Under certain circumstances, blood neutrophils (PMNs) release reactive oxygen metabolites or other agents that cause injury to organs. The possibility that some chemicals produce acute organ toxicity indirectly by stimulating blood PMNs to release oxygen radicals or other injurious substances has not been extensively explored as a general mechanism of toxicity. The overall goal of the proposed research is to characterize the stimulatory effects of certain dumpsite chemicals (DSCs) on PMNs and to evaluate the importance of PMN stimulation in their acute toxicities. Initial studies will focus on volatile organic chemicals (VOCs) chosen for study for all of the subprojects, namely, trichloroethylene (TCE), 1,1,1,-trichloroethane, toluene, methylene chloride, carbon tetrachloride (CCI4), and benzene. Dieldrin will also be examined since our preliminary studies have revealed that it affects PMN function. The first series of experiments will be performed using rat PMNs in vitro. The ability of DSCs to stimulate several membrane-associated PMN responses will be examined and concentration/response curves generated. These functional responses will include oxygen radical release, lysosomal enzyme release, PMN aggregation and chemotaxis. In addition, cytotoxicity of DSCs toward PMNs will be evaluated. Next, synergistic interactions among DSCs and between DSCs and certain PMN stimulators will be examined. This is important since exposure of people to multiple DSCs occurs, and these DScs may act synergistically to produce organ dysfunction or alter susceptibility of individuals to pathogens. For DScs that are found to stimulate or prime PMNs, the roles of calcium and alterations in membrane fluidity and membrane potential in their mechanism of action will be evaluated. Species differences in response of PMNs to selected DSCs will be evaluated, as will the possibility that the effects of DSCs apply also to other phagocytic cells (i.e., macrophages). If DSCs produce toxicity in vivo via their abilities to stimulate PMNs, then depletion of blood PMNs should reduce the toxicity. This will be tested in rats depleted of PMNs by an anti-PMN serum. DSCs that stimulate or prime PMNs in animals will be tested for their ability to do so in human PMNs in vitro using flow cytometric techniques to assess PMN functions. Finally, PMNs from blood of rats exposed acutely and chronically to DSCs will be evaluated to determine if they are altered in their responsiveness to stimulating agents. Blood from these rats will be obtained as part of the chronic studies in vivo described as another subproject in this proposal. These studies involving investigators active in several subprojects will uncover novel, toxic effects of DSCs, explore potentially important toxicological interactions, and perhaps suggest a useful biological marker for exposure of individuals to DSCs.
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