Differentiation of viral and autoimmune central nervous system inflammation by kynurenine pathway.

OBJECTIVE: To determine whether the metabolites of Kynurenine pathway (KP) could serve as biomarkers for distinguishing between viral CNS infections and autoimmune neuroinflammatory diseases, especially anti-N-methyl-D-aspartate receptor encephalitis (NMDARE) and herpes virus encephalitis (HSE). METHODS: This study enrolled CSF samples from 76 patients with viral CNS infections, autoimmune neuroinflammatory, and non-inflammatory neurological diseases. We measured cerebrospinal fluid (CSF) concentrations of tryptophan (Trp) and kynurenine (Kyn) by ELISA. RESULTS: Kyn concentrations and Kyn/Trp ratios were highly increased (p < 0.001, viral vs. autoimmune) in viral CNS infections, whereas patients with autoimmune neuroinflammatory and non-inflammatory diseases exhibited low concentrations. Furthermore, Kyn concentrations and Kyn/Trp ratio turned out to be excellent biomarkers to distinguish between herpes simplex encephalitis (HSE) and NMDARE (AUC 0.920 and AUC 0.906), whereas Trp concentrations were similar in all three groups. INTERPRETATION: The results suggest that elevated CSF Kyn concentrations and Kyn/Trp ratio may serve as biomarkers for distinguishing viral CNS infections from autoimmune neuroinflammatory diseases. In particular, the distinction between HSE and NMDARE is of great clinical relevance. Further studies are warranted to investigate the potential of CSF Kyn levels and Kyn/Trp ratio as routine parameters in patients with CNS diseases.

Kynurenic acid and psychotic symptoms and personality traits in twins with psychiatric morbidity.

Increased cytokines and kynurenic acid (KYNA) levels in cerebrospinal fluid (CSF) have been reported in patients with schizophrenia and bipolar disorder. The aim of the present study was to investigate cytokines and kynurenines in the CSF of twin pairs discordant for schizophrenia or bipolar disorder and to study these CSF markers in relation to psychotic symptoms and personality traits. CSF levels of tryptophan (TRP), KYNA, quinolinic acid (QUIN), interleukin (IL)-6, IL-8 and tumor necrosis factor-alpha (TNF-α) were analyzed in 23 twins with schizophrenia or bipolar disorder, and in their not affected co-twins. Ratings of psychotic symptoms and personality traits were made using the Scales for Assessment of Negative and Positive symptoms, the Structured Clinical Interview for DSM-IV - Axis II Disorders, and the Schizotypal Personality Questionnaire - Brief. A total score for psychotic symptoms and personality traits was constructed for analysis. CSF KYNA was associated with the score for psychotic symptom and personality traits. TNF-α and IL-8 were associated, and the intra-pair differences scores of TNF-α and IL-8 were highly correlated. Intraclass correlations indicated genetic influences on CSF KYNA, TRP, IL-8 and TNF-α. The association between KYNA and psychotic symptoms further supports a role of KYNA in psychotic disorders.

Kynurenine Pathway Activation in Human African Trypanosomiasis.

Background: The kynurenine pathway of tryptophan oxidation is associated with central nervous system (CNS) inflammatory pathways. Inhibition of this pathway ameliorates CNS inflammation in rodent models of the late (meningoencephalitic) stage of human African trypanosomiasis (HAT). In this study, we evaluate whether the kynurenine pathway is activated in clinical HAT and associated with CNS inflammatory responses. Methods: We measured cerebrospinal fluid (CSF) tryptophan and kynurenine metabolite concentrations in patients infected with Trypanosoma brucei rhodesiense, using liquid chromatography-mass spectrometry. Results: Kynurenine concentration in CSF was increased in both the early and late stages of disease, with a progressive increase in tryptophan oxidation associated with stage progression. Kynurenine pathway activation was associated with increases in neuroinflammatory markers, but there was no clear relationship to neurological symptoms. Conclusions: CNS kynurenine pathway activation occurs during HAT, including cases prior to the current diagnostic cutoff for late-stage infection, providing evidence for early CNS involvement in HAT. Metabolite data demonstrate that the kynurenine-3-monooxygenase and kynurenine aminotransferase branches of the kynurenine pathway are active. The association between tryptophan oxidation and CNS inflammatory responses as measured by CSF interleukin 6 (IL-6) concentration supports a role of kynurenine metabolites in the inflammatory pathogenesis of late-stage HAT.

