Therapeutic effects of fatty acid binding protein 1 in mice with pulmonary fibrosis by regulating alveolar epithelial regeneration.

INTRODUCTION: Idiopathic pulmonary fibrosis is a progressive fibrotic lung disease with limited therapeutic options and high lethality, related to alveolar type II epithelial (ATII) cell dysregulation, the abnormal repair of alveolar epithelial cells and activation of fibroblasts promote the development of pulmonary fibrosis. Fatty acid binding protein 1 (FABP1) was significantly downregulated in the fibrotic state by proteomics screening in our previous date, and the ATII cell dysregulation can be mediated by FABP1 via regulating fatty acid metabolism and intracellular transport. The aim of this study was to evaluate the role and potential mechanism of FABP1 in the development of pulmonary fibrosis. METHODS: Proteomics screening was used to detect changes of the protein profiles in two different types (induced by bleomycin and silica, respectively) of pulmonary fibrosis models. The localisation of FABP1 in mouse lung was detected by Immunofluorescence and immunohistochemistry. Experimental methods such as lung pathology, micro-CT, western blotting, small animal imaging in vivo, EdU, etc were used to verify the role of FABP1 in pulmonary fibrosis. RESULTS: The expression of FABP1 in the mouse lung was significantly reduced in the model of pulmonary fibrosis from our proteomic analysis and immunological methods, the double immunofluorescence staining showed that FABP1 was mainly localised in type II alveolar epithelial cells. Additionally, the expression of FABP1 was negatively correlated with the progression of pulmonary fibrosis. Further in vivo and in vitro experiments showed that overexpression of FABP1 alleviated pulmonary fibrosis by protecting alveolar epithelium from injury and promoting cell survival. CONCLUSION: Our findings provide a proof-of-principle that FABP1 may represent an effective treatment for pulmonary fibrosis by regulating alveolar epithelial regeneration, which may be associated with the fatty acid metabolism in ATII cells.

Citrus peel extract protects against diesel exhaust particle-induced chronic obstructive pulmonary disease-like lung lesions and oxidative stress.

Chronic obstructive pulmonary disease (COPD) is the third leading cause of death worldwide and characterized by emphysema, small airway remodeling and mucus hypersecretion. Citrus peels have been widely used as food spices and in traditional Chinese medicine for chronic lung disease. Given that citrus peels are known for containing antioxidants and anti-inflammatory compounds, we hypothesize that citrus peel intake can suppress oxidative stress and inflammatory response to air pollution exposure, thereby alleviating COPD-like pathologies. This study aimed to investigate the efficacy of citrus peel extract, namely Guang Chenpi (GC), in preventing the development of COPD induced by diesel exhaust particles (DEPs) and its potential mechanism. DEP-induced COPD-like lung pathologies, inflammatory responses and oxidative stress with or without GC treatment were examined in vivo and in vitro. Our in vivo study showed that GC was effective in decreasing inflammatory cell counts and inflammatory mediator (IL-17A and TNF-α) concentrations in bronchoalveolar lavage fluid (BALF). Pretreatment with GC extract also significantly decreased oxidative stress in the serum and lung tissue of DEP-induced COPD rats. Furthermore, GC pretreatment effectively reduced goblet cell hyperplasia (PAS positive cells) and fibrosis of the small airways, decreased macrophage infiltration as well as carbon loading in the peripheral lungs, and facilitated the resolution of emphysema and small airway remodeling in DEP-induced COPD rats. An in vitro free radical scavenging assay revealed robust antioxidant potential of GC in scavenging DPPH free radicals. Moreover, GC demonstrated potent capacities in reducing ROS production and enhancing SOD activity in BEAS-2B cells stimulated by DEPs. GC treatment significantly attenuated the increased level of IL-8 and MUC5AC from DEP-treated BEAS-2B cells. Mechanistically, GC treatment upregulated the protein level of Nrf-2 and could function via MAPK/NF-κB signaling pathways by suppressing the phosphorylation of p38, JNK and p65. Citrus peel extract is effective in decreasing oxidative stress and inflammatory responses of the peripheral lungs to DEP exposure. These protective effects further contributed to the resolution of COPD-like pathologies.

Intracellular hydroxyproline imprinting following resolution of bleomycin-induced pulmonary fibrosis.

