Oxidative Stress in Autism

Formation of anti-oxidative compounds from cysteine and methylation procedures involving folate.

MS = B12 dependent methionine synthetase

MAT=methionine adenosyltransfurase

SAM=S-adenosyl-methionine

SAH=S-adenosylhomocysteine

AK=Adenosyl kinase

ADA=adenosine deaminase.

CBS=B6 dependent cystathionine beta-synthase

MTase=Methyl transfurase

THF=tetrahydrofolate

5-CH3THF=5-methyl tetrahydrofolate

SAHH=SAH hyrolase

Current position

It is difficult to realise that the human body is protected from oxidation of its tissues when we spent so much energy taking oxygen from the air. In Amyotrophic lateral sclerosis (ALS), Parkinson’s disease (PD) and Alzheimer’s disease (AD) there is an indication of oxidative stress, where molecules seem damaged due to the oxidative molecules. However, quite reasonably it could be that damage takes place due to some other pathological process and the oxidation of the molecules becomes permitted as a result of this. I.e. the oxidative stress could be primary or secondary.

In autism there appears to be evidence that the oxidative stress (i.e. an increased inability to prevent oxidation of tissue) comes first.

Oxidative stress biomarkers

Although under histopathology reactive oxidative species (ROS) can be shown it is more difficult to carry this out using blood or urine

Reviews in autism of oxidative stress
Blood and Urine Biochemistry
Glutathione levels
Selenium,
Zinc and copper
Nitrous oxide in red cells
Mitochondrial function changes? (see genetics page)
Histopathology (also of the vascular wall and gut wall)
Treatment
In Gut wall of Inflammatory Bowel Disease
Physiology

Oxidation

There is a standard range of oxidative processes that take place and prevented by physiological systems. See this to understand why the changes may be involved with other biochemistry seen in the body of the autistic child.

Oxidative Stress: Review

Kern JK, Jones AM. Evidence of toxicity, oxidative stress, and neuronal insult in autism. J Toxicol Environ Health B Crit Rev. 2006 Nov-Dec;9(6):485-99. (a good review, but would tend to suggest that the oxidative stress came from the damage rather than the other way around. Also goes into glutathione and its chemical involvement).

McGinnis WR. Oxidative stress in autism. Altern Ther Health Med. 2004 Nov-Dec;10(6):22-36 (he explains more easily why it should be involved).

Chauhan A, Chauhan V. Oxidative stress in autism. Pathophysiology. 2006 Aug;13(3):171-81. (a recent review, but spending a lot of time looking at specific compounds in erythrocyte membranes that they had showed to be raised)

James SJ, Cutler P, Melnyk S, Jernigan S, Janak L, Gaylor DW, Neubrander JA. Metabolic biomarkers of increased oxidative stress and impaired methylation capacity in children with autism. Am J Clin Nutr. 2004 Dec;80(6):1611-7 (this goes through a chain of compounds in the methionine cycle, which depends on B12. They found a decrease in glutathione but a decrease (not significant) in homocysteine, which is used to make it through a chain that requires B6. The only compound in the cycle that seemed raised was s-adenosylhomocysteine, which is used for methylation donor possibly elsewhere)

Akyol O, Zoroglu SS, Armutcu F, Sahin S, Gurel A. Nitric oxide as a physiopathological factor in neuropsychiatric disorders. In Vivo. 2004 May-Jun;18(3):377-90. (There is substantial and mounting evidence that subtle abnormalities of reactive oxygen species (ROS) and nitric oxide (NO) may underlie a wide range of neuropsychiatric disorders. NO has chemical properties that make it uniquely suitable as an intracellular and intercellular messenger. It is produced by the activity of nitric oxide synthases which are present in peripheral tissues and in neurons. On the other hand, NO is known to be an oxygen radical in the central and peripheral nervous systems. NO has been implicated in a number of physiological functions such as noradrenaline and dopamine releases, memory and learning and certain pathologies such as schizophrenia, bipolar disorder and major depression. There are plenty of other articles showing NO to be associated with the disease process but little proof that they are not secondary to other pathogenic processes)

Tsaluchidu S, Cocchi M, Tonello L, Puri BK. Fatty acids and oxidative stress in psychiatric disorders. BMC Psychiatry. 2008 Apr 17;8 Suppl 1:S5. (this makes it clear that many of the psychiatry and mental problems have oxidative stress published data…and so autism should not be looked on as a condition on its own in this respect, but that the oxidation is secondary to the other aspects of the disease)

