Resistin-like molecule-β is a human airway remodelling mediator

Bronchial epithelial transcriptomics and experimental validation reveal asthma severity-related neutrophilc signatures and potential treatments

Airway epithelial transcriptome analysis of asthma patients with different severity was used to disentangle the immune infiltration mechanisms affecting asthma exacerbation, which may be advantageous to asthma treatment. Here we introduce various bioinformatics methods and develop two models: an OVA/CFA-induced neutrophil asthma mouse model and an LPS-induced human bronchial epithelial cell damage model. Our objective is to investigate the molecular mechanisms, potential targets, and therapeutic strategies associated with asthma severity. Multiple bioinformatics methods identify meaningful differences in the degree of neutrophil infiltration in asthma patients with different severity. Then, PTPRC, TLR2, MMP9, FCGR3B, TYROBP, CXCR1, S100A12, FPR1, CCR1 and CXCR2 are identified as the hub genes. Furthermore, the mRNA expression of 10 hub genes is determined in vivo and in vitro models. Reperixin is identified as a pivotal drug targeting CXCR1, CXCR2 and MMP9. We further test the potential efficiency of Reperixin in 16HBE cells, and conclude that Reperixin can attenuate LPS-induced cellular damage and inhibit the expression of them. In this study, we successfully identify and validate several neutrophilic signatures and targets associated with asthma severity. Notably, Reperixin displays the ability to target CXCR1, CXCR2, and MMP9, suggesting its potential therapeutic value for managing deteriorating asthma.

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.

Effects of human adipose tissue- and bone marrow-derived mesenchymal stem cells on airway inflammation and remodeling in a murine model of chronic asthma

It is challenging to overcome difficult-to-treat asthma, and cell-based therapies are attracting increasing interest. We assessed the effects of mesenchymal stem cell (MSC) treatments using a murine model of chronic ovalbumin (OVA)-challenged asthma. We developed a murine model of chronic allergic asthma using OVA sensitization and challenge. Human adipose-derived MSCs (hADSCs) or human bone marrow-derived MSCs (hBMSCs) were administered. We measured the levels of resistin-like molecule-β (RELM-β). We also measured RELM-β in asthma patients and normal controls. OVA-challenged mice exhibited increased airway hyper-responsiveness, inflammation, and remodeling. hBMSC treatment remarkably decreased airway hyper-responsiveness but hADSC treatment did not. Both MSCs alleviated airway inflammation, but hBMSCs tended to have a more significant effect. hBMSC treatment reduced Th2-cytokine levels but hADSC treatment did not. Both treatments reduced airway remodeling. The RELM-β level decreased in the OVA-challenged control group, but increased in both treatment groups. We found that the serum level of RELM-β was lower in asthma patients than controls. MSC treatments alleviated the airway inflammation, hyper-responsiveness, and remodeling associated with chronic asthma. hBMSCs were more effective than hADSCs. The RELM-β levels increased in both treatment groups; the RELM-β level may serve as a biomarker of MSC treatment efficacy.

Regulatory Peptides in Asthma

Numerous regulatory peptides play a critical role in the pathogenesis of airway inflammation, airflow obstruction and hyperresponsiveness, which are hallmarks of asthma. Some of them exacerbate asthma symptoms, such as neuropeptide Y and tachykinins, while others have ameliorating properties, such as nociception, neurotensin or β-defensin 2. Interacting with peptide receptors located in the lungs or on immune cells opens up new therapeutic possibilities for the treatment of asthma, especially when it is resistant to available therapies. This article provides a concise review of the most important and current findings regarding the involvement of regulatory peptides in asthma pathology.

Resistin: A journey from metabolism to cancer

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Resistin levels have been associated with several pathological disorders such as metabolic disorders, cancers etc.

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Resistin exists in three isoforms namely RELM-α, β and γ.

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High resistin level activates inflammatory pathways, promotes metabolic disorders and is associated with carcinogenesis.

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Increase in the resistin level impairs the therapeutic response by inducing stemness or resistance, in cancer cells.

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Conventional drugs which alter resistin level could have therapeutic implications in several pathological disorders.

