Induction of regulated upon activation, normal T cells expressed and secreted (RANTES) and transforming growth factor-beta 1 in airway epithelial cells by Mycoplasma pneumoniae

Mycoplasmas as Host Pantropic and Specific Pathogens: Clinical Implications, Gene Transfer, Virulence Factors, and Future Perspectives

Mycoplasmas as economically important and pantropic pathogens can cause similar clinical diseases in different hosts by eluding host defense and establishing their niches despite their limited metabolic capacities. Besides, enormous undiscovered virulence has a fundamental role in the pathogenesis of pathogenic mycoplasmas. On the other hand, they are host-specific pathogens with some highly pathogenic members that can colonize a vast number of habitats. Reshuffling mycoplasmas genetic information and evolving rapidly is a way to avoid their host's immune system. However, currently, only a few control measures exist against some mycoplasmosis which are far from satisfaction. This review aimed to provide an updated insight into the state of mycoplasmas as pathogens by summarizing and analyzing the comprehensive progress, current challenge, and future perspectives of mycoplasmas. It covers clinical implications of mycoplasmas in humans and domestic and wild animals, virulence-related factors, the process of gene transfer and its crucial prospects, the current application and future perspectives of nanotechnology for diagnosing and curing mycoplasmosis, Mycoplasma vaccination, and protective immunity. Several questions remain unanswered and are recommended to pay close attention to. The findings would be helpful to develop new strategies for basic and applied research on mycoplasmas and facilitate the control of mycoplasmosis for humans and various species of animals.

Pathological and Immunohistochemical Studies of Experimental Mycoplasma pneumoniae in Gerbils (Meriones unguiculatus)

Mycoplasma pneumoniae (Mp) is a leading cause of human community-acquired pneumonia. To investigate the pathogenesis of the infection, 36 gerbils were intranasally inoculated with Mp culture (30 animals) or sterile mycoplasma broth (6 animals) and euthanized from 1 to 5 weeks post infection. A morphological and immunohistochemical study was carried out in all animals to determine the cellular populations present in lung parenchyma. Polyclonal and monoclonal antibodies were used to detect antigens of Mp and CD3, CD4, CD8 and CD79 lymphocytes, as well as cells containing S100 and major histocompatibility complex class II (MHC-II) antigens. There was progressive infiltration of mononuclear cells in the lamina propria of bronchi and bronchioles, and hyperplasia of the bronchus-associated lymphoid tissue (BALT) in the infected animals. BALT contained dendritic cells immunopositive to S100 and MHC-II and numerous CD3, CD4 and CD79 lymphocytes. The immunohistochemical results showed that T lymphocytes, particularly CD4 and CD79 cells, may play a role in the immune response of gerbils against Mp. This experimental model is valuable for investigation of the pathogenesis of Mp infection and may assist in the development of therapeutic strategies.

Cells and Culture Systems Used to Model the Small Airway Epithelium

The pulmonary epithelium is divided into upper, lower, and alveolar (or small) airway epithelia and acts as the mechanical and immunological barrier between the external environment and the underlying submucosa. Of these, the small airway epithelium is the principal area of gas exchange and has high immunological activity, making it a major area of cell biology, immunology, and pharmaceutical research. As animal models do not faithfully represent the human pulmonary system and ex vivo human lung samples have reliability and availability issues, cell lines, and primary cells are widely used as small airway epithelial models. In vitro, these cells are mostly cultured as monolayers (2-dimensional cultures), either media submerged or at air-liquid interface. However, these 2-dimensional cultures lack a three dimension-a scaffolding extracellular matrix, which establishes the intercellular network in the in vivo airway epithelium. Therefore, 3-dimensional cell culture is currently a major area of development, where cells are cultured in a matrix or are cultured in a manner that they develop ECM-like scaffolds between them, thus mimicking the in vivo phenotype more faithfully. This review focuses on the commonly used small airway epithelial cells, their 2-dimensional and 3-dimensional culture techniques, and their comparative phenotype when cultured under these systems.

