Oxidation of chloride and thiocyanate by isolated leukocytes

Edwin Thomas, M. Fishman

Research output: Contribution to journalArticle

97 Citations (Scopus)

Abstract

Peroxidase-catalyzed oxidation of chloride (Cl-) and thiocyanate (SCN-) was studied using neutrophils from human blood and eosinphils and macrophages from rat peritoneal exudates. The aims were to determine whether Cl- or SCN- is preferentially oxidized and whether leukocytes oxidize SCN- to the antimicrobial oxidizing agent hypothiocyanite (OSCN-). Stimulated neutrophils produced H2O2 and secreted myeloperoxidase. Under conditions similar to those in plasma (0.14 M Cl-, 0.02-0.12 mM SCN-), myeloperoxidase catalyzed the oxidation of Cl- to hypochlorous acid (HOCl), which reacted with ammonia and amines to yield chloramines. HOCl and chloramine reacted with SCN- to yield products without oxidizing activity, so that high SCN- blocked accumulation of chloramines in the extracellular medium. Under conditions similar to those in saliva and the surface of the oral mucosa (20 mM Cl-, 0.1-3 mM SCN-), myeloperoxidase catalyzed the oxidation of SCN- to OSCN-, which accumulated in the medium to concentrations of up to 40-70 μM. Sulfonamide compounds increased the yield of stable oxidants to 0.2-0.3 mM by reacting with OSCN- to yield derivatives analogous to chloramines. Stimulated eosinophils produced H2O2 and secreted eosinophil peroxidase, which catalyzed the oxidation of SCN- to OSCN- regardless of Cl- concentration. Stimulated macrophages produced H2O2 but had low peroxidase activity. OSCN- was produced when SCN- was 0.1 mM or higher and myeloperoxidase, eosinophil peroxidase, or lactoperoxidase was added. The results indicate that SCN- rather than Cl- may be the physiologic substrate (electron donor) for eosinophil peroxidase and that OSCN- may contribute to leukocyte antimicrobial activity under conditions that favor oxidation of SCN- rather than Cl-.

Original languageEnglish (US)
Pages (from-to)9694-9702
Number of pages9
JournalJournal of Biological Chemistry
Volume261
Issue number21
StatePublished - Dec 1 1986

Fingerprint

Chlorides
Leukocytes
Peroxidase
Oxidation
Chloramines
Eosinophil Peroxidase
Hypochlorous Acid
Macrophages
Oxidants
Neutrophils
Lactoperoxidase
Antimicrobial agents
thiocyanate
Sulfonamides
Mouth Mucosa
Peritoneal Macrophages
Exudates and Transudates
Anti-Infective Agents
hypothiocyanite ion
Saliva

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Cite this

Oxidation of chloride and thiocyanate by isolated leukocytes. / Thomas, Edwin; Fishman, M.

In: Journal of Biological Chemistry, Vol. 261, No. 21, 01.12.1986, p. 9694-9702.

Research output: Contribution to journalArticle

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