Vascular endothelial growth factor and related molecules in acute lung injury

Novel insights into the potential applications of stem cells in pulmonary hypertension therapy

Pulmonary hypertension (PH) refers to a group of deadly lung diseases characterized by vascular lesions in the microvasculature and a progressive increase in pulmonary vascular resistance. The prevalence of PH has increased over time. Currently, the treatment options available for PH patients have limited efficacy, and none of them can fundamentally reverse pulmonary vascular remodeling. Stem cells represent an ideal seed with proven efficacy in clinical studies focusing on liver, cardiovascular, and nerve diseases. Since the potential therapeutic effect of mesenchymal stem cells (MSCs) on PH was first reported in 2006, many studies have demonstrated the efficacy of stem cells in PH animal models and suggested that stem cells can help slow the deterioration of lung tissue. Existing PH treatment studies basically focus on the paracrine action of stem cells, including protein regulation, exosome pathway, and cell signaling; however, the specific mechanisms have not yet been clarified. Apoptotic and afunctional pulmonary microvascular endothelial cells (PMVECs) and alveolar epithelial cells (AECs) are two fundamental promoters of PH although they have not been extensively studied by researchers. This review mainly focuses on the supportive communication and interaction between PMVECs and AECs as well as the potential restorative effect of stem cells on their injury. In the future, more studies are needed to prove these effects and explore more radical cures for PH.

Revolutionizing the Treatment of Idiopathic Pulmonary Fibrosis: From Conventional Therapies to Advanced Drug Delivery Systems

Idiopathic pulmonary fibrosis (IPF) is a chronic and progressive interstitial lung disease that has been well-reported in the medical literature. Its incidence has risen, particularly in light of the recent COVID-19 pandemic. Conventionally, IPF is treated with antifibrotic drugs-pirfenidone and nintedanib-along with other drugs for symptomatic treatments, including corticosteroids, immunosuppressants, and bronchodilators based on individual requirements. Several drugs and biologicals such as fluorofenidone, thymoquinone, amikacin, paclitaxel nifuroxazide, STAT3, and siRNA have recently been evaluated for IPF treatment that reduces collagen formation and cell proliferation in the lung. There has been a great deal of research into various treatment options for pulmonary fibrosis using advanced delivery systems such as liposomal-based nanocarriers, chitosan nanoparticles, PLGA nanoparticles, solid lipid nanocarriers, and other nanoformulations such as metal nanoparticles, nanocrystals, cubosomes, magnetic nanospheres, and polymeric micelles. Several clinical trials are also ongoing for advanced IPF treatments. This article elaborates on the pathophysiology of IPF, its risk factors, and different advanced drug delivery systems for treating IPF. Although extensive preclinical data is available for these delivery systems, the clinical performance and scale-up studies would decide their commercial translation.

Role of biomarkers and molecular signaling pathways in acute lung injury

BACKGROUND

Acute lung injury (ALI) is caused by bacterial, fungal, and viral infections. When pathogens invade the lungs, the immune system responds by producing cytokines, chemokines, and interferons to promote the infiltration of phagocytic cells, which are essential for pathogen clearance. Their excess production causes an overactive immune response and a pathological hyper-inflammatory state, which leads to ALI. Until now, there is no particular pharmaceutical treatment available for ALI despite known inflammatory mediators like neutrophil extracellular traps (NETs) and reactive oxygen species (ROS).

OBJECTIVES

Therefore, the primary objective of this review is to provide the clear overview on the mechanisms controlling NETs, ROS formation, and other relevant processes during the pathogenesis of ALI. In addition, we have discussed the significance of epithelial and endothelial damage indicators and several molecular signaling pathways associated with ALI.

METHODS

The literature review was done from Web of Science, Scopus, PubMed, and Google Scholar for ALI, NETs, ROS, inflammation, biomarkers, Toll- and nucleotide-binding oligomerization domain (NOD)-like receptors, alveolar damage, pro-inflammatory cytokines, and epithelial/endothelial damage alone or in combination.

RESULTS

This review summarized the main clinical signs of ALI, including the regulation and distinct function of epithelial and endothelial biomarkers, NETs, ROS, and pattern recognition receptors (PRRs).

CONCLUSION

However, no particular drugs including vaccine for ALI has been established. Furthermore, there is a lack of validated diagnostic tools and a poor predictive rationality of current therapeutic biomarkers. Hence, extensive and precise research is required to speed up the process of drug testing and development by the application of artificial intelligence technologies, structure-based drug design, in-silico approaches, and drug repurposing.

Protective effects of Eleutheroside E against high-altitude pulmonary edema by inhibiting NLRP3 inflammasome-mediated pyroptosis

Eleutheroside E (EE) is a primary active component of Acanthopanax senticosus, which has been reported to inhibit the expression of inflammatory genes, but the underlying mechanisms remain elusive. High-altitude pulmonary edema (HAPE) is a severe complication of high-altitude exposure occurring after ascent above 2500 m. However, effective and safe preventative measures for HAPE still need to be improved. This study aimed to elucidate the preventative potential and underlying mechanism of EE in HAPE. Rat models of HAPE were established through hypobaric hypoxia. Mechanistically, hypobaric hypoxia aggravates oxidative stress and upregulates (pro)-inflammatory cytokines, activating NOD-like receptor protein 3 (NLRP3) inflammasome-mediated pyroptosis, eventually leading to HAPE. EE suppressed NLRP3 inflammasome-mediated pyroptosis by inhibiting the nuclear translocation of nuclear factor kappa-Β (NF-κB), thereby protecting the lung from HAPE. However, nigericin (Nig), an NLRP3 activator, partially abolished the protective effects of EE. These findings suggest EE is a promising agent for preventing HAPE induced by NLRP3 inflammasome-mediated pyroptosis.

Endothelial progenitor cells in the host defense response

Extensive injury of endothelial cells in blood vasculature, especially in the microcirculatory system, frequently occurs in hosts suffering from sepsis and the accompanied systemic inflammation. Pathological factors, including toxic components derived from invading microbes, oxidative stress associated with tissue ischemia/reperfusion, and vessel active mediators generated during the inflammatory response, are known to play important roles in mediating endothelial injury. Collapse of microcirculation and tissue edema developed from the failure of endothelial barrier function in vital organ systems, including the lung, brain, and kidney, are detrimental, which often predict fatal outcomes. The host body possesses a substantial capacity for maintaining vascular homeostasis and repairing endothelial damage. Bone marrow and vascular wall niches house endothelial progenitor cells (EPCs). In response to septic challenges, EPCs in their niche environment are rapidly activated for proliferation and angiogenic differentiation. In the meantime, release of EPCs from their niches into the blood stream and homing of these vascular precursors to tissue sites of injury are markedly increased. The recruited EPCs actively participate in host defense against endothelial injury and repair of damage in blood vasculature via direct differentiation into endothelial cells for re-endothelialization as well as production of vessel active mediators to exert paracrine and autocrine effects on angiogenesis/vasculogenesis. In recent years, investigations on significance of EPCs in host defense and molecular signaling mechanisms underlying regulation of the EPC response have achieved substantial progress, which promotes exploration of vascular precursor cell-based approaches for effective prevention and treatment of sepsis-induced vascular injury as well as vital organ system failure.

PLCβ2 Promotes VEGF-Induced Vascular Permeability

BACKGROUND

Regulation of vascular permeability is critical to maintaining tissue metabolic homeostasis. VEGF (vascular endothelial growth factor) is a key stimulus of vascular permeability in acute and chronic diseases including ischemia reperfusion injury, sepsis, and cancer. Identification of novel regulators of vascular permeability would allow for the development of effective targeted therapeutics for patients with unmet medical need.

METHODS

In vitro and in vivo models of VEGFA-induced vascular permeability, pathological permeability, quantitation of intracellular calcium release and cell entry, and phosphatidylinositol 4,5-bisphosphate levels were evaluated with and without modulation of PLC (phospholipase C) β2.

RESULTS

Global knock-out of PLCβ2 in mice resulted in blockade of VEGFA-induced vascular permeability in vivo and transendothelial permeability in primary lung endothelial cells. Further work in an immortalized human microvascular cell line modulated with stable knockdown of PLCβ2 recapitulated the observations in the mouse model and primary cell assays. Additionally, loss of PLCβ2 limited both intracellular release and extracellular entry of calcium following VEGF stimulation as well as reduced basal and VEGFA-stimulated levels of phosphatidylinositol 4,5-bisphosphate compared to control cells. Finally, loss of PLCβ2 in both a hyperoxia-induced lung permeability model and a cardiac ischemia:reperfusion model resulted in improved animal outcomes when compared with wild-type controls.

CONCLUSIONS

The results implicate PLCβ2 as a key positive regulator of VEGF-induced vascular permeability through regulation of both calcium flux and phosphatidylinositol 4,5-bisphosphate levels at the cellular level. Targeting of PLCβ2 in a therapeutic setting may provide a novel approach to regulating vascular permeability in patients.

