Human Lung Mucous Glands Manifest Evidence of the H+/K+-ATPase Proton Pump

Proton pump inhibitor use and risk of pneumonia: a self-controlled case series study

BACKGROUND

Recent research indicates that use of proton pump inhibitors (PPIs) is associated with pneumonia, but existing evidence is inconclusive because of methodological issues. This study aimed to answer whether PPI-use increases risk of pneumonia while taking the methodological concerns of previous research into account.

METHODS

This population-based and nationwide Swedish study conducted in 2005-2019 used a self-controlled case series design. Data came from national registries for medications, diagnoses, and mortality. Conditional fixed-effect Poisson regression provided incidence rate ratios (IRR) with 95% confidence intervals (CI) for pneumonia comparing PPI-exposed periods with unexposed periods in the same individuals, thus controlling for confounding. Analyses were stratified by PPI-treatment duration, sex, age, and smoking-related diseases. Use of histamine type-2 receptor antagonists (used for the same indications as PPIs) and risk of pneumonia was analysed for assessing the validity and specificity of the results for PPI-therapy and pneumonia.

RESULTS

Among 519,152 patients with at least one pneumonia episode during the study period, 307,709 periods of PPI-treatment occurred. PPI-use was followed by an overall 73% increased risk of pneumonia (IRR 1.73, 95% CI 1.71-1.75). The IRRs were increased across strata of PPI-treatment duration, sex, age, and smoking-related disease status. No such strong association was found between histamine type-2 receptor antagonist use and risk of pneumonia (IRR 1.08, 95% CI 1.02-1.14).

CONCLUSIONS

PPI-use seems to be associated with an increased risk of pneumonia. This finding highlights a need for caution in using PPIs in individuals with a history of pneumonia.

Proton pump inhibitor usage associates with higher risk of first episodes of pneumonia and peritonitis in peritoneal dialysis patients

Background

A large number of studies have shown that proton pump inhibitors (PPIs) are associated with infection events. Therefore, we retrospectively evaluated the association of PPI therapy with the occurrence of first pneumonia and peritoneal dialysis(PD)-related peritonitis events in the maintenance PD patients.

Methods

We collected PD patients in two large hospitals from January 1, 2012 to December 31, 2016, and divided them into the PPI group and the non-PPI group. Multivariate Cox proportional hazards models were applied to evaluate the cumulative incidence and hazard ratios (HRs). Inverse probability of treatment weight (IPTW) method was used to adjust for covariate imbalance between the two groups and further confirm our findings.

Results

Finally, 656 PD patients were included for data analysis, and the results showed that PPI usage was associated with an increased risk of pneumonia [HR 1.71; 95% CI 1.06-2.76; p = 0.027] and peritonitis [HR 1.73; 95% CI 1.24-2.40; p = 0.001]. IPTW-adjusted HRs for the association of PPIs with pneumonia and peritonitis were 1.58 (95% CI:1.18-2.12; p = 0.002) and 2.33 (95% CI:1.91-2.85; p < 0.001), respectively. Moreover, the competitive risk model proved that under the conditions of competition for other events(including transfer to hemodialysis therapy, kidney transplant, transfer from our research center, loss to follow-up, and death), the differences in endpoints events between the two groups were still statistically significant (p = 0.009, p < 0.001, respectively).

Conclusions

PPIs was associated with an increased risk of first pneumonia and PD-related peritonitis events in PD patients, which reminds clinicians to be cautious when prescribing acid-suppressing drugs for PD patients.

Proton Pump Inhibitors: Current Use and the Risk of Coronavirus Infectious Disease 2019 Development and its Related Mortality. Meta-analysis

BACKGROUND

The ongoing Coronavirus Infectious Disease (COVID-19) pandemic is a global health crisis that has had a magnanimous worldwide impact on all aspects of people's lives. Several observational studies investigated the relationship between Proton Pump Inhibitors use and the risk of COVID-19 development and mortality.

AIM OF THE STUDY

The aim of this meta-analysis is to investigate the association between current PPIs use and the development of COVID-19 as well as its mortality.

