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Soluble Fas mRNA is dominantly expressed in cases with silicosis
T Otsuki1, H Sakaguchi, A Tomokuni
1Department of Hygiene, Kawasaki Medical School, Okayama, Japan.
Abstract:
Although it is well known that cases with silicosis exhibit various immunological abnormalities, the mechanisms involved in the occurrence of immuno-dysfunction or dysregulation induced by silica compounds have not yet been determined. Fas is a well-known cell surface molecule that is involved in the apoptosis pathway that belongs to the tumour necrosis factor-receptor family. Soluble Fas (sFas) is produced as an alternatively spliced product of the Fas gene and protects cells from apoptosis due to antagonization of the binding between membrane form of the Fas gene (mFas) and the Fas ligand. To determine the role of the Fas/Fas ligand system in silica-induced immunological abnormalities, we investigated Fas and Fas-ligand message expression levels using the multiplex reverse transcription-polymerase chain reaction (RT-PCR) method with peripheral blood mononuclear cells from silicosis cases with no clinical symptoms of autoimmune diseases. Although the relative expression levels of the Fas or Fas-ligand genes were not remarkably altered in these cases, we observed the sFas message was dominantly expressed compared with mFas expression. These results suggest that self-recognizing clones in cases with silicosis survive for decades, escaping the exclusion mechanisms induced by apoptosis. Then they cause the appearance of autoantibodies and the acquisition of autoimmune diseases sequentially.
Insights
Silica exposure in silicosis patients leads to immune system dysfunction. Dominant soluble Fas (sFas) expression allows self-recognizing cells to survive, potentially causing autoimmune diseases.
Area of Science:
- Immunology
- Toxicology
- Molecular Biology
Background:
- Silicosis is linked to immunological abnormalities, but the underlying mechanisms remain unclear.
- The Fas/Fas ligand system regulates apoptosis and immune cell survival.
- Soluble Fas (sFas) can inhibit apoptosis, potentially impacting immune regulation.
Purpose of the Study:
- To investigate the role of the Fas/Fas ligand system in silica-induced immune abnormalities.
- To analyze Fas and Fas-ligand gene expression in silicosis patients without autoimmune disease symptoms.
Main Methods:
- Multiplex reverse transcription-polymerase chain reaction (RT-PCR) was used.
- Peripheral blood mononuclear cells (PBMCs) from silicosis cases were analyzed.
- Expression levels of Fas, membrane-bound Fas (mFas), and soluble Fas (sFas) were quantified.
Main Results:
- Relative expression of Fas and Fas-ligand genes showed no significant alterations.
- Soluble Fas (sFas) message was found to be dominantly expressed compared to membrane-bound Fas (mFas).
Conclusions:
- Dominant sFas expression may allow self-recognizing immune cells to escape apoptosis and survive long-term.
- This prolonged survival of self-reactive clones could lead to autoantibody formation and subsequent autoimmune diseases in silicosis patients.