The cellular and mediator basis of asthma in relation to natural history

Local and systemic immunological parameters associated with remission of asthma symptoms in children

The immunological and clinical parameters that are associated with asthma remission are poorly understood. The cytokine and local mediator changes associated with the resolution of asthma symptoms were examined in three groups of subjects 12-18 years of age (n = 15 in each group): (a) continuing asthma group (CA) who had persistent symptoms since early childhood, (b) an age, sex and atopic status-matched group who had persistent symptoms in early childhood but in whom these had resolved (RA), and (c) a non-atopic, non-asthmatic control group. Clinical parameters, sputum cell counts, peripheral blood mononuclear cell (PBMC) cytokine production and activation marker expression were determined. All of the CA had methacholine airway hyperresponsiveness compared with only half of the RA subjects. The CA showed elevated numbers of eosinophils and increased ECP and IL-5 in sputum, which were not observed in the RA. PBMC cytokine studies revealed increased production of the type 1 cytokines IL-12, IFN-γ and TNF-α in the CA group compared with the RA group, under a range of activation conditions, however, the production of IL-4 and IL-5 were unchanged. These findings suggest that decreased type 1 cytokine expression as well as decreased eosinophilic inflammation is associated with the resolution of asthma symptoms.

Comparative clinical evaluation of ketotifen and montelukast sodium in asthmatic Iraqi patients

Asthma is a common and chronic inflammatory condition of the airways whose cause is not completely understood. Although many classes of drugs are used for management of asthma, the response is variable due to multifactor reasons. This study was designed to evaluate the outcome of using ketotifen or montelukast sodium in Iraqi asthmatic patients. Single blinded randomized clinical trial was utilized, in which 100 asthmatic patients were recruited from Al-Karama hospital and randomized into two groups; 1st group (50 patients, treated with ketotifen for 4 weeks) and 2nd group (50 patients treated with montelukast sodium for 4 weeks). Asthma symptom score and wheezing were recorded at the beginning (first visit) and at the end of the study (after one month). Pulmonary function tests (PFTs) were performed by spirometry, and the patients' use of asthma drugs and their symptoms were evaluated at each visit. The result showed that asthma symptom, chest wheezing, and PFT values were significantly improved in the two groups at the end of the study compared to first visit (p < 0.05). All symptoms were significantly lower and PFT values were higher in the 2nd group compared to 1st group (p < 0.05). In conclusion, both ketotifen and montelukast sodium showed significant changes in asthma symptoms and PFT after one month of treatment, but the changes were more significant with montelukast group (2nd group) compared with ketotifen group (1st group) and this indicate that montelukast was more effective than ketotifen in treatment of asthmatic patients.

Genetics and gene-environment interactions in atopic diseases. The Norwegian Mother and Child Cohort Study

OBJECTIVES

The Norwegian Mother and Child Cohort Study (MoBa) aims to provide new insights in a broad variety of diseases. The goal of the study is to understand pathways in disease development, and identify preventive measures. Several designs are suitable for studying genetics in complex diseases like asthma and allergy, in MoBa.

METHODS

MoBa is a prospective population based cohort of 100 000 pregnancies, following offspring into adulthood. Enrollment started in 1999, and will be completed in 2008. A biobank with samples from the mother, father and child, together with detailed questionnaires from early pregnancy and childhood constitute the basis of the study. When studying complex diseases like asthma, a design with case-parent triads is useful. Parental effects and interactions between maternal and fetal genes can be detected. Stratifying triads by environmental exposure enables assessment of gene-environment interactions.

RESULTS

By July 2006, more than 73,000 pregnancies have been included, with nearly 7,000 siblings and 1,300 pairs of twins enrolled. Biological samples are processed and stored at the biobank. The first children are reaching age seven in 2006.

CONCLUSION

The MoBa cohort provides an excellent basis for studying genetic, epigenetic and environmental influences on complex diseases.

Acute severe asthma

Acute severe asthma remains a major economic and health burden. The natural history of acute decompensations is one of resolution and only about 0.4% of patients succumb overall. Mortality in medical intensive care units is higher but is less than 3% of hospital admissions. "Near-fatal" episodes may be more frequent, but precise figures are lacking. However, about 30% of medical intensive care unit admissions require intubation and mechanical ventilation with mortality of 8%. Morbidity and mortality increase with socioeconomic deprivation and ethnicity. Seventy to 80% of patients in emergency departments clear within 2 hours with standardized care. The relapse rate varies between 7 and 15%, depending on how aggressively the patient is treated. The airway obstruction in the 20-30% of people resistant to adrenergic agonists in the emergency department slowly reverses over 36-48 hours but requires intense treatment to do so. Current therapeutic options for this group consist of ipratropium and corticosteroids in combination with beta2 selective drugs. Even so, such regimens are not optimal and better approaches are needed. The long-term prognosis after a near-fatal episode is poor and mortality may approach 10%.

Stem cell factor expression, mast cells and inflammation in asthma

The Kit ligand SCF or stem cell factor (SCF) is a multipotent growth factor, acting as an important growth factor for human mast cells. SCF induces chemotaxis and survival of the mast cell, as well as proliferation and differentiation of immature mast cells from CD34(+) progenitors. Additionally, SCF enhances antigen-induced degranulation of human lung-derived mast cells, and induces a mast cell hyperplasia after subcutaneous administration. SCF expression increases in the airways of asthmatic patients, and this is reversed after treatment with glucocorticoids. A role for SCF may thus be hypothesized in diseases associated with a local increase in the number and/or activation of mast cells, as occurring in the airways in asthma. SCF will be reviewed as a potential therapeutic target in asthma, to control the regulation of mast cell number and activation. We here report the main pathways of SCF synthesis and signalling, and its potential role on airway function and asthma.

Bronchial hyperresponsiveness and the development of asthma and COPD in asymptomatic individuals: SAPALDIA cohort study

BACKGROUND

Bronchial hyperresponsiveness (BHR) is a common feature of asthma. However, BHR is also present in asymptomatic individuals and its clinical and prognostic significance is unclear. We hypothesised that BHR might play a role in the development of chronic obstructive pulmonary disease (COPD) as well as asthma.

