Englen M D, Taylor S M, Laegreid W W, Liggitt H D, Silflow R M, Breeze R G, Leid R W
Department of Veterinary Microbiology and Pathology, College of Veterinary Medicine, Washington State University, Pullman 99164-7040.
Exp Lung Res. 1989 Jul;15(4):511-26. doi: 10.3109/01902148909069615.
The molecular events involved in both the initiation and development of silicosis are at present poorly defined, although mediators released from macrophages exposed to silica particles are believed to play a role. We have investigated the in vitro production of arachidonic acid (AA) metabolites in adherent bovine alveolar macrophages (BAM) incubated with crystalline silica. BAM were prelabeled with 3H-AA and incubated with 0.5-5.0 mg silica. Lipid metabolites released into the culture medium were analyzed by high-performance liquid chromatography. Simultaneously, lactate dehydrogenase (LDH) was assayed to provide an indication of cell injury. No 5-lipoxygenase metabolites were detected at the lowest silica dose tested (0.5 mg/well), but 5-hydroxyeicosatetraenoic acid (5-HETE) was the major AA metabolite detected between 1.5 and 5.0 mg of silica. A fivefold increase in the production of leukotriene B4 (LTB4) and its two nonenzymatic diastereomers (Isomers I and II) was observed as the silica concentration was increased from 1.0 to 5.0 mg. In contrast, the release of cyclooxygenase products declined with increasing concentrations of silica. LDH release increased in a linear, dose-dependent fashion in the range of silica doses used. The kinetics of eicosanoid release was investigated over a 3-h interval and LDH release was assayed for each time point. Within 15 min following silica addition, a shift to the production of 5-lipoxygenase metabolites was observed, accompanied by a reduction in cyclooxygenase products. This rapid alteration in AA metabolism preceded cell injury as measured by LDH release. These results demonstrate that silica is a powerful stimulator of arachidonic acid metabolism in BAM. Moreover, silica selectively stimulates the 5-lipoxygenase pathway as the dose of silica increases. Our results suggest that dysfunction in arachidonate metabolism could contribute to the pathogenesis of silicosis.
尽管人们认为，暴露于二氧化硅颗粒的巨噬细胞释放的介质在矽肺的发生和发展过程中发挥了作用，但目前参与矽肺发生和发展的分子事件仍不清楚。我们研究了与结晶二氧化硅一起孵育的贴壁牛肺泡巨噬细胞（BAM）中花生四烯酸（AA）代谢产物的体外产生情况。用3H-AA对BAM进行预标记，并与0.5-5.0mg二氧化硅一起孵育。通过高效液相色谱法分析释放到培养基中的脂质代谢产物。同时，检测乳酸脱氢酶（LDH）以指示细胞损伤。在测试的最低二氧化硅剂量（0.5mg/孔）下未检测到5-脂氧合酶代谢产物，但在1.5至5.0mg二氧化硅之间检测到的主要AA代谢产物是5-羟基二十碳四烯酸（5-HETE）。随着二氧化硅浓度从1.0mg增加到5.0mg，白三烯B4（LTB4）及其两种非酶促非对映异构体（异构体I和II）的产生增加了五倍。相比之下，随着二氧化硅浓度的增加，环氧化酶产物的释放减少。在所使用的二氧化硅剂量范围内，LDH释放呈线性、剂量依赖性增加。在3小时的时间间隔内研究了类花生酸释放的动力学，并对每个时间点检测LDH释放。添加二氧化硅后15分钟内，观察到向5-脂氧合酶代谢产物产生的转变，同时环氧化酶产物减少。这种AA代谢的快速改变先于通过LDH释放测量的细胞损伤。这些结果表明，二氧化硅是BAM中花生四烯酸代谢的有力刺激物。此外，随着二氧化硅剂量的增加，二氧化硅选择性地刺激5-脂氧合酶途径。我们的结果表明，花生四烯酸代谢功能障碍可能导致矽肺的发病机制。