Resolvin D1 attenuates polyinosinic-polycytidylic acid-induced inflammatory signaling in human airway epithelial cells via TAK1

The respiratory epithelium consists of lung sentinel cells, which are the first to contact inhaled inflammatory insults, including air pollutants, smoke, and microorganisms. To avoid damaging exuberant or chronic inflammation, the inflammatory process must be tightly controlled and terminated once the insult is mitigated. Inflammation resolution is now known to be an active process involving a new genus of lipid mediators, called "specialized proresolving lipid mediators," that includes resolvin D1 (RvD1). We and others have reported that RvD1 counteracts proinflammatory signaling and promotes resolution. A knowledge gap is that the specific cellular targets and mechanisms of action for RvD1 remain largely unknown. In this article, we identified the mechanism whereby RvD1 disrupts inflammatory mediator production induced by the viral mimic polyinosinic-polycytidylic acid [poly(I:C)] in primary human lung epithelial cells. RvD1 strongly suppressed the viral mimic poly(I:C)-induced IL-6 and IL-8 production and proinflammatory signaling involving MAPKs and NF-κB. Most importantly, we found that RvD1 inhibited the phosphorylation of TAK1 (TGF-β-activated kinase 1), a key upstream regulatory kinase common to both the MAPK and NF-κB pathways, by inhibiting the formation of a poly(I:C)-induced signaling complex composed of TAK1, TAB1 (TAK1 binding protein), and TRAF6 (TNF receptor-associated factor 6). We confirmed that ALX/FPR2 and GPR32, two RvD1 receptors, were expressed on human small airway epithelial cells. Furthermore, blocking these receptors abrogated the inhibitory action of RvD1. In this article, we present the idea that RvD1 has the potential to be used as an anti-inflammatory and proresolving agent, possibly in the context of exuberant host responses to damaging respirable agents such as viruses.

Novel aspects on the pathogenesis of Mycoplasma pneumoniae pneumonia and therapeutic implications

Mycoplasma pneumoniae (Mp) is a leading cause of community acquired pneumonia. Knowledge regarding Mp pneumonia obtained from animal models or human subjects has been discussed in many different reports. Accumulated expertise concerning this critical issue has been hard to apply clinically, and potential problems may remain undiscovered. Therefore, our multidisciplinary team extensively reviewed the literature regarding Mp pneumonia, and compared findings from animal models with those from human subjects. In human beings, the characteristic pathological features of Mp pneumonia have been reported as alveolar infiltration with neutrophils and lymphocytes and lymphocyte/plasma cell infiltrates in the peri-bronchovascular area. Herein, we demonstrated the novel aspects of Mp pneumonia that the severity of the Mp pneumonia seemed to depend on the host innate immunity to the Mp, which might be accelerated by antecedent Mp exposure (re-exposure or latent respiratory infection) through up-regulation of Toll-like receptor 2 expression on bronchial epithelial cells and alveolar macrophages. The macrolides therapy might be beneficial for the patients with macrolide-resistant Mp pneumonia via not bacteriological but immunomodulative effects. This exhaustive review focuses on pathogenesis and extends to some therapeutic implications such as clarithromycin, and discusses the various diverse aspects of Mp pneumonia. It is our hope that this might lead to new insights into this common respiratory disease.

Identification of a mechanism for lung inflammation caused by Mycoplasma pneumoniae using a novel mouse model

Human Mycoplasma pneumoniae (MP) pneumonia is characterized by alveolar infiltration with neutrophils and lymphocytes and lymphocyte/plasma cell infiltrates in the peri-bronchovascular area (PBVA). No mouse model has been able to mimic the pathological features seen in human MP pneumonia, such as plasma cell-rich lymphocytic infiltration in PBVA. To figure out the mechanism for inflammation by MP infection using a novel mouse model that mimics human MP pneumonia, mice were pre-immunized intraperitoneally with Th2 stimulating adjuvant, alum, alone or MP extracts with an alum, followed by intratracheal challenge with MP extracts. The toll-like receptor-2, which is the major receptor for mycoplasma cell wall lipoproteins, was strongly up-regulated in alveolar macrophages in a latter group after the pre-immunization but prior to the intratracheal challenge. Those findings demonstrated that acceleration of innate immunity by antecedent antigenic stimulation can be an important positive-feedback mechanism in lung inflammation during MP pneumonia.

