Müller glia-mediated protection of retinal ganglion cells from ethambutol-induced neurotoxicity through brain-derived neurotrophic factor
Ethambutol (EMB)-associated optic neuropathy is the most common toxic optic neuropathy and poses a significant visual threat worldwide. This study aimed to investigate the neuroprotective roles of Mu¨ller glia, the most abundant macroglia in the retina, and their associated growth factors in supporting retinal ganglion cells (RGCs) under EMB-induced toxicity. Induced RGC-like cells (iRGCs), differentiated from human induced pluripotent stem cells, and Müller glial cell line MIO-M1 were used as cellular models. RNA sequencing revealed that EMB significantly disrupted neurotrophin and BDNF-associated pathways in iRGCs. Co-culture with MIO-M1 cells markedly enhanced the survival of iRGCs during EMB exposure. mRNA of BDNF and nerve growth factor (NGF) were elevated in MIO-M1 cells, while only BDNF improved the survival and morphological integrity of iRGCs under EMB treatment. Administration of BDNF also improved the survival of RGC in mouse retinal explants. The pro-survival effect of BDNF was suppressed by GNF5837, a pan-TRK inhibitor. Among the three downstream effectors of BDNF signaling, AKT was most prominently activated by BDNF in EMB-treated iRGCs, compared to ERK and PLC?1. Furthermore, the protective effect of BDNF was blocked by the AKT inhibitor MK-2206 but not by the ERK inhibitor GDC-0094. Müller glia confer neuroprotection to RGCs under EMB-induced stress, primarily via BDNF signaling. AKT functions as the key downstream effector mediating this protective response. These findings suggest that the BDNF-AKT signaling may serve as a promising therapeutic target for EMB-associated optic neuropathy. Overall design: The response of week 4 iRGCs to EMB was investigated by using RNA sequencing.