An investigation of the impact of the location and timing of antigen-specific T cell division on airways inflammation

Treatment with a sphingosine analog after the inception of house dust mite-induced airway inflammation alleviates key features of experimental asthma

Background

In vivo phosphorylation of sphingosine analogs with their ensuing binding and activation of their cell-surface sphingosine-1-phosphate receptors is regarded as the main immunomodulatory mechanism of this new class of drugs. Prophylactic treatment with sphingosine analogs interferes with experimental asthma by impeding the migration of dendritic cells to draining lymph nodes. However, whether these drugs can also alleviate allergic airway inflammation after its onset remains to be determined. Herein, we investigated to which extent and by which mechanisms the sphingosine analog AAL-R interferes with key features of asthma in a murine model during ongoing allergic inflammation induced by Dermatophagoides pteronyssinus.

Methods

BALB/c mice were exposed to either D. pteronyssinus or saline, intranasally, once-daily for 10 consecutive days. Mice were treated intratracheally with either AAL-R, its pre-phosphorylated form AFD-R, or the vehicle before every allergen challenge over the last four days, i.e. after the onset of allergic airway inflammation. On day 11, airway responsiveness to methacholine was measured; inflammatory cells and cytokines were quantified in the airways; and the numbers and/or viability of T cells, B cells and dendritic cells were assessed in the lungs and draining lymph nodes.

Results

AAL-R decreased airway hyperresponsiveness induced by D. pteronyssinus by nearly 70%. This was associated with a strong reduction of IL-5 and IL-13 levels in the airways and with a decreased eosinophilic response. Notably, the lung CD4⁺ T cells were almost entirely eliminated by AAL-R, which concurred with enhanced apoptosis/necrosis in that cell population. This inhibition occurred in the absence of dendritic cell number modulation in draining lymph nodes. On the other hand, the pre-phosphorylated form AFD-R, which preferentially acts on cell-surface sphingosine-1-phosphate receptors, was relatively impotent at enhancing cell death, which led to a less efficient control of T cell and eosinophil responses in the lungs.

Conclusion

Airway delivery of the non-phosphorylated sphingosine analog, but not its pre-phosphorylated counterpart, is highly efficient at controlling the local T cell response after the onset of allergic airway inflammation. The mechanism appears to involve local induction of lymphocyte apoptosis/necrosis, while mildly affecting dendritic cell and T cell accumulation in draining lymph nodes.

Triphala (PADMA) extract alleviates bronchial hyperreactivity in a mouse model through liver and spleen immune modulation and increased anti-oxidative effects

OBJECTIVES

Triphala (TRP), a herbal extract from Tibetan medicine, has been shown to affect lymphocytes and natural killer T (NKT) cell function. We hypothesize that TRP could ameliorate bronchial hyperreactivity through immune-cell modulations.

METHODS

Asthma mouse models were generated through intraperitoneal (IP) injections of ovalbumin (OVA)/2 weeks followed by repeated intranasal OVA challenges. Mice were then treated with normal saline (OVA/NS) or Triphala (OVA/TRP). Data were compared with mice treated with inhaled budesonide. All groups were assessed for allergen-induced hyperreactivity; lymphocytes from lungs, livers and spleens were analyzed for OVA-induced proliferation and their alterations were determined by flow cytometry. Oxidative reactivity using chemiluminescence, serum anti-OVA antibodies level and lung histology were assessed.

RESULTS

Both TRP and budesonide significantly ameliorated functional and histological OVA-induced bronchial hyperreactivity. TRP had no effect on serum anti-OVA antibodies as compared with decreased levels following budesonide treatment. Furthermore, a significant increase in lung and spleen CD4 counts and a decrease in the liver were noted after TRP treatments. Bronchoalveolar fluid from TRP-treated animals but not from the budesonide-treated animals showed anti-oxidative effects.

CONCLUSION

TRP and budesonide caused a significant decrease in bronchial reactivity. TRP treatment altered immune-cell distributions and showed anti-oxidative properties. These findings suggest that immune-cell modulation with TRP can ameliorate lung injury.

Treatment of allergic asthma: modulation of Th2 cells and their responses

Atopic asthma is a chronic inflammatory pulmonary disease characterised by recurrent episodes of wheezy, laboured breathing with an underlying Th2 cell-mediated inflammatory response in the airways. It is currently treated and, more or less, controlled depending on severity, with bronchodilators e.g. long-acting beta agonists and long-acting muscarinic antagonists or anti-inflammatory drugs such as corticosteroids (inhaled or oral), leukotriene modifiers, theophyline and anti-IgE therapy. Unfortunately, none of these treatments are curative and some asthmatic patients do not respond to intense anti-inflammatory therapies. Additionally, the use of long-term oral steroids has many undesired side effects. For this reason, novel and more effective drugs are needed. In this review, we focus on the CD4+ Th2 cells and their products as targets for the development of new drugs to add to the current armamentarium as adjuncts or as potential stand-alone treatments for allergic asthma. We argue that in early disease, the reduction or elimination of allergen-specific Th2 cells will reduce the consequences of repeated allergic inflammatory responses such as lung remodelling without causing generalised immunosuppression.

