Expression of the anaphylatoxin receptors C3aR and C5aR is increased in fatal asthma

Adult anaphylaxis: A state-of-the-art review

Anaphylaxis is the most severe among acute allergic diseases and potentially life threatening. Despite its increasing frequency and related burden, it remains often underdiagnosed and improperly managed. Its multisystemic involvement, protean clinical manifestations and its rapid onset are contributory factors. In recent years new acquisitions have shed light into its pathogenesis pathways (and related biomarkers), triggers, factors increasing its severity, along with peculiar clinical manifestations. These breakthrough discoveries have contributed to phenotyping and endotyping this disease, possibly paving the way to a personalized approach which is not available at present. Moreover, to disseminate awareness and standardize diagnostic criteria and management practices, several guidelines and consensus reports, albeit mainly intended for specialist care, have been issued. We here discuss the latest issues in the field of anaphylaxis from the perspective of the emergency and/or internal medicine physician, so to improve its early recognition and treatment in the acute setting and favor allergology referral to implement therapeutical and preventive strategies, such as allergen identification in unclear cases and desensitizing therapies when available (e.g., for Hymenoptera venom allergy).

Will the asthma revolution fostered by biologics also benefit adult ICU patients?

PURPOSE

Asthma exacerbations are inflammatory events that rarely result in full hospitalization following an ER visit. Unfortunately, certain patients require prolonged support, including occasional external lung support through ECMO or ECCOR (with subsequent further exposure to other life-threatening issues), and some die. In parallel, biologics are revolutionizing severe asthma management, mostly in T2 high patients.

METHODS

We extensively reviewed the current unmet needs surrounding ICU-admitted asthma exacerbations, with a focus on currently available drugs and the underlying biological processes involved. We explored whether currently available T2-targeting drugs can reasonably be seen as potential players not only for relapse prevention but also as candidate drugs for a faster resolution of such episodes. The patient's perspective was also sought.

RESULTS

About 30% of asthma exacerbations admitted to the ICU do not resolve within five days. Persistent severe airway obstruction despite massive doses of corticosteroids and maximal pharmacologically induced bronchodilation is the main cause of treatment failure. Previous ICU admission is the main risk factor for such episodes and may eventually be considered as a T2 surrogate marker. Fatal asthma cases are hallmarked by poorly steroid-sensitive T2-inflammation associated with severe mucus plugging. New, fast-acting T2-targeting biologics (already used for preventing asthma exacerbations) have the potential to circumvent steroid sensitivity pathways and decrease mucus plugging. This unmet need was confirmed by patients who reported highly negative, traumatizing experiences.

CONCLUSIONS

There is room for improvement in the management of ICU-admitted severe asthma episodes. Clinical trials assessing how biologics might improve ICU outcomes are direly needed.

Evaluation and management of the critically ill adult asthmatic in the emergency department setting

INTRODUCTION

Asthma is a common reason for presentation to the Emergency Department and is associated with significant morbidity and mortality. While patients may have a relatively benign course, there is a subset of patients who present in a critical state and require emergent management.

OBJECTIVE

This narrative review provides evidence-based recommendations for the assessment and management of patients with severe asthma.

DISCUSSION

It is important to consider a broad differential diagnosis for the cause and potential mimics of asthma exacerbation. Once the diagnosis is determined, the majority of the assessment is based upon the clinical examination. First line therapies for severe exacerbations include inhaled short-acting beta agonists, inhaled anticholinergics, intravenous steroids, and magnesium. Additional therapies for refractory cases include parenteral epinephrine or terbutaline, helium‑oxygen mixture, and consideration of ketamine. Intravenous fluids should be administered, as many of these patients are dehydrated and at risk for hypotension if they receive positive pressure ventilatory support. Noninvasive positive pressure ventilation may prevent the need for endotracheal intubation. If mechanical ventilation is required, it is important to avoid breath stacking by setting a low respiratory rate and allowing permissive hypercapnia. Patients with severe asthma exacerbations will require intensive care unit admission.

CONCLUSIONS

This review provides evidence-based recommendations for the assessment and management of severe asthma with a focus on the emergency clinician.

The anaphylatoxin C3a primes model colonic epithelial cells for expression of inflammatory mediators through Gαi

Multiple studies have identified that complement becomes activated during inflammation of the intestines yet it is unclear what roles the split complement molecules play. The epithelium, in particular, may be impacted and accordingly, we first discovered that colonic cell lines indeed possess the C5aR. Here we examined whether these cells also possess the C3aR. We determined that T84, HT-29 and Caco2 all possess C3aR mRNA and protein; T84 and HT29 were used to further explore the consequence of C3a binding the C3aR. C3a led to increased mRNA for CXCL2, CXCL8 and CXCL11. Polarized T84 monolayers responded to apically applied C3a with increased CXCL8 mRNA more rapidly than if the C3a was applied basolaterally. Polarized monolayers also increased permeability when treated with C3a. ERK1/2 was activated by C3a and the increase in CXCL8 mRNA was ERK-dependent in both T84 and HT-29. C3a resulted in activation of Gαi, determined by the ERK1/2 signal showing sensitivity to pertussis toxin. The transmembrane signal was further mapped to include Ras and c-Raf. Finally, we show that the C3aR is expressed by primary cells in mouse enteroids. We conclude that complement activation will contribute to the epithelial response during inflammation through C3a binding to the C3aR including by priming the cells to upregulate mRNA for selected chemokines.

Anaphylaxis in the 21st century: phenotypes, endotypes, and biomarkers

Anaphylaxis is the most serious of all allergic reactions and can be fatal. The diagnosis is frequently delayed, and misdiagnosis often occurs with asthma or urticaria. Biomarkers such as tryptase are not routinely checked, and appropriate treatment with epinephrine is not administered in a majority of cases, increasing the risk of poor outcomes. The objective of this review is to provide a better understanding of the pathophysiology of anaphylaxis with a description of phenotypes, endotypes, and biomarkers available in both the clinical and research settings. Expanding knowledge with regard to the presentation, causes, and triggers for anaphylaxis among health care providers will improve its diagnosis and management, increase patient safety, and decrease morbidity and mortality.