METHODS

Pubmed, Google Scholar, ScienceDirect and medRxiv were searched until November 21, 2020 using the following keywords: proton pump inhibitors and COVID-19 as well as their related MESH terms. The studies considered in the meta-analysis were either cohort or case-control in design and adjusted for confounding factors. The quality of the studies included in this meta-analysis was assessed using the Newcastle-Ottawa Scale. In addition, a random-effects model was used to calculate the pooled Odds Ratio (ORs) and the corresponding confidence interval (95% CI). Heterogeneity was evaluated using The Cochran's Q heterogeneity test and I2 statistic.

RESULTS

Six observational studies with 195,230 participants were included. In this meta-analysis, current use of PPIs increased risk of COVID-19 development (OR = 1.19; 95% CI: 0.62-2.28) and mortality (OR = 1.67; 95% CI: 1.41-1.97).

CONCLUSIONS

Our meta-analysis indicates that current PPIs use significantly increased the risk of COVID-19 mortality, but it did not reach a significant threshold in regards to the risk of COVID-19 development.

The risk of community-acquired pneumonia in children using gastric acid suppressants

BACKGROUND

With the increased use of acid suppressants, significant potential complications such as community-acquired pneumonia (CAP) are becoming more apparent. Paradoxically, in spite of an increased focus on potential complications, there is an increased use of acid suppressants in children and a lack of data specifically targeting the association between acid suppressants and CAP. Our main objective was to evaluate the risk of CAP in children using acid suppressants (proton pump inhibitors (PPIs) and/or histamine-2 receptor antagonists (H2RAs)).

METHODS

We performed a cohort study using data from the UK Clinical Practice Research Datalink. All patients aged 1 month to 18 years with a prescription of acid suppressants were included and matched to up to four unexposed children. Time-varying Cox proportional hazards models were used to estimate the risk of CAP. The cohort consisted of 84 868 exposed and 325 329 unexposed children.

RESULTS

Current use of PPIs and H2RAs was associated with an increased risk of CAP (adjusted hazard ratio 2.05 (95% CI 1.90-2.22) and 1.80 (95% CI 1.67-1.94), respectively). The risk was even greater in patients with respiratory disease. Long-term use (≥211 days) of PPIs and H2RAs led to a significantly greater risk of CAP compared with short-term use (<31 days). After cessation of therapy, the risk remained increased for the following 7 months.

CONCLUSION

The use of acid suppressants in children was associated with a doubled risk of CAP. This risk increased with chronic use and respiratory disease, and remained increased after discontinuation of therapy.

Xenopus epidermal and endodermal epithelia as models for mucociliary epithelial evolution, disease, and metaplasia

The Xenopus embryonic epidermis is a powerful model to study mucociliary biology, development, and disease. Particularly, the Xenopus system is being used to elucidate signaling pathways, transcription factor functions, and morphogenetic mechanisms regulating cell fate specification, differentiation and cell function. Thereby, Xenopus research has provided significant insights into potential underlying molecular mechanisms for ciliopathies and chronic airway diseases. Recent studies have also established the embryonic epidermis as a model for mucociliary epithelial remodeling, multiciliated cell trans-differentiation, cilia loss, and mucus secretion. Additionally, the tadpole foregut epithelium is lined by a mucociliary epithelium, which shows remarkable features resembling mammalian airway epithelia, including its endodermal origin and a variable cell type composition along the proximal-distal axis. This review aims to summarize the advantages of the Xenopus epidermis for mucociliary epithelial biology and disease modeling. Furthermore, the potential of the foregut epithelium as novel mucociliary model system is being highlighted. Additional perspectives are presented on how to expand the range of diseases that can be modeled in the frog system, including proton pump inhibitor-associated pneumonia as well as metaplasia in epithelial cells of the airway and the gastroesophageal region.

