Phosphodiesterase inhibitors in the treatment of inflammatory diseases

Phosphodiesterase 4 (PDE4) belongs to a family of enzymes which catalyzes the breakdown of 3, 5'-adenosine cyclic monophosphate (cAMP) and is ubiquitously expressed in inflammatory cells. There is little evidence that inflammatory diseases are caused by increased expression of this isoenzyme, although human inflammatory cell activity can be suppressed by selective PDE4 inhibitors. Consequently, there is intense interest in the development of selective PDE4 inhibitors for the treatment of a range of inflammatory diseases, including asthma, chronic obstructive pulmonary disease (COPD), inflammatory bowel disease, and psoriasis. Recent clinical trials with roflumilast in COPD have confirmed the therapeutic potential of targeting PDE4 and recently roflumilast has been approved for marketing in Europe and the USA, although side effects such as gastrointestinal disturbances, particularly nausea and emesis as well as headache and weight loss, may limit the use of this drug class, at least when administered by the oral route. However, a number of strategies are currently being pursued in attempts to improve clinical efficacy and reduce side effects of PDE4 inhibitors, including delivery via the inhaled route, development of nonemetic PDE4 inhibitors, mixed PDE inhibitors, and/or antisense biologicals targeted toward PDE4.

Airway responsiveness in an allergic rabbit model

BACKGROUND

Animal models of allergy and bronchial hyperresponsiveness (BHR) are useful in researching pulmonary diseases and evaluating drug effects on the airways. Neonatally immunised rabbits exhibit several features of asthma as adults, including early and late airway responses following antigen challenge, oedema and inflammatory cell infiltration into the lung, BHR to inhaled histamine and methacholine (compared with naïve rabbits) and exacerbations of BHR following antigen challenge. Therefore this model can be used to investigate the underlying mechanisms of BHR and for the preclinical evaluation of new drugs for the treatment of asthma.

AIM

To describe the characteristics of airway responses in a rabbit model of allergic inflammation and to evaluate the relationship between skin test reactivity to antigen, airway inflammation and BHR.

METHODS

New Zealand White rabbits were neonatally immunised against Alternaria tenius. At 3 months of age, airway responsiveness was measured to aerosolised histamine, methacholine or allergen. Bronchoalveolar lavage (BAL) was performed and cell counts recorded. Direct skin tests were performed to assess skin reactivity to allergen and passive cutaneous anaphylaxis (PCA) tests were performed to determine titres of circulating IgE.

RESULTS

In a population of allergic rabbits, allergen challenge induced a significant bronchoconstriction, airway inflammation and BHR. Skin test responsiveness to allergen did not correlate with various indices of pulmonary mechanics e.g. baseline sensitivity to methacholine and histamine, or allergen-induced BHR. In contrast, skin test responsiveness did predict airway inflammation as assessed by measurements of eosinophil recruitment to the lung.

CONCLUSION

The allergic rabbit is a useful model to further our understanding of allergic diseases. Recording lung function using a minimally invasive procedure allows repeated measurements to be made in rabbits longitudinally, and each animal may thus be used as its own control. Our observations do not support the use of skin responsiveness to allergen as a predictor of airway sensitivity as we observed no correlation between skin sensitivity and airway responsiveness to inhaled histamine, methacholine or allergen. However, skin reactivity did predict airway inflammation as assessed by measurements of eosinophil recruitment to the lung. Our results also further highlight the likely dissociation between airway inflammation and BHR.

Rheumatoid nodule and combined pulmonary carcinoma: topographic correlations; a case report and review of the literature

An association between rheumatoid arthritis (RA) and malignancies has been ascertained and patients with RA appear to be at higher risk of lymphoma and lung cancer. The higher risk of the latter malignancy may be related to rheumatoid interstitial lung disease and immunosuppressive therapies. Herein we illustrate the case of a 59-year-old male smoker affected by RA and treated with cortisone, methotrexate and TNF-α antagonists, who underwent right lower lobectomy for a nodular lesion. On microscopic examination, the lesion consisted of two distinct areas: a central area of fibrinoid necrosis, bordered by histiocytes in a palisaded arrangement, lymphocytes and a 0.4 cm thick peripheral area constituted by a combined small cell anaplastic carcinoma, adenocarcinoma and squamous cell carcinoma. The combination of three histotypes is very rare in such a small tumour. In our case, it may be hypothesized that synchronous, heterogeneous mutations occurred in different type of committed cells or in stem cells, due to the production of cytokines by RA nodule histiocytes and lymphocytes, which are contiguous to the carcinomatous area. Since few studies have evaluated the topographic correlation between tumors and rheumatoid lung lesions, further morphological and molecular studies are needed to clarify this association and the pathogenetic relationship between RA and cancer of the lung.

