“Disturbances of Tryptophan Metabolism and Human Health” King-Thom Chung Department of Biology

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“Disturbances of Tryptophan Metabolism and Human Health” King-Thom Chung Department of Biology The University of Memphis Memphis, TN 39152. Do Tryptophan Metabolites Really Cause Cancer ?. Cancer. Tryptophan (W). Tryptophan (73-22-3) Essential amino acid Aromatic amino acid - PowerPoint PPT Presentation

Transcript of “Disturbances of Tryptophan Metabolism and Human Health” King-Thom Chung Department of Biology

  • Disturbances of Tryptophan Metabolism and Human Health

    King-Thom Chung Department of BiologyThe University of MemphisMemphis, TN 39152

  • Do Tryptophan Metabolites Really Cause Cancer ?Tryptophan (W)Cancer

  • Tryptophan (73-22-3) Essential amino acidAromatic amino acidCoded by only a single codon UGGSusceptible to Silent MutationIndoleIUPAC: (D)--Amino-3-indolepropionic acid (R)-2-Amino-3-(3-indolyl)propionic acid (S)-2-Amino-3-(3-indolyl)propionic acid

  • Sources of TryptophanRed meat, Turkey and chicken,Cheese, cheddar, other milk productsChocolateProduced industrially by using microorganisms with Indole as precursor

  • Functions of TryptophanA. Synthesizes Serotonin and Melatonin: Serotonin: neurotransmitter, vasoconstrictor: depression, schizophrenia, obesity, autoimmune disorder and immune deficiency, and probably in cancer. Melatonin: Sleep patterns, Zn uptake, Appetite patterns, mood, etc.

    B. Synthesizes Niacin (Vitamin B3 ): In the Liver

    C. Synthesizes Protein:

  • Tryptophan Deficiency Related Human Diseases 1. Cataracts Totter. J. R. and Day, P. L. Cataract and other ocular changes resulting from tryptophan deficiency. J. Nutri., 24:159, 1942. Ferraro, A. and Roizin, L. Ocular involvement in rats on diet deficient in amino acids. I. tryptophan. Arch. Ophthalmol., 38,331, 1947. 2. Corneal vascularization Sydenstricker, V. P., Hall, W. K. Bowels, L. L. And Schmidt, H. L., Jr., The corneal vascularization resulting from deficiencies of amino acids in the rat. J. Nutr., 34, 481, 1947.

    3. Hematological manifestation of anemia, reduction in plasma proteins, fatty liver, and pancreatic atrophy.

    4. Pellagra

  • Tryptophan Metabolism1. Nicotinamide Pathway 2. Serotonin pathway2. Indole pathway

  • Nicotinamide pathway

  • NAD Pathway source : Metacyc database

  • Tryptophan Metabolism

    A. Nicotinamide Pathway:1. Mainly occurs in the liver through various intermediate compounds: Xanthurenic acid , Kynurenine, 3-hydroxykynurenine , anthranlic acid, 3-hydroxyanthranilic acid, xanthurenine tryptamine, etc.

    2. Conjugation (Glucuronidation, Sulphate esterification) in the liver.

    3. Filtered into KidneyDeconjugation in the bladder by glucuronidase and sulphurylase and interact with the bladder tissue or excreted through urine------- Bladder Cancer ?

    B. Serotonin Pathway 5-hydroxytryptophan- Serotonin--Melatonin Occur in the serotonergic cells in the brain and intestine and by the platelets.

    C. Indole Pathway Occur in the GI tract and excreted or reabsorbed into the blood- Colorectal cancer?

  • Decongugation of Glucouronides and Sulfate EstersLiver turns tryptophan metabolites into glucouronides and sulphate estersThese metabolites are excreted to urine and accumulate in bladderBladder has sulphurylases and -glucouronidase which cleave these conjugatesand revert them to original metabolites which may cause cancer Glucouronidation and sulphate esterisationGlucuronides and sulphate esters aredeconjugatedBy action ofGlucuronidase and sulphurylaseIn Bladder

  • Bladder CancerThe uncontrolled proliferations of cells in the urinary bladderEspecially in the transitional cells that line the inner membrane of thebladderTransitional cell lining of the bladderBladder with transitional carcinoma

  • Statistics of Bladder Cancer

    4th most prevalent among men and 8th most prevalent among women

    38, 000 males 14, 000 females (USA, 2008)

    Chemotherapy is offered.