Highly Pathogenic PRRSV-Infected Alveolar Macrophages Impair the Function of Pulmonary Microvascular Endothelial Cells

The porcine reproductive and respiratory syndrome virus (PRRSV), especially the highly pathogenic strains, can cause serious acute lung injury (ALI), characterized by extensive hemorrhage, inflammatory cells and serous fluid infiltration in the lung vascular system. Meanwhile, the pulmonary microvascular endothelial cells (PMVECs) are essential for forming the air–blood barrier and keeping the water–salt balance to prevent leakage of circulating nutrients, solutes, and fluid into the underlying tissues. As well, they tightly regulate the influx of immune cells. To determine the possible relationship between the PMVECs’ function changes and lung vascular permeability during PRRSV infection, the PMVECs were co-cultured with HP-PRRSV-inoculated primary pulmonary alveolar macrophages (PAMs) in transwell model, and then the RNA sequencing (RNA-seq) and comprehensive bioinformatics analysis were carried out to characterize the dynamic transcriptome landscapes of PMVECs. In total, 16,489 annotated genes were identified, with 275 upregulated and 270 downregulated differentially expressed genes (DEGs) were characterized at both 18 and 24 h post PRRSV inoculation. The GO terms and KEGG pathways analysis indicated that the immune response, metabolic pathways, cell death, cytokine–cytokine receptor interaction, viral responses, and apoptotic process are significantly regulated upon co-culture with PRRSV-infected PAMs. Moreover, according to the TERR and dextran flux assay results, dysregulation of TJ proteins, including CLDN1, CLDN4, CLDN8, and OCLN, is further confirmed to correlate with the increased permeability of PMVECs. These transcriptome profiles and DEGs will provide valuable clues for further exploring the roles of PMVECs in PRRSV-induced ALI in the future.

A hitchhiker's guide through the COVID-19 galaxy

Numerous reviews have summarized the epidemiology, pathophysiology and the various therapeutic aspects of Coronavirus disease 2019 (COVID-19), but a practical guide on "how to treat whom with what and when" based on an understanding of the immunological background of the disease stages remains missing. This review attempts to combine the current knowledge about the immunopathology of COVID-19 with published evidence of available and emerging treatment options. We recognize that the information about COVID-19 and its treatment is rapidly changing, but hope that this guide offers those on the frontline of this pandemic an understanding of the host response in COVID-19 patients and supports their ongoing efforts to select the best treatments tailored to their patient's clinical status.

The "Angiogenic Switch" and Functional Resources in Cyclic Sports Athletes

Regular physical activity in cyclic sports can influence the so-called “angiogenic switch”, which is considered as an imbalance between proangiogenic and anti-angiogenic molecules. Disruption of the synthesis of angiogenic molecules can be caused by local changes in tissues under the influence of excessive physical exertion and its consequences, such as chronic oxidative stress and associated hypoxia, metabolic acidosis, sports injuries, etc. A review of publications on signaling pathways that activate and inhibit angiogenesis in skeletal muscles, myocardium, lung, and nervous tissue under the influence of intense physical activity in cyclic sports. Materials: We searched PubMed, SCOPUS, Web of Science, Google Scholar, Clinical keys, and e-LIBRARY databases for full-text articles published from 2000 to 2020, using keywords and their combinations. Results: An important aspect of adaptation to training loads in cyclic sports is an increase in the number of capillaries in muscle fibers, which improves the metabolism of skeletal muscles and myocardium, as well as nervous and lung tissue. Recent studies have shown that myocardial endothelial cells not only respond to hemodynamic forces and paracrine signals from neighboring cells, but also take an active part in heart remodeling processes, stimulating the growth and contractility of cardiomyocytes or the production of extracellular matrix proteins in myofibroblasts. As myocardial vascularization plays a central role in the transition from adaptive heart hypertrophy to heart failure, further study of the signaling mechanisms involved in the regulation of angiogenesis in the myocardium is important in sports practice. The study of the “angiogenic switch” problem in the cerebrovascular and cardiovascular systems allows us to claim that the formation of new vessels is mediated by a complex interaction of all growth factors. Although the lungs are one of the limiting systems of the body in cyclic sports, their response to high-intensity loads and other environmental stresses is often overlooked. Airway epithelial cells are the predominant source of several growth factors throughout lung organogenesis and appear to be critical for normal alveolarization, rapid alveolar proliferation, and normal vascular development. There are many controversial questions about the role of growth factors in the physiology and pathology of the lungs. The presented review has demonstrated that when doing sports, it is necessary to give a careful consideration to the possible positive and negative effects of growth factors on muscles, myocardium, lung tissue, and brain. Primarily, the “angiogenic switch” is important in aerobic sports (long distance running). Conclusions: Angiogenesis is a physiological process of the formation of new blood capillaries, which play an important role in the functioning of skeletal muscles, myocardium, lung, and nervous tissue in athletes. Violation of the “angiogenic switch” as a balance between proangiogenic and anti-angiogenic molecules can lead to a decrease in the functional resources of the nervous, musculoskeletal, cardiovascular, and respiratory systems in athletes and, as a consequence, to a decrease in sports performance.

Bevacizumab regulates inflammatory cytokines and inhibits VEGFR2 signaling pathway in an ovalbumin-induced rat model of airway hypersensitivity

BACKGROUND

Bevacizumab with anti-angiogenesis properties reduces the vascular endothelial growth factor (VEGF) level and has widely been used to treat various diseases such as lung diseases and chronic obstructive pulmonary disease (COPD). This study, therefore, aimed to consider the effects of bevacizumab on VEGF receptor 2 (VEGFR2) and lung inflammation of the ovalbumin-induced rat model of airway hypersensitivity.

MATERIALS AND METHODS

Twenty-one male Wistar rats were randomly divided into 3 groups (n = 7 in each group): (1) control, (2) ovalbumin (OVA)-sensitized, and (3) OVA-sensitized with bevacizumab (OVA + Bmab). Groups 2 and 3 were sensitized with ovalbumin (OVA) and aluminum hydroxide on days 1, 8 and challenged with OVA on day 15 by atomization for 10 days (inhalation). After OVA sensitization, the OVA + Bmab was treated with bevacizumab for 2 weeks. VEGFR2 was semiquantitatively analyzed in the lungs by immunohistochemistry. VEGF was measured in the lung tissue by ELISA method. The mRNA of IL-10 and IL-6 lung tissue were measured by real-time PCR.

RESULTS

Ovalbumin exposure promoted the expression of VEGF and resulted in inflammatory factors overexpression (p ≤ 0.05). However, rats in OVA + Bmab group showed significantly a decrease in VEGFR2 and IL-1β, IL-6, TNFα, and an increase in IL-10 (p ≤ 0.05).

CONCLUSION

The results show that bevacizumab efficiently diminishes bronchial inflammation via reducing the expression of VEGFR2, and IL-6 genes and enhancing the expression of IL-10 gene. Hence, bevacizumab could be considered as a potential candidate drug to control pathological conditions relevant to airway hypersensitivity.

Hyperoxia-induced bronchopulmonary dysplasia: better models for better therapies

Bronchopulmonary dysplasia (BPD) is a chronic lung disease caused by exposure to high levels of oxygen (hyperoxia) and is the most common complication that affects preterm newborns. At present, there is no cure for BPD. Infants can recover from BPD; however, they will suffer from significant morbidity into adulthood in the form of neurodevelopmental impairment, asthma and emphysematous changes of the lung. The development of hyperoxia-induced lung injury models in small and large animals to test potential treatments for BPD has shown some success, yet a lack of standardization in approaches and methods makes clinical translation difficult. In vitro models have also been developed to investigate the molecular pathways altered during BPD and to address the pitfalls associated with animal models. Preclinical studies have investigated the efficacy of stem cell-based therapies to improve lung morphology after damage. However, variability regarding the type of animal model and duration of hyperoxia to elicit damage exists in the literature. These models should be further developed and standardized, to cover the degree and duration of hyperoxia, type of animal model, and lung injury endpoint, to improve their translational relevance. The purpose of this Review is to highlight concerns associated with current animal models of hyperoxia-induced BPD and to show the potential of in vitro models to complement in vivo studies in the significant improvement to our understanding of BPD pathogenesis and treatment. The status of current stem cell therapies for treatment of BPD is also discussed. We offer suggestions to optimize models and therapeutic modalities for treatment of hyperoxia-induced lung damage in order to advance the standardization of procedures for clinical translation.

Upregulation of endothelial cell-derived exosomal microRNA-125b-5p protects from sepsis-induced acute lung injury by inhibiting topoisomerase II alpha

OBJECTIVE

Emerging evidence has revealed that exosomal microRNAs (miRNAs) are implicated in human diseases. However, role of exosomal miR-125b-5p in sepsis-induced acute lung injury (ALI) remains further explored. We focused on the effect of exosomal miR-125b-5p on ALI progression via targeting topoisomerase II alpha (TOP2A).

METHODS

The ALI mouse models were established by cecal ligation and perforation, which were then treated with miR-125b-5p agomir or overexpressed TOP2A. Next, the pathological structure of ALI mouse lung tissues were observed, miR-125b-5p, TOP2A and vascular endothelial growth factor (VEGF) expression was determined, and the lung water content, inflammatory response, protein content in bronchoalveolar lavage fluid (BALF) and cell apoptosis in ALI mouse lung tissues were assessed. Exosomes were extracted from endothelial cells (ECs) and identified, which were then injected into the modeled mice to observe their roles in ALI. The targeting relationship between miR-125b-5p and TOP2A was confirmed.

