Asbestos fibers induce chronic lung inflammation and have been associated (WHO estimate) with 105 lung cancer deaths per year worldwide. In the lung, immune cells (macrophages) attempt to engulf inhaled foreign materials (like asbestos), secreting inflammatory molecules. The inability of macrophages to effectively remove asbestos leads to chronic inflammation and disease. Although the health effects of asbestos have been extensively investigated, this study examines the role of fiber length on phagocytosis and molecular inflammatory responses so as to characterize fiber toxicity at the cellular level. A major challenge is obtaining fibers of the same diameter, d, but differing in length, L. Glass fibers, with d ~1�m, were used as a model for asbestos. Samples with different measured length distributions were prepared: aggressive crushing for short fibers (L < 15 �m) and successive sedimentation for long fibers (L < 15 �m).The interactions of MH-S murine alveolar macrophages with the fibers were analyzed by time-lapse video microscopy, to qualitatively describe attempted phagocytosis in real time, and by flow cytometry, to quantitatively measure attachment and internalization of fibers. Short fibers were observed (microscopy) to bind to macrophages, being internalized with little effort; macrophages literally wrestled with long fibers over many hours, usually with unsuccessful internalization; short fibers were twice as likely to be internalized as the long fibers. Production of pro-inflammatory molecules was measured following exposure of macrophages to a range of fiber doses. Tumor necrosis factor alpha (TNF- a), a potent, general inflammatory secreted cytokine, was measured by ELISA. Cyclooxygenase-2 (Cox-2), an enzyme in cells that produces radical intermediates and is upregulated in mesothelioma, was measured by Western blot.Both exhibited a dose-dependent increase that was greater for long fibers than for short fibers. These results corroborate the critical importance of fiber length in both physical and biochemical cell response and support epidemiological observations of higher toxicity for longer fibers.

Role of fiber length on phagocytosis and inflammatory response

247th National Meeting (2014)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.