METHODS

In 1991 respiratory symptoms and BHR to methacholine were evaluated in 7126 of the 9651 participants in the SAPALDIA cohort study. Eleven years later 5825 of these participants were re-evaluated, of whom 4852 performed spirometric tests. COPD was defined as an FEV1/FVC ratio of <0.70.

RESULTS

In 1991 17% of participants had BHR, of whom 51% were asymptomatic. Eleven years later the prevalence of asthma, wheeze, and shortness of breath in formerly asymptomatic subjects with or without BHR was, respectively, 5.7% v 2.0%, 8.3% v 3.4%, and 19.1% v 11.9% (all p<0.001). Similar differences were observed for chronic cough (5.9% v 2.3%; p = 0.002) and COPD (37.9% v 14.3%; p<0.001). BHR conferred an adjusted odds ratio (OR) of 2.9 (95% CI 1.8 to 4.5) for wheezing at follow up among asymptomatic participants. The adjusted OR for COPD was 4.5 (95% CI 3.3 to 6.0). Silent BHR was associated with a significantly accelerated decline in FEV1 by 12 (5-18), 11 (5-16), and 4 (2-8) ml/year in current smokers, former smokers and never smokers, respectively, at SAPALDIA 2.

CONCLUSIONS

BHR is a risk factor for an accelerated decline in FEV1 and the development of asthma and COPD, irrespective of atopic status. Current smokers with BHR have a particularly high loss of FEV1.

Stigmatization of anorexia nervosa

OBJECTIVE

The current study examined the perceptions about an individual with anorexia nervosa (AN) relative to perceptions about a healthy person and a person with another mental or nonmental illness.

METHOD

Ninety-one participants recruited from the community completed questionnaires targeting perceptions about 4 individuals: a healthy person, a person with asthma, a person with schizophrenia, and a person with AN.

RESULTS

Evaluations of personal characteristics were most negative for persons with AN. Participants believed the person with AN was most to blame for his/her condition, was best able to pull him/herself together if he/she wanted to, and was most acting this way for attention and that biological factors were least relevant in developing the illness.

CONCLUSION

Negative perceptions of a person with AN fell into stigma categories of self-attribution and responsibility. These attitudes may contribute to reluctance to seek treatment among individuals with AN.

Long-acting beta2-agonists: comparative pharmacology and clinical outcomes

Salmeterol and formoterol are both long-acting beta(2)-adrenoceptor agonists (beta(2)-agonists). They both provide excellent bronchodilating and bronchoprotective effects in patients with asthma but their are some differences between these two long-acting beta(2)-agonists in vitro and in vivo. Formoterol has a greater potency and intrinsic activity than salmeterol, which can become especially apparent at higher doses than that clinically recommended, and in contracted bronchi. Long-term use of long-acting beta(2)-agonists can induce tolerance, which can be partially reversed with corticosteroids. Long-acting beta(2)-agonists have some anti-inflammatory effects in vitro, but data in vivo are less convincing. Compared with doubling the dose of inhaled corticosteroids, the addition of inhaled long-acting beta(2)-agonists to inhaled corticosteroids improves symptom control in patients with asthma and reduces both the exacerbation rate of asthma and hospital admission rate. No enhanced airway responsiveness or loss of perception of dyspnea has been observed with the use of inhaled long-acting beta(2)-agonists. Monotherapy with long-acting beta(2)-agonists is not recommended.

Biological effects of montelukast, a cysteinyl-leukotriene receptor-antagonist, on T lymphocytes

BACKGROUND

Montelukast (MNT), a cysteinyl-leukotriene receptor (Cys-LTR) antagonist, has anti-inflammatory activity in the treatment of allergic diseases. If this effect is due only to blocking leukotrienes or also owing to inhibiting proliferation and survival of inflammatory cells, is actually unknown.

OBJECTIVE

Testing the hypothesis that MNT could influence T lymphocyte functional behaviour in vitro.

METHODS

Normal T lymphocytes were analysed for surface expression of Cys-LTR(1) and Cys-LTR(2) by means of monoclonal antibodies (mAbs), in the resting state and after activation with T helper type 2 cytokine or T cell receptor (TcR) stimulation. Proliferative activity, as well as IL-4 andIFN-gamma production, were simultaneously determined in samples exposed to molar concentrations of MNT from 10(-8) to 10(-5). Programmed cell death in cultured samples was evaluated by means of propidium iodide and fluorescein isothiocyanate-conjugated anti-Annexin V mAb staining. The complementary DNA microarray technique was adopted to identify gene products involved in apoptosis induction.

RESULTS

Resting T cells expressed low levels of Cys-LTR. Upon anti-CD3 mAb activation, a progressive increase in Cys-LTR(1) and -LTR(2) expression was observed. Exposure to MNT reduced proliferative response to TcR engagement, increased IFN-gamma production and led to apoptosis at minimal concentrations of 10(-6) M. A progressive loss in BAD and B cell lymphoma/leukaemia-2 activities, and an increase in the expression of CD27, TRAF3, TRAIL, p53 and Fas genes were also observed.

CONCLUSIONS

Biological effects of MNT delineate a complex picture of gene activation and repression, probably induced by Cys-LTR blockade. The induction of apoptosis in allergen-specific T cell population, as a final result, appears fundamental in the treatment of asthma.

Role of tumor necrosis factor alpha in asthma

Asthma is a heterogeneous disease in which various cytokines orchestrate airway inflammation. Tumor necrosis alpha (TNF-alpha) is a proinflammatory cytokine that has been implicated in the modulation of inflammation in various diseases, including asthma. Although TNF-alpha blocking strategies have been an effective therapeutic modality in diseases such as rheumatoid arthritis, their role in asthma and the effects of the blockade in asthma is poorly understood. This article examines the role of TNF-alpha in asthma and the effects of blocking TNF-alpha as a possible therapeutic option in patients with severe corticosteroid-dependent asthma.

Relationship between dietary antioxidants and childhood asthma: more epidemiological studies are needed

Approximately 15 million Americans including over 5 million children suffer from asthma, the most common chronic disease in childhood. The prevalence of pediatric asthma has risen sharply over the past four decades, with the sharpest increases occurring in children younger than 6 years and in urban, predominantly minority, populations. The reasons for this dramatic increase are not yet clear. Recent epidemiological studies indicate a higher prevalence of dietary antioxidant deficiency among asthmatics patients. However, the results of these studies are inconsistent or even contradictory. Epidemiological studies with robust design and use of novel epidemiological tools are urgently needed to examine the impact of dietary antioxidants on the incidence of asthma in preschool children. An incidence density case-control study which includes non-atopic controls, who are matched for age, gender, race, study center and sampling time to each asthmatic case will offer a robust study design. A validated food frequency questionnaire and an asthma and atopy severity score can be used to interview the parents of the recruited children. Risk set sampling may enable us to explore possible associations between the type and quantity of dietary antioxidants and the development and severity of asthma in such an epidemiological study.

