ABSTRACT
BACKGROUND: Arginine is an amino acid that serves as a substrate for the enzymes nitric oxide synthase (NOS) and arginase, leading to synthesis of NO and ornithine, respectively. As such, arginine has the potential to influence diverse fundamental processes in the lung. METHODS: We used mice deficient in cationic amino acid transporter (CAT) 2 in models of allergic airway inflammation and pulmonary fibrosis. RESULTS: We report that the arginine transport protein CAT2 was over-expressed in the lung during the induction of allergic airway inflammation. Furthermore, CAT2 mRNA was strongly induced by transgenically over-expressed IL-4, and allergen-induced expression was dependent upon signal-transducer-and-activator-of-transcription (STAT) 6. In situ mRNA hybridization demonstrated marked staining of CAT2, predominantly in scattered mononuclear cells. Analysis of allergic airway inflammation and bleomycin-induced inflammation in CAT2-deficient mice revealed that while inflammation was independent of CAT2 expression, bleomycin-induced fibrosis was dependent upon CAT2. Mechanistic analysis revealed that arginase activity in macrophages was partly dependent on CAT2. CONCLUSION: Taken together, these results identify CAT2 as a regulator of fibrotic responses in the lung.
Subject(s)
Amino Acid Transport Systems, Basic/metabolism , Asthma/metabolism , Lung/metabolism , Pulmonary Fibrosis/metabolism , Amino Acid Transport Systems, Basic/deficiency , Amino Acid Transport Systems, Basic/genetics , Animals , Arginase/metabolism , Arginine/metabolism , Asthma/chemically induced , Asthma/genetics , Asthma/immunology , Bleomycin , Collagen/metabolism , Cytokines/metabolism , Disease Models, Animal , Inflammation Mediators/metabolism , Interleukin-4/genetics , Interleukin-4/metabolism , Lung/immunology , Macrophages/enzymology , Mice , Mice, Inbred C57BL , Mice, Knockout , Mice, Transgenic , Ovalbumin , Pulmonary Fibrosis/chemically induced , Pulmonary Fibrosis/genetics , Pulmonary Fibrosis/immunology , RNA, Messenger/metabolism , STAT6 Transcription Factor/deficiency , STAT6 Transcription Factor/genetics , Up-RegulationABSTRACT
Arginine is an amino acid that serves as a substrate for nitric oxide synthase and arginase. As such, arginine has the potential to influence diverse fundamental processes in the lung. Here we report that the arginine transport protein, cationic amino acid transporter (CAT)2, has a critical role in regulating lung inflammatory responses. Analysis of CAT2-deficient mice revealed spontaneous inflammation in the lung. Marked eosinophilia, associated with up-regulation of eotaxin-1, was present in the bronchoalveolar lavage fluid of 3-week-old CAT2-deficient mice. The eosinophilia was gradually replaced by neutrophilia in adult mice, while eotaxin-1 levels decreased and GRO-alpha levels increased. Despite the presence of activated alveolar macrophages in CAT2-deficient mice, NO production was compromised in these cells. Examination of dendritic cell activation, which can be affected by NO release, indicated increased dendritic cell activation in the lungs of CAT2-deficient mice. This process was accompanied by an increase in the number of memory T cells. Thus, our data suggest that CAT2 regulates anti-inflammatory processes in the lungs via regulation of dendritic cell activation and subsequent T cell responses.
