Abstract
Mice lacking the IL-1R-associated kinase 4 (IRAK4) are completely resistant to LPS-induced endotoxic disorder or the TLR9 agonist CpG DNA plus d-galactosamine-induced acute liver injury (ALI), whereas wild-type strains succumb. However, translational drugs against sepsis or ALI remain elusive. Lonicerae flos extract is undergoing the clinical trial phase I in LPS-injected healthy human volunteers for sepsis treatment. In the current study, chlorogenic acid (CGA), a major anti-inflammatory constituent of lonicerae flos extract, rescued endotoxic mortality of LPS-intoxicated C57BL/6 mice, as well as ameliorated ALI of LPS/d-galactosamine-challenged C57BL/6 mice. As a mechanism, CGA inhibited various TLR agonist-, IL-1α-, or high-mobility group box-1-stimulated autophosphorylation (activation) of IRAK4 in peritoneal macrophages from C57BL/6 or C3H/HeJ mice via directly affecting the kinase activity of IRAK4, a proximal signal transducer in the MyD88-mediated innate immunity that enhances transcriptional activity of NF-κB or AP-1. CGA consequently attenuated protein or mRNA levels of NF-κB/AP-1 target genes encoding TNF-α, IL-1α, IL-6, and high-mobility group box-1 in vivo under endotoxemia or ALI. Finally, this study suggests IRAK4 as a molecular target of CGA in the treatment of innate immunity-related shock and organ dysfunction following insult of various TLR pathogens from bacteria and viruses.