Resistin-like molecule-beta in scleroderma-associated pulmonary hypertension

Leukotriene B4 levels in CHD-associated paediatric pulmonary hypertension

BACKGROUND

The aim of this study is to evaluate the role of leukotriene B4, an inflammatory mediator, in the development of pulmonary hypertension in paediatric patients with CHD with left-right shunt.

METHODS

The study included forty patients with CHD with left-right shunts. Based on haemodynamic data obtained from cardiac diagnostic catheterisation, 25 patients who met the criteria for pulmonary arterial hypertension were included in the patient group. The control group comprised 15 patients who did not meet the criteria. The standard cardiac haemodynamic study was conducted. Leukotriene B4 levels were assessed in blood samples taken from both pulmonary arteries and peripheral veins.

RESULTS

The median age of patients with pulmonary arterial hypertension was 10 months (range: 3-168), while the median age of the control group was 50 months (range: 3-194). In the pulmonary hypertension group, the median pulmonary artery systolic/diastolic/mean pressures were 38/18/24 mmHg, compared to 26/10/18 mmHg in the control group. Leukotriene B4 levels in pulmonary artery blood samples were significantly higher in the pulmonary arterial hypertension group compared to the controls (p < 0.05). Peripheral leukotriene B4 levels were also elevated in the pulmonary arterial hypertension group in comparison to the control group, though the difference was not statistically significant.

CONCLUSION

The discovery of elevated leukotriene B4 levels in pulmonary artery samples from paediatric patients with pulmonary arterial hypertension secondary to CHD with left-to-right shunt suggests that local inflammation may have a pathological role in the development of pulmonary arterial hypertension.

Human Resistin Induces Cardiac Dysfunction in Pulmonary Hypertension

Background Cardiac failure is the primary cause of death in most patients with pulmonary arterial hypertension (PH). As pleiotropic cytokines, human resistin (Hresistin) and its rodent homolog, resistin-like molecule α, are mechanistically critical to pulmonary vascular remodeling in PH. However, it is still unclear whether activation of these resistin-like molecules can directly cause PH-associated cardiac dysfunction and remodeling. Methods and Results In this study, we detected Hresistin protein in right ventricular (RV) tissue of patients with PH and elevated resistin-like molecule expression in RV tissues of rodents with RV hypertrophy and failure. In a humanized mouse model, cardiac-specific Hresistin overexpression was sufficient to cause cardiac dysfunction and remodeling. Dilated hearts exhibited reduced force development and decreased intracellular Ca2+ transients. In the RV tissues overexpressing Hresistin, the impaired contractility was associated with the suppression of protein kinase A and AMP-activated protein kinase. Mechanistically, Hresistin activation triggered the inflammation mediated by signaling of the key damage-associated molecular pattern molecule high-mobility group box 1, and subsequently induced pro-proliferative Ki67 in RV tissues of the transgenic mice. Intriguingly, an anti-Hresistin human antibody that we generated protected the myocardium from hypertrophy and failure in the rodent PH models. Conclusions Our data indicate that Hresistin is expressed in heart tissues and plays a role in the development of RV dysfunction and maladaptive remodeling through its immunoregulatory activities. Targeting this signaling to modulate cardiac inflammation may offer a promising strategy to treat PH-associated RV hypertrophy and failure in humans.

Resistin-like molecules: a marker, mediator and therapeutic target for multiple diseases

Resistin-like molecules (RELMs) are highly cysteine-rich proteins, including RELMα, RELMβ, Resistin, and RELMγ. However, RELMs exhibit significant differences in structure, distribution, and function. The expression of RELMs is regulated by various signaling molecules, such as IL-4, IL-13, and their receptors. In addition, RELMs can mediate numerous signaling pathways, including HMGB1/RAGE, IL-4/IL-4Rα, PI3K/Akt/mTOR signaling pathways, and so on. RELMs proteins are involved in wide range of physiological and pathological processes, including inflammatory response, cell proliferation, glucose metabolism, barrier defense, etc., and participate in the progression of numerous diseases such as lung diseases, intestinal diseases, cardiovascular diseases, and cancers. Meanwhile, RELMs can serve as biomarkers, risk predictors, and therapeutic targets for these diseases. An in-depth understanding of the role of RELMs may provide novel targets or strategies for the treatment and prevention of related diseases. Video abstract.

Blood Levels of Indicators of Lower Respiratory Tract Damage in Chronic Bronchitis in Patients with Abdominal Obesity

Objective: to study biomolecules associated with pathology in the respiratory system, in particular, with the development of chronic bronchitis in patients with abdominal obesity. Materials and methods: This is a pilot study. The main group consisted of 158 people with chronic bronchitis, divided into two subgroups: one with abdominal obesity, and the other without it. The control group consisted of 68 people without chronic bronchitis. We determined the blood levels of SP-A, SP-D, α1-antitrypsin, CC16, PARC, and RELM-β. Results: In the first subgroup, patients significantly more often complained of coughing, experienced shortness of breath 1.5 times more often with light physical exertion and 2.7 times more often with moderate physical exertion. In these patients, a Tiffeneau–Pinelli index (FEV1/FVC) below 70% was 1.8 times more common, more patients had FEV1 and FVC of less than 80%, and presented a statistically significant decrease in SP-A, α1-antitrypsin, CC16 levels and an increase in PARC levels than in the second subgroup. Conclusion: In patients with chronic bronchitis and abdominal obesity, there is a decrease in the levels of SP-A, α1-antitrypsin, CC16 and an increase in the level of PARC compared with patients without abdominal obesity, which is probably due to the presence of an additional source of chronic inflammation associated with adipose tissue.

FIZZ2 as a Biomarker for Acute Exacerbation of Chronic Obstructive Pulmonary Disease

PURPOSE

Found in inflammatory zone 2 (FIZZ2) is associated with lung inflammation. The aim of the study was to investigate the expression and utility of FIZZ2 as a marker for chronic obstructive pulmonary disease (COPD).

METHODS

Immunohistochemistry was used to detect the expression of FIZZ2 in COPD. The serum concentration of FIZZ2 was measured by enzyme-linked immunosorbent assay and the episodes of acute exacerbations of COPD (AECOPD) in the following year were recorded.

RESULTS

FIZZ2 expression was elevated in bronchial epithelial cells (0.217 ± 0.021 vs 0.099 ± 0.010, p < 0.0001) and negatively correlated with the pulmonary function (FEV1/FVC%) (p = 0.0149) and positively correlated with the smoking index (p = 0.0241). Serum level of FIZZ2 in COPD were significantly higher than that in healthy controls (561.6 ± 70.71 vs 52.24 ± 20.52 pg/ml, p < 0.0001) and increased with the COPD severity. Serum levels of FIZZ2 negatively correlated with the pulmonary function [Forced Vital Capacity (FVC), Forced Expiratory Volume (FEV1), FEV1%, FEV1/FVC) (r =  - 0.3086, - 0.3529, - 0.3343, and - 0.2676, respectively, p = 0.0003, p < 0.0001, p < 0.0001, p = 0.0014). The expression of human serum FIZZ2 was positively correlated with the smoking index (r = 0.2749, p = 0.0015). There was a positive correlation between the FIZZ2 concentration and the frequency of AECOPD episodes in the following year (r = 0.7291, p < 0.0001).

CONCLUSION

FIZZ2 expression was elevated in patients with COPD and its serum concentration might be a potential biomarker for AECOPD.

The Inflammatory Response Induced by RELMβ Upregulates IL-8 and IL-1β Expression in Bronchial Epithelial Cells in COPD

Purpose

Chronic obstructive pulmonary disease (COPD) is associated with a complex inflammatory regulatory network. Resistin-like molecule β (RELMβ) is highly expressed in the lungs of COPD patients. We aimed to investigate the proinflammatory effect of RELMβ on airway epithelial cells in COPD.

Methods

First, a GEO dataset was used to analyze the expression of the RELMβ gene in the COPD and control groups as well as the protein levels of RELMβ in the sera of outpatients with COPD and normal control subjects in our hospital. We also stimulated 16HBE bronchial epithelial cells with recombinant RELMβ protein and analyzed the expression of IL-8 and IL-1β. We upregulated and downregulated the gene expression of RELMβ in 16HBE cells and analyzed the expression of the inflammatory cytokines IL-8 and IL-1β. In addition, we also examined the mechanism by which the p38 MAPK signaling pathway contributed to the regulation of IL-8 and IL-1β expression by RELMβ.

