Is Progression of Pulmonary Fibrosis due to Ventilation-induced Lung Injury?
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ABSTRACT:
SUBMITTER: Albert RK
PROVIDER: S-EPMC6635778 | biostudies-literature | 2019 Jul
REPOSITORIES: biostudies-literature
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Is Progression of Pulmonary Fibrosis due to Ventilation-induced Lung Injury?
Albert Richard K RK Smith Bradford B Perlman Carrie E CE Schwartz David A DA
American journal of respiratory and critical care medicine 20190701 2
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Project description:Single-lung ventilation (SLV) associated acute lung injury is similar to ischemia reperfusion (IR) injury which is usually occurred during lung surgery. Olmesartan (Olm), a novel angiotensin receptor blocker (ARB), has been reported to ameliorate organ IR injury. Several recent studies have shown that lung microbiota may be involved in pulmonary diseases, but the effect of pulmonary microbiota in SLV-induced lung injury has not been reported. This study aims to determine the mechanism of how Olm attenuates SLV induced lung injury. Our data showed that 7 days Olm treatment before modeling markedly alleviated SLV-induced lung injury by suppressing inflammation and reactive oxygen species. Bronchoalveolar lavage fluid samples from the injured side were collected for 16S rRNA gene-based sequencing analysis and 53 different bacteria at the genus and species levels were identified. Furthermore, the injured lung samples were collected for metabolomics analysis using liquid chromatography-mass spectrometry analyses to explore differential metabolites. The Kyoto Encyclopedia of Genes and Genomes (KEGG) was applied to analyze the correlation between differential metabolites and lung microbiota. A total of 38 pathways were identified according to differential metabolites and 275 relevant pathways were enriched via analyzing the microbial community, 24 pathways were both identified by analyzing either metabolites or microbiota, including pyrimidine metabolism, purine metabolism, aminoacyl-tRNA biosynthesis and ATP-binding cassette transporter. Besides classical blockage of the renin-angiotensin II system, Olm could also alleviate SLV-induced lung injury by rewiring the interaction between pulmonary microbiota and metabolites.
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Project description:This experiment investigated the role of mechanical ventilation (MV) in modulating lung's transcriptional response to LPS. Twenty four C57/B6 male mice were randomized to four groups: 1. Control, 2. MV, 3. LPS and 4. MV+LPS. Expression profiling of whole lungs revealed a significant augmentation of the transcriptional response in the combined MV+LPS group relative to the other 3 conditions. Keywords: repeat sample
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Project description:Despite many reports about pulmonary blood vessels in lung fibrosis, the contribution of lymphatics to fibrosis is unknown. We examined the mechanism and consequences of lymphatic remodeling in mice with lung fibrosis after bleomycin injury or telomere dysfunction. Widespread lymphangiogenesis was observed after bleomycin treatment and in fibrotic lungs of prospero homeobox 1-enhanced green fluorescent protein (Prox1-EGFP) transgenic mice with telomere dysfunction. In loss-of-function studies, blocking antibodies revealed that lymphangiogenesis 14 days after bleomycin treatment was dependent on vascular endothelial growth factor (Vegf) receptor 3 signaling, but not on Vegf receptor 2. Vegfc gene and protein expression increased specifically. Extensive extravasated plasma, platelets, and macrophages at sites of lymphatic growth were potential sources of Vegfc. Lymphangiogenesis peaked at 14 to 28 days after bleomycin challenge, was accompanied by doubling of chemokine (C-C motif) ligand 21 in lung lymphatics and tertiary lymphoid organ formation, and then decreased as lung injury resolved by 56 days. In gain-of-function studies, expansion of the lung lymphatic network by transgenic overexpression of Vegfc in club cell secretory protein (CCSP)/VEGF-C mice reduced macrophage accumulation and fibrosis and accelerated recovery after bleomycin treatment. These findings suggest that lymphatics have an overall protective effect in lung injury and fibrosis and fit with a mechanism whereby lung lymphatic network expansion reduces lymph stasis and increases clearance of fluid and cells, including profibrotic macrophages.
