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

Abstract

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 GABAB receptor agonist of RGCs against hypoxia-induced apoptosis. Cobalt chloride (CoCl2) was applied to mimic hypoxia. Primary rat RGCs were subjected to CoCl2 with or without baclofen treatment, and RNA interference techniques were used to knock down the GABAB2 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. GABAB2 mRNA expression was determined using quantitative real-time polymerase chain reaction (qRT-PCR) analysis. Our study revealed that CoCl2 significantly induced RGC apoptosis and that baclofen reversed these effects. CoCl2-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 CoCl2. Knockdown of GABAB2 and the inactivation of the Akt pathway by inhibitors reduced the protective effect of baclofen on CoCl2-treated RGCs. Taken together, these results demonstrate that baclofen protects RGCs from CoCl2-induced apoptosis by increasing Akt activity and by suppressing the PERK pathway and CHOP activation.

GABA promotes survival and axonal regeneration in identifiable descending neurons after spinal cord injury in larval lampreys

“…Present results indicate that the activation of GABAB receptors by GABA/baclofen can inhibit caspase activation after SCI in identifiable descending neurons, which is a key step to preventing the development of apoptosis and promoting neuronal survival. Previous work in other models of CNS injury also showed that a baclofen treatment can inhibit caspase activation (model of kainic-acid induced seizure in rats: Wei et al, 2012; models of ischemic brain injury in rats: Han et al, 2008;Liu et al, 2015; model of chemical hypoxia in retinal ganglion cells in rats: Fu et al, 2016). Our study shows that the activation of GABAB receptors can also prevent apoptosis after a traumatic SCI.…”

Local Delivery of β-Elemene Improves Locomotor Functional Recovery by Alleviating Endoplasmic Reticulum Stress and Reducing Neuronal Apoptosis in Rats with Spinal Cord Injury

“…Using this system, we demonstrated that CoCl 2 was able to induce VSC4.1 motor neuronal ER stress and cause apoptosis in a dose-dependent manner. Our results are consistent with previous reports that the PERKeIF2α-ATF4 pathway was activated by CoCl 2 [44]. Then, we explored the effect of β-elemene on neuronal apoptosis induced by ER stress, with our results suggesting that β-elemene reduces VSC4.1 motor neuronal apoptosis by inhibiting the phosphorylation of PERK and eIF2α and the expression of ATF4.…”

GABA promotes survival and axonal regeneration in identifiable descending neurons after spinal cord injury in larval lampreys

“…Present results indicate that the activation of GABAB receptors by GABA/baclofen can inhibit caspase activation after SCI in identifiable descending neurons, which is a key step to preventing the development of apoptosis and promoting neuronal survival. Previous work in other models of CNS injury also showed that a baclofen treatment can inhibit caspase activation (model of kainic-acid-induced seizure in rats: 29 ; models of ischaemic brain injury in rats: 27 , 31 ; model of chemical hypoxia in retinal ganglion cells in rats: 66 ). Our study shows that the activation of GABAB receptors can also prevent apoptosis after a traumatic SCI.…”