Enhanced Release of an Alveolar Macrophage-Derived Chemoattractant for Fibroblasts in Rats after Asbestos Inhalation

Abstract

Our studies indicate the effects of in vivo asbestos exposure on the ability of alveolar macrophages (AM) to elaborate a chemoattractant for fibroblast using a rat model of asbestos inhalation. Two groups of rats were exposed by intermittent inhalation (6 hr/day for 5 days/week over a total period of 4 weeks) to either amphibole (crocidolite) or serpentine (chrysotile) asbestos. A group of control rats were sham-exposed to clean air only. The animals were sacrificed 2-5 months after the cessation of exposure. The AM were obtained from the 3 exposure groups in 2 different rat strains by the bronchoalveolar lavage and the cultured in RPMI-1640 medium for 24-96 hr at 37°C. The supernatants from cultured AM were tested for chemotactic activity towards fetal rat skin fibroblasts in a chemotactic assay using 8 μm pore-size filters. The culture supernatants of AM obtained from crocidolite-exposed rats exhibited a significantly greater chemotactic activity towards rat fibroblasts than similar culture supernatants from sham-exposed control animals (p<0.01) in both rat strains. Significant chemotactic activity was observed after chrysotile exposure (p<0.05) in ACI rats but not in Fischer-344 rats. Maximal chemoattractant release from AM was noted after 48 hr in culture. Preliminary characterization of the chemoattractant has shown that it is a thermolabile and trypsin sensitive factor whose activity was partially reduced after dialysis. Since AM accumulate at sites of intrapulmonary asbestos deposition, these findings may have relevance to the pathologic accumulation of interstitial lung fibroblasts which occurs during asbestos-mediated lung injury. © 1993, JAPANESE SOCIETY OF VETERINARY SCIENCE. All rights reserved.