RESUMO
Dengue is characterized as one of the most important arthropod-borne human viral diseases, representing a public health problem. Increased activation of immune cells is involved in the progression of infection to severe forms. Recently, our group demonstrated the contribution of platelet-monocyte interaction to inflammatory responses in dengue, adding to evolving evidence that platelets have inflammatory functions and can regulate different aspects of innate immune responses. Furthermore, stimuli-specific-activated platelets can promote phenotypic changes and metabolic reprogramming in monocytes. Thus, this study aimed to evaluate the roles of dengue virus (DENV)-activated platelets on immunometabolic reprogramming of monocytes in vitro, focusing on lipid droplet (LD) biogenesis. We demonstrated that platelets exposed to DENV in vitro form aggregates with monocytes and signal to LD formation and CXCL8/IL-8, IL-10, CCL2, and PGE2 secretion. Pharmacologic inhibition of LD biogenesis prevents PGE2 secretion, but not CXCL8/IL-8 release, by platelet-monocyte complexes. In exploring the mechanisms involved, we demonstrated that LD formation in monocytes exposed to DENV-activated platelets is partially dependent on platelet-produced MIF. Additionally, LD formation is higher in monocytes, which have platelets adhered on their surface, suggesting that beyond paracrine signaling, platelet adhesion is an important event in platelet-mediated modulation of lipid metabolism in monocytes. Together, our results demonstrate that activated platelets aggregate with monocytes during DENV infection and signal to LD biogenesis and the secretion of inflammatory mediators, which may contribute to dengue immunopathogenesis.
Assuntos
Plaquetas/imunologia , Citocinas/imunologia , Vírus da Dengue/imunologia , Dengue/imunologia , Gotículas Lipídicas/imunologia , Monócitos/imunologia , Transdução de Sinais/imunologia , Plaquetas/patologia , Dengue/patologia , Feminino , Humanos , Gotículas Lipídicas/patologia , Masculino , Monócitos/patologiaRESUMO
Leptin is a cytokine, produced mainly by mature adipocytes, that regulates the central nervous system, mainly to suppress appetite and stimulate energy expenditure. Leptin also regulates the immune response by controlling activation of immunomodulatory cells, including eosinophils. While emerging as immune regulatory cells with roles in adipose tissue homeostasis, eosinophils have a well-established ability to synthesize pro-inflammatory molecules such as lipid mediators, a key event in several inflammatory pathologies. Here, we investigated the impact and mechanisms involved in leptin-driven activation of eicosanoid-synthesizing machinery within eosinophils. Direct in vitro activation of human or mouse eosinophils with leptin elicited synthesis of lipoxygenase as well as cyclooxygenase products. Displaying selectivity, leptin triggered synthesis of LTC4 and PGD2, but not PGE2, in parallel to dose-dependent induction of lipid body/lipid droplets biogenesis. While dependent on PI3K activation, leptin-driven eosinophil activation was also sensitive to pertussis toxin, indicating the involvement of G-protein coupled receptors on leptin effects. Leptin-induced lipid body-driven LTC4 synthesis appeared to be mediated through autocrine activation of G-coupled CCR3 receptors by eosinophil-derived CCL5, inasmuch as leptin was able to trigger rapid CCL5 secretion, and neutralizing anti-RANTES or anti-CCR3 antibodies blocked lipid body assembly and LTC4 synthesis induced by leptin. Remarkably, autocrine activation of PGD2 G-coupled receptors DP1 and DP2 also contributes to leptin-elicited lipid body-driven LTC4 synthesis by eosinophils in a PGD2-dependent fashion. Blockade of leptin-induced PGD2 autocrine/paracrine activity by a specific synthesis inhibitor or DP1 and DP2 receptor antagonists, inhibited both lipid body biogenesis and LTC4 synthesis induced by leptin stimulation within eosinophils. In addition, CCL5-driven CCR3 activation appears to precede PGD2 receptor activation within eosinophils, since neutralizing anti-CCL5 or anti-CCR3 antibodies inhibited leptin-induced PGD2 secretion, while it failed to alter PGD2-induced LTC4 synthesis. Altogether, sequential activation of CCR3 and then PGD2 receptors by autocrine ligands in response to leptin stimulation of eosinophils culminates with eosinophil activation, characterized here by assembly of lipidic cytoplasmic platforms synthesis and secretion of the pleiotropic lipid mediators, PGD2, and LTC4.