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Blood and urine biochemistry

Ming X, Stein TP, Brimacombe WG t al. Increased excretion of a lipid peroxidation biomarker in autism. Prostaglandins Leukot. Essent Fatty Acids 2005;73:379-84. (We evaluated children with autism for the presence of two oxidative stress biomarkers. Urinary excretion of 8-hydroxy-2-deoxyguanosine (8-OHdG) and 8-isoprostane-F2alpha (8-iso-PGF2alpha) were determined in 33 children with autism and 29 healthy controls. 8-iso-PGF2alpha levels were significantly higher in children with autism. The majority of autistic subjects showed a moderate increase in isoprostane levels while a smaller group of autistic children showed dramatic increases in their isoprostane levels. There was a trend of an increase in 8-OHdG levels in children with autism but it did not reach statistical significance. This basically showed that it was not a reliable diagnostic test but it could be used for other factors and for assessing treatment in certain patients)

Sweeten TL, Posey DL, Shankar S, McDougle CJ. High nitric oxide production in autistic distorder: a possible role for interferon-gamma. Biol. Phych 2004:55;434-437.

Paşca SP, Nemeş B, Vlase L, Gagyi CE, Dronca E, Miu AC, Dronca M. High levels of homocysteine and low serum paraoxonase 1 arylesterase activity in children with autism. Life Sci. 2006 Apr 4;78(19):2244-8. (and low glutathione peroxidase) in serum. These were taken as indicators of oxidative stress).

James SJ, Melnyk S, Jernigan S, Cleves MA, Halsted CH, Wong DH, Cutler P, Bock K, Boris M, Bradstreet JJ, Baker SM, Gaylor DW. Metabolic endophenotype and related genotypes are associated with oxidative stress in children with autism. Am J Med Genet B Neuropsychiatr Genet. 2006 Dec 5;141(8):947-56. (plasma S-adenosyl methionine to S-adenosylhomocysteine is an indicator of methylation capacity and were significantly decreased in autistics.)

Zoroğlu SS, Yürekli M, Meram I, Söğüt S, Tutkun H, Yetkin O, Sivasli E, Savaş HA, Yanik M, Herken H, Akyol O. Pathophysiological role of nitric oxide and adrenomedullin in autism. Cell Biochem Funct. 2003 Mar;21(1):55-60. (nitric oxide (NO) is involved in the aetiopathogenesis of many neuropsychiatric disorders such as schizophrenia, bipolar disorder, depression, Alzheimer's disease, Hungtington disease and stroke. Although it has not been investigated yet, several recent studies proposed that NO may have a pathophysiological role in autism. Adrenomedullin (AM), a recently discovered 52-amino acid peptide hormone, induces vasorelaxation by activating adenylate cyclase and also by stimulating NO release. AM immune reactivity is present in the brain consistent with a role as a neurotransmitter. It has been stated that NO and AM do function in the regulation of many neurodevelopmental processes. The mean values of plasma total nitrite and AM levels in the autistic group were significantly higher than control values, respectively (p < 0.001, p = 0.028). There is no correlation between total nitrite and AM levels (r = 0.11, p = 0.31).)

Adams et al. found that DMSA treatment (chelation of metals) resulted in a great improvement or normalization of RBC (red blood cell) levels of glutathione after just 1 round (3 days) of DMSA treatment, with benefits lasting at least 1-2 months

Chauhan V, Chauhan A, Cohen IL, Brown WT, Sheikh A. Alteration in amino-glycerophospholipids levels in the plasma of children with autism: a potential biochemical diagnostic marker. Life Sci. 2004 Feb 13;74(13):1635-43. (observed that levels of phosphatidylethanolamine (PE) were decreased while phosphatidylserine (PS) were increased in the erythrocyte membranes of children with autism as compared to their non-autistic developmentally normal siblings). How this fits in it unclear

Chauhan A, Chauhan V, Brown WT, Cohen I. Oxidative stress in autism: increased lipid peroxidation and reduced serum levels of ceruloplasmin and transferrin--the antioxidant proteins. Life Sci. 2004 Oct 8;75(21):2539-49. (Lipid peroxidation was found to be elevated in autism indicating that oxidative stress is increased in this disease. Levels of major antioxidant proteins namely, transferrin (iron-binding protein) and ceruloplasmin (copper-binding protein) in the serum, were significantly reduced in autistic children as compared to their developmentally normal non-autistic siblings. A striking correlation was observed between reduced levels of these proteins and loss of previously acquired language skills in children with autism. These results indicate altered regulation of transferrin and ceruloplasmin in autistic children who lose acquired language skills. It is suggested that such changes may lead to abnormal iron and copper metabolism in autism, and that increased oxidative stress may have pathological role in autism. More statistics are required but this is the sort of data that would be extremely useful for all studies involving treatments and assessments)

