Effect of Acid and Pepsin on Gene Expression in Laryngeal Fibroblasts

Topical Alginate Protection against Pepsin-Mediated Esophageal Damage: E-Cadherin Proteolysis and Matrix Metalloproteinase Induction

Epithelial barrier dysfunction is a hallmark of gastroesophageal reflux disease (GERD) related to symptom origination, inflammatory remodeling and carcinogenesis. Alginate-based antireflux medications were previously shown to topically protect against peptic barrier disruption, yet the molecular mechanisms of injury and protection were unclear. Herein, Barrett's esophageal (BAR-T) cells were pretreated with buffered saline (HBSS; control), dilute alginate medications (Gaviscon Advance or Gaviscon Double Action, Reckitt Benckiser), a viscosity-matched placebo, or ADAM10 and matrix metalloproteinase (MMP) inhibitors before exposure to HBSS pH7.4 or pH4 ± 1 mg/mL pepsin for 10-60 min. Cell viability was assessed by ATP assay; mediators of epithelial integrity, E-cadherin, ADAM10, and MMPs were examined by Western blot and qPCR. Alginate rescued peptic reduction of cell viability (p < 0.0001). Pepsin-pH4 yielded E-cadherin fragments indicative of regulated intramembrane proteolysis (RIP) which was not rescued by inhibitors of known E-cadherin sheddases. Transcriptional targets of E-cadherin RIP fragments were elevated at 24 h (MMP-1,2,9,14; p < 0.01). Alginate rescued E-cadherin cleavage, ADAM10 maturation, and MMP induction (p < 0.01). Results support RIP as a novel mechanism of peptic injury during GERD. Alginate residue after wash-out to mimic physiologic esophageal clearance conferred lasting protection against pepsin-induced molecular mechanisms that may exacerbate GERD severity and promote carcinogenesis in the context of weakly acidic reflux.

Effect of Proton Pump Inhibitor on the Outcome of Laryngeal Microsurgery in Patients With Vocal Fold Mucosal Disease With Reflux Symptoms

OBJECTIVES

To evaluate the effect of proton pump inhibitor (PPI) after laryngeal microsurgery (LMS) in patients with benign vocal fold (VF) mucosal disease and in patients with overt reflux symptom according to subjective and objective voice assessment.

METHODS

The improvement of voice handicap index-10 (VHI-10) score, reflux symptom index (RSI) score, grade, roughness, breathiness, asthenia, and strain (GRBAS) score, Jitter, Shimmer, noise to harmonics ratio (NHR), maximum phonation time of acoustic voice analysis RESULTS: A total of 47 patients (PPI group [n = 24] and non-PPI group [n = 23]) completed the study. The scores for VHI-10, RSI, GRBAS, and acoustic parameters significantly improved in both groups after surgery. In the subgroup analysis of patients with overt reflux symptoms (RSI ≥ 13; non-PPI group [n = 12], PPI group [n = 15]), significant between-group differences were observed in terms of the improvement in NHR and the strain factor.

CONCLUSION

Postoperative PPI administration in patients with VF benign mucosal disease with reflux symptoms might improve subjective and objective voice outcomes after LMS.

Pepsin exposure in a non-acidic environment upregulates mucin 5AC (MUC5AC) expression via matrix metalloproteinase 9 (MMP9)/nuclear factor κB (NF-κB) in human airway epithelial cells

BACKGROUND

Gastric reflux (GR) is a backflow of gastric content to the aerodigestive tract. GR was previously found to be associated with inflammatory airway diseases and a potential cause of airway remodeling. Chronic exposure to gastric content may induce damage from nose to lung, because digestive enzymes and acidity are toxic to airway epithelial cells. Recently, the toxicity of pepsin in a non-acidic environment was found to increase proinflammatory cytokines and receptors in the epithelium of the aerodigestive tract. However, the effect of pepsin in non-acidic conditions on mucin expression has not been investigated in human airway epithelial cells. The purpose of this study was to evaluate the effect of pepsin on mucin 5AC (MUC5AC) expression in upper and lower airway epithelial cells as an important potential factor of non-acidic GR-related airway inflammation.

METHODS

In NCI-H292 cells and human nasal epithelial cells (HNEpCs), the effects and signaling pathways of pepsin on MUC5AC expression were examined using reverse-transcription polymerase chain reaction (RT-PCR), real-time PCR, enzyme immunoassay, zymography, Western blot, and immunofluorescence staining.

RESULTS

Pepsin increased MUC5AC expression in non-acidic condition of NCI-H292 cells and HNEpCs. Further, pepsin activated matrix metalloproteinase 9 (MMP9) and phosphorylated nuclear factor κB (NF-κB). Moreover, inhibitors of MMP9 and NF-κB significantly attenuated pepsin-induced MUC5AC expression, and the knockdown of NF-κB by small interfering RNA (siRNA) significantly blocked pepsin-induced MUC5AC expression in human airway epithelial cells.

CONCLUSION

These findings suggest that pepsin increased MUC5AC expression in non-acidic conditions via the activation of MMP9 and NF-κB in human airway epithelial cells.

Role of Matrix Metalloproteinases 7 in the Pathogenesis of Laryngopharyngeal Reflux: Decreased E-cadherin in Acid exposed Primary Human Pharyngeal Epithelial Cells

Cleavage