RESUMEN
Genome-wide association studies have identified risk loci associated with the development of inflammatory bowel disease, while epidemiological studies have emphasized that pathogenesis likely involves host interactions with environmental elements whose source and structure need to be defined. Here, we identify a class of compounds derived from dietary, microbial, and industrial sources that are characterized by the presence of a five-membered oxazole ring and induce CD1d-dependent intestinal inflammation. We observe that minimal oxazole structures modulate natural killer T cell-dependent inflammation by regulating lipid antigen presentation by CD1d on intestinal epithelial cells (IECs). CD1d-restricted production of interleukin 10 by IECs is limited through activity of the aryl hydrocarbon receptor (AhR) pathway in response to oxazole induction of tryptophan metabolites. As such, the depletion of the AhR in the intestinal epithelium abrogates oxazole-induced inflammation. In summary, we identify environmentally derived oxazoles as triggers of CD1d-dependent intestinal inflammatory responses that occur via activation of the AhR in the intestinal epithelium.
Asunto(s)
Colitis/patología , Dieta , Intestinos/patología , Oxazoles/farmacología , Receptores de Hidrocarburo de Aril/metabolismo , Transducción de Señal/efectos de los fármacos , Animales , Antígenos CD1d/genética , Antígenos CD1d/metabolismo , Colitis/inducido químicamente , Colitis/metabolismo , Modelos Animales de Enfermedad , Células Epiteliales/citología , Células Epiteliales/efectos de los fármacos , Células Epiteliales/metabolismo , Indolamina-Pirrol 2,3,-Dioxigenasa/metabolismo , Interleucina-10/metabolismo , Intestinos/citología , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Células T Asesinas Naturales/inmunología , Interferencia de ARN , ARN Interferente Pequeño/metabolismo , Receptores de Hidrocarburo de Aril/antagonistas & inhibidores , Receptores de Hidrocarburo de Aril/genética , Triptófano/metabolismoRESUMEN
Gasdermin D (GSDMD) is the common effector for cytokine secretion and pyroptosis downstream of inflammasome activation and was previously shown to form large transmembrane pores after cleavage by inflammatory caspases to generate the GSDMD N-terminal domain (GSDMD-NT)1-10. Here we report that GSDMD Cys191 is S-palmitoylated and that palmitoylation is required for pore formation. S-palmitoylation, which does not affect GSDMD cleavage, is augmented by mitochondria-generated reactive oxygen species (ROS). Cleavage-deficient GSDMD (D275A) is also palmitoylated after inflammasome stimulation or treatment with ROS activators and causes pyroptosis, although less efficiently than palmitoylated GSDMD-NT. Palmitoylated, but not unpalmitoylated, full-length GSDMD induces liposome leakage and forms a pore similar in structure to GSDMD-NT pores shown by cryogenic electron microscopy. ZDHHC5 and ZDHHC9 are the major palmitoyltransferases that mediate GSDMD palmitoylation, and their expression is upregulated by inflammasome activation and ROS. The other human gasdermins are also palmitoylated at their N termini. These data challenge the concept that cleavage is the only trigger for GSDMD activation. They suggest that reversible palmitoylation is a checkpoint for pore formation by both GSDMD-NT and intact GSDMD that functions as a general switch for the activation of this pore-forming family.
Asunto(s)
Gasderminas , Lipoilación , Proteínas de Unión a Fosfato , Especies Reactivas de Oxígeno , Animales , Femenino , Humanos , Masculino , Ratones , Aciltransferasas/metabolismo , Microscopía por Crioelectrón , Cisteína/metabolismo , Gasderminas/química , Gasderminas/metabolismo , Inflamasomas/metabolismo , Liposomas/metabolismo , Liposomas/química , Mitocondrias/metabolismo , Proteínas de Unión a Fosfato/química , Proteínas de Unión a Fosfato/metabolismo , Piroptosis , Especies Reactivas de Oxígeno/metabolismo , Células THP-1RESUMEN
Coevolution of beneficial microorganisms with the mammalian intestine fundamentally shapes mammalian physiology. Here, we report that the intestinal microbe Bacteroides fragilis modifies the homeostasis of host invariant natural killer T (iNKT) cells by supplementing the host's endogenous lipid antigen milieu with unique inhibitory sphingolipids. The process occurs early in life and effectively impedes iNKT cell proliferation during neonatal development. Consequently, total colonic iNKT cell numbers are restricted into adulthood, and hosts are protected against experimental iNKT cell-mediated, oxazolone-induced colitis. In studies with neonatal mice lacking access to bacterial sphingolipids, we found that treatment with B. fragilis glycosphingolipids-exemplified by an isolated peak (MW = 717.6) called GSL-Bf717-reduces colonic iNKT cell numbers and confers protection against oxazolone-induced colitis in adulthood. Our results suggest that the distinctive inhibitory capacity of GSL-Bf717 and similar molecules may prove useful in the treatment of autoimmune and allergic disorders in which iNKT cell activation is destructive.