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Project description:Pulmonary fibrosis is a progressive disease for which no curative treatment exists. We have previously engineered dermal fibroblasts to produce extracellular vesicles with tissue reparative properties dubbed activated specialized tissue effector extracellular vesicles (ASTEX). Here, we investigate the therapeutic utility of ASTEX in vitro and in a mouse model of bleomycin-induced lung injury. RNA sequencing demonstrates that ASTEX are enriched in micro-RNAs (miRs) cargo compared with EVs from untransduced dermal fibroblast EVs (DF-EVs). Treating primary macrophages with ASTEX reduced interleukin (IL)6 expression and increased IL10 expression compared with DF-EV-exposed macrophages. Furthermore, exposure of human lung fibroblasts or vascular endothelial cells to ASTEX reduced expression of smooth muscle actin, a hallmark of myofibroblast differentiation (respectively). In vivo, intratracheal administration of ASTEX in naïve healthy mice demonstrated a favorable safety profile with no changes in body weight, lung weight to body weight, fibrotic burden, or histological score 3 weeks postexposure. In an acute phase (short-term) bleomycin model of lung injury, ASTEX reduced lung weight to body weight, IL6 expression, and circulating monocytes. In a long-term setting, ASTEX improved survival and reduced fibrotic content in lung tissue. These results suggest potential immunomodulatory and antifibrotic properties of ASTEX in lung injury.
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Project description:A diverse group of toxicants has been identified that cause injury to the lung including gases (eg, ozone, chlorine), particulates/aerosols (eg, diesel exhaust, fly ash, other combustion products, mustards, nanomaterials, silica, asbestos), chemotherapeutics (eg, bleomycin), and radiation. The pathologic response to these toxicants depends on the dose and duration of exposure and their physical/chemical properties. A common response to pulmonary toxicant exposure is an accumulation of proinflammatory/cytotoxic M1 macrophages at sites of tissue injury, followed by the appearance of anti-inflammatory/wound repair M2 macrophages. It is thought that the outcome of the pathogenic responses to toxicants depends on the balance in the activity of these macrophage subpopulations. Overactivation of either M1 or M2 macrophages leads to injury and disease pathogenesis. Thus, the very same macrophage-derived mediators, released in controlled amounts to destroy injurious materials and pathogens (eg, reactive oxygen species, reactive nitrogen species, proteases, tumor necrosis factor α) and initiate wound repair (eg, transforming growth factor β, connective tissue growth factor, vascular endothelial growth factor), can exacerbate acute lung injury and/or induce chronic disease such as fibrosis, chronic obstructive pulmonary disease, and asthma, when released in excess. This review focuses on the role of macrophage subsets in acute lung injury and chronic fibrosis. Understanding how these pathologies develop following exposure to toxicants, and the contribution of resident and inflammatory macrophages to disease pathogenesis may lead to the development of novel approaches for treating lung diseases.
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Project description:Mechanical ventilation of lungs suffering from microatelectases may trigger the development of acute lung injury (ALI). Direct lung injury by bleomycin results in surfactant dysfunction and microatelectases at day 1 while tissue elastance and oxygenation remain normal. Computational simulations of alveolar micromechanics 1-day post-bleomycin predict persisting microatelectases throughout the respiratory cycle and increased alveolar strain during low positive end-expiratory pressure (PEEP) ventilation. As such, we hypothesize that mechanical ventilation in presence of microatelectases, which occur at low but not at higher PEEP, aggravates and unmasks ALI in the bleomycin injury model. Rats were randomized and challenged with bleomycin (B) or not (H = healthy). One day after bleomycin instillation the animals were ventilated for 3 h with PEEP 1 (PEEP1) or 5 cmH2O (PEEP5) and a tidal volume of 10 ml/kg bodyweight. Tissue elastance was repetitively measured after a recruitment maneuver to investigate the degree of distal airspace instability. The right lung was subjected to bronchoalveolar lavage (BAL), the left lung was fixed for design-based stereology at light- and electron microscopic level. Prior to mechanical ventilation, lung tissue elastance did not differ. During mechanical ventilation tissue elastance increased in bleomycin-injured lungs ventilated with PEEP = 1 cmH2O but remained stable in all other groups. Measurements at the conclusion of ventilation showed the largest time-dependent increase in tissue elastance after recruitment in B/PEEP1, indicating increased instability of distal airspaces. These lung mechanical findings correlated with BAL measurements including elevated BAL neutrophilic granulocytes as well as BAL protein and albumin in B/PEEP1. Moreover, the increased septal wall thickness and volume of peri-bronchiolar-vascular connective tissue in B/PEEP1 suggested aggravation of interstitial edema by ventilation in presence of microatelectases. At the electron microscopic level, the largest surface area of injured alveolar epithelial was observed in bleomycin-challenged lungs after PEEP = 1 cmH2O ventilation. After bleomycin treatment cellular markers of endoplasmic reticulum stress (p-Perk and p-EIF-2α) were positive within the septal wall and ventilation with PEEP = 1 cmH2O ventilation increased the surface area stained positively for p-EIF-2α. In conclusion, hidden microatelectases are linked with an increased pulmonary vulnerability for mechanical ventilation characterized by an aggravation of epithelial injury.
