FIZZ1 plays a crucial role in early stage airway remodeling of OVA-induced asthma

Gene Expression and Metabolome Analysis Reveals Anti-Inflammatory Impacts of 11,17diHDoPE on PM10-Induced Mouse Lung Inflammation

Oxylipins, the metabolites of polyunsaturated fatty acids, are vital in regulating cell proliferation and inflammation. Among these oxylipins, specialized pro-resolving mediators notably contribute to inflammation resolution. Previously, we showed that the specialized pro-resolving mediators isomer 11,17dihydroxy docosapentaenoic acid (11,17diHDoPE) can be synthesized in bacterial cells and exhibits anti-inflammatory effects in mammalian cells. This study investigates the in vivo impact of 11,17diHDoPE in mice exposed to particulate matter 10 (PM10). Our results indicate that 11,17diHDoPE significantly mitigates PM10-induced lung inflammation in mice, as evidenced by reduced pro-inflammatory cytokines and pulmonary inflammation-related gene expression. Metabolomic analysis reveals that 11,17diHDoPE modulates inflammation-related metabolites such as threonine, 2-keto gluconic acid, butanoic acid, and methyl oleate in lung tissues. In addition, 11,17diHDoPE upregulates the LA-derived oxylipin pathway and downregulates arachidonic acid- and docosahexaenoic acid-derived oxylipin pathways in serum. Correlation analyses between gene expression and metabolite changes suggest that 11,17diHDoPE alleviates inflammation by interfering with macrophage differentiation. These findings underscore the in vivo role of 11,17diHDoPE in reducing pulmonary inflammation, highlighting its potential as a therapeutic agent for respiratory diseases.

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.

Artesunate inhibits airway remodeling in asthma via the MAPK signaling pathway

Background: Artesunate (ART), is a semi-synthetic water-soluble artemisinin derivative extracted from the plant Artemisia annua, which is often used to treating malaria. In vivo and in vitro studies suggested it may help decrease inflammation and attenuate airway remodeling in asthma. However, its underlying mechanism of action is not elucidated yet. Herein, an attempt is made to investigate the ART molecular mechanism in treating asthma.

Methods: The BALB/c female mice sensitized via ovalbumin (OVA) have been utilized to establish the asthma model, followed by carrying out ART interventions. Lung inflammation scores by Haematoxylin and Eosin (H&E), goblet cell hyperplasia grade by Periodic Acid-Schiff (PAS), and collagen fibers deposition by Masson trichrome staining have been utilized for evaluating how ART affected asthma. RNA-sequencing (RNA-seq) analyses were performed to identify differentially expressed genes (DEGs). The DEGs were analyzed by Gene Ontology (GO) terms, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, and Protein-Protein interaction (PPI) function analyses. Hub clusters were found by Cytoscape MCODE. Subsequently, Real-Time quantitative PCR (RT-qPCR) verified the mRNA expression profiles of DEGs. Finally, immunohistochemistry (IHC) and western blots have validated the relevant genes and potential pathways.

Results: ART considerably attenuated inflammatory cell infiltration, mucus secretion, and collagen fibers deposition. KEGG pathway analysis revealed that the ART played a protective role via various pathways including the mitogen-activated protein kinase (MAPK) pathway as one of them. Moreover, ART could alleviate the overexpression of found in inflammatory zone 1(FIZZ1) as revealed by IHC and Western blot analyses. ART attenuated OVA-induced asthma by downregulating phosphorylated p38 MAPK.

Conclusion: ART exerted a protective function in a multitarget and multi-pathway on asthma. FIZZ1 was a possible target for asthma airway remodeling. The MARK pathway was one of the key pathways by which ART protected against 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.

Mechanistic study of salidroside on ovalbumin-induced asthmatic model mice based on untargeted metabolomics analysis

Salidroside (SAL) is a natural component derived from Rhodiola rosea and is well known for its wide range of biological activities such as its anti-inflammatory and anti-oxidative properties. However, its effects and mechanisms of action related to asthma have not been well explored yet. Recent studies have found that changes in host metabolism are closely related to the progression of asthma. Many natural components can ameliorate asthma by affecting host metabolism. The use of untargeted metabolomics can allow for a better understanding of the metabolic regulatory mechanisms of herbs on asthma. This study aimed to demonstrate the anti-asthmatic effects and metabolic regulatory mechanisms of SAL. In this study, the therapeutic effects of SAL on asthmatic mice were tested at first. Secondly, the effects of SAL on the airway inflammatory reaction, oxidative stress, and airway remodeling were investigated. Finally, untargeted metabolomics analysis was used to explore the influence of SAL on lung metabolites. The results showed that SAL had a significant therapeutic effect on asthmatic model mice. Moreover, SAL treatment lowered interleukin (IL)-4, IL-5, and IL-13 levels but elevated interferon gamma (IFN-γ) and IL-10 levels in bronchoalveolar lavage fluid (BALF). Additionally, it also increased superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities and decreased methane dicarboxylic aldehyde (MDA) levels in the lungs. Besides, SAL-treated mice showed decreased expression of smooth muscle actin (α-SMA), matrix metallopeptidase 2 (MMP2), matrix metallopeptidase 9 (MMP9), and transforming growth factor-beta 1 (TGF-β1) in the lung. Untargeted metabolomics analysis showed 31 metabolites in the lungs that were influenced by SAL. These metabolites were related to pyrimidine metabolism, steroid hormone biosynthesis, and tricarboxylic acid (TCA) cycle. In conclusion, SAL treatment can reduce the inflammatory response, oxidative stress, and airway remodeling in asthmatic model mice. The mechanism of SAL in the treatment of asthma may be related to the regulation of pyrimidine metabolism, steroid hormone biosynthesis, and the TCA cycle. Further studies can be carried out using targeted metabolomics and in vitro models to deeply elucidate the anti-inflammatory and anti-oxidative mechanisms of SAL on asthma based on regulating metabolism.

