Hypoxia-induced mitogenic factor has proangiogenic and proinflammatory effects in the lung via VEGF and VEGF receptor-2

Resistin Pathway as Novel Mechanism of Post-lung Transplantation Bronchial Stenosis

BACKGROUND

Bronchial stenosis remains a significant source of morbidity among lung transplant recipients. Though infection and anastomotic ischemia have been proposed etiologies of the development of bronchial stenosis, the pathophysiologic mechanism has not been well elucidated.

METHODS

In this single-centered prospective study, from January 2013 through September 2015, we prospectively collected bronchoalveolar lavage (BAL) and endobronchial epithelial brushings from the direct anastomotic site of bronchial stenosis of bilateral lung transplant recipients who developed unilateral post-transplant bronchial stenosis. Endobronchial epithelial brushings from the contralateral anastomotic site without bronchial stenosis and BAL from bilateral lung transplant recipients who did not develop post-transplant bronchial stenosis were used as controls. Total RNA was isolated from the endobronchial brushings and real-time polymerase chain reaction reactions were performed. Electrochemiluminescence biomarker assay was used to measure 10 cytokines from the BAL.

RESULTS

Out of 60 bilateral lung transplant recipients, 9 were found to have developed bronchial stenosis with 17 samples adequate for analysis. We observed a 1.56 to 70.8 mean-fold increase in human resistin gene expression in the anastomotic bronchial stenosis epithelial cells compared with nonstenotic airways. Furthermore, IL-1β (21.76±10.96 pg/mL; control 0.86±0.44 pg/mL; P <0.01) and IL-8 levels (990.56±326.60 pg/mL; control 20.33±1.17 pg/mL; P <0.01) were significantly elevated in the BAL of the lung transplant patients who developed anastomotic bronchial stenosis.

CONCLUSION

Our data suggest that the development of postlung transplantation bronchial stenosis may be in part mediated through the human resistin pathway by IL-1β induced transcription factor nuclear factor-κβ activation and downstream upregulation of IL-8 in alveolar macrophages. Further study is needed in the larger patient cohorts and to determine its potential therapeutic role in the management of post-transplant bronchial stenosis.

In the Search for Biomarkers of Pulmonary Arterial Hypertension, Are Cytokines IL-2, IL-4, IL-6, IL-10, and IFN-Gamma the Right Indicators to Use?

Pulmonary arterial hypertension (PAH) is a complex disorder characterized by increased pressure in the pulmonary arteries, leading to right heart failure. While the exact mechanisms underlying PAH are not fully understood, cytokines have been implicated in the pathogenesis of the disease. Cytokines play a crucial role in regulating immune responses and inflammation. These small proteins also play a key role in shaping the immunophenotype, which refers to the specific characteristics and functional properties of immune cells, which can have a significant impact on the development of PAH. The aim of this study was to determine the immunophenotype and the concentration of selected cytokines, IL-2, IL-4, IL-6, IL-10, and IFN-gamma, in patients diagnosed with PAH (with particular emphasis on subtypes) in relation to healthy volunteers. Based on the obtained results, we can conclude that in patients with PAH, the functioning of the immune system is deregulated as a result of a decrease in the percentage of selected subpopulations of immune cells in peripheral blood and changes in the concentration of tested cytokines in relation to healthy volunteers. In addition, a detailed analysis showed that there are statistically significant differences between the PAH subtypes and the tested immunological parameters. This may indicate a significant role of the immune system in the pathogenesis of PAH.

Resistin-like Molecule α and Pulmonary Vascular Remodeling: A Multi-Strain Murine Model of Antigen and Urban Ambient Particulate Matter Co-Exposure

Pulmonary hypertension (PH) has a high mortality and few treatment options. Adaptive immune mediators of PH in mice challenged with antigen/particulate matter (antigen/PM) has been the focus of our prior work. We identified key roles of type-2- and type-17 responses in C57BL/6 mice. Here, we focused on type-2-response-related cytokines, specifically resistin-like molecule (RELM)α, a critical mediator of hypoxia-induced PH. Because of strain differences in the immune responses to type 2 stimuli, we compared C57BL/6J and BALB/c mice. A model of intraperitoneal antigen sensitization with subsequent, intranasal challenges with antigen/PM (ovalbumin and urban ambient PM2.5) or saline was used in C57BL/6 and BALB/c wild-type or RELMα-/- mice. Vascular remodeling was assessed with histology; right ventricular (RV) pressure, RV weights and cytokines were quantified. Upon challenge with antigen/PM, both C57BL/6 and BALB/c mice developed pulmonary vascular remodeling; these changes were much more prominent in the C57BL/6 strain. Compared to wild-type mice, RELMα-/- had significantly reduced pulmonary vascular remodeling in BALB/c, but not in C57BL/6 mice. RV weights, RV IL-33 and RV IL-33-receptor were significantly increased in BALB/c wild-type mice, but not in BALB/c-RELMα-/- or in C57BL/6-wild-type or C57BL/6-RELMα-/- mice in response to antigen/PM2.5. RV systolic pressures (RVSP) were higher in BALB/c compared to C57BL/6J mice, and RELMα-/- mice were not different from their respective wild-type controls. The RELMα-/- animals demonstrated significantly decreased expression of RELMβ and RELMγ, which makes these mice comparable to a situation where human RELMβ levels would be significantly modified, as only humans have this single RELM molecule. In BALB/c mice, RELMα was a key contributor to pulmonary vascular remodeling, increase in RV weight and RV cytokine responses induced by exposure to antigen/PM2.5, highlighting the significance of the genetic background for the biological role of RELMα.

Ythdf2 promotes pulmonary hypertension by suppressing Hmox1-dependent anti-inflammatory and antioxidant function in alveolar macrophages

Pulmonary hypertension (PH) is a devastating disease characterized by irreversible pulmonary vascular remodeling (PVR) that causes right ventricular failure and death. The early alternative activation of macrophages is a critical event in the development of PVR and PH, but the underlying mechanisms remain elusive. Previously we have shown that N⁶-methyladenosine (m⁶A) modifications of RNA contribute to phenotypic switching of pulmonary artery smooth muscle cells and PH. In the current study, we identify Ythdf2, an m⁶A reader, as an important regulator of pulmonary inflammation and redox regulation in PH. In a mouse model of PH, the protein expression of Ythdf2 was increased in alveolar macrophages (AMs) during the early stages of hypoxia. Mice with a myeloid specific knockout of Ythdf2 (Ythdf2^{Lyz2 Cre}) were protected from PH with attenuated right ventricular hypertrophy and PVR compared to control mice and this was accompanied by decreased macrophage polarization and oxidative stress. In the absence of Ythdf2, heme oxygenase 1 (Hmox1) mRNA and protein expression were significantly elevated in hypoxic AMs. Mechanistically, Ythdf2 promoted the degradation of Hmox1 mRNA in a m⁶A dependent manner. Furthermore, an inhibitor of Hmox1 promoted macrophage alternative activation, and reversed the protection from PH seen in Ythdf2^{Lyz2 Cre} mice under hypoxic exposure. Together, our data reveal a novel mechanism linking m⁶A RNA modification with changes in macrophage phenotype, inflammation and oxidative stress in PH, and identify Hmox1 as a downstream target of Ythdf2, suggesting that Ythdf2 may be a therapeutic target in PH.

