High mobility group 1 B-box mediates activation of human endothelium

Treutiger CJ, Mullins GE, Johansson A-SM,Rouhiainen A, Rauvala HME, Erlandsson-Harris H,Andersson U, Yang H, Tracey KJ, Andersson J,Palmblad JEW (Center for Infectious Medicine;Center for Inflammation and HaematologyResearch; Karolinska Institute at HuddingeUniversity Hospital, Stockholm, Sweden, FinnishRed Cross Blood Transfusion Service; Institute ofBiotechnology, University of Helsinki; Helsinki,Finland, Center for Molecular Medicine, KarolinskaInstitutet, Stockholm, Sweden and North Shore-LongIsland Jewish Research Institute, NY, USA). Highmobility group 1 B-box mediates activation of humanendothelium. J Intern Med 2003; 254: 375–385.Objectives. Severe sepsis and septic shock is aconsequence of a generalized inflammatory systemicresponse because of an invasive infection that mayresult in acute organ dysfunction. Mortality is highdespite access to modern intensive care units. Thenuclear DNA binding protein high mobility group 1(HMGB1) protein has recently been suggested to actas a late mediator of septic shock via its function asa macrophage-derived pro-inflammatory cytokine(J Exp Med 2000; 192: 565, Science 1999; 285:248). We investigated the pro-inflammatoryactivities of the A-box and the B-box of HMGB1 onhuman umbilical venular endothelial cells (HUVEC).Design. The HUVEC obtained from healthy donorswere used for experiments. Recombinant humanfull-length HMGB1, A-box and B-box were cloned bypolymerase chain reaction (PCR) amplification froma human brain quick-clone cDNA. The activation ofHUVEC was studied regarding (i) upregulation ofadhesion molecules, (ii) the release of cytokines andchemokines, (iii) the adhesion of neutrophils toHUVEC, (iv) the activation of signalling transductionpathways and (v) the involvement of the receptor foradvanced glycation end-products (RAGE).Results. The full-length protein and the B-box ofHMGB1 dose-dependently activate HUVEC toupregulate adhesion molecules such as ICAM-1,VCAM-1 and E-selectin and to release IL-8 andG-CSF. The activation of HUVEC could be inhibitedto 50% by antibodies directed towards the RAGE.HMGB1-mediated HUVEC stimulation resulted inphosphorylation of the ELK-1 signal transductionprotein and a nuclear translocation of p65 plusc-Rel, suggesting that HMGB1 signalling is regulatedin endothelial cells through NF-jB.Conclusions. The HMGB1 acts as a potent pro-inflammatory cytokine on HUVEC and the activity ismainly mediated through the B-box of the protein.HMGB1 may be a key factor mediating part of thepro-inflammatory response occurring in septic shockand severe inflammation.Keywords: cytokine, endotoxin, high mobilitygroup 1, human umbilical venular endothelialcells, inflammation.