RESULTS

MiR-125b-5p was downregulated while TOP2A was upregulated in ALI mice. MiR-125b-5p elevation or ECs-derived exosomes promoted VEGF expression, improved pathological changes and restrained lung water content, inflammatory response, protein content in BALF and cell apoptosis in lung tissues ALI mice. TOP2A overexpression reversed the repressive role of miR-125b-5p upregulation in ALI, while downregulated miR-125b-5p abrogated the effect of ECs-derived exosomes on ALI. TOP2A was confirmed as a direct target gene of miR-125b-5p.

CONCLUSION

Our study indicates that ECs-derived exosomes overexpressed miR-125b-5p to protect from sepsis-induced ALI by inhibiting TOP2A, which may contribute to ALI therapeutic strategies.

PR1P Stabilizes VEGF and Upregulates Its Signaling to Reduce Elastase-induced Murine Emphysema

Emphysema is a progressive and fatal lung disease with no cure that is characterized by thinning, enlargement, and destruction of alveoli, leading to impaired gas exchange. Disease progression is due in part to dysregulation of VEGF (vascular endothelial growth factor) signaling in the lungs and increased lung-cell apoptosis. Here we asked whether PR1P (Prominin-1-derived peptide), a novel short peptide we designed that increases VEGF binding to endothelial cells, could be used to improve outcome in in vitro and in vivo models of emphysema. We used computer simulation and in vitro and in vivo studies to show that PR1P upregulated endogenous VEGF receptor-2 signaling by binding VEGF and preventing its proteolytic degradation. In so doing, PR1P mitigated toxin-induced lung-cell apoptosis, including from cigarette-smoke extract in vitro and from LPS in vivo in mice. Remarkably, inhaled PR1P led to significantly increased VEGF concentrations in murine lungs within 30 minutes that remained greater than twofold above that of control animals 24 hours later. Finally, inhaled PR1P reduced acute lung injury in 4- and 21-day elastase-induced murine emphysema models. Taken together, these results highlight the potential of PR1P as a novel therapeutic agent for the treatment of emphysema or other lung diseases characterized by VEGF signaling dysregulation.

Low-Molecular-Weight Heparin Reduces Ventilation-Induced Lung Injury through Hypoxia Inducible Factor-1α in a Murine Endotoxemia Model

Patients with sepsis frequently require mechanical ventilation (MV) to survive. However, MV has been shown to induce the production of proinflammatory cytokines, causing ventilator-induced lung injury (VILI). It has been demonstrated that hypoxia-inducible factor (HIF)-1α plays a crucial role in inducing both apoptotic and inflammatory processes. Low-molecular-weight heparin (LMWH) has been shown to have anti-inflammatory activities. However, the effects of HIF-1α and LMWH on sepsis-related acute lung injury (ALI) have not been fully delineated. We hypothesized that LMWH would reduce lung injury, production of free radicals and epithelial apoptosis through the HIF-1α pathway. Male C57BL/6 mice were exposed to 6-mL/kg or 30-mL/kg MV for 5 h. Enoxaparin, 4 mg/kg, was administered subcutaneously 30 min before MV. We observed that MV with endotoxemia induced microvascular permeability; interleukin-6, tumor necrosis factor-α, macrophage inflammatory protein-2 and vascular endothelial growth factor protein production; neutrophil infiltration; oxidative loads; HIF-1α mRNA activation; HIF-1α expression; bronchial epithelial apoptosis; and decreased respiratory function in mice (p < 0.05). Endotoxin-induced augmentation of VILI and epithelial apoptosis were reduced in the HIF-1α-deficient mice and in the wild-type mice following enoxaparin administration (p < 0.05). Our data suggest that enoxaparin reduces endotoxin-augmented MV-induced ALI, partially by inhibiting the HIF-1α pathway.

VEGF and FGF-2: Promising targets for the treatment of respiratory disorders

The endothelial cells play a crucial role in the progression of angiogenesis, which causes cell re-modulation, proliferation, adhesion, migration, invasion and survival. Angiogenic factors like cytokines, cell adhesion molecules, growth factors, vasoactive peptides, proteolytic enzymes (metalloproteinases) and plasminogen activators bind to their receptors on endothelial cells and activate the signal transduction pathways like epidermal growth factor receptor (EGFR phosphatidylinositol 3-kinase and (PI3K)/AKT/mammalian target of rapamycin (mTOR) which initiate the process of angiogenesis. Cytokines that stimulate angiogenesis include direct and indirect proangiogenic markers. The direct proangiogenic group of markers consists of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (FGF-2) and hepatocyte growth factor (HGF) whereas the indirect proangiogenic markers include transforming growth factor-beta (TGF-β), interleukin 6 (IL-6), interleukin 8 (IL-8) and platelet-derived growth factor (PDGF). VEGF and FGF-2 are the strongest activators of angiogenesis which stimulate migration and proliferation of endothelial cells in existing vessels to generate and stabilize new blood vessels. VEGF is released in hypoxic conditions as an effect of the hypoxia-inducible factor (HIF-1α) and causes re-modulation and inflammation of bronchi cell. Cell re-modulation and inflammation leads to the development of various lung disorders like pulmonary hypertension, chronic obstructive pulmonary disease, asthma, fibrosis and lung cancer. This indicates that there is a firm link between overexpression of VEGF and FGF-2 with lung disorders. Various natural and synthetic drugs are available for reducing the overexpression of VEGF and FGF-2 which can be helpful in treating lung disorders. Researchers are still searching for new angiogenic inhibitors which can be helpful in the treatment of lung disorders. The present review emphasizes on molecular mechanisms and new drug discovery focused on VEGF and FGF-2 inhibitors and their role as anti-angiogenetic agents in lung disorders.

SU5416 attenuated lipopolysaccharide-induced acute lung injury in mice by modulating properties of vascular endothelial cells

Background and aim: A potent and selective vascular endothelial growth factor receptor (VEGFR) inhibitor SU5416, has been developed for the treatment of solid human tumors. The binding of VEGF to VEGFR plays a crucial role in the pathophysiology of respiratory disorders. However, the impact of SU5416 on lipopolysaccharide (LPS)-induced acute lung injury (ALI) remains unclear. Thus, this study aimed to illuminate the biofunction of SU5416 in the mouse model of ALI.

Methods: Wild-type (WT) and toll-like receptor 4 (TLR4)-deficient (TLR4^−/-) C57BL/6 mice were used to establish LPS-induced ALI model. The primary pulmonary microvascular endothelial cell (PMVEC) was extracted for detection of endothelial barrier function.

Results: LPS significantly increased the number of inflammatory cells and inflammatory cytokines in bronchoalveolar lavage fluid (BALF). In addition, LPS increased alveolar epithelial cells injury, inflammation infiltration and vascular permeability of PMVEC in WT and TLR4^−/- mice. Western blotting experiment indicated VEGF/VEGFR and TLR4/NF-κB pathways were involved in the progression of LPS-stimulated ALI. Consistent with previous research, dexamethasone treatment appeared to be an effective therapeutic for mice with ALI. Moreover, treatment with SU5416 dramatically attenuated LPS-induced immune responses in mice lung tissues via inhibiting VEGF/VEGFR and TLR4/NF-κB pathways. Finally, SU5416 also decreased vascular permeability of PMVEC in vitro.

Conclusion: SU5416 ameliorated alveolar epithelial cells injury and histopathological changes in mice lung via inhibiting VEGF/VEGFR and TLR4/NF-κB signaling pathways. We also confirmed that SU5416 could restrain vascular permeability in PMVEC through improving the integrity of endothelial cell. These findings suggested that SU5416 may serve as a potential agent for the treatment of patients with ALI.

Mechanosensing and Mechanoregulation of Endothelial Cell Functions

Vascular endothelial cells (ECs) form a semiselective barrier for macromolecules and cell elements regulated by dynamic interactions between cytoskeletal elements and cell adhesion complexes. ECs also participate in many other vital processes including innate immune reactions, vascular repair, secretion, and metabolism of bioactive molecules. Moreover, vascular ECs represent a unique cell type exposed to continuous, time-dependent mechanical forces: different patterns of shear stress imposed by blood flow in macrovasculature and by rolling blood cells in the microvasculature; circumferential cyclic stretch experienced by the arterial vascular bed caused by heart propulsions; mechanical stretch of lung microvascular endothelium at different magnitudes due to spontaneous respiration or mechanical ventilation in critically ill patients. Accumulating evidence suggests that vascular ECs contain mechanosensory complexes, which rapidly react to changes in mechanical loading, process the signal, and develop context-specific adaptive responses to rebalance the cell homeostatic state. The significance of the interactions between specific mechanical forces in the EC microenvironment together with circulating bioactive molecules in the progression and resolution of vascular pathologies including vascular injury, atherosclerosis, pulmonary edema, and acute respiratory distress syndrome has been only recently recognized. This review will summarize the current understanding of EC mechanosensory mechanisms, modulation of EC responses to humoral factors by surrounding mechanical forces (particularly the cyclic stretch), and discuss recent findings of magnitude-specific regulation of EC functions by transcriptional, posttranscriptional and epigenetic mechanisms using -omics approaches. We also discuss ongoing challenges and future opportunities in developing new therapies targeting dysregulated mechanosensing mechanisms to treat vascular diseases. © 2019 American Physiological Society. Compr Physiol 9:873-904, 2019.

