Neurotoxins and Autism

Recently, a great concern has risen about the increasing prevalence of autism as a neurodevelopmental disorder. Environmental factors as significant contributors to children’s health through a wide range of routes are linked to remarkable increases in this disorder. It is well known and accepted that young children are more vulnerable to environmental toxins, compared to adults. Modern day lifestyles with more mercury and lead exposures, fast food, cell phones, and microwaves place children at higher risk of neurotoxicity. Moreover, a huge number of synthetic chemicals termed as high-production-volume (HPV) chemicals are found in many products such as medications, cosmetics, building materials, plastic, and car fuels. These HPVs highly contribute to brain damage in developing infants. Other environmental toxins include thalidomide, valproic acid, misoprostol, and many infectious agents among which are pathogenic bacteria or their metabolites are found to be neurotoxic and/or linked to incidences of autism. This chapter summarizes the most important routes of exposure to environmental neurotoxins and explains how these toxins are related to the remarkable increase in the prevalence of autism through different etiological mechanisms such as oxidative stress, neuroinflammation, impaired neurochemistry and glutamate excitotoxicity

Neuroprotective effect of creatine against propionic acid toxicity in neuroblastoma SH-SY5Y cells in culture

This work aimed to verify propionic acid toxic effects, and to investigate the possible neuroprotective effects of creatine against it. Propionic acid (PA) toxicity together with the effect of creatine (CR) was studied on neuroblastoma SH-SY5Y brain cells in culture. In the first group, cells were divided and treated with different concentrations of PA, while the second group was pre-treated with creatine to test its neuroprotective effect in PA-intoxicated cells. Comet assay and DNA fragmentation studies were used to examine genotoxicity and apoptosis of cells. The results emphasized the neurotoxicity of propionate to neuroblastoma cell line SH-SY5Y by DNA fragmentation that increased in a dose- and time-dependent manner. More importantly, our data confirms a possible neuroprotective effect of creatine against the neurotoxic effect of propionic acid. The obtained in vitro data supports and explains the in vivo neurotoxic effect of PA and proves its DNA damaging effect which could clarify its role in the etiology of autism, a phenomenon recently raised by many researchers. It also supported the accumulating literature which describes creatine as a potential bioactive agent against neurotoxicity. With sufficient research and clinical trials in future, this could prove to be successful in treatment or management of autism as a neurodevelopmental disorder recently related to PA neurotoxicity.Keywords: Propionic acid, creatine, SH-SY5Y, comet assay, DNA fragmentation assay, apoptosis, neuroprotection.African Journal of Biotechnology Vol. 12(31), pp. 4925-493

Elimination of high-refined-sugar diet as treatment strategy for autistic features induced in a rodent model

Purpose: To investigate the potency of ampicillin in altering gut flora in the presence of a high-sucrose diet in rat pups, and to determine its effect on selected neurotransmitters and a cytokine as markers of the persistent autistic features repeatedly induced in orally administered propionic acid rat pups..Methods: Twenty-eight young male Wistar albino rats were divided into four equal groups. The first group served as a control. The second group received an oral neurotoxic dose of propionic acid (PPA, 250 mg/kg body weight/day) for 3 days. The third group was treated with ampicillin (50 mg/kg for 3 weeks) with a standard diet. The fourth group was given the same dose of ampicillin with a high-sucrose diet for 10 weeks.Results: The results showed a significant (p < 0.001) decrease in the investigated neurotransmitters in PPA- and ampicillin-treated rat pups (norepinephrine by 32.49 and 14.58 %, dopamine by 31.45 and 20.22 %, serotonin by 35.99 and 29.09 %), as well as a remarkable increase (p < 0.001) in the proinflammatory cytokine, IL-6 (30.07and 6.07 %). The high-sucrose diet also significantly (p < 0.001) enhanced the neurotoxic effect of ampicillin.Conclusion: The observed dietary modulation of the gut microbiota, coupled with the subsequent modulation of brain neurochemistry and inflammation, demonstrates the considerable potential of dietary intervention through the elimination of highly refined sugar as a treatment strategy to prevent and treat autism.Keywords: Neurotoxicity, Ampicillin, Propionic acid, Neurotransmitters, Cytokines, High-sucrose die

