Compartmentalization of Vascular Endothelial Growth Factor to the Epithelial Surface of the Human Lung

Pathogenesis and Physiologic Mechanisms of Neonatal Pulmonary Hypertension: Preclinical Studies

Neonatal pulmonary hypertension (PH) is a devastating disorder of the pulmonary vasculature characterized by elevated pulmonary vascular resistance and mean pulmonary arterial pressure. Occurring predominantly because of maldevelopment or maladaptation of the pulmonary vasculature, PH in neonates is associated with suboptimal short-term and long-term outcomes because its pathobiology is unclear in most circumstances, and it responds poorly to conventional pulmonary vasodilators. Understanding the pathogenesis and pathophysiology of neonatal PH can lead to novel strategies and precise therapies. The review is designed to achieve this goal by summarizing pulmonary vascular development and the pathogenesis and pathophysiology of PH associated with maladaptation, bronchopulmonary dysplasia, and congenital diaphragmatic hernia based on evidence predominantly from preclinical studies. We also discuss the pros and cons of and provide future directions for preclinical studies in neonatal PH.

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.

Inhibition of LPA-LPAR1 and VEGF-VEGFR2 Signaling in IPF Treatment

Due to the complex mechanism and limited treatments available for pulmonary fibrosis, the development of targeted drugs or inhibitors based on their molecular mechanisms remains an important strategy for prevention and treatment. In this paper, the downstream signaling pathways mediated by VEGFR and LPAR1 in pulmonary cells and the role of these pathways in pulmonary fibrosis, as well as the current status of drug research on the targets of LPAR1 and VEGFR2, are described. The mechanism by which these two pathways regulate vascular leakage and collagen deposition leading to the development of pulmonary fibrosis are analyzed, and the mutual promotion of the two pathways is discussed. Here we propose the development of drugs that simultaneously target LPAR1 and VEGFR2, and discuss the important considerations in targeting and safety.

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.

Pulmonary Fibrosis as a Result of Acute Lung Inflammation: Molecular Mechanisms, Relevant In Vivo Models, Prognostic and Therapeutic Approaches

Pulmonary fibrosis is a chronic progressive lung disease that steadily leads to lung architecture disruption and respiratory failure. The development of pulmonary fibrosis is mostly the result of previous acute lung inflammation, caused by a wide variety of etiological factors, not resolved over time and causing the deposition of fibrotic tissue in the lungs. Despite a long history of study and good coverage of the problem in the scientific literature, the effective therapeutic approaches for pulmonary fibrosis treatment are currently lacking. Thus, the study of the molecular mechanisms underlying the transition from acute lung inflammation to pulmonary fibrosis, and the search for new molecular markers and promising therapeutic targets to prevent pulmonary fibrosis development, remain highly relevant tasks. This review focuses on the etiology, pathogenesis, morphological characteristics and outcomes of acute lung inflammation as a precursor of pulmonary fibrosis; the pathomorphological changes in the lungs during fibrosis development; the known molecular mechanisms and key players of the signaling pathways mediating acute lung inflammation and pulmonary fibrosis, as well as the characteristics of the most common in vivo models of these processes. Moreover, the prognostic markers of acute lung injury severity and pulmonary fibrosis development as well as approved and potential therapeutic approaches suppressing the transition from acute lung inflammation to fibrosis are discussed.

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.

Regional and organ-level responses to local lung irradiation in sheep

Lung is a dose-limiting organ in radiotherapy. This may limit tumour control when effort is made in planning to limit the likelihood of radiation-induced lung injury (RILI). Understanding the factors that dictate susceptibility to radiation-induced pulmonary fibrosis will aid in the prevention and management of RILI, and may lead to more effective personalized radiotherapy treatment. As the interaction of regional and organ-level responses may shape the chronic consequences of RILI, we sought to characterise both aspects of the response in an ovine model. A defined volume of left pulmonary parenchyma was prescribed 5 fractions of 6 Gy within 14 days while the contralateral lung dose was constrained. Radiographic changes via computed tomography (CT) were documented to define differences in radio-exposed lung relative to non-exposed lung at d21, d63 and d171 (n = 2), and at d21, d147 and d227 (n = 2). Gross and histologic lung changes were evaluated in samples derived at necropsy examination to define the chronic pulmonary response to radiation. Irradiated lung demonstrated reduced radio-density and increased homogeneity as evidenced from texture based radiomic feature analysis, relative to the control lung. At necropsy, the radiation field was readily defined by pallor on the pleural surface, which was also evident on the cut surface of fixed lung specimens. The degree and homogeneity of pallor reflected the sparse presence of erythrocytes in alveolar septal capillaries of radiation-exposed lung. These changes contrasted with dilated and congested microvasculature in the contralateral control lung. Referencing data to measurements made in control lung volumes of sheep experiencing acute RILI indicated that interstitial collagen continues to deposit in the radio-exposed lung field. Overall lung vascularity increased during the chronic response, as evidenced by increased expression of endothelial cell marker (CD31); however, vascularity was consistently decreased in irradiated lung and was negatively correlated with lung collagen. Other organ-level responses included increased expression of alpha smooth muscle actin (ASMA), increased numbers of proliferating cells (Ki67 positive), and cells expressing the dendritic cell-lysosomal associated membrane protein (DC-LAMP) antigen. The chronic response to RILI in this model is effected at both the whole organ and local lung level. Whilst the long-term consequences of exposure to radiation involved the continued deposition of collagen in the radiation field, organ-level responses also included increased vascularization and increased expression of ASMA, Ki67 and DC-LAMP. Interrupting the interplay between these aspects may influence susceptibility to pulmonary fibrosis after radiotherapy. We advocate for the importance of large animal model systems in pursuing these opportunities to target local, organ-level and systemic mechanisms in parallel within the same subject over time.

Role of VEGF Polymorphisms in the Susceptibility and Severity of Interstitial Lung Disease

The search for biomarkers that can help to establish an early diagnosis and prognosis of interstitial lung disease (ILD) is of potential interest. VEGF polymorphisms have been implicated in the development of several lung disorders. Consequently, we assessed, for the first time, the role of VEGF polymorphisms in the susceptibility and severity of ILD. A total of 436 Caucasian ILD patients (244 with idiopathic interstitial pneumonias (IIPs) and 192 with non-IIP) and 536 ethnically-matched healthy controls were genotyped for VEGF rs833061, rs1570360, rs2010963, rs3025020, and rs3025039 polymorphisms by TaqMan assays. Pulmonary function tests were collected from all the patients. VEGF serum levels were determined by ELISA in a subgroup of patients. No VEGF genotype, allele, carrier, or haplotype differences were found between ILD patients and controls as well as between IIP and non-IIP patients. However, an association of rs1570360 with IIP in women and also with lung function in IIP patients was found. None of the VEGF polymorphisms were associated with VEGF levels. In conclusion, our results suggest that VEGF does not seem to play a relevant role in ILD, although rs1570360 may influence the severity of ILD in women and a worse outcome in IIP patients.

Roles of lung-recruited monocytes and pulmonary Vascular Endothelial Growth Factor (VEGF) in resolving Ventilator-Induced Lung Injury (VILI)

Monocytes and vascular endothelial growth factor (VEGF) have profound effects on tissue injury and repair. In ventilator-induced lung injury (VILI), monocytes, the majority of which are Ly6C+high, and VEGF are known to initiate lung injury. However, their roles in post-VILI lung repair remain unclear. In this study, we used a two-hit mouse model of VILI to identify the phenotypes of monocytes recruited to the lungs during the resolution of VILI and investigated the contributions of monocytes and VEGF to lung repair. We found that the lung-recruited monocytes were predominantly Ly6C+low from day 1 after the insult. Meanwhile, contrary to inflammatory cytokines, pulmonary VEGF decreased upon VILI but subsequently increased significantly on days 7 and 14 after the injury. There was a strong positive correlation between VEGF expression and proliferation of alveolar epithelial cells in lung sections. The expression pattern of VEGF mRNA in lung-recruited monocytes was similar to that of pulmonary VEGF proteins, and the depletion of monocytes significantly suppressed the increase of pulmonary VEGF proteins on days 7 and 14 after VILI. In conclusion, during recovery from VILI, the temporal expression patterns of pulmonary growth factors are different from those of inflammatory cytokines, and the restoration of pulmonary VEGF by monocytes, which are mostly Ly6C+low, is associated with pulmonary epithelial proliferation. Lung-recruited monocytes and pulmonary VEGF may play crucial roles in post-VILI lung repair.