Respiratory Syncytial Virus Exacerbates OVA-mediated asthma in mice through C5a-C5aR regulating CD4+T cells Immune Responses

Asthma exacerbation could be induced by respiratory syncytial virus (RSV), and the underlying pathogenic mechanism is related to complement activation. Although complement might regulate CD4⁺T cells immune responses in asthma model, this regulation existed in RSV-induced asthma model remains incompletely characterrized. In this study, we assessed the contribution of C5a-C5aR to CD4⁺T cell immune responses in RSV-infected asthma mice. Female BALB/C mice were sensitized and challenged with ovalbumin (OVA) while treated with RSV infection and C5a receptor antagonist (C5aRA) during challenge period. RSV enhanced lung damage, airway hyperresponsiveness, and C5aR expressions in asthma mice, while C5aRA alleviated these pathologic changes. The percentages of Th1, Th2 and Th17 cells were increased, while the percentage of Treg cells was decreased in RSV-infected asthma mice compared with asthma mice. IFN-γ, IL-4, IL-10 and IL-17A levels have similar trend with Th1, Th2, Th17 and Treg cells. Notably, above changes of CD4⁺T cells and their related cytokines were reversed by C5aRA. Together, the data indicates that RSV infection could apparently increase C5a and C5aR expression in the pathogenesis of RSV-infected asthma mice, meanwhile C5aRA prevents some of the CD4⁺T cells immune changes that are induced by RSV.

Diagnosis and management of anaphylaxis in precision medicine

Anaphylaxis is the most severe and frightening of the allergic reactions, placing patients at high risk and demanding prompt recognition and immediate management by health care providers. Yet because its symptoms imitate those of other diseases, such as asthma and urticaria, current data suggest that its diagnosis is often missed, with underuse of tryptase measurement; its treatment is delayed, with little use of epinephrine; and its underlying cause or causes are poorly investigated. Deaths from anaphylaxis are difficult to investigate because of miscoding. Surprisingly, patients treated with new and powerful chemotherapy agents and humanized mAbs present with nonclassical symptoms of anaphylaxis, and patients may present with unrecognized clonal mast cell disorders with KIT mutations may present as Hymenoptera-induced or idiopathic anaphylaxis. The goal of this review is to recognize the presentations of anaphylaxis with the description of its current phenotypes, to provide new insight and understanding of its mechanisms and causes through its endotypes, and to address its biomarkers for broad clinical use. Ultimately, the aim is to empower allergists and heath care providers with new tools that can help alleviate patients' symptoms, preventing and protecting them against anaphylaxis.

Regulation of Eosinophil and Group 2 Innate Lymphoid Cell Trafficking in Asthma

Asthma is an inflammatory disease usually characterized by increased Type 2 cytokines and by an infiltration of eosinophils to the airways. While the production of Type 2 cytokines has been associated with T_H2 lymphocytes, increasing evidence indicates that group 2 innate lymphoid cells (ILC2) play an important role in the production of the Type 2 cytokines interleukin (IL)-5 and IL-13, which likely amplifies the recruitment of eosinophils from the blood to the airways. In that regard, recent asthma treatments have been focusing on blocking Type 2 cytokines, notably IL-4, IL-5, and IL-13. These treatments mainly result in decreased blood or sputum eosinophil counts as well as decreased asthma symptoms. This supports that therapies blocking eosinophil recruitment and activation are valuable tools in the management of asthma and its severity. Herein, we review the mechanisms involved in eosinophil and ILC2 recruitment to the airways, with an emphasis on eotaxins, other chemokines as well as their receptors. We also discuss the involvement of other chemoattractants, notably the bioactive lipids 5-oxo-eicosatetraenoic acid, prostaglandin D₂, and 2-arachidonoyl-glycerol. Given that eosinophil biology differs between human and mice, we also highlight and discuss their responsiveness toward the different eosinophil chemoattractants.

Mechanism of TH2/TH17-predominant and neutrophilic TH2/TH17-low subtypes of asthma

BACKGROUND

The mechanism of T_H2/T_H17-predominant and T_H2/T_H17-low asthma is unknown.

OBJECTIVE

We sought to study the immune mechanism of T_H2/T_H17-predominant and T_H2/T_H17-low asthma.

METHODS

In a previously reported cohort of 60 asthmatic patients, 16 patients were immunophenotyped with T_H2/T_H17-predominant asthma and 22 patients with T_H2/T_H17-low asthma. We examined bronchoalveolar lavage (BAL) fluid leukocytes, cytokines, mediators, and epithelial cell function for these asthma subgroups.

RESULTS

Patients with T_H2/T_H17-predominant asthma had increased IL-1β, IL-6, IL-23, C3a, and serum amyloid A levels in BAL fluid, and these correlated with IL-1β and C3a levels. T_H2/T_H17 cells expressed higher levels of the IL-1 receptor and phospho-p38 mitogen-activated protein kinase. Anakinra, an IL-1 receptor antagonist protein, inhibited BAL T_H2/T_H17 cell counts. T_H2/T_H17-low asthma had 2 distinct subgroups: neutrophilic asthma (45%) and pauci-inflammatory asthma (55%). This contrasted with patients with T_H2/T_H17-predominant and T_H2-predominant asthma, which included neutrophilic asthma in 6% and 0% of patients, respectively. BAL fluid neutrophils strongly correlated with BAL fluid myeloperoxidase, IL-8, IL-1α, IL-6, granulocyte colony-stimulating factor, and GM-CSF levels. Sixty percent of the patients with neutrophilic asthma had a pathogenic microorganism in BAL culture, which suggested a subclinical infection.

CONCLUSION

We uncovered a critical role for the IL-1β pathway in patients with T_H2/T_H17-predminant asthma. A subgroup of patients with T_H2/T_H17-low asthma had neutrophilic asthma and increased BAL fluid IL-1α, IL-6, IL-8, granulocyte colony-stimulating factor, and GM-CSF levels. IL-1α was directly involved in IL-8 production and likely contributed to neutrophilic asthma. Sixty percent of neutrophilic patients had a subclinical infection.

Complement C3a Mobilizes Dental Pulp Stem Cells and Specifically Guides Pulp Fibroblast Recruitment. J Endod. 2016;42:1377-1384. [PMID: 27497510 DOI: 10.1016/j.joen.2016.06.011]

INTRODUCTION

Complement activation is considered a major mechanism in innate immunity. Although it is mainly involved in initiating inflammation, recent data reported its involvement in other processes such as tissue regeneration. In the dental pulp, complement C5a fragment has been shown to be involved in the recruitment of dental pulp stem cells (DPSCs). This study sought to investigate the possible role of C3a, another complement fragment, in the early steps of dentin-pulp regeneration.

METHODS

Expression of C3a receptor (C3aR) was investigated by immunofluorescence and reverse transcriptase polymerase chain reaction on cultured pulp fibroblasts, STRO-1-sorted DPSCs, as well as on human tooth sections in vivo. The effect of C3a on proliferation of both DPSCs and pulp fibroblasts was investigated by MTT assay. Cell migration under a C3a gradient was investigated by using microfluidic chemotaxis chambers.

RESULTS

C3aR was expressed in vivo as well as in cultured pulp fibroblasts co-expressing fibroblast surface protein and in DPSCs co-expressing STRO-1. Addition of recombinant C3a induced a significant proliferation of both cell types. When subjected to a C3a gradient, DPSCs were mobilized but not specifically recruited, whereas pulp fibroblasts were specifically recruited following a C3a gradient.