LC-MS/MS-based quantification of kynurenine metabolites, tryptophan, monoamines and neopterin in plasma, cerebrospinal fluid and brain.

AIM: The kynurenine (KYN) pathway is implicated in diseases such as cancer, psychiatric, neurodegenerative and autoimmune disorders. Measurement of KYN metabolite levels will help elucidating the involvement of the KYN pathway in the disease pathology and inform drug development. METHODOLOGY: Samples of plasma, cerebrospinal fluid or brain tissue were spiked with deuterated internal standards, processed and analyzed by LC-MS/MS; analytes were chromatographically separated by gradient elution on a C18 reversed phase analytical column without derivatization. CONCLUSION: We established an LC-MS/MS method to measure 11 molecules, namely tryptophan, KYN, 3-OH-KYN, 3-OH-anthranilic acid, quinolinic acid, picolinic acid, kynurenic acid, xanthurenic acid, serotonin, dopamine and neopterin within 5.5 min, with sufficient sensitivity to quantify these molecules in small sample volumes of plasma, cerebrospinal fluid and brain tissue.

Increased levels of IL-6 in the cerebrospinal fluid of patients with chronic schizophrenia--significance for activation of the kynurenine pathway.

BACKGROUND: Accumulating evidence indicates that schizophrenia is associated with brain immune activation. While a number of reports suggest increased cytokine levels in patients with schizophrenia, many of these studies have been limited by their focus on peripheral cytokines or confounded by various antipsychotic treatments. Here, well-characterized patients with schizophrenia, all receiving olanzapine treatment, and healthy volunteers were analyzed with regard to cerebrospinal fluid (CSF) levels of cytokines. We correlated the CSF cytokine levels to previously analyzed metabolites of the kynurenine (KYN) pathway. METHODS: We analyzed the CSF from patients and controls using electrochemiluminescence detection with regard to cytokines. Cell culture media from human cortical astrocytes were analyzed for KYN and kynurenic acid (KYNA) using high-pressure liquid chromatography or liquid chromatography/mass spectrometry. RESULTS: We included 23 patients and 37 controls in our study. Patients with schizophrenia had increased CSF levels of interleukin (IL)-6 compared with healthy volunteers. In patients, we also observed a positive correlation between IL-6 and the tryptophan:KYNA ratio, indicating that IL-6 activates the KYN pathway. In line with this, application of IL-6 to cultured human astrocytes increased cell medium concentration of KYNA. LIMITATIONS: The CSF samples had been frozen and thawed twice before analysis of cytokines. Median age differed between patients and controls. When appropriate, all present analyses were adjusted for age. CONCLUSION: We have shown that IL-6, KYN and KYNA are elevated in patients with chronic schizophrenia, strengthening the idea of brain immune activation in patients with this disease. Our concurrent cell culture and clinical findings suggest that IL-6 induces the KYN pathway, leading to increased production of the N-methyl-D-aspartate receptor antagonist KYNA in patients with schizophrenia.

Disorder in the serotonergic system due to tryptophan hydroxylation impairment: a cause of hypothalamic syndrome?

