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Effect of fiber length on glass microfiber cytotoxicity
T Blake1, V Castranova, D Schwegler-Berry
1Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Morgantown, West Virginia 26505-2888, USA.
Abstract:
Fiber length has been implicated as a determinant of fiber toxicity. Fibers of narrowly defined length can be generated by dielectrophoretic classifiers. Since the quantities of fibers produced are very small, we developed a rat alveolar macrophage microculture system to study the toxicity of these samples. The objective of this study was to examine the role of fiber length on the cytotoxicity of Manville code 100 (JM-100) fibers. Rat alveolar macrophages were cultured with 0-500 microg/ml of 5 lengths of JM-100 fibers on 96-well plates. After 18 h, well supernatants were removed and lactate dehydrogenase (LDH) activity was measured to assess cell damage. Chemiluminescence (CL), an assessment of macrophage function, was measured by adding lucigenin with or without zymosan, a particulate stimulus, to appropriate wells. For each fiber length the effects were concentration dependent: CL declined and LDH rose with increasing fiber concentration. Comparing the effects of different lengths showed the greatest toxicity from a relatively long fiber sample (mean length = 17 microm). Microscopic examination of the interaction of fibers with macrophages revealed multiple macrophages attached along the length of the long fibers. This suggests that frustrated, or incomplete, phagocytosis may be a factor in the increased toxicity of longer fibers. Overall the results demonstrate that length is an important determinant of toxicity for JM-100 fibers.
Insights
Fiber length significantly impacts toxicity. Longer Manville code 100 (JM-100) fibers showed greater cytotoxicity to rat alveolar macrophages, suggesting incomplete phagocytosis contributes to this effect.
Area of Science:
- Toxicology
- Materials Science
- Cell Biology
Background:
- Fiber length is a key factor influencing material toxicity.
- Precise fiber lengths can be isolated using dielectrophoretic classifiers.
- Small sample quantities necessitate sensitive toxicity testing methods.
Purpose of the Study:
- To investigate the role of fiber length in the cytotoxicity of Manville code 100 (JM-100) fibers.
- To evaluate the impact of JM-100 fiber length on rat alveolar macrophage viability and function.
Main Methods:
- Rat alveolar macrophages were cultured with five different lengths of JM-100 fibers at varying concentrations.
- Lactate dehydrogenase (LDH) activity was measured to assess cell damage.
- Chemiluminescence (CL) was measured to evaluate macrophage function, with and without zymosan stimulation.
Main Results:
- Both cell damage (LDH) and macrophage function (CL) were concentration-dependent for all fiber lengths.
- The longest fiber sample (mean length = 17 microm) exhibited the highest cytotoxicity.
- Microscopy revealed extensive macrophage attachment to longer fibers, indicating frustrated phagocytosis.
Conclusions:
- Fiber length is a critical determinant of JM-100 fiber toxicity.
- Longer fibers induce greater toxicity in rat alveolar macrophages, potentially due to incomplete phagocytosis.
- The findings highlight the importance of considering fiber dimensions in toxicological assessments.