Vascular endothelial growth factor contributes to lung vascular hyperpermeability in sepsis-associated acute lung injury

Vascular endothelial growth factor (VEGF) is a prime regulator of vascular permeability. Acute lung injury (ALI) is characterized by high-permeability pulmonary edema in addition to refractory hypoxemia and diffuse pulmonary infiltrates. In this study, we examined whether VEGF can be implicated as a pulmonary vascular permeability factor in sepsis-associated ALI. We found that a great increase in lung vascular leak occurred in mice instilled intranasally with lipopolysaccharide (LPS), as assessed by IgM levels in bronchoalveolar lavage fluid. Treatment with the VEGF-neutralizing monoclonal antibody bevacizumab significantly reduced this hyperpermeability response, suggesting active participation of VEGF in non-cardiogenic lung edema associated with LPS-induced ALI. However, this was not solely attributable to excessive levels of intrapulmonary VEGF. Expression levels of VEGF were significantly reduced in lung tissues from mice with both intranasal LPS administration and cecal ligation and puncture (CLP)-induced sepsis, which may stem from decreases in non-endothelial cells-dependent VEGF production in the lungs. In support of this assumption, stimulation with LPS and interferon-γ (IFN-γ) significantly increased VEGF in human pulmonary microvascular endothelial cells (HPMECs) at mRNA and protein levels. Furthermore, a significant rise in plasma VEGF levels was observed in CLP-induced septic mice. The increase in VEGF released from HPMECs after LPS/IFN-γ challenge was completely blocked by either specific inhibitor of mitogen-activated protein kinase (MAPK) subgroups. Taken together, our results indicate that VEGF can contribute to the development of non-cardiogenic lung edema in sepsis-associated ALI due to increased VEGF secretion from pulmonary vascular endothelial cells through multiple MAPK-dependent pathways.

Damage-Associated Molecular Patterns and Their Signaling Pathways in Primary Blast Lung Injury: New Research Progress and Future Directions

Primary blast lung injury (PBLI) is a common cause of casualties in wars, terrorist attacks, and explosions. It can exist in the absence of any other outward signs of trauma, and further develop into acute lung injury (ALI) or a more severe acute respiratory distress syndrome (ARDS). The pathogenesis of PBLI at the cellular and molecular level has not been clear. Damage-associated molecular pattern (DAMP) is a general term for endogenous danger signals released by the body after injury, including intracellular protein molecules (HMGB1, histones, s100s, heat shock proteins, eCIRP, etc.), secretory protein factors (IL-1β, IL-6, IL-10, TNF-α, VEGF, complements, etc.), purines and pyrimidines and their derived degradation products (nucleic acids, ATP, ADP, UDPG, uric acid, etc.), and extracellular matrix components (hyaluronic acid, fibronectin, heparin sulfate, biglycan, etc.). DAMPs can be detected by multiple receptors including pattern recognition receptors (PRRs). The study of DAMPs and their related signaling pathways, such as the mtDNA-triggered cGAS-YAP pathway, contributes to revealing the molecular mechanism of PBLI, and provides new therapeutic targets for controlling inflammatory diseases and alleviating their symptoms. In this review, we focus on the recent progress of research on DAMPs and their signaling pathways, as well as the potential therapeutic targets and future research directions in PBLI.

Vascular Endothelial Growth Factor-121 Administration Mitigates Halogen Inhalation-Induced Pulmonary Injury and Fetal Growth Restriction in Pregnant Mice

Background Circulating levels of sFLT-1 (soluble fms-like tyrosine kinase 1), the extracellular domain of vascular endothelial growth factor (VEGF) receptor 1, and its ratio to levels of placental growth factor are markers of the occurrence and severity of preeclampsia. Methods and Results C57BL/6 pregnant mice on embryonic day 14.5 (E14.5), male, and non-pregnant female mice were exposed to air or to Br2 at 600 ppm for 30 minutes and were treated with vehicle or with VEGF-121 (100 μg/kg, subcutaneously) daily, starting 48 hours post-exposure. Plasma, bronchoalveolar lavage fluid, lungs, fetuses, and placentas were collected 120 hours post-exposure. In Br2-exposed pregnant mice, there was a time-dependent and significant increase in plasma levels of sFLT-1 which correlated with increases in mouse lung wet/dry weights and bronchoalveolar lavage fluid protein content. Supplementation of exogenous VEGF-121 improved survival and weight gain, reduced lung wet/dry weights, decreased bronchoalveolar lavage fluid protein levels, enhanced placental development, and improved fetal growth in pregnant mice exposed to Br2. Exogenous VEGF-121 administration had no effect in non-pregnant mice. Conclusions These results implicate inhibition of VEGF signaling driven by sFLT-1 overexpression as a mechanism of pregnancy-specific injury leading to lung edema, maternal mortality, and fetal growth restriction after bromine gas exposure.

Vascular Niche in Lung Alveolar Development, Homeostasis, and Regeneration

Endothelial cells (ECs) constitute small capillary blood vessels and contribute to delivery of nutrients, oxygen and cellular components to the local tissues, as well as to removal of carbon dioxide and waste products from the tissues. Besides these fundamental functions, accumulating evidence indicates that capillary ECs form the vascular niche. In the vascular niche, ECs reciprocally crosstalk with resident cells such as epithelial cells, mesenchymal cells, and immune cells to regulate development, homeostasis, and regeneration in various organs. Capillary ECs supply paracrine factors, called angiocrine factors, to the adjacent cells in the niche and orchestrate these processes. Although the vascular niche is anatomically and functionally well-characterized in several organs such as bone marrow and neurons, the effects of endothelial signals on other resident cells and anatomy of the vascular niche in the lung have not been well-explored. This review discusses the role of alveolar capillary ECs in the vascular niche during development, homeostasis and regeneration.

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.

Protective effects of febuxostat against paraquat-induced lung toxicity in rats: Impact on RAGE/PI3K/Akt pathway and downstream inflammatory cascades

AIMS

The herbicide paraquat causes fatal lung toxicity by induction of xanthine oxidase, production of free radicals and inflammation. Febuxostat, a xanthine oxidase inhibitor and anti-gout has recently shown anti-inflammatory activity. Accordingly, this study was carried out to investigate whether febuxostat may attenuate paraquat-induced lung toxicity and to explore the possible underlying mechanisms.

MAIN METHODS

Rats were administered either vehicle, a single dose of paraquat (30 mg/kg, i.p.), febuxostat (15 mg/kg, oral), or both for 14 successive days. Serum LDH and sRAGE were estimated. Lung tissue xanthine oxidase activity, SOD, TAC, MDA, and RAGE, HMGB1 gene expression, PI3K/Akt and β-catenin protein expression, MMP-9, IL-8, VEGF and COX-2 gene expression were estimated.

KEY FINDINGS

Results showed that paraquat induced lung injury characterized by enhanced oxidative stress and inflammation, upregulated RAGE, HMGB1 gene expression, PI3K/Akt and β-catenin protein expression. Administration of febuxostat inhibited the deleterious effects of paraquat on lung through inhibition of xanthine oxidase activity and related oxidative stress, downregulation of RAGE/PI3K/Akt pathway, and suppression of β-catenin protein expression and its downstream inflammatory mediators.

SIGNIFICANCE

The present study showed that febuxostat may abrogate paraquat-induced lung toxicity and demonstrated a novel mechanism for its ameliorative effects.

Physiological Role of Vascular Endothelial Growth Factors as Homeostatic Regulators

The vascular endothelial growth factor (VEGF) family of proteins are key regulators of physiological systems. Originally linked with endothelial function, they have since become understood to be principal regulators of multiple tissues, both through their actions on vascular cells, but also through direct actions on other tissue types, including epithelial cells, neurons, and the immune system. The complexity of the five members of the gene family in terms of their different splice isoforms, differential translation, and specific localizations have enabled tissues to use these potent signaling molecules to control how they function to maintain their environment. This homeostatic function of VEGFs has been less intensely studied than their involvement in disease processes, development, and reproduction, but they still play a substantial and significant role in healthy control of blood volume and pressure, interstitial volume and drainage, renal and lung function, immunity, and signal processing in the peripheral and central nervous system. The widespread expression of VEGFs in healthy adult tissues, and the disturbances seen when VEGF signaling is inhibited support this view of the proteins as endogenous regulators of normal physiological function. This review summarizes the evidence and recent breakthroughs in understanding of the physiology that is regulated by VEGF, with emphasis on the role they play in maintaining homeostasis. © 2017 American Physiological Society. Compr Physiol 8:955-979, 2018.

