Effect of 1,25(OH)2 D3 and 20(OH)D3 on interleukin-1β-stimulated interleukin-6 and -8 production by human gingival fibroblasts

Abstract

Background and objective: Vitamin D-1,25(OH)₂ D₃ or 1,25D3-maintains healthy osseous tissue, stimulates the production of the antimicrobial peptide cathelicidin and has anti-inflammatory effects, but it can cause hypercalcemia. Evidence links diminished serum levels of 1,25D3 with increased gingival inflammation. Periodontitis progression is associated with increased local production of inflammatory mediators by immune cells and gingival fibroblasts. These include interleukin (IL)-6, a regulator of osteoclastic bone resorption, and the neutrophil chemoattractant IL-8, both regulated by signaling pathways, including NF-κB and MAPK/AP-1. The objectives were to determine the effects of 1,25D3 or a non-calcemic analog, 20-hydroxyvitamin D₃ -20(OH)D₃ or 20D3-on IL-1β-stimulated IL-6 and IL-8 production, and NF-κB and MAPK/AP-1 activation, by human gingival fibroblasts.

Material and methods: Human gingival fibroblasts were incubated ± IL-1β, with or without exposure to 1,25D3 or 20D3. IL-6 and IL-8 in culture supernatants were measured by enzyme-linked immunosorbent assay. NF-κB (p65) and AP-1 (phospho-cJun) and were measured in nuclear extracts via binding to specific oligonucleotides. Data were analyzed using ANOVA and Scheffe's F procedure for post hoc comparisons.

Results: IL-1β-stimulated IL-6 and IL-8 levels were both significantly inhibited (40%-60%) (P<.045) by 1,25D3, but not 20D3 (0%-15% inhibition, not statistically significant). Both 1,25D3 and 20D3 significantly and similarly inhibited IL-1β-stimulated nuclear levels of p65 and phospho-cJun (P<.02).

Conclusion: Reduction of the activation of NF-κB and AP-1 alone is not able to inhibit strongly the IL-1β stimulated IL-6 and IL-8 gene expression. 1,25D3 but not 20D3 may affect some of the many other factors/processes/pathways that in turn regulate the expression of these genes. However, the results suggest that topical application of ligands of the vitamin D receptor may be useful in the local treatment of periodontitis while reducing adverse systemic effects.

Keywords: cytokine(s); fibroblasts; periodontitis; vitamin D.