Söğüt S, Zoroğlu SS, Ozyurt H, Yilmaz HR, Ozuğurlu F, Sivasli E, Yetkin O, Yanik M, Tutkun H, Savaş HA, Tarakçioğlu M, Akyol O. Changes in nitric oxide levels and antioxidant enzyme activities may have a role in the pathophysiological mechanisms involved in autism.Clin Chim Acta. 2003 May;331(1-2):111-7. (little data)

Zoroglu SS, Armutcu F, Ozen S, et al. Increased oxidative stress and altered activities of erythrocyte free radical scavenging enzymes in autism. Eur Arch Psychiatry Clin Neurosci. 2004;254:143-147. (In the autistic group, increased thiobarbaric acid reactive substance levels (p < 0.001) and xanthine oxidase activity (p < 0.001) and SOD activity (p < 0.001), decreased catalase (p < 0.001) activity and unchanged adenosine demaminase activity were detected. They take this to suggest oxidative stress and processes taking place). This is an important finding.

Yorbik O, Sayal A, Akay C, Akbiyik DI, Sohmen T. Investigation of antioxidant enzymes in children with autistic disorder. Prostaglandins Leukot Essent Fatty Acids. 2002;67:341-343. (Activities of erythrocyte SOD, erythrocyte and plasma glutathione peroxidase in autistic children were significantly lower than normals, but glutathione levels were not)

Chauhan A, Chauhan V, Brown WT, Cohen I. Oxidative stress in autism: increased lipid peroxidation and reduced serum levels of ceruloplasmin and transferrin-the antioxidant proteins. Life Sci. 2004;75:2539-2549.

Golse B, Debray-Ritzen P, Durosay P, Puget K, Michelson AM. [Alterations in two enzymes: superoxide dismutase and glutathion peroxidase in developmental infantile psychosis (infantile autism) (author's transl)] Rev Neurol (Paris). 1978 Nov;134(11):699-705.

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Histopathology

Elizabeth M. Sajdel-Sulkowska, Boguslaw Lipinski, Herb Windom, Tapan Audhya and Woody McGinnis. Oxidative Stress in Autism: Elevated Cerebellar 3-nitrotyrosine Levels. American Journal of Biochemistry and Biotechnology 4 (2): 73-84, 2008. (Increased levels by 68% . An increase in Hg but not statistically significant)

Yao Y, Walsh WJ, McGinnis WR, Praticò D. Altered vascular phenotype in autism: correlation with oxidative stress. Arch Neurol. 2006 Aug;63(8):1161-4. (this was done by looking for urinary molecules that were indicators of endothelial irritation: prostaglandin F, isoprostane, and a thromboxane B

Teresa A. Evans, Sandra L. Siedlak, Liang Lu, Xiaoming Fu, Zeneng Wang, Woody R. McGinnis, Evelyn Fakhoury, Rudy J. Castellani, Stanley L. Hazen, William J. Walsh, Allen T. Lewis, Robert G. Salomon, Mark A. Smith, George Perry and Xiongwei Zhu. The Autistic Phenotype Exhibits a Remarkably Localized Modification of Brain Protein by Products of Free Radical-Induced Lipid Oxidation. American Journal of Biotechnology and Biochemistry 4 (2): 61-72, 2008. (Oxidative damage has been documented in the peripheral tissues of autism patients. In this study, we sought evidence of oxidative injury in autistic brain. Carboxyethyl pyrrole (CEP) and iso[4]levuglandin (iso[4]LG)E2-protein adducts, that are uniquely generated through peroxidation of docosahexaenoate and arachidonate-containing lipids respectively, and heme oxygenase-1 were detected immunocytochemically in cortical brain tissues and by ELISA in blood plasma. Significant immunoreactivity toward all three of these markers of oxidative damage in the white matter and often extending well into the grey matter of axons was found in every case of autism examined. This striking threadlike pattern appears to be a hallmark of the autistic brain as it was not seen in any control brain, young or aged, used as controls for the oxidative assays. This is an important finding in that they did the experiments and did them with controls who they tried to have as dying of similar diseases. The finding was that in autism were specifically different. The references in this article are up to date as a review)

