RESUMO
BACKGROUND: Factor XII (FXII) is a multifunctional protease capable of activating thrombotic and inflammatory pathways. FXII has been linked to thrombosis in extracorporeal membrane oxygenation (ECMO), but the role of FXII in ECMO-induced inflammatory complications has not been studied. We used novel gene-targeted FXII- deficient rats to evaluate the role of FXII in ECMO-induced thromboinflammation. METHODS: FXII-deficient (FXII-/-) Sprague-Dawley rats were generated using CRISPR/Cas9. A minimally invasive venoarterial (VA) ECMO model was used to compare wild-type (WT) and FXII-/- rats in 2 separate experimental cohorts: rats placed on ECMO without pharmacologic anticoagulation and rats anticoagulated with argatroban. Rats were maintained on ECMO for 1 hour or until circuit failure occurred. Comparisons were made with unchallenged rats and rats that underwent a sham surgical procedure without ECMO. RESULTS: FXII-/- rats were maintained on ECMO without pharmacologic anticoagulation with low resistance throughout the 1-hour experiment. In contrast, WT rats placed on ECMO without anticoagulation developed thrombotic circuit failure within 10 minutes. Argatroban provided a means to maintain WT and FXII-/- rats on ECMO for the 1-hour time frame without thrombotic complications. Analyses of these rats demonstrated that ECMO resulted in increased neutrophil migration into the liver that was significantly blunted by FXII deficiency. ECMO also resulted in increases in high molecular weight kininogen cleavage and complement activation that were abrogated by genetic deletion of FXII. CONCLUSIONS: FXII initiates hemostatic system activation and key inflammatory sequelae in ECMO, suggesting that therapies targeting FXII could limit both thromboembolism and inopportune inflammatory complications in this setting.
RESUMO
Hypoxia-inducible factor 1α (HIF-1α) regulates the immunometabolic phenotype of macrophages, including the orchestration of inflammatory and antimicrobial processes. Macrophages deficient in HIF-1α produce excessive quantities of the anti-inflammatory cytokine interleukin 10 (IL-10) during infection with the intracellular fungal pathogen Histoplasma capsulatum (R. A. Fecher, M. C. Horwath, D. Friedrich, J. Rupp, G. S. Deepe, J Immunol 197:565-579, 2016, https://doi.org/10.4049/jimmunol.1600342). Thus, the macrophage fails to become activated in response to proinflammatory cytokines and remains the intracellular niche of the pathogen. Here, we identify the tricarboxylic acid (TCA) cycle metabolite fumarate as the driver of IL-10 during macrophage infection with H. capsulatum in the absence of HIF-1α. Accumulation of fumarate reduced expression of a HIF-1α-dependent microRNA (miRNA), miR-27a, known to mediate decay of Il10 mRNA. Inhibition of fumarate accrual in vivo limited IL-10 and fungal growth. Our data demonstrate the critical role of HIF-1α in shaping appropriate TCA cycle activity in response to infection and highlight the consequences of a dysregulated immunometabolic response. IMPORTANCE Histoplasma capsulatum and related Histoplasma species are intracellular fungal pathogens endemic to broad regions of the globe, including the Americas, Africa, and Asia. While most infections resolve with mild or no symptoms, failure of the host to control fungal growth produces severe disease. Previously, we reported that loss of a key transcriptional regulator, hypoxia-inducible factor 1α (HIF-1α), in macrophages led to a lethal failure to control growth of Histoplasma (R. A. Fecher, M. C. Horwath, D. Friedrich, J. Rupp, G. S. Deepe, J Immunol 197:565-579, 2016, https://doi.org/10.4049/jimmunol.1600342). Inhibition of phagocyte activation due to excessive interleukin 10 by HIF-1α-deficient macrophages drove this outcome. In this study, we demonstrate that HIF-1α maintains contextually appropriate TCA cycle metabolism within Histoplasma-infected macrophages. The absence of HIF-1α results in excessive fumarate production that alters miRNA-27a regulation of interleukin-10. HIF-1α thus preserves the capacity of macrophages to transition from a permissive intracellular niche to the site of pathogen killing.