Use of within-group designs to test anti-tussive drugs in conscious guinea-pigs

INTRODUCTION

Cough is a common medical problem for which there are few effective drug treatments. A limited understanding of the mechanisms of induction and maintenance of cough and a paucity of suitable animal models frustrate drug discovery efforts to find novel anti-tussives. As in humans, guinea-pigs evoke a cough reflex upon exposure to tussive agents such as citric acid and capsaicin; both of which have been widely used to assess novel anti-tussive drugs. However, the potential for using within-group designs in drug development has received little attention and such designs may offer a way of assisting the drug discovery effort in the area of cough as well as other areas.

METHODS

Cough can be monitored in conscious guinea-pigs by placing animals in a Perspex chamber, in which air is continually exchanged by use of negative pressure and drug delivery of aerosols to the chamber can be accurately timed. Cough in response to a tussive agent (e.g. 0.2-0.4M citric acid; 10-30 microM capsaicin) is detected by the simultaneous microphonic recording of audible signals characteristic of the cough response as well as by positive pressure changes in the chamber generated by a cough dependent rapid expiration of air from the lungs. Both the sound and pressure signals are recorded using an online analyzer, whilst the number of coughs can be analyzed off-line. The number of coughs over a 15 min period is used to quantitate tussive events.

RESULTS

Reproducible cough can be detected in animals using cross-over designs that lend themselves to drug studies. Both the time and concentration dependence of anti-tussive drug action can be evaluated in the same animal. Furthermore, the effect of different anti-tussive drugs can be evaluated thereby reducing between group error and thereby improving the sensitivity of the test.

DISCUSSION

Repeated measures design improves the precision with which to evaluate anti-tussive drugs in preclinical models and could be used to make the drug discovery process more efficient.

Bronchial fibrolipomatous hamartoma associated with peculiar unusual bronchial lesions of the peripheral lung

Multiple hamartomas of the lung are uncommon. The few cases described to date are multiple parenchymal hamartomas or multiple endobronchial and parenchymal hamartomas. Herein, an original case is described which is characterized by the association between an endobronchial hamartoma and multiple, unusual, bronchial lesions of the peripheral lung.

Analysis of macrophage migration inhibitory factor (MIF) in patients with idiopathic pulmonary fibrosis

By proteomic approach we previously characterised bronchoalveolar lavage (BAL) protein profiles of patients with idiopathic pulmonary fibrosis (IPF), sarcoidosis and systemic sclerosis. Among differently expressed proteins we identified macrophage migration inhibitory factor (MIF), a multi-function pleiotropic cytokine. This study was performed to validate our findings by a further proteomic approach and ELISA in a larger population of patients and controls. MIF expression in lung tissue was also evaluated by immunohistochemistry. MIF was identified in all 2-DE gels of IPF patients and it was significantly increased compared to controls (p<0.05). This result was confirmed by ELISA: MIF concentrations were significantly higher in IPF patients than controls (p<0.001) and were directly correlated with neutrophil percentages (p=0.0095). Immunohistochemical analysis revealed enhanced expression in bronchiolar epithelium, alveolar epithelium, and fibroblastic foci. In conclusion, MIF is a pleiotropic cytokine that could be involved in the pathogenesis of IPF, being particularly abundant in BAL of these patients and mainly expressed in the areas of active fibrosis.

VATS for congenital lobar emphysema: a case report

Congenital lobar emphysema (CLE) is a rare congenital lung disease consisting in overinflation of a pulmonary lobe. Adult onset of CLE is therefore unusual, often presented with mild symptoms. The authors report a very uncommon case of congenital segmental emphysema diagnosed in a 21-year-old non-smoking man because of recurrent right pneumothorax. Indication to pulmonary resection was established according to functional limitation, radiological findings of right upper lobe segmental emphysema with corresponding bronchial agenesia, scintigraphic result of extremely reduced ventilation and perfusion of lung emphysematous area and recurrency of pneumothorax. The intervention was carried out by 3-portal video-assisted thoracic surgery (VATS) using single-lung ventilation leading to determine precisely how much lung to resect thanks to the obvious and clear-cut distinction between functioning and non functioning parenchyma of the upper lobe. A stapler wedge resection by VATS was thus obtained, that, as far as the author's knowledge, it is the first case of endoscopic parenchymal sparing resection in CLE. Even though congenital lobar emphysema is rare, clinical awareness of this condition is important for early diagnosis and effective surgical treatment that in this case led to favourable

RESULTS

The VATS procedure seems to be an advantageous approach.