Subject(s)
Cationic Amino Acid Transporter 2/metabolism , Homeostasis/physiology , Inflammation , Lung/immunology , Animals , Cationic Amino Acid Transporter 2/deficiency , Dendritic Cells/cytology , Dendritic Cells/immunology , Immunologic Memory/immunology , Lung/cytology , Lung/pathology , Lymphocyte Activation/immunology , Macrophage Activation/immunology , Macrophages, Alveolar/enzymology , Mice , Nitric Oxide Synthase/metabolism , Phenotype , T-Lymphocytes/immunologyABSTRACT
The mechanisms of idiopathic pulmonary fibrosis pathogenesis, a chronic and progressive interstitial lung disease, remain elusive. The complement system, a crucial arm of the innate immune response, plays a pivotal role in several pathological disorders; however, the contribution of individual complement components to lung fibrosis has not yet been examined. Complement factor 5 (C5) and its cleavage product C5a are critical mediators in inflammatory diseases. Thus, to evaluate the role of C5 in lung fibrosis, we compared congenic C5-sufficient and C5-deficient mice in a well-characterized murine model of bleomycin-induced pulmonary fibrosis. C5-deficient mice had an exaggerated inflammatory phenotype compared with C5-sufficient mice during acute bleomycin-induced lung injury. These findings suggest a protective and anti-inflammatory role for C5, which was linked to the regulation of matrix metalloproteinases involved in cell migration. In contrast, C5 had a detrimental effect during chronic stages of bleomycin-induced injury, indicating a profibrotic role for C5. This deleterious activity for C5 was associated with expression of the fibrogenic cytokine TGF-beta1 and matrix metalloproteinase-3, an important mediator in fibroblast contraction. Altogether, our data reveal novel and opposing roles for C5 in both inflammation and tissue repair. Furthermore, these findings provide insight into the development of new therapeutic strategies for idiopathic pulmonary fibrosis patients.
Subject(s)
Bleomycin , Complement C5/physiology , Pulmonary Fibrosis/chemically induced , Pulmonary Fibrosis/immunology , Animals , Antibodies, Blocking/administration & dosage , Antibodies, Blocking/therapeutic use , Antibodies, Monoclonal/administration & dosage , Antibodies, Monoclonal/therapeutic use , Chronic Disease , Collagen/antagonists & inhibitors , Collagen/biosynthesis , Complement C5/antagonists & inhibitors , Complement C5/deficiency , Complement C5/genetics , Complement C5a/physiology , Disease Models, Animal , Fibroblasts/drug effects , Fibroblasts/enzymology , Fibroblasts/immunology , Fibroblasts/metabolism , Lung/drug effects , Lung/immunology , Lung/metabolism , Lung/pathology , Matrix Metalloproteinase 3/biosynthesis , Matrix Metalloproteinase Inhibitors , Matrix Metalloproteinases/biosynthesis , Mice , Mice, Congenic , Mice, Inbred C57BL , NIH 3T3 Cells , Pulmonary Fibrosis/mortality , Pulmonary Fibrosis/prevention & control , RNA, Messenger/antagonists & inhibitors , RNA, Messenger/biosynthesis , Transforming Growth Factor beta/antagonists & inhibitors , Transforming Growth Factor beta/biosynthesis , Transforming Growth Factor beta/genetics , Transforming Growth Factor beta1ABSTRACT
The selectin family of cell adhesion molecules is widely thought to promote inflammatory reactions by facilitating leukocyte recruitment. However, it was unexpectedly found that mice with targeted deletion of the P-selectin gene (PsKO mice) developed unpolarized type 1/type 2 cytokine responses and severely aggravated liver pathology following infection with the type 2-promoting pathogen Schistosoma mansoni. In fact, liver fibrosis, which is dependent on interleukin 13 (IL-13), increased by a factor of more than 6, despite simultaneous induction of the antifibrotic cytokine interferon gamma (IFN-gamma). Inflammation, as measured by granuloma size, also increased significantly in the absence of P-selectin. When infected PsKO mice were treated with neutralizing anti-IFN-gamma monoclonal antibodies, however, granuloma size was restored to wild-type levels; this finding revealed the potent proinflammatory role of IFN-gamma when expressed concomitantly with IL-13. Untreated PsKO mice also exhibited a significant (sixfold) reduction in decoy IL-13 receptor (IL-13 receptor alpha-2) expression when compared with infected wild-type animals. It is noteworthy, however, that when decoy receptor activity was restored in PsKO mice by treatment with soluble IL-13 receptor alpha-2-Fc, the exacerbated fibrotic response was completely inhibited. Thus, reduced expression of the decoy IL-13 receptor mediated by the elevated type 1 cytokine response probably accounts for the enhanced activity of IL-13 in PsKO mice and for the resultant increase in collagen deposition. In conclusion, the current study has revealed the critical role of P-selectin in the progression of chronic liver disease caused by schistosome parasites. By suppressing IFN-gamma and up-regulating the decoy IL-13 receptor, P-selectin dramatically inhibits the pathologic tissue remodeling that results from chronic type 2 cytokine-mediated inflammation.