VEGF (Vascular Endothelial Growth Factor) and Fibrotic Lung Disease

Interstitial lung disease (ILD) encompasses a group of heterogeneous diseases characterised by varying degrees of aberrant inflammation and fibrosis of the lung parenchyma. This may occur in isolation, such as in idiopathic pulmonary fibrosis (IPF) or as part of a wider disease process affecting multiple organs, such as in systemic sclerosis. Anti-Vascular Endothelial Growth Factor (anti-VEGF) therapy is one component of an existing broad-spectrum therapeutic option in IPF (nintedanib) and may become part of the emerging therapeutic strategy for other ILDs in the future. This article describes our current understanding of VEGF biology in normal lung homeostasis and how changes in its bioavailability may contribute the pathogenesis of ILD. The complexity of VEGF biology is particularly highlighted with an emphasis on the potential non-vascular, non-angiogenic roles for VEGF in the lung, in both health and disease.

Differential Expression of VEGF-Axxx Isoforms Is Critical for Development of Pulmonary Fibrosis

RATIONALE

Fibrosis after lung injury is related to poor outcome, and idiopathic pulmonary fibrosis (IPF) can be regarded as an exemplar. Vascular endothelial growth factor (VEGF)-A has been implicated in this context, but there are conflicting reports as to whether it is a contributory or protective factor. Differential splicing of the VEGF-A gene produces multiple functional isoforms including VEGF-A₁₆₅a and VEGF-A₁₆₅b, a member of the inhibitory family. To date there is no clear information on the role of VEGF-A in IPF.

OBJECTIVES

To establish VEGF-A isoform expression and functional effects in IPF.

METHODS

We used tissue sections, plasma, and lung fibroblasts from patients with IPF and control subjects. In a bleomycin-induced lung fibrosis model we used wild-type MMTV mice and a triple transgenic mouse SPC-rtTA^+/-TetoCre^+/-LoxP-VEGF-A^+/+ to conditionally induce VEGF-A isoform deletion specifically in the alveolar type II (ATII) cells of adult mice.

MEASUREMENTS AND MAIN RESULTS

IPF and normal lung fibroblasts differentially expressed and responded to VEGF-A₁₆₅a and VEGF-A₁₆₅b in terms of proliferation and matrix expression. Increased VEGF-A₁₆₅b was detected in plasma of progressing patients with IPF. In a mouse model of pulmonary fibrosis, ATII-specific deficiency of VEGF-A or constitutive overexpression of VEGF-A₁₆₅b inhibited the development of pulmonary fibrosis, as did treatment with intraperitoneal delivery of VEGF-A₁₆₅b to wild-type mice.

CONCLUSIONS

These results indicate that changes in the bioavailability of VEGF-A sourced from ATII cells, namely the ratio of VEGF-A_xxxa to VEGF-A_xxxb, are critical in development of pulmonary fibrosis and may be a paradigm for the regulation of tissue repair.

Effects of trauma, hemorrhagic shock, and chronic stress on lung vascular endothelial growth factor

BACKGROUND

Vascular endothelial growth factor (VEGF) and its receptors (VEGFR-1 and VEGFR-2) regulate vascular permeability and endothelial cell survival. We hypothesized that hemorrhagic shock (HS) and chronic stress (CS) would increase expression of lung VEGF and its receptors, potentiating pulmonary edema in lung tissue.

MATERIALS AND METHODS

Male Sprague-Dawley rats aged 8-9 wk were randomized: naïve control, lung contusion (LC), LC followed by HS (LCHS), and LCHS with CS in a restraint cylinder for 2 h/d (LCHS/CS). Animals were sacrificed on days 1 and 7. Expressions of lung VEGF, VEGFR-1, and VEGFR-2 were determined by polymerase chain reaction. Lung Injury Score (LIS) was graded on light microscopy by inflammatory cell counts, interstitial edema, pulmonary edema, and alveolar integrity (range: 0 = normal; 8 = severe injury).

RESULTS

Seven days after LC, lung VEGF and VEGFR-1 were increased, and lung tissue healed (LIS: 0.8 ± 0.8). However, 7 d after LCHS and LCHS/CS, lung VEGF and VEGFR-1 expressions were decreased. VEGFR-2 was also decreased after LCHS/CS. LIS was elevated 7 d after LCHS and LCHS/CS (6.5 ± 1.0 and 8.2 ± 0.8). Increased LIS after LCHS and LCHS/CS was because of higher inflammatory cell counts, increased interstitial edema, and loss of alveolar integrity, whereas pulmonary edema was unchanged.

CONCLUSIONS

Elevation of lung VEGF and VEGFR-1 expressions after LC alone was associated with healing of injured lung tissue. Expressions of VEGF, VEGFR-1, and VEGFR-2 were reduced after LCHS and LCHS/CS, and injured lung tissue did not heal. Persistent lung injury after severe trauma was because of inflammation rather than pulmonary edema.

Thyroid Transcription Factor 1 Reprograms Angiogenic Activities of Secretome

Through both gain- and loss-of-TTF-1 expression strategies, we show that TTF-1 positively regulates vascular endothelial growth factor (VEGF) and that the VEGF promoter element contains multiple TTF-1-responsive sequences. The major signaling receptor for VEGF, i.e VEGFR2, also appears to be under a direct and positive regulation of TTF-1. The TTF-1-dependent upregulation of VEGF was moderately sensitive to rapamycin, implicating a partial involvement of mammalian target of rapamycin (mTOR). However, hypoxia did not further increase the secreted VEGF level of the TTF-1⁺ lung cancer cells. The TTF-1-induced VEGF upregulation occurs in both compartments (exosomes and exosome-depleted media (EDM)) of the conditioned media. Surprisingly, the EDM of TTF-1⁺ lung cancer cells (designated EDM-TTF-1⁺) displayed an anti-angiogenic activity in the endothelial cell tube formation assay. Mechanistic studies suggest that the increased granulocyte-macrophage colony-stimulating factor (GM-CSF) level in the EDM-TTF-1⁺ conferred the antiangiogenic activities. In human lung cancer, the expression of TTF-1 and GM-CSF exhibits a statistically significant and positive correlation. In summary, this study provides evidence that TTF-1 may reprogram lung cancer secreted proteome into an antiangiogenic state, offering a novel basis to account for the long-standing observation of favorable prognosis associated with TTF-1⁺ lung adenocarcinomas.

Nailfold videocapillaroscopy and serum VEGF levels in scleroderma are associated with internal organ involvement

Purpose

Nailfold videocapillaroscopy (NVC) identifies the microvascular hallmarks of systemic sclerosis (SSc) and vascular endothelial growth factor (VEGF) and may play a pivotal role in the associated vasculopathy. The aim of the present study was to compare NVC alterations with clinical subsets, internal organ involvement, and serum VEGF levels in a cohort of selected SSc cases.

Methods

We studied 44 patients with SSc who were evaluated within 3 months from enrollment by NVC, skin score, severity index, pulmonary function tests, carbon monoxide diffusing capacity (DLCO), echocardiography, pulmonary high-resolution computed tomography (HRCT), gastroesophageal (GE) endoscopy or manometry or X-ray, and serum autoantibodies. Serum VEGF-A levels were determined by ELISA in 72 SSc patients and 31 healthy controls.

Results

Giant capillaries were inversely correlated with age (p = 0.034, r = −0.34) and to the extent of reticular pattern at HRCT (p = 0.04, r = −0.5). Avascular areas were directly correlated with capillaroscopy skin ulcer risk index (CSURI) (p = 0.006, r = +0.4) and severity index (p = 0.004, r = +0.5). The mean capillary density was directly correlated to the ulcer number (p = 0.02, r = +0.4) and to DLCO/alveolar volume (p = 0.02, r = +0.4) and inversely correlated with severity index (p = 0.01, r = −0.4) and skin score (p = 0.02, r = −0.4). Serum VEGF levels were higher in the SSc population vs controls (p = 0.03) and inversely correlated with DLCO (p = 0.01, r =−0.4) and directly with ground-glass and reticular pattern at HRCT (p = 0.04, r = +0.4 for both).