Resistin, a small secretory molecule, has been implicated to play an important role in the development of insulin resistance under obese condition. For the past few decades, it has been linked to various cellular and metabolic functions. It has been associated with diseases like metabolic disorders, cardiovascular diseases and cancers. Numerous clinical studies have indicated an increased serum resistin level in pathological disorders which have been reported to increase mortality rate in comparison to low resistin expressing subjects. Various molecular studies suggest resistin plays a pivotal role in proliferation, metastasis, angiogenesis, inflammation as well as in regulating metabolism in cancer cells. Therefore, understanding the role of resistin and elucidating its’ associated molecular mechanism will give a better insight into the management of these disorders. In this article, we summarize the diverse roles of resistin in pathological disorders based on the available literature, clinicopathological data, and a compiled study from various databases. The article mainly provides comprehensive information of its role as a target in different treatment modalities in pre as well as post-clinical studies.

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.

Investigating resistin like beta (RETNLB) as a tumor promoter for oral squamous cell carcinoma

BACKGROUND

Oral cavity cancer ranks the sixth most common malignancy worldwide, of which oral squamous cell carcinoma is the predominant type. This study aimed to investigate the function and the underlying mechanism of resistin like beta (RETNLB) in oral squamous cell carcinoma.

METHODS

The data of oral squamous cell carcinoma samples from The Cancer Genome Atlas database was used to examine RETNLB expression and assess its correlation with the clinical outcomes. Biological functions of RETNLB on the growth, invasion and migration of cells were determined by cell counting kit 8, clonogenic growth, and Transwell assays. Gene set enrichment analysis was utilized to identify the important gene sets associated with RETNLB expression, which was further confirmed by western blot.

RESULTS

We found that RETNLB was upregulated in oral squamous cell carcinoma tissues and cells. High expression of RETNLB was closely linked to age and pathological tumor, and significantly related to poor survival of oral squamous cell carcinoma patients. Further functional experiments showed that knockdown of RETNLB significantly reduced the viability, mobility and invasiveness of cells. Moreover, gene set enrichment analysis suggested that Toll-like receptor signaling pathway was significantly correlated with high RETNLB expression. Further western blot analysis verified that silencing RETNLB could notably suppress the protein levels of Toll-like receptor 2, Toll-like receptor 4 and phosphor- extracellular signal-regulated kinase.

CONCLUSIONS

These results suggested that downregulation of RETNLB may restrain the progression of oral squamous cell carcinoma by inactivating TLR/2/4/ERK pathway.

Initiation and Pathogenesis of Severe Asthma with Fungal Sensitization

Fungi represent one of the most diverse and abundant eukaryotes on earth, and their ubiquity and small proteolytically active products make them pervasive allergens that affect humans and other mammals. The immunologic parameters surrounding fungal allergies are still not fully elucidated despite their importance given that a large proportion of severe asthmatics are sensitized to fungal allergens. Herein, we explore fungal allergic asthma with emphasis on mouse models that recapitulate the characteristics of human disease, and the main leukocyte players in the pathogenesis of fungal allergies. The endogenous mycobiome may also contribute to fungal asthma, a phenomenon that we discuss only superficially, as much remains to be discovered.

Effects of Obesity on Airway and Systemic Inflammation in Asthmatic Children

BACKGROUND

Obese asthma is a complex syndrome with certain phenotypes that differ in children and adults. There is no clear evidence regarding the presence of additive or synergistic pathological interaction between obesity and asthma in children.

OBJECTIVES

Our aim was to demonstrate the interaction of obesity and asthma in children in terms of airway and systemic inflammation by a controlled observational study.

METHODS

Four groups were formed: asthma obese (AO), asthma nonobese (ANO), non-AO (NAO), nonasthma nonobese (NANO). Spirometry test, fractional exhaled nitric oxide (FeNO) test, skin prick test, serum inflammatory biomarkers (C-reactive protein, C3, C4, adiponectin, leptin, resistin, periostin, YKL-40, Type 1, and Type 2 cytokines) were conducted and evaluated in all participants. Sputum inflammatory cells (sputum eosinophils and neutrophils) were evaluated in patients who could produce induced sputum and obesity-asthma interactions were determined.

