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Published on: January 24, 2016
The lipopolysaccharide-triggered mesangial transcriptome: Evaluating the role of interferon regulatory factor-1
1Simmons Arthritis Research Center, Division of Rheumatology, Center for Immunology, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
Insights
Innate stimuli like lipopolysaccharide (LPS) trigger sequential gene expression in mesangial cells. While interferon regulatory factor-1 (IRF-1) is rapidly expressed, it is not essential for cell activation or nephritis development.
Area of Science:
- Immunology
- Molecular Biology
- Genomics
Background:
- The dynamic changes in mesangial cell gene expression following innate immune stimulation remain largely uncharacterized.
- Understanding these transcriptional events is crucial for deciphering kidney immune responses.
Purpose of the Study:
- To comprehensively map the mesangial cell transcriptome evolution after innate immune trigger stimulation.
- To investigate the role of early-response genes, specifically interferon regulatory factor-1 (IRF-1), in mesangial cell activation and kidney disease.
Main Methods:
- Murine mesangial cell lines were stimulated with lipopolysaccharide (LPS), a key innate immune trigger.
- Transcriptome-wide gene expression profiling was performed using a 17,000 gene oligonucleotide array at multiple time points (1, 6, 24, and 60 hours post-LPS).
- Key findings were validated using real-time PCR and ELISA; IRF-1's role was assessed via RNA interference and in IRF-1-deficient mice.
Main Results:
- Lipopolysaccharide (LPS) stimulation induced distinct waves of gene expression, with early genes like interferon regulatory factor-1 (IRF-1) and chemokines (ScyA2/MCP1, ScyA20/MIP3alpha) rapidly upregulated.
- Later-expressing genes included growth factors (GM-CSF, PDGF), cytokines, and matrix-modulating enzymes (MMP11, MMP13).
- Despite rapid IRF-1 induction by various innate stimuli, its blockade or deficiency did not impede LPS-induced mesangial cell activation or anti-glomerular basement membrane (GBM) nephritis development.
Conclusions:
- Innate immune stimuli orchestrate sequential gene expression programs in mesangial cells.
- Interferon regulatory factor-1 (IRF-1) acts as an early-transient transcription factor but is not a critical mediator of mesangial cell activation or anti-GBM disease pathogenesis.
Background:
Presently, we do not have a clear picture of how the mesangial transcriptome evolves following stimulation. The present study was designed to address this, using an innate trigger to stimulate murine mesangial cells.
Methods:
Three independent mesangial cell lines derived from C57BL/6 mice were stimulated with lipopolysaccharide (LPS). The mesangial cell transcriptomes were defined 1, 6, 24, and 60 hours poststimulation with LPS, using a 17,000 gene oligonucleotide array.
Results:
Interferon regulatory factor-1 (IRF-1), ScyA2/MCP1, ScyA20/MIP3alpha (ScyB1/Gro1, and ScyB2/MIP2alpha/Gro2 were the earliest genes to be hyperexpressed after LPS stimulation. Later-appearing genes included ScyA7/MCP3, ScyD1/fractalkine, GM-CSF/CSF-2, PDGF, epiregulin, NfKb, C/EBP, TIMP-1, MMP11, MMP13, PTGS2/COX2, SpI2-1, Spp1, PAI-1, VCAM-1, C3, and defensin-beta1, among others. Several of these changes were validated by real-time polymerase chain reaction (PCR) or enzyme-linked immunosorbent assay (ELISA). Rapid IRF-1 hyperexpression was also noted following stimulation of mesangial cells with peptidoglycan, poly I:poly C, interferon-gamma?(IFN-gamma), and heat-aggregated IgG. However, the blocking of IRF-1 using RNA interference and the use of mesangial cells isolated from IRF-1-deficient mice could not substantiate an obligatory role for IRF-1 in LPS-induced mesangial cell activation. Likewise, IRF-1 deficiency did not impact the development of anti-glomerular basement membrane (GBM)-induced immune nephritis.
Conclusion:
Innate stimuli such as LPS appear to trigger successive waves of mesangial cell gene expression. Although IRF-1 surfaces as an "early-on, early-off" transcription factor following several different triggers, it does not appear to be an essential molecule for mesangial cell activation by innate triggers or for anti-GBM disease.
