Pannexin1 channel inhibition attenuates neutrophil recruitment upon acetaminophen-induced hepatotoxicity

Background and aims: Pannexins constitute a relative new family of transmembrane proteins that form channels linking the cytoplasmic compartment with the extracellular environ- ment. Recent research showed that pannexin1 channel inhibi- tion alleviates acetaminophen-induced hepatotoxicity in mice. However, the mechanisms underlying this observation are not entirely clear. On the other hand, monocyte migration has been reported to be mediated in part by pannexin1-depentent ade- nosine triphosphate release in vitro and fine-tuned chemotactic responses of neutrophils seem to require pannexin1 signaling. To check if this also holds true in vivo, in casu in a model of acetaminophen-induced hepatotoxicity, leukocyte recruitment was monitored following inhibition of pannexin1 channel opening. Methods: C57BL/6J mice were overdosed with acet- aminophen followed by treatment with the pannexin1 channel inhibitor 10Panx1 after 1.5 hours. Sampling was performed 6 and 24 hours after acetaminophen administration. In addition to the evaluation of clinically relevant read-outs, such as serum aminotransaminase and cytokine levels, hepatic quantities of inflammatory monocytes (CD45+CD11bhiLy6ChiF4/80lo cells), neutrophils (CD45+CD11bhiLy6G+ cells) and Kupffer cells (CD45+Ly6G-F4/80hiCD11bint cells) were measured using flow cytometric analysis. Tumor necrosis factor α content of these particular cell populations was assessed in parallel. Results: Compared to untreated animals, acetaminophen-overdosed mice showed less Kupffer cells, but increased numbers of liver neutrophils and monocytes. Upon blockage of pannexin1 channels, a significantly reduced amount of neutrophils were recruited to the liver, while no differences were observed in the number of monocytes and Kupffer cells. Concomitantly, diminished tumor necrosis factor α production by monocytes was measured following pannexin1 channel inhibition. Conclusion: These results suggest the involvement of pannexin1 channels in neutrophil recruitment and tumor necrosis factor α production by monocytes during acetaminophen-induced hepatotoxicity in mice.