Breath Ammonia Reduction Ratio (ARR) Measures Dialysis Efficacy

Contemporary evidence supports the centuries old notion that expired breath and the headspaces above body fluids and products can serve as biomarkers of organ function. Clinical responsiveness to alterations in clinical status or therapy is dependent upon timely, accurate, relevant physiological data. Current measures of urea and creatinine to assess renal urea reduction are invasive and cannot be repeated frequently or reported quickly enough to define individual response to treatment in real time. In contrast, breath analysis is minimally invasive and can provide real time information about low molecular weight volatile organic compounds (VOCs) such as ammonia1,2

Classification Algorithms for SIFT-MS Medical Diagnosis

Selected Ion Flow Tube - Mass Spectrometry (SIFTMS) is an analytical technique for the real-time quantification of trace gases in air or breath samples. The SIFT-MS system can potentially offer unique capability in the early and rapid detection of a wide variety of diseases, infectious bacteria and patient conditions, by using a classifier to differentiate between control and test groups. By identifying which masses and Volatile Organic Compounds (VOCs) contribute most strongly towards a successful classification, biomarkers for a particular disease state may be discovered. A classification method is presented and validated in a simple study in which saturated nitrogen in tedlar bags was differentiated from dry nitrogen in tedlar bags. Several biomarkers were identified, with the most reliable being N2H+.H2O, and isotopes and water clusters of H3O+, as expected. The classifier was then applied in a clinical setting to differentiate between patient breath samples after one and four hours of dialysis treatment. Biomarkers for classification were ammonia, acetaldehyde, ethanol, isoprene and acetone. The model classifies significantly better than random, with an ROC area of 0.89

Identifying peroxidases and their oxidants in the early pathology of cystic fibrosis

We aimed to determine whether myeloperoxidase (MPO) is the main peroxidase present in the airways of children with cystic fibrosis (CF) and to assess which oxidants it produces and whether they are associated with clinical features of CF. Children with CF (n = 54) and without CF (n = 16) underwent bronchoscopy and bronchoalveolar lavage (BAL) for assessment of pulmonary infection and inflammation. BAL fluid was analyzed for MPO, halogenated tyrosines as markers of hypohalous acids, thiocyanate, and protein carbonyls. MPO was the only peroxidase detected in BAL samples from children with CF and its concentration was markedly higher than in controls. Levels of 3-chlorotyrosine and 3-bromotyrosine in proteins were higher in the CF group. They correlated with neutrophils and MPO. The concentration of thiocyanate in BAL samples was below 1 mu M. Protein carbonyl levels correlated with MPO and halogenated tyrosines in patients with CF. Levels of MPO and halogenated tyrosines were higher in children with infections, especially Pseudomonas aeruginosa, and in the presence of respiratory symptoms. They also correlated with the Kanga clinical score. Our findings suggest that MPO produces hypobromous acid as well as hypochlorous acid in the airways of children with CF and that these oxidants are involved in the early pathogenesis of CF. (C) 2010 Elsevier Inc. All rights reserved

Pathways for the decay of organic dichloramines and liberation of antimicrobial chloramine gases

When neutrophils phagocytose bacteria, they generate the cytotoxic agent hypochlorous acid (HOCl). The specific role that HOCl plays in bacterial killing is unclear. In the phagosome, it should react with neutrophil proteins to form protein chloramines and dichloramines. We investigated the stability of model dichloramines that are likely to be formed on N-terminal amino acids and Lys residues of proteins contained within phagosomes. Dichloramines were much more unstable than their analogous monochloramines. The stability was affected by substituents on the R-carbon. Amino acid dichloramines were extremely unstable, indicating that an R-carboxyl group facilitated decomposition. In general, the absence of a substituent enhanced stability. The carboxyl group on N-terminal Glu residues favored break down, but this effect was not apparent with Asp residues. Unstable dichloramines that contained a substituent on their R-carbon were cytotoxic and killed 50% of 105 Staphylococcus aureus (LD50) at a dose of approximately 2.5 nmol. Their cytotoxicity declined with time. The dichloramines of N-R-acetyl Lys and taurine were not bactericidal up to 10 nmol per 105 S. aureus. None of the analogous monochloramines were cytotoxic at this dose. Dichloramines decomposed to yield chlorimines, aldehydes, and the inorganic gases ammonia monochloramine (NH2Cl) and ammonia dichloramine (NHCl2). The LD50 values were determined for NH2Cl (0.37 ( 0.14 nmol), NHCl2 (0.08 ( 0.02 nmol), and HOCl (0.14 ( 0.04 nmol). Stable products formed during the breakdown of dichloramines were not bactericidal. We propose a potential antimicrobial mechanism that explains in part how HOCl can react mainly with neutrophil components but still promote killing of phagocytosed bacteria. HOCl produced in phagosomes will react with amine groups on neutrophil proteins to form unstable dichloramines that will liberate cytotoxic NH2Cl and NHCl2. These gases will contribute to killing of ingested bacteri

Mass spectrometric analysis of HOCl- and free-radical-induced damage to lipids and proteins

In inflammatory diseases, release of oxidants leads to oxidative damage to biomolecules. HOCl (hypochlorous acid), released by the myeloperoxidase/H2O2/ClGêÆ system, can cause formation of phospholipid chlorohydrins, or +¦-chloro-fatty aldehydes from plasmalogens. It can attack several amino acid residues in proteins, causing post-translational oxidative modifications of proteins, but the formation of 3-chlorotyrosine is one of the most stable markers of HOCl-induced damage. Soft-ionization MS has proved invaluable for detecting the occurrence of oxidative modifications to both phospholipids and proteins, and characterizing the products generated by HOCl-induced attack. For both phospholipids and proteins, the application of advanced mass spectrometric methods such as product or precursor ion scanning and neutral loss analysis can yield information both about the specific nature of the oxidative modification and the biomolecule modified. The ideal is to be able to apply these methods to complex biological or clinical samples, to determine the site-specific modifications of particular cellular components. This is important for understanding disease mechanisms and offers potential for development of novel biomarkers of inflammatory diseases. In the present paper, we review some of the progress that has been made towards this goa