Natural compounds for neuroprotection: from molecular mechanisms of neuroinflammation to in vivo evidence in parkinson’s disease models

Neurodegenerative diseases (NDDs) are multifactorial disorders characterized by the progressive loss of neuronal integrity and function. Despite decades of research, no disease-modifying therapies are currently available. Among the mechanisms contributing to their pathogenesis, neuroinflammation and oxidative stress play a pivotal role, promoting neuronal damage and disease progression. Natural compounds have attracted increasing attention for their pleiotropic multi-target activities, making them promising candidates to counteract neurodegeneration. This PhD project aimed to identify and characterize natural molecules with neuroprotective and anti-neuroinflammatory properties, focusing on their mechanisms of action both in vitro and in vivo. First, essential oils (EOs) and aqueous residues (ARs) from three industrial hemp (Cannabis sativa L.) varieties were evaluated in LPS-activated BV-2 microglial cells. The EO from the Gorilla Glue variety showed the strongest anti-inflammatory and antioxidant effects, largely attributed to its sesquiterpene components, particularly α-humulene, (E)-caryophyllene, and caryophyllene oxide, acting through complementary mechanisms. Subsequently, the study explored the phenolic secoiridoid oleocanthal (OL), a major constituent of extra virgin olive oil, and its oxidized derivative oleocanthalic acid (OA). OL exhibited potent anti-inflammatory effects in microglial cells, mainly driven by the modulation of the TLR4-CD14 receptor complex and inhibition of p38 MAPK signaling. Proteomic analysis confirmed the selectivity and multi-target nature of its action. This anti-neuroinflammatory activity was lost upon oxidation to OA. In vivo, OL displayed neuroprotective properties in Drosophila models of Parkinson’s disease by counteracting dopaminergic neuron loss, opening the way for further investigation. Finally, characterization of LPS-induced oxidative responses in BV-2 cells revealed a dynamic interplay between inflammation and the antioxidant defenses, which respond differently depending on the pro-inflammatory stimulus intensity. Collectively, these findings highlight the therapeutic potential of natural compounds, particularly OL, as multi-target agents capable of modulating neuroinflammation, oxidative stress, and neuronal survival, offering new perspectives for NDD prevention and treatment.