CONCLUSIONS

These results provide the first demonstration of C3aR expression in the dental pulp and demonstrate that C3a is involved in increasing DPSCs and fibroblast proliferation, in mobilizing DPSCs, and in specifically guiding fibroblast recruitment. This provides an additional link to the tight correlation between inflammation and tissue regeneration.

Phenotypic responses of differentiated asthmatic human airway epithelial cultures to rhinovirus

Objectives

Human airway epithelial cells are the principal target of human rhinovirus (HRV), a common cold pathogen that triggers the majority of asthma exacerbations. The objectives of this study were 1) to evaluate an in vitro air liquid interface cultured human airway epithelial cell model for HRV infection, and 2) to identify gene expression patterns associated with asthma intrinsically and/or after HRV infection using this model.

Methods

Air-liquid interface (ALI) human airway epithelial cell cultures were prepared from 6 asthmatic and 6 non-asthmatic donors. The effects of rhinovirus RV-A16 on ALI cultures were compared. Genome-wide gene expression changes in ALI cultures following HRV infection at 24 hours post exposure were further analyzed using RNA-seq technology. Cellular gene expression and cytokine/chemokine secretion were further evaluated by qPCR and a Luminex-based protein assay, respectively.

Main Results

ALI cultures were readily infected by HRV. RNA-seq analysis of HRV infected ALI cultures identified sets of genes associated with asthma specific viral responses. These genes are related to inflammatory pathways, epithelial structure and remodeling and cilium assembly and function, including those described previously (e.g. CCL5, CXCL10 and CX3CL1, MUC5AC, CDHR3), and novel ones that were identified for the first time in this study (e.g. CCRL1).

Conclusions

ALI-cultured human airway epithelial cells challenged with HRV are a useful translational model for the study of HRV-induced responses in airway epithelial cells, given that gene expression profile using this model largely recapitulates some important patterns of gene responses in patients during clinical HRV infection. Furthermore, our data emphasize that both abnormal airway epithelial structure and inflammatory signaling are two important asthma signatures, which can be further exacerbated by HRV infection.

Crosstalk between TGF-β1 and complement activation augments epithelial injury in pulmonary fibrosis

The epithelial complement inhibitory proteins (CIPs) cluster of differentiation 46 and 55 (CD46 and CD55) regulate circulating immune complex-mediated complement activation in idiopathic pulmonary fibrosis (IPF). Our previous studies demonstrated that IL-17A mediates epithelial injury via transforming growth factor β1 (TGF-β1) and down-regulates CIPs. In the current study, we examined the mechanistic role of TGF-β1 in complement activation-mediated airway epithelial injury in IPF pathogenesis. We observed lower epithelial CIP expression in IPF lungs compared to normal lungs, associated with elevated levels of complement component 3a and 5a (C3a and C5a), locally and systemically. In normal primary human small airway epithelial cells (SAECs) treated with TGF-β1 (10 ng/ml), C3a, or C5a (100 nM), we observed loss of CIPs and increased poly(ADP-ribose) polymerase (PARP) activation [also observed with RNA interference (RNAi) of CD46/CD55]. TGF-β1-mediated loss of CIPs and Snail induction [SNAI1; a transcriptional repressor of E-cadherin (E-CAD)] was blocked by inhibiting mitogen-activated protein kinase (p38MAPK; SB203580) and RNAi silencing of SNAI1. C3a- and C5a-mediated loss of CIPs was also blocked by p38MAPK inhibition. While C3a upregulated TGFb transcripts, both C3a and C5a down-regulated SMAD7 (negative regulator of TGF-β), and whereas TGF-β1 induced C3a/C5a receptor (C3aR/C5aR) expression, pharmacologic C3aR/C5aR inhibition protected against C3a-/C5a-mediated loss of CIPs. Taken together, our results suggest that epithelial injury in IPF can be collectively amplified as a result of TGF-β1-induced loss of CIPs leading to complement activation that down-regulates CIPs and induces TGF-β1 expression

Toll-like receptors 2, 3 and 4 and thymic stromal lymphopoietin expression in fatal asthma

BACKGROUND

Airway inflammation in asthma involves innate immune responses. Toll-like receptors (TLRs) and thymic stromal lymphopoietin (TSLP) are thought to be involved in airway inflammation, but their expression in asthmatics' both large and small airways has not been investigated.

OBJECTIVE

To analyse the expression of TLR2, TLR3, TLR4 and TSLP in large and small airways of asthmatics and compare their expression in smoking and non-smoking asthmatics; to investigate whether TLR expression is associated with eosinophilic or neutrophilic airway inflammation and with Mycoplasma pneumoniae and Chlamydophila pneumoniae infection.

METHODS

Using immunohistochemistry and image analysis, we investigated TLR2, TLR3, TLR4 and TSLP expression in large and small airways of 24 victims of fatal asthma, FA, (13 non-smokers, 11 smokers) and nine deceased control subjects (DCtrl). TLRs were also measured in 18 mild asthmatics (MA) and 12 healthy controls (HCtrl). M. pneumoniae and C. pneumoniae in autopsy lung tissue were analysed using real-time polymerase chain reaction. Airway eosinophils and neutrophils were measured in all subjects.

RESULTS

Fatal asthma patients had higher TLR2 in the epithelial and outer layers of large and small airways compared with DCtrls. Smoking asthmatics had lower TLR2 levels in the inner and outer layers of the small airways than non-smoking asthmatics. TSLP was increased in the epithelial and outer layers of the large airways of FA. FA patients had greater TLR3 expression in the outer layer of large airways and greater TLR4 expression in the outer layer of small airways. Eosinophilic airway inflammation was associated with TLR expression in the epithelium of FA. No bacterial DNA was detected in FA or DCtrls. MA and HCtrls had only a small difference in TLR3 expression.

CONCLUSIONS AND CLINICAL RELEVANCE

Increased expression of TLR 2, 3 and 4 and TSLP in fatal asthma may contribute to the acute inflammation surrounding asthma deaths.

Genomic perspectives in inter-individual adverse responses following nanomedicine administration: The way forward

The underlying mechanism of intravenous infusion-related adverse reactions inherent to regulatory-approved nanomedicines still remains elusive. There are substantial inter-individual differences in observed adverse reactions, which may include cardiovascular, broncho-pulmonary, muco-cutaneous, neuro-psychosomatic and autonomic manifestations. Although nanomedicine-mediated triggering of complement activation has been suggested to be a significant contributing factor to these adverse events, complement activation may still proceed in non-responders. Whether these reactions share similar immunological mechanisms and underpinning genetic factors with drug hypersensitivity syndrome remains to be investigated. Genetic association studies could be a powerful tool to dissect causative factors and reveal the multiple molecular pathways that induce infusion related adverse reactions. It is envisaged that such research may lead to the design of reliable in vitro profiling tests for risk assessment and treatment decisions, thereby revolutionizing the practice of medicine with nanopharmaceuticals. Such procedures may further improve regulatory approval processes for nanomedicines currently in the pipeline and decrease the overall cost of health care. Here we discuss some key innate immunity genes and their polymorphisms in relation to nanomedicine infusion-mediated symptomatic responses.