Results

RELMβ expression was increased in COPD tissues in different data sets and in the serum of COPD patients in our hospital. IL-8 and IL-1β expression was also increased in COPD tissues with high RELMβ gene expression in different data sets. The RELMβ gene was mainly related to inflammatory factors and inflammatory signaling pathways in the PPI regulatory network. Experiments at the cellular level showed that RELMβ promoted the expression of the inflammatory cytokines IL-8 and IL-1β, and this regulation was mediated by the p38 MAPK signaling pathway.

Conclusion

RELMβ can promote the expression of the inflammatory cytokines IL-8 and IL-1β in bronchial epithelial cells of patients with COPD and exert inflammatory effects. RELMβ may be a potential target for the treatment of COPD.

The inflammatory role of dysregulated IRS2 in pulmonary vascular remodeling under hypoxic conditions

Pulmonary hypertension (PH) is a devastating disease characterized by progressive elevation of pulmonary vascular resistance, right ventricular failure, and ultimately death. We have shown previously that insulin receptor substrate 2 (IRS2), a molecule highly critical to insulin resistance and metabolism, has an anti-inflammatory role in Th2-skewed lung inflammation and pulmonary vascular remodeling. Here, we investigated the hypothesis that IRS2 has an immunomodulatory role in human and experimental PH. Expression analysis showed that IRS2 was significantly decreased in the pulmonary vasculature of patients with pulmonary arterial hypertension and in rat models of PH. In mice, genetic ablation of IRS2 enhanced the hypoxia-induced signaling pathway of Akt and Forkhead box O1 (FOXO1) in the lung tissue and increased pulmonary vascular muscularization, proliferation, and perivascular macrophage recruitment. Furthermore, mice with homozygous IRS2 gene deletion showed a significant gene dosage-dependent increase in pulmonary vascular remodeling and right ventricular hypertrophy in response to hypoxia. Functional studies with bone marrow-derived macrophages isolated from homozygous IRS2 gene-deleted mice showed that hypoxia exposure led to enhancement of the Akt and ERK signaling pathway followed by increases in the pro-PH macrophage activation markers, vascular endothelial growth factor-A and arginase 1. Our data suggest that IRS2 contributes to anti-inflammatory effects by regulating macrophage activation and recruitment, which may limit the vascular inflammation, remodeling, and right ventricular hypertrophy that are seen in PH pathology. Restoring the IRS2 pathway may be an effective therapeutic approach for the treatment of PH and right heart failure.

Transcriptome analysis reveals key genes modulated by ALK5 inhibition in a bleomycin model of systemic sclerosis

Objective

SSc is a rheumatic autoimmune disease affecting roughly 20 000 people worldwide and characterized by excessive collagen accumulation in the skin and internal organs. Despite the high morbidity and mortality associated with SSc, there are no approved disease-modifying agents. Our objective in this study was to explore transcriptomic and model-based drug discovery approaches for SSc.

Methods

In this study, we explored the molecular basis for SSc pathogenesis in a well-studied mouse model of scleroderma. We profiled the skin and lung transcriptomes of mice at multiple timepoints, analysing the differential gene expression that underscores the development and resolution of bleomycin-induced fibrosis.

Results

We observed shared expression signatures of upregulation and downregulation in fibrotic skin and lung tissue, and observed significant upregulation of key pro-fibrotic genes including GDF15, Saa3, Cxcl10, Spp1 and Timp1. To identify changes in gene expression in responses to anti-fibrotic therapy, we assessed the effect of TGF-β pathway inhibition via oral ALK5 (TGF-β receptor I) inhibitor SB525334 and observed a time-lagged response in the lung relative to skin. We also implemented a machine learning algorithm that showed promise at predicting lung function using transcriptome data from both skin and lung biopsies.

Conclusion

This study provides the most comprehensive look at the gene expression dynamics of an animal model of SSc to date, provides a rich dataset for future comparative fibrotic disease research, and helps refine our understanding of pathways at work during SSc pathogenesis and intervention.

Hypoxia-Induced Mitogenic Factor: A Multifunctional Protein Involved in Health and Disease

Hypoxia-induced mitogenic factor (HIMF), also known as resistin-like molecule α (RELMα) or found in inflammatory zone 1 (FIZZ1) is a member of the RELM protein family expressed in mice. It is involved in a plethora of physiological processes, including mitogenesis, angiogenesis, inflammation, and vasoconstriction. HIMF expression can be stimulated under pathological conditions and this plays a critical role in pulmonary, cardiovascular and metabolic disorders. The present review summarizes the molecular characteristics, and the physiological and pathological roles of HIMF in normal and diseased conditions. The potential clinical significance of these findings for human is also discussed.

The Role of Hypoxia-Induced Mitogenic Factor in Organ-Specific Inflammation in the Lung and Liver: Key Concepts and Gaps in Knowledge Regarding Molecular Mechanisms of Acute or Immune-Mediated Liver Injury

Hypoxia-induced mitogenic factor (HIMF), which is also known as resistin-like molecule α (RELM-α), found in inflammatory zone 1 (FIZZ1), or resistin-like alpha (retlna), is a cysteine-rich secretory protein and cytokine. HIMF has been investigated in the lung as a mediator of pulmonary fibrosis, inflammation and as a marker for alternatively activated macrophages. Although these macrophages have been found to have a role in acute liver injury and acetaminophen toxicity, few studies have investigated the role of HIMF in acute or immune-mediated liver injury. The aim of this focused review is to analyze the literature and examine the effects of HIMF and its human homolog in organ-specific inflammation in the lung and liver. We followed the guidelines set by PRISMA in constructing this review. The relevant checklist items from PRISMA were included. Items related to meta-analysis were excluded because there were no randomized controlled clinical trials. We found that HIMF was increased in most models of acute liver injury and reduced damage from acetaminophen-induced liver injury. We also found strong evidence for HIMF as a marker for alternatively activated macrophages. Our overall risk of bias assessment of all studies included revealed that 80% of manuscripts demonstrated some concerns in the randomization process. We also demonstrated some concerns (54.1%) and high risk (45.9%) of bias in the selection of the reported results. The need for randomization and reduction of bias in the reported results was similarly detected in the studies that focused on HIMF and the liver. In conclusion, we propose that HIMF could be utilized as a marker for M2 macrophages in immune-mediated liver injury. However, we also detected the need for randomized clinical trials and additional experimental and human prospective studies in order to fully comprehend the role of HIMF in acute or immune-mediated liver injury.

Predictive and Prognostic Utility of the Serum Level of Resistin-Like Molecule Beta for Risk Stratification in Patients with Community-Acquired Pneumonia

Despite progress in intensive care, the morbidity and mortality of patients with community-acquired pneumonia (CAP) remains high. Furthermore, the predictive and prognostic utility of resistin-like molecule beta (RELM-β) in patients with CAP is uncertain. This study investigated the role of RELM-β in patients with CAP and evaluated its correlation with disease severity and the risk of death. A prospective, multicenter study was conducted in 2017, and admission serum levels of RELM-β were detected using quantitative enzyme-linked immunosorbent assay. A total of 114 and 112 patients with severe CAP (SCAP) and non-severe CAP (NSCAP) were enrolled, respectively, with 15 healthy controls. Patients with SCAP, especially non-survivors, had significantly higher levels of serum RELM-β than patients with NSCAP. RELM-β levels positively correlated with severity scores and consistently predicted SCAP in patients with CAP (area under the curve = 0.794). Increased levels of RELM-β were closely related to the severity and prognosis of patients with CAP. The accuracy of 30-day mortality predictions of CURB-65 (confusion, urea, respiratory rate, blood pressure, and age ≥ 65 years) can be significantly improved when combined with RELM-β levels. The level of RELM-β can assist clinicians in risk stratification of patients with CAP in early stages.

Resistin-like molecule β acts as a mitogenic factor in hypoxic pulmonary hypertension via the Ca2+-dependent PI3K/Akt/mTOR and PKC/MAPK signaling pathways

Background

Pulmonary arterial smooth muscle cell (PASMC) proliferation plays a crucial role in hypoxia-induced pulmonary hypertension (HPH). Previous studies have found that resistin-like molecule β (RELM-β) is upregulated de novo in response to hypoxia in cultured human PASMCs (hPASMCs). RELM-β has been reported to promote hPASMC proliferation and is involved in pulmonary vascular remodeling in patients with PAH. However, the expression pattern, effects, and mechanisms of action of RELM-β in HPH remain unclear.

