A case-control study evaluating the relationship between thimerosal-containing haemophilus influenzae type b vaccine administration and the risk for a pervasive developmental disorder diagnosis in the United States

The emerging role of α7nAChRs/caspase-3/Nrf-2 signaling pathway in citicoline improved autistic behavior induced by thimerosal in mice

AIMS

Autism spectrum disorder (ASD) is a global concern,affecting around 75 million individuals.Various factors contribute to ASD,including mercury-containing preservatives like thimerosal (Thim) found in some vaccines.This study explored whether citicoline could be a therapeutic option for Thim-induced neuronal damage in a mouse model of ASD.Additionally,the study investigated the effects of citicoline on the α7nAChRs/Akt/Nrf2/caspase-3 pathway,which may be involved in the development of ASD.

MATERIALS AND METHODS

The study separated newborn mice into four groups.The control group received saline injections,while the Thim group received intramuscular injections of 3000 μg Hg/kg Thim on days 7,9,11,and 15 after birth.The two citicoline groups were administered Thim followed by intraperitoneal injections of 250 mg/kg or 500 mg/kg citicoline for three weeks.Afterward,various parameters were assessed, including growth,behavior,brain histopathology,oxidative stress,apoptotic,and inflammatory markers.

KEY FINDINGS

Untreated Thim-exposed mice exhibited significant brain damage,which was substantially alleviated by citicoline treatment.This beneficial effect was associated with increased expressions and concentrations of brain α7nAChRs and Akt, increased brain content of Nrf2, and the hippocampus contents of acetylcholine. Citicoline treatment decreased the brain levels of oxidative stress markers (MDA and NO),the apoptotic marker caspase-3,and pro-inflammatory markers (NF-κB,TNF-α,and IL-1β). The drug also increased the brain GPx activity.

SIGNIFICANCE

Based on the results of this study,the α7nAChRs pathway appears to be essential for the therapeutic effectiveness of citicoline in treating Thim-induced ASD in mice.

Treadmill Exercise Improves Stereotypical Behaviors in Autistic Rats: Treadmill Exercise Improves ASD

Background: Autism spectrum disorder (ASD) is identified by developmental deficits that lead to repetitive/stereotypic patterns of behavior and impaired social interactions. Studies have been indicated that exercise can decrease stereotypic behaviors in animal models of ASD. This research was designed to discover the effects of different models of forced exercise on stereotypical behaviors in a rat model of ASD induced by thimerosal (THIM). Materials and Methods: Fifty-six male Wistar rats were divided into eight groups. The rats were received saline (1 ml/kg) or THIM (300 μg Hg/kg) by four intramuscular injections on 7, 9, 11, and 15 postnatal days. The rats were also treated by several protocols of treadmill exercise, including non-sedentary, sedentary, protocol 1, protocol 2, and a combination of protocols 1 and 2. Results: Our study showed that THIM decreased the grooming time compared to the control group. Moreover, protocol 2 exercise significantly decreased grooming time in stranger zone 2 compared to the THIM group. Conclusions: Our results showed that stereotypical behaviors exaggerated by THIM and moderate exercise could improve ASD-associated behaviors in the THIM-treated rats. Hence, moderate exercise may be a useful protocol for the treatment of ASD.

A study on the potential reprotoxic effects of thimerosal in male albino rats

Thimerosal is ethyl mercury based compound which is being used as a preservative in vaccines since decades. Pharmaceutical products and vaccines that contain thimerosal are among the potential source of mercury exposure. Current research was intended to ascertain the reprotoxic effects of thimerosal on rat testes. Twenty-four adult male albino rats were sorted into four groups (n = 6). The first group was a control group. Rats of experimental Group 2, 3 and 4 were treated with various dosages of thimerosal (0.5, 10, 50 mg/kg) respectively. Rats were decapitated after thirty days of trial and different parameters were analyzed. Thimerosal exposure resulted in a significant decrease in antioxidant enzyme activities including catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), glutathione reductase (GSR) and increased levels of thiobarbituric acid reactive substances (TBARS). Different doses of thimerosal significantly decreased (p < 0.05) the concentration of plasma testosterone, luteinizing hormone (LH) and follicle stimulating hormone (FSH). Additionally, Daily sperm production (DSP) and efficiency of daily sperm production were significantly reduced followed by thimerosal exposure. Moreover, thimerosal significantly (p < 0.05) decreased the primary spermatocytes, secondary spermatocytes, number of spermatogonia along with spermatids. Thimerosal induced adverse histopathological and morphological changes in testicular tissues such as decreased Leydig cells, diameter of seminiferous tubules, tunica albuginea height and epithelial height. On the other hand, the increase in tubular lumen and interstitial spaces was observed due to thimerosal. These outcomes indicated that thimerosal has potential reprotoxic effects in male albino rats.