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.

LKB1 deficiency upregulates RELM-α to drive airway goblet cell metaplasia

Targeting airway goblet cell metaplasia is a novel strategy that can potentially reduce the chronic obstructive pulmonary disease (COPD) symptoms. Tumor suppressor liver kinase B1 (LKB1) is an important regulator of the proliferation and differentiation of stem/progenitor cells. In this study, we report that LKB1 expression was downregulated in the lungs of patients with COPD and in those of cigarette smoke-exposed mice. Nkx2.1^Cre; Lkb1^f/f mice with conditional loss of Lkb1 in mouse lung epithelium displayed airway mucus hypersecretion and pulmonary macrophage infiltration. Single-cell transcriptomic analysis of the lung tissues from Nkx2.1^Cre; Lkb1^f/f mice further revealed that airway goblet cell differentiation was altered in the absence of LKB1. An organoid culture study demonstrated that Lkb1 deficiency in mouse airway (club) progenitor cells promoted the expression of FIZZ1/RELM-α, which drove airway goblet cell differentiation and pulmonary macrophage recruitment. Additionally, monocyte-derived macrophages in the lungs of Nkx2.1^Cre; Lkb1^f/f mice exhibited an alternatively activated M2 phenotype, while expressing RELM-α, which subsequently aggravated airway goblet cell metaplasia. Our findings suggest that the LKB1-mediated crosstalk between airway progenitor cells and macrophages regulates airway goblet cell metaplasia. Moreover, our data suggest that LKB1 agonists might serve as a potential therapeutic option to treat respiratory disorders associated with goblet cell metaplasia.

Role of the Immune System Elements in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a relatively rare disease, but, today, its incidence tends to increase. The severe course of the disease and poor patient survival rate make PAH a major diagnostic and therapeutic challenge. For this reason, a thorough understanding of the pathogenesis of the disease is essential to facilitate the development of more effective therapeutic targets. Research shows that the development of PAH is characterized by a number of abnormalities within the immune system that greatly affect the progression of the disease. In this review, we present key data on the regulated function of immune cells, released cytokines and immunoregulatory molecules in the development of PAH, to help improve diagnosis and targeted immunotherapy.

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.

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 adipokine Retnla deficiency increases responsiveness to cardiac repair through adiponectin-rich bone marrow cells

Resistin-like alpha (Retnla) is a member of the resistin family and known to modulate fibrosis and inflammation. Here, we investigated the role of Retnla in the cardiac injury model. Myocardial infarction (MI) was induced in wild type (WT), Retnla knockout (KO), and Retnla transgenic (TG) mice. Cardiac function was assessed by echocardiography and was significantly preserved in the KO mice, while worsened in the TG group. Angiogenesis was substantially increased in the KO mice, and cardiomyocyte apoptosis was markedly suppressed in the KO mice. By Retnla treatment, the expression of p21 and the ratio of Bax to Bcl2 were increased in cardiomyocytes, while decreased in cardiac fibroblasts. Interestingly, the numbers of cardiac macrophages and unsorted bone marrow cells (UBCs) were higher in the KO mice than in the WT mice. Besides, phosphorylated histone H3(+) cells were more frequent in bone marrow of KO mice. Moreover, adiponectin in UBCs was notably higher in the KO mice compared with WT mice. In an adoptive transfer study, UBCs were isolated from KO mice to transplant to the WT infarcted heart. Cardiac function was better in the KO-UBCs transplanted group in the WT-UBCs transplanted group. Taken together, proliferative and adiponectin-rich bone marrow niche was associated with substantial cardiac recovery by suppression of cardiac apoptosis and proliferation of cardiac fibroblast.

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.

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.

Systemic evaluation and localization of resistin expression in normal human tissues by a newly developed monoclonal antibody

Resistin and resistin-like molecules are pleiotropic cytokines that are involved in inflammatory diseases. Our previous work suggested that resistin has the potential to be used as a biomarker and therapeutic target for human pulmonary arterial hypertension. However, data are limited on the distribution of resistin in healthy human organs. In this study, we used our newly developed anti-human resistin (hResistin) antibody to immunohistochemically detect the expression, localization, and intracellular/extracellular compartmentalization of hResistin in a full human tissue panel from healthy individuals. The potential cross reactivity of this monoclonal anti-hResistin IgG1 with normal human tissues also was verified. Results showed that hResistin is broadly distributed and principally localized in the cytoplasmic granules of macrophages scattered in the interstitium of most human tissues. Bone marrow hematopoietic precursor cells also exhibited hResistin signals in their cytoplasmic granules. Additionally, hResistin labeling was observed in the cytoplasm of nervous system cells. Notably, the cytokine activity of hResistin was illustrated by positively stained extracellular material in most human tissues. These data indicate that our generated antibody binds to the secreted hResistin and support its potential use for immunotherapy to reduce circulating hResistin levels in human disease. Our findings comprehensively document the basal expression patterns of hResistin protein in normal human tissues, suggest a critical role of this cytokine in normal and pathophysiologic inflammatory processes, and offer key insights for using our antibody in future pharmacokinetic studies and immunotherapeutic strategies.

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.

Hypoxia-inducible factor-1 α deletion in myeloid lineage attenuates hypoxia-induced pulmonary hypertension

Hypoxemia is seen in patients with pulmonary hypertension and hypoxic pulmonary vasoconstriction worsens their clinical condition. However, vasoconstriction is not the only aspect through which hypoxia induces the progression to pulmonary hypertension. Hypoxia‐inducible factor‐1α (HIF‐1α) is a transcription factor responding to hypoxic conditions by regulating hundreds of genes involved in angiogenesis, erythropoiesis, inflammation, and proliferation. We sought to determine the contribution of HIF‐1α in myeloid lineage cells to the pulmonary vascular response to chronic exposure to hypoxia. We generated myeloid‐specific HIF‐1α knockout (MyeHIF1KO) mice by using Cre‐lox P system, and exposed them to hypoxic conditions for 3 weeks to induce pulmonary hypertension. Macrophages from MyeHIF1KO and control mice were used for western blotting, RT‐qPCR, chemotaxis assay, and ATP assay. MyeHIF1KO mice exposed to hypoxia for 3 weeks exhibited a significant reduction in the right ventricular systolic pressure accompanied by a decrease in the ratio of the right ventricular weight to left ventricular weight, muscularization of the small pulmonary arteries, and infiltration of macrophages into the lung and right ventricle compared with control mice. HIF‐1α‐deficient peritoneal macrophages showed less migration toward monocyte chemoattractant protein‐1 and a decrease in intracellular ATP levels. These results indicate that HIF‐1α in macrophages contributes to the progression of pulmonary vascular remodeling and pulmonary hypertension induced by chronic exposure to hypoxic conditions. The inhibition of myeloid‐specific HIF‐1α may be a novel therapeutic strategy for the treatment of pulmonary hypertension.

