Change in airway responsiveness to inhaled house dust from childhood to adulthood

NAP1-RELATED PROTEIN1 and 2 negatively regulate H2A.Z abundance in chromatin in Arabidopsis

In eukaryotes, DNA wraps around histones to form nucleosomes, which are compacted into chromatin. DNA-templated processes, including transcription, require chromatin disassembly and reassembly mediated by histone chaperones. Additionally, distinct histone variants can replace core histones to regulate chromatin structure and function. Although replacement of H2A with the evolutionarily conserved H2A.Z via the SWR1 histone chaperone complex has been extensively studied, in plants little is known about how a reduction of H2A.Z levels can be achieved. Here, we show that NRP proteins cause a decrease of H2A.Z-containing nucleosomes in Arabidopsis under standard growing conditions. nrp1-1 nrp2-2 double mutants show an over-accumulation of H2A.Z genome-wide, especially at heterochromatic regions normally H2A.Z-depleted in wild-type plants. Our work suggests that NRP proteins regulate gene expression by counteracting SWR1, thereby preventing excessive accumulation of H2A.Z.

The histone variant H2A.Z is deposited by the SWR1 complex to replace H2A in Arabidopsis, but the mechanism of H2A.Z removal is unclear. Here, the authors show that NRP proteins can regulate gene expression by counteracting SWR1 and prevent excessive accumulation of H2A.Z.

Agreement between current and active asthma classification methods, Asthma Call-back Survey, 2011-2012

OBJECTIVE

Various approaches have been developed to identify persons with asthma using survey data. To assess agreement between current and active asthma classifications, 2011-2012 Asthma Call-back Survey landline telephone household data from 38 states, District of Columbia, and Puerto Rico for adults aged ≥18 years who have ever been told by a health professional they have asthma were analyzed.

METHODS

Respondents were classified to have current asthma if they reported still having asthma, and active asthma if they reported within the past year: 1) talking to a doctor about asthma, 2) taking asthma medication, or 3) having any symptoms of asthma. Agreement between classifications was assessed using the Kappa statistic.

RESULTS

Among adults ever told by a health professional they have asthma, an estimated 72% had current asthma and 75% had active asthma. Overall, 67% of individuals met classifications of both current and active asthma and 20% had neither current nor active asthma (Kappa = 0.68). The Kappa increased to 0.72 when talking to a doctor about asthma was removed from the active asthma classification.

CONCLUSIONS

Results indicated substantial agreement between current and active asthma. Agreement was strengthened when talking to a doctor about asthma was removed from the active asthma classification.

Phenotypic differences between asymptomatic airway hyperresponsiveness and remission of asthma

BACKGROUND

The present study aimed to illustrate differences in characteristics and perception of dyspnea between young atopic adults who have no history of asthma (never-asthmatics) with or without asymptomatic airway hyperresponsiveness (AHR) and those who had childhood asthma and consider themselves to be grown out of the disease (past-asthmatics).

METHODS

Blood parameters, lung function and methacholine PC(20) were measured in 88 never-asthmatics and 24 past-asthmatics. A perception score of dyspnea at 20% fall in FEV(1) (PS(20)) was obtained by interpolation of the two last points on the perception (modified Borg scale)/fall in FEV(1) curve during methacholine challenge.

RESULTS

Thirty-one of 88 never-asthmatics and eighteen of 24 past-asthmatics exhibited AHR (PC(20) was <8 mg/ml). Higher levels of specific IgE to house dust mite in past-asthmatics were observed than never-asthmatics with and without AHR. Mean values of FEV(1) and FEF(25-75) (%predicted) were significantly lower in past-asthmatics than never-asthmatics without AHR, and the values in never-asthmatics with AHR were intermediate between never-asthmatics without AHR and past-asthmatics. PC(20) was not significantly different between past-asthmatics and never-asthmatics with AHR. Of particular interest was that PS(20) was significantly lower in never-asthmatics with AHR compared with past-asthmatics.

CONCLUSION

The present findings suggest the possibilities that presence or absence of past history of outgrow of childhood asthma might be associated with airway narrowing, sensitization to house dust mite and perception of dyspnea in young asymptomatic adults with atopy and AHR.

