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Liu Y, Zhai E, Chen J, Qian Y, Zhao R, Ma Y, Liu J, Huang Z, Cai S, Chen J. m 6 A-mediated regulation of PBX1-GCH1 axis promotes gastric cancer proliferation and metastasis by elevating tetrahydrobiopterin levels. Cancer Commun (Lond) 2022; 42:327-344. [PMID: 35261206 PMCID: PMC9017753 DOI: 10.1002/cac2.12281] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2021] [Revised: 01/03/2022] [Accepted: 02/28/2022] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Methyltransferase 3 (METTL3)-mediated N6-methyladenosine (m6 A) RNA modification has been demonstrated to be a potential factor in promoting gastric cancer (GC). METTL3 regulates a series of signaling pathways by modifying various mRNAs. This study aimed to identify novel METTL3-mediated signaling pathways and explored possible targets for use in the clinical setting of gastric cancer. METHODS To investigate the proliferation and metastatic capacity of GC cell lines with METTL3 knockdown, a xenograft, lung metastasis, and popliteal lymph node metastasis model was used. The m6 A-modified RNA immunoprecipitation (Me-RIP) sequence was utilized to explore the target mRNAs of METTL3. Cell counting kit 8 and transwell assays were performed to investigate the promoting function of pre-B cell leukemia homeobox 1 (PBX1) and GTP cyclohydrolase 1 (GCH1). Western blotting and chromatin immunoprecipitation were employed to confirm the involvement of the METTL3-PBX1-GCH1 axis. ELISA and liquid chromatography-mass spectrometry were used to explore the biological function of tetrahydrobiopterin (BH4 ). RESULTS Knockdown of METTL3 suppressed xenograft tumor growth and lung/lymph node metastasis in vivo. Mechanistically, we found that METTL3 combined with and stabilized PBX1 mRNAs. Chromatin immunoprecipitation (ChIP) and further experiments suggested that PBX1 acted as a transcription factor inducing GCH1 expression. Moreover, the METTL3-PBX1-GCH1 axis increased BH4 levels in GC cells, thereby promoting tumor progression. CONCLUSIONS This study suggested that METTL3 enzymes promote tumor growth and lung/lymph node metastasis via METTL3-PBX1-GCH1 axis increasing BH4 levels in GC.
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Affiliation(s)
- Yinan Liu
- Division of Gastrointestinal Surgery Centerthe First Affiliated Hospital of Sun Yat‐sen UniversityGuangzhouGuangdong510080P. R. China
- Gastric Cancer CenterSun Yat‐sen UniversityGuangzhouGuangdong510080P. R. China
- Laboratory of Surgerythe First Affiliated Hospital of Sun Yat‐sen UniversityGuangzhouGuangdong510080P. R. China
| | - Ertao Zhai
- Division of Gastrointestinal Surgery Centerthe First Affiliated Hospital of Sun Yat‐sen UniversityGuangzhouGuangdong510080P. R. China
- Gastric Cancer CenterSun Yat‐sen UniversityGuangzhouGuangdong510080P. R. China
| | - Junting Chen
- Division of Gastrointestinal Surgery Centerthe First Affiliated Hospital of Sun Yat‐sen UniversityGuangzhouGuangdong510080P. R. China
- Gastric Cancer CenterSun Yat‐sen UniversityGuangzhouGuangdong510080P. R. China
| | - Yan Qian
- Division of Gastrointestinal Surgery Centerthe First Affiliated Hospital of Sun Yat‐sen UniversityGuangzhouGuangdong510080P. R. China
- Gastric Cancer CenterSun Yat‐sen UniversityGuangzhouGuangdong510080P. R. China
| | - Risheng Zhao
- Division of Gastrointestinal Surgery Centerthe First Affiliated Hospital of Sun Yat‐sen UniversityGuangzhouGuangdong510080P. R. China
- Gastric Cancer CenterSun Yat‐sen UniversityGuangzhouGuangdong510080P. R. China
| | - Yan Ma
