Baclofen Protects Primary Rat Retinal Ganglion Cells from Chemical Hypoxia-Induced Apoptosis Through the Akt and PERK Pathways

摘要

Retinal ganglion cells (RGCs) consume large quantities of energy to convert light information into a neuronal signal, which makes them highly susceptible to hypoxic injury. This study aimed to investigate the potential protection by baclofen, a GABA_(B)receptor agonist of RGCs against hypoxia-induced apoptosis. Cobalt chloride (CoCl_(2)) was applied to mimic hypoxia. Primary rat RGCs were subjected to CoCl_(2)with or without baclofen treatment, and RNA interference techniques were used to knock down the GABA_(B)2 gene in the primary RGCs. The viability and apoptosis of RGCs were assessed using cell viability and terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) assays, Hoechst staining, and flow cytometry. The expression of cleaved caspase-3, bcl-2, bax, Akt, phospho-Akt, protein kinase RNA (PKR)-like ER kinase (PERK), phospho-PERK, eIF2α, phospho-eIF2α, ATF-4 and CCAAT/enhancer-binding protein homologous protein (CHOP) were measured using western blotting. GABA_(B)2 mRNA expression was determined using quantitative real-time polymerase chain reaction (qRT-PCR) analysis. Our study revealed that CoCl_(2)significantly induced RGC apoptosis and that baclofen reversed these effects. CoCl_(2)-induced reduction of Akt activity was also reversed by baclofen. Baclofen prevented the activation of the PERK pathway and the increase in CHOP expression induced by CoCl_(2). Knockdown of GABA_(B)2 and the inactivation of the Akt pathway by inhibitors reduced the protective effect of baclofen on CoCl_(2)-treated RGCs. Taken together, these results demonstrate that baclofen protects RGCs from CoCl_(2)-induced apoptosis by increasing Akt activity and by suppressing the PERK pathway and CHOP activation.