Autonomic nervous system control of the cardiovascular and respiratory systems in asthma

Do asthma patients with panic disorder really have worse asthma? A comparison of physiological and psychological responses to a methacholine challenge

BACKGROUND

Panic disorder (PD) has been linked to worse asthma outcomes. Some suggest that asthmatics with PD have worse underlying asthma; others argue that worse outcomes are a result of their tendency to over-report symptoms. This study aimed to measure physiological and psychological responses to a simulated asthma attack (methacholine challenge test: MCT) in asthmatics with and without PD.

METHODS

Asthmatics with (n = 19) and without (n = 20) PD were recruited to undergo a MCT. Patients completed subjective symptom questionnaires (Panic Symptom Scale, Borg Scale) before and after a MCT. Physiological measures including heart rate (HR), and systolic and diastolic blood pressure (SBP/DBP) were also recorded.

RESULTS

Analyses, adjusting for age and sex, revealed no difference in methacholine concentration required to induce a 20% drop in forced expiratory volume in one second (FEV1: F = 0.21, p = .652). However, PD patients reported worse subjective symptoms, including greater ratings of dyspnea (F = 8.81, p = .006) and anxiety (F = 9.44, p = .004), although they exhibited lower levels of physiological arousal (i.e., HR, SBP/DBP). An interaction effect also indicated that PD, relative to non-PD, patients reported more panic symptoms post-MCT (F = 5.05, p = .031).

CONCLUSIONS

Asthmatics with PD report higher levels of subjective distress, despite exhibiting lower levels of physiological arousal, with no evidence of greater airway responsiveness. Results suggest that worse outcomes in PD patients may be more likely due to a catastrophization of bodily symptoms, rather than worse underlying asthma. Interventions designed to educate patients on how to distinguish and manage anxiety in the context of asthma are needed.

8-Oxoguanine DNA glycosylase-1-driven DNA base excision repair: role in asthma pathogenesis

PURPOSE OF REVIEW

To provide both an overview and evidence of the potential cause of oxidative DNA base damage and repair signaling in chronic inflammation and histological changes associated with asthma.

RECENT FINDINGS

Asthma is initiated/maintained by immunological, genetic/epigenetic, and environmental factors. It is a world-wide health problem, as current therapies suppress symptoms rather than prevent/reverse the disease, largely due to gaps in understanding its molecular mechanisms. Inflammation, oxidative stress, and DNA damage are inseparable phenomena, but their molecular roles in asthma pathogenesis are unclear. It was found that among oxidatively modified DNA bases, 8-oxoguanine (8-oxoG) is one of the most abundant, and its levels in DNA and body fluids are considered a biomarker of ongoing asthmatic processes. Free 8-oxoG forms a complex with 8-oxoG DNA glycosylase-1 and activates RAS-family GTPases that induce gene expression to mobilize innate and adaptive immune systems, along with genes regulating airway hyperplasia, hyper-responsiveness, and lung remodeling in atopic and nonatopic asthma.

SUMMARY

DNA's integrity must be maintained to prevent mutation, so its continuous repair and downstream signaling 'fuel' chronic inflammatory processes in asthma and form the basic mechanism whose elucidation will allow the development of new drug targets for the prevention/reversal of lung diseases.

Genome-wide linkage and regional association study of blood pressure response to the cold pressor test in Han Chinese: the genetic epidemiology network of salt sensitivity study

BACKGROUND

Blood pressure (BP) response to cold pressor test (CPT) is associated with increased risk of cardiovascular disease. We performed a genome-wide linkage scan and regional association analysis to identify genetic determinants of BP response to CPT.

METHODS AND RESULTS

A total of 1961 Chinese participants completed the CPT. Multipoint quantitative trait linkage analysis was performed, followed by single-marker and gene-based analyses of variants in promising linkage regions (logarithm of odds ≥2). A suggestive linkage signal was identified for systolic BP response to CPT at 20p13 to 20p12.3, with a maximum multipoint logarithm of odds score of 2.37. On the basis of regional association analysis with 1351 single nucleotide polymorphisms in the linkage region, we found that marker rs2326373 at 20p13 was significantly associated with mean arterial pressure responses to CPT (P=8.8×10(-6)) after false discovery rate adjustment for multiple comparisons. A similar trend was also observed for systolic BP response (P=0.03) and diastolic BP response (P=4.6×10(-5)). Results of gene-based analyses showed that variants in genes MCM8 and SLC23A2 were associated with systolic BP response to CPT (P=4.0×10(-5) and 2.7×10(-4), respectively), and variants in genes MCM8 and STK35 were associated with mean arterial pressure response to CPT (P=1.5×10(-5) and 5.0×10(-5), respectively).

