N-Oleoyl dopamine induces IL-10 via central nervous system TRPV1 and improves endotoxemia and sepsis outcomes.

BACKGROUND: The transient receptor potential vanilloid 1 (TRPV1) participates in thermosensation and inflammatory pain, but its immunomodulatory mechanisms remain enigmatic. N-Oleoyl dopamine (OLDA), an endovanilloid and endocannabinoid, is a TRPV1 agonist that is produced in the central nervous system and the peripheral nervous system. We studied the anti-inflammatory effects and TRPV1-dependent mechanisms of OLDA in models of inflammation and sepsis. METHODS: Mice were challenged intratracheally or intravenously with LPS, or intratracheally with S. aureus to induce pneumonia and sepsis, and then were treated intravenously with OLDA. Endpoints included plasma cytokines, leukocyte activation marker expression, mouse sepsis scores, lung histopathology, and bacterial counts. The role of TRPV1 in the effects of OLDA was determined using Trpv1-/- mice, and mice with TRPV1 knockdown pan-neuronally, in peripheral nervous system neurons, or in myeloid cells. Circulating monocytes/macrophages were depleted using clodronate to determine their role in the anti-inflammatory effects of OLDA in endotoxemic mice. Levels of exogenous OLDA, and of endovanilloids and endocannabinoids, at baseline and in endotoxemic mice, were determined by LC-MS/MS. RESULTS: OLDA administration caused an early anti-inflammatory response in endotoxemic and septic mice with high serum levels of IL-10 and decreased levels of pro-inflammatory cytokines. OLDA also reduced lung injury and improved mouse sepsis scores. Blood and lung bacterial counts were comparable between OLDA- and carrier-treated mice with S. aureus pneumonia. OLDA's effects were reversed in mice with pan-neuronal TRPV1 knockdown, but not with TRPV1 knockdown in peripheral nervous system neurons or myeloid cells. Depletion of monocytes/macrophages reversed the IL-10 upregulation by OLDA in endotoxemic mice. Brain and blood levels of endovanilloids and endocannabinoids were increased in endotoxemic mice. CONCLUSIONS: OLDA has strong anti-inflammatory actions in mice with endotoxemia or S. aureus pneumonia. Prior studies focused on the role of peripheral nervous system TRPV1 in modulating inflammation and pneumonia. Our results suggest that TRPV1-expressing central nervous system neurons also regulate inflammatory responses to endotoxemia and infection. Our study reveals a neuro-immune reflex that during acute inflammation is engaged proximally by OLDA acting on neuronal TRPV1, and through a multicellular network that requires circulating monocytes/macrophages, leads to the systemic production of IL-10.

Activation of CB1R Promotes Lipopolysaccharide-Induced IL-10 Secretion by Monocytic Myeloid-Derived Suppressive Cells and Reduces Acute Inflammation and Organ Injury.

Cannabis sativa and its principal components, Δ9-tetrahydrocannabinol (Δ9-THC) and cannabidiol, are increasingly being used to treat a variety of medical problems, including inflammatory conditions. Although studies suggest that the endocannabinoid system has immunomodulatory properties, there remains a paucity of information on the effects of cannabinoids on immunity and on outcomes of infection and injury. We investigated the effects and mechanism(s) of action of cannabinoid receptor agonists, including Δ9-THC, on inflammation and organ injury in endotoxemic mice. Administration of Δ9-THC caused a dramatic early upregulation of plasma IL-10 levels, reduced plasma IL-6 and CCL-2 levels, led to better clinical status, and attenuated organ injury in endotoxemic mice. The anti-inflammatory effects of Δ9-THC in endotoxemic mice were reversed by a cannabinoid receptor type 1 (CB1R) inverse agonist (SR141716), and by clodronate-induced myeloid-cell depletion, but not by genetic invalidation or blockade of other putative Δ9-THC receptors, including cannabinoid receptor type 2, TRPV1, GPR18, GPR55, and GPR119. Although Δ9-THC administration reduced the activation of several spleen immune cell subsets, the anti-inflammatory effects of Δ9-THC were preserved in splenectomized endotoxemic mice. Finally, using IL-10-GFP reporter mice, we showed that blood monocytic myeloid-derived suppressive cells mediate the Δ9-THC-induced early rise in circulating IL-10. These results indicate that Δ9-THC potently induces IL-10, while reducing proinflammatory cytokines, chemokines, and related organ injury in endotoxemic mice via the activation of CB1R. These data have implications for acute and chronic conditions that are driven by dysregulated inflammation, such as sepsis, and raise the possibility that CB1R-signaling may constitute a novel target for inflammatory disorders.

