Piceatannol attenuates retinal endothelial cell dysfunction by modulating microglial polarization via the CCL5/CCR5/NF-κB axis

Diabetic retinopathy (DR) remains a leading cause of visual impairment worldwide and is characterized by retinal microvascular dysfunction and chronic neuroinflammation. The pathogenesis of DR involves the activation of retinal microglia, which release a variety of pro-inflammatory cytokines, thereby amplifying inflammatory signaling and compromising the structural and functional integrity of the retinal vasculature. Piceatannol (PIC), a bioactive polyphenolic compound, has demonstrated potent anti-inflammatory properties and beneficial effects on vascular homeostasis. However, its role and underlying mechanisms in DR remain largely unexplored. An integrated approach combining network pharmacology and transcriptomic analyses was employed to systematically identify the potential molecular targets of PIC in DR. Molecular docking was first performed to predict the interaction between PIC and C-C motif chemokine receptor 5 (CCR5), followed by experimental validation of the binding affinity. In vitro and in vivo DR models were established using high glucose (HG)-stimulated microglia and streptozotocin-induced diabetic mice, respectively. The effects of PIC on microglial polarization, retinal vascular permeability, and inflammatory responses were subsequently evaluated. A total of 159 overlapping targets associated with both PIC and DR were identified, among which CCR5 emerged as a key target. In diabetic mice, PIC treatment restored retinal thickness, reduced the formation of acellular capillaries, and attenuated retinal vascular leakage. CCR5 was predominantly expressed in retinal microglia, whereas its ligand, CCL5, was significantly upregulated in DR. PIC inhibited microglial activation and M1 polarization, reduced the secretion of pro-inflammatory cytokines, and promoted the expression of M2-associated markers through modulation of the CCL5/CCR5/NF-κB signalling pathway. In vitro, PIC suppressed HG-induced M1 polarization of microglia and preserved the expression of endothelial tight junction proteins, including ZO-1 and Claudin-5. Furthermore, CCR5 knockdown and pharmacological activation experiments confirmed the central role of CCR5 in mediating the protective effects of PIC. PIC exerts protective effects on retinal microvascular function in DR by regulating microglial polarization. Specifically, it suppresses the pro-inflammatory M1 phenotype while promoting the anti-inflammatory M2 phenotype through inhibition of the CCL5/CCR5/NF-κB signaling pathway. Collectively, these findings suggest that PIC may represent a promising therapeutic candidate for the prevention and treatment of DR.