CONCLUSIONS

Within a suggestive linkage region on chromosome 20, we identified a novel variant associated with BP responses to CPT. We also found gene-based associations of MCM8, SLC23A2, and STK35 in this region. Additional work is warranted to confirm these findings.

CLINICAL TRIAL REGISTRATION URL

http://www.clinicaltrials.gov; Unique identifier: NCT00721721.

Mental health and asthma in China: the Guangzhou Biobank Cohort Study

BACKGROUND

There is consistent evidence of the co-occurrence of poor mental health and asthma in Western populations. Since the experience and expression of mental health is partly culturally determined, it is of interest to examine if similar associations are found in other cultural settings. In that regard, very little is known about the association between mental health and asthma in Asian countries, such as China.

PURPOSE

The aim of this study was to investigate the relationship between mental health and asthma in a large sample from China.

METHOD

We used data from the Guangzhou Biobank Cohort Study phase 3 (n = 9,280). Participants reported physician-diagnosed asthma. Mental health measures included the 15-item Chinese version of the Geriatric Depression Scale (GDS-C) and the SF-12 Mental Component Summary (MCS) score. We compared the prevalence of asthma by GDS-C and MCS scores by estimating prevalence ratios (PRs) and their corresponding 95% confidence intervals (95% CI), using Poisson regression.

RESULTS

Compared to those without depression, the prevalence of asthma was higher in those with moderate or severe depression levels (PR = 2.63, 95% CI = 1.58–4.40 and PR = 4.43, 95% CI = 1.62–12.09, p for trend ≤0.0001). The prevalence of asthma increased by 46% with every 1 standard deviation increase of the GDS-C score (PR = 1.46, 95% CI = 1.24–1.73). The MCS score was not associated with asthma.

CONCLUSION

Depressive symptoms were associated with asthma prevalence in a Chinese population. Further research into the mechanism and potential directions of causality is warranted.

Coexisting chronic conditions associated with mortality and morbidity in adult patients with asthma

OBJECTIVE

Many asthma patients suffer from chronic conditions other than asthma. We investigated the specific contribution of common comorbidities on mortality and morbidity in adult asthma.

METHODS

In an observational study of adults with incident asthma identified between 1999 and 2003 using National Veterans Affairs and Centers for Medicare and Medicaid Services encounter databases (n = 25 975, follow-up 3.0 ± 1.7 years), association between 13 most prevalent comorbidities (hypertension, ischemic heart disease (IHD), osteoarthritis, rheumatoid arthritis, diabetes, mental disorders, substance/drug abuse, enlarged prostate, depression, cancer, alcoholism, HIV and heart failure) and four conditions previously associated with asthma (sleep apnea, gastroesophageal reflux disease (GERD), rhinitis and sinusitis) and mortality, hospitalizations and asthma exacerbations were assessed using multivariate regression analyses adjusted for other clinically important covariates.

RESULTS

HIV followed by alcoholism and mental disorders among 18-45-years old, and heart failure, diabetes, IHD and cancer among those ≥ 65 years old were associated with an increased risk of all-cause mortality. Many conditions were associated with increased risk for all-cause hospitalizations, but the increased risk was consistent across all ages for mental disorders. For asthma exacerbations, mental disorder followed by substance abuse and IHD were associated with increased risk among those 18-45 years old, and chronic sinusitis, mental disorder and IHD among those ≥ 65-years old. GERD was associated with decreased risk for asthma exacerbation in all ages.

CONCLUSIONS

Many comorbidities are associated with poor outcome in adult asthmatics and their effect differs by age. Mental disorders are associated with increased risk of mortality and morbidity across ages.

DIFFERENTIATING PHYSIOLOGICAL EFFECTS OF MIDTERM BREAK IN A PROLONGED ONLINE GAME PLAYING

With the development of widespread Internet access, online game playing has become a popular event. As a result, more attention is being paid to the potentially negative physical and psychological effects on prolonged computer worker or online game player. To date, related physical problems that have been identified include fatigue, physical pain, insomnia, epileptic seizures, and even sudden death. Therefore, midterm break may be necessary for an online game player. This study tries to differentiate the physiological effects of two groups, with and without a midterm break, during a prolonged online game playing. Our experimental results showed that sympathetic system is overwhelming the parasympathetic nervous system significantly in group B without break, while it remains unchanged in group A. Due to the fight or flight response of the sympathetic system, participants with midterm break wanted to play more after event. Participants without break did not feel stressed after a continuous two hours' online game playing. These interesting findings may need further investigation in the future.