The protective effect of Moringa oleifera plant extract against glutamate-induced DNA damage and reduced cell viability in a primary retinal ganglion cell line

Background Glutamate excitotoxicity can cause DNA damage and is linked to many retinal and neurological disorders. In mammals, the visual signal from the eyes to the brain is conducted only by retinal ganglion cells (RGCs), which can be damaged by overstimulation of glutamate receptors. Methodology We examined the protective effects of Moringa oleifera seed extract against glutamate-induced DNA damage in RGCs. RGCs cells were treated with 5, 10, 50, or 100 µg/ml of M. oleifera seed extract and glutamate separately and then assessed for DNA damage using the comet assay. We also evaluated the viability of the RGCs after both treatments using the MTT test. Additionally, RGCs were pretreated with M. oleifera seed extract (50 or 100 µg/ml) for 2 h before glutamate treatment (100 µg/ml) to determine the potential protective effects of M. oleifera. We performed a phytochemical analysis of the M. oleifera seed extract using standard reactions. Results The M. oleifera seed extract was found to be rich in many phytochemicals. We observed a significant dose-dependent elevation in all comet assay variables in glutamate-treated RGCs, whereas M. oleifera seed extract treatments did not show any significant change in DNA integrity. Conclusion M. oleifera seed extract demonstrates neuroprotective effects, which suggests it may help to prevent the development of many neurodegenerative disorders

Mechanism of nitrogen metabolism-related parameters and enzyme activities in the pathophysiology of autism

<p>Abstract</p> <p>Background</p> <p>There is evidence that impaired metabolism play an important role in the etiology of many neuropsychiatric disorders. Although this has not been investigated to date, several recent studies proposed that nitrogen metabolism-related parameters may have a pathophysiological role in autism.</p> <p>Methods</p> <p>The study enrolled 20 Saudi boys with autism aged 4 to 12 years and 20 healthy controls matched for age and gender. Levels of creatine, urea, ammonia, gamma-aminobutyric acid (GABA), glutamate:glutamine (Glu:Gln) ratio, and enzymatic activities of glutamate dehydrogenase, 5'-nucleotidase, and adenosine deaminase (ADA) were determined in plasma samples from both groups.</p> <p>Results</p> <p>We found a significant elevation of creatine, 5'-nucleotidase, GABA, and glutamic acid and a significant decrease in the enzymatic activity of ADA and glutamine level in patients with autism compared with healthy controls. The most significant variation between the two groups was found in the Glu:Gln ratio.</p> <p>Conclusion</p> <p>A raised Glu:Gln ratio together with positive correlations in creatine, GABA, and 5'-nucleotidase levels could contribute to the pathophysiology of autism, and might be useful diagnostic markers. The mechanism through which these parameters might be related to autism is discussed in detail.</p

Structural basis of acute intermittent porphyria and the relationship between mutations in human porphobilinogen deaminase and enzyme activity