Gastric H+/K+-ATPase Expression in Normal Laryngeal Tissue and Laryngeal Carcinoma

Background

Several studies have suggested that laryngopharyngeal reflux disease (LPRD) or gastroesophageal reflux disease (GERD) is an independent risk factor for laryngeal carcinoma. However, it remains unclear whether either condition affects the level of H⁺/K⁺-ATPase expression in laryngeal carcinoma.

Materials and Methods

Immunohistochemistry, real-time RT-PCR, and Western blotting were used to explore the distributions of proton pump (H⁺/K⁺-ATPase) α- and β-subunits in normal laryngeal tissue and laryngeal carcinoma.

Results

Messenger RNAs encoding both the α- and β-subunits were found in the normal epiglottic, ventricular fold, vocal fold, and arytenoid mucosae, as well as epiglottic cartilage. The distributions and expression levels of H+/K+-ATPase α-subunits in various laryngeal subregions did not significantly differ in IHC, RT-PCR, or Western blotting. However, Western blotting revealed a significant difference between the expression level of the β-subunit protein in the epiglottic cartilage and the levels in other sites. The expression levels of both subunits were significantly higher in carcinomatous than in paracarcinomatous tissue and normal laryngeal tissue. The mean follow-up duration was 66.2 months (range, 17–162 months). In all, 4 patients died during follow-up, 4 were lost to follow-up, and 22 were alive and free of disease at the end of follow-up. Two patients developed lung metastases and six developed disease recurrences (at 2, 8, 14, 16, 36, and 41 months). The 3- and 5-year overall survival (OS) rates were 93.0% and 77.0%, respectively. Univariate analyses showed that the 5-year OSs were significantly associated with the T, N, and clinical stages but not with age, alcohol use, pathological differentiation, or the expression levels of the α- or β-subunits (as revealed by IHC, RT-PCR, or Western blotting). However, in multivariate regression analyses, the 5-year OSs were not significantly associated with any clinicopathological factor or the expression levels of either subunit.

Conclusion

H⁺/K⁺-ATPase is expressed in the normal larynx, including in the epiglottic cartilage and the mucosae of the epiglottis, ventricular fold, and arytenoid vocal fold. The expression levels of the H⁺/K⁺-ATPase α- and β-subunits in laryngeal carcinomas were higher than in normal laryngeal tissues.

Anti-parietal cell autoimmunity is associated with an accelerated decline of lung function in IPF patients

BACKGROUND

Autoantibodies against lung epithelial antigens are often detected in patients with Idiopathic Pulmonary Fibrosis (IPF). Anti-Parietal Cell Antibodies (APCA) target the H+/K+ATPase (proton pump). APCA prevalence and lung H+/K+ATPase expression was never studied in IPF patients.

METHODS

We retrospectively collected clinical, lung function and imaging data from APCA positive patients (APCA+IPF) and compared them with APCA negative IPF patients matched on the date of diagnostic assessment. H+/K+ATPase expression was assessed with immunohistochemistry and PCR.

RESULTS

Among 138 IPF patients diagnosed between 2007 and 2014 and tested for APCA, 19 (13.7%) APCA+ patients were identified. APCA+IPF patients were 16 men and 3 women, mean age 71 years. The median titer of APCA was 1:160. A pernicious anemia was present in 5 patients and preceded the fibrosis in 3 cases. With a mean follow up of 31 months, 2 patients had an exacerbation and 7 patients died. As compared with 19 APCA- IPF patients, APCA+IPF patients had a less severe disease with better DLCO (57% vs 43% predicted), preserved PaO₂ (85 ± 8 mmHg vs 74 ± 11 mmHg), a lower rate of honeycombing on HRCT (58% vs 89%), but they experienced an accelerated decline of FVC (difference 61.4 ml/year; p = .0002). The H+/K+ATPase was strongly expressed by hyperplastic alveolar epithelial cells in the fibrotic lung.

CONCLUSION

Anti-parietal cell autoimmunity is detected in some IPF patients and is associated with an accelerated decline of lung function. Anti-parietal cell autoimmunity may promote lung fibrosis progression.

