Identification of plasma proteins that are susceptible to thiol oxidation by hypochlorous acid and N-chloramines

TY - JOUR

T1 - Identification of plasma proteins that are susceptible to thiol oxidation by hypochlorous acid and N-chloramines

AU - Summers, Fiona A

AU - Morgan, Philip E

AU - Davies, Michael Jonathan

AU - Hawkins, Clare Louise

PY - 2008/9

Y1 - 2008/9

N2 - Hypochlorous acid (HOCl), the major strong oxidant produced by myeloperoxidase, reacts readily with free amino groups to form N-chloramines. Although HOCl and N-chloramines play an important role in the human immune system by killing bacteria and invading pathogens, they have also been shown to cause damage to tissues, which is believed to contribute to a number of diseases. It has been shown previously that N-chloramines react more readily with protein thiols than with other targets in plasma, but the nature of the plasma thiol-containing proteins oxidized is unknown. In this study, the ability of N-chloramines to selectively oxidize thiol-containing plasma proteins was determined using the thiol-specific probe, 5-iodoacetamidofluorescein, combined with two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Experiments were performed with N-chloramines formed on Nalpha-acetyl-lysine, Nalpha-acetyl-histidine (HisCA), glycine, taurine, and ammonia. With the exception of HisCA, the N-chloramines were more efficient than HOCl at oxidizing plasma thiols. The thiol-containing plasma proteins alpha1-antitrypsin and transthyretin were found to be oxidized in addition to albumin, with this treatment resulting in the inactivation of alpha1-antitrypsin. A similar selectivity of reaction and extent of thiol oxidation were also observed with myeloperoxidase in the presence of hydrogen peroxide and chloride ions.

AB - Hypochlorous acid (HOCl), the major strong oxidant produced by myeloperoxidase, reacts readily with free amino groups to form N-chloramines. Although HOCl and N-chloramines play an important role in the human immune system by killing bacteria and invading pathogens, they have also been shown to cause damage to tissues, which is believed to contribute to a number of diseases. It has been shown previously that N-chloramines react more readily with protein thiols than with other targets in plasma, but the nature of the plasma thiol-containing proteins oxidized is unknown. In this study, the ability of N-chloramines to selectively oxidize thiol-containing plasma proteins was determined using the thiol-specific probe, 5-iodoacetamidofluorescein, combined with two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Experiments were performed with N-chloramines formed on Nalpha-acetyl-lysine, Nalpha-acetyl-histidine (HisCA), glycine, taurine, and ammonia. With the exception of HisCA, the N-chloramines were more efficient than HOCl at oxidizing plasma thiols. The thiol-containing plasma proteins alpha1-antitrypsin and transthyretin were found to be oxidized in addition to albumin, with this treatment resulting in the inactivation of alpha1-antitrypsin. A similar selectivity of reaction and extent of thiol oxidation were also observed with myeloperoxidase in the presence of hydrogen peroxide and chloride ions.

KW - Blood Proteins

KW - Chloramines

KW - Electrophoresis, Polyacrylamide Gel

KW - Female

KW - Humans

KW - Hypochlorous Acid

KW - Male

KW - Oxidants

KW - Oxidation-Reduction

KW - Peroxidase

KW - Reference Values

KW - Sulfhydryl Compounds

KW - alpha 1-Antitrypsin

U2 - 10.1021/tx8001719

DO - 10.1021/tx8001719

M3 - Journal article

C2 - 18698849

SN - 0893-228X

VL - 21

SP - 1832

EP - 1840

JO - Chemical Research in Toxicology

JF - Chemical Research in Toxicology

IS - 9

ER -