PubMed Health⌕ Search

Biomedical subjects

N Stoy

Publications and source records attributed to N Stoy.

11 recordsLinked to original sources
PubMed2006

Blood 5-hydroxytryptamine, 5-hydroxyindoleacetic acid and melatonin levels in patients with either Huntington's disease or chronic brain injury.

Following a study of oxidative tryptophan metabolism to kynurenines, we have now analysed the blood of patients with either Huntington's disease or traumatic brain injury for levels of 5-hydroxytryptamine (5-HT), 5-hydroxyindoleacetic acid (5-HIAA) and melatonin. There were no differences in the baseline levels of these compounds between patients and healthy controls. Tryptophan depletion did not reduce 5-HT levels in either the controls or in the patients with Huntington's disease, but it increased 5-HT levels in patients with brain injury and lowered 5-HIAA in the control and Huntington's disease groups. An oral tryptophan load did not modify 5-HT levels in the patients but increased 5-HT in control subjects. The tryptophan load restored 5-HIAA to baseline levels in controls and patients with brain injury, but not in those with Huntington's disease, in whom 5-HIAA remained significantly depressed. Melatonin levels increased on tryptophan loading in all subjects, with levels in patients with brain injury increasing significantly more than in controls. Baseline levels of neopterin and lipid peroxidation products were higher in patients than in controls. It is concluded that both groups of patients exhibit abnormalities in tryptophan metabolism, which may be related to increased inflammatory status and oxidative stress. Interactions between the kynurenine, 5-HT and melatonin pathways should be considered when interpreting changes of tryptophan metabolism.

Administration, Oral↗
PubMed2006

Purine metabolism and clinical status of patients with rheumatoid arthritis treated with dipyridamole.

The anti-inflammatory activities of methotrexate and sulphasalazine may be mediated by increases in endogenous adenosine levels. Since the vascular protective drug dipyridamole inhibits the uptake and metabolism of adenosine we have now tested this compound in patients with rheumatoid arthritis to assess its effects on their symptoms. Forty patients (aged 18-75 years) received dipyridamole 400 mg/day or placebo. The levels of adenosine and its major metabolites were determined by high performance liquid chromatography (HPLC) in blood samples taken at baseline and at monthly intervals during treatment for 6 months. After three months of treatment there was a significant reduction in the modified Health Assessment Questionnaire (mHAQ) score, but these effects were not maintained, and dipyridamole did not modify disease severity scores or the levels of adenosine and its metabolites. We conclude that the symptoms of rheumatoid arthritis were not modified by treatment with dipyridamole.

Adenosine↗
PubMed2006

Tryptophan metabolism and oxidative stress in patients with chronic brain injury.

The kynurenine pathway generates the excitotoxic N-methyl-d-aspartate receptor agonist, quinolinic acid and the glutamate antagonist, kynurenic acid, as well as free-radical generators. We investigated the status of the pathway following severe brain injury sustained at least 1 year previously in 15 patients compared with controls. At baseline, patients with brain injury showed increased levels of neopterin, erythrocyte sedimentation rate, C-reactive protein and peroxidation products in the blood compared with controls, indicating persistent inflammation and oxidative stress. At baseline and following tryptophan depletion, more tryptophan was converted to kynurenine in patients than controls, but less kynurenine was converted into the neuroprotectant, kynurenic acid. This suggests that neuroprotection by kynurenic acid may be inadequate in brain-damaged patients even many years after injury. On tryptophan loading, patients metabolized more kynurenine into kynurenic acid than controls, a process which may be neuroprotective. In addition, lower levels of 3-hydroxykynurenine and 3-hydroxyanthranilic acid in patients after tryptophan loading should be protective since these compounds generate free radicals. The results suggest that for brain-damaged patients, increased activation of the kynurenine pathway, oxidative stress and raised levels of inflammation continue many years after the original insult, possibly contributing to the continuing cerebral dysfunction in these patients.

Adult↗
PubMed2005

Tryptophan metabolism and oxidative stress in patients with Huntington's disease.

Abnormalities in the kynurenine pathway may play a role in Huntington's disease (HD). In this study, tryptophan depletion and loading were used to investigate changes in blood kynurenine pathway metabolites, as well as markers of inflammation and oxidative stress in HD patients and healthy controls. Results showed that the kynurenine : tryptophan ratio was greater in HD than controls in the baseline state and after tryptophan depletion, indicating increased indoleamine dioxygenase activity in HD. Evidence for persistent inflammation in HD was provided by elevated baseline levels of C-reactive protein, neopterin and lipid peroxidation products compared with controls. The kynurenate : kynurenine ratio suggested lower kynurenine aminotransferase activity in patients and the higher levels of kynurenine in patients at baseline, after depletion and loading, do not result in any differences in kynurenic acid levels, providing no supportive evidence for a compensatory neuroprotective role for kynurenic acid. Quinolinic acid showed wide variations in blood levels. The lipid peroxidation data indicate a high level of oxidative stress in HD patients many years after disease onset. Levels of the free radical generators 3-hydroxykynurenine and 3-hydroxyanthranilic acid were decreased in HD patients, and hence did not appear to contribute to the oxidative stress. It is concluded that patients with HD exhibit abnormal handling of tryptophan metabolism and increased oxidative stress, and that these factors could contribute to ongoing brain dysfunction.

Adolescent↗
PubMed2004

Tryptophan loading induces oxidative stress.