The role of house dust mite elimination in the management of childhood asthma: an unresolved issue

Indoor allergens are likely to be direct environmental causes of asthma and mite exposure, and sensitization is the most important environmental risk factor for childhood asthma in temperate zones. Analagous to occupational asthma, allergen avoidance in asthmatic children sensitized and exposed to mite allergens is associated with a reduction in airway hyperresponsiveness and symptoms associated with improvement in lung function. The long-term effect of this strategy needs to be prospectively evaluated considering both the timing and duration of exposure, as well as the timing and duration of removal. In order to be successful, it is important to achieve and maintain a major reduction on allergen levels, for a long period of time.

Long-term outcomes in paediatric asthma

Over the years the aims of asthma management have changed markedly from effective prednisolone treatment of symptoms and exacerbations towards more use of continuous prophylactic treatment. With our new understanding of the disease and its management definition of the aims of treatment and assessment of optimal asthma control have become much more complex. Even in times of evidence-based medicine our asthma management is based upon findings of effects on various outcomes in somewhat short-term (<1 year) controlled studies. However, assumptions about long-term effects upon the basis of findings in such studies should be made with great caution. Good examples of this are studies which assess the risk of systemic effects and clinical adverse effects of inhaled corticosteroids. From such studies it has become clear that systemic effects detected in short-term trials may have no predictive value of long-term adverse effects. Thus steroid-induced changes in lower leg growth rates assessed by knemometry do not predict long-term statural growth. Moreover, steroid-induced changes in statural growth over 1 year are not predictive of effects upon attained adult height. In contrast, reduced growth caused by uncontrolled asthma disease also seems to affect attained adult height adversely. These findings suggest that long-term outcomes should play a larger role when future asthma management strategies are decided. Some important long-term outcomes of asthma management in children include cure or remission of the disease, prevention of complications of the disease (airway remodelling, adverse effects upon growth/adult height, peak bone mineral density, physical impairment and psychosocial development) or its pharmacological management (adverse effects upon adult height, peak bone mineral density). More controlled long-term studies (several years) are needed to provide a better understanding of how these outcomes are best achieved.

The prognosis of bronchial asthma in childhood in Hungary: a long-term follow-up

The aim of this study was to determine the prognosis of bronchial asthma in childhood in Hungary. One hundred and forty five adults (96 men and 49 women) with a clinical history of childhood bronchial asthma were examined at the age of 28 years or above (mean age 37.6, SD 5.9 years). The patients completed questionnaires concerning their asthmatic and accompanying allergic symptoms in childhood, at the age of 18 and at present. They were all prick-tested with 12 inhalant allergens. The results showed that 42.8% of the patients had become symptom-free, but 57.2% still had intermittent or persisting asthmatic symptoms in adulthood. More patients had intermittent day-time (59%) and night-time (67%) asthmatic symptoms than persistent symptoms (41% and 33%). Accompanying allergic diseases (rhinitis, conjunctivitis, dermal and gastrointestinal diseases, and drug andfood allergies) in childhood did not definitely affect the prognosis of the bronchial asthma. The proportion of females with allergic diseases increased, and among patients with skin diseases it was significantly higher than the proportion of affected males. At the age of 18, allergic rhinitis was more frequent than in childhood. The frequencies of other allergic disorders did not change significantly. In the patients with asthmatic symptoms, molds and cat-hair allergies were more frequent than in the symptom-free group. The long-term prognosis of bronchial asthma in childhood in Hungary is relatively good, but fewer than half of the patients became symptom-free. The complaints of most of the patients were mild, but one in seven of all the adults suffered from moderate or serious bronchial asthma. Household allergens may contribute to the persistence of asthmatic symptoms.