Asthma deaths outside the hospital in an urban community from 2004 to 2008

BACKGROUND

Several studies have been performed reviewing medical examiner's autopsy reports of asthma deaths. None, to our knowledge, have focused on the characteristics of asthma deaths in the urban community alone.

OBJECTIVE

To characterize factors related to asthma deaths occurring outside the hospital setting in an urban community.

METHODS

We reviewed the medical records of 22 patients who died outside the hospital of asthma and underwent autopsy performed by the Milwaukee County medical examiner from 2004 to 2008.

RESULTS

The mean age of the patients was 32 years (range, 12-71 years), 11 patients were male, and 14 patients (64%) were African American. Seventeen patients (77%) died during the night or shortly on awakening. Twelve patients (55%) died in June, July, or August. A history of illicit drug, alcohol, or tobacco use was discovered in 13 patients (59%). Toxicologic test results for drugs of abuse were positive in 4 patients (18%). Twenty patients were using or overusing a short-acting β-agonist, 1 patient was taking omalizumab, and none were taking long-acting β-agonists alone. Two patients were taking no medications. Asthma severity and medication adherence were not consistently reported. Lung pathologic testing revealed eosinophils in 18 patients and a lack of neutrophils in every case.

CONCLUSION

In this small and limited series of asthma deaths occurring in an urban setting outside the hospital, individuals were more likely to be African Americans, with deaths occurring more frequently at night, during the summer months, and in those with substance abuse and not taking anti-inflammatory asthma medications.

C3a and C5a promote renal ischemia-reperfusion injury

Renal ischemia reperfusion injury triggers complement activation, but whether and how the small proinflammatory fragments C3a and C5a contribute to the pathogenesis of this injury remains to be elucidated. Using C3aR-, C5aR-, or C3aR/C5aR-deficient mice and models of renal ischemia-reperfusion injury, we found that deficiency of either or both of these receptors protected mice from injury, but the C3aR/C5aR- and C5aR-deficient mice were most protected. Protection from injury was associated with less cellular infiltration and lower mRNA levels of kidney injury molecule-1, proinflammatory mediators, and adhesion molecules in postischemic kidneys. Furthermore, chimera studies showed that the absence of C3aR and C5aR on renal tubular epithelial cells or circulating leukocytes attenuated renal ischemia-reperfusion injury. In vitro, C3a and C5a stimulation induced inflammatory mediators from both renal tubular epithelial cells and macrophages after hypoxia/reoxygenation. In conclusion, although both C3a and C5a contribute to renal ischemia-reperfusion injury, the pathogenic role of C5a in this injury predominates. These data also suggest that expression of C3aR and C5aR on both renal and circulating leukocytes contributes to the pathogenesis of renal ischemia-reperfusion injury.

Complement C5A regulates prolabor mediators in human placenta

Human preterm and term parturition is associated with inflammatory cascades in the uteroplacental unit. Activation of the complement cascade releases potent proinflammatory mediators, including the anaphylatoxin C5a, which exerts its biological effects through its receptors, C5AR (also known as CD88) and C5L2, official symbol GPR77. To date, there are few data available on the role of C5a and CD88 in human pregnancy, so the aim of this study was to determine the effect of C5a and CD88 on some key inflammatory pathways involved in human parturition. Placental tissue samples were obtained from normal pregnancies at the time of Cesarean section. Human placental and fetal membranes were incubated in the absence (basal control) or presence of 0.5 μg/ml (~60 nM) human recombinant C5a for 24 h. Concentrations of proinflammatory cytokines, prostaglandins, and 8-isoprostane (a marker of oxidative stress) were quantified by ELISA and secretory matrix metalloproteinases (MMPs) activity by zymography. NFKB DNA binding activity and NFKBIA (IkappaB-alpha; inhibitor of NFKB) protein degradation were analyzed by ELISA and Western blotting, respectively. In the presence of C5a, proinflammatory cytokines (IL6 and IL8), cyclooxygenase (COX)-2; official symbol PTGS2) expression, and subsequent prostaglandin (PGE(2) and PGF(2alpha)), MMP9 enzyme production, and NFKB DNA activation were all significantly increased. The C5a-induced prolabor responses were significantly reduced by treatment with the selective CD88 antagonist PMX53 and the NFKB inhibitor BAY 11-7082. We conclude that C5a upregulates prolabor mediators in human gestational tissues via CD88-mediated NFKB activation.

Pentraxin 3 (PTX3) expression in allergic asthmatic airways: role in airway smooth muscle migration and chemokine production

Background

Pentraxin 3 (PTX3) is a soluble pattern recognition receptor with non-redundant functions in inflammation and innate immunity. PTX3 is produced by immune and structural cells. However, very little is known about the expression of PTX3 and its role in allergic asthma.

Objectives and Methods

We sought to determine the PTX3 expression in asthmatic airways and its function in human airway smooth muscle cells (HASMC). In vivo PTX3 expression in bronchial biopsies of mild, moderate and severe asthmatics was analyzed by immunohistochemistry. PTX3 mRNA and protein were measured by real-time RT-PCR and ELISA, respectively. Proliferation and migration were examined using ³H-thymidine incorporation, cell count and Boyden chamber assays.

Results

PTX3 immunoreactivity was increased in bronchial tissues of allergic asthmatics compared to healthy controls, and mainly localized in the smooth muscle bundle. PTX3 protein was expressed constitutively by HASMC and was significantly up-regulated by TNF, and IL-1β but not by Th2 (IL-4, IL-9, IL-13), Th1 (IFN-γ), or Th-17 (IL-17) cytokines. In vitro, HASMC released significantly higher levels of PTX3 at the baseline and upon TNF stimulation compared to airway epithelial cells (EC). Moreover, PTX3 induced CCL11/eotaxin-1 release whilst inhibited the fibroblast growth factor-2 (FGF-2)-driven HASMC chemotactic activity.

Conclusions

Our data provide the first evidence that PTX3 expression is increased in asthmatic airways. HASMC can both produce and respond to PTX3. PTX3 is a potent inhibitor of HASMC migration induced by FGF-2 and can upregulate CCL11/eotaxin-1 release. These results raise the possibility that PTX3 may play a dual role in allergic asthma.

