Bypassing Androgens: Retina-Targeted 17β-Estradiol Delivery via DHED Eye Drops Ameliorates Orchiectomy-Induced Shifts in the Male Rat Visual Cortex Proteome

Mass spectrometry-based proteomics has become instrumental for elucidating the molecular mechanisms of neurodegeneration, enabling the identification of disease-associated proteomic alterations and protein-level responses to therapeutic interventions. Building on our previous proteomic characterization of the orchiectomized (ORX) Brown Norway male rat retina as a model of androgen deprivation, we extend this investigation to the visual cortex (VC), a key node in the visual pathway. Here we report the first comprehensive proteomic characterization of ORX-VC employing nanoflow liquid chromatography-tandem mass spectrometry complemented by bioinformatic pathway analyses and quantitative assessment of selected protein markers of ORX-induced changes. Our discovery-driven proteomics approach revealed over 500 differentially expressed proteins following ORX. Principal component analysis showed complete separation between ORX and naïve groups with no overlap, indicating a profound effect of androgen deprivation on the VC proteome. Ingenuity Pathway Analysis^® predicted that the widespread proteome dysregulation included oxidative stress as a primary contributor, alongside estrogen receptor (ESR) predominance over androgen receptor signaling, consistent with our prior findings in the ORX retina. To explore whether this ESR predominance translates to a benefit of E2 supplementation alone, independent of circulating testosterone, we utilized our DHED (10β,17β-dihydroxyestra-1,4-dien-3-one) prodrug as eye drops to target E2 formation into the retina. Quantitative assessment demonstrated that this approach resulted in attenuation of ORX-induced expression changes in a selected panel of key proteins. These findings warrant future studies to determine whether this effect extends across the full spectrum of ORX-induced proteomic shifts and confers a benefit for vision preservation.