Update in asthma 2007

Defining severe asthma - an approach to find new therapies

Asthma is a chronic inflammatory disease that has reached epidemic proportions worldwide. It is treatable in the majority of patients, but there is no cure. Moreover, a proportion of patients suffer from severe, difficult-to-control disease with daily symptoms and high morbidity, making it imperative that we continue to improve our understanding of the underlying mechanisms of this disease. Severe asthma is a heterogeneous condition. A systematic approach to identify specific asthma phenotypes, including clinical characteristics and inflammatory processes, is the first step toward individualized, logical therapy. This review focuses on the need to characterize severe asthma phenotypes and on novel, targeted molecular treatment options currently under development.

Asthma management in sickle cell disease

Asthma is a common comorbid factor in sickle cell disease (SCD). However, the incidence of asthma in SCD is much higher than expected compared to rates in the general population. Whether "asthma" in SCD is purely related to genetic and environmental factors or rather is the consequence of the underlying hemolytic and inflammatory state is a topic of recent debate. Regardless of the etiology, hypoxemia induced by bronchoconstriction and inflammation associated with asthma exacerbations will contribute to a cycle of sickling and subsequent complications of SCD. Recent studies confirm that asthma predisposes to complications of SCD such as pain crises, acute chest syndrome, and stroke and is associated with increased mortality. Early recognition and aggressive standard of care management of asthma may prevent serious pulmonary complications and reduce mortality. However, data regarding the management of asthma in SCD is very limited. Clinical trials are needed to evaluate the effectiveness of current asthma therapy in patients with SCD and coincident asthma, while mechanistic studies are needed to delineate the underlying pathophysiology.

Two for one: cyclic AMP mediates the anti-inflammatory and anti-spasmodic properties of the non-anesthetic lidocaine analog JMF2-1

Inhalation of JMF2-1, an analog of lidocaine with reduced anesthetic activity, prevents airway contraction and lung inflammation in experimental asthma models. We sought to test if the JMF2-1 effects are a consequence of increased intracellular cAMP levels in asthma cell targets, such as smooth muscle cells and T cells. Functional effect of JMF2-1 on carbachol-induced contraction of intact or epithelial-denuded rat trachea was assessed in conventional organ baths. cAMP was quantified by radioimmunoassay in cultured guinea pig tracheal smooth muscle cells, as well as lymph node cells from BALB/c mice, exposed to JMF2-1. We found that JMF2-1 (0.1-1mM) concentration-dependently inhibited epithelium-intact tracheal ring contraction induced by carbachol challenge. The antispasmodic effect remained unaltered following epithelium removal or pretreatment with NG-nitro-L-arginine methyl ester (100μM), but it was clearly sensitive to 9-(tetrahydro-2-furyl) adenine (SQ22,536, 100μM), an adenylate cyclase inhibitor. JMF2-1 (300 and 600μM) also dose-dependently increased cAMP intracellular levels of both cultured airway smooth muscle cells and T lymphocytes. This effect was consistently abrogated by SQ22,536 and reproduced by forskolin in both systems. JMF2-1 induced apoptosis of anti-CD3 activated T cells in a mechanism sensitive to zIETD, indicating that JMF2-1 mediates caspase-8-dependent apoptosis. Furthermore, forskolin also inhibited anti-CD3 induced T cell proliferation and survival. Our results suggest that JMF2-1 inhibits respiratory smooth muscle contraction as well as T cell proliferation and survival through enhancement of intracellular cAMP levels. These findings may help to explain the anti-inflammatory and antispasmodic effects of JMF2-1 observed in previous studies.

Lidocaine-derivative JMF2-1 prevents ovalbumin-induced airway inflammation by regulating the function and survival of T cells

BACKGROUND

Inhalation of the local anaesthetic lidocaine has been suggested to be beneficial for asthmatics, but airway anaesthesia is unpleasant and may exacerbate bronchoconstriction. Our previous study showed that inhalation of the lidocaine analogue JMF2-1 can elicit the anti-inflammatory properties of lidocaine without anaesthesia. This prompted further research on the mechanism of action and putative therapeutic application of JMF2-1.

OBJECTIVE

We tested the hypothesis that JMF2-1 would prevent allergen-induced lung inflammation and airway hyperresponsiveness (AHR) by modulating T cell function in vivo and in vitro. Methods Local and systemic changes in leucocyte levels, cytokine production and lung mechanics were examined in a murine model of lung inflammation. JMF2-1 (0.05-2%) or saline was aerosolized twice a day during the ovalbumin (OVA)-provocation period (19-21 days post-sensitization). Analyses were performed 24 h after the final challenge. Primary cultured lymph node cells were used to assess the effects of JMF2-1 (100-600 μm) at the cellular level.

RESULTS

OVA challenge resulted in lung recruitment of CD4(+) T cells and eosinophils, increased generation of inflammatory cytokines and AHR to inhaled methacholine within 24 h. These changes were prevented by JMF2-1 nebulization, and occurred in parallel with an increase in the number of apoptotic cells in the lung. JMF2-1 treatment did not alter levels of CD4(+) or CD8(+) T cells in the thymus or lymph nodes of naïve mice, although it inhibited OVA-induced IL-13 production and the lymphocyte proliferative response in vitro. It also induced apoptosis of OVA-activated lymphocytes in a mechanism sensitive to z-VAD, indicating that JMF2-1 mediates caspase-dependent apoptosis.

CONCLUSION

Inhalation of JMF2-1 prevents the cardinal features of asthma by reducing T(H) 2 cytokine generation and lung eosinophilic inflammatory infiltrates via local inhibition of T cell function and survival. JMF2-1 may represent a novel therapeutic alternative for asthma control with distinct advantages over local anaesthetics.

Novel biomarkers in asthma: chemokines and chitinase-like proteins

PURPOSE OF REVIEW

Allergic asthma is a frequent lung disease in Western civilizations and is characterized by airway inflammation and tissue remodeling. Without early diagnosis and specific treatment, asthma results in a loss of lung function, impaired quality of life and the risk to die from uncontrolled asthma attacks. Thus, there is a need for specific biomarkers to detect asthma as soon as possible and to initiate the correct clinical treatment.

RECENT FINDINGS

Recent studies have highlighted the potential role of the chemokine (C-C motif) ligand 17 and the chitinase-like protein YKL-40 as novel biomarkers in asthma. Patient studies suggest that these proteins could be useful to identify asthmatics, to characterize disease severity or both in patients with asthma. Functional studies indicate that these molecules are more than correlated epiphenomena and instead contribute in significant ways to asthma pathogenesis.

SUMMARY

Assessments of chemokine (C-C motif) ligand 17 and YKL-40 may allow physicians to more accurately diagnose and predict the course of asthma and thereby allow therapy to be appropriately tailored for a given patient.

Why is effective treatment of asthma so difficult? An integrated systems biology hypothesis of asthma

A hypothesis is presented that asthma is not only an airway disease, but that the disease involves the entire lung, and that the chronicity of asthma and asthma exacerbations can perhaps be explained if one considers asthma as a systemic disease. Increased lung-not only airway-vascularity may be the result of the action of angiogenesis factors, such as vascular endothelial growth factor (VEGF) and sphingosine-1-phosphate (S1P). A bone-marrow lung axis can be postulated as one element of the systemic nature of the asthma syndrome, in which the inflamed lung emits chemotactic signals, which the bone marrow responds to by releasing cells that contribute to lung angiogenesis. A molecular model of the pathobiology of asthma can be built by connecting hypoxia-inducible transcription factor-1 alpha, VEGF S1P, and bone-marrow precursor cell mobilization and acknowledging that angiogenesis is part of the inflammatory response.

Asthma management: reinventing the wheel in sickle cell disease

Asthma is a common comorbidity in sickle cell disease (SCD) with a reported prevalence of 30-70%. The high frequency of asthma in this population cannot be attributed to genetic predisposition alone, and likely reflects in part, the contribution of overlapping mechanisms shared between these otherwise distinct disorders. There is accumulating evidence that dysregulated arginine metabolism and in particular, elevated arginase activity contributes to pulmonary complications in SCD. Derangements of arginine metabolism are also emerging as newly appreciated mechanism in both asthma and pulmonary hypertension independent of SCD. Patients with SCD may potentially be at risk for an asthma-like condition triggered or worsened by hemolysis-driven release of erythrocyte arginase and low nitric oxide bioavailability, in addition to classic familial asthma. Mechanisms that contributed to asthma are complex and multifactorial, influenced by genetic polymorphisms as well as environmental and infectious triggers. Given the association of asthma with inflammation, oxidative stress and hypoxemia, factors known to contribute to a vasculopathy in SCD, and the consequences of these factors on sickle erythrocytes, comorbid asthma would likely contribute to a vicious cycle of sickling and subsequent complications of SCD. Indeed a growing body of evidence documents what should come as no surprise: Asthma in SCD is associated with acute chest syndrome, stroke, pulmonary hypertension, and early mortality, and should therefore be aggressively managed based on established National Institutes of Health Guidelines for asthma management. Barriers to appropriate asthma management in SCD are discussed as well as strategies to overcome these obstacles in order to provide optimal care.

Neonatal bacillus Calmette-Guérin vaccination inhibits de novo allergic inflammatory response in mice via alteration of CD4+CD25+ T-regulatory cells

AIM

The hygiene hypothesis suggests a lack of bacterial infections would favor the development of allergic diseases. Mycobacterium bovis bacille Calmette-Guérin (BCG) infection can inhibit allergen-induced asthma reactions, but the underlying mechanism of this infection on the immunological responses is unclear. T-regulatory (Treg) cells are thought to play a role as a crucial immunoregulatory cells that are capable of regulating adaptive immune responses. We conducted this study to investigate whether the protective effect of the BCG vaccination on allergic pulmonary inflammation is associated with the alteration of CD4+CD25+ Treg cells in a murine asthma model and the mechanisms of Treg cells.

METHODS

Newborn C57BL/6 mice were vaccinated 3 times with BCG on d 0, 7, and 14 and subsequently sensitized and challenged with ovalbumin. Eosinophil infiltration was investigated. The frequencies of spleen CD4+CD25+ Treg cells and the expression of specific transcriptional factor Foxp3 were assayed. The cytotoxic lymphocyte associated antigen (CTLA)-4 expression and cytokine interleukin-10 (IL-10) and transforming growth factor-beta (TGF-beta) levels were measured.

RESULTS

We showed that treatment of mice with BCG inhibited de novo allergic inflammatory response in a mouse model of asthma. BCG treatments are associated with the increase of CD4+CD25+ Treg cells and Foxp3 expression, accompanied by an increased CTLA-4 expression and cytokine IL-10 and TGF-beta levels (P<0.05).

CONCLUSION

Neonatal BCG vaccinations ameliorate de novo local eosinophilic inflammation induced by allergen and increase the numbers of CD4+CD25+ Treg cells and Foxp3 expression. The cell-cell contact inhibition and regulatory cytokine production may be involved in the regulatory mechanism.