Asunto(s)
Bacteroides fragilis/metabolismo , Colitis/inmunología , Glicoesfingolípidos/metabolismo , Células T Asesinas Naturales/inmunología , Animales , Animales Recién Nacidos , Proliferación Celular , Colitis/inducido químicamente , Colitis/prevención & control , Colon/crecimiento & desarrollo , Colon/microbiología , Ratones , Ratones Endogámicos C57BL , Células T Asesinas Naturales/citología , OxazolonaRESUMEN
The human gut microbiome constantly converts natural products derived from the host and diet into numerous bioactive metabolites1-3. Dietary fats are essential micronutrients that undergo lipolysis to release free fatty acids (FAs) for absorption in the small intestine4. Gut commensal bacteria modify some unsaturated FAs-for example, linoleic acid (LA)-into various intestinal FA isomers that regulate host metabolism and have anticarcinogenic properties5. However, little is known about how this diet-microorganism FA isomerization network affects the mucosal immune system of the host. Here we report that both dietary factors and microbial factors influence the level of gut LA isomers (conjugated LAs (CLAs)) and that CLAs in turn modulate a distinct population of CD4+ intraepithelial lymphocytes (IELs) that express CD8αα in the small intestine. Genetic abolition of FA isomerization pathways in individual gut symbionts significantly decreases the number of CD4+CD8αα+ IELs in gnotobiotic mice. Restoration of CLAs increases CD4+CD8αα+ IEL levels in the presence of the transcription factor hepatocyte nuclear factor 4γ (HNF4γ). Mechanistically, HNF4γ facilitates CD4+CD8αα+ IEL development by modulating interleukin-18 signalling. In mice, specific deletion of HNF4γ in T cells leads to early mortality from infection by intestinal pathogens. Our data reveal a new role for bacterial FA metabolic pathways in the control of host intraepithelial immunological homeostasis by modulating the relative number of CD4+ T cells that were CD4+CD8αα+.
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Ácidos Grasos , Microbioma Gastrointestinal , Linfocitos Intraepiteliales , Animales , Humanos , Ratones , Linfocitos T CD8-positivos/inmunología , Linfocitos T CD8-positivos/metabolismo , Ácidos Grasos/química , Ácidos Grasos/metabolismo , Mucosa Intestinal/inmunología , Mucosa Intestinal/metabolismo , Linfocitos Intraepiteliales/inmunología , Linfocitos Intraepiteliales/metabolismo , Isomerismo , Ratones Endogámicos C57BL , Receptores de Antígenos de Linfocitos T alfa-beta/metabolismo , Linfocitos T CD4-Positivos/inmunología , Linfocitos T CD4-Positivos/metabolismo , Lipólisis , Ácido Linoleico/metabolismo , Inmunidad MucosaRESUMEN
Susceptibility to tuberculosis is historically ascribed to an inadequate immune response that fails to control infecting mycobacteria. In zebrafish, we find that susceptibility to Mycobacterium marinum can result from either inadequate or excessive acute inflammation. Modulation of the leukotriene A(4) hydrolase (LTA4H) locus, which controls the balance of pro- and anti-inflammatory eicosanoids, reveals two distinct molecular routes to mycobacterial susceptibility converging on dysregulated TNF levels: inadequate inflammation caused by excess lipoxins and hyperinflammation driven by excess leukotriene B(4). We identify therapies that specifically target each of these extremes. In humans, we identify a single nucleotide polymorphism in the LTA4H promoter that regulates its transcriptional activity. In tuberculous meningitis, the polymorphism is associated with inflammatory cell recruitment, patient survival and response to adjunctive anti-inflammatory therapy. Together, our findings suggest that host-directed therapies tailored to patient LTA4H genotypes may counter detrimental effects of either extreme of inflammation.
