Interleukin-13 induces PSGL-1/P–selectin–dependent adhesion of eosinophils, but not neutrophils, to human umbilical vein endothelial cells under flow

Proteomic profiling for biomarker discovery in heparin-induced thrombocytopenia

ABSTRACT

New analytical techniques can assess hundreds of proteins simultaneously with high sensitivity, facilitating the observation of their complex interplay and role in disease mechanisms. We hypothesized that proteomic profiling targeting proteins involved in thrombus formation, inflammation, and the immune response would identify potentially new biomarkers for heparin-induced thrombocytopenia (HIT). Four existing panels of the Olink proximity extension assay covering 356 proteins involved in thrombus formation, inflammation, and immune response were applied to randomly selected patients with suspected HIT (confirmed HIT, n = 32; HIT ruled out, n = 38; and positive heparin/platelet factor 4 [H/PF4] antibodies, n = 28). The relative difference in protein concentration was analyzed using a linear regression model adjusted for sex and age. To confirm the test results, soluble P-selectin was determined using enzyme-linked immunosorbent assay (ELISA) in above mentioned patients and an additional second data set (n = 49). HIT was defined as a positive heparin-induced platelet activation assay (washed platelet assay). Among 98 patients of the primary data set, the median 4Ts score was 5 in patients with HIT, 4 in patients with positive H/PF4 antibodies, and 3 in patients without HIT. The median optical density of a polyspecific H/PF4 ELISA were 3.0, 0.9, and 0.3. Soluble P-selectin remained statistically significant after multiple test adjustments. The area under the receiver operating characteristic curve was 0.81 for Olink and 0.8 for ELISA. Future studies shall assess the diagnostic and prognostic value of soluble P-selectin in the management of HIT.

Cordyceps militaris polysaccharide alleviates ovalbumin-induced allergic asthma through the Nrf2/HO-1 and NF-κB signaling pathways and regulates the gut microbiota

Polysaccharides, as one of the main types of bioactive components of Cordyceps militaris, have anti-allergic asthma effects. Herein, an ovalbumin-induced allergic asthma mouse model was established to assess the potential mechanisms of the separated and purified Cordyceps militaris polysaccharide (CMP). CMP is an α-pyranose with a molecular weight of 15.94 kDa that consists of Glc, Man, Gal, Xyl, Ara and GlcA in a molar ratio of 81.25:21.96:13.88:3.92:3.58:1.00. CMP improved inflammatory cytokine levels, alleviated the histopathological changes in the lung and intestinal tissues, regulated the expression of mRNA and proteins related to oxidative stress and inflammatory pathways, reversed gut dysbiosis at the phylum and family levels and improved microbiota function in allergic asthma mice. Moreover, it was found that the levels of inflammatory cytokines in lung tissue of mice were significantly correlated with some intestinal microbial communities. Overall, CMP improved oxidative stress and the inflammatory response in allergic asthma mice by regulating the Nrf2/HO-1 and NF-κB signaling pathways, which may be closely correlation with maintaining the stability of the gut microbiota.

Dupilumab pharmacokinetics and effect on type 2 biomarkers in children with moderate-to-severe asthma

BACKGROUND

Type 2 inflammation is common in children with asthma. Dupilumab, a human antibody, blocks signaling of interleukin-4/-13, key and central drivers of type 2 inflammation. In the VOYAGE (NCT02948959) study, dupilumab reduced severe asthma exacerbations and improved lung function in children aged 6-11 years with uncontrolled, moderate-to-severe asthma.

OBJECTIVE

To assess pharmacokinetics of dupilumab and type 2 biomarker changes in children with type 2 asthma in VOYAGE.

METHODS

Patients were randomized to dupilumab 100 mg (≤30 kg) or 200 mg (>30 kg) or placebo every 2 weeks (q2w) for 52 weeks. Dupilumab concentrations and changes in type 2 biomarkers were assessed at each visit.

RESULTS

Dupilumab concentrations in serum reached steady state by Week 12, with mean concentrations of 51.2 mg/L and 79.4 mg/L in children receiving dupilumab 100 mg q2w and 200 mg q2w, respectively (therapeutic range in adults and adolescents: 29-80 mg/L). Reductions in type 2 biomarkers were comparable between regimens, and greater in patients treated with dupilumab vs placebo. In children treated with dupilumab 100 mg and 200 mg q2w, median percent changes (Q1, Q3) from baseline at Week 52 were, respectively, -78.6% (-86.3, -69.80) and -78.6% (-84.9, -70.1) for serum total IgE, -53.6% (-66.4, -34.6) and -43.7% (-58.6, -28.5) for TARC, -25.7% (-60.0, 27.6) and -33.3% (-60.6, 16.6) for blood eosinophils, and -47.7% (-73.8, 18.9) and -55.6% (-73.6, -20.0) for FeNO.

CONCLUSION

Weight-tiered dose regimens achieved mean concentrations within the dupilumab therapeutic range. Median decreases in type 2 biomarker levels were similar between dose regimens.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02948959.

Eosinophilic inflammation: An Appealing Target for Pharmacologic Treatments in Severe Asthma

Severe asthma is characterized by different endotypes driven by complex pathologic mechanisms. In most patients with both allergic and non-allergic asthma, predominant eosinophilic airway inflammation is present. Given the central role of eosinophilic inflammation in the pathophysiology of most cases of severe asthma and considering that severe eosinophilic asthmatic patients respond partially or poorly to corticosteroids, in recent years, research has focused on the development of targeted anti-eosinophil biological therapies; this review will focus on the unique and particular biology of the eosinophil, as well as on the current knowledge about the pathobiology of eosinophilic inflammation in asthmatic airways. Finally, current and prospective anti-eosinophil therapeutic strategies will be discussed, examining the reason why eosinophilic inflammation represents an appealing target for the pharmacological treatment of patients with severe asthma.

The onset, development and pathogenesis of severe neutrophilic asthma

Bronchial asthma is divided into Th2 high, Th2 low and mixed types. The Th2 high type is dominated by eosinophils while the Th2 low type is divided into neutrophilic and paucigranulocytic types. Eosinophilic asthma has gained increased attention recently, and its pathogenesis and treatment are well understood. However, severe neutrophilic asthma requires more in-depth research because its pathogenesis is not well understood, and no effective treatment exists. This review looks at the advances made in asthma research, the pathogenesis of neutrophilic asthma, the mechanisms of progression to severe asthma, risk factors for asthma exacerbations, and biomarkers and treatment of neutrophilic asthma. The pathogenesis of neutrophilic asthma is further discussed from four aspects: Th17-type inflammatory response, inflammasomes, exosomes and microRNAs. This review provides direction for the mechanistic study, diagnosis and treatment of neutrophilic asthma. The treatment of neutrophilic asthma remains a significant challenge for clinical therapists and is an important area of future clinical research.

Biological agents targeting interleukin-13 for atopic dermatitis

INTRODUCTION

Atopic dermatitis (AD) is a chronic inflammatory skin disease that is pathogenically driven by type-2 inflammation. Interleukin-13 (IL-13) plays a central role in AD pathogenesis, as confirmed by the clinical efficacy of agents that selectively block IL-13, although their therapeutic value and place-in-therapy are incompletely defined.

AREAS COVERED

The aim of this review article is to describe preclinical and clinical data regarding selective IL-13 inhibitors investigated in AD. In particular, we discuss the clinical outcomes obtained with lebrikizumab and tralokinumab, which are in a more advanced phase of development.

