The lipopolysaccharide-triggered mesangial transcriptome: Evaluating the role of interferon regulatory factor-1

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/MIP3α (ScyB1/Grol, and ScyB2/MIP2α/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-β1, 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-γ ?(IFN-γ), 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.