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Effects of various man-made mineral fibers on cell apoptosis and viability
Hermine Dika Nguea1, Bertrand Rihn, Delphine Mahon
1Laboratoire de Bactériologie-Virologie, Faculté de Médecine de Nancy, Unité Mixte de Recherche CNRS-UHP, 7565, BP 184, 54505 Vandoeuvre-lès-Nancy, France. hermine.dika-nguea@saint-gobain.com
Abstract:
Evaluating the pathogenic potentials of man-made mineral fibers (MMMF) is an important task performed by the European Community. Noting that it has been proposed that the use of laboratory animals for scientific tests should be reduced or phased out, macrophages then become the cells of choice for conducting in vitro studies. We have evaluated the in vitro toxicity of six commercial stonewool fibers (A, B1, B2, C, D, and E) on U-937 cells. The physical interaction between U-937 cells and MMMF was observed using scanning electron microscopy, and the cytotoxicity was evaluated by studying cell viability using MTT assay and cell apoptosis with an ELISA detection kit. Scanning electron microscopy (SEM) analysis has shown that long fibers can be covered by several macrophages, and that a small fiber can be completely engulfed by one cell. With 50 microg/mL of MMMF, a decrease in cell viability appeared after seven days of incubation, whereas 200 microg/mL induced loss of viability and apoptosis after one day. Fiber D, comprising a high proportion of fibers >20 microm in length and a high concentration of MgO, induced the highest loss in viability and the highest rate of apoptosis compared to the other five fibers. Whether this toxic effect is related to either the physical characteristics of the fibers (such as length), or to the high concentration of magnesium is still to be determined. Because the results can be rapidly obtained, the proposed model is suitable for studying the toxicities of mineral components, even if the tested concentrations are far from the ones reached in the lung.
Insights
This study assessed the in vitro toxicity of stonewool fibers on U-937 cells, finding Fiber D induced significant cell death and apoptosis. This research supports reducing animal testing for man-made mineral fibers (MMMF) safety evaluations.
Area of Science:
- Toxicology
- Materials Science
- Cell Biology
Background:
- Man-made mineral fibers (MMMF) safety evaluation is crucial for European Community regulations.
- There is a growing need to reduce or phase out animal testing in scientific research.
- Macrophages are increasingly utilized for in vitro toxicity studies as alternatives to animal models.
Purpose of the Study:
- To evaluate the in vitro toxicity of six commercial stonewool fibers on U-937 cells.
- To investigate the interaction between U-937 cells and MMMF using scanning electron microscopy.
- To assess cytotoxicity and apoptosis induced by different MMMF.
Main Methods:
- U-937 cells were exposed to six commercial stonewool fibers (A, B1, B2, C, D, E).
- Scanning electron microscopy (SEM) was used to observe cell-fiber interactions.
- Cytotoxicity was measured using MTT assay, and apoptosis was detected with an ELISA kit.
Main Results:
- SEM showed macrophages engulfing or covering MMMF, with longer fibers being covered by multiple cells.
- A concentration of 50 microg/mL MMMF decreased cell viability after seven days; 200 microg/mL induced loss of viability and apoptosis after one day.
- Fiber D, characterized by long fibers (>20 microm) and high MgO content, caused the highest cytotoxicity and apoptosis.
Conclusions:
- The U-937 cell model provides a rapid method for assessing the in vitro toxicity of mineral fibers.
- Fiber D exhibited the most significant toxic effects, but the specific causative factor (fiber length or MgO content) requires further investigation.
- This in vitro approach offers a viable alternative for evaluating MMMF toxicity, aligning with efforts to reduce animal testing.
