NF-κB-mediated inflammatory damage is differentially affected in SH-SY5Y and C6 cells treated with...

Previous studies have demonstrated that 27-hydroxycholesterol (27-OHC), a cholesterol metabolite, was involved in the inflammatory process of Alzheimer's disease (AD). The present study aimed to investigate the 27-OHC-induced inflammatory damage to neurons and astrocytes and the underlying mechanism(s) accounting for this damage. Human neuroblastoma cells (SH-SY5Y cells) and rat glioma cells (C6 cells) were treated with vehicle or 27-OHC (5, 10, or 20 μM) for 24 hr. The levels of secreted interleukin-1β (IL-1β), interleukin-10 (IL-10), tumor necrosis factor alpha (TNF-α), and inducible nitric oxide synthase (iNOS) were determined by using an enzyme-linked immunosorbent assay (ELISA). Immunofluorescence staining was used to determine the cellular expression of toll-like receptor 4 (TLR4) and transforming growth factor-β (TGF-β). The mRNA and protein expression levels of nuclear factor-κB p65 (NF-κB p65), nuclear factor-κB p50 (NF-κB p50) and cyclooxygenase-2 (COX-2) in both SH-SY5Y and C6 cells were also detected by real-time PCR and Western blot, respectively. The results of this study showed that 27-OHC treatment increased secretion of TNF-α and iNOS and decreased secretion of IL-10, upregulated expression of TGF-β, NF-κB p65 and p50, and downregulated expression of COX-2 in SH-SY5Y cells. In C6 cells, treatment with 27-OHC resulted in decreased secretion of IL-1β, IL-10, TNF-α, and iNOS, and increased expression of TLR4 and TGF-β. These results suggest that 27-OHC may cause inflammatory damage to neurons by activating the TGF-β/NF-κB signaling pathway and to astrocytes by activating the TLR4/TGF-β signaling, which results in the subsequent release of inflammatory cytokines.