Proton Pump Inhibitors Did Not Increase Risk of Pneumonia in Patients With Chronic Obstructive Pulmonary Disease

Background

Chronic obstructive pulmonary disease (COPD) involves the airways and pneumonia is a major cause of mortality. Proton pump inhibitors (PPIs) were found to have a positive association with pneumonia. The aim of this study was to investigate the impact of PPIs on the risk of pneumonia in patients with COPD.

Methods

This was a nationwide, population-based, case-control study using data from the National Health Insurance Research Database in Taiwan. The enrolled cases were defined as patients with COPD and appearance of pneumonia between 2001 and 2005. The control group was age- and sex-matched 1:2 with the cases without pneumonia. Potential confounders such as coronary artery disease, hypertension, diabetes mellitus, heart failure, chronic kidney disease, and prescriptions of glucocorticoids over 2 weeks, were included in the analysis. Prescriptions for PPIs were identified and entered into the analysis.

Results

A total of 10,131 COPD patients, including 3,377 cases with pneumonia and 6,754 without, were identified. There were 213 (5.3%) and 436 (6.5%) cases with concurrent PPIs in the two groups, respectively, and the risk of pneumonia was similar (aOR = 0.96; 95% CI: 0.83 - 1.10). Further subgroup analysis found no differences for younger patients (younger than 70 years old; aOR = 1.04; 95% CI: 0.83 - 1.10), elderly patients (older than 70 years old; aOR = 0.96; 95% CI: 0.81 - 1.15), short-term use of PPIs (less than 30 days; aOR = 1.12; CI: 0.53 - 2.34), medium-term use of PPIs (30 - 90 days; aOR = 0.86; CI: 0.72 - 1.03), or long-term use of PPIs (longer than 90 days; aOR = 0.97; CI: 0.81 - 1.15).

Conclusion

PPIs did not contribute to a greater occurrence of pneumonia in COPD patients compared with non-users in this population-based case-control study. Further research is required.

Inhibition of gastric H+,K+-ATPase by 4-(2-butyl-6,7-dichloro-2-cyclopentylindan-1-on-5-yl)oxybutyric acid (DCPIB), an inhibitor of volume-regulated anion channel

4-(2-Butyl-6,7-dichloro-2-cyclopentylindan-1-on-5-yl)oxybutyric acid (DCPIB) has been used as an inhibitor of volume-regulated anion channel (VRAC), which is expressed in almost all cells (IC50 is around 4 µM). Here, we found that DCPIB significantly inhibited the activities of gastric proton pump (H+,K+-ATPase) in isolated gastric tubulovesicles and the membrane sample of the H+,K+-ATPase-expressing cells, and their IC50 values were around 9 µM. In the tubulovesicles, no significant expression of leucine rich repeat containing 8 family member A (LRRC8A), an essential component of VRAC, was observed. The inhibitory effect of DCPIB was also found in the membrane sample obtained from the cells in which LRRC8A had been knocked down. On the other hand, DCPIB had no significant effect on the activity of Na+,K+-ATPase or Ca2+-ATPase. In the H+,K+-ATPase-expressing cells, DCPIB inhibited the 86Rb+ transport activity of H+,K+-ATPase but not that of Na+,K+-ATPase. DCPIB had no effect on the activity of Cl- channels other than VRAC in the cells. These results suggest that DCPIB directly inhibits H+,K+-ATPase activity. DCPIB may be a beneficial tool for studying the H+,K+-ATPase function in vitro.

Risk of community-acquired pneumonia with outpatient proton-pump inhibitor therapy: a systematic review and meta-analysis

BACKGROUND

Proton-pump inhibitors (PPIs) are among the most frequently prescribed medications. Community-acquired pneumonia (CAP) is a common cause of morbidity, mortality and healthcare spending. Some studies suggest an increased risk of CAP among PPI users. We conducted a systematic review and meta-analysis to determine the association between outpatient PPI therapy and risk of CAP in adults.