Changes in TNF-α, IL-6, IL-10 and VEGF in rats with ARDS and the effects of dexamethasone

Changes in tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), IL-10 and vascular endothelial growth factor (VEGF) in serum and bronchoalveolar lavage fluid (BALF) in rats with acute respiratory distress syndrome (ARDS) and the intervention effect of dexamethasone were observed to explore the theoretical basis of dexamethasone in the treatment of ARDS. Seventy-two rats were randomly divided into normal control group (group N, n=24), ARDS model group (group L, n=24) and dexamethasone group (group D, n=24). The ARDS rat model was established by jointly injecting oleic acid and lipopolysaccharide via the caudal vein, while rats in group D received intervention with dexamethasone. The wet/dry weight ratios of lung tissues were measured, and the levels of TNF-α, IL-6, IL-10 and VEGF in serum and BALF were measured via enzyme-linked immunosorbent assay. The wet/dry weight ratio of lung tissues of rats in group D was significantly decreased compared with that in group L (P<0.05 or P<0.01). The levels of TNF-α, IL-6 and VEGF in serum and BALF of rats in group L and D were obviously increased compared with those in group N at each time point (P<0.01). The levels of TNF-α, IL-6 and VEGF in serum and BALF of rats in group D were significantly decreased compared with those in group L (P<0.01). In conclusion, there is a serious imbalance between anti-inflammatory response and inflammatory response in rats with ARDS induced by oleic acid combined with lipopolysaccharide of Escherichia coli, whereas dexamethasone can alleviate lung injury through inhibiting expression levels of inflammatory factors and promoting expression levels of anti-inflammatory factors.

A vascular endothelial growth factor receptor gene variant is associated with susceptibility to acute respiratory distress syndrome

BACKGROUND

The acute respiratory distress syndrome (ARDS) is one of the main causes of mortality in adults admitted to intensive care units. Previous studies have demonstrated the existence of genetic variants involved in the susceptibility and outcomes of this syndrome. We aimed to identify novel genes implicated in sepsis-induced ARDS susceptibility.

METHODS

We first performed a prioritization of candidate genes by integrating our own genomic data from a transcriptomic study in an animal model of ARDS and from the only published genome-wide association study of ARDS study in humans. Then, we selected single nucleotide polymorphisms (SNPs) from prioritized genes to conduct a case-control discovery association study in patients with sepsis-induced ARDS (n = 225) and population-based controls (n = 899). Finally, we validated our findings in an independent sample of 661 sepsis-induced ARDS cases and 234 at-risk controls.

RESULTS

Three candidate genes were prioritized: dynein cytoplasmic-2 heavy chain-1, fms-related tyrosine kinase 1 (FLT1), and integrin alpha-1. Of those, a SNP from FLT1 gene (rs9513106) was associated with ARDS in the discovery study, with an odds ratio (OR) for the C allele of 0.76, 95% confidence interval (CI) 0.58-0.98 (p = 0.037). This result was replicated in an independent study (OR = 0.78, 95% CI = 0.62-0.98, p = 0.039), showing consistent direction of effects in a meta-analysis (OR = 0.77, 95% CI = 0.65-0.92, p = 0.003).

CONCLUSIONS

We identified FLT1 as a novel ARDS susceptibility gene and demonstrated that integration of genomic data can be a valid procedure to identify novel susceptibility genes. These results contribute to previous firm associations and functional evidences implicating FLT1 gene in other complex traits that are mechanistically linked, through the key role of endothelium, to the pathophysiology of ARDS.

Attenuation of murine acute lung injury by PF-573,228, an inhibitor of focal adhesion kinase

Acute lung injury (ALI) is characterized by endothelial barrier disruption resulting in increased vascular permeability. As focal adhesion kinase (FAK), a non-receptor protein tyrosine kinase, is involved in endothelial cell (EC) barrier regulation, we hypothesized that FAK inhibition could attenuate agonist-induced EC barrier disruption relevant to ALI. Human lung EC were pretreated with one of three pharmacologic FAK inhibitors, PF-573,228 (PF-228, 10 μM), PF-562,271 (PF-271, 5 μM) or NVP-TAE226 (TAE226, 5 μM) for 30 min prior to treatment with thrombin (1 U/ml, 30 min). Western blotting confirmed attenuated thrombin-induced FAK phosphorylation associated with all three inhibitors. Subsequently, EC were pretreated with either PF-228 (10 μM), TAE226 (5 μM) or PF-271 (5 μM) for 30 min prior to thrombin stimulation (1 U/ml) followed by measurements of barrier integrity by transendothelial electrical resistance (TER). Separately, EC grown in transwell inserts prior to thrombin (1 U/ml) with measurements of FITC-dextran flux after 30 min confirmed a significant attenuation of thrombin-induced EC barrier disruption by PF-228 alone. Finally, in a murine ALI model induced by LPS (1.25 mg/ml, IT), rescue treatment with PF-228 was associated with significantly reduced lung injury. Our findings PF-228, currently being studied in clinical trials, may serve as a novel and effective therapeutic agent for ALI.

Pathogenic CD8+ T Cells Cause Increased Levels of VEGF-A in Experimental Malaria-Associated Acute Respiratory Distress Syndrome, but Therapeutic VEGFR Inhibition Is Not Effective

Malaria is a severe disease and kills over 400,000 people each year. Malarial complications are the main cause of death and include cerebral malaria and malaria-associated acute respiratory distress syndrome (MA-ARDS). Despite antimalarial treatment, lethality rates of MA-ARDS are still between 20 and 80%. Patients develop pulmonary edema with hemorrhages and leukocyte extravasation in the lungs. The vascular endothelial growth factor-A (VEGF-A) and the placental growth factor (PlGF) are vascular permeability factors and may be involved in the disruption of the alveolar-capillary membrane, leading to alveolar edema. We demonstrated increased pulmonary VEGF-A and PlGF levels in lungs of mice with experimental MA-ARDS. Depletion of pathogenic CD8⁺ T cells blocked pulmonary edema and abolished the increase of VEGF-A and PlGF. However, neutralization of VEGF receptor-2 (VEGFR-2) with the monoclonal antibody clone DC101 did not decrease pulmonary pathology. The broader spectrum receptor tyrosine kinase inhibitor sunitinib even increased lung pathology. These data suggest that the increase in alveolar VEGF-A and PlGF is not a cause but rather a consequence of the pulmonary pathology in experimental MA-ARDS and that therapeutic inhibition of VEGF receptors is not effective and even contra-indicated.

Stimulatory Secretions of Airway Epithelial Cells Accelerate Early Repair of Tracheal Epithelium

Airway stem/progenitor epithelial cells (AECs) are notable for their differentiation capacities in response to lung injury. Our previous finding highlighted the regenerative capacity of AECs following transplantation in repairing tracheal injury and reducing the severity of alveolar damage associated acute lung injury in a rabbit model. The goal of this study is to further investigate the potential of AECs to re-populate the tracheal epithelium and to study their stimulatory effect on inhibiting pro-inflammatory cytokines, epithelial cell migration and proliferation, and epithelial-to-mesenchymal transition (EMT) process following tracheal injury. Two in vitro culture assays were applied in this study; the direct co-culture assay that involved a culture of decellularised tracheal epithelium explants and AECs in a rotating tube, and indirect co-culture assay that utilized microporous membrane-well chamber system to separate the partially decellularised tracheal epithelium explants and AEC culture. The co-culture assays provided evidence of the stimulatory behaviour of AECs to enhance tracheal epithelial cell proliferation and migration during early wound repair. Factors that were secreted by AECs also markedly suppressed the production of IL-1β and IL-6 and initiated the EMT process during tracheal remodelling.

VEGF synthesis is induced by prostacyclin and TGF-β in distal lung fibroblasts from COPD patients and control subjects: Implications for pulmonary vascular remodelling

BACKGROUND AND OBJECTIVE

Involvement of pulmonary vascular remodelling is a characteristic sign in COPD. Vascular mediators such as vascular endothelial growth factor (VEGF) and prostacyclin may regulate fibroblast activity. The objective was to study the synthesis of VEGF and interactions with prostacyclin and transforming growth factor (TGF)-β₁ in lung fibroblasts from patients with COPD and healthy control subjects. To further explore the autocrine role of synthesized VEGF on fibroblast activity, studies were performed in human lung fibroblasts (HFL-1).

METHODS

Primary distal lung fibroblast cultures were established from healthy individuals and from COPD patients (GOLD stage IV). Lung fibroblasts were stimulated with the prostacyclin analogue iloprost and the profibrotic stimuli TGF-β₁ . VEGF synthesis was measured in the cell culture medium. Changes in proliferation rate, migration and synthesis of the extracellular matrix (ECM) proteins proteoglycans were analysed after stimulations with VEGF-A isoform 165 (VEGF₁₆₅ ; 1-10 000 pg/mL) in HFL-1.