RESULTS

A total of 153 participants aged 6-18 years were included in the study, including the AO group (n = 46), the ANO group (n = 45), the NAO group (n = 30), and the NANO group (n = 32). IL-4 (p < 0.001), IL-5 (p < 0.001), IL-13 (p < 0.001), resistin (p < 0.001), and YKL-40 (p < 0.001) levels were higher in patients with asthma independent of obesity. The lowest adiponectin level was found in the AO group and obesity-asthma interaction was detected (p < 0.001). Sputum eosinophilia (p < 0.01), sputum neutrophilia (p < 0.01), and FeNO levels (p = 0.07) were higher in asthmatic patients independent of obesity. In the group with paucigranulocytic inflammation, resistin and YKL-40 levels were significantly lower than in the group without paucigranulocytic inflammation (p < 0.01).

CONCLUSION

No interaction was found between obesity and asthma in terms of airway inflammation. Interaction between obesity and asthma was shown in terms of adiponectin level and resistin/adiponectin and leptin/adiponectin ratios. It was found that serum YKL-40 and resistin levels could be associated with airway inflammation.

The pathophysiological role of adipokines in the development of bronchial asthma combined with obesity

The combined course of bronchial asthma (BA) and obesity is one of the urgent medical and social problems that requires a comprehensive and careful study in connection with a decrease in the quality of life of such patients, an increase in the frequency, duration of hospitalization and a high economic burden for the state as a whole. The relationship between BA and obesity is now confirmed by numerous studies, at the same time, despite the variability of the proposed mechanisms of pathogenetic effects of obesity on asthma, metabolic aspects of the relationship of these diseases need further study. Adipose tissue hormones are responsible for the energy homeostasis of the body therefore, excessive accumulation of adipose tissue is accompanied by the development of an imbalance in metabolic processes in various organs and tissues. Due to the emergence of new scientific data on the role and function of adipokines in the body, metabolic effects of adipokines are considered in the focus of their pathophysiological association with obesity and asthma. This literary review highlights the current understanding of the role of metabolic effects of the most studied adipokines (resistin, retinol-binding protein, leptin and adiponectin) in the development of obesity and BA. Gender and age-dependent features of adipokine levels in BA and obesity are described. Data on the confirmed role of adiponectin and leptin in the progression of BA combined with obesity are presented. It has been shown that the role of resistin and retinol-binding protein in the development of BA combined with obesity has not been studied. It is demonstrated that further study of metabolic activity of adipokines in BA is an actual and perspective direction of researches which will allow to develop new diagnostic and therapeutic strategies in patients with BA with obesity.

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.

Inhibition of RELM-β prevents hypoxia-induced overproliferation of human pulmonary artery smooth muscle cells by reversing PLC-mediated KCNK3 decline

AIMS

Although resistin-like molecule β (RELM-β) is involved in the pathological processes of various lung diseases, such as pulmonary inflammation, asthma and fibrosis, its potential roles in hypoxic pulmonary arterial hypertension (PAH) remain largely unknown. The study aims to investigate whether RELM-β contributes to hypoxia-induced excessive proliferation of human pulmonary artery smooth muscle cells (PASMCs) and to explore the potential mechanisms of this process.

MAIN METHODS

Human PASMCs were exposed to normoxia or hypoxia (1% O₂) for 24 h. siRNA targeting RELM-β was transfected into cells. Protein levels of KCNK3, RELM-β, pSTAT3 and STAT3 were determined by immunoblotting. The translocation of NFATc2 and expression of KCNK3 were visualized by immunofluorescence. 5-ethynyl-2'-deoxyuridine assays and cell counting kit-8 assays were performed to assess the proliferation of PASMCs.

KEY FINDINGS

(1) Chronic hypoxia significantly decreased KCNK3 protein levels while upregulating RELM-β protein levels in human PASMCs, which was accompanied by excessive proliferation of cells. (2) RELM-β could promote human PASMCs proliferation and activate the STAT3/NFAT axis by downregulating KCNK3 protein under normoxia. (3) Inhibition of RELM-β expression effectively prevented KCNK3-mediated cell proliferation under hypoxia. (4) Phospholipase C (PLC) inhibitor U-73122 could not only prevent the hypoxia/RELM-β-induced decrease in KCNK3 protein, but also inhibit the enhanced cell viability caused by hypoxia/RELM-β. (5) Both hypoxia and RELM-β could downregulate membrane KCNK3 protein levels by enhancing endocytosis.

