leukotriene-b4 and Silicosis

Topics: Animals; Endosomes; Humans; Inflammation; JNK Mitogen-Activated Protein Kinases; Leukotriene B4; Lipid Metabolism; Molecular Targeted Therapy; Neutrophils; Pneumonia; Signal Transduction; Silicon Dioxide; Silicosis

Silicosis is a lung inflammatory disease caused by chronic exposure to crystalline silica (CS). Leukotriene B

Topics: Animals; Cell Line; Humans; Inflammasomes; Inflammation; Interleukin-1beta; Leukotriene B4; Macrophages; Mast Cells; Mice; Mice, Inbred C57BL; Mitogen-Activated Protein Kinase 8; Neutrophils; NLR Family, Pyrin Domain-Containing 3 Protein; Phagosomes; rab GTP-Binding Proteins; rab5 GTP-Binding Proteins; RAW 264.7 Cells; Silicon Dioxide; Silicosis

Leukotrienes (LTs) are involved in the pathogenesis of lung fibrosis and were increased in exhaled breath condensate (EBC) of the patients with pneumoconiosis. However the possible influence of extra-pulmonary disorders on the EBC markers is not known. Therefore in parallel with EBC, LTs' levels in the plasma and urine were measured in patients with pneumoconiosis (45 × asbestos exposure, 37 × silica exposure) and in 27 controls. Individual LTs B4, C4, D4 and E4 were measured by liquid chromatography - electrospray ionization - tandem mass spectrometry (LC-ESI-MS/MS). In EBC, LT D4 and LT E4 were increased in both groups of patients (p<0.001 and p<0.05), comparing with the controls. Both LT B4 and cysteinyl LTs were elevated in asbestos-exposed subjects (p<0.05). Asbestosis with more severe radiological signs (s1/s2-t3/u2) and lung functions impairment has shown higher cysteinyl LTs and LT C4 in the EBC (p<0.05) than mild asbestosis (s1/s0-s1/s1). In addition, in the subjects with asbestosis, cysteinyl LTs in EBC correlated with TLC (-0.313, p<0.05) and TLCO/Hb (-0.307, p<0.05), and LT C4 with TLC (-0.358, p<0.05). In pneumoconioses, EBC appears the most useful from the 3 fluids studied.

Topics: Aged; Asbestosis; Breath Tests; Female; Humans; Leukotriene B4; Leukotriene C4; Leukotriene D4; Leukotriene E4; Leukotrienes; Male; Middle Aged; Radiography; Respiratory Function Tests; Severity of Illness Index; Silicosis

Silicosis leads to altered release of fibrogenic and immunomodulating mediators from alveolar macrophages (AM). Since 5-lipoxygenase metabolites have been shown to possess proinflammatory effects and to promote the release of cytokines such as tumor necrosis factor-alpha (TNF-alpha) from mononuclear phagocytes, we determined leukotriene secretion from silica-exposed AM. Rats were exposed to an aerosol of silica particles for 8 days and AM were harvested by bronchoalveolar lavage 5 to 7 mo after exposure. AM from both air-sham control and silica-exposed rats displayed minimal spontaneous leukotriene release upon in vitro culture. Stimulation with opsonized zymosan particles induced leukotriene B4 (LTB4) and leukotriene C4 (LTC4) secretion, which was much greater in control AM than in AM from silica-dusted rats. The reverse was found for zymosan-induced TNF-alpha production, which was higher in AM from silica-exposed than from control rats. To study the interrelation between leukotriene and TNF-alpha release, we incubated zymosan-stimulated AM with the 5-lipoxygenase inhibitor VZ 65. VZ 65 suppressed zymosan-induced TNF-alpha release from AM in a dose-dependent manner, and TNF-alpha production could be restored almost completely by addition of LTB4. These experiments demonstrate that silica exposure resulted in a decreased LTB4 and LTC4 production from AM, which may represent a regulatory mechanism to counterbalance enhanced TNF-alpha production during silicosis.

Topics: Animals; Arachidonate 5-Lipoxygenase; Bronchoalveolar Lavage Fluid; Down-Regulation; Leukotriene B4; Macrophages, Alveolar; Male; Rats; Rats, Inbred F344; Silicosis; SRS-A; Tumor Necrosis Factor-alpha

Alveolar macrophages (AM) can play a crucial role in the pathogenesis of pulmonary disease via their ability to produce potent inflammatory and fibrogenic mediators. We found that rat AM cultured with 1 to 100 micrograms/ml of silica particles or asbestos fibers produced tumor necrosis factor (TNF) and leukotriene B4 (LTB4) in a concentration-dependent fashion, whereas latex beads, an inert phagocytic stimulus, failed to induce significant augmentation of either TNF or LTB4. In a time course study, AM stimulated for 2 h with silica or asbestos produced an increased amount of LTB4, which preceded the rise in TNF activity detected 7 and 24 h after culture initiation. The induction appears to involve the synthesis of new protein since actinomycin D and cycloheximide abrogate the majority of the stimulatory effect. We next examined the role of LTB4 in mineral-dust-induced TNF production. The lipoxygenase inhibitors nordihydroguaiaretic acid (NDGA) and AA861 used at 1 to 50 micrograms/ml reduced in a concentration-dependent fashion asbestos- or silica-stimulated TNF release. On the other hand, "reconstitutive" experiments in which we added exogenous LTB4 (10(-14) to 10(-8) M) to AM treated with lipoxygenase inhibitors showed partial restoration of TNF production induced by chrysotile or silica, with peak effect at 10(-10)M LTB4. The present study demonstrated that AM incubated in the presence of chrysotile A or silica can produce both LTB4 and TNF and that endogenous lipoxygenase metabolites as well as exogenous LTB4 can act to amplify TNF production. These observations suggest a common mechanism by which asbestos and silica may modulate the production of inflammatory and fibrogenic cytokines.

Topics: Animals; Asbestos; Asbestosis; Bronchoalveolar Lavage Fluid; Cells, Cultured; Dose-Response Relationship, Drug; Homeostasis; Leukotriene B4; Macrophages; Male; Pulmonary Alveoli; Rats; Rats, Inbred Strains; Silicon Dioxide; Silicosis; Specific Pathogen-Free Organisms; Time Factors; Tumor Necrosis Factor-alpha