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Isolation of nine gene sequences induced by silica in murine macrophages
Abstract:
Macrophage activation by silica is the initial step in the development of silicosis. To identify genes that might be involved in silica-mediated activation, RAW 264.7 mouse macrophages were treated with silica for 48 h, and a subtracted cDNA library enriched for silica-induced genes (SIG) was constructed and differentially screened. Nine cDNA clones (designated SIG-12, -14, -20, -41, -61, -81, -91, -92, and -111) were partially sequenced and compared with sequences in GenBank/EMBL databases. SIG-12, -14, and -20 corresponded to the genes for ribosomal proteins L13a, L32, and L26, respectively. SIG-61 is the mouse homologue of p21 RhoC. SIG-91 is identical to the 67-kDa high-affinity laminin receptor. Four genes were not identified and are novel. All of the mRNAs corresponding to the nine cloned cDNAs were inducible by silica. Steady-state levels of mRNAs in RAW 264.7 cells treated with various macrophage activators and inducers of signal transduction pathways were determined. A complex pattern of induction and repression was found, indicating that upon phagocytosis of silica particles, many regulatory mechanisms of gene expression are simultaneously triggered.
Insights
Silica exposure activates macrophages, initiating silicosis. This study identified novel silica-induced genes (SIG) in macrophages, revealing complex gene expression regulation during this process.
Area of Science:
- Immunology
- Molecular Biology
- Toxicology
Background:
- Macrophage activation by silica is a critical early event in silicosis development.
- Understanding the molecular mechanisms underlying silica-induced macrophage activation is crucial for developing targeted therapies.
Purpose of the Study:
- To identify novel genes involved in silica-mediated macrophage activation.
- To investigate the gene expression patterns in macrophages upon silica exposure.
Main Methods:
- RAW 264.7 mouse macrophages were treated with silica.
- A subtracted cDNA library enriched for silica-induced genes (SIG) was constructed and differentially screened.
- Partial sequencing and database comparison of identified cDNA clones.
Main Results:
- Nine silica-induced genes (SIG) were identified, including ribosomal proteins (L13a, L32, L26), the mouse homologue of p21 RhoC (SIG-61), and the 67-kDa high-affinity laminin receptor (SIG-91).
- Four novel genes were also discovered.
- All identified genes showed silica-inducible mRNA expression.
- Analysis of mRNA levels revealed complex induction and repression patterns in response to various macrophage activators and signal transduction inducers.
Conclusions:
- Silica phagocytosis triggers intricate regulatory mechanisms of gene expression in macrophages.
- The identified SIGs provide potential targets for understanding and mitigating silicosis pathogenesis.