Asunto(s)
Infecciones por Mycobacterium/tratamiento farmacológico , Infecciones por Mycobacterium/inmunología , Tuberculosis Meníngea/tratamiento farmacológico , Tuberculosis Meníngea/inmunología , Animales , Modelos Animales de Enfermedad , Humanos , Inflamación/inmunología , Leucotrieno A4/genética , Leucotrieno A4/inmunología , Leucotrieno B4/genética , Leucotrieno B4/inmunología , Lipoxinas/inmunología , Mitocondrias/metabolismo , Infecciones por Mycobacterium/genética , Mycobacterium marinum , Polimorfismo Genético , Polimorfismo de Nucleótido Simple , Regiones Promotoras Genéticas , Transducción de Señal , Transcripción Genética , Tuberculosis Meníngea/genética , Factor de Necrosis Tumoral alfa/metabolismo , Pez Cebra/embriología , Pez Cebra/inmunologíaRESUMEN
Small molecules derived from symbiotic microbiota critically contribute to intestinal immune maturation and regulation1. However, little is known about the molecular mechanisms that control immune development in the host-microbiota environment. Here, using a targeted lipidomic analysis and synthetic approach, we carried out a multifaceted investigation of immunomodulatory α-galactosylceramides from the human symbiont Bacteroides fragilis (BfaGCs). The characteristic terminal branching of BfaGCs is the result of incorporation of branched-chain amino acids taken up in the host gut by B. fragilis. A B. fragilis knockout strain that cannot metabolize branched-chain amino acids showed reduced branching in BfaGCs, and mice monocolonized with this mutant strain had impaired colonic natural killer T (NKT) cell regulation, implying structure-specific immunomodulatory activity. The sphinganine chain branching of BfaGCs is a critical determinant of NKT cell activation, which induces specific immunomodulatory gene expression signatures and effector functions. Co-crystal structure and affinity analyses of CD1d-BfaGC-NKT cell receptor complexes confirmed the interaction of BfaGCs as CD1d-restricted ligands. We present a structural and molecular-level paradigm of immunomodulatory control by interactions of endobiotic metabolites with diet, microbiota and the immune system.
Asunto(s)
Aminoácidos de Cadena Ramificada/inmunología , Aminoácidos de Cadena Ramificada/metabolismo , Bacteroides fragilis/metabolismo , Galactosilceramidas/inmunología , Galactosilceramidas/metabolismo , Microbioma Gastrointestinal/inmunología , Simbiosis/inmunología , Aminoácidos de Cadena Ramificada/química , Animales , Antígenos CD1d/inmunología , Bacteroides fragilis/genética , Humanos , Ratones , Modelos Animales , Modelos Moleculares , Células T Asesinas Naturales/citología , Células T Asesinas Naturales/inmunología , Receptores de Antígenos de Linfocitos T/inmunología , Transducción de Señal/inmunologíaRESUMEN
The metabolic pathways encoded by the human gut microbiome constantly interact with host gene products through numerous bioactive molecules1. Primary bile acids (BAs) are synthesized within hepatocytes and released into the duodenum to facilitate absorption of lipids or fat-soluble vitamins2. Some BAs (approximately 5%) escape into the colon, where gut commensal bacteria convert them into various intestinal BAs2 that are important hormones that regulate host cholesterol metabolism and energy balance via several nuclear receptors and/or G-protein-coupled receptors3,4. These receptors have pivotal roles in shaping host innate immune responses1,5. However, the effect of this host-microorganism biliary network on the adaptive immune system remains poorly characterized. Here we report that both dietary and microbial factors influence the composition of the gut BA pool and modulate an important population of colonic FOXP3+ regulatory T (Treg) cells expressing the transcription factor RORγ. Genetic abolition of BA metabolic pathways in individual gut symbionts significantly decreases this Treg cell population. Restoration of the intestinal BA pool increases colonic RORγ+ Treg cell counts and ameliorates host susceptibility to inflammatory colitis via BA nuclear receptors. Thus, a pan-genomic biliary network interaction between hosts and their bacterial symbionts can control host immunological homeostasis via the resulting metabolites.