The critical role of complement alternative pathway regulator factor H in allergen-induced airway hyperresponsiveness and inflammation

Activation of the alternative pathway of complement plays a critical role in the development of allergen-induced airway hyperresponsiveness (AHR) and inflammation in mice. Endogenous factor H, a potent inhibitor of the alternative pathway, is increased in the airways of sensitized and challenged mice, but its role in regulating inflammation or AHR has been unknown. We found that blocking the tissue-binding function of factor H with a competitive antagonist increased complement activation and tissue inflammation after allergen challenge of sensitized mice. Conversely, administration of a fusion protein that contains the iC3b/C3d binding region of complement receptor 2 linked to the inhibitory region of factor H, a molecule directly targeting complement-activating surfaces, protected mice in both primary and secondary challenge models of AHR and lung inflammation. Thus, although endogenous factor H does play a role in limiting the development of AHR, strategies to deliver the complement-regulatory region of factor H specifically to the site of inflammation provide greater protection than that afforded by endogenous regulators. Such an agent may be an effective therapy for the treatment of asthma.

High-affinity immunoglobulin E receptor expression is increased in large and small airways in fatal asthma

BACKGROUND

IgE and its high-affinity receptor FcɛRI play an important role in allergy and asthma. The distribution of FcɛRI expression in the airways and within the airway wall, however, is largely unknown.

OBJECTIVE

In this study, we aimed to map the distribution of FcɛRI in different layers of large airways (LA) and small airways (SA) in lung tissue from non-smoking and smoking patients who died of asthma [fatal asthma (FA)] and non-smoking controls (CTR).

METHODS

Postmortem lung tissue from 24 cases of non-smoking FA, 13 smoking FA patients and from 19 subjects who died of non-pulmonary causes (CTR) was immunohistochemically stained for FcɛRI and AA1 (mast cell tryptase marker). The expression of these markers was analysed in inner, muscle, and outer layers of both LA and SA by image analysis.

RESULTS

FcɛRI expression was higher in non-smoking and smoking FA compared with CTR in the inner and outer layer of SA. In the outer layer of LA, FcɛRI expression was higher in non-smoking FA compared with CTR. AA1 was higher in non-smoking FA compared with smoking FA and CTR in the outer layer of the SA, which was correlated with FcɛRI in this layer.

CONCLUSION

Our results show that the expression of FcɛRI is higher in both LA and SA in FA compared with CTR. These differences are predominantly found in the outer layer where they can be attributed in part to the increased mast cell numbers. These results indicate an increased capacity to mount IgE-mediated reactions in FA, both in LA and SA.

What do asthmatics have to fear from food and additive allergy?

International studies report marked increases in the prevalence of food allergy, along with increases in hospital admissions and emergency presentations for severe allergic reactions due to foods. The prevalence of self-reported food allergy is common, but generally exceeds that which can be verified from challenge studies, although nut allergies appear to be an important exception to this rule. Studies examining food allergy deaths suggest that those who die of food allergy usually have co-existent asthma. Adolescents and young adults are at most risk, and adrenaline auto-injectors are sub-optimally used. Food chemical sensitivity is very commonly reported but not usually verified by challenge testing. However, the exception to this is sulphite sensitivity, which can elicit reproducible reactions in some. The increasing prevalence of severe food allergies and awareness of its risk in those with asthma demands an especially rigorous approach to the diagnosis and management of co-existent food allergy and asthma, especially in young people who appear to be at most risk from death from severe food allergy.

Correlation of plasma complement split product levels with allergic respiratory disease activity and relation to allergen immunotherapy

BACKGROUND

Allergens, including dust mite and grass pollen, and mast cell tryptase are known to generate the complement split products (CSPs) C5a and C3a, which can then trigger allergic inflammation. The relation of these anaphylatoxin levels to clinical allergic disease responses is not known.

OBJECTIVE

To evaluate the relationship of plasma CSP levels to allergic respiratory disease variables in an adult cohort.

METHODS

A cross-sectional survey was used to assess the association of plasma C5a desArg and C3a desArg levels with clinical allergic respiratory disease variables. Furthermore, a time course of the effect of routine allergen immunotherapy on plasma CSP levels and cutaneous and pulmonary responses was determined.

RESULTS

Adult plasma C5a desArg levels correlate with asthma severity as determined by a physician (P = .01) and by Asthma Quality of Life Questionnaire scores (P < .01). Change in plasma C5a desArg levels 1 hour after immunotherapy is associated with baseline rhinoconjunctivitis symptom severity (P = .03), change in total mean wheal diameter (P = .05), and total dust mite dosage (P = .04). Change in plasma C3a desArg levels 3 hours after immunotherapy correlates with change in total mean wheal diameter induced by dust mite (P = .01). Change in plasma CSP levels after immunotherapy did not correlate with change in spirometric outcome.

CONCLUSIONS

Plasma C5a desArg levels reflect allergic respiratory disease severity as assessed by physicians and correlate with Asthma Quality of Life Questionnaire scores. Changes in CSP levels after immunotherapy reflect cutaneous allergic responses, especially to dust mite allergen.

Regulation of human mast cell and basophil function by anaphylatoxins C3a and C5a

Allergic diseases such as asthma result from inappropriate immunologic responses to common environmental allergens in genetically susceptible individuals. Following allergen exposure, interaction of dendritic cells (DC) with CD4(+) T cells leads to the production of Th2 cytokines, which induce B cells to synthesize IgE molecules (sensitization phase). These IgE molecules bind to their high affinity receptors (FcvarepsilonRI) on the surface of mast cells and basophils and their subsequent cross-linking by allergen results in the release of preformed and newly synthesized mediators, which cause bronchoconstriction, lung inflammation and airway hyperresponsiveness (AHR) in asthma (effector phase). The complement components C3a and C5a levels are increased in the lungs of patients with asthma and are likely generated via the actions of both allergen and mast cell proteases. In vivo studies with rodents have shown that while C3a facilitates allergen sensitization in some models C5a inhibits this response. Despite this difference, both anaphylatoxins promote lung inflammation and AHR in vivo indicating that cells other than DC and T cells likely mediate the functional effects of C3a and C5a in asthma. This review focuses on the contribution of C3a and C5a in the pathogenesis of asthma with a particular emphasis on mast cells and basophils. It discusses the mechanisms by which anaphylatoxins activate mast cells and basophils and the associated signaling pathways via which their receptors are regulated by priming and desensitization.

Exposure to ambient levels of particles emitted by traffic worsens emphysema in mice

OBJECTIVES

We investigated effects of chronic exposure (2 months) to ambient levels of particulate matter (PM) on development of protease-induced emphysema and pulmonary remodeling in mice.

METHODS

Balb/c mice received nasal drop of either papain or normal saline and were kept in two exposure chambers situated in an area with high traffic density. One of them received ambient air and the other had filters for PM.

RESULTS

mean concentration of PM10 was 2.68 +/- 0.38 and 33.86 +/- 2.09 microg/m3, respectively, in the filtered and ambient air chambers (p < 0.001). After 2 months of exposure, lungs from papain-treated mice kept in the chamber with ambient air presented greater values of mean linear intercept, an increase in density of collagen fibers in alveolar septa and in expression of 8-isoprostane (p = 0.002, p < 0.05 and p = 0.002, respectively, compared to papain-treated mice kept in the chamber with filtered air). We did not observe significant differences between these two groups in density of macrophages and in amount of cells expressing matrix metalloproteinase-12. There were no significant differences in saline-treated mice kept in the two chambers.