Assuntos
Eosinófilos/imunologia , Leptina/metabolismo , Leucotrieno C4/biossíntese , Receptores CCR3/metabolismo , Receptores Imunológicos/metabolismo , Receptores de Prostaglandina/metabolismo , Animais , Células Cultivadas , Quimiocina CCL5/antagonistas & inibidores , Quimiocina CCL5/metabolismo , Eosinófilos/citologia , Eosinófilos/efeitos dos fármacos , Eosinófilos/metabolismo , Feminino , Humanos , Hidantoínas/farmacologia , Oxirredutases Intramoleculares/antagonistas & inibidores , Oxirredutases Intramoleculares/metabolismo , Leptina/imunologia , Leucotrieno C4/imunologia , Gotículas Lipídicas/imunologia , Gotículas Lipídicas/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Piperidinas/farmacologia , Cultura Primária de Células , Prostaglandina D2/metabolismo , Receptores CCR3/antagonistas & inibidores , Receptores CCR3/imunologia , Receptores Imunológicos/antagonistas & inibidores , Receptores Imunológicos/imunologia , Receptores de Prostaglandina/antagonistas & inibidores , Receptores de Prostaglandina/imunologia , Proteínas Recombinantes/imunologia , Proteínas Recombinantes/metabolismoRESUMO
Lipid droplets (lipid bodies, LDs) are dynamic organelles that have important roles in regulating lipid metabolism, energy homeostasis, cell signaling, membrane trafficking, and inflammation. LD biogenesis, composition, and functions are highly regulated and may vary according to the stimuli, cell type, activation state, and inflammatory environment. Increased cytoplasmic LDs are frequently observed in leukocytes and other cells in a number of infectious diseases. Accumulating evidence reveals LDs participation in fundamental mechanisms of host-pathogen interactions, including cell signaling and immunity. LDs are sources of eicosanoid production, and may participate in different aspects of innate signaling and antigen presentation. In addition, intracellular pathogens evolved mechanisms to subvert host metabolism and may use host LDs, as ways of immune evasion and nutrients source. Here, we review mechanisms of LDs biogenesis and their contributions to the infection progress, and discuss the latest discoveries on mechanisms and pathways involving LDs roles as regulators of the immune response to protozoan infection.
Assuntos
Interações Hospedeiro-Parasita , Gotículas Lipídicas/imunologia , Metabolismo dos Lipídeos , Lipídeos/biossíntese , Biogênese de Organelas , Animais , Apresentação de Antígeno , Homeostase , Interações Hospedeiro-Patógeno , Humanos , Camundongos , Transporte Proteico , Infecções por Protozoários/imunologia , Transdução de Sinais/imunologiaRESUMO
During the onset of Trypanosoma cruzi infection, an effective immune response is necessary to control parasite replication and ensure host survival. Macrophages have a central role in innate immunity, acting as an important trypanocidal cell and triggering the adaptive immune response through antigen presentation and cytokine production. However, T. cruzi displays immune evasion mechanisms that allow infection and replication in macrophages, favoring its chronic persistence. One potential mechanism is the release of T. cruzi strain Y extracellular vesicle (EV Y), which participate in intracellular communication by carrying functional molecules that signal host cells and can modulate the immune response. The present work aimed to evaluate immune modulation by EV Y in C57BL/6 mice, a prototype resistant to infection by T. cruzi strain Y, and the effects of direct EV Y stimulation of macrophages in vitro. EV Y inoculation in mice prior to T. cruzi infection resulted in increased parasitemia, elevated cardiac parasitism, decreased plasma nitric oxide (NO), reduced NO production by spleen cells, and modulation of cytokine production, with a reduction in TNF-α in plasma and decreased production of TNF-α and IL-6 by spleen cells from infected animals. In vitro assays using bone marrow-derived macrophages showed that stimulation with EV Y prior to infection by T. cruzi increased the parasite internalization rate and release of infective trypomastigotes by these cells. In this same scenario, EV Y induced lipid body formation and prostaglandin E2 (PGE2) production by macrophages even in the absence of T. cruzi. In infected macrophages, EV Y decreased production of PGE2 and cytokines TNF-α and IL-6 24 h after infection. These results suggest that EV Y modulates the host response in favor of the parasite and indicates a role for lipid bodies and PGE2 in immune modulation exerted by EVs.
Assuntos
Doença de Chagas/imunologia , Vesículas Extracelulares/imunologia , Interações Hospedeiro-Parasita/imunologia , Macrófagos Peritoneais/imunologia , Trypanosoma cruzi/imunologia , Animais , Doença de Chagas/parasitologia , Chlorocebus aethiops , Dinoprostona/imunologia , Dinoprostona/metabolismo , Modelos Animais de Doenças , Humanos , Evasão da Resposta Imune , Gotículas Lipídicas/imunologia , Gotículas Lipídicas/metabolismo , Ativação de Macrófagos/imunologia , Macrófagos Peritoneais/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Baço/citologia , Baço/imunologia , Trypanosoma cruzi/metabolismo , Células VeroRESUMO
In mammals, lipid droplets (LDs) are ubiquitous organelles that modulate immune and inflammatory responses through the production of lipid mediators. In insects, it is unknown whether LDs play any role during the development of immune responses. We show that Aedes aegypti Aag2 cells - an immune responsive cell lineage - accumulates LDs when challenged with Enterobacter cloacae, Sindbis, and Dengue viruses. Microarray analysis of Aag2 challenged with E.cloacae or infected with Dengue virus revealed high transcripts levels of genes associated with lipid storage and LDs biogenesis, correlating with the increased LDs numbers in those conditions. Similarly, in mosquitoes, LDs accumulate in midgut cells in response to Serratia marcescens and Sindbis virus or when the native microbiota proliferates, following a blood meal. Also, constitutive activation of Toll and IMD pathways by knocking-down their respective negative modulators (Cactus and Caspar) increases LDs numbers in the midgut. Our results show for the first time an infection-induced LDs accumulation in response to both bacterial and viral infections in Ae. Aegypti, and we propose a role for LDs in mosquito immunity. These findings open new venues for further studies in insect immune responses associated with lipid metabolism.