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Ácidos y Sales Biliares/metabolismo , Microbioma Gastrointestinal , Homeostasis , Intestinos/inmunología , Intestinos/microbiología , Miembro 3 del Grupo F de la Subfamilia 1 de Receptores Nucleares/inmunología , Linfocitos T Reguladores/inmunología , Animales , Ácidos y Sales Biliares/química , Ratones Endogámicos C57BL , Miembro 3 del Grupo F de la Subfamilia 1 de Receptores Nucleares/genéticaRESUMEN
Lipopolysaccharides (LPS) and lipooligosaccharides (LOS) are located in the outer membrane of Gram-negative bacteria and are comprised of three distinctive parts: lipid A, core oligosaccharide (OS), and O-antigen. The structure of each region influences bacterial stability, toxicity, and pathogenesis. Here, we highlight the use of targeted activated-electron photodetachment (a-EPD) tandem mass spectrometry to characterize LPS and LOS from two crucial players in the human gut microbiota, Escherichia coli Nissle and Bacteroides fragilis. a-EPD is a hybrid activation method that uses ultraviolet photoirradiation to generate charge-reduced radical ions followed by collisional activation to produce informative fragmentation patterns. We benchmark the a-EPD method for top-down characterization of triacyl LOS from E. coli R2, then focus on characterization of LPS from E. coli Nissle and B. fragilis. Notably, a-EPD affords extensive fragmentation throughout the backbone of the core OS and O-antigen regions of LPS from E. coli Nissle. This hybrid approach facilitated the elucidation of structural details for LPS from B. fragilis, revealing a putative hexuronic acid (HexA) conjugated to lipid A.
Asunto(s)
Escherichia coli , Lipopolisacáridos , Lipopolisacáridos/química , Escherichia coli/química , Bacteroides fragilis/química , Electrones , Espectrometría de Masas en TándemRESUMEN
The orphan nuclear receptor Nurr1 is critical for the development, maintenance and protection of midbrain dopaminergic (mDA) neurons. Here we show that prostaglandin E1 (PGE1) and its dehydrated metabolite, PGA1, directly interact with the ligand-binding domain (LBD) of Nurr1 and stimulate its transcriptional function. We also report the crystallographic structure of Nurr1-LBD bound to PGA1 at 2.05 Å resolution. PGA1 couples covalently to Nurr1-LBD by forming a Michael adduct with Cys566, and induces notable conformational changes, including a 21° shift of the activation function-2 helix (H12) away from the protein core. Furthermore, PGE1/PGA1 exhibit neuroprotective effects in a Nurr1-dependent manner, prominently enhance expression of Nurr1 target genes in mDA neurons and improve motor deficits in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-lesioned mouse models of Parkinson's disease. Based on these results, we propose that PGE1/PGA1 represent native ligands of Nurr1 and can exert neuroprotective effects on mDA neurons, via activation of Nurr1's transcriptional function.
Asunto(s)
Alprostadil/metabolismo , Miembro 2 del Grupo A de la Subfamilia 4 de Receptores Nucleares/metabolismo , Prostaglandinas A/metabolismo , Animales , Línea Celular Tumoral , Cristalografía por Rayos X , Dopamina/metabolismo , Humanos , Ligandos , Masculino , Ratones , Ratones Endogámicos BALB C , Ratones Endogámicos C57BL , Neuronas/metabolismo , Fármacos Neuroprotectores/farmacología , Miembro 2 del Grupo A de la Subfamilia 4 de Receptores Nucleares/química , Miembro 2 del Grupo A de la Subfamilia 4 de Receptores Nucleares/genética , Unión Proteica , Ratas , Transducción de Señal , Transcripción GenéticaRESUMEN
The mammalian immune system is tolerized to trillions of microbes residing on bodily surfaces and can discriminate between symbionts and pathogens despite their having related microbial structures. Mechanisms of innate immune activation and the subsequent signaling pathways used by symbionts to communicate with the adaptive immune system are poorly understood. Polysaccharide A (PSA) of Bacteroides fragilis is the model symbiotic immunomodulatory molecule. Here we demonstrate that PSA-dependent immunomodulation requires the Toll-like receptor (TLR) 2/1 heterodimer in cooperation with Dectin-1 to initiate signaling by the downstream phosphoinositide 3-kinase (PI3K) pathway, with consequent CREB-dependent transcription of antiinflammatory genes, including antigen presentation and cosignaling molecules. High-resolution LC-MS/MS analysis of PSA identified a previously unknown small molecular-weight, covalently attached bacterial outer membrane-associated lipid that is required for activation of antigen-presenting cells. This archetypical commensal microbial molecule initiates a complex collaborative integration of Toll-like receptor and C-type lectin-like receptor signaling mechanisms culminating in the activation of the antiinflammatory arm of the PI3K pathway that serves to educate CD4+ Tregs to produce the immunomodulatory cytokine IL-10. Immunomodulation is a key function of the microbiome and is a focal point for developing new therapeutic agents.
