POTENTIAL NEUROREGENERATIVE AND NEUROPROTECTIVE EFFECTS OF LEMON PEEL POLYPHENOLIC RICH-EXTRACT IN ZEBRAFISH SPINAL CORD INJURY

Flavonoids, a diverse class of phytochemicals found in fruits, vegetables, and herbs, are widely recognized for their anti- inflammatory, antioxidant, and neuroprotective properties. These compounds modulate gene expression and molecular pathways, mitigating pathological processes such as inflammation, oxidative stress, and neurodegeneration. Notably, flavonoids can reduce the production of reactive oxygen species, activate antioxidant enzymes, and inhibit pro-inflammatory cytokines such as tumor necrosis factor- alpha (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6). This study explores the neuroprotective and neuroregenerative potential of a polyphenolic-rich lemon peel extract in a zebrafish model of spinal cord injury (SCI), a debilitating condition characterized by primary mechanical damage followed by secondary injury processes, including neuroinflammation, oxidative stress, and apoptosis. Using transgenic zebrafish embryos (Tg[huc:gfp]), the polyphenolic-rich lemon peel extract was administered at a concentration of 25 μg/ml from 0 days post-fertilization (dpf). SCI was induced at 3 dpf, and larvae were subsequently treated with the extract. Key assessments revealed that the polyphenolic-rich lemon peel extract significantly enhanced survival rates and promoted axonal regrowth, as evidenced by the increased formation of axonal bridges in treated groups compared to sham controls. Additionally, EdU-based assays demonstrated a marked increase in cell proliferation at the lesion site two days post-injury in the treated group. POTENTIAL NEUROREGENERATIVE AND NEUROPROTECTIVE EFFECTS OF LEMON PEEL POLYPHENOLIC RICH-EXTRACT IN ZEBRAFISH SPINAL CORD INJURY iii Molecular analysis highlighted the extract’s ability to downregulate pro-inflammatory markers (IL-1β, TNF-α, and IL-8) while upregulating the antioxidant enzyme Sod1. Furthermore, the treatment activated key neuroregenerative pathways, including Wnt/β-catenin, as shown by the upregulation of Wnt3, Lef1, and NeuroD1, which are crucial for neuronal survival, axonal regeneration, and tissue repair. These findings underscore the therapeutic potential of polyphenolic-rich lemon peel extract in promoting neuroprotection and regeneration after SCI. The extract improved survival rates, reduced inflammation, enhanced oxidative defenses, and supported cellular proliferation and axonal regrowth. While this study provides a strong foundation for the use of flavonoids in SCI treatment, further investigations in higher vertebrate models are needed to confirm translational applicability and elucidate underlying mechanisms. This research highlights the potential of natural compounds in advancing sustainable and effective therapies for SCI and related neurodegenerative conditions.