PEDF is an antifibrosis factor that inhibits the activation of fibroblasts in a bleomycin-induced pulmonary fibrosis rat model

Overexpressed pigment epithelium-derived factor alleviates pulmonary hypertension in two rat models induced by monocrotaline and SU5416/hypoxia

BACKGROUND

Pulmonary hypertension (PH) is a progressive and fatal cardiopulmonary disease characterized by vascular remodeling and is associated with endothelial-to-mesenchymal transition (EndoMT). The pigment epithelium-derived factor (PEDF), a secretory protein widely distributed in multiple organs, has been shown to demonstrate anti-EndoMT activity in cardiovascular diseases. In the present study, the role of PEDF in PH was investigated.

METHODS

For PEDF overexpression, Sprague Dawley rats were infected with an adeno-associated virus through injection via the internal jugular vein. To establish PH models, the animals were subjected to monocrotaline or Sugen/hypoxia. Four weeks later, pulmonary artery angiography was performed, and hemodynamic parameters, right ventricular function, and vascular remodeling were evaluated. EndoMT and cell proliferation in the pulmonary arteries were assessed via immunofluorescence staining. Moreover, pulmonary artery endothelial cells (PAECs) isolated from experimental PH rats were cultured to investigate the underlying molecular mechanisms involved.

RESULTS

PEDF expression was significantly downregulated in PAECs from PH patients and PH model rats. Overexpressed PEDF alleviated the development of PH by improving pulmonary artery morphology and perfusion, reducing pulmonary artery pressure, improving right ventricular function, and alleviating vascular remodeling. PEDF inhibits EndoMT and reduces excessive PAEC proliferation. Moreover, PEDF overexpression reduced EndoMT in cultured PAECs by competitively inhibiting the binding of wnt to LRP6 and downregulating phosphorylation at the 1490 site of LRP6.

CONCLUSIONS

Our findings suggest that PEDF may be a potential therapeutic target for PH. We also found that PEDF can inhibit EndoMT in PAECs and may exert these effects by inhibiting the Wnt/LRP6/β-catenin pathway.

The mechanism of gut-lung axis in pulmonary fibrosis

Pulmonary fibrosis (PF) is a terminal change of a lung disease that is marked by damage to alveolar epithelial cells, abnormal proliferative transformation of fibroblasts, excessive deposition of extracellular matrix (ECM), and concomitant inflammatory damage. Its characteristics include short median survival, high mortality rate, and limited treatment effectiveness. More in-depth studies on the mechanisms of PF are needed to provide better treatment options. The idea of the gut-lung axis has emerged as a result of comprehensive investigations into the microbiome, metabolome, and immune system. This theory is based on the material basis of microorganisms and their metabolites, while the gut-lung circulatory system and the shared mucosal immune system act as the connectors that facilitate the interplay between the gastrointestinal and respiratory systems. The emergence of a new view of the gut-lung axis is complementary and cross-cutting to the study of the mechanisms involved in PF and provides new ideas for its treatment. This article reviews the mechanisms involved in PF, the gut-lung axis theory, and the correlation between the two. Exploring the gut-lung axis mechanism and treatments related to PF from the perspectives of microorganisms, microbial metabolites, and the immune system. The study of the gut-lung axis and PF is still in its early stages. This review systematically summarizes the mechanisms of PF related to the gut-lung axis, providing ideas for subsequent research and treatment of related mechanisms.

PEDF inhibits LPS-induced acute lung injury in rats and promotes lung epithelial cell survival by upregulating PPAR-γ

BACKGROUND

The progression of acute lung injury (ALI) involves numerous pathological factors and complex mechanisms, and cause the destruction of epithelial and endothelial barriers. Pigment epithelium-derived factor (PEDF) is an angiogenesis inhibitor and a potential anti-inflammatory factor. The purpose of this study was to investigate the effect of PEDF on lipopolysaccharide (LPS)-induced ALI in rats.

METHODS

In vivo, pathological and injury related factors examination were performed on rat lung to investigate the effect of PEDF on ALI. In vitro, the effect of PEDF on inflammatory injury and apoptosis of lung epithelial type II RLE-6TN cell was evaluated, and the expression of inflammatory factors and related pathway proteins and PPAR-γ (in the presence or absence of PPAR-γ inhibitors) were analyzed.

RESULTS

In vivo results showed that PEDF inhibited the inflammatory factor expression (TNF-α, IL-6 and IL-1β) and progression of ALI and reduced lung cell apoptosis in rats. In vitro results showed that PEDF could effectively inhibit LPS-stimulated inflammatory damage and apoptosis of RLE-6TN cells. PEDF inhibited the RLE-6TN cell injury by enhancing the expression of PPAR-γ.