RESUMEN
Underlying mechanisms for how bacterial infections contribute to active resolution of acute inflammation are unknown. Here, we performed exudate leukocyte trafficking and mediator-metabololipidomics of murine peritoneal Escherichia coli infections with temporal identification of pro-inflammatory (prostaglandins and leukotrienes) and specialized pro-resolving mediators (SPMs). In self-resolving E. coli exudates (10(5) colony forming units, c.f.u.), the dominant SPMs identified were resolvin (Rv) D5 and protectin D1 (PD1), which at 12 h were at significantly greater levels than in exudates from higher titre E. coli (10(7) c.f.u.)-challenged mice. Germ-free mice had endogenous RvD1 and PD1 levels higher than in conventional mice. RvD1 and RvD5 (nanograms per mouse) each reduced bacterial titres in blood and exudates, E. coli-induced hypothermia and increased survival, demonstrating the first actions of RvD5. With human polymorphonuclear neutrophils and macrophages, RvD1, RvD5 and PD1 each directly enhanced phagocytosis of E. coli, and RvD5 counter-regulated a panel of pro-inflammatory genes, including NF-κB and TNF-α. RvD5 activated the RvD1 receptor, GPR32, to enhance phagocytosis. With self-limited E. coli infections, RvD1 and the antibiotic ciprofloxacin accelerated resolution, each shortening resolution intervals (R(i)). Host-directed RvD1 actions enhanced ciprofloxacin's therapeutic actions. In 10(7) c.f.u. E. coli infections, SPMs (RvD1, RvD5, PD1) together with ciprofloxacin also heightened host antimicrobial responses. In skin infections, SPMs enhanced vancomycin clearance of Staphylococcus aureus. These results demonstrate that specific SPMs are temporally and differentially regulated during infections and that they are anti-phlogistic, enhance containment and lower antibiotic requirements for bacterial clearance.
Asunto(s)
Antibacterianos/farmacología , Ácidos Docosahexaenoicos/metabolismo , Infecciones por Escherichia coli/metabolismo , Escherichia coli/efectos de los fármacos , Infecciones Estafilocócicas/metabolismo , Animales , Antibacterianos/uso terapéutico , Escherichia coli/inmunología , Infecciones por Escherichia coli/tratamiento farmacológico , Infecciones por Escherichia coli/microbiología , Humanos , Hipotermia/prevención & control , Macrófagos/inmunología , Masculino , Ratones , Ratones Endogámicos C57BL , Viabilidad Microbiana/efectos de los fármacos , Neutrófilos/inmunología , Peritonitis/tratamiento farmacológico , Peritonitis/metabolismo , Peritonitis/microbiología , Fagocitosis , Enfermedades de la Piel/tratamiento farmacológico , Enfermedades de la Piel/metabolismo , Enfermedades de la Piel/microbiología , Infecciones Estafilocócicas/tratamiento farmacológico , Infecciones Estafilocócicas/microbiología , Staphylococcus aureus/efectos de los fármacos , Staphylococcus aureus/inmunología , Vancomicina/farmacología , Vancomicina/uso terapéuticoRESUMEN
Acute inflammation and its resolution are essential processes for tissue protection and homeostasis. In this context, specialized proresolving mediators derived from polyunsaturated fatty acids are of interest. In this study, we report that resolvin E2 (RvE2) from eicosapentaenoic acid is endogenously produced during self-limited murine peritonitis in both the initiation and resolution phases. RvE2 (1-10 nM) carries potent leukocyte-directed actions that include: 1) regulating chemotaxis of human neutrophils; and 2) enhancing phagocytosis and anti-inflammatory cytokine production. These actions appear to be mediated by leukocyte G-protein-coupled receptors as preparation of labeled RvE2 gave direct evidence for specific binding of radiolabeled RvE2 to neutrophils (K(d) 24.7 ± 10.1 nM) and resolvin E1 activation of recombinant G-protein-coupled receptors was assessed. In addition to the murine inflammatory milieu, RvE2 was also identified in plasma from healthy human subjects. RvE2 rapidly downregulated surface expression of human leukocyte integrins in whole blood and dampened responses to platelet-activating factor. Together, these results indicate that RvE2 can stimulate host-protective actions throughout initiation and resolution in the innate inflammatory responses.
