Obesity-associated lysosomal nitrosative stress promotes retinopathy

Obesity and diabetes are major risk factors causing vision loss around the world, yet the molecular mechanisms linking obesity to retinal pathology remain incompletely understood. While chronic inflammation and dysregulated vascular endothelial growth factor (VEGF) signaling are established contributors to retinopathy, their integration within the context of obesity has not been fully elucidated. Retinal transcriptomic RNA sequencing datasets from patients with type 2 diabetes mellitus (T2DM) and obese mouse models were retrieved from the GEO database. Meta-analysis was performed using MetaVolcanoR to identify differentially expressed genes associated with obesity- and diabetes-related retinal alterations. The functional impact of cathepsin B (CTSB) S-nitrosylation on retinal VEGF expression was investigated in diet-induced obese wild-type and transgenic mouse models through molecular and biochemical approaches, including biotin switch assay, ELISA, and quantitative RT-PCR, etc. We conducted a meta-analysis of retinal transcriptomic datasets from T2DM patients and obese mouse models and found that obesity promotes retinal inflammation and vascular endothelial cell proliferation and migration signatures. These transcriptomic profiles were further confirmed by biochemical analysis and gene expression analysis in mice with diet-induced obesity. Moreover, we demonstrated that obesity increased retinal inducible nitric oxide synthase (iNOS) expression but suppressed S-nitrosoglutathione reductase (GSNOR) activity, two essential regulators for nitrosative stress. At the cellular level, we showed that obesity promoted retinal lysosomal nitrosative stress, leading to impaired retinal CTSB activity, a critical lysosomal enzyme. Of note, in the context of obesity, the nitrosative stress-promoted lysosomal impairment is correlated with an accumulation of retinal VEGF. Functionally, suppression of nitrosative stress by iNOS deletion reduced retinal VEGF expression and restored retinal lysosomal function in obese mice. In contrast, elevation of nitrosative stress by GSNOR deletion in obese mice worsened the retinal lysosomal nitrosative stress and lysosomal enzymatic defects. Our findings identify lysosomal nitrosative stress as a pivotal mediator that links obesity-driven inflammation to impaired VEGF homeostasis in the retina, thereby advancing our understanding of the molecular underpinnings of obesity-associated retinopathy.