Proteolytic potential of human neutrophil membranes

A synergistic role for proteases in the degradation of extracellular matrix proteins has been proposed. Plasma membrane was isolated from a neutrophil homogenate, on a sucrose gradient, and shown to activate gelatinolysis when purified 92 kDa gelatinase was added to the medium. This stimulatory activity was enhanced by the addition of phorbol 12-myristate 13-acetate (PMA), in a dose-dependent manner, and was partially sensitive to phenylmethylsulfonyl fluoride treatment. The effect was abolished by the addition of 1 M KCl or 0.05% Brij 35 extraction. Both elastase and urinary type plasminogen activator were shown to be involved in the process. Moreover, upon neutrophil stimulation by PMA, 92 kDa gelatinase, as elastase, became associated with the plasma membrane, as shown by a subcellular fractionation experiment. These in vitro observations suggest that human neutrophils may be able, in vivo, to recruit endogenous or exogenous proteinases to mediate proteolysis associated with diapedesis and chemotactism during the inflammation process.