Assuntos
Fumaratos/metabolismo , Histoplasma/fisiologia , Histoplasmose/metabolismo , Subunidade alfa do Fator 1 Induzível por Hipóxia/metabolismo , Interleucina-10/metabolismo , Macrófagos/microbiologia , MicroRNAs/metabolismo , Animais , Ciclo do Ácido Cítrico , Histoplasma/genética , Histoplasmose/genética , Histoplasmose/microbiologia , Humanos , Subunidade alfa do Fator 1 Induzível por Hipóxia/genética , Interleucina-10/genética , Macrófagos/metabolismo , Camundongos , MicroRNAs/genéticaRESUMO
Interactions between the microbiota and mammalian host are essential for defense against infection, but the microbial-derived cues that mediate this relationship remain unclear. Here, we find that intestinal epithelial cell (IEC)-associated commensal bacteria, segmented filamentous bacteria (SFB), promote early protection against the pathogen Citrobacter rodentium, independent of CD4+ T cells. SFB induced histone modifications in IECs at sites enriched for retinoic acid receptor motifs, suggesting that SFB may enhance defense through retinoic acid (RA). Consistent with this, inhibiting RA signaling suppressed SFB-induced protection. Intestinal RA levels were elevated in SFB mice, despite the inhibition of mammalian RA production, indicating that SFB directly modulate RA. Interestingly, RA was produced by intestinal bacteria, and the loss of bacterial-intrinsic aldehyde dehydrogenase activity decreased the RA levels and increased infection. These data reveal RA as an unexpected microbiota-derived metabolite that primes innate defense and suggests that pre- and probiotic approaches to elevate RA could prevent or combat infections.
Assuntos
Bactérias/metabolismo , Enteropatias/metabolismo , Simbiose , Tretinoína/metabolismo , Animais , Bacillus cereus , Bifidobacterium bifidum , Linfócitos T CD4-Positivos , Citrobacter rodentium , Células Epiteliais , Código das Histonas , Interações entre Hospedeiro e Microrganismos , Enteropatias/microbiologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Microbiota , Óxido Nítrico , Transdução de SinaisRESUMO
Macrophages are indispensable immune cells tasked at eliminating intracellular pathogens. Mycobacterium tuberculosis (Mtb), one of the most virulent intracellular bacterial pathogens known to man, infects and resides within macrophages. While macrophages can be provoked by extracellular stimuli to inhibit and kill Mtb bacilli, these host defense mechanisms can be blocked by limiting nutritional metabolites, such as amino acids. The amino acid L-arginine has been well described to enhance immune function, especially in the context of driving macrophage nitric oxide (NO) production in mice. In this study, we aimed to establish the necessity of L-arginine on anti-Mtb macrophage function independent of NO. Utilizing an in vitro system, we identified that macrophages relied on NO for only half of their L-arginine-mediated host defenses and this L-arginine-mediated defense in the absence of NO was associated with enhanced macrophage numbers and viability. Additionally, we observed macrophage glycolysis to be driven by both L-arginine and mechanistic target of rapamycin (mTOR), and inhibition of glycolysis or mTOR reduced macrophage control of Mtb as well as macrophage number and viability in the presence of L-arginine. Our data underscore L-arginine as an essential nutrient for macrophage function, not only by fueling anti-mycobacterial NO production, but also as a central regulator of macrophage metabolism and additional host defense mechanisms.
Assuntos
Arginina/metabolismo , Suplementos Nutricionais , Macrófagos/imunologia , Mycobacterium tuberculosis/imunologia , Tuberculose/dietoterapia , Animais , Arginina/administração & dosagem , Argininossuccinato Liase/genética , Argininossuccinato Liase/metabolismo , Argininossuccinato Sintase/genética , Argininossuccinato Sintase/metabolismo , Sobrevivência Celular , Modelos Animais de Doenças , Humanos , Ativação de Macrófagos , Macrófagos/metabolismo , Camundongos , Camundongos Knockout , Óxido Nítrico/metabolismo , Cultura Primária de Células , Células RAW 264.7 , Tuberculose/imunologia , Tuberculose/microbiologiaRESUMO
Obesity is a prevalent predisposing factor to non-alcoholic fatty liver disease (NAFLD), the most common chronic liver disease in the developed world. NAFLD spectrum of disease involves progression from steatosis (NAFL), to steatohepatitis (NASH), cirrhosis and hepatocellular carcinoma (HCC). Despite clinical and public health significance, current FDA approved therapies for NAFLD are lacking in part due to insufficient understanding of pathogenic mechanisms driving disease progression. The etiology of NAFLD is multifactorial. The induction of both systemic and tissue inflammation consequential of skewed immune cell metabolic state, polarization, tissue recruitment, and activation are central to NAFLD progression. Here, we review the current understanding of the above stated cellular and molecular processes that govern macrophage contribution to NAFLD pathogenesis and how adipose tissue and liver crosstalk modulates macrophage function. Notably, the manipulation of such events may lead to the development of new therapies for NAFLD.
