Spilanthol-rich essential oil from Acmella oleracea and its nanoemulsion: anti-inflammatory strategy for the prevention of neurodegeneration

Neurodegenerative diseases have grown as a major health and societal challenge nowadays. These diseases share common pathological features like accumulation of misfolded proteins, mitochondrial disfunction, excitotoxicity, oxidative stress and inflammation. In the last years, neuroinflammation, caused by over-acting microglia, has emerged as a key element of the pathogenesis of these diseases. Therefore, the modulation of pro- inflammatory molecules from microglia could be a promising strategy to counteract neurodegeneration. Acmella oleracea (L.) is a medicinal plant whose wide use as traditional remedy is linked to its pharmacological properties, such as anti-inflamma- tory, antioxidant, analgesic and hepatoprotective1. These effects have been mostly related to its main secondary metabolite the alkylamide spilanthol. In this study, we investigated the anti-in- flammatory activities of a spilanthol-rich essential oil from A. oleracea (AO) in BV-2 microglial cells. Cells were treated with AO, pure spilanthol(S) or a nanoemulsion (NE), (composed by AO, ethyl oleate, and polysorbate 80) for 24 h, then exposed to LPS. All the treatments significantly increased cell viability (MTT assay) in respect to cells only exposed to LPS. Interestingly, AO and NE also reduced ROS levels (DCFH-DA assay), while S had no effect on this parameter. To verify if this protec- tion could be ascribed to an anti-inflammatory mechanism, the expression of IL-1b and TNF-a, COX-2 and iNOS was evaluated by RT-PCR. Interestingly, all the treatments reduced the expression of these inflammatory mediators. These results suggest AO as a potential therapeutic agent in neurodegenerative diseases thanks to its antioxidant and anti-inflammatory activities. Of note, this work also evidences a promising application of NE as a new technological formulation to further increase the potential of this essential oil.