Mechanisms of Gastric Juice-Induced Hyperpermeability of the Cultured Human Tracheal Epithelium

doi:10.1378/chest.111.2.454

Chest

Volume 111, Issue 2, February 1997, Pages 454-459

https://doi.org/10.1378/chest.111.2.454 Get rights and content

Purpose

The respiratory aspiration of the stomach contents causes severe lung damage called aspiration pneumonia. The present study was undertaken to elucidate whether mucosal exposure of gastric juice causes hyperpermeability of the human airway epithelium and to determine the mechanisms responsible for gastric juice-induced airway epithelial damage.

Materials and methods

Gastric juice was collected from 46 normal adults via gastroscope and samples were analyzed for pH, osmolarity, and concentration of pepsin and trypsin. Tracheal surface epithelial cells were obtained from 16 autopsies, cultured onto porous filters, and mounted in the Ussing chamber. Electrical conductance (G) was measured before and after exposure of cells to gastric juice or Krebs-Henseleit solution with pH at 1.8, 2.8, 4.0, or 7.4 in the presence or absence of pepsin. D-[³H] mannitol flux study across the epithelial layer and histologic observations using an inverted microscope were also performed after exposure of cells to gastric juice.

Results

Exposure of cultured human tracheal epithelium to gastric juice caused increases in G in a time- and pH-dependent fashion. A pepsin inhibitor (pepstatin A) inhibited gastric juice-induced increases in G at a pH of 2.8, and the addition of pepsin augmented increases in G induced by the Krebs-Henseleit solution at a pH of 1.8 and 2.8. Lowering the osmolarity of the solution to levels similar to gastric juice also potentiated increases in G induced by acid and pepsin. Gastric juice caused increases in D-[³H] mannitol flux across the epithelial layer bidirectionally, and microscopic observation revealed separation of the intercellular space and cell detachment from culture vessels after exposure of cells to gastric juice.

Conclusion

Gastric juice causes hyperpermeability across human airway epithelium probably through the additive effects of gastric acid, pepsin activity, and lower osmolarity.

Section snippets

Collection of Gastric Juice

Gastric juice was collected from 46 patients (mean age, 33 years; range, 18 to 42 years) who complained of GI symptoms such as stomach pain, nausea, or heartburn, and were judged to have no overt gastroduodenal disease with endoscopic examination. The patients had fasted for more than 12 h and had not taken antacid drugs, histamine H₂-blockers, or proton pump inhibitors before the endoscopic examination. A flexible fiberoptic gastroscope (9.8 mm outer diameter; GIF-XK 200; Olympus; Tokyo,

Composition of the Gastric Juice

Table 1 shows the physicochemical properties and enzymatic analysis of the gastric juice that was exposed to the cultured human tracheal epithelial cells. The pH of the gastric juice was as low as 1.77±0.21 and the gastric juice contained a significant amount of proteolytic enzyme, pepsin.

Effects of pH of the Gastric Juice on G

Figure 1 shows time course changes in G induced by the crude gastric juice (pH, 1.77±0.21) and gastric juice adjusted to a pH of 2.8, a pH of 4.0, and a pH of 7.4 in the cultured tracheal epithelium. The pH of

Discussion

The cultures of airway epithelium used were poorly differentiated with a baseline short-circuit current less than 10% that of human bronchial epithelium.¹⁸ Ultrastructurally, they were highly flattened and lacked both cilia and secretory granules. The culture conditions developed by Yamaya et al⁷ produce human tracheal epithelial cells little different from the native tissue in their ultrastructure and electrical properties.¹⁹ By using the cultured human tracheal epithelium, we showed that

References (26)