Assuntos
Suscetibilidade a Doenças , Macrófagos/imunologia , Macrófagos/metabolismo , Hepatopatia Gordurosa não Alcoólica/etiologia , Hepatopatia Gordurosa não Alcoólica/metabolismo , Animais , Biomarcadores , Movimento Celular , Plasticidade Celular/imunologia , Citocinas/metabolismo , Gerenciamento Clínico , Modelos Animais de Doenças , Metabolismo Energético , Humanos , Mediadores da Inflamação/metabolismo , Hepatopatia Gordurosa não Alcoólica/patologia , Hepatopatia Gordurosa não Alcoólica/terapia , Transdução de SinaisRESUMO
The CD44 gene encodes several protein isoforms due to alternative splicing and post translational modifications. Given that CD44 variant isoform 9 (CD44v9) is expressed within Spasmolytic Polypeptide/TFF2-Expressing Metaplasia (SPEM) glands during repair, CD44v9 may be play a funcitonal role during the process of regeneration of the gastric epithelium. Here we hypothesize that CD44v9 marks a regenerative cell lineage responsive to infiltrating macrophages during regeneration of the gastric epithelium. Ulcers were induced in CD44-deficient (CD44KO) and C57BL/6 (BL6) mice by a localized application of acetic acid to the serosal surface of the stomach. Gastric organoids expressing CD44v9 were derived from mouse stomachs and transplanted at the ulcer site of CD44KO mice. Ulcers, CD44v9 expression, proliferation and histology were measured 1, 3, 5 and 7-days post-injury. Human-derived gastric organoids were generated from stomach tissue collected from elderly (>55 years) or young (14-20 years) patients. Organoids were transplanted into the stomachs of NOD scid gamma (NSG) mice at the site of injury. Gastric injury was induced in NRG-SGM3 (NRGS) mice harboring human-derived immune cells (hnNRGS) and the immune profile anlayzed by CyTOF. CD44v9 expression emerged within regenerating glands the ulcer margin in response to injury. While ulcers in BL6 mice healed within 7-days post-injury, CD44KO mice exhibited loss of repair and epithelial regeneration. Ulcer healing was promoted in CD44KO mice by transplanted CD55v9-expressing gastric organoids. NSG mice exhibited loss of CD44v9 expression and gastric repair. Transplantation of human-derived gastric organoids from young, but not aged stomachs promoted repair in NSG mouse stomachs in response to injury. Finally, compared to NRGS mice, huNRGS animals exhibited reduced ulcer sizes, an infiltration of human CD162+ macrophages and an emergence of CD44v9 expression in SPEM. Thus, during repair of the gastic epithelium CD44v9 emerges within a regenerative cell lineage that coincides with macrophage inflitration within the injured mucosa. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Assuntos
Mucosa Gástrica/fisiologia , Receptores de Hialuronatos/genética , Regeneração/fisiologia , Úlcera Gástrica/metabolismo , Adolescente , Fatores Etários , Idoso , Animais , Células Cultivadas , Mucosa Gástrica/patologia , Variação Genética/fisiologia , Humanos , Receptores de Hialuronatos/metabolismo , Receptores de Hialuronatos/fisiologia , Macrófagos/fisiologia , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos NOD , Camundongos Knockout , Pessoa de Meia-Idade , Organoides/citologia , Organoides/transplante , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Isoformas de Proteínas/fisiologia , Regeneração/genética , Úlcera Gástrica/genética , Úlcera Gástrica/patologia , Cicatrização/fisiologia , Adulto JovemRESUMO
Modulation of T cell proliferation and function by immunoregulatory myeloid cells are an essential means of preventing self-reactivity and restoring tissue homeostasis. Consumption of amino acids such as arginine and tryptophan by immunoregulatory macrophages is one pathway that suppresses local T cell proliferation. Using a reduced complexity in vitro macrophage-T cell co-culture system, we show that macrophage arginase-1 is the only factor required by M2 macrophages to block T cells in G1, and this effect is mediated by l-arginine elimination rather than metabolite generation. Tracking how T cells adjust their metabolism when deprived of arginine revealed the significance of macrophage-mediated arginine deprivation to T cells. We found mTORC1 activity was unaffected in the initial G1 block. After 2 days of arginine deprivation, mTORC1 activity declined paralleling a selective down-regulation of SREBP target gene expression, whereas mRNAs involved in glycolysis, gluconeogenesis, and T cell activation were unaffected. Cell cycle arrest was reversible at any point by exogenous arginine, suggesting starved T cells remain poised awaiting nutrients. Arginine deprivation-induced cell cycle arrest was mediated in part by Rictor/mTORC2, providing evidence that this nutrient recognition pathway is a central component of how T cells measure environmental arginine.