Activation/oxidation of vascular endothelium

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Oxidative processes: physiology and pathology

The major cause of damage to cells results from reactive oxygen species (ROS) – induced alterations of proteins and DNA. This comes about from the reactive electrophilic oxidation products from polyunsaturated fatty acyls in membrane lipids. Under normal conditions ROS are cleared from the celll by the action of superoxide dismutase (SOD), catalase, or glutathione peroxidase (GPx). SOD, as MnSOD in the mitochondria and CuZnSOD in the cytoplasm removes superoxide anion by converting it into hydrogen perodixe. Catalase and CPx reduce this H2O2 to water. In the presence of unbound Cu, under certain conditions SOD can promote oxidateive injury owing to a Cu catalyzed Haber-Weiss reaction of H2O2 to generate –OH, a potent ROS. Statistically significant elevations in ZnCuSOD were documented in erythrocytes and in platelets of autistic individuals compared with controls (see above). This was remarkably clear but could still not explain the actual cause of the oxidation that was taking place. Glutathione is looked on as a relatively useful molecule to stabilize the oxidative state of proteins etc. Hence, the finding of low levels of glutathione in plasma and acts as a cofactor for the severely depressed levels of GPx (-44% in erythrocytes) an antioxidant enzyme, is also indicative of oxidation taking place. As a result, the H2O2 formed by the action of SOD would not be efficiently removed owing to diminished levels of GPx. The imbalance is exacerbated by the low plasma glutathione levels.

If you look at the biochemical pathways at the head of the page, you can see that glutathione is formed from cysteine and this is replaced from the diet or through homocysteine. This cycle involved tetrahydrofolate and methylation systems. If there is simply too little ability to produce this then the levels of glutathione will drop. Currently it is not all that clear if the reason for the glutatione levels being low in red cells is because of lack of production or it being used up in preventing oxidation. One factor showed that it was possible to raise glutathione levels by treatment with B12 and cysteine. For information about its involvement in treatment.

This is to show how hydrogen peroxide is converted to water through the donation of hydrogen through glutathione and how other acyl donors can be similarly turned into hydroxyls by the same process.

Treatment: findings

MacFabe DF, Cain DP, Rodriguez-Capote K, Franklin AE, Hoffman JE, Boon F, Taylor AR, Kavaliers M, Ossenkopp KP. Neurobiological effects of intraventricular propionic acid in rats: possible role of short chain fatty acids on the pathogenesis and characteristics of autism spectrum disorders. Behav Brain Res. 2007 Jan 10;176(1):149-69. (purely showing that some dietary factor may show toxicity through oxidative stress and may produce pseudo autistic effects)

Dolske MC, Spollen J, McKay S, Lancashire E, Talbert L. A preliminary trial of ascorbic acid as supplemental therapy for autism. Prog Neuropsychopharmacol Biol Psychiatry. 1993;17:765-774. (a preliminary study suggesting improvement in clinical symptoms)

Rossignol DA, Rossignol LW, James SJ, Melnyk S, Mumper E. The effects of hyperbaric oxygen therapy on oxidative stress, inflammation, and symptoms in children with autism: an open-label pilot study. BMC Pediatr. 2007 Nov 16;7:36. (this is mainly to show that hyperbaric oxygen may be adequately safe and shows no results in terms of treatment currently)

Oxidative stress in gut wall of inflammatory bowel disease

At this point we don’t have the data for this in autism and the gut changes that might be expected. The literature is quite wide for other forms of IBD.

Aw TY. intestinal glutathione: determinant of mucosal peroxide transport, metabolism, and oxidative susceptibility. Toxicol Appl Pharmacol. 2005 May 1;204(3):320-8. Review.

Tsunada S, Iwakiri R, Ootani H, Aw TY, Fujimoto K. Redox imbalance in the colonic mucosa of ulcerative colitis. Scand J Gastroenterol. 2003 Sep;38(9):1002-3.

Sido B, Seel C, Hochlehnert A, Breitkreutz R, Dröge W. Low intestinal glutamine level and low glutaminase activity in Crohn's disease: a rational for glutamine supplementation? Dig Dis Sci. 2006 Dec;51(12):2170-9. Epub 2006 Nov

Sido B, Hack V, Hochlehnert A, Lipps H, Herfarth C, Dröge W. Impairment of intestinal glutathione synthesis in patients with inflammatory bowel disease. Gut. 1998 Apr;42(4):485-92.

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