Subject(s)
Hepatitis/prevention & control , Interferon-gamma/metabolism , Liver Cirrhosis/prevention & control , P-Selectin/metabolism , Receptors, Interleukin/metabolism , Schistosomiasis/metabolism , Animals , Antibodies, Monoclonal/pharmacology , Chronic Disease , Cytokines/metabolism , Eosinophilia/pathology , Female , Granuloma, Respiratory Tract/pathology , Interferon-gamma/immunology , Interleukin-13 Receptor alpha1 Subunit , Liver Cirrhosis/pathology , Lung Diseases/pathology , Mice , Mice, Inbred C57BL , Mice, Knockout/genetics , P-Selectin/genetics , Protein Isoforms/metabolism , Receptors, Interleukin-13ABSTRACT
Highly polarized type 2 cytokine responses can be harmful and even lethal to the host if they are too vigorous or persist too long. Therefore, it is important to elucidate the mechanisms that down-regulate these reactions. Interleukin (IL)-13 has emerged as a central mediator of T helper cell (Th)2-dominant immune responses, exhibiting a diverse array of functional activities including regulation of airway hyperreactivity, resistance to nematode parasites, and tissue remodeling and fibrosis. Here, we show that IL-13 receptor (R)alpha2 is a critical down-regulatory factor of IL-13-mediated tissue fibrosis induced by the parasitic helminth Schistosoma mansoni. IL-13Ralpha2 expression was induced after the onset of the fibrotic response, IL-10, IL-13, and Stat6 dependent, and inhibited by the Th1-inducing adjuvant IL-12. Strikingly, schistosome-infected C57BL/6 and BALB/c IL-13Ralpha2-deficient mice showed a marked exacerbation in hepatic fibrosis, despite displaying no change in granuloma size, tissue eosinophilia, or mastocytosis. Fibrosis increased despite the fact that IL-13 levels decreased significantly in the liver and serum. Importantly, pathology was prevented when IL-13Ralpha2-deficient mice were treated with a soluble IL-13Ralpha2-Fc construct, formally demonstrating that their exacerbated fibrotic response was due to heightened IL-13 activity. Together, these studies illustrate the central role played by the IL-13Ralpha2 in the down-regulation of a chronic and pathogenic Th2-mediated immune response.
Subject(s)
Interleukin-13/physiology , Liver Cirrhosis/immunology , Receptors, Interleukin/metabolism , Schistosomiasis mansoni/immunology , Th2 Cells/immunology , Animals , Down-Regulation , Female , Humans , Interleukin-13/immunology , Interleukin-13 Receptor alpha1 Subunit , Liver/immunology , Liver/metabolism , Liver/parasitology , Liver/pathology , Liver Cirrhosis/pathology , Mice , Mice, Inbred BALB C , Mice, Inbred C57BL , Mice, Knockout , Receptors, Interleukin/genetics , Receptors, Interleukin/immunology , Receptors, Interleukin-13 , Receptors, Interleukin-4/genetics , Receptors, Interleukin-4/immunology , Receptors, Interleukin-4/metabolism , Schistosoma mansoni/immunology , Schistosomiasis mansoni/pathologyABSTRACT
En numerosas regiones del Continente Americano y aun de Argentina existe superposición de áreas endémicas de dos importantes parasitoses como son la enfermedad de Chagas y la leishmaniasis. Los parásitos causantes de ambas pertenecen a la misma familia (Trypanosomatidae) por lo que el diagnóstico serológico diferencial con antígenos convencionales se ve dificultado por la existencia de fenómenos de reactividad cruzada. En este trabajo estudiamos pacientes provenientes de una zona endémica para ambas parasitosis (Tartagal-Orán, Salta) que consultaron por lesiones cutáneas o mucoctáneas compatibles con leishmaniasis. El estudio de los sueros, utilizando Ag complejos de Leishmania, mostró inusualmente altos porcentajes de positividad para pacientes leishmaniásicos. El análisis empleando pruebas convencionales frente a Ag heterólogos complejos de T. cruzi, reveló que la mayoría daban positivas