Effects of soluble stimuli on human monocyte secretion

BN 52021 (a platelet activating factor-receptor antagonist) decreases alveolar macrophage-mediated lung injury in experimental extrinsic allergic alveolitis

Several lines of research indirectly suggest that platelet activating factor (PAF) may intervene in the pathogenesis of extrinsic allergic alveolitis (EAA). The specific aim of our study was to evaluate the participation of PAF on macrophage activation during the acute phase of EAA in an experimental model of this disease developed in guinea pigs. Initially we measured the concentration of PAF in bronchoalvedar lavage fluid, blood and lung tissue. In a second phase we evaluate the participation of PAF on alveolar macrophage activation and parenchymal lung injury. The effect of PAF on parenchymal lung injury was evaluated by measuring several lung parenchymatous lesion indices (lung index, bronchoalvedar lavage fluid (BALF) lactic hydrogenase activity and BALF alkaline phosphatase activity) and parameters of systemic response to the challenge (acute phase reagents). We observed that induction of the experimental EAA gave rise to an increase in the concentration of PAF in blood and in lung tissue. The use of the PAF-receptor antagonist BN52021 decreases the release of lysosomal enzymes (beta-glucuronidase and tartrate-sensitive acid phosphatase) to the extracellular environment both in vivo and in vitro. Furthermore, antagonism of the PAF receptors notably decreases pulmonary parenchymatous lesion. These data suggest that lung lesions from acute EAA are partly mediated by local production of PAF.

Role of lysosomal enzymes released by alveolar macrophages in the pathogenesis of the acute phase of hypersensitivity pneumonitis

Hydrolytic enzymes are the major constituents of alveolar macrophages (AM) and have been shown to be involved in many aspects of the inflammatory pulmonary response. The aim of this study was to evaluate the role of lysosomal enzymes in the acute phase of hypersensitivity pneumonitis (HPs). An experimental study on AM lysosomal enzymes of an HP-guinea-pig model was performed. The results obtained both in vivo and in vitro suggest that intracellular enzymatic activity decrease is, at least partly, due to release of lysosomal enzymes into the medium. A positive but slight correlation was found between extracellular lysosomal activity and four parameters of lung lesion (lung index, bronchoalveolar fluid total (BALF) protein concentration, BALF LDH and BALF alkaline phosphatase activities). All the above findings suggest that the AM release of lysosomal enzymes during HP is a factor involved, although possibly not the only one, in the pulmonary lesions appearing in this disease.

Neutrophil-independence of the initiation of colonic injury. Comparison of results from three models of experimental colitis in the rat

Although the role of neutrophils in the pathogenesis of several forms of gastrointestinal injury has been well demonstrated, their role in the development of experimental colonic injury is less clear. To examine whether neutrophils play a role in the development of experimental colitides, the effects of a sustained neutropenia on multiple indices of colonic injury in rats was examined 24 hr following the initiation of colitis with the intrarectal application of acetic acid, trinitrobenzene sulfonic acid (TNBS)-ethanol, or the potent proinflammatory agent, phorbol-12-myristate-13-acetate (PMA). In comparison to animals with normal neutrophil counts and colitis induced by any of the three agents, no attenuation in macroscopic damage or histopathologic injury was observed in neutropenic animals exhibiting a greater than 95% reduction in circulating neutrophils and 85% reduction in tissue-associated myeloperoxidase activity. Although the tissue edema associated with acetic acid or PMA-induced colitis was not reduced by neutropenia, the colonic edema associated with TNBS colitis was attenuated by prior neutrophil depletion with anti-neutrophil antiserum. Despite our initial hypothesis that neutrophils played a key role in the genesis of experimental colitis (especially that induced by PMA), the results demonstrated that these cells are not essential for the development of the major pathological features of colitis induced by this agent, acetic acid, or TNBS. Although these results support the proposal that in these models of colitis, inflammation develops secondary to injury (rather than the converse), further studies will be necessary to elucidate the role of inflammatory cells other than neutrophils in the genesis of experimental colitides.

In vitro study of mediators of inflammation in multiple sclerosis

Prostaglandin E levels have previously been demonstrated to be elevated in multiple sclerosis (MS). We have further investigated other products of activated macrophages related to inflammation. We report here on prostaglandin E and its relationship to interleukin 1, tumor necrosis factor, and leukotriene B4 produced by macrophages from blood and cerebrospinal fluid of MS patients and controls in vitro. Interleukin and tumor necrosis factor are elevated significantly after stimulation in MS, while leukotriene B4 production by blood macrophages is depressed compared to other neurological disease and normal healthy controls. In 40% of MS patients tested, peripheral blood macrophages spontaneously produced elevated levels of interleukin 1. All mediators of inflammation are produced in increased amounts by MS cerebrospinal fluid leukocytes after stimulation. Macrophages from MS blood are not as sensitive as controls to nonsteroidal inhibitors specific for lipoxygenase or cyclo-oxygenase pathways. Positive correlations of elevations in production of such mediators of inflammation as prostaglandin E, interleukin 1, and tumor necrosis factor in MS were significant. Elevated production of these mediators in combination with insensitivity to inhibitors of inflammation suggests a role for activated macrophages in the demyelination process.