Collagen is the major structural protein in the human body controlling tissue architecture, cell growth and differentiation. The destruction of this key connective tissue component during inflammation is important in the pathogenesis of a host of disease states affecting every organ system in the body. One of the hallmarks of acute inflammatory damage is the influx of large numbers of blood neutrophils into the affected site. Neutrophils can potentially degrade collagens by releasing the lysosomal enzymes, collagenase and gelatinase, but these enzymes are stored in latent inactive forms. Thus, once the metalloenzymes are released into the extracellular milieu, they must be activated in order to catalyze collagen degradation. In this study we will 1) examine the ability of human neutrophils to activate collagenase and gelatinase, 2) elucidate the processes responsible for metalloenzyme activation and 3) identify and assess the physiologic role of collagenase-gelatinase inhibitors. Specifically, isolated neutrophils will be triggered with soluble, phagocytizeable or chemotactic stimuli and the release of active and latent metalloenzymes assessed in collagenolytic assays using radiolabeled native or denatured type I collagen. Emphasis will be placed on determining the relative roles of oxygen dependent and independent processes utilized by the intact neutrophil to activate and regulate the collagenolytic enzymes. Identification of physiologically relevant control mechanisms in the intact cell system will then lead to the extension of these studies to cell-free analyses with purified enzymes in order to elucidate the biochemical processes responsible for activation. Finally, the role of specific plasma and platelet-derived metalloproteinase inhibitors will be examined for their ability to modulate both collagenase and gelatinase activity in both the intact cell and cell-free systems. The identifcation of the human neutrophil as a mobile source of active collagenolytic enzymes coupled with an elucidation of the processes regulating activity will not only provide new insights into the pathophysiology of collagen destruction but will also dictate the construction of rational therapeutic interventions.