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.

HIMF (Hypoxia-Induced Mitogenic Factor) Signaling Mediates the HMGB1 (High Mobility Group Box 1)-Dependent Endothelial and Smooth Muscle Cell Crosstalk in Pulmonary Hypertension

OBJECTIVE

HIMF (hypoxia-induced mitogenic factor; also known as FIZZ1 [found in inflammatory zone-1] or RELM [resistin-like molecule-α]) is an etiological factor of pulmonary hypertension (PH) in rodents, but its underlying mechanism is unclear. We investigated the immunomodulatory properties of HIMF signaling in PH pathogenesis. Approach and Results: Gene-modified mice that lacked HIMF (KO [knockout]) or overexpressed HIMF human homolog resistin (hResistin) were used for in vivo experiments. The pro-PH role of HIMF was verified in HIMF-KO mice exposed to chronic hypoxia or sugen/hypoxia. Mechanistically, HIMF/hResistin activation triggered the HMGB1 (high mobility group box 1) pathway and RAGE (receptor for advanced glycation end products) in pulmonary endothelial cells (ECs) of hypoxic mouse lungs in vivo and in human pulmonary microvascular ECs in vitro. Treatment with conditioned medium from hResistin-stimulated human pulmonary microvascular ECs induced an autophagic response, BMPR2 (bone morphogenetic protein receptor 2) defects, and subsequent apoptosis-resistant proliferation in human pulmonary artery (vascular) smooth muscle cells in an HMGB1-dependent manner. These effects were confirmed in ECs and smooth muscle cells isolated from pulmonary arteries of patients with idiopathic PH. HIMF/HMGB1/RAGE-mediated autophagy and BMPR2 impairment were also observed in pulmonary artery (vascular) smooth muscle cells of hypoxic mice, effects perhaps related to FoxO1 (forkhead box O1) dampening by HIMF. Experiments in EC-specific hResistin-overexpressing transgenic mice confirmed that EC-derived HMGB1 mediated the hResistin-driven pulmonary vascular remodeling and PH.

CONCLUSIONS

In HIMF-induced PH, HMGB1-RAGE signaling is pivotal for mediating EC-smooth muscle cell crosstalk. The humanized mouse data further support clinical implications for the HIMF/HMGB1 signaling axis and indicate that hResistin and its downstream pathway may constitute targets for the development of novel anti-PH therapeutics in humans.

EXPRESS: Gremlin1 blocks vascular endothelial growth factor signalling in the pulmonary microvascular endothelium

The bone morphogenetic protein (BMP) antagonist gremlin 1 plays a central role in the pathogenesis of hypoxic pulmonary hypertension (HPH). Recently, non-canonical functions of gremlin 1 have been identified, including specific binding to the vascular endothelial growth factor receptor-2 (VEGFR2). We tested the hypothesis that gremlin 1 modulates VEGFR2 signaling in the pulmonary microvascular endothelium.

We examined the effect of gremlin 1 haploinsufficiency on the expression of VEGF responsive genes and proteins in the hypoxic (10% O2) murine lung in vivo. Using human microvascular endothelial cells in vitro we examined the effect of gremlin 1 on VEGF signaling.

Gremlin 1 haploinsufficiency (Grem1+/–) attenuated the hypoxia-induced increase in gremlin 1 observed in the wild-type mouse lung. Reduced gremlin 1 expression in hypoxic Grem1+/– mice restored VEGFR2 expression and endothelial nitric oxide synthase (eNOS) expression and activity to normoxic values. Recombinant monomeric gremlin 1 inhibited VEGFA-induced VEGFR2 activation, downstream signaling, and VEGF-induced increases in Bcl-2, cell number, and the anti-apoptotic effect of VEGFA in vitro.

These results show that the monomeric form of gremlin 1 acts as an antagonist of VEGFR2 activation in the pulmonary microvascular endothelium. Given the previous demonstration that inhibition of VEGFR2 causes marked worsening of HPH, our results suggest that increased gremlin 1 in the hypoxic lung, in addition to blocking BMP receptor type-2 (BMPR2) signaling, contributes importantly to the development of PH by a non-canonical VEGFR2 blocking activity.

Role of the HIF-1 signaling pathway in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is the most common cause of chronic morbidity and mortality. However, the molecular mechanisms underlying COPD remain largely unknown. The purpose of the present study was to investigate the expression patterns of hypoxia-inducible factor 1α (HIF-1α), vascular endothelial growth factor (VEGF), and VEGF receptor 2 (R2) in regard to the HIF-1 signaling pathway in COPD. The expressions of HIF-1α, VEGF and VEGFR2 were examined and quantified in the human lung tissues of 102 subjects with a defined smoking status, with or without COPD. The expressions of HIF-1α, VEGF and VEGFR2 were observed to be increased in the lung tissues collected from smoking COPD subjects when compared with those tissues from smoking subjects without COPD and non-smoking subjects without COPD. The expression of HIF-1α was shown to be positively associated with the expression of VEGF and VEGFR2. In addition, increased expression of HIF-1α, VEGF and VEGFR2 reflected the disease severity of COPD. The key findings obtained from the present study indicated that high expression of HIF-1α, VEGF and VEGFR2 may be associated with decreased lung function and reduced quality of life, contributing to disease progression in COPD.

Hypoxia-Induced Mitogenic Factor Promotes Cardiac Hypertrophy via Calcium-Dependent and Hypoxia-Inducible Factor-1α Mechanisms