EXPERT OPINION

Biological agents that neutralize IL-13 have demonstrated clinical benefits in treating AD with excellent safety profiles. Robust clinical evidence exists in support of tralokinumab, which underwent phase III trials, met the predefined primary endpoints, and is approaching the market. In contrast, clinical trial testing for lebrikizumab needs to be completed to fully assess its therapeutic potential.

PLAIN LANGUAGE SUMMARY

Atopic dermatitis (AD) is a chronic pathological inflammatory skin disease that results from type-2 inflammation. Selective interleukin-13 (IL-13) inhibitors have shown clinical efficacy against AD, suggesting that IL-13 plays a central in AD pathogenesis. However, the therapeutic value and place-in-therapy of IL-13 inhibitors are incompletely defined. The aim of this review article is to describe preclinical and clinical data for selective IL-13 inhibitors against AD, including lebrikizumab and tralokinumab, which are in a more advanced phase of development. The up-to-date overview of the strengths and limitations of different agents used to treat AD discussed in this article might be useful in driving treatment decision.

Novel Pathophysiological Mechanisms of Thrombosis in Myeloproliferative Neoplasms

PURPOSE OF REVIEW

Thrombosis remains a leading cause of morbidity and mortality in BCR/ABL negative myeloproliferative neoplasms (MPN). Circulating blood cells are both increased in quantity and qualitatively abnormal in MPN, resulting in an increased thrombotic risk. Herein, we review recently elucidated mechanisms of MPN thrombosis and discuss implications of drugs currently under investigation for MPN.

RECENT FINDINGS

Recent studies highlight that in JAK2^V617F granulocytes and platelets, thrombo-inflammatory genes are upregulated. Furthermore, in JAK2^V617F granulocytes, protein expression of integrin CD11b, tissue factor, and leukocyte alkaline phosphatase are all increased. Overall, myeloid cells, namely neutrophils, may contribute in several ways, such as through increased adhesion via β1 integrin binding to VCAM1, increased infiltration, and enhanced inducibility to extrude neutrophil extracellular traps. Non-myeloid inflammatory cells may also contribute via secretion of cytokines. With regard to red blood cells, number, rigidity, adhesion, and generation of microvesicles may lead to increased vascular resistance as well as increased cell-cell interactions that promote rolling and adhesion. Platelets may also contribute in a similar fashion. Lastly, the vasculature is also increasingly appreciated, as several studies have demonstrated increased endothelial expression of pro-coagulant and pro-adhesive proteins, such as von Willebrand factor or P-selectin in JAK2^V617F endothelial cells. With the advent of molecular diagnostics, MPN therapeutics are advancing beyond cytoreduction. Our increased understanding of pro-inflammatory and thrombotic pathophysiology in MPN provides a rational basis for evaluation of in-development MPN therapeutics to reduce thrombosis.

The protective role of Zingerone in a murine asthma model via activation of the AMPK/Nrf2/HO-1 pathway

Asthma is one of the most common illnesses associated with chronic airway inflammation; however, there are currently no effective therapies apart from glucocorticoids. Zingerone (ZIN), an active compound isolated from ginger, has been reported to have a broad spectrum of pharmacological properties. In this study, Zingerone was administrated to H₂O₂-stimulated mouse airway epithelial cell line MLE12 cells and asthmatic mice. The concentration of cytokines was evaluated using enzyme-linked immunosorbent assay (ELISA). Hematoxylin-eosin (HE), Periodic Acid-Schiff (PAS) and Masson staining were used for histological analyses. Protein levels in cells or lung tissues were determined using western blot, immunohistochemistry staining. The results showed that treatment with Zingerone dramatically inhibited oxidative stress and the inflammatory response in MLE12 cells stimulated with H₂O₂ and asthmatic mice. Furthermore, Zingerone treatment could decrease the expression of phosphorylated (p)-IκBα and p65 (nuclear) and increase the expression of phosphorylation of AMP-activated protein kinase (p-AMPK), nuclear factor erythroid-2-related factor 2 (Nrf2), and hemeoxygenase-1 (HO-1) to alleviate oxidative damage and inflammation both in vivo and in vitro. In addition, Zingerone treatment reduced the exudation and infiltration of inflammatory cells and suppressed goblet cell hyperplasia in a murine asthma model. Treatment with Zingerone also decreased the level of interleukin (IL)-4, IL-5, IL-13, and increased the level of interferon gamma (IFN-γ) in the BALF and attenuated airway hyperresponsiveness (AHR). However, inhibition of AMPK or Nrf2 suppressed the cellular protective, antioxidative, and anti-inflammatory properties of Zingerone. Taken together, these results demonstrate that Zingerone possesses the potential to relieve asthma via upregulating the AMPK/Nrf2/HO-1 signaling pathway.

An endothelial microRNA-1-regulated network controls eosinophil trafficking in asthma and chronic rhinosinusitis

BACKGROUND

Airway eosinophilia is a prominent feature of asthma and chronic rhinosinusitis (CRS), and the endothelium plays a key role in eosinophil trafficking. To date, microRNA-1 (miR-1) is the only microRNA known to be regulated in the lung endothelium in asthma models.

OBJECTIVE

We sought to determine the role of endothelial miR-1 in allergic airway inflammation.

METHODS

We measured microRNA and mRNA expression using quantitative RT-PCR. We used ovalbumin and house dust mite models of asthma. Endothelium-specific overexpression of miR-1 was achieved through lentiviral vector delivery or induction of a transgene. Tissue eosinophilia was quantified by using Congo red and anti-eosinophil peroxidase staining. We measured eosinophil binding with a Sykes-Moore adhesion chamber. Target recruitment to RNA-induced silencing complex was assessed by using anti-Argonaute2 RNA immunoprecipitation. Surface P-selectin levels were measured by using flow cytometry.

RESULTS

Serum miR-1 levels had inverse correlations with sputum eosinophilia, airway obstruction, and number of hospitalizations in asthmatic patients and sinonasal tissue eosinophilia in patients with CRS. IL-13 stimulation decreased miR-1 levels in human lung endothelium. Endothelium-specific overexpression of miR-1 reduced airway eosinophilia and asthma phenotypes in murine models and inhibited IL-13-induced eosinophil binding to endothelial cells. miR-1 recruited P-selectin, thymic stromal lymphopoietin, eotaxin-3, and thrombopoietin receptor to the RNA-induced silencing complex; downregulated these genes in the lung endothelium; and reduced surface P-selectin levels in IL-13-stimulated endothelial cells. In our asthma and CRS cohorts, miR-1 levels correlated inversely with its target genes.

CONCLUSION

Endothelial miR-1 regulates eosinophil trafficking in the setting of allergic airway inflammation. miR-1 has therapeutic potential in asthmatic patients and patients with CRS.

Lymphatic Valves Separate Lymph Flow Into a Central Stream and a Slow-Moving Peri-Valvular Milieu

The lymphatic system plays a pivotal role in the transport of fats, waste, and immune cells, while also serving as a metastatic route for select cancers. Using live imaging and particle tracking, we experimentally characterized the lymph flow field distal from the inguinal lymph node in the vicinity of normal bileaflet and malformed unileaflet intraluminal valves. Particle tracking experiments demonstrated that intraluminal lymphatic valves concentrate higher velocity lymph flow in the center of the vessel, while generating adjacent perivalvular recirculation zones. The recirculation zones are characterized by extended particle residence times and low wall shear stress (WSS) magnitudes in comparison to the rest of the lymphangion. A malformed unileaflet valve skewed lymph flow toward the endothelium on the vessel wall, generating a stagnation point and a much larger recirculation zone on the opposite wall. These studies define physical consequences of bileaflet and unileaflet intraluminal lymphatic valves that affect lymph transport and the generation of a heterogeneous flow field that affects the lymphatic endothelium nonuniformly. The characterized flow fields were recreated in vitro connecting different flow environments present in the lymphangion to a lymphatic endothelial cell (LEC) pro-inflammatory phenotype. Unique and detailed insight into lymphatic flow is provided, with potential applications to a variety of diseases that affect lymph transport and drug delivery.

