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.