Modulations in extracellular calcium lead to H+-ATPase-dependent acid secretion: a clarification of PPI failure

The H⁺,K⁺-ATPase was identified as the primary proton secretory pathway in the gastric parietal cell and is the pharmacological target of agents suppressing acid secretion. Recently, we identified a second acid secretory protein expressed in the parietal cell, the vacuolar H⁺-ATPase (V-type ATPase). The aim of the present study was to further characterize H⁺-ATPase activation by modulations in extracellular calcium via the calcium sensing receptor (CaSR). Isolated gastric glands were loaded with the pH indicator dye BCECF-AM [2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein acetoxymethyl ester] to measure intracellular pH. Experiments were conducted in the absence of sodium and potassium to monitor H⁺-ATPase-specific transport activity. CaSR was activated with the calcimimetic R568 (400 nM) and/or by modulations in extracellular Ca²⁺. Elevation in calcium concentrations increased proton extrusion from the gastric parietal cell. Allosteric modification of the CaSR via R568 and calcium increased vacuolar H⁺-ATPase activity significantly (ΔpH/min_lowCa²⁺_(0.1mM) = 0.001 ± 0.001, ΔpH/min_normalCa²⁺_(1.0mM) = 0.033 ± 0.004, ΔpH/min_highCa²⁺_(5.0mM) = 0.051 ± 0.005). Carbachol significantly suppressed calcium-induced gastric acid secretion via the H⁺-ATPase under sodium- and potassium-free conditions. We conclude that the V-type H⁺-ATPase is tightly linked to CaSR activation. We observed that proton pump inhibitor (PPI) exposure does not modulate H⁺-ATPase activity. This elevated blood calcium activation of the H⁺-ATPase could provide an explanation for recurrent reflux symptoms while taking a PPI therapy. NEW & NOTEWORTHY This study emphasizes the role of the H⁺-ATPase in acid secretion. We further demonstrate the modification of this proton excretion pathway by extracellular calcium and the activation of the calcium sensing receptor CaSR. The novelty of this paper is based on the modulation of the H⁺-ATPase via both extracellular Ca (activation) and the classical secretagogues histamine and carbachol (inactivation). Both activation and inactivation of this proton pump are independent of PPI modulation.

Evaluation of gastro-oesophageal reflux disease in wheezy infants using 24-h oesophageal combined impedance and pH monitoring

BACKGROUND AND STUDY AIMS

Gastro-oesophageal reflux disease (GERD) is incriminated as a cause of non-asthmatic infantile wheeze. To date, no diagnostic test is considered standard for GERD-related airway reflux diagnosis. Oesophageal combined multiple channel intraluminal impedance and pH (MII-pH) monitoring is proposed to be a sensitive tool for evaluation of all GERD including infantile wheeze. We aimed to determine the GERD prevalence amongst wheezy infants in the first year of life using combined MII-pH versus pH monitoring alone and evaluate the sensitivity and specificity of objective MII-pH monitoring parameters in GERD-associated infantile wheeze diagnosis compared to those of lipid-laden macrophage index (LLMI).

PATIENTS AND METHODS

Thirty-eight wheezy infants below 1year of age were evaluated for GERD using oesophageal combined MII-pH monitoring and LLMI.

RESULTS

Totally, 60.5% of cases had abnormal MII-pH; only 7.9% of them had abnormal pH monitoring. LLMI was significantly higher in wheezy infants with abnormal MII-pH than infants with normal MII-pH monitoring (112±88 versus 70±48; P=0.036). The current definitions of abnormal MII-pH study, reflux index≥10% and distal reflux episodes≥100, had low sensitivity (23%) but high specificity (100% and 96%, respectively) in GERD-related aspiration diagnosis defined by LLMI≥100. Using ROC curves, bolus contact time≥2.4% and proximal reflux episodes≥46 had 61% and 54% sensitivity and 64% and 76% specificity, respectively, in GERD-related aspiration diagnosis.

