Modulation of neuroinflammation by essential oils obtained from different hemp varieties

Nowadays, the progressive aging of the population due to the increase in longevity is a tangible event for the worldwide population. It represents a success for the scientific community thanks to the progress of science, but at the same time, it will mean a great challenge for the immediate future. Indeed, with the increase in life expectancy, we have witnessed a parallel increase in chronic-degenerative diseases, especially neurodegenerative diseases which mainly affect the elderly population. The etiology of neurodegenerative diseases is multifactorial, but they share key pathological features like oxidative stress and neuroinflammation. During neuroinflammation, a crucial role is played by microglia which constitute resident immune cells in the central nervous system. Nevertheless, pathological conditions like Alzheimer’s disease, Parkinson’s disease, multiple sclerosis, stroke, and other neurological disorders, are associated with the hyperactivation of microglial cells. This phenomenon leads to the release of several pro-inflammatory mediators like cytokines and reactive oxygen species (ROS) leading to neuronal damage. Recently, the regulation of microglial immune-related functions through the endocannabinoid system has emerged as a potential neuroprotective strategy. Essential oils (EOs) obtained from hemp inflorescences are rich in interesting bioactive molecules like terpenes and terpenoids able to prevent the progression and help in the management of several chronic-degenerative diseases including neurodegenerative diseases. In this regard, improving the knowledge of different hemp varieties or cultivars to obtain EOs enriched in specific bioactive phytochemicals may be advantageous. This study aimed to investigate the anti-inflammatory properties of EOs obtained from inflorescences of different hemp varieties in BV-2 microglial cells. Cells were treated with increasing concentrations of EOs for 2 h and then activated with LPS 100 ng/mL for 24 h. One of the tested EOs, named Gorilla Glue (GG), demonstrated promising anti-inflammatory potential. Nitric oxide production, measured by Griess assay, was significantly reduced by 5x10-3 μL/mL EO treatment with respect to LPS. The treatment with EO decreased the gene expression of inflammatory mediators such as IL-1β, IL-6, TNF-α, COX-2, iNOS, and NLRP3 and increased the gene expression of anti-inflammatory mediators such as IL-4 and Arg1 compared to LPS. The anti-inflammatory effect could be ascribed to the significant reduction of the NFkB-nuclear translocation, probably mediated by the inhibition of the phosphorylation of p38 MAPK, as evidenced by immunofluorescence and Western Blot analyses, respectively. GG EO was able to counteract LPS-induced oxidative stress by significantly reducing ROS levels and increasing GSH levels. The main compounds found in GG EO were (E)-caryophyllene (17.6%), selina-3,7(11)-diene (12.5%), selina-4(15),7(11)-diene (7.1%) and α-humulene (4.7%). We tested (E)-caryophyllene and α-humulene for their anti-inflammatory activity. α-humulene was able to counteract the increase of all the pro-inflammatory mediators tested, while (E)-caryophyllene only upregulated the anti-inflammatory cytokine IL-4. These results suggest a specific contribution of different bioactive compounds to the positive effects shown, thus suggesting this EO is a promising protective agent in neurodegenerative diseases due to its anti-inflammatory properties.