engleski

Protein thiol oxidation and paraoxonase 1 activity in patients with chronic obstructive pulmonary disease

Introduction: Chronic obstructive pulmonary disease (COPD) is characterized by chronic local and systemic inflammation, and increased oxidative stress. Cigarette smoking is the major etiological factor responsible for COPD. Reactive oxygen species, generated by cigarette smoke and by activated lung and peripheral blood cells, may disturb redox balance through oxidation of plasma proteins. Paraoxonase 1 (PON1) is an HDL-associated enzyme with three cysteine residues in positions 41, 284 and 353 ; C41 and C353 form a disulfide bond while C284 is free. The enzyme has both antiatherogenic and antioxidative properties. Materials and methods: The study was carried out on 107 COPD patients (32 smokers, 28 ex-smokers, 47 non-smokers) and 45 healthy volunteers (16 smokers, 13 ex-smokers, 16 non-smokers). Serum protein thiols were measured by a spectrophotometric method using 5, 5’ -dithiobis-(2-nitrobenzoic acid) (DTNB). Paraoxonase activity of PON1 was assayed by monitoring the release of p-nitrophenol from paraoxon in the absence (basal PON1 activity) or in the presence of NaCl (salt-stimulated PON1 activity). Results: Proteins thiol concentration was significantly decreased in COPD patients compared with healthy individuals, and this reduction of free sulfhydryl groups was not dependent on smoking status or disease severity (GOLD grade). In addition, both basal and salt-stimulated PON1 activity were also significantly lower in COPD patients. Conclusion: The decrease in protein thiols observed in COPD patients suggests the increased oxidative stress in those individuals which may explain in part the reduction in PON1 paraoxonase activity.

chronic obstructive pulmonary disease; paraoxonase; oxidative stress

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