Inhibition of neutrophil superoxide production by human plasma α1‐antitrypsin

Abstract
We report here that human plasma α1-antitrypsin (α1-AT) inhibited human neutrophil O2 release elicited by a variety of stimulants. In comparison, the inhibitory capacities of two serine protease inhibitors, l-1-tosylamide 2-phenylethylchloromethyl ketone (TPCK) and soybean trypsin inhibitor (SBTI) and the human recombinant α1-AT mutant, α1-AT-Arg358 were in the order: α1-AT - TPCK> α1-AT-Arg358 > SBTI when cells were stimulated with concanavalin A plus cytochalasin E. These data suggest that, in human inflammatory fluks containing relatively high concentrations of α1-AT (such as rheumatoid arthritis synovial fluids) (i) α1-AT may down-regulate the inflammatory process by inhibiting the neurophil respiratory burst and (ii) serpin oxidation by neutrophil-released oxygen species is unlikely to occur.