HIMF (hypoxia-induced mitogenic factor/found in inflammatory zone 1/resistin like α) is a secretory and cytokine-like protein and serves as a critical stimulator of hypoxia-induced pulmonary hypertension. With a role for HIMF in heart disease unknown, we explored the possible roles for HIMF in cardiac hypertrophy by overexpressing and knocking down HIMF in cardiomyocytes and characterizing HIMF gene (himf) knockout mice. We found that HIMF mRNA and protein levels were upregulated in phenylephrine-stimulated cardiomyocyte hypertrophy and our mouse model of transverse aortic constriction-induced cardiac hypertrophy, as well as in human hearts with dilated cardiomyopathy. Furthermore, HIMF overexpression could induce cardiomyocyte hypertrophy, as characterized by elevated protein expression of hypertrophic biomarkers (ANP [atrial natriuretic peptide] and β-MHC [myosin heavy chain-β]) and increased cell-surface area compared with controls. Conversely, HIMF knockdown prevented phenylephrine-induced cardiomyocyte hypertrophy and himf ablation in knockout mice significantly attenuated transverse aortic constriction-induced hypertrophic remodeling and cardiac dysfunction. HIMF overexpression increased the cytosolic Ca²⁺ concentration and activated the CaN-NFAT (calcineurin-nuclear factor of activated T cell) and MAPK (mitogen-activated protein kinase) pathways; this effect could be prevented by reducing cytosolic Ca²⁺ concentration with L-type Ca²⁺ channel blocker nifedipine or inhibiting the CaSR (Ca²⁺ sensing receptor) with Calhex 231. Furthermore, HIMF overexpression increased HIF-1α (hypoxia-inducible factor) expression in neonatal rat ventricular myocytes, and HIMF knockout inhibited HIF-1α upregulation in transverse aortic constriction mice. Knockdown of HIF-1α attenuated HIMF-induced cardiomyocyte hypertrophy. In conclusion, HIMF has a critical role in the development of cardiac hypertrophy, and targeting HIMF may represent a potential therapeutic strategy.

Here, there and everywhere: Resistin-like molecules in infection, inflammation, and metabolic disorders

The Resistin-Like Molecules (RELM) α, β, and γ and their namesake, resistin, share structural and sequence homology but exhibit significant diversity in expression and function within their mammalian host. RELM proteins are expressed in a wide range of diseases, such as: microbial infections (eg. bacterial and helminth), inflammatory diseases (eg. asthma, fibrosis) and metabolic disorders (eg. diabetes). While the expression pattern and molecular regulation of RELM proteins are well characterized, much controversy remains over their proposed functions, with evidence of host-protective and pathogenic roles. Moreover, the receptors for RELM proteins are unclear, although three receptors for resistin, decorin, adenylyl cyclase-associated protein 1 (CAP1), and Toll-like Receptor 4 (TLR4) have recently been proposed. In this review, we will first summarize the molecular regulation of the RELM gene family, including transcription regulation and tissue expression in humans and mouse disease models. Second, we will outline the function and receptor-mediated signaling associated with RELM proteins. Finally, we will discuss recent studies suggesting that, despite early misconceptions that these proteins are pathogenic, RELM proteins have a more nuanced and potentially beneficial role for the host in certain disease settings.

Pulmonary hypertensive vasculopathy in parenchymal lung diseases and/or hypoxia: Number 1 in the Series "Pathology for the clinician" Edited by Peter Dorfmüller and Alberto Cavazza

Pulmonary hypertension (PH) with complicating chronic lung diseases and/or hypoxia falls into group 3 of the updated classification of PH. Patients with chronic obstructive lung disease (COPD), diffuse lung disease (such as idiopathic pulmonary fibrosis (IPF)) and with sleep disordered breathing are particularly exposed to the risk of developing PH. Although PH in such a context is usually mild, a minority of patients exhibit severe haemodynamic impairment, defined by a mean pulmonary arterial pressure (mPAP) of ≥35 mmHg or mPAP values ranging between 25 mmHg and 35 mmHg with a low cardiac index (<2 L·min^-1·m^-2). The overlap between lung parenchymal disease and PH heavily affects life expectancy in such a patient population and complicates their therapeutic management. In this review we illustrate the pathological features and the underlying pathophysiological mechanisms of pulmonary circulation in chronic lung diseases, with an emphasis on COPD, IPF and obstructive sleep apnoea syndrome.

Hypoxia-Induced Mitogenic Factor Acts as a Nonclassical Ligand of Calcium-Sensing Receptor, Therapeutically Exploitable for Intermittent Hypoxia-Induced Pulmonary Hypertension

Hypoxia-induced mitogenic factor (HIMF) is an inflammatory cytokine playing important role(s) in the development of hypoxic pulmonary hypertension. The molecular target mediating HIMF-stimulated downstream events remains unclear. The coimmunoprecipitation screen identified extracellular calcium-sensing receptor (CaSR) as the binding partner for HIMF in pulmonary artery smooth muscle cells. The yeast 2-hybrid assay then revealed the binding of HIMF to the intracellular, not the extracellular, domain of extracellular CaSR. The binding of HIMF enhanced the activity of extracellular CaSR and mediated hypoxia-evoked proliferation of pulmonary artery smooth cells and the development of pulmonary vascular remodeling and pulmonary hypertension, all of which was specifically attenuated by a synthesized membrane-permeable peptide flanking the core amino acids of the intracellular binding domain of extracellular CaSR. Thus, HIMF induces pulmonary hypertension as a nonclassical ligand of extracellular CaSR, and the binding motif of extracellular CaSR can be therapeutically exploitable.

Molecular mechanisms of pulmonary response progression in crystalline silica exposed rats

An understanding of the mechanisms underlying diseases is critical for their prevention. Excessive exposure to crystalline silica is a risk factor for silicosis, a potentially fatal pulmonary disease. Male Fischer 344 rats were exposed by inhalation to crystalline silica (15 mg/m³, six hours/day, five days) and pulmonary response was determined at 44 weeks following termination of silica exposure. Additionally, global gene expression profiling in lungs and BAL cells and bioinformatic analysis of the gene expression data were done to understand the molecular mechanisms underlying the progression of pulmonary response to silica. A significant increase in lactate dehydrogenase activity and albumin content in BAL fluid (BALF) suggested silica-induced pulmonary toxicity in the rats. A significant increase in the number of alveolar macrophages and infiltrating neutrophils in the lungs and elevation in monocyte chemoattractant protein-1 (MCP-1) in BALF suggested the induction of pulmonary inflammation in the silica exposed rats. Histological changes in the lungs included granuloma formation, type II pneumocyte hyperplasia, thickening of alveolar septa and positive response to Masson's trichrome stain. Microarray analysis of global gene expression detected 94 and 225 significantly differentially expressed genes in the lungs and BAL cells, respectively. Bioinformatic analysis of the gene expression data identified significant enrichment of several disease and biological function categories and canonical pathways related to pulmonary toxicity, especially inflammation. Taken together, these data suggested the involvement of chronic inflammation as a mechanism underlying the progression of pulmonary response to exposure of rats to crystalline silica at 44 weeks following termination of exposure.

