Targeting SMOX Preserves Optic Nerve Myelin, Axonal Integrity, and Visual Function in Multiple Sclerosis.

Multiple sclerosis (MS) is a highly disabling chronic neurological condition affecting young adults. Inflammation, demyelination, and axonal damage are key pathological features of MS and its animal model, experimental autoimmune encephalomyelitis (EAE). Our previous work demonstrated that inhibiting spermine oxidase (SMOX) with MDL72527, a selective irreversible pharmacological inhibitor, significantly reduced clinical symptoms, retinal ganglion cell (RGC) loss, and optic nerve inflammation in EAE mice. The present study explored the broader therapeutic potential of SMOX inhibition, focusing on myelin preservation, axonal integrity, and visual function in the EAE model. Electron microscopy of optic nerve cross-sections showed significant preservation of myelin thickness and axonal integrity due to SMOX inhibition. The quantitative assessment showed that g-ratio and axon count metrics were significantly improved in MDL72527-treated EAE mice compared to their vehicle-treated counterparts. Immunofluorescence studies confirmed these findings, showing increased preservation of myelin and axonal proteins in MDL72527-treated EAE mice compared to the vehicle-treated group. Functional assessment studies (Electroretinography) demonstrated significant improvement in RGC function and axonal conduction in EAE mice treated with MDL72527. Furthermore, SMOX inhibition downregulated the expression of galectin3 (Gal3), a mediator of neuroinflammation, indicating Gal3's role in SMOX-mediated neuroprotection. This study provides compelling evidence for the potential of SMOX inhibition as a therapeutic strategy in multiple sclerosis and other demyelinating disorders.