    (references?)

  • Factors in Etiology of Bladder Cancer

    1. Exposure to industrial carcinogens like 4-Aminobiphenyl, 2-Aminonaphthol, Benzidine, -Naphythlamine

    2. Cigarette smoking

    3. Disturbance of tryptohan metabolism when intake of excessive amount of tryptophan

    4. Nutritional inbalanace : Deficiency of vitamin B6. Combination of excessive intake of tryptohan and deficiency of vitamin B, resulting in accumulation of tryptohan metabolites such as: Xanthurenic acid (XA), Kynurenine and 3-hydroxy Kynurenine, anthranilic acid, and 3-hydroxyanthranilic acid, etc. in the urine.

    5. Infections of bladder : protozoan parasites of Schistosoma Cystitis, etc.

  • Implication of Tryptophan as a Cause for Bladder CancerA. Suggesting Evidences1. Smokers excreted more tryptophan metabolites in the urine than that of non smokers. (Kerr et al. 1965)2. Hill, M. J. (1974) suggested that tryptohan might be converted to carcinogenic metabolites by intestinal bacteria. (Hill, M. J. 1974. Cancer 34:816. )3. Tryptohan concentration were higher in the feces of rat fed with all-meat diet than that of rats fed with normal chow diet (Chung et al. 1975. J. Natl Cancer Inst., 54: 1073-1078).4. Co-carcinogenicity of tryptophan: No carcinogenic effect was observed when the hamsters were treated with high tryptophan diet, however these animals developed high incidences of tumors in bladder when their diets were supplemented with both tryptophan and acetyl 2-aminoflourerene. (Oyasu et al. 1972)5. Most of the tryptophan metabolites were positive in Ames test when treated with nitrite. (Hashizume et al. 1991)

    B. Not supportive Information1. Patients treated with the bladder cancer also excreted same level of the tryptophan metabolites as before. (Wolf et al. 1975)2. Patients with schistomiasis were more susceptible to bladder cancer due to the rupture caused by the eggs of the parasite. (Badawi et al. 1994) 3. Industrial workers had high risk of cancer than that of those in rural area although they excreted comparable levels of tryptophan metabolites.

  • Comparison of fecal tryptophan contents of rats on all-meat and on normal chow diet Tryptophan concentration (mole/100 mg /wet weight) ___________________________________________________ All-Meat dietNorma diet __________________________________________________ 0.051* 0.023* __________________________________________________ Average of 9 days sampling. *p< 0.001

    From: Chung et al., J. Natl Cancer Inst., 54:1073-1078, 1975.

  • Proposed Molecular Mechanisms of Carcinogenesis caused by Tryptophan MetabolitesBecause of the chemical structure similar with industrial carcinogens, it is possible to have the similar molecular mechanisms 1. Induction of the formation of Reactive Oxygen Species (ROS) Hydroxyl radical (OH_.), Superoxide radical (O2.-) Hydrogen Peroxide (H2O2)2. Formation of DNA adducts through the generation of cinnabaric acid.3. Formation of DNA adducts through lipid peroxidation.4. Metal ion mediated oxidation.5. Receptor mediated mis-regulation of genes involved in carcinogenesis.6. Inhibition of cellular apoptosis due to deficiency of niacin.

  • Structural similarities of anthranilic acid, kynurenine, naphthylamine and their carcinogenic hydroxy metabolites

  • Formation of cinnabarinate by autoxidation of the anthranilic acid1.O2 mediated.2. Cinnabarinate may react with the DNA to form an adduct, and cause mutations.

