Role of IL-6 in an IL-10 and IL-4 double knockout mouse model uniquely susceptible to acetaminophen-induced liver injury

Drug-induced hepatitis remains a challenging problem for drug development and safety because of the lack of animal models. In the current work, we discovered a unique interaction that makes mice deficient in both IL-10 and IL-4 (IL-10/4(-/-)) highly sensitive to the hepatotoxic effects of acetaminophen (APAP). Male C57Bl/6 wild type (WT) and mice deficient in one or more cytokines were treated with 120 mg/kg APAP. Within 24 h after WT, IL-10(-/-), IL-4(-/-), or IL-10/4(-/-) mice were administered APAP, 75% of the IL-10/4(-/-) mice died of massive hepatic injury while all other genotypes were resistant to liver toxicity at this dose of APAP. The unique susceptibility of IL-10/4(-/-) mice was associated with reduced levels of liver glutathione and remarkably high serum levels of IL-6 and several proinflammatory factors including TNF-alpha, IFN-gamma, macrophage inflammatory protein-1 alpha (MIP-1 alpha), monocyte chemoattractant protein-1 (MCP-1), macrophage inflammatory protein-2 (MIP-2), and osteopontin (OPN) as well as nitric oxide (NO). IL-6 appeared to have a causal role in controlling the unique susceptibility of IL-10/4(-/-) mice to APAP-induced liver disease (AILD) because IL-6 neutralizing antibody reversed the high sensitivity of these mice to AILD. Moreover, IL-10/4/6(-/-) mice were also resistant to the enhanced susceptibility to AILD and expressed relatively low levels of most proinflammatory factor genes that were elevated in the IL-10/4(-/-) mice. In conclusion, liver homeostasis following AILD appears to be highly dependent on the activities of both IL-10 and IL-4, which together help prevent overexpression of IL-6 and other potential hepatotoxic factors.