Autonomic nervous system abnormalities in cystic fibrosis

Regional brain tissue changes in patients with cystic fibrosis

BACKGROUND

Cystic fibrosis (CF) patients present with a variety of symptoms, including mood and cognition deficits, in addition to classical respiratory, and autonomic issues. This suggests that brain injury, which can be examined with non-invasive magnetic resonance imaging (MRI), is a manifestation of this condition. However, brain tissue integrity in sites that regulate cognitive, autonomic, respiratory, and mood functions in CF patients is unclear. Our aim was to assess regional brain changes using high-resolution T1-weighted images based gray matter (GM) density and T2-relaxometry procedures in CF over control subjects.

METHODS

We acquired high-resolution T1-weighted images and proton-density (PD) and T2-weighted images from 5 CF and 15 control subjects using a 3.0-Tesla MRI. High-resolution T1-weighted images were partitioned to GM-tissue type, normalized to a common space, and smoothed. Using PD- and T2-weighted images, whole-brain T2-relaxation maps were calculated, normalized, and smoothed. The smoothed GM-density and T2-relaxation maps were compared voxel-by-voxel between groups using analysis of covariance (covariates, age and sex; SPM12, p < 0.001).

RESULTS

Significantly increased GM-density, indicating tissues injury, emerged in multiple brain regions, including the cerebellum, hippocampus, amygdala, basal forebrain, insula, and frontal and prefrontal cortices. Various brain areas showed significantly reduced T2-relaxation values in CF subjects, indicating predominant acute tissue changes, in the cerebellum, cerebellar tonsil, prefrontal and frontal cortices, insula, and corpus callosum.

CONCLUSIONS

Cystic fibrosis subjects show predominant acute tissue changes in areas that control mood, cognition, respiratory, and autonomic functions and suggests that tissue changes may contribute to symptoms resulting from ongoing hypoxia accompanying the condition.

Effects of a Short-Term Resistance-Training Program on Heart Rate Variability in Children With Cystic Fibrosis-A Randomized Controlled Trial

Background: Cystic fibrosis (CF) affects the autonomic nervous system (ANS) and exercise in healthy children modulates the interaction between sympathetic and parasympathetic activity. This study aimed to evaluate the effects of a short-term resistance exercise program on heart rate variability (HRV) in children and adolescents with CF.

Methods: A randomized controlled trial was carried out in children diagnosed with CF aged 6–18 years. Individuals were divided into two groups: control (CON) and resistance-training (EX). Individuals in the EX group completed an individualized guided resistance program (5-RM—60–80%) for 8 weeks (3 sessions of 60 min/week). Upper and lower limbs exercises (seated bench press, seated lateral row, and leg press) were used. HRV was measured using a Suunto watch with subjects in lying position.

Results: Nineteen subjects (13 boys) were included (CON = 11; and EX = 8). Mean age was 12.2 ± 3.3, FEV₁ (forced expiratory volume in the first second) z-score was 1.72 ± 1.54 and peak oxygen consumption (VO₂peak) 42.7 ± 7.4 mL.Kg^–1.min^–1. Exercise induced significant changes in the frequency-domain variables, including a decrease in LF power (p = 0.001, d = 0.98) and LF/HF ratio (p = 0.020, d = 0.92), and an increase in HF power (p = 0.001, d = −0.97), compared to the CON group. No significant changes were found for time-domain variables, although increases with a moderate effect size were seen for SDNN (p = 0.152, d = −0.41) and RMSSD (p = 0.059, d = −0.49) compared to the CON group.

Conclusion: A short-term resistance exercise-training program was able to modulate HRV in children and adolescents with CF presenting mild to moderate lung function impairment and good physical condition.

Clinical Trial Registration:www.ClinicalTrials.gov, identifier NCT04293926.

Neuropeptides in asthma, chronic obstructive pulmonary disease and cystic fibrosis

The nervous system mediates key airway protective behaviors, including cough, mucus secretion, and airway smooth muscle contraction. Thus, its involvement and potential involvement in several airway diseases has become increasingly recognized. In the current review, we focus on the contribution of select neuropeptides in three distinct airway diseases: asthma, chronic obstructive pulmonary disease (COPD), and cystic fibrosis. We present data on some well-studied neuropeptides, as well as call attention to a few that have not received much consideration. Because mucus hypersecretion and mucus obstruction are common features of many airway diseases, we place special emphasis on the contribution of neuropeptides to mucus secretion. Finally, we highlight evidence implicating involvement of neuropeptides in mucus phenotypes in asthma, COPD and cystic fibrosis, as well as bring to light knowledge that is still lacking in the field.