Conclusions

Our data suggest the importance of NVC not only for the diagnosis, but also for the global evaluation of SSc patients. Of note, serum VEGF levels may act as a biomarker of interstitial lung involvement.

Structural and molecular regulation of lung maturation by intratracheal vascular endothelial growth factor administration in the normally grown and placentally restricted fetus

Inhibition of hypoxia signalling leads to respiratory distress syndrome (RDS), whereas administration of vascular endothelial growth factor (VEGF), the most widely characterized hypoxia responsive factor, protects from RDS. In the lung of the chronically hypoxaemic placentally restricted (PR) fetus, there is altered regulation of hypoxia signalling. This leads to reduced surfactant maturation in late gestation and provides evidence for the increased risk of RDS in growth restricted neonates at birth. We evaluated the effect of recombinant human VEGF administration with respect to bypassing the endogenous regulation of hypoxia signalling in the lung of the normally grown and PR sheep fetus. There was no effect of VEGF administration on fetal blood pressure or fetal breathing movements. We examined the effect on the expression of genes regulating VEGF signalling (FLT1 and KDR), angiogenesis (ANGPT1, AQP1, ADM), alveolarization (MMP2, MMP9, TIMP1, COL1A1, ELN), proliferation (IGF1, IGF2, IGF1R, MKI67, PCNA), inflammation (CCL2, CCL4, IL1B, TNFA, TGFB1, IL10) and surfactant maturation (SFTP-A, SFTP-B, SFTP-C, SFTP-D, PCYT1A, LPCAT, LAMP3, ABCA3). Despite the effects of PR on the expression of genes regulating airway remodelling, inflammatory signalling and surfactant maturation, there were very few effects of VEGF administration on gene expression in the lung of both the normally grown and PR fetus. There were, however, positive effects of VEGF administration on percentage tissue, air space and numerical density of SFTP-B positive alveolar epithelial cells in fetal lung tissue. These results provide evidence for the stimulatory effects of VEGF administration on structural maturation in the lung of both the normally grown and PR fetus.

The role of tyrosine kinases in the pathogenesis of idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive lung disease with a median survival time from diagnosis of 2-3 years. Although the pathogenic pathways have not been fully elucidated, IPF is believed to be caused by persistent epithelial injury in genetically susceptible individuals. Tyrosine kinases are involved in a range of signalling pathways that are essential for cellular homeostasis. However, there is substantial evidence from in vitro studies and animal models that receptor tyrosine kinases, such as the platelet-derived growth factor receptor, vascular endothelial growth factor receptor and fibroblast growth factor receptor, and non-receptor tyrosine kinases, such as the Src family, play critical roles in the pathogenesis of pulmonary fibrosis. For example, the expression and release of tyrosine kinases are altered in patients with IPF, while specific tyrosine kinases stimulate the proliferation of lung fibroblasts in vitro. Agents that inhibit tyrosine kinases have shown anti-fibrotic and anti-inflammatory effects in animal models of pulmonary fibrosis. Recently, the tyrosine kinase inhibitor nintedanib has shown positive results in two phase III trials in patients with IPF. Here, we summarise the evidence for involvement of specific tyrosine kinases in the pathogenesis of IPF and the development of tyrosine kinase inhibitors as treatments for IPF.

Thioredoxin-1 redox signaling regulates cell survival in response to hyperoxia

The most common form of newborn chronic lung disease, bronchopulmonary dysplasia (BPD), is thought to be caused by oxidative disruption of lung morphogenesis, which results in decreased pulmonary vasculature and alveolar simplification. Although cellular redox status is known to regulate cellular proliferation and differentiation, redox-sensitive pathways associated with these processes in developing pulmonary epithelium are unknown. Redox-sensitive pathways are commonly regulated by cysteine thiol modifications. Therefore two thiol oxidoreductase systems, thioredoxin and glutathione, were chosen to elucidate the roles of these pathways on cell death. Studies herein indicate that thiol oxidation contributes to cell death through impaired activity of glutathione-dependent and thioredoxin (Trx) systems and altered signaling through redox-sensitive pathways. Free thiol content decreased by 71% with hyperoxic (95% oxygen) exposure. Increased cell death was observed during oxygen exposure when either the Trx or the glutathione-dependent system was pharmacologically inhibited with aurothioglucose (ATG) or buthionine sulfoximine, respectively. However, inhibition of the Trx system yielded the smallest decrease in free thiol content (1.44% with ATG treatment vs 21.33% with BSO treatment). Although Trx1 protein levels were unchanged, Trx1 function was impaired during hyperoxic treatment as indicated by progressive cysteine oxidation. Overexpression of Trx1 in H1299 cells utilizing an inducible construct increased cell survival during hyperoxia, whereas siRNA knockdown of Trx1 during oxygen treatment reduced cell viability. Overall, this indicated that a comparatively small pool of proteins relies on Trx redox functions to mediate cell survival in hyperoxia, and the protective functions of Trx1 are progressively lost by its oxidative inhibition. To further elucidate the role of Trx1, potential Trx1 redox protein-protein interactions mediating cytoprotection and cell survival pathways were determined by utilizing a substrate trap (mass action trapping) proteomics approach. With this method, known Trx1 targets were detected, including peroxiredoxin-1as well as novel targets, including two HSP90 isoforms (HSP90AA1 and HSP90AB1). Reactive cysteines within the structure of HSP90 are known to modulate its ATPase-dependent chaperone activity through disulfide formation and S-nitrosylation. Whereas HSP90 expression is unchanged at the protein level during hyperoxic exposure, siRNA knockdown significantly increased hyperoxic cell death by 2.5-fold, indicating cellular dependence on HSP90 chaperone functions in response to hyperoxic exposure. These data support the hypothesis that hyperoxic impairment of Trx1 has a negative impact on HSP90-oxidative responses critical to cell survival, with potential implications for pathways implicated in lung development and the pathogenesis of BPD.

Cytoskeletal dynamics and lung fluid balance

This article examines the role of the endothelial cytoskeleton in the lung's ability to restrict fluid and protein to vascular space at normal vascular pressures and thereby to protect lung alveoli from lethal flooding. The barrier properties of microvascular endothelium are dependent on endothelial cell contact with other vessel-wall lining cells and with the underlying extracellular matrix (ECM). Focal adhesion complexes are essential for attachment of endothelium to ECM. In quiescent endothelial cells, the thick cortical actin rim helps determine cell shape and stabilize endothelial adherens junctions and focal adhesions through protein bridges to actin cytoskeleton. Permeability-increasing agonists signal activation of "small GTPases" of the Rho family to reorganize the actin cytoskeleton, leading to endothelial cell shape change, disassembly of cortical actin rim, and redistribution of actin into cytoplasmic stress fibers. In association with calcium- and Src-regulated myosin light chain kinase (MLCK), stress fibers become actinomyosin-mediated contractile units. Permeability-increasing agonists stimulate calcium entry and induce tyrosine phosphorylation of VE-cadherin (vascular endothelial cadherin) and β-catenins to weaken or pull apart endothelial adherens junctions. Some permeability agonists cause latent activation of the small GTPases, Cdc42 and Rac1, which facilitate endothelial barrier recovery and eliminate interendothelial gaps. Under the influence of Cdc42 and Rac1, filopodia and lamellipodia are generated by rearrangements of actin cytoskeleton. These motile evaginations extend endothelial cell borders across interendothelial gaps, and may initiate reannealing of endothelial junctions. Endogenous barrier protective substances, such as sphingosine-1-phosphate, play an important role in maintaining a restrictive endothelial barrier and counteracting the effects of permeability-increasing agonists.

The ultra-early protective effect of ulinastatin on rabbit acute lung injury induced by paraquat

Objective

To study ultra-early pathophysiological changes of rabbit acute lung injury (ALI) caused by paraquat (PQ) and discuss the ultra-early protective effect of ulinastatin on rabbit ALI due to PQ.

Methods

30 New Zealand white rabbits were randomly divided into a control group, a paraquat group and an ulinastatin intervention group with 10 rabbits in each group. For paraquat group and intervention group a single dose of paraquat (35mg/kg) was injected intraperitoneally to establish rabbit models of ALI. The control group was injected an equal volume of saline. The intervention group was treated with 100Ku/kg ulinastatin immediately after the establishment of the ALI model. The respective experimental groups underwent 320-slice CT perfusion scan of pleural at 2h, 4h and 6h time point after modeling to get CTP (CT Perfusion) images and related parameters. 2mL blood was collected in the marginal ear vein to determine the mass concentration of the vascular endothelial growth factor (VEGF). The animals were killed by air embolism after 6h and lung tissue was taken for pathology observation.

