Histidine-Rich Glycoprotein Inhibits High Mobility Group Box 1-Mediated Pathways in Vascular Endothelial Cells

Abstract

Background: High mobility group box-1 (HMGB1) protein has been postulated to play a pathogenic role in severe sepsis. Histidine-rich glycoprotein (HRG) was proposed as a new biomarker to predict the outcome of sepsis patients and demonstrated to improve survival rate and relieve symptom of septic mice. However, its effect on HMGB1 signaling has never been investigated. Our research focuses on the effects of HRG on HMGB1 mobilization and HMGB1-mediated pathway in endothelial cells and the involvement of specific receptors for HRG. Methods: A variety of biochemical assays were applied to explore the effects of HRG on HMGB1 release and HMGB1-mediated signal pathway in EA.hy 926 endothelial cells. The receptor for HRG was identified using co-immunoprecipitation experiments and surface plasmon resonance analysis. Findings: HRG potently inhibited the LPS-induced translocation and release of HMGB1 and effectively suppressed rHMGB1-induced ICAM-1 and VCAM-1 expression, inflammatory cytokines secretion and NF-κB activation in EA.hy 926 endothelial cells. HRG also inhibited HMGB1 release and HMGB1-mediated inflammatory responses in LPS-injected mice. Moreover, we first clarified that these protective effects of HRG on endothelial cells were mediated through C-type lectin domain family 1 member A (CLEC-1A) receptor. Interpretation: The present findings strongly support the supplementary therapy with HRG in sepsis and will provide the new insights into the understanding of the functional role of CLEC1A in the maintenance of vascular endothelial cells. Funding Statement: This research was supported by grants from AMED (no. 18im0210109h0002) and from the Secom Science and Technology Foundation to M.N., a Grant-in-Aid for Scientific Research (no.15H04686 to M.N.), a Grant-in-Aid for Young Scientists (no. 17K15580 to H.W.), and a Grant-in-Aid for Scientific Research (no. 16K08232 to K.T.) from the Japan Society for the Promotion of Science (JSPS). The author S.G. was supported by the scholarship from China Scholarship Council. Declaration of Interests: The authors declare no conflicts of interest. Ethics Approval Statement: Human neutrophils were isolated from peripheral blood obtained from healthy volunteers in accordance with ethics approval and guidelines of Okayama University and the Declaration of Helsinki. All animal experiments were approved by the university's committee and performed according to the guidelines of Okayama University on animal experiments.