Pulmonary toxicity and global gene expression changes in response to sub-chronic inhalation exposure to crystalline silica in rats

Exposure to crystalline silica results in serious adverse health effects, most notably, silicosis. An understanding of the mechanism(s) underlying silica-induced pulmonary toxicity is critical for the intervention and/or prevention of its adverse health effects. Rats were exposed by inhalation to crystalline silica at a concentration of 15 mg/m³, 6 hr/day, 5 days/week for 3, 6 or 12 weeks. Pulmonary toxicity and global gene expression profiles were determined in lungs at the end of each exposure period. Crystalline silica was visible in lungs of rats especially in the 12-week group. Pulmonary toxicity, as evidenced by an increase in lactate dehydrogenase (LDH) activity and albumin content and accumulation of macrophages and neutrophils in the bronchoalveolar lavage (BAL), was seen in animals depending upon silica exposure duration. The most severe histological changes, noted in the 12-week exposure group, consisted of chronic active inflammation, type II pneumocyte hyperplasia, and fibrosis. Microarray analysis of lung gene expression profiles detected significant differential expression of 38, 77, and 99 genes in rats exposed to silica for 3-, 6-, or 12-weeks, respectively, compared to time-matched controls. Among the significantly differentially expressed genes (SDEG), 32 genes were common in all exposure groups. Bioinformatics analysis of the SDEG identified enrichment of functions, networks and canonical pathways related to inflammation, cancer, oxidative stress, fibrosis, and tissue remodeling in response to silica exposure. Collectively, these results provided insights into the molecular mechanisms underlying pulmonary toxicity following sub-chronic inhalation exposure to crystalline silica in rats.

Metronomic cyclophosphamide activation of anti-tumor immunity: tumor model, mouse host, and drug schedule dependence of gene responses and their upstream regulators

Background

Cyclophosphamide (CPA) can activate immunogenic tumor cell death, which induces immune-based tumor ablation and long-term anti-tumor immunity in a syngeneic C57BL/6 (B6) mouse GL261 glioma model when CPA is given on a 6-day repeating metronomic schedule (CPA/6d). In contrast, we find that two other syngeneic B6 mouse tumors, LLC lung carcinoma and B16F10 melanoma, do not exhibit these drug-induced immune responses despite their intrinsic sensitivity to CPA cytotoxicity.

Methods

To elucidate underlying mechanisms, we investigated gene expression and molecular pathway changes associated with the disparate immune responsiveness of these tumors to CPA/6d treatment.

Results

Global transcriptome analysis indicated substantial elevation of basal GL261 immune infiltration and strong CPA/6d activation of GL261 immune stimulatory pathways and their upstream regulators, but without preferential depletion of negative immune regulators compared to LLC and B16F10 tumors. In LLC tumors, where CPA/6d treatment is shown to be anti-angiogenic, CPA/6d suppressed VEGFA target genes and down regulated cell adhesion and leukocyte transendothelial migration genes. In GL261 tumors implanted in adaptive immune-deficient scid mice, where CPA/6d-induced GL261 regression is incomplete and late tumor growth rebound can occur, T cell receptor signaling and certain cytokine-cytokine receptor responses seen in B6 mice were deficient. Extending the CPA treatment interval from 6 to 9 days (CPA/9d) − which results in a strong but transient natural killer cell response followed by early tumor growth rebound − induced fewer cytokines and increased expression of drug metabolism genes.

Conclusions

These findings elucidate molecular response pathways activated by intermittent metronomic CPA treatment and identify deficiencies that characterize immune-unresponsive tumor models and drug schedules.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2597-2) contains supplementary material, which is available to authorized users.

Role Of Hif2α Oxygen Sensing Pathway In Bronchial Epithelial Club Cell Proliferation

Oxygen-sensing pathways executed by the hypoxia-inducible factors (HIFs) induce a cellular adaptive program when oxygen supply becomes limited. However, the role of the HIF oxygen-sensing pathway in the airway response to hypoxic stress in adulthood remains poorly understood. Here we found that in vivo exposure to hypoxia led to a profound increase in bronchial epithelial cell proliferation mainly confined to Club (Clara) cells. Interestingly, this response was executed by hypoxia-inducible factor 2α (HIF2α), which controls the expression of FoxM1, a recognized proliferative factor of Club cells. Furthermore, HIF2α induced the expression of the resistin-like molecules α and β (RELMα and β), previously considered bronchial epithelial growth factors. Importantly, despite the central role of HIF2α, this proliferative response was not initiated by in vivo Vhl gene inactivation or pharmacological inhibition of prolyl hydroxylase oxygen sensors, indicating the molecular complexity of this response and the possible participation of other oxygen-sensing pathways. Club cells are principally involved in protection and maintenance of bronchial epithelium. Thus, our findings identify a novel molecular link between HIF2α and Club cell biology that can be regarded as a new HIF2α-dependent mechanism involved in bronchial epithelium adaptation to oxygen fluctuations.

Resistin-Like Molecule α in Allergen-Induced Pulmonary Vascular Remodeling

Resistin-like molecule α (RELMα) has mitogenic, angiogenic, vasoconstrictive, and chemokine-like properties and is highly relevant in lung pathology. Here, we used RELMα knockout (Retnla(-/-)) mice to investigate the role of RELMα in pulmonary vascular remodeling after intermittent ovalbumin (OVA) challenge. We compared saline- and OVA-exposed wild-type (WT) mice and found that OVA induced significant increases in right ventricular systolic pressure, cardiac hypertrophy, pulmonary vascular remodeling of intra-alveolar arteries, goblet cell hyperplasia in airway epithelium, and intensive lung inflammation, especially perivascular inflammation. Genetic ablation of Retnla prevented the OVA-induced increase in pulmonary pressure and cardiac hypertrophy seen in WT mice. Histological analysis showed that Retnla(-/-) mice exhibited less vessel muscularization, less perivascular inflammation, reduced medial thickness of intra-alveolar vessels, and fewer goblet cells in upper airway epithelium (250-600 μm) than did WT animals after OVA challenge. Gene expression profiles showed that genes associated with vascular remodeling, including those related to muscle protein, contractile fibers, and actin cytoskeleton, were expressed at a lower level in OVA-challenged Retnla(-/-) mice than in similarly treated WT mice. In addition, bronchoalveolar lavage from OVA-challenged Retnla(-/-) mice had lower levels of cytokines, such as IL-1β, -1 receptor antagonist, and -16, chemokine (C-X-C motif) ligand 1, -2, -9, -10, and -13, monocyte chemoattractant protein-1, macrophage colony-stimulating factor, TIMP metallopeptidase inhibitor-1, and triggering receptor expressed on myeloid cells-1, than did that from WT mice when analyzed by cytokine array dot blots. Retnla knockout inhibited the OVA-induced T helper 17 response but not the T helper 2 response. Altogether, our results suggest that RELMα is involved in immune response-induced pulmonary vascular remodeling and the associated increase in inflammation typically observed after OVA challenge.

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.

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.

