Tumor necrosis factor increases the elastolytic potential of adherent neutrophils: a role for hypochlorous acid

Neutrophils adhered to biologic surfaces exhibit proteolytic cleavage of surface proteins even in the presence of proteinase inhibitors. Such proteolysis is restricted to the pericellular space and appears to require the dual action of proteinases and reactive oxygen species. The present study was designed to investigate the mechanism by which tumor necrosis factor-alpha (TNF) stimulates neutrophil proteolysis. Tissue culture wells were coated with insoluble 3H-labeled elastin substrate. Human blood neutrophils (0.5 to 2.0 x 10(6) cells/ml/well) were incubated in the coated wells for 4 to 18 h at 37 degrees C in the presence of varying concentrations of serum or purified alpha 1-antitrypsin (A1AT). TNF (0 to 1,000 U/ml) was also present in the incubations. Elastin degradation was determined as soluble 3H-elastin fragments released into the supernatants. As previously reported, cells (no TNF) exhibited spontaneous elastolysis even in the presence of 1% serum or 4 microM AlAT. Compared with cells incubated alone (no TNF), TNF increased elastolysis 3-fold in the 4-h incubations and 83% in 18-h incubations. TNF also significantly increased proteolysis when neutrophils were concurrently treated with phorbol myristate acetate or N-formylmethionylleucylphenylalanine. Since TNF is known to prime neutrophils for hypochlorous acid (HOCl) release, the present study hypothesized that the enhancement of proteolysis by TNF was related to increased release of HOCl. First, TNF caused a 4-fold increase in HOCl release by neutrophils adhered to elastin surfaces. Second, the effect of methionine on elastolysis by adherent neutrophils was studied.(ABSTRACT TRUNCATED AT 250 WORDS)