OVA-induced airway hyperresponsiveness alters murine heart rate variability and body temperature

Altered autonomic (ANS) tone in chronic respiratory disease is implicated as a factor in cardiovascular co-morbidities, yet no studies address its impact on cardiovascular function in the presence of murine allergic airway (AW) hyperresponsiveness (AHR). Since antigen (Ag)-induced AHR is used to model allergic asthma (in which ANS alterations have been reported), we performed a pilot study to assess measurement feasibility of, as well as the impact of allergic sensitization to ovalbumin (OVA) on, heart rate variability (HRV) in a murine model. Heart rate (HR), body temperature (T_B), and time- and frequency-domain HRV analyses, a reflection of ANS control, were obtained in chronically instrumented mice (telemetry) before, during and for 22 h after OVA or saline aerosolization in sensitized (OVA) or Alum adjuvant control exposed animals. OVA mice diverged significantly from Alum mice with respect to change in HR during aerosol challenge (P < 0.001, Two-Way ANOVA; HR max change Ctrl = +80 ± 10 bpm vs. OVA = +1 ± 23 bpm, mean ± SEM), and displayed elevated HR during the subsequent dark cycle (P = 0.006). Sensitization decreased the T_B during aerosol challenge (P < 0.001). Sensitized mice had decreased HRV prior to challenge (SDNN: P = 0.038; Low frequency (LF) power: P = 0.021; Low/high Frequency (HF) power: P = 0.042), and increased HRV during Ag challenge (RMSSD: P = 0.047; pNN6: P = 0.039). Sensitized mice displayed decreased HRV subsequent to OVA challenge, primarily in the dark cycle (RMSSD: P = 0.018; pNN6: P ≤ 0.001; LF: P ≤ 0.001; HF: P = 0.040; LF/HF: P ≤ 0.001). We conclude that implanted telemetry technology is an effective method to assess the ANS impact of allergic sensitization. Preliminary results show mild sensitization is associated with reduced HRV and a suppression of the acute T_B-response to OVA challenge. This approach to assess altered ANS control in the acute OVA model may also be beneficial in chronic AHR models.

Efficacy of anticholinergic drugs in asthma

Although bronchial hyperresponsiveness to cholinergic agents is a main feature of asthma, the role of anticholinergic drugs in chronic asthma management has been largely underestimated. Several single-dose studies comparing acute bronchodilation induced by ipratropium bromide with salbutamol have shown that salbutamol was more effective than ipratropium in asthma treatment. Recently, tiotropium has been studied in asthma, when added to low-dose inhaled corticosteroids in unselected moderate asthmatics or in patients with uncontrolled asthma, or patients with chronic obstructive pulmonary disease and history of asthma. Later, studies on patients with Arg/Arg β(2)-receptor polymorphism demonstrated a similar efficacy of tiotropium in comparison with salmeterol when both were added to low-dose inhaled corticosteroids. Further long-term studies are currently in progress, for the evaluation of the efficacy of tiotropium on clinical asthma control, and on the rate and severity of asthma exacerbations, as well as the potential modification of inflammatory mechanisms and varying efficacy in specific asthma phenotypes (such as smoking asthmatics).

The association of asthma and wheezing with major depressive episodes: an analysis of 245 727 women and men from 57 countries

BACKGROUND

Epidemiological studies have shown that asthma is positively associated with depression. Most of this evidence stems from individual studies conducted in Western populations (e.g. Europe, North America and Australia). It is still unclear whether such findings generalize to non-Western countries. To address this question, the present study investigated the association of asthma and wheezing with depression in a large multi-national sample.

METHODS

We used data from the 2002 World Health Survey. Participants reported physician-diagnosed asthma and attacks of wheezing within the past 12 months. Questions on depressive symptoms, their duration and persistence were used to define presence of a major depressive episode (MDE) within the past 12 months. ORs and 95% CIs were estimated by logistic regression for the entire sample, by continent (Australia, Europe, South America, Asia and Africa) and by country. Complete information was available for 57 countries.

RESULTS

Both asthma and wheezing were associated with MDE in the entire sample (OR=2.37, 95% CI=2.10-2.66 and OR=3.06, 95% CI=2.75-3.40, respectively). Similar associations were found for all continents with generally stronger ORs in South America, Asia and Africa for both asthma (ORs ≥ 1.8) and wheezing (ORs  ≥ 2.8). On the country level, wheezing showed a consistent pattern of association with MDE. Similar patterns were found for asthma.

