Decreased ceruloplasmin ferroxidase activity in cigarette smokers.

Ceruloplasmin is one of the most important antioxidant proteins in serum. Ceruloplasmin functions as a ferroxidase that oxidizes iron to the Fe3+ state, thereby preventing Fe2+-catalyzed lipid peroxidation and cellular damage. Despite increased antigenic amounts of ceruloplasmin, cigarette smoker serum has previously been shown to exhibit significantly less antioxidant activity than non-smoker serum. We demonstrate that the decreased antioxidant activity of cigarette smoker serum may be explained by a decrease in ceruloplasmin ferroxidase activity. Smokers had a 14% decrease in serum ceruloplasmin ferroxidase activity (units per milliliter) compared with nonsmokers. There was a 24% decrease in ferroxidase activity per milligram of ceruloplasmin in smokers compared with nonsmokers (0.32 +/- 0.009 U/mg vs 0.42 +/- 0.020 U/mg, p less than 0.005). Smoker serum also contained significantly less ceruloplasmin-specific antioxidant activity than nonsmoker serum. These observations may explain the decrement in smoker serum antioxidant activity that could predispose cigarette smokers to increased oxidant injury.