Reprogramming alternative macrophage polarization by GATM-mediated endogenous creatine synthesis: A potential target for HDM-induced asthma treatment

Cellular energy metabolism plays a crucial role in the regulation of macrophage polarization and in the execution of immune functions. A recent study showed that Slc6a8-mediated creatine uptake from exogenous supplementation modulates macrophage polarization, yet little is known about the role of the de novo creatine de novobiosynthesis pathway in macrophage polarization. Here, we observed that glycine amidinotransferase (GATM), the rate-limiting enzyme for creatine synthesis, was upregulated in alternative (M2) polarized macrophages, and was dependent on the transcriptional factor STAT6, whereas GATM expression was suppressed in the classical polarized (M1) macrophage. Next, we revealed that exogenous creatine supplementation enhanced IL-4-induced M2 polarization, confirming recent work. Furthermore, we revealed that genetic ablation of GATM did not affect expression of M1 marker genes (Nos2, IL1b, IL12b) or the production of nitric oxide in both peritoneal macrophages (PMs) and bone marrow-derived macrophages (BMDMs). By contrast, expression levels of M2 markers (Arg1, Mrc1, Ccl17 and Retnla) were lower following GATM deletion. Moreover, we found that deletion of GATM in resident alveolar macrophages (AMs) significantly blocked M2 polarization but with no obvious effect on the number of cells in knockout mice. Lastly, an upregulation of GATM was found in lung tissue and bronchoalveolar lavage fluid macrophages from HDM-induced asthmatic mice. Our study uncovers a previously uncharacterized role for the de novo creatine biosynthesis enzyme GATM in M2 macrophage polarization, which may be involved in the pathogenesis of related inflammatory diseases such as an T helper 2 (Th2)-associated allergic asthma.

Reprogramming alternative macrophage polarization by GATM-mediated endogenous creatine synthesis: A potential target for HDM-induced asthma treatment

Cellular energy metabolism plays a crucial role in the regulation of macrophage polarization and in the execution of immune functions. A recent study showed that Slc6a8-mediated creatine uptake from exogenous supplementation modulates macrophage polarization, yet little is known about the role of the de novo creatine de novobiosynthesis pathway in macrophage polarization. Here, we observed that glycine amidinotransferase (GATM), the rate-limiting enzyme for creatine synthesis, was upregulated in alternative (M2) polarized macrophages, and was dependent on the transcriptional factor STAT6, whereas GATM expression was suppressed in the classical polarized (M1) macrophage. Next, we revealed that exogenous creatine supplementation enhanced IL-4-induced M2 polarization, confirming recent work. Furthermore, we revealed that genetic ablation of GATM did not affect expression of M1 marker genes (Nos2, IL1b, IL12b) or the production of nitric oxide in both peritoneal macrophages (PMs) and bone marrow-derived macrophages (BMDMs). By contrast, expression levels of M2 markers (Arg1, Mrc1, Ccl17 and Retnla) were lower following GATM deletion. Moreover, we found that deletion of GATM in resident alveolar macrophages (AMs) significantly blocked M2 polarization but with no obvious effect on the number of cells in knockout mice. Lastly, an upregulation of GATM was found in lung tissue and bronchoalveolar lavage fluid macrophages from HDM-induced asthmatic mice. Our study uncovers a previously uncharacterized role for the de novo creatine biosynthesis enzyme GATM in M2 macrophage polarization, which may be involved in the pathogenesis of related inflammatory diseases such as an T helper 2 (Th2)-associated allergic asthma.

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.

Lipoxin A4 inhibits ovalbumin-induced airway inflammation and airway remodeling in a mouse model of asthma

Asthma is a chronic respiratory disease, which is characterized by airway inflammation, remodeling and airway hyperresponsiveness. Airway remodeling is caused by long-term inflammation of the airways. Lipoxin A4 (LXA4) is a natural eicosanoid with powerful anti-inflammatory properties, and has been shown to serve a critical role in orchestrating pulmonary inflammation and airway hyper-responsiveness in asthmatic mice. However, its effect on airway remodeling is unknown. Female BALB/c mice were used to establish a mouse model of asthma which were sensitized and challenged by ovalbumin (OVA). LXA4 was intranasally administrated prior to the challenge. The results of our study indicated that LXA4 suppressed the OVA-induced inflammatory cell infiltration and T helper type 2 (Th2) cytokines secretion in the mouse model of asthma. Characteristics of airway remodeling, such as thickening of the bronchial wall and smooth muscle, overdeposition of collagen, and overexpression of α-smooth muscle actin (α-SMA) and collagen-I were reversed by LXA4. Furthermore, LXA4 suppressed the aberrant activation of the signal transducer and activator of transcription 3 (STAT3) pathway in the lung tissues of asthmatic mice. In conclusion, these findings demonstrated that LXA4 alleviated allergic airway inflammation and remodeling in asthmatic mice, which may be related to the inhibition of STAT3 pathway.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Tranglutaminase 2 contributes to the asthmatic inflammation by modulating activation of alveolar macrophages

BACKGROUND

Transglutaminase 2 (TG2), a multifunctional calcium-dependent acyltransferase, is upregulated in asthmatic airways and reported to play a role in the pathogenesis of allergic asthma. However, the underlying mechanism is not fully understood.

OBJECTIVE

To investigate the role of TG2 in alternative activation of alveolar macrophages by using murine asthma model.

METHODS

TG2 expression was assessed in induced sputum of 21 asthma patients and 19 healthy controls, and lung tissue of ovalbumin (OVA)-induced murine asthma model. To evaluate the role of TG2 in asthma, we developed an OVA asthma model in both TG2 null and wild-type mice. The expression of M2 macrophage markers was measured by fluorescence-activated cell sorting (FACS) after OVA sensitization and challenge. To evaluate the effect of TG2 inhibition in vitro, interleukin 4 (IL-4) or IL-13-stimulated expression of M2 macrophage markers was measured in CRL-2456 cells in the presence and absence of a TG2 inhibitor.

