[Study on the susceptibility of human corneal epithelial cells to Acanthamoeba in a hypoxia condition]

Objective: To investigate the regulation mechanism of Acanthamoeba-induced immune responses of human corneal epithelial cells in a hypoxia condition. Methods: Telomerase-immortalized human epithelial cells (THCEs) challenged with Acanthamoeba (1×10⁶/ml) were incubated under normoxic (21% O₂) (control group) or hypoxic (1% O₂) (experiment group) conditions respectively. The mRNA of toll-like receptor (TLR4), myeloid differentiation factor 88 (MyD88), nuclear factor kappa-B (NF-κB), tumor necrosis factor-α (TNF-α), interleukin-8 (IL-8), interferon-β (IFN-β), and the protein level of TLR4, inhibitor of nuclear factor kappa-Bα (IκBα), phosphorylated extracellular-signal related kinase 1/2 (p-ERK1/2) and phosphorylated IκBα (p-IκBα) were detected. Enzyme-linked immunosorbent assay (ELISA) was used to detect the secretion of the inflammatory cytokines (TNF-α, IL-8 and IFN-β). Results: The mRNA levels of Acanthamoeba-induced TLR4, MyD88, NF-κB, TNF-α, IFN-β and IL-8 in THCEs under hypoxia was down-regulated by 47%, 41%, 45%, 53%, 36% and 50% respectively, compared to control group. And the protein levels of p-IκBα and p-ERK1/2 were significantly down-regulated by 56% and 55%, respectively, while the protein expression of IκBα was increased. The secretions of TNF-α, IL-8 and IFN-β under hypoxia were reduced by 46%, 28% and 35%, respectively. Conclusion: Hypoxia might attenuated the inflammatory response of the human corneal epithelial cells against Acanthamoeba infection by suppressing TLR4 signaling.