RESULTS

Iloprost and TGF-β₁ significantly increased VEGF synthesis in both fibroblasts from COPD patients and control subjects. TGF-β₁ -induced VEGF synthesis was significantly reduced by the cyclooxygenase inhibitor indomethacin in fibroblasts from COPD patients. VEGF significantly increased proliferation rate and migration capacity in HFL-1. VEGF also significantly increased synthesis of the ECM proteins biglycan and perlecan. The VEGF receptors (VEGFR), VEGFR1, VEGFR2 and VEGFR3, were all expressed in primary lung fibroblasts and HFL-1.

CONCLUSION

VEGF is synthesized in high amounts by distal lung fibroblasts and may have a crucial role in ongoing vascular remodelling processes in the distal lung compartments.

Clinical significance of serum vascular endothelial growth factor in young male asthma patients

BACKGROUND/AIMS

Vascular endothelial growth factor (VEGF) is an important mediator of angiogenesis. However, little is known about the potential use of serum levels of VEGF as a biomarker for asthma. We investigated the differences in VEGF levels among normal controls, stable asthma patients, and those with exacerbation of acute asthma. All subjects were young males.

METHODS

We measured VEGF levels in each patient group, and examined any serial changes in those with acute exacerbation.

RESULTS

VEGF levels were significantly higher in stable asthmatic patients and even more so in acute asthmatic patients, compared to healthy controls. However, there was no correlation between VEGF levels and forced expiratory volume in 1 second in patients with stable asthma. In addition, there were no correlations between VEGF levels and asthma control test scores. In patients with acute exacerbation, VEGF levels significantly increased during the acute period; their levels decreased gradually at 7 and 14 days after treatment.

CONCLUSIONS

Compared to normal control patients, the serum levels of VEGF were elevated in stable asthma patients and even more elevated in patients with acute exacerbation. However, the role of VEGF as a biomarker in stable asthma is limited. In patients with acute exacerbation, VEGF levels were associated with clinical improvements.

VEGF Production by Ly6C+high Monocytes Contributes to Ventilator-Induced Lung Injury

Background

Mechanical ventilation is a life-saving procedure for patients with acute respiratory failure, although it may cause pulmonary vascular inflammation and leakage, leading to ventilator-induced lung injury (VILI). Ly6C^+high monocytes are involved in the pathogenesis of VILI. In this study, we investigated whether pulmonary infiltrated Ly6C^+high monocytes produce vascular endothelial growth factor (VEGF) and contribute to VILI.

Methods

A clinically relevant two-hit mouse model of VILI, with intravenous lipopolysaccharide (LPS, 20 ng/mouse) immediately before high tidal volume (HTV, 20 mL/kg) ventilation (LPS+HTV), was established. Blood gas and respiratory mechanics were measured to ensure the development of VILI. Flow cytometry and histopathological analyses revealed pulmonary infiltration of leukocytes subsets. Clodronate liposomes were intravenously injected to deplete pulmonary monocytes. In vitro endothelial cell permeability assay with sorted Ly6C^+high monocytes condition media assessed the role of Ly6C^+high monocytes in vascular permeability.

Results

LPS+HTV significantly increased total proteins, TNF-α, IL-6, vascular endothelial growth factor (VEGF) and mononuclear cells in the bronchoalveolar lavage fluid (BALF). Pulmonary Ly6C^+high monocytes (SSC^lowCD11b⁺F4/80⁺Ly6C^+high), but not Ly6C^+low monocytes (SSC^lowCD11b⁺F4/80⁺Ly6C^+low), were significantly elevated starting at 4 hr. Clodronate liposomes were able to significantly reduce pulmonary Ly6C^+high monocytes, and VEGF and total protein in BALF, and restore PaO₂/FiO₂. There was a strong correlation between pulmonary Ly6C^+high monocytes and BALF VEGF (R² = 0.8791, p<0.001). Moreover, sorted Ly6C^+high monocytes were able to produce VEGF, resulting in an increased permeability of endothelial cell monolayer in an in vitro endothelial cell permeability assay.

Conclusion

VEGF produced by pulmonary infiltrated Ly6C^+high monocytes regulates vasculature permeability in a two-hit model of HTV-induced lung injury. Ly6C^+high monocytes play an important role in the pathogenesis of VILI.

Erythropoietin attenuates renal and pulmonary injury in polymicrobial induced-sepsis through EPO-R, VEGF and VEGF-R2 modulation

Sepsis remains the most important cause of acute kidney injury (AKI) and acute lung injury (ALI) in critically ill patients. The cecal ligation and puncture (CLP) model in experimental mice reproduces most of the clinical features of sepsis. Erythropoietin (EPO) is a well-known cytoprotective multifunctional hormone, which exerts anti-inflammatory, anti-oxidant, anti-apoptotic and pro-angiogenic effects in several tissues. The aim of this study was to evaluate the underlying mechanisms of EPO protection through the expression of the EPO/EPO receptor (EPO-R) and VEGF/VEF-R2 systems in kidneys and lungs of mice undergoing CLP-induced sepsis. Male inbred Balb/c mice were divided in three experimental groups: Sham, CLP, and CLP+EPO (3000IU/kg sc). Assessment of renal functional parameters, survival, histological examination, immunohistochemistry and/or Western blottings of EPO-R, VEGF and VEGF-R2 were performed at 18h post-surgery. Mice demonstrated AKI by elevation of serum creatinine and renal histologic damage. EPO treatment attenuates renal dysfunction and ameliorates kidney histopathologic changes. Additionally, EPO administration attenuates deleterious septic damage in renal cortex through the overexpression of EPO-R in tubular interstitial cells and the overexpression of the pair VEGF/VEGF-R2. Similarly CLP- induced ALI, as evidenced by parenchymal lung histopathologic alterations, was ameliorated through pulmonary EPO-R, VEGF and VEGF-R2 over expression suggesting and improvement in endothelial survival and functionality. This study demonstrates that EPO exerts protective effects in kidneys and lungs in mice with CLP-induced sepsis through the expression of EPO-R and the regulation of the VEGF/VEGF-R2 pair.

Angiopoietin-2 expression in patients with an acute exacerbation of idiopathic interstitial pneumonias

BACKGROUND AND OBJECTIVE

We hypothesized that increased pulmonary vascular permeability may play a role in the pathogenesis of an acute exacerbation of the idiopathic interstitial pneumonias (AE-IIPs). Angiopoietin-2 (Ang-2) promotes endothelial activation, destabilization, and inflammation. The purpose of this study was to examine whether Ang-2 expression was associated with the pathogenesis of AE-IIPs.

METHODS

Twenty-three patients with AE-IIP patients, 18 acute lung injury/acute respiratory distress syndrome (ALI/ARDS) patients, 37 idiopathic pulmonary fibrosis (IPF) patients, and 33 healthy volunteers (HVs) were enrolled. The serum level of Ang-2 was measured by an enzyme-linked immunosorbent assay.

RESULTS

The serum levels of Ang-2 were higher in AE-IIPs and ALI/ARDS patients than in IPF patients and HVs; the BALF levels of Ang-2 were also higher than in IPF patients. There was a positive correlation between the serum level of Ang-2 and the CRP in patients with AE-IIP patients, whereas a significant positive correlation was found between the serum Ang-2 level and the CRP or SOFA scores of the ALI/ARDS patients. Although the baseline Ang-2 level was not related to survival, the Ang-2 levels significantly declined in survivors during treatment, while they did not change in non-survivors.

CONCLUSIONS

Increased pulmonary vascular permeability and inflammation due to Ang-2 may play a role in the pathogenesis of AE-IIPs.

The Vascular Endothelial Growth Factors-Expressing Character of Mesenchymal Stem Cells Plays a Positive Role in Treatment of Acute Lung Injury In Vivo

Recently, mesenchymal stem cells (MSC) have been proved to be beneficial in acute respiratory distress syndrome (ARDS). Vascular endothelial growth factor (VEGF) is an important angiogenesis factor that MSC release. However, the precise role of VEGF-expressing character of MSC in the MSC treatment for ARDS remains obscure. Here, we firstly knocked down the gene VEGF in MSC (MSC-ShVEGF) with lentiviral transduction. Then we injected the MSC-ShVEGF to rats with lipopolysaccharide-induced acute lung injury (ALI) via the tail vein. Data showed that MSC transplantation significantly increased VEGF levels in the lung, reduced lung permeability, protected lung endothelium from apoptosis, facilitated VE-cadherin recovery, controlled inflammation, and attenuated lung injury. However, VEGF gene knockdown in MSC led to relatively insufficient VEGF expression in the injured lung and significantly diminished the therapeutic effects of MSC on ALI, suggesting an important role of VEGF-expressing behavior of MSC in the maintenance of VEGF in the lung and the MSC treatment for ALI. Hence, we conclude that MSC restores the lung permeability and attenuates lung injury in rats with ALI in part by maintaining a “sufficient” VEGF level in the lung and the VEGF-expressing character of MSC plays a positive role in the therapeutic effects of MSC on ARDS.

