Comparison of mono- and dichlorinated tyrosines with carbonyls for detection of hypochlorous acid modified proteins

Hypochlorous acid is a potent oxidant capable of oxidizing and chlorinating proteins. Based on its indiscriminant reactivity, it is proposed to play a major role in tissue damage associated with a range of inflammatory diseas es. We have determined the relative tendencies for formation of protein car bonyls, chlorinated tyrosine residues, and epitopes recognized by an antibo dy raised against hypochlorous acid oxidized protein (HOP-1) when albumin i s treated with hypochlorous acid. We have also tested the specificity of th e HOP-1 antibody by measuring how effectively it recognizes proteins oxidiz ed by hypobromous acid. 3-Chlorotyrosine, along with a new marker of hypoch lorous acid dependent protein modification, 3,5-dichlorotyrosine, was forme d at the lowest doses of hypochlorous acid that were capable of generating protein carbonyls. Comparatively high doses of hypochlorous acid were neede d to generate epitopes recognized by HOP-1, which were also produced by hyp obromous acid. Our study demonstrates that it is advantageous to measure pr otein carbonyls and HOP-1 epitopes in conjunction with chlorinated tyrosine s when attempting to identify the oxidants responsible for inflammatory tis sue damage. (C) 2000 Academic Press.