Dual blockade of IL-4 and IL-13 with dupilumab, an IL-4Rα antibody, is required to broadly inhibit type 2 inflammation

BACKGROUND

Dupilumab, a fully human monoclonal antibody that binds IL-4Rα and inhibits signaling of both IL-4 and IL-13, has shown efficacy across multiple diseases with underlying type 2 signatures and is approved for treatment of asthma, atopic dermatitis, and chronic sinusitis with nasal polyposis. We sought to provide a comprehensive analysis of the redundant and distinct roles of IL-4 and IL-13 in type 2 inflammation and report dupilumab mechanisms of action.

METHODS

Using primary cell assays and a mouse model of house dust mite-induced asthma, we compared IL-4 vs IL-13 vs IL-4Rα blockers.

RESULTS

Intranasal administration of either IL-4 or IL-13 confers an asthma-like phenotype in mice by inducing immune cell lung infiltration, including eosinophils, increasing cytokine/chemokine expression and mucus production, thus demonstrating redundant functions of these cytokines. We further teased out their respective contributions using human in vitro culture systems. Then, in a mouse asthma model by comparing in head-to-head studies, either IL-4 or IL-13 inhibition to dual IL-4/IL-13 inhibition, we demonstrate that blockade of both IL-4 and IL-13 is required to broadly block type 2 inflammation, which translates to protection from allergen-induced lung function impairment. Notably, only dual IL-4/IL-13 blockade prevented eosinophil infiltration into lung tissue without affecting circulating eosinophils, demonstrating that tissue, but not circulating eosinophils, contributes to disease pathology.

CONCLUSIONS

Overall, these data support IL-4 and IL-13 as key drivers of type 2 inflammation and help provide insight into the therapeutic mechanism of dupilumab, a dual IL-4/IL-13 blocker, in multiple type 2 diseases.

Mechanisms of eosinophilic inflammation

Eosinophils play roles in the pathogenesis of various diseases. In order to accumulate within sites of inflammation, eosinophils must adhere to, and migrate across the microvasculature. These processes are largely controlled by type 2-immune responses; interleukin (IL)-4 and IL-13 induce the expression of endothelial adhesion molecule vascular cell adhesion molecule-1 (VCAM-1), a representative adhesive ligand for eosinophils, while also stimulating generations of CC chemokines from structural cells, including epithelial cells. VCAM-1 and CC chemokines synergistically induce transmigration of eosinophils to the tissue inflammation site. Another type 2 cytokine, IL-5, prolongs survival, and enhances the effector functions of eosinophils. Recently, accumulating evidence has established that corticosteroid-resistant group 2 innate lymphoid cells are cellular sources for IL-5. Another immunological mechanism that may be contributing to eosinophilic inflammation involves type 1 immune system-associated molecules such as interferons and IP-10. In addition to these immune pathways, lipid mediators, such as cysteinyl leukotrienes, directly provoke the infiltration and activation of eosinophils. Extracellular matrix proteins including periostin also induce the adhesion and activation of eosinophils. Finally, activated neutrophils can also induce eosinophil transmigration. In summary, various mechanisms are involved within eosinophilic inflammation, and effective therapeutic strategies targeting these pathways should be established.

Contributions of Eosinophils to Human Health and Disease

The human eosinophil has long been thought to favorably influence innate mucosal immunity but at times has also been incriminated in disease pathophysiology. Research into eosinophil biology has uncovered a number of interesting contributions by eosinophils to health and disease. However, it appears that not all eosinophils from all species are created equal. It remains unclear, for example, exactly how having eosinophils benefits the human host when helminth infections in the developed world have become scarce. This review focuses on our current state of knowledge as it relates to human eosinophils. When information is lacking, we discuss lessons learned from mouse studies that may or may not directly apply to human biology and disease. It is an exciting time to be an "eosinophilosopher" because the use of biologic agents that selectively target eosinophils provides an unprecedented opportunity to define the contribution of this cell to eosinophil-associated human diseases.

Non-hematopoietic STAT6 induces epithelial tight junction dysfunction and promotes intestinal inflammation and tumorigenesis

Enhanced gut permeability due to dysregulated epithelial tight junction is often associated with inflammatory bowel diseases (IBD), which have a greater risk for developing colorectal cancer. STAT6 activation was detected in inflamed colonic epithelium of active IBD patients, suggesting a role of epithelial STAT6 in colitis development. Here, we demonstrated that non-hematopoietic STAT6, but not hematopoietic STAT6, triggered DSS-induced colitis and subsequent tumorigenesis. This could be due to the enhancing-effect of STAT6 on gut permeability and microbiota translocation via interruption of epithelial tight junction integrity. Mechanistically, long-myosin light-chain kinase (MLCK1) was identified as a target of STAT6, leading to epithelial tight junction dysfunction and microbiota-driven colitis. Furthermore, neutralization of IL-13, which was primarily derived from type 2 innate lymphoid cells (ILC2) in a microbiota-dependent way, inhibited epithelial STAT6 activation and improved gut permeability and DSS-induced colitis. Importantly, pharmacological inhibition of STAT6 reduces murine intestinal tumor formation, and tumoral p-STAT6 levels positively correlated to the clinical stage and poor prognosis of human colorectal cancer. Thus, our study reveals a direct role of STAT6 in the disruption of epithelial tight junction integrity and colitis development, and suggests STAT6 as a potential therapeutic and prophylactic target for IBD and colitis-associated cancer.

The diversity of myeloid immune cells shaping wound repair and fibrosis in the lung

In healthy circumstances the immune system coordinates tissue repair responses in a tight balance that entails efficient inflammation for removal of potential threats, proper wound closure, and regeneration to regain tissue function. Pathological conditions, continuous exposure to noxious agents, and even ageing can dysregulate immune responses after injury. This dysregulation can lead to a chronic repair mechanism known as fibrosis. Alterations in wound healing can occur in many organs, but our focus lies with the lung as it requires highly regulated immune and repair responses with its continuous exposure to airborne threats. Dysregulated repair responses can lead to pulmonary fibrosis but the exact reason for its development is often not known. Here, we review the diversity of innate immune cells of myeloid origin that are involved in tissue repair and we illustrate how these cell types can contribute to the development of pulmonary fibrosis. Moreover, we briefly discuss the effect of age on innate immune responses and therefore on wound healing and we conclude with the implications of current knowledge on the avenues for future research.

The role of non-invasive modalities for assessing inflammation in patients with non-cystic fibrosis bronchiectasis

INTRODUCTION

Bronchiectasis is a heterogeneous entity, taking into account clinical characteristics, inflammatory response, effectiveness of treatment and frequency of exacerbations. In stable state non-cystic fibrosis (non-CF) bronchiectasis, little is known about non-invasive techniques used for evaluating airway inflammation in obstructive airway diseases.