W Rick et al.
Pepsin
G Lake-Bakaar et al.
Urinary immunoreactive trypsin excretion: a non-invasive screening test for pancreatic cancer
Lancet
(1979)
ME Meyerhoff et al.
Ion-selective electrodes
AG Gornall et al.
Determination of serum proteins by means of the biuret reaction
J Biol Chem
(1949)
CL Mendelson
The aspiration of stomach contents into the lungs during obstetric anesthesia
Am J Obstet Gynecol
(1946)
JW Wynne et al.
Respiratory aspiration of stomach contents
Ann Intern Med
(1977)
JR Teabeaut
Aspiration of gastric contents: an experimental study
Am J Pathol
(1952)
WC Awe et al.
The pathophysiology of aspiration pneumonitis
Surgery
(1966)
LJ Greenfield et al.
Pulmonary effects of experimental graded aspiration of hydrochloric acid
Ann Surg
(1969)
JW Wynne et al.
Tracheal mucosal damage after aspiration: a scanning electron microscope study
Am Rev Respir Dis
(1981)

RT Lewis et al.

Cardiorespiratory studies in critical illness: changes in aspiration pneumonitis

Arch Surg

(1971)

M Yamaya et al.

Differentiated structure and function of cultures from human tracheal epithelium

Am J Physiol

(1992)

JE Murphy et al.

Evaluation of renal function, and water, and electrolyte, and acid base balance

Cited by (23)