BACKGROUND: Idiopathic pulmonary fibrosis (IPF) is a fatal lung disease with few treatment options. The poor success in developing anti-IPF strategies has impelled researchers to reconsider the importance of the choice of animal model and assessment methodologies. Currently, it is still not settled whether the bleomycin-induced lung fibrosis mouse model finally returns to resolution. METHODS: This study aimed to follow the dynamic fibrotic features of bleomycin-treated mouse lungs over extended durations through a combination of the latest technologies (micro-computed tomography imaging and histological detection of degraded collagens) and traditional methods. In addition, we also applied immunohistochemistry to explore the distribution of all hydroxyproline-containing molecules. RESULTS: As determined by classical biochemical methods, total lung hydroxyproline contents reached a peak at 4 weeks after bleomycin injury and maintained a steady high level thereafter until the end of the experiments (16 weeks). This result seemed to partially contradict with the changes of other fibrosis evaluation parameters, which indicated a gradual degradation of collagens and a recovery of lung aeration after the fibrosis peak. This inconsistency was well reconciled by our data from immunostaining against hydroxyproline and fluorescent peptide staining against degraded collagen, together showing large amounts of hydroxyproline-rich degraded collagen fragments detained and enriched within the intracellular regions at 10 or 16 weeks rather than at 4 weeks after bleomycin treatment. CONCLUSIONS: Our present data not only offer respiratory researchers a new perspective towards the resolution nature of mouse lung fibrosis, but also remind them to be cautious when using the hydroxyproline content assay to evaluate the severity of fibrosis.

Pulmonary fibrosis alters gut microbiota and associated metabolites in mice: An integrated 16S and metabolomics analysis.

AIMS: The "gut-lung axis" reflects intimate connection and bidirectional effect between gut and lung, involving numerous lung diseases. Pulmonary fibrosis is a progressive interstitial lung disease with high fatality rate, so far, its association with gut remains unexplored. We investigated the correlation between pulmonary fibrosis and gut microbiota. MATERIALS AND METHODS: We collected feces from two pulmonary fibrotic models respectively, and performed a combinatory study using 16S rDNA sequencing and non-targeted metabonomics. Correlation matrix was used to indicate the correlation between microbiome, metabolites and fibrotic indicators, and the possibility of gut microbiota in identifying pulmonary fibrosis was assessed by ROC analysis. KEY FINDINGS: 412 genera of microflora and 26 kinds of metabolites were synchronously altered with same trend in two models but differed observably with control. Among these, 7 microorganisms and 9 metabolites were the typical representatives, which were correlated significantly and highly correlated with fibrotic indicators shown by correlation matrix. ROC analysis indicated that it was dependable to identify pulmonary fibrosis by using gut microorganisms and metabolites in both models (AUC > 0.85, p < 0.01). SIGNIFICANCE: In summary, our findings first revealed a previously unknown correlation between gut and pulmonary fibrosis in mouse models, which creates novel insights of the interaction between pulmonary fibrosis and gut microbiota.

Serpina3n is closely associated with fibrotic procession and knockdown ameliorates bleomycin-induced pulmonary fibrosis.

OBJECTIVE: Pulmonary fibrosis is a fatal interstitial lung disease that is characterized by excessive accumulation of extracellular matrix (ECM) and remodeling of lung. The precise mechanisms underlying pulmonary fibrosis still remain unclear. In the current study, we aimed to investigate the alteration and function of serine (or cysteine) peptidase inhibitor, clade A, member 3 N (Serpina3n) in pulmonary fibrotic models and explore the potential mechanisms. METHODS: We induced pulmonary fibrosis in mice by silica and bleomycin respectively and determined Serpina3n in lung tissues, and then verified the expression of Serpina3n and its correlation with pulmonary fibrosis at seven time points in a bleomycin longstanding model. Moreover, adeno-associated virus type 9 (AAV9)-mediated Serpina3n knockdown was used to treat pulmonary fibrosis in the bleomycin model, whose possible mechanisms would be preliminarily explored by detecting chymotrypsin C as an example. RESULTS: Serpina3n was up-regulated significantly in lungs of both models at mRNA and protein levels relative to control. Notably, the expression of Serpina3n peaked during the 3rd week and then decreased until nearly normal levels during the 10th week, which was closely related to fibrotic procession in bleomycin-treated mice. AAV-mediated Serpina3n knockdown in the lung tissues alleviated bleomycin-induced fibrotic symptoms at various levels and disinhibit chymotrypsin C. CONCLUSIONS: Our study revealed that Serpina3n is a critical regulator in pulmonary fibrosis and suggested Serpina3n inhibition as a potential therapeutic strategy in chronic pulmonary injuries.