METHODS

We conducted systematic searches of MEDLINE, EMBASE, CINAHL, Cochrane Central Register of Controlled Trials, Scopus and Web of Science on February 3, 2014. Case-control studies, case-crossover, cohort studies and randomized controlled trials reporting outpatient PPI exposure and CAP diagnosis for patients ≥18 years old were eligible. Our primary outcome was the association between CAP and PPI therapy. A secondary outcome examined the risk of hospitalization for CAP and subgroup analyses evaluated the association between PPI use and CAP among patients of different age groups, by different PPI doses, and by different durations of PPI therapy.

RESULTS

Systematic review of 33 studies was performed, of which 26 studies were included in the meta-analysis. These 26 studies included 226,769 cases of CAP among 6,351,656 participants. We observed a pooled risk of CAP with ambulatory PPI therapy of 1.49 (95% CI 1.16, 1.92; I2 99.2%). This risk was increased during the first month of therapy (OR 2.10; 95% CI 1.39, 3.16), regardless of PPI dose or patient age. PPI therapy also increased risk for hospitalization for CAP (OR 1.61; 95% CI: 1.12, 2.31).

DISCUSSION

Outpatient PPI use is associated with a 1.5-fold increased risk of CAP, with the highest risk within the first 30 days after initiation of therapy. Providers should be aware of this risk when considering PPI use, especially in cases where alternative regimens may be available or the benefits of PPI use are uncertain.

ATP4a is required for development and function of the Xenopus mucociliary epidermis - a potential model to study proton pump inhibitor-associated pneumonia

Proton pump inhibitors (PPIs), which target gastric H(+)/K(+)ATPase (ATP4), are among the most commonly prescribed drugs. PPIs are used to treat ulcers and as a preventative measure against gastroesophageal reflux disease in hospitalized patients. PPI treatment correlates with an increased risk for airway infections, i.e. community- and hospital-acquired pneumonia. The cause for this correlation, however, remains elusive. The Xenopus embryonic epidermis is increasingly being used as a model to study airway-like mucociliary epithelia. Here we use this model to address how ATP4 inhibition may affect epithelial function in human airways. We demonstrate that atp4a knockdown interfered with the generation of cilia-driven extracellular fluid flow. ATP4a and canonical Wnt signaling were required in the epidermis for expression of foxj1, a transcriptional regulator of motile ciliogenesis. The ATP4/Wnt module activated foxj1 downstream of ciliated cell fate specification. In multiciliated cells (MCCs) of the epidermis, ATP4a was also necessary for normal myb expression, apical actin formation, basal body docking and alignment of basal bodies. Furthermore, ATP4-dependent Wnt/β-catenin signaling in the epidermis was a prerequisite for foxa1-mediated specification of small secretory cells (SSCs). SSCs release serotonin and other substances into the medium, and thereby regulate ciliary beating in MCCs and protect the epithelium against infection. Pharmacological inhibition of ATP4 in the mature mucociliary epithelium also caused a loss of MCCs and led to impaired mucociliary clearance. These data strongly suggest that PPI-associated pneumonia in human patients might, at least in part, be linked to dysfunction of mucociliary epithelia of the airways.

Acid-suppressive medication use in acute stroke and hospital-acquired pneumonia

OBJECTIVE

Pneumonia is a morbid complication of stroke, but evidence-based strategies for its prevention are lacking. Acid-suppressive medications have been associated with increased risk for nosocomial pneumonia in hospitalized patients. It is unclear whether these results can be extrapolated to stroke patients, where other factors strongly modulate pneumonia risk. We investigated the association between acid-suppressive medication and hospital-acquired pneumonia in patients with acute stroke.

METHODS

All patients hospitalized with acute ischemic stroke or intracerebral hemorrhage in a large, urban academic medical center in Boston, Massachusetts from June 2000 to June 2010 who were ≥18 years of age and hospitalized for ≥2 days were eligible for inclusion. Acid-suppressive medication use was defined as any pharmacy charge for a proton-pump inhibitor or histamine-2 receptor antagonist. Multivariate logistic regression was used to control for confounders. The main outcome measure was hospital-acquired pneumonia, defined via International Classification of Diseases, Ninth Revision, Clinical Modification codes.

