SafeMinds - Autism Mercury Thimerosal

Summary of Science Demonstrating the Harmful Nature of Mercury in Vaccines

Animal Research

COMPARISON OF ORGANIC AND INORGANIC MERCURY DISTRIBUTION IN SUCKLING RATS
Orct T, Blanusa M, Lazarus M, Varnai VM, Kostial K. J. Appl. Toxicol. 2006; 26: 536-539.

Orct compared body distribution of organic mercury (thimerosal) and inorganic mercury in suckling rats imitating the vaccination schedule of infants. The levels of mercury were higher in the liver and kidney of the inorganic group and the thimerosal group demonstrated higher levels in the blood and brain tissue. Brain retention of mercury in the thimerosal group was 1.5 times higher than the inorganic mercury group, which confirms the fact that thimerosal more easily crosses the blood-brain barrier and may result in significant accumulation with repeated exposure.

IMMUNOSUPPRESSIVE AND AUTOIMMUNE EFFECTS OF THIMEROSAL IN MICE
Havarinasab S, Haggqvist B, Bjorn E, Pollard KM Hultman P. Toxicol Appl Pharmacol. 2005 Apr 15;204(2):109-21

Havarinasab studied the effect of thimerosal by treating A.SW (H-2S) mice, susceptible to induction of autoimmunity by heavy metals, with thimerosal in drinking water developed antinuclear antibodies (ANoA) whereas mice sharing background genes with the A.SW and B10.S strain, but with a different H-2 haplotype, did not develop ANoA, linking the susceptibility to H-2. They concluded that thimerosal has initial immunosuppressive effects similar to those of MeHg. However, in contrast to MeHg, thimerosal treatment leads in genetically susceptible mice to a second phase with strong immunostimulation and autoimmunity, which is T-cell dependent, H-2 linked and may at least partly be due to the inorganic mercury derived from the metabolism of ethyl mercury.
NEUROTOXIC EFFECTS OF POSTNATAL THIMEROSAL ARE MOUSE STRAIN DEPENDENT
Hornig M, Chian D, Lipkin WI. Molecular Psychiatry. 2004 Sep;9(9):833-45.

Hornig exposed autoimmune-prone infant mice with thimerosal-containing vaccines at the dose given to human infants adjusted for mouse weight. This investigation reported a number of observable effects including growth delay; reduced locomotion; exaggerated response to novelty; and densely packed, hyperchromic hippocampal neurons with altered glutamate receptors and transporters. Strains resistant to autoimmunity were not susceptible. These findings implicate genetic influences and provide a model for investigating thimerosal-related neurotoxicity.

EFFECT OF THIMEROSAL, A PRESERVATIVE IN VACCINES, ON INTRACELLULAR CA2+ CONCENTRATION OF RAT CEREBELLAR NEURONS
Ueha-Ishibashi T, Oyama Y, Nakao H, Umebayashi C, Nishizaki Y, Tatsuishi T, Iwase K, Murao K, Seo H. Toxicology 2004 Jan 15;195(1):77-84.

Ueha-Ishibashi investigated the effect of thimerosal on cerebellar neurons dissociated from 2-week-old rats was compared with those of methylmercury. 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 and increased intercellular concentrations of Ca2+. Thimerosal was also found to exert cytotoxic actions on cerebellar granule neurons and its potency was similar to that of methylmercury. The FDA and EPA use methymercury as their toxicity standard, so demonstration of equivalence shows the potential of thimerosal to cause the same harm as methylmercury, for which more research exists.

THIMEROSAL DISTRIBUTION AND METABOLISM IN NEONATAL MICE: COMPARISON WITH METHYL MERCURY
Neurotoxicology. 2007 Feb 23; : 17382399
Grazyna Zareba, Elsa Cernichiari, Rieko Hojo, Scott Mc Nitt, Bernard Weiss, Moiz M Mumtaz, Dennis E Jones, Thomas W Clarkson
Department of Environmental Medicine, University of Rochester, School of Medicine and Dentistry, Rochester, NY, USA.