BACKGROUND: The hypothalamus regulates basic homeostasis such as appetite, circadian rhythm, autonomic and pituitary functions. Dysregulation in these functions results in the hypothalamic syndrome, a rare disorder of various origins. Since serotonin (5-HT) modulates most of the above-mentioned homeostasis, a defect in the serotonergic system can possibly participate in this syndrome. METHODS: We describe a girl suffering from hypothalamic syndrome with a decreased concentration of 5-hydroxytryptophan (5-HTP) and a normal level of tryptophan in the cerebrospinal fluid (CSF) suggesting a functional defect in tryptophan hydroxylase (TPH). TPH is a rate-limiting enzyme in the synthesis of the neurotransmitter 5-HT. RESULTS: Therapeutic intervention with 5-HTP, carbidopa and a specific serotonin reuptake inhibitor significantly improved her clinical symptoms and caused biochemical normalisation of neurotransmitters. CONCLUSION: The girl described had the typical symptoms of a hypothalamic disorder and a defective serotonergic metabolism, a relationship which has not been reported before. Therapeutic interventions to restore 5-HT metabolism resulted in clinical improvement. We suggest that investigation of 5-HT metabolism in CSF of patients with this rare disorder is included in the aetiological work-up.

CSF concentrations of brain tryptophan and kynurenines during immune stimulation with IFN-alpha: relationship to CNS immune responses and depression.

Cytokine-induced activation of indoleamine 2,3-dioxygenase (IDO) catabolizes L-tryptophan (TRP) into L-kynurenine (KYN), which is metabolized to quinolinic acid (QUIN) and kynurenic acid (KA). QUIN and KA are neuroactive and may contribute to the behavioral changes experienced by some patients during exposure to inflammatory stimuli such as interferon (IFN)-alpha. A relationship between depressive symptoms and peripheral blood TRP, KYN and KA during treatment with IFN-alpha has been described. However, whether peripheral blood changes in these IDO catabolites are manifest in the brain and whether they are related to central nervous system cytokine responses and/or behavior is unknown. Accordingly, TRP, KYN, QUIN and KA were measured in cerebrospinal fluid (CSF) and blood along with CSF concentrations of relevant cytokines, chemokines and soluble cytokine receptors in 27 patients with hepatitis C after approximately 12 weeks of either treatment with IFN-alpha (n=16) or no treatment (n=11). Depressive symptoms were assessed using the Montgomery-Asberg Depression Rating Scale. IFN-alpha significantly increased peripheral blood KYN, which was accompanied by marked increases in CSF KYN. Increased CSF KYN was in turn associated with significant increases in CSF QUIN and KA. Despite significant decreases in peripheral blood TRP, IFN-alpha had no effect on CSF TRP concentrations. Increases in CSF KYN and QUIN were correlated with increased CSF IFN-alpha, soluble tumor necrosis factor-alpha receptor 2 and monocyte chemoattractant protein-1 as well as increased depressive symptoms. In conclusion, peripheral administration of IFN-alpha activated IDO in concert with central cytokine responses, resulting in increased brain KYN and QUIN, which correlated with depressive symptoms.

Central neurochemical ultradian variability in depression.

UNLABELLED: Depression is characterized by blunted behavior and neuroendocrine function that generally improve with antidepressant treatment. This study examined intrinsic variability in brain neurotransmitter function, since it may be a source of blunted behavior and neuroendocrine function in depression and a marker for the illness, and has not previously been analyzed using wavelet decomposition. To measure variability in monoamine metabolites, lumbar cerebrospinal fluid (CSF) was collected in serial samples in depressed patients before and after treatment. We hypothesized that changes in variability would be observed after treatment. Mechanisms that control such variability may be critical to the pathophysiology of depression. METHOD: Time series data was obtained from serial ten-min sampling over a 24-hr period (N=144) from thirteen depressed patients, with a repeat collection after 5 weeks of antidepressant (sertraline or bupropion) treatment. Concentrations of tryptophan (TRP), the monoamine metabolites 5-HIAA (metabolite of serotonin) and HVA (metabolite of dopamine), and the HVA:5HIAA ratio were transformed to examine power in slowly (160 min/cycle) to rapidly (20 min/cycle) occurring events. Power, the sum of the squares of the coefficients in each d (detail) wavelet, reflects variability within a limited frequency bandwidth for that wavelet. Pre-treatment to post-treatment comparisons were conducted with repeated measures ANOVA. RESULTS: Antidepressant treatment was associated with increased power in the d2 wavelet from the HVA (p=0.03) and the HVA:5-HIAA ratio (p=0.03) series. The d1 and d3 wavelets showed increased power following antidepressant treatment for the ratio series (d1, p=0.01; d3, p=0.05). Significant changes in power were not observed for the 5-HIAA data series. Power differences among analytes suggest that the findings are specific to each system. CONCLUSION: The wavelet transform analysis shows changes in neurochemical signal variability following antidepressant treatment. Patterns or degrees of variability may be as important as, or possibly more important than, the mean levels of monoamine transmitters. Studies of variability observed in healthy individuals and a larger depressed sample will be needed to verify a relationship with mood and treatment response. Neurochemical measures of time-variability may be a pivotal marker in depression.