Macrophage FABP4 is required for neutrophil recruitment and bacterial clearance in Pseudomonas aeruginosa pneumonia.

Fatty acid binding protein 4 (FABP4), an intracellular lipid chaperone and adipokine, is expressed by lung macrophages, but the function of macrophage-FABP4 remains elusive. We investigated the role of FABP4 in host defense in a murine model of Pseudomonas aeruginosa pneumonia. Compared with wild-type (WT) mice, FABP4-deficient (FABP4-/-) mice exhibited decreased bacterial clearance and increased mortality when challenged intranasally with P. aeruginosa. These findings in FABP4-/- mice were associated with a delayed neutrophil recruitment into the lungs and were followed by greater acute lung injury and inflammation. Among leukocytes, only macrophages expressed FABP4 in WT mice with P. aeruginosa pneumonia. Chimeric FABP4-/- mice with WT bone marrow were protected from increased mortality seen in chimeric WT mice with FABP4-/- bone marrow during P. aeruginosa pneumonia, thus confirming the role of macrophages as the main source of protective FABP4 against that infection. There was less production of C-X-C motif chemokine ligand 1 (CXCL1) in FABP4-/- alveolar macrophages and lower airway CXCL1 levels in FABP4-/- mice. Delivering recombinant CXCL1 to the airways protected FABP4-/- mice from increased susceptibility to P. aeruginosa pneumonia. Thus, macrophage-FABP4 has a novel role in pulmonary host defense against P. aeruginosa infection by facilitating crosstalk between macrophages and neutrophils via regulation of macrophage CXCL1 production.-Liang, X., Gupta, K., Rojas Quintero, J., Cernadas, M., Kobzik, L., Christou, H., Pier, G. B., Owen, C. A., Çataltepe, S. Macrophage FABP4 is required for neutrophil recruitment and bacterial clearance in Pseudomonas aeruginosa pneumonia.

Delayed Administration of Recombinant Plasma Gelsolin Improves Survival in a Murine Model of Penicillin-Susceptible and Penicillin-Resistant Pneumococcal Pneumonia.

Therapy to enhance host immune defenses may improve outcomes in serious infections, especially for antibiotic-resistant pathogens. Recombinant human plasma gelsolin (rhu-pGSN), a normally circulating protein, has beneficial effects in diverse preclinical models of inflammation and injury. We evaluated delayed therapy (24-48 hours after challenge) with rhu-pGSN in a mouse model of pneumococcal pneumonia. rhu-pGSN without antibiotics increased survival and reduced morbidity and weight loss after infection with either penicillin-susceptible or penicillin-resistant pneumococci (serotypes 3 and 14, respectively). rhu-pGSN improves outcomes in a highly lethal pneumococcal pneumonia model when given after a clinically relevant delay, even in the setting of antimicrobial resistance.

Correction: The Influence of Programmed Cell Death in Myeloid Cells on Host Resilience to Infection with Legionella pneumophila or Streptococcus pyogenes.

[This corrects the article DOI: 10.1371/journal.ppat.1006032.].

The relative resistance of children to sepsis mortality: from pathways to drug candidates.

Attempts to develop drugs that address sepsis based on leads developed in animal models have failed. We sought to identify leads based on human data by exploiting a natural experiment: the relative resistance of children to mortality from severe infections and sepsis. Using public datasets, we identified key differences in pathway activity (Pathprint) in blood transcriptome profiles of septic adults and children. To find drugs that could promote beneficial (child) pathways or inhibit harmful (adult) ones, we built an in silico pathway drug network (PDN) using expression correlation between drug, disease, and pathway gene signatures across 58,475 microarrays. Specific pathway clusters from children or adults were assessed for correlation with drug-based signatures. Validation by literature curation and by direct testing in an endotoxemia model of murine sepsis of the most correlated drug candidates demonstrated that the Pathprint-PDN methodology is more effective at generating positive drug leads than gene-level methods (e.g., CMap). Pathway-centric Pathprint-PDN is a powerful new way to identify drug candidates for intervention against sepsis and provides direct insight into pathways that may determine survival.

