Up-regulation of CB2 receptors in reactive astrocytes in canine degenerative myelopathy, a disease model of amyotrophic lateral sclerosis.

Targeting the CB2 receptor afforded neuroprotection in SOD1G93A mutant mice, a model of amyotrophic lateral sclerosis (ALS). The neuroprotective effects of CB2 receptors were facilitated by their up-regulation in the spinal cord in SOD1G93A mutant mice. Herein, we have investigated whether a similar CB2 receptor up-regulation, as well as parallel changes in other endocannabinoid elements, are evident in the spinal cord of dogs with degenerative myelopathy (DM), caused from mutations in the superoxide dismutase 1 gene (SOD1). We used well-characterized post-mortem spinal cords from unaffected and DM-affected dogs. Tissues were used first to confirm the loss of motor neurons using Nissl staining, which was accompanied by glial reactivity (elevated GFAP and Iba-1 immunoreactivity). Next, we investigated possible differences in the expression of endocannabinoid genes measured by qPCR between DM-affected and control dogs. We found no changes in the CB1 receptor (also found with CB1 receptor immunostaining) as well as in NAPE-PLD, DAGL, FAAH and MAGL enzymes. In contrast, CB2 receptor levels were significantly elevated in DM-affected dogs determined by qPCR and Western-blotting, results reconfirmed in the grey matter using CB2 receptor immunostaining. Using double-labelling immunofluorescence, CB2 receptor immunolabelling co-localized with GFAP but not Iba-1, indicating up-regulation of CB2receptors on astrocytes in DM-affected dogs. In summary, our results demonstrated a marked up-regulation of CB2 receptors occurring in the spinal cord in canine DM, which was concentrated in activated astrocytes. Such receptors may be used as a potential target to enhance the neuroprotective effects exerted by these glial cells.

© 2017. Published by The Company of Biologists Ltd.