Asunto(s)
Quimiotaxis/inmunología , Ácido Eicosapentaenoico/análogos & derivados , Inmunidad Innata , Neutrófilos/inmunología , Fagocitosis/inmunología , Animales , Quimiotaxis/efectos de los fármacos , Regulación hacia Abajo/efectos de los fármacos , Regulación hacia Abajo/inmunología , Ácido Eicosapentaenoico/sangre , Ácido Eicosapentaenoico/inmunología , Ácido Eicosapentaenoico/farmacología , Femenino , Humanos , Inflamación/sangre , Inflamación/inmunología , Inflamación/patología , Integrinas/biosíntesis , Integrinas/inmunología , Masculino , Ratones , Neutrófilos/metabolismo , Neutrófilos/patología , Fagocitosis/efectos de los fármacos , Factor de Activación Plaquetaria/inmunología , Factor de Activación Plaquetaria/metabolismoRESUMEN
Asthma is a disease of airway inflammation that in most cases fails to resolve. The resolution of inflammation is an active process governed by specific chemical mediators, including D-series resolvins. In this study, we determined the impact of resolvin D1 (RvD1) and aspirin-triggered RvD1 (AT-RvD1) on the development of allergic airway responses and their resolution. Mice were allergen sensitized, and RvD1, AT-RvD1 (1, 10, or 100 ng), or vehicle was administered at select intervals before or after aerosol allergen challenge. RvD1 markedly decreased airway eosinophilia and mucus metaplasia, in part by decreasing IL-5 and IκBα degradation. For the resolution of established allergic airway responses, AT-RvD1 was even more efficacious than RvD1, leading to a marked decrease in the resolution interval for lung eosinophilia, decrements in select inflammatory peptide and lipid mediators, and more rapid resolution of airway hyperreactivity to methacholine. Relative to RvD1, AT-RvD1 resisted metabolic inactivation by macrophages, and AT-RvD1 significantly enhanced macrophage phagocytosis of IgG-OVA-coated beads in vitro and in vivo, a new proresolving mechanism for the clearance of allergen from the airways. In conclusion, RvD1 and AT-RvD1 can serve as important modulators of allergic airway responses by decreasing eosinophils and proinflammatory mediators and promoting macrophage clearance of allergen. Together, these findings identify D-series resolvins as potential proresolving therapeutic agents for allergic responses.
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Asma/inmunología , Ácidos Docosahexaenoicos/inmunología , Hipersensibilidad/inmunología , Animales , Aspirina/farmacología , Asma/metabolismo , Western Blotting , Líquido del Lavado Bronquioalveolar/química , Líquido del Lavado Bronquioalveolar/inmunología , Quimiotaxis de Leucocito/inmunología , Citocinas/biosíntesis , Modelos Animales de Enfermedad , Ácidos Docosahexaenoicos/metabolismo , Perfilación de la Expresión Génica , Hipersensibilidad/metabolismo , Inmunohistoquímica , Macrófagos/inmunología , Masculino , Ratones , Isoformas de Proteínas/inmunología , Isoformas de Proteínas/metabolismo , Reacción en Cadena en Tiempo Real de la Polimerasa , Reacción en Cadena de la Polimerasa de Transcriptasa InversaRESUMEN
The mammalian gut is the most densely colonized organ by microbial species, which are in constant contact with the host throughout life. Hosts have developed multifaceted cellular and molecular mechanisms to distinguish and respond to benign and pathogenic bacteria. In addition to relatively well-characterized innate and adaptive immune cells, a growing body of evidence shows additional important players in gut mucosal immunity. Among them, unconventional immune cells, including innate lymphoid cells (ILCs) and unconventional T cells, are essential for maintaining homeostasis. These cells rapidly respond to bacterial signals and bridge the innate immunity and adaptive immunity in the mucosal barrier. Here, we focus on the types and roles of these immune cells in physiological and pathological conditions as prominent mechanisms by which the host immune system communicates with the gut microbiota in health and diseases.
