RESUMEN
BACKGROUD: The mechanism by which monosodium urate (MSU) crystals induce inflammation is not completely understood. Few studies have shown that MSU is capable of stimulating the release of IL-1ß in the absence of LPS treatment. The purinergic P2X7 receptor is involved in the release of IL-1ß in inflammatory settings caused by crystals, as is the case in silicosis. METHODS: We investigated the role of P2X7 receptor in sterile MSU-induced inflammation by evaluating peritonitis and paw edema. In in vitro models, we performed the experiments using peritoneal macrophages and THP-1 cells. We measured inflammatory parameters using ELISA and immunoblotting. We measured cell recruitment using cell phenotypic identification and hemocytometer counts. RESULTS: Our in vivo data showed that animals without P2X7 receptors generated less paw edema, less cell recruitment, and lower levels of IL-1ß release in a peritonitis model. In the in vitro model, we observed that MSU induced dye uptake by the P2X7 receptor. In the absence of the receptor, or when it was blocked, MSU crystals induced less IL-1ß release and this effect corresponded to the concentration of extracellular ATP. Moreover, MSU treatment induced HMGB1 release; pre-treatment with P2X7 antagonist reduced the amount of HMGB1 in cell supernatants. CONCLUSIONS: IL-1ß secretion induced by MSU depends on P2X7 receptor activation and involves HMGB1 release. GENERAL SIGNIFICANCE: We propose that cell activation caused by MSU crystals induces peritoneal macrophages and THP-1 cells to release ATP and HMGB1, causing IL-1ß secretion via P2X7 receptor activation.
Asunto(s)
Proteína HMGB1/genética , Inflamación/genética , Interleucina-1beta/genética , Receptores Purinérgicos P2X7/genética , Ácido Úrico/toxicidad , Adenosina Trifosfato/genética , Animales , Modelos Animales de Enfermedad , Edema/inducido químicamente , Edema/genética , Edema/patología , Humanos , Inflamación/inducido químicamente , Macrófagos Peritoneales/efectos de los fármacos , Macrófagos Peritoneales/patología , Ratones , Peritonitis/inducido químicamente , Peritonitis/genética , Peritonitis/patología , Silicosis/genética , Silicosis/patología , Células THP-1 , Ácido Úrico/químicaRESUMEN
Leishmania and other parasites display several mechanisms to subvert host immune cell function in order to achieve successful infection. The ATP receptor P2X7, an agonist-gated cation channel widely expressed in macrophages and other cells of the immune system, is also coupled to inflammasome activation, IL-1 beta secretion, production of reactive oxygen species, cell death and the induction of the permeabilization of the plasma membrane to molecules of up to 900 Da. P2X7 receptors can function as an effective microbicidal triggering receptor in macrophages infected with several microorganisms including Mycobacteria tuberculosis, Chlamydia and Leishmania. We have previously shown that its expression is up-regulated in macrophages infected with L. amazonensis and that infected cells also display an increase in P2X7-induced apoptosis and membrane permeabilization to some anionic fluorescent dyes. In an independent study we recently showed that the phenomenon of macrophage membrane permeabilization can involve at least two distinct pathways for cations and anions respectively. Here, we re-addressed the effects of ATP-induced P2X7-associated phenomena in macrophages infected with L. amazonensis and demonstrated that the P2X7-associated dye uptake mechanisms are differentially modulated. While the membrane permeabilization for anionic dyes is up-modulated, as previously described, the uptake of cationic dyes is strongly down-modulated. These results unveil new characteristics of two distinct permeabilization mechanisms associated with P2X7 receptors in macrophages and provide the first evidence indicating that these pathways can be differentially modulated in an immunologically relevant situation. The possible importance of these results to the L. amazonensis escape mechanism is discussed.