A Consensus Definitive Classification of Scavenger Receptors and Their Roles in Health and Disease.

Scavenger receptors constitute a large family of proteins that are structurally diverse and participate in a wide range of biological functions. These receptors are expressed predominantly by myeloid cells and recognize a diverse variety of ligands including endogenous and modified host-derived molecules and microbial pathogens. There are currently eight classes of scavenger receptors, many of which have multiple names, leading to inconsistencies and confusion in the literature. To address this problem, a workshop was organized by the United States National Institute of Allergy and Infectious Diseases, National Institutes of Health, to help develop a clear definition of scavenger receptors and a standardized nomenclature based on that definition. Fifteen experts in the scavenger receptor field attended the workshop and, after extensive discussion, reached a consensus regarding the definition of scavenger receptors and a proposed scavenger receptor nomenclature. Scavenger receptors were defined as cell surface receptors that typically bind multiple ligands and promote the removal of nonself or altered-self targets. They often function by mechanisms that include endocytosis, phagocytosis, adhesion, and signaling that ultimately lead to the elimination of degraded or harmful substances. Based on this definition, nomenclature and classification of these receptors into 10 classes were proposed. This classification was discussed at three national meetings and input from participants at these meetings was requested. The following manuscript is a consensus statement that combines the recommendations of the initial workshop and incorporates the input received from the participants at the three national meetings.

Future Research Directions in Pneumonia. NHLBI Working Group Report.

Pneumonia is a complex pulmonary disease in need of new clinical approaches. Although triggered by a pathogen, pneumonia often results from dysregulations of host defense that likely precede infection. The coordinated activities of immune resistance and tissue resilience then dictate whether and how pneumonia progresses or resolves. Inadequate or inappropriate host responses lead to more severe outcomes such as acute respiratory distress syndrome and to organ dysfunction beyond the lungs and over extended time frames after pathogen clearance, some of which increase the risk for subsequent pneumonia. Improved understanding of such host responses will guide the development of novel approaches for preventing and curing pneumonia and for mitigating the subsequent pulmonary and extrapulmonary complications of pneumonia. The NHLBI assembled a working group of extramural investigators to prioritize avenues of host-directed pneumonia research that should yield novel approaches for interrupting the cycle of unhealthy decline caused by pneumonia. This report summarizes the working group's specific recommendations in the areas of pneumonia susceptibility, host response, and consequences. Overarching goals include the development of more host-focused clinical approaches for preventing and treating pneumonia, the generation of predictive tools (for pneumonia occurrence, severity, and outcome), and the elucidation of mechanisms mediating immune resistance and tissue resilience in the lung. Specific areas of research are highlighted as especially promising for making advances against pneumonia.

Inactivation of common hospital acquired pathogens on surfaces and in air utilizing engineered water nanostructures (EWNS) based nano-sanitizers.

Infectious diseases represent a major public health challenge worldwide. There are various modes for the transmission of these diseases, with surface and airborne transmission being two of the most important ones. The inefficiencies of current intervention methods have resulted in the emergence of nosocomial infections. Here, we report the use of a nanotechnology based antimicrobial platform using Engineered Water Nanostructures (EWNS) generated using a combined electrospray and ionization of an aqueous suspension of various active ingredients (AIs). These EWNS based nano-sanitizers were tested in terms of their ability to efficiently deliver AI and inactivate Acinetobacter baumannii and influenza H1N1/PR/8 on both surfaces and air. Results indicate a significant reduction in the concertation of the pathogens, while the delivered to pathogen AI doses required for inactivation were miniscule (nanogram level), indicating the viability of such nano-carrier platform as an intervention technology against infectious microorganisms.

Gene control of tyrosine kinase TIE2 and vascular manifestations of infections.