CONCLUSION

Combined MII-pH is superior to pH monitoring in reflux-associated infantile wheeze diagnosis. Objective data including proximal reflux episodes and bolus contact time should be combined with the current parameters used in reflux-associated infantile wheeze diagnosis.

Clinical Utility of Bronchoalveolar Lavage Pepsin in Diagnosis of Gastroesophageal Reflux among Wheezy Infants

Background. There is no gold standard test for diagnosis of gastroesophageal reflux disease (GERD) associated infantile wheezing. Objectives. To evaluate the value of bronchoalveolar lavage (BAL) pepsin assay in diagnosis of GERD in wheezy infants. Methods. Fifty-two wheezy infants were evaluated for GERD using esophageal combined impedance-pH (MII-pH) monitoring, esophagogastroduodenoscopy with esophageal biopsies, and BAL pepsin. Tracheobronchial aspirates from 10 healthy infants planned for surgery without history of respiratory problems were examined for pepsin. Results. Wheezy infants with silent reflux and wheezy infants with typical GERD symptoms but normal MII-pH had significantly higher BAL pepsin compared to healthy control (45.3 ± 8.6 and 42.8 ± 8 versus 29 ± 2.6, P < 0.0001 and P = 0.011, resp.). BAL pepsin had sensitivity (61.7%, 72 %, and 70%) and specificity (55.5%, 52.9%, and 53%) to diagnose GERD associated infantile wheeze compared to abnormal MII-pH, reflux esophagitis, and lipid laden macrophage index, respectively. Conclusion. A stepwise approach for assessment of GERD in wheezy infants is advised. In those with silent reflux, a trial of antireflux therapy is warranted with no need for further pepsin assay. But when combined MII-pH is negative despite the presence of typical GERD symptoms, pepsin assay will be needed to rule out GERD related aspiration.

The Relationship Between Gastroesophageal Reflux and Chronic Unexplained Cough in Children

The aim of this study was to assess the association between chronic cough and acid or weakly acid gastroesophageal reflux (GER) determined by 24-hour multichannel intraluminal impedance-pH monitoring and to assess whether the association is age dependent. Overall 150 children (mean age 7.5 years; range 0.3-18.0 years; male/female 90/60) were enrolled. Median of 87.5% (0% to 100%) of all cough episodes were associated with reflux; 9% (0% to 100%) with acidic and 60% (0% to 100%) with weakly acidic episodes. In 52 children (34.7%), all cough episodes were associated with GER (100% association). Children younger than 2 years had significantly higher number of cough episodes associated with total (P = .03) and weakly acidic GER (P = .01). Binary logistic regression confirmed that only increase in age decreases the risk for complete (100%) association between cough episode and GER. Cough is significantly associated with weakly acidic GER and children of younger age are at higher risk.

Weakly acidic gastroesophageal refluxes are frequently triggers in young children with chronic cough

OBJECTIVE

To evaluate whether the proportion of acid and weakly acidic refluxes preceding cough bursts could be different in infants, preschool- and school-aged children with chronic, unexplained cough.

PATIENTS AND METHODS

One hundred six children with unexplained chronic cough, not receiving acid suppressive therapy, underwent impedance-pH monitoring. They were divided into Group A: <2 years (21 pts), Group B: ≥2 to ≤6 years (41 pts), and Group C: >6 years (44 pts). Reflux was defined as acid (pH <4), weakly acidic (WA; pH 4-7), and weakly alkaline (pH >7).Cough episodes were considered temporally associated with gastroesophageal reflux (GER) when occurring within 2 min after a GER episode.