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Microbioma Gastrointestinal , Microbiota , Animales , Inmunidad Innata , Mucosa Intestinal/microbiología , Linfocitos , Bacterias , Inmunidad Mucosa , MamíferosRESUMEN
Symbiotic microbiota critically contribute to host immune homeostasis in effector cell-specific manner. For exclusion of microbial component, germ-free animals have been the gold standard method. However, total removal of the entire gut microbiota of an animal from birth significantly skews physiological development. On the other hand, removal of gut microbiota from conventional mice using oral antibiotics has its own limitations, especially lack of consistency and the requirement for long-term treatment period. Here, we introduce an improved regimen to quickly remove gut microbiota and to maintain sterility, that is well received by animals without refusal. Rapid and consistent exclusion of resident bacteria in the gut lumen revealed kinetic differences among colonic lymphocyte subsets, which cannot be observed with typical germ-free animal models. Furthermore, the proposed method distinguished the mechanism of microbiota contribution as a direct stimulus to capable effector cells and a homeostatic cue to maintain such cell types.
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Microbioma Gastrointestinal , Microbiota , Animales , Ratones , Microbiota/fisiología , Colon , Bacterias/genética , Bacterias/metabolismo , HomeostasisRESUMEN
Bioactive metabolites produced by symbiotic microbiota causally impact host health and disease, nonetheless, incomplete functional annotation of genes as well as complexities and dynamic nature of microbiota make understanding species-level contribution in production and actions difficult. Alpha-galactosylceramides produced by Bacteroides fragilis (BfaGC) are one of the first modulators of colonic immune development, but biosynthetic pathways and the significance of the single species in the symbiont community still remained elusive. To address these questions at the microbiota level, we have investigated the lipidomic profiles of prominent gut symbionts and the metagenome-level landscape of responsible gene signatures in the human gut. We first elucidated the chemical diversity of sphingolipid biosynthesis pathways of major bacterial species. In addition to commonly shared ceramide backbone synthases showing two distinct intermediates, alpha-galactosyltransferase (agcT), the necessary and sufficient component for BfaGC production and host colonic type I natural killer T (NKT) cell regulation by B. fragilis, was characterized by forward-genetics based targeted metabolomic screenings. Phylogenetic analysis of agcT in human gut symbionts revealed that only a few ceramide producers have agcT and hence can produce aGCs, on the other hand, structurally conserved homologues of agcT are widely distributed among species lacking ceramides. Among them, alpha-glucosyl-diacylglycerol(aGlcDAG)-producing glycosyltransferases with conserved GT4-GT1 domains are one of the most prominent homologs in gut microbiota, represented by Enterococcus bgsB . Of interest, aGlcDAGs produced by bgsB can antagonize BfaGC-mediated activation of NKT cells, showing the opposite, lipid structure-specific actions to regulate host immune responses. Further metagenomic analysis of multiple human cohorts uncovered that the agcT gene signature is almost exclusively contributed by B. fragilis , regardless of age, geographical and health status, where the bgsB signature is contributed by >100 species, of which abundance of individual microbes is highly variable. Our results collectively showcase the diversities of gut microbiota producing biologically relevant metabolites in multiple layers-biosynthetic pathways, host immunomodulatory functions and microbiome-level landscapes in the host.