Methods

We assessed the expression pattern, mitogenetic effect, and mechanism of action of RELM-β in a rat HPH model and in hPASMCs.

Results

Overexpression of RELM-β caused hemodynamic changes in a rat model of HPH similar to those induced by chronic hypoxia, including increased mean right ventricular systolic pressure (mRVSP), right ventricular hypertrophy index (RVHI) and thickening of small pulmonary arterioles. Knockdown of RELM-β partially blocked the increases in mRVSP, RVHI, and vascular remodeling induced by hypoxia. The phosphorylation levels of the PI3K, Akt, mTOR, PKC, and MAPK proteins were significantly up- or downregulated by RELM-β gene overexpression or silencing, respectively. Recombinant RELM-β protein increased the intracellular Ca²⁺ concentration in primary cultured hPASMCs and promoted hPASMC proliferation. The mitogenic effects of RELM-β on hPASMCs and the phosphorylation of PI3K, Akt, mTOR, PKC, and MAPK were suppressed by a Ca²⁺ inhibitor.

Conclusions

Our findings suggest that RELM-β acts as a cytokine-like growth factor in the development of HPH and that the effects of RELM-β are likely to be mediated by the Ca²⁺-dependent PI3K/Akt/mTOR and PKC/MAPK pathways.

Implication of Potassium Channels in the Pathophysiology of Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a rare and severe cardiopulmonary disease without curative treatments. PAH is a multifactorial disease that involves genetic predisposition, epigenetic factors, and environmental factors (drugs, toxins, viruses, hypoxia, and inflammation), which contribute to the initiation or development of irreversible remodeling of the pulmonary vessels. The recent identification of loss-of-function mutations in KCNK3 (KCNK3 or TASK-1) and ABCC8 (SUR1), or gain-of-function mutations in ABCC9 (SUR2), as well as polymorphisms in KCNA5 (Kv1.5), which encode two potassium (K⁺) channels and two K⁺ channel regulatory subunits, has revived the interest of ion channels in PAH. This review focuses on KCNK3, SUR1, SUR2, and Kv1.5 channels in pulmonary vasculature and discusses their pathophysiological contribution to and therapeutic potential in PAH.

Resistin family proteins in pulmonary diseases

The family of resistin-like molecules (RELMs) consists of four members in rodents (RELMα/FIZZ1/HIMF, RELMβ/FIZZ2, Resistin/FIZZ3, and RELMγ/FIZZ4) and two members in humans (Resistin and RELMβ), all of which exhibit inflammation-regulating, chemokine, and growth factor properties. The importance of these cytokines in many aspects of physiology and pathophysiology, especially in cardiothoracic diseases, is rapidly evolving in the literature. In this review article, we attempt to summarize the contribution of RELM signaling to the initiation and progression of lung diseases, such as pulmonary hypertension, asthma/allergic airway inflammation, chronic obstructive pulmonary disease, fibrosis, cancers, infection, and other acute lung injuries. The potential of RELMs to be used as biomarkers or risk predictors of these diseases also will be discussed. Better understanding of RELM signaling in the pathogenesis of pulmonary diseases may offer novel targets or approaches for the development of therapeutics to treat or prevent a variety of inflammation, tissue remodeling, and fibrosis-related disorders in respiratory, cardiovascular, and other systems.

The Network of Colonic Host Defense Peptides as an Innate Immune Defense Against Enteropathogenic Bacteria

Host defense peptides, abundantly secreted by colonic epithelial cells and leukocytes, are proposed to be critical components of an innate immune response in the colon against enteropathogenic bacteria, including Shigella spp., Salmonella spp., Clostridium difficile, and attaching and effacing Escherichia coli and Citrobacter rodentium. These short cationic peptides are bactericidal against both Gram-positive and -negative enteric pathogens, but may also exert killing effects on intestinal luminal microbiota. Simultaneously, these peptides modulate numerous cellular responses crucial for gut defenses, including leukocyte chemotaxis and migration, wound healing, cytokine production, cell proliferation, and pathogen sensing. This review discusses recent advances in our understanding of expression, mechanisms of action and microbicidal and immunomodulatory functions of major colonic host defense peptides, namely cathelicidins, β-defensins, and members of the Regenerating islet-derived protein III (RegIII) and Resistin-like molecule (RELM) families. In a theoretical framework where these peptides work synergistically, aspects of pathogenesis of infectious colitis reviewed herein uncover roles of host defense peptides aimed to promote epithelial defenses and prevent pathogen colonization, mediated through a combination of direct antimicrobial function and fine-tuning of host immune response and inflammation. This interactive host defense peptide network may decode how the intestinal immune system functions to quickly clear infections, restore homeostasis and avoid damaging inflammation associated with pathogen persistence during infectious colitis. This information is of interest in development of host defense peptides (either alone or in combination with reduced doses of antibiotics) as antimicrobial and immunomodulatory therapeutics for controlling infectious colitis.

Cellular inflammation in pulmonary hypertension: Detailed analysis of lung and right ventricular tissue, circulating immune cells and effects of a dual endothelin receptor antagonist

Growing evidence suggests that inflammation is crucially involved in the pathogenesis of pulmonary hypertension (PH) and consecutive right heart failure. The present study analyzed the inflammatory response in lung and right ventricle in a rat model of PH and evaluated the effects of the dual endothelin receptor antagonist (ERA) Macitentan. PH was induced by monocrotalin (60 mg/kg body weight s.c.) in Sprague-Dawley rats (PH, n = 10) and compared to healthy controls (CON, n = 10) as well as monocrotalin-induced, macitentan-treated rats (THER, n = 10). Detection of Dendritic cells (DCs), regulatory T cells (Tregs) and others as well as RT-PCR based inflammatory gene expression analysis were performed. Circulating DCs and Tregs were quantified by flow cytometry in the rat model and in PH patients (n = 70) compared to controls (n = 52). Inflammatory cells were increased in lung and right ventricular tissue, whereas DCs and Tregs were decreased in blood. Expression of 17 genes in the lung and 20 genes in the right ventricle were relevantly (>2.0 fold) regulated in the PH group. These effects were, at least in part, attenuated in response to Macitentan treatment. In humans as well as rats, immune cells showed significant correlations to clinical, echocardiographic, and haemodynamic parameters. PH is accompanied by a distinct inflammatory response in lung and right but not left ventricular tissue attenuated by Macitentan. Correlations of circulating DCs as well as tissue resident immune cells with parameters reflecting right ventricular function raise the idea of both, promising biomarkers and novel treatment strategies.

RELMα Licenses Macrophages for Damage-Associated Molecular Pattern Activation to Instigate Pulmonary Vascular Remodeling

Pulmonary hypertension (PH) is a debilitating disease characterized by remodeling of the lung vasculature. In rodents, resistin-like molecule-α (RELMα, also known as HIMF or FIZZ1) can induce PH, but the signaling mechanisms are still unclear. In this study, we used human lung samples and a hypoxia-induced mouse model of PH. We found that the human homolog of RELMα, human (h) resistin, is upregulated in macrophage-like inflammatory cells from lung tissues of patients with idiopathic PH. Additionally, at PH onset in the mouse model, we observed RELMα-dependent lung accumulation of macrophages that expressed high levels of the key damage-associated molecular pattern (DAMP) molecule high-mobility group box 1 (HMGB1) and its receptor for advanced glycation end products (RAGE). In vitro, RELMα/hresistin-induced macrophage-specific HMGB1/RAGE expression and facilitated HMGB1 nucleus-to-cytoplasm translocation and extracellular secretion. Mechanistically, hresistin promoted HMGB1 posttranslational lysine acetylation by preserving the NAD⁺-dependent deacetylase sirtuin (Sirt) 1 in human macrophages. Notably, the hresistin-stimulated macrophages promoted apoptosis-resistant proliferation of human pulmonary artery smooth muscle cells in an HMGB1/RAGE-dependent manner. In the mouse model, RELMα also suppressed the Sirt1 signal in pulmonary macrophages in the early posthypoxic period. Notably, recruited macrophages in the lungs of these mice carried the RELMα binding partner Bruton tyrosine kinase (BTK). hResistin also mediated the migration of human macrophages by activating BTK in vitro. Collectively, these data reveal a vascular-immune cellular interaction in the early PH stage and suggest that targeting RELMα/DAMP-driven macrophages may offer a promising strategy to treat PH and other related vascular inflammatory diseases.

