title: Carbenoxolone blocks endotoxin-induced protein kinase R (PKR) activation and high mobility group box 1 (HMGB1) release.
abstract: The pathogen- and damage-associated molecular patterns (for example, bacterial endotoxin and adenosine 5'-triphosphate [ATP]) activate the double-stranded RNA-activated protein kinase R (PKR) to trigger the inflammasome-dependent high mobility group box 1 (HMGB1) release. Extracellular ATP contributes to the inflammasome activation through binding to the plasma membrane purinergic P2X7 receptor (P2X7R), triggering the opening of P2X7R channels and the pannexin-1 (panx-1) hemichannels permeable for larger molecules up to 900 daltons. It was previously unknown whether panx-1 channel blockers can abrogate lipopolysaccharide (LPS)-induced PKR activation and HMGB1 release in innate immune cells. Here we demonstrated that a major gancao (licorice) component (glycyrrhizin, or glycyrrhizic acid) derivative, carbenoxolone (CBX), dose dependently abrogated LPS-induced HMGB1 release in macrophage cultures with an estimated IC50 ≈ 5 μmol/L. In an animal model of polymicrobial sepsis (induced by cecal ligation and puncture [CLP]), repetitive CBX administration beginning 24 h after CLP led to a significant reduction of circulating and peritoneal HMGB1 levels, and promoted a significant increase in animal survival rates. As did P2X7R antagonists (for example, oxidized ATP, oATP), CBX also effectively attenuated LPS-induced P2X7R/panx-1 channel activation (as judged by Lucifer Yellow dye uptake) and PKR phosphorylation in primary peritoneal macrophages. Collectively, these results suggested that CBX blocks LPS-induced HMGB1 release possibly through impairing PKR activation, supporting the involvement of PKR in the regulation of HMGB1 release.
authors.affiliation: The Feinstein Institute for Medical Research, Manhasset, New York, USA. wll2@nshs.edu
authors.forename: Wei
authors.initials: W
authors.lastname: Li
authors.forename: Jianhua
authors.initials: J
authors.lastname: Li
authors.forename: Andrew E
authors.initials: AE
authors.lastname: Sama
authors.forename: Haichao
authors.initials: H
authors.lastname: Wang
mesh_terms: D000818:Animals; D002229:Carbenoxolone / Q000008:administration & dosage*; D002460:Cell Line; D002478:Cells, Cultured; D024243:HMGB1 Protein / Q000037:antagonists & inhibitors* / Q000378:metabolism; D008070:Lipopolysaccharides; D017737:Macrophages, Peritoneal / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D058486:Receptors, Purinergic P2X7 / Q000378:metabolism; D018805:Sepsis / Q000188:drug therapy* / Q000378:metabolism; D019892:eIF-2 Kinase / Q000037:antagonists & inhibitors* / Q000378:metabolism
chemical_list: D024243:HMGB1 Protein; C582808:HMGB1 protein, mouse; D008070:Lipopolysaccharides; D058486:Receptors, Purinergic P2X7; D019892:eIF-2 Kinase; D002229:Carbenoxolone