Pulmonary responses to tracheal or esophageal acidification in guinea pigs with airway inflammation

Contribution of comorbidities to obesity-related asthma in children

Children with obesity are at increased risk for developing asthma that is difficult to control. A complicating factor to asthma management among these children is likely the commonplace co-morbidities that also result from obesity. We discuss three common obesity-related comorbidities which appear to complicate the effective management of asthma, including hypovitaminosis D, obstructive sleep apnea and gastro-esophageal reflux. Each conditions requires more research to understand their effects on asthma management.

Preschool Wheezing and Gastro-Esophageal Reflux: --Causal or Casual Coincidence? Update from Literature

Gastroesophageal reflux (GER) and wheeze are two common conditions in children. GER has been advocated as a causative factor for explaining recurrent to persistent respiratory symptoms at any age. This association very often means that many children with cough, wheezing, or recurrent respiratory infections receive empirical anti-reflux medications. The causal relationship is still largely discussed. Compared to the large number of studies in infants and adolescents, literature on the relationship between GER and wheeze in preschool children is scarce and inconclusive. The aim of the present narrative review was to summarize what is known so far, and what the literature has proposed in the last 20 years, on the relationship between preschool wheezing and GER. In preschool children with respiratory symptoms there is a high rate of positivity of reflux testing, for this reason pH-MII testing and endoscopy are recommended. Flexible bronchoscopy may be useful to exclude anatomical abnormalities as the cause of wheezing in infancy and preschool years. Several biomarkers, as well as empirical anti-reflux therapy, have been proposed for the diagnosis of GER-related airway diseases, but the conclusions of these studies are controversial or even conflicting. There is a great need for future clinical trials to confirm or rule out the association.

Idiopathic pulmonary fibrosis and gastroesophageal reflux disease: A population-based, case-control study

BACKGROUND

It is unknown whether gastroesophageal reflux disease (GERD) is a risk factor or consequence of idiopathic pulmonary fibrosis (IPF). This study aimed to determine whether patients with IPF were more likely to have GERD compared with age- and sex-matched controls who either had 1) interstitial lung disease (ILD) other than IPF or 2) no diagnosed lung disease (population control).

METHODS

We used the medical records-linkage system of the Rochester Epidemiology Project (REP) to identify patients with IPF who resided in Olmsted County, Minnesota, from January 1, 1997, through June 30, 2017. IPF cases were each matched with patients from 2 control groups (non-IPF ILD controls and population controls). We used conditional logistic regression to model associations between GERD diagnosis and IPF case status. P values were adjusted for multiple comparisons by using the Bonferroni adjustment (P values < .025 were considered statistically significant).

RESULTS

One hundred thirteen IPF cases were identified and matched to 226 population controls and 226 controls with non-IPF ILD. After multivariable adjustment, the odds of having GERD were 1.78 times higher (95% CI, 1.09-2.91; P = .02) in IPF cases compared with population controls. After multivariable adjustment, the odds of having GERD were 0.46 times lower (95% CI, 0.23-0.94; P = .03) in IPF cases compared with non-IPF ILD controls.

CONCLUSION

GERD may be an important contributor to the development of lung fibrosis. Thus, it should be investigated and addressed adequately when detected in patients with IPF and patients with non-IPF ILD.

Genotype tailored treatment of mild symptomatic acid reflux in children with uncontrolled asthma (GenARA): Rationale and methods

