Project description:Differences in infection kinetics and host response between Burkholderia multivorans and Burkholderia cenocepacia were demonstrated in a pulmonary infection model in BALB/c mice. B. multivorans persisted in the lung, while B. cenocepacia was cleared. Indirect immunofluorescence and electron microscopy of B. multivorans-infected lungs localized bacteria to macrophages. Clearance of B. cenocepacia was associated with greater interleukin-1beta and neutrophil responses than the responses induced by B. multivorans.
Project description:Despite IL-9 functioning as a pleiotropic cytokine in mucosal environments, the IL-9-responsive cell repertoire is still not well defined. Here, we found that IL-9 mediates proallergic activities in the lungs by targeting lung macrophages. IL-9 inhibits alveolar macrophage expansion and promotes recruitment of monocytes that develop into CD11c+ and CD11c- interstitial macrophage populations. Interstitial macrophages were required for IL-9-dependent allergic responses. Mechanistically, IL-9 affected the function of lung macrophages by inducing Arg1 activity. Compared with Arg1-deficient lung macrophages, Arg1-expressing macrophages expressed greater amounts of CCL5. Adoptive transfer of Arg1+ lung macrophages but not Arg1- lung macrophages promoted allergic inflammation that Il9r-/- mice were protected against. In parallel, the elevated expression of IL-9, IL-9R, Arg1, and CCL5 was correlated with disease in patients with asthma. Thus, our study uncovers an IL-9/macrophage/Arg1 axis as a potential therapeutic target for allergic airway inflammation.
Project description:The MEK1/2-ERK1/2 pathway has been implicated in regulating the inflammatory response to lung injury and infection, and pharmacologic MEK1/2 inhibitor compounds are reported to reduce detrimental inflammation in multiple animal models of disease, in part through modulation of leukocyte responses. However, the specific contribution of myeloid MEK1 in regulating acute lung injury (ALI) and its resolution remain unknown. Here, the role of myeloid Mek1 was investigated in a murine model of LPS-induced ALI (LPS-ALI) by genetic deletion using the Cre-floxed system (LysMCre × Mekfl), and human alveolar macrophages from healthy volunteers and patients with acute respiratory distress syndrome (ARDS) were obtained to assess activation of the MEK1/2-ERK1/2 pathway. Myeloid Mek1 deletion results in a failure to resolve LPS-ALI, and alveolar macrophages lacking MEK1 had increased activation of MEK2 and the downstream target ERK1/2 on day 4 of LPS-ALI. The clinical significance of these findings is supported by increased activation of the MEK1/2-ERK1/2 pathway in alveolar macrophages from patients with ARDS compared with alveolar macrophages from healthy volunteers. This study reveals a critical role for myeloid MEK1 in promoting resolution of LPS-ALI and controlling the duration of macrophage proinflammatory responses.
Project description:Exposure of the lung to radiation produces injury and inflammatory responses that result in microenvironmental alterations, which can promote the development of pneumonitis and/or pulmonary fibrosis. It has been shown that after other toxic insults, macrophages become phenotypically polarized in response to microenvironmental signals, orchestrating the downstream inflammatory responses. However, their contribution to the development of the late consequences of pulmonary radiation exposure remains unclear. To address this issue, fibrosis-prone C57BL/6J mice or pneumonitis-prone C3H/HeJ mice were whole-lung irradiated with 0 or 12.5 Gy and lung digests were collected between 3 and 26 weeks after radiation exposure. CD45(+) leukocytes were isolated and characterized by flow cytometry, and alveolar, interstitial and infiltrating macrophages were also detected. Ly6C, expressed by pro-inflammatory monocytes and macrophages, and mannose receptor (CD206), a marker of alternative activation, were assessed in each subpopulation. While the total number of pulmonary macrophages was depleted at 3 weeks after lung irradiation relative to age-matched controls in both C57 and C3H mice, identification of discrete subpopulations showed that this loss in cell number occurred in the alveolar, but not the interstitial or infiltrating, subsets. In the alveolar macrophages of both C57 and C3H mice, this correlated with a loss in the proportion of cells that expressed CD206 and F4/80. In contrast, in interstitial and infiltrating macrophages, the proportion of cells expressing these markers was increased at several time points after irradiation, with this response generally more pronounced in C3H mice. Radiation exposure was also associated with elevations in the proportion of alveolar and interstitial macrophage subpopulations expressing Ly6C and F4/80, with this response occurring at earlier time points in C57 mice. Although the radiation dose used in this study was not isoeffective for the inflammatory response in the two strains, the differences observed in the responses of these discrete macrophage populations between the fibrosis-prone versus pneumonitis-prone mice nonetheless suggest a possible role for these cells in the development of long-term consequences of pulmonary radiation exposure.