Cystic Fibrosis and the Nervous System

Cystic fibrosis (CF) is a life-shortening autosomal recessive disorder caused by mutations in the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR). CFTR is an anion channel that conducts bicarbonate and chloride across cell membranes. Although defective anion transport across epithelial cells is accepted as the basic defect in CF, many of the features observed in people with CF and organs affected by CF are modulated by the nervous system. This is of interest because CFTR expression has been reported in both the peripheral and central nervous systems, and it is well known that the transport of anions, such as chloride, greatly modulates neuronal excitability. Thus it is predicted that in CF, lack of CFTR in the nervous system affects neuronal function. Consistent with this prediction, several nervous system abnormalities and nervous system disorders have been described in people with CF and in animal models of CF. The goal of this special feature article is to highlight the expression and function of CFTR in the nervous system. Special emphasis is placed on nervous system abnormalities described in people with CF and in animal models of CF. Finally, features of CF that may be modulated by or attributed to faulty nervous system function are discussed.

Use of Human Minor Salivary Glands in Basic and Applied Secretion Research

Previous findings from studies utilizing human labial and palatine minor salivary glands are reviewed. These studies took histopathological, biochemical, and ultrastructural approaches, and focused on control and diseased glands. Disease-oriented summarizations are used, and control results are discussed in the context of disease-related findings. Findings are reviewed separately for electrolytes, macromolecules, and ultrastructure. In control subjects, minor gland salivary electrolyte concentrations are dependent on flow rate, and this dependence may be altered by diseases such as cystic fibrosis as-well as by inflammatory situations such as graft-versus-host disease. There is also evidence that salivary electrolyte secretion processes are not similar in labial and palatine minor glands. Studies of salivary macromolecular composition are reviewed for control subjects and for patients with graft-versus-host disease and Sjögren's syndrome. The findings indicate that the macromolecular contents of labial and palatine gland saliva are similar, but that both are significantly different from that for major gland saliva. Finally, studies attempting to measure disease-related changes in intracellular composition are reviewed. It is concluded that the minor salivary glands are important models for the study of exocrine gland physiology and pathophysiology in man.

Reproducibility of Heart Rate Variability Indices in Children with Cystic Fibrosis

Fundamental to the potential utilisation of heart rate variability (HRV) indices as a prognostic tool is the reproducibility of these measures. The purpose of the present study was therefore to investigate the reproducibility of 24-hour derived HRV indices in a clinical paediatric population. Eighteen children (10 boys; 12.4 ± 2.8 years) with mild to moderate Cystic Fibrosis (CF; FVC: 83 ± 12% predicted; FEV1: 80 ± 9% predicted) and eighteen age- and sex-matched controls (10 boys; 12.5 ± 2.7 years) wore a combined ECG and accelerometer for two consecutive days. Standard time and frequency domain indices of HRV were subsequently derived. Reproducibility was assessed by Bland-Altman plots, 95% limits of agreement and intra-class correlation coefficients (ICC). In both groups, there was no systematic difference between days, with the variables demonstrating a symmetrical, homoscedastic distribution around the zero line. The time domain parameters demonstrated a good to excellent reproducibility irrespective of the population considered (ICC: 0.56 to 0.86). In contrast, whilst the frequency domain parameters similarly showed excellent reproducibility in the healthy children (ICC: 0.70 to 0.96), the majority of the frequency domain parameters illustrated a poor to moderate reproducibility in those with CF (ICC: 0.22 to 0.43). The exceptions to this trend were the normalised LF and HF components which were associated with a good to excellent reproducibility. These findings thereby support the utilisation of time and relative frequency domain HRV indices as a prognostic tool in children with CF. Furthermore, the present results highlight the excellent reproducibility of HRV in healthy children, indicating that this may be a useful tool to assess intervention effectiveness in this population.

Effects of exercise intensity compared to albuterol in individuals with cystic fibrosis

BACKGROUND

Although exercise is a vital component of the therapy prescribed to individuals with cystic fibrosis (CF), it is not a priority due to a finite amount of treatment time and the view that exercise is not as beneficial as pharmacological treatments by many individuals with CF. We sought to compare the therapeutic benefits of exercise and their prescribed bronchodilator albuterol.

METHODS

CF (n = 14) and healthy (n = 16) subjects completed three visits, a baseline screening with VO2 max test and two treatment visits. On the two treatment visits, subjects completed spirometry and diffusing capacity of the lungs for nitric oxide (DLNO) maneuvers either at baseline, 60, and 110 min post-albuterol administration, or at baseline and the midway point of three separate 15 min exercise bouts at low, moderate and vigorous intensity (25, 50 and 65% of the maximum workload, respectively).