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Project description:Mechanical ventilation is necessary for patients with acute respiratory failure, but can cause or propagate lung injury. We previously identified cyclooxygenase-2 as a candidate gene in mechanical ventilation-induced lung injury. Our objective was to determine the role of cyclooxygenase-2 in mechanical ventilation-induced lung injury and the effects of cyclooxygenase-2 inhibition on lung inflammation and barrier disruption. Mice were mechanically ventilated at low and high tidal volumes, in the presence or absence of pharmacologic cyclooxygenase-2-specific inhibition with 3-(4-methylsulphonylphenyl)-4-phenyl-5-trifluoromethylisoxazole (CAY10404). Lung injury was assessed using markers of alveolar-capillary leakage and lung inflammation. Cyclooxygenase-2 expression and activity were measured by Western blotting, real-time PCR, and lung/plasma prostanoid analysis, and tissue sections were analyzed for cyclooxygenase-2 staining by immunohistochemistry. High tidal volume ventilation induced lung injury, significantly increasing both lung leakage and lung inflammation relative to control and low tidal volume ventilation. High tidal volume mechanical ventilation significantly induced cyclooxygenase-2 expression and activity, both in the lungs and systemically, compared with control mice and low tidal volume mice. The immunohistochemical analysis of lung sections localized cyclooxygenase-2 expression to monocytes and macrophages in the alveoli. The pharmacologic inhibition of cyclooxygenase-2 with CAY10404 significantly decreased cyclooxygenase activity and attenuated lung injury in mice ventilated at high tidal volume, attenuating barrier disruption, tissue inflammation, and inflammatory cell signaling. This study demonstrates the induction of cyclooxygenase-2 by mechanical ventilation, and suggests that the therapeutic inhibition of cyclooxygenase-2 may attenuate ventilator-induced acute lung injury.
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Project description:BackgroundPatients in intensive care units (ICUs) often received broad-spectrum antibiotic treatment and Acinetobacter baumannii (A.b.) and Pseudomonas aeruginosa (P.a.) were the most common pathogens causing ventilator-associated pneumonia (VAP). This study aimed to examine the effects and mechanism of mechanical ventilation (MV) on A.b.-induced lung injury and the involvement of alveolar macrophages (AMs).MethodsC57BL/6 wild-type (WT) and c-Jun N-terminal kinase knockout (JNK1-/-) mice received MV for 3 h at 2 days after nasal instillation of A.b., P.a. (1 × 106 colony-forming unit, CFU), or normal saline.ResultsIntranasal instillation of 106 CFU A.b. in C57BL/6 mice induced a significant increase in total cells and protein levels in the bronchoalveolar lavage fluid (BALF) and neutrophil infiltration in the lungs. MV after A.b. instillation increases neutrophil infiltration, interleukin (IL)-6 and vascular cell adhesion molecule (VCAM) mRNA expression in the lungs and total cells, IL-6 levels, and nitrite levels in the BALF. The killing activity of AMs against A.b. was lower than against P.a. The diminished killing activity was parallel with decreased tumor necrosis factor-α production by AMs compared with A.b. Inducible nitric oxide synthase inhibitor, S-methylisothiourea, decreased the total cell number in BALF on mice receiving A.b. instillation and ventilation. Moreover, MV decreased the A.b. and P.a. killing activity of AMs. MV after A.b. instillation induced less total cells in the BALF and nitrite production in the serum of JNK1-/- mice than those of WT mice.ConclusionA.b. is potent in inducing neutrophil infiltration in the lungs and total protein in the BALF. MV enhances A.b.-induced lung injury through an increase in the expression of VCAM and IL-6 levels in the BALF and a decrease in the bacteria-killing activity of AMs. A lower inflammation level in JNK1-/- mice indicates that A.b.-induced VAP causes lung injury through JNK signaling pathway in the lungs.
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