Development of bronchial hyperresponsiveness during childhood

Bronchial hyperresponsiveness (BHR) produces the characteristic pathological abnormalities seen in asthma and clearly plays a central role in the pathophysiology of asthma. The presence of BHR has been demonstrated in infants with asthma, as has the possibility of BHR persisting through the childhood period. The level of BHR may not only reflect the state of the airways, as a marker of airway dysfunction, but may also predict the persistent prognosis of the disease. Thus, measurement of BHR may provide important information about the symptoms and lung function in children with asthma. In view of multiple pathophysiological mechanisms, BHR does not seem to have a single cause. Many potential confounding variables, such as age, gender and genetic status, and some environmental factors, such as allergens, infections, and pollutants, could be responsible for the establishment of childhood BHR. There may be differences between the mechanisms that induce transient BHR and the mechanisms that induce persistent BHR. Also, there may be differences between the causes that induce BHR in the infantile period and the causes that maintain persistent BHR during childhood asthma. There is also disagreement as to the most suitable method to measure BHR in children, especially in infants. The assessment of BHR in young children has not been uniformly successful, and measurements of BHR changes over the childhood period (are associated with a number of problems. To resolve these problems, there may be two ways to study childhood BHR. One is to use age-matched specific techniques to clarify the precise BHR in each age group; the other is to use simple techniques that can be performed over the childhood period on a large number of subjects. In studies of infantile respirator, dysfunction the ultimate goal is to establish a simple, noninvasive method by which measurements of respiratory function may be obtained in infants. Further investigations and acceptable methods will be needed to clarify, the mechanisms involved in the establishment of asthma throughout the childhood period.

Childhood antecedents of adult respiratory disease

This review examines the relations between early childhood lower respiratory symptoms and adult respiratory disease. The problems associated with investigating potential associations between respiratory disease in children and adults are discussed. Some studies have limitations because they are retrospective and early childhood respiratory symptoms have not been accurately diagnosed. Therefore, in this review, particular attention is paid to longitudinal studies (some from birth) that have used strict diagnostic criteria for respiratory episodes. These studies provide unique insights into the risk factors for the development of childhood respiratory problems and for persistence of symptoms into adulthood. Although cross-sectional studies have indicated that early childhood respiratory disease is more frequent in adults with respiratory disease, evidence from longitudinal studies suggests that respiratory symptoms such as wheezing, are transient in the majority of infants and result from developmentally small airways. These longitudinal investigations have also indicated that persistence of symptoms into later childhood is associated with atopy. The important role of cigarette-smoke exposure as a risk factor for abnormal pulmonary development, persistence of respiratory disease and reduction in lung function is discussed. The discovery of genetic markers associated with respiratory syndromes such as asthma, should facilitate studies that investigate the childhood antecedents of adult respiratory disease. Future longitudinal studies using genetic markers, will allow relations between specific genotypes and phenotypic outcomes to be examined.

Strategies for the management of asthma

The aims of treating patients with asthma are to relieve symptoms, to prevent symptoms and exacerbations, and to prevent long-term deterioration in lung function. It is the role of medical practitioners to inform the patient what asthma is, and to develop a plan to achieve the aims for the individual, recognizing that asthma is frequently a chronic, lifelong disease. Most patients can be diagnosed, assessed for severity and causes, and treated in primary care practices, however, sometimes help from an asthma clinic of a specialist is required. The most important management decision is to determine whether the patient needs inhaled corticosteroids; subsequently, decisions about dose, duration and method of delivery of treatment can be tailored to the individual depending on the preferences and social conditions of the patient. The aim of this article is to present the latest strategies for the management of asthma and the simplest methods for their implementation. Important new strategies include careful assessment of the severity; immediate introduction of a plan that is tailored of the individual and aimed at the possible reversing of the disease; detailed instructions for management of exacerbations and the combined use of inhaled corticosteroids with a long-acting bronchodilator. It is becoming clear that these strategies obviate dependence on oral corticosteroids in newly diagnosed asthmatic patients. Furthermore, relatively low doses of inhaled corticosteroids can be used to maintain good control if used in conjunction with other therapies. The role of newly developed antagonists to leukotrienes is not yet known but it may well be useful in mild asthma and in special forms of the disease, such as those sensitive to aspirin. In the future, the most important strategy will be to prevent the disease.