Transgenic smooth muscle expression of the human CysLT1 receptor induces enhanced responsiveness of murine airways to leukotriene D4

Cysteinyl leukotrienes (CysLTs) exert potent proinflammatory actions and contribute to many of the symptoms of asthma. Using a model of allergic sensitization and airway challenge with Aspergillus fumigatus (Af), we have found that Th2-type inflammation and airway hyperresponsiveness (AHR) to methacholine (MCh) were associated with increased LTD(4) responsiveness in mice. To explore the importance of increased CysLT signaling in airway smooth muscle function, we generated transgenic mice that overexpress the human CysLT1 receptor (hCysLT(1)R) via the alpha-actin promoter. These receptors were expressed abundantly and induced intracellular calcium mobilization in airway smooth muscle cells from transgenic mice. Force generation in tracheal ring preparations ex vivo and airway reactivity in vivo in response to LTD(4) were greatly amplified in hCysLT(1)R-overexpressing mice, indicating that the enhanced signaling induces coordinated functional changes of the intact airway smooth muscle. The increase of AHR imposed by overexpression of the hCysLT(1)R was greater in transgenic BALB/c mice than in transgenic B6 x SJL mice. In addition, sensitization- and challenge-induced increases in airway responsiveness were significantly greater in transgenic mice than that of nontransgenic mice compared with their respective nonsensitized controls. The amplified AHR in sensitized transgenic mice was not due to an enhanced airway inflammation and was not associated with similar enhancement in MCh responsiveness. These results indicate that a selective hCysLT(1)R-induced contractile mechanism synergizes with allergic AHR. We speculate that hCysLT(1)R signaling contributes to a hypercontractile state of the airway smooth muscle.

Food allergy as a risk factor for life-threatening asthma in childhood: a case-controlled study

BACKGROUND

No objective clinical risk factors exist for pediatric life-threatening asthma.

OBJECTIVES

In this study, we address whether persistent food allergy and degree of atopy are risk factors for life-threatening asthma.

METHODS

By use of a case-controlled design, children (1-16 years) ventilated for an exacerbation of asthma were enrolled. Each case was matched by sex, age, and ethnicity, with 2 controls who had attended with a non-life-threatening exacerbation. All subjects were assessed by means of a questionnaire, spirometry, and skin prick or RAST testing. The data were analyzed by conditional logistic regression.

RESULTS

Nineteen cases and 38 controls were enrolled. Compared with controls, cases were found to have the following risk factors: food allergy (odds ratio, 8.58; 95% CI, 1.85-39.71), multiple allergic diagnoses (4.42; 1.17-16.71), early onset of asthma (6.48; 1.36-30.85), and frequent admissions (14.2; 1.77-113.59). After regression analysis, only frequent admission with asthma (9.85; 1.04-93.27) and food allergy (5.89; 1.06-32.61) were independently associated with life-threatening asthma. Half the cases had food allergy compared with only 10% of controls.

CONCLUSION

This study demonstrates that poorly controlled asthma and food allergy are significant risk factors for life-threatening asthma. More intensive management of this high-risk group of children might help to reduce future morbidity and mortality.

Comparison of the bronchodilating effects of inhaled formoterol, salmeterol and salbutamol in asthmatic patients

Ten subjects with various degrees of asthma severity underwent a three-day trial, with the aim of evaluating the bronchodilating effect of inhaled formoterol (12 micro g), in comparison with salbutamol (200 micro g) and salmeterol (50 micro g). The bronchodilation afforded by formoterol paralleled that of salbutamol in rapidity (mean percentage increases in functional measurements (FEV(1)) vs. baseline recorded 5 min after drug administration: 7.7%, 9.3%, and 0.3% for salbutamol, formoterol and salmeterol, respectively) and that of salmeterol in duration (mean percentage increases in FEV(1) vs. baseline recorded 12h after drug administration: 16.8% and 15.9% for formoterol and salmeterol, respectively). Moreover, the maximal effect of formoterol resulted to be slightly higher in comparison with salbutamol (P<0.001) and salmeterol (P<0.05); in this regard, the mean percentage increases in FEV(1) vs. baseline recorded 2h after salbutamol and formoterol, and 4h after salmeterol were 22.3%, 29.5%, and 24.6%, respectively. Therefore, these results suggest that formoterol can be used, in addition to its utilization as long-acting bronchodilator, also as an effective rescue medication for the immediate relief of asthma symptoms.

Nitric oxide in respiratory diseases

The formation and modulation of nitric oxide (NO) in the lungs is reviewed. Its beneficial and deleterious roles in airways diseases, including asthma, chronic obstructive pulmonary disease, and cystic fibrosis, and in animal models is discussed. The pharmacological effects of agents that modulate NO production or act as NO donors are described. The clinical pharmacology of these agents is described and the therapeutic potential for their use in airways disease is considered.

Bronchial challenges with aerosolized food in asthmatic, food-allergic children

BACKGROUND

Allergic asthma is usually considered to be provoked by aeroallergens. However, we have recently recognized a group of children with food allergies who also develop asthma when exposed to the aerosolized form of the food.

METHODS

Between 1997 and 1999 we prospectively identified children with an immunoglobulin (Ig)E-mediated food allergy who develop asthma on inhalational exposure to the relevant food allergen while it is being cooked. Subjects were exposed for 20 min to the aerosolized form of the allergen and the symptoms and the lung function were monitored. Aerosolization was achieved by cooking the food in a small room. Where possible challenges were double-blinded.

RESULTS

We identified 12 children with an IgE-mediated food allergy who developed asthma on inhalational exposure to food. The implicated foods were fish, chickpea, milk, egg or buckwheat. Nine out of the 12 children consented to undergo a bronchial food challenge. Five challenges were positive with objective clinical features of asthma. Additionally, two children developed late-phase symptoms with a decrease in lung function. Positive reactions were seen with fish, chickpea and buckwheat. There were no reactions to the seven placebo challenges.