Post-intubation tracheobronchomalacia in a young adult: A rare case report
2018, Respiratory Medicine Case Reports
Citation Excerpt :
We proposed a mechanism of prolonged internal compression that can predispose degeneration of normal cartilage. For GERD, studies in the past proposed repeated exposure of tracheal tissue to an acid milieu and digestive enzymes from GERD might alter the matrix protein structure, resulting in the reduced tensile strength of tracheal tissue, leading to TBM [3,4]. Primary TBM is less likely in this case.
Tracheobronchomalacia (TBM) is characterized by weakness of cartilaginous supporting structures of tracheal and bronchial walls, resulting in central airway obstruction. It is a rare condition that can occur after prolonged intubation. Here, we report a 26-year-old, alcoholic male who had TBM, mild subglottic, and severe tracheal stenosis following 2 weeks of intubation.
Subglottic and tracheal stenosis can occur after extubation but TBM is uncommon. The exact mechanism is still unknown but post-intubation TBM is a life-threatening condition with high morbidity and mortality if left untreated. Early detection and timely management can improve the outcome of patients.
Acid stress in the pathology of asthma
2004, Journal of Allergy and Clinical Immunology
Citation Excerpt :
Indeed, this chemical reaction almost certainly explains the immediate 2–log-order increase in exhaled NO seen on instillation of 0.1 N hydrochloric acid into the canine lung.78 Airway hydration and mucous production can be affected by pH. A pH of 5.0 activates outwardly rectifying chloride channels in rat fetal lung epithelial cells,79 and pH appears to be an important determinant of the airway epithelial hyperpermeability caused by exposure to gastric contents.80 Furthermore, the viscosity of sputum can be greatly increased at slightly low pH values.
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.
Acid aspiration induces bacterial pneumonia by enhanced bacterial adherence in mice
2002, Microbial Pathogenesis
The issue of whether acid aspiration facilitates bacterial pneumonia caused by Pseudomonas aeruginosa by enhanced bacterial adherence was examined in mice. Survival or the number of bacteria in lung tissues was evaluated after an intratracheal challenge of hydrochloric acid (HCl), a sublethal dose of P. aeruginosa, or both in mice. Bacterial adherence to the tracheal epithelium after acid aspiration was also examined by scanning electron microscopy. A simultaneous intratracheal challenge of 50 μl of 10⁻¹ N HCl, but not 10⁻² to 10⁻⁴ N HCl, combined with a sublethal dose of P. aeruginosa significantly increased the number of bacteria in the lung tissues and decreased survival, while all mice that received either HCl or P. aeruginosa survived. Significantly higher numbers of adherent bacteria on the tracheal epithelium were found in mice that received 10⁻¹N HCl, compared with mice that received HCl (10⁻² to 10⁻⁴ N) or saline. These data indicate that acid aspiration induced airway epithelial injury and enhanced P. aeruginosa adherence to the epithelium, and led to the subsequent development of bacterial pneumonia in mice. Enhanced bacterial adherence on the acid-injured epithelium may explain fatal bacterial pneumonias in patients with respiratory aspiration of gastric contents.
Function of the eustachian tube after weekly exposure to pepsin/hydrochloric acid
2001, Otolaryngology - Head and Neck Surgery
Objective: To determine the effects of repeated pepsin/hydrochloric acid (HCl) exposure on the eustachian tube (ET). Study Design and Setting: ET function was studied in 22 rats. Group I (control) rats received transtympanic phosphate buffered saline solution; groups II (0.5 mg/ml) and III (2.0 mg/ml) received transtympanic pepsin/HCl. Test solutions were applied on day 0 with ET function evaluated on days 1, 2, 3, and 7 after exposure. Each 7-day period represents 1 cycle; all groups underwent 4 cycles. ET function was evaluated using passive opening and closing pressure, and active clearance of positive and negative pressure tests. Results: Rats exposed to pepsin/HCl had elevated passive opening pressures and a decreased ability to clear positive and negative pressure. A temporal relationship exists. Conclusion: The results suggest middle ear exposure to pepsin/HCl leads to ET dysfunction in rats, and that this dysfunction is enhanced with repeated exposures. Significance: Gastroesophageal reflux may induce ET dysfunction. (Otolaryngol Head Neck Surg 2001;125:123-9.)
Combined effects of both bacteria and gastric juice on pneumonia in mice
1999, Respiration Physiology
The effects of a combined inoculation of gastric juice and Streptococcus pneumoniae on the lungs of mice was investigated. Survival rates of mice inoculated with bacteria alone, gastric juice alone, and both bacteria and gastric juice were compared over 18 days. Xanthine oxidase (XO) activities in the lung tissues of mice inoculated with bacteria and gastric juice were measured and injected with a free radical scavenger, pyran-superoxide dismutase (pyran-SOD). A high mortality rate was observed in mice inoculated with both gastric juice and Streptococcus pneumoniae (81%). Mice inoculated with either Streptococcus pneumoniae or gastric juice showed a separate mortality rate of up to 10% during 18 days after inoculation. XO activity in the lung tissue of the mice inoculated with both gastric juice and bacteria was higher than in mice inoculated with either of them separately. The high mortality rate in the group inoculated with both two agents was reduced to 25% by the administration of pyran-SOD. XO activity raised by Streptococcus pneumoniae and gastric juice was significantly reduced by pyran-SOD. Thus, we suggest an important role in the combined effects of gastric juice and bacteria on pneumonia.
Proton pump inhibitor ameliorates taste disturbance among patients with laryngopharyngeal reflux: A randomized controlled study
2019, Tohoku Journal of Experimental Medicine

View all citing articles on Scopus

View full text

Chest

Mechanisms of Gastric Juice-Induced Hyperpermeability of the Cultured Human Tracheal Epithelium

Purpose

Materials and methods

Results

Conclusion

Section snippets

Collection of Gastric Juice

Composition of the Gastric Juice

Effects of pH of the Gastric Juice on G

Discussion

Lancet

J Biol Chem

Am J Obstet Gynecol

Respiratory aspiration of stomach contents

Ann Intern Med

Aspiration of gastric contents: an experimental study

Am J Pathol

The pathophysiology of aspiration pneumonitis

Surgery

Pulmonary effects of experimental graded aspiration of hydrochloric acid

Ann Surg

Tracheal mucosal damage after aspiration: a scanning electron microscope study

Am Rev Respir Dis

Cardiorespiratory studies in critical illness: changes in aspiration pneumonitis

Arch Surg

Differentiated structure and function of cultures from human tracheal epithelium

Am J Physiol

Evaluation of renal function, and water, and electrolyte, and acid base balance