OBJECTIVES

We sought to evaluate the associations between induced sputum and clinical/radiologic characteristics, and the differences between biomarkers expressing Th1 and Th2 response in patients with non-CF bronchiectasis and to compare our findings with a previously studied population of patients with asthma and COPD.

METHODS

We evaluated prospectively collected data from subjects with bronchiectasis. Comparisons were made between clinical, radiographic and physiologic characteristics, as well as induced sputum markers using appropriate statistical tools. We compared the levels of sputum markers with those of a previously studied cohort of asthma and COPD patients.

RESULTS

We enrolled 40 subjects (21men, mean age 63.5yrs) with bronchiectasis. Fifteen subjects (37.5%) had a neutrophilic phenotype, 7 (17.5%) had an eosinophilic phenotype, 3 (12.5%) had a mixed neutrophilic-eosinophilic phenotype and 15 (37.5%) had a paucigranulocytic phenotype. Subjects with sputum neutrophilia had more severe bronchiectasis in HRCT and higher levels of IL-8 in sputum, whereas subjects with eosinophilia had higher levels of FeNO, greater bronchodilator reversibility and higher sputum IL-13. Sputum IL-8 levels were higher in subjects exhibiting frequent exacerbations and correlated with neutrophils in sputum (r=0.799), the extent of bronchiectasis in HRCT (r=0.765) and post-bronchodilator FEV₁ (r=-0.416). Sputum IL-13 levels correlated with sputum eosinophils (r=0.656) and bronchodilator reversibility (r=0.441). Neutrophilic bronchiectasis exhibited comparable IL-8 levels to COPD, whereas eosinophilic bronchiectasis showed significantly lower IL-13 levels compared to asthma.

CONCLUSIONS

Sputum cell counts and IL-8 and IL-13 correlate with distinct clinical and functional measurements of disease severity and therefore may have a role for non-invasively assessing inflammation in non-cystic fibrosis bronchiectasis.

Glycobiology of Eosinophilic Inflammation: Contributions of Siglecs, Glycans, and Other Glycan-Binding Proteins

The historical focus on protein-protein interactions in biological systems, at the expense of attention given to interactions between other classes of molecules, has overlooked important and clinically relevant processes and points of potential clinical intervention. For example, the significance of protein-carbohydrate interactions, especially in the regulation of immune responses, has recently received greater recognition and appreciation. This review discusses several ways by which cell-surface lectin-glycan interactions can modulate eosinophil function, particularly at the levels of eosinophil recruitment and survival, and how such interactions can be exploited therapeutically. A primary focus is on discoveries concerning Siglec-8, a glycan-binding protein selectively expressed on human eosinophils, and its closest functional paralog in the mouse, Siglec-F. Recent advances in the synthesis of polymeric ligands, the identification of physiological ligands for Siglec-8 and Siglec-F in the airway, and the determination of the basis of glycan ligand discrimination of Siglec-8 are discussed. Important similarities and differences between these siglecs are outlined. Eosinophil expression of additional glycan-binding proteins or their glycan ligands, including interactions involving members of the selectin, galectin, and siglec families, is summarized. The roles of these molecules in eosinophil recruitment, survival, and inflammation are described. Finally, the modulation of these interactions and potential therapeutic exploitation of glycan-binding proteins and their ligands to ameliorate eosinophil-associated diseases are considered.

The Biology of Eosinophils and Their Role in Asthma

This review will describe the structure and function of the eosinophil. The roles of several relevant cell surface molecules and receptors will be discussed. We will also explore the systemic and local processes triggering eosinophil differentiation, maturation, and migration to the lungs in asthma, as well as the cytokine-mediated pathways that result in eosinophil activation and degranulation, i.e., the release of multiple pro-inflammatory substances from eosinophil-specific granules, including cationic proteins, cytokines, chemokines growth factors, and enzymes. We will discuss the current understanding of the roles that eosinophils play in key asthma processes such as airway hyperresponsiveness, mucus hypersecretion, and airway remodeling, in addition to the evidence relating to eosinophil–pathogen interactions within the lungs.

Pathogenesis of asthma: implications for precision medicine

The pathogenesis of asthma is complex and multi-faceted. Asthma patients have a diverse range of underlying dominant disease processes and pathways despite apparent similarities in clinical expression. Here, we present the current understanding of asthma pathogenesis. We discuss airway inflammation (both T2^HIGH and T2^LOW), airway hyperresponsiveness (AHR) and airways remodelling as four key factors in asthma pathogenesis, and also outline other contributory factors such as genetics and co-morbidities. Response to current asthma therapies also varies greatly, which is probably related to the inter-patient differences in pathogenesis. Here, we also summarize how our developing understanding of detailed pathological processes potentially translates into the targeted treatment options we require for optimal asthma management in the future.

P-, but not E- or L-, selectin-mediated rolling adhesion persistence in hemodynamic flow diverges between metastatic and leukocytic cells

The ability of leukocytic cells to engage selectins via rolling adhesion is critical to inflammation, but selectins are also implicated in mediating metastatic dissemination. Using a microfluidic- and flow-based cell adhesion chromatography experimental and analytical technique, we interrogated the cell-subtype differences in engagement and sustainment of rolling adhesion on P-, E-, and L-selectin-functionalized surfaces in physiological flow. Our results indicate that, particularly at low concentrations of P-selectin, metastatic but not leukocytic cells exhibit reduced rolling adhesion persistence, whereas both cell subtypes exhibited reduced persistence on L-selectin and high persistence on E-selectin, differences not revealed by flow cytometry analysis or reflected in the extent or velocity of rolling adhesion. Conditions under which adhesion persistence was found to be significantly reduced corresponded to those exhibiting the greatest sensitivity to a selectin-antagonist. Our results suggest that potentially therapeutically exploitable differences in metastatic and leukocytic cell subtype interactions with selectins in physiological flow are identifiable through implementation of functional assays of adhesion persistence in hemodynamic flow utilizing this integrated, flow-based cell adhesion chromatography analytical technique.

Eosinophilic Lung Disease

Eosinophils are involved in the pathogenesis of a number of lung diseases. Recent advances in eosinophil biology have now produced clinically applicable therapies that seek to counter eosinophilia in blood and lungs. This article reviews the basic biology of eosinophils and their role in mediating T-helper 2 cell responses. The current status of anticytokine therapy for eosinophilic lung disease is discussed. A clinical approach to eosinophilic lung disease based on symptoms and radiography is generated. The clinical significance of persistent eosinophilia in lung transplant patients and patients with asthma will receive special emphasis.

Caveolae: A Role in Endothelial Inflammation and Mechanotransduction?

Vascular inflammation and disease progression, such as atherosclerosis, are in part a consequence of haemodynamic forces generated by changes in blood flow. The haemodynamic forces, such as shear stress or stretch, interact with vascular endothelial cells, which transduce the mechanical stimuli into biochemical signals via mechanosensors, which can induce an upregulation in pathways involved in inflammatory signaling. However, it is unclear how these mechanosensors respond to shear stress and most significantly what cellular mechanisms are involved in sensing the haemodynamic stimuli. This review explores the transition from shear forces, stretch and pressure to endothelial inflammation and the process of mechanotransduction, specifically highlighting evidence to suggest that caveolae play as a role as mechanosensors.

