Analysis of interleukin-1ß-modulated mRNA gene transcription in human gingival keratinocytes by epithelia-specific cDNA microarrays

Background/objectives: Proinflammatory cytokines such as interleukin‐1β are known to be synthesized in oral gingivitis and periodontitis and lead to the activation of the transcription factor nuclear factor‐κB (NF‐κB). Although numerous effects of interleukin‐1β on mesenchymal cells are known, e.g. up‐regulation of intercellular adhesion moelcule‐1 in endothelial cells, little is known of the effects of interleukin‐1β on oral keratinocytes. The purpose of the present study was to seek interleukin‐1β‐mediated alterations in mRNA gene transcription and a putative activation of NF‐κB in oral gingival keratinocytes.

Methods: As an in vitro model for gingivitis and periodontitis, immortalized human gingival keratinocytes (IHGK) were stimulated with the proinflammatory cytokine interleukin‐1β. An epithelia‐specific cDNA microarray was used to analyze mRNA expression profiles from IHGK cells treated with 200 units interleukin‐1β/ml for 3, 6, 9, 12, and 24 h. Indirect immunofluorescence was carried out to detect NF‐κB in IHGK following interleukin‐1β treatment.

Results: Detailed analysis revealed distinct patterns of time‐dependent changes, including genes induced or repressed early (3–6 h) or late (12–24 h) after interleukin‐1β treatment. Differentially expressed genes were involved in (i) cell stress, (ii) DNA repair, (iii) cell cycle and proliferation, (iv) anti‐pathogen response, (v) extracellular matrix turnover, and (vi) angiogenesis. A large number of genes were responsive to NF‐κB and induction was concomitant with nuclear translocation of the p65 RelA subunit of NF‐κB. Interestingly, many of these genes contain multiple NF‐κB binding sites in their promoters.

Conclusion: Analysis of altered gene expression allows identification of gene networks associated with inflammatory responses. In addition to a number of well‐known genes involved in gingivitis and periodontitis, we identified novel candidates that might be associated with the onset and maintenance of an inflammatory disease.