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Clara cell regulation of the inflammatory response

ABSTRACT: Chronic lung diseases are marked by excessive inflammation and epithelial remodeling. Reduced Clara cell secretory function and corresponding decreases in the abundance of the major Clara cell secreted protein, CCSP, are characteristically seen in these disease states. We sought to define the impact of Clara cell and CCSP depletion on regulation of the lung inflammatory response. We used chemical and genetic mouse models of Clara cell and CCSP deficiency (CCSP-/-) coupled with P. aeruginosa lipopolysaccharide (LPS) elicited inflammation. Exposure of Clara cell depleted or CCSP-/- mice to LPS resulted in augmented inflammation as assessed by polymorphonuclear leukocyte recruitment to the airspace. Gene expression analysis and pathway modeling of the CCSP-/- inflammatory response implicated increased TNF-alpha signaling. Consistent with this model was the demonstration of significantly elevated TNF-alpha in airway fluid of LPS-stimulated CCSP-/- mice compared to similarly exposed wild type mice. Increased LPS-elicited TNF-alpha production was also observed in cultured lung macrophages from CCSP-/- mice compared to wild type mice. We demonstrate that macrophages from Clara cell depleted and CCSP-/- mice displayed increased TLR4 surface expression. Our results provide evidence that Clara cells can attenuate inflammation through regulation of macrophage behavior and suggest that epithelial remodeling leading to reduced Clara cell secretory function is an important factor that increases the intensity of lung inflammation in chronic lung disease.

ORGANISM(S): Mus musculus

PROVIDER: GSE16409 | GEO | 2009/06/04

SECONDARY ACCESSION(S): PRJNA116309

REPOSITORIES: GEO

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Project description:Background: Environmental lipopolysaccharide (LPS) and microbial component-enriched organic dusts cause significant lung diseases. These environmental exposures induce the recruitment and activation of distinct lung monocyte/macrophage subpopulations involved in disease pathogenesis. Given monocyte/macrophage activation is tightly linked to metabolism, the objective of these studies was to determine the role of the immunometabolic regulator, aconitate decarboxylase 1 (ACOD1), in environmental exposure-induced lung inflammation. Methods: Wild-type (WT) mice were intratracheally instilled (I.T.) with 10 ug LPS or saline. Whole lungs were profiled using bulk RNA sequencing or sorted to isolate monocyte/macrophage subpopulations. Sorted subpopulations were then characterized transcriptomically using a NanoString innate immunity multiplex array 48 hours post-exposure. Next, WT and Acod1-/- mice were instilled with LPS, 25% organic dust extract (ODE), or saline with serum, bronchoalveolar lavage fluid (BALF), and lung tissues collected. BALF metabolites of the tricarboxylic acid (TCA) cycle were quantified by mass-spectrometry. Cytokines/chemokines and tissue remodeling mediators were quantitated by ELISA. Lung immune cells were characterized by flow cytometry. Whole body plethysmography was performed 3 hours post-LPS with WT and Acod1-/- mice. Results: By bulk sequencing, Acod1 was one of the most significantly upregulated genes following LPS (vs. saline) exposure of murine whole lungs. Transcriptomic profiling of sorted lung monocyte/macrophage subpopulations corroborated Acod1 significance. Acod1-/- mice treated with LPS (vs. WT) demonstrated decreased BALF levels of itaconate, TCA cycle reprogramming, decreased BALF neutrophils, increased lung CD4+ T cells, decreased BALF and lung levels of TNF-a, and decreased BALF CXCL1. In comparison, Acod1-/- mice treated with ODE (vs. WT) demonstrated decreased serum pentraxin-2, BALF levels of itaconate, lung total cell, neutrophil, monocyte, and B cell infiltrates with decreased BALF levels of TNF-a, IL-6, and decreased lung CXCL1. Mediators of tissue remodeling (TIMP1, MMP8, MMP9) were also decreased in the LPS-exposed Acod1-/- mice, with MMP-9 also decreased in the ODE-exposed Acod1-/- mice. Lung function assessments demonstrated a blunted response to LPS-induced airway hyper-responsiveness in Acod1-/- mice. Conclusion: Acod1 is robustly upregulated in the lungs following LPS-exposure and encodes a key immunometabolic regulator. ACOD1 mediates the pro-inflammatory response to acute inhaled, environmental LPS and organic dust exposure-induced lung inflammation.

Project description:Multipotent stromal cells (MSCs) are currently in clinical trials for a number of inflammatory diseases. Recent studies have demonstrated the ability of MSCs to attenuate inflammation in rodent models of acute lung injury (ALI) suggesting that MSCs may also be beneficial in treating ALI. To better understand how human MSCs (hMSCs) may act in ALI, the lungs of immunocompetent mice were exposed to lipopolysaccharide (LPS) and 4 hr later bone marrow derived hMSCS were delivered by oropharyngeal aspiration (OA). Administration of hMSCs significantly reduced the expression of pro-inflammatory cytokines, neutrophil counts and total protein in bronchoalveolar lavage. There was a concomitant reduction in pulmonary edema as indicated by a decrease in lung wet/dry weight ratio. The anti-inflammatory effects of hMSCs were not dependent on localization to the lung, as intraperitoneal administration of hMSCs also attenuated LPS-induced inflammation in the lung. Microarray analysis revealed significant induction of TNF-α-induced protein 6 (TSG-6) expression by hMSCs 12 hr after OA delivery to LPS-exposed lungs. Knockdown of TSG-6 expression in hMSCs by RNA interference abrogated most of their anti-inflammatory effects. In addition, intra-pulmonary delivery of recombinant human TSG-6 reduced LPS-induced inflammation in the lung. These results show that hMSCs recapitulate the observed beneficial effects of rodent MSCs in animal models of ALI and suggest that the anti-inflammatory properties of hMSCs in the lung are explained, at least in part, by activation of hMSCs to secrete TSG-6. Eight- to 10-week-old female BALB/C mice were treated with either 1 mg/kg lipopolysaccharide (LPS) in 100 μl PBS or an equal volume of PBS, as vehicle control, by oropharyngeal aspiration (OA). Four hours after LPS exposure, 250,000 human multipotent stromal cells in 100 μl of PBS were given by OA and 30 min later a second dose of equal concentration was administered, for a total of 500,000 hMSC. As a control, 200 μl PBS was delivered as described above. After 12 h, total RNA was isolated from (A) lungs of LPS-exposed mice treated with either hMSCs (LPS+MSC) or PBS (LPS+PBS), and (B) lungs of PBS-exposed mice treated with hMSCs (PBS+MSC). To obtain additional controls, hMSCs were mixed in vitro with either LPS- (LPS+MSC in vitro mix) or PBS-exposed (PBS+MSC in vitro mix) mouse lungs just before RNA isolation. RNA samples containing mouse and human RNA were first analyzed for amount of human RNA based on human GAPDH signal from real-time RT PCR. Samples with similar human RNA content were used for both mouse and human microarrays

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Clara cell regulation of the inflammatory response

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