  • Formation of Reactive Oxygen Species through formation of radicalTrp-metabolite + O2Trp-metabolite * + O2-H2O2 + Fe 2+H2O2 + O2-HO. + OH- + Fe3+H2O2 + Fe 2+Try-Metabolite*+ Fe 2+Fe3+ + Trp metaboliteSODFenton reactionTryptophan metabolites like kynurenine, 3-hydroxylkynurenine, anthranilic acid, 3-hydroxy anthranilic acid are excited to form these free radicals and mediate molecules

  • Tryptophan and Reactive Oxygen Species

  • ResultsEffect of 3-hydroxyanthranilinic acid on DNA damage in response to change in Cu2+

  • ResultsEffect of 3-hydroxyanthranilinic acid on DNA damage in response to change in Cu2+

  • Effect of Cu2+ on DNA damage in response to change in 3-hydroxyanthranilinic acid Results

  • Results

    S NoMetabolite Transition metalConcentration (M)Result13-hydroxyanthranilinic acid_0-1000_23-hydroxyanthranilinic acidCu2+0-1000+

    3Anthranilic acid_0-1000_4Anthranilic acidCu2+, Fe2+, Mn2+0-1000_5KynurenineCu2+, Fe2+, Mn2+0-1000_6kynurenine Cu2+, Fe2+, Mn2+0-1000_73-hydroxykynurenine0-1000_

  • Lipid peroxidation caused by Tryptophan metabolitesHydroxyl radicals transfer electron by attacking lipid membranes leading to formation of lipid radicals generating malondialdehyde that forms DNA adductsmalondialdehyde

  • Plasmid relaxation assayProduction of hydroxyl radical or singlet oxygen radicals would cause damage to the plasmid DNA thus relaxing the supercoiled plasmid to relaxed form.Relative mobilities of various plasmids on gel electrophoresis

  • Lipid peroxidation caused by Tryptophan metabolitesHydroxyl radicals transfer electron by attacking lipid membranes leading to formation of lipid radicals generating malondialdehyde that forms DNA adductsmalondialdehyde

  • CarcinogenCo-carcinogenEffectSpecimensource2-AAFTryptophanBladder tumorsRatDunning et al. 19502-AAFTryptophanAbnormal excretion of tryptophan metabolitesratDyer and Morris, 1961TryptophanNoNo effectWistar ratsBoyland et al. 1958Tryptophan2-AAFBladder tumorsWistar ratsBoyland et al. 1958*3-KN, 3-HKN, AA, 3-HAA, XANoBladder tumorsmiceBryan et al. 1971TryptophanNoBladder hyperplasiabeagle dogsOliver et al. 1978TryptophanExposure to 4-aminobiphenyl or 2-naphthylamineBladder tumorsbeagle dogsOliver et al. 1978Indole2-AAFNeoplasmshamster Oyasu et al. 1970TryptophanCCl4 or aflatoxin B1 or bothLiver cirrhosis, megalocytosis, hepatomaWistar ratsRoschlau et al. 1962Tryptophan B6 deficiencyBladder tumorsWistar ratsYoshida et al. 1970; Birt et al. 1987Tryptophan metabolitesNoHyperplasia and eventually tumorsmiceSims and Renwick, 1982TryptophanSaccharinAdditive effect on carcinogenesisSims and Renwick, 1982

    CarcinogenCo-carcinogenEffectSpecimensource2-AAFTryptophanBladder tumorsRatDunning et al. 19502-AAFTryptophanAbnormal excretion of tryptophan metabolitesratDyer and Morris, 1961TryptophanNoNo effectWistar ratsBoyland et al. 1958Tryptophan2-AAFBladder tumorsWistar ratsBoyland et al. 1958*3-KN, 3-HKN, AA, 3-HAA, XANoBladder tumorsmiceBryan et al. 1971TryptophanNoBladder hyperplasiabeagle dogsOliver et al. 1978TryptophanExposure to 4-aminobiphenyl or 2-naphthylamineBladder tumorsbeagle dogsOliver et al. 1978Indole2-AAFNeoplasmshamster Oyasu et al. 1970TryptophanCCl4 or aflatoxin B1 or bothLiver cirrhosis, megalocytosis, hepatomaWistar ratsRoschlau et al. 1962Tryptophan B6 deficiencyBladder tumorsWistar ratsYoshida et al. 1970; Birt et al. 1987Tryptophan metabolitesNoHyperplasia and eventually tumorsmiceSims and Renwick, 1982TryptophanSaccharinAdditive effect on carcinogenesisSims and Renwick, 1982

