YTHDF1-regulated ALOX5 in retinal pigment epithelial cells under hypoxia enhances VEGF expression and promotes viability, migration, and angiogenesis of vascular endothelial cells.

Upregulation of vascular endothelial growth factor (VEGF) and enhanced angiogenesis have been implicated in the severe progression of age-related macular degeneration (AMD). Abnormal arachidonate 5-lipoxygenase (ALOX5) is associated with AMD pathogenesis. However, no reports have shown the causal role of ALOX5 in angiogenesis during AMD. In the present study, ARPE-19 cells were exposed to hypoxia, an inducer of VEGF expression. Potential proteins implicated in AMD progression were predicted using bioinformatics. RNA affinity antisense purification-mass spectrometry (RAP-MS) was applied to identify the binding proteins of ALOX5 3'UTR. Expression of ALOX5 and YTH N6-methyladenosine RNA-binding protein 1 (YTHDF1) was detected by qRT-PCR and western blotting. VEGF expression and secretion were assessed by immunofluorescence and ELISA, respectively. The chicken embryo chorioallantoic membrane (CAM) was used to analyze the effect of ALOX5 on angiogenesis. RNA stability was assayed using the Actinomycin D assay. The results show that hypoxia promoted cell growth and increased VEGF expression in ARPE-19 cells. ALOX5 was associated with AMD progression, and hypoxia upregulated ALOX5 expression in ARPE-19 cells. ALOX5 silencing reduced VEGF expression induced by hypoxia in ARPE-19 cells. Moreover, the conditioned medium of ALOX5-silenced ARPE-19 cells could suppress the viability and migration of HUVECs and diminish angiogenesis in the CAM. Furthermore, YTHDF1 was validated to bind to ALOX5 3'UTR, and YTHDF1 promoted ALOX5 expression by elevating the stability of ALOX5 mRNA. In conclusion, our findings demonstrate that YTHDF1-regulated ALOX5 increases VEGF expression in hypoxia-exposed ARPE-19 cells and enhances the viability, migration, and angiogenesis of vascular endothelial cells.