Boosting 2-AG (but Not Anandamide) Protected Dopamine Neurons in a Mouse Model of Parkinson's Disease | Research

The takeaway

In a chronic mouse model of Parkinson's disease, inhibiting MAGL (which raises 2-AG levels) reduced dopamine loss and increased protective growth factor expression, while inhibiting FAAH (which raises anandamide) did not.

Readers interested in the endocannabinoid system's role in neurodegenerative disease.

MAGL inhibition reduced dopamine depletion and increased neuroprotective GDNF expression

What the researchers found

Researchers tested two strategies for boosting endocannabinoid levels in a chronic Parkinson's disease mouse model. The MAGL inhibitor KML29, which elevates 2-AG, significantly reduced striatal dopamine depletion caused by the neurotoxin MPTP. The FAAH inhibitor PF-3845, which elevates anandamide, did not.

KML29 also increased expression of GDNF (glial cell line-derived neurotrophic factor), a protein that supports dopamine neuron survival. In contrast, PF-3845 had no effect on neurotrophic factor expression but did decrease CB2 receptor expression that had been elevated by the neurotoxin.

Follow-up experiments in cultured microglia showed that 2-AG directly increased GDNF expression, suggesting that microglia (the brain's immune cells) may mediate the neuroprotective effects of MAGL inhibition.

Why it matters

Parkinson's disease involves the progressive loss of dopamine neurons, and current treatments manage symptoms without slowing disease progression. This study suggests that the two main endocannabinoids, 2-AG and anandamide, have fundamentally different neuroprotective potential, with 2-AG appearing to actively protect dopamine neurons through microglia-mediated growth factor release.

The numbers in context

Both inhibitors dosed at 10 mg/kg. KML29 (MAGL inhibitor) significantly attenuated dopamine depletion. PF-3845 (FAAH inhibitor) did not. KML29 increased GDNF expression. 2-AG increased GDNF expression in cultured microglia. BDNF expression was not affected by either treatment.

How the study worked

Mice received the neurotoxin MPTP/probenecid chronically to model Parkinson's disease. They were simultaneously treated with either the MAGL inhibitor KML29 (10 mg/kg) or the FAAH inhibitor PF-3845 (10 mg/kg). Striatal dopamine levels, endocannabinoid levels, and gene expression of neurotrophic factors and cannabinoid receptors were measured. Primary mouse microglia cultures were used for mechanistic follow-up.

What this study cannot tell us

This was an animal study using a chemical model of Parkinson's disease (MPTP), which does not fully replicate the human disease. The MAGL inhibitor KML29 was given alongside the neurotoxin rather than after disease onset, so this was more prevention than treatment. Long-term effects and behavioral outcomes were not assessed.

How to read the evidence

Preliminary evidence from a single animal study. Neuroprotective effects of MAGL inhibition in humans with Parkinson's disease have not been tested.

When this study was published

Published in 2017. Preclinical research on endocannabinoid-based neuroprotection.

The bigger picture

The endocannabinoid system has long been considered a potential therapeutic target for neurodegenerative diseases. This study clarifies that not all endocannabinoid-boosting strategies are equal: the 2-AG pathway through MAGL inhibition appears more promising for Parkinson's disease than the anandamide pathway through FAAH inhibition, potentially because 2-AG engages microglia to produce neuroprotective factors.

Questions still open

Would MAGL inhibition still be protective if started after dopamine loss has already begun? Could MAGL inhibitors be developed as disease-modifying treatments for Parkinson's? Why do 2-AG and anandamide have such different neuroprotective profiles despite both being endocannabinoids?

Common questions

Does this mean cannabis could help with Parkinson's disease?

This study looked at a very specific pharmacological approach (selectively boosting 2-AG levels), not cannabis itself. Cannabis contains THC and CBD, which act differently from selective MAGL inhibitors. The study does suggest the endocannabinoid system is relevant to Parkinson's, but using cannabis would not replicate these results.

What is the difference between 2-AG and anandamide?

Both are endocannabinoids (compounds the body naturally produces that act on cannabinoid receptors), but they are produced and broken down by different enzymes and appear to have different biological roles. This study found that 2-AG was neuroprotective in a Parkinson's model while anandamide was not.

Read the original research

Contrasting effects of selective MAGL and FAAH inhibition on dopamine depletion and GDNF expression in a chronic MPTP mouse model of Parkinson's disease.

Neurochemistry international, 110, 14-24

View on PubMed ↗Publisher’s paper ↗

Citation

Pasquarelli, Noemi; Porazik, Christoph; Bayer, Hanna; Buck, Eva; Schildknecht, Stefan; Weydt, Patrick; Witting, Anke; Ferger, Boris. (2017). Contrasting effects of selective MAGL and FAAH inhibition on dopamine depletion and GDNF expression in a chronic MPTP mouse model of Parkinson's disease.. Neurochemistry international, 110, 14-24. https://doi.org/10.1016/j.neuint.2017.08.003