High expression of RELM-α correlates with poor prognosis and promotes angiogenesis in gastric cancer

Accumulating evidence indicates that resistin-like molecule-α (RELM-α) is involved in angiogenesis, while the clinical significance and the exact role of RELM-α in gastric cancer remain obscure. The aim of the present study was to evaluate the clinical significance of RELM-α in gastric cancer, and to investigate its effective mechanisms in order to identify a potential therapeutic target. The expression levels of RELM-α in 92 gastric cancer and adjacent normal tissues were investigated and the relationship between RELM-α expression and the clinicopathological characteristics was explored. To investigate the potential role of RELM-α in gastric cancer cell biological behavior, the cell proliferation, migration and invasion assays were conducted using two gastric cancer cell lines (SGC7901 and MKN45). We also assessed whether RELM-α gene silencing modulates angiogenesis using small interference RNA in cancer cell lines, and investigated its effect on nuclear factor (NF)-κB activation and vascular endothelial growth factor (VEGF) and MMP-9 expression. Contrasting sharply with the strong RELM-α-positive tumors, adjacent normal tissues and cell lines exhibited negative or weakly positive expression (P<0.01). High expression level of RELM-α was associated with advanced stage and tumor size (P<0.01). The silencing of RELM-α expression by Ad5/F35-siRNA treatment significantly inhibited cell migratory and invasive ability in SGC7901 and MKN45 gastric cancer cells compared with the control and Ad5/F35 vector-transfected cell lines (P<0.01). However, the silencing of RELM-α expression also significantly blocked NF-κB activation and attenuated VEGF and MMP-9 expression. The data demonstrated that RELM-α is a promising novel biomarker of angiogenesis in patients with gastric cancer. The study identified that the silencing of RELM-α expression may regulate the proliferation, invasion and migration of gastric cancer cells by targeting VEGF/MMP-9, and the mechanism involved tissue angiogenesis via the NF-κB signaling pathway.

Retnla overexpression attenuates allergic inflammation of the airway

Resistin-like molecule alpha (Retnla), also known as ‘Found in inflammatory zone 1’, is a secreted protein that has been found in bronchoalveolar lavage (BAL) fluid of ovalbumin (OVA)-induced asthmatic mice and plays a role as a regulator of T helper (Th)2-driven inflammation. However, the role of Retnla in the progress of Th2-driven airway inflammation is not yet clear. To better understand the function of Retnla in Th2-driven airway inflammation, we generated Retnla-overexpressing (Retnla-Tg) mice. Retnla-Tg mice showed increased expression of Retnla protein in BAL fluid and airway epithelial cells. Retnla overexpression itself did not induce any alteration in lung histology or lung function compared to non-Tg controls. However, OVA-sensitized/challenged Retnla-Tg mice had decreased numbers of cells in BAL and inflammatory cells accumulating in the lung. They also showed a reduction in mucus production in the airway epithelium, concomitant with a decreased Muc5ac level. These results were accompanied by reduced levels of Th2 cytokines, including interleukin (IL)-4, IL-5, and IL-13, with no effect on levels of OVA-specific immunoglobulin isotypes. Furthermore, phosphorylation of ERK was markedly reduced in the lungs of OVA-challenged Retnla-Tg mice. Taken together, these results indicates that Retnla protects against Th2-mediated inflammation in an experimental mouse model of asthma, suggesting that therapeutic approaches to enhance the production of Retnla or Retnla-like molecules could be valuable for preventing allergic lung inflammation.

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.

Activation of VCAM-1 and its associated molecule CD44 leads to increased malignant potential of breast cancer cells

VCAM-1 (CD106), a transmembrane glycoprotein, was first reported to play an important role in leukocyte adhesion, leukocyte transendothelial migration and cell activation by binding to integrin VLA-1 (α4β1). In the present study, we observed that VCAM-1 expression can be induced in many breast cancer epithelial cells by cytokine stimulation in vitro and its up-regulation directly correlated with advanced clinical breast cancer stage. We found that VCAM-1 over-expression in the NMuMG breast epithelial cells controls the epithelial and mesenchymal transition (EMT) program to increase cell motility rates and promote chemoresistance to doxorubicin and cisplatin in vitro. Conversely, in the established MDAMB231 metastatic breast cancer cell line, we confirmed that knockdown of endogenous VCAM-1 expression reduced cell proliferation and inhibited TGFβ1 or IL-6 mediated cell migration, and increased chemosensitivity. Furthermore, we demonstrated that knockdown of endogenous VCAM-1 expression in MDAMB231 cells reduced tumor formation in a SCID xenograft mouse model. Signaling studies showed that VCAM-1 physically associates with CD44 and enhances CD44 and ABCG2 expression. Our findings uncover the possible mechanism of VCAM-1 activation facilitating breast cancer progression, and suggest that targeting VCAM-1 is an attractive strategy for therapeutic intervention.

FIZZ1 promotes airway remodeling through the PI3K/Akt signaling pathway in asthma

Found in inflammatory zone 1 (FIZZ1) plays a vital role in pulmonary inflammation and angiogenesis. In addition, FIZZ1 plays a role in the early stages of airway remodeling in asthma by increasing the expression of α smooth muscle actin (α-SMA) and type I collagen. However, the role of FIZZ1 in the airway remodeling of asthma remains unclear. In the present study, FIZZ1 was identified to be upregulated in ovalbumin (OVA)-induced asthmatic mice, along with phosphorylated protein kinase B (Akt). Following FIZZ1 recombinant protein co-culture in the murine lung epithelial-cell line, Akt phosphorylation was upregulated, however, following transfection with FIZZ1-small hairpin RNA, the phosphorylation levels were decreased. The variation in α-SMA and type I collagen expression levels was consistent with the Akt phosphorylation levels. Intratracheal administration of LY294002 and Akt inhibitor IV to the asthmatic mice was capable of reducing airway inflammation, downregulating the expression of α-SMA, type I collagen and fibronectin-1 and increasing the expression of E-cadherin. In conclusion, the present study demonstrated that FIZZ1 promoted airway remodeling in asthma via the phosphoinositide 3-kinase (PI3K)/Akt signaling pathway. Blocking the PI3K/Akt signaling pathway may attenuate the early stages of airway remodeling induced by OVA by regulating the abnormal process of epithelial-mesenchymal transition.

The in vivo fibrotic role of FIZZ1 in pulmonary fibrosis

FIZZ (found in inflammatory zone) 1, a member of a cysteine-rich secreted protein family, is highly induced in lung allergic inflammation and bleomycin induced lung fibrosis, and primarily expressed by airway and type II alveolar epithelial cells. This novel mediator is known to stimulate α-smooth muscle actin and collagen expression in lung fibroblasts. The objective of this study was to investigate the in vivo effects of FIZZ1 on the development of lung fibrosis by evaluating bleomycin-induced pulmonary fibrosis in FIZZ1 deficient mice. FIZZ1 knockout mice exhibited no detectable abnormality. When these mice were treated with bleomycin they exhibited significantly impaired pulmonary fibrosis relative to wild type mice, along with impaired proinflammatory cytokine/chemokine expression. Deficient lung fibroblast activation was also noted in the FIZZ1 knockout mice. Moreover, recruitment of bone marrow-derived cells to injured lung was deficient in FIZZ1 knockout mice. Interestingly in vitro FIZZ1 was shown to have chemoattractant activity for bone marrow cells, including bone marrow-derived dendritic cells. Finally, overexpression of FIZZ1 exacerbated fibrosis. These findings suggested that FIZZ1 exhibited profibrogenic properties essential for bleomycin induced pulmonary fibrosis, as reflected by its ability to induce myofibroblast differentiation and recruit bone marrow-derived cells.

