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[Dysregulation of Fas and related molecules in silicosis patients]
Akiko Takata-Tomokuni1, Yoshie Miura, Fuminori Hyodoh
1Department of Hygiene, Kawasaki Medical School, Kurashiki, Japan.
Abstract:
Silicosis patients not only suffer from respiratory disorders but also from autoimmune diseases. To clarify the mechanisms involved in the occurrence of the dysregulation of autoimmunity found in silicosis patients, we have been focusing on investigation of the Fas and Fas-related molecules in the Fas-mediated apoptotic pathway, since Fas is one of the most important molecules regulating autoimmunity in mainly T cells. Our findings showed that silicosis patients exhibited elevated serum soluble Fas levels, increased relative expression of soluble Fas and DcR 3 genes in peripheral blood mononuclear cells, other highly detectable variant messages of Fas transcripts, relatively decreased expression of several physiological inhibitors (Sentrin, I-Fline, ICAD/DFF45, and survivin), and dominancy of lower membrane Fas expressers in lymphocytes when compared with healthy volunteers. These parameters also constitute immunological factors with serum immunogulobulin G and the titer of anti-nuclear autoantibodies. In addition, anti-caspase 8 autoantibody and anti-Fas autoantibody were also detected in the serum from silicosis patients, and a functional assay showed that anti-Fas antibody stimulated Fas-mediated apoptosis. Taken together, we hypothesize that there are two subpopulations of silicosis lymphocytes. One is a long-term survival fraction including a self-recognizing fraction showing lower membrane Fas and inhibition of Fas/Fas ligand bindings in the extracellular region. The other is a fraction exhibiting apoptosis caused by silica/silicates, recruiting from bone marrow, showing higher membrane Fas and sensitive to anti-Fas autoantibody. Further investigations should be performed to confirm the effects of silica/silicates on the human immune system.
Insights
Silicosis patients show immune system dysregulation, with altered Fas molecule expression linked to autoimmune diseases. Further research is needed to understand silica
Area of Science:
- Immunology
- Toxicology
- Cell Biology
Background:
- Silicosis is associated with respiratory disorders and autoimmune diseases.
- The Fas-mediated apoptotic pathway plays a crucial role in regulating autoimmunity, particularly in T cells.
- Understanding the mechanisms of immune dysregulation in silicosis is essential.
Purpose of the Study:
- To investigate the role of Fas and related molecules in the Fas-mediated apoptotic pathway in silicosis patients.
- To clarify the mechanisms underlying autoimmune dysregulation in silicosis.
Main Methods:
- Analysis of serum soluble Fas levels.
- Measurement of gene expression (soluble Fas, DcR 3, Fas transcripts) in peripheral blood mononuclear cells.
- Assessment of physiological inhibitors (Sentrin, I-Fline, ICAD/DFF45, survivin) and membrane Fas expression in lymphocytes.
- Detection of autoantibodies (anti-caspase 8, anti-Fas) and immunological factors (serum immunoglobulin G, anti-nuclear autoantibodies).
- Functional assay of anti-Fas antibody effects on apoptosis.
Main Results:
- Silicosis patients exhibited elevated serum soluble Fas levels and increased soluble Fas and DcR 3 gene expression.
- Decreased expression of physiological inhibitors and a predominance of lower membrane Fas expressers in lymphocytes were observed.
- Anti-caspase 8 and anti-Fas autoantibodies were detected, with anti-Fas antibody stimulating Fas-mediated apoptosis.
Conclusions:
- Silicosis lymphocytes may comprise two subpopulations: a long-term survival fraction with low membrane Fas and inhibited Fas/Fas ligand binding, and a fraction prone to apoptosis with high membrane Fas, sensitive to anti-Fas autoantibody.
- These findings suggest complex immune dysregulation in silicosis involving the Fas pathway.
- Further research is required to confirm the effects of silica/silicates on the human immune system.