CONCLUSIONS

PEDF is an anti-inflammatory factor, which can inhibit apoptosis of lung epithelial cells by upregulating the expression of PPAR-γ and reducing LPS-induced ALI in rats.

The endothelium in lung fibrosis: a core signaling hub in disease pathogenesis?

Pulmonary fibrosis (PF) is a progressive chronic lung disease characterized by excessive deposition of extracellular matrix (ECM) and structural destruction, associated with a severe 5-year mortality rate. The onset of the disease is thought to be triggered by chronic damage to the alveolar epithelium. Since the pulmonary endothelium is an important component of the alveolar-capillary niche, it is also affected by the initial injury. In addition to ensuring proper gas exchange, the endothelium has critical functional properties, including regulation of vascular tone, inflammatory responses, coagulation, and maintenance of vascular homeostasis and integrity. Recent single-cell analyses have shown that shifts in endothelial cell (EC) subtypes occur in PF. Furthermore, the increased vascular remodeling associated with PF leads to deteriorated outcomes for patients, underscoring the importance of the vascular bed in PF. To date, the causes and consequences of endothelial and vascular involvement in lung fibrosis are poorly understood. Therefore, it is of great importance to investigate the involvement of EC and the vascular system in the pathogenesis of the disease. In this review, we will outline the current knowledge on the role of the pulmonary vasculature in PF, in terms of abnormal cellular interactions, hyperinflammation, vascular barrier disorders, and an altered basement membrane composition. Finally, we will summarize recent advances in extensive therapeutic research and discuss the significant value of novel therapies targeting the endothelium.

Insights on the mechanism of bleomycin to induce lung injury and associated in vivo models: A review

Acute lung injury leads to the development of chronic conditions such as idiopathic pulmonary fibrosis (IPF), chronic obstructive pulmonary disease (COPD), asthma as well as alveolar sarcoma. Various investigations are being performed worldwide to understand the pathophysiology of these diseases, develop novel bioactive compounds and inhibitors to target the ailment. Generally, in vivo models are used to understand the disease outcome and therapeutic suppressing effects for which the animals are chemically or physically induced to mimic the onset of definite disease conditions. Amongst the chemical inducing agents, Bleomycin (BLM) is the most successful inducer. It is reported to target various receptors and activate inflammatory pathways, cellular apoptosis, epithelial mesenchymal transition leading to the release of inflammatory cytokines, and proteases. Mice is one of the most widely used animal model for BLM induced pulmonary associated studies apart from rat, rabbit, sheep, pig, and monkey. Although, there is considerable variation amongst in vivo studies for BLM induction which suggests a detailed study on the same to understand the mechanism of action of BLM at molecular level. Hence, herein we have reviewed various chemical inducers, mechanism of action of BLM in inducing lung injury in vivo, its advantages and disadvantages. Further, we have also discussed the rationale behind various in vivo models and recent development in BLM induction for various animals.

Roles of pigment epithelium-derived factor in cardiomyocytes: implications for use as a cardioprotective therapeutic

OBJECTIVES

Cardiovascular diseases are the leading cause of death worldwide, with patients having limited options for treatment. Pigment epithelium-derived factor (PEDF) is an endogenous multifunctional protein with several mechanisms of action. Recently, PEDF has emerged as a potential cardioprotective agent in response to myocardial infarction. However, PEDF is also associated with pro-apoptotic effects, complicating its role in cardioprotection. This review summarises and compares knowledge of PEDF's activity in cardiomyocytes with other cell types and draws links between them. Following this, the review offers a novel perspective of PEDF's therapeutic potential and recommends future directions to understand the clinical potential of PEDF better.

KEY FINDINGS

PEDF's mechanisms as a pro-apoptotic and pro-survival protein are not well understood, despite PEDF's implication in several physiological and pathological activities. However, recent evidence suggests that PEDF may have significant cardioprotective properties mediated by key regulators dependent on cell type and context.

CONCLUSIONS

While PEDF's cardioprotective activity shares some key regulators with its apoptotic activity, cellular context and molecular features likely allow manipulation of PEDF's cellular activity, highlighting the importance of further investigation into its activities and its potential to be applied as a therapeutic to mitigate damage from a range of cardiac pathologies.