  • CarcinogenCo-carcinogenEffectSpecimensource2-AAFTryptophanBladder tumorsRatDunning et al. 19502-AAFTryptophanAbnormal excretion of tryptophan metabolitesratDyer and Morris, 1961TryptophanNoNo effectWistar ratsBoyland et al. 1958Tryptophan2-AAFBladder tumorsWistar ratsBoyland et al. 1958*3-KN, 3-HKN, AA, 3-HAA, XANoBladder tumorsmiceBryan et al. 1971TryptophanNoBladder hyperplasiabeagle dogsOliver et al. 1978TryptophanExposure to 4-aminobiphenyl or 2-naphthylamineBladder tumorsbeagle dogsOliver et al. 1978Indole2-AAFNeoplasmshamster Oyasu et al. 1970TryptophanCCl4 or aflatoxin B1 or bothLiver cirrhosis, megalocytosis, hepatomaWistar ratsRoschlau et al. 1962Tryptophan B6 deficiencyBladder tumorsWistar ratsYoshida et al. 1970; Birt et al. 1987Tryptophan metabolitesNoHyperplasia and eventually tumorsmiceSims and Renwick, 1982TryptophanSaccharinAdditive effect on carcinogenesisSims and Renwick, 1982

    CarcinogenCo-carcinogenEffectSpecimensource2-AAFTryptophanBladder tumorsRatDunning et al. 19502-AAFTryptophanAbnormal excretion of tryptophan metabolitesratDyer and Morris, 1961TryptophanNoNo effectWistar ratsBoyland et al. 1958Tryptophan2-AAFBladder tumorsWistar ratsBoyland et al. 1958*3-KN, 3-HKN, AA, 3-HAA, XANoBladder tumorsmiceBryan et al. 1971TryptophanNoBladder hyperplasiabeagle dogsOliver et al. 1978TryptophanExposure to 4-aminobiphenyl or 2-naphthylamineBladder tumorsbeagle dogsOliver et al. 1978Indole2-AAFNeoplasmshamster Oyasu et al. 1970TryptophanCCl4 or aflatoxin B1 or bothLiver cirrhosis, megalocytosis, hepatomaWistar ratsRoschlau et al. 1962Tryptophan B6 deficiencyBladder tumorsWistar ratsYoshida et al. 1970; Birt et al. 1987Tryptophan metabolitesNoHyperplasia and eventually tumorsmiceSims and Renwick, 1982TryptophanSaccharinAdditive effect on carcinogenesisSims and Renwick, 1982

  • Receptor mediated CarcinogenesisAh receptor (aryl hydro carbon receptor) mediates many toxicological reactions.Strong affinity to tetra dihlorodibenzodioxin (dioxin) that mediates carcinogenesis. Tryptamine and Indole acetic acid had good affinity to the Ah receptor,Induce receptor mediated binding to the DNA (gene) and regulate high expression of the gene leading to carcinogenesis.Cytochrome P4501A1 is a well characterized Ah-TCDD inducible Gene.TA competitively displaces the strong ligand TCDD resulting in a hint for the underlying mechanism for carcinogenesis (?)

  • Modification of the tryptophan metabolites by the Xenobiotic metabolizing enzymes (XMEs) The tryptophan metabolite generated induces the generation of P450 and phase II enzymes that alter the compound

    Mechanism similar to the classic dioxin toxicity.Mimura et al. 2003

  • Induction of XMEs by tryptophan metabolitesMimura et al. 2003

  • Ah receptor dependent binding to DNACompetitive displacement of TCDDby IAA and TA

  • Metal mediated carcinogenic effect (Hypothesis)1. Mitochondria plays a role in apoptosis of cell.

    2. Three forms of SOD: Mn-SOD, CuZn-SOD, Fe-SOD. Mn-SOD in mitochondria is chiefly responsible for cell apoptosis.

    3. The displacement of Mn in SOD by Fe-SOD may prevent it from going to apoptosis, which promotes Cancer

  • Deficiency of Niacin (Tryptophan metabolism) leads to propagation of CancerNiacin cofactor in tryptophan catabolismT cell recognize tryptophan metabolites as a signal to destroy pathogens or carcinogenic cells Low Niacin leads low Tryptophan metabolites down the path (?)T cells do not recognize the carcinogenic cells leading to propagation of the cancercell.

  • Conclusion?Tryptophan metabolites may generate ROS and thus cause mutations.Affinity of tryptophan-ligands to various receptors, which lead to carcinogenesisFactors that determine requirement of a co-metabolite to promote mutagenesisRole of tryptophan metabolites in the Immune system.

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