Ligands of the endothelial-enriched tunica interna endothelial cell kinase 2 (Tie2) are markedly imbalanced in severe infections associated with vascular leakage, yet regulation of the receptor itself has been understudied in this context. Here, we show that TIE2 gene expression may constitute a novel vascular barrier control mechanism in diverse infections. Tie2 expression declined rapidly in wide-ranging models of leak-associated infections, including anthrax, influenza, malaria, and sepsis. Forced Tie2 suppression sufficed to attenuate barrier function and sensitize endothelium to permeability mediators. Rapid reduction of pulmonary Tie2 in otherwise healthy animals attenuated downstream kinase signaling to the barrier effector vascular endothelial (VE)-cadherin and induced vascular leakage. Compared with wild-type littermates, mice possessing one allele of Tie2 suffered more severe vascular leakage and higher mortality in two different sepsis models. Common genetic variants that influence TIE2 expression were then sought in the HapMap3 cohort. Remarkably, each of the three strongest predicted cis-acting SNPs in HapMap3 was also associated with the risk of acute respiratory distress syndrome (ARDS) in an intensive care unit cohort of 1,614 subjects. The haplotype associated with the highest TIE2 expression conferred a 28% reduction in the risk of ARDS independent of other major clinical variables, including disease severity. In contrast, the most common haplotype was associated with both the lowest TIE2 expression and 31% higher ARDS risk. Together, the results implicate common genetic variation at the TIE2 locus as a determinant of vascular leak-related clinical outcomes from common infections, suggesting new tools to identify individuals at unusual risk for deleterious complications of infection.

The Influence of Programmed Cell Death in Myeloid Cells on Host Resilience to Infection with Legionella pneumophila or Streptococcus pyogenes.

Pathogen clearance and host resilience/tolerance to infection are both important factors in surviving an infection. Cells of the myeloid lineage play important roles in both of these processes. Neutrophils, monocytes, macrophages, and dendritic cells all have important roles in initiation of the immune response and clearance of bacterial pathogens. If these cells are not properly regulated they can result in excessive inflammation and immunopathology leading to decreased host resilience. Programmed cell death (PCD) is one possible mechanism that myeloid cells may use to prevent excessive inflammation. Myeloid cell subsets play roles in tissue repair, immune response resolution, and maintenance of homeostasis, so excessive PCD may also influence host resilience in this way. In addition, myeloid cell death is one mechanism used to control pathogen replication and dissemination. Many of these functions for PCD have been well defined in vitro, but the role in vivo is less well understood. We created a mouse that constitutively expresses the pro-survival B-cell lymphoma (bcl)-2 protein in myeloid cells (CD68(bcl2tg), thus decreasing PCD specifically in myeloid cells. Using this mouse model we explored the impact that decreased cell death of these cells has on infection with two different bacterial pathogens, Legionella pneumophila and Streptococcus pyogenes. Both of these pathogens target multiple cell death pathways in myeloid cells, and the expression of bcl2 resulted in decreased PCD after infection. We examined both pathogen clearance and host resilience and found that myeloid cell death was crucial for host resilience. Surprisingly, the decreased myeloid PCD had minimal impact on pathogen clearance. These data indicate that the most important role of PCD during infection with these bacteria is to minimize inflammation and increase host resilience, not to aid in the clearance or prevent the spread of the pathogen.

TNF Drives Monocyte Dysfunction with Age and Results in Impaired Anti-pneumococcal Immunity.

Monocyte phenotype and output changes with age, but why this occurs and how it impacts anti-bacterial immunity are not clear. We found that, in both humans and mice, circulating monocyte phenotype and function was altered with age due to increasing levels of TNF in the circulation that occur as part of the aging process. Ly6C+ monocytes from old (18-22 mo) mice and CD14+CD16+ intermediate/inflammatory monocytes from older adults also contributed to this "age-associated inflammation" as they produced more of the inflammatory cytokines IL6 and TNF in the steady state and when stimulated with bacterial products. Using an aged mouse model of pneumococcal colonization we found that chronic exposure to TNF with age altered the maturity of circulating monocytes, as measured by F4/80 expression, and this decrease in monocyte maturation was directly linked to susceptibility to infection. Ly6C+ monocytes from old mice had higher levels of CCR2 expression, which promoted premature egress from the bone marrow when challenged with Streptococcus pneumoniae. Although Ly6C+ monocyte recruitment and TNF levels in the blood and nasopharnyx were higher in old mice during S. pneumoniae colonization, bacterial clearance was impaired. Counterintuitively, elevated TNF and excessive monocyte recruitment in old mice contributed to impaired anti-pneumococcal immunity since bacterial clearance was improved upon pharmacological reduction of TNF or Ly6C+ monocytes, which were the major producers of TNF. Thus, with age TNF impairs inflammatory monocyte development, function and promotes premature egress, which contribute to systemic inflammation and is ultimately detrimental to anti-pneumococcal immunity.