Collagen type I alters the proteomic signature of macrophages in a collagen morphology-dependent manner

Idiopathic pulmonary fibrosis is a progressive lung disease that causes scarring and loss of lung function. Macrophages play a key role in fibrosis, but their responses to altered morphological and mechanical properties of the extracellular matrix in fibrosis is relatively unexplored. Our previous work showed functional changes in murine fetal liver-derived alveolar macrophages on fibrous or globular collagen morphologies. In this study, we applied differential proteomics to further investigate molecular mechanisms underlying the observed functional changes. Macrophages cultured on uncoated, fibrous, or globular collagen-coated plastic were analyzed by liquid chromatography-mass spectrometry. The presence of collagen affected expression of 77 proteins, while 142 were differentially expressed between macrophages grown on fibrous or globular collagen. Biological process and pathway enrichment analysis revealed that culturing on any type of collagen induced higher expression of enzymes involved in glycolysis. However, this did not lead to a higher rate of glycolysis, probably because of a concomitant decrease in activity of these enzymes. Our data suggest that macrophages sense collagen morphologies and can respond with changes in expression and activity of metabolism-related proteins. These findings suggest intimate interactions between macrophages and their surroundings that may be important in repair or fibrosis of lung tissue.

Jinlian Xiaodu Decoction Protects against Bleomycin-Induced Pulmonary Fibrosis in Rats

Background

Jinlian Xiaodu Decoction (JXD) was reported to have anti-inflammatory and lung protection effects. This study aimed to explore the role and mechanism of JXD on bleomycin (BLM)-induced pulmonary fibrosis (PF).

Methods

The UHPLC-Q/TOF-MS system was applied to analyze JXD composition. The PF model was established by BLM intratracheal administration in Wistar rats. Subsequently, BLM-treated rats were intragastrically administered with dexamethasone (DXM, 1 g/kg/d) or JXD (3.5, 7 or 14 g/kg/d). Next, the lung coefficient was calculated; H&E, Masson, and TUNEL staining were used for lung morphological analysis and apoptosis assessment. Bronchoalveolar lavage fluid (BALF) biochemical analysis was conducted to count the inflammatory cell number. The expression of inflammatory factors mRNA in the lung tissue and BALF were measured by qRT-PCR. The content and activity of oxidative stress-related proteins were detected. The expression of PF-related, apoptosis-related, and TGF-β1 pathway-related protein were assessed by immunohistochemistry or Western blot.

Results

Twenty-six compounds were identified from JXD in both negative and positive ion modes. In BLM-induced rats, JXD reduced the lung coefficient and alleviated PF injury. JXD decreased inflammatory cell count and TNF-α, IL-1β, IL-6, and MCP-1 content. Meanwhile, JXD blunted BLM-induced oxidative stress and a high level of HYP. Furthermore, TUNEL analysis found that JXD inhibited cell apoptosis and increased Bcl-2/Bax ratio in BLM-induced lung. Moreover, JXD relieved the role of BLM on α-SMA, TGF-β1, collagen I, fibronectin, E-cadherin protein expression, and the phosphorylation of Smad2/3 in PF rat.

Conclusion

This study revealed the protective effect and possible element of JXD on BLM-caused PF.

Serum Pigment Epithelium-Derived Factor Levels are Associated with Estradiol and Decrease After Adjusting for Alanine Aminotransferase in Chinese Women Based on Multiple Linear Regression Analysis

PURPOSE

To assess changes in pigment epithelium-derived factor (PEDF) levels in patients with metabolic syndrome (MetS) and to investigate sexual dimorphism in serum PEDF levels and their relationships with estradiol.

METHODS

A total of 318 individuals (145 men, 173 women) who underwent health examinations in our department were selected. Serum PEDF, estradiol and other metabolic parameters were determined. Homeostasis model assessment of insulin resistance (HOMA- IR) and homeostasis model assessment of β-cell function (HOMA-β) were calculated to evaluate insulin resistance and β-cell function, respectively. Multiple linear regression analysis was used to analyse the factors influencing serum PEDF.

RESULTS

Serum PEDF levels were significantly higher in subjects with MetS in both men and women (12.09±2.75 vs 8.97±3.19 μg/mL in men and 11.31±2.79 vs 8.40±2.32 μg/mL in women, MetS vs non-MetS, P<0.001). Correlation analysis showed that serum PEDF levels were significantly correlated with body mass index (BMI), waist circumference, waist-to-hip ratio, diastolic blood pressure (DBP), fasting and 2-h postprandial glucose, fasting and 2-h postprandial insulin, HOMA-β, HOMA-IR, hemoglobin A1c (HbA1c), alanine aminotransferase (ALT), aspartate aminotransferase (AST), uric acid (UA), triacylglycerol (TG) and high-density lipoprotein cholesterol (HDL-C). Elevated ALT, HOMA-IR and TG were significant predictors of increased PEDF concentrations. In women, estradiol was inversely correlated with PEDF levels (r=-0.25, P=0.011), and the association was no longer significant after adjustment for ALT.

CONCLUSION

PEDF could be used as a biomarker of MetS in both men and women. This study reported for the first time that circulating PEDF displays sexual dimorphism, which could be related to estrogen. The association between estrogen and circulating PEDF levels was attenuated after adjusting for ALT.