RESUMEN
Control of the inflammatory response is of wide interest given its important role in many diseases. In recent years we identified novel mechanisms and lipid mediators that play an active role in stimulating the resolution of self-limited acute inflammation. These novel pro-resolving mediators include the essential fatty acid-derived lipoxins, resolvins, protectins and maresins. Members of each possess a unique pro-resolving mechanism of action; each limits neutrophilic infiltration, regulates local mediators (chemokines, cytokines) as well as stimulates macrophage-enhanced clearance of apoptotic PMN, cellular debris and microbes. Given this unique mechanism of action, resolvins have already been shown to play pivotal roles in regulating key events in a wide range of experimental inflammatory diseases. These pro-resolving mediators also provide a molecular link between omega-3 essential fatty acids (e.g. EPA, DHA) and the resolution process of inflammation and tissue homeostasis. Here, we review recent evidence obtained using chiral LC-MS-MS-based lipidomics to identify a novel 18S-series of resolvins derived from EPA. Resolvin E1 possesses potent actions in vivo and in vitro demonstrated now in many laboratories, and herein we review comparisons in E-series resolvin biosynthesis and action of 18S-resolvin E1 and 18S-resolvin E2. The biosynthesis and formation of both 18S and 18R-series are enhanced with aspirin treatment and involve the utilization of dietary EPA as well as recombinant human 5-lipoxygenase and LTA(4) hydrolase in their stereospecific biosynthesis. Herein we also demonstrate the utility of LC-MS-MS-based lipidomics in identifying resolvins, protectins and related products in marine organisms such as Engraulis (Peruvian anchovy). These new findings emphasize the utility of chiral LC-MS-MS lipidomics and the potential for identifying new resolution circuits with chiral LC-MS-MS-based lipidomics and metabolomics.
Asunto(s)
Aspirina/farmacología , Ácidos Docosahexaenoicos/análisis , Ácidos Docosahexaenoicos/química , Mediadores de Inflamación/metabolismo , Metabolismo de los Lípidos/efectos de los fármacos , Animales , Araquidonato 5-Lipooxigenasa/metabolismo , Ácidos Docosahexaenoicos/biosíntesis , Epóxido Hidrolasas/metabolismo , HumanosRESUMEN
Besides the prototypic innate and adaptive pathways, immune responses by innate-like lymphocytes have gained significant attention due to their unique roles. Among innate-like lymphocytes, unconventional T cells such as NKT cells and mucosal-associated invariant T (MAIT) cells recognize small nonpeptide molecules of specific chemical classes. Endogenous or microbial ligands are loaded to MHC class I-like molecule CD1d or MR1, and inducing immediate effector T cell and ligand structure is one of the key determinants of NKT/MAIT cell functions. Unconventional T cells are in close, constant contact with symbiotic microbes at the mucosal layer, and CD1d/MR1 can accommodate diverse metabolites produced by gut microbiota. There is a strong interest to identify novel immunoactive molecules of endobiotic (symbiont-produced) origin as new NKT/MAIT cell ligands, as well as new cognate Ags for previously uncharacterized unconventional T cell subsets. Further studies will open an possibility to explore basic biology as well as therapeutic potential.
Asunto(s)
Microbioma Gastrointestinal , Antígenos de Histocompatibilidad Clase I , Ligandos , Activación de Linfocitos , Antígenos de Histocompatibilidad Menor/metabolismoRESUMEN
Lipid phosphate phosphatases are a family of enzymes with diverse cellular metabolic functions. Phospholipid phosphatase 6 (PLPP6) is a regulator of cellular polyisoprenyl phosphates; however, its in vivo functions remain to be determined. Here, mouse PLPP6 was characterized to possess similar catalytic properties as the human enzyme. Plpp6 knockout mice (Plpp6 -/- ) were generated and displayed decreased airway allergen sensitization, pointing to a role for PLPP6 in the early events of lung allergic responses. Dendritic cell (DC) responses were investigated and endocytosis of allergen via macropinocytosis was decreased in Plpp6 -/- DCs that had lower cholesterol content. When reversed by cholesterol loading, the DC macropinocytosis defect is corrected. Adoptive transfer of Plpp6 -/- DCs to wild-type mice during sensitization was sufficient to decrease allergen-induced responses. Together, our findings have identified PLPP6 as a pivotal regulator of DC cholesterol content and macropinocytosis, cellular mechanisms that are important for pathologic responses in allergen-induced lung inflammation.