RESULTS

With moderate exercise the increase in DLNO was double (39 ± 8 vs 15  ± 6% change) and the level of bronchodilation similar (23% change) when compared to 110 min post-albuterol in individuals with CF. During exercise FVC became reduced (-309 ± 66 mL with moderate exercise) and the increase in FEV1 was attenuated (103 ± 39 vs 236 ± 58 mL, exercise vs. albuterol) when compared with the response to albuterol in individuals with CF. Epinephrine (EPI) release increased 39, 72 and 144% change with low, moderate and vigorous intensity exercise respectively for individuals with CF, but this increase was blunted when compared to healthy subjects.

CONCLUSION

Our results suggest that moderate intensity exercise is the optimal intensity for individuals with CF, as low intensity exercise increases EPI less than 50% and vigorous intensity exercise is over taxing, such that airflow can be restricted. Although the duration of the beneficial effect is uncertain, exercise can promote greater improvements in gas diffusion and comparable bronchodilation when compared to albuterol.

Inflammation, oxidative stress, and cardiovascular disease risk factors in adults with cystic fibrosis

Cystic fibrosis (CF) represents one of a number of localized lung and non-lung diseases with an intense chronic inflammatory component associated with evidence of systemic oxidative stress. Many of these chronic inflammatory diseases are accompanied by an array of atherosclerotic processes and cardiovascular disease (CVD), another condition strongly related to inflammation and oxidative stress. As a consequence of a dramatic increase in long-lived patients with CF in recent decades, the specter of CVD must be considered in these patients who are now reaching middle age and beyond. Buttressed by recent data documenting that CF patients exhibit evidence of endothelial dysfunction, a recognized precursor of atherosclerosis and CVD, the spectrum of risk factors for CVD in CF is reviewed here. Epidemiological data further characterizing the presence and extent of atherogenic processes in CF patients would seem important to obtain. Such studies should further inform and offer mechanistic insights into how other chronic inflammatory diseases potentiate the processes leading to CVDs.

CFTR-deficient pigs display peripheral nervous system defects at birth

Peripheral nervous system abnormalities, including neuropathy, have been reported in people with cystic fibrosis. These abnormalities have largely been attributed to secondary manifestations of the disease. We tested the hypothesis that disruption of the cystic fibrosis transmembrane conductance regulator (CFTR) gene directly influences nervous system function by studying newborn CFTR(-/-) pigs. We discovered CFTR expression and activity in Schwann cells, and loss of CFTR caused ultrastructural myelin sheath abnormalities similar to those in known neuropathies. Consistent with neuropathic changes, we found increased transcripts for myelin protein zero, a gene that, when mutated, can cause axonal and/or demyelinating neuropathy. In addition, axon density was reduced and conduction velocities of the trigeminal and sciatic nerves were decreased. Moreover, in vivo auditory brainstem evoked potentials revealed delayed conduction of the vestibulocochlear nerve. Our data suggest that loss of CFTR directly alters Schwann cell function and that some nervous system defects in people with cystic fibrosis are likely primary.

Lung function and airway hyperresponsiveness in adult patients with sickle cell disease

BACKGROUND

Lung disease is a major cause of morbidity and death in sickle cell disease. Although airway hyperresponsiveness has been noted in children, there are no studies in adult sickle cell patients. The aim of this study was to investigate the prevalence of airway hyperresponsiveness in adult sickle cell patients.

METHODS

Twenty-six patients with sickle cell disease (10 HbSC, 9 HbSS, and 7 HbSbeta) were compared with 28 normal control subjects. Pulmonary function tests, including spirometry, measurements of single-breath diffusing capacity and the methacholine challenge test were performed.

RESULTS

There were no significant differences in age, gender, or height between groups. Restrictive ventilatory defect was observed in six patients (24%) in the sickle cell disease group. Obstructive ventilatory defect and reduced diffusing lung DLCO capacity was observed in all sickle cell disease subgroups. A positive methacholine challenge test was obtained in eight (31%) sickle cell patients and in two of the 28 controls (7%).

CONCLUSION

These features suggest that there is a high prevalence of airway hyperresponsiveness in adult patients with sickle cell disease without a history of reactive airway disease.

Ageing, late-onset asthma and the beta-adrenoceptor

Late-onset asthma in old age is a common clinical problem. There are similarities between receptor and post-receptor beta 2-adrenoceptor abnormalities reported in young asthmatics and in elderly normal subjects. Recent evidence lends some support to the idea of the 'aging' beta 2-adrenoceptor as a contributory factor in the development of late-onset asthma, although questions of the validity of the peripheral mononuclear cell model and of receptor tachyphylaxis to intrinsic and extrinsic beta-adrenoceptor agonists remain unresolved. Further work should focus on in vivo studies of airway receptor function and on beta 2-adrenoceptor-mediated pathways other than smooth muscle-related bronchoconstriction.

