Nitric oxide inhibits androgen receptor-mediated collagen production in human gingival fibroblasts.

Lin S-J, Lu H-K, Lee H-W, Chen Y-C, Li C-L, Wang L-F. Nitric oxide inhibits androgen receptor-mediated collagen production in human gingival fibroblasts. J Periodont Res 2012; 47: 701710. (c) 2012 John Wiley & Sons A/S Background and Objective: In our previous study, we found that flutamide [an androgen receptor (AR) antagonist] inhibited the up-regulation of collagen induced by interleukin (IL)-1 beta and/or nifedipine in gingival fibroblasts. The present study attempted to verify the role of nitric oxide (NO) in the IL-1 beta/nifedipine-AR pathway in gingival overgrowth. Material and Methods: Confluent gingival fibroblasts derived from healthy individuals (n = 4) and those with dihydropyridine-induced gingival overgrowth (DIGO) (n = 6) were stimulated for 48 h with IL-1 beta (10 ng/mL), nifedipine (0.34 mu m) or IL-1 beta + nifedipine. Gene and protein expression were analyzed with real-time RT-PCR and western blot analyses, respectively. Meanwhile, Sircol dye-binding and the Griess reagent were, respectively, used to detect the concentrations of total soluble collagen and nitrite in the medium. Results: IL-1 beta and nifedipine simultaneously up-regulated the expression of the AR and type-I collagen a1 [Cola1(I)] genes and the total collagen concentration in DIGO cells (p < 0.05). IL-1 beta strongly increased the expression of inducible nitric oxide synthase (iNOS) mRNA and the nitrite concentration in both healthy and DIGO cells (p < 0.05). However, co-administration of IL-1 beta and nifedipine largely abrogated the expression of iNOS mRNA and the nitrite concentration with the same treatment. Spearmans correlation coefficients revealed a positive correlation between the AR and total collagen (p < 0.001), but they both showed a negative correlation with iNOS expression and the NO concentration (p < 0.001). The iNOS inhibitor, 1400W, enhanced IL-1 beta-induced AR expression; furthermore, the NO donor, NONOate, diminished the expression of the AR to a similar extent in gingival fibroblasts derived from both healthy patients and DIGO patients (p < 0.05). Conclusion: IL-1 beta-induced NO attenuated AR-mediated collagen production in human gingival fibroblasts. The iNOS/NO system down-regulated the axis of AR/Cola1(I) mRNA expression and the production of AR/total collagen proteins by DIGO cells.