Capacity of ceruloplasmin to scavenge products of the respiratory burst of neutrophils is not altered by the products of reactions catalyzed by myeloperoxidase.

Ceruloplasmin (CP) is a copper-containing ferroxidase of blood plasma, acting as an acute phase reactant during inflammation. The effect of oxidative modification of CP induced by oxidants produced by myeloperoxidase, such as HOCl, HOBr and HOSCN, on its spectral, enzymatic and anti-inflammatory properties was studied. We monitored chemiluminescence of lucigenin and luminal along with fluorescence of hydroethidine and scopoletin to assay the inhibition by CP of the neutrophilic respiratory burst induced by phorbol 12-myristate 13-acetate (PMA) or formyl-methionyl-leucyl-phenylalanine (fMLP). Superoxide dismutase activity of CP and its capacity to reduce the production of oxidants in respiratory burst of neutrophils remained virtually unchanged upon modifications caused by HOCl, HOBr and HOSCN. Meanwhile, the absorption of type I copper ions at 610 nm became reduced along with a drop of the ferroxidase and amino oxidase activities of CP. Likewise its inhibitory effect on halogenating activity of myeloperoxidase was diminished. Sera of either healthy donors or patients with Wilson disease were co-incubated with neutrophils from healthy volunteers. In these experiments, we observed a reverse correlation between the content of CP in sera and the rate of hydrogen peroxide production by activated neutrophils. In conclusion, CP is likely to play a role of an anti-inflammatory factor tempering the neutrophil respiratory burst in the bloodstream despite the MPO-mediated oxidative modifications.