SIGNIFICANCE

RELM-β activation is responsible for hypoxia-induced excessive proliferation of human PASMCs. Interfering with RELM-β may alleviate the progression of hypoxic PAH by upregulating PLC-dependent KCNK3 expression.

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.

HIF Oxygen Sensing Pathways in Lung Biology

Cellular responses to oxygen fluctuations are largely mediated by hypoxia-inducible factors (HIFs). Upon inhalation, the first organ inspired oxygen comes into contact with is the lungs, but the understanding of the pulmonary HIF oxygen-sensing pathway is still limited. In this review we will focus on the role of HIF1α and HIF2α isoforms in lung responses to oxygen insufficiency. In particular, we will discuss novel findings regarding their role in the biology of smooth muscle cells and endothelial cells in the context of hypoxia-induced pulmonary vasoconstriction. Moreover, we will also discuss recent studies into HIF-dependent responses in the airway epithelium, which have been even less studied than the HIF-dependent vascular responses in the lungs. In summary, we will review the biological functions executed by HIF1 or HIF2 in the pulmonary vessels and epithelium to control lung responses to oxygen fluctuations as well as their pathological consequences in the hypoxic lung.

Chronic features of allergic asthma are enhanced in the absence of resistin-like molecule-beta

Asthma is characterized by inflammation and architectural changes in the lungs. A number of immune cells and mediators are recognized as initiators of asthma, although therapeutics based on these are not always effective. The multifaceted nature of this syndrome necessitate continued exploration of immunomodulators that may play a role in pathogenesis. We investigated the role of resistin-like molecule-beta (RELM-β), a gut antibacterial, in the development and pathogenesis of Aspergillus-induced allergic airways disease. Age and gender matched C57BL/6J and Retnlb^−/− mice rendered allergic to Aspergillus fumigatus were used to measure canonical markers of allergic asthma at early and late time points. Inflammatory cells in airways were similar, although Retnlb^−/− mice had reduced tissue inflammation. The absence of RELM-β elevated serum IgA and pro-inflammatory cytokines in the lungs at homeostasis. Markers of chronic disease including goblet cell numbers, Muc genes, airway wall remodelling, and hyperresponsiveness were greater in the absence RELM-β. Specific inflammatory mediators important in antimicrobial defence in allergic asthma were also increased in the absence of RELM-β. These data suggest that while characteristics of allergic asthma develop in the absence of RELM-β, that RELM-β may reduce the development of chronic markers of allergic airways disease.

Elevated Expression of IL-33 and TSLP in the Airways of Human Asthmatics In Vivo: A Potential Biomarker of Severe Refractory Disease

The epithelial cytokines IL-33, thymic stromal lymphopoietin (TSLP), and IL-25 have been implicated in asthma pathogenesis because they promote Th2-type cytokine synthesis, but their expression is relatively poorly documented in "real-life" human asthma. Using bronchoalveolar lavage fluid (BALF), we measured airway concentrations of these mediators and compared them with those of Th1- and Th2-type cytokines, airway infiltration of neutrophils and eosinophils, and lung function in a large group of asthmatic patients with a range of disease severity (n = 70) and control subjects (n = 30). The median BALF concentrations of IL-33, TSLP, IL-4, IL-5, IL-13, and IL-12p70, but not IL-25, IL-2, or IFN-γ, were significantly elevated in asthmatics compared with controls (p < 0.05). The concentrations of IL-33 and TSLP, but not IL-25, correlated inversely with the lung function (forced expiratory volume in the first second) of asthmatics (IL-33: r = -0.488, p < 0.0001; TSLP: r = -0.565, p < 0.0001) independently of corticosteroid therapy. When divided according to disease severity and corticosteroid therapy, all subgroups of asthmatics had elevated median numbers of eosinophils in BALF, whereas the patients with more severe disease who were treated with corticosteroids had higher numbers of neutrophils compared with milder asthmatics not so treated and control subjects (p < 0.05). The data implicate TSLP and IL-33 in the pathogenesis of asthma that is characterized by persistent airway inflammation and impaired lung function despite intensive corticosteroid therapy, highlighting them as potential molecular targets.