The end organ defect in cystic fibrosis; a hypothesis: disinhibited inositol cycle activation?

Activation of the inositol cycle by a factor capable of by-passing the normal controls on exocrine secretion by an interaction with a coupling protein could produce effects similar to a calcium ionophore or the ciliary dyskinesia factor. The chloride permeability defect may represent a secondary adaptive change, able to limit the consequences of this via an acid shift in intracellular pH. The model predicts that lithium treatment would limit the effects of the disease.

Ocular findings in cystic fibrosis

We examined 32 patients with cystic fibrosis, paying special attention to optic nerve performance and pupillary function. Decreased visual acuity occurred in nine of 64 eyes. Three of 17 patients (18%) who used chloramphenicol had bilaterally delayed P100 waves of the visual-evoked response of greater than 3 standard deviations. This was not found in patients who did not use chloramphenicol. Contrast sensitivity in patients with cystic fibrosis was decreased at every spatial frequency when compared to healthy controls. This decrease was noted in patients who did and did not use chloramphenicol, suggesting that chloramphenicol is not the only cause of decreased contrast sensitivity in cystic fibrosis. With pharmacologic pupil testing we determined that patients with cystic fibrosis display a preganglionic oculosympathetic paresis that corresponded to the disease severity, as measured by the Shwachman score.

Use of human minor salivary glands in basic and applied secretion research

Previous findings from studies utilizing human labial and palatine minor salivary glands are reviewed. These studies took histopathological, biochemical, and ultrastructural approaches, and focused on control and diseased glands. Disease-oriented summarization are used, and control results are discussed in the context of disease-related findings. Findings are reviewed separately for electrolytes, macromolecules, and ultrastructure. In control subjects, minor gland salivary electrolyte concentrations are dependent on flow rate, and this dependence may be altered by diseases such as cystic fibrosis as well as by inflammatory situations such as graft-versus-host disease. There is also evidence that salivary electrolyte secretion processes are not similar in labial and palatine minor glands. Studies of salivary macromolecular composition are reviewed for control subjects and for patients with graft-versus-host disease and Sjögren's syndrome. The findings indicate that the macromolecular contents of labial and palatine gland saliva are similar, but that both are significantly different from that for major gland saliva. Finally, studies attempting to measure disease-related changes in intracellular composition are reviewed. It is concluded that the minor salivary glands are important models for the study of exocrine gland physiology and pathophysiology in man.

Pathophysiology of Cystic Fibrosis with Emphasis on Salivary Gland Involvement

Cystic fibrosis (CF) is a fatal autosomal recessive disorder which affects all exocrine glands, or perhaps all epithelial surfaces. The three organs most consistently affected are the eccrine sweat gland, which produces excessively salty sweat; the lung, in which chronic obstructive pulmonary disease invariably develops and is usually the cause of mortality; and the pancreas, which fails to produce adequate bicarbonate ion and water in nearly all patients, and produces inadequate digestive enzymes in most, giving rise to pancreatic insufficiency. However, the liver, reproductive tracts, intestine, sinuses, and salivary glands are also regularly affected. In the sweat gland and in the airways, passive chloride permeability is reduced, accounting for the salty sweat and probably contributing to the dehydrated mucus in the airways. In organs apart from the sweat gland, a common feature of the disease is the plugging of glandular acini and ductules by precipitated secretions. Salivary glands have been extensively studied in CF because of both the accessibility of the glands and their products, and the mix of mucous and serous components in the salivary glands. However, there is no unanimity in the results from parotid and submandibular glands. In the labial (mucous) glands, the sodium content of secreted product and in the secretory granules is markedly elevated, and histologically the acini are plugged with eosinophilic material. Functional studies of CF salivary glands have also yielded inconsistent data. Cultured cell systems combined with molecular biologic approaches offer promise in tracing the fundamental CF defect in salivary and other epithelial systems.