- Division of Gastrointestinal Surgery Centerthe First Affiliated Hospital of Sun Yat‐sen UniversityGuangzhouGuangdong510080P. R. China
- Gastric Cancer CenterSun Yat‐sen UniversityGuangzhouGuangdong510080P. R. China
| | - Jianqiu Liu
- Division of Gastrointestinal Surgery Centerthe First Affiliated Hospital of Sun Yat‐sen UniversityGuangzhouGuangdong510080P. R. China
- Gastric Cancer CenterSun Yat‐sen UniversityGuangzhouGuangdong510080P. R. China
| | - Zhixin Huang
- Division of Gastrointestinal Surgery Centerthe First Affiliated Hospital of Sun Yat‐sen UniversityGuangzhouGuangdong510080P. R. China
- Gastric Cancer CenterSun Yat‐sen UniversityGuangzhouGuangdong510080P. R. China
| | - Shirong Cai
- Division of Gastrointestinal Surgery Centerthe First Affiliated Hospital of Sun Yat‐sen UniversityGuangzhouGuangdong510080P. R. China
- Gastric Cancer CenterSun Yat‐sen UniversityGuangzhouGuangdong510080P. R. China
| | - Jianhui Chen
- Division of Gastrointestinal Surgery Centerthe First Affiliated Hospital of Sun Yat‐sen UniversityGuangzhouGuangdong510080P. R. China
- Gastric Cancer CenterSun Yat‐sen UniversityGuangzhouGuangdong510080P. R. China
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Ning DS, Ma J, Peng YM, Li Y, Chen YT, Li SX, Liu Z, Li YQ, Zhang YX, Jian YP, Ou ZJ, Ou JS. Apolipoprotein A-I mimetic peptide inhibits atherosclerosis by increasing tetrahydrobiopterin via regulation of GTP-cyclohydrolase 1 and reducing uncoupled endothelial nitric oxide synthase activity. Atherosclerosis 2021; 328:83-91. [PMID: 34118596 DOI: 10.1016/j.atherosclerosis.2021.05.019] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Revised: 05/20/2021] [Accepted: 05/27/2021] [Indexed: 02/03/2023]
Abstract
BACKGROUND AND AIMS The apolipoprotein A-I mimetic peptide D-4F, among its anti-atherosclerotic effects, improves vasodilation through mechanisms not fully elucidated yet. METHODS Low-density lipoprotein (LDL) receptor null (LDLr-/-) mice were fed Western diet with or without D-4F. We then measured atherosclerotic lesion formation, endothelial nitric oxide synthase (eNOS) phosphorylation and its association with heat shock protein 90 (HSP90), nitric oxide (NO) and superoxide anion (O2•-) production, and tetrahydrobiopterin (BH4) and GTP-cyclohydrolase 1 (GCH-1) concentration in the aorta. Human umbilical vein endothelial cells (HUVECs) and aortas were treated with oxidized LDL (oxLDL) with or without D-4F; subsequently, BH4 and GCH-1 concentration, NO and O2•- production, eNOS association with HSP90, and endothelium-dependent vasodilation were measured. RESULTS Unexpectedly, eNOS phosphorylation, eNOS-HSP90 association, and O2•- production were increased, whereas BH4 and GCH-1 concentration and NO production were reduced in atherosclerosis. D-4F significantly inhibited atherosclerosis, eNOS phosphorylation, eNOS-HSP90 association, and O2•- generation but increased NO production and BH4 and GCH-1 concentration. OxLDL reduced NO production and BH4 and GCH-1 concentration but enhanced O2•- generation and eNOS association with HSP90, and impaired endothelium-dependent vasodilation. D-4F inhibited the overall effects of oxLDL. CONCLUSIONS Hypercholesterolemia enhanced uncoupled eNOS activity by decreasing GCH-1 concentration, thereby reducing BH4 levels. D-4F reduced uncoupled eNOS activity by increasing BH4 levels through GCH-1 expression and decreasing eNOS phosphorylation and eNOS-HSP90 association. Our findings elucidate a novel mechanism by which hypercholesterolemia induces atherosclerosis and D-4F inhibits it, providing a potential therapeutic approach.
