Category: Clinical Pharmacology
Purpose: : In the last 10 years, CB2 receptor has been emerged as a promising therapeutic target for treating multiple neurodegenerative disease (NDD) conditions such as Alzheimer’s (AD), Parkinson’s (PD), HIV and multiple sclerosis. CB2 receptors are predominantly expressed in the immune cells such as microglia, natural killer cells, B cells and macrophages with low or no detectible level in neurons in the central nervous system. During neuroinflammation, CB2 receptor expression is upregulated in microglial cells thus modulating the activated microglia can be a potential therapeutic approach for treating neurodegenerative diseases. When microglia cells are activated, the phenotype is changed from surveillance (M0) phenotype to an activated pro-inflammatory phenotype (M1) which contributes to increased inflammation and progression of neurodegenerative diseases. Selective CB2 inverse agonists can serve as novel anti-inflammatory therapeutics by switching the microglial cell neurotoxic M1 phenotype to an M2 pro-healing neuroprotective effect phenotype which is the key step in modulating the neuroinflammatory process
Methods: Two microglial cells were used, C8-B4 murine and SV40 immortalized human microglia cells for on cell polarization assay. Cells were treated with LPS (an M1 stimulus) for one hour. After 1 hour, compounds 231 and 97 were added and the cells were incubated for 24 hours. Expression of cell surface markers CD16/32, CD68 (M1 associated) and CD204, CD206 (M2 associated) were measured. For the molecular pathway study, the SV40 cells were treated with LPS for 30 minutes prior to drug treatment. Changes in signaling protein phosphorylation were measured at 45, 60, 90, 150, 210 and 360 minutes post stimulation and drug treatment.
Results: Compounds 231 and 97 triggered a shift in murine and human microglia polarization from a pro-inflammatory M1 to an anti-inflammatory M2 phenotype after 24 hours. The M1 markers were significantly decreased and M2 markers significantly increased compared to LPS after drug treatment. In addition, 97 and 231 increased JNK, c-JUN, CREB and p38 levels and decreased ERK1/2 and NFkB representing a unique anti-inflammatory mechanism of CB2 inverse agonists in microglia. These data suggest that CB2 inverse agonists can serve as a novel class of compounds for treating neuroinflammation in central nervous system diseases.
Conclusion: Cannabinoid receptor 2 inverse agonists can modulate the neuroinflammation by polarizing the microglia from M1 ( pro-inflammatory) to M2 (Anti-inflammatory) phenotype.