In previous studies tryptophan loads have been administered to human subjects in order to raise central levels of 5-hydroxytryptamine (5HT) and assess the effects of 5HT on behaviour and mood. However, tryptophan is metabolised primarily along the oxidative kynurenine pathway. In this study a 6 g oral tryptophan load was administered to 15 healthy volunteers and the levels of kynurenines and lipid peroxidation products (indicative of oxidative stress) were measured. The results demonstrate that tryptophan loading produces a highly significant increase in lipid peroxidation products in parallel with increased kynurenines. The oxidative stress may result from the generation of quinolinic acid, 3-hydroxykynurenine, and 3-hydroxyanthranilic acid, all of which are known to have the ability to generate free radicals. The results may have implications for the use of tryptophan loading in psychiatric practice, and for the chronic use of diets high in tryptophan.

Adult↗
PubMed2004

Purine modulation of cytokine release during diuretic therapy of rheumatoid arthritis.

Since free radicals are implicated in rheumatoid arthritis (RA) and since uric acid is a free radical scavenger, we examined the effects of treating RA patients with with the diuretic bumetanide to try to improve their arthritic control. Seventy patients, aged 18-75 years, were randomised to receive bumetanide 4 mg/day or placebo. Uric acid levels increased, but not that of other purines, in the blood of drug-treated patients compared with placebo-treated controls. There were no significant changes in clinical measurements of disease activity or in ESR or CRP levels. There were no over all differences in the blood levels of the cytokines, nor in the basal or stimulated production of cytokines from the blood cultures. The adenosine receptor agonist 5'N-ethylcarboxamido-adenosine (NECA) used to modify cytokine release in cultures of whole blood taken from the patients, depressed the release of tumour necrosis factor-alpha (TNFalpha), but failed to depress the release of interleukin-1b (IL-1b) or interleukin-6 (IL-6), a difference from earlier studies of healthy control subjects and, thus, a difference which may contribute to the disease activity.

Adenosine-5'-(N-ethylcarboxamide)↗
PubMed2001

Macrophage biology and pathobiology in the evolution of immune responses: a functional analysis.

A number of general principles of macrophage biology and pathobiology are formulated to define the contribution of macrophages to the kinetics and sequencing of innate and adaptive immune responses more precisely. The application of these principles to modelling immune responses and to macrophage-based treatments of immune disorders is discussed. The concept of innate peripheral tolerance is developed. It is suggested that macrophage activation could be a primary determinant of nearly every aspect of immune responsiveness, both normal and abnormal, as might be predicted from the innate immune response to 'danger' being evolutionarily more primitive than the adaptive.

Adaptation, Physiological↗
PubMedDate not supplied

Levels of lipid peroxidation products in a chronic inflammatory disorder.

We have examined the plasma levels of the lipid peroxidation products 4-hydroxy-nonenal and malondialdehyde in a carefully controlled study of age and sex-matched subjects with rheumatoid arthritis in whom potentially confounding influences such as disease modifying anti-rheumatic drugs (DMARDs), self-medication and vitamin supplements were eliminated. The plasma concentrations of the antioxidants uric acid and vitamin E were also measured. The results reveal a strong and consistent inverse correlation between the levels of lipid peroxidation products in the plasma and erythrocyte sedimentation rate (ESR). There is no indication that vitamin E or urate function as the major antioxidant agent in arthritis, as has been suggested in more seriously affected patients. It is concluded that there is no evidence that vitamin E is more important, and urate less important as an antioxidant in mild arthritis. The correlation between lipid peroxidation and ESR suggests a more complex relationship than has been assumed.

Adult↗
PubMedDate not supplied

Modulation of cytokine release by purine receptors in patients with rheumatoid arthritis.

OBJECTIVE: Since adenosine receptors are known to modulate the release of some inflammatory mediators in control subjects, we have examined the effects of the mixed A1 and A2 adenosine receptor agonist 5'-N-ethylcarboxamidoadenosine (NECA) on basal and lipopolysaccharide (LPS)-induced cytokine release in diluted whole blood cultures from rheumatoid arthritis (RA) patients and healthy volunteers. METHODS: Twenty-eight patients with rheumatoid arthritis aged 18-75 years gave their voluntary consent to participate and give a blood sample. Basal levels of tumour necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta) and interleukin-6 (IL-6) were measured by ELISA, and whole blood cultures were prepared to assess the effects of LPS activation. RESULTS: Following a 40-hour incubation, activation of adenosine receptors by NECA, added to the cell cultures from rheumatoid arthritis patients, was found to suppress both the basal and LPS-induced release of TNF-alpha and IL-1beta, while causing an increase in the release of both basal and LPS-induced IL-6. In healthy volunteers basal cytokines were undetectable, but NECA alone induced the release of all three cytokines. Stimulated levels of TNF-alpha were more than double those in patients. In the control blood cultures, NECA suppressed LPS-induced release of TNF-alpha and IL-1beta, but increased IL-6 release. CONCLUSIONS: Adenosine receptor stimulation has a differential effect on the release of pro-inflammatory cytokines, and may induce cytokine release in normal subjects. Stimulated release of TNF-alpha is substantially lower in patients with rheumatoid arthritis than in control subjects, possibly indicating saturation, exhaustion or down-regulation of the release process.

Adenosine-5'-(N-ethylcarboxamide)↗