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 is a predictor of asthma risk and resistin:adiponectin ratio is a negative predictor of lung function in asthma

BACKGROUND

Adipokines, such as resistin and adiponectin, modify inflammation and may contribute to increased asthma risk and severity in obese people.

OBJECTIVE

To examine plasma resistin and resistin:adiponectin ratio (i) in asthmatics compared to healthy controls, (ii) according to asthma severity, obesity and gender (iii) following weight loss in obese asthmatics.

METHODS

In a cross-sectional observational study of asthmatic adults (n = 96) and healthy controls (n = 46), plasma resistin and adiponectin were measured. In a separate intervention study, obese asthmatic adults (n = 27) completed a 10-week weight loss intervention and plasma resistin and adiponectin concentrations were analysed.

RESULTS

Plasma resistin and resistin:adiponectin ratio were higher in asthma compared to controls and were higher again in subjects with a severe vs. mild-to-moderate asthma pattern. Amongst asthmatic subjects, resistin was not modified by gender or obesity, while adiponectin was lower in males and obese subjects. As a result, resistin:adiponectin ratio was higher in obese males, non-obese males and obese females, compared to non-obese females. In a logistic regression model, plasma resistin concentration was a predictor of asthma risk. In a multiple linear regression model, plasma resistin:adiponectin ratio was a negative predictor of FEV1 in asthma. Following weight loss, neither resistin, adiponectin nor resistin:adiponectin ratio was changed. However, the change (∆) in %body fat was associated with ∆ resistin:adiponectin ratio. Post-intervention ∆ resistin was negatively correlated with both ∆FRC and ∆RV.

CONCLUSION AND CLINICAL RELEVANCE

This study demonstrates that resistin and resistin:adiponectin ratio are higher in asthma and are higher again in subjects who have more severe disease. Resistin:adiponectin ratio is highest in obese male asthmatics. As resistin is a predictor of asthma risk and resistin:adiponectin is a predictor of FEV1 in asthma, these adipokines may be contributing to the obese asthma phenotype, thus providing a potential therapeutic target for obese asthma.

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.

Activin-A is overexpressed in severe asthma and is implicated in angiogenic processes

Activin-A is a pleiotropic cytokine that regulates allergic inflammation. Its role in the regulation of angiogenesis, a key feature of airways remodelling in asthma, remains unexplored. Our objective was to investigate the expression of activin-A in asthma and its effects on angiogenesis in vitro.Expression of soluble/immunoreactive activin-A and its receptors was measured in serum, bronchoalveolar lavage fluid (BALF) and endobronchial biopsies from 16 healthy controls, 19 patients with mild/moderate asthma and 22 severely asthmatic patients. In vitro effects of activin-A on baseline and vascular endothelial growth factor (VEGF)-induced human endothelial cell angiogenesis, signalling and cytokine release were compared with BALF concentrations of these cytokines in vivo.Activin-A expression was significantly elevated in serum, BALF and bronchial tissue of the asthmatics, while expression of its protein receptors was reduced. In vitro, activin-A suppressed VEGF-induced endothelial cell proliferation and angiogenesis, inducing autocrine production of anti-angiogenic soluble VEGF receptor (R)1 and interleukin (IL)-18, while reducing production of pro-angiogenic VEGFR2 and IL-17. In parallel, BALF concentrations of soluble VEGFR1 and IL-18 were significantly reduced in severe asthmatics in vivo and inversely correlated with angiogenesis.Activin-A is overexpressed and has anti-angiogenic effects in vitro that are not propagated in vivo, where reduced basal expression of its receptors is observed particularly in severe asthma.

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.