Asthma causes enormous suffering and cost for children in the US and around the world [1-3]. Co-morbid gastroesophageal reflux disease (GERD) makes asthma management more difficult due to increased symptoms. Proton pump inhibitor (PPI) drugs are effective at improving to GERD symptoms, however they have demonstrated only modest and variable effects on asthma control in the setting of co-morbid GERD. Importantly, PPI metabolism and efficacy depend on CYP2C19 genotype. The Genotype Tailored Treatment of Symptomatic Acid Reflux in Children with Uncontrolled Asthma (GenARA) study is a randomized, double-blind, placebo-controlled trial to determine if genotype-tailored PPI dosing improves asthma symptoms among children with inadequately controlled asthma and GERD symptoms. This study has an innovative design to both assess the efficacy of genotype-tailored PPI dosing and perform pharmacokinetic modeling of the oral PPI Lansoprazole. Children ages 6-17 years old with clinician-diagnosed asthma and mild GERD symptoms will submit a saliva sample for CYP2C19 genotyping. Participants will undergo a two-step randomization to: (1) genotype-tailored versus conventional dosing of open-label oral lansoprazole for pharmacokinetic modeling, and (2) genotype-tailored lansoprazole daily versus placebo for 24 weeks to determine the effect of genotype-tailored PPI dosing on asthma control. Measures of asthma control, spirometry, and nasal washes during acute illnesses will be collected at 8-week intervals throughout the study. GenARA will better define the effects of CYP2C19 genotype on the dose response of lansoprazole in children and adolescents and assess if a novel dosing regimen improves GERD and asthma control.

Sex-specific airway hyperreactivity and sex-specific transcriptome remodeling in neonatal piglets challenged with intra-airway acid

Acute airway acidification is a potent stimulus of sensory nerves and occurs commonly with gastroesophageal reflux disease, cystic fibrosis, and asthma. In infants and adults, airway acidification can acutely precipitate asthma-like symptoms, and treatment-resistant asthma can be associated with gastroesophageal reflux disease. Airway protective behaviors, such as mucus secretion and airway smooth muscle contraction, are often exaggerated in asthma. These behaviors are manifested through activation of neural circuits. In some populations, the neural response to acid might be particularly important. For example, the immune response in infants is relatively immature compared with adults. Infants also have a high frequency of gastroesophageal reflux. Thus, in the current study, we compared the transcriptomes of an airway-nervous system circuit (e.g., tracheal epithelia, nodose ganglia, and brain stem) in neonatal piglets challenged with intra-airway acid. We hypothesized that the identification of parallel changes in the transcriptomes of two neutrally connected tissues might reveal the circuit response, and, hence, molecules important for the manifestation of asthma-like features. Intra-airway acid induced airway hyperreactivity and airway obstruction in male piglets. In contrast, female piglets displayed airway obstruction without airway hyperreactivity. Pairwise comparisons revealed parallel changes in genes directly implicated in airway hyperreactivity ( scn10a) in male acid-challenged piglets, whereas acid-challenged females exhibited parallel changes in genes associated with mild asthma ( stat 1 and isg15). These findings reveal sex-specific responses to acute airway acidification and highlight distinct molecules within a neural circuit that might be critical for the manifestation of asthma-like symptoms in pediatric populations.

Effect of butylphthalide intervention on experimental autoimmune myositis in guinea pigs

Idiopathic inflammatory myopathies are a group of rare muscular diseases that are characterized by acute, subacute or chronic proximal and symmetric muscle weakness, muscle fiber necrosis and infiltration of inflammatory cells, particularly activated CD8⁺ cytotoxic T cells and phagocytes. 3-n-butylphthalide (NBP) protects mitochondria and reduces the inflammatory response in multiple disease models. In myositis, it has remained elusive whether NBP can protect muscle cells from muscle fiber injury. Experimental autoimmune myositis (EAM) was induced in a total of 40 guinea pigs by myosin immunization. After 4 weeks, low- or high-dose NBP solution was intraperitoneally injected. Saline solution was used as a negative control. After 10 days, the clinical manifestations were assessed by determining rodent grasping power, histopathological changes, Ca²⁺-adenosinetriphosphatase (ATPase) activity by an ATPase kit, and mRNA expression of interferon (IFN)-γ, retinoic acid receptor-related orphan nuclear receptor (ROR)γt and forkhead box (Fox) p3 in muscle tissue by reverse-transcription quantitative polymerase chain reaction analysis. It was demonstrated that NBP improved the myodynamia of guinea pigs with EAM and reduced the pathological inflammatory cell infiltration in a dose-dependent manner. NBP improved the Ca²⁺-ATPase activity of the muscle mitochondrial membrane and muscle plasma membrane in animals with EAM. It also reduced the mRNA expression of IFN-γ and RORγt, and significantly increased the mRNA expression of Foxp3 in muscle tissue. These results provided a basis for the consideration of NBP as a novel agent for the treatment of myositis and other muscular diseases associated with autoimmunity and inflammation.