Prognostic factors for the outcome of childhood asthma in adolescence

By the second decade of life asthma symptoms often abate and it may seem that patients with mild asthma have "outgrown" the disease. Unfortunately this is likely to be the exception rather than the rule. Although the severity of asthma symptoms fluctuates with time, the inherited tendency towards respiratory symptoms never disappears and many teenagers who seem to be free of symptoms do, in fact, have persistent asthma. During symptom-free periods subclinical, but nevertheless significant, airways obstruction and/or bronchial hyperresponsiveness may be present. It is not unusual for adults who have been asymptomatic for a number of years to redevelope asthma symptoms. Indeed, much of the so-called adult onset asthma has its roots in childhood. Levison concluded that, in these subjects, it is often not the asthma that is outgrown but the paediatrician. The more severe asthma is in childhood the more likely it is that the disease will persist in adulthood. A complete list of the characteristics of the disease in childhood, and the potential risk factors associated with an unfavourable prognosis, such as pulmonary function and bronchial responsiveness and markers of airway inflammation, is therefore needed. As properly matched and controlled prospective long term studies have not been published it has not been possible to evaluate the effects on prognosis of any single class of antiasthma agent. Such studies are needed to find out if it is possible to alter the natural history of the disease. In theory modern asthma treatments, because they are able to improve symptoms and underlying disease phenomena, are also beneficial in the long term prognosis of childhood asthma. The majority of patients with persistent asthma included in the currently available studies were not receiving adequate treatment. Since compliance with therapeutic regimens in asthma, especially in adolescence, is low, a monitoring system is needed to guarantee adequate follow up and treatment during and beyond puberty.

Circadian variation of bronchial caliber and antigen-induced late asthmatic response

To study whether circadian variation of bronchial caliber participates in causing late asthmatic response (LAR), house-dust inhalation was made at 10 AM and 6 PM on separate days in 6 house-dust-sensitive asthmatic children aged 8 to 13 years. Bronchial obstruction was assessed through measurements of FEV1 at 4-h intervals from 24 h before to 24 h after the inhalation. The LAR, which is a 15 percent or greater decrease in FEV1 from the value at the same hour of the previous day, occurred 4 h or later after the inhalation in all challenges. The mean (+/- SD) time to the occurrence of the lowest FEV1 (maximum LAR) following the morning inhalation was 14.7 +/- 2.1 h versus 10.0 +/- 2.2 h following the evening inhalation (p < 0.05). Regardless of the hour of inhalation, FEV1 after the inhalation was lowest or near-lowest at 2 AM in all. Therefore, the maximum LAR was indistinguishable from the trough of further amplified circadian variation in FEV1 following the inhalation. These findings suggest that the downward arm of circadian variation may partially participate in causing the LAR.

Effects of beta 2-receptor agonists on airway responsiveness

Airway hyper-responsiveness is one of the characteristics of asthma. It may be distinguished by airway hyper-sensitivity and an increase of the maximal response plateau. Short-acting beta 2-agonists have an acute protective effect on airway sensitivity, which is shorter in duration than the bronchodilating effect, without affecting the maximal response plateau. Long-term treatment has no beneficial effect on airway responsiveness. A diminishment of the protection against metacholine- and histamine-induced airway obstruction and a rebound increase of this after cessation of continuous treatment have been reported. Single doses of long-acting beta 2-agonists give a prolonged protection against methacholine- and histamine-induced airway sensitivity of at least 12 hours. A small decrease in the maximal response plateau has been noted. Currently, there is little data on long-term treatment. One study has described the development of tolerance to the protecting effect on methacholine-induced airway sensitivity after 2 months treatment. However, a protection by 1.0 doubling dose remained and the bronchodilating effect was not influenced. So far, no rebound increase in airway sensitivity has been reported after cessation of continuous treatment.

Influence of a positive family history and associated allergic diseases on the natural course of asthma

The outcome of childhood asthma was studied in a cohort of 406 asthmatic children, with emphasis on the influence of family history for allergic disease, as well as the influence of associated allergic diseases on prognosis. Sixty-two per cent had a positive family history for atopy. In young adulthood no differences, either in symptoms or lung function were demonstrated in comparison to subjects with a negative family history. Fifty-two per cent of the children had no other allergic disease, 48% had either eczema or hay fever or both. When subjects were stratified based on associated allergic disease, no differences in outcome in adulthood were revealed either. It is concluded that neither a positive family history, nor concurrent associated allergic diseases in the child contribute to the prognosis of asthma from childhood to young adulthood. Therefore, environmental factors as well as patient characteristics (including lung function level, level of bronchial responsiveness) are likely to be more important for the prognosis.