AIM:To observe the effects of hypoxia on the expression of Toll-like receptor 4 (TLR4) in cultured human retinal pigment epithelium (RPE) cells.METHODS:Chemical hypoxic model was established by treating the cultured human RPE cells with 200μmol/L CoCl2.The location of TLR4 in human RPE cells was observed by immunofluorescence assay,and RT-PCR together with Western blot were applied to detect the expression of TLR4 2,4,8,12,24 hours after the treatment.RESULTS:Immunofluorescence assay revealed that TLR4 was slightly expressed in human RPE cells under normoxic condition.After hypoxic treatment,there was a significant increase in green fluorescence within the cytoplasm.TLR4 expression tend to intensify over time and peaked at 12 hours,which was confirmed by RT-PCR and Western blot assay exhibiting TLR4 mRNA/protein levels (P<0.05).The expression levels began to decrease at 24 hours,and there was statistical significance among the groups.CONCLUSION:Hypoxia can strengthen TLR4 expression in cultured human RPE cells.