Acid-Sensing Ion Channel 1a Contributes to Airway Hyperreactivity in Mice

Neurons innervating the airways contribute to airway hyperreactivity (AHR), a hallmark feature of asthma. Several observations suggested that acid-sensing ion channels (ASICs), neuronal cation channels activated by protons, might contribute to AHR. For example, ASICs are found in vagal sensory neurons that innervate airways, and asthmatic airways can become acidic. Moreover, airway acidification activates ASIC currents and depolarizes neurons innervating airways. We found ASIC1a protein in vagal ganglia neurons, but not airway epithelium or smooth muscle. We induced AHR by sensitizing mice to ovalbumin and found that ASIC1a^-/- mice failed to exhibit AHR despite a robust inflammatory response. Loss of ASIC1a also decreased bronchoalveolar lavage fluid levels of substance P, a sensory neuropeptide secreted from vagal sensory neurons that contributes to AHR. These findings suggest that ASIC1a is an important mediator of AHR and raise the possibility that inhibiting ASIC channels might be beneficial in asthma.

Inflammatory response mechanisms exacerbating hypoxemia in coexistent pulmonary fibrosis and sleep apnea

Mediators of inflammation, oxidative stress, and chemoattractants drive the hypoxemic mechanisms that accompany pulmonary fibrosis. Patients with idiopathic pulmonary fibrosis commonly have obstructive sleep apnea, which potentiates the hypoxic stimuli for oxidative stress, culminating in systemic inflammation and generalized vascular endothelial damage. Comorbidities like pulmonary hypertension, obesity, gastroesophageal reflux disease, and hypoxic pulmonary vasoconstriction contribute to chronic hypoxemia leading to the release of proinflammatory cytokines that may propagate clinical deterioration and alter the pulmonary fibrotic pathway. Tissue inhibitor of metalloproteinase (TIMP-1), interleukin- (IL-) 1α, cytokine-induced neutrophil chemoattractant (CINC-1, CINC-2α/β), lipopolysaccharide induced CXC chemokine (LIX), monokine induced by gamma interferon (MIG-1), macrophage inflammatory protein- (MIP-) 1α, MIP-3α, and nuclear factor- (NF-) κB appear to mediate disease progression. Adipocytes may induce hypoxia inducible factor (HIF) 1α production; GERD is associated with increased levels of lactate dehydrogenase (LDH), alkaline phosphatase (ALP), and tumor necrosis factor alpha (TNF-α); pulmonary artery myocytes often exhibit increased cytosolic free Ca2+. Protein kinase C (PKC) mediated upregulation of TNF-α and IL-1β also occurs in the pulmonary arteries. Increased understanding of the inflammatory mechanisms driving hypoxemia in pulmonary fibrosis and obstructive sleep apnea may potentiate the identification of appropriate therapeutic targets for developing effective therapies.

Bronchoalveolar pH and inflammatory biomarkers in newly diagnosed IPF and GERD patients: a case-control study

Background

Several studies have suggested that idiopathic pulmonary fibrosis (IPF) may be related to repeated aspiration of gastric contents over long periods of time. We aimed to investigate differences between pH measured directly in the lung, and biomarkers of acute inflammation in patients with newly diagnosed IPF and in patients with newly diagnosed GERD.

Material/Methods

All subjects (N=61) underwent collection of medical history, physical examination, pulmonary function testing, bronchoscopy, endoscopy, arterial blood gas analyses, and biochemical testing.

Results

Previously diagnosed GERD was found in 56.7%, typical symptoms of reflux in 80%, and Helicobacter pylori in gastric biopsy specimens in 76.6% of the cases. pH in peripheral branches of bronchi in the cases was 5.32±0.44 and was 6.27±0.31 (p<0.001) in the control group. The average values of LDH, ALP, and CRP in bronchoalveolar aspirate and in serum, as well as TNF-α in bronchoalveolar aspirate, were significantly higher in IPF patients.

