Neuroprotection by dimethyl fumarate following ventral root crush in C57BL/6J mice

CNS lesions usually result in permanent loss of function and are an important problem in the medical field. In order to investigate neuroprotection/degeneration mechanisms and the synaptic plasticity of motoneurons, in addition to the potential for a variety of treatments, different experimental models of axonal injury have been proposed. Recent studies have tested the immunomodulatory drug dimethyl fumarate (DMF) for the treatment of neurodegenerative diseases and have shown promising outcomes. Therefore, in this work, we investigated the effects of DMF with regard to neuroprotection and its influence on the glial response in C57BL/6J animals subjected to crushing of the motor roots in the lumbar intumescence of the spinal cord. The animals were divided into a vehicle-treated injury group (0.08 % methylcellulose solution control group, n = 7) and injured groups treated with DMF at different doses (15, 30, 45, 90 and 180 mg/kg; n = 6-7 per dose). The 90 mg/kg dose showed the best neuroprotective results, so it was used for treatment over a period of eight weeks. Neuronal survival was assessed through Nissl staining, and functional recovery was evaluated with the CatWalk system (walking track test) and the von Frey test (mechanoreception). Immunohistochemistry was used to assess synaptic coverage and astroglial and microglial reactivity using the primary antibodies anti-synaptophysin (pre-synaptic terminal pan marker), GAD65 (GABAergic pre-synaptic terminations - inhibitory), and VGLUT1 (glutamatergic pre-synaptic terminations - excitatory). Glial reactions were evaluated with anti-IBA1 (microglia) and GFAP (astrocytes). Gene transcript levels of IL-3, IL-4, TNF-α, IL-6, TGF-β, iNOS-M1, and arginase-M2 were quantified by RT-qPCR. The results indicated that treatment with DMF, at a dose of 90 mg/kg, promoted neuroprotection and immunomodulation towards an anti-inflammatory response. It also resulted in greater preservation of inhibitory synapses and reduced astroglial reactivity, providing a more favorable environment for sensorimotor recovery.