CONCLUSIONS

We conclude that exposure to urban levels of PM worsens protease-induced emphysema and increases pulmonary remodeling. We suggest that an increase in oxidative stress induced by PM exposure influences this response. These pulmonary effects of PM were observed only in mice with emphysema.

The role of the anaphylatoxins in health and disease

The anaphylatoxin (AT) C3a, C5a and C5a-desArg are generally considered pro-inflammatory polypeptides generated after proteolytic cleavage of C3 and C5 in response to complement activation. Their well-appreciated effector functions include chemotaxis and activation of granulocytes, mast cells and macrophages. Recent evidence suggests that ATs are also generated locally within tissues by pathogen-, cell-, or contact system-derived proteases. This local generation of ATs is important for their pleiotropic biologic effects beyond inflammation. The ATs exert most of the biologic activities through ligation of three cognate receptors, i.e. the C3a receptor, the C5a receptor and the C5a receptor-like, C5L2. Here, we will discuss recent findings suggesting that ATs regulate cell apoptosis, lipid metabolism as well as innate and adaptive immune responses through their impact on antigen-presenting cells and T cells. As we will outline, such regulatory functions of ATs and their receptors play important roles in the pathogenesis of allergy, autoimmunity, neurodegenerative diseases, cancer and infections with intracellular pathogens.

Pulmonary periarterial inflammation in fatal asthma

BACKGROUND

To date, little information has been available about pulmonary artery pathology in asthma. The pulmonary artery supplies the distal parts of the lungs and likely represents a site of immunological reaction in allergic inflammation. The objective of this study was to describe the inflammatory cell phenotype of pulmonary artery adventitial inflammation in lung tissue from patients who died of asthma.

METHODS

We quantified the different inflammatory cell types in the periarterial region of small pulmonary arteries in lung tissue from 22 patients who died of asthma [fatal asthma (FA)] and 10 control subjects. Using immunohistochemistry and image analysis, we quantified the cell density for T lymphocytes (CD3, CD4, CD8), B lymphocytes (CD20), eosinophils, mast cells (chymase and tryptase), and neutrophils in the adventitial layer of pulmonary arteries with a diameter smaller than 500 microm.

RESULTS

Our data (median/interquartile range) demonstrated increased cell density of mast cells [FA=271.8 (148.7) cells/mm2; controls=177.0 (130.3) cells/mm2, P=0.026], eosinophils [FA=23.1 (58.6) cells/mm2; controls=0.0 (2.3) cells/mm2, P=0.012], and neutrophils [FA=50.4 (85.5) cells/mm2; controls=2.9 (30.5) cells/mm2, P=0.009] in the periarterial space in FA. No significant differences were found for B and T lymphocytes or CD4+ or CD8+ subsets. Chymase/tryptase positive (MCCT) mast cells predominated over tryptase (MCT) mast cells in the perivascular arterial space in both asthma patients and controls [MCCT/(MCCT+MCT)=0.91 (0-1) in FA and 0.75 (0-1) in controls, P=0.86].

CONCLUSIONS

Our results show that the adventitial layer of the pulmonary artery participates in the inflammatory process in FA, demonstrating increased infiltration of mast cells, eosinophils, and neutrophils, but not of T and B lymphocytes.

Isotype and IgG subclass distribution of autoantibody response to alpha-enolase protein in adult patients with severe asthma

PURPOSE

A possible involvement of autoimmune mechanism in the pathogenesis of bronchial asthma has been proposed. Recently, alpha-enolase protein was identified as a major autoantigen recognized by circulating IgG autoantibodies in patients with severe asthma. To evaluate a possible pathogenetic significance of these autoantibodies in severe asthma, isotype (IgG, IgA, IgM, and IgE) and IgG subclass (IgG1, IgG2, IgG3, and IgG4) distributions of autoantibodies to recombinant human alpha-enolase protein were analyzed.

PATIENTS AND METHODS

We examined serum samples from 10 patients with severe asthma and 7 patients with mild-to-moderate asthma, and 5 healthy controls by immunoblot analysis. Severe asthma was defined as patients having at least 1 severe asthmatic exacerbation requiring an emergency department visit or admission in the last year despite continuous typical therapies.

RESULTS

IgG1 was the predominant IgG subclass antibody response to alpha-enolase protein in patients with severe asthma. IgG1 autoantibody to alpha-enolase protein was detected in 7 of 10 patients with severe asthma (70%), 1 of 7 patients with mild-to-moderate asthma (14.3%), and none of 5 healthy controls (0%) (chi-square test; p < 0.05). IgA, IgM, and IgE autoantibodies to alpha-enolase protein could not be detected in patients with severe asthma.

CONCLUSION

IgG1 subclass was the predominant type of autoantibody response to alpha-enolase protein in patients with severe asthma, suggests a possibility of IgG1 autoantibody-mediated complement activation in the pathogenesis of severe asthma.

Overexpression of the anaphylatoxin receptors, complement anaphylatoxin 3a receptor and complement anaphylatoxin 5a receptor, in the nasal mucosa of patients with mild and severe persistent allergic rhinitis

BACKGROUND

Although the complement anaphylatoxin peptides, complement anaphylatoxin 3a (C3a) and complement anaphylatoxin 5a (C5a), are implicated in the inflammatory process in allergic rhinitis, a direct interaction between allergic mucosa and complement receptors has not been demonstrated.

OBJECTIVE

We investigated the expressional levels and distributional patterns of the C3a receptor (C3aR) and C5a receptor (C5aR) in normal, mild, and severe persistent allergic nasal mucosa.

METHODS

Immunohistochemistry and Western blotting using C3aR and C5aR antibodies were applied to normal nasal, mild, and severe persistent allergic nasal mucosa.

RESULTS

Complement anaphylatoxin 5a receptor was detected in the inflammatory cells of normal and allergic nasal mucosa, and its expression level was significantly higher in allergic nasal mucosa than normal nasal mucosa. C3aR in normal and allergic nasal mucosa was commonly expressed in nonmyeloid cells such as epithelial cells, submucosal glands, and nerve fibers. In addition, C3aR was expressed in the endothelium of cavernous sinuses and the surrounding perivascular muscle layer in severe persistent allergic nasal mucosa, but not in normal and mild allergic nasal mucosa. Western blotting demonstrated that the expression level of C3aR was significantly increased in severe persistent allergic nasal mucosa compared with normal and mild nasal mucosa.