Conclusions

The more acidic environment in the bronchoalveolar aspirate of the IPF subjects could contribute to the development or progression of IPF, possibly via changes in local metabolism or by damaging local cells and tissue. However, further studies with larger numbers of patients are required to clarify the role of gastric fluid aspiration in IPF pathogenesis. Our preliminary work has identified inflammatory biomarkers LDH, ALP, and TNF-α as potentially important in the pathologic processes in IPF. Further research is needed to determine their importance in clinical intervention and patient care.

Gastro-oesophageal reflux and respiratory symptoms in Busselton adults: the effects of bodyweight and sleep apnoea

BACKGROUND/AIM

Respiratory symptoms and gastro-oesophageal reflux disease (GORD) are common within the general population. Although a number of epidemiological studies have addressed their relationship, none has investigated the confounding effects of body mass index (BMI) and obstructive sleep apnoea (OSA), both of which are associated with reflux.

METHODS

Men and women (2700) from the 2005-2007 cross-sectional Busselton health survey were included. Questionnaire data included demography, information on general health, asthma, cough, wheeze, dyspnoea and reflux symptoms (never, monthly or less often and weekly or more often). BMI, risk of OSA (Berlin questionnaire definition), spirometry and airway hyperresponsiveness (AHR) were recorded. The effects of BMI and OSA on the relationship between respiratory and reflux symptoms were examined using logistic regression models, expressed as adjusted odds ratios for risk of respiratory symptoms by reflux symptom category.

RESULTS

Fifty per cent had reflux symptoms (5-10% weekly or more often). Reflux symptoms had strong positive, dose-related associations with cough/phlegm, breathlessness, chest tightness and wheeze in the last 12 months (P < 0.001), but were not related to diagnosed asthma or AHR. Twenty-three per cent were at high risk of OSA and 63% had a BMI of >25 (22% > 30). Increased weight or high risk of OSA did not affect the relationship between respiratory symptoms and reflux symptoms.

CONCLUSION

The relationship between reflux and respiratory symptoms was independent of BMI, high risk of OSA or AHR. These findings suggest that reflux contributes directly to respiratory symptoms.

The treatment of asthma in obesity

The world is facing an unprecedented epidemic of obesity. This epidemic has led to major changes in the epidemiology of common diseases such as asthma. Obesity is a major risk factor for new-onset asthma. This article will discuss the role of mechanical and metabolic factors, as well as obesity-related comorbidities, in both causing airway disease and also affecting response to therapy in obese asthmatics. Asthma in obese individuals probably includes a spectrum of disease with at least two distinct phenotypes: early-onset allergic disease complicated by obesity and late-onset disease developing in the setting of obesity. Both phenotypes are distinct from asthma in lean individuals. Treatment of asthma in obesity needs to consider altered response to controller therapy, and the fact that mechanical factors, metabolic inflammation and other comorbidities are probably contributing to airway disease. Future studies should focus on the development of therapies specifically tailored towards the treatment of asthma in obesity.

Gastroesophageal reflux disease and airway hyperresponsiveness: concomitance beyond the realm of chance?

Gastroesophageal reflux disease and asthma are both quite common the world over, and they can coexist. However, the nature of the relationship between these two diseases remains unclear. In this study, we review controversial aspects of the relationships among asthma, airway hyperresponsiveness, and gastroesophageal reflux disease in adults and in children.

Respiratory mechanics and lung tissue remodeling in a hepatopulmonary syndrome rat model

Intrapulmonary vasodilation is a hallmark of the hepatopulmonary syndrome (HPS). However, its effects on respiratory mechanical properties and lung morphology are unknown. To determine these effects, 28 rats were randomly divided to control and experimental HPS groups (eHPS). The spontaneous breathing pattern, gas exchange, respiratory system mechanical properties, and lung and liver morphology of the rats were evaluated. Tidal volume, minute ventilation and mean inspiratory flow were significantly reduced in the eHPS group. Chest wall pressure dissipation against the resistive and viscoelastic components and elastic elastance were increased in the eHPS group. The lung resistive pressure dissipation was lower but the viscoelastic pressure was higher in the eHPS group. The airway volume proportion of collagen and elastic fibers was increased in the eHPS animals (16% and 51.7%; P<0.05 and P<0.001, respectively). The proportion of collagen volume in the vasculature increased 29% in the eHPS animals (P<0.01). HPS presents with respiratory system mechanical disarray as well as airway and vascular remodeling.