P-Selectin Expressed by a Human SELP Transgene Is Atherogenic in Apolipoprotein E-Deficient Mice

OBJECTIVE

During inflammation, P-selectin expressed on activated endothelial cells and platelets mediates rolling adhesion of leukocytes. Atherosclerosis-prone mice crossed with P-selectin-deficient (Selp(-/-)) mice develop smaller lesions. Cytokines, such as tumor necrosis factor-α, increase Selp transcripts and augment atherosclerosis in mice. However, they decrease SELP transcripts in humans, challenging assumptions that human P-selectin is atherogenic. We used mice expressing a human SELP transgene to examine the atherogenic role of P-selectin.

APPROACH AND RESULTS

We crossed apolipoprotein E-deficient (Apoe(-/-)) mice with Selp(-/-) mice or transgenic mice expressing the entire human SELP gene (TgSELP(+/-)). Aortas developed larger, macrophage-rich atheromas in Apoe(-/-)Selp(-/-)TgSELP(+/-) mice than in Apoe(-/-)Selp(-/-) mice after 8 or 16 weeks on a Western diet. Confocal microscopy of Apoe(-/-)Selp(-/-)TgSELP(+/-) aortas revealed staining for human P-selectin in endothelial cells overlying atheromas but not in lesional macrophages. We also observed staining for human P-selectin in aortic endothelial cells of 3- to 4-week-old Apoe(-/-)Selp(-/-)TgSELP(+/-) weanlings before atheromas developed. Furthermore, human SELP transcripts were ≈3-fold higher in aortas of Apoe(-/-)Selp(+/-)TgSELP(+/-) weanlings than in Selp(+/-)TgSELP(+/-) weanlings, whereas murine Selp and Sele transcripts were equivalent in weanlings of both genotypes. Human SELP transcripts in aortas of Apoe(-/-)Selp(+/-)TgSELP(+/-) mice remained nearly constant during 16 weeks on a Western diet, whereas murine Selp and Sele transcripts progressively increased. Bone marrow transplantation in Apoe(-/-)Selp(-/-) and Apoe(-/-)Selp(-/-)TgSELP(+/-) mice demonstrated that both platelets and endothelial cells must express human P-selectin to promote atherogenesis.

CONCLUSIONS

P-selectin expressed by human SELP is atherogenic in Apoe(-/-) mice, suggesting that P-selectin contributes to atherogenesis in humans.

Eosinophilic airway inflammation: role in asthma and chronic obstructive pulmonary disease

The chronic lung diseases, asthma and chronic obstructive pulmonary disease (COPD), are common affecting over 500 million people worldwide and causing substantial morbidity and mortality. Asthma is typically associated with Th2-mediated eosinophilic airway inflammation, in contrast to neutrophilic inflammation observed commonly in COPD. However, there is increasing evidence that the eosinophil might play an important role in 10-40% of patients with COPD. Consistently in both asthma and COPD a sputum eosinophilia is associated with a good response to corticosteroid therapy and tailored strategies aimed to normalize sputum eosinophils reduce exacerbation frequency and severity. Advances in our understanding of the multistep paradigm of eosinophil recruitment to the airway, and the consequence of eosinophilic inflammation, has led to the development of new therapies to target these molecular pathways. In this article we discuss the mechanisms of eosinophilic trafficking, the tools to assess eosinophilic airway inflammation in asthma and COPD during stable disease and exacerbations and review current and novel anti-eosinophilic treatments.

Eosinophilia in Pulmonary Disorders

Lung disease associated with marked peripheral blood eosinophilia is unusual and nearly always clinically significant. Once recognized, it is generally easy to manage, albeit with long-term systemic corticosteroids. A failure to respond to oral steroids in the context of good compliance suggests a malignant cause for the eosinophilia. An important development is the introduction of antieosinophil therapies, particularly those directed against the interleukin 5 pathway, which is hoped to provide benefit in the full spectrum of eosinophilic lung disease as well as asthma, reducing the burden of side effects and resultant comorbidities.

Histone deacetylation of memory T lymphocytes by You-Gui-Wan alleviates allergen-induced eosinophilic airway inflammation in asthma

Background

You-Gui pills (You-Gui-Wan; YGW) can promote T lymphocyte proliferation and differentiation, and restore Th1/Th2 balance in the treatment of asthma, but their mechanism of action is not fully known. This study aims to explore whether YGW can induce histone deacetylation or acetylation in memory T lymphocytes (Tm) for improvement of airway inflammation in asthma.

Methods

CD4⁺CD45RB^low cells, as Tm, were obtained by magnetic-activated cell sorting and flow cytometry from the spleens of BALB/c mice with ovalbumin (OVA)-induced asthma. Tm were cocultured with hydrocortisone (CORT; 1000 nM), serum containing low (0.225 g/kg), moderate (0.9 g/kg), or high (3.6 g/kg) doses of YGW, or medium only, and then adoptively transferred into naïve mice (n = 5 per group). Recipient mice were challenged with aerosolized OVA. The levels of IL-4, IL-5, IL-13, and IFN-γ in culture supernatants and bronchoalveolar lavage fluid (BALF) from the OVA-challenged mice were measured by ELISA. Histone deacetylase (HDAC) and histone acetyltransferase (HAT) activities and protein expressions of T-bet, GATA-3, and HDAC1–11 in lung tissue were measured by western blotting analyses. The alveolar eosinophilic inflammation index (AEII) was evaluated in the lungs of adoptive transfer recipient mice.

Results

YGW reduced inflammation and eosinophil infiltration into the lung tissues as evidenced by histology, with similar effects to those of CORT. High-, moderate-, and low-YGW increased HDAC (P < 0.0001, P = 0.0009 and P = 0.0253 respectively) and decreased HAT (P = 0.0001, P = 0.0000 and P = 0.0039, respectively) activities in dose-dependent manners in the lung tissues of adoptive transfer recipient mice. Increased histone deacetylation of Tm by YGW reduced the AEII by reducing GATA-3 (P = 0.014),IL-4 (P = 0.0004), IL-5 (P = 0.0067), and IL-13 (P = 0.0002), and inducing IFN-γ release (P = 0.0375). Moreover, YGW reduced inflammatory cytokines such as IL-4, IL-5, and IL-13 by upregulating the activities of HDAC7 (P = 0.003)/10 (P = 0.003), HDAC11 (P < 0.0001), and HDAC9–11 (P < 0.0001, P < 0.0001 and P < 0.0001, respectively), respectively, and increased IFN-γ release by increasing HDAC9 (P < 0.0001).

Conclusions

Histone deacetylation of Tm was observed during alleviation of allergen-induced eosinophilic airway inflammation in asthma by YGW.

Molecular biology of atopic dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin disease with specific genetic and immunological mechanisms. The rapid development of new techniques in molecular biology had ushered in new discoveries on the role of cytokines, chemokines, and immune cells in the pathogenesis of AD. New polymorphisms of AD are continually being reported in different populations. The physical and immunological barrier of normal intact skin is an important part of the innate immune system that protects the host against microbials and allergens that are associated with AD. Defects in the filaggrin gene FLG may play a role in facilitating exposure to allergens and microbial pathogens, which may induce Th2 polarization. Meanwhile, Th22 cells also play roles in skin barrier impairment through IL-22, and AD is often considered to be a Th2/Th22-dominant allergic disease. Mast cells and eosinophils are also involved in the inflammation via Th2 cytokines. Release of pruritogenic substances by mast cells induces scratching that further disrupts the skin barrier. Th1 and Th17 cells are mainly involved in chronic phase of AD. Keratinocytes also produce proinflammatory cytokines such as thymic stromal lymphopoietin (TSLP), which can further affect Th cells balance. The immunological characteristics of AD may differ for various endotypes and phenotypes. Due to the heterogeneity of the disease, and the redundancies of these mechanisms, our knowledge of the pathophysiology of the disease is still incomplete, which is reflected by the absence of a cure for the disease.

