title: Scavenger receptor A (SR-A) is required for LPS-induced TLR4 mediated NF-κB activation in macrophages.
abstract: Recent evidence suggests that the macrophage scavenger receptor class A (SR-A, aka, CD204) plays a role in the induction of innate immune and inflammatory responses. We investigated whether SR-A will cooperate with Toll-like receptors (TLRs) in response to TLR ligand stimulation. Macrophages (J774/a) were treated with Pam2CSK4, (TLR2 ligand), Polyinosinic:polycytidylic acid (Poly I:C) (TLR3 ligand), and Lipopolysaccharides (LPS) (TLR4 ligand) for 15 min in the presence or absence of fucoidan (the SR-A ligand). The levels of phosphorylated IκBα (p-IκBα) were examined by Western blot. We observed that Poly I:C and LPS alone, but not Pam2CSK4 or fucoidan increased the levels of p-IκBα. However, LPS-induced increases in p-IκBα levels were further enhanced when presence of the fucoidan. Immunoprecipitation and double fluorescent staining showed that LPS stimulation promotes SR-A association with TLR4 in the presence of fucoidan. To further confirm our observation, we isolated peritoneal macrophages from SR-A deficient (SR-A(-/-)), TLR4(-/-) and wild type (WT) mice, respectively. The peritoneal macrophages were treated with LPS for 15min in the presence and absence of fucoidan. We observed that LPS-stimulated TNFα and IL-1β production was further enhanced in the WT macrophages, but did not in either TLR4(-/-) or SR-A(-/-) macrophages, when fucoidan was present. Similarly, in the presence of fucoidan, LPS-induced IκBα phosphorylation, NF-κB binding activity, and association between TLR4 and SR-A were significantly enhanced in WT macrophages compared with LPS stimulation alone. The data suggests that SR-A is needed for LPS-induced inflammatory responses in macrophages.
authors.affiliation: Department of Surgery, James Quillen College of Medicine, East Tennessee State University, Johnson City, TN 37614, USA.
authors.forename: Honghui
authors.initials: H
authors.lastname: Yu
authors.forename: Tuanzhu
authors.initials: T
authors.lastname: Ha
authors.forename: Li
authors.initials: L
authors.lastname: Liu
authors.forename: Xiaohui
authors.initials: X
authors.lastname: Wang
authors.forename: Ming
authors.initials: M
authors.lastname: Gao
authors.forename: Jim
authors.initials: J
authors.lastname: Kelley
authors.forename: Race
authors.initials: R
authors.lastname: Kao
authors.forename: David
authors.initials: D
authors.lastname: Williams
authors.forename: Chuanfu
authors.initials: C
authors.lastname: Li
mesh_terms: D000818:Animals; D016207:Cytokines / Q000378:metabolism; D004357:Drug Synergism; D020672:I-kappa B Proteins / Q000378:metabolism; D018836:Inflammation Mediators / Q000378:metabolism; D008024:Ligands; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008264:Macrophages / Q000187:drug effects* / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011134:Polysaccharides / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects; D051117:Scavenger Receptors, Class A / Q000378:metabolism*; D013997:Time Factors; D051197:Toll-Like Receptor 4 / Q000378:metabolism*
chemical_list: D016207:Cytokines; D020672:I-kappa B Proteins; D018836:Inflammation Mediators; D008024:Ligands; D008070:Lipopolysaccharides; C495140:Msr1 protein, mouse; D016328:NF-kappa B; C000606205:Nfkbia protein, mouse; D011134:Polysaccharides; D051117:Scavenger Receptors, Class A; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4; D000072000:NF-KappaB Inhibitor alpha; C007789:fucoidan