Effects of obstructive sleep apnea and gastroesophageal reflux disease on asthma control in obesity

BACKGROUND

Obesity is a risk factor for asthma. Obese asthmatics often have poor asthma control and respond poorly to therapy. It has been suggested that co-morbidities associated with obesity, such as reflux and obstructive sleep apnea, could be important factors contributing to poor asthma control in obese patients.

OBJECTIVES

The purpose of this study was to determine if (1) reflux and/or (2) symptoms of sleep apnea contribute to poor asthma control in obesity.

METHODS

We studied asthmatic subjects participating in a trial of reflux treatment. Participants underwent baseline evaluation of asthma symptoms and lung function. Overall 304 participants underwent esophageal pH probe testing; 246 participants were evaluated for obstructive sleep apnea symptoms.

RESULTS

Of 402 participants in this trial, 51% were obese. Role of reflux in asthma control. Those with higher body mass index (BMI) reported a higher prevalence of reflux symptoms, but the prevalence of pH probe acid reflux was similar in all groups. Reflux was not associated with measures of asthma control in obese patients. Role of obstructive sleep apnea in asthma control. Symptoms and self-report of obstructive sleep apnea were more common with increasing BMI and associated with worse asthma control as measured by the Juniper Asthma Control questionnaire and Asthma Symptom Utility Index.

CONCLUSIONS

Our data suggest that obstructive sleep apnea, but not gastroesophageal reflux disease, may contribute significantly to poor asthma control in obese patients.

Sensory detection and responses to toxic gases: mechanisms, health effects, and countermeasures

The inhalation of reactive gases and vapors can lead to severe damage of the airways and lung, compromising the function of the respiratory system. Exposures to oxidizing, electrophilic, acidic, or basic gases frequently occur in occupational and ambient environments. Corrosive gases and vapors such as chlorine, phosgene, and chloropicrin were used as warfare agents and in terrorist acts. Chemical airway exposures are detected by the olfactory, gustatory, and nociceptive sensory systems that initiate protective physiological and behavioral responses. This review focuses on the role of airway nociceptive sensory neurons in chemical sensing and discusses the recent discovery of neuronal receptors for reactive chemicals. Using physiological, imaging, and genetic approaches, Transient Receptor Potential (TRP) ion channels in sensory neurons were shown to respond to a wide range of noxious chemical stimuli, initiating pain, respiratory depression, cough, glandular secretions, and other protective responses. TRPA1, a TRP ion channel expressed in chemosensory C-fibers, is activated by almost all oxidizing and electrophilic chemicals, including chlorine, acrolein, tear gas agents, and methyl isocyanate, the highly noxious chemical released in the Bhopal disaster. Chemicals likely activate TRPA1 through covalent protein modification. Animal studies using TRPA1 antagonists or TRPA1-deficient mice confirmed the role of TRPA1 in chemically induced respiratory reflexes, pain, and inflammation in vivo. New research shows that sensory neurons are not merely passive sensors of chemical exposures. Sensory channels such as TRPA1 are essential for maintenance of airway inflammation in asthma and may contribute to the progression of airway injury following high-level chemical exposures.