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Affiliation(s)
- Da-Sheng Ning
- Division of Cardiac Surgery, Heart Center, The First Affiliated Hospital, Sun Yat-sen University, PR China; National-Guangdong Joint Engineering Laboratory for Diagnosis and Treatment of Vascular Diseases, PR China; NHC Key Laboratory of Assisted Circulation, Sun Yat-sen University, PR China; Guangdong Provincial Engineering and Technology Center for Diagnosis and Treatment of Vascular Diseases, PR China
| | - Jian Ma
- Division of Cardiac Surgery, Heart Center, The First Affiliated Hospital, Sun Yat-sen University, PR China; National-Guangdong Joint Engineering Laboratory for Diagnosis and Treatment of Vascular Diseases, PR China; NHC Key Laboratory of Assisted Circulation, Sun Yat-sen University, PR China; Guangdong Provincial Engineering and Technology Center for Diagnosis and Treatment of Vascular Diseases, PR China
| | - Yue-Ming Peng
- Division of Cardiac Surgery, Heart Center, The First Affiliated Hospital, Sun Yat-sen University, PR China; National-Guangdong Joint Engineering Laboratory for Diagnosis and Treatment of Vascular Diseases, PR China; NHC Key Laboratory of Assisted Circulation, Sun Yat-sen University, PR China; Guangdong Provincial Engineering and Technology Center for Diagnosis and Treatment of Vascular Diseases, PR China
| | - Yan Li
- Division of Cardiac Surgery, Heart Center, The First Affiliated Hospital, Sun Yat-sen University, PR China; National-Guangdong Joint Engineering Laboratory for Diagnosis and Treatment of Vascular Diseases, PR China; NHC Key Laboratory of Assisted Circulation, Sun Yat-sen University, PR China; Guangdong Provincial Engineering and Technology Center for Diagnosis and Treatment of Vascular Diseases, PR China
| | - Ya-Ting Chen
- Division of Cardiac Surgery, Heart Center, The First Affiliated Hospital, Sun Yat-sen University, PR China; National-Guangdong Joint Engineering Laboratory for Diagnosis and Treatment of Vascular Diseases, PR China; NHC Key Laboratory of Assisted Circulation, Sun Yat-sen University, PR China; Guangdong Provincial Engineering and Technology Center for Diagnosis and Treatment of Vascular Diseases, PR China
| | - Shang-Xuan Li
- Division of Cardiac Surgery, Heart Center, The First Affiliated Hospital, Sun Yat-sen University, PR China; National-Guangdong Joint Engineering Laboratory for Diagnosis and Treatment of Vascular Diseases, PR China; NHC Key Laboratory of Assisted Circulation, Sun Yat-sen University, PR China; Guangdong Provincial Engineering and Technology Center for Diagnosis and Treatment of Vascular Diseases, PR China
| | - Zui Liu
- Division of Cardiac Surgery, Heart Center, The First Affiliated Hospital, Sun Yat-sen University, PR China; National-Guangdong Joint Engineering Laboratory for Diagnosis and Treatment of Vascular Diseases, PR China; NHC Key Laboratory of Assisted Circulation, Sun Yat-sen University, PR China; Guangdong Provincial Engineering and Technology Center for Diagnosis and Treatment of Vascular Diseases, PR China
| | - Yu-Quan Li
- Division of Cardiac Surgery, Heart Center, The First Affiliated Hospital, Sun Yat-sen University, PR China; National-Guangdong Joint Engineering Laboratory for Diagnosis and Treatment of Vascular Diseases, PR China; NHC Key Laboratory of Assisted Circulation, Sun Yat-sen University, PR China; Guangdong Provincial Engineering and Technology Center for Diagnosis and Treatment of Vascular Diseases, PR China