The Novel Potential Therapeutic Utility of Montelukast in Alleviating Autistic Behavior Induced by Early Postnatal Administration of Thimerosal in Mice

BACKGROUND AND AIM: Thimerosal (THIM) is a mercury-containing preservative widely used in many biological and medical products including many vaccines. It has been accused of being a possible etiological factor for some neurodevelopmental disorders such as autistic spectrum disorders (ASDs). In our study, the potential therapeutic effect of montelukast, a leukotriene receptor antagonist used to treat seasonal allergies and asthma, on THIM mice model (ASDs model) was examined.

METHODOLOGY

Newborn mice were randomly distributed into three groups: (Group 1) Control (Cont.) group received saline injections. (Group 2) THIM-treated (THIM) group received THIM intramuscular (IM) at a dose of 3000 μg Hg/kg on postnatal days 7, 9, 11, and 15. (Group 3) Montelukast-treated (Monte) group received THIM followed by montelukast sodium (10 mg/kg/day) intraperitoneal (IP) for 3 weeks. Mice were evaluated for growth development, social interactions, anxiety, locomotor activity, and cognitive function. Brain histopathology, alpha 7 nicotinic acetylcholine receptors (α7nAChRs), nuclear factor kappa B p65 (NF-κB p65), apoptotic factor (Bax), and brain injury markers were evaluated as well.

RESULTS

THIIM significantly impaired social activity and growth development. Montelukast mitigated THIM-induced social deficit probably through α7nAChRs upregulation, NF-κB p65, Bax, and brain injury markers downregulation, thus suppressing THIM-induced neuronal toxicity and inflammation.

CONCLUSION

Neonatal exposure to THIM can induce growth retardation and abnormal social interactions similar to those observed in ASDs. Some of these abnormalities could be ameliorated by montelukast via upregulation of α7nAChRs that inhibited NF-κB activation and significant suppression of neuronal injury and the associated apoptosis.

Current Knowledge on Endocrine Disrupting Chemicals (EDCs) from Animal Biology to Humans, from Pregnancy to Adulthood: Highlights from a National Italian Meeting

Wildlife has often presented and suggested the effects of endocrine disrupting chemicals (EDCs). Animal studies have given us an important opportunity to understand the mechanisms of action of many chemicals on the endocrine system and on neurodevelopment and behaviour, and to evaluate the effects of doses, time and duration of exposure. Although results are sometimes conflicting because of confounding factors, epidemiological studies in humans suggest effects of EDCs on prenatal growth, thyroid function, glucose metabolism and obesity, puberty, fertility, and on carcinogenesis mainly through epigenetic mechanisms. This manuscript reviews the reports of a multidisciplinary national meeting on this topic.

Mercury-associated diagnoses among children diagnosed with pervasive development disorders

Nelson and Bauman (Pediatrics 111:674-679, 2003) previously hypothesized that pervasive developmental disorder (PDD) was not associated with mercury (Hg) exposure because the medical conditions associated with Hg exposure were not associated with PDD. A hypothesis-testing longitudinal case-control study evaluated the frequency of medically diagnosed conditions previously associated with Hg poisoning, including: epilepsy, dysarthria, failure to thrive, cerebral palsy, or contact dermatitis and other eczema among children preceding their eventual PDD diagnosis (cases) compared to controls. A retrospective examination of medical records within the Vaccine Safety Datalink (VSD) was undertaken. Cases diagnosed with PDD (n = 534) were born from 1991 to 2000 and continuously enrolled until their PDD diagnosis. Controls (n = 26,367) were born from 1991 to 1993 and continuously enrolled from birth for 7.22 years. Within the first 5 years of life, cases compared to controls were significantly (p < 0.0001) more likely to be assigned a diagnosis of contact dermatitis and other eczema (odds ratio (OR) = 2.033), dysarthria (OR = 23.992), epilepsy (OR = 5.351), failure to thrive (OR = 25.3), and cerebral palsy (OR = 4.464). Similar results were observed when the data were separated by gender. Overall, the results of the present study and recently published studies provide direct evidence supporting a link in twelve of twelve categories (100%) of Hg poisoning associated symptoms as defined by Nelson and Bauman (Pediatrics 111:674-679, 2003) and symptoms observed in those with a PDD diagnosis. The results of this study support the biological plausibility of Hg poisoning to induce PDD diagnoses and rejection of the Nelson and Bauman (Pediatrics 111:674-679, 2003) hypothesis because those with a PDD diagnosis have an increased frequency of conditions previously associated with Hg poisoning.