CSF monoamine patterns in pathological gamblers and healthy controls.

Previous reports on compounds in the cerebrospinal fluid (CSF) of pathological gamblers have focused on disturbed NA, DA and 5-HT function in the central nervous system. We have analysed precursors, transmitters and transmitter metabolites in 3 x 6 ml of CSF obtained from one female and 11 male pathological gamblers and 11 healthy male controls lumbar punctured at the L4-5 level after 8 h of fasting without preceding strict bedrest. Pathological gamblers displayed lower CSF levels of tryptophan and 5-HT while the opposite was the case for 5-HIAA, tyrosine, DA, HVA, DOPAC and HMPG. In contrast to previous studies, the NA level did not differ between pathological gamblers and healthy controls. A disrupted CSF gradient was noted for tryptophan, 5-HT, DA, HVA, DOPAC, NA and HMPG, but only in pathological gamblers. A disrupted gradient was found for 5-HIAA in both pathological gamblers and healthy controls. The results are in line with the presence of altered indoleamine and catecholamine function in pathological gamblers as well as an altered CSF transport from the brain to the lumbar compartment in such gamblers.

Patients with carcinoid syndrome exhibit symptoms of aggressive impulse dysregulation.

OBJECTIVE: Carcinoid tumors can produce excessive amounts of biogenic amines, notably serotonin. We assessed psychiatric symptoms in carcinoid patients and peripheral metabolism of tryptophan, the precursor of serotonin. METHODS: Twenty consecutive patients with carcinoid syndrome underwent a structured psychiatric interview applying DSM-IV (Diagnostical Statistical Manual) criteria. Tumor activity was measured by determination of 24-hour urine excretion of 5-hydroxyindoleacetic acid (5-HIAA) and platelet serotonin levels. Plasma tryptophan levels were measured and compared with sex- and age-matched references. RESULTS: Fifteen patients (75%) fulfilled diagnostic DSM-IV criteria for a disorder of impulse control. Tryptophan plasma levels were lower in patients compared with controls (p =.031) and were correlated negatively with urinary 5-HIAA excretion (p =.001). CONCLUSIONS: Impulse control disorders are prevalent in patients with carcinoid syndrome. The serotonin production by the tumor possibly decreases the tryptophan pool in the cerebrospinal fluid, which is the essential substrate for the production of brain serotonin as a pivotal neurotransmitter.

Effects of electromagnetic fields on the levels of biogenic amine metabolites, quinolinic acid, and beta-endorphin in the cerebrospinal fluid of dairy cows.

Eight multiparous non-lactating pregnant Holstein cows at 198 +/- 35 d of gestation, weighing 608 +/- 24 kg, were confined to wooden metabolic cages in an electric and magnetic field chamber with a 12:12 h light:dark cycle. Subarachnoidal catheters were installed 5 d before the activation of the electric and magnetic fields. The cows were exposed to electric and magnetic fields (60 Hz, 10 kV/m and 30 microT) continuously except for the feeding and cleaning time for an average of 21.44 +/- 1.4 h per day for a period of 30 d. Cerebrospinal fluid samples were collected on three consecutive days before an exposure period of 30 d, on the last 3 d of the exposure period, and for 3 d starting 5 d after the exposure period. The concentrations of beta-endorphin, tryptophan, 5-hydroxyindoleacetic acid, homovanillic acid, 3-methoxy-4-hydroxyphenylethyleneglycol and quinolinic acid in cerebrospinal fluid were determined. There was a significant increase in quinolinic acid, and a trend towards an increase in tryptophan, findings consistent with a weakening of the blood-brain barrier due to exposure to the electric and magnetic fields.

