Asatryan L1, Freire D1, Lazaro RG2, Tsukamoto H2 and Davies DL1
1School of Pharmacy, University of Southern California, Los Angeles, USA
2Research Center for Alcoholic Liver Disease and Pancreatitis and Cirrhosis, School of Medicine, University of Southern California, Los Angeles, USA
In the search for novel targets for chronic alcohol-induced inflammatory responses, we recently started exploring the therapeutic potential of ATP-gated purinergic P2X7 receptors (P2X7Rs). Despite the recognized important role in several neurodegenerative pathologies and inflammatory conditions, the role of P2X7Rs in ethanol-induced inflammation and organ damage is still unknown. Using a chronic ethanol exposure model of alcohol liver disease that combines intragastric (iG) ethanol feeding and high fat diet (Hybrid) in C57BL/6J mice, our recent work demonstrated an increased expression of P2X7Rs that paralleled neuroinflammatory changes in several ethanol-sensitive brain regions. These findings served the basis for the hypothesis that there is a functional link between P2X7Rs and chronic ethanol-induced inflammatory response leading to organ damage. To further test this hypothesis, in the present study we tested the effects of a P2X7R pharmacological inhibitor on inflammatory responses in brain and liver using a 4 week Hybrid treatment schedule. A specific P2X7R antagonist, A804598 (5 mg/kg), was applied 3 times a week through an iG catheter. After 4 weeks of vehicle or antagonist treatment, brain (hippocampus, amygdale) and liver tissues were isolated and tested for 1) changes in histological features and 2) gene expression of critical mediators linked to inflammation, apoptosis and signaling. The antagonist treatment abolished Hybrid-induced astrocyte proliferation observed as reduction in GFAP-positive cell number in hippocampal slices. Using custom Taqman gene expression plates and qRT-PCR, we found that the antagonist reversed the increases in inflammatory cytokines, chemokines and signaling molecules including IL1β, TNFα, CCL2, CXCR2, TLR3, Nlrp3, IL1R in both hippocampus and amygdala. In parallel, initial results demonstrated that there was a small decrease in the extent of liver steatosis with the antagonist. Ongoing work is testing changes in gene expression for inflammatory markers in liver tissues. Collectively, the findings support a role for P2X7Rs in chronic ethanol-induced inflammatory response and suggest that P2X7R antagonism may represent a novel therapy against ethanol-induced brain damage.
[Support: NIAAA/NIH AA017243, INIA West Pilot Project, Zumberge Individual Research Award (LA), A022448 (DD) and the USC School of Pharmacy]