HMOX1 and diabetic retinopathy: The Kelch-like ECH-associated protein 1 (Keap1)-nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway, a key defense system, and its target genes, including superoxide dismutase 1 (SOD1), heme oxygenase-1 (HO-1) and glutamate–cysteine ligase catalytic subunit (GCLc), are impaired in ECs exposed to high glucose (HG) levels (13) and in the retinas of donors with diabetic retinopathy (14).