Assuntos
Arginina/metabolismo , Proteínas de Transporte/metabolismo , Pontos de Checagem do Ciclo Celular/imunologia , Proliferação de Células , Complexos Multiproteicos/metabolismo , Células Mieloides/imunologia , Linfócitos T/imunologia , Serina-Treonina Quinases TOR/metabolismo , Animais , Células Cultivadas , Técnicas de Cocultura , Tolerância Imunológica , Terapia de Imunossupressão , Ativação Linfocitária , Alvo Mecanístico do Complexo 2 de Rapamicina , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Camundongos Knockout , Células Mieloides/metabolismo , Proteínas Proto-Oncogênicas c-akt/metabolismo , Proteína Companheira de mTOR Insensível à Rapamicina , Linfócitos T/metabolismoRESUMO
Effective cancer immunotherapy requires overcoming immunosuppressive tumor microenvironments. We found that local nitric oxide (NO) production by tumor-infiltrating myeloid cells is important for adoptively transferred CD8(+) cytotoxic T cells to destroy tumors. These myeloid cells are phenotypically similar to inducible nitric oxide synthase (NOS2)- and tumor necrosis factor (TNF)-producing dendritic cells (DC), or Tip-DCs. Depletion of immunosuppressive, colony stimulating factor 1 receptor (CSF-1R)-dependent arginase 1(+) myeloid cells enhanced NO-dependent tumor killing. Tumor elimination via NOS2 required the CD40-CD40L pathway. We also uncovered a strong correlation between survival of colorectal cancer patients and NOS2, CD40, and TNF expression in their tumors. Our results identify a network of pro-tumor factors that can be targeted to boost cancer immunotherapies.
Assuntos
Células Dendríticas/imunologia , Imunoterapia Adotiva/métodos , Neoplasias/imunologia , Neoplasias/terapia , Óxido Nítrico Sintase Tipo II/imunologia , Linfócitos T Citotóxicos/imunologia , Fator de Necrose Tumoral alfa/imunologia , Animais , Arginase/biossíntese , Arginase/imunologia , Antígenos CD40/imunologia , Ligante de CD40/imunologia , Linhagem Celular Tumoral , Humanos , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Óxido Nítrico Sintase Tipo II/biossíntese , Microambiente Tumoral , Fator de Necrose Tumoral alfa/biossínteseRESUMO
Tuberculosis (TB) granulomas are compact, organized agglomerations of infected and uninfected macrophages, T cells, neutrophils, and other immune cells. Within the granuloma, several unique metabolic adaptations occur to modify the behavior of immune cells, potentially favoring bacterial persistence balanced with protection against immunopathology. These include the induction of arginase-1 in macrophages to temper nitric oxide (NO) production and block T cell proliferation, inhibition of oxygen-requiring NO production in hypoxic regions, and induction of tryptophan-degrading enzymes that modify T cell proliferation and function. The spatial and time-dependent organization of granulomas further influences immunometabolism, for example through lactate production by activated macrophages, which can induce arginase-1. Although complex, the metabolic changes in and around TB granulomas can be potentially modified by host-directed therapies. While elimination of the TB bacilli is often the goal of any anti-TB therapy, host-directed approaches must also account for the possibility of immunopathologic damage to the lung.