Decreased interleukin-18 response in asthmatic children with severe Mycoplasma pneumoniae pneumonia

Purpose

Mycoplasma pneumoniae (M. pneumoniae) is a common causative agent of pneumonia in children. The aim of this study is to determine whether there is any difference in selected cytokine or chemokines response in asthmatic children compared to non-asthmatic children during acute M. pneumoniae pneumonia.

Methods

Seventy-five children, 6–12 years of age, admitted with M. pneumoniae pneumonia were enrolled. Two patient groups were defined: the children with known asthma (N = 40) and non-asthmatic children (N = 35). Interleukin (IL)-18 and selected chemokines, IL-8, CXCL9, CXCL10, and regulation upon activation normal T-cell expressed and secreted (RANTES) were measured by means of ELISA in the plasma samples of the patients collected on admission. We investigated the values of these mediators in relation to the asthma status and symptom severity of the patients. Twenty age-matched, non-infected controls were also studied.

Results

Plasma levels of IL-18 and the chemokines increased significantly in the patients with M. pneumoniae pneumonia compared to non-infected, age-matched controls (P < 0.01). However, the asthmatic patients showed significantly reduced IL-18 and CXCL10 responses (P < 0.01, <0.05, respectively) and had more severe pneumonia symptoms (P < 0.01) compared to non-asthmatic patients. IL-18 was significantly lower in severe pneumonia group than in non-severe group (P < 0.05).

Conclusions

Our study suggests that IL-18 and the chemokines are importantly involved in the pathogenesis of M. pneumoniae pneumonia. It also indicates that some asthmatic children have deficient IL-18 response when affected by M. pneumoniae pneumonia, which might be associated with more severe pneumonia observed in this group of patients.

The impact of steroids given with macrolide therapy on experimental Mycoplasma pneumoniae respiratory infection

BACKGROUND

Systemic steroids have been advocated in addition to antimicrobial therapy for severe Mycoplasma pneumoniae pneumonia. We evaluated the efficacy of clarithromycin, dexamethasone, and combination therapy for M. pneumoniae respiratory infection.

METHODS

Mice infected with M. pneumoniae were treated with clarithromycin, dexamethasone, combined clarithromycin/dexamethasone, or placebo daily; mice were evaluated at baseline and after 1, 3, and 6 days of therapy. Outcome variables included M. pneumoniae culture, lung histopathologic score (HPS), and bronchoalveolar lavage cytokine, chemokine, and growth factor concentrations.

RESULTS

Clarithromycin monotherapy resulted in the greatest reductions in M. pneumoniae concentrations. After 3 days of treatment, combination therapy significantly reduced lung HPS compared with placebo, clarithromycin, and dexamethasone alone, whereas, after 6 days of therapy, clarithromycin alone and combination therapy significantly reduced lung HPS compared with placebo. Concentrations of interleukin (IL)-12 p40, RANTES, macrophage chemotactic protein-1, and cytokine-induced neutrophil chemoattractant were significantly lower in mice treated with clarithromycin alone and/or combination therapy compared with dexamethasone alone and/or placebo; combination therapy resulted in a significantly greater reduction than clarithromycin alone for IL-12 p40 and RANTES.

CONCLUSIONS

Although monotherapy with clarithromycin had the greatest effect on reducing concentrations of M. pneumoniae, combination therapy had the greatest effect on decreasing levels of cytokines and chemokines as well as pulmonary histologic inflammation.