CONCLUSIONS

Despite a range of country differences that could affect the association of asthma with depression, such as access to health care, the results of this study indicate that the co-occurrence of asthma and depression is a universal phenomenon.

Inflammation and cardiorespiratory control: the role of the vagus nerve

Inflammation and immunity have been implicated in a wide variety of diseases and disorders ranging from asthma to cardiovascular disease to hemorrhagic shock. In this review we will briefly consider the evidence for the neural concomitants of immunomodulation. First, we will briefly review the anatomy and physiology of the cardiorespiratory system. Then we will review the anatomy and physiology of neural-immune communication. The nucleus of the solitary tract is a site of integration of both the afferent and efferent neural regulation of the cardiorespiratory as well as the immune system. Then we will provide an overview of what is known about neuroimmunomodulation from both animal and human studies including neuroimaging and clinical studies. Finally, we will discuss a possible role of this neural circuitry in asthma related health disparities.

Autonomic dysfunction in older people

The autonomic nervous system comprises the sympathetic, parasympathetic and enteric nervous systems and plays an integral role in homeostasis. This includes cardiovascular and temperature control, glucose metabolism, gastrointestinal and reproductive function and increasing evidence to support its involvement in the inflammatory response to infection and cancer. Ageing is associated with autonomic dysfunction, and many clinical syndromes associated with older adults are due to inadequate autonomic responses to physiological stressors. The aim of this review is to explore the relationship between autonomic dysfunction and ageing illustrated with examples of maladaptive autonomic responses in a variety of different clinical syndromes including an exploration of autonomic cellular changes. Appropriate investigation and management strategies are outlined, recognizing the fine balance needed to improve symptoms without creating further medical complications.

Depressive symptoms, social support, and risk of adult asthma in a population-based cohort study

OBJECTIVE

To investigate the association between depressive symptoms, social support, and prevalent as well as incident asthma. Depressive symptoms and social support may affect the development of asthma. This relationship could be mediated by health behaviors and/or inflammatory processes. Evidence from prospective cohort studies on depressive symptoms and social support in relation to asthma risk in adults remains sparse.

METHODS

Between 1992 and 1995, a population-based sample of 5114 middle-aged adults completed questionnaires covering depressive symptoms, social support, self-reported asthma, and potential confounders. Among those alive in 2002/2003, 4010 (83%) were followed-up by questionnaires. Associations with prevalent and incident asthma were estimated by prevalence ratios (PR) and risk ratios (RR) along with corresponding 95% confidence intervals (CIs), using Poisson regression. PRs and RRs were adjusted for demographics, family history of asthma, smoking, alcohol consumption, body mass index, and physical exercise.

RESULTS

Cross-sectional analyses indicated that the prevalence of asthma was positively associated with depressive symptoms and inversely related to social support. Prospective analysis suggested a 24% increased risk of asthma with each 1-standard deviation increase in depressive symptoms (RR, 1.24; 95% CI, 1.02, 1.50), whereas the social support z score showed an inverse association with asthma incidence (RR, 0.71; 95% CI, 0.58, 0.88). Analyses with tertiles suggested similar, but nonsignificant, associations. Omitting health-related life-style variables from the multivariable models did not substantially alter these associations.

CONCLUSIONS

Risk of adult asthma was found to increase with depressive symptoms and to decrease with social support. These associations do not seem to be explained by health-related life-style factors.

Tachycardia in adults with cystic fibrosis is associated with normal autonomic function

BACKGROUND

Whether autonomic dysfunction contributes to tachycardia in cystic fibrosis (CF) is unknown.

METHODS

Heart rate variability (HRV) was assessed to determine high frequency power and the low/high frequency power ratio (HF, LF/HF) as markers of vagal and sympathovagal balance, respectively, under spontaneous and controlled breathing (15 breaths per minute (bpm)) conditions in 17 CF and 17 healthy control subjects.

RESULTS

Under spontaneously breathing conditions, the CF group was tachycardic (75.4 ± 11.2 vs 60.2 ± 9.0 br/min P < 0.001) and tachypnoeic (22.6 ± 5.8 vs 13.6 ± 4.1 br/min, P= 0.001) compared with controls. No significant difference in HRV was observed between groups during spontaneous or controlled breathing. Coexistent diabetes mellitus and β(2) agonist use were not associated with altered autonomic control. During controlled breathing, the CF group showed a negative correlation between forced expiratory volume in 1 s (FEV(1)) % predicted and HF power (P= 0.013, r=-0.59) and a positive correlation between FEV(1) % predicted and LF/HF ratio (P= 0.002, r= 0.69) suggesting an exaggerated normal vagal response.