Thimerosal, which releases the ethyl mercury radical as the active species, has been used as a preservative in many currently marketed vaccines throughout the world. Because of concerns that its toxicity could be similar to that of methyl mercury, it is no longer incorporated in many vaccines in the United States. There are reasons to believe, however, that the disposition and toxicity of ethyl mercury compounds, including thimerosal, may differ substantially from those of the methyl form. The current study sought to compare, in neonatal mice, the tissue concentrations, disposition and metabolism of thimerosal with that of methyl mercury. ICR mice were given single intramuscular injections of thimerosal or methyl mercury (1.4 mg Hg kg(-1)) on postnatal day 10 (PND 10). Tissue samples were collected daily on PND 11-14. Most analysed tissues demonstrated different patterns of tissue distribution and a different rate of mercury decomposition. The mean organic mercury in the brain and kidneys was significantly lower in mice treated with thimerosal than in the methyl mercury-treated group. In the brain, thimerosal-exposed mice showed a steady decrease of organic mercury levels following the initial peak, whereas in the methyl mercury-exposed mice, concentrations peaked on day 2 after exposure. In the kidneys, thimerosal-exposed mice retained significantly higher inorganic mercury levels than methyl mercury-treated mice. In the liver both organic and inorganic mercury concentrations were significantly higher in thimerosal-exposed mice than in the methyl mercury group. Ethyl mercury was incorporated into growing hair in a similar manner to methyl mercury. The data showing significant kinetic differences in tissue distribution and metabolism of mercury species challenge the assumption that ethyl mercury is toxicologically identical to methyl mercury. Copyright (c) 2007 John Wiley & Sons, Ltd.

GENDER-SELECTIVE TOXICITY OF THIMEROSAL
Exp Toxicol Pathol. 2008 Sep 2.
Branch DR.
Departments of Medicine and Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada; Division of Cell and Molecular Biology, Toronto General Research Institute, Toronto, Ontario, Canada; Research and Development, Canadian Blood Services, Immunology Hub, Toronto Centre, Toronto, Ontario, Canada.

A recent report shows a correlation of the historical use of thimerosal in therapeutic immunizations with the subsequent development of autism; however, this association remains controversial. Autism occurs approximately four times more frequently in males compared to females; thus, studies of thimerosal toxicity should take into consideration gender-selective effects. The present study was originally undertaken to determine the maximum tolerated dose (MTD) of thimersosal in male and female CD1 mice. However, during the limited MTD studies, it became apparent that thimerosal has a differential MTD that depends on whether the mouse is male or female. At doses of 38.4-76.8mg/kg using 10% DMSO as diluent, seven of seven male mice compared to zero of seven female mice tested succumbed to thimerosal. Although the thimerosal levels used were very high, as we were originally only trying to determine MTD, it was completely unexpected to observe a difference of the MTD between male and female mice. Thus, our studies, although not directly addressing the controversy surrounding thimerosal and autism, and still preliminary due to small numbers of mice examined, provide, nevertheless, the first report of gender-selective toxicity of thimerosal and indicate that any future studies of thimerosal toxicity should take into consideration gender-specific differences.

INDUCTION OF METALLOTHIONEIN IN MOUSE CEREBELLUM AND CEREBRUM WITH LOW-DOSE THIMEROSAL INJECTION.
Minami T, Miyata E, Sakamoto Y, Yamazaki H, Ichida S.
Department of Life Sciences, School of Science & Engineering, Kinki University, 3-4-1 Kowakae, Higashi-osaka, Osaka, 577-8502, Japan, minamita@life.kindai.ac.jp.
Cell Biol Toxicol. 2009 Apr 9. [Epub ahead of print]

