ALKBH5 causes retinal pigment epithelium anomalies and choroidal neovascularization in age-related macular degeneration via the AKT/mTOR pathway.

Retinal pigment epithelium (RPE) dysfunction and choroidal neovascularization (CNV) are predominant features of age-related macular degeneration (AMD), with an unclear mechanism. Herein, we show that RNA demethylase α-ketoglutarate-dependent dioxygenase alkB homolog 5 (ALKBH5) is up-regulated in AMD. In RPE cells, ALKBH5 overexpression associates with depolarization, oxidative stress, disturbed autophagy, irregular lipid homeostasis, and elevated VEGF-A secretion, which subsequently promotes proliferation, migration, and tube formation of vascular endothelial cells. Consistently, ALKBH5 overexpression in mice RPE correlates with various pathological phenotypes, including visual impairments, RPE anomalies, choroidal neovascularization (CNV), and interrupted retinal homeostasis. Mechanistically, ALKBH5 regulates retinal features through its demethylation activity. It targets PIK3C2B and regulates the AKT/mTOR signaling pathway with YTHDF2 as the N6-methyladenosine reader. IOX1, an ALKBH5 inhibitor, suppresses hypoxia-induced RPE dysfunction and CNV progression. Collectively, we demonstrate that ALKBH5 induces RPE dysfunction and CNV progression in AMD via PIK3C2B-mediated activation of the AKT/mTOR pathway. Pharmacological inhibitors of ALKBH5, like IOX1, are promising therapeutic options for AMD.

m6A modification of circSPECC1 suppresses RPE oxidative damage and maintains retinal homeostasis.

Age-related macular degeneration (AMD) is a leading cause of irreversible vision loss in the elderly population with unclear pathogenic mechanism. Herein, we detect downregulated circSPECC1 expression in retinal pigment epithelium (RPE) of AMD patients. In RPE cells, circSPECC1 insufficiency leads to oxidative stress-induced ferroptosis, depolarization, and irregular lipid metabolism. Consistently, in mice, circSPECC1 deficiency induces visual impairments and RPE anomalies and interrupts retinal homeostasis. Mechanically, nuclear export of circSPECC1 transcript depends on its N6-methyladenosine (m6A) level with YTHDC1 as the reader. CircSPECC1 directly sponges miR-145-5p to block its interaction with CDKN1A. Overexpressing miR-145-5p aggravates RPE dysfunctions, mimicking circSPECC1 silencing effects. Retinal phenotypes induced by circSPECC1 insufficiency are alleviated by miR-145-5p inhibition and are aggravated by miR-145-5p overexpression. Collectively, circSPECC1, mediated by m6A modification and sponging miR-145-5p, resists oxidative stress injuries and maintains lipid metabolism in RPE. Pharmacological supplementation of circSPECC1 is a promising therapeutic option for atrophic retinopathies like AMD.