Involvement of the endocannabinoid system in the inhibition of Sindbis virus replication: a preliminary study

BACKGROUND: Sindbis virus (Alphaviridae) is a plus-strand RNA virus that is dependent on the host cell for replication. Cannabinoid (CB) receptors are found on most human cells, including virally infected cells. Activation of cannabinoid receptors has been shown to alter normal cellular physiology. This study aimed to assess how agonist (ACEA) or antagonists/inverse agonist (AM251) of the cannabinoid receptors would alter the cellular environment and impact Sindbis virus replication. METHODS: Human hepatoma (Huh7) cells were used as our model for viral replication. Cells were infected with Sindbis virus (SINV) and then treated with CB agonist (ACEA) (10 μM) or antagonist/inverse agonist (AM-251) (10 μM) and virus replication was monitored. A double subgenomic Sindbis virus containing a green fluorescent protein (GFP) reporter gene inserted into a 3′ subgenomic promoter was utilized for these assays to quickly measure viral replication. GFP fluorescent cells were analyzed using flow cytometry to measure the percentage of cells expressing the viral reporter and also quantify the levels of GFP fluorescence. RESULT: Treatment of SINV-infected Huh7 cells with CB1 receptor antagonist/inverse agonist (AM251, 10 μM) resulted in a significant decrease in viral replication, while infected cells treated with a CB1 receptor agonist (ACEA, 10 μM) resulted in a significant increase of viral infection. The data indicates that activation of CB1 receptor by cannabinoids significantly influences the ability of Sindbis virus to replicate in the host cell. CONCLUSION: Blocking CB1 receptor activity with 10 μM AM251 reduced viral replication, but activating the CB1 receptor with 10 μM ACEA resulted in an increase in viral infection. These results indicate cannabinoids may significantly impact a virus replicating in human liver cells. Future confirmation with other viruses and cell lines will be performed to better understand the impact of cannabinoids on viral infections.