Thimerosal, an ethyl mercury compound, is used worldwide as a vaccine preservative. We previously observed that the mercury concentration in mouse brains did not increase with the clinical dose of thimerosal injection, but the concentration increased in the brain after the injection of thimerosal with lipopolysaccharide, even if a low dose of thimerosal was administered. Thimerosal may penetrate the brain, but is undetectable when a clinical dose of thimerosal is injected; therefore, the induction of metallothionein (MT) messenger RNA (mRNA) and protein was observed in the cerebellum and cerebrum of mice after thimerosal injection, as MT is an inducible protein. MT-1 mRNA was expressed at 6 and 9 h in both the cerebrum and cerebellum, but MT-1 mRNA expression in the cerebellum was three times higher than that in the cerebrum after the injection of 12 microg/kg thimerosal. MT-2 mRNA was not expressed until 24 h in both organs. MT-3 mRNA was expressed in the cerebellum from 6 to 15 h after the injection, but not in the cerebrum until 24 h. MT-1 and MT-3 mRNAs were expressed in the cerebellum in a dose-dependent manner. Furthermore, MT-1 protein was detected from 6 to 72 h in the cerebellum after 12 microg/kg of thimerosal was injected and peaked at 10 h. MT-2 was detected in the cerebellum only at 10 h. In the cerebrum, little MT-1 protein was detected at 10 and 24 h, and there were no peaks of MT-2 protein in the cerebrum. In conclusion, MT-1 and MT-3 mRNAs but not MT-2 mRNA are easily expressed in the cerebellum rather than in the cerebrum by the injection of low-dose thimerosal. It is thought that the cerebellum is a sensitive organ against thimerosal. As a result of the present findings, in combination with the brain pathology observed in patients diagnosed with autism, the present study helps to support the possible biological plausibility for how low-dose exposure to mercury from thimerosal-containing vaccines may be associated with autism.

An earlier study by the same lab related to the above article:

EFFECTS OF LIPOPOLYSACCHARIDE AND CHELATOR ON MERCURY CONTENT IN THE CEREBRUM OF THIMEROSAL-ADMINISTERED MICE
Takeshi Minami, Keisuke Oda, Naoya Gima, Hideo Yamazaki
Environmental Toxicology and Pharmacology
Volume 24, Issue 3, November 2007, Pages 316-320

Thimerosal is one of the best-known preservative agents for vaccines in the world but a relationship between its use and autism has long been suspected so that its effects on the brain need more detailed research. We here examined the influence of lipopolysaccharide injury to the blood–brain barrier on the penetration of mercury from thimerosal into mouse cerebrums, as well as the effect of chelator of heavy metals on cerebrum mercury content. Mercury can be expected to be detected in the cerebrum of normal mice, because the metal is present in standard mouse chow. When 60 μg/kg of thimerosal was subcutaneously injected into the mouse, the mercury content in the cerebrum was significantly higher 48 h after the thimerosal injection with a maximum peak after 72 h. In addition, mercury content in the cerebrum was still higher on day 7 than in the control group. When lipopolysaccharide was pre-injected into mice to induce damage on blood–brain barrier, the mercury content in the cerebrum was significantly higher at 24 and 72 h after the injection of 12 μg/kg of thimerosal compared to the control group, this dose alone does not cause any increase. The mercury content in the cerebrums of mice was decreased to the control group level on day 7 when a chelator, dimercaprol, was administered once a day from days 3 to 6 after a 60 μg/kg, s.c. injection. In addition, d-penicillamine as a chelator decreased the mercury contents in the cerebrum after the high dose administration. In conclusion, a physiological dose of thimerosal did not increase the content of mercury in the cerebrum, but levels were increased when damage to the blood–brain barrier occurred in mice injected with thimerosal. In addition, a chelator of heavy metals may be useful to remove mercury from the cerebrum.

EFFECTS OF INTERMITTENT, VACCINATION-LIKE SCHEME, THIMEROSAL ADMINISTRATION ON RAT DEVELOPMENT AND BEHAVIOUR.
Olczak M., Duszczyk M., Mierzejewski P. & Majewska M. D.
Dept. Pharmacol. Inst. Psychiatry & Neurology, Warsaw, Poland
Publication ref.: FENS Abstr., vol.4, 083.19, 2008

Mercury from thimerosal, which was added to many child vaccines, is one of the agents suspected to be responsible for autism epidemics observed in the past two decades. Data analysis from Vaccine Adverse Event Reporting System of the Center for Disease Control and Prevention (USA) documented that children immunized with vaccines containing thimerosal were several times more likely do develop autism and other neurodevelopmental diseases/disorders than those, who did not receive thimerosal. In this study we examined the potential neurotoxic effects of different cumulative doses of thimerosal, from 0.040 mg/kg to 25 mg/kg, administered to rats s.c. or i. m. in four doses on postnatal days 7-14. Three strains of rats were tested: Wistar, Lewis and Brown Norway. Development and behaviour or the experimental animals was monitored. At different developmental stages (between weeks 4 and 22 of age) several behavioral tests were conducted, which included open field locomotor activity, motor coordination, pain reaction (hot plate), water maze learning and memory test, prepulse inhibition, and social interaction test. Brains of thimerosal treated rats accumulated a significant amount of mercury. They were examined for histopathological changes. Generally, rats appeared to be quite resistant to overt neurotoxic effects of thimerosal at doses tested, although higher doses of this drug caused subtle changes on some behavioral measures, which appear to be species and sex dependent. Significant thimerosal effects on pain reaction, certain learning parameters and prepulse inhibition were observed. Also some aspects of social interactions were altered. Behavioural and histopathological data will be presented in the context of putative rat model of mercury-mediated neurodevelopmental pathologies. Funded by EC grant MEXC-CT-2006-42371 to M. D. Majewska.