Vascular endothelial growth factor signaling in hypoxia and inflammation

Infection, cancer and cardiovascular diseases are the major causes for morbidity and mortality in the United States according to the Center for Disease Control. The underlying etiology that contributes to the severity of these diseases is either hypoxia induced inflammation or inflammation resulting in hypoxia. Therefore, molecular mechanisms that regulate hypoxia-induced adaptive responses in cells are important areas of investigation. Oxygen availability is sensed by molecular switches which regulate synthesis and secretion of growth factors and inflammatory mediators. As a consequence, tissue microenvironment is altered by re-programming metabolic pathways, angiogenesis, vascular permeability, pH homeostasis to facilitate tissue remodeling. Hypoxia inducible factor (HIF) is the central mediator of hypoxic response. HIF regulates several hundred genes and vascular endothelial growth factor (VEGF) is one of the primary target genes. Understanding the regulation of HIF and its influence on inflammatory response offers unique opportunities for drug development to modulate inflammation and ischemia in pathological conditions.

Eosinophils as diagnostic tools in chronic lung disease

Chronic lung diseases are very common and form a major threat to large proportions of the population with increased morbidity and mortality. Asthma is one of the most common eosinophilic airway diseases. However, there is growing evidence that eosinophilic inflammation is also important in subgroups of patients with chronic obstructive pulmonary disease, chronic cough and idiopathic pulmonary fibrosis. Several studies have shown that sputum eosinophilia is associated with a favorable response to treatment of corticosteroids in both asthma and chronic obstructive pulmonary disease, and tailored strategies aimed to normalize sputum eosinophils have resulted in a significant reduction in exacerbation rates. In this article, the authors review the role of eosinophilic inflammation in the diagnosis and management of chronic respiratory diseases.

Phenotyping airways disease: an A to E approach

The airway diseases asthma and chronic obstructive pulmonary disease (COPD) are heterogeneous conditions with overlapping pathophysiological and clinical features. It has previously been proposed that this heterogeneity may be characterized in terms of five relatively independent domains labelled from A to E, namely airway hyperresponsiveness (AHR), bronchitis, cough reflex hypersensitivity, damage to the airways and surrounding lung parenchyma, and extrapulmonary factors. Airway hyperresponsiveness occurs in both asthma and COPD, accounting for variable day to day symptoms, although the mechanisms most likely differ between the two conditions. Bronchitis, or airway inflammation, may be predominantly eosinophilic or neutrophilic, with different treatments required for each. Cough reflex hypersensitivity is thought to underlie the chronic dry cough out of proportion to other symptoms that can occur in association with airways disease. Structural changes associated with airway disease (damage) include bronchial wall thickening, airway smooth muscle hypertrophy, bronchiectasis and emphysema. Finally, a variety of extrapulmonary factors may impact upon airway disease, including rhinosinusitis, gastroesophageal reflux disease, obesity and dysfunctional breathing. This article discusses the A to E concept in detail and describes how this framework may be used to assess and treat patients with airway diseases in the clinic.

Statins Attenuate the Increase in P-Selectin Produced by Prolonged Exercise

Strenuous endurance exercise increases inflammatory markers and acutely increases cardiovascular risk; however, statins may mitigate this response. We measured serum levels of p-selectin in 37 runners treated with statins and in 43 nonstatin treated controls running the 2011 Boston Marathon. Venous blood samples were obtained the day before (PRE) as well as within 1 hour after (FINISH) and 24 hours after (POST) the race. The increase in p-selectin immediately after exercise was lower in statin users (PRE to FINISH: 20.5 ± 19.4 ng/mL) than controls (PRE to FINISH: 30.9 ± 27.1 ng/mL; P < 0.001). The increase in p-selectin 24 hours after exercise was also lower in statin users (PRE to POST: 21.5 ± 26.6 ng/mL) than controls (PRE to POST: 29.3 ± 31.9 ng/mL; P < 0.001). Furthermore, LDL-C was positively correlated with p-selectin at FINISH and POST (P < 0.01 and P < 0.05, resp.), irrespective of drug treatment, suggesting that lower levels of LDL-C are associated with a reduced inflammatory response to exercise. We conclude that statins blunt the exercise-induced increase in p-selectin following a marathon and that the inflammatory response to a marathon varies directly with LDL-C levels.

Interleukin-13 protects from atherosclerosis and modulates plaque composition by skewing the macrophage phenotype

Atherosclerotic lesions are characterized by the accumulation of oxidized LDL (OxLDL) and the infiltration of macrophages and T cells. Cytokine expression in the microenvironment of evolving lesions can profoundly contribute to plaque development. While the pro-atherogenic effect of T helper (Th) 1 cytokines, such as IFN-γ, is well established, the role of Th2 cytokines is less clear. Therefore, we characterized the role of the Th2 cytokine interleukin (IL)-13 in murine atherosclerosis. Here, we report that IL-13 administration favourably modulated the morphology of already established atherosclerotic lesions by increasing lesional collagen content and reducing vascular cell adhesion molecule-1 (VCAM-1)-dependent monocyte recruitment, resulting in decreased plaque macrophage content. This was accompanied by the induction of alternatively activated (M2) macrophages, which exhibited increased clearance of OxLDL compared to IFN-γ-activated (M1) macrophages in vitro. Importantly, deficiency of IL-13 results in accelerated atherosclerosis in LDLR^−/− mice without affecting plasma cholesterol levels. Thus, IL-13 protects from atherosclerosis and promotes a favourable plaque morphology, in part through the induction of alternatively activated macrophages.

Severely blunted allergen-induced pulmonary Th2 cell response and lung hyperresponsiveness in type 1 transient receptor potential channel-deficient mice

Transient receptor potential channels (TRPCs) are widely expressed and regulate Ca²⁺ entry in the cells that participate in the pathophysiology of airway hyperreactivity, inflammation, and remodeling. In vitro studies point to a role for TRPC1-mediated Ca²⁺ signaling in several of these cell types; however, physiological evidence is lacking. Here we identify TRPC1 signaling as proinflammatory and a regulator of lung hyperresponsiveness during allergen-induced pulmonary response. TRPC1-deficient (Trpc1(-/-)) mice are hyposensitive to methacholine challenge and have significantly reduced allergen-induced pulmonary leukocyte infiltration coupled with an attenuated T helper type 2 (Th2) cell response. Upon in vitro allergen exposure, Trpc1(-/-) splenocytes show impaired proliferation and T cell receptor-induced IL-2 production. A high number of germinal centers in spleens of Trpc1(-/-) mice and elevated levels of immunoglobulins in their serum are indicative of dysregulated B cell function and homeostasis. Thus we propose that TRPC1 signaling is necessary in lymphocyte biology and in regulation of allergen-induced lung hyperresponsiveness, making TRPC1 a potential target for treatment of immune diseases and asthma.