Results

The reginal blood flow (rBF) and reginal blood volume (rBV) of paraquat group at 2,4,6 h time point were significantly (P <0.05) lower than those of control group. The intervention group rBF and rBV at 2, 4 and 6 h time points were significantly higher (P <0.05) compared to paraquat group. The permeability surface (rPS) and VEGF mass concentration of paraquat group at 2,4,6 h time point were significantly higher than the control group (P <0.05), and the intervention group rPS and VEGF mass concentrations at 2,4,6h time point were significantly lower (P <0.05) than those of paraquat group. Pathological detection indicators of paraquat group (congestive capillary percentage, the number of red blood cells outside of capillaries, percentage of capillaries with basement membrane damage) were significantly higher (P <0.05) at 6h time point compared with the control group, while significantly lower (P <0.05) in intervention group than in paraquat groups. Pathological observation under light microscope showed in paraquat group obvious inflammatory cell infiltration, alveolar epithelial cell hyperplasia, widened alveolar septum, visible focal hemorrhage, visible acute and chronic inflammatory cell infiltration in bronchioles cavity; under electron microscopy alveolar epithelial cell degeneration and necrosis, vascular welling of the endothelial cells, basement membrane rupture, a lot of exudates in alveolar space. In the intervention group, the above the symptoms were mitigated.

Conclusion

In the ultra-early stage of rabbit ALI induced by PQ, pulmonary vascular endothelial cell is damaged and serum VEGF mass concentration and pulmonary vascular permeability increase. Early ulinastatin intervention can reduce serum VEGF level and PQ-induced vascular permeability amplitude, indicating that ulinastatin has a protective effect on pulmonary vascular endothelial cells.

miRNA regulated pathways in late stage murine lung development

Background

MicroRNAs play important roles in regulating biological processes, including organ morphogenesis and maturation. However, little is known about specific pathways regulated by miRNA during lung development. Between the canalicular and saccular stages of the developing lung several important cellular events occur, including the onset of surfactant synthesis, microvascular remodeling and structural preparation for subsequent alveolarization. The miRNAs that are actively regulated, and the identity of their targets during this important developmental interval in the lung remain elusive.

Results

Using TLDA low density real-time PCR arrays, the expression of 376 miRNAs in male and female fetal mouse lungs of gestational days E15 – E18 were profiled. Statistical analyses identified 25 and 37 miRNAs that changed significantly between sexes and with gestation, respectively. In silico analysis using Ingenuity Pathway Analysis (IPA) identified specific pathways and networks known to be targets of these miRNAs which are important to lung development. Pathways that are targeted by sex regulated miRNAs include retinoin, IGFR1, Tp53 and Akt. Pathways targeted by gestation-regulated miRNAs include VEGFA and mediators of glucose metabolism.

Conclusion

MiRNAs are differentially regulated across time and between sexes during the canalicular and saccular stages of lung development. Sex-associated differential miRNA expression may regulate the differences in structural and functional male and female lung development, as shown by networks generated using in silico analysis. These data provide a valuable resource to further enhance the understanding of miRNA control of lung development and maturation.

Elevated VEGF Levels in Pulmonary Edema Fluid and PBMCs from Patients with Acute Hantavirus Pulmonary Syndrome

Hantavirus pulmonary syndrome is characterized by vascular permeability, hypoxia, and acute pulmonary edema. Vascular endothelial growth factor (VEGF) is induced by hypoxia, potently induces vascular permeability, and is associated with high-altitude-induced pulmonary edema. Hantaviruses alter the normal regulation of β3 integrins that restrict VEGF-directed permeability and hantavirus infected endothelial cells are hyperresponsive to the permeabilizing effects of VEGF. However, the role of VEGF in acute pulmonary edema observed in HPS patients remains unclear. Here we retrospectively evaluate VEGF levels in pulmonary edema fluid (PEF), plasma, sera, and PBMCs from 31 HPS patients. VEGF was elevated in HPS patients PEF compared to controls with the highest levels observed in PEF samples from a fatal HPS case. VEGF levels were highest in PBMC samples during the first five days of hospitalization and diminished during recovery. Significantly increased PEF and PBMC VEGF levels are consistent with acute pulmonary edema observed in HPS patients and HPS disease severity. We observed substantially lower VEGF levels in a severe HPS disease survivor after extracorporeal membrane oxygenation. These findings suggest the importance of patients' VEGF levels during HPS, support the involvement of VEGF responses in HPS pathogenesis, and suggest targeting VEGF responses as a potential therapeutic approach.

The Role of the Endothelium in HPS Pathogenesis and Potential Therapeutic Approaches

American hantaviruses cause a highly lethal acute pulmonary edema termed hantavirus pulmonary syndrome (HPS). Hantaviruses nonlytically infect endothelial cells and cause dramatic changes in barrier functions of the endothelium without disrupting the endothelium. Instead hantaviruses cause changes in the function of infected endothelial cells that normally regulate fluid barrier functions of capillaries. The endothelium of arteries, veins, and lymphatic vessels is unique and central to the function of vast pulmonary capillary beds, which regulate pulmonary fluid accumulation. The endothelium maintains vascular barrier functions through a complex series of redundant receptors and signaling pathways that serve to both permit fluid and immune cell efflux into tissues and restrict tissue edema. Infection of the endothelium provides several mechanisms for hantaviruses to alter capillary permeability but also defines potential therapeutic targets for regulating acute pulmonary edema and HPS disease. Here we discuss interactions of HPS causing hantaviruses with the endothelium, potential endothelial cell-directed permeability mechanisms, and therapeutic targeting of the endothelium as a means of reducing the severity of HPS disease.

Vascular endothelial growth factor enhances macrophage clearance of apoptotic cells

Efficient clearance of apoptotic cells from the lung by alveolar macrophages is important for the maintenance of tissue structure and function. Lung tissue from humans with emphysema contains increased numbers of apoptotic cells and decreased levels of vascular endothelial growth factor (VEGF). Mice treated with VEGF receptor inhibitors have increased numbers of apoptotic cells and develop emphysema. We hypothesized that VEGF regulates apoptotic cell clearance by alveolar macrophages (AM) via its interaction with VEGF receptor 1 (VEGF R1). Our data show that the uptake of apoptotic cells by murine AMs and human monocyte-derived macrophages is inhibited by depletion of VEGF and that VEGF activates Rac1. Antibody blockade or pharmacological inhibition of VEGF R1 activity also decreased apoptotic cell uptake ex vivo. Conversely, overexpression of VEGF significantly enhanced apoptotic cell uptake by AMs in vivo. These results indicate that VEGF serves a positive regulatory role via its interaction with VEGF R1 to activate Rac1 and enhance AM apoptotic cell clearance.

Exogenous surfactant protects against endotoxin induced acute respiratory distress syndrome in rodents via vascular endothelial growth factor

Vascular endothelial growth factor (VEGF) is a potent angiogenic factor which is abundantly expressed in the normal lung and is released by numerous cell types. Using a bacteria-induced lung injury model and surfactant therapy in rats, VEGF expression in lung was investigated. Sprague Dawley male rats were divided into four groups: buffer controls; rats challenged with LPS (055:B5 E. coli); challenged with LPS and treated with porcine surfactant (P-SF); and challenged with LPS and treated with synthetic surfactant (S-SF). The expressions of VEGF, PCNA, and BrdU were studied. VEGF protein expression was decreased in comparison to the control rats, as seen by both Western immunoblot and immunohistochemistry. Protein expression of PCNA and proliferation index as determined by both PCNA and BrdU immunostaining were also seen to be decreased in the LPS-treated animals, and with the surfactant treatment the expression was increased. The downregulation of VEGF in the alveolar space may reflect the recovery from acute lung injury, which leads to the limited endothelial permeability, and may participate in the decrease in capillary number, as observed during acute respiratory distress syndrome with potentially significant clinical consequences.