Assuntos
Metabolismo Energético , Granuloma/etiologia , Granuloma/metabolismo , Interações Hospedeiro-Patógeno , Mycobacterium tuberculosis/imunologia , Tuberculose/imunologia , Tuberculose/patologia , Adaptação Fisiológica , Aminoácidos/metabolismo , Animais , Arginina/metabolismo , Respiração Celular , Colágeno/metabolismo , Interações Hospedeiro-Patógeno/imunologia , Humanos , Hipóxia/imunologia , Hipóxia/metabolismo , Ativação Linfocitária/imunologia , Macrófagos/imunologia , Macrófagos/metabolismo , Macrófagos/microbiologia , Óxido Nítrico/biossíntese , Espécies Reativas de Nitrogênio/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Estresse Fisiológico , Linfócitos T/imunologia , Linfócitos T/metabolismo , Triptofano/metabolismo , Tuberculose/complicações , Tuberculose/microbiologiaRESUMO
Cancer can involve non-resolving, persistent inflammation where varying numbers of tumor-associated macrophages (TAMs) infiltrate and adopt different activation states between anti-tumor M1 and pro-tumor M2 phenotypes. Here, we resolve a cascade causing differential macrophage phenotypes in the tumor microenvironment. Reduction in TNF mRNA production or loss of type I TNF receptor signaling resulted in a striking pattern of enhanced M2 mRNA expression. M2 gene expression was driven in part by IL-13 from eosinophils co-recruited with inflammatory monocytes, a pathway that was suppressed by TNF. Our data define regulatory nodes within the tumor microenvironment that balance M1 and M2 populations. Our results show macrophage polarization in cancer is dynamic and dependent on the balance between TNF and IL-13, thus providing a strategy for manipulating TAMs.
Assuntos
Macrófagos/metabolismo , Neoplasias/metabolismo , Fator de Necrose Tumoral alfa/metabolismo , Animais , Linhagem Celular Tumoral , Expressão Gênica , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Nus , Neoplasias/patologia , Transdução de Sinais , Microambiente TumoralRESUMO
Microbicidal NO production is reliant on inducible NO synthase-mediated L-arginine metabolism in macrophages (MΦs). However, L-arginine supply can be restricted by arginase activity, resulting in inefficient NO output and inhibition of antimicrobial MΦ function. MΦs circumvent this by converting L-citrulline to L-arginine, thereby resupplying substrate for NO production. In this article, we define the metabolic signature of mycobacteria-infected murine MΦs supplied L-arginine, L-citrulline, or both amino acids. Using liquid chromatography-tandem mass spectrometry, we determined that L-arginine synthesized from L-citrulline was less effective as a substrate for arginase-mediated L-ornithine production compared with L-arginine directly imported from the extracellular milieu. Following Mycobacterium bovis bacillus Calmette-Guérin infection and costimulation with IFN-γ, we observed that MΦ arginase activity did not inhibit production of NO derived from L-citrulline, contrary to NO inhibition witnessed when MΦs were cultured in L-arginine. Furthermore, we found that arginase-expressing MΦs preferred L-citrulline over L-arginine for the promotion of antimycobacterial activity. We expect that defining the consequences of L-citrulline metabolism in MΦs will provide novel approaches for enhancing immunity, especially in the context of mycobacterial disease.
