Assessment of in vivo mast cell reactivity in patients with systemic mastocytosis.

BACKGROUND: Patients with systemic mastocytosis (SM) have clinical signs of mast cell (MC) activation and increased levels of MC mediators. It is unclear whether the increased mediator levels are caused by increased numbers of tissue MCs, or whether these cells in affected individuals have a hyperactive phenotype. OBJECTIVE: To determine reactivity of the skin and the airways to directly acting mediators and indirectly acting mast cell secretagogues in subjects with SM. METHODS: Skin reactivity to morphine and histamine, and airway responsiveness to mannitol and methacholine, was assessed in 15 patients with SM, 11 patients with allergic asthma (A) and 13 healthy controls (HC). Serum tryptase and urinary metabolites of the MC mediators histamine and prostaglandin D2 were measured, as well as ex vivo basophil histamine release. RESULTS: Mast cell mediators in the blood and urine were significantly higher in patients with SM than in HC and A controls. Responsiveness to local activation of skin MCs (by morphine) and airway MCs (by mannitol) was similar in SM and HC groups. Likewise, end-organ responsiveness in the skin to histamine, and in the airways to methacholine, was similar in all three subject groups. There was no evidence of increased basophil reactivity in SM patients. CONCLUSIONS AND CLINICAL RELEVANCE: Mast cells in the skin and airways of subjects with SM do not exhibit hyper-reactivity towards the MC-activating stimuli morphine and mannitol, respectively. Therefore, the highly elevated baseline levels of MC mediators in SM are most likely due to increased MC numbers, rather than altered MC responsiveness. The underlying mechanisms could involve leakage of MC mediators, or dysfunctions in mediator synthesis, storage and release. One clinical implication of our study is that there is no contraindication to perform skin tests using morphine in subjects with mastocytosis.

A quantitative LC/MS method targeting urinary 1-methyl-4-imidazoleacetic acid for safety monitoring of the global histamine turnover in clinical studies.

Anaphylaxis is a potentially life-threatening condition triggered mainly by the release of inflammatory mediators, notably histamine. In pharmaceutical research, drug discovery, and clinical evaluation, it may be necessary to accurately assess the potential of a compound, event, or disorder to promote the release of histamine. In contrast to the measurement of plasma histamine, determination of the stable metabolite 1-methyl-4-imidazoleacetic acid (tele-MIAA) in urine provides a noninvasive and more reliable methodology to monitor histamine release. This study presents a repeatable high-performance liquid chromatography coupled to electrospray mass spectrometry (LC-ESI-MS) method where tele-MIAA is baseline separated from its structural isomer 1-methyl-5-imidazoleacetic acid (pi-MIAA) and an unknown in human urine. The ion-pairing chromatography method, in reversed-phase mode, based on 0.5 mM tridecafluoroheptanoic acid demonstrated high repeatability and was applied in a clinical development program that comprised a large number of clinical samples from different cohorts. The inter- and intra-run precision of the method for tele-MIAA were 8.4 and 4.3%, respectively, at the mean urinary concentration level, while method accuracy was between -16.2 and 8.0% across the linear concentration range of 22-1,111 ng mL(-1). Overall, method precision was greater than that reported in previously published methods and enabled the identification of gender differences that were independent of age or demography. The median concentration measured in female subjects was 3.0 µmol mmol(-1) of creatinine, and for male subjects, it was 2.1 µmol mmol(-1) of creatinine. The results demonstrate that the method provides unprecedented accuracy, precision, and practicality for the measurement of tele-MIAA in large clinical settings.

New modes of data partitioning based on PARS peak alignment for improved multivariate biomarker/biopattern detection in 1H-NMR spectroscopic metabolic profiling of urine.

This paper addresses the possibility of mathematically partition and process urine 1H-NMR spectra to enhance the efficiency of the subsequent multivariate data analysis in the context of metabolic profiling of a toxicity study. We show that by processing the NMR data with the peak alignment using reduced set mapping (PARS) algorithm and the use of sparse representation of the data results in the information contained in the original NMR data being preserved with retained resolution but free of the problem of peak shifts. We can now describe a method for differential expression analysis of NMR spectra by using prior knowledge, i.e., the onset of dosing, a partitioning not possible to achieve using raw or bucketed data. In addition we also outline a scheme for soft removal of "biological noise" from the aligned data: exhaustive bio-noise subtraction (EBS). The result is a straightforward protocol for detection of peaks that appear as a consequence of the drug response. In other words, it is possible to elucidate peak origin, either from endogenous substances or from the administered drug/biomarkers. The partition of data originating from the normally regulating metabolome can, furthermore, be analyzed free of the superimposed biological noise. The proposed protocol results in enhanced interpretability of the processed data, i.e., a more refined metabolic trace, simplification of detection of consistent biomarkers, and a simplified search for metabolic end products of the administered drug.