Pathophysiology of cystic fibrosis with emphasis on salivary gland involvement

Cystic fibrosis (CF) is a fatal autosomal recessive disorder which affects all exocrine glands, or perhaps all epithelial surfaces. The three organs most consistently affected are the eccrine sweat gland, which produces excessively salty sweat; the lung, in which chronic obstructive pulmonary disease invariably develops and is usually the cause of mortality; and the pancreas, which fails to produce adequate bicarbonate ion and water in nearly all patients, and produces inadequate digestive enzymes in most, giving rise to pancreatic insufficiency. However, the liver, reproductive tracts, intestine, sinuses, and salivary glands are also regularly affected. In the sweat gland and in the airways, passive chloride permeability is reduced, accounting for the salty sweat and probably contributing to the dehydrated mucus in the airways. In organs apart from the sweat gland, a common feature of the disease is the plugging of glandular acini and ductules by precipitated secretions. Salivary glands have been extensively studied in CF because of both the accessibility of the glands and their products, and the mix of mucous and serous components in the salivary glands. However, there is no unanimity in the results from parotid and submandibular glands. In the labial (mucous) glands, the sodium content of secreted product and in the secretory granules is markedly elevated, and histologically the acini are plugged with eosinophilic material. Functional studies of CF salivary glands have also yielded inconsistent data. Cultured cell systems combined with molecular biologic approaches offer promise in tracing the fundamental CF defect in salivary and other epithelial systems.

Supraventricular tachycardia in patients with cystic fibrosis

Reports on arrhythmias in cystic fibrosis (CF) patients are limited. Four CF patients treated at our center had recurrent supraventricular tachycardia (SVT). Three had cor pulmonale, as evidenced by echocardiogram, and all had baseline tachycardia. Twenty-four hour Holter monitoring in three patients showed ectopic atrial pacing and premature atrial and ventricular contractions in one patient, rare PVCs in another, and SVT in all three. All patients had significant bronchospasm requiring the use of theophylline, prednisone, and frequent daily doses of beta-2 adrenergic agonists; two also used nebulized atropine. Average theophylline level for the group was 13.4 micrograms/ml during SVT. There was no correlation between pulmonary obstruction and the frequency of SVT. Factors such as cor pulmonale, ectopy, hypoxia, infection, intensive combination bronchodilator therapy, and corticosteroids probably interacted to precipitate SVT. Altered autonomic responses and a myocardial infiltrative process noted in some patients with CF may also play a role in causing arrhythmias.

Cystic fibrosis heterozygotes have normal autonomic innervation of the heart

Five simple tests of autonomic nerve function based on measurements of cardiovascular responses to various stimuli were used to investigate possible autonomic dysfunction in obligate heterozygotes for cystic fibrosis. There were no significant differences between the heterozygotes and control groups in any of the tests, suggesting that cystic fibrosis heterozygotes have normal autonomic innervation of the heart.

Effects of reserpine and isoproterenol on elemental distribution in submandibular gland of rat

The effects of a single dose of reserpine or isoproterenol on the acinar cells of rat submandibular gland were investigated by electron microscopy and X-ray microanalysis. About 4 h after injection of reserpine, the cellular Ca concentration started to increase and at 24 h a level two to three times the control value was reached. The mucus content of the cells increased in parallel with the Ca concentrations. Isoproterenol stimulation depleted the acinar cells of their mucus. Resynthesis of mucus was visible at 8-12 h after injection. Changes in cellular Ca concentrations followed the mucus content of the cells. After 24 h both the mucus content and the Ca concentration were significantly increased over the control values. High-resolution X-ray microanalysis on thin cryosections showed that the calcium was accumulated in the mucus granules, both after reserpine and after isoproterenol administration. The newly synthesized mucus was also more calcium-rich than the original mucus. The effect of a single isoproterenol stimulation on elemental content of rat submandibular gland acinar cells was not significantly different from that of chronic isoproterenol treatment. Chronic treatment with reserpine resulted in a higher cellular Na/K ratio than a single dose.

The chronically isoproterenol-treated rat in the study of cystic fibrosis: X-ray microanalysis of the submandibular gland

The chronically isoproterenol-treated rat has been proposed as an animal model for cystic fibrosis. Ultrastructural studies showed enlarged cells with abnormally large mucus granules that were more often fused than in control animals. X-ray microanalysis of mucous acinar cells showed a significant increase in calcium levels, but unaffected magnesium levels. Combined treatment with isoproterenol and reserpine caused a very large increase in cellular calcium levels that appeared to be an addition of the single effects and increased magnesium levels (as in glands of rats treated with reserpine only). Chronic treatment with isoproterenol, reserpine, or both substances tended to decrease cellular potassium levels. Chronic exposure to the specific beta 1-agonist prenalterol or the specific beta 2-agonist terbutaline did not affect cellular calcium or potassium levels. It is concluded that chronic isoproterenol treatment affects the elemental composition of mucous acinar cells of rat submandibular gland differently from chronic reserpine treatment. The increase in cellular calcium concentration after chronic isoproterenol treatment does not appear to be due to an effect via beta-adrenergic receptors.