CONCLUSIONS

We have presented a prospective series of children with food allergy who developed symptoms of asthma with exposure to aerosolized food allergens. Our data demonstrates that, as in the case of other aeroallergens, inhaled food allergens can produce both early- and late-phase asthmatic responses. This highlights the importance of considering foods as aeroallergens in children with coexistent food allergy and allergic asthma. For these children, dietary avoidance alone may not be sufficient and further environmental measures may be required to limit exposure to aerosolized food.

Prevalence of endothelial nitric oxide synthase gene polymorphisms in patients with atopic asthma

BACKGROUND

Asthma is a common multifactorial disease, the aetiology of which is attributable to both environmental and genetic factors. The endothelial nitric oxide synthase (NOS3) gene has been implicated in asthma pathogenesis.

OBJECTIVE

This study investigated associations of 27 base-pair tandem repeat polymorphism in intron 4 and the Glu298Asp (G894T) variant of the NOS3 gene with atopic asthma in a Czech population.

METHODS

Polymerase chain reaction was used to determine the NOS3 genotypes in subjects with atopic asthma (n = 163) and random controls (n = 209).

RESULTS

The NOS3 allele or genotype distributions did not differ significantly between the control and asthma groups. However, the common genotype (bb) of the NOS3 polymorphism in intron 4 was found to be significantly associated with total IgE levels (P = 0.006), specific IgE levels for feathers (P = 0.0002) and a positive skin prick test for hay (P = 0.004). In one atopic patient, we identified an additional 27-bp repeat in the NOS3 gene (NOS3c), which occurred in heterozygous combination with the NOS3b allele (NOS3b/c genotype). In addition, we describe a new polymorphism (A5495G) in the NOS3 gene, which was in almost complete linkage disequilibrium with the NOS3 repeat polymorphism in intron 4. The Glu298Asp variant was not associated with asthma and/or related atopic phenotypes in our study.

CONCLUSION

Neither the NOS3 'b' allele nor the NOS3 'b/b' genotype showed any general association with atopic asthma, but they were associated with atopy-related phenotypes. We conclude that the NOS3 gene polymorphisms may act as disease modifiers in atopic asthma phenotype in our population.

The natural history of asthma and early intervention

The understanding of the natural history of asthma has changed significantly during the last 4 decades, with the view that asthma is a disease of chronic inflammation and varying degrees of severity replacing that of it being a disease of reversible airway obstruction. Treatment has progressed in accordance with the growing knowledge about the pathophysiologic mechanisms of asthma. Nevertheless, much remains unknown, especially about how to treat asthma effectively. Pharmacogenetics, an emerging field in which the knowledge of the genetic basis of a disease is applied to its treatment, may ultimately lead investigators to define many unanswered questions about asthma therapy. Asthma occurs early in childhood, but the ideal time for intervention and the most effective treatment strategy are yet unknown for young patients. The lack of response to a therapy may indicate the course of the disease as much as a lack of treatment efficacy. It may be that including such variables as airway hyperresponsiveness in treatment goals will not only become routine but will result in improved long-term asthma treatment as well. The progress in defining asthma and targeting treatment toward specific pathophysiologic mechanisms should lead to better-defined optimal strategies for treating asthma in children.

Impact of montelukast on symptoms in mild-to-moderate persistent asthma and exercise-induced asthma: results of the ASTHMA survey. Adding Singulair Treatment to Handle symptoms in Mild to moderate Asthmatics

A nation-wide survey was undertaken in Belgium among general practitioners (GPs) to evaluate the impact of the leukotriene receptor antagonist (LTRA) montelukast on the control of asthma symptoms, after at least 4 weeks of treatment. Patients from 6 years of age were eligible if they were suffering from mild-to-moderate persistent asthma which was still symptomatic despite inhaled corticosteroids (ICS) treatment, or from exercise-induced asthma. Patient general satisfaction was evaluated by recording the willingness to continue the treatment. A total of 1360 GPs took part in the study and more than 11000 patients were included in the survey. Of the included patients, 85% were receiving inhaled corticosteroids, 60% of whom were also on long-acting beta2-agonists (LABA). However, despite the use of daily controller medication, 92% of the patients still reported limitation of activities, 49% difficulties with sleep and 45% early morning awakening due to asthma. Moreover, 78% of the patients used rescue medication more than twice a week. At the end of the survey, 90% of the patients expressed their willingness to continue montelukast therapy. Of the patients having symptoms at the start of the study, 87% reported amelioration in sleep while on montelukast therapy, 80% less frequent early morning awakening, 85% better ability to perform daily activities and 77% decreased need for rescue medication.

Glutathione-S-transferase family of enzymes

The loci encoding the glutathione-S-transferase (GST) enzymes comprise a large supergene family located on at least seven chromosomes. The function of the GST enzymes has traditionally been considered to be the detoxication of electrophiles by glutathione conjugation. A wide variety of endogenous (e.g. by-products of reactive oxygen species activity) and exogenous (e.g. polycyclic aromatic hydrocarbons) electrophilic substrates have been identified. Interestingly, recent data has suggested a role, at least for the pi class gene product, in jun kinase inhibition. Since many GST genes are polymorphic, there has been considerable interest in determining whether particular allelic variants are associated with altered risk (or outcome) of a variety of diseases. We describe recent studies in patients with asthma and cutaneous basal cell carcinoma that demonstrate associations between GSTP1 and GSTT1 genotypes and disease phenotypes. Thus, GSTP1val(105)/val(105) was protective against asthma symptoms and GSTT1 null was associated with a subgroup of basal cell carcinoma patients who develop large numbers of primary tumours in clusters. Importantly, these associations were characterised by relatively large odds ratios (0.11 and 7.4, respectively) implying that the allelic variants exert a substantial biological effect. These and other data indicate the importance of GST polymorphism in determining disease phenotype.

Onset and persistence of childhood asthma: predictors from infancy

OBJECTIVE

In a prospective study of children with a family history of asthma, asthma onset by 3 years of age was found previously to be positively associated with variables from the first year of life, including elevated total immunoglobulin E (IgE), frequent respiratory infections, and parenting difficulties. We followed this cohort of genetically at-risk children to investigate the relationship between factors assessed in infancy and asthma, allergy, and psychological status at school age.

