several voltage-gated and ligand-gated ion channels that regulate neuronal excitability and Ca2+ signaling have been associated with ASDs. In addition, Ca2+-regulated signaling proteins involved in synapse formation and dendritic growth have been implicated in ASDs. These recent advances suggest a set of signaling pathways that might have a role in generating these increasingly prevalent disorders.

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Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
Volume 423, Issues 1-2, 25 January 1999, Pages 65-72

Uptake, cellular distribution and DNA damage produced by mercuric chloride in a human fetal hepatic cell line

Leticia Bucio, Cecilia García, Verónica Souza, Elizabeth Hernández, Cristina González, Miguel Betancourt and Ma. Concepción Gutiérrez-Ruiz

Abstract
A human hepatic cell line (WRL-68 cells) was employed to investigate the uptake of the toxic heavy metal mercury. Hg accumulation in WRL-68 cells is a time and concentration dependent process. A rapid initial phase of uptake was followed by a second slower phase. The transport does not require energy and at low HgCl2 concentrations (<50 μM) Hg transport occurs by temperature-insensitive processes. Subcellular distribution of Hg was: 48% in mitochondria, 38% in nucleus and only 8% in cytosolic fraction and 7% in microsomes. Little is known at the molecular level concerning the genotoxic effects following the acute exposure of eucaryotic cells to low concentrations of Hg. Our results showed that Hg induced DNA single-strand breaks or alkali labile sites using the single-cell gel electrophoresis assay (Comet assay). The percentage of damaged nucleus and the average length of DNA migration increased as metal concentration and time exposure increased. Lipid peroxidation, determined as malondialdehyde production in the presence of thiobarbituric acid, followed the same tendency, increased as HgCl2 concentration and time of exposure increased. DNA damage recovery took 8 h after partial metal removed with PBS–EGTA.

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Naviaux RK.  The spectrum of mitochondrial disease, in Mitochondrial and Metabolic Disorders-a primary care physician’s guide. Psy-Ed Corp., Oradell, NJ, pp. 3-10, 1997.

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Mutagenesis, Vol. 15, No. 6, 525-530, November 2000
Mutagenicity of mercury chloride and mechanisms of cellular defence: the role of metal-binding proteins

Franziska Schurz1, Monica Sabater-Vilar2 and Johanna Fink-Gremmels2*

Department of Analytical and Molecular Pharmacology, TNO Pharma Zeist and 2 Department of Veterinary Pharmacy, Pharmacology and Toxicology, University of Utrecht, The Netherlands

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Oxidative Stress in Autism, Chauhan (PDF)

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Oxidative Stress in Autism, Review (PDF)

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Metabolic biomarkers of increased oxidative stress and impaired methylation capacity in children with autism, James et al (PDF)

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Developmental Regression and Mitochondrial Dysfunction in a Child With Autism(PDF)

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Mitochondrial Energy-Deficient Endophenotype in Autism (PDF)

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Oxidative Stress in Autism: Elevated Cerebellar 3-nitrotyrosine Levels (PDF)

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Bridging from Cells to Cognition in Autism Pathophysiology: Biological
Pathways to Defective Brain Function and Plasticity
 (PDF)

1Matthew P. Anderson, 2Brian S. Hooker and 3Martha R. Herbert

American Journal of Biochemistry and Biotechnology 4 (2): 167-176, 2008

We review evidence to support a model where the disease process underlying autism may begin when an in utero or early postnatal environmental, infectious, seizure, or autoimmune insult triggers an immune response that increases reactive oxygen species (ROS) production in the brain that leads to DNA damage (nuclear and mitochondrial) and metabolic enzyme blockade and that these inflammatory and oxidative stressors persist beyond early development (with potential further exacerbations), producing ongoing functional consequences.