AAVrh.10-mediated genetic delivery of bevacizumab to the pleura to provide local anti-VEGF to suppress growth of metastatic lung tumors

Vascular endothelial growth factor (VEGF) produced by tumor cells has a central role in stimulating angiogenesis required for tumor growth. Humanized monoclonal anti-VEGF antibody (bevacizumab, Avastin), approved as a treatment for non-squamous, non-small cell lung cancer, requires administration every 3 weeks. We hypothesized that an intrapleural administration of an adeno-associated virus (AAV) vector expressing an anti-VEGF-A antibody equivalent of bevacizumab would result in sustained anti-VEGF-A localized expression within the lung and suppress metastatic tumor growth. The AAV vector AAVrh.10alphaVEGF encodes the light chain and heavy chain complementary DNAs of monoclonal antibody A.4.6.1, a murine antibody that specifically recognizes human VEGF-A with the same antigen-binding site as bevacizumab. A metastatic lung tumor model was established in severe combined immunodeficient mice by intravenous administration of human DU145 prostate carcinoma cells. Intrapleural administration of AAVrh.10alphaVEGF directed long-term expression of the anti-human VEGF-A antibody in lung, as shown by sustained, high-level anti-human VEGF titers in lung epithelial lining fluid for 40 weeks, which was the duration of the study. In the AAVrh.10alphaVEGF-treated animals, tumor growth was significantly suppressed (P<0.05), the numbers of blood vessels and mitotic nuclei in the tumor was decreased (P<0.05) and there was increased survival (P<0.05). Thus, intrapleural administration of an AAVrh.10 vector, encoding the murine monoclonal antibody equivalent of bevacizumab, effectively suppresses the growth of metastatic lung tumors, suggesting AAV-mediated gene transfer to the pleura to deliver bevacizumab locally to the lung as a novel alternative platform to conventional monoclonal antibody therapy.

High concentrations of vascular endothelial growth factor reduce stretch-induced apoptosis of alveolar type II cells

Vascular endothelial growth factor (VEGF) has protective as well as injurious effects in ARDS/acute lung injury. The influence of VEGF was investigated in a model of stretch-induced apoptosis. High-amplitude mechanical stretch induced the secretion of VEGF. High VEGF concentrations may prevent stretch-induced apoptosis by restoring stretch-impaired phospatidylinositol-3 kinase signalling.

BACKGROUND AND OBJECTIVE

Vascular endothelial growth factor (VEGF) is strongly expressed in the alveolar epithelium. VEGF has been shown to exhibit protective as well as injurious effects in ARDS/acute lung injury. We therefore investigated the influence of VEGF in a model of stretch-induced apoptosis.

METHODS

Isolated rat alveolar type II (ATII) cells were subjected to high-amplitude cyclic mechanical stretch (40 per minute, 30% change in surface area) for 24 h. VEGF gene expression was investigated by real-time reverse transcription-PCR. Concentrations of VEGF in culture supernatants of stretched cells were determined by ELISA. Apoptosis of cells following stretching was assessed by flow cytometry.

RESULTS

Vascular endothelial growth factor gene expression increased during the first 4 h of stretching and then declined to a similar level to that of static control cells. VEGF concentrations in cell supernatants increased in response to mechanical stretch, as compared with those in supernatants of static control cells. Incubation of ATII cells with higher concentrations of VEGF (50 ng/mL) during stretching inhibited apoptosis, presumably by restoring stretch-impaired phosphatidylinositol-3 kinase signalling. However, blocking free VEGF in the supernatant with an anti-VEGF antibody did not influence stretch-induced apoptosis.

CONCLUSIONS

These findings suggest that high-amplitude mechanical stretch induced secretion of VEGF, which in high concentrations, may prevent stretch-induced apoptosis. In this model, however, the protective influence of VEGF was not essential for survival of ATII cells subjected to high-amplitude mechanical stretch.

VEGF in the lung: a role for novel isoforms

Vascular endothelial cell growth factor (VEGF) is a potent mitogen and permogen that increases in the plasma and decreases in the alveolar space in respiratory diseases such as acute respiratory distress syndrome (ARDS). This observation has led to controversy over the role of this potent molecule in lung physiology and disease. We hypothesized that some of the VEGF previously detected in normal lung may be of the anti-angiogenic family (VEGF(xxx)b) with significant potential effects on VEGF bioactivity. VEGF(xxx)b protein expression was assessed by indirect immunohistochemistry in normal and ARDS tissue. Expression of VEGF(xxx)b was also detected by immunoblotting in normal lung tissue, primary human alveolar type II (ATII) cells, and bronchoalveolar lavage (BAL) fluid in normal subjects and by ELISA in normal, "at risk," and ARDS subjects. The effect of VEGF(165) and VEGF(165)b on both human primary endothelial cells and alveolar epithelial cell proliferation was assessed by [(3)H]thymidine uptake. We found that VEGF(165)b was widely expressed in normal healthy lung tissue but is reduced in ARDS lung. VEGF(121)b and VEGF(165)b were present in whole lung, BAL, and ATII lysate. The proliferative effect of VEGF(165) on both human primary endothelial cells and human alveolar epithelial cells was significantly inhibited by VEGF(165)b (P < 0.01). These data demonstrate that the novel VEGF(xxx)b family members are expressed in normal lung and are reduced in ARDS. A specific functional effect on primary human endothelial and alveolar epithelial cells has also been shown. These data suggest that the VEGF(xxx)b family may have a role in repair after lung injury.

Functions of type II pneumocyte-derived vascular endothelial growth factor in alveolar structure, acute inflammation, and vascular permeability

Vascular endothelial growth factor-A (VEGF) is a potent regulator of vascular permeability, inflammatory response, and cell survival in the lung. To explore the functions of VEGF produced locally in type II pneumocytes, we generated mice with a conditional deletion of VEGF-A using Cre recombinase driven by the human surfactant protein C (SPC) promoter. In 7- to 10-week-old VEGF-knockout (SPC-VEGF-KO) mice, lung histology and physiology were essentially normal, except for higher dynamic lung compliance and lower pulmonary vascular permeability. Emphysema was seen in 28- to 32-week-old animals. To investigate the role of type II pneumocyte-derived VEGF in acute lung injury, we challenged 7- to 10-week-old SPC-VEGF-KO mice and their wild-type littermates with intestinal ischemia-reperfusion. Bronchoalveolar lavage fluid total cell count, pulmonary permeability, and lung injury score were significantly attenuated, and total lung VEGF levels were significantly lower in SPC-VEGF-KO mice compared with wild-type controls. In SPC-VEGF-KO mice, activated caspase 3-positive type II epithelial cells were increased after intestinal ischemia-reperfusion, even though there was no significant difference in the total number of cells positive for terminal deoxynucleotidyl transferase dUTP nick-end labeling. We conclude that VEGF in type II cells helps protect alveolar epithelial cells from caspase-dependent apoptosis. However, VEGF produced from type II cells may contribute to increased vascular permeability during acute lung injury.

Relationship between vascular endothelial growth factor + 936 genotype and plasma/epithelial lining fluid vascular endothelial growth factor protein levels in patients with and at risk for ARDS

BACKGROUND

Vascular endothelial growth factor (VEGF) is postulated to have a role in ARDS. The functional VEGF + 936 polymorphic T allele is associated with an increased susceptibility to and severity of ARDS. The reasons for this are unclear. We hypothesized that the T allele would be associated with an alteration in the relation between epithelial lining fluid (ELF) and plasma VEGF levels as a potential explanation for its association with susceptibility to and severity of ARDS.

METHODS

Plasma and ELF VEGF protein levels were measured by enzyme-linked immunosorbent assay from 10 at-risk patients receiving mechanical ventilation and 16 ARDS patients with the T allele, as well as 18 at-risk patients receiving mechanical ventilation and 26 ARDS patients without the T allele (wild-type CC genotype).

RESULTS

The T allele was associated with a significantly lower mean ELF VEGF level in ARDS patients (2,090 +/- 758 pg/mL vs 3,292 +/- 865 pg/mL, p < 0.05) and mean ELF/plasma VEGF level ratio (13.7 +/- 4.6 pg/mL vs 94.7 +/- 51.2 pg/mL, p < 0.01). There was no relation between the T allele and plasma VEGF level, oxygenation, or acute physiology score in at-risk and ARDS patients. ELF VEGF levels were significantly higher than plasma levels in both cohorts except for at-risk patients without the T allele (wild-type CC genotype).