Lung Circulation

The circulation of the lung is unique both in volume and function. For example, it is the only organ with two circulations: the pulmonary circulation, the main function of which is gas exchange, and the bronchial circulation, a systemic vascular supply that provides oxygenated blood to the walls of the conducting airways, pulmonary arteries and veins. The pulmonary circulation accommodates the entire cardiac output, maintaining high blood flow at low intravascular arterial pressure. As compared with the systemic circulation, pulmonary arteries have thinner walls with much less vascular smooth muscle and a relative lack of basal tone. Factors controlling pulmonary blood flow include vascular structure, gravity, mechanical effects of breathing, and the influence of neural and humoral factors. Pulmonary vascular tone is also altered by hypoxia, which causes pulmonary vasoconstriction. If the hypoxic stimulus persists for a prolonged period, contraction is accompanied by remodeling of the vasculature, resulting in pulmonary hypertension. In addition, genetic and environmental factors can also confer susceptibility to development of pulmonary hypertension. Under normal conditions, the endothelium forms a tight barrier, actively regulating interstitial fluid homeostasis. Infection and inflammation compromise normal barrier homeostasis, resulting in increased permeability and edema formation. This article focuses on reviewing the basics of the lung circulation (pulmonary and bronchial), normal development and transition at birth and vasoregulation. Mechanisms contributing to pathological conditions in the pulmonary circulation, in particular when barrier function is disrupted and during development of pulmonary hypertension, will also be discussed.

A Pathophysiologic Approach to Biomarkers in Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) is an acute-onset hypoxic condition with radiographic bilateral lung infiltration. It is characterized by an acute exudative phase combining diffuse alveolar damage and lung edema followed by a later fibroproliferative phase. Despite an improved understanding of ARDS pathobiology, our ability to predict the development of ARDS and risk-stratify patients with the disease remains limited. Biomarkers may help to identify patients at the highest risk of developing ARDS, assess response to therapy, predict outcome, and optimize enrollment in clinical trials. After a short description of ARDS pathobiology, here, we review the scientific evidence that supports the value of various ARDS biomarkers with regard to their major biological roles in ARDS-associated lung injury and/or repair. Ongoing research aims at identifying and characterizing novel biomarkers, in order to highlight relevant mechanistic explorations of lung injury and repair, and to ultimately develop innovative therapeutic approaches for ARDS patients. This review will focus on the pathophysiologic, diagnostic, and therapeutic implications of biomarkers in ARDS and on their utility to ultimately improve patient care.

Revascularization of the graft in obliterative bronchiolitis after heterotopic tracheal transplantation

Obliterative bronchiolitis is the principal long-term problem for lung transplant patients. One of the simplest and most reproducible animal models of obliterative bronchiolitis is heterotopic tracheal transplantation in subcutaneous tissue, where the graft is not primarily vascularized. We demonstrate here the rapid graft revascularization and the kinetics of expression of its angiogenic and lymphatic factors. We performed iso- and allotracheal transplantations harvested on day 0-21. The number of functional blood vessels, quantified after intravenous biotinylated dextran administration, increased from D0 (0 for both iso- and allografts) to D21 (44 ± 8 vessels/mm(2) in isografts and 22 ± 3 in allografts, P < 0.001 for both vs. D0). VEGF mRNA expression assessed by qPCR peaked on D1 (4.3-fold increase in isografts and 4.0-fold in allografts, P < 0.0001 for both vs. D0), but receded thereafter. Angiopoietin-1, involved in the maturation of the neoformed vessels, increased later on, by 6.2-fold (P < 0.05) in isografts and 11.5-fold in allografts (P < 0.001) by D21, and angiopoietin-2 by 7.8-fold in isografts (P < 0.05) and 13.8-fold in allografts (P < 0.01). Although always present in the iso- and allografts, there were significantly more and larger LYVE1(+) lymphatic vessels at D21 in allografts than in isografts. Thus, we demonstrate that tracheal grafts are rapidly revascularized by functional blood and lymphatic vessels, due to early VEGF and subsequent angiopoietins expression, which is a new advantage of this model, in addition to its ease of use, reproducibility, and viability in the absence of immunosuppressive treatment.

The immunological balance between host and parasite in malaria

Coevolution of humans and malaria parasites has generated an intricate balance between the immune system of the host and virulence factors of the parasite, equilibrating maximal parasite transmission with limited host damage. Focusing on the blood stage of the disease, we discuss how the balance between anti-parasite immunity versus immunomodulatory and evasion mechanisms of the parasite may result in parasite clearance or chronic infection without major symptoms, whereas imbalances characterized by excessive parasite growth, exaggerated immune reactions or a combination of both cause severe pathology and death, which is detrimental for both parasite and host. A thorough understanding of the immunological balance of malaria and its relation to other physiological balances in the body is of crucial importance for developing effective interventions to reduce malaria-related morbidity and to diminish fatal outcomes due to severe complications. Therefore, we discuss in this review the detailed mechanisms of anti-malarial immunity, parasite virulence factors including immune evasion mechanisms and pathogenesis. Furthermore, we propose a comprehensive classification of malaria complications according to the different types of imbalances.

Decreased VEGF Level Is Associated with Elevated Ferritin Concentration in Bronchoalveolar Lavage Fluid of Children with Interstitial Lung Diseases

BACKGROUND

A decreased level of vascular endothelial growth factor (VEGF) was previously described in bronchoalveolar lavage fluid (BALF) of adults with interstitial lung diseases (ILD) due to bronchial epithelial cell apoptosis and its proteolytic degradation. Elevated intrapulmonary ferritin was produced by alveolar cells that promoted oxidative injury in such patients.

OBJECTIVES

In this study, we analyzed the concentrations of VEGF and ferritin in BALF samples of ILD children and studied the relationship between their levels and the degree of inflammation.

METHODS

BALF and serum concentration of VEGF as well as ferritin and albumin in BALF samples were measured using enzyme-linked immunosorbent assay in children with idiopathic interstitial pneumonia (n = 16), hypersensitivity pneumonitis (n = 11) and idiopathic pulmonary hemosiderosis (n = 3). Twenty-four age- and gender-matched subjects with suspicious foreign body aspiration served as a control group.

RESULTS

VEGF per albumin levels in BALF were significantly decreased in ILD children compared to controls (1,075 [784-1,415] pg/mg albumin vs. 2,741 [1,131-4,660] pg/mg albumin, p = 0.0008). These values showed a significant negative correlation with inflammatory markers of total immune cell count in BALF (r = -0.411, p = 0.002) and serum C-reactive protein (r = -0.367, p = 0.006). Although serum VEGF was augmented in ILD children versus controls, no difference was observed among the ILD groups. In addition, BALF ferritin/albumin level (688 [188-1,571] ng/mg albumin vs. 256 [178-350] ng/mg albumin, p = 0.022) was significantly higher than normal in ILD individuals, especially in idiopathic pulmonary hemosiderosis.

CONCLUSION

Depressed VEGF and increased ferritin in BALF may reflect the severity of chronic pulmonary inflammation in altered respiratory epithelium of childhood ILD.

Deleted in malignant brain tumors 1 (DMBT1) elicits increased VEGF and decreased IL-6 production in type II lung epithelial cells

BACKGROUND

Deleted in malignant brain tumors 1 (DMBT1) is an innate defence protein expressed in the lungs of preterm infants and adults. Recent studies showed that DMBT1 is important in angiogenesis and can bind to different growth factors including VEGF. We aimed at examining relationships between VEGF and IL-6 levels to DMBT1 expression in the lungs of preterm and term infants and in lung epithelial cells in vitro.

METHODS

We examined by ELISA VEGF levels in 120 tracheal aspirates of 57 preterm and term infants and tested for correlation with different perinatal factors as well as with DMBT1 levels. To examine the effect of DMBT1 on VEGF and IL-6 expression we compared type II lung epithelial A549 cells stably transfected with a DMBT1 expression plasmid (DMBT1+ cells) to A549 cells stably transfected with an empty expression plasmid (DMBT1- cells). The concentrations of VEGF and IL-6 were determined via ELISA in the supernatant of the unstimulated cells and after stimulation with LPS, TNFα and Phorbol-12-myristate-13-acetate (PMA).

RESULTS

The VEGF levels in the tracheal aspirates of preterm and term infants were significantly correlated with DMBT1 levels (p = 0.0032), the postnatal age (p = 0.0073) and the presence of neonatal infection/sepsis (p = 0.0002). Unstimulated DMBT1+ A549 cells showed significantly higher VEGF expression (p = 0.0017) than DMBT1- cells. Significantly elevated VEGF levels were also confirmed for DMBT1+ cells after stimulation with TNFα (p = 0.0008), LPS (p = 0.0232) and PMA (p = 0.0025). The IL-6 levels were comparable in DMBT1+ versus DMBT1- cells without stimulation (p = 0.6028), but they were significantly reduced in DMBT1+ cells after stimulation with TNFα (p = 0.0003), LPS (p = 0.0088) and PMA (p = 0.0039).

CONCLUSIONS

The data indicate that DMBT1 promotes VEGF and suppresses IL-6 production in alveolar tissues, which could point to DMBT1 having a possible role in the transition from inflammation to regeneration and being a potentially useful clinical marker.