METHODS

A cohort of 150 children who were at risk for developing asthma were identified prenatally on the basis of the mothers' having asthma. For 28 children, the father had asthma as well, putting them at bilateral genetic risk. Families primarily were middle and upper middle class Caucasians. Parents came to the clinic during the third trimester of pregnancy for assessments of medical and psychosocial functioning. A home visit took place when the infant was 3 weeks old, when parenting risk was assessed before the onset of any asthma symptoms. Parenting difficulties included problems with infant caregiving as well as components of maternal functioning, such as postpartum depression and inadequate marital support. Blood was drawn for serum IgE at 6 months of age. Parents and offspring subsequently came to the clinic multiple times, with the last clinic visit during the child's sixth year. Follow-up at age 6 involved a clinic visit for allergy and psychosocial evaluations, consisting of interviews and a behavior questionnaire. Seventy-seven children received the allergy and psychosocial evaluation, 26 received the psychosocial evaluation in the clinic, and 30 families received telephone interviews and mailed in questionnaires. Additional monitoring of families by telephone and mail was maintained over the next 2 years, until the children were 8, to ensure accurate characterization of the course of illness. Comprehensive medical records were obtained and reviewed for all health care contacts. Children were designated as having asthma when there was documentation in medical records of physician-diagnosed asthma, observed wheezing, and/or prescription of asthma medications during the time period when the child was between 6 and 8 years of age. Parental reports of the occurrence of asthma corroborated the medical record data.

RESULTS

Data regarding asthma status were available for 145 children through 8 years of age. Forty (28%) of the children manifested asthma between 6 and 8 years of age. Among variables previously reported to predict asthma onset by age 3, 3 proved to have significant univariate relationships with asthma between ages 6 and 8: elevated IgE levels measured when the children were 6 months of age, global ratings of parenting difficulties measured when infants were 3 weeks old, and higher numbers of respiratory infections in the first year of life. Among these offspring of mothers with asthma, paternal asthma showed a significant association with asthma between ages 6 and 8. Eczema in the first year was not significantly related to later asthma. Multiple logistic regression showed that the model that best predicted asthma at ages 6 to 8 from infancy variables included 2 main effects. The adjusted odds ratio for 6-month IgE was 2.15 (1.51, 3.05) and for parenting difficulties was 2.07 (1.15, 3.71). Although socioeconomic status (SES) was not associated with asthma at ages 6 to 8, families of lower SES were more likely to be rated as having parenting difficulties early in the child's life. The mothers of lower SES breastfed for a shorter period of time and were more likely to smoke during their infant's first year. There were more respiratory infections during the first year of life among infants whose mother was rated as having more parenting difficulties. Mothers who reported smoking breastfed their infants for a shorter length of time. Male gender was significantly associated with higher IgE levels when infants were 6 months of age. Laboratory testing was completed for 77 children at age 6. Total serum IgE levels were significantly higher for the children with asthma between ages 6 and 8. Skin-prick testing showed that the children with asthma had significantly more positive skin test reactions than did the children without asthma. Psychosocial interview data at 6 years of age were available for 103 families, and behavioral questionnaires were available for 133 families. On the basis of 6-year interviews, children with asthma were rated as being at greater psychological risk than were the children without asthma. Mothers' Child Behavior Checklist (CBCL) ratings of their children's behavior indicated higher internalizing scores for the children with asthma as compared with the children without asthma. Like the 6-month IgE, 6-year IgE was higher for boys. IgE levels measured at 6 months of age were significantly correlated with 6-year IgE levels. Parenting difficulties measured at 3 weeks were significantly correlated with 6-year measures of maternal depression, CBCL Internalizing score, and Child Psychological Risk (CPR) score. There also were significant correlations among the psychosocial variables assessed when the children were 6 years of age; maternal depression was significantly associated with child CBCL Internalizing score and CPR score, and the last 2 also were significantly correlated. Multiple logistic regression showed that 2 concurrently measured variables entered the model showing the strongest associations with asthma at ages 6 to 8. The adjusted odds ratio for CPR score was 3.21 (1.29-7.96) and for 6-year IgE was 1.71 (1.04-2.80).

CONCLUSIONS

This study of the natural history of childhood asthma focused on the development of asthma into the school-age years in a genetically at-risk group of children. The relationships between biological and psychosocial variables in the first year and school-age asthma support the formulation of asthma as beginning early in life, with the developing immune system interacting with environmental influences. The data provide support for the possible contribution of psychosocial factors to asthma onset and persistence into childhood.

Allergen-induced impairment of bronchoprotective nitric oxide synthesis in asthma

BACKGROUND

Endogenous nitric oxide protects against airway hyperresponsiveness (AHR) to bradykinin in mild asthma, whereas AHR to bradykinin is enhanced by inhaled allergens.

OBJECTIVE

Hypothesizing that allergen exposure impairs bronchoprotective nitric oxide within the airways, we studied the effect of the inhaled nitric oxide synthase (NOS) inhibitor N(G)-monomethyl-L-arginine (L-NMMA) on AHR to bradykinin before and after allergen challenge in 10 subjects with atopic asthma.

METHODS

The study consisted of 3 periods (1 diluent and 2 allergen challenges). AHR to bradykinin (PD(20)BK) was examined before and 48 hours after allergen challenge, both after double-blinded pretreatment with L-NMMA or placebo. The accompanying expression of the various NOS isoforms (ecNOS, nNOS, and iNOS) was examined by means of immunohistochemistry in bronchial biopsies obtained after diluent and allergen challenge.

RESULTS

After placebo, AHR to BK worsened after allergen challenge in comparison with before allergen challenge (PD(20)BK, 70.8 nmol [range, 6.3-331] and 257 nmol [35.5-2041], respectively; P =.0004). After L-NMMA, preallergen and postallergen PD(20)BK values (50.1 nmol [1.8-200] vs 52.5 nmol [6.9-204]; P =.88) were similarly reduced (P <.01) and not different from the postplacebo/postallergen value (P >.05). After allergen challenge, the intensity of staining in bronchial epithelium decreased for ecNOS (P =.03) and increased for iNOS (P =.009). These changes in immunostaining were correlated with the accompanying worsening in AHR to BK (R(s) = -0.66 and 0.71; P <.04).