Immune modulation of ovalbumin-induced lung injury in mice using β-glucosylceramide and a potential role of the liver

CD1d-restricted natural killer T (NKT) cells are implicated in the pathogenesis of asthma. β-Glucosylceramide (GC), a naturally occurring lipid, was previously shown to alter NKT cell distribution in the liver. We hypothesized that GC can affect lung and liver NKT cell distribution and ameliorate asthma. Mice were sensitized by intra-peritoneal injection of ovalbumin (OVA) for 2 weeks followed by repeated intranasal OVA challenges to induce lung injury mimicking asthma. OVA induced asthma groups were either treated by intranasal instillation of normal saline, intranasal instillation of GC or inhaled budesonide. To investigate the role of the liver, hepatic fibrosis was induced using carbon tetrachloride prior to asthma induction. Allergen induced bronchoconstriction was measured prior to sacrifice. Isolated lymphocytes from lungs, livers and spleens were analyzed for OVA induced proliferation and flow cytometry. Liver and lung histology, serum aminotransferase and anti-OVA antibodies level were assessed. Treatment with GC significantly reduced OVA induced airway responsiveness (p<0.001) similar to inhaled budesonide. GC significantly reduced the peri-bronchial and peri-vascular inflammatory infiltration mainly through an effect on T cells, as suggested by decreased T cell proliferation (p=0.009). Liver CD4 and NKT cells significantly increased after GC treatment suggesting liver involvement. Inducing hepatic fibrosis blunted the propagation of asthma in spite of sufficient increase of serum anti-OVA titers. GC has an immunomodulatory effect on a murine model of experimental asthma. We also suggest that the liver acts as an immunomodulatory organ and might have a regulatory effect on pulmonary diseases.

B lymphocytes in inflammatory airway diseases

B lymphocytes are key players in all facets of adaptive immune responses and are responsible for the production of IgE antibodies, initiators of allergic hypersensitivity reactions. Recent evidence indicates that B cells may be a crucial player in allergic and inflammatory airway pathology, directly populating upper and lower airway tissues. This review examines human and animal studies that directly demonstrated the presence of B lymphocytes in airway tissues and elaborates on their function as antibody-secreting cells, antigen-presenting cells and producers of inflammatory and regulatory cytokines. B lymphocytes appear to contribute to multiple facets of immune homeostasis in inflammatory diseases of the upper and lower airways.

A murine model of stress controllability attenuates Th2-dominant airway inflammatory responses

Epidemiological and experimental studies suggest a positive correlation between chronic respiratory inflammatory disease and the ability to cope with adverse stress. Interactions between neuroendocrine and immune systems are believed to provide insight toward the biological mechanisms of action. The utility of an experimental murine model was employed to investigate the immunological consequences of stress-controllability and ovalbumin-induced airway inflammation. Pre-conditioned uncontrollable stress exacerbated OVA-induced lung histopathological changes that were typical of Th2-predominant inflammatory response along respiratory tissues. Importantly, mice given the ability to exert control over aversive stress attenuated inflammatory responses and reduced lung pathology. This model represents a means of investigating the neuro-immune axis in defining mechanisms of stress and respiratory disease.

Color-coded real-time cellular imaging of lung T-lymphocyte accumulation and focus formation in a mouse asthma model

BACKGROUND

A critical role for CD4(+)T(H)2 cells in the pathogenesis of acute asthma has been demonstrated in the studies of human asthma as well as of animal models of asthma. T(H)2-cell migration into the lung is crucial for the initiation of asthma phenotype, but the dynamics of this process are poorly understood because it has been difficult to visualize this process.

OBJECTIVE

Our aim was to image the cellular dynamics of the migration of T(H)2 cells into the lung of living animals in a mouse model of asthma and identify the cellular processes required for the initiation of the asthma phenotype.

METHODS

We developed a color-coded real-time imaging model of cell migration into the lung using green fluorescent protein (GFP) and red fluorescent protein (RFP) transgenic CD4 T cells.

RESULTS

Selective accumulation of antigen-specific CD4 T cells in the lungs was quantitatively imaged in a mouse model of asthma. The inhibition of accumulation by dexamethasone was imaged. Accumulating GFP(+) T(H)2 cells formed foci in the lungs from 6 to 20 hours after antigen inhalation. This process was also inhibited by the administration of anti-intercellular adhesion molecule 1 or anti-vascular cell adhesion molecule 1 mAbs. Two days after inhalation of antigen, GFP(+) T(H)2 cells were detected in the area of eosinophil infiltration.

CONCLUSION

Focus formation generated by accumulating antigen-specific T(H)2 cells in the lung appeared to be a critical process in the initiation of the asthma phenotype. This new model enables the study of in vivo cell biology of airway inflammation and novel drug discovery for lung inflammatory diseases.