| | - Yi-Xin Zhang
- Division of Hypertension and Vascular Diseases, Heart Center, The First Affiliated Hospital, Sun Yat-sen University, PR China; National-Guangdong Joint Engineering Laboratory for Diagnosis and Treatment of Vascular Diseases, PR China; NHC Key Laboratory of Assisted Circulation, Sun Yat-sen University, PR China; Guangdong Provincial Engineering and Technology Center for Diagnosis and Treatment of Vascular Diseases, PR China
| | - Yu-Peng Jian
- Division of Cardiac Surgery, Heart Center, The First Affiliated Hospital, Sun Yat-sen University, PR China; National-Guangdong Joint Engineering Laboratory for Diagnosis and Treatment of Vascular Diseases, PR China; NHC Key Laboratory of Assisted Circulation, Sun Yat-sen University, PR China; Guangdong Provincial Engineering and Technology Center for Diagnosis and Treatment of Vascular Diseases, PR China
| | - Zhi-Jun Ou
- Division of Hypertension and Vascular Diseases, Heart Center, The First Affiliated Hospital, Sun Yat-sen University, PR China; National-Guangdong Joint Engineering Laboratory for Diagnosis and Treatment of Vascular Diseases, PR China; NHC Key Laboratory of Assisted Circulation, Sun Yat-sen University, PR China; Guangdong Provincial Engineering and Technology Center for Diagnosis and Treatment of Vascular Diseases, PR China
| | - Jing-Song Ou
- Division of Cardiac Surgery, Heart Center, The First Affiliated Hospital, Sun Yat-sen University, PR China; National-Guangdong Joint Engineering Laboratory for Diagnosis and Treatment of Vascular Diseases, PR China; NHC Key Laboratory of Assisted Circulation, Sun Yat-sen University, PR China; Guangdong Provincial Engineering and Technology Center for Diagnosis and Treatment of Vascular Diseases, PR China; Guangdong Provincial Key Laboratory of Brain Function and Disease,Guangzhou, 510080, PR China.
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Togo K, Ishihara T, Yamamoto K, Sawada H. Older-onset levodopa-responsive parkinsonism with normal DAT-SPECT and pterin hypometabolism. BMJ Case Rep 2021; 14:e240067. [PMID: 33962918 PMCID: PMC8108657 DOI: 10.1136/bcr-2020-240067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/11/2021] [Indexed: 11/03/2022] Open
Abstract
Pterin species participate in dopamine biosynthesis, and abnormal pteridine metabolism contributes to reduced dopamine. GTP cyclohydrolase 1 (GCH-1) deficiency, which triggers pteridine hypometabolism and normally develops in childhood, can mediate an adult-onset decrease in levodopa production and dopa-responsive dystonia (DRD), with normal dopamine transporter single-photon emission computed tomography (DAT-SPECT). A recent study described normal DAT-SPECT in adult-onset cases with GCH-1 mutations, clinically diagnosed with Parkinson's disease, which raises the possibility that the abnormal metabolism of pteridine may be a differential diagnosis for adult-onset parkinsonism. We report an older patient with levodopa-responsive parkinsonism with normal DAT-SPECT, or scans without evidence of dopamine deficit (SWEDD), whose biochemical analysis showed pterin hypometabolism, which occurs in GCH-1-deficient DRD. Surprisingly, this patient presented no dystonia or GCH-1 gene mutation or deletion. This case suggests that low pterin metabolism should be considered in older-onset levodopa-responsive parkinsonism with normal DAT-SPECT, even without GCH-1 mutations or deletions.