Physiological and pathological angiogenesis in the adult pulmonary circulation

Angiogenesis occurs during growth and physiological adaptation in many systemic organs, for example, exercise-induced skeletal and cardiac muscle hypertrophy, ovulation, and tissue repair. Disordered angiogenesis contributes to chronic inflammatory disease processes and to tumor growth and metastasis. Although it was previously thought that the adult pulmonary circulation was incapable of supporting new vessel growth, over that past 10 years new data have shown that angiogenesis within this circulation occurs both during physiological adaptive processes and as part of the pathogenic mechanisms of lung diseases. Here we review the expression of vascular growth factors in the adult lung, their essential role in pulmonary vascular homeostasis and the changes in their expression that occur in response to physiological challenges and in disease. We consider the evidence for adaptive neovascularization in the pulmonary circulation in response to alveolar hypoxia and during lung growth following pneumonectomy in the adult lung. In addition, we review the role of disordered angiogenesis in specific lung diseases including idiopathic pulmonary fibrosis, acute adult distress syndrome and both primary and metastatic tumors of the lung. Finally, we examine recent experimental data showing that therapeutic enhancement of pulmonary angiogenesis has the potential to treat lung diseases characterized by vessel loss.

Deferoxamine preconditioning potentiates mesenchymal stem cell homing in vitro and in streptozotocin-diabetic rats

OBJECTIVE

Today, cell therapy is considered a promising alternative in treatment of several diseases such as type 1 diabetes. Loss of transplanted stem cell and more importantly scarcity in the number of cells reaching to target tissue is a major obstacle in cell therapy. There is evidences showing that deferoxamine (DFO), an iron chelator, increases the mobilization and homing of progenitor cells through increasing the stability of hypoxia-inducible factor 1α (HIF-1α) protein. In this study, the effect of DFO on some factors involved in homing of bone marrow-derived mesenchymal stem cell was investigated, and the other objectives of this research were to determine whether DFO is able to increase migration and subsequent homing of mesenchymal stem cell (MSCs) both in vitro and in vivo in streptozotocin-diabetic rats.

RESEARCH DESIGN AND METHODS

MSCs were treated by DFO in minimal essential medium α (αMEM) for 24 h. The expression and localization of HIF-1α were evaluated by western blotting and immunocytochemistry. The expression of C-X-C chemokine receptor type 4 (CXCR-4) and chemokine receptor 2 (CCR2) were assessed by western blotting and RT-PCR. The activity of matrix metalloproteinases (MMP) -2 and -9 were measured by gelatin zymography. Finally, in vitro migration of MSCs toward different concentrations of stromal cell-derived factor and monocyte chemotactic protein-1 were also evaluated. To demonstrate the homing of MSCs in vivo, DFO-treated chloromethyl-benzamidodialkylcarbocyanine-labeled MSCs were injected into the tail vein of rats, and the number of stained MSCs reaching to the pancreas were determined after 24 h.

RESULTS

In DFO-treated MSCs, expression of HIF-1α (p < 0.001), CXCR4 (p < 0.001), CCR2 (p < 0.001), and the activity of MMP-2 (p < 0.01) and MMP-9 (p < 0.05) were significantly increased compared to control groups. Elevation of HIF-1α, upregulation of CXCR4/CCR2 and higher activity of MMP-2/MMP-9 in DFO-treated MSCs were reversed by 2-methoxyestradiol (2-ME; 5 μmol), a HIF-1α inhibitor. The in vitro migrations as well as in vivo homing of DFO-treated MSCs were also significantly higher than control groups (p < 0.05).

CONCLUSIONS

Preconditioning of MSCs by DFO prior to transplantation could increase homing of MSCs through affecting some chemokine receptors as well as proteases involved and eventually improving the efficacy of cell therapy.

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.

Exercise training attenuated chronic cigarette smoking-induced up-regulation of FIZZ1/RELMα in lung of rats

FIZZ/RELM is a new gene family named "found in inflammatory zone" (FIZZ) or "resistin-like molecule" (RELM). FIZZ1/RELMα is specifically expressed in lung tissue and associated with pulmonary inflammation. Chronic cigarette smoking up-regulates FIZZ1/RELMα expression in rat lung tissues, the mechanism of which is related to cigarette smoking-induced airway hyperresponsiveness. To investigate the effect of exercise training on chronic cigarette smoking-induced airway hyperresponsiveness and up-regulation of FIZZ1/RELMα, rat chronic cigarette smoking model was established. The rats were treated with regular exercise training and their airway responsiveness was measured. Hematoxylin and eosin (HE) staining, immunohistochemistry and in situ hybridization of lung tissues were performed to detect the expression of FIZZ1/RELMα. Results revealed that proper exercise training decreased airway hyperresponsiveness and pulmonary inflammation in rat chronic cigarette smoking model. Cigarette smoking increased the mRNA and protein levels of FIZZ1/RELMα, which were reversed by the proper exercise. It is concluded that proper exercise training prevents up-regulation of FIZZ1/RELMα induced by cigarette smoking, which may be involved in the mechanism of proper exercise training modulating airway hyperresponsiveness.

The role of hypoxia in pulmonary vascular diseases: a perspective

From the discovery of hypoxic pulmonary vasoconstriction, responses to hypoxia have been considered as representative for the many alterations in lung vessels that occur in several chronic lung diseases, including pulmonary hypertension, interstitial pulmonary fibrosis, acute respiratory distress syndrome, and chronic obstructive pulmonary disease. An essential part of preclinical research to explain the pathobiology of these diseases has been centered on the exposure of small and large animals to hypoxia. This review aims to summarize pivotal results of clinical and preclinical research on hypoxia, which still have important implications for researchers today.

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.

Nuclear factor erythroid 2-related factor 2 nuclear translocation induces myofibroblastic dedifferentiation in idiopathic pulmonary fibrosis

AIMS

Oxidants have been implicated in the pathophysiology of idiopathic pulmonary fibrosis (IPF), especially in myofibroblastic differentiation. We aimed at testing the hypothesis that nuclear factor erythroid 2-related factor 2 (Nrf2), the main regulator of endogenous antioxidant enzymes, is involved in fibrogenesis via myofibroblastic differentiation. Fibroblasts were cultured from the lungs of eight controls and eight IPF patients. Oxidants-antioxidants balance, nuclear Nrf2 expression, and fibroblast phenotype (α-smooth muscle actin and collagen I expression, proliferation, migration, and contraction) were studied under basal conditions and after Nrf2 knockdown or activation by Nrf2 or Keap1 siRNA transfection. The effects of sulforaphane (SFN), an Nrf2 activator, on the fibroblast phenotype were tested under basal and pro-fibrosis conditions (transforming growth factor β [TGF-β]).