TGF-β1-induced SMAD2/3/4 activation promotes RELM-β transcription to modulate the endothelium-mesenchymal transition in human endothelial cells

Endothelial-to-mesenchymal transition (EndMT), which is characterized by increased proliferation, migration and invasion of endothelial cells, increased expression of mesenchymal markers and reduced expression of endothelial markers, has been reported to be closely related to the pathogenesis of several diseases, including pulmonary fibrosis. Resistin-like molecule-β (RELM-β), also known as "found in inflammatory zone 2″ (FIIZ2), plays an essential role in airway remodeling and pulmonary fibrosis; however, its role and mechanism in EndMT remain unclear. Herein, we used TGF-β1-induced EndMT cell model in human umbilical vein endothelial cells (HUVECs) and human primary pulmonary artery endothelial cells (HPAECs) to investigate the function and mechanism of RELM-β in TGF-β1-induced EndMT in endothelial cell lines. We found that TGF-β1 stimulation significantly upregulated RELM-β expression; RELM-β knockdown could attenuate TGF-β1-induced cell proliferation and migration of endothelial cell lines and changes in protein levels of EndMT markers. SB432542, an inhibitor of SMADs, could partially reverse TGF-β1-induced RELM-β expression, endothelial cell migration and changes in EndMT marker protein levels. SMADs complex exerted its effects through SMAD2/3/4 complex mediating RELM-β transcription. In conclusion, TGF-β1 induces RELM-β transcription to promote EndMT in HUVECs and HPAECs through activation of SMAD2/3/4; blocking SMADs-mediated RELM-β transcription might ameliorate TGF-β1-induced EndMT in endothelial cells.

Circulating Protein Biomarkers in Systemic Sclerosis Related Pulmonary Arterial Hypertension: A Review of Published Data

Pulmonary arterial hypertension (PAH) develops in 7-12% of patients with systemic sclerosis (SSc) and is associated with a 3 year survival of 52%. Early detection by screening is therefore recommended for all patients with SSc. Historically, screening has been performed using echocardiography and measurement of gas transfer. More recently the DETECT protocol, using a combination of biomarkers (including N-terminal pro-brain natriuretic peptide) and clinical parameters, has been developed. The optimal method of screening for PAH with high sensitivity and specificity is, however, not clear. Protein expression differences between different SSc disease phenotypes have been reported, and include alterations in concentration of NT-proBNP, endoglin, soluble vascular endothelial growth factor receptor 1, placenta growth factor, growth differentiation factor-15, vascular endothelial growth factor alpha, resistin-like molecule beta, and soluble thrombomodulin. This review summarizes the current knowledge of these protein changes in patients with SSc and PAH.

Role of cardiac inflammation in right ventricular failure

Right ventricular failure (RVF) is the main determinant of mortality in patients with pulmonary arterial hypertension (PAH). Although the exact pathophysiology underlying RVF remains unclear, inflammation may play an important role, as it does in left heart failure. Perivascular pulmonary artery and systemic inflammation is relatively well studied and known to contribute to the initiation and maintenance of the pulmonary vascular insult in PAH. However, less attention has been paid to the role of cardiac inflammation in RVF and PAH. Consistent with many other types of heart failure, cardiac inflammation, triggered by systemic and local stressors, has been shown in RVF patients as well as in RVF animal models. RV inflammation likely contributes to impaired RV contractility, maladaptive remodelling and a vicious circle between RV and pulmonary vascular injury. Although the potential to improve RV function through anti-inflammatory therapy has not been tested, this approach has been applied clinically in left ventricular failure patients, with variable success. Because inflammation plays a dual role in the development of both pulmonary vascular pathology and RVF, anti-inflammatory therapies may have a potential double benefit in patients with PAH and associated RVF.

Deletion of resistin-like molecule-beta attenuates angiotensin II-induced abdominal aortic aneurysm

In the present study, we want to test whether deletion of resistin-like molecule-beta (RELMβ) attenuates angiotensin II (Ang II)-induced formation of abdominal aortic aneurysm (AAA). RELMβ gene expression was inhibited by siRNA both in vivo and in vitro. Apolipoprotein E-knockout (ApoE^−/−) mice were randomly divided into saline, Ang II, siRNA negative control (si-NC) and siRNA RELMβ (si-RELMβ) groups (n=15 each), and mice in the last three groups underwent Ang II infusion for 4 weeks to induce AAA. RELMβ gene deficiency significantly decreased AAA incidence and severity, which was associated with reduced macrophage accumulation and decreased expression of proinflammatory cytokines (monocyte chemoattractant protein 1 and interleukin 6), matrix metalloproteinase 2 (MMP-2) and MMP-9 in the aortic wall. In cultured macrophages, RELMβ deficiency blunted the response of macrophages to Ang II and downregulated the levels of proinflammatory cytokines, MMP-2 and MMP-9. Recombinant RELMβ promoted the secretion of proinflammatory cytokines, MMP-2 and MMP-9 in macrophages and activated extracellular signal-regulated kinase 1/2 (ERK1/2) and c-Jun N-terminal kinase (JNK) signaling, which was reversed with pretreatment with inhibitors of ERK1/2 and JNK. Deletion of RELMβ attenuated Ang II-induced AAA formation in ApoE^−/− mice. The inherent mechanism may involve the reduced expression of proinflammatory cytokines, MMP-2 and MMP-9, which was mediated by ERK1/2 and JNK activation. Therefore, inhibiting RELMβ secretion may be a novel approach for anti-aneurysm treatment.

Resistin-Like Molecule-β Promotes Invasion and Migration of Gastric Carcinoma Cells

Background

Resistin-like molecule-β (RELMβ) is a novel secretory protein from intestinal goblet cells and participates in epithelial differentiation, tumor occurrence, and immune response. RELMβ is absent in normal gastric mucosa but is abundantly expressed in gastric carcinoma tissues, and is correlated with tumor invasion and metastasis. Epithelial-mesenchymal transition (EMT) is an important mechanism governing tumor cell invasion. This study thus investigated the modulation of RELMβ in gastric cancer metastasis and its correlation with EMT.

Material/Methods

We used RELMβ-low expression AGS cell line of gastric cancer and normal mucosa cell line GES1 as in vitro models, on which RELMβ0-expressing vector was transfected. The invasion and migration of cells were quantified by Transwell assay. EMT-related protein including E-cadherin, N-cadherin, Snail, and Vimentin were detected by Western blotting in transfected AGS cells.

Results

RELMβ transfection significantly potentiated invasion and migration abilities of AGS cells, whose RELMβ protein level was significantly elevated compared to those in untransfected AGS or GES1 cells. After RELMβ transfection, EMT-related proteins, including N-cadherin, Snail, and Vimentin levels, were elevated, but E-cadherin expression was depressed.

Conclusions

RELMβ-overexpression can facilitate invasion and migration of gastric carcinoma cells and it increases the expression of EMT-related proteins, such as N-cadherin, Snail, Vimentin, but decreases E-cadherin level, thus promoting the progression of EMT.

Resistin-like molecule-β (RELM-β) targets airways fibroblasts to effect remodelling in asthma: from mouse to man

BACKGROUND

RELM-β has been implicated in airways inflammation and remodelling in murine models. Its possible functions in human airways are largely unknown. The aim was to address the hypothesis that RELM-β plays a role in extracellular matrix deposition in asthmatic airways.

METHODS

The effects of RELM-β gene deficiency were studied in a model of allergen exposure in mice sensitised and challenged with Aspergillus fumigatus (Af). RELM-β expression was investigated in bronchial biopsies from asthmatic patients. Direct regulatory effects of RELM-β on human lung fibroblasts were examined using primary cultures and the MRC5 cell line in vitro.

RESULTS

Sensitisation and challenge of wild-type mice with Af-induced release of RELM-β with a time course coincident with that of procollagen in the airways. Af-induced expression of mRNA encoding some, but not all ECM in the lung parenchyma was attenuated in RELM-β-/- mice. RELM-β expression was significantly increased in the bronchial submucosa of human asthmatics compared with controls, and its expression correlated positively with that of fibronectin and α-smooth muscle actin. In addition to epithelial cells, macrophages, fibroblasts and vascular endothelial cells formed the majority of cells expressing RELM-β in the submucosa. Exposure to RELM-β increased TGF-β1, TGF-β2, collagen I, fibronectin, smooth muscle α-actin, laminin α1, and hyaluronan and proteoglycan link protein 1 (Hapl1) production as well as proliferation by human lung fibroblasts in vitro. These changes were associated with activation of ERK1/2 in MRC5 cells.

