Converting enzyme-independent release of tumor necrosis factor alpha and IL-1 beta from a stimulated human monocytic cell line in the presence of activated neutrophils or purified proteinase 3

Two important cytokines mediating inflammation are tumor necrosis factor cu (TNF alpha) and IL-1 beta, both of which require conversion to soluble for ms by converting enzymes. The importance of TNF alpha-converting enzyme and IL-lp-converting. enzyme in the production of circulating TNF alpha and IL -1 beta in response to systemic challenges has been demonstrated by the use of specific converting enzyme inhibitors. Many inflammatory responses, how ever, are not systemic but instead are localized. In these situations relea se and/or activation of cytokines may be different from that seen in respon se to a systemic stimulus, particularly because associations of various cel l populations in these foci allows for the exposure of procytokines to the proteolytic enzymes produced by activated neutrophils, neutrophil elastase (NE), proteinase 3 (PR3), and cathepsin G (Cat G), To investigate the possi bility of alternative processing of TNF alpha and/or IL-1 beta by neutrophi l-derived proteinases, immunoreactive TNF alpha and IL-1 beta release from lipopolysaccharide-stimulated THP-1 cells was measured in the presence of a ctivated human neutrophils. Under these conditions, TNFa and IL-1 beta rele ase was augmented 2- to 5-fold. In the presence of a specific inhibitor of NE and PR3, enhanced release of both cytokines was largely abolished; howev er, in the presence of a NE and Cat G selective inhibitor, secretory leucoc yte proteinase inhibitor, reduction of the enhanced release was minimal. Th is finding suggested that the augmented release was attributable to PR3 but not NE nor Cat G. Use of purified enzymes confirmed this conclusion. These results indicate that there may be alternative pathways for the production of these two proinflammatory cytokines, particularly in the context of loc al inflammatory processes.