RESUMO
Polyunsaturated fatty acids (PUFAs) and their metabolites are potent regulators of inflammation. Generally, omega (n)-3 PUFAs are considered proresolving whereas n-6 PUFAs are classified as proinflammatory. In this study, we characterized the inflammatory response in murine peritonitis and unexpectedly found the accumulation of adrenic acid (AdA), a poorly studied n-6 PUFA. Functional studies revealed that AdA potently inhibited the formation of the chemoattractant leukotriene B4 (LTB4), specifically in human neutrophils, and this correlated with a reduction of its precursor arachidonic acid (AA) in free form. AdA exposure in human monocyte-derived macrophages enhanced efferocytosis of apoptotic human neutrophils. In vivo, AdA treatment significantly alleviated arthritis in an LTB4-dependent murine arthritis model. Our findings are, to our knowledge, the first to indicate that the n-6 fatty acid AdA effectively blocks production of LTB4 by neutrophils and could play a role in resolution of inflammation in vivo.
Assuntos
Anti-Inflamatórios/metabolismo , Artrite Experimental/imunologia , Ácidos Graxos Ômega-6/metabolismo , Ácidos Graxos Insaturados/metabolismo , Peritonite/imunologia , Animais , Anti-Inflamatórios/análise , Ácido Araquidônico/metabolismo , Artrite Experimental/patologia , Células Cultivadas , Ácidos Graxos Ômega-6/análise , Ácidos Graxos Insaturados/análise , Humanos , Leucotrieno B4/metabolismo , Lipidômica , Macrófagos/imunologia , Macrófagos/metabolismo , Masculino , Camundongos , Camundongos Transgênicos , Neutrófilos/imunologia , Neutrófilos/metabolismo , Lavagem Peritoneal , Peritonite/patologia , Cultura Primária de Células , Células THP-1 , Zimosan/administração & dosagem , Zimosan/imunologiaRESUMO
INTRODUCTION: The effector functions of immunoglobulin G (IgG) are mediated by interaction of its Fc region with Fc receptors (FcγRs) and/or the complement system. The three main pathways of complement activation converge at C3. However, C3-independent pathways can activate C5 and other downstream complement components during IgG-initiated inflammatory responses. These C3-independent pathways of C5 activation are triggered by activating FcγRs in some systems or can be activated by factors of the coagulation cascade such as thrombin. Here we studied the interplay of C3, C5, and activating FcγRs in a model of spontaneous autoantibody-driven arthritis. METHODS: We utilized the K/BxN TCR transgenic mouse model of arthritis. We bred K/BxN mice bearing targeted or naturally-occurring mutations in one or more of the genes encoding complement components C3, C5, and FcRγ, the cytoplasmic signaling chain shared by the activating FcγRs. We measured arthritis development, the production of arthritogenic autoantibodies, T cell activation status and cytokine synthesis. In addition, we treated mice with anti-C5 monoclonal antibodies or with the thrombin inhibitor argatroban. RESULTS: We have previously shown that genetic deficiency of C5 protects K/BxN mice from the development of arthritis. We found here that C3-deficient K/BxN mice developed arthritis equivalent in severity to C3-sufficient animals. Arthritis also developed normally in K/BxN mice lacking both C3 and FcRγ, but could be ameliorated in these animals by treatment with anti-C5 monoclonal antibody or by treatment with argatroban. Production of arthritogenic autoantibodies, T cell activation, and T cell cytokine production were not affected by the absence of C3, C5, and/or FcRγ. CONCLUSIONS: In K/BxN mice, C5-dependent autoantibody-driven arthritis can occur in the genetic absence of both complement C3 and activating FcγRs. Our findings suggest that in this setting, thrombin activates C5 to provoke arthritis.
Assuntos
Artrite/imunologia , Autoanticorpos/imunologia , Complemento C3/imunologia , Complemento C5/imunologia , Receptores de IgG/imunologia , Animais , Anticorpos Monoclonais/imunologia , Anticorpos Monoclonais/farmacologia , Antitrombinas/farmacologia , Arginina/análogos & derivados , Artrite/genética , Artrite/metabolismo , Autoanticorpos/sangue , Coagulação Sanguínea/efeitos dos fármacos , Coagulação Sanguínea/imunologia , Ativação do Complemento/efeitos dos fármacos , Ativação do Complemento/imunologia , Complemento C3/deficiência , Complemento C3/genética , Complemento C5/deficiência , Complemento C5/genética , Feminino , Citometria de Fluxo , Glucose-6-Fosfato Isomerase/imunologia , Imuno-Histoquímica , Masculino , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos NOD , Camundongos Knockout , Camundongos Transgênicos , Ácidos Pipecólicos/farmacologia , Receptores de Antígenos de Linfócitos T/genética , Receptores de Antígenos de Linfócitos T/imunologia , Receptores de Antígenos de Linfócitos T/metabolismo , Receptores de IgG/deficiência , Receptores de IgG/genética , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/imunologia , SulfonamidasRESUMO
INTRODUCTION: Neuromedin U (NMU) is a neuropeptide with pro-inflammatory activity. The primary goal of this study was to determine if NMU promotes autoantibody-induced arthritis. Additional studies addressed the cellular source of NMU and sought to define the NMU receptor responsible for its pro-inflammatory effects. METHODS: Serum containing arthritogenic autoantibodies from K/BxN mice was used to induce arthritis in mice genetically lacking NMU. Parallel experiments examined whether NMU deficiency impacted the early mast-cell-dependent vascular leak response induced by these autoantibodies. Bone-marrow chimeric mice were generated to determine whether pro-inflammatory NMU is derived from hematopoietic cells or stromal cells. Mice lacking the known NMU receptors singly and in combination were used to determine susceptibility to serum-transferred arthritis and in vitro cellular responses to NMU. RESULTS: NMU-deficient mice developed less severe arthritis than control mice. Vascular leak was not affected by NMU deficiency. NMU expression by bone-marrow-derived cells mediated the pro-arthritogenic effect. Deficiency of all of the known NMU receptors, however, had no impact on arthritis severity and did not affect the ability of NMU to stimulate intracellular calcium flux. CONCLUSIONS: NMU-deficient mice are protected from developing autoantibody-induced inflammatory arthritis. NMU derived from hematopoietic cells, not neurons, promotes the development of autoantibody-induced inflammatory arthritis. This effect is mediated by a receptor other than the currently known NMU receptors.