Evolution of the Vertebrate Resistin Gene Family

Resistin (encoded by Retn) was previously identified in rodents as a hormone associated with diabetes; however human resistin is instead linked to inflammation. Resistin is a member of a small gene family that includes the resistin-like peptides (encoded by Retnl genes) in mammals. Genomic searches of available genome sequences of diverse vertebrates and phylogenetic analyses were conducted to determine the size and origin of the resistin-like gene family. Genes encoding peptides similar to resistin were found in Mammalia, Sauria, Amphibia, and Actinistia (coelacanth, a lobe-finned fish), but not in Aves or fish from Actinopterygii, Chondrichthyes, or Agnatha. Retnl originated by duplication and transposition from Retn on the early mammalian lineage after divergence of the platypus, but before the placental and marsupial mammal divergence. The resistin-like gene family illustrates an instance where the locus of origin of duplicated genes can be identified, with Retn continuing to reside at this location. Mammalian species typically have a single copy Retn gene, but are much more variable in their numbers of Retnl genes, ranging from 0 to 9. Since Retn is located at the locus of origin, thus likely retained the ancestral expression pattern, largely maintained its copy number, and did not display accelerated evolution, we suggest that it is more likely to have maintained an ancestral function, while Retnl, which transposed to a new location, displays accelerated evolution, and shows greater variability in gene number, including gene loss, likely evolved new, but potentially lineage-specific, functions.

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.

Human resistin and the RELM of Inflammation in diabesity

The initial discovery of resistin and resistin-like molecules (RELMs) in rodents suggested a role for these adipocytokines in molecular linkage of obesity, Type 2 Diabetes mellitus and metabolic syndrome. Since then, it became apparent that the story of resistin and RELMs was very much of mice and men. The putative role of this adipokine family evolved from that of a conveyor of insulin resistance in rodents to instigator of inflammatory processes in humans. Structural dissimilarity, variance in distribution profiles and a lack of corroborating evidence for functional similarities separate the biological functions of resistin in humans from that of rodents. Although present in gross visceral fat deposits in humans, resistin is a component of inflammation, being released from infiltrating white blood cells of the sub-clinical chronic low grade inflammatory response accompanying obesity, rather than from the adipocyte itself. This led researchers to further explore the functions of the resistin family of proteins in inflammatory-related conditions such as atherosclerosis, as well as in cancers such as endometrial and gastric cancers. Although elevated levels of resistin have been found in these conditions, whether it is causative or as a result of these conditions still remains to be determined.

Adiponectin, Leptin, and Resistin in Asthma: Basic Mechanisms through Population Studies

Adipokines, factors produced by adipose tissue, may be proinflammatory (such as leptin and resistin) or anti-inflammatory (such as adiponectin). Effects of these adipokines on the lungs have the potential to evoke or exacerbate asthma. This review summarizes basic mechanistic data through population-based and clinical studies addressing the potential role of adipokines in asthma. Augmenting circulating concentrations of adiponectin attenuates allergic airway inflammation and airway hyperresponsiveness in mice. Murine data is supported by human data that suggest that low serum adiponectin is associated with greater risk for asthma among women and peripubertal girls. Further, higher serum total adiponectin may be associated with lower clinical asthma severity among children and women with asthma. In contrast, exogenous administration of leptin results in augmented allergic airway hyperresponsiveness in mice. Alveolar macrophages obtained from obese asthmatics are uniquely sensitive to leptin in terms of their potential to augment inflammation. Consistent with this basic mechanistic data, epidemiologic studies demonstrate that higher serum leptin is associated with greater asthma prevalence and/or severity and that these associations may be stronger among women, postpubertal girls, and prepubertal boys. The role of adipokines in asthma is still evolving, and it is not currently known whether modulation of adipokines may be helpful in asthma prevention or treatment.

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.

Adipokine adiponectin is a potential protector to human bronchial epithelial cell for regulating proliferation, wound repair and apoptosis: comparison with leptin and resistin

Epidemiological data indicate an increasing incidence of asthma in the obese individuals recent decades, while very little is known about the possible association between them. Here, we compared the roles of adipocyte-derived factors, including leptin, adiponectin and resistin on proliferation, wound repair and apoptosis in human bronchial epithelial cells (HBECs) which play an important role in the pathogenesis of asthma. The results showed that exogenous globular adiponectin (gAd) promoted proliferation, cell-cycle and wound repair of HBECs. This effect may be relevant to Ca(2+)/calmodulin signal pathway. Besides, gAd inhibited apoptosis induced by ozone and release of lactate dehydrogenase (LDH) of HBECs via regulated adipoR1 and reactive oxygen species. No effects of leptin or resistin on proliferation, wound repair and apoptosis of HBECs were detectable. These data indicate that airway epithelium is the direct target of gAd which plays an important role in protecting HBECs from mechanical or oxidant injuries and may have therapeutic implications in the treatment of asthma.

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.