[Biochemical changes in cerebrospinal fluid associated with the neurotoxic action of HIV-1]. / Alteraciones bioquímicas del líquido cefalorraquídeo asociadas a la acción neurotóxica del HIV-1.

The aim of this study is to evaluate the usefulness of different markers to diagnose neurologic and psychiatric diseases due to HIV-1 infection Increased concentration of quinolenic acid has been implicated in the neurologic deficits and brain atrophy that may accompany infection with the HIV-1 virus. CFS concentrations of quinolenic acid have been implicated in the pathogenesis of the AIDS dementia complex. Cytokines liberation are very altered and this factor may be correlated with direct toxicity about central nervous system cells. Also are increased the values of neopterin. In the different stages of AIDS, the highest values are obtained in dementia complex. Neopterin, tryptofan and kinorenina, in blood and CFS are directly correlated with neurologic and psychiatry sintomatology. The highest values of soluble intercellular adhesion molecule 1 are found in HIV encephalopathy As well as are important the values, in CSF and blood of beta-2-M, Ag HIV, Ac41, tumor necrosis factor-alpha in the neurologic disease in HIV-1 infection

Neopterin production and tryptophan degradation in acute Lyme neuroborreliosis versus late Lyme encephalopathy.

Fourteen patients with Borrelia burgdorferi infection were investigated for possible abnormalities of tryptophan and neopterin metabolism. Four patients (2 were investigated before therapy, 2 when therapy had been already started) had acute Lyme neuroborreliosis, and 10 patients were investigated months to years after an acute infection. Increased concentrations of neopterin and of the tryptophan-degradation product, L-kynurenine, were detected in the cerebrospinal fluid of patients with acute Lyme neuroborreliosis; one patient presented with subnormal tryptophan. Similar but less marked changes were seen in the treated patients and in some of the patients with Lyme encephalopathy. No such abnormalities were seen in the serum of the patients. The data indicate a role of the immune system and particularly of endogenously formed cytokines, like interferon-gamma and tumour necrosis factor-alpha, effecting tryptophan and neopterin metabolism in patients with acute Lyme neuroborreliosis.

Tryptophan and serotonin metabolism in familial erythrophagocytic lymphohistiocytosis.

Reduced concentrations of tryptophan and 5-hydroxyindoleacetic acid (the major CSF metabolite of serotonin) were found in the cerebrospinal fluid of two children with familial erythrophagocytic lymphohistiocytosis. This was associated with elevated cerebrospinal fluid neopterin concentrations indicating increased macrophage activity within the central nervous system. In one child, cytotoxic therapy induced a complete clinical remission and an increase of tryptophan and 5-hydroxyindoleacetic acid concentrations to normal; during a subsequent relapse, concentrations of these analytes again fell below normal. In the other child, in whom therapy produced only a transient improvement, tryptophan and 5-hydroxyindoleacetic acid concentrations remained low and the child died. It is likely that increased activity of indoleamine 2,3-dioxygenase induced by the activation of macrophages was responsible for the disturbance in serotonin and tryptophan homeostasis within the brain. Excessive tryptophan catabolism and the disturbance of serotonin turnover may play a role in the aetiology of the neurological symptoms seen in familial erythrophagocytic lymphohistiocytosis.

Plasma and CSF tryptophan in cancer anorexia.

Eighteen untreated cancer patients and ten sex- and age-matched healthy volunteers were studied. In all patients eating behavior was investigated by means of a specific questionnaire from which the presence of anorexia and anorexia-related symptoms was assessed. To investigate the role of tryptophan in cancer anorexia, fasting plasma and CSF levels of tryptophan and other neutral amino acids were assayed in patients and controls. Cancer patients showed abnormally high plasma free tryptophan levels. In case of patients with cancer anorexia a significant rise of the ratio in plasma between free and tryptophan/large neutral amino acids, competing with tryptophan for its brain entry, was observed. This increase was correlated to a consistent rise of CSF tryptophan levels suggesting a specific role of the serotoninergic system in the pathogenesis of cancer anorexia.

