Human phagocytes play a pivotal role in mediating tissue damage in a variety of inflammatory disease states. In order to gain insights into the pathogenesis of tissue injury during inflammation, our attention will focus on the ability of two populations of human phagocytes, the neutrophil and monocyte, to generate and utilize a group of highly reactive chlorinated, oxygen metabolites. We will examine the abililty of physiologically relevant, immune stimuli to trigger the phagocytes to generate and utilize the chlorinated oxidants in a number of in vitro model systems specifically chosen to mimic in vivo inflammatory processes. Emphasis will be placed on two types of cell-derived oxidants, a short-lived specied with characteristics similar if not identical to hypochlorous acid and a newly described, long-lived oxidant with properties identical to those of N-chloroamines. Based on the known chemical characteristics of these oxidants, their biological impact will be assessed in separate but parallel in vitro systems. Specifically we will 1) examine and quantitate the ability of immune triggered phagocytes to generate hypochlorous acid, 2) determine the ability of the intact phagocyte to utilize this oxidant to mediate extracellular cytotoxicity, 3) study the biochemical features of hypochlorous acid dependent damage and 4) assess the ability of target cells to regulate their sensitivity to oxidant attack by the chlorinated oxidant. In the other portions of this study we will determine the ability of phagocytes to generate endogenous N-chloramines and examine the factors controlling their production. Finally, we will carefully evaluate the chemical reactivity of the N-chloroamines in order to provide rational guidelines for predicting their ability to interact with inflammatory mediators and target cell populations. Taken together, these studies will provide new information into the pathogenesis of inflammation at the cellular and molecular level and should allow us to plan rationale therapeutic interventions aimed at attenuating tissue destruction in disease states.
