Involvement of Keap1/Nrf2 and the antioxidant defence in cytoprotective effects induced by cannabis polyphenols in SH-SY5Y neuronal cells

Oxidative stress (OS) is widely recognized as a central promoter to the pathogenesis of neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS) and primary lateral sclerosis (PLS). Cannabis sativa L. synthesizes a complex array of bioactive compounds that extends well beyond the well-known cannabinoids to include a diverse suite of polyphenols, terpenes, fatty acids, tocopherols, and proteins. The non-cannabinoid polyphenolic fraction is composed primarily of flavonoids, stilbenoids, lignans, and lignanamides, which contribute substantially to the plant's antioxidant, anti-inflammatory, and neuroprotective properties. This study investigates the redox-modulating and cytoprotective properties of a polyphenolic fraction derived from Cannabis sativa L. in SH-SY5Y neuroblastoma cells. Neurons were treated with various concentrations of the aqueous polyphenolic cannabis extract and exposed to oxidative stress using hydrogen peroxide (100 µM). Protein and gene expression related to redox signalling were analyzed via Western blot and qPCR, and molecular docking studies were performed in silico. Furthermore, antioxidant enzymes activity was measured by spectrophotometry. Results revealed that the phenolic fraction significantly activated the Keap1/Nrf2 pathway, increased expression of PRDX1 and PRDX3, and enhanced endogenous antioxidant defences. Simultaneously, it reduced endoplasmic reticulum stress-induced apoptosis (via Bax/Bcl-2 modulation) and attenuated inflammatory markers, including NO, NF-κB2, IL-6, and IL-8. In silico docking studies identified Leu583 as a key residue in Nrf2-ligand interactions. These findings suggest that Cannabis sativa L. polyphenols are key bioactive compounds modulating redox homeostasis and inflammation, and offering neuroprotective benefits with potential relevance in diseases involving mitochondrial dysfunction and oxidative damage.