This thesis deals with several human mutations that involve conserved arginine residues. Using molecular biology techniques, several recombinant human ubiquitous mutant porphobilinogen deaminases have been generated from cDNA specifying the enzyme and the recombinant mutant proteins have been overexpressed in E. coli.Three arginine mutants, Arg 149 Gln, Arg 167 Gln and Arg 173 Gln were generated using PCR mutagenesis. Arg 149 Gln exhibits a CRIM-ve phenotype whereas Arg 167 Gln and Arg 173 Gln are examples of CRIM+ve mutations. The mutant deaminases have been investigated with respect to their specific activity, thermal stability and the presence of the dipyrromethane cofactor. Arg 167 Gln exhibits weak enzyme activity but is particularly interesting because it accumulates stable, partially assembled enzyme intermediate complexes. Both Arg 149 Gln and Arg 173 Gln mutants are essentially inactive, contain no dipyrromethane cofactor and exist as heat labile apo-enzymes.Two other mutants, Arg 167 Trp and Trp 198 Ter, have also been investigated. The Arg 167 Trp mutant exhibits similar properties to the Arg 167 Gln mutant, showing weak enzyme activity and forming stable enzyme intermediate complexes. In contrast, the Trp 198 Ter mutant, the most common cause of AIP in Sweden, is an insoluble and completely inactive truncated protein.Finally, studies have been initiated to crystallize and to determine the 3-dimensional structure of the Arg 167 Gln ubiquitous human deaminase mutant A preliminary X-ray structure at a resolution of 2.65 A, was obtained that shows only small differences from the E. coli enzyme, except for a large insertion in domain 3 that partially resolved. Some insight into substrate binding is obtained from the structure.</p

Biogenic Silver Nanoparticles from Two Varieties of Agaricus bisporus and Their Antibacterial Activity

Agaricus bisporus, the most widely cultivated mushroom, is safe to eat and enriched with protein and secondary metabolites. We prepared silver nanoparticles (AgNPs) from two varieties of A. bisporus and tested their antibacterial activity The synthesized AgNPs were initially confirmed by UV-Vis spectroscopy peaks at 420 and 430 nm for white and brown mushrooms AgNPs, respectively. AgNPs were further characterized by zeta sizer, transmission electronic microscopy (TEM), Fourier transform infrared (FTIR), and energy-dispersive X-ray spectroscopy (EDX) prior to antibacterial activity by the well diffusion method against six bacterial strains which include Staphylococcus aureus, Staphylococcus epidermis, Bacillus subtilis, Escherichia coli, Salmonella typhi, and Pseudomonas aeruginosa. TEM results revealed a spherical shape with an average diameter of about 11 nm in the white mushroom extract and 5 nm in the brown mushroom extract. The presence of elemental silver in the prepared AgNPs was confirmed by EDS. The IR spectrum of the extract confirmed the presence of phenols, flavonoids, carboxylic, or amide groups which aided in the reduction and capping of synthesized AgNPs. The AgNPs from both extracts showed almost the same results; however, nanoparticles prepared from brown mushrooms were smaller in size with strong antibacterial activity

Glutamate excitotoxicity induced by orally administered propionic acid, a short chain fatty acid can be ameliorated by bee pollen

Abstract Background Rodent models may guide investigations towards identifying either environmental neuro-toxicants or drugs with neuro-therapeutic effects. This work aims to study the therapeutic effects of bee pollen on brain glutamate excitotoxicity and the impaired glutamine-glutamate- gamma amino butyric acid (GABA) circuit induced by propionic acid (PPA), a short chain fatty acid, in rat pups. Methods Twenty-four young male Western Albino rats 3–4 weeks of age, and 45–60 g body weight were enrolled in the present study. They were grouped into four equal groups: Group 1, the control received phosphate buffered saline at the same time of PPA adminstration; Group 2, received 750 mg/kg body weight divided into 3 equal daily doses and served as acute neurotoxic dose of PPA; Group 3, received 750 mg/kg body weight divided in 10 equal doses of 75 mg/kg body weight/day, and served as the sub-acute group; and Group 4, the therapeutic group, was treated with bee pollen (50 mg/kg body weight) for 30 days after acute PPA intoxication. GABA, glutamate and glutamine were measured in the brain homogenates of the four groups. Results The results showed that PPA caused multiple signs of excitotoxicity, as measured by the elevation of glutamate and the glutamate/glutamine ratio and the decrease of GABA, glutamine and the GABA/glutamate ratio. Bee pollen was effective in counteracting the neurotoxic effects of PPA to a certain extent. Conclusion In conclusion, bee pollen demonstrates ameliorating effects on glutamate excitotoxicity and the impaired glutamine-glutamate-GABA circuit as two etiological mechanisms in PPA-induced neurotoxicity