Assuntos
Arginina/metabolismo , Citrulina/metabolismo , Macrófagos/metabolismo , Óxido Nítrico/metabolismo , Tuberculose/imunologia , Animais , Arginase/metabolismo , Arginina/biossíntese , Células Cultivadas , Interferon gama/farmacologia , Ativação de Macrófagos/efeitos dos fármacos , Macrófagos/imunologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Mycobacterium bovis/imunologia , Óxido Nítrico Sintase Tipo II/metabolismo , Tuberculose/microbiologiaRESUMO
Tristetraprolin (TTP) is an inducible zinc finger AU-rich RNA-binding protein essential for enforcing degradation of mRNAs encoding inflammatory chemokines and cytokines. Most studies on TTP center on the connection between mRNA half-life and inflammatory output, because loss of TTP amplifies inflammation by increasing the stability of AU-rich mRNAs. Here, we focused on how TTP controls cytokine and chemokine production in the nonresolving inflammation of cancer using tissue-specific approaches. In contrast with model in vitro macrophage systems, we found constitutive TTP expression in late-stage tumor-associated macrophages (TAM). However, TTP's effects on AU-rich mRNA stability were negligible and limited by constitutive p38α MAPK activity, which was the main driver of proinflammatory cytokine production in TAMs at the posttranscriptional level. Instead, elimination of TTP caused excessive protein production of inflammatory mediators, suggesting TTP-dependent translational suppression of AU-rich mRNAs. Manipulation of the p38α-TTP axis in macrophages has significant effects on the growth of tumors and therefore represents a means to manipulate inflammation in the tumor microenvironment.
Assuntos
Citocinas/metabolismo , Inflamação/metabolismo , Macrófagos/metabolismo , Estabilidade de RNA , Tristetraprolina/metabolismo , Animais , Inflamação/patologia , Mediadores da Inflamação/metabolismo , Macrófagos/patologia , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Proteína Quinase 14 Ativada por Mitógeno/metabolismo , Neoplasias Experimentais/metabolismo , Neoplasias Experimentais/patologia , Processamento Pós-Transcricional do RNA , Tristetraprolina/genéticaRESUMO
Nonresolving inflammation expands a heterogeneous population of myeloid suppressor cells capable of inhibiting T cell function. This heterogeneity has confounded the functional dissection of individual myeloid subpopulations and presents an obstacle for antitumor immunity and immunotherapy. Using genetic manipulation of cell death pathways, we found the monocytic suppressor-cell subset, but not the granulocytic subset, requires continuous c-FLIP expression to prevent caspase-8-dependent, RIPK3-independent cell death. Development of the granulocyte subset requires MCL-1-mediated control of the intrinsic mitochondrial death pathway. Monocytic suppressors tolerate the absence of MCL-1 provided cytokines increase expression of the MCL-1-related protein A1. Monocytic suppressors mediate T cell suppression, whereas their granulocytic counterparts lack suppressive function. The loss of the granulocytic subset via conditional MCL-1 deletion did not alter tumor incidence implicating the monocytic compartment as the functionally immunosuppressive subset in vivo. Thus, death pathway modulation defines the development, survival, and function of myeloid suppressor cells.
Assuntos
Proteína Reguladora de Apoptosis Semelhante a CASP8 e FADD/metabolismo , Granulócitos/fisiologia , Monócitos/fisiologia , Proteína de Sequência 1 de Leucemia de Células Mieloides/metabolismo , Células Mieloides/fisiologia , Neoplasias Experimentais/imunologia , Animais , Apoptose/genética , Proteína Reguladora de Apoptosis Semelhante a CASP8 e FADD/genética , Linfócitos T CD8-Positivos/imunologia , Carcinogênese/genética , Caspase 8/metabolismo , Diferenciação Celular/genética , Linhagem Celular Tumoral , Linhagem da Célula/genética , Técnicas de Cocultura , Proteína de Domínio de Morte Associada a Fas/genética , Proteína de Domínio de Morte Associada a Fas/metabolismo , Tolerância Imunológica/genética , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Antígenos de Histocompatibilidade Menor , Proteína de Sequência 1 de Leucemia de Células Mieloides/genética , Transplante de Neoplasias , Proteínas Proto-Oncogênicas c-bcl-2/genética , Proteínas Proto-Oncogênicas c-bcl-2/metabolismo , RNA Interferente Pequeno/genética , Transdução de Sinais/genéticaRESUMO
Lung granulomas develop upon Mycobacterium tuberculosis (Mtb) infection as a hallmark of human tuberculosis (TB). They are structured aggregates consisting mainly of Mtb-infected and -uninfected macrophages and Mtb-specific T cells. The production of NO by granuloma macrophages expressing nitric oxide synthase-2 (NOS2) via l-arginine and oxygen is a key protective mechanism against mycobacteria. Despite this protection, TB granulomas are often hypoxic, and bacterial killing via NOS2 in these conditions is likely suboptimal. Arginase-1 (Arg1) also metabolizes l-arginine but does not require oxygen as a substrate and has been shown to regulate NOS2 via substrate competition. However, in other infectious diseases in which granulomas occur, such as leishmaniasis and schistosomiasis, Arg1 plays additional roles such as T-cell regulation and tissue repair that are independent of NOS2 suppression. To address whether Arg1 could perform similar functions in hypoxic regions of TB granulomas, we used a TB murine granuloma model in which NOS2 is absent. Abrogation of Arg1 expression in macrophages in this setting resulted in exacerbated lung granuloma pathology and bacterial burden. Arg1 expression in hypoxic granuloma regions correlated with decreased T-cell proliferation, suggesting that Arg1 regulation of T-cell immunity is involved in disease control. Our data argue that Arg1 plays a central role in the control of TB when NOS2 is rendered ineffective by hypoxia.