Protective role of alpha-lipoic acid in impairments of social and stereotyped behaviors induced by early postnatal administration of thimerosal in male rat

Aim Thimerosal, a mercury-containing preservative has been widely used in a number of biological and drug products, including many vaccines, and has been studied as a possible etiological factor for some neurodevelopmental disabilities. Here, the protective effects of Alpha Lipoic Acid (ALA), an organosulfur compound derived from Octanoic Acid, on Thimerosal-induced behavioral abnormalities in rat were examined.

METHODS

108 male Wistar rats were divided into three cohorts and treated as follows: 1) Thimerosal at different doses (30, 300, or 3000 μg Hg/kg) in four i.m. injections on 7, 9, 11, 15postnatal days. 2) ALA (at doses of 5, 10 and 20 mg/kg), following the same order; 3) single dose of Thimerosal (3000 μg Hg/kg) plus ALA at different doses (5, 10 or 20 mg/kg), by the previously described method. A saline treated control group and a ALA vehicle control (0.1% NaOH) were also included. At 5 and 8 weeks after birth, rats were evaluated with behavioral tests, to assess locomotor activity, social interactions and stereotyped behaviors, respectively.

RESULTS

The data showed that Thimerosal at all doses (30, 300 and 3000 μg Hg/kg) significantly impacted locomotor activity. Thimerosal at doses of 300 and 3000 but not 30 μg Hg/kg impaired social and stereotyped behaviors. In contrast, ALA (at doses of 5, 10 and 20 mg/kg) did not alter behaviors by itself, at doses of 20 mg/kg, it reduced social interaction deficits induced by the highest dose of Thimerosal (3000 μg Hg/kg). Moreover, ALA, at all doses prevented the adverse effects of Thimerosal on stereotyped behaviors.

CONCLUSIONS

the results of this preclinical study, consistent with previous studies on mice and rats, reveals that neonatal dose-dependent exposure to Thimerosal mimicking the childhood vaccine schedule can induce abnormal social interactions and stereotyped behaviors similar to those observed in neurodevelopmental disorders such as autism, and, for the first time, revealed that these abnormalities may be ameliorated by ALA. This indicates that ALA may protect against mercurial-induced abnormal behaviors.

Blood Mercury, Arsenic, Cadmium, and Lead in Children with Autism Spectrum Disorder

Environmental factors have been implicated in the etiology of autism spectrum disorder (ASD); however, the role of heavy metals has not been fully defined. This study investigated whether blood levels of mercury, arsenic, cadmium, and lead of children with ASD significantly differ from those of age- and sex-matched controls. One hundred eighty unrelated children with ASD and 184 healthy controls were recruited. Data showed that the children with ASD had significantly (p < 0.001) higher levels of mercury and arsenic and a lower level of cadmium. The levels of lead did not differ significantly between the groups. The results of this study are consistent with numerous previous studies, supporting an important role for heavy metal exposure, particularly mercury, in the etiology of ASD. It is desirable to continue future research into the relationship between ASD and heavy metal exposure.

Systematic Assessment of Research on Autism Spectrum Disorder (ASD) and Mercury Reveals Conflicts of Interest and the Need for Transparency in Autism Research

Historically, entities with a vested interest in a product that critics have suggested is harmful have consistently used research to back their claims that the product is safe. Prominent examples are: tobacco, lead, bisphenol A, and atrazine. Research literature indicates that about 80-90% of studies with industry affiliation found no harm from the product, while only about 10-20% of studies without industry affiliation found no harm. In parallel to other historical debates, recent studies examining a possible relationship between mercury (Hg) exposure and autism spectrum disorder (ASD) show a similar dichotomy. Studies sponsored and supported by industry or entities with an apparent conflict of interest have most often shown no evidence of harm or no "consistent" evidence of harm, while studies without such affiliations report positive evidence of a Hg/autism association. The potentially causal relationship between Hg exposure and ASD differs from other toxic products since there is a broad coalition of entities for whom a conflict of interest arises. These include influential governmental public health entities, the pharmaceutical industry, and even the coal burning industry. This review includes a systematic literature search of original studies on the potential relationship between Hg and ASD from 1999 to August 2015, finding that of the studies with public health and/or industry affiliation, 86% reported no relationship between Hg and ASD. However, among studies without public health and/or industry affiliation, only 21% find no relationship between Hg and ASD. The discrepancy in these results suggests a bias indicative of a conflict of interest.

The association of environmental toxicants and autism spectrum disorders in children

Autism spectrum disorders (ASDs) is a set of complex neurodevelopment disorders that is prevalent in children and is increasing at a steady rate in recent years. However, the etiology of autism is still poorly understood. Humans are at higher risk of chemical exposure than in the past as a result of the increasing usage of chemicals in various fields, including food preservation, agriculture, industrial production, etc. A number of environmental agents have been suggested as contributing factors to ASD pathogenesis, which includes heavy metals (Hg and Pb), persistent organic pollutants (DDT, PBDEs and PCBs) and emerging chemicals of concern (phthalates and BPA). These three main categories of toxicants could be the cause of ASD in children. Recent research into the causes of ASD that have been linked to environment factors are reviewed in this paper. There are evidence supporting the etiological link between exposure to environmental toxicants and the development of ASD. Children exposed to these toxicants in the environment exhibit signature traits of ASD and have been reported with high body burdens of these chemicals and/or their metabolites, which may provide an explanation for the observed relation, yet comprehensive evidence in humans is limited, highlighting the need for further research.