CONCLUSION

The data are consistent with the hypothesis that elevated RELM-β expression in asthmatic airways contributes to airways remodelling at least partly by increasing fibroblast proliferation and differentiation with resulting deposition of extracellular matrix proteins.

Hypoxia-Inducible Factor 1α Is a Critical Downstream Mediator for Hypoxia-Induced Mitogenic Factor (FIZZ1/RELMα)-Induced Pulmonary Hypertension

OBJECTIVE

Pulmonary hypertension (PH) is characterized by progressive elevation of pulmonary vascular resistance, right ventricular failure, and ultimately death. We have shown that in rodents, hypoxia-induced mitogenic factor (HIMF; also known as FIZZ1 or resistin-like molecule-β) causes PH by initiating lung vascular inflammation. We hypothesized that hypoxia-inducible factor-1 (HIF-1) is a critical downstream signal mediator of HIMF during PH development.

APPROACH AND RESULTS

In this study, we compared the degree of HIMF-induced pulmonary vascular remodeling and PH development in wild-type (HIF-1α(+/+)) and HIF-1α heterozygous null (HIF-1α(+/-)) mice. HIMF-induced PH was significantly diminished in HIF-1α(+/-) mice and was accompanied by a dysregulated vascular endothelial growth factor-A-vascular endothelial growth factor receptor 2 pathway. HIF-1α was critical for bone marrow-derived cell migration and vascular tube formation in response to HIMF. Furthermore, HIMF and its human homolog, resistin-like molecule-β, significantly increased interleukin (IL)-6 in macrophages and lung resident cells through a mechanism dependent on HIF-1α and, at least to some extent, on nuclear factor κB.

CONCLUSIONS

Our results suggest that HIF-1α is a critical downstream transcription factor for HIMF-induced pulmonary vascular remodeling and PH development. Importantly, both HIMF and human resistin-like molecule-β significantly increased IL-6 in lung resident cells and increased perivascular accumulation of IL-6-expressing macrophages in the lungs of mice. These data suggest that HIMF can induce HIF-1, vascular endothelial growth factor-A, and interleukin-6, which are critical mediators of both hypoxic inflammation and PH pathophysiology.

Interleukin-4 Receptor α Signaling in Myeloid Cells Controls Collagen Fibril Assembly in Skin Repair

Activation of the immune response during injury is a critical early event that determines whether the outcome of tissue restoration is regeneration or replacement of the damaged tissue with a scar. The mechanisms by which immune signals control these fundamentally different regenerative pathways are largely unknown. We have demonstrated that, during skin repair in mice, interleukin-4 receptor α (IL-4Rα)-dependent macrophage activation controlled collagen fibril assembly and that this process was important for effective repair while having adverse pro-fibrotic effects. We identified Relm-α as one important player in the pathway from IL-4Rα signaling in macrophages to the induction of lysyl hydroxylase 2 (LH2), an enzyme that directs persistent pro-fibrotic collagen cross-links, in fibroblasts. Notably, Relm-β induced LH2 in human fibroblasts, and expression of both factors was increased in lipodermatosclerosis, a condition of excessive human skin fibrosis. Collectively, our findings provide mechanistic insights into the link between type 2 immunity and initiation of pro-fibrotic pathways.

Loss of Hif-2α Rescues the Hif-1α Deletion Phenotype of Neonatal Respiratory Distress In Mice

Hypoxia is a state of decreased oxygen reaching the tissues of the body. During prenatal development, the fetus experiences localized occurrences of hypoxia that are essential for proper organogenesis and survival. The response to decreased oxygen availability is primarily regulated by hypoxia-inducible factors (HIFs), a family of transcription factors that modulate the expression of key genes involved in glycolysis, angiogenesis, and erythropoiesis. HIF-1α and HIF-2α, two key isoforms, are important in embryonic development, and likely are involved in lung morphogenesis. We have recently shown that the inducible loss of Hif-1α in lung epithelium starting at E4.5 leads to death within an hour of parturition, with symptoms similar to neonatal respiratory distress syndrome (RDS). In addition to Hif-1α, Hif-2α is also expressed in the developing lung, although the overlapping roles of Hif-1α and Hif-2α in this context are not fully understood. To further investigate the independent role of Hif-2α in lung epithelium and its ability to alter Hif-1α-mediated lung maturation, we generated two additional lung-specific inducible Hif-α knockout models (Hif-2α and Hif-1α+Hif-2α). The intrauterine loss of Hif-2α in the lungs does not lead to decreased viability or observable phenotypic changes in the lung. More interestingly, survivability observed after the loss of both Hif-1α and Hif-2α suggests that the loss of Hif-2α is capable of rescuing the neonatal RDS phenotype seen in Hif-1α-deficient pups. Microarray analyses of lung tissue from these three genotypes identified several factors, such as Scd1, Retlnγ, and Il-1r2, which are differentially regulated by the two HIF-α isoforms. Moreover, network analysis suggests that modulation of hormone-mediated, NF-κB, C/EBPα, and c-MYC signaling are central to HIF-mediated changes in lung development.

FIZZ1-induced myofibroblast transdifferentiation from adipocytes and its potential role in dermal fibrosis and lipoatrophy

Subcutaneous lipoatrophy characteristically accompanies dermal fibrosis with de novo emergence of myofibroblasts such as in systemic sclerosis or scleroderma. Recently dermal adipocytes were shown to have the capacity to differentiate to myofibroblasts in an animal model. Transforming growth factor β can induce this phenomenon in vitro; however its in vivo significance is unclear. Because found in inflammatory zone 1 (FIZZ1) is an inducer of myofibroblast differentiation but an inhibitor of adipocyte differentiation, we investigated its potential role in adipocyte transdifferentiation to myofibroblast in dermal fibrosis. FIZZ1 caused significant and rapid suppression of the expression of fatty acid binding protein 4 and peroxisome proliferator-activated receptor-γ in adipocytes, consistent with dedifferentiation with loss of lipid and Oil Red O staining. The suppression was accompanied subsequently with stimulation of α-smooth muscle actin and type I collagen expression, indicative of myofibroblast differentiation. In vivo FIZZ1 expression was significantly elevated in the murine bleomycin-induced dermal fibrosis model, which was associated with significant reduction in adipocyte marker gene expression and subcutaneous lipoatrophy. Finally, FIZZ1 knockout mice exhibited significantly reduced bleomycin-induced dermal fibrosis with greater preservation of the subcutaneous fat than wild-type mice. These findings suggested that the FIZZ1 induction of adipocyte transdifferentiation to myofibroblast might be a key pathogenic mechanism for the accumulation of myofibroblasts in dermal fibrosis.

Deoxynivalenol inhibits the expression by goblet cells of intestinal mucins through a PKR and MAP kinase dependent repression of the resistin-like molecule β

SCOPE

The food-associated mycotoxin deoxynivalenol (DON) is known to affect intestinal functions. However, its effect on intestinal mucus is poorly characterized.

METHODS AND RESULTS

We analyzed the effects of DON on human goblet cells (HT29-16E cells) and porcine intestinal explants. Results showed that subtoxic doses of DON (as low as 1 μM) decreased mucin (MUC) production. qPCR analysis demonstrated that this inhibition was due to a specific decrease in the level of mRNA encoding for the intestinal membrane-associated (MUC1) and the secreted MUCs (MUC2, MUC3). Mechanistic studies demonstrated that DON effect relied on the activation of the protein kinase R and the mitogen-activated protein kinase p38 ultimately leading to the inhibition of the expression of resistin-like molecule beta, a known positive regulator of MUC expression.

CONCLUSION

Taken together, our results show that at low doses found in food and feed, DON is able to affect the expression and production of MUCs by human and animal goblet cells. Due to the important role of MUCs in the barrier function and in the interaction of commensal bacteria with the host, such effect could explain the observed modifications in the microbial diversity and the increased susceptibility to enteric infection following exposure to DON.

