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Effects of transforming growth factor-beta 1 on nitric oxide synthesis by C2C12 skeletal myocytes
G Williams1, L Becker, D Bryant
1Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas 75235-9063, USA.
Abstract:
The production of nitric oxide (NO) via the inducible form of NO synthase (iNOS) is regulated by a complex network of cytokines and endogenous hormones. Among these, transforming growth factor-beta (TGF-beta 1) is known to suppress iNOS expression and NO production by many cell types. To determine the effect of TGF-beta 1 on NO production by skeletal muscle cells, we stimulated C2C12 myocytes with interferon-gamma (IFN) and interleukin-1 (IL-1) in the presence or absence of TGF-beta 1. In contrast to findings in macrophages, TGF-beta 1 markedly enhanced NO production by skeletal muscle cells. Increases in NO production reflected significant increases in iNOS immunoreactive protein and iNOS mRNA. Elevated iNOS mRNA levels associated with TGF-beta 1 treatment were not due to an alteration in mRNA stability, but rather reflected a significantly increased transcriptional rate of the iNOS gene. These findings indicate that TGF-beta 1 enhances iNOS expression in skeletal muscle cells and suggest that the regulation of NO production by TGF-beta 1 may depend on the cell type studied.
Insights
Transforming growth factor-beta 1 (TGF-beta 1) significantly boosts nitric oxide (NO) production in skeletal muscle cells by increasing inducible NO synthase (iNOS) gene transcription, contrary to its suppressive effects in other cell types.
Area of Science:
- Cellular biology
- Immunology
- Molecular biology
Background:
- Nitric oxide (NO) production is regulated by inducible NO synthase (iNOS).
- Transforming growth factor-beta 1 (TGF-beta 1) typically suppresses iNOS expression and NO production.
- Skeletal muscle cells represent a distinct cellular context for NO regulation.
Purpose of the Study:
- To investigate the effect of TGF-beta 1 on NO production in skeletal muscle cells.
- To elucidate the molecular mechanisms underlying TGF-beta 1's influence on iNOS expression in this cell type.
Main Methods:
- C2C12 myocytes were stimulated with interferon-gamma (IFN) and interleukin-1 (IL-1).
- TGF-beta 1 was added in the presence or absence of IFN and IL-1.
- iNOS protein and mRNA levels were quantified.
- mRNA stability and gene transcriptional rates were assessed.
Main Results:
- Contrary to findings in macrophages, TGF-beta 1 markedly enhanced NO production in skeletal muscle cells.
- This enhancement correlated with increased iNOS immunoreactive protein and iNOS mRNA levels.
- Elevated iNOS mRNA resulted from increased gene transcription, not altered mRNA stability.
Conclusions:
- TGF-beta 1 significantly enhances iNOS expression and NO production in skeletal muscle cells.
- The regulatory role of TGF-beta 1 in NO production is cell-type dependent.
- These findings highlight novel mechanisms in skeletal muscle NO signaling.