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Evidence of Mitochondrial Dysfunction in Autism and Implications for Treatment(PDF)

Daniel A. Rossignol, J. Jeffrey Bradstreet

Abstract: Classical mitochondrial diseases occur in a subset of individuals with autism and are usually caused by genetic anomalies or mitochondrial respiratory pathway deficits. However, in many cases of autism, there is evidence of mitochondrial dysfunction (MtD) without the classic features associated with mitochondrial disease. MtD appears to be more common in autism and presents with less severe signs and symptoms. It is not associated with discernable mitochondrial pathology in muscle biopsy specimens despite objective evidence of lowered mitochondrial functioning. Exposure to environmental toxins is the likely etiology for MtD in autism. This dysfunction then contributes to a number of diagnostic symptoms and comorbidities observed in autism including: cognitive impairment, language deficits, abnormal energy metabolism, chronic gastrointestinal problems, abnormalities in fatty acid oxidation, and increased oxidative stress. MtD and oxidative stress may also explain the high male to female ratio found in autism due to increased male vulnerability to these dysfunctions. Biomarkers for mitochondrial dysfunction have been identified, but seem widely under-utilized despite available therapeutic interventions. Nutritional supplementation to decrease oxidative stress along with factors to improve reduced glutathione, as well as hyperbaric oxygen therapy (HBOT) represent supported and rationale approaches. The underlying pathophysiology and autistic symptoms of affected individuals would be expected to either improve or cease worsening once effective treatment for MtD is implemented.

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Mitochondrial delivery is essential for synaptic potentiation.  

Biol Bull. 2007 Apr;212(2):169-75.  Tong JJ

Biophysics and Physiology, University of California, Irvine, CA 92697, USA. tongja@uci.edu

Mitochondria, as portable generators that power synaptic function, regulate the ATP supply and calcium homeostasis in the neuron. As molecular interactions within the synapses before and after the potentiation are beginning to be elucidated, the deciding moment during the tetanic stimulation that gives rise to the strengthening of the synapse remains a mystery. Here, I recorded electrically from an intact Drosophila nervous system, while simultaneously using time-lapse confocal microscopy to visualize mitochondria labeled with green fluorescent protein. I show that tetanic stimulation triggers a fast delivery of mitochondria to the synapse, which facilitates synaptic potentiation. Rotenone, an inhibitor of mitochondrial electron transport chain complex I, suppresses mitochondrial transport and abolishes the potentiation of the synapse. Expression of neurofibromin, which improves mitochondrial ATP synthesis in the neuron, enhances the movements of mitochondria to the synapse and promotes post-tetanic potentiation. These findings provide unprecedented evidence that the mitochondrial delivery to the synapse is critical for cellular learning.

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Mitochondria at the synapse.

Neuroscientist. 2006 Aug;12(4):291-9.

Ly CVVerstreken P

Department of Neuroscience and Molecular and Human Genetics, Howard Hughes Medical Institute Baylor College of Medicine, Houston, TX 77030, USA. cindy.ly@bcm.tmc.edu

Synapses are packed with mitochondria, complex organelles with roles in energy metabolism, cell signaling, and calcium homeostasis. However, the precise mechanisms by which mitochondria influence neurotrans mission remain undefined. In this review, the authors discuss pharmacological and genetic analyses of synaptic mitochondrial function, focusing on their role in Ca2+ buffering and ATP production. Additionally, they will summarize recent data that implicate synaptic mitochondria in the regulation of neurotransmitter release during intense neuronal activity and link these findings to the pathogenesis of neurodegenerative diseases that feature disrupted synaptic mitochondria, including amyotrophic lateral sclerosis and hereditary spastic paraplegia.

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J Child Neurol. 2002 Jun;17(6):435-9.

Mitochondrial dysfunction in patients with hypotonia, epilepsy, autism, and developmental delay: HEADD syndrome

Fillano JJ, Goldenthal MJ, Rhodes CH, Marín-García J.
Department of Pediatrics, Dartmouth Hitchcock Medical Center, Lebanon, NH, USA.