Project description:Bone-marrow transplantation is an effective cell therapy but requires myeloablation, which increases infection risk and mortality. Recent lineage-tracing studies documenting that resident macrophage populations self-maintain independently of haematological progenitors prompted us to consider organ-targeted, cell-specific therapy. Here, using granulocyte-macrophage colony-stimulating factor (GM-CSF) receptor-β-deficient (Csf2rb(-/-)) mice that develop a myeloid cell disorder identical to hereditary pulmonary alveolar proteinosis (hPAP) in children with CSF2RA or CSF2RB mutations, we show that pulmonary macrophage transplantation (PMT) of either wild-type or Csf2rb-gene-corrected macrophages without myeloablation was safe and well-tolerated and that one administration corrected the lung disease, secondary systemic manifestations and normalized disease-related biomarkers, and prevented disease-specific mortality. PMT-derived alveolar macrophages persisted for at least one year as did therapeutic effects. Our findings identify mechanisms regulating alveolar macrophage population size in health and disease, indicate that GM-CSF is required for phenotypic determination of alveolar macrophages, and support translation of PMT as the first specific therapy for children with hPAP.
Project description:Excess macrophages and smooth muscle cells (SMCs) characterize many cardiovascular diseases, but crosstalk between these cell types is poorly defined. Pulmonary hypertension (PH) is a lethal disease in which lung arteriole SMCs proliferate and migrate, coating the normally unmuscularized distal arteriole. We hypothesized that increased macrophage platelet-derived growth factor-B (PDGF-B) induces pathological SMC burden in PH. Our results indicate that clodronate attenuates hypoxia-induced macrophage accumulation, distal muscularization, PH, and right ventricle hypertrophy (RVH). With hypoxia exposure, macrophage Pdgfb mRNA was upregulated in mice, and LysM‑Cre mice carrying floxed alleles for hypoxia-inducible factor 1a, hypoxia-inducible factor 2a, or Pdgfb had reduced macrophage Pdgfb and were protected against distal muscularization and PH. Conversely, LysM‑Cre von-Hippel Lindaufl/fl mice had increased macrophage Hifa and Pdgfb and developed distal muscularization, PH, and RVH in normoxia. Similarly, Pdgfb was upregulated in macrophages from human idiopathic or systemic sclerosis-induced pulmonary arterial hypertension patients, and macrophage-conditioned medium from these patients increased SMC proliferation and migration via PDGF-B. Finally, in mice, orotracheal administration of nanoparticles loaded with Pdgfb siRNA specifically reduced lung macrophage Pdgfb and prevented hypoxia-induced distal muscularization, PH, and RVH. Thus, macrophage-derived PDGF-B is critical for pathological SMC expansion in PH, and nanoparticle-mediated inhibition of lung macrophage PDGF-B has profound implications as an interventional strategy for PH.
Project description:Idiopathic pulmonary fibrosis (IPF) is serious chronic lung disease with limited therapeutic approaches. Inflammation and immune disorders are considered as the main factors in the initiation and development of pulmonary fibrosis. Inspired by the key roles of macrophages during the processes of inflammation and immune disorders, here, we report a new method for direct drug delivery into the in-situ fibrotic tissue sites in vitro and in vivo. First, liposomes containing dexamethasone (Dex-L) are prepared and designed to entry into the macrophages in the early hours, forming the macrophages loaded Dex-L delivery system (Dex-L-MV). Chemokine and cytokine factors such as IL-6, IL-10, Arg-1 are measured to show the effect of Dex-L to the various subtypes of macrophages. Next, we mimic the inflammatory and anti-inflammatory microenvironment by co-culture of polarized/inactive macrophage and fibroblast cells to show the acute inflammation response of Dex-L-MV. Further, we confirm the targeted delivery of Dex-L-MV into the inflammatory sites in vivo, and surprisingly found that injected macrophage containing Dex can reduce the level of macrophage infiltration and expression of the markers of collagen deposition during the fibrotic stage, while causing little systematic toxicity. These data demonstrated the suitability and immune regulation effect of Dex-L-MV for the anti-pulmonary process. It is envisaged that these findings are a step forward toward endogenous immune targeting systems as a tool for clinical drug delivery.
Project description:In chronic obstructive pulmonary disease (COPD/emphysema) we have shown a reduced ability of lung and alveolar (AM) macrophages to phagocytose apoptotic cells (defective 'efferocytosis'), associated with evidence of secondary cellular necrosis and a resultant inflammatory response in the airway. It is unknown whether this defect is present in cancer (no COPD) and if so, whether this results from soluble mediators produced by cancer cells. We investigated efferocytosis in AM (26 controls, 15 healthy smokers, 37 COPD, 20 COPD+ non small cell lung cancer (NSCLC) and 8 patients with NSCLC without COPD) and tumor and tumor-free lung tissue macrophages (21 NSCLC with/13 without COPD). To investigate the effects of soluble mediators produced by lung cancer cells we then treated AM or U937 macrophages with cancer cell line supernatant and assessed their efferocytosis ability. We qualitatively identified Arachidonic Acid (AA) metabolites in cancer cells by LC-ESI-MSMS, and assessed the effects of COX inhibition (using indomethacin) on efferocytosis. Decreased efferocytosis was noted in all cancer/COPD groups in all compartments. Conditioned media from cancer cell cultures decreased the efferocytosis ability of both AM and U937 macrophages with the most pronounced effects occurring with supernatant from SCLC (an aggressive lung cancer type). AA metabolites identified in cancer cells included PGE2. The inhibitory effect of PGE2 on efferocytosis, and the involvement of the COX-2 pathway were shown. Efferocytosis is decreased in COPD/emphysema and lung cancer; the latter at least partially a result of inhibition by soluble mediators produced by cancer cells that include PGE2.