CONCLUSIONS

These data indicate that allergen exposure in asthma induces increased airway hyperresponsiveness to bradykinin through impaired release of bronchoprotective nitric oxide associated with downregulation of ecNOS. This suggests that new therapeutic strategies towards restoring the balance among the NOS isoforms during asthma exacerbations are warranted.

The anti-inflammatory effects of leukotriene-modifying drugs and their use in asthma

Asthma is a chronic inflammatory disease of the airways. Anti-inflammatory drug therapy, primarily using corticosteroids, is now considered the first-line treatment in the management of all grades of asthma severity. Although corticosteroids are believed to be the most potent anti-inflammatory agents available, they do not suppress all inflammatory mediators involved in the asthmatic response. Leukotrienes, which are lipid mediators generated from the metabolism of arachidonic acid, play an important role in the pathogenesis of asthma. They produce bronchospasm, increase bronchial hyperresponsiveness, mucus production, and mucosal edema, and enhance airway smooth muscle cell proliferation and eosinophil recruitment into the airways, and their synthesis or release is unaffected by corticosteroid administration. The use of leukotriene synthesis inhibitors or leukotriene receptor antagonists as anti-inflammatory therapies in asthma has therefore been investigated. Beneficial effects of leukotriene-modifying drugs have been demonstrated in the management of all grades of asthma severity, and there is evidence that certain patient groups (such as those with exercise-induced asthma or aspirin-induced asthma) may be particularly suitable for such therapy.

Benefits of high altitude allergen avoidance in atopic adolescents with moderate to severe asthma, over and above treatment with high dose inhaled steroids

Some patients with severe asthma cannot be controlled with high doses of inhaled steroids (ICS), which may be related to ongoing environmental allergen exposure. We investigated whether 10 weeks of high altitude allergen avoidance leads to sustained benefits regarding clinical and inflammatory markers of disease control in adolescents with persistent asthma despite treatment with high dose ICS. Eighteen atopic asthmatic adolescents (12-18 yr, 500-2000 microg ICS daily) with established house dust mite allergy, participated in a parallel-group study. Quality of life (PAQL), lung function, bronchial hyperresponsiveness (BHR) to adenosine and histamine, induced sputum and urine samples were collected repeatedly from 10 patients during a 10-week admission period to the Swiss Alps (alt. 1560 m) and at 6 weeks after return to sea level. Results were compared with those in eight patients, studied in their home environment at sea level for a similar time period. Throughout the study, asthma medication remained unchanged in both groups. During admission to high altitude, PAQL, lung function, BHR to adenosine and histamine, and urinary levels of eosinophil protein X (U-EPX), leukotriene E4 (U-LTE4) and 9alpha11beta prostaglandin F2 (U-9alpha11beta PGF2) improved significantly (P < 0.05), with a similar tendency for sputum eosinophils (P < 0.07). Furthermore, the changes in PAQL and BHR to adenosine and histamine were greater in the altitude than in the control group (P < 0.05). At 6 weeks after renewed allergen exposure at sea level, the improvements in PAQL (P < 0.05), BHR to adenosine (P < 0.07) and histamine (P < 0.05), as well as U-EPX (P < 0.05) and U-LTE4 (P < 0.05) were maintained. A short period of high altitude allergen avoidance, on top of regular treatment with ICS and long-acting beta2-agonists, results in improvement of asthma, as assessed by clinical and inflammatory markers of disease severity. These findings indicate that short-term, rigorous allergen avoidance can improve the long-term control of severe asthma over and above what can be achieved even by high doses of inhaled steroids.

New perspectives in asthma treatment

The recent advances in the knowledge of the basic mechanisms underlying asthmatic inflammation have significantly contributed to the delineation of new therapeutic perspectives for asthma. There are currently three main approaches to the development of novel antiasthma treatments: 1) improvement in existing classes of drugs 2) identification of new compounds able to interfere with the complex network of proinflammatory mediators, cytokines, chemokines, and adhesion molecules involved in the pathogenesis of asthma 3) utilization of new forms of immunotherapy aimed at blocking the unbalanced Th2 response which characterizes the pathophysiology of asthma. Such a remarkable expansion in available therapeutic options will probably allow us, over the next decade, to treat asthma by more selectively targeting the pathogenetic events responsible for this widespread airway disease.

The pathobiology of acute asthma

Acute bronchial asthma is a common problem with immense medical and economic impacts. It is estimated that this disease affects 12 to 14 million people in the United States with costs in excess of $6 billion per year. Most of the morbidity and all of the mortality of asthma tends to be associated with acute exacerbations, and treatment of these events accounts for the majority of expenditures in money and health care resources. Unfortunately, the factors that contribute to the destabilization of asthma are rarely studied and much of the pathogenesis and pathobiology of acute asthma remains unknown. This article examines these issues and suggests treatment for acute asthma.

Reducing IgE levels as a strategy for the treatment of asthma

IgE secretion by B lymphocytes defines the allergic state and nearly all asthmatics have higher than normal IgE levels in serum following adjustment for age and sex. It is thought that allergic mechanisms may be responsible for the increasing prevalence of asthma. In particular, in utero changes may encourage T cells to differentiate into Th2 subtypes. Th2 cells produce cytokines such as IL-4 and IL-5, which can act indirectly via B cells, mast cells and eosinophils to mediate the asthma phenotype. Alternatively, IL-4 and IL-13 may act directly on the airway. Th2 lymphocyte inflammation in asthma predisposes subjects to B cell and IgE-mediated airway inflammation. IgE binds to receptors on the surface of a variety of effector cells causing them to release a variety of mediators that promote airway hyperresponsiveness, mucus secretion and increased vascular permeability. Several strategies for decreasing IgE have been developed as a possible treatment for asthma. For example, anti-IgE monoclonal antibodies such as rhuMAb-E25 and CGP 56901 block binding of IgE to its high-affinity receptor and have been shown to reduce IgE levels in humans without causing anaphylaxis. IgE levels must be nearly completely suppressed. Recent clinical studies in subjects with asthma have shown that rhuMAb-E25 attenuates both the early and late phase responses to inhaled allergen, and reduces the associated increase in eosinophils in induced sputum. rhuMAb-E25 is well tolerated and has shown promising results in improving symptoms and lung function in patients with moderate to severe asthma. Other strategies for decreasing IgE levels include interferon gamma, IL-4 antibodies, IL-4 receptor antibodies and soluble IL-4 receptors.

