Acetaminophen-induced hepatotoxicity in mice is dependent on Tlr9 and the Nalp3 inflammasome

• Published in: The Journal of clinical investigation 2009-02, Vol.119 (2), p.305-314
• Main Authors: Imaeda, Avlin B, Watanabe, Azuma, Sohail, Muhammad A, Mahmood, Shamail, Mohamadnejad, Mehdi, Sutterwala, Fayyaz S, Flavell, Richard A, Mehal, Wajahat Z
• Format: Article
• Language: English
• Subjects: Acetaminophen; Acetaminophen - toxicity; Analgesics; Analgesics, Non-Narcotic - toxicity; Animals; Apoptosis; Apoptosis - drug effects; Aspirin; Aspirin - pharmacology; Biomedical research; Care and treatment; Carrier Proteins - physiology; Caspase Inhibitors; Cell Line; Complications and side effects; Cyclooxygenase Inhibitors - pharmacology; Cytokines; DNA methylation; Dose-Response Relationship, Drug; Genetic aspects; Health aspects; Humans; Immunity, Innate; Inflammation; Inflammation - chemically induced; Interleukin-18 - biosynthesis; Interleukin-1beta - biosynthesis; Liver; Liver - drug effects; Liver - pathology; Liver failure; Mice; Mice, Inbred C57BL; Mortality; NLR Family, Pyrin Domain-Containing 3 Protein; Proteins; Risk factors; Signal Transduction; Toll-Like Receptor 9 - physiology
• ISSN: 0021-9738; 1558-8238
• DOI: 10.1172/jci35958

Hepatocyte death results in a sterile inflammatory response that amplifies the initial insult and increases overall tissue injury. One important example of this type of injury is acetaminophen-induced liver injury, in which the initial toxic injury is followed by innate immune activation. Using mice deficient in Tlr9 and the inflammasome components Nalp3 (NACHT, LRR, and pyrin domain-containing protein 3), ASC (apoptosis-associated speck-like protein containing a CARD), and caspase-1, we have identified a nonredundant role for Tlr9 and the Nalp3 inflammasome in acetaminophen-induced liver injury. We have shown that acetaminophen treatment results in hepatocyte death and that free DNA released from apoptotic hepatocytes activates Tlr9. This triggers a signaling cascade that increases transcription of the genes encoding pro-IL-1beta and pro-IL-18 in sinusoidal endothelial cells. By activating caspase-1, the enzyme responsible for generating mature IL-1beta and IL-18 from pro-IL-1beta and pro-IL-18, respectively, the Nalp3 inflammasome plays a crucial role in the second step of proinflammatory cytokine activation following acetaminophen-induced liver injury. Tlr9 antagonists and aspirin reduced mortality from acetaminophen hepatotoxicity. The protective effect of aspirin on acetaminophen-induced liver injury was due to downregulation of proinflammatory cytokines, rather than inhibition of platelet degranulation or COX-1 inhibition. In summary, we have identified a 2-signal requirement (Tlr9 and the Nalp3 inflammasome) for acetaminophen-induced hepatotoxicity and some potential therapeutic approaches.