estas reacciones. La utilización de 2 técnicas no convencionales para el diagnóstico de enfermedad de Chagas, permitó dividir los pacientes en 2 grupos: 1. Con evidencias de infección por T. cruzi: aquellos que dieron positivo en ELISA utilizando un Ag específico purificado con un Ac monoclonal (Ag163B6) o que presentaban un patrón de bandas característico de pacientes chagásicos por "immunoblotting" frente a epimastigotes; 2. Pacientes sin evidencias de infección por T. cruzi: aquellos negativos para ambas técnicas. Se pudo comprobar así que más del 50 por ciento de los leishmaniásicos presentaba fuertes evidencias de una infección concomitante con T. cruzi. Además, el alto grado de reactividad cruzada quedó de manifesto en el grupo de pacientes sin evidencia de infección por T. cruzi, ya que el 60 por ciento dio positivas al menos 2 reacciones convencionales considerándoselos por ende como chagásicos, pero dieron negativas ambas reacciones específicas. Estos resultados destacan la importancia de contar con Ag definidos y técnicas apropriadas para el diagnóstico serológico diferencial de estas parasitosis, lo cual cobra mayor importancia en las zonas donde ambas son endémicas.
Subject(s)
Humans , Male , Female , Child , Adolescent , Adult , Middle Aged , Chagas Disease/blood , Leishmania mexicana/isolation & purification , Leishmaniasis, Cutaneous/blood , Trypanosoma cruzi/isolation & purification , Antibodies, Monoclonal , Antigens , Argentina , Cross Reactions , Diagnosis, Differential , Chagas Disease/immunology , Enzyme-Linked Immunosorbent Assay , Fluorescent Antibody Technique , Hemagglutination Tests , Immunoblotting , Leishmaniasis, Cutaneous/immunologyABSTRACT
En numerosas regiones del Continente Americano y aun de Argentina existe superposición de áreas endémicas de dos importantes parasitoses como son la enfermedad de Chagas y la leishmaniasis. Los parásitos causantes de ambas pertenecen a la misma familia (Trypanosomatidae) por lo que el diagnóstico serológico diferencial con antígenos convencionales se ve dificultado por la existencia de fenómenos de reactividad cruzada. En este trabajo estudiamos pacientes provenientes de una zona endémica para ambas parasitosis (Tartagal-Orán, Salta) que consultaron por lesiones cutáneas o mucoctáneas compatibles con leishmaniasis. El estudio de los sueros, utilizando Ag complejos de Leishmania, mostró inusualmente altos porcentajes de positividad para pacientes leishmaniásicos. El análisis empleando pruebas convencionales frente a Ag heterólogos complejos de T. cruzi, reveló que la mayoría daban positivas estas reacciones. La utilización de 2 técnicas no convencionales para el diagnóstico de enfermedad de Chagas, permitó dividir los pacientes en 2 grupos: 1. Con evidencias de infección por T. cruzi: aquellos que dieron positivo en ELISA utilizando un Ag específico purificado con un Ac monoclonal (Ag163B6) o que presentaban un patrón de bandas característico de pacientes chagásicos por "immunoblotting" frente a epimastigotes; 2. Pacientes sin evidencias de infección por T. cruzi: aquellos negativos para ambas técnicas. Se pudo comprobar así que más del 50 por ciento de los leishmaniásicos presentaba fuertes evidencias de una infección concomitante con T. cruzi. Además, el alto grado de reactividad cruzada quedó de manifesto en el grupo de pacientes sin evidencia de infección por T. cruzi, ya que el 60 por ciento dio positivas al menos 2 reacciones convencionales considerándoselos por ende como chagásicos, pero dieron negativas ambas reacciones específicas. Estos resultados destacan la importancia de contar con Ag definidos y técnicas apropriadas para el diagnóstico serológico diferencial de estas parasitosis, lo cual cobra mayor importancia en las zonas donde ambas son endémicas. (AU)
