Cathepsin H drives hypoxia-associated inflammatory and angiogenic programs in diabetic retinopathy and represents a potential therapeutic target.

Diabetic retinopathy (DR) arises from intertwined inflammatory, metabolic, and hypoxia-driven angiogenic programs, yet upstream regulators coordinating these processes remain incompletely defined. Here, we used an integrative multi-omics and experimental framework to identify cathepsin H (CTSH) as a candidate causal driver of proliferative DR (PDR). By combining GWAS, eQTL, pQTL, and mQTL datasets with Mendelian randomization, summary-data-based Mendelian randomization, and Bayesian colocalization, CTSH emerged as the strongest genetically supported candidate across discovery and validation analyses. In the UK Biobank (UKB), circulating CTSH was elevated in diabetic retinopathy and independently predicted incident disease. Single-cell transcriptomic analyses localized CTSH predominantly to myeloid compartments within fibrovascular membranes and linked CTSH-high states to inflammatory, hypoxic, and angiogenic programs. In high-glucose-stimulated THP-1 monocytes, CTSH promoted reactive oxygen species accumulation, NF-κB activation, and increased IL-6, TNF-α, HIF-1α, and VEGF expression, whereas CTSH silencing reversed these effects. Structure-guided virtual screening identified Eriocitrin as a lead CTSH-binding candidate. In db/db mice, intravitreal Eriocitrin improved inner-retinal function, restored OCTA-derived vascular metrics, and partially rescued retinal structure, with efficacy comparable to anti-VEGF treatment across several endpoints. Molecular analyses further showed coordinated suppression of inflammatory, hypoxic, angiogenic, and NF-κB signaling. Together, these findings identify CTSH as an upstream immunometabolic regulator of DR-related inflammatory and angiogenic biology, with the strongest genetic support observed for PDR, and support CTSH targeting as a potential multi-pathway therapeutic strategy beyond VEGF inhibition.