CONCLUSION

CF patients have normal autonomic function.

A review of candidate pathways underlying the association between asthma and major depressive disorder

OBJECTIVE

To consider the mechanisms that may link asthma and major depressive disorder (MDD). Asthma and MDD co-occur at higher rates than expected, but whether this reflects shared underlying pathophysiological mechanisms is not known.

METHODS

A review of the epidemiological data linking asthma and MDD was conducted and the possible biological mechanisms that could account for the high rate of this comorbidity were reviewed.

RESULTS

MDD occurs in almost half of patients with asthma assessed in tertiary care centers. Dysregulation of the hypothalamic pituitary adrenal axis may predispose people to both MDD and asthma, and similar alterations in the immune, autonomic nervous, and other key systems are apparent and may contribute to this increased risk of co-occurrence.

CONCLUSIONS

High rates of MDD in asthma may result from the stress of chronic illness, the medications used to treat it, or a combination of the two. The high level of co-occurrence may also reflect dysregulation of certain stress-sensitive biological processes that contribute to the pathophysiology of both conditions.

The development of allergic inflammation

Allergic disorders, such as anaphylaxis, hay fever, eczema and asthma, now afflict roughly 25% of people in the developed world. In allergic subjects, persistent or repetitive exposure to allergens, which typically are intrinsically innocuous substances common in the environment, results in chronic allergic inflammation. This in turn produces long-term changes in the structure of the affected organs and substantial abnormalities in their function. It is therefore important to understand the characteristics and consequences of acute and chronic allergic inflammation, and in particular to explore how mast cells can contribute to several features of this maladaptive pattern of immunological reactivity.

Psychological factors in asthma

Asthma has long been considered a condition in which psychological factors have a role. As in many illnesses, psychological variables may affect outcome in asthma via their effects on treatment adherence and symptom reporting. Emerging evidence suggests that the relation between asthma and psychological factors may be more complex than that, however. Central cognitive processes may influence not only the interpretation of asthma symptoms but also the manifestation of measurable changes in immune and physiologic markers of asthma. Furthermore, asthma and major depressive disorder share several risk factors and have similar patterns of dysregulation in key biologic systems, including the neuroendocrine stress response, cytokines, and neuropeptides. Despite the evidence that depression is common in people with asthma and exerts a negative impact on outcome, few treatment studies have examined whether improving symptoms of depression do, in fact, result in better control of asthma symptoms or improved quality of life in patients with asthma.

Neuropeptides activate human mast cell degranulation and chemokine production

During neuronal-induced inflammation, mast cells may respond to stimuli such as neuropeptides in an FcepsilonRI-independent manner. In this study, we characterized human mast cell responses to substance P (SP), nerve growth factor (NGF), calcitonin gene-related peptide (CGRP) and vasoactive intestinal polypeptide (VIP) and compared these responses to human mast cell responses to immunoglobulin E (IgE)/anti-IgE and compound 48/80. Primary cultured mast cells, generated from CD34(+) progenitors in the presence of stem cell factor and interleukin-6 (IL-6), and human cultured mast cells (LAD2) were stimulated with these and other stimuli (gastrin, concanavalin A, radiocontrast media, and mannitol) and their degranulation and chemokine production was assessed. VIP and SP stimulated primary human mast cells and LAD cells to degranulate; gastrin, concanavalin A, radiocontrast media, mannitol, CGRP and NGF did not activate degranulation. While anti-IgE stimulation did not induce significant production of chemokines, stimulation with VIP, SP or compound 48/80 potently induced production of monocyte chemoattractant protein-1, inducible protein-10, monokine induced by interferon-gamma (MIG), RANTES (regulated on activation, normal, T-cell expressed, and secreted) and IL-8. VIP, SP and compound 48/80 also activated release of tumour necrosis factor, IL-3 and granulocyte-macrophage colony-stimulating factor, but not IL-4, interferon-gamma or eotaxin. Human mast cells expressed surface neurokinin 1 receptor (NK1R), NK2R, NK3R and VIP receptor type 2 (VPAC2) but not VPAC1 and activation of human mast cells by IgE/anti-IgE up-regulated expression of VPAC2, NK2R, and NK3R. These studies demonstrate the pattern of receptor expression and activation of mast cell by a host of G-protein coupled receptor ligands and suggest that SP and VIP activate a unique signalling pathway in human mast cells. These results are likely to have direct relevance to neuronally induced inflammatory diseases.