RESULTS

The expression of both TG2 and M2 markers was increased in the sputum of asthmatics compared with that of healthy controls. The expression of TG2 was increased in macrophages of OVA mice. Airway hyperresponsiveness, and the number of inflammatory cells, including eosinophils, was significantly reduced in TG2 null mice compared with wild-type mice. Enhanced expression of M2 markers in OVA mice was normalized by TG2 knockout. IL-4 or IL-13-stimulated expression of M2 markers in alveolar macrophages was also attenuated by TG2 inhibitor treatment in vitro.

CONCLUSION

Our results suggest that TG2-mediated modulation of alveolar macrophage polarization plays important roles in the pathogenesis of asthma.

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 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.

Lung developmental arrest caused by PDGF-A deletion: consequences for the adult mouse lung

PDGF-A is a key contributor to lung development in mice. Its expression is needed for secondary septation of the alveoli and deletion of the gene leads to abnormally enlarged alveolar air spaces in mice. In humans, the same phenotype is the hallmark of bronchopulmonary dysplasia (BPD), a disease that affects premature babies and may have long lasting consequences in adulthood. So far, the knowledge regarding adult effects of developmental arrest in the lung is limited. This is attributable to few follow-up studies of BPD survivors and lack of good experimental models that could help predict the outcomes of this early age disease for the adult individual. In this study, we used the constitutive lung-specific Pdgfa deletion mouse model to analyze the consequences of developmental lung defects in adult mice. We assessed lung morphology, physiology, cellular content, ECM composition and proteomics data in mature mice, that perinatally exhibited lungs with a BPD-like morphology. Histological and physiological analyses both revealed that enlarged alveolar air spaces remained until adulthood, resulting in higher lung compliance and higher respiratory volume in knockout mice. Still, no or only small differences were seen in cellular, ECM and protein content when comparing knockout and control mice. Taken together, our results indicate that Pdgfa deletion-induced lung developmental arrest has consequences for the adult lung at the morphological and functional level. In addition, these mice can reach adulthood with a BPD-like phenotype, which makes them a robust model to further investigate the pathophysiological progression of the disease and test putative regenerative therapies.

Alternatively activated macrophages; a double-edged sword in allergic asthma

BACKGROUND

Macrophages are heterogenous phagocytic cells with an important role in the innate immunity. They are, also, significant contributors in the adaptive immune system. Macrophages are the most abundant immune cells in the lung during allergic asthma, which is the most common chronic respiratory disease of both adults and children. Macrophages activated by Th1 cells are known as M1 macrophages while those activated by IL-4 and IL-13 are called alternatively activated macrophages (AAM) or M2 cells. AAM are subdivided into four distinct subtypes (M2a, M2b, M2c and M2d), depending on the nature of inducing agent and the expressed markers. BODY: IL-4 is the major effector cytokine in both alternative activation of macrophages and pathogenesis of asthma. Thus, the role of M2a macrophages in asthma is a major concern. However, this is controversial. Therefore, further studies are required to improve our knowledge about the role of IL-4-induced macrophages in allergic asthma, through precisive elucidation of the roles of specific M2a proteins in the pathogenesis of asthma. In the current review, we try to illustrate the different functions of M2a macrophages (protective and pathogenic roles) in the pathogenesis of asthma, including explanation of how different M2a proteins and markers act during the pathogenesis of allergic asthma. These include surface markers, enzymes, secreted proteins, chemokines, cytokines, signal transduction proteins and transcription factors.

CONCLUSIONS

AAM is considered a double-edged sword in allergic asthma. Finally, we recommend further studies that focus on increased selective expression or suppression of protective and pathogenic M2a markers.

Fibroblast-to-myofibroblast transition in bronchial asthma

Bronchial asthma is a chronic inflammatory disease in which bronchial wall remodelling plays a significant role. This phenomenon is related to enhanced proliferation of airway smooth muscle cells, elevated extracellular matrix protein secretion and an increased number of myofibroblasts. Phenotypic fibroblast-to-myofibroblast transition represents one of the primary mechanisms by which myofibroblasts arise in fibrotic lung tissue. Fibroblast-to-myofibroblast transition requires a combination of several types of factors, the most important of which are divided into humoural and mechanical factors, as well as certain extracellular matrix proteins. Despite intensive research on the nature of this process, its underlying mechanisms during bronchial airway wall remodelling in asthma are not yet fully clarified. This review focuses on what is known about the nature of fibroblast-to-myofibroblast transition in asthma. We aim to consider possible mechanisms and conditions that may play an important role in fibroblast-to-myofibroblast transition but have not yet been discussed in this context. Recent studies have shown that some inherent and previously undescribed features of fibroblasts can also play a significant role in fibroblast-to-myofibroblast transition. Differences observed between asthmatic and non-asthmatic bronchial fibroblasts (e.g., response to transforming growth factor β, cell shape, elasticity, and protein expression profile) may have a crucial influence on this phenomenon. An accurate understanding and recognition of all factors affecting fibroblast-to-myofibroblast transition might provide an opportunity to discover efficient methods of counteracting this phenomenon.

Hematopoietic cell-derived RELMα regulates hookworm immunity through effects on macrophages

Resistin-like molecule α (RELMα) is a highly secreted protein in type 2 (Th2) cytokine-induced inflammation including helminth infection and allergy. In infection with Nippostrongylus brasiliensis (Nb), RELMα dampens Th2 inflammatory responses. RELMα is expressed by immune cells, and by epithelial cells (EC); however, the functional impact of immune versus EC-derived RELMα is unknown. We generated bone marrow (BM) chimeras that were RELMα deficient (RELMα^{-/ -} ) in BM or non BM cells and infected them with Nb. Non BM RELMα^-/- chimeras had comparable inflammatory responses and parasite burdens to RELMα^+/+ mice. In contrast, both RELMα^-/- and BM RELMα^-/- mice exhibited increased Nb-induced lung and intestinal inflammation, correlated with elevated Th2 cytokines and Nb killing. CD11c⁺ lung macrophages were the dominant BM-derived source of RELMα and can mediate Nb killing. Therefore, we employed a macrophage-worm co-culture system to investigate whether RELMα regulates macrophage-mediated Nb killing. Compared to RELMα^{+ /+} macrophages, RELMα^-/- macrophages exhibited increased binding to Nb and functionally impaired Nb development. Supplementation with recombinant RELMα partially reversed this phenotype. Gene expression analysis revealed that RELMα decreased cell adhesion and Fc receptor signaling pathways, which are associated with macrophage-mediated helminth killing. Collectively, these studies demonstrate that BM-derived RELMα is necessary and sufficient to dampen Nb immune responses, and identify that one mechanism of action of RELMα is through inhibiting macrophage recruitment and interaction with Nb. Our findings suggest that RELMα acts as an immune brake that provides mutually beneficial effects for the host and parasite by limiting tissue damage and delaying parasite expulsion.