Cerebral tryptophan metabolism in humans in relation to malignant pain.

The authors investigated the cerebral metabolism of tryptophan in patients suffering from malignant pain by means of CSF dosage of tryptophan (Trp), 5-hydroxytryptophan (5-HTP), serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA). The level of 5-HIAA in patients with pain was 66.48 +/- 13.67 ng/ml, while in those without pain was 25.05 +/- 13.25 ng/ml; the difference was statistically significant, p = 0.001. Trp, 5-HTP and 5-HT levels did not register significant differences in the two groups of patients, although a tendency to lower values was seen in patients with pain, supporting the hypothesis of increased turnover of this metabolic pathway in cancer patients. A statistically significant inverse correlation was also found between cerebral Trp levels and pain levels measured on the Scott-Huskisson visual analogue scale. The data obtained confirm the importance of the cerebral serotoninergic pathway in pain modulation and the interest which CSF analysis may have for the assessment of patients suffering from pain.

Effects of oral clonidine premedication on concentrations of cortisol and monoamine neurotransmitters and their metabolites in cerebrospinal fluid and plasma.

Forty-two healthy male patients (aged 19-40 years), undergoing orthopaedic surgery under spinal anaesthesia (3 ml isobaric 0.5% bupivacaine), were given clonidine 4.5 micrograms kg-1 orally either 2 (Group I, n = 10) or 4 (Group II, n = 10) hours before the operation, diazepam 0.15 mg kg-1 orally (Group III, n = 10) or a placebo tablet (Group IV, n = 12) 2 h before the operation. Plasma concentrations of cortisol, noradrenaline (NA), adrenaline (A), 3,4-dihydroxyphenylglycol (DHPG) and dihydroxyphenylacetic acid (DOPAC) were assayed from venous blood samples just before premedication and just before the spinal block. Cerebrospinal fluid (CSF) concentrations of cortisol, tryptophan, 5-hydroxyindoleacetic acid and catecholamine metabolites were assayed from a sample taken before the spinal block. The plasma NA concentrations of the patients in the groups receiving clonidine decreased clearly compared with the other groups (P less than 0.05). The NA metabolite DHPG was also lower in Groups I and II than in Group III (P less than 0.05) after premedication. Plasma A concentrations were lower in Groups I and III than in Group IV (P less than 0.05). The CSF concentrations of the different substances were similar in all groups. In Group I the sensory blockade lasted significantly longer than in Group III (P less than 0.05) and the mean duration of motor blockade was longer in Group I than in Groups III and IV (P less than 0.05). Two patients in both clonidine groups developed bradycardia (heart rate less than 45 min-1) requiring atropine treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Cerebrospinal fluid monoamine precursor and metabolite levels in children treated for leukemia: age and sex effects and individual variability.

Lumbar cerebrospinal fluid (CSF) was obtained from children during and following treatment for acute lymphoblastic leukemia (ALL). One hundred ninety-two CSF samples from 50 subjects, which were selected to minimize the effects of the disease and its treatment (i.e., to approach "normality" as closely as possible), were analyzed for the monoamine precursors tyrosine (Tyr) and tryptophan (Trp) and the metabolites homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA). Levels of HVA (p less than 0.0001), 5-HIAA (p less than 0.002), and Tyr (p less than 0.05) decreased with age from 3 to 17 years. Significant correlations were observed between the acid metabolites HVA and 5-HIAA (r = 0.79) and between the amino acid precursors Tyr and Trp (r = 0.71). Within individuals, levels of all four compounds were relatively stable over time, with total mean coefficient of variation ranging from 20% to 25%. No significant sex differences for CSF levels of HVA, 5-HIAA, Tyr, or Trp were found. Assessment of CSF monoamine precursors and metabolites in children treated for ALL may provide a method for understanding the chronic effect of CNS trauma on the ontogeny of monoamine systems.