RESULTS

The cohort comprised 1,676 admissions. Acid-suppressive medication was ordered in 1,340 (80%) and hospital-acquired pneumonia occurred in 289 (17.2%). The unadjusted incidence of hospital-acquired pneumonia was higher in the group exposed to acid-suppressive medication compared to those unexposed (20.7% vs 3.6%, odds ratio [OR] = 7.0, 95% confidence interval [CI] = 3.9-12.7). After adjustment, the OR of hospital-acquired pneumonia in the exposed group was 2.3 (95% CI = 1.2-4.6). The association was significant for proton-pump inhibitors (OR = 2.7, 95% CI = 1.4-5.4), but not for histamine-2 receptor antagonists (OR = 1.6, 95% CI = 0.8-3.4).

INTERPRETATION

In this large hospital-based cohort of patients presenting with acute stroke, acid-suppressive medication use was associated with increased odds of hospital-acquired pneumonia.

Oropharyngeal flora in patients admitted to the medical intensive care unit: clinical factors and acid suppressive therapy

Acid suppression therapy in critically ill patients significantly reduces the incidence of stress ulceration and gastrointestinal (GI) bleeding; however, recent studies suggest that proton pump inhibitors (PPIs) increase the risk of pneumonia. We wanted to test the hypothesis that acid suppressive therapy promotes alteration in the bacterial flora in the GI tract and leads to colonization of the upper airway tract with pathogenic species, potentially forming the biological basis for the observed increased incidence of pneumonia in these patients. This was a prospective observational study on patients (adults 18 years or older) admitted to the medical intensive care unit (MICU) at a tertiary care centre. Exclusion criteria included all patients with a diagnosis of pneumonia at admission, with infection in the upper airway, or with a history of significant dysphagia. Oropharyngeal cultures were obtained on day 1 and days 3 or 4 of admission. We collected data on demographics, clinical information, and severity of the underlying disease using APACHE II scores. There were 110 patients enrolled in the study. The mean age was 49±16 years, 50 were women, and the mean APACHE II score was 9.8 ± 6.5. Twenty per cent of the patients had used a PPI in the month preceding admission. The first oropharyngeal specimen was available in 110 cases; a second specimen at 72-96 h was available in 68 cases. Seventy-five per cent of the patients admitted to the MICU had abnormal flora. In multivariate logistic regression, diabetes mellitus and PPI use were associated with abnormal oral flora on admission. Chronic renal failure and a higher body mass index reduced the frequency of abnormal oral flora on admission. Most critically ill patients admitted to our MICU have abnormal oral flora. Patients with diabetes and a history of recent PPI use are more likely to have abnormal oral flora on admission.

Risk of fracture and pneumonia from acid suppressive drugs

A recently published systematic review and meta-analysis, incorporating all relevant studies on the association of acid suppressive medications and pneumonia identified up to August 2009, revealed that for every 200 patients, treated with acid suppressive medication, one will develop pneumonia. They showed the overall risk of pneumonia was higher among people using proton pump inhibitors (PPIs) [adjusted odds ratio (OR) = 1.27, 95% CI: 1.11-1.46, I² = 90.5%] and Histamine_-2 receptor antagonists (H₂RAs) (adjusted OR = 1.22, 95% CI: 1.09-1.36, I² = 0.0%). In the randomized controlled trials, use of H₂RAs was associated with an elevated risk of hospital-acquired pneumonia (relative risk 1.22, 95% CI: 1.01-1.48, I² = 30.6%). Another meta-analysis of 11 studies published between 1997 and 2011 found that PPIs, which reduce stomach acid production, were associated with increased risk of fracture. The pooled OR for fracture was 1.29 (95% CI: 1.18-1.41) with use of PPIs and 1.10 (95% CI: 0.99-1.23) with use of H₂RAs, when compared with non-use of the respective medications. Long-term use of PPIs increased the risk of any fracture (adjusted OR = 1.30, 95% CI: 1.15-1.48) and of hip fracture risk (adjusted OR = 1.34, 95% CI: 1.09-1.66), whereas long-term H₂RA use was not significantly associated with fracture risk. Clinicians should carefully consider when deciding to prescribe acid-suppressive drugs, especially for patients who are already at risk for pneumonia and fracture. Since it is unnecessary to achieve an achlorhydric state in order to resolve symptoms, we recommend using the only minimum effective dose of drug required to achieve the desired therapeutic goals.