Ethnicity, childhood environment and atopic disorder

BACKGROUND

The International Study of Asthma and Allergies in Childhood (ISAAC) has demonstrated large differences in the prevalence of atopic disorders in children between different regions in the world. Populations with a higher standard of living and a more westernized lifestyle tend to have higher rates of atopy and asthma. Many hypotheses regarding environmental causes of atopic disorder focus on the early childhood environment.

OBJECTIVE

To study the influence of ethnicity and country of birth for the prevalence of atopic disorders.

METHODS

The prevalence of atopic disorders in Swedish residents born in Turkey and Chile, who settled in Sweden as adults in the 1980s, was compared with their own Swedish-born children and a sample of Swedish-born parents and their children in interview data from the Survey of Living Conditions in 1996. The study group included 1734 adults 27-60 years of age and their 2964 children aged 3-15.

RESULTS

The Chilean-born parents and their children had the highest risk for allergic asthma; adjusted odds ratios (ORs) 2.2 (1.2-4.0) and 2.7 (1.6-4.5), respectively, and allergic rhino-conjunctivitis; OR 1.6 (1.1-3) and 1.6 (1.1-2.5) in both groups, when compared with the Swedish-born parents and their children. The Turkish-born parents and their children had the lowest risk for allergic rhino-conjunctivitis; both groups had OR 0.6 (0. 4-0.9) and the children in this group also had the lowest risk for eczema; OR; 0.4 (0.3-0.7). The risk for all atopic disorders was lower in the Turkish group compared with the Chileans.

CONCLUSION

This study demonstrates that ethnicity is an important determinant of atopic disorder independent of the external childhood environment. The value of international comparisons of environment and risk for atopic disorders can be questioned until more is known about factors related to ethnicity, such as genetic susceptibility and diet, for the development of atopy.

Agravos respiratórios decorrentes da atividade agrícola

As doenças respiratórias são um importante problema crítico para trabalhadores rurais, uma vez constatada evidência de aumento significativo do risco de morbidade e mortalidade, por problemas respiratórios, em trabalhadores agrícolas. Este fato é de grande importância especialmente nos países em desenvolvimento, onde grande parte da população depende da agricultura como fonte de subsistência. Sabidamente, pessoas envolvidas em atividades agrícolas estão potencialmente expostas a vários agentes como poeira inorgânica do solo, poeira orgânica, gases tóxicos, pesticidas, etc. O aparelho respiratório pode reagir a estes insultos ao nível de vias aéreas superiores com rinite, sinusite e otite. As vias aéreas inferiores podem responder desencadeando ou agravando asma brônquica, com o quadro conhecido como síndrome asthma-like, com obstrução crônica e lesões causadas por poeira orgânica, pneumonite por hipersensibilidade e fibrose intersticial. Assim, se faz necessário uma identificação precisa dos possíveis agentes etiológicos e conseqüentes medidas profiláticas das doenças respiratórias decorrentes da atividade agrícola.

Airway inflammation and remodeling in asthma

An important advance in our understanding of the pathophysiology of asthma has been the discovery that airway inflammation is not confined to severe asthma but also characterizes mild and moderate asthma. Inflammation in asthma may be the result of a peculiar type of lymphocytic inflammation whereby Th2 lymphocytes secrete cytokines that orchestrate cellular inflammation and promote airway hyperresponsiveness. The term "airway remodeling" in asthma refers to structural changes that occur in conjunction with, or because of, chronic airway inflammation. Airway remodeling results in alterations in the airway epithelium, lamina propria, and submucosa, leading to thickening of the airway wall. The consequences of airway remodeling in asthma may include incompletely reversible airway narrowing, bronchial hyperresponsivenesss, airway edema, and mucus hypersecretion. Airway remodeling in asthma thus may predispose persons with asthma to asthma exacerbations and even death from airway obstruction caused by smooth muscle contraction, airway edema, and mucus plugging. Although much has been learned in the past 25 years about the pathophysiology of airway inflammation and airway remodeling in asthma, important questions remain about the relation between airway inflammation and remodeling, the natural history of airway remodeling, and the effects of current asthma treatments on remodeled airways.

Mechanisms of occupational asthma

BACKGROUND

The pathogenesis and the pathologic alterations of occupational asthma are similar to those of nonoccupational asthma. Occupational asthma may therefore represent a useful model of "human asthma" to investigate mechanisms and pathophysiology of asthma in general. In an occupational setting the cause and onset of asthma may be easily identified, and the natural history may be examined in follow-up studies. The mechanisms involved in occupational asthma include genetic predisposition, immunologically mediated responses, as well as nonspecific airway inflammation. In particular, high molecular weight (eg, grain dust, flour) and some low molecular weight sensitizers (eg, acid anhydrides and platinum halide salts) have been shown to induce occupational asthma through an immunoglobulin E (IgE)-dependent mechanism, while cell-dependent immunologic mechanisms are likely to be more relevant for occupational asthma induced by other low molecular weight sensitizers (eg, toluene diisocyanate and plicatic acid contained in western red cedar). The pathology of the airway mucosa of occupational asthma is remarkably similar to the pathology of nonoccupational asthma, ie, characterized by infiltration and accumulation of eosinophils, mast cells, and activated lymphocytes along with subepithelial fibrosis. In this article, the most relevant mechanisms are discussed with particular reference to the similarities and discrepancies between occupational and nonoccupational asthma.

Acute respiratory effects of diaper emissions

Mice were monitored with pneumotachographs while they breathed emissions of three brands of disposable diapers (described herein as brands A, B, and C) and one brand of cloth diapers for 1 hr. The authors used a computerized version of the ASTM-E-981 test method to measure changes in the pattern and frequency of respiration. In response to two brands of disposable diapers, many mice exhibited reduced mid-expiratory airflow velocity, sensory irritation, and pulmonary irritation. During the peak effects, brand A caused sensory irritation in 47% of the breaths and reduced mid-expiratory airflow velocity in 17% of the breaths (n = 39 mice), whereas the respective percentages noted for brand B were 20% and 15% of the breaths (n = 28 mice). The effects were generally larger during repeat exposures to these emissions, with up to 89% of breaths showing sensory irritation in response to brand A and up to 35% of breaths showing reduced mid-expiratory airflow velocity with brand B. A third brand of disposable diapers caused increases in respiratory rate, tidal volume, and mid-expiratory airflow velocity. The emissions of cloth diapers produced only slight SI and slight PI. Chemical analysis of the emissions revealed several chemicals with documented respiratory toxicity. The results demonstrate that some types of disposable diapers emit mixtures of chemicals that are toxic to the respiratory tract. Disposable diapers should be considered as one of the factors that might cause or exacerbate asthmatic conditions.