Pidotimod exacerbates allergic pulmonary infection in an OVA mouse model of asthma

Pidotimod is a synthetic dipeptide with biological and immuno‑modulatory properties. It has been widely used for treatment and prevention of recurrent respiratory infections. However, its impact on the regulation of allergic pulmonary inflammation is still not clear. In the current study, an ovalbumin (OVA)‑induced allergic asthma model was used to investigate the immune‑modulating effects of pidotimod on airway eosinophilia, mucus metaplasia and inflammatory factor expression compared with dexamethasone (positive control). The authors determined that treatment with pidotimod exacerbated pulmonary inflammation as demonstrated by significantly increased eosinophil infiltration, dramatically elevated immunoglobulin E production, and enhanced T helper 2 response. Moreover, treatment failed to attenuate mucus production in lung tissue, and did not reduce OVA‑induced high levels of FIZZ1 and Arg1 expression in asthmatic mice. In contrast, administration of dexamethasone was efficient in alleviating allergic airway inflammation in OVA‑induced asthmatic mice. These data indicated that pidotimod as an immunotherapeutic agent should be used cautiously and the effectiveness for controlling allergic asthma needs further evaluation and research.

Obesity/Type II diabetes alters macrophage polarization resulting in a fibrotic tendon healing response

Type II Diabetes (T2DM) dramatically impairs the tendon healing response, resulting in decreased collagen organization and mechanics relative to non-diabetic tendons. Despite this burden, there remains a paucity of information regarding the mechanisms that govern impaired healing of diabetic tendons. Mice were placed on either a high fat diet (T2DM) or low fat diet (lean) and underwent flexor tendon transection and repair surgery. Healing was assessed via mechanical testing, histology and changes in gene expression associated with collagen synthesis, matrix remodeling, and macrophage polarization. Obese/diabetic tendons healed with increased scar formation and impaired mechanical properties. Consistent with this, prolonged and excess expression of extracellular matrix (ECM) components were observed in obese/T2DM tendons. Macrophages are involved in both inflammatory and matrix deposition processes during healing. Obese/T2DM tendons healed with increased expression of markers of pro-inflammatory M1 macrophages, and elevated and prolonged expression of M2 macrophages markers that are involved in ECM deposition. Here we demonstrate that tendons from obese/diabetic mice heal with increased scar formation and increased M2 polarization, identifying excess M2 macrophage activity and matrix synthesis as a potential mechanism of the fibrotic healing phenotype observed in T2DM tendons, and as such a potential target to improve tendon healing in T2DM.

Update on the role of alternatively activated macrophages in asthma

Lung macrophages link innate and adaptive immune responses during allergic airway inflammatory responses. Alveolar macrophages (AMs) and interstitial macrophages are two different phenotypes that differentially exert immunological function under physiological and pathological conditions. Exposure to pathogen induces polarization of AM cells into classically activated macrophages (M1 cells) and alternatively activated macrophages (M2 cells). M1 cells dominantly express proinflammatory cytokines such as TNF-α and IL-1 β and induce lung inflammation and tissue damage. M2 cells are further divided into M2a and M2c subsets. M2a cells dominantly produce allergic cytokines IL-4 and IL-13, but M2c cells dominantly produce anti-inflammatory cytokine IL-10. M2a and M2c cells are differently involved in initiation, inflammation resolution, and tissue remodeling in the different stages of asthma. Microenvironment dynamically influences polarization of AM cells. Cytokines, chemokines, and immune-regulatory cells interplay and affect the balance between the polarization of M1 and M2 cells, subsequently influencing disease progression. Thus, modulation of AM phenotypes through molecular intervention has therapeutic potential in the treatment of asthma and other allergic inflammatory diseases. This review updated recent advances in polarization and functional specialization of these macrophage subtypes with emphasis on modulation of polarization of M2 cells in asthma of human subjects and animal models.

FIZZ1 Promotes Airway Remodeling in Asthma Through the PTEN Signaling Pathway

The aim of our study was to elucidate the function and signaling pathway of found in inflammatory zone 1 (FIZZ1) in airway remodeling in asthma. We used a mice model sensitized and challenged by ovalbumin (OVA) to evaluate the expression of FIZZ1, type I collagen, and fibronectin-1 in the airway in asthma. To investigate the signaling pathway regulated by FIZZ1, we treated a cultured murine lung epithelium cell-12 (MLE-12) with FIZZ1 recombination protein, silenced the expression of FIZZ1 with FIZZ1-shRNA in vitro, and then detected phosphorylated phosphatase and tensin homolog deleted on chromosome 10 (PTEN) and expression of type I collagen and fibronectin-1 (FN-1) by Western blotting. In addition, we increased the expression of PTEN by PTEN plasmid transfection then detected the expression of type I collagen and fibronectin-1 in MLE-12 by Western blot analysis and immunofluorescence cytochemistry technology, respectively. First, the expression of FIZZ1, type I collagen, and fibronectin-1 was significantly elevated in the lungs of OVA-challenged mice compared with saline-treated control animals. Secondly, the phosphorylation of PTEN was decreased in MLE-12 treated with FIZZ1 recombination protein in vitro. On the contrary, the phosphorylation of PTEN was increased in MLE-12 cells transfected with FIZZ1-shRNA. Thirdly, results of the Western blot analysis and immunofluorescence cytochemistry showed that expression of type I collagen and fibronectin-1 was increased in cells treated with FIZZ1 recombination protein, while the levels of type I collagen and fibronectin-1 were significantly decreased in cells transfected with PTEN plasmid. FIZZ1 may be a critical cytokine in airway remodeling in asthma. This study indicates that targeting FIZZ1 and/or PTEN may be a new therapeutic strategy for asthma.