Airway responses to esophageal acidification

The effects of esophageal acidification on airway function are unclear. Some have found that the esophageal acidification causes a small increase in airway resistance, but this change is too small to cause significant symptoms. The aims of this study were to investigate the effects of esophageal acidification on multiple measures of airway function in chloralose-anesthetized cats. The esophagus was cannulated and perfused with either 0.1 M PBS or 0.1 N HCl at 1 ml/min as the following parameters were quantified in separate experiments: diameter of bronchi (n = 5), tracheal mucociliary transport rate (n = 4), tracheobronchial mucus secretion (n = 7), and lung function (n = 6). We found that esophageal acidification for 10-30 min decreased bronchial diameters primarily of the smaller low-resistance airways (10-22%, P < 0.05), decreased tracheal mucociliary transport (53%, 8.7 +/- 2.4 vs. 4.1 +/- 1.3 mm/min, P < 0.05), increased tracheobronchial mucus secretion (147%, 3.4 +/- 0.7 vs. 8.4 +/- 2.6 mg/10 min, P < 0.05), and caused no change in total lung resistance or dynamic compliance (P > 0.05). Considering that tracheal mucociliary transport rate is governed in part by mucus secretion, we concluded that the primary airway response to esophageal acidification observed is increased mucus secretion. Airway constriction may act to assist in rapid secretion of mucus and to increase the effectiveness of coughing while not affecting lung resistance or compliance. Given the buffering capabilities of mucus, esophageal acidification activates appropriate physiological responses that may act to neutralize gastroesophageal reflux that reaches the larynx, pharynx, or lower airways.

The frontiers of reflux disease

Gastroesophageal reflux disease has frequently been implicated in a wide variety of complications beyond the esophagus. These so-called "extraesophageal" disorders range from diseases of the respiratory tract, such as asthma and bronchitis, to more remote sites and conditions such as otitis and dental erosion. Many articles proposing a link between reflux disease and a multitude of extraesophageal complications have been published, but indisputable evidence that these conditions are caused by reflux disease is rare. Much of the support for a link between reflux disease and a number of extraesophageal complications is based on the observation that reflux disease frequently coexists with other disorders. A causal link is difficult to prove, however, and this review aims to critically evaluate the available evidence, looking, where possible, at longitudinal studies, expert diagnoses, and response to acid-suppressive therapy as a means of determining the true relationship between GERD and its putative extraesophageal complications.

Effects of exercise training on papain-induced pulmonary emphysema in Wistar rats

The purpose of the present study was to evaluate the role of exercise training on the development of papain-induced emphysema in rats. Our hypothesis was that the increase in pulmonary tissue stretching associated with exercise could increase the severity of a protease-induced emphysema. Wistar rats were randomly assigned to four groups (n = 10 for each group) that received, respectively, intratracheal infusion of papain (6 mg in 1 ml of 0.9% NaCl) or vehicle and were submitted or not to a protocol of exercise on a treadmill. Rats exercised at 13.3 m/min, 6 days/wk, for 9 wk (increasing exercise time, from 10 to 35 min). We measured respiratory system elastance and resistance, the size and weight of the heart, and pulmonary mean linear intercept (Lm). After 9 wk of exercise training, there were no differences in respiratory system resistance and elastance values among the four experimental groups. Volume of the heart was significantly greater in rats submitted to exercise training (P = 0.007) compared with sedentary rats due to increases in volumes of both right and left cardiac chambers. Lm was significantly greater in rats that received papain compared with saline-infused rats (P = 0.025). Surprisingly, this was true, even though there was no significant decrease in elastance, possibly due to connective tissue remodeling. However, Lm was significantly greater in papain + exercise rats compared with rats that received papain and were not submitted to exercise. We conclude that exercise training can increase alveolar damage induced by papain infusion.

Acid stress in the pathology of asthma

Although alteration of airway pH may serve an innate host defense capacity, it also is implicated in the pathophysiology of obstructive airway diseases. Acid-induced asthma appears in association with gastroesophageal reflux after accidental inhalation of acid (fog, pollution, and workplace exposure) and in the presence of altered airway pH homeostasis. Endogenous and exogenous exposures to acids evoke cough, bronchoconstriction, airway hyperreactivity, microvascular leakage, and heightened production of mucous, fluid, and nitric oxide. Abnormal acidity of the airways is reflected in exhaled breath assays. The intimate mechanisms of acid-induced airway obstruction are dependent on activation of capsaicin-sensitive sensory nerves. Protons activate these nerves with the subsequent release of tachykinins (major mediators of this pathway) that, in conjunction with kinins, nitric oxide, oxygen radicals, and proteases, modulate diverse aspects of airway dysfunction and inflammation. The recognition that acid stress might initiate or exacerbate airway obstructive symptomatology has prompted the consideration of new therapies targeting pH homeostasis.