RESUMEN
Sepsis is a serious clinical problem. Negative regulation of innate immunity is associated with sepsis progression, but the underlying mechanisms remains unclear. Here we show that the receptor CD300f promotes disease progression in sepsis. CD300f -/- mice were protected from death after cecal ligation and puncture (CLP), a murine model of septic peritonitis. CD300f was highly expressed in mast cells and recruited neutrophils in the peritoneal cavity. Analysis of mice (e.g., mast cell-deficient mice) receiving transplants of wild-type or CD300f -/- mast cells or neutrophils indicated that CD300f deficiency did not influence intrinsic migratory abilities of neutrophils, but enhanced neutrophil chemoattractant production (from mast cells and neutrophils) in the peritoneal cavity of CLP-operated mice, leading to robust accumulation of neutrophils which efficiently eliminated Escherichia coli. Ceramide-CD300f interaction suppressed the release of neutrophil chemoattractants from Escherichia coli-stimulated mast cells and neutrophils. Administration of the reagents that disrupted the ceramide-CD300f interaction prevented CLP-induced sepsis by stimulating neutrophil recruitment, whereas that of ceramide-containing vesicles aggravated sepsis. Extracellular concentrations of ceramides increased in the peritoneal cavity after CLP, suggesting a possible role of extracellular ceramides, CD300f ligands, in the negative-feedback suppression of innate immune responses. Thus, CD300f is an attractive target for the treatment of sepsis.
Asunto(s)
Ceramidas/metabolismo , Infiltración Neutrófila , Neutrófilos/metabolismo , Peritonitis/etiología , Peritonitis/metabolismo , Receptores Inmunológicos/metabolismo , Sepsis/etiología , Sepsis/metabolismo , Animales , Anticuerpos Monoclonales/farmacología , Biopsia , Ceramidas/antagonistas & inhibidores , Factores Quimiotácticos/biosíntesis , Quimiotaxis de Leucocito , Modelos Animales de Enfermedad , Fragmentos Fc de Inmunoglobulinas/inmunología , Fragmentos Fc de Inmunoglobulinas/farmacología , Masculino , Mastocitos/inmunología , Mastocitos/metabolismo , Ratones , Ratones Noqueados , Infiltración Neutrófila/inmunología , Neutrófilos/inmunología , Neutrófilos/patología , Peritonitis/mortalidad , Peritonitis/patología , Receptores Inmunológicos/antagonistas & inhibidores , Sepsis/mortalidad , Sepsis/patologíaRESUMEN
LPS triggers inflammatory responses; however, the negative regulation of LPS responses in vivo remains poorly understood. CD300f is an inhibitory receptor among the CD300 family of paired activating and inhibitory receptors. We have previously identified ceramide as a ligand for CD300f and shown that the binding of ceramide to CD300f inhibits IgE-mediated mast cell activation and allergic responses in mouse models. Here we identify the critical role of CD300f in inhibiting LPS-induced skin inflammation. CD300f deficiency remarkably enhanced LPS-induced skin edema and neutrophil recruitment in mice. Higher levels of factors that increase vascular permeability and of factors that induce neutrophil recruitment were detected in LPS-injected skin pouch exudates of CD300f-/- mice as compared with wild-type mice. CD300f was highly expressed in mast cells and recruited neutrophils, but not in macrophages, among skin myeloid cells. CD300f deficiency failed to influence the intrinsic migratory ability of neutrophils. Ceramide-CD300f binding suppressed the release of chemical mediators from mast cells and from neutrophils in response to LPS. Adoptive transfer experiments indicated that mast cells mediated enhanced edema in LPS-stimulated skin of CD300f-/- mice, whereas mast cells together with recruited neutrophils mediated robust neutrophil accumulation. Importantly, administering a ceramide antibody or ceramide-containing vesicles enhanced or suppressed LPS-induced skin inflammation of wild-type mice, respectively. Thus, ceramide-CD300f binding inhibits LPS-induced skin inflammation, implicating CD300f as a negative regulator of Toll-like receptor 4 (TLR4) signaling in vivo.