title: Alginate microsphere compositions dictate different mechanisms of complement activation with consequences for cytokine release and leukocyte activation.
abstract: The inflammatory potential of 12 types of alginate-based microspheres was assessed in a human whole blood model. The inflammatory potential could be categorized from low to high based on the four main alginate microsphere types; alginate microbeads, liquefied core poly-l-ornithine (PLO)-containing microcapsules, liquefied core poly-l-lysine (PLL)-containing microcapsules, and solid core PLL-containing microcapsules. No complement or inflammatory cytokine activation was detected for the Ca/Ba alginate microbeads. Liquefied core PLO- and PLL-containing microcapsules induced significant fluid phase complement activation (TCC), but with low complement surface deposition (anti-C3c), and a low proinflammatory cytokine secretion, with exception of an elevated MCP-1(CCL2) secretion. The solid core PLL-containing microcapsules generated lower TCC but a marked complement surface deposition and significant induction of the proinflammatory cytokines interleukin (IL-1)β, TNF, IL-6, the chemokines IL-8 (CXCL8), and MIP-1α (CCL3) and MCP-1(CCL2). Inhibition with compstatin (C3 inhibitor) completely abolished complement surface deposition, leukocyte adhesion and the proinflammatory cytokines. The C5 inhibitions partly lead to a reduction of the proinflammatory cytokines. The leukocyte adhesion was abolished by inhibitory antibodies against CD18 and partly reduced by CD11b, but not by CD11c. Anti-CD18 significantly reduced the (IL-1)β, TNF, IL-6 and MIP-1α and anti-CD11b significantly reduced the IL-6 and VEGF secretion. MCP-1 was strongly activated by anti-CD18 and anti-CD11b. In conclusion the initial proinflammatory cytokine responses are driven by the microspheres potential to trigger complement C3 (C3b/iC3b) deposition, leukocyte activation and binding through complement receptor CR3 (CD11b/CD18). MCP-1 is one exception dependent on the fluid phase complement activation mediated through CR3.
authors.affiliation: Centre of Molecular Inflammation Research, and Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, Trondheim, Norway.
authors.forename: Pontus
authors.initials: P
authors.lastname: Ørning
authors.affiliation: Centre of Molecular Inflammation Research, and Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, Trondheim, Norway.
authors.forename: Kine Samset
authors.initials: KS
authors.lastname: Hoem
authors.affiliation: Centre of Molecular Inflammation Research, and Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, Trondheim, Norway; Department of Biotechnology, Norwegian University of Science and Technology, Trondheim, Norway.
authors.forename: Abba Elizabeth
authors.initials: AE
authors.lastname: Coron
authors.affiliation: Department of Biotechnology, Norwegian University of Science and Technology, Trondheim, Norway.
authors.forename: Gudmund
authors.initials: G
authors.lastname: Skjåk-Bræk
authors.affiliation: Centre of Molecular Inflammation Research, and Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, Trondheim, Norway; Department of Immunology, Oslo University Hospital, and K.G. Jebsen IRC, University of Oslo, Norway; Research Laboratory, Nordland Hospital Bodø, and Faculty of Health Sciences, K.G. Jebsen TREC, University of Tromsø, Norway.
authors.forename: Tom Eirik
authors.initials: TE
authors.lastname: Mollnes
authors.affiliation: Research Laboratory, Nordland Hospital Bodø, and Faculty of Health Sciences, K.G. Jebsen TREC, University of Tromsø, Norway.
authors.forename: Ole-Lars
authors.initials: OL
authors.lastname: Brekke
authors.affiliation: Centre of Molecular Inflammation Research, and Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, Trondheim, Norway.
authors.forename: Terje
authors.initials: T
authors.lastname: Espevik
authors.affiliation: Centre of Molecular Inflammation Research, and Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, Trondheim, Norway; Liaison Committee between the Central Norway Regional Health Authority (RHA) and the Norwegian University of Science and Technology (NTNU), Norway. Electronic address: anne.m.rokstad@ntnu.no.
authors.forename: Anne Mari
authors.initials: AM
authors.lastname: Rokstad
mesh_terms: D000464:Alginates / Q000008:administration & dosage* / Q000737:chemistry / Q000494:pharmacology; D039481:CD11b Antigen / Q000378:metabolism; D003167:Complement Activation / Q000187:drug effects; D015932:Complement C3c / Q000378:metabolism; D016207:Cytokines / Q000378:metabolism*; D020723:Glucuronic Acid / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology; D006603:Hexuronic Acids / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology; D006801:Humans; D007962:Leukocytes / Q000187:drug effects* / Q000378:metabolism; D008863:Microspheres
chemical_list: D000464:Alginates; D039481:CD11b Antigen; D016207:Cytokines; D006603:Hexuronic Acids; C509295:ITGAM protein, human; D015932:Complement C3c; D020723:Glucuronic Acid
keywords: Alginate microcapsules; C5a; CR3 (CD11b/CD18); Complement component 3; Inflammation; Polycation