Influences of interferon-gamma on cell proliferation and interleukin-6 production in Down syndrome derived fibroblasts

Objective: Down syndrome, a frequently encountered genetic disorder, is usually associated with medical problems related to infectious disease, such as periodontal diseases and prolonged wound healing. Although affected individuals are considered to have clinical problems related to high interferon (IFN) sensitivity, the molecular mechanisms of IFN activities are not completely understood. Design: Down syndrome derived fibroblasts, Detroit 539 (D1) and Hs 52.Sk (D2) cells, were used. To analyse the expressions of interferon (IFN) receptors and downstream of IFN-γ, western blotting was performed. Cell proliferation was determined by counting cells following trypan blue staining. Media levels of IL-1β, TNF-α, and IL-6 were quantified using ELISA. Results: IFN-γ receptor 2 and IFN-α receptor 1, but not IFN-γ receptor 1, were highly expressed in D1 and D2 cells, as compared to the control fibroblast cells. Cell proliferation by D1 and D2 cells was lower than that by the control fibroblasts, further, IFN-γ had a greater effect to inhibit cell proliferation by D1 and D2 cells. In addition, IFN-γ treatment increased the phosphorylation of STAT1 and MAPK in D1 cells as compared to normal fibroblasts. Also, the presence of exogenous IFN-γ in the growth medium significantly induced IL-6, but not IL-1β or TNF-α, in D1 and D2 cells. Conclusion: Taken together, our results are consistent with hypersensitive reactions to IFN-γ seen in patients with Down syndrome and may provide useful information to elucidate the mechanisms of IFN-γ activities in those individuals.