RESULTS

Impedance-pH detected 55.50 (39.00-76.00) reflux episodes/patient with an acid-to-WA reflux event ratio of 3.31 (1.55-8.33). This parameter was significantly lower in Group A (1.33 [0.41-3.40]) than in Group B (3.06 [2.00-6.50]; P < 0.05] and Group C (5.09 [2.34-12.43; P < 0.001]). No cough episode was preceded by weakly alkaline refluxes in any patient. During impedance-pH recording, 93 patients (87.7%) had at least one cough episode that had been preceded by impedance refluxes in 83 patients. In this latter group (83 pts), the median number of cough episodes was 12.0 (5.0-25.5), of which 48.15% (30.15-71.43%) were preceded by refluxes; GER-preceded cough episodes were similar in the three groups. The majority of children had cough episodes preceded by acid refluxes in the total population (78.3%), in Group B (80.5%) and in Group C (93.7%), but not in Group A (40.0%; P < 0.001).

CONCLUSIONS

In addition to acid, also a significant proportion of WA GER may precede cough episodes in young children with persistent cough, possibly explaining the inconstant effects of anti-acid treatment on respiratory symptoms.

Acid and weakly acid gastroesophageal refluxes and type of respiratory symptoms in children

OBJECTIVES

To evaluate the association between the frequency of acid reflux (AR) and weakly acid reflux (WAR) and specific respiratory symptoms (RS) in childhood.

STUDY DESIGN

We retrospectively reviewed medical records of children with difficult-to-treat RS, not under acid suppressive therapy, and with a positive multiple intraluminal esophageal impedance (pH/MII) monitoring. To discriminate children with prevalent AR and WAR events, a ROC curve was designed and the distribution of the different RS in children with prevalent AR or WAR events was analyzed.

RESULTS

A higher number of AR over WAR events was detected (p < 0.0001) but the WAR-to-AR events ratio progressively decreased with the age of the subjects (p < 0.01). Similar total number of reflux events was found in the three age group and in children with a more prevalent WAR or AR. The most prevalent RS, equally distributed among the three age groups, were persistent and/or nocturnal cough, wheezy bronchitis/asthma, and recurrent lower respiratory tract infections (RLRTI). Apnoea was most frequent in infants (p = 0.036). A higher frequency of RLRTI, but not of nocturnal cough or wheezy bronchitis/asthma, was shown in WAR as compared with AR patients (p = 0.040), and specifically those in the school-aged group (p = 0.013). Age and WAR were respectively identified as independent predictors of apnoea and RLRTI (p < 0.05).

CONCLUSION

WAR events are common in children with gastroesophageal reflux and difficult-to-treat RS and often associated with RLRTI. These findings support the role of pH/MII monitoring in the evaluation of these patients and may explain the disappointing clinical results often observed with anti-acid treatments.

Tracheal compression by aberrant innominate artery: clinical presentations in infants and children, indications for surgical correction by aortopexy, and short- and long-term outcome

BACKGROUND

Aberrant innominate artery (AIA) may cause various degrees of tracheal compression (TC).

PURPOSE

The aim of this study is to define the clinical manifestations of AIA-induced TC and outcome after aortopexy in infants and older children.

METHODS

Children with significant AIA-induced TC were evaluated, and information after surgery or conservative management was obtained by telephonic interview after 1 to 4 years since discharge.

RESULTS

Overall, 15 infants (mean age, 8 months; group A) and 13 older children (mean age, 56 months; group B) were evaluated. Although median age at onset of symptoms was comparable in the 2 groups, mean delay to diagnosis was higher in group B (P < .0001). Analysis of the most prevalent symptoms showed that reflex apneas were more frequent in group A (P = .02), whereas chronic "intractable" cough was more frequent in group B (P < .001). Because of the type and severity of symptoms and the degree of TC, 16 patients underwent aortopexy. Follow-up evaluation showed, in all but 1 patient, a significant improvement in symptoms and quality of life, measured by a modified Visick score.

CONCLUSIONS

Aberrant innominate artery-TC leads to a variety of respiratory disorders, with a difference in prevalence between infants and older children. When choice of treatment is based on clinical presentation and degree of TC, a good clinical outcome may be obtained also in children in whom aortopexy is indicated, that is, those presenting initially with more severe symptoms.