Targeting Enolase in Reducing Secondary Damage in Acute Spinal Cord Injury in Rats
Spinal cord injury (SCI) is a complex debilitating condition leading to permanent life-long neurological deficits. The complexity of SCI suggests that a concerted multi-targeted therapeutic approach is warranted to optimally improve function. Damage to spinal cord is complicated by an increased detrimental response from secondary injury factors mediated by activated glial cells and infiltrating macrophages. While elevation of enolase especially neuron specific enolase (NSE) in glial and neuronal cells is believed to trigger inflammatory cascades in acute SCI, alteration of NSE and its subsequent effects in acute SCI remains unknown. This study measured NSE expression levels and key inflammatory mediators after acute SCI and investigated the role of ENOblock, a novel small molecule inhibitor of enolase, in a male Sprague–Dawley (SD) rat SCI model. Serum NSE levels as well as cytokines/chemokines and metabolic factors were evaluated in injured animals following treatment with vehicle alone or ENOblock using Discovery assay. Spinal cord samples were also analyzed for NSE and MMPs 2 and 9 as well as glial markers by Western blotting. The results indicated a significant decrease in serum inflammatory cytokines/chemokines and NSE, alterations of metabolic factors and expression of MMPs in spinal cord tissues after treatment with ENOblock (100 µg/kg, twice). These results support the hypothesis that activation of glial cells and inflammation status can be modulated by regulation of NSE expression and activity. Analysis of SCI tissue samples by immunohistochemistry confirmed that ENOblock decreased gliosis which may have occurred through reduction of elevated NSE in rats. Overall, elevation of NSE is deleterious as it promotes extracellular degradation and production of inflammatory cytokines/chemokines and metabolic factors which activates glia and damages neurons. Thus, reduction of NSE by ENOblock may have potential therapeutic implications in acute SCI.
KeywordsSpinal cord injury Enolase Glia Cytokines and chemokines Matrix metalloproteinases
This work was supported by grants from the South Carolina Spinal Cord Injury Research Fund (SCIRF 2015 P-01 and SCIRF #2016 I-03 to A. Haque), National Institutes of Health (R01 CA129560 to A. Haque), and the Veterans Administration (I01 BX001262 and I01 BX002349 to N. Banik). We thank Ms. Margaret Romano of Histology and Immunohistochemistry Laboratory at the Department of Pathology and Laboratory Medicine at MUSC for her technical assistance with the immunohistochemistry.
Compliance with Ethical Standards
Conflict of interest
The authors have no financial conflict of interest.
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