RESULTS

Decreased Nrf2 expression was associated with a myofibroblast phenotype in IPF compared with control fibroblasts. Nrf2 knockdown induced oxidative stress and myofibroblastic differentiation in control fibroblasts. Conversely, Nrf2 activation increased antioxidant defences and myofibroblastic dedifferentation in IPF fibroblasts. SFN treatment decreased oxidants, and induced Nrf2 expression, antioxidants, and myofibroblastic dedifferentiation in IPF fibroblasts. SFN inhibited TGF-β profibrotic deleterious effects in IPF and control fibroblasts and restored antioxidant defences. Nrf2 knockdown abolished SFN antifibrosis effects, suggesting that they were Nrf2 mediated.

INNOVATION AND CONCLUSION

Our findings confirm that decreased nuclear Nrf2 plays a role in myofibroblastic differentiation and that SFN induces human pulmonary fibroblast dedifferentiation in vitro via Nrf2 activation. Thus, Nrf2 could be a novel therapeutic target in IPF.

Hypoxia-induced inflammation in the lung: a potential therapeutic target in acute lung injury?

Acute lung injury (ALI) is a severe form of hypoxic lung disease responsible for a large number of deaths worldwide. Despite recent advances in supportive care, no reduction in mortality has been evident since the introduction of a standard consensus definition almost two decades ago. New strategies are urgently required to help design effective therapies for this condition. A key pathological feature of ALI involves regional alveolar hypoxia. Because alveolar hypoxia in isolation, such as that encountered at high altitude, causes an inflammatory pulmonary phenotype in the absence of any other pathogenic stimuli, these regions may not be passive bystanders but may actually contribute to the pathogenesis and progression of lung injury. Unique transcriptional responses to hypoxia in the lung apparently allow it to express an inflammatory phenotype at levels of hypoxia that would not produce such a response in other organs. We will review recent advances in our understanding of these unique transcriptional responses to moderate levels of alveolar hypoxia, which may provide new insights into the pathogenesis of ALI.

Resistin-like molecule α stimulates proliferation of mesenchymal stem cells while maintaining their multipotency

Resistin-like molecule α (RELMα) is highly upregulated in the lungs of mice subjected to hypoxia. It is secreted from pulmonary epithelium and causes potent mitogenic, angiogenic, and vasoconstrictive effects in the lung vasculature. By using bone marrow transplantation in mice, we previously showed that RELMα is able to increase the number of bone marrow-derived cells in lung tissue, especially in the remodeling pulmonary vasculature. The current study investigated the effect of RELMα on progenitor stem cell content in mouse lung. Hypoxia, while stimulating RELMα expression, caused an increase in the number of Sca1(+)/CD45(-) progenitor cells in lungs of wild-type mice, but not in lungs of RELMα knockout mice. An in vitro study with cultured mesenchymal stem cells (MSCs) showed that RELMα induced a robust proliferative response that was dependent on Phosphatidylinositol 3-kinase/Akt and Erk activation. RELMα treatment of MSCs caused upregulation of a large number of genes involved in cell cycle, mitosis, organelle, and cytoskeleton biogenesis, and DNA metabolism. MSCs cultured in RELMα-supplemented media were able to maintain their differentiation potential into adipogenic, osteogenic, or mesenchymal phenotypes, although adipogenic differentiation was partially inhibited. These results demonstrate that RELMα may be involved in stem cell proliferation in the lung, without affecting differentiation potential.

A therapeutic role for mesenchymal stem cells in acute lung injury independent of hypoxia-induced mitogenic factor

Bone marrow mesenchymal stem cells (BM-MSCs) have therapeutic potential in acute lung injury (ALI). Hypoxia-induced mitogenic factor (HIMF) is a lung-specific growth factor that participates in a variety of lung diseases. In this study, we evaluated the therapeutic role of BM-MSC transplantation in lipopolysaccharide (LPS)- induced ALI and assessed the importance of HIMF in MSC transplantation. MSCs were isolated and identified, and untransduced MSCs, MSCs transduced with null vector or MSCs transduced with a vector encoding HIMF were transplanted into mice with LPS-induced ALI. Histopathological changes, cytokine expression and indices of lung inflammation and lung injury were assessed in the various experimental groups. Lentiviral transduction did not influence the biological features of MSCs. In addition, transplantation of BM-MSCs alone had significant therapeutic effects on LPS-induced ALI, although BM-MSCs expressing HIMF failed to improve the histopathological changes observed with lung injury. Unexpectedly, tumour necrosis factor α levels in lung tissues, lung oedema and leucocyte infiltration into lungs were even higher after the transplantation of MSCs expressing HIMF, followed by a significant increase in lung hydroxyproline content and α-smooth muscle actin expression on day 14, as compared to treatment with untransduced MSCs. BM-MSC transplantation improved LPS-induced lung injury independent of HIMF.

The suppressive effects of Bursopentine (BP5) on oxidative stress and NF-ĸB activation in lipopolysaccharide-activated murine peritoneal macrophages

BACKGROUND/AIM

Bursopentine (BP5) is a novel thiol-containing pentapeptide isolated from chicken bursa of Fabricius, and is reported to exert immunomodulatory effects on B and T lymphocytes. It has been found that some thiol compounds, such as glutathione (GSH) and N-acetylcysteine (NAC) protect living cells from oxidative stress. This led us to investigate whether BP5 had any ability to protect macrophages from oxidative stress as well as any mechanism that might underlie this process.

METHODS

Murine peritoneal macrophages activated by lipopolysaccharide (LPS) (2 μg/ml) were treated with single bouts (0, 25, 50, and 100 μM) of BP5.

RESULTS

BP5 potently suppressed the markers for oxidative stress, including nitric oxide (NO), reactive oxygen species (ROS), lipid peroxidation, and protein oxidation. It also decreased the expression and activity of inducible nitric oxide synthase (iNOS) and promoted a protective antioxidant state by elevating GSH content and by activating the expression and activity of certain key antioxidant and redox enzymes, including glutathione peroxidase (GPx), glutathione reductase (GR), superoxide dismutase (SOD) and catalase (CAT). This suppressive effect on oxidative stress was accompanied by down-regulated expression and activity of nuclear factor kappa B (NF-κB).

CONCLUSION

These findings demonstrate that BP5 can protect LPS-activated murine peritoneal macrophages from oxidative stress. BP5 may have applications as an anti-oxidative stress reagent.

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.