Assuntos
Arginase/metabolismo , Granuloma/enzimologia , Hipóxia/enzimologia , Macrófagos/enzimologia , Mycobacterium tuberculosis , Tuberculose Pulmonar/enzimologia , Animais , Arginase/genética , Arginase/imunologia , Arginina/genética , Arginina/imunologia , Arginina/metabolismo , Proliferação de Células/genética , Modelos Animais de Doenças , Granuloma/genética , Granuloma/imunologia , Granuloma/patologia , Humanos , Hipóxia/genética , Hipóxia/imunologia , Hipóxia/patologia , Pulmão/enzimologia , Pulmão/imunologia , Pulmão/patologia , Macrófagos/imunologia , Macrófagos/patologia , Camundongos , Camundongos Knockout , Óxido Nítrico/genética , Óxido Nítrico/imunologia , Óxido Nítrico/metabolismo , Óxido Nítrico Sintase Tipo II/genética , Óxido Nítrico Sintase Tipo II/imunologia , Óxido Nítrico Sintase Tipo II/metabolismo , Linfócitos T/imunologia , Linfócitos T/metabolismo , Linfócitos T/patologia , Tuberculose Pulmonar/genética , Tuberculose Pulmonar/imunologia , Tuberculose Pulmonar/patologiaRESUMO
Newborn infants are highly susceptible to infection. This defect in host defence has generally been ascribed to the immaturity of neonatal immune cells; however, the degree of hyporesponsiveness is highly variable and depends on the stimulation conditions. These discordant responses illustrate the need for a more unified explanation for why immunity is compromised in neonates. Here we show that physiologically enriched CD71(+) erythroid cells in neonatal mice and human cord blood have distinctive immunosuppressive properties. The production of innate immune protective cytokines by adult cells is diminished after transfer to neonatal mice or after co-culture with neonatal splenocytes. Neonatal CD71(+) cells express the enzyme arginase-2, and arginase activity is essential for the immunosuppressive properties of these cells because molecular inhibition of this enzyme or supplementation with L-arginine overrides immunosuppression. In addition, the ablation of CD71(+) cells in neonatal mice, or the decline in number of these cells as postnatal development progresses parallels the loss of suppression, and restored resistance to the perinatal pathogens Listeria monocytogenes and Escherichia coli. However, CD71(+) cell-mediated susceptibility to infection is counterbalanced by CD71(+) cell-mediated protection against aberrant immune cell activation in the intestine, where colonization with commensal microorganisms occurs swiftly after parturition. Conversely, circumventing such colonization by using antimicrobials or gnotobiotic germ-free mice overrides these protective benefits. Thus, CD71(+) cells quench the excessive inflammation induced by abrupt colonization with commensal microorganisms after parturition. This finding challenges the idea that the susceptibility of neonates to infection reflects immune-cell-intrinsic defects and instead highlights processes that are developmentally more essential and inadvertently mitigate innate immune protection. We anticipate that these results will spark renewed investigation into the need for immunosuppression in neonates, as well as improved strategies for augmenting host defence in this vulnerable population.