Increased risk for an atypical autism diagnosis following Thimerosal-containing vaccine exposure in the United States: A prospective longitudinal case-control study in the Vaccine Safety Datalink

BACKGROUND

Thimerosal is an organic-mercury (Hg)-containing compound (49.55% Hg by weight) historically added to many multi-dose vials of vaccine as a preservative and still added to some vaccines today. Concerns about the toxic effects from Thimerosal-containing childhood vaccines and the risk of an atypical autism diagnosis were evaluated in this study.

METHODS

A hypothesis-testing, prospective longitudinal, case-control study assessed exposure to Hg from Thimerosal-containing hepatitis B vaccines (TM-HepB) among cases diagnosed with atypical autism (n=164) and controls (n=15,216). Automated medical records for subjects born from 1991 to 2000 and continuously enrolled in the Vaccine Safety Datalink (VSD) database were examined.

RESULTS

Cases diagnosed with atypical autism were statistically significantly more likely to have received greater overall and dose-dependent exposures to Hg from TM-HepB vaccines administered within the first month of life, first two months of life, and first six months of life than the controls. Similar phenomena were observed when cases and controls were separated by gender.

CONCLUSIONS

Routine childhood vaccination is an important public health tool to reduce infectious diseases. The present study provides important epidemiological evidence significantly associating increasing Hg exposure from Thimerosal-containing childhood vaccines and the subsequent risk of atypical autism diagnosis, and suggests that Thimerosal should be eliminated from vaccines.

Abnormal Brain Connectivity Spectrum Disorders Following Thimerosal Administration: A Prospective Longitudinal Case-Control Assessment of Medical Records in the Vaccine Safety Datalink

BACKGROUND

Autism spectrum disorder (ASD), tic disorder (TD), and hyperkinetic syndrome of childhood (attention deficit disorder [ADD]/attention deficit hyperactivity disorder [ADHD]) are disorders recently defined as abnormal connectivity spectrum disorders (ACSDs) because they show a similar pattern of abnormal brain connectivity. This study examines whether these disorders are associated with exposure to thimerosal, a mercury (Hg)-based preservative.

METHODS

A hypothesis testing case-control study evaluated the Vaccine Safety Datalink for the potential dose-dependent odds ratios (ORs) for diagnoses of ASD, TD, and ADD/ADHD compared to controls, following exposure to Hg from thimerosal-containing Haemophilus influenzae type b vaccines administrated within the first 15 months of life. Febrile seizures, cerebral degeneration, and unspecified disorders of metabolism, which are not biologically plausibly linked to thimerosal, were examined as control outcomes.

RESULTS

On a per 25 μg Hg basis, cases diagnosed with ASD (OR = 1.493), TD (OR = 1.428), or ADD/ADHD (OR = 1.503) were significantly (P < .001) more likely than controls to have received increased Hg exposure. Similar relationships were observed when separated by gender. Cases diagnosed with control outcomes were no more likely than controls to have received increased Hg exposure.

CONCLUSION

The results suggest that Hg exposure from thimerosal is significantly associated with the ACSDs of ASD, TD, and ADD/ADHD.

The relationship between mercury and autism: A comprehensive review and discussion

The brain pathology in autism spectrum disorders (ASD) indicates marked and ongoing inflammatory reactivity with concomitant neuronal damage. These findings are suggestive of neuronal insult as a result of external factors, rather than some type of developmental mishap. Various xenobiotics have been suggested as possible causes of this pathology. In a recent review, the top ten environmental compounds suspected of causing autism and learning disabilities were listed and they included: lead, methyl-mercury, polychorinated biphenyls, organophosphate pesticides, organochlorine pesticides, endocrine disruptors, automotive exhaust, polycyclic aromatic hydrocarbons, polybrominated diphenyl ethers, and perfluorinated compounds. This current review, however, will focus specifically on mercury exposure and ASD by conducting a comprehensive literature search of original studies in humans that examine the potential relationship between mercury and ASD, categorizing, summarizing, and discussing the published research that addresses this topic. This review found 91 studies that examine the potential relationship between mercury and ASD from 1999 to February 2016. Of these studies, the vast majority (74%) suggest that mercury is a risk factor for ASD, revealing both direct and indirect effects. The preponderance of the evidence indicates that mercury exposure is causal and/or contributory in ASD.