Pancreatic ascites hemoglobin contributes to the systemic response in acute pancreatitis

Upon hemolysis extracellular hemoglobin causes oxidative stress and cytotoxicity due to its peroxidase activity. Extracellular hemoglobin may release free hemin, which increases vascular permeability, leukocyte recruitment, and adhesion molecule expression. Pancreatitis-associated ascitic fluid is reddish and may contain extracellular hemoglobin. Our aim has been to determine the role of extracellular hemoglobin in the local and systemic inflammatory response during severe acute pancreatitis in rats. To this end we studied taurocholate-induced necrotizing pancreatitis in rats. First, extracellular hemoglobin in ascites and plasma was quantified and the hemolytic action of ascitic fluid was tested. Second, we assessed whether peritoneal lavage prevented the increase in extracellular hemoglobin in plasma during pancreatitis. Third, hemoglobin was purified from rat erythrocytes and administered intraperitoneally to assess the local and systemic effects of ascitic-associated extracellular hemoglobin during acute pancreatitis. Extracellular hemoglobin and hemin levels markedly increased in ascitic fluid and plasma during necrotizing pancreatitis. Peroxidase activity was very high in ascites. The peritoneal lavage abrogated the increase in extracellular hemoglobin in plasma. The administration of extracellular hemoglobin enhanced ascites; dramatically increased abdominal fat necrosis; upregulated tumor necrosis factor-α, interleukin-1β, and interleukin-6 gene expression; and decreased expression of interleukin-10 in abdominal adipose tissue during pancreatitis. Extracellular hemoglobin enhanced the gene expression and protein levels of vascular endothelial growth factor (VEGF) and other hypoxia-inducible factor-related genes in the lung. Extracellular hemoglobin also increased myeloperoxidase activity in the lung. In conclusion, extracellular hemoglobin contributes to the inflammatory response in severe acute pancreatitis through abdominal fat necrosis and inflammation and by increasing VEGF and leukocyte infiltration into the lung.

IMD-4690, a novel specific inhibitor for plasminogen activator inhibitor-1, reduces allergic airway remodeling in a mouse model of chronic asthma via regulating angiogenesis and remodeling-related mediators

Plasminogen activator inhibitor (PAI)-1 is the principal inhibitor of plasminogen activators, and is responsible for the degradation of fibrin and extracellular matrix. IMD-4690 is a newly synthesized inhibitor for PAI-1, whereas the effect on allergic airway inflammation and remodeling is still unclear. We examined the in vivo effects by using a chronic allergen exposure model of bronchial asthma in mice. The model was generated by an immune challenge for 8 weeks with house dust mite antigen, Dermatophagoides pteronyssinus (Dp). IMD-4690 was intraperitoneally administered during the challenge. Lung histopathology, hyperresponsiveness and the concentrations of mediators in lung homogenates were analyzed. The amount of active PAI-1 in the lungs was increased in mice treated with Dp. Administration with IMD-4690 reduced an active/total PAI-1 ratio. IMD-4690 also reduced the number of bronchial eosinophils in accordance with the decreased expressions of Th2 cytokines in the lung homogenates. Airway remodeling was inhibited by reducing subepithelial collagen deposition, smooth muscle hypertrophy, and angiogenesis. The effects of IMD-4690 were partly mediated by the regulation of TGF-β, HGF and matrix metalloproteinase. These results suggest that PAI-1 plays crucial roles in airway inflammation and remodeling, and IMD-4690, a specific PAI-1 inhibitor, may have therapeutic potential for patients with refractory asthma due to airway remodeling.

The Effects of Portulaca oleracea on Hypoxia-Induced Pulmonary Edema in Mice

Portulaca oleracea L. (PO) is known as "a vegetable for long life" due to its antioxidant, anti-inflammatory, and other pharmacological activities. However, the protective activity of the ethanol extract of PO (EEPO) against hypoxia-induced pulmonary edema has not been fully investigated. In this study, we exposed mice to a simulated altitude of 7000 meters for 0, 3, 6, 9, and 12 h to observe changes in the water content and transvascular leakage of the mouse lung. It was found that transvascular leakage increased to the maximum in the mouse lung after 6 h exposure to hypobaric hypoxia. Prophylactic administration of EEPO before hypoxic exposure markedly reduced the transvascular leakage and oxidative stress, and inhibited the upregulation of NF-kB in the mouse lung, as compared with the control group. In addition, EEPO significantly reduced the levels of proinflammatory cytokines and cell adhesion molecules in the lungs of mice, as compared with the hypoxia group. Our results show that EEPO can reduce initial transvascular leakage and pulmonary edema under hypobaric hypoxia conditions.

Mode of action of nintedanib in the treatment of idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive and ultimately fatal disease characterised by fibrosis of the lung parenchyma and loss of lung function. Although the pathogenic pathways involved in IPF have not been fully elucidated, IPF is believed to be caused by repetitive alveolar epithelial cell injury and dysregulated repair, in which there is uncontrolled proliferation of lung fibroblasts and differentiation of fibroblasts into myofibroblasts, which excessively deposit extracellular matrix (ECM) proteins in the interstitial space. A number of profibrotic mediators including platelet-derived growth factor (PDGF), fibroblast growth factor (FGF) and transforming growth factor-β are believed to play important roles in the pathogenesis of IPF. Nintedanib is a potent small molecule inhibitor of the receptor tyrosine kinases PDGF receptor, FGF receptor and vascular endothelial growth factor receptor. Data from in vitro studies have shown that nintedanib interferes with processes active in fibrosis such as fibroblast proliferation, migration and differentiation, and the secretion of ECM. In addition, nintedanib has shown consistent anti-fibrotic and anti-inflammatory activity in animal models of lung fibrosis. These data provide a strong rationale for the clinical efficacy of nintedanib in patients with IPF, which has recently been demonstrated in phase III clinical trials.

Nintedanib interferes with processes active in fibrosis, e.g. fibroblast proliferation, migration anddifferentiationhttp://ow.ly/Iae9z

Redox signaling in acute pancreatitis

Acute pancreatitis is an inflammatory process of the pancreatic gland that eventually may lead to a severe systemic inflammatory response. A key event in pancreatic damage is the intracellular activation of NF-κB and zymogens, involving also calcium, cathepsins, pH disorders, autophagy, and cell death, particularly necrosis. This review focuses on the new role of redox signaling in acute pancreatitis. Oxidative stress and redox status are involved in the onset of acute pancreatitis and also in the development of the systemic inflammatory response, being glutathione depletion, xanthine oxidase activation, and thiol oxidation in proteins critical features of the disease in the pancreas. On the other hand, the release of extracellular hemoglobin into the circulation from the ascitic fluid in severe necrotizing pancreatitis enhances lipid peroxidation in plasma and the inflammatory infiltrate into the lung and up-regulates the HIF-VEGF pathway, contributing to the systemic inflammatory response. Therefore, redox signaling and oxidative stress contribute to the local and systemic inflammatory response during acute pancreatitis.

Azithromycin attenuates cigarette smoke extract-induced oxidative stress injury in human alveolar epithelial cells

Cigarette smoking has been verified to be one of the most important etiological factors causing the development of bronchogenic carcinoma and chronic obstructive pulmonary disease. Azithromycin (AZM) has been demonstrated to have antioxidant capacity. In the present study, whether AZM is able to attenuate cigarette smoke extract (CSE)-induced A549 cell oxidative stress injury was investigated. Cells were incubated with CSE in the presence or absence of AZM. Cell viability was measured using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The expression of vascular endothelial growth factor (VEGF) was analyzed using western blotting and ELISA. The expression of epithelial cell structural proteins, zona occludens (ZO)-1 and occludin was determined using western blotting and immunofluorescence staining. Reactive oxygen species (ROS) production was examined by flow cytometry and fluorescence staining. The results demonstrated that the exposure of A549 cells to CSE decreased cell viability in a dose- and time-dependent manner. AZM significantly attenuated the CSE-induced decreases in the expression of VEGF and epithelial cell structural proteins, including ZO-1 and occludin. CSE also stimulated ROS production in the A549 cell, while AZM significantly reversed the effects of CSE. In addition, the inhibition of ROS by N-acetyl-L-cysteine had similar effects as AZM on the expression of VEGF and epithelial cell structural proteins and also enhanced cell proliferation. In conclusion, AZM attenuated CSE-induced oxidative stress injury in A549 cells and may be a promising therapeutic agent for smoking-associated pulmonary diseases.

Effect of Melilotus suaveolens extract on pulmonary microvascular permeability by downregulating vascular endothelial growth factor expression in rats with sepsis

A typical indicator of sepsis is the development of progressive subcutaneous and body-cavity edema, which is caused by the breakdown of endothelial barrier function, leading to a marked increase in vascular permeability. Microvascular leakage predisposes to microvascular thrombosis, breakdown of microcirculatory flow and organ failure, which are common events preceding mortality in patients with severe sepsis. Melilotus suaveolens (M. suaveolens) is a Traditional Tibetan Medicine. Previous pharmacological studies have demonstrated that an ethanolic extract of M. suaveolens has powerful anti-inflammatory activity and leads to an improvement in capillary permeability. However, the mechanisms underlying its pharmacological activity remain elusive. The present study aimed to assess the impact of M. suaveolens extract tablets on pulmonary vascular permeability, and their effect on regulating lung inflammation and the expression of vascular endothelial growth factor (VEGF) in the lung tissue of rats with sepsis. A cecal ligation and puncture (CLP) sepsis model was established for both the control and treatment groups. ~2 h prior to surgery, 25 mg/kg of M. suaveolens extract tablet was administered to the treatment group. Polymerase chain reaction and western blot analyses were used to assess the expression of nuclear factor (NF)-κB and VEGF in the lung tissue, and ELISA was applied to detect changes in serum tumor necrosis factor-α as well as interleukins (IL) -1, -4, -6, and -10. The lung permeability, wet/dry weight ratio and lung pathology were determined. The results demonstrated that in the lung tissue of CLP-rats with sepsis, M. suaveolens extract inhibited the expression of NF-κB, reduced the inflammatory response and blocked the expression of VEGF, and thus significantly decreased lung microvascular permeability. The effects of M. Suaveolens extract may be of potential use in the treatment of CLP-mediated lung microvascular permeability.