CONCLUSION

The T allele is associated with a significant decrease in ELF levels and the ELF/plasma ratio in ARDS patients. This may explain the increased susceptibility and physiologic derangement in ARDS patients with the T allele. We speculate VEGF has a protective function in the lung. Further studies are necessary to clarify the underlying mechanisms.

Vascular endothelial growth factor receptor and coreceptor expression in human acute respiratory distress syndrome

BACKGROUND

Acute respiratory distress syndrome (ARDS) is characterized by the development of noncardiogenic pulmonary edema, which has been related to the bioactivity of vascular endothelial growth factor (VEGF). Vascular endothelial growth factor receptors and coreceptors regulate this bioactivity. We hypothesized VEGF receptors 1 and 2 (VEGFR1, VEGFR2) and coreceptor neuropilin-1 (NRP-1) would be expressed in human lung tissue with a significant change in expression in ARDS lung.

METHODS

Archival "normal" (no lung pathology and non-ARDS), "early" (within 48 hours), and "later" (after day 7) ARDS lung-tissue sections (n = 5) were immunostained for VEGFR1, VEGFR2, and NRP-1 from human subjects (n = 4). Staining was assessed densitometrically using Histometrix software.

RESULTS

VEGFR1, VEGFR2, and NRP-1 were expressed on both sides of the alveolar-capillary membrane in both normal and ARDS human lung tissue. In later ARDS, there was a significant up-regulation of VEGFR1 and VEGFR2 versus normal and early ARDS (P < .0001). Neuropilin-1 was down-regulated in early ARDS versus normal lung (P < .05), with normalization in later ARDS (P < .001).

CONCLUSION

Differential temporal VEGFR1, VEGFR2, and NRP-1 up-regulation occurs in human ARDS, providing evidence of further functional regulation of VEGF bioactivity via VEGFR2 consistent with a protective role for VEGF in lung injury recovery. The mechanisms behind these observations remain to be clarified.

Vascular Endothelial Growth Factor (VEGF) isoform expression and activity in human and murine lung injury

BACKGROUND

The properties of vascular endothelial growth factor (VEGF) as a potent vascular permogen and mitogen have led to investigation of its potential role in lung injury. Alternate spliced VEGF transcript generates several isoforms with potentially differing functions. The purpose of this study was to determine VEGF isoform expression and source in normal and ARDS subjects and investigate the expression and regulation of VEGF isoforms by human alveolar type 2 (ATII) cells.

METHODS

VEGF protein expression was assessed immunohistochemically in archival normal and ARDS human lung tissue. VEGF isoform mRNA expression was assessed in human and murine lung tissue. Purified ATII cells were cultured with proinflammatory cytokines prior to RNA extraction/cell supernatant sampling/proliferation assay.

MEASUREMENTS AND MAIN RESULTS

VEGF was expressed on alveolar epithelium, vascular endothelium and alveolar macrophages in normal and ARDS human lung tissue. Increases in VEGF expression were detected in later ARDS in comparison to both normal subjects and early ARDS (p < 0.001). VEGF121, VEGF165 and VEGF189 isoform mRNA expression increased in later ARDS (p < 0.05). The ratio of soluble to cell-associated isoforms was lower in early ARDS than normal subjects and later ARDS and also in murine lung injury. ATII cells constitutionally produced VEGF165 and VEGF121 protein which was increased by LPS (p < 0.05). VEGF165 upregulated ATII cell proliferation (p < 0.001) that was inhibited by soluble VEGF receptor 1 (sflt) (p < 0.05).

CONCLUSION

These data demonstrate that changes in VEGF isoform expression occur in ARDS which may be related to their production by and mitogenic effect on ATII cells; with potentially significant clinical consequences.

Circulating vascular endothelial growth factor and systemic inflammatory markers in patients with stable and exacerbated chronic obstructive pulmonary disease

The aim of the present study was to assess circulating levels of VEGF (vascular endothelial growth factor), a biomarker with prognostic significance in cardiovascular disease, and markers of systemic inflammation in patients with stable and exacerbated COPD (chronic obstructive pulmonary disease). Lung function parameters, arterial blood gas analysis and circulating levels of VEGF, IL-6 (interleukin-6), TNF-alpha (tumour necrosis factor-alpha), CRP (C-reactive protein), fibrinogen and the peripheral blood neutrophil cell count were assessed in 30 patients on admission to the hospital for acute exacerbation of COPD, in 30 age-, gender- and BMI (body mass index)-matched patients with stable COPD, and 30 matched controls with normal lung function. Patients with acute exacerbated COPD had higher circulating concentrations of VEGF (P<0.001), IL-6 (P<0.05) and CRP (P<0.01) and an increased blood neutrophil cell count (P<0.05) compared with patients with stable COPD and healthy controls. VEGF levels in exacerbated COPD correlated with systemic inflammatory markers, such as CRP (r=0.61, P<0.005), IL-6 (r=0.46; P<0.01) and fibrinogen (r=0.39, P<0.05). In patients with stable COPD, there was a significant relationship between circulating VEGF levels and the percentage of the predicted FEV(1) (forced expiratory volume in 1 s) (r=0.47, P<0.01). Recovery from the exacerbation resulted in a significant decrease in both circulating VEGF levels and markers of systemic inflammation. In conclusion, circulating levels of VEGF and markers of systemic inflammation are up-regulated in patients with acute exacerbated COPD and decrease after recovery from the exacerbation.

Cell-cell junctions and vascular endothelial growth factor in rat lung as affected by ischemia/reperfusion and preconditioning with inhaled nitric oxide

BACKGROUND

Previous investigations have shown that short term inhalation of nitric oxide (NO) before ischemia and reperfusion (I/R) prevents I/R-related consequences on lung function. Here we correlate effects of NO-induced preconditioning, especially on the lung permeability barrier, with analysis of cell junction proteins and the level of vascular endothelial growth factor (VEGF).

METHODS

A rat model of left lung in situ I/R was used. After left lateral thoracotomy, left lung ischemia was maintained for 60 min, followed by 30 min or 4 h (h) reperfusion (I/R groups). In the NO groups, inhalation of NO (10 min, 15 ppm) preceded I/R. Animals in control groups underwent sham surgery without NO inhalation and ischemia. The extent of I/R injury was assessed in terms of oxygenation (arterial PO(2)) and lung permeability (Evans blue extravasation). Expression of junctional proteins and phosphorylation was determined in complete protein extracts from lung tissue, whereas the adherens junction (AJ) core complex was analyzed in Triton extracts by co-immunoprecipitation using antibodies against E-cadherin and VE-cadherin.

RESULTS

The inhalation of NO prevented the I/R-induced increase of permeability at 30 min reperfusion, and the PO(2) increased from 27% of controls in the I/R group to 77% in the NO group. Left lung I/R correlated with a progressive loss of cadherins (VE-cadherin, E-cadherin, desmoglein 1) during reperfusion, whereas AJ catenins were largely preserved. Preconditioning with NO resulted in an increased ratio of catenins (alpha- and beta-catenin) to E-cadherin in immunoprecipitates and in reduced phosphorylation of beta-catenin. A reduction of VEGF in left lung lavage fluid was observed at 4 h but not at 30 min reperfusion.

CONCLUSIONS

The NO-induced changes of the AJ complex may have contributed to the stabilization of the lung permeability barrier during reperfusion.

Vascular endothelial growth factor in severe sepsis and septic shock

BACKGROUND

Vascular endothelial growth factor (VEGF) levels have been shown to be elevated in severe sepsis. We investigated the value of VEGF in predicting organ dysfunction and hospital mortality in adult patients with severe sepsis.

METHODS

We conducted a prospective observational cohort study in 24 closed multidisciplinary intensive care units (ICU) in Finland. All ICU admission episodes (4500) were screened for severe sepsis from November 1, 2004, to February 28, 2005. Patients were eligible if they fulfilled the criteria for severe sepsis.