Interleukin 13- and interleukin 17A-induced pulmonary hypertension phenotype due to inhalation of antigen and fine particles from air pollution

Pulmonary hypertension has a marked detrimental effect on quality of life and life expectancy. In a mouse model of antigen-induced pulmonary arterial remodeling, we have recently shown that coexposure to urban ambient particulate matter (PM) significantly increased the thickening of the pulmonary arteries and also resulted in significantly increased right ventricular systolic pressures. Here we interrogate the mechanism and show that combined neutralization of interleukin 13 (IL-13) and IL-17A significantly ameliorated the increase in right ventricular systolic pressure, the circumferential muscularization of pulmonary arteries, and the molecular change in the right ventricle. Surprisingly, our data revealed a protective role of IL-17A for the antigen- and PM-induced severe thickening of pulmonary arteries. This protection was due to the inhibition of the effects of IL-13, which drove this response, and the expression of metalloelastase and resistin-like molecule α. However, the latter was redundant for the arterial thickening response. Anti-IL-13 exacerbated airway neutrophilia, which was due to a resulting excess effect of IL-17A, confirming concurrent cross inhibition of IL-13- and IL-17A-dependent responses in the lungs of animals exposed to antigen and PM. Our experiments also identified IL-13/IL-17A-independent molecular reprogramming in the lungs induced by exposure to antigen and PM, which indicates a risk for arterial remodeling and protection from arterial constriction. Our study points to IL-13- and IL-17A-coinduced inflammation as a new template for biomarkers and therapeutic targeting for the management of immune response-induced pulmonary hypertension.

The role of inflammation in hypoxic pulmonary hypertension: from cellular mechanisms to clinical phenotypes

Hypoxic pulmonary hypertension (PH) comprises a heterogeneous group of diseases sharing the common feature of chronic hypoxia-induced pulmonary vascular remodeling. The disease is usually characterized by mild to moderate pulmonary vascular remodeling that is largely thought to be reversible compared with the progressive irreversible disease seen in World Health Organization (WHO) group I disease. However, in these patients, the presence of PH significantly worsens morbidity and mortality. In addition, a small subset of patients with hypoxic PH develop "out-of-proportion" severe pulmonary hypertension characterized by pulmonary vascular remodeling that is irreversible and similar to that in WHO group I disease. In all cases of hypoxia-related vascular remodeling and PH, inflammation, particularly persistent inflammation, is thought to play a role. This review focuses on the effects of hypoxia on pulmonary vascular cells and the signaling pathways involved in the initiation and perpetuation of vascular inflammation, especially as they relate to vascular remodeling and transition to chronic irreversible PH. We hypothesize that the combination of hypoxia and local tissue factors/cytokines ("second hit") antagonizes tissue homeostatic cellular interactions between mesenchymal cells (fibroblasts and/or smooth muscle cells) and macrophages and arrests these cells in an epigenetically locked and permanently activated proremodeling and proinflammatory phenotype. This aberrant cellular cross-talk between mesenchymal cells and macrophages promotes transition to chronic nonresolving inflammation and vascular remodeling, perpetuating PH. A better understanding of these signaling pathways may lead to the development of specific therapeutic targets, as none are currently available for WHO group III disease.

Inflammation and immunity in the pathogenesis of pulmonary arterial hypertension

This review summarizes an expanding body of knowledge indicating that failure to resolve inflammation and altered immune processes underlie the development of pulmonary arterial hypertension. The chemokines and cytokines implicated in pulmonary arterial hypertension that could form a biomarker platform are discussed. Pre-clinical studies that provide the basis for dysregulated immunity in animal models of the disease are reviewed. In addition, we present therapies that target inflammatory/immune mechanisms that are currently enrolling patients, and discuss others in development. We show how genetic and metabolic abnormalities are inextricably linked to dysregulated immunity and adverse remodeling in the pulmonary arteries.

Adventitial fibroblasts induce a distinct proinflammatory/profibrotic macrophage phenotype in pulmonary hypertension

Macrophage accumulation is not only a characteristic hallmark but is also a critical component of pulmonary artery remodeling associated with pulmonary hypertension (PH). However, the cellular and molecular mechanisms that drive vascular macrophage activation and their functional phenotype remain poorly defined. Using multiple levels of in vivo (bovine and rat models of hypoxia-induced PH, together with human tissue samples) and in vitro (primary mouse, rat, and bovine macrophages, human monocytes, and primary human and bovine fibroblasts) approaches, we observed that adventitial fibroblasts derived from hypertensive pulmonary arteries (bovine and human) regulate macrophage activation. These fibroblasts activate macrophages through paracrine IL-6 and STAT3, HIF1, and C/EBPβ signaling to drive expression of genes previously implicated in chronic inflammation, tissue remodeling, and PH. This distinct fibroblast-activated macrophage phenotype was independent of IL-4/IL-13-STAT6 and TLR-MyD88 signaling. We found that genetic STAT3 haplodeficiency in macrophages attenuated macrophage activation, complete STAT3 deficiency increased macrophage activation through compensatory upregulation of STAT1 signaling, and deficiency in C/EBPβ or HIF1 attenuated fibroblast-driven macrophage activation. These findings challenge the current paradigm of IL-4/IL-13-STAT6-mediated alternative macrophage activation as the sole driver of vascular remodeling in PH, and uncover a cross-talk between adventitial fibroblasts and macrophages in which paracrine IL-6-activated STAT3, HIF1α, and C/EBPβ signaling are critical for macrophage activation and polarization. Thus, targeting IL-6 signaling in macrophages by completely inhibiting C/EBPβ or HIF1α or by partially inhibiting STAT3 may hold therapeutic value for treatment of PH and other inflammatory conditions characterized by increased IL-6 and absent IL-4/IL-13 signaling.

Hypoxia-induced mitogenic factor (FIZZ1/RELMα) induces endothelial cell apoptosis and subsequent interleukin-4-dependent pulmonary hypertension

Pulmonary hypertension (PH) is characterized by elevated pulmonary artery pressure that leads to progressive right heart failure and ultimately death. Injury to endothelium and consequent wound repair cascades have been suggested to trigger pulmonary vascular remodeling, such as that observed during PH. The relationship between injury to endothelium and disease pathogenesis in this disorder remains poorly understood. We and others have shown that, in mice, hypoxia-induced mitogenic factor (HIMF, also known as FIZZ1 or RELMα) plays a critical role in the pathogenesis of lung inflammation and the development of PH. In this study, we dissected the mechanism by which HIMF and its human homolog resistin (hRETN) induce pulmonary endothelial cell (EC) apoptosis and subsequent lung inflammation-mediated PH, which exhibits many of the hallmarks of the human disease. Systemic administration of HIMF caused increases in EC apoptosis and interleukin (IL)-4-dependent vascular inflammatory marker expression in mouse lung during the early inflammation phase. In vitro, HIMF, hRETN, and IL-4 activated pulmonary microvascular ECs (PMVECs) by increasing angiopoietin-2 expression and induced PMVEC apoptosis. In addition, the conditioned medium from hRETN-treated ECs had elevated levels of endothelin-1 and caused significant increases in pulmonary vascular smooth muscle cell proliferation. Last, HIMF treatment caused development of PH that was characterized by pulmonary vascular remodeling and right heart failure in wild-type mice but not in IL-4 knockout mice. These data suggest that HIMF contributes to activation of vascular inflammation at least in part by inducing EC apoptosis in the lung. These events lead to subsequent PH.

Resistin-like molecule-β is induced following bronchoconstriction of asthmatic airways

BACKGROUND AND OBJECTIVE

Resistin-like molecule-β (RELM-β) is a necessary and sufficient stimulus for airway remodelling in animal models of asthma, but until recently, its role in human disease had not been investigated. The hypothesis that RELM-β expression would increase with increasing asthma severity and further increase following acute bronchoconstrictor challenges has been examined.

METHODS

Bronchial biopsies from healthy subjects and patients with mild and severe asthma were immunostained for RELM-β, as were airway biopsies obtained in mild asthmatics before and 4 days after repeated inhalation challenges with either allergen, methacholine or methacholine preceded by salbutamol as a control. Bronchial brushings were also evaluated for RELM-β mRNA.

RESULTS

RELM-β immunoreactivity, which co-localized to airway epithelial cells, increased with disease severity; healthy volunteers, median per cent epithelial area 1.98%, mild asthma 3.49% and severe asthma 5.89% (P < 0.001 between groups). RELM-β immunoreactivity significantly and inversely correlated in asthma with forced expiratory volume in 1 s % predicted (P = 0.005). Acute changes in immunoexpression were evident after repeated inhalation challenge with allergen (2.15 % to 4.35 % (P = 0.01)) and methacholine (4.21 % to 6.16 % (P = 0.01)) but did not change in the salbutamol/methacholine challenge group. These changes correlated with change in basement membrane thickness (r = 0.38, P = 0.02). Epithelial RELM-β gene expression was not altered in asthma.