Phagocytic Receptors Activate Syk and Src Signaling during Borrelia burgdorferi Phagocytosis.

Phagocytosis of the Lyme disease-causing pathogen Borrelia burgdorferi has been shown to be important for generating an inflammatory response to the pathogen. As a result, understanding the mechanisms of phagocytosis has been an area of great interest in the field of Lyme disease. Several cell surface receptors that participate in B. burgdorferi phagocytosis have been reported, including the scavenger receptor MARCO and integrin α3ß1. We sought to define the mechanisms by which these receptors mediate phagocytosis and to identify signaling pathways activated downstream of these receptors upon contact with B. burgdorferi We identified both Syk and Src signaling pathways as ones that participate in B. burgdorferi phagocytosis and the resulting cytokine activation. In our studies, we found that both MARCO and integrin ß1 play a role in the activation of the Src kinase pathway. However, only integrin ß1 participates in the activation of Syk. Interestingly, the integrin activates Syk without the help of the signaling adaptor Dap12 or FcRγ. Thus, we report that multiple pathways participate in B. burgdorferi internalization and that different cell surface receptors act simultaneously in cooperation and independently to mediate phagocytosis.

Childhood tolerance of severe influenza: a mortality analysis in mice.

During the 1918 influenza pandemic, children experienced substantially lower mortality than adults, a striking but unexplained finding. Whether this was due to enhanced resistance (reduced virus load) or better tolerance (reduced impact of infection) has not been defined. We found that prepubertal mice infected with H1N1 influenza virus also showed greater survival than infected pubertal mice, despite similar virus loads. Transcriptome profiling of infected lungs identified estrogen as a regulator of susceptibility in both sexes and also linked better survival to late expression of IL-1ß. Blocking puberty with gonadectomy or a gonadotropin-releasing hormone antagonist improved survival. Estrogen or testosterone (which can be converted to estrogen) restored susceptibility of gonadectomized pubertal mice to influenza mortality, but dihydrotestosterone (which cannot be converted to estrogen) did not. Estrogen receptor blockade with fulvestrant in both male and female pubertal mice resulted in improved survival, even when given 3 days after infection. Moreover, late, but not early, IL-1ß neutralization after infection was also protective. These findings indicate that pubertal increases in estrogen in both sexes are associated with increased mortality during influenza. This helps explain the reduced mortality of children seen with influenza in 1918 and might also be relevant to childhood tolerance to many other infectious diseases.

Transgenerational transmission of asthma risk after exposure to environmental particles during pregnancy.

Exposure to environmental particles during pregnancy increases asthma susceptibility of the offspring. We tested the hypothesis that this transmission continues to F2 and F3 generations and occurs via epigenetic mechanisms. We compared allergic susceptibility of three generations of BALB/c offspring after a single maternal exposure during pregnancy to diesel exhaust particles or concentrated urban air particles. After pregnant dams received intranasal instillations of particle suspensions or control, their F1, F2, and F3 offspring were tested in a low-dose ovalbumin protocol for sensitivity to allergic asthma. We found that the elevated susceptibility after maternal exposure to particles during pregnancy persists into F2 and, with lesser magnitude, into F3 generations. This was evident from elevated eosinophil counts in bronchoalveolar lavage (BAL) fluid, histopathological changes of allergic airway disease, and increased BAL levels of IL-5 and IL-13. We have previously shown that dendritic cells (DCs) can mediate transmission of risk upon adoptive transfer. Therefore, we used an enhanced reduced representation bisulfite sequencing protocol to quantify DNA methylation in DCs from each generation. Distinct methylation changes were identified in F1, F2, and F3 DCs. The subset of altered loci shared across the three generations were not linked to known allergy genes or pathways but included a number of genes linked to chromatin modification, suggesting potential interaction with other epigenetic mechanisms (e.g., histone modifications). The data indicate that pregnancy airway exposure to diesel exhaust particles (DEP) triggers a transgenerationally transmitted asthma susceptibility and suggests a mechanistic role for epigenetic alterations in DCs in this process.