PDE4 inhibitors: current status

Phosphodiesterase4 inhibitors are currently under development for the treatment of respiratory diseases including asthma and chronic obstructive pulmonary disease. The rationale for the development of this drug class stems from our understanding of the role of PDE4 in suppressing the function of a range of inflammatory and resident cells thought to contribute toward the pathogenesis of these diseases. Similarly, numerous preclinical in vivo studies have shown that PDE4 inhibitors suppress characteristic features of these diseases, namely, cell recruitment, activation of inflammatory cells and physiological changes in lung function in response to a range of insults to the airways. These potentially beneficial actions of PDE4 inhibitors have been successfully translated in phase II and III clinical trials with roflumilast and cilomilast. However, dose limiting side effects of nausea, diarrhoea and headache have tempered the enthusiasm of this drug class for the treatment of these respiratory diseases. A number of strategies are currently being pursued in attempts to improve clinical efficacy and reduce side effects, including delivery via the inhaled route, and/or development of non-emetic PDE4 inhibitors and mixed PDE inhibitors.

HIV-1 Tat mimetic of VEGF correlates with increased microvessels density in AIDS-related diffuse large B-cell and Burkitt lymphomas

Angiogenic switch marks the beginning of tumor’s strategy to acquire independent blood supply. In some subtypes of non-Hodgkin’s lymphomas, higher local vascular endothelial growth factor (VEGF) expression correlates with increased microvessel density. However, this local VEGF expression is higher only in tumors with elevated expression of the receptors of the growth factor, suggesting an autocrine growth-promoting feedback loop. Several studies have indicated that VEGF receptors are also targeted by Tat protein from the HIV-1-infected cells. Given the similarity of the basic region of Tat to the angiogenic factors (basic fibroblast growth factor, VEGF), Tat mimics these proteins and binds to their receptors. We evaluated the role of HIV-1 Tat in regulating the level of VEGF expression and microvessel density in the AIDS-related diffuse large B-cell (DLBCL) and Burkitt lymphomas (BL). By luciferase assay, we showed that VEGF promoter activity was downregulated in vitro in cells transfected with Tat. Reduced VEGF protein expression in primary HIV-1 positive BL and DLBCL, compared to the negative cases, supported the findings of promoter downregulation from the cell lines. Microvascular density assessed by CD34 expression was, however, higher in HIV-1 positive than in HIV-1 negative tumors. These results suggest that Tat has a wider angiogenic role, besides the regulation of VEGF expression. Thus, targeting Tat protein itself and stabilizing transient silencing of VEGF expression or use of monoclonal antibodies against their receptors in the AIDS-associated tumors will open a window for future explorable pathways in the management of angiogenic phenotypes in the AIDS-associated non-Hodgkin’s lymphomas.

Adenosine receptors and asthma

The accumulation of evidence implicating a role for adenosine in the pathogenesis of asthma has led to investigations into all adenosine receptor subtypes as potential therapeutic targets for the treatment of asthma. Selective A(1) receptor antagonists are currently in preclinical development since adenosine has been shown experimentally to mediate various features of asthma through this receptor such as bronchoconstriction, mucus secretion and inflammation. The A(2A) receptor is expressed on most inflammatory cells implicated in asthma, and as A(2A) stimulation activates adenylate cyclase and consequently elevates cAMP, selective A(2A) receptor agonists have now reached clinical development. However, initial reports concerning their efficacy are inconclusive. A(2B) receptor antagonists are also under investigation based on the rationale that inhibiting the effects of adenosine on mast cells would be beneficial, in addition to other reported pro-inflammatory effects mediated by the A(2B) receptor on cells such as airway smooth muscle, epithelial cells and fibroblasts. Whilst the effects in pre-clinical models are promising, their efficacy in the clinical setting has also yet to be reported. Finally, adenosine A(3) receptor stimulation has been demonstrated to mediate inhibitory effects on eosinophils since it also elevates cAMP. However, some experimental reports suggest that A(3) antagonists mediate anti-inflammatory effects, thus the rationale for A(3) receptor ligands as therapeutic agents remains to be determined. In conclusion, establishing the precise role of adenosine in the pathogenesis of asthma and developing appropriate subtype selective agonists/antagonists represents an exciting opportunity for the development of novel therapeutics for the treatment of asthma.

