Faculty Bibliography

The immune defence mechanisms of fish seem to be related and similarly competent to those of mammals. Because of this, there is an increased interest in the immune responses of fish as models for higher vertebrates in immunological/immunotoxicological studies. Macrophages (M phi), phagocytic cells of the mammalian and teleost immune system which reside in tissues, represent a quiescent population of cells. However, upon stimulation, alterations in the physiology of these resident M phi occur which can be defined in terms of activation. This study was undertaken to determine whether biological markers used to assess mammalian M phi activation are applicable for use with fish M phi. Cells were recovered from the peritoneal cavity of non-injected and Aeromonas salmonicida-injected fish, and differences between resident and elicited M phi were evaluated with respect to protein content, phagocytic competence, enzyme activities and hydrogen peroxide production. Results demonstrate that biological markers used to assess mammalian M phi activation, with the exception of acid phosphatase activity, can be used to characterize the activation state of trout M phi, and that the activation process in both fish and mammals may occur by similar mechanism(s)

Lead, an immunomodulator and potential human carcinogen, is a major airborne pollutant in industrial environments which poses a serious threat to human health. Despite the wide-spread occurrence of respirable lead particles in the air, and the potential human health risks, effects associated with inhalation of particulate lead on the the lung have been poorly studied. This study was performed to determine whether inhalation of particulate lead oxide (PbO), at a concentration below the currently acceptable air lead standard for occupational exposure, disrupts macrophage (M phi) functions important for maintaining pulmonary immunocompetence. These functions include phagocytosis, production of reactive oxygen intermediates, and the biological activity of tumor necrosis factor-alpha (TNF-alpha). Rabbits exposed to PbO at 30 micrograms/m3 for 4 days (3 hr/day) were sacrificed and their lungs lavaged immediately, 24 hr, and 72 hr after the final exposure. Lactate dehydrogenase (a marker of lung cell damage) and lysozyme activity (a marker of lysosome permeability), measured in the lavage fluid, were significantly increased 24 and 72 hr after exposure. PbO produced neutrophil infiltration nor effects on M phi viability or total numbers. Effects on M phi functions were as follows. Phagocytic uptake of latex particles was reduced with increasing post-exposure time reaching a maximum inhibition at 72 hr. Inhalation of PbO enhanced hydrogen peroxide (H2O2) and superoxide anion radical (O2-) production in a time-dependent manner; effects on H2O2 began at 24 hr and were persistent up to 72 hr. Effects on TNF-alpha release/activity appeared earliest and were persistent up to 72 hr. Immediately and 24 hr after exposure, lipopolysaccharide-stimulated activity of TNF-alpha was depressed by 62 and 50%, respectively; after 72 hr, TNF-alpha release was significantly enhanced compared to control levels. Results demonstrate that the lung is a sensitive target for the toxic effects of inhaled lead. This study provides the first evidence that inhalation of particulate lead, at an occupationally relevant concentration, and in the absence of elevated blood lead levels, alters pulmonary M phi functions critical for lung defense against inhaled antigens. Our findings may have important implications for human health and should be considered when evaluating the health risks associated with inhaled lead

Treatment of cultured mouse macrophages with either of two different vanadium compounds was shown to affect the production/release of two major immunoregulatory cytokines. The pentavalent vanadium compound ammonium metavanadate was shown previously to disrupt cell-mediated immunity at the earliest stages of an in vivo anti-Listerial response, in that mice treated with vanadium displayed decreased accessory cell recruitment and numbers of activated macrophages at infection sites. To determine whether these effects were due to vanadium-induced alterations in the production of biologically-active mediators, mouse macrophage-like WEHI-3 cells were treated in vitro with ammonium metavanadate or vanadium pentoxide prior to stimulation with lipopolysaccharide endotoxin (LPS). After stimulation, monokine (tumor necrosis factor-alpha and interleukin-1) and prostaglandin E2 (PGE2) activities were assessed. Both vanadium compounds decreased recovered monokine activities; measured TNF alpha concentrations were also reduced. Spontaneous release of the IL-1/TNF-regulating prostanoid PGE2 was significantly increased by the highest concentration of vanadate tested, although LPS-stimulated PGE2 production was unaffected by either compound. These results indicate that, in vitro, pentavalent vanadium can interfere with immunoregulatory mediators critical for maintaining host immunocompetence

There is considerable interest in the potential health effects resulting from inhalation of acidic aerosols. However, except for well documented irritant effects and acid-induced changes in lung clearance function, other potential health effects have not been well defined. This study was designed to provide further insight regarding the relationship of sulfuric acid aerosol to the pathogenesis of respiratory disease by describing the effects of inhaled acid on the release and/or activity of biologically active mediators critical for maintaining pulmonary immunocompetence and resistance against infectious diseases. Results of this study demonstrated that a single inhalation exposure of rabbits to environmentally relevant and higher concentrations of sulfuric acid depresses the release/activity of lipopolysaccharide-stimulated tumor necrosis factor-alpha and also reduces the ability of pulmonary macrophages to produce superoxide anion radical in response to opsonised zymosan. These findings should be considered when evaluating the health risks associated with sulfuric acid exposure