Immunomodulators targeting MARCO expression improve resistance to postinfluenza bacterial pneumonia.

Downregulation of the alveolar macrophage (AM) receptor with collagenous structure (MARCO) leads to susceptibility to postinfluenza bacterial pneumonia, a major cause of morbidity and mortality. We sought to determine whether immunomodulation of MARCO could improve host defense and resistance to secondary bacterial pneumonia. RNAseq analysis identified a striking increase in MARCO expression between days 9 and 11 after influenza infection and indicated important roles for Akt and Nrf2 in MARCO recovery. In vitro, primary human AM-like monocyte-derived macrophages (AM-MDMs) and THP-1 macrophages were treated with IFNγ to model influenza effects. Activators of Nrf2 (sulforaphane) or Akt (SC79) caused increased MARCO expression and a MARCO-dependent improvement in phagocytosis in IFNγ-treated cells and improved survival in mice with postinfluenza pneumococcal pneumonia. Transcription factor analysis also indicated a role for transcription factor E-box (TFEB) in MARCO recovery. Overexpression of TFEB in THP-1 cells led to marked increases in MARCO. The ability of Akt activation to increase MARCO expression in IFNγ-treated AM-MDMs was abrogated in TFEB-knockdown cells, indicating Akt increases MARCO expression through TFEB. Increasing MARCO expression by targeting Nrf2 signaling or the Akt-TFEB-MARCO pathway are promising strategies to improve bacterial clearance and survival in postinfluenza bacterial pneumonia.

Free actin impairs macrophage bacterial defenses via scavenger receptor MARCO interaction with reversal by plasma gelsolin.

Lung injury can release intracellular actin into the alveolar milieu and is also associated with increased susceptibility to secondary infections. We investigated the effect of free (extracellular) actin on lung macrophage host defense functions. Western blot analysis demonstrated free actin release into the lung lavage fluids of mouse models of ozone injury, influenza infection, and secondary pneumococcal pneumonia and in samples from patients following burn and inhalation injury. Using levels comparable with those observed in lung injury, we found that free actin markedly inhibited murine lung macrophage binding and uptake in vitro of S. pneumoniae, S. aureus, and E. coli, (e.g., S. pneumoniae, mean %inhibition, actin vs. vehicle: 85 ± 0.3 (SD); n = 22, P < .001). Similar effects were observed on the ability of primary human macrophages to bind and ingest fluorescent Saureus (~75% inhibition). Plasma gelsolin (pGSN), a protein that functions to bind and cleave actin, restored bacterial binding and uptake by both murine and human macrophages. Scavenger receptor inhibitors reduced binding of fluorescent actin by murine macrophages [fluorescence index (×10-3) after incubation with vehicle, actin, or actin + polyinosinic acid, respectively: 0.8 ± 0.7, 101.7 ± 50.7, or 52.7 ± 16.9; n = 5-6, P < 0.05]. In addition, actin binding was reduced in a MARCO/SR-AI/II-deficient cell line and by normal AMs obtained from MARCO-/- mice. After release from injured cells during lung injury, free actin likely contributes to impaired host defense by blocking scavenger receptor binding of bacteria. This mechanism for increased risk of secondary infections after lung injury or inflammation may represent another target for therapeutic intervention with pGSN.

IL-10-dependent Tr1 cells attenuate astrocyte activation and ameliorate chronic central nervous system inflammation.