EFFECTS OF POSTNATAL ADMINISTRATION OF THIMEROSAL ON RAT DEVELOPMENT AND BEHAVIOR.
Michalina Duszczyk, Mieszko Olczak, Pawe Mierzejewski, Dorota M. Majewska.
Department of Pharmacology and Physiology of the Central Nervous System, Institute of Psychiatry and Neurology, Warsaw, Poland.
Pharmacological Reports. 2008 60; p261-262

Numerous clinical findings support hypothesis that mercury, which was added to many infant vaccines in the form of thimerosal between 2000–2004, may be one of the factors responsible for autism epidemics currently observed all over the world. Data from Adverse Event Reporting of the Center for Disease Control and Prevention (USA) provide strong epidemiological evidence for a link between vaccine-thimerosal exposure and autism or other neurodevelopmental disorders/diseases. The onset of autistic symptoms in children often follows the administration of vaccine thimerosal and symptom emergence is consistent with the expression of developmental mercury toxicity.

In this study, we examined potential neurodevelopmental outcomes following postnatal exposure of rats to thimerosal (Sigma-Aldrich), administered sc or im from 0.040 mg/kg to 50 mg/kg in four equal doses on days 7–14 after birth. Three strains of rats were used in this experiment: Wistar, Lewis and Brown Norway. Development and behavior of experimental animals was observed. Various behavioral tests were carried out, which evaluated: open field locomotor and exploratory activity, motor coordination, pain reaction (hot plate), learning and memory (water maze), prepulse inhibition, sociability (social interaction test). Growth of animals was monitored and after animal sacrifice, weigh of brains was measured. Thimerosal had variable, often biphasic, effects on different measured behaviors, which were strain- and dose-dependent, but no dramatic behavioral impairments were observed at doses tested. Data will be discussed in the context of rodent model of autism following postnatal exposure to mercury. [Note: autism is 4 times more prevalent in boys than girls, and no one has been able to identify why. The differential gender effects of thimerosal and mercury might explain why.]

GENDER-SELECTIVE TOXICITY OF THIMEROSAL.
Branch DR.
Departments of Medicine and Laboratory Medicine and Pathobiology, University of Toronto, Ontario, Canada. don.branch@utoronto.ca
Exp Toxicol Pathol. 2009 Mar;61(2):133-6. Epub 2008 Sep 3.

Abstract:
Despite the indispensable role thyroid hormone (TH) plays in brain development, only a small number of genes have been identified to be directly regulated by TH and its precise mechanism of action remains largely unknown, partly because most of the previous studies have been carried out at postnatal day 15 or later. In the present study, we screened for TH-responsive genes in the developing mouse cerebellum at postnatal day 4 when morphological alterations because of TH status are not apparent. Among the new candidate genes selected by comparing gene expression profiles of experimentally hypothyroid, hypothyroid with postnatal thyroxine replacement, and control animals using oligoDNA microarrays, six genes were confirmed by real-time PCR to be positively (orc1l, galr3, sort1, nlgn3, cdk5r2, and zfp367) regulated by TH. Among these, sort1, cdk5r2, and zfp367 were up-regulated already at 1 h after a single injection of thyroxine to the hypothyroid or control animal, suggesting them to be possible primary targets of the hormone. Cell proliferation and apoptosis examined by BrdU incorporation and terminal deoxynucleotide transferase-mediated dUTP nick-end labeling assay revealed that hypothyroidism by itself did not enhance apoptosis at this stage, but rather increased cell survival, possibly through regulation of these newly identified genes.