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Affiliation(s)
- Kazuyuki Togo
- Department of Neurology, National Hospital Organization Utano National Hospital, Kyoto, Japan
- Neurology, Osaka University Graduate School of Medicine, Suita, Japan
| | - Toshiya Ishihara
- Department of Neurology, National Hospital Organization Utano National Hospital, Kyoto, Japan
| | - Kenji Yamamoto
- Department of Neurology, National Hospital Organization Utano National Hospital, Kyoto, Japan
| | - Hideyuki Sawada
- Department of Neurology, National Hospital Organization Utano National Hospital, Kyoto, Japan
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Fanet H, Capuron L, Castanon N, Calon F, Vancassel S. Tetrahydrobioterin (BH4) Pathway: From Metabolism to Neuropsychiatry. Curr Neuropharmacol 2021; 19:591-609. [PMID: 32744952 PMCID: PMC8573752 DOI: 10.2174/1570159x18666200729103529] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Revised: 07/03/2020] [Accepted: 07/23/2020] [Indexed: 11/22/2022] Open
Abstract
Tetrahydrobipterin (BH4) is a pivotal enzymatic cofactor required for the synthesis of serotonin, dopamine and nitric oxide. BH4 is essential for numerous physiological processes at periphery and central levels, such as vascularization, inflammation, glucose homeostasis, regulation of oxidative stress and neurotransmission. BH4 de novo synthesis involves the sequential activation of three enzymes, the major controlling point being GTP cyclohydrolase I (GCH1). Complementary salvage and recycling pathways ensure that BH4 levels are tightly kept within a physiological range in the body. Even if the way of transport of BH4 and its ability to enter the brain after peripheral administration is still controversial, data showed increased levels in the brain after BH4 treatment. Available evidence shows that GCH1 expression and BH4 synthesis are stimulated by immunological factors, notably pro-inflammatory cytokines. Once produced, BH4 can act as an anti- inflammatory molecule and scavenger of free radicals protecting against oxidative stress. At the same time, BH4 is prone to autoxidation, leading to the release of superoxide radicals contributing to inflammatory processes, and to the production of BH2, an inactive form of BH4, reducing its bioavailability. Alterations in BH4 levels have been documented in many pathological situations, including Alzheimer's disease, Parkinson's disease and depression, in which increased oxidative stress, inflammation and alterations in monoaminergic function are described. This review aims at providing an update of the knowledge about metabolism and the role of BH4 in brain function, from preclinical to clinical studies, addressing some therapeutic implications.
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Affiliation(s)
- H. Fanet
- INRAe, Nutrition and Integrated Neurobiology, UMR 1286, Bordeaux, France
- Université de Bordeaux, Nutrition and Integrated Neurobiology, UMR 1286, Bordeaux, France
- Faculty of Pharmacy, Université Laval, Quebec City, QC, Canada
- Neurosciences Axis, Centre de Recherche du CHU de Québec-Université Laval, Quebec City, QC, Canada
- OptiNutriBrain International Associated Laboratory (NurtriNeuro France-INAF Canada), Quebec City, Canada
| | - L. Capuron
- INRAe, Nutrition and Integrated Neurobiology, UMR 1286, Bordeaux, France
- Université de Bordeaux, Nutrition and Integrated Neurobiology, UMR 1286, Bordeaux, France
- OptiNutriBrain International Associated Laboratory (NurtriNeuro France-INAF Canada), Quebec City, Canada
| | - N. Castanon
- INRAe, Nutrition and Integrated Neurobiology, UMR 1286, Bordeaux, France
- Université de Bordeaux, Nutrition and Integrated Neurobiology, UMR 1286, Bordeaux, France
- OptiNutriBrain International Associated Laboratory (NurtriNeuro France-INAF Canada), Quebec City, Canada
| | - F. Calon
- Faculty of Pharmacy, Université Laval, Quebec City, QC, Canada
- Neurosciences Axis, Centre de Recherche du CHU de Québec-Université Laval, Quebec City, QC, Canada
- OptiNutriBrain International Associated Laboratory (NurtriNeuro France-INAF Canada), Quebec City, Canada
| | - S. Vancassel
- INRAe, Nutrition and Integrated Neurobiology, UMR 1286, Bordeaux, France
- Université de Bordeaux, Nutrition and Integrated Neurobiology, UMR 1286, Bordeaux, France
