Histamine metabolism in asthma

Metabolomics applied to urine samples in childhood asthma; differentiation between asthma phenotypes and identification of relevant metabolites

Asthma is a heterogeneous disorder and one of the most common chronic childhood diseases. An improved characterization of asthma phenotypes would be invaluable for the understanding of the pathogenic mechanisms and the correct treatment of this disease. The aim of this pilot study was to explore the potential of metabolomics applied to urine samples in characterizing asthma, and to identify the most representative metabolites. Urine samples of 41 atopic asthmatic children (further subdivided in sub-groups according to the symptoms) and 12 age-matched controls were analyzed. Untargeted metabolic profiles were collected by LC-MS, and studied by multivariate analysis. The group of the asthmatics was differentiated by a model that proved to be uncorrelated with the chronic assumption of controller drugs on the part of the patients. The distinct sub-groups were also appropriately modeled. Further investigations revealed a reduced excretion of urocanic acid, methyl-imidazoleacetic acid and a metabolite resembling the structure of an Ile-Pro fragment in the asthmatics. The meaning of these findings was discussed and mainly correlated with the modulation of immunity in asthma. Metabolic profiles from urines have revealed the potential to characterize asthma and enabled the identification of metabolites that may have a role in the underlying inflammation.

Determination of N-methylhistamine in urine as an indicator of histamine release in immediate allergic reactions

The use of the urine histamine metabolite, N-methylhistamine (N-MH), as a parameter of histamine release in immediate allergic reactions was investigated. Baseline levels were determined in 34 normal control subjects and 29 atopic patients. Increases of urine N-MH values were measured during histamine infusions and in venom-allergic patients receiving bee-sting challenges. N-MH was determined by a newly developed radioimmunoassay. Baseline levels in control subjects and atopic patients demonstrated no significant differences. With regard to challenge tests, fluctuation of N-MH levels during a 6-hour period was measured. Random 6-hour increases in healthy and atopic subjects ranged from 5% to 41%. Before infusion of histamine (0.25 micrograms/kg/min for 30 minutes), baseline values were 137 +/- 11.4 micrograms N-MH per gram of creatinine and 9 +/- 1.1 micrograms N-MH per hour (n = 9). Levels peaked 1 hour after infusion at 275 +/- 45 micrograms/gm of creatinine and 44 +/- 5.6 micrograms/hr and decreased to resting levels after 2 hours. Metabolization by N-MH accounted for 9.5% +/- 4.9% (range, 2.4% to 18.4%) of infused histamine in the urine of the nine subjects. Bee-sting challenges were performed in 12 patients and three control subjects. Only in three patients experiencing generalized urticaria, nausea, dyspnea, and hypotension were significant increases of urine N-MH levels (138%, 144%, and 238%) observed. All other patients and three normal control subjects demonstrated normal local reactions without increase of N-MH values.(ABSTRACT TRUNCATED AT 250 WORDS)

Measurement of imidazoleacetic acid in urine by gas chromatography-mass spectrometry

Imidazoleacetic acid (IAA), a histamine and histidine metabolite, was quantified in human urine by gas chromatography-mass spectrometry (GC-MS). The acid was separated by ion-exchange chromatography, derivatized as the n-butyl ester with boron trifluoride-butanol and the derivative extracted with chloroform. GC-MS analysis was carried out by selected-ion monitoring of ions m/z 81 and m/z 83 corresponding, respectively, to IAA and [15N,15N']IAA used as internal standard. The mean IAA content in urine was about 8.02 nmol/mg of creatinine. The specificity of measurement was rigorously established by GC retention time, peak shape, ion abundance ratios, and recovery experiments. The method is capable of quantifying IAA in 0.05 ml of urine and in amounts as low as 0.20 nmol.

A sensitive double isotopic, chromatographic method for the determination of histamine. I: Studies with authentic histamine

This paper presents a method for the determination of histamine using an internal standard of 14C-labelled histamine, which together with an unknown sample of unlabelled histamine is dansylated with 3H-labelled dansyl chloride. The products of this dansylation are then separated on thin-layer-chromatographic plates coated with micropolyamide. The spot of dansylhistamine is scraped off and the content of histamine in the unknown sample is calculated from the 3H/14C-ratio in the spot.

Studies on histamine metabolism in intrinsic bronchial asthma

Histamine metabolism was investigated in patients with intrinsic asthma, during the acute phase and in remission, by determination of the urinary excretion of histamine metabolites. During acute attacks the excretion of methylhistamine (MeHi) and 1-methyl-4-imidazoleacetic acid (MeImAA) was significantly increased compared with healthy subjects. The excretion of MeHi was significantly increased during acute attacks compared with remission. The excretion of MeImAA was also increased, but the difference was not significant. The correlation between the excretion of MeHi and MeImAA was highly significant. Corticosteroids, given to some patients during remission, did not affect the excretion of histamine and its metabolites. Smoking and respiratory infection during the acute attacks were both accompanied by increased excretion of MeHi. The results indicate that there is an increased histamine turnover in acute attacks of intrinsic bronchial asthma.

Histamine levels in plasma, blood, and urine in severe asthma, and the effect of corticosteroid treatment

Plasma, whole blood, and urinary histamine levels have been determined in 64 normal subjects, in 10 patients with severe asthma, and in 10 control patients with other illnesses. The mean whole blood levels did not differ between the three groups. The mean plasma level in the asthmatics was significantly greater than that of the normal subjects but not of the control patients. The urinary histamine output was lower in the control patients than in the normal subjects but in the asthmatics did not differ from that of the normals. Corticosteroid therapy caused a marked fall, often to barely detectable levels, of the whole blood histamine concentration of the asthmatic patients and restored the plasma levels to normal but did not affect urinary histamine levels.