REFRACTORY CERAMIC FIBERS ACTIVATE ALVEOLAR MACROPHAGE EICOSANOID ANDCYTOKINE RELEASE

Refractory ceramic fiber has been developed for industrial processes r equiring materials with high thermal and mechanical stability. To eval uate the biological activity of this fiber, rat alveolar macrophages w ere exposed for less than or equal to 24 h to 0-1,000 mu g/ml of refra ctory ceramic fiber, crocidolite asbestos, silica (fibrogenic particle s), or titanium dioxide (a nonfibrogenic particle), and eicosanoid, tu mor necrosis factor-alpha (TNF), and lactate dehydrogenase release wer e measured. Particle dimensions were determined by electron microscopy . Radioactivity coeluting with leukotriene B-4 (LTB(4)) and immunoreac tive LTB(4) and TNF release increased after refractory ceramic fiber a nd were similar in magnitude after asbestos but less than after silica . For example, the total [H-3]eicosanoid release increased 3.9-fold af ter refractory ceramic fiber, 4.6-fold after asbestos, and 8.7-fold af ter silica. Refractory ceramic fiber and asbestos also have similar pa rticle dimensions (diameter, length, and surface area). Inasmuch as ma crophage-derived LTB(4) and TNF are potent mediators in inflammatory e vents, including migration and activation of neutrophils, these findin gs suggest that refractory ceramic fiber can activate macrophages in v itro to release mediators relevant to in vivo findings of inflammation and fibrotic lung disease in laboratory animals.