The Immunomodulatory Effect of You-Gui-Wan on Dermatogoides-pteronyssinus-Induced Asthma

The traditional Chinese medicine You-Gui-Wan (YGW) contains ten species of medicinal plants and has been used to improve health in remissive states of asthma for hundreds of years in Asia. However, little is known about the immunomodulatory mechanisms in vivo. Therefore, this study investigated the pathologic and immunologic responses to YGW in mice that had been repeatedly exposed to Dermatogoides-pteronyssinus (Der p). YGW reduced Der-p-induced airway hyperresponsiveness and total IgE in serum. It also inhibited eosinophil infiltration by downregulating the protein expression of IL-5 in serum and changed the Th2-bios in BALF by upregulating IL-12. Results of the collagen assay and histopathologic examination showed that YGW reduced airway remodeling in the lung. In addition, after YGW treatment there was a relative decrease in mRNA expression of TGF-β1, IL-13, eotaxin, RANTES, and MCP-1 in lung in the YGW group. The results of EMSA and immunohistochemistry revealed that YGW inhibited NF-κB expression in epithelial lung cells. YGW exerts its regulative effects in chronic allergic asthmatic mice via its anti-inflammatory activity and by inhibiting the progression of airway remodeling.

Role of chitin and chitinase/chitinase-like proteins in inflammation, tissue remodeling, and injury

The 18 glycosyl hydrolase family of chitinases is an ancient gene family that is widely expressed from prokaryotes to eukaryotes. In mammals, despite the absence of endogenous chitin, a number of chitinases and chitinase-like proteins (C/CLPs) have been identified. However, their roles have only recently begun to be elucidated. Acidic mammalian chitinase (AMCase) inhibits chitin-induced innate inflammation; augments chitin-free, allergen-induced Th2 inflammation; and mediates effector functions of IL-13. The CLPs BRP-39/YKL-40 (also termed chitinase 3-like 1) inhibit oxidant-induced lung injury, augments adaptive Th2 immunity, regulates apoptosis, stimulates alternative macrophage activation, and contributes to fibrosis and wound healing. In accord with these findings, levels of YKL-40 in the lung and serum are increased in asthma and other inflammatory and remodeling disorders and often correlate with disease severity. Our understanding of the roles of C/CLPs in inflammation, tissue remodeling, and tissue injury in health and disease is reviewed below.

RNA aptamer therapy for vaso-occlusion in sickle cell disease

Patients with sickle cell disease (SCD) often suffer painful vaso-occlusive episodes caused in part by the adhesion of sickle erythrocytes (SS-RBC) to the vascular endothelium. To investigate inhibition of SS-RBC adhesion as a possible treatment for vaso-occlusion, 2 adhesion molecules, α(v)β(3) and P-selectin, were targeted by high-affinity RNA aptamers. An in vitro flow chamber assay was used to test the antiadhesion activity of α(v)β(3) aptamer clone 17.16. Human SS-RBC were passed across a confluent monolayer of thrombin-stimulated human umbilical vein endothelial cells (HUVEC) at a constant rate. α(v)β(3) aptamer reduced SS-RBC adhesion to activated endothelial cells to the level seen with untreated HUVEC. An aptamer reactive with complement component 8 was used as a negative control and exerted no inhibition, confirming the specificity of α(v)β(3) aptamer (P=0.04). At 2 dyn/cm(2) shear stress, 30 nM α(v)β(3) aptamer showed maximal effect in decreasing SS-RBC adhesion to HUVEC. The antiadhesive activity of the P-selectin aptamer clone PF377 was also tested using HUVEC pretreated with IL-13 to upregulate expression of P-selectin as seen in activated endothelial cells. At 1 dyn/cm(2) shear stress, 60 nM of P-selectin aptamer had antiadhesion activity similar to heparin, a known inhibitor of SS-RBC adhesion to P-selectin. A negative control did not prevent adhesion (P=0.05). These data show the potential utility of aptamers to block endothelial adhesion molecules to prevent or treat vaso-occlusion in SCD.

Differential regulation of human and murine P-selectin expression and function in vivo

Basal and inducible expression of human P-selectin in transgenic mice differs from that of murine P-selectin, resulting in distinct functions.

Leukocytes roll on P-selectin after its mobilization from secretory granules to the surfaces of platelets and endothelial cells. Tumor necrosis factor (TNF), IL-1β, and lipopolysaccharide increase synthesis of P-selectin in murine but not in human endothelial cells. To explore the physiological significance of this difference in gene regulation, we made transgenic mice bearing the human Selp gene and crossed them with mice lacking murine P-selectin (Selp^−/−). The transgenic mice constitutively expressed human P-selectin in platelets, endothelial cells, and macrophages. P-selectin mediated comparable neutrophil migration into the inflamed peritoneum of transgenic and wild-type (WT) mice. Leukocytes rolled similarly on human or murine P-selectin on activated murine platelets and in venules of the cremaster muscle subjected to trauma. However, TNF increased murine P-selectin in venules, slowing rolling and increasing adhesion, whereas it decreased human P-selectin, accelerating rolling and decreasing adhesion. Both P- and E-selectin mediated basal rolling in the skin of WT mice, but E-selectin dominated rolling in transgenic mice. During contact hypersensitivity, murine P-selectin messenger (m) RNA was up-regulated and P-selectin was essential for leukocyte recruitment. However, human P-selectin mRNA was down-regulated and P-selectin contributed much less to leukocyte recruitment. These findings reveal functionally significant differences in basal and inducible expression of human and murine P-selectin in vivo.

Eosinophils, bronchitis and asthma: pathogenesis of cough and airflow obstruction

Eosinophilic airway inflammation is commonly observed in chronic cough in patients with asthma and non-asthmatic eosinophilic bronchitis. Indeed asthma and non-asthmatic eosinophilic bronchitis are amongst the commonest causes of chronic cough accounting for about 25 and 10% of cases respectively. In most cases the trigger that causes the cough is uncertain; however removal of potential triggers is important to consider in particular with respect to occupational exposure to known sensitizers. In both conditions the cough improves subjectively and objectively following treatment with corticosteroids. This improvement is associated with the presence of an airway eosinophilia, but whether eosinophilic inflammation is the cause of cough or an epiphenomenon is uncertain. The success of anti-IL5 to reduce eosinophilic inflammation and asthma exacerbations contrasts with the lack of efficacy to modify cough in asthma and therefore challenges a causal association. Both asthma and non-asthmatic eosinophilic bronchitis can lead onto airway remodeling and result in persistent airflow obstruction. However, response to corticosteroid therapy in both conditions is generally very good and the limited long term data available suggests that both usually have a benign course. Interestingly, improvement in airway remodeling in response to anti-IL5 observed using CT imaging and analysis of sub-epithelial matrix deposition does suggest that the eosinophil may play a causal role in airway remodeling.

Interleukin-13: prospects for new treatments

IL-13 is a T-helper type 2 cytokine. Animal models have implicated IL-13 as a critical cytokine in the development of asthma and chronic obstructive pulmonary disease (COPD). In vitro IL-13 exerts important effects on both structural and inflammatory cells within the airway and has the capacity to drive the clinical features of airways disease. In asthma, this view is strongly supported by associations with IL-13 genetic polymorphisms and increased mRNA and protein expression in blood, sputum and bronchial submucosa. In particular, IL-13 up-regulation is associated with severe disease. Current evidence in COPD is conflicting, with some reports supporting and others refuting a role for IL-13. Early clinical trials of anti-IL-13 therapies in asthma have shown promise, and the results of further efficacy studies are eagerly awaited.

