SAHH-mediated homocysteine dysregulation drives diabetic retinopathy progression through ferroptosis-dependent...

Homocysteine (Hcy) metabolic dysregulation has been implicated in the progression of diabetic retinopathy (DR), but the underlying molecular mechanisms remain incompletely understood. This study aims to identify key factors mediating the role of Hcy in DR and explore the molecular mechanisms by which S-adenosylhomocysteine hydrolase (SAHH)-mediated Hcy metabolic dysregulation contributes to DR pathogenesis.

Human retinal microvascular endothelial cells (RMECs) were cultured under high-glucose conditions. Levels of Hcy, inflammatory factors, expression of glial fibrillary acidic protein (GFAP), as well as cell migration, invasion, tube formation, and ferroptosis-related markers were detected using ELISA, qPCR, Western blot, and immunofluorescence techniques. A rat model of type 1 diabetes mellitus (T1DM) and an Hcy gavage model were established, and retinal pathological changes were evaluated by HE staining, Doppler ultrasound, and Evans blue staining. SAHH gene silencing was achieved using siRNA and AAV-shSAHH, followed by transcriptome sequencing to identify downstream signaling pathways.

In vitro, high glucose combined with Hcy treatment increased intracellular Hcy levels, upregulated inflammatory factors and GFAP expression, inhibited cell proliferation, and promoted cell migration, invasion, iron accumulation, and oxidative stress. In vivo, similar pathological changes were observed in a DR rat model, and these were exacerbated by Hcy gavage. Conversely, SAHH silencing via siRNA in cultured cells reduced Hcy content and inflammation, while increasing cell proliferation, downregulating GFAP, impairing migration, invasion, and tube formation, and decreasing intracellular iron accumulation and oxidative stress. Transcriptome sequencing combined with molecular validation revealed that the SAHH-Hcy axis is associated with ferroptosis in DR, potentially by downregulating SLC7A11/GPX4 signaling, disrupting cellular iron ion transport and GSH-dependent antioxidant homeostasis, which further triggers oxidative stress and iron overload, and is closely associated with the occurrence and development of retinal lesions.

SAHH-mediated Hcy dysmetabolism acts as a key driver in DR by suppressing the SLC7A11/GPX4 antioxidant axis, impairing GSH synthesis, inducing iron overload and lipid peroxidation, and ultimately triggering ferroptosis.