title: Human CRP defends against the toxicity of circulating histones.
abstract: C-reactive protein (CRP) is an acute-phase protein that plays an important defensive role in innate immunity against bacterial infection, but it is also upregulated in many noninfectious diseases. The generic function of this highly conserved molecule in diseases that range from infection, inflammation, trauma, and malignancy is not well understood. In this article, we demonstrate that CRP defends the human body against the toxicity of histones released into the circulation after extensive cell death. In vitro, CRP significantly alleviates histone-induced endothelial cell damage, permeability increase, and platelet aggregation. In vivo, CRP rescues mice challenged with lethal doses of histones by inhibiting endothelial damage, vascular permeability, and coagulation activation, as reflected by significant reductions in lung edema, hemorrhage, and thrombosis. In patients, elevation of CRP significantly increases the capacity to neutralize extracellular histones in the circulation. We have also confirmed that CRP interacts with individual histones in vitro and forms CRP-histone complexes in serum from patients with both elevated CRP and histones. CRP is able to compete with phospholipid-containing liposomes for the binding to histones. This explains how CRP prevents histones from integrating into cell membranes, which would otherwise induce calcium influx as the major mechanism of cytotoxicity caused by extracellular histones. Because histone elevation occurs in the acute phase of numerous critical illnesses associated with extensive cell death, CRP detoxification of circulating histones would be a generic host defense mechanism in humans.
authors.affiliation: Department of Blood Sciences, Royal Liverpool and Broadgreen University Hospitals National Health Service Trust, Liverpool L7 8XP, United Kingdom.
authors.forename: Simon T
authors.initials: ST
authors.lastname: Abrams
authors.forename: Nan
authors.initials: N
authors.lastname: Zhang
authors.forename: Caroline
authors.initials: C
authors.lastname: Dart
authors.forename: Susan Siyu
authors.initials: SS
authors.lastname: Wang
authors.forename: Jecko
authors.initials: J
authors.lastname: Thachil
authors.forename: Yunyan
authors.initials: Y
authors.lastname: Guan
authors.forename: Guozheng
authors.initials: G
authors.lastname: Wang
authors.forename: Cheng-Hock
authors.initials: CH
authors.lastname: Toh
mesh_terms: D000818:Animals; D002097:C-Reactive Protein / Q000378:metabolism* / Q000633:toxicity*; D002199:Capillary Permeability / Q000187:drug effects; D002851:Chromatography, High Pressure Liquid; D006657:Histones / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018408:Patch-Clamp Techniques
chemical_list: D006657:Histones; D002097:C-Reactive Protein