SEE WINGER AND ZAMVIL DOI101093/BRAIN/AWW121 FOR A SCIENTIFIC COMMENTARY ON THIS ARTICLE: The innate immune system plays a central role in the chronic central nervous system inflammation that drives neurological disability in progressive forms of multiple sclerosis, for which there are no effective treatments. The mucosal immune system is a unique tolerogenic organ that provides a physiological approach for the induction of regulatory T cells. Here we report that nasal administration of CD3-specific antibody ameliorates disease in a progressive animal model of multiple sclerosis. This effect is IL-10-dependent and is mediated by the induction of regulatory T cells that share a similar transcriptional profile to Tr1 regulatory cells and that suppress the astrocyte inflammatory transcriptional program. Treatment results in an attenuated inflammatory milieu in the central nervous system, decreased microglia activation, reduced recruitment of peripheral monocytes, stabilization of the blood-brain barrier and less neurodegeneration. These findings suggest a new therapeutic approach for the treatment of progressive forms of multiple sclerosis and potentially other types of chronic central nervous system inflammation.

A Chronic Obstructive Pulmonary Disease Susceptibility Gene, FAM13A, Regulates Protein Stability of ß-Catenin.

RATIONALE: A genetic locus within the FAM13A gene has been consistently associated with chronic obstructive pulmonary disease (COPD) in genome-wide association studies. However, the mechanisms by which FAM13A contributes to COPD susceptibility are unknown. OBJECTIVES: To determine the biologic function of FAM13A in human COPD and murine COPD models and discover the molecular mechanism by which FAM13A influences COPD susceptibility. METHODS: Fam13a null mice (Fam13a(-/-)) were generated and exposed to cigarette smoke. The lung inflammatory response and airspace size were assessed in Fam13a(-/-) and Fam13a(+/+) littermate control mice. Cellular localization of FAM13A protein and mRNA levels of FAM13A in COPD lungs were assessed using immunofluorescence, Western blotting, and reverse transcriptase-polymerase chain reaction, respectively. Immunoprecipitation followed by mass spectrometry identified cellular proteins that interact with FAM13A to reveal insights on FAM13A's function. MEASUREMENTS AND MAIN RESULTS: In murine and human lungs, FAM13A is expressed in airway and alveolar type II epithelial cells and macrophages. Fam13a null mice (Fam13a(-/-)) were resistant to chronic cigarette smoke-induced emphysema compared with Fam13a(+/+) mice. In vitro, FAM13A interacts with protein phosphatase 2A and recruits protein phosphatase 2A with glycogen synthase kinase 3ß and ß-catenin, inducing ß-catenin degradation. Fam13a(-/-) mice were also resistant to elastase-induced emphysema, and this resistance was reversed by coadministration of a ß-catenin inhibitor, suggesting that FAM13A could increase the susceptibility of mice to emphysema development by inhibiting ß-catenin signaling. Moreover, human COPD lungs had decreased protein levels of ß-catenin and increased protein levels of FAM13A. CONCLUSIONS: We show that FAM13A may influence COPD susceptibility by promoting ß-catenin degradation.

Alternative activation of macrophages and pulmonary fibrosis are modulated by scavenger receptor, macrophage receptor with collagenous structure.

Alternative activation of alveolar macrophages is linked to fibrosis following exposure to asbestos. The scavenger receptor, macrophage receptor with collagenous structure (MARCO), provides innate immune defense against inhaled particles and pathogens; however, a receptor for asbestos has not been identified. We hypothesized that MARCO acts as an initial signaling receptor for asbestos, polarizes macrophages to a profibrotic M2 phenotype, and is required for the development of asbestos-induced fibrosis. Compared with normal subjects, alveolar macrophages isolated from patients with asbestosis express higher amounts of MARCO and have greater profibrotic polarization. Arginase 1 (40-fold) and IL-10 (265-fold) were higher in patients. In vivo, the genetic deletion of MARCO attenuated the profibrotic environment and pulmonary fibrosis in mice exposed to chrysotile. Moreover, alveolar macrophages from MARCO(-/-) mice polarize to an M1 phenotype, whereas wild-type mice have higher Ym1 (>3.0-fold) and nearly 7-fold more active TGF-ß1 in bronchoalveolar lavage (BAL) fluid (BALF). Arg(432) and Arg(434) in domain V of MARCO are required for the polarization of macrophages to a profibrotic phenotype as mutation of these residues reduced FIZZ1 expression (17-fold) compared with cells expressing MARCO. These observations demonstrate that a macrophage membrane protein regulates the fibrotic response to lung injury and suggest a novel target for therapeutic intervention.