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

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

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.

Thalidomide inhibits alternative activation of macrophages in vivo and in vitro: a potential mechanism of anti-asthmatic effect of thalidomide

Background

Thalidomide is known to have anti-inflammatory and immunomodulatory actions. However, the effect and the anti-asthmatic mechanism of thalidomide in the pathogenesis of asthmatic airways are not fully understood.

Objective

This study is designed to determine the effect and the potential mechanism of thalidomide in the pathogenesis of asthmatic airways using animal model of allergic asthma.

Methods

Six-week-old female BALB/C mice were sensitized with alum plus ovalbumin (OVA) and were exposed to OVA via intranasal route for 3 days for challenge. Thalidomide 200 mg/kg was given via gavage twice a day from a day before the challenge and airway hyperresponsivenss (AHR), airway inflammatory cells, and cytokines in bronchoalveolar lavage fluids (BALF) were evaluated. The expression levels of pro-inflammatory cytokines and other mediators were evaluated using ELISA, real time (RT)-qPCR, and flow cytometry. CRL-2456, alveolar macrophage cell line, was used to test the direct effect of thalidomide on the activation of macrophages in vitro.

Results

The mice with thalidomide treatment showed significantly reduced levels of allergen-induced BALF and lung inflammation, AHR, and the expression of a number of pro-inflammatory cytokines and mediators including Th2 related, IL-17 cytokines, and altered levels of allergen-specific IgG1/IgG2a. Of interesting note, thalidomide treatment significantly reduced expression levels of allergen- or Th2 cytokine-stimulated alternative activation of macrophages in vivo and in vitro.

Conclusion

These studies highlight a potential use of thalidomide in the treatment of allergic diseases including asthma. This study further identified a novel inhibitory effect of thalidomide on alternative activation of macrophages as a potential mechanism of anti-asthmatic effect of thalidomide.

Perinatal paracetamol exposure in mice does not affect the development of allergic airways disease in early life

Background

Current data concerning maternal paracetamol intake during pregnancy, or intake during infancy and risk of wheezing or asthma in childhood is inconclusive based on epidemiological studies. We have investigated whether there is a causal link between maternal paracetamol intake during pregnancy and lactation and the development of house dust mite (HDM) induced allergic airways disease (AAD) in offspring using a neonatal mouse model.

Methods

Pregnant mice were administered paracetamol or saline by oral gavage from the day of mating throughout pregnancy and/or lactation. Subsequently, their pups were exposed to intranasal HDM or saline from day 3 of life for up to 6 weeks. Assessments of airway hyper-responsiveness, inflammation and remodelling were made at weaning (3 weeks) and 6 weeks of age.

Results

Maternal paracetamol exposure either during pregnancy and/or lactation did not affect development of AAD in offspring at weaning or at 6 weeks. There were no effects of maternal paracetamol at any time point on airway remodelling or IgE levels.

Conclusions

Maternal paracetamol did not enhance HDM induced AAD in offspring. Our mechanistic data do not support the hypothesis that prenatal paracetamol exposure increases the risk of childhood asthma.

Lunasin alleviates allergic airway inflammation while increases antigen-specific Tregs

Lunasin is a naturally occurring peptide isolated from soybeans and has been explored in cancer treatment. Lunasin inhibits NF-κB activation and thus pro-inflammatory cytokine and mediator production in macrophages. In this study we demonstrate that lunasin can effectively suppress allergic airway inflammation in two murine models of asthma. In an OVA+Alum sensitization model, intranasal lunasin treatment at the time of OVA challenges significantly reduced total cells counts in bronchoalveolar lavage (BAL) fluid and eosinophilia, peribronchiolar inflammatory infiltration, goblet cell metaplasia and airway IL-4 production. In an OVA+LPS intranasal sensitization model, lunasin treatment either at the time of sensitization or challenge has similar effects in suppress allergic airway inflammation including significantly reduced total cell and eosinophil counts in BAL fluid, inflammatory gene Fizz1 expression in the lung, and IL-4 production by OVA re-stimulated cells from mediastinal lymph nodes. We further show that intranasal instillation of OVA+lunasin significantly increases OVA-specific regulatory T cell (Treg) accumulation in the lung comparing to OVA only treatment. Taken together, our results suggest lunasin as an anti-inflammatory agent can be potentially used in asthma therapy or as an adjuvant to enhance the induction of antigen-specific Tregs and thus boost the efficacy of allergy immunotherapy.

Acute chlorine gas exposure produces transient inflammation and a progressive alteration in surfactant composition with accompanying mechanical dysfunction

Acute Cl2 exposure following industrial accidents or military/terrorist activity causes pulmonary injury and severe acute respiratory distress. Prior studies suggest that antioxidant depletion is important in producing dysfunction, however a pathophysiologic mechanism has not been elucidated. We propose that acute Cl2 inhalation leads to oxidative modification of lung lining fluid, producing surfactant inactivation, inflammation and mechanical respiratory dysfunction at the organ level. C57BL/6J mice underwent whole-body exposure to an effective 60ppm-hour Cl2 dose, and were euthanized 3, 24 and 48h later. Whereas pulmonary architecture and endothelial barrier function were preserved, transient neutrophilia, peaking at 24h, was noted. Increased expression of ARG1, CCL2, RETLNA, IL-1b, and PTGS2 genes was observed in bronchoalveolar lavage (BAL) cells with peak change in all genes at 24h. Cl2 exposure had no effect on NOS2 mRNA or iNOS protein expression, nor on BAL NO3(-) or NO2(-). Expression of the alternative macrophage activation markers, Relm-α and mannose receptor was increased in alveolar macrophages and pulmonary epithelium. Capillary surfactometry demonstrated impaired surfactant function, and altered BAL phospholipid and surfactant protein content following exposure. Organ level respiratory function was assessed by forced oscillation technique at 5 end expiratory pressures. Cl2 exposure had no significant effect on either airway or tissue resistance. Pulmonary elastance was elevated with time following exposure and demonstrated PEEP refractory derecruitment at 48h, despite waning inflammation. These data support a role for surfactant inactivation as a physiologic mechanism underlying respiratory dysfunction following Cl2 inhalation.

