Abstract
We reported that high-mobility group Box-1 (HMGB1) was involved in excitoneurotoxicity in the retina. Although HMGB1 is known to activate nuclear factor kappa B (NF-κB), the role of NF-κB in excitotoxicity is still controversial. Here, we demonstrated that NF-κB activation induced by intravitreal NMDA led to the retinal neurotoxicity via activation of astrocytes. Male Sprague-Dawley rats were anesthetized with ketamine (90 mg/kg, i.p) and xylazine (10 mg/kg, i.p.), and NMDA (200 nmol/eye) and bovine HMGB1 (μg/eye) were intravitreally injected. Triptolide (500 pmol/eye), BAY 11-7082 (500 pmol/eye), and IMD-0354 (7.5 nmol/eye), NF-κB inhibitors, were co-injected with NMDA or HMGB1. Retinal sections were obtained seven days after intravitreal injection. Cell loss in the ganglion cell layer was observed in the HMGB1- and the NMDA-treated retina. All of the NF-κB inhibitors used in this study reduced the damage. BAY 11-7082 reduced the expression of phosphorylated NF-κB 12 hours after NMDA injection, upregulation of GFAP immunoreactivity induced by NMDA 12 and 48 hours after NMDA injection, and the number of TUNEL-positive cells 48 hours after NMDA injection. The results suggest that NF-κB p65 was phosphorylated in the GFAP-positive astrocytes, and that the activation of the glial cells, such as astrocytes and Müller cells, was involved in the delayed neuronal cell death that occurs 48 hours after NMDA injection or later. Prevention of NF-κB activation is a candidate for the treatment of retinal neurodegeneration associated with excitotoxicity, such as glaucoma and central retinal artery occlusion.