CONCLUSIONS

RELM-β may play an important role not only in animal models of airway remodelling, but also in human airway pathology.

Hypoxia-induced mitogenic factor (HIMF/FIZZ1/RELMα) in chronic hypoxia- and antigen-mediated pulmonary vascular remodeling

Background

Both chronic hypoxia and allergic inflammation induce vascular remodeling in the lung, but only chronic hypoxia appears to cause PH. We investigate the nature of the vascular remodeling and the expression and role of hypoxia-induced mitogenic factor (HIMF/FIZZ1/RELMα) in explaining this differential response.

Methods

We induced pulmonary vascular remodeling through either chronic hypoxia or antigen sensitization and challenge. Mice were evaluated for markers of PH and pulmonary vascular remodeling throughout the lung vascular bed as well as HIMF expression and genomic analysis of whole lung.

Results

Chronic hypoxia increased both mean pulmonary artery pressure (mPAP) and right ventricular (RV) hypertrophy; these changes were associated with increased muscularization and thickening of small pulmonary vessels throughout the lung vascular bed. Allergic inflammation, by contrast, had minimal effect on mPAP and produced no RV hypertrophy. Only peribronchial vessels were significantly thickened, and vessels within the lung periphery did not become muscularized. Genomic analysis revealed that HIMF was the most consistently upregulated gene in the lungs following both chronic hypoxia and antigen challenge. HIMF was upregulated in the airway epithelial and inflammatory cells in both models, but only chronic hypoxia induced HIMF upregulation in vascular tissue.

Conclusions

The results show that pulmonary vascular remodeling in mice induced by chronic hypoxia or antigen challenge is associated with marked increases in HIMF expression. The lack of HIMF expression in the vasculature of the lung and no vascular remodeling in the peripheral resistance vessels of the lung is likely to account for the failure to develop PH in the allergic inflammation model.

Molecular pathogenesis of pulmonary arterial hypertension

Recent clinical and experimental studies are redefining the cellular and molecular bases of pulmonary arterial hypertension (PAH). The genetic abnormalities first identified in association with the idiopathic form of PAH--together with a vast increase in our understanding of cell signaling, cell transformation, and cell-cell interactions; gene expression; microRNA processing; and mitochondrial and ion channel function--have helped explain the abnormal response of vascular cells to injury. Experimental and clinical studies now converge on the intersection and interactions between a genetic predisposition involving the BMPR2 signaling pathway and an impaired metabolic and chronic inflammatory state in the vessel wall. These deranged processes culminate in an exuberant proliferative response that occludes the pulmonary arterial (PA) lumen and obliterates the most distal intraacinar vessels. Here, we describe emerging therapies based on preclinical studies that address these converging pathways.

Exosomes mediate the cytoprotective action of mesenchymal stromal cells on hypoxia-induced pulmonary hypertension

BACKGROUND

Hypoxia induces an inflammatory response in the lung manifested by alternative activation of macrophages with elevation of proinflammatory mediators that are critical for the later development of hypoxic pulmonary hypertension. Mesenchymal stromal cell transplantation inhibits lung inflammation, vascular remodeling, and right heart failure and reverses hypoxic pulmonary hypertension in experimental models of disease. In this study, we aimed to investigate the paracrine mechanisms by which mesenchymal stromal cells are protective in hypoxic pulmonary hypertension.

METHODS AND RESULTS

We fractionated mouse mesenchymal stromal cell-conditioned media to identify the biologically active component affecting in vivo hypoxic signaling and determined that exosomes, secreted membrane microvesicles, suppressed the hypoxic pulmonary influx of macrophages and the induction of proinflammatory and proproliferative mediators, including monocyte chemoattractant protein-1 and hypoxia-inducible mitogenic factor, in the murine model of hypoxic pulmonary hypertension. Intravenous delivery of mesenchymal stromal cell-derived exosomes (MEX) inhibited vascular remodeling and hypoxic pulmonary hypertension, whereas MEX-depleted media or fibroblast-derived exosomes had no effect. MEX suppressed the hypoxic activation of signal transducer and activator of transcription 3 (STAT3) and the upregulation of the miR-17 superfamily of microRNA clusters, whereas it increased lung levels of miR-204, a key microRNA, the expression of which is decreased in human pulmonary hypertension. MEX produced by human umbilical cord mesenchymal stromal cells inhibited STAT3 signaling in isolated human pulmonary artery endothelial cells, demonstrating a direct effect of MEX on hypoxic vascular cells.

CONCLUSION

This study indicates that MEX exert a pleiotropic protective effect on the lung and inhibit pulmonary hypertension through suppression of hyperproliferative pathways, including STAT3-mediated signaling induced by hypoxia.

Choosing the right antibody for resistin-like molecule (RELM/FIZZ) family members

The family of resistin-like molecules (RELM), also known as found in inflammatory zone (FIZZ), consists of four members in mouse (RELMα/FIZZ1/HIMF, RELMβ/FIZZ2, Resistin/FIZZ3, and RELMγ/FIZZ4) and two members in human (resistin and RELMβ). The importance of these proteins in many aspects of physiology and pathophysiology, especially inflammatory processes, is rapidly evolving in the literature, and many investigators are beginning to work in this field. Most published studies focus on only one isoform, do not evaluate other isoforms that might be present, and have not tested for the specificity of the antibody used. Because RELM isoforms have high sequence and structural similarity and both distinct and overlapping functions, it is important to use a specific antibody to distinguish each isoform in the study. We constructed and established HEK 293 cell lines that constitutively express each isoform. Using these cell lines, we determined the specificity of antibodies (both commercially available and laboratory-made) to each isoform by Western blot and immunofluorescence. Some of the antibodies showed specificity in Western blotting but were not applicable in immunofluorescence. Others showed cross reactivity in Western blot assays. Our results indicate that RELM antibody specificity should be taken into account when using them in research and interpreting data obtained with them.

Pertussis toxin exacerbates and prolongs airway inflammatory responses during Bordetella pertussis infection

Throughout infection, pathogenic bacteria induce dramatic changes in host transcriptional repertoires. An understanding of how bacterial factors influence host reprogramming will provide insight into disease pathogenesis. In the human respiratory pathogen Bordetella pertussis, the causative agent of whooping cough, pertussis toxin (PT) is a key virulence factor that promotes colonization, suppresses innate immune responses during early infection, and causes systemic disease symptoms. To determine the full extent of PT-associated gene regulation in the airways through the peak of infection, we measured global transcriptional profiles in the lungs of BALB/c mice infected with wild-type (WT) or PT-deficient (ΔPT) B. pertussis. ΔPT bacteria were inoculated at a dose equivalent to the WT dose and at a high dose (ΔPT(high)) to distinguish effects caused by higher bacterial loads achieved in WT infection from effects associated with PT. The results demonstrated that PT was associated with a significant upregulation of immune and inflammatory response genes as well as several other genes implicated in airway pathology. In contrast to the early, transient responses observed for ΔPT(high) infection, WT infection induced a prolonged expression of inflammatory genes and increased the extent and duration of lung histopathology. In addition, the administration of purified PT to ΔPT(high)-infected mice 1 day after bacterial inoculation exacerbated and prolonged inflammatory responses and airway pathology. These data indicate that PT not only is associated with exacerbated host airway responses during peak B. pertussis infection but also may inhibit host mechanisms of attenuating and resolving inflammation in the airways, suggesting possible links between PT and pertussis disease symptoms.

Effects of resistin-like molecule β over-expression on gastric cancer cells in vitro

AIM: To investigate the effects of resistin-like molecule β (RELMβ) over-expression on the invasion, metastasis and angiogenesis of gastric cancer cells.

METHODS: Human RELMβ encoding expression vector was constructed and transfected into the RELMβ lowly-expressed gastric cancer cell lines SGC-7901 and MKN-45. Gene expression was measured by Western blotting, reverse transcription polymerase chain reaction (PCR) and real-time quantitative PCR. Cell proliferation was measured by 2-(4,5-dimethyltriazol-2-yl)-2,5-diphenyl tetrazolium bromide colorimetry, colony formation and 5-ethynyl-20-deoxyuridine incorporation assays. The in vitro migration, invasion and metastasis of cancer cells were measured by cell adhesion assay, scratch assay and matrigel invasion assay. The angiogenic capabilities of cancer cells were measured by tube formation of endothelial cells.