Effect of Ca2EDTA on zinc mediated inflammation and neuronal apoptosis in hippocampus of an in vivo mouse model of hypobaric hypoxia

Background

Calcium overload has been implicated as a critical event in glutamate excitotoxicity associated neurodegeneration. Recently, zinc accumulation and its neurotoxic role similar to calcium has been proposed. Earlier, we reported that free chelatable zinc released during hypobaric hypoxia mediates neuronal damage and memory impairment. The molecular mechanism behind hypobaric hypoxia mediated neuronal damage is obscure. The role of free zinc in such neuropathological condition has not been elucidated. In the present study, we investigated the underlying role of free chelatable zinc in hypobaric hypoxia-induced neuronal inflammation and apoptosis resulting in hippocampal damage.

Methods

Adult male Balb/c mice were exposed to hypobaric hypoxia and treated with saline or Ca₂EDTA (1.25 mM/kg i.p) daily for four days. The effects of Ca₂EDTA on apoptosis (caspases activity and DNA fragmentation), pro-inflammatory markers (iNOS, TNF-α and COX-2), NADPH oxidase activity, poly(ADP ribose) polymerase (PARP) activity and expressions of Bax, Bcl-2, HIF-1α, metallothionein-3, ZnT-1 and ZIP-6 were examined in the hippocampal region of brain.

Results

Hypobaric hypoxia resulted in increased expression of metallothionein-3 and zinc transporters (ZnT-1 and ZIP-6). Hypobaric hypoxia elicited an oxidative stress and inflammatory response characterized by elevated NADPH oxidase activity and up-regulation of iNOS, COX-2 and TNF-α. Furthermore, hypobaric hypoxia induced HIF-1α protein expression, PARP activation and apoptosis in the hippocampus. Administration of Ca₂EDTA significantly attenuated the hypobaric hypoxia induced oxidative stress, inflammation and apoptosis in the hippocampus.

Conclusion

We propose that hypobaric hypoxia/reperfusion instigates free chelatable zinc imbalance in brain associated with neuroinflammation and neuronal apoptosis. Therefore, zinc chelating strategies which block zinc mediated neuronal damage linked with cerebral hypoxia and other neurodegenerative conditions can be designed in future.

α1-acid glycoprotein disrupts capillary-like tube formation of human lung microvascular endothelia

PURPOSE

The acute phase protein, α1-acid glycoprotein, is expressed in the lung, and influences endothelial cell function. We asked whether it might regulate angiogenesis in human lung microvascular endothelia.

MATERIALS AND METHODS

α1-acid glycoprotein was isolated from human serum by HPLC ion exchange chromatography. Its effects on endothelial cell functions including capillary-like tube formation on Matrigel, migration in a wounding assay, chemotaxis in a modified Boyden chamber, adhesion, and transendothelial flux of the permeability tracer, (14)C-albumin, were tested.

RESULTS

α1-acid glycoprotein dose-dependently inhibited capillary-like tube formation without loss of cell viability. At ≥0.50 mg/mL, it inhibited tube formation >70%, and at 0.75 mg/mL, >97%. α1-acid glycoprotein dose- and time-dependently restrained EC migration into a wound as early as 2 hours, and in washout studies, did so reversibly. It was inhibitory against vascular endothelial growth factor-A and fibroblast growth factor-2-driven migration but failed to inhibit chemotactic responsiveness. When α1-acid glycoprotein was added to preformed tubes, it provoked their almost immediate disassembly. As early as 15 minutes, it induced tube network collapse without endothelial cell-cell disruption. It exerted a biphasic effect on cell adhesion to the Matrigel substrate. At lower concentrations (0.05-0.25 mg/mL), it increased cell adhesion, whereas at higher concentrations (≥0.75 mg/mL) decreased adhesion. In contrast, it had no effect on transendothelial (14)C-albumin flux.

CONCLUSION

α1-acid glycoprotein, at concentrations found under physiological conditions, rapidly inhibits endothelial cell capillary-like tube formation that may be explained through diminished cell adhesion to the underlying matrix and/or reversibly decreased cell migration.

PlGF mediates neutrophil elastase-induced airway epithelial cell apoptosis and emphysema

Background

Chronic pulmonary obstructive disease (COPD) has become the fourth leading cause of death worldwide. Cigarette smoking induces neutrophil elastase (NE) and contributes to COPD, but the detailed mechanisms involved are not fully established. In an animal model of pulmonary emphysema, there are increased expressions of placenta growth factor (PlGF) and lung epithelial (LE) cell apoptosis. This study hypothesized that excessive NE may up-regulate PlGF and that PlGF-induced LE apoptosis mediates the pathogenesis of pulmonary emphysema.

Methods

Human bronchial epithelial cells, BEAS-2B, and primary mouse type II alveolar epithelial cells were treated with NE. The PlGF promoter activity was examined by luciferase activity assay, while PlGF expression and secretion were evaluated by RT-PCR, Western blotting, and ELISA. Both cell lines were treated with PlGF to evaluate its effects and the downstream signaling pathways leading to LE cell apoptosis. PlGF knockout and wild-type mice were instilled with NE to determine the roles of PlGF and its downstream molecules in NE-promoted mice pulmonary apoptosis and emphysema phenotype.

Results

The transcriptional factor, early growth response gene-1, was involved in the NE-promoted PlGF promoter activity, and the expression and secretion of PlGF mRNA and protein in LE cells. PlGF-induced LE cell apoptosis and NE-induced mice pulmonary apoptosis and emphysema were mediated by the downstream c-Jun N-terminal kinase (JNK) and protein kinase C (PKC)δ signaling pathways.

Conclusion

The NE-PlGF-JNK/PKCδ pathway contributes to the pathogenesis of LE cell apoptosis and emphysema. PlGF and its downstream signaling molecules may be potential therapeutic targets for COPD.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-014-0106-1) contains supplementary material, which is available to authorized users.

Elastase induces lung epithelial cell autophagy through placental growth factor: a new insight of emphysema pathogenesis

Chronic obstructive pulmonary disease (COPD) is a devastating disease, which is associated with increasing mortality and morbidity. Therefore, there is a need to clearly define the COPD pathogenic mechanism and to explore effective therapies. Previous studies indicated that cigarette smoke (CS) induces autophagy and apoptosis in lung epithelial (LE) cells. Excessive ELANE/HNE (elastase, neutrophil elastase), a factor involved in protease-antiprotease imbalance and the pathogenesis of COPD, causes LE cell apoptosis and upregulates the expression of several stimulus-responsive genes. However, whether or not elastase induces autophagy in LE cell remains unknown. The level of PGF (placental growth factor) is higher in COPD patients than non-COPD controls. We hypothesize that elastase induces PGF expression and causes autophagy in LE cells. In this study, we demonstrated that porcine pancreatic elastase (PPE) induced PGF expression and secretion in LE cells in vitro and in vivo. The activation of MAPK8/JNK1 (mitogen-activated protein kinase 8) and MAPK14/p38alpha MAPK signaling pathways was involved in the PGF mediated regulation of the TSC (tuberous sclerosis complex) pathway and autophagy in LE cells. Notably, PGF-induced MAPK8 and MAPK14 signaling pathways mediated the inactivation of MTOR (mechanistic target of rapamycin), the upregulation of MAP1LC3B/LC3B (microtubule-associated protein 1 light chain 3 β) and the increase of autophagosome formation in mice. Furthermore, the PPE-induced autophagy promotes further apoptosis in vitro and in vivo. In summary, elastase-induced autophagy promotes LE cell apoptosis and pulmonary emphysema through the upregulation of PGF. PGF and its downstream MAPK8 and MAPK14 signaling pathways are potential therapeutic targets for the treatment of emphysema and COPD.

Using a non-invasive assessment of lung injury in a murine model of acute lung injury

Arterial oxygen saturation has not been assessed sequentially in conscious mice as a direct consequence of an in vivo murine model of acute lung injury. Here, we report daily changes in arterial oxygen saturation and other cardiopulmonary parameters by using infrared pulse oximetry following intratracheal lipopolysaccharide (IT-LPS) for up to 9 days, and following IT-phosphate buffered saline up to 72 h as a control. We show that arterial oxygen saturation decreases, with maximal decline at 96 h post IT-LPS. Blood oxygen levels negatively correlate with 7 of 10 quantitative markers of murine lung injury, including neutrophilia and interleukin-6 expression. This identifies infrared pulse oximetry as a method to non-invasively monitor arterial oxygen saturation following direct LPS instillations.