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.

IL-33 markedly activates murine eosinophils by an NF-κB-dependent mechanism differentially dependent upon an IL-4-driven autoinflammatory loop

Eosinophils are major effector cells in type 2 inflammatory responses and become activated in response to IL-4 and IL-33, yet the molecular mechanisms and cooperative interaction between these cytokines remain unclear. Our objective was to investigate the molecular mechanism and cooperation of IL-4 and IL-33 in eosinophil activation. Eosinophils derived from bone marrow or isolated from Il5-transgenic mice were activated in the presence of IL-4 or IL-33 for 1 or 4 h, and the transcriptome was analyzed by RNA sequencing. The candidate genes were validated by quantitative PCR and ELISA. We demonstrated that murine-cultured eosinophils respond to IL-4 and IL-33 by phosphorylation of STAT-6 and NF-κB, respectively. RNA sequence analysis of murine-cultured eosinophils indicated that IL-33 induced 519 genes, whereas IL-4 induced only 28 genes, including 19 IL-33-regulated genes. Interestingly, IL-33 induced eosinophil activation via two distinct mechanisms, IL-4 independent and IL-4 secretion/autostimulation dependent. Anti-IL-4 or anti-IL-4Rα Ab-treated cultured and mature eosinophils, as well as Il4- or Stat6-deficient cultured eosinophils, had attenuated protein secretion of a subset of IL-33-induced genes, including Retnla and Ccl17. Additionally, IL-33 induced the rapid release of preformed IL-4 protein from eosinophils by a NF-κB-dependent mechanism. However, the induction of most IL-33-regulated transcripts (e.g., Il6 and Il13) was IL-4 independent and blocked by NF-κB inhibition. In conclusion, we have identified a novel activation pathway in murine eosinophils that is induced by IL-33 and differentially dependent upon an IL-4 auto-amplification loop.

Selenium status alters the immune response and expulsion of adult Heligmosomoides bakeri worms in mice

Heligmosomoides bakeri is a nematode with parasitic development exclusively in the small intestine of infected mice that induces a potent STAT6-dependent Th2 immune response. We previously demonstrated that host protective expulsion of adult H. bakeri worms from a challenge infection was delayed in selenium (Se)-deficient mice. In order to explore mechanisms associated with the delayed expulsion, 3-week-old female BALB/c mice were placed on a torula yeast-based diet with or without 0.2 ppm Se, and after 5 weeks, they were inoculated with H. bakeri infective third-stage larvae (L3s). Two weeks after inoculation, the mice were treated with an anthelmintic and then rested, reinoculated with L3s, and evaluated at various times after reinoculation. Analysis of gene expression in parasite-induced cysts and surrounding tissue isolated from the intestine of infected mice showed that the local-tissue Th2 response was decreased in Se-deficient mice compared to that in Se-adequate mice. In addition, adult worms recovered from Se-deficient mice had higher ATP levels than worms from Se-adequate mice, indicating greater metabolic activity in the face of a suboptimal Se-dependent local immune response. Notably, the process of worm expulsion was restored within 2 to 4 days after feeding a Se-adequate diet to Se-deficient mice. Expulsion was associated with an increased local expression of Th2-associated genes in the small intestine, intestinal glutathione peroxidase activity, secreted Relm-β protein, anti-H. bakeri IgG1 production, and reduced worm fecundity and ATP-dependent metabolic activity.

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.

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.

The p110δ subunit of PI3K regulates bone marrow-derived eosinophil trafficking and airway eosinophilia in allergen-challenged mice

Trafficking and recruitment of eosinophils during allergic airway inflammation is mediated by the phosphatidylinositol 3-kinase (PI3K) family of signaling molecules. The role played by the p110δ subunit of PI3K (PI3K p110δ) in regulating eosinophil trafficking and recruitment was investigated using a selective pharmacological inhibitor (IC87114). Treatment with the PI3K p110δ inhibitor significantly reduced murine bone marrow-derived eosinophil (BM-Eos) adhesion to VCAM-1 as well as ICAM-1 and inhibited activation-induced changes in cell morphology associated with reduced Mac-1 expression and aberrant cell surface localization/distribution of Mac-1 and α4. Infused BM-Eos demonstrated significantly decreased rolling and adhesion in inflamed cremaster muscle microvessels of mice treated with IC87114 compared with vehicle-treated mice. Furthermore, inhibition of PI3K p110δ significantly attenuated eotaxin-1-induced BM-Eos migration and prevented eotaxin-1-induced changes in the cytoskeleton and cell morphology. Knockdown of PI3K p110δ with siRNA in BM-Eos resulted in reduced rolling, adhesion, and migration, as well as inhibition of activation-induced changes in cell morphology, validating its role in regulating trafficking and migration. Finally, in a mouse model of cockroach antigen-induced allergic airway inflammation, oral administration of the PI3K p110δ inhibitor significantly inhibited airway eosinophil recruitment, resulting in attenuation of airway hyperresponsiveness in response to methacholine, reduced mucus secretion, and expression of proinflammatory molecules (found in inflammatory zone-1 and intelectin-1). Overall, these findings indicate the important role played by PI3K p110δ in mediating BM-Eos trafficking and migration by regulating adhesion molecule expression and localization/distribution as well as promoting changes in cell morphology that favor recruitment during inflammation.