Prenatal factors and occurrence of rhinitis and eczema among offspring

BACKGROUND

It has recently been suggested that an atopic phenotype may already be programmed in utero. We examine here the association between prenatal factors and the subsequent development of allergic rhinitis and eczema among offspring.

METHODS

The analyses were based on 8088 children in a population-based prospective birth cohort started in northern Finland in 1985-6.

RESULTS

The prevalences of allergic rhinitis and allergic eczema by the age of 7 years among 8088 children were 3.3% and 6.7%, respectively. The results indicate that low parity, febrile infections in pregnancy, and the use of contraceptives before pregnancy increased the risk of allergic disorders among children. Bleeding in the first trimester and a greater weight gain during pregnancy appeared to be risk factors for rhinitis only. Children whose mothers experienced infections in the first trimester had ORs of 2.65 (95% CI 1.50-4.69) for rhinitis and 1.63 (95% CI 1.00-2.69) for eczema after adjustment for potential confounders.

CONCLUSIONS

Obstetric complications and infection in pregnancy may increase the risk of allergic disorders among the offspring.

Recognizing early asthma

Asthma symptoms often develop during the first years of life. Longitudinal studies show that at least 40% of children with wheezing lower respiratory illnesses (LRIs) during the first 3 years of life still have wheezing episodes at 6 years of age. Thus, it is important to identify children at risk of developing asthma, and to distinguish these from those in whom early wheezing is likely to be transient. This is complicated, however, by the variable nature of asthma and the lack of specific and sensitive markers. Genetic markers and epidemiologic risk factors for asthma have been identified, but cannot be used to predict the development of asthma in an individual patient. Similarly, infants who subsequently develop asthma in childhood have higher serum immunoglobulin E (IgE) and peripheral eosinophil counts than those who do not develop asthma, but, again, these factors are not sufficiently sensitive and specific to allow identification of children at risk of developing asthma. An algorithm is presented that outlines possible criteria to determine the risk of developing asthma in infants.

Respiratory toxicity in mice exposed to mattress covers

To evaluate factors that might contribute to the rise in prevalence of childhood asthma, we allowed groups of male Swiss-Webster mice to breath the emissions of six brands of waterproof crib mattress covers for 1 h. We used a computerized version of ASTM-E-981 test method to monitor respiratory frequency, pattern, and airflow velocity. Single exposure to the emissions of these mattress covers caused various combinations of sensory irritation, pulmonary irritation, and decreases in mid-expiratory airflow velocity. At the peak effects of these emissions, sensory irritation ranged from 9% to 51% of the breaths, pulmonary irritation ranged from 4% to 16% of the breaths, and airflow limitation ranged from 9% to 38% of the breaths. Three brands caused airflow limitation that persisted for at least 24 h after a single 1-h exposure of naive mice to these emissions. Repeat exposures to the emissions of four brands caused more marked effects (i.e., up to 96% of the breaths showing sensory irritation, up to 44% of the breaths showing pulmonary irritation, and up to 75% of the breaths showing airflow limitation). Histological evaluation of the lungs revealed a mild inflammatory response, with focal collections of polymorphonuclear leukocytes and edema, but there were no eosinophils and no bronchial mucosa changes. We used gas chromatography/mass spectrometry to evaluate one of the test atmospheres, and there was evidence of chemicals for which toxic properties have been documented previously. The results of our study demonstrated that some mattress covers emit mixtures of chemicals that can cause a variety of acute toxic effects in mice, including asthma-like reactions.

Age at adoption, ethnicity and atopic disorder: a study of internationally adopted young men in Sweden

Epidemiological and laboratory studies have implied that the environment during early childhood is important for the risk of developing atopic disorders. In this study we analyzed the prevalence of asthma, hayfever and eczema among 1901 internationally adopted young men at the military-induction medical examination in relation to indicators of their early childhood environment. The adopted young men who came to Sweden before 2 years of age suffered from asthma, hayfever and eczema significantly more often than those who came to Sweden between 2 and 6 years of age; the risk ratios (RR) were 1.6, 2.5 and 2.1, respectively. The young men who were born in the Far East were identified as being particularly susceptible to the development of hayfever and eczema, with RRs of 1.3 and 1.7. This study demonstrates that the environment during the first 6 years of life has a profound influence on the risk of suffering from atopic disorders as young adults.

Role of T-helper type 2 cytokines in down-modulation of fas mRNA and receptor on the surface of activated CD4(+) T cells: molecular basis for the persistence of the allergic immune response

The mechanisms responsible for persistence of T lymphocytes at the sites of allergic inflammation are not completely understood. Activated T cells, usually expressing Fas on their surface, undergo activation-induced apoptotic death, thus limiting the dangerous consequences of a persistent immune reaction. We have previously shown that pulmonary T lymphocytes from untreated asthmatic subjects do not express surface Fas receptors nor do they contain Fas mRNA, yet they display normal levels of Fas ligand. This is not an inherited defect and is confined to mucosal T cells. To gain insights into the mechanism responsible for these findings, we performed a set of experiments with both purified Dermatophagoides pteronyssinus allergen and recombinant human cytokines: interleukin 2 (IL-2), IL-4, IL-5, transforming growth factor beta1, interferon gamma, and granulocyte-macrophage colony-stimulating factor (GM-CSF). In vitro exposure of purified CD4(+) lymphocytes to allergen yielded only transient up-regulation of surface Fas but did not influence susceptibility to Fas-mediated cell death. T-helper type 2 cytokines (IL-4, IL-5, and GM-CSF) had a dose-dependent and specific inhibitory effect on Fas mRNA, suggesting a new fundamental biological role in the survival of inflammatory cells during allergen exposure.