Assuntos
Antígenos CD/metabolismo , Células Eritroides/imunologia , Infecções por Escherichia coli/imunologia , Tolerância Imunológica/imunologia , Listeriose/imunologia , Receptores da Transferrina/metabolismo , Animais , Animais Recém-Nascidos , Arginase/genética , Arginase/metabolismo , Suscetibilidade a Doenças/imunologia , Ativação Enzimática/efeitos dos fármacos , Inibidores Enzimáticos/farmacologia , Células Eritroides/enzimologia , Escherichia coli/imunologia , Feminino , Sangue Fetal/citologia , Humanos , Tolerância Imunológica/efeitos dos fármacos , Tolerância Imunológica/genética , Listeria monocytogenes/imunologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Fator de Necrose Tumoral alfa/metabolismoRESUMO
Th2-driven lung inflammation increases Arginase 1 (Arg1) expression in alternatively-activated macrophages (AAMs). AAMs modulate T cell and wound healing responses and Arg1 might contribute to asthma pathogenesis by inhibiting nitric oxide production, regulating fibrosis, modulating arginine metabolism and restricting T cell proliferation. We used mice lacking Arg1 in myeloid cells to investigate the contribution of Arg1 to lung inflammation and pathophysiology. In six model systems encompassing acute and chronic Th2-mediated lung inflammation we observed neither a pathogenic nor protective role for myeloid-expressed Arg1. The number and composition of inflammatory cells in the airways and lungs, mucus secretion, collagen deposition, airway hyper-responsiveness, and T cell cytokine production were not altered if AAMs were deficient in Arg1 or simultaneously in both Arg1 and NOS2. Our results argue that Arg1 is a general feature of alternative activation but only selectively regulates Th2 responses. Therefore, attempts to experimentally or therapeutically inhibit arginase activity in the lung should be examined with caution.
Assuntos
Arginase/metabolismo , Células Mieloides/imunologia , Células Mieloides/metabolismo , Pneumonia/imunologia , Pneumonia/metabolismo , Células Th2/imunologia , Animais , Antígenos de Helmintos/imunologia , Arginase/genética , Aspergillus/imunologia , Expressão Gênica , Granuloma/imunologia , Granuloma/metabolismo , Granuloma/patologia , Ativação de Macrófagos/genética , Ativação de Macrófagos/imunologia , Macrófagos/imunologia , Macrófagos/metabolismo , Macrófagos/patologia , Camundongos , Camundongos Knockout , Células Mieloides/patologia , Ovalbumina/imunologia , Pneumonia/genética , Pneumonia/patologia , Schistosoma mansoni/imunologiaRESUMO
Nitric oxide (NO) defends against intracellular pathogens, but its synthesis must be regulated due to cell and tissue toxicity. During infection, macrophages import extracellular arginine to synthesize NO, generating the byproduct citrulline. Accumulated intracellular citrulline is thought to fuel arginine synthesis catalyzed by argininosuccinate synthase (Ass1) and argininosuccinate lyase (Asl), which would lead to abundant NO production. Instead, we find that citrulline is exported from macrophages during early stages of NO production with <2% retained for recycling via the Ass1-Asl pathway. Later, extracellular arginine is depleted, and Ass1 expression allows macrophages to synthesize arginine from imported citrulline to sustain NO output. Ass1-deficient macrophages fail to salvage citrulline in arginine-scarce conditions, leading to their inability to control mycobacteria infection. Thus, extracellular arginine fuels rapid NO production in activated macrophages, and citrulline recycling via Ass1 and Asl is a fail-safe system that sustains optimum NO production.
Assuntos
Argininossuccinato Sintase/metabolismo , Macrófagos/imunologia , Macrófagos/metabolismo , Mycobacterium bovis/imunologia , Óxido Nítrico/metabolismo , Animais , Arginina/metabolismo , Argininossuccinato Sintase/genética , Células Cultivadas , Citrulina/metabolismo , CamundongosRESUMO
Macrophage infiltration often occurs in cancer and has stimulated new efforts to define macrophage function within solid tumors. The macrophage, a myelophagocytic cell of the immune system, is at the front line of pathogen defense, wound healing, and maintaining homeostasis within the body. However, increased macrophage numbers during cancer generally correlates with poor prognosis. This chapter will focus on the function of myelophagocytic cells within solid tumors, their potential roles in tumor progression, and the possibilities of their manipulation as a component of cancer therapy.