Alternaria induces STAT6-dependent acute airway eosinophilia and epithelial FIZZ1 expression that promotes airway fibrosis and epithelial thickness

The fungal allergen, Alternaria, is specifically associated with severe asthma, including life-threatening exacerbations. To better understand the acute innate airway response to Alternaria, naive wild-type (WT) mice were challenged once intranasally with Alternaria. Naive WT mice developed significant bronchoalveolar lavage eosinophilia following Alternaria challenge when analyzed 24 h later. In contrast to Alternaria, neither Aspergillus nor Candida induced bronchoalveolar lavage eosinophilia. Gene microarray analysis of airway epithelial cell brushings demonstrated that Alternaria-challenged naive WT mice had a >20-fold increase in the level of expression of found in inflammatory zone 1 (FIZZ1/Retnla), a resistin-like molecule. Lung immunostaining confirmed strong airway epithelial FIZZ1 expression as early as 3 h after a single Alternaria challenge that persisted for ≥5 d and was significantly reduced in STAT6-deficient, but not protease-activated receptor 2-deficient mice. Bone marrow chimera studies revealed that STAT6 expressed in lung cells was required for epithelial FIZZ1 expression, whereas STAT6 present in bone marrow-derived cells contributed to airway eosinophilia. Studies investigating which cells in the nonchallenged lung bind FIZZ1 demonstrated that CD45(+)CD11c(+) cells (macrophages and dendritic cells), as well as collagen-1-producing CD45(-) cells (fibroblasts), can bind to FIZZ1. Importantly, direct administration of recombinant FIZZ1 to naive WT mice led to airway eosinophilia, peribronchial fibrosis, and increased thickness of the airway epithelium. Thus, Alternaria induces STAT6-dependent acute airway eosinophilia and epithelial FIZZ1 expression that promotes airway fibrosis and epithelial thickness. This may provide some insight into the uniquely pathogenic aspects of Alternaria-associated asthma.

Macrophages in allergic asthma: fine-tuning their pro- and anti-inflammatory actions for disease resolution

Macrophages exert prominent effects in the defense of the respiratory tract from airborne pathogens. These cells are specialized to recognize, phagocytose, and destroy these infectious agents and then promote appropriate tissue repair after successful pathogen clearance. For reasons that are not presently clear, macrophages appear to be inappropriately activated during asthma responses. Evidence stems from the appearance of either classically (or M1) and alternatively activated (or M2) cells in the alveolar compartment of asthmatic lung. Macrophages localized in the interstitial area of the lung appear to be less prone to polarization toward either the M1 or M2 phenotype as these cells predominately express interleukin-10 and exhibit immunoregulatory properties. Effective treatment of clinical asthma, regardless of severity, might depend on restoring an appropriate balance between M1, M2, and immunoregulatory macrophages in the lung.

N-Glycans differentially regulate eosinophil and neutrophil recruitment during allergic airway inflammation

Allergic airway inflammation, including asthma, is usually characterized by the predominant recruitment of eosinophils. However, neutrophilia is also prominent during severe exacerbations. Cell surface-expressed glycans play a role in leukocyte trafficking and recruitment during inflammation. Here, the involvement of UDP-N-acetylglucosamine:α-6-D-mannoside β1,6-N-acetylglucosaminyltransferase V (MGAT5)-modified N-glycans in eosinophil and neutrophil recruitment during allergic airway inflammation was investigated. Allergen-challenged Mgat5-deficient (Mgat5(-/-)) mice exhibited significantly attenuated airway eosinophilia and inflammation (decreased Th2 cytokines, mucus production) compared with WT counterparts, attributable to decreased rolling, adhesion, and survival of Mgat5(-/-) eosinophils. Interestingly, allergen-challenged Mgat5(-/-) mice developed airway neutrophilia and increased airway reactivity with persistent elevated levels of proinflammatory cytokines (IL-17A, TNFα, IFNγ)). This increased neutrophil recruitment was also observed in LPS- and thioglycollate (TG)-induced inflammation in Mgat5(-/-) mice. Furthermore, there was significantly increased recruitment of infused Mgat5(-/-) neutrophils compared with WT neutrophils in the peritoneal cavity of TG-exposed WT mice. Mgat5(-/-) neutrophils demonstrated enhanced adhesion to P-selectin as well as increased migration toward keratinocyte-derived chemokine compared with WT neutrophils in vitro along with increased calcium mobilization upon activation and expression of elevated levels of CXCR2, which may contribute to the increased neutrophil recruitment. These data indicate an important role for MGAT5-modified N-glycans in differential regulation of eosinophil and neutrophil recruitment during allergic airway inflammation.

Fibrocytes: emerging effector cells in chronic inflammation

Fibrocytes are mesenchymal cells that arise from monocyte precursors. They are present in injured organs and have both the inflammatory features of macrophages and the tissue remodelling properties of fibroblasts. Chronic inflammatory stimuli mediate the differentiation, trafficking and accumulation of these cells in fibrosing conditions associated with autoimmunity, cardiovascular disease and asthma. This Opinion article discusses the immunological mediators controlling fibrocyte differentiation and recruitment, describes the association of fibrocytes with chronic inflammatory diseases and compares the potential roles of fibrocytes in these disorders with those of macrophages and fibroblasts. It is hoped that this information prompts new opportunities for the study of these unique cells.

Serum amyloid P attenuates M2 macrophage activation and protects against fungal spore-induced allergic airway disease

BACKGROUND

Aspergillus fumigatus conidia aggravate asthmatic responses. Lung macrophages normally kill fungal conidia, but the presence of type 2 cytokines during asthma contributes to the alternative (or M2) activation of these cells, which secrete proallergic factors and exhibit impaired innate immunity.

OBJECTIVE

Considering that pentraxins modulate macrophage function, we examined the effect of C-reactive protein (CRP) and serum amyloid P (SAP) in an experimental model of A fumigatus-induced allergic airway disease.

