title: Measuring chlorine bleach in biology and medicine.
abstract: BACKGROUND
  Chlorine bleach, or hypochlorous acid, is the most reactive two-electron oxidant produced in appreciable amounts in our bodies. Neutrophils are the main source of hypochlorous acid. These champions of the innate immune system use it to fight infection but also direct it against host tissue in inflammatory diseases. Neutrophils contain a rich supply of the enzyme myeloperoxidase. It uses hydrogen peroxide to convert chloride to hypochlorous acid.
  
  
  METHODS
  We give a critical appraisal of the best methods to measure production of hypochlorous acid by purified peroxidases and isolated neutrophils. Robust ways of detecting it inside neutrophil phagosomes where bacteria are killed are also discussed. Special attention is focused on reaction-based fluorescent probes but their visual charm is tempered by stressing their current limitations. Finally, the strengths and weaknesses of biomarker assays that capture the footprints of chlorine in various pathologies are evaluated.
  
  
  CONCLUSIONS
  Detection of hypochlorous acid by purified peroxidases and isolated neutrophils is best achieved by measuring accumulation of taurine chloramine. Formation of hypochlorous acid inside neutrophil phagosomes can be tracked using mass spectrometric analysis of 3-chlorotyrosine and methionine sulfoxide in bacterial proteins, or detection of chlorinated fluorescein on ingestible particles. Reaction-based fluorescent probes can also be used to monitor hypochlorous acid during phagocytosis. Specific biomarkers of its formation during inflammation include 3-chlorotyrosine, chlorinated products of plasmalogens, and glutathione sulfonamide.
  
  
  CONCLUSIONS
  These methods should bring new insights into how chlorine bleach is produced by peroxidases, reacts within phagosomes to kill bacteria, and contributes to inflammation. This article is part of a Special Issue entitled Current methods to study reactive oxygen species - pros and cons and biophysics of membrane proteins. Guest Editor: Christine Winterbourn.
authors.affiliation: Centre for Free Radical Research, Department of Pathology, University of Otago Christchurch, P.O. Box 4345, Christchurch, New Zealand. Electronic address: tony.kettle@otago.ac.nz.
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Kettle
authors.forename: Amelia M
authors.initials: AM
authors.lastname: Albrett
authors.forename: Anna L
authors.initials: AL
authors.lastname: Chapman
authors.forename: Nina
authors.initials: N
authors.lastname: Dickerhof
authors.forename: Louisa V
authors.initials: LV
authors.lastname: Forbes
authors.forename: Irada
authors.initials: I
authors.lastname: Khalilova
authors.forename: Rufus
authors.initials: R
authors.lastname: Turner
mesh_terms: D000818:Animals; D006801:Humans; D006997:Hypochlorous Acid / Q000032:analysis*; D007249:Inflammation / Q000378:metabolism*; D009504:Neutrophils / Q000378:metabolism*; D009195:Peroxidase / Q000378:metabolism
chemical_list: D006997:Hypochlorous Acid; D009195:Peroxidase
keywords: Hypochlorous acid; Inflammation; Myeloperoxidase; Neutrophil; Peroxidase; Reactive oxygen species