A group of 12 children clinically presenting with hypotonia, intractable epilepsy, autism, and developmental delay, who did not fall into previously described categories of mitochondrial encephalomyopathy, were evaluated for mitochondrial respiratory enzyme activity levels, mitochondrial DNA, and mitochondrial structural abnormalities. Reduced levels in specific respiratory activities were found solely in enzymes with subunits encoded by mitochondrial DNA in seven of eight biopsied skeletal muscle specimens evaluated. Five cases exhibited increased levels of large-scale mitochondrial DNA deletions, whereas pathogenic point mutations previously described in association with mitochondrial encephalomyopathies were not found. Mitochondrial structural abnormalities were present in three of four patients examined. Our findings suggest that mitochondrial dysfunction, including extensive abnormalities in specific enzyme activities, mitochondrial structure, and mitochondrial DNA integrity, may be present in children with a clinical constellation including hypotonia, epileptic seizures, autism, and developmental delay. The acronym HEADD is presented here to facilitate pursuit of mitochondrial defects in patients with this clinical constellation after other causes have been excluded.

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Histol Histopathol. 2005 Jul;20(3):957-67.

Role of oxidative damage in the pathogenesis of viral infections of the nervous system.

Valyi-Nagy T, Dermody TS.
Department of Pathology, College of Medicine, University of Illinois at Chicago, Chicago, Illinois, USA.

Oxidative stress, primarily due to increased generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS), is a feature of many viral infections. ROS and RNS modulate the permissiveness of cells to viral replication, regulate host inflammatory and immune responses, and cause oxidative damage to both host tissue and progeny virus. The lipid-rich nervous system is particularly susceptible to lipid peroxidation, an autocatalytic process that damages lipid-containing structures and yields reactive by-products, which can covalently modify and damage cellular macromolecules. Oxidative injury is a component of acute encephalitis caused by herpes simplex virus type 1 and reovirus, neurodegenerative disease caused by human immunodeficiency virus and murine leukemia virus, and subacute sclerosing panencephalitis caused by measles virus. The extent to which oxidative damage plays a beneficial role for the host by limiting viral replication is largely unknown. An enhanced understanding of the role of oxidative damage in viral infections of the nervous system may lead to therapeutic strategies to reduce tissue damage during viral infection without impeding the host antiviral response.

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Mitochondria and neuronal activity (PDF)

Oliver Kann and Richard Kovács

Am J Physiol Cell Physiol 292:641-657, 2007. First published Nov 8, 2006; doi:10.1152/ajpcell.00222.2006

Mitochondria are central for various cellular processes that include ATP production, intracellular Ca2 signaling, and generation of reactive oxygen species. Neurons critically depend on mitochondrial function to establish membrane excitability and to execute the complex processes of neurotransmission and plasticity. While much information about mitochondrial properties is available from studies on isolated mitochondria and dissociated cell cultures, less is known about mitochondrial function in intact neurons in brain tissue. However, a detailed description of the interactions between mitochondrial function, energy metabolism, and neuronal activity is crucial for the understanding of the complex physiological behavior of neurons, as well as the pathophysiology of various neurological diseases. The combination of new fluorescence imaging techniques, electrophysiology, and brain slice preparations provides a powerful tool to study mitochondrial function during neuronal activity, with high spatiotemporal resolution. This review summarizes recent findings on mitochondrial Ca2 transport, mitochondrial membrane potential (m), and energy metabolism during neuronal activity. We will first discuss interactions of these parameters for experimental stimulation conditions that can be related to the physiological range. We will then describe how mitochondrial and metabolic dysfunction develops during pathological neuronal activity, focusing on temporal lobe epilepsy and its experimental models. The aim is to illustrate that 1) the structure of the mitochondrial compartment is highly dynamic in neurons, 2) there is a fine-tuned coupling between neuronal activity and mitochondrial function, and 3) mitochondria are of central importance for the complex behavior of neurons.

One thought on “The Science on Autism, Mitochondria, and Mercury

  1. Pingback: The Science on Autism, Mitochondria, and Mercury | Through The … | Autistic Information

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