Western Blot Confirmation of the H+/K+-ATPase Proton Pump in the Human Larynx and Submandibular Gland

Objective. The authors have previously demonstrated the H+/K+-ATPase (proton pump) in human larynx and lung glands via immunohistochemistry (IHC). The present hypothesis is that the proton pump is expressed in other seromucinous glands of the digestive tract that can be confirmed by IHC and Western blot analysis.

Study Design. Prospective controlled tissue analysis study.

Setting. Academic medical institution.

Methods. Ten anonymous fresh-frozen donor specimens were obtained, comprising 3 submandibular glands, 4 larynges, and 3 normal stomach specimens for control. Submandibular gland sections were immunostained with 2 monoclonal antibodies selectively reactive with α or β subunits of the H+/K+-ATPase. Western blot analysis was performed on all specimens.

Results. Consistent IHC staining was observed in the submandibular gland specimens for both α and β subunits. Western blot analysis revealed very strong expression for the stomach at 100 kDa, corresponding to the α protein, and weak but notable banding for all larynx and submandibular gland specimens. Similar findings were noted for the 60- to 80-kDa glycosylated β subunit protein, as well as the 52-kDa β subunit precursor for all specimens.

Conclusion. The H+/K+-ATPase (proton) pump is present in the human larynx and submandibular gland although in much lower concentrations than in the stomach. Proton pump involvement in human aerodigestive seromucinous glands may have a role in protecting mucosa from acid environments (local or systemic), explain heightened laryngeal sensitivity in those patients with laryngopharyngeal reflux, and be a site of action for proton pump inhibitor pharmacotherapy.

Proton pump inhibitor-associated pneumonia: Not a breath of fresh air after all?

Over the past two decades, proton pump inhibitors (PPIs) have emerged as highly effective and relatively safe agents for the treatment of a variety of gastrointestinal disorders. Unfortunately, this desirable pharmacological profile has also contributed to superfluous and widespread use in both the inpatient and outpatient settings. While generally well-tolerated, research published over the last decade has associated these agents with increased risks of Clostridium difficile disease, fractures likely due to calcium malabsorption and both community-acquired (CAP) and hospital-acquired pneumonias (HAP). The mechanism behind PPI-associated pneumonia may be multifactorial, but is thought to stem from compromising the stomach’s “acid mantle” against gastric colonization of acid-labile pathogenic bacteria which then may be aspirated. A secondary postulate is that PPIs, through their inhibition of extra-gastric H⁺/K⁺-ATPase enzymes, may reduce the acidity of the upper aerodigestive tract, thus resulting in increased bacterial colonization of the larynx, esophagus and lungs. To date, several retrospective case control studies have been published looking at the association between PPI use and CAP. Some studies found a temporal relationship between PPI exposure and the incidence of pneumonia, but only two could define a dose-response relationship. Furthermore, other studies found an inverse correlation between duration of PPI use and risk of CAP. In terms of HAP, we reviewed two retrospective cohort studies and one prospective study. One retrospective study in a medical ICU found no increased association of HAP in PPI-exposed patients compared to no acid-lowering therapy, while the other in cardiothoracic surgery patients showed a markedly increased risk compared to those receiving H₂RAs. The one prospective study in ICU patients showed an increased risk of HAP with PPIs, but not with H₂RAs. In conclusion, the current literature shows a slight trend toward an association between PPI use and pneumonia and an increased risk with PPIs over H₂RAs, but the findings are not consistent across all studies. Larger controlled trials still need to be done to better identify the risk that PPIs impart towards patients contracting CAP or HAP. Until these are completed, we will have to continue to extrapolate across smaller controlled trials to predict the associated risks in our respective patient populations. In the interim, it appears prudent to limit the use of PPIs to situations where they are clinically indicated and, in such cases, use them at the lowest effective dose. In the case of prescribing for stress ulcer prophylaxis in ICU patients, perhaps H₂RAs should be used as the preferred agents over PPIs.

