Inhibition of Ammonia-Chloramine Generation and of Damage to Vascular Endothelium by Taurine and β-Alanine

Abstract

Hypochlorous acid (HOCl) produced by myeloperoxidase reacts with ammonia to form highly toxic ammonia-chloramine (NH₂Cl) in vivo. We examined the abilities of various amino acids to compete with ammonia to form only mildly toxic chloramines with HOCl. Amino acid-chloramines (RNHCl) were generated by reacting amino acids with HOCl, and showed maximum absorption near 250nm. Glycine, taurine, and β-alanine readily formed hydrophilic chloramines with high absorption at 250nm. The ESR spectrum of HOCl changed to that of RNHCl by reacting HOCl with each of these three amino acids. Taurine and β-alanine inhibited vascular endothelium lesions due to active oxygen species generated by neutrophils that had been stimulated by opsonized zymosan and phorbol myristate acetate.