CONCLUSION

On the basis of the location of C3aR and C5aR, C5aR may play a role in activation of inflammatory cells, whereas C3aR may mediate mucus secretion and mucosal swelling in allergic nasal mucosa, especially severe persistent allergic nasal mucosa.

Generation of anaphylatoxins by human beta-tryptase from C3, C4, and C5

Both mast cells and complement participate in innate and acquired immunity. The current study examines whether beta-tryptase, the major protease of human mast cells, can directly generate bioactive complement anaphylatoxins. Important variables included pH, monomeric vs tetrameric forms of beta-tryptase, and the beta-tryptase-activating polyanion. The B12 mAb was used to stabilize beta-tryptase in its monomeric form. C3a and C4a were best generated from C3 and C4, respectively, by monomeric beta-tryptase in the presence of low molecular weight dextran sulfate or heparin at acidic pH. High molecular weight polyanions increased degradation of these anaphylatoxins. C5a was optimally generated from C5 at acidic pH by beta-tryptase monomers in the presence of high molecular weight dextran sulfate and heparin polyanions, but also was produced by beta-tryptase tetramers under these conditions. Mass spectrometry verified that the molecular mass of each anaphylatoxin was correct. Both beta-tryptase-generated C5a and C3a (but not C4a) were potent activators of human skin mast cells. These complement anaphylatoxins also could be generated by beta-tryptase in releasates of activated skin mast cells. Of further biologic interest, beta-tryptase also generated C3a from C3 in human plasma at acidic pH. These results suggest beta-tryptase might generate complement anaphylatoxins in vivo at sites of inflammation, such as the airway of active asthma patients where the pH is acidic and where elevated levels of beta-tryptase and complement anaphylatoxins are detected.

Regulated complement deposition on the surface of human endothelial cells: effect of tobacco smoke and shear stress

Cigarette smoke and hemodynamic stress both contribute to vascular inflammation and associated atherosclerosis. We recently demonstrated direct activation of complement components C4 and C3 on human endothelial cells (EC). The present study was designed to explore complement activation on bone marrow microvascular endothelial cells (BMEC) and human umbilical vein endothelial cells (HUVEC) in response to endothelial cell injury by tobacco smoke extract, shear stress, or other known inflammatory and atherogenic mediators, lipopolysaccharide (LPS) and INF-gamma. Following treatment, confluent EC monolayers were exposed to plasma (60 min, 37 degrees C), and cell surface deposition of stable complement derivatives C4d, iC3b and SC5b-9 was measured in situ using an ELISA approach. Consistent with previous results, moderate levels of C4d, iC3b and SC5b-9 deposition were observed on native EC monolayers exposed to human plasma. Tobacco smoke and shear stress enhanced EC C4d deposition. In contrast, LPS and INF-gamma failed to affect EC mediated complement activation, despite evidence of EC activation illustrated by ICAM-1 expression. The combination of tobacco smoke and shear stress nearly doubled EC C4d expression. No increases in iC3b or SC5b-9 were noted, suggesting inhibition of classical and alternative pathway C3 convertase assembly or activity. Indeed, concomitantly increased surface expression of complement regulatory proteins CD35 (CR1) and CD55 was observed following EC exposure to tobacco smoke and shear stress. These results suggest that a balance between complement activation and regulation exists at the EC surface, and may impact vascular injury leading to thrombosis, arteriosclerosis, and atherogenesis.

The role of the complement anaphylatoxins in the recruitment of eosinophils

Eosinophils are blood and tissue immune cells that participate in a diverse range of activities normally beneficial for the host defense, but in circumstances of untoward inflammatory conditions these cells can be responsible for pathological responses. Accordingly the transit of eosinophils from the blood to tissues is a subject of considerable importance in immunology. In this article we review how the complement anaphylatoxins, C3a and C5a bring about eosinophil extravasation. These mediators do not merely provide a chemotactic or haptotactic gradient but are responsible for orchestrating innumerable responses by other cells types, including of endothelial cells, mast cells, and basophils in order to create an environment that is conducive for eosinophil infiltration. C5a has the capacity to prime the endothelium directly to present P-selectin, and C5a stimulated generation of eosinophil hydrogen peroxide and other oxidants can cause additional upregulation of endothelial P-selectin and ICAM-1. Moreover, the anaphylatoxins have the ability to recruit mast cells and basophils and can stimulate these cells to release IL-4 and IL-13, which by augmenting endothelial VCAM-1, convey some selectivity for eosinophils. The anaphylatoxins also have the capability to evoke the release and activation of eosinophil MMP-9, which is employed by this cell type to digest its way past the subendothelial matrix. Finally, because C3a and C5a can stimulate the generation of nitric oxide along with the secretion of histamine and LTC4 from several cell types, the anaphylatoxins can bring about an increase in vascular permeability that facilitates eosinophil accumulation at sites of allergic inflammation.

Use of monoclonal antibodies to assess expression of anaphylatoxin receptors in rat and murine models of lung inflammation

The anaphylatoxins C3a and C5a are involved in the pathophysiology of microbial as well as allergic inflammation in the lungs. Besides their expression in leukocytes, receptors for C3a and C5a (C3aR and C5aR) have been noted in alveolar and bronchial epithelial cells, bronchial smooth muscle cells as well as in vascular endothelial and smooth muscle cells of normal and inflamed human and murine lungs. Recently, however, expression of anaphylatoxin receptors in parenchymal cells of the lung (and kidney) has been challenged. Using well-characterized monoclonal antibodies (mabs) against murine and rat anaphylatoxin receptors, we reexamined the pulmonary distribution of C3aR and C5aR. Immunohistochemistry was performed on frozen sections of lung tissues from normal mice and rats as well as from animals subjected to lipopolysaccharide (LPS)-induced inflammation or from MRL/lpr mice suffering from autoimmune disease. Furthermore, ovalbumin (OVA)-induced models of allergic asthma in the rat and mouse were investigated. Prominent expression of both anaphylatoxin receptors was detectable in resident as well as infiltrating leukocytes. No C3aR protein was observed in alveolar macrophages. Upon LPS- and OVA-challenge as well as in autoimmune inflammation, numbers of infiltrating leukocytes expressing prominent amounts of anaphylatoxin receptors increased. Even under these highly inflammatory conditions, however, expression of C3aR and C5aR was not inducible in parenchymal cells. Thus, our findings identify infiltrating leukocytes as a prominent source of anaphylatoxin receptors in inflamed lungs. A direct involvement of parenchymal cells in anaphylatoxin-mediated pulmonary inflammation is unlikely.

The impact of comorbid atopic disease on asthma: clinical expression and treatment

Clinically, asthma and allergic rhinitis involve separate regions of the respiratory tract while representing a common underlying inflammatory syndrome. Much evidence supports an epidemiologic association between the diseases, paranasal sinus involvement in both conditions, and parallel relationship in severity and treatment outcomes. Pathophysiologic mechanisms, including immunoglobulin E (IgE)- mediated inflammation, are also shared. Blocking IgE with the recombinant humanized monoclonal antibody omalizumab demonstrated clinical efficacy in patients with upper and lower airway diseases. IgE blockade, leukotriene modulation, and B-cell depletion therapy have all exhibited success in chronic inflammation, reinforcing and expanding the beneficial role of immunomodulation of global mediators.

