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Nogo-B protects mice against lipopolysaccharide-induced acute lung injury

ABSTRACT: Purpose: Acute lung injury (ALI) is a severe clinical disorder characterized by diffused capillary-alveolar barrier damage and noncardiogenic lung edema induced by excessive inflammation reactions. Nogo-B, a member of the reticulon 4 protein family, plays a critical role in modulating macrophages and neutrophils’ function in inflammation. Its role in ALI remains unclear. Methods: Pulmonary expression of Nogo-B was investigated in a LPS-induced ALI mice model. The effects and the underline mechanisms of Nogo-B expression on the severity of lung injury was assessed using histological examination, Bronchoalveolar lavage fluid (BALF) protein and inflammatory cells and cytokines measurement, and microarray analysis. Results: Nogo-B was normally highly expressed in the lungs of naïve C57BL/6 mice. Intra-tracheal instillation of LPS significantly repressed the Nogo-B expression in lung tissues and BALF cells of ALI mice. In addition, over-expression of pulmonary Nogo-B using an adenovirus vector which expresses a Nogo-B-RFP-3-flag fusion protein (Ad-Nogo-B) significantly prolonged the survival time of mice challenged with lethal dose of LPS. Histological results and BALF protein measurement convinced that Ad-Nogo-B treated mice had less severity of lung injury and alveolar protein exudation, as compared with control adenovirus treated mice (Ad-RFP). They also had higher MCP-1 secretion and alveolar macrophages infiltration, but lower neutrophils infiltration. Finally, using microarray analysis, we identified a protective gene, PTX3, was highly elevated in Ad-Nogo-B treated mice. Conclusions: Nogo-B played a protective role in LPS-induced ALI, which might exert its role through modulation of inflammatory response and PTX3 secretion.

ORGANISM(S): Mus musculus

PROVIDER: GSE48787 | GEO | 2013/07/12

SECONDARY ACCESSION(S): PRJNA211644

REPOSITORIES: GEO

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Project description:Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) is an inflammatory process of the lungs characterized by increased permeability of the alveolar-capillary membrane with subsequent interstitial/alveolar edema and diffuse alveolar damage. ALI/ARDS can be the results of either direct or indirect lung injury, with pneumonia being the most common direct pulmonary insult and sepsis the most common extra-pulmonary cause. In this study, we employed the murine lipopolysaccharide (LPS)-induced direct and indirect lung injury model to explore the pathogenic mechanisms of pulmonary and extra-pulmonary ARDS, using an unbiased, discovery and quantitative proteomic approach. A total of 1,017 proteins were both identified and quantified in bronchoalveolar lavage fluid (BALF) from control, intratracheal LPS (I.T. LPS, 0.1 mg/kg) and intraperitoneal LPS (I.P. LPS, 5 mg/kg) treated mice. The two LPS groups shared 13 up-regulated and 22 down-regulated proteins compared to the control group. Among them, molecules related to bronchial and type II alveolar epithelial cell functions including cell adhesion molecule 1 and surfactant protein B were reduced, whereas lactotransferrin and resistin like alpha involved in lung innate immunity were upregulated in both LPS groups. Proteomic profiling also identified significant differences in BALF proteins between I.T. and I.P. LPS groups. Ingenuity pathway analysis revealed that acute-phase response signaling was activated by both I.T. and I.P. LPS, however, the magnitude of activation is much greater in I.T. LPS group compared to I.P. LPS group. Intriguingly, two canonical signaling pathways, liver X receptor/retinoid X receptor activation and the production of nitric oxide and reactive oxygen species in macrophages, were activated by I.T. LPS but suppressed by I.P. LPS. In addition, CXCL15 (also known as lungkine) was also up-regulated by I.T LPS but down-regulated by I.P. LPS. In conclusion, our quantitative discovery-based proteomic approach identified commonalities as well as significant differences in BALF protein expression profiles in LPS-induced direct and indirect lung injury, and importantly, LPS-induced indirect lung injury results in suppression of select components of lung innate immunity, which could contribute to the so-called “immunoparalysis” in sepsis patients.

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.

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Nogo-B protects mice against lipopolysaccharide-induced acute lung injury

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