Epidemiology, clinical manifestations, pathogenesis and laboratory detection of Mycoplasma pneumoniae infections

Since its initial description in the 1940s and eventual elucidation as a highly evolved pathogenic bacterium, Mycoplasma pneumoniae has come to be recognized as a worldwide cause of primary atypical pneumonia. Beyond its ability to cause severe lower respiratory illness and milder upper respiratory symptoms it has become apparent that a wide array of extrapulmonary infectious and postinfectious events may accompany the infections in humans caused by this organism. Autoimmune disorders and chronic diseases such as asthma and arthritis are increasingly being associated with this mycoplasma, which frequently persists in individuals for prolonged periods. The reductive evolutionary process that has led to the minimal genome of M. pneumoniae suggests that it exists as a highly specialized parasitic bacterium capable of residing in an intracellular state within the respiratory tissues, occasionally emerging to produce symptoms. This review includes discussion of some of the newer aspects of our knowledge on this pathogen, characteristics of clinical infections, how it causes disease, the recent emergence of macrolide resistance, and the status of laboratory diagnostic methods.

Leukotriene D4-induced, epithelial cell-derived transforming growth factor beta1 in human bronchial smooth muscle cell proliferation

BACKGROUND

Cysteinyl-leukotrienes (cys-LTs) orchestrate many pathognomonic features of asthma in animal models of allergic airway inflammation, including bronchial smooth muscle cell (BSMC) hyperplasia. However, because cys-LTs alone do not induce mitogenesis in monocultures of human BSMC, the effect observed in vivo seemingly involves indirect mechanisms, which are still undefined.

OBJECTIVE

This study aims to investigate the regulatory role of leukotriene (LT)D(4) on TGF-beta1 expression in airway epithelial cells and the consequence of this interplay on BSMC proliferation.

METHODS

HEK293 cells stably transfected with cys-LT receptor 1 (CysLT1) (293LT1) were stimulated with LTD(4) and TGF-beta1 mRNA and protein expression was measured using Northern blot and ELISA, respectively. Conditioned medium (CM) harvested from LTD(4)-treated cells was then assayed for its proliferative effect on primary human BSMC. TGF-beta1 mRNA expression was also determined in tumoural type II pneumocytes A549 and in normal human bronchial epithelial cells (NHBE) following LTD(4) stimulation.

RESULTS

The results demonstrated that LTD(4)-induced TGF-beta1 mRNA production in a time- and concentration-dependent manner in 293LT1. TGF-beta1 secretion was also up-regulated and CM from LTD(4)-treated 293LT1 was shown to increase BSMC proliferation in a TGF-beta1-dependent manner. The increased expression of TGF-beta1 mRNA by LTD(4) also occured in A549 and NHBE cells via a CysLT1-dependent mechanism.

CONCLUSION

In conclusion, elevated expression of cys-LTs in asthmatic airways might contribute to BSMC hyperplasia and concomitant clinical features of asthma such as airway hyperresponsiveness via a paracrine loop involving TGF-beta1 production by airway epithelial cells.

Inhibition of message for FcepsilonRI alpha chain blocks mast cell IL-4 production induced by co-culture with Mycoplasma pneumoniae

We have previously described the activation of RBL-2H3 mast cells for IL-4 production by Mycoplasma pneumoniae but the mechanism remains unclear. M. pneumoniae binds eukaryotic cells primarily through sialoglycoproteins on the target cell surface. This study was undertaken to determine whether the sialated FcepsilonRI alpha chain on RBL cells is important for M. pneumoniae-induced IL-4 production. We found that IgE-mediated IL-4 release by a series of RBL sublines correlated with the release induced by M. pneumoniae. Further, aggregation of FcgammaRII (CD32) in RBL cells using a monoclonal antibody inhibited both IgE-mediated and mycoplasma-induced IL-4 production, providing further evidence for an Fc receptor-mediated mechanism of activation. To examine the role of FcepsilonRI in mycoplasma-induced IL-4 release, we created stably transfected RBL sublines using a vector expressing a short hairpin sequence designed to inhibit message for the FcepsilonRI alpha chain. IgE-induced IL-4 production by the transfected sublines was reduced in similar proportion to the degree of message suppression. M. pneumoniae-induced IL-4 production in the four transfected sublines was completely blocked in contrast to results with the controls or parent RBL cells. We conclude that the heavily glycosylated FcepsilonRI alpha chain is required for activation of mast cells for IL-4 production by M. pneumoniae.

