The protecting role of Ganoderma lucidum polysaccharides on the retinal neurovascular units in rats with retinal ischemia-reperfusion injury

This study investigates the protective mechanisms of Ganoderma lucidum polysaccharides (GLP) on retinal neurovascular units (NVUs) in a rat model of retinal ischemia-reperfusion injury (RIR), focusing on oxidative stress, glial activation, vascular dysfunction, and functional recovery. RIR was induced in postnatal day 6 (P6) Sprague-Dawley rats by anterior chamber perfusion (70 mmHg intraocular pressure for 1 h). Rats were treated with daily intragastric GLP (35, 70, or 140 mg/kg/d) for 7 days (P13). Retinal integrity was assessed via: Histopathology (H&E, TUNEL staining); Electroretinography (ERG) and photopic negative response (PhNR); immunofluorescence (GFAP, IBA-1); Optical coherence tomography angiography (OCTA); Western blotting and qPCR (Nrf2/HO-1, VEGF/HIF-1α/Notch, Cx43/AQP4 pathways); Oxidative stress markers (SOD activity, MDA content by ELISA). Ganoderma lucidum polysaccharides (GLP) at 70 mg/kg significantly attenuated retinal thinning and structural disorganization induced by RIR, with reduced apoptosis observed via TUNEL staining. GLP (140 mg/kg) upregulated Nrf2 and HO-1 protein expression, increased superoxide dismutase (SOD) activity, and decreased malondialdehyde (MDA) content in retinal tissues. GLP enhanced amplitudes of ERG a-waves, b-waves, and PhNR across multiple stimulus intensities. Immunofluorescence revealed decreased GFAP and IBA-1 expression in GLP-treated groups, indicating inhibition of reactive astrogliosis and microglial activation. OCTA demonstrated reduced vascular tortuosity and increased capillary perfusion density. Down regulation of VEGF, HIF-1α, and Notch proteins, alongside upregulation of VE-cadherin and eNOS mRNA, was confirmed by Western blot and qPCR.Neurovascular unit regulation: GLP modulated Cx43 and AQP4 expression, restoring intercellular communication within retinal neurovascular units. GLP significantly counteract retinal oxidative stress injury, inhibit reactive gliosis, suppress neovascularization, stabilize endothelial adhesive junctions, and protect retinal electrophysiological function while improving vascular function in RIR rats, suggesting that GLP possess certain intervention effects on abnormalities in the retinal neurovascular unit following RIR injury.