RESULTS: Transfection of RELMβ vector into SGC-7901 and MKN-45 cells resulted in over-expression of RELMβ, which did not influence the cellular proliferation. However, over-expression of RELMβ suppressed the in vitro adhesion, invasion and metastasis of cancer cells, accompanied by decreased expression of matrix metalloproteinase-2 (MMP-2) and MMP-9. Moreover, transfection of RELMβ attenuated the expression of vascular endothelial growth factor and in vitro angiogenic capabilities of cancer cells.

CONCLUSION: Over-expression of RELMβ abolishes the invasion, metastasis and angiogenesis of gastric cancer cells in vitro, suggesting its potentials as a novel therapeutic target for gastric cancer.

FIZZ2/RELM-β induction and role in pulmonary fibrosis

Found in inflammatory zone (FIZZ) 2, also known as resistin-like molecule (RELM)-β, belongs to a novel cysteine-rich secreted protein family named FIZZ/RELM. Its function is unclear, but a closely related family member, FIZZ1, has profibrotic activities. The human ortholog of rodent FIZZ1 has not been identified, but human FIZZ2 has significant sequence homology to both rodent FIZZ2 (59%) and FIZZ1 (50%). Given the greater homology to rodent FIZZ2, analyzing the role of FIZZ2 in a rodent model of bleomycin-induced pulmonary fibrosis would be of greater potential relevance to human fibrotic lung disease. The results showed that FIZZ2 was highly induced in lungs of rodents with bleomycin-induced pulmonary fibrosis and of human patients with idiopathic pulmonary fibrosis. FIZZ2 expression was induced in rodent and human lung epithelial cells by Th2 cytokines, which was mediated via STAT6 signaling. The FIZZ2 induction in murine lungs was found to be essential for pulmonary fibrosis, as FIZZ2 deficiency significantly suppressed pulmonary fibrosis and associated enhanced extracellular matrix and cytokine gene expression. In vitro analysis indicated that FIZZ2 could stimulate type I collagen and α-smooth muscle actin expression in lung fibroblasts. Furthermore, FIZZ2 was shown to have chemoattractant activity for bone marrow (BM) cells, especially BM-derived CD11c(+) dendritic cells. Notably, lung recruitment of BM-derived cells was impaired in FIZZ2 knockout mice. These findings suggest that FIZZ2 is a Th2-associated multifunctional mediator with potentially important roles in the pathogenesis of fibrotic lung diseases.

Plexiform lesions in pulmonary arterial hypertension composition, architecture, and microenvironment

Pulmonary arterial hypertension (PAH) is a debilitating disease with a high mortality rate. A hallmark of PAH is plexiform lesions (PLs), complex vascular formations originating from remodeled pulmonary arteries. The development and significance of these lesions have been debated and are not yet fully understood. Some features of PLs resemble neoplastic disorders, and there is a striking resemblance to glomeruloid-like lesions (GLLs) in glioblastomas. To further elucidate PLs, we used in situ methods, such as (fluorescent) IHC staining, three-dimensional reconstruction, and laser microdissection, followed by mRNA expression analysis. We generated compartment-specific expression patterns in the lungs of 25 patients (11 with PAH associated with systemic shunts, 6 with idiopathic PAH, and 8 controls) and GLLs from 5 glioblastomas. PLs consisted of vascular channels lined by a continuously proliferating endothelium and backed by a uniform myogenic interstitium. They also showed up-regulation of remodeling-associated genes, such as HIF1a, TGF-β1, VEGF-α, VEGFR-1/-2, Ang-1, Tie-2, and THBS1, but also of cKIT and sprouting-associated markers, such as NOTCH and matrix metalloproteinases. The cellular composition and signaling seen in GLLs in neural neoplasms differed significantly from those in PLs. In conclusion, PLs show a distinct cellular composition and microenvironment, which contribute to the plexiform phenotype and set them apart from other processes of vascular remodeling in patients with PAH. Neoplastic models of angiogenesis seem to be of limited use in further study of plexiform vasculopathy.

Early macrophage recruitment and alternative activation are critical for the later development of hypoxia-induced pulmonary hypertension

BACKGROUND

Lung inflammation precedes the development of hypoxia-induced pulmonary hypertension (HPH); however, its role in the pathogenesis of HPH is poorly understood. We sought to characterize the hypoxic inflammatory response and to elucidate its role in the development of HPH. We also aimed to investigate the mechanisms by which heme oxygenase-1, an anti-inflammatory enzyme, is protective in HPH.

METHODS AND RESULTS

We generated bitransgenic mice that overexpress human heme oxygenase-1 under doxycycline control in an inducible, lung-specific manner. Hypoxic exposure of mice in the absence of doxycycline resulted in early transient accumulation of monocytes/macrophages in the bronchoalveolar lavage. Alveolar macrophages acquired an alternatively activated phenotype (M2) in response to hypoxia, characterized by the expression of found in inflammatory zone-1, arginase-1, and chitinase-3-like-3. A brief 2-day pulse of doxycycline delayed, but did not prevent, the peak of hypoxic inflammation, and could not protect against HPH. In contrast, a 7-day doxycycline treatment sustained high heme oxygenase-1 levels during the entire period of hypoxic inflammation, inhibited macrophage accumulation and activation, induced macrophage interleukin-10 expression, and prevented the development of HPH. Supernatants from hypoxic M2 macrophages promoted the proliferation of pulmonary artery smooth muscle cells, whereas treatment with carbon monoxide, a heme oxygenase-1 enzymatic product, abrogated this effect.

CONCLUSIONS

Early recruitment and alternative activation of macrophages in hypoxic lungs are critical for the later development of HPH. Heme oxygenase-1 may confer protection from HPH by effectively modifying the macrophage activation state in hypoxia.

Pulmonary Arterial Hypertension-A Deadly Complication of Systemic Sclerosis

Pulmonary arterial hypertension (PAH) is a devastating disease with limited therapeutic options. Moreover, when PAH occurs in patients diagnosed with systemic sclerosis, worse outcomes are observed. The purpose of this review is to discuss the etiologies of PAH found in the systemic sclerosis patient, limitations of current medical therapies, and, finally, potential therapies for patients with this combination.

Hypoxia-induced mitogenic factor/FIZZ1 induces intracellular calcium release through the PLC-IP(3) pathway

Hypoxia-induced mitogenic factor (HIMF), also known as "found in inflammatory zone 1" (FIZZ1) or resistin-like molecule-alpha (RELMalpha), is a profound vasoconstrictor of the pulmonary circulation and a strong mitogenic factor in pulmonary vascular smooth muscle. To further understand the mechanism of these contractile and mitogenic responses, we examined the effect of HIMF on intracellular Ca(2+) in human pulmonary artery smooth muscle cells (SMC). Ca(2+) imaging in fluo 4-loaded human pulmonary artery SMC revealed that recombinant murine HIMF increased intracellular Ca(2+) concentration ([Ca(2+)](i)) in a sustained and oscillatory manner. This increase occurred independent of extracellular Ca(2+) influx. Pretreatment of human pulmonary artery SMC with U-73122, a specific inhibitor of phosphatidylinositol-phospholipase C (PLC) completely prevented the HIMF-induced Ca(2+) signal. The [Ca(2+)](i) increase was also abolished by pretreatment with 2-aminoethoxydiphenyl borate (2-APB), an inositol 1,4,5-trisphosphate (IP(3)) receptor antagonist. Ryanodine pretreatment did not affect initiation of [Ca(2+)](i) activation or internal release but reduced [Ca(2+)](i) at the plateau phase. Pretreatment with the Galpha(i)-specific inhibitor pertussis toxin and the Galpha(s)-specific inhibitor NF-449 did not block the Ca(2+) signal. Knockdown of Galpha(q/11) expression did not prevent Ca(2+) release, but the pattern of Ca(2+) release changed from the sustained oscillatory transients with prolonged plateau to a series of short [Ca(2+)](i) transients that return to baseline. However, pretreatment with the tyrosine kinase inhibitor genistein completely inhibited the internal Ca(2+) release. These results demonstrate that HIMF can stimulate intracellular Ca(2+) release in human pulmonary artery SMC through the PLC signaling pathway in an IP(3)- and tyrosine phosphorylation-dependent manner and that Galpha(q/11) protein-coupled receptor and ryanodine receptor contribute to the increase of [Ca(2+)](i).