Background: Calycosin is thought to have anti-cancer and anti-inflammatory characteristics; however, more research is needed to determine how it impacts retinal pigment epithelium (RPE) cells. This study aims to explore the effects of calycosin on RPE cells under hypoxia.

Methods: Experimental hypoxia was induced by treating RPE cells with cobalt chloride for 2, 4, and 6 h. To investigate the effect of calycosin on RPE cells under hypoxia, RPE cells were treated with calycosin and cobalt chloride (CoCl₂). Cells were assessed for viability (Cell Counting Kit-8 assay) and apoptosis (flow cytometry). Inflammatory cytokines (enzyme-linked immunosorbent assay) and genes or proteins related to apoptosis and the hypoxia-inducible factor-1α (HIF-1α)/nuclear factor-κB (NF-κB) axis (quantitative real-time polymerase chain reaction and western blot) were measured.

Results: Under hypoxic conditions, RPE cells showed reduced viability but increased levels of inflammation and apoptosis. The NF-κB pathway was activated, and HIF-1α, apoptosis/NF-κB pathway-related proteins (cleaved caspase-3, cleaved poly (ADP-ribose) polymerase (PARP); phosphorylated-p65 (p-p65), p-p65/p65), and inflammatory cytokines (interleukin-6 (IL-6) and interleukin-8 (IL-8)) were upregulated (p < 0.001). Calycosin weakened the effects of hypoxia on RPE cells (p < 0.05).

Conclusion: Calycosin inhibits the HIF-1α/NF-κB axis and protects RPE cells from hypoxia-induced inflammation and apoptosis.