Studies examining effects of air pollutants often use single compounds, while 'real world' exposures are to more than one chemical. Thus, it is necessary to assess responses following inhalation of chemical mixtures. Rabbits were exposed for 3 hr to sulfuric acid aerosol at 0, 50, 75, or 125 micrograms/m3 in conjunction with ozone at 0, 0.1, 0.3, or 0.6 ppm, following which broncho-pulmonary lavage was performed. Various pulmonary response endpoints related to general cytotoxicity and macrophage function were examined. In addition, a goal of the study was to define an improved approach to the analysis of data sets involving binary pollutant mixtures. Results were evaluated using analysis of variance with multiple linear contrasts to determine the significance of any effect in the pollutant-exposed groups compared to sham control animals and to assess the type, and extent, of any toxicological interaction between acid and ozone. Interaction was considered to occur when the effects of combined exposure were either significantly greater or less than additive. Pollutant exposures had no effect on lavage fluid levels of lactate dehydrogenase, prostaglandins E2 and F2 alpha, nor on the numbers, viability, or types of immune cells recovered by lavage. Phagocytic activity of macrophages was depressed at the two highest acid levels and at all levels of ozone. Exposure to all mixtures showed significant antagonism. Superoxide production by stimulated macrophages was depressed by acid exposure at the two highest concentrations, while ozone alone had no effect. Significant antagonistic interaction was observed following exposure to mixtures of 75 or 125 micrograms/m3 acid with 0.1 or 0.3 ppm ozone. The activity of tumor necrosis factor elicited from stimulated macrophages was depressed by acid at 75 and 125 micrograms/m3 while ozone had no effect. Exposure to mixtures of 125 micrograms/m3 acid with 0.3 or 0.6 ppm ozone resulted in synergistic interaction. This study provided additional evidence for antagonism between two common air pollutants and demonstrated that the type of interaction between sulfuric acid and ozone depended upon the endpoint but that the magnitude of any interaction was not always related to the exposure concentrations of the constituent pollutants

Ozone (O3) is a toxic gaseous pollutant that has been implicated in laboratory studies as a potential lung carcinogen or cocarcinogen in mice. To begin to assess the role of altered macrophage (M phi) responses as a possible mechanism by which O3 may influence carcinogenesis, we examined the effects of repeated in vivo O3 exposure on pulmonary M phi functional and biochemical activities deemed important in tumor surveillance, and host defense in general. Rabbits were exposed by inhalation to 1 ppm O3 for 3 d (2 h/d) and the lungs were lavaged immediately (t0) and 24 h (t24) after exposure. Results demonstrate that O3 reduced M phi viability and increased the number of neutrophils collected immediately after exposure. Effects of O3 on M phi movement were as follows: random migration was depressed immediately after the final exposure and chemotactic migration increased after 24 h. M phi-mediated cytotoxicity toward xenogeneic tumor cells in vitro was significantly depressed, compared to control, immediately and 24 h after O3 exposure. Release of cytotoxic factors deemed important for mediating tumor cell destruction was also assessed. Spontaneous and stimulated production of tumor necrosis factor, as measured by cytotoxicity toward LM cells (a clone of L-929 mouse fibroblasts), was unaffected by exposure to O3. Zymosan-stimulated production of superoxide anion radical (.O2-) was depressed at t0 and increased at t24; however, no significant effects on H2O2 production by resting or zymosan-stimulated M phi were observed at either time interval. Inhaled toxicants such as O3, which can compromise M phi functions important in tumor surveillance, could potentially alter host susceptibility to pulmonary cancer. Results of this study have important implications for human health, and demonstrate the need for further studies examining the carcinogenic/cocarcinogenic potential of O3

The immune defense mechanisms of fish are not as well characterized as those of mammals but seem to be related and similarly competent. Because of this, there is an increased interest in the immune responses of fish as models for higher vertebrates in immunotoxicological studies. Prior to such studies, baseline criteria for specific components of the immune response needed to be established. For this study, we have examined trout macrophage morphology using light and scanning electron microscopy, phagocytic activity, random and stimulus-directed migration, and superoxide anion radical (O2-) production for resident and lipopolysacharide (LPS) or Aeromonas salmonicidae-elicited rainbow trout (Oncorhynchus mykiss) peritoneal macrophages (M phi). Following peritoneal lavage, greater than 89% of the cells were M phi as determined by differential counts and nonspecific esterase staining. Immunization with LPS and A. salmonicidae increased M phi number approximately 5 and 13-fold, respectively, and overall size. Trout M phi were phagocytically active engulfing serum opsonized latex particles and were mobile, migrating both randomly and in a directed fashion towards formyl-methionine-L-leucine-L-phenylalanine (FMLP) and trout serum-derived complement fragment C5a. Concentrations of FMLP (100 nM) and C5a (0.01-1%) effective for attracting trout M phi are the same as those used to attract rabbit M phi. Resident trout M phi produced negligable quantities of .O2- following stimulation with 1 micrograms/ml phorbol myristate acetate; Aeromonas-elicited M phi produced .O2- in a time-dependent manner which peaked after 60 min at 2.9 nmol per 2 x 10(5) cells and then declined. The results of this study provide a data base for future toxicological studies with trout peritoneal M phi and indicate the usefulness of this system for immunotoxicological studies