METHODS

The effects of SAP and CRP on M2 macrophage differentiation were examined in vitro, and the in vivo effects of these pentraxins were analyzed in the asthma model.

RESULTS

SAP inhibited the generation of M2 markers, such as arginase and the chitinase Ym-1, through an FcγR-dependent mechanism in cultured macrophages. This effect correlated with a decrease in signal transducer and activator of transcription 6 (STAT6) phosphorylation in SAP-treated M2 macrophages. In vivo treatment with SAP significantly decreased methacholine-induced bronchial resistance, mucus cell metaplasia, the number of "found in inflammatory zone 1" (FIZZ1)-positive cells in the lungs, and collagen deposition compared with the control group. CRP had a modest effect on M2 differentiation, and in vivo treatment with CRP had a minor effect or exacerbated A fumigatus-induced lung disease. Finally, the adoptive transfer of SAP-pretreated M2 macrophages into allergic mice significantly attenuated disease when compared with nontransferred or M2-transferred control groups.

CONCLUSIONS

These findings demonstrate that SAP is a potent inhibitor of M2 macrophage differentiation and represents a novel therapy in A fumigatus-induced allergic disease.

Allergen-induced airway remodeling is impaired in galectin-3-deficient mice

The role played by the beta-galactoside-binding lectin galectin-3 (Gal-3) in airway remodeling, a characteristic feature of asthma that leads to airway dysfunction and poor clinical outcome in humans, was investigated in a murine model of chronic allergic airway inflammation. Wild-type (WT) and Gal-3 knockout (KO) mice were subjected to repetitive allergen challenge with OVA up to 12 wk, and bronchoalveolar lavage fluid (BALF) and lung tissue collected after the last challenge were evaluated for cellular features associated with airway remodeling. Compared to WT mice, chronic OVA challenge in Gal-3 KO mice resulted in diminished remodeling of the airways with significantly reduced mucus secretion, subepithelial fibrosis, smooth muscle thickness, and peribronchial angiogenesis. The higher degree of airway remodeling in WT mice was associated with higher Gal-3 expression in the BALF as well as lung tissue. Cell counts in BALF and lung immunohistology demonstrated that eosinophil infiltration in OVA-challenged Gal-3 KO mice was significantly reduced compared with that WT mice. Evaluation of cellular mediators associated with eosinophil recruitment and airway remodeling revealed that levels of eotaxin-1, IL-5, IL-13, found in inflammatory zone 1, and TGF-beta were substantially lower in Gal-3 KO mice. Finally, leukocytes from Gal-3 KO mice demonstrated decreased trafficking (rolling) on vascular endothelial adhesion molecules compared with that of WT cells. Overall, these studies demonstrate that Gal-3 is an important lectin that promotes airway remodeling via airway recruitment of inflammatory cells, specifically eosinophils, and the development of a Th2 phenotype as well as increased expression of eosinophil-specific chemokines and profibrogenic and angiogenic mediators.

Targeting the airway smooth muscle for asthma treatment

Asthma is a complex respiratory disease whose incidence has increased worldwide in the last decade. Currently there is no cure for asthma. Although bronchodilator and anti-inflammatory medications are effective medicines in some asthmatic patients, it is clear that an unmet therapeutic need persists for a subpopulation of individuals with severe asthma. This chronic lung disease is characterized by airflow limitation, lung inflammation, and remodeling that includes increased airway smooth muscle (ASM) mass. In addition to its contractile properties, the ASM also contributes to the inflammatory process by producing active mediators, which modify the extracellular matrix composition and interact with inflammatory cells. These undesirable functions make interventions aimed at reducing ASM abundance an attractive strategy for novel asthma therapies. The following three mechanisms could limit the accumulation of smooth muscle: decreased cell proliferation, augmented cell apoptosis, and reduced cell migration into the smooth muscle layer. Inhibitors of the mevalonate pathway or statins hold promise for asthma treatment, because they exhibit anti-inflammatory, antimigratory, and antiproliferative effects in preclinical and clinical studies, and they can target the smooth muscle. This review will discuss current knowledge of ASM biology and identify gaps in the field to stimulate future investigations of the cellular mechanisms that control ASM overabundance in asthma. Targeting ASM has the potential to be an innovative venue of treatment for patients with asthma.

Deficiency of endothelial heparan sulfates attenuates allergic airway inflammation

The effect of targeted inactivation of the gene encoding N-deacetylase/N-sulfotransferase-1 (Ndst1), a key enzyme involved in the biosynthesis of heparan sulfate (HS) chains, on the inflammatory response associated with allergic inflammation in a murine model of OVA-induced acute airway inflammation was investigated. OVA-exposed Ndst1(f/f)TekCre(+) (mutant) mice deficient in endothelial and leukocyte Ndst1 demonstrated significantly decreased allergen-induced airway hyperresponsiveness and inflammation characterized by a significant reduction in airway recruitment of inflammatory cells (eosinophils, macrophages, neutrophils, and lymphocytes), diminished IL-5, IL-2, TGF-beta1, and eotaxin levels, as well as decreased expression of TGF-beta1 and the angiogenic protein FIZZ1 (found in inflammatory zone 1) in lung tissue compared with OVA-exposed Ndst1(f/f)TekCre(-) wild-type littermates. Furthermore, murine eosinophils demonstrated significantly decreased rolling on lung endothelial cells (ECs) from mutant mice compared with wild-type ECs under conditions of flow in vitro. Treatment of wild-type ECs, but not eosinophils, with anti-HS Abs significantly inhibited eosinophil rolling, mimicking that observed with Ndst1-deficient ECs. In vivo, trafficking of circulating leukocytes in lung microvessels of allergen-challenged Ndst1-deficient mice was significantly lower than that observed in corresponding WT littermates. Endothelial-expressed HS plays an important role in allergic airway inflammation through the regulation of recruitment of inflammatory cells to the airways by mediating interaction of leukocytes with the vascular endothelium. Furthermore, HS may also participate by sequestering and modulating the activity of allergic asthma-relevant mediators such as IL-5, IL-2, and TGF-beta1.