Use of acid-suppressive drugs and risk of pneumonia: a systematic review and meta-analysis

BACKGROUND

Observational studies and randomized controlled trials have yielded inconsistent findings about the association between the use of acid-suppressive drugs and the risk of pneumonia. We performed a systematic review and meta-analysis to summarize this association.

METHODS

We searched three electronic databases (MEDLINE [PubMed], Embase and the Cochrane Library) from inception to Aug. 28, 2009. Two evaluators independently extracted data. Because of heterogeneity, we used random-effects meta-analysis to obtain pooled estimates of effect.

RESULTS

We identified 31 studies: five case-control studies, three cohort studies and 23 randomized controlled trials. A meta-analysis of the eight observational studies showed that the overall risk of pneumonia was higher among people using proton pump inhibitors (adjusted odds ratio [OR] 1.27, 95% confidence interval [CI] 1.11-1.46, I(2) 90.5%) and histamine(2) receptor antagonists (adjusted OR 1.22, 95% CI 1.09-1.36, I(2) 0.0%). In the randomized controlled trials, use of histamine(2) receptor antagonists was associated with an elevated risk of hospital-acquired pneumonia (relative risk 1.22, 95% CI 1.01-1.48, I(2) 30.6%).

INTERPRETATION

Use of a proton pump inhibitor or histamine(2) receptor antagonist may be associated with an increased risk of both community- and hospital-acquired pneumonia. Given these potential adverse effects, clinicians should use caution in prescribing acid-suppressive drugs for patients at risk.

Unexpected consequences of proton pump inhibitor use

Proton pump inhibitors (PPIs) are among the most widely prescribed classes of medications for gastroesophageal and laryngopharyngeal reflux diseases. There is emerging evidence that the pathogenesis of disease in laryngeal mucosa is not just related to refluxed acid, but also the presence of pepsin and acidic microenvironments. The widespread use of PPIs is also calling into question potential complications of PPI use. This commentary expands upon these issues with other potential unexpected consequences, and considers the importance of determining a proper approach to patient management.

Gastroesophageal reflux disease (GERD): is there more to the story?

Gastroesophageal reflux disease (GERD) affects both men and women worldwide, with the most common symptom of GERD being frequent heartburn. If left untreated, more serious diseases including esophagitis and/or esophageal cancer may result. GERD has been commonly held to be the result of gastric acid refluxing into the esophagus. Recent work, however, has shown that there are acid-producing cells in the upper aerodigestive tract. In addition, acid-producing bacteria located within the upper gastrointestinal tract and oral cavity may also be a contributing factor in the onset of GERD. Proton pump inhibitors (PPIs) are commonly prescribed for treating GERD; these drugs are designed to stop the production of gastric acid by shutting down the H(+)/K(+)-ATPase enzyme located in parietal cells. PPI treatment is systemic and therefore significantly different than traditional antacids. Although a popular treatment choice, PPIs exhibit substantial interpatient variability and commonly fail to provide a complete cure to the disease. Recent studies have shown that H(+)/K(+)-ATPases are expressed in tissues outside the stomach, and the effects of PPIs in these nongastric tissues have not been fully explored. Likewise, acid-producing bacteria containing proton pumps are present in both the oral cavity and esophagus, and PPI use may also adversely affect these bacteria. The use of PPI therapy is further complicated by the two philosophical approaches to treating this disease: to treat only symptoms or to treat continuously. The latter approach frequently results in unwanted side effects which may be due to the PPIs acting on nongastric tissues or the microbes which colonize the upper aerodigestive tract.