Mycoplasma pneumoniae-an emerging extra-pulmonary pathogen

Mycoplasma is a well-recognised pathogen that colonises mucosal surfaces of humans and animals. Mycoplasma pneumoniae infects the upper and lower respiratory tracts of children and adults, leading to a wide range of respiratory and non-respiratory clinical conditions. M. pneumoniae infection is frequently considered in the differential diagnosis of patients with respiratory illnesses, and is commonly managed empirically with macrolides and fluoroquinolones. This contrasts with patients who present with non-respiratory symptoms in the context of a recent or current unrecognised M. pneumoniae infection, for whom this pathogen is rarely considered in the initial differential diagnosis. This review considers the microbiological, epidemiological, pathogenic and clinical features of this frequent pathogen that need to be considered in the differential diagnosis of respiratory and non-respiratory infections.

Controversy surrounding the increased expression of TGF beta 1 in asthma

Asthma is a waxing and waning disease that leads to structural changes in the airways, such as subepithelial fibrosis, increased mass of airway smooth muscle and epithelial metaplasia. Such a remodeling of the airways futher amplifies asthma symptoms, but its etiology is unknown. Transforming growth factor β1 is a pleiotropic cytokine involved in many fibrotic, oncologic and immunologic diseases and is believed to play an essential role in airway remodeling that occurs in asthmatic patients. Since it is secreted in an inactive form, the overall activity of this cytokine is not exclusively determined by its level of expression, but also by extensive and complex post-translational mechanisms, which are all importanin modulating the magnitude of the TGFβ1 response. Even if TGFβ1 upregulation in asthma is considered as a dogma by certain investigators in the field, the overall picture of the published litterature is not that clear and the cellular origin of this cytokine in the airways of asthmatics is still a contemporaneous debate. On the other hand, it is becoming clear that TGFβ1 signaling is increased in the lungs of asthmatics, which testifies the increased activity of this cytokine in asthma pathogenesis. The current work is an impartial and exhaustive compilation of the reported papers regarding the expression of TGFβ1 in human asthmatics. For the sake of comparison, several studies performed in animal models of the disease are also included. Inconsistencies observed in human studies are discussed and conclusions as well as trends from the current state of the litterature on the matter are proposed. Finally, the different points of regulation that can affect the amplitude of the TGFβ1 response are briefly revised and the possibility that TGFβ1 is disregulated at another level in asthma, rather than simply in its expression, is highlighted.

Mycoplasma pneumoniae host–pathogen studies in an air–liquid culture of differentiated human airway epithelial cells

The interaction between Mycoplasma pneumonaie and the airway epithelium in vivo is complex and multifaceted. While multiple in vitro studies have been conducted studying this interaction with cell lines and animal cell and organ culture models, the interactions between M. pneumoniae and fully differentiated human airway epithelium in air-liquid interface culture remains unexplored. In the present study we investigated M. pneumoniae interactions with airway epithelium utilizing an air-liquid interface culture of differentiated normal human bronchial epithelial (NHBE) cells. Utilizing confocal microscopy we found that M. pneumoniae cells bound initially to ciliated epithelial cells, but colonization became more evenly distributed over the entire surface with time. M. pneumoniae infection resulted in stimulation of intercellular adhesion molecule 1 (ICAM-1) gene expression and soluble ICAM-1 production in this culture system.

Respiratory infections and asthma

Respiratory tract infections caused by both viruses and/or atypical bacteria are involved in the pathogenesis of asthma. In particular, several viruses such as respiratory syncytial virus, rhinovirus and influenza/parainfluenza viruses may favour the expression of the asthmatic phenotype, being also implicated in the induction of disease exacerbations. Within this pathological context, a significant role can also be played by airway bacterial colonizations and infections due to Chlamydiae and Mycoplasms. All these microbial agents probably interfere with complex immunological pathways, thus contributing to induce and exacerbate asthma in genetically predisposed individuals.