- OptiNutriBrain International Associated Laboratory (NurtriNeuro France-INAF Canada), Quebec City, Canada
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Shinozaki K, Nishio Y, Ayajiki K, Yoshida Y, Masada M, Kashiwagi A, Okamura T. Pitavastatin Restores Vascular Dysfunction in Insulin-Resistant State by Inhibiting NAD(P)H Oxidase Activity and Uncoupled Endothelial Nitric Oxide Synthase-Dependent Superoxide Production. J Cardiovasc Pharmacol 2007; 49:122-30. [PMID: 17414223 DOI: 10.1097/fjc.0b013e31802f5895] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
3-Hydroxyl-3-methylglutaryl coenzyme A reductase inhibitors (statins) may benefit the vasculopathy of insulin resistance independent of its lipid-lowering effects. Because imbalance of nitric oxide (NO) and superoxide anion (O(2)(-)) formation may lead to vascular dysfunction, we investigated the effect of statin on vasomotion of insulin-resistant state to clarify the mechanism by which statin ameliorates the impaired function. In the isolated aorta, contraction induced by angiotensin II was more potent in Zucker fatty rats (ZF) compared with that in Zucker lean rats. Both angiotensin II type 1 receptor expression and O(2)(-) production were upregulated in ZF. In addition, deficiency of tetrahydrobiopterin (BH4) contributes to the endothelial dysfunction in ZF. Oral administration of pitavastatin for 8 weeks normalized angiotensin II-induced vasoconstriction and endothelial function in ZF. Pitavastatin treatment of ZF increased vascular BH4 content, which was associated with twofold increase in endothelial NO synthase (eNOS) activity as well as a 60% reduction in endothelial O(2)(-) production. The treatment also markedly downregulated protein expression of angiotensin II type 1 receptor and gp91phox, whereas expression of guanosine triphosphate cyclohydrolase I was upregulated. Pitavastatin restores vascular dysfunction by inhibiting NAD(P)H oxidase activity and uncoupled eNOS-dependent O(2)(-) production.
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Affiliation(s)
- Kazuya Shinozaki
- Department of Pharmacology, Shiga University of Medical Science, Otsu, Shiga, Japan
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Schallreuter KU, Zschiesche M, Moore J, Panske A, Hibberts NA, Herrmann FH, Metelmann HR, Sawatzki J. In vivo evidence for compromised phenylalanine metabolism in vitiligo. Biochem Biophys Res Commun 1998; 243:395-9. [PMID: 9480820 DOI: 10.1006/bbrc.1997.8107] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Human epidermal melanocytes and keratinocytes express mRNA for all enzymes involved in de novo synthesis/recycling of the cofactor (6R) L-erythro 5,6,7,8 tetrahydrobiopterin (6BH4) in normal healthy individuals. An enhanced epidermal de novo synthesis was identified in association with decreased epidermal phenylalanine hydroxylase and 4a carbinolamine dehydratase in patients with vitiligo. The latter event leads to an accumulation of the nonenzymatic isomer (7R) L-erythro 5,6,7,8 tetrahydrobiopterin (7BH4) inhibiting phenylalanine hydroxylase (PAH) with an apparent Ki = 10(-6) M. One consequence of decreased epidermal PAH activities would be a build-up of L-phenylalanine. To substantiate this consideration, FT-Raman spectroscopy was utilised to study in vivo total phenylalanine levels at 1004 cm-1 in involved and uninvolved skin of 23 patients with vitiligo, showing in all cases increased levels of phenylalanine in involved compared to uninvolved skin of the same individual. Additionally the peripheral blood L-phenylalanine turnover was determined over time after a single oral loading with L-phenylalanine in 32 patients (100 mg/kg body weight). All patients demonstrated slower kinetics from L-phenylalanine to L-tyrosine, but 41% of the group showed significantly slower kinetics under these conditions. None of the patients presented peripheral hyperphenylalaninemia without loading. Our results demonstrate for the first time a phenylalanine build-up in the involved epidermis of patients with vitiligo. These data support the earlier observation of a defective epidermal pterin metabolism in this disease.
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Affiliation(s)
- K U Schallreuter
- Department of Biomedical Sciences, University of Bradford, West Yorkshire, United Kingdom
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