Hibiscus sabdariffa extract protects HT-22 cells from glutamate-induced neurodegeneration by upregulating glutamate transporters and exerts lifespan extension in C. elegans via DAF-16 mediated pathway

BACKGROUND: Glutamate toxicity is involved in several neurodegenerative conditions, including Alzheimer’s disease. OBJECTIVE: The study aims to investigate the neuroprotective efficacy of ethanol extract of Hibiscus sabdariffa calyces (HS) against glutamate-induced toxicity in HT-22 cells and induce anti-aging property in Caenorhabditis elegans. METHODS: HT-22 cells were pre-treated with HS followed by glutamate and evaluated for the neuroprotective effect using cell viability assay, confocal microscopic analysis, qPCR, Western blot, and docking analysis. Induction of anti-aging property in C. elegans with HS extract was analyzed through physiological assays and qPCR analysis. RESULTS: GC-MS analysis of the HS extract showed the presence of 19 compounds with antioxidant properties including oleamide,2-(diethoxymethyl)furan and 5-methylfurfural. In vitro studies reveal that glutamate exerted toxicity in HT-22 cells by inducing oxidative stress, depleting glutathione, downregulating glutamate transporters, antioxidant genes, inducing autophagy (Beclin-1, Atg-5, Atg-7, LC3-II) by the activation of MAPK (p38, JNK) pathway, and causing apoptosis. However, pre-treatment with HS extract (5, 10μg/ml) reversed the effect and offered neuroprotection. In silico studies showed that the compounds of HS extract can bind effectively and inhibit the activity of NMDAR, calpain-1 and GSK-3β. In C. elegans, HS extended lifespan, reduced the accumulation of lipofuscin, modulated healthspan-related genes and downregulated the expression of daf-2. CONCLUSION: Our results indicate that HS with its bioactive components exhibits neuroprotective activity by upregulating glutamate transporters, inhibiting autophagy and exerts anti-aging property through DAF-16 dependent mechanism.