RESUMO
Systemic lupus erythematosus is characterized by dysregulated activation of T and B cells and autoantibodies to nuclear antigens and, in some cases, lipid antigens. Liposomes with nonbilayer phospholipid arrangements induce a disease resembling human lupus in mice, including IgM and IgG antibodies against nonbilayer phospholipid arrangements. As the effect of these liposomes on the innate immune response is unknown and innate immune system activation is necessary for efficient antibody formation, we evaluated the effect of these liposomes on Toll-like receptor (TLR) signaling, cytokine production, proinflammatory gene expression, and T, NKT, dendritic, and B cells. Liposomes induce TLR-4- and, to a lesser extent, TLR-2/TLR-6-dependent signaling in TLR-expressing human embryonic kidney (HEK) cells and bone marrow-derived macrophages. Mice with the lupus-like disease had increased serum concentrations of proinflammatory cytokines, C3a and C5a; they also had more TLR-4-expressing splenocytes, a higher expression of genes associated with TRIF-dependent TLR-4-signaling and complement activation, and a lower expression of apoptosis-related genes, compared to healthy mice. The percentage of NKT and the percentage and activation of dendritic and B2 cells were also increased. Thus, TLR-4 and TLR-2/TLR-6 activation by nonbilayer phospholipid arrangements triggers an inflammatory response that could contribute to autoantibody production and the generation of a lupus-like disease in mice.
Assuntos
Lipossomos/farmacologia , Lúpus Eritematoso Sistêmico/imunologia , Receptor 2 Toll-Like/imunologia , Receptor 4 Toll-Like/imunologia , Receptor 6 Toll-Like/imunologia , Animais , Autoanticorpos/biossíntese , Autoanticorpos/sangue , Clorpromazina/farmacologia , Citocinas/biossíntese , Citocinas/sangue , Diglicerídeos/farmacologia , Modelos Animais de Doenças , Feminino , Flagelina/farmacologia , Regulação da Expressão Gênica , Células HEK293 , Humanos , Imunoglobulina G/biossíntese , Imunoglobulina G/sangue , Imunoglobulina M/biossíntese , Imunoglobulina M/sangue , Inflamação , Lipopolissacarídeos/farmacologia , Lipossomos/química , Lúpus Eritematoso Sistêmico/induzido quimicamente , Lúpus Eritematoso Sistêmico/genética , Lúpus Eritematoso Sistêmico/patologia , Camundongos , Camundongos Endogâmicos BALB C , Oligopeptídeos/farmacologia , Ácidos Fosfatídicos/química , Ácidos Fosfatídicos/farmacologia , Fosfatidilcolinas/química , Fosfatidilcolinas/farmacologia , Fosfatidilserinas/química , Fosfatidilserinas/farmacologia , Receptor 2 Toll-Like/agonistas , Receptor 2 Toll-Like/genética , Receptor 4 Toll-Like/agonistas , Receptor 4 Toll-Like/genética , Receptor 6 Toll-Like/agonistas , Receptor 6 Toll-Like/genéticaRESUMO
Non-bilayer phospholipid arrangements are three-dimensional structures that can form when anionic phospholipids with an intermediate form of the tubular hexagonal phase II (H(II)), such as phosphatidic acid, phosphatidylserine or cardiolipin, are present in a bilayer of lipids. The drugs chlorpromazine and procainamide, which trigger a lupus-like disease in humans, can induce the formation of non-bilayer phospholipid arrangements, and we have previously shown that liposomes with non-bilayer arrangements induced by these drugs cause an autoimmune disease resembling human lupus in mice. Here we show that liposomes with non-bilayer phospholipid arrangements induced by Mn²âº cause a similar disease in mice. We extensively characterize the physical properties and immunological reactivity of liposomes made of the zwitterionic lipid phosphatidylcholine and a H(II)-preferring lipid, in the absence or presence of Mn²âº, chlorpromazine or procainamide. We use an hapten inhibition assay to define the epitope recognized by sera of mice with the disease, and by a monoclonal antibody that binds specifically to non-bilayer phospholipid arrangements, and we report that phosphorylcholine and glycerolphosphorylcholine, which form part of the polar region of phosphatidylcholine, are the only haptens that block the binding of the tested antibodies to non-bilayer arrangements. We propose a model in which the negatively charged H(II)-preferring lipids form an inverted micelle by electrostatic interactions with the positive charge of Mn²âº, chlorpromazine or procainamide; the inverted micelle is inserted into the bilayer of phosphatidylcholine, whose polar regions are exposed and become targets for antibody production. This model may be relevant in the pathogenesis of human lupus.