Lysophosphatidylcholine Induces NLRP3 Inflammasome-Mediated Foam Cell Formation and Pyroptosis in Human Monocytes and Endothelial Cells.

Foam cells are specialized lipid-loaded macrophages derived from monocytes and are a key pathological feature of atherosclerotic lesions. Lysophosphatidylcholine (LPC) is a major lipid component of the plasma membrane with a broad spectrum of proinflammatory activities and plays a key role in atherosclerosis. However, the role of LPC in lipid droplet (LD) biogenesis and the modulation of inflammasome activation is still poorly understood. In the present study, we investigated whether LPC can induce foam cell formation through an analysis of LD biogenesis and determined whether the cell signaling involved in this process is mediated by the inflammasome activation pathway in human endothelial cells and monocytes. Our results showed that LPC induced foam cell formation in both types of cells by increasing LD biogenesis via a NLRP3 inflammasome-dependent pathway. Furthermore, LPC induced pyroptosis in both cells and the activation of the inflammasome with IL-1ß secretion, which was dependent on potassium efflux and lysosomal damage in human monocytes. The present study described the IL-1ß secretion and foam cell formation triggered by LPC via an inflammasome-mediated pathway in human monocytes and endothelial cells. Our results will help improve our understanding of the relationships among LPC, LD biogenesis, and NLRP3 inflammasome activation in the pathogenesis of atherosclerosis.

Schistosomal Lipids Activate Human Eosinophils via Toll-Like Receptor 2 and PGD2 Receptors: 15-LO Role in Cytokine Secretion.

Parasite-derived lipids may play important roles in host-pathogen interactions and immune evasion mechanisms. Remarkable accumulation of eosinophils is a characteristic feature of inflammation associated with parasitic disease, especially caused by helminthes. Infiltrating eosinophils are implicated in the pathogenesis of helminth infection by virtue of their capacity to release an array of tissue-damaging and immunoregulatory mediators. However, the mechanisms involved in the activation of human eosinophils by parasite-derived molecules are not clear. Here we investigated the effects and mechanisms of schistosomal lipids-induced activation of human eosinophils. Our results showed that stimulation of human eosinophils in vitro with total lipid extracts from adult worms of S. mansoni induced direct activation of human eosinophils, eliciting lipid droplet biogenesis, synthesis of leukotriene (LT) C4 and eoxin (EX) C4 (14,15 LTC4) and secretion of eosinophil pre-formed TGFß. We demonstrated that main eosinophil activating components within S. mansoni lipid extract are schistosomal-derived lysophosphatidylcholine (LPC) and prostaglandin (PG)D2. Moreover, TLR2 is up-regulated in human eosinophils upon stimulation with schistosomal lipids and pre-treatment with anti-TLR2 inhibited both schistosomal lipids- and LPC-, but not PGD2-, induced lipid droplet biogenesis and EXC4 synthesis within eosinophils, indicating that TLR2 mediates LPC-driven human eosinophil activation. By employing PGD2 receptor antagonists, we demonstrated that DP1 receptors are also involved in various parameters of human eosinophil activation induced by schistosomal lipids, but not by schistosomal LPC. In addition, schistosomal lipids and their active components PGD2 and LPC, triggered 15-LO dependent production of EXC4 and secretion of TGFß. Taken together, our results showed that schistosomal lipids contain at least two components-LPC and PGD2-that are capable of direct activation of human eosinophils acting on distinct eosinophil-expressed receptors, noticeably TLR2 as well as DP1, trigger human eosinophil activation characterized by production/secretion of pro-inflammatory and immunoregulatory mediators.

Schistosomal-derived lysophosphatidylcholine triggers M2 polarization of macrophages through PPARγ dependent mechanisms.

