An Investigation of Airway Acidification in Asthma Using Induced Sputum

Abstract

Patients with asthma show lower pH than healthy subjects. Patients with poorly controlled asthma seem to have the lowest induced-sputum pH, independent of the GINA (Global Initiative for Asthma) severity level. In conclusion, induced sputum is a feasible, repeatable, noninvasive method to measure airway pH. The pH in induced sputum may reflect a different aspect of asthma from sputum eosinophils and be related to different pathophysiologic factors.

Extracellular acidification stimulates IL-6 production and Ca2+mobilization through proton-sensing OGR1 receptors in human airway smooth muscle cells

“…Previous studies have shown that airway acidification is a well-recognized symptom in asthma and contributes to the pathophysiology of the disease (26,40). The pH of the airway of healthy subjects is in the range of 7.5 to 7.7, and that of patients with asthma is from 5.2 to 7.1, depending on the severity (26,40).…”

“…The pH of the airway of healthy subjects is in the range of 7.5 to 7.7, and that of patients with asthma is from 5.2 to 7.1, depending on the severity (26,40). It is known that protons sensitize the capsaicin-sensitive TRPV1 channel and/or ASICs in sensory nerves, producing local axonal reflexes with the subsequent release of tachykinins for the induction of cough and other asthmatic symptoms (17,40).…”

“…It is well known that asthma is associated with airway acidification (22,26,40), which has been shown to play both beneficial roles, i.e., inhibition of the survival of bacteria under an acidic environment, and detrimental roles, i.e., severe breath-inhibiting cough, bronchial obstruction, and bronchial hyperresponsiveness (40). Moreover, asthma symptoms are known to be exacerbated by acid stress to the airway caused by gastro-esophageal reflux disease (40).…”

Emerging roles for the pH-sensing G protein-coupled receptors in response to acidotic stress

“…Respiratory acidosis has been observed in several respiratory diseases, such as chronic obstructive pulmonary disease (COPD) and asthma. 12,[61][62][63] Asthma is a chronic inflammatory disease, which is associated with bronchial hyper-responsiveness, airway inflammation, remodeling, and acidic features. Ichimonji et al demonstrated in human airway smooth muscle cells that GPR68 mediated extracellular acidification-induced production of pro-inflammatory cytokine IL-6 and increased intracellular Ca 2+ concentration.…”

Tracheal aspirate pH is alkaline in pre-term human infants

“…Recent evidence suggests that abnormal airway pH may be a determinant of lung disease [3][4][5][6][7][8]. Mature alveolar type-II cells secrete surfactant at low pH (,3-5) [6].…”