Cannabinoids increase type 1 cannabinoid receptor expression in a cell culture model of striatal neurons: Implications for Huntington's disease

The type 1 cannabinoid receptor (CB₁) is a G protein-coupled receptor that is expressed at high levels in the striatum. Activation of CB ₁ increases expression of neuronal trophic factors and inhibits neurotransmitter release from GABA-ergic striatal neurons. CB1 mRNA levels can be elevated by treatment with cannabinoids in non-neuronal cells. We wanted to determine whether cannabinoid treatment could induce CB1 expression in a cell culture model of striatal neurons and, if possible, determine the molecular mechanism by which this occurred. We found that treatment of STHdh^7/7 cells with the cannabinoids ACEA, mAEA, and AEA produced a CB1receptor- dependent increase in CB1 promoter activity, mRNA, and protein expression. This response was Akt- and NF-kB-dependent. Because decreased CB₁ expression is thought to contribute to the pathogenesis of Huntington's disease (HD), we wanted to determine whether cannabinoids could increase CB1 expression in STHdh^7/111 and ^111/111 cells expressing the mutant huntingtin protein. We observed that cannabinoid treatment increased CB1 mRNA levels approximately 10-fold in STHdh^7/111 and ^111/111 cells, compared to vehicle treatment. Importantly, cannabinoid treatment improved ATP production, increased the expression of the trophic factor BDNF-2, and the mitochondrial regulator PGC1α, and reduced spontaneous GABA release, in HD cells. Therefore, cannabinoid-mediated increases in CB1 levels could reduce the severity of some molecular pathologies observed in HD.