title: Interaction between uric acid and HMGB1 translocation and release from endothelial cells.
abstract: We aimed to investigate the potential relationship between alarmins [acting via Toll-like receptor-4 (TLR4)], uric acid (UA), and high-mobility group box-1 protein (HMGB1) during acute kidney injury. UA, which is significantly increased in the circulation following renal ischemia-reperfusion injury (IRI), was used both in vitro and in vivo as an early response-signaling molecule to determine its ability to induce the secretion of HMGB1 from endothelial cells. Treatment of human umbilical vein endothelial cells (HUVEC) with UA resulted in increased HMGB1 mRNA expression, acetylation of nuclear HMGB1, and its subsequent nuclear-cytoplasmic translocation and release into the circulation, as determined by Western blotting and immunofluorescence. Treatment of HUVEC with UA and a calcium mobilization inhibitor (TMB-8) or a MEK/Erk pathway inhibitor (U0126) prevented translocation of HMGB1 from the nucleus, resulting in reduced cytoplasmic and circulating levels of HMGB1. Once released, HMGB1 in autocrine fashion promoted further HMGB1 release while also stimulating NF-κB activity and increased angiopoietin-2 expression and protein release. Transfection of HUVEC with TLR4 small interfering (si) RNA reduced HMGB1 levels during UA and HMGB1 treatment. In summary, UA after IRI mediates the acetylation and release of HMGB1 from endothelial cells by mechanisms that involve calcium mobilization, the MEK/Erk pathway, and activation of TLR4. Once released, HMGB1 promotes its own further cellular release while acting as an autocrine and paracrine to activate both proinflammatory and proreparative mediators.
authors.affiliation: Department of Medicine, New York Medical College, Valhalla, NY 10595, USA.
authors.forename: May M
authors.initials: MM
authors.lastname: Rabadi
authors.forename: Mei-Chuan
authors.initials: MC
authors.lastname: Kuo
authors.forename: Tammer
authors.initials: T
authors.lastname: Ghaly
authors.forename: Seham M
authors.initials: SM
authors.lastname: Rabadi
authors.forename: Mia
authors.initials: M
authors.lastname: Weber
authors.forename: Michael S
authors.initials: MS
authors.lastname: Goligorsky
authors.forename: Brian B
authors.initials: BB
authors.lastname: Ratliff
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D042783:Endothelial Cells / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D024243:HMGB1 Protein / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D020930:MAP Kinase Kinase Kinases / Q000235:genetics / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000502:physiology; D008297:Male; D051379:Mice; D021381:Protein Transport; D034622:RNA Interference; D034741:RNA, Small Interfering; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism; D014527:Uric Acid / Q000494:pharmacology*
chemical_list: D024243:HMGB1 Protein; D034741:RNA, Small Interfering; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; D014527:Uric Acid; D048049:Extracellular Signal-Regulated MAP Kinases; D020930:MAP Kinase Kinase Kinases; D002118:Calcium