Expression Profile of Human Gingival Fibroblasts Induced by Interleukin-1β Reveals Central Role of Nuclear Factor-Kappa B Stabilizing Human Gingival Fibroblasts During Inflammation

Background: Interleukin (IL)-1 beta is a key cytokine in the pathogenesis of periodontitis, and it induces inflammatory mediators in periodontal diseases. We developed immortalized human gingival fibroblasts (HGFs), investigated the effects of IL-1 beta on the gene expression using expression arrays containing similar to 40,000 genes, and tested the role of nuclear factor-kappa B (NF-kappa B) in maintaining an activated HGF population. Methods: Total RNA was isolated from IL-1 beta-induced and mock-induced control cells. Gene expression analyses were performed using expression arrays and confirmed by quantitative real-time polymerase chain reaction. Western blot analysis to show inhibitor of kappa B-alpha (I kappa B alpha) phosphorylation and immunostaining of cells for NF-kappa B nuclear translocation were performed. Apoptosis was confirmed by assay of poly ADP-ribose polymerase (PARP) cleavage. Results: A total of 382 probe sets corresponding to 254 genes were differentially expressed in IL-1 beta-induced cells (P <0.001). A total of 215 genes were upregulated, and 39 genes were downregulated. Most notable NF-kappa B pathway members (NF kappa B1, NF kappa B2, I kappa B alpha, I kappa B epsilon, I kappa B zeta, REL, RELB, and TA-NFKBH) were upregulated. I kappa B alpha was phosphorylated, and NF-kappa B accumulated in the nucleus. An IL-1 beta-induced set of 27 genes was downregulated by an NF-kappa B inhibitor, leading to a decreased number of viable cells and suggesting an antiapoptotic role for NF-kappa B. Conclusions: IL-1 beta leads to a large number of significant expression changes consistent with a pathologic role in periodontitis, including enhancement of inflammatory cytokines, chemokines, transcription factors, matrix metalloproteinases, adhesion molecules, and especially NF-kappa B-dependent antiapoptotic genes. NF-kappa B activation blocks apoptosis, thereby stabilizing the HGF population in inflammation. J Periodontol 2009;80:833-849.