Gastrin induces the interaction between human mononuclear leukocytes and endothelial cells through the endothelial expression of P-selectin and VCAM-1

Gastric mucosal inflammation is frequently associated with hypergastrinemia, and a correlation exists between the level of gastrin and degree of gastritis. We have previously observed that gastrin promotes leukocyte-endothelial interactions and contributes to Helicobacter-induced inflammation in the rat mesentery. In the present study, we aimed to evaluate a possible proinflammatory activity of gastrin in humans. The interaction between human leukocytes [U-937 cells, peripheral blood polymorphonuclear (PMN), and peripheral blood mononuclear (PBMC) cells] and human umbilical vein endothelial cells (HUVEC) was analyzed in static and dynamic conditions. The endothelial expression of adhesion molecules [P-selectin, E-selectin, intercellular adhesion molecule-1, vascular cell adhesion molecule (VCAM)-1] was analyzed by flow cytometry and fluorescent microscopy screening. Gastrin increased the static adhesion of U-937 cells to HUVEC (1 h; 10(-9) M: 122 +/- 9%; 10(-8) M: 143 +/- 17%; 10(-7) M: 162 +/- 14% vs. control, all P < 0.05). Incubation of HUVEC with gastrin (4 h) also increased PBMC rolling (vehicle: 63 +/- 12; 10(-9) M: 109 +/- 29; 10(-8) M: 141 +/- 24; 10(-7) M: 261 +/- 16 leukocytes/min, P < 0.05) and adhesion (vehicle: 3 +/- 2, 10(-9) M: 11 +/- 4, 10(-8) M: 17 +/- 5, 10(-7) M: 15 +/- 5 leukocytes/mm(2), all P < 0.05) in the parallel-plate flow chamber. Treatment of PBMC with gastrin had no effects. The cholecystokinin (CCK)-2 receptor antagonist (L-365,260, 10(-7) M) prevented the effects of gastrin. P-selectin and VCAM-1 expression were enhanced by gastrin, and neutralizing antibodies against these molecules prevented PBMC rolling and adhesion. Gastrin did not affect the interactions between HUVEC and PMN. Gastrin induces interactions between human mononuclear leukocytes and endothelial cells through the activation of CCK-2 receptors and the enhancement of endothelial P-selectin and VCAM-1.

Eosinophil progenitors in allergy and asthma - do they matter?

Allergic inflammation is associated with marked infiltration of eosinophils in affected tissues. The eosinophil is believed to be a key effector cells in allergen induced asthma pathogenesis. However, the role of eosinophils in the clinical manifestation of asthma has recently been questioned, since therapies directed against eosinophil infiltration (i.e. anti-interleukin-5) failed to improve clinical symptoms such as airways hyper-responsiveness (AHR) in patients with asthma. Although eosinophils in peripheral blood and the airways were largely depleted after anti-IL-5 treatment, residual eosinophilia in lung tissue persisted, which permits speculation that the remaining eosinophils may be sufficient to drive the asthma symptomatology. Furthermore, recent findings suggest that primitive eosinophil progenitor cells traffic from the bone marrow to sites of inflammation in response to allergen exposure. These progenitors may then differentiate in situ and thus provide an ongoing supply of mature pro-inflammatory cells and secretory mediators that augment the inflammatory response. In the present article, we will review the evidence for these findings, and discuss the rationale for targeting hematopoiesis and their migration pathways in the treatment of allergic diseases. Furthermore, this review will highlight the hypothesis that both IL-5- and CCR3-mediated signaling pathways may need to be targeted in order to control the inflammation and AHR associated with asthma.

Transgenic expression of interleukin-13 in the skin induces a pruritic dermatitis and skin remodeling

IL-13 has been implicated in the pathogenesis of allergic diseases, including atopic dermatitis (AD). However, a direct role of IL-13 in AD has not been established. We aimed to develop an inducible transgenic model in which IL-13 can be expressed in the skin and to define the resulting dermal phenotype and mechanisms involved. The keratin 5 promoter was used with a tetracycline-inducible system to target IL-13 to the skin. The clinical manifestations, dermal histology, cytokine gene regulation, and systemic immune responses in the transgenic mice were assessed. IL-13 was produced exclusively in the skin and caused a chronic inflammatory phenotype characterized by xerosis and pruritic eczematous lesions; dermal infiltration of CD4+ T cells, mast cells, eosinophils, macrophages, and Langerhans cells; upregulation of chemokine and cytokine genes, including thymic stromal lymphopoietin; and skin remodeling with fibrosis and increased vasculature. The dermal phenotype was accompanied by elevated serum total IgE and IgG1 and increased production of IL-4 and IL-13 by CD4+ cells from lymphoid tissues and peripheral blood mononuclear cells. IL-13 is a potent stimulator of dermal inflammation and remodeling and this transgenic model of AD is a good tool for investigating the underlying mechanisms in the pathogenesis of AD.

The physiology of leukocyte recruitment: an in vivo perspective

The mechanisms of leukocyte recruitment have been studied extensively in vitro and have shed light on the basic molecular structure-function relationship of adhesion and signaling molecules involved in this essential immune response. This review will summarize how these in vitro observations extend to leukocyte behavior in inflamed blood vessels in the microcirculation. We highlight physiological results that might not have been predicted from in vitro systems. Special attention is placed on the physiology of rolling, adhesion, and intralumenal crawling in blood vessels. The importance of the glycocalyx, secondary tethers, shear, and the microenvironment are discussed. Docking structures forming rings of adhesion molecules together with a novel endothelial dome-like structure in vivo during transmigration are highlighted. Transcellular and paracellular emigration out of inflamed blood vessels is also discussed. The last section highlights leukocyte recruitment in some organs that do not always follow the accepted paradigm of leukocyte recruitment.

Role and regulation of sickle red cell interactions with other cells: ICAM-4 and other adhesion receptors

Erythrocytes containing primarily hemoglobin S (SS RBCs) are abnormally adherent. We now know that SS RBCs express numerous adhesion molecules, and that many of these can undergo activation. SS RBCs exposed briefly to epinephrine show markedly increased adhesion to both laminin and endothelial cells. In vivo, infusion of epinephrine-activated but not unstimulated SS RBCs causes RBC adhesion, vaso-occlusion, organ trapping, and shortened RBC survival in the circulation. Epinephrine treatment of SS RBCs before infusion also induces adhesion of murine leukocytes to vascular walls. Indeed, in vitro, SS RBCs can activate leukocyte adhesion and cytokine production. We now have demonstrated both in vitro and in vivo evidence for the importance of RBC signaling and have also shown that SS RBC adhesion is determined by genetic polymorphisms in the signaling pathway that activates adhesion. These advances will hopefully lead to new therapeutic modalities for sickle cell disease.

Leukocyte adhesion in the liver: distinct adhesion paradigm from other organs

It is well known that leukocyte recruitment is a multi-step cascade that requires an initial tethering to the endothelium of post-capillary venules followed by rolling along the vessel wall until appropriate activating molecules are encountered which cause firm adhesion and emigration out of the vasculature. Recruitment of leukocytes in the post-sinusoidal venules of the liver follows a similar paradigm. However, distinct from most other organs is the observation that many leukocytes can also be seen adhering in the sinusoids which are specialized hepatic capillaries. In this review, the lack of importance of rolling in sinusoids is discussed. The molecular mechanisms leading to adhesion in the liver sinusoids can occur via integrin-dependent as well as integrin-independent mechanisms. In addition to the "classical" beta(1)- and beta(2)-integrin adhesion, some of the "non-classical" (non-integrin dependent) pathways including CD44 and vascular adhesion protein-1, are discussed.