Use of monoclonal antibodies to assess expression of anaphylatoxin receptors in tubular epithelial cells of human, murine and rat kidneys

To assess published evidence of anaphylatoxin receptor expression in renal tubular epithelial cells, monoclonal antibodies (mAbs) against human, mouse and rat receptors for C5a and C3a (C5aR, C3aR) were raised using receptor-expressing transfectants as immunogens. Applying these reagents in immunohistochemistry, we observed that mAbs with reactivities against three distinct epitopes of human C5aR N-terminus recognized tissue macrophages but not at all renal tubular epithelial cells. These findings were surprising, as strong tubular staining had been previously demonstrated by mAbs raised against a synthetic N-terminal C5aR peptide. To extend our study to mammalian kidneys, renal specimens from normal rats as well as LPS-treated Balb/c and MRL/lpr mice, which suffered from lupus-type nephritis, were examined. Similar to humans, mAbs against murine or rat C5aR strongly recognized infiltrating leukocytes in situ whereas tubular epithelial cells remained negative. As a mAb has been previously used to document C3aR expression in renal tubular epithelial cells, kidney specimens were examined using newly established mAbs against different epitopes of human, murine and rat C3aR. In contrast to published evidence, C3aR was detectable exclusively in interstitial leukocytes but not in epithelial tubular cells of normal and diseased tissues. Taken together, our findings question a direct involvement of tubular epithelial cells in anaphylatoxin-mediated renal inflammation. Furthermore, as we demonstrate in the case of anaphylatoxin receptors, cross-reactivities of mAbs may constitute as yet underestimated pitfalls in immunohistochemical antigen detection.

Complement C3a regulates Muc5ac expression by airway Clara cells independently of Th2 responses

RATIONALE

The factors that control the secretion of epithelial mucins are essential to understanding obstructive airway diseases such as asthma. Although the complement anaphylatoxin C3a and its receptor have been shown to promote many features of allergic lung inflammation, the contribution to mucin expression has not been elucidated.

OBJECTIVES

To determine if the C3a receptor with its ligand regulates airway epithelial mucin production.

METHODS

Mice deficient in the C3a receptor were examined in a model of allergic airway disease for the presence of goblet cells and the gel-forming secreted mucin Muc5ac.

MEASUREMENTS AND MAIN RESULTS

Lungs from antigen-challenged C3a receptor-deficient mice revealed a dramatic decrease in goblet cells and Muc5ac compared with challenged wild-type control animals. These differences were dependent on C3a binding to its receptor since intranasal challenge with C3a induced the formation of goblet cells only in wild-type but not C3a receptor-deficient mice. Increased numbers of goblet cells were also found in C3a-stimulated RAG-1-deficient mice demonstrating a mechanism independent of T lymphocytes and Th2 cytokines, mediators which have been shown to regulate mucin expression. A direct physiological role for C3a in these models was further demonstrated in cultures of airway epithelial Clara cells, which not only express the C3a receptor but also produce Muc5ac in response to C3a.

CONCLUSIONS

These studies identify a novel C3a receptor-dependent mechanism in the development of airway epithelial goblet cells and regulation of Muc5ac production and implicate C3a as a mediator of airway obstruction in asthma.

Induction of C3 and CCL2 by C3a in keratinocytes: a novel autocrine amplification loop of inflammatory skin reactions

The complement fragment-3a (C3a) acts via a G protein-coupled C3aR and is of importance in allergic and inflammatory diseases. Recent studies suggest the presence of complement proteins in the epidermal compartment and synthesis of some of these proteins (C3, factor B, and factor H) by human primary keratinocytes (KCs) during inflammation. However, expression of C3aR and its role in human KCs is not elucidated thus far. In this study, we demonstrate the expression of C3aR on KCs as detected by quantitative real-time RT-PCR and flow cytometry. IFN-gamma and IFN-alpha strongly up-regulated the surface expression of C3aR on KCs among all other cytokines tested. After up-regulation of C3aR by IFN-gamma and IFN-alpha, we observed the induction of five genes (CCL2, CCL5, CXCL8, CXCL10, and C3) after stimulation of KCs with C3a in microarray analysis. We confirmed the induction of C3 and CCL2 at RNA and protein levels. Furthermore, incubation of C3 with skin mast cells tryptase resulted in the generation of C3 fragments with C3a activity. In conclusion, our data illustrate that epidermal KCs express functional C3aR. The increases of C3 and CCL2 synthesis by C3a and C3 activation by skin mast cell tryptase delineates a novel amplification loop of complement activation and inflammatory responses that may influence the pathogenesis of allergic/inflammatory skin diseases.

Complement in lung disease

Complement proteins play an integral role in both innate and adaptive immune responses of the host. Complement activation leads to the formation of bioactive molecules including the anaphylatoxins, C3a and C5a, and the lytic membrane attack complex (C5b-9). These molecules trigger a series of events that culminate in the recruitment of phagocytic cells, release of cytokines/chemokines and reactive oxygen species, enhanced expression of adhesion molecules and apoptosis at the site of inflammation. Several animal models provide evidence that this series of events forms the basis for the pathophysiology found in many lung diseases, such as asthma and acute respiratory distress syndrome. Clinical data further confirm these findings. This review briefly discusses recent data from such studies.

Anaphylaxis, killer allergy: long-term management in the community

Traditionally, physicians are trained to diagnose and treat anaphylaxis as an acute emergency in a health care setting. In addition to this crucial and time-honored role, we should be cognizant of our wider responsibility to (1) provide a risk assessment for individuals with anaphylaxis, (2) prevent future anaphylaxis episodes by developing long-term personalized risk reduction strategies for affected individuals, and (3) emphasize anaphylaxis education. Risk assessment should include verification of the trigger factor or factors for the anaphylaxis episode by obtaining a comprehensive history and performing relevant investigations, including allergen skin tests and measurement of allergen-specific IgE in serum. In addition, the potential effect of comorbidities and concurrently administered medications on the recognition and emergency treatment of subsequent episodes should be determined. Risk reduction strategies should be personalized to include information about avoidance of specific triggers and initiation of relevant specific preventive treatment (eg, venom immunotherapy). At-risk individuals should be coached in the use of self-injectable epinephrine and equipped with an anaphylaxis emergency action plan and with accurate medical identification. Anaphylaxis education should be provided for these individuals, their families and caregivers, health care professionals, and the general public. Further development of an optimal diagnostic test for anaphylaxis and of tests and algorithms to predict future risk and prevent fatality are urgently needed.