The Inhibition of Fatty Acid Amide Hydrolase-4 Affords Neuroprotection in a Toxic Model Induced by 6-Hydroxydopamine in Caenorhabditis elegans Nematodes.

Parkinson's disease (PD) is a neurodegenerative disorder characterized by progressive loss of dopaminergic neurons. Drugs modulating the endocannabinoid system (ECS) emerge as promising tools for reducing symptomatology and/or progression of this disease. Here, the protective potential of ECS regulation against 6-hydroxydopamine (6-OHDA)-induced neuronal damage was evaluated in the nematode, Caenorhabditis elegans. First, the effect of the endocannabinoid anandamide (AEA; 1 to 100 µM) was tested in adult nematodes. As this eCB had no protective effects on the 6-OHDA-induced increased neurodegeneration, an alternative treatment was tested by exposing worms to JZL184, an inhibitor of the enzyme fatty acid amide hydrolase-4 (FAAH-4). In contrast to AEA, this compound readily induced a protective effect in dopaminergic neurons exposed to 6-OHDA, also increasing worm survival. JZL184 also improved the ability of nematodes to detect food, a behavioral task associated with an intact dopaminergic system. The protective activity induced by FAAH-4 inhibition was also confirmed using the mutant OD3609 strain, a faah-4 gene knockout nematode. This strain was more resistant to 6-OHDA compared to the wild-type N2 strain, in parameters of survival and food seeking behavior. In the CL2166 strain, pretreatment with JZL184 increased the expression of the gst-4 gene at 3 and 24 h following the exposure to 6-OHDA, indicating an antioxidant response. The effects of JZL184 (50 µM) and the endocannabinoid 2-arachidonoylglycerol (2-AG; 1-100 µM) were evaluated on 6-OHDA-induced reactive oxygen species (ROS) generation. This was based on the hypothesis that the protective effects observed following FAAH-4 inhibition may be mediated by 2-AG. Both JZL-184 and 2-AG attenuated ROS formation 24 h after 6-OHDA exposure. Altogether, these results suggest that the use of the pharmacological inhibitor of eCB degradation is effective in affording neuroprotection, also indicating that the activation of antioxidant responses mediated by the ECS is a process conserved through the evolution in the nematode.