A novel fungal alkaloid protects retinal ganglion cells against glutamate-induced excitotoxicity in vitro and in vivo via activation of GABA pathway.

Retinal ganglion cells (RGCs) degeneration drives irreversible vision loss in glaucoma, ischemic/hereditary optic neuropathies, and demyelinating disorders, yet current therapies inadequately prevent RGC death. While fungal-derived compounds have revolutionized drug discovery, their neuroprotective potential remains underexplored. This study investigates the soil-derived fungus Umbelopsis sp. DWS 372 for novel neuroprotective agents targeting RGC preservation. Ten previously uncharacterized alkaloids and polyketides (1-10), including a new natural product (10), were isolated from rice-fermented cultures and structurally elucidated through NMR, HRESIMS, quantum-chemical calculations, and X-ray diffraction. Their neuroprotection activity against RGCs excitotoxicity was assessed. Compound 1 exhibited optimal efficacy, rescuing R28 cells from excitotoxicity (reducing ROS and cell death at 2 μM) in vitro, and mitigated NMDA-induced RGCs loss and improved visual function in vivo. Transcriptomics revealed that GABAergic modulation involved pathways are the primary mechanism of compound 1, including notch signaling and fatty acid metabolism. Similarity ensemble approach and molecular docking implied it is a GABA receptor agonist, which was further confirmed by the activity reduction caused by GABAA and GABAB receptor antagonists in the co-administration experiments, as well as the affinities to GABAA and GABAB receptor detected in the cellular thermal shift assays. This study identifies compound 1 as a novel neuroprotective lead, acting as a GABAA and GABAB non-selective agonist. Its efficacy in preserving RGCs and visual function highlights its potential for glaucoma therapy and broader neurodegenerative disease applications.