Analysis of endocannabinoid receptors and enzymes in the post-mortem motor cortex and spinal cord of amyotrophic lateral sclerosis patients.

OBJECTIVE:

We have investigated the endocannabinoid system in the motor cortex of motor neuron disease (MND) patients.

METHODS:

Post-mortem samples from MND patients and controls were used for immunostaining and/or Western blotting analysis of endocannabinoid elements.

RESULTS:

We did not find any evidence of neuronal losses in the motor cortex of MND patients, but elevations in glial markers Iba-1 and GFAP were evident. We found no changes in FAAH and MAGL enzymes and in the CB₁ receptor, which correlated with the lack of cortical neuron death. By contrast, the Western blotting analysis of CB₂ receptors proved an increase in the motor cortex corroborated by immunostaining, correlating with the elevated gliosis in these patients. Double-labeling analyses revealed that this elevated CB₂ receptor immunostaining was located in GFAP-labelled astroglial cells. However, we also found CB₂ receptor labeling in cortical neurons confirmed with double immunofluorescence with the neuronal marker MAP-2. This was also found in the spinal cord, using double-labeling with the spinal motor neuron marker choline-acetyl transferase. This happened in both patients and controls, despite these neurons experienced an important degeneration in patients reflected in reduced Nissl staining, TDP-43 immunostaining and CB₁ receptor levels measured by Western blotting.

CONCLUSION:

We have confirmed that CB₂ receptors are elevated in the motor cortex of MND patients associated with the reactive gliosis. This phenomenon is previous to neuronal losses. We also found CB₂ receptors in cortical and spinal motor neurons. These observations support that targeting this receptor may serve for developing neuroprotective therapies in MNDs.