Induction of IL-6 in co-culture of bronchial epithelial cells and eosinophils is regulated by p38 MAPK and NF-kappaB

BACKGROUND

Prominent infiltration of eosinophils into the airway mucosa and release of inflammatory mediators upon their adhesion onto airway epithelial cells are the immunopathogical mechanisms of allergic asthma.

OBJECTIVE

We investigated the effect of normal and paraformaldyhyde-fixed human eosinophils on BEAS-2B cells, a human bronchial epithelial cell line, for the release of inflammatory cytokine interleukin (IL)-6.

METHODS

Interleukin-6 in cell culture supernatant, protein amount of p38 mitogen-activated protein kinase (MAPK), and nuclear factor-kappaB (NF-kappaB) activity in BEAS-2B cells were analyzed by Western blot and enzyme-linked immunosorbent assay (ELISA). IL-6 gene expression was assessed by reverse transcriptase-polymerase chain reaction (RT-PCR), and p38 MAPK activity and inhibitor (I)kappaB-alpha induction were evaluated by Western blot.

RESULTS

Co-culture of BEAS-2B cells and eosinophils induced a significant elevation of IL-6 expression in BEAS-2B cells. Interaction of eosinophils and BEAS-2B cells led to a marked induction in phospho-p38 MAPK, phospho-IkappaB-alpha and activity of NF-kappaB in BEAS-2B cells. NF-kappaB inhibitor BAY 11-7082 and p38 MAPK inhibitor SB 203580 significantly decreased IL-6 release in a co-culture of BEAS-2B cells and eosinophils. Fixed human eosinophils were able to maintain their ability to induce IL-6 release in co-culture, activate p38 MAPK and NK-kappaB, and up-regulate IL-6 gene expression in BEAS-2B cells.

CONCLUSIONS

These data indicate that the interaction of eosinophils and bronchial epithelial cells plays an important role in airway inflammation, at least partly, via IL-6 induction.

Role of atypical bacterial infection of the lung in predisposition/protection of asthma

Asthma is a common inflammatory disease of the airways that results in airway narrowing and wheezing. Allergic asthma is characterised by a T-helper cell-type (Th) 2 response, immunoglobulin (Ig) E production, and eosinophilic influx into the airways. Recently, many clinical studies have implicated Mycoplasma pneumoniae and Chlamydia pneumoniae in the development and exacerbation of both chronic and acute asthma. It is widely accepted that M. pneumoniae and C. pneumoniae infections require Th1 immunity for clearance; therefore, according to the hygiene hypothesis, these infections should be protective against asthma. Here, we review the clinical evidence for the association and mechanisms of predisposition to and protection against asthma by these infections. We will examine the following question: Is it the absence of infection or the age of the individual on infection that confers susceptibility or resistance to asthma and does this vary between normal and predisposed individuals? We put forward a hypothesis of the effects of these infections on the development and prevention of asthma and how novel preventative and treatment strategies involving these microbes may be targeted against asthma.

Low-dose, long-term macrolide therapy in asthma: An overview

Macrolides, a class of antimicrobials isolated from Streptomycetes more than 50 years ago, are used extensively to treat sinopulmonary infections in humans. In addition, a growing body of experimental and clinical evidence indicates that long-term (years), low (sub-antimicrobial)-dose 14- and 15-membered ring macrolide antibiotics, such as erythromycin, clarithromycin, roxithromycin and azithromycin, express immunomodulatory and tissue reparative effects that are distinct from their anti-infective properties. These salutary effects are operative in various lung disorders, including diffuse panbronchiolitis, cystic fibrosis, persistent chronic rhinosinusitis, nasal polyposis, bronchiectasis, asthma and cryptogenic organizing pneumonia.

The purpose of this overview is to outline the immunomodulatory effects of macrolide antibiotics in patients with asthma.