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Modulating the alveolar milieu to enhance resolution of fibrotic lung injury.

ABSTRACT: Fibrotic lung injury is often attributed to a myriad of factors, including environmental exposure, age, genetic predisposition, epigenetics, coexisting conditions, acute lung injury, and viral infection. No effective therapies, other than lung transplantation, have proven effective against lung fibrosis. Loss of cellular homeostasis mechanisms in alveolar epithelial type I cells and any inability of type II progenitor cells to resist and repair epithelial injury are indicators that impaired response to injury and regeneration is a critical component of this disorder. The alveolar epithelium has a limited repertoire of responses to injury, which are dictated by the alveolar milieu, a repository of cytokines and growth factors that affect recruitment of other cells to the site of injury, or the proliferation of resident cells at the site of injury. The identification and characterization of the cytokines, growth factors, and other biomarkers that dictate the response to disease is key to understanding, diagnosing, treating, and determining the trajectory of various lung disorders. Corrective therapy of the alveolar milieu may therefore prove to be beneficial in many presently serious and incurable lung diseases that likely begin and progress with injury to the alveolar epithelium.

SUBMITTER: Garcia O

PROVIDER: S-EPMC5830702 | biostudies-literature | 2012 Jul

REPOSITORIES: biostudies-literature

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Modulating the alveolar milieu to enhance resolution of fibrotic lung injury.

Garcia Orquidea O Buckley Sue S Navarro Sonia S Driscoll Barbara B Warburton David D

Proceedings of the American Thoracic Society 20120701 3

Fibrotic lung injury is often attributed to a myriad of factors, including environmental exposure, age, genetic predisposition, epigenetics, coexisting conditions, acute lung injury, and viral infection. No effective therapies, other than lung transplantation, have proven effective against lung fibrosis. Loss of cellular homeostasis mechanisms in alveolar epithelial type I cells and any inability of type II progenitor cells to resist and repair epithelial injury are indicators that impaired resp ...[more]

PMID: 22802284

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Project description:Mechanical ventilation is an essential lifesaving therapy in acute respiratory distress syndrome (ARDS) that may cause ventilator-induced lung injury (VILI) through a positive feedback between altered alveolar mechanics, edema, surfactant inactivation, and injury. Although the biophysical forces that cause VILI are well documented, a knowledge gap remains in the quantitative link between altered parenchymal structure (namely alveolar derecruitment and flooding), pulmonary function, and VILI. This information is essential to developing diagnostic criteria and ventilation strategies to reduce VILI and improve ARDS survival. To address this unmet need, we mechanically ventilated mice to cause VILI. Lung structure was measured at three air inflation pressures using design-based stereology, and the mechanical function of the pulmonary system was measured with the forced oscillation technique. Assessment of the pulmonary surfactant included total surfactant, distribution of phospholipid aggregates, and surface tension lowering activity. VILI-induced changes in the surfactant included reduced surface tension lowering activity in the typically functional fraction of large phospholipid aggregates and a significant increase in the pool of surface-inactive small phospholipid aggregates. The dominant alterations in lung structure at low airway pressures were alveolar collapse and flooding. At higher airway pressures, alveolar collapse was mitigated and the flooded alveoli remained filled with proteinaceous edema. The loss of ventilated alveoli resulted in decreased alveolar gas volume and gas-exchange surface area. These data characterize three alveolar phenotypes in murine VILI: flooded and non-recruitable alveoli, unstable alveoli that derecruit at airway pressures below 5 cmH2O, and alveoli with relatively normal structure and function. The fraction of alveoli with each phenotype is reflected in the proportional changes in pulmonary system elastance at positive end expiratory pressures of 0, 3, and 6 cmH2O.

Project description:BackgroundFibrotic liver injury is a progressive scarring event, which may permanently affect liver function and progress into devastating end-stage liver diseases due to the absence of effective therapies. Si-Wu-Tang (SWT), a traditional Chinese medicine formula used in clinic to treat gynecological disorders for centuries, has been investigated in recent preliminary findings for its role in alleviating chronic liver diseases. Here we aim to elucidate the therapeutic effects and possible mechanisms of SWT against fibrotic liver injury.MethodsUHPLC-MS/MS was performed to investigate the chemical characterization of SWT. After intragastrically administered with carbon tetrachloride (CCl4) every 3 days for 1-week, C57BL/6 mice were orally administered with SWT (5.2, 10.4 and 20.8 g/kg) once daily for 3 weeks along with CCl4 challenge. Liver function was determined by the measurement of serum biomarkers, hematoxylin and eosin (H&E) and Masson's trichrome staining. Intestinal inflammatory infiltration and the disruption of intestinal barrier were examined by H&E and E-cadherin immunohistochemical staining. The microbial composition of intestinal content was determined by 16S rRNA sequencing. Serum bile acids (BAs) profiling was analyzed by LC-MS/MS. Simultaneously, the expression of genes of interest was determined by qPCR and western blot.ResultsSWT exhibited remarkable therapeutic effects on CCl4-induced liver fibrosis, as indicated by improved collagen accumulation in livers, intestinal barrier injury and hepatic and intestinal inflammatory response. Results of 16S rRNA sequencing revealed that SWT treatment strikingly restructured intestinal microbiota in fibrotic mice by increasing the relative abundances of Bacteroides and Lachnoclostridium and decreasing the relative abundances of Alistipes and Rikenellaceae. UHPLC-MS/MS data suggested that SWT altered the composition of BAs in circulation as evidenced by increased unconjugated BAs like cholic acid and chenodeoxycholic acid but decreased conjugated BAs including taurocholic acid and taurodeoxycholic acid, compared to that in CCl4 mice. Notably, SWT efficiently improved the imbalance of BA homeostasis in livers caused by CCl4 via activating farnesoid X receptor (FXR)-fibroblast growth factor 15 enterohepatic and FXR-small heterodimer partner hepatic pathways.ConclusionSWT decreased inflammatory response, reconstructed gut microbiota-mediated BA homeostasis as well as activated FXR pathways, which eventually protected against CCl4-induced fibrotic liver injury.

Dataset Information

Modulating the alveolar milieu to enhance resolution of fibrotic lung injury.

Publications

Modulating the alveolar milieu to enhance resolution of fibrotic lung injury.

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