Mansonic schistosomiasis is a disease caused by the trematode Schistosoma mansoni, endemic to tropical countries. S. mansoni infection induces the formation of granulomas and potent polarization of Th2-type immune response. There is great interest in understanding the mechanisms used by this parasite that causes a modulation of the immune system. Recent studies from our group demonstrated that lipids of S. mansoni, including lysophosphatidylcholine (LPC) have immunomodulatory activity. In the present study, our aim was to investigate the role of lipids derived from S. mansoni in the activation and polarization of macrophages and to characterize the mechanisms involved in this process. Peritoneal macrophages obtained from wild type C57BL/6mice or bone marrow derived macrophages were stimulated in vitro with lipids extracted from adult worms of S. mansoni. We demonstrated that total schistosomal-derived lipids as well as purified LPC induced alternatively activated macrophages/M2 profile observed by increased expression of arginase-1, mannose receptor, Chi3l3, TGFß and production of IL-10 and PGE2 24h after stimulation. The involvement of the nuclear receptor PPARγ in macrophage response against LPC was investigated. Through Western blot and immunofluorescence confocal microscopy we demonstrated that schistosomal-derived LPC induces increased expression of PPARγ in macrophages. The LPC-induced increased expression of arginase-1 were significantly inhibited by the PPAR-γ antagonist GW9662. Together, these results demonstrate an immunomodulatory role of schistosomal-derived LPC in activating macrophages to a profile of the type M2 through PPARγ-dependent mechanisms, indicating a novel pathway for macrophage polarization triggered by parasite-derived LPC with potential implications to disease pathogenesis.

Estudo do papel dos lipídios derivados de schistosoma mansoni na ativação e polarização de macrófagos / Study of the role of lipids derived from Schistosoma mansoni in activation and polarization of macrophages

A esquistossomose mansônica, endemia parasitária típica das Américas, Ásia e África, é causada pela infecção de trematódeos da espécie Schistosoma mansoni. A infecção por este trematódeo induz no hospedeiro a formação de granulomas e uma potente polarização da resposta imune para o tipo Th2. Os helmintos podem ser apresentados em diferentes estágios do seu ciclo de vida dentro de um hospedeiro humano, e cada estágio do desenvolvimento pode apresentar diferentes combinações de glicoconjugados reconhecidos de diferentes formas pelo hospedeiro. Estudos recentes do nosso grupo demonstraram que lipídeos de S. mansoni, incluindo a lisofosfatidilcolina, possuem atividade imunomoduladora. No presente trabalho investigamos o papel imunomodulador dos lipídeos de Schistosoma mansoni, em especial a LPC, na ativação de macrófagos e os possíveis mecanismos envolvidos neste processoDemonstramos que a lisofosfatidilcolina (LPC) esquistossomal estimula a formação de corpúsculos lipídicos de forma dependente de TLR2 em macrófagos peritoneais após 24 h de estimulação in vitro, ao mesmo tempo em que induz aumento na expressão desse receptor. Entretanto, a LPC não induz aumento na produção de óxido nítrico (NO) em macrófagos, e em altas concentrações foi capaz de inibir a indução de NO gerada por LPS. Além disso, a LPC esquistossomal induziu em macrófagos um perfil de ativação do tipo M2, observado pelo aumento da expressão de arginase-1 e produção de IL-10 e PGE2. A participação do receptor nuclear PPARgama na resposta de macrófagos frente a LPC esquistossomal foi investigada. Através de diferentes técnicas demonstramos que a LPC induz aumento da expressão de PPARgama em macrófagos...

Schistosomiasis mansoni, an endemic parasitic disease typical of the Americas, Asia andAfrica, is caused by infection of trematode species of Schistosoma mansoni. The trematodeinfection in the host induces the formation of granulomas and potent polarization of Th2-typeimmune response. Helminths can be presented in different stages of their life cycle in ahuman host, and each stage of development can have different combinations of differentforms of glycoconjugates recognized by the host. Recent studies from our group demonstratedthat lipids of S. mansoni, including lysophosphatidylcholine, have immunomodulatoryactivity. In the present work, we investigated the immunomodulatory role of lipids ofSchistosoma mansoni in the activation of macrophages and the possible mechanisms involvedin this process. We demonstrated that lysophosphatidylcholine (LPC) from S. mansonistimulates the formation of lipid bodies in peritoneal macrophages in a TLR2 dependentmanner after 24 h of in vitro stimulation, while it induces increased expression of thisreceptor. However, LPC failed to induce increased production of nitric oxide (NO) inmacrophages and in high concentrations was able to inhibit the induction of NO generated byLPS. Moreover, the schistosomal-derived LPC induced in macrophages an profile of M2activation observed by increased expression of arginase-1, and production of IL-10 andPGE2. Participation of the nuclear receptor PPAR gamma in macrophage response againstLPC was investigated. Through various techniques we demonstrated that the LPC inducesincreased expression of PPAR gamma in macrophages...