RESULTS

Severe sepsis was found in 470 patients. Laboratory samples were obtained after informed consent from 250 patients at study entry (day 0) and from 215 patients after 72 h. These samples were compared with samples from 30 healthy individuals. The ICU mortality was 13.2% and hospital mortality 26%. Median serum VEGF concentrations on day 0 were 423 pg/mL (interquartile range [IQR] 159 and 858 pg/mL), and after 72 h were 521 pg/mL (IQR 182 and 1092 pg/mL), which were both higher than in healthy controls (P = 0.029 and 0.003, respectively). Low VEGF concentrations were associated with more severe renal and hematological dysfunction (Sequential Organ Failure Assessment scores 3-4 compared with scores 0-2). VEGF concentrations in day 0 and after 72 h were lower in nonsurvivors (P = 0.01 and <0.01, respectively) than in survivors, but the receiver operating characteristic curve analyses of concentrations of VEGF on day 0 and at 72 h revealed areas under the curve of 0.58 and 0.63 (95% confidence limits 0.48-0.68 and 0.54-0.72, P = 0.1 and 0.009, respectively).

CONCLUSIONS

VEGF concentrations are increased in patients with severe sepsis. Low concentrations are associated with hematological and renal dysfunction. VEGF concentrations were lower in nonsurvivors than in survivors, but did not adequately predict hospital mortality in patients with severe sepsis.

Prenatal administration of vitamin A alters pulmonary and plasma levels of vascular endothelial growth factor in the developing mouse

Vitamin A and the retinoids play a unique role in mammalian embryonic and foetal development and are essential for both cellular differentiation and the establishment of normal morphogenesis. Vascular endothelial growth factor (VEGF) is a known potent mitogenic factor that plays a key role in lung development and function maintenance. In order to contribute to a better knowledge of the modulating effects of vitamin A in lung development, we investigated the effects of the antenatal administration of vitamin A on VEGF expression in lungs and plasma from foetuses and neonates. Pregnant mice were subjected to subcutaneous administration of vitamin A on the 12th gestational day. The lungs and plasma from foetuses and neonates were collected daily from the 15th gestational day till the day of birth. Our results show that vitamin A modulates VEGF concentrations both in lungs and plasma. Statistically significant differences were observed at gestational days 15 (P = 0.004 for lungs; P < 0.0001 for plasma), 16 (P < 0.0001 for lungs and plasma) and 18 (P < 0.0001 for lungs; P < 0.05 for plasma). Vitamin A tends to increase the expression of this factor in the lung, particularly during the critical period of perinatal adaptation to postnatal life. These effects seem to be spatial and temporally regulated, and point out to the important role of vitamin A during lung development.

Vascular endothelial growth factor promotes physical wound repair and is anti-apoptotic in primary distal lung epithelial and A549 cells

OBJECTIVE

There is evidence to suggest a beneficial role for growth factors, including vascular endothelial growth factor (VEGF), in tissue repair and proliferation after injury within the lung. Whether this effect is mediated predominantly by actions on endothelial cells or epithelial cells is unknown. This study tested the hypothesis that VEGF acts as an autocrine trophic factor for human adult alveolar epithelial cells and that under situations of pro-apoptotic stress, VEGF reduces cell death.

DESIGN

In vitro cell culture study looking at the effects of 0.03% H2O2 on both A549 and primary distal lung epithelial cells.

MEASUREMENT AND MAIN RESULTS

Primary adult human distal lung epithelial cells express both the soluble and membrane-associated VEGF isoforms and VEGF receptors 1 and 2. At physiologically relevant doses, soluble VEGF isoforms stimulate wound repair and have a proliferative action. Specific receptor ligands confirmed that this effect was mediated by VEGF receptor 1. In addition to proliferation, we demonstrate that VEGF reduces A549 and distal lung epithelial cell apoptosis when administered after 0.03% H2O2 injury. This effect occurs due to reduced caspase-3 activation and is phosphatidylinositol 3'-kinase dependent.

CONCLUSION

In addition to its known effects on endothelial cells, VEGF acts as a growth and anti-apoptotic factor on alveolar epithelial cells. VEGF treatment may have potential as a rescue therapy for diseases associated with alveolar epithelial damage such as acute respiratory distress syndrome.

Protective role of vascular endothelial growth factor in endotoxin-induced acute lung injury in mice

BACKGROUND

Vascular endothelial growth factor (VEGF), a substance that stimulates new blood vessel formation, is an important survival factor for endothelial cells. Although overexpressed VEGF in the lung induces pulmonary edema with increased lung vascular permeability, the role of VEGF in the development of acute lung injury remains to be determined.

METHODS

To evaluate the role of VEGF in the pathogenesis of acute lung injury, we first evaluated the effects of exogenous VEGF and VEGF blockade using monoclonal antibody on LPS-induced lung injury in mice. Using the lung specimens, we performed TUNEL staining to detect apoptotic cells and immunostaining to evaluate the expression of apoptosis-associated molecules, including caspase-3, Bax, apoptosis inducing factor (AIF), and cytochrome C. As a parameter of endothelial permeability, we measured the albumin transferred across human pulmonary artery endothelial cell (HPAEC) monolayers cultured on porous filters with various concentrations of VEGF. The effect of VEGF on apoptosis HPAECs was also examined by TUNEL staining and active caspase-3 immunoassay.

RESULTS

Exogenous VEGF significantly decreased LPS-induced extravascular albumin leakage and edema formation. Treatment with anti-VEGF antibody significantly enhanced lung edema formation and neutrophil emigration after intratracheal LPS administration, whereas extravascular albumin leakage was not significantly changed by VEGF blockade. In lung pathology, pretreatment with VEGF significantly decreased the numbers of TUNEL positive cells and those with positive immunostaining of the pro-apoptotic molecules examined. VEGF attenuated the increases in the permeability of the HPAEC monolayer and the apoptosis of HPAECs induced by TNF-alpha and LPS. In addition, VEGF significantly reduced the levels of TNF-alpha- and LPS-induced active caspase-3 in HPAEC lysates.

CONCLUSION

These results suggest that VEGF suppresses the apoptosis induced by inflammatory stimuli and functions as a protective factor against acute lung injury.

Clinical implications for vascular endothelial growth factor in the lung: friend or foe?

Vascular endothelial growth factor (VEGF) is a potent mediator of angiogenesis which has multiple effects in lung development and physiology. VEGF is expressed in several parts of the lung and the pleura while it has been shown that changes in its expression play a significant role in the pathophysiology of some of the most common respiratory disorders, such as acute lung injury, asthma, chronic obstructive pulmonary disease, obstructive sleep apnea, idiopathic pulmonary fibrosis, pulmonary hypertension, pleural disease, and lung cancer. However, the exact role of VEGF in the lung is not clear yet, as there is contradictory evidence that suggests either a protective or a harmful role. VEGF seems to interfere in a different manner, depending on its amount, the location, and the underlying pathologic process in lung tissue. The lack of VEGF in some disease entities may provide implications for its substitution, whereas its overexpression in other lung disorders has led to interventions for the attenuation of its action. Many efforts have been made in order to regulate the expression of VEGF and anti-VEGF antibodies are already in use for the management of lung cancer. Further research is still needed for the complete understanding of the exact role of VEGF in health and disease, in order to take advantage of its benefits and avoid its adverse effects. The scope of the present review is to summarize from a clinical point of view the changes in VEGF expression in several disorders of the respiratory system and focus on its diagnostic and therapeutic implications.

Change in plasma vascular endothelial growth factor during onset and recovery from acute mountain sickness

There is an increasing body of evidence suggesting that altered vascular permeability may be an important component of the pathogenesis of acute mountain sickness (AMS). Vascular endothelial growth factor (VEGF) is a potent permeability factor subject to hypoxic regulation but its role in the pathogenesis of AMS is yet to be defined. We examined the relationship between plasma VEGF and AMS on ascent to high altitude and subsequent acclimatisation. Thirty-eight healthy lowlanders (median age 21, range 18-31) flew to La Paz, Bolivia (3650 m) on the Apex 2 research expedition. After 4-5 days acclimatisation, they ascended by vehicle over 90 min to the Chacaltaya laboratory (5200 m). We measured plasma VEGF in venous blood at sea level and at 6 h and 3 and 7 days at 5200 m. AMS was scored using the Lake Louise consensus system. Using serial measurement of plasma VEGF at 5200 m, following partial acclimatisation at 3650 m, we demonstrated a highly significant change in VEGF levels (P<0.0005) with a rise in VEGF in approximately 80% of subjects by day 7 at 5200 m. We found no evidence of an association between AMS and change in VEGF levels on ascent to either 3650 or 5200 m. We provide novel data of change in plasma VEGF levels during acclimatisation to high altitude, but our results do not support the hypothesis that circulating unbound VEGF is an important component of the pathogenesis of AMS.