Elevated expression of adenosine A1 receptor in bronchial biopsy specimens from asthmatic subjects

Asthmatics, unlike healthy subjects, experience bronchoconstriction in response to inhaled adenosine, and extracellular adenosine concentrations are elevated in the bronchoalveolar lavage fluid and exhaled breath condensate of asthmatic subjects. However, little is known about the location and expression of adenosine receptors in asthmatic airways. The aim of the present study was to investigate the distribution of adenosine A(1) receptors in bronchial biopsy specimens from mildly asthmatic steroid-naïve subjects and then compare the degree of expression with that of healthy subjects. Biopsy sections were immunostained using an adenosine A(1) receptor antibody, the selectivity of which was validated in specific experiments. Image analysis was then performed in order to determine differences in immunostaining intensity. Immunostaining of biopsy sections from the asthmatic subjects revealed strong expression of the A(1) receptor, located predominantly in the bronchial epithelium and bronchial smooth muscle. In comparison, very weak immunostaining was observed in biopsy specimens obtained from healthy subjects. Image analysis revealed that the intensity of positive staining of the asthmatic bronchial epithelium and smooth muscle regions was significantly greater than that observed for the healthy epithelium and smooth muscle. In conclusion, the sensitivity of asthmatics to inhaled adenosine coupled with increased adenosine A(1) receptor expression implies that these receptors play a role in the pathophysiology of this disease.

Role of sex hormones in allergic inflammation in mice

BACKGROUND

A number of clinical studies have documented both a pro- and anti-inflammatory role for sex hormones in the context of lung inflammation and worsening of asthma.

OBJECTIVE

To determine the role of sex hormones in a murine model of allergic inflammation and airway hyper-responsiveness (AHR) induced by ovalbumin (OVA).

METHODS

Female BALB/c were sensitized to OVA on days 0 and 7 and subsequently challenged on day 14 over a 3-day period. Mice had their ovaries removed either 7 days before or 8 days after the first OVA injection on day 0. Pulmonary eosinophilia and AHR were measured 24 h following the last antigen challenge. In other experiments, ovariectomized mice (Ovx) were pre-treated with oestradiol benzoate. In further studies, the effect of the oestradiol antagonist tamoxifen on allergic inflammation in intact mice was evaluated. Spleens from all groups were collected for proliferation assays and measurement of cytokine release.

RESULTS

Removal of the ovaries 7 days before sensitization to OVA significantly inhibited lung eosinophilia and IL-5 levels in lung lavage. Furthermore, airway reactivity (maximum response) but not sensitivity (PC100) to methacholine were significantly reduced in these mice. Proliferation of spleen cells and release of IL-5 collected from Ovx mice was significantly attenuated compared with spleen cells obtained from non-Ovx mice. Ovx mice treated with oestradiol benzoate presented partially restored levels of eosinophils and IL-5 in sensitized mice. Moreover, pharmacological antagonism of the effect of endogenous oestrogen with tamoxifen significantly reduced the number of eosinophils in the lung of intact sensitized mice, reproducing the effect of ovariectomy, and suggested a role for oestrogen in the process of antigen sensitization in female mice. In contrast, removal of ovaries 8 days after the first OVA injection failed to alter significantly pulmonary eosinophilia or AHR to methacholine in comparison with non-Ovx mice. Moreover, removal of the ovaries 8 days after the sensitization period induced a significant increase in levels of IL-5 in lung fluid. Spleen cells collected from these mice also had a significantly higher proliferation index and production of IL-5 in response to OVA than non-Ovx mice. Treatment with oestradiol benzoate partially reduced levels of eosinophils present in the lung of Ovx mice, supporting an anti-inflammatory role of sex hormones during the effector phase of the response to inhaled antigen.

CONCLUSION

Sex hormones play a dual role in regulating allergic lung inflammation in mice.

Statistics in pharmacology

Statistics is an important tool in pharmacological research that is used to summarize (descriptive statistics) experimental data in terms of central tendency (mean or median) and variance (standard deviation, standard error of the mean, confidence interval or range) but more importantly it enables us to conduct hypothesis testing. This is of particular importance when attempting to determine whether the pharmacological effect of one drug is superior to another which clearly has implications for drug development and getting that next paper published in a respectable journal! Therefore, it is essential for pharmacologists to have an understanding of the uses and abuses of statistics. With this in mind, the British Journal of Pharmacology has commissioned a number of review articles to highlight the uses of statistics in experimental design and analysis.

[Work related mesothelioma: analysis of cases discovered at the Section for Occupational Medicine and Toxicology of Siena University during the years 2000-2007]

This study focuses on the spread of mesothelioma in Siena. The population consisted of 30 patients. The diagnosis was made through histopathological and immunoistochemical or cytological and immunoistochemical analysis. The association between malignant masothelioma and exposure to asbestos was deduced by the occupational history. The mesothelioma was noted both in traditional industries and other jobs such as the chain of manifacture, plumbers, electricians, carpenters, installers of asbestos insulation and construction workers. Thus it is possible to find other malignant and nonmalignant asbestos-related diseases more frequently than mesothelioma. There is an evident risk in rebuilding, so the development of new cases due to these exposures is expected.

Routine assessment of hormonal receptor and her-2/neu status underscores the need for more therapeutic targets in Kenyan women with breast cancer

OBJECTIVE

To report the expression of estrogen receptors, progesterone receptors and human epidermal growth factor receptor (Her-2/neu) in 158 Kenyan women with breast cancer and correlation with other prognostic indicators in this high-risk group. This study stressed the importance of routine assessment of the steroid receptors and Her-2/neu as a mode of therapeutic selection of patients for antihormonal or targeting monoclonal antibody (Herceptin) therapy, directed at the juxtamembrane domain of Her-2/neu protein in the developing countries such as Kenya.

STUDY DESIGN

The study population consisted of 158 female patients with histologically confirmed breast carcinoma seen at the pathology department of The Nairobi Hospital. An immunohistochemical (IHC) study of ER, PR and Her-2/neu was conducted, followed by fluorescent in situ hybridization (FISH) validation for Her-2/neu gene amplification in cases initially scored as positive 2+ with IHC. Mastectomy samples registered at the pathology department of The Nairobi Hospital were used for this study. The study was approved by the institution's ethical review committee and informed consent obtainedfrom the concerned patients.

RESULTS

In the studied cohort, positivity for both hormonal receptors and Her-2/neu was noted in 10 (6.33%) cases and negativity in 44 (27.85%) cases. Conversely, Her-2/neu negativity was noted in 32 (20.25%) cases with both steroid receptors positive and Her-2/neu positivity with both steroid receptors negative in 20 (12.66%) cases. Overall, no predictive factor was found in the Her-2/neu amplified 31/153 (20.26%) cases completely assessed with IHC and FISH. Grade III invasive ductal carcinomas, however, had a high prevalence of Her-2/neu overexpression. Association of both menopausal status (p = 0.044) and progesterone receptor status (p = 0.004) with high grade tumors were found to be statistically significant at 95% CI (p < 0.5). Consistent with other studies, Her-2/neu overexpression in this cohort was 20.26%.

CONCLUSION

Her-2/neu positivity may activate ER expression through signaling kinases, and the combined target of mitogenic estrogen plus the monoclonal antibody therapy against Her-2/neu-overexpressing tumors expand chances of survival for patients in developing countries such as Kenya. The cost factor for these tests, selection for appropriate combined therapies and lack of awareness were noted as limiting factors for access to basic health care service and resulted in advanced tumor grade at time of patient presentation.

Immunohistochemical co-localization of transient receptor potential vanilloid (TRPV)1 and sensory neuropeptides in the guinea-pig respiratory system

Electrophysiological studies within the lung have documented the presence of heterogenous groups of afferent fibers composed of Adelta and C-fibers and studies of somatosensory nerves within the skin reveal a complex pattern of distribution of sensory neuropeptides and transient receptor potential vanilloid (TRPV)1 positive nerves. However, the anatomical location of these different subpopulations of nerves within the lung has not been extensively studied. In the present study we have demonstrated that TRPV1 axons represented only a small proportion of the total number of PGP9.5 staining nerves within guinea-pig tracheal epithelium and only half the number of TRPV1 axons was immunopositive for substance P. In contrast, most TRPV1 positive neurones found within guinea-pig intrapulmonary airways were found to co-localize with sensory neuropeptides substance P and calcitonin gene-related peptide within and beneath the epithelium, around blood vessels, within airway smooth muscle and alveoli, indicative of heterogeneity of TRPV1 positive axons throughout the airways. However, in the smooth muscle layer of the trachea there was evidence of substance P and calcitonin gene-related peptide containing nerves that did not stain for TRPV1. We also demonstrated a complete loss of TRVP1 positive axons in the trachea and intrapulmonary airways and associated loss of bronchoconstriction induced by capsaicin, in animals chronically treated with capsaicin. However, some neuropeptide immunoreactive axons remained in the smooth muscle layer of capsaicin-treated animals which could represent the small subset of neuropeptide containing fibers which do not co-localize with TRPV1. We have provided evidence of heterogeneity of TRPV1 positive nerve fibers, including fibers characterized by lack of co-localization with neuropeptides in various regions of the airways and the existence of neuropeptide containing fibers that were not TRPV1 positive in guinea-pigs.

Effect of Mycobacterium tuberculosis chaperonins on bronchial eosinophilia and hyper-responsiveness in a murine model of allergic inflammation

BACKGROUND

Epidemiological evidence suggests that infection with Mycobacterium tuberculosis protects children against asthma. Several laboratories have shown that, in mouse models of allergic inflammation, administration of the whole live tuberculosis vaccine, Mycobacterium bovis bacillus Calmette-Guerin (BCG), prevents ovalbumin (OVA)-induced pulmonary eosinophilia.

OBJECTIVE

The aim of this study was to characterize specific M. tuberculosis molecules that are known to modulate immune responses to see if they affected pulmonary eosinophilia and bronchial hyper-responsiveness.

METHODS

C57Bl/6 mice were sensitized to OVA on days 0 and 7 and subsequently challenged with OVA on day 14 over a 3-day period. Pulmonary eosinophilia and bronchial hyper-responsiveness were measured 24 h following the last antigen challenge. In some groups, mice were pre-treated with M. tuberculosis or M. tuberculosis chaperonins (Cpns)60.1, 60.2 and 10, and the effect of this treatment on the allergic inflammatory response to aerosolized OVA was established.

RESULTS

We show that M. tuberculosis Cpns inhibit allergen-induced pulmonary eosinophilia in the mouse. Of the three Cpns produced by M. tuberculosis, Cpn60.1, Cpn10 and Cpn60.2, the first two are effective in preventing eosinophilia when administered by the intra-tracheal route. Furthermore, the increase in airways sensitivity to inhaled methacholine following OVA challenge of immunized mice was suppressed following treatment with Cpn60.1. The allergic inflammatory response was also characterized by an increase in Th2 cytokines IL-4 and IL-5 in bronchoalveolar lavage fluid, which was also suppressed following treatment with Cpn60.1.

CONCLUSION

These data show that bacterial Cpns can suppress eosinophil recruitment and bronchial hyper-responsiveness in a murine model of allergic inflammation.

A comparison of the pharmacological modulation of hyperalgesia and bronchial hyperresponsiveness

It has been proposed that there may be similarities in the mechanisms contributing toward hyperalgesia/allodynia observed in various clinical pain syndromes and bronchial hyperresponsiveness (BHR) in asthma. Both features are characterized by an increase in responsivity to various stimuli. In the case of pain, these include increase in responsiveness to mechanical and thermal stimuli whilst asthmatics bronchoconstrict in response to substances that are otherwise innocuous. A variety of mediators can induce hyperalgesia and pain when injected into the skin and these same mediators are also released during an inflammatory insult in the airways and in many cases can induce hyperresponsiveness experimentally. In this review, a comparison of the pharmacological modulation of afferent activity in hyperalgesia and in BHR will be made to ascertain whether any commonality exists between the treatment of these two disease states.

Role of cytokines and chemokines in bronchial hyperresponsiveness and airway inflammation

Over the last decade there has been an intense interest in the potential role of cytokines and chemokines as important mediators in various atopic diseases, including asthma and the mechanisms by which these mediators regulate airway inflammation and bronchial hyperresponsiveness. This research effort has recently culminated in the publication of clinical studies that have assessed the role of interleukin (IL)-4 [Borish et al., Am J Respir Crit Care Med 160, 1816-1823 (1999)], IL-5 [Leckie et al., Lancet 356, 2144-2148 (2000)], and IL-12 [Bryan et al., Lancet 356, 2149-2153 (2000)] in allergic asthma, and the results have been disappointing. This is not surprising given the pleiotropic role cytokines play in the allergic response confirmed by numerous animal studies providing evidence of functional redundancy. The alternative view is that our current concepts in asthma pathogenesis need significant revision. This review will summarise the evidence for the role of cytokines and chemokines in various aspects of asthma pathophysiology; namely, bronchial hyperresponsiveness, eosinophil recruitment to the airways, mucus secretion, and airway remodelling.