Document Detail


A mechanism of quinolinic acid formation by brain in inflammatory neurological disease. Attenuation of synthesis from L-tryptophan by 6-chlorotryptophan and 4-chloro-3-hydroxyanthranilate.
MedLine Citation:
PMID:  8293279     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Quinolinic acid (QUIN), kynurenic acid (KYNA) and L-kynurenine (L-KYN) are neuroactive kynurenine pathway metabolites that accumulate in inflammatory neurological diseases. These increases were attributed to the induction of indoleamine-2,3-dioxygenase (IDO), the enzyme that converts L-tryptophan into L-KYN. Direct conversion of L-tryptophan into QUIN by brain tissue occurs in conditions of CNS inflammation, but not by normal brain tissue. To investigate whether increased activity of enzymes distal to IDO may determine L-KYN conversion to QUIN, rhesus macaques were inoculated with poliovirus directly into the spinal cord, as a model of focal inflammatory neurological disease (FASEB J. 6, 2977-2989, 1992). Induction of spinal cord IDO (35.9-fold) accompanied smaller, but proportional increases in kynurenine-3-hydroxylase (2.4-fold) and kynureninase (2.3-fold) activities, which were correlated to CSF and tissue QUIN levels, as well as to measures of inflammatory lesions. 3-Hydroxyanthranilate-3,4-dioxygenase activity was unchanged. Cerebrospinal fluid KYNA levels increased in proportion to both IDO activity and L-KYN accumulation, though kynurenine aminotransferase activity was unaffected. Cerebrospinal fluid neopterin, a marker of macrophage and immune activation, accumulated in proportion to the responsive enzymes and metabolites. The cell types involved in producing QUIN were investigated in vitro. Human foetal brain cultures consisting of astrocytes and neurons converted large quantities of [13C6]L-tryptophan into L-KYN when stimulated by gamma-interferon, but very little [13C6]QUIN was formed unless macrophages (THP-1 cells) were first added to the cultures (to model a key component of brain inflammation). [13C6]L-Tryptophan was converted into [13C6]QUIN by either gamma-interferon stimulated macrophages, or following intracisternal administration into poliovirus-infected macaques. Inhibitors of the kynurenine pathway, 6-chlorotryptophan and 4-chloro-3-hydroxyanthranilic acid, attenuated [13C6]QUIN formation by macrophages, and when co-infused with [13C6]L-tryptophan into poliovirus-infected macaques. These results suggest roles for increased activities of IDO, kynurenine-3-hydroxylase and kynureninase in accelerating the synthesis of QUIN, L-KYN and KYNA in conditions of brain inflammation. Macrophage infiltrates, and perhaps microglia, are important sources of QUIN, whereas constitutive brain cells and macrophages are sources of L-KYN. Drugs that inhibit kynurenine pathway enzymes attenuate QUIN formation in the CNS, and provide tools to examine the consequences of reduced QUIN accumulation.
Authors:
M P Heyes; K Saito; E O Major; S Milstien; S P Markey; J H Vickers
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Brain : a journal of neurology     Volume:  116 ( Pt 6)     ISSN:  0006-8950     ISO Abbreviation:  Brain     Publication Date:  1993 Dec 
Date Detail:
Created Date:  1994-03-03     Completed Date:  1994-03-03     Revised Date:  2005-11-17    
Medline Journal Info:
Nlm Unique ID:  0372537     Medline TA:  Brain     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  1425-50     Citation Subset:  AIM; IM    
Affiliation:
Section on Analytical Biochemistry, National Institute of Mental Health, Bethesda, MD 20892.
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MeSH Terms
Descriptor/Qualifier:
3-Hydroxyanthranilic Acid / analogs & derivatives,  pharmacology
Animals
Biopterin / analogs & derivatives,  analysis
Brain / metabolism
Encephalitis / enzymology,  metabolism*
Fetus / metabolism
Indoleamine-Pyrrole 2,3,-Dioxygenase
Kynurenic Acid / analysis,  metabolism*
Kynurenine / analysis,  metabolism*
Macaca mulatta
Myelitis / enzymology,  metabolism*
Neopterin
Poliomyelitis / enzymology,  metabolism
Quinolinic Acid / analysis,  metabolism*
Tryptophan / analogs & derivatives,  metabolism,  pharmacology
Tryptophan Oxygenase / metabolism
Chemical
Reg. No./Substance:
17808-35-4/6-chlorotryptophan; 22150-76-1/Biopterin; 23219-33-2/4-chloro-3-hydroxyanthranilic acid; 343-65-7/Kynurenine; 492-27-3/Kynurenic Acid; 548-93-6/3-Hydroxyanthranilic Acid; 670-65-5/Neopterin; 73-22-3/Tryptophan; 89-00-9/Quinolinic Acid; EC 1.13.11.11/Tryptophan Oxygenase; EC 1.13.11.42/Indoleamine-Pyrrole 2,3,-Dioxygenase

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