Acetaminophen (APAP) toxicity is the most common cause of acute liver failure in industrialized countries. Understanding the mechanisms of APAP-induced liver injury as well as other forms of sterile liver injury is critical to improve the care of patients. Recent studies demonstrate that danger signaling and inflammasome activation play a role in APAP-induced injury. The aim of these investigations was to test the hypothesis that benzyl alcohol (BA) is a therapeutic agent that protects against APAP-induced liver injury by modulation of danger signaling. APAP-induced liver injury was dependent, in part, on Toll-like receptor (TLR)9 and receptor for advanced glycation endproducts (RAGE) signaling. BA limited liver injury over a dose range of 135-540 μg/g body weight or when delivered as a pre-, concurrent, or post-APAP therapeutic. Furthermore, BA abrogated APAP-induced cytokines and chemokines as well as high-mobility group box 1 release. Moreover, BA prevented APAP-induced inflammasome signaling as determined by interleukin (IL)-1β, IL-18, and caspase-1 cleavage in liver tissues. Interestingly, the protective effects of BA on limiting liver injury and inflammasome activation were dependent on TLR4 signaling, but not TLR2 or CD14. Cell-type-specific knockouts of TLR4 were utilized to further determine the protective mechanisms of BA. These studies found that TLR4 expression specifically in myeloid cells (LyzCre-tlr4-/-) were necessary for the protective effects of BA.
Conclusion: BA protects against APAP-induced acute liver injury and reduced inflammasome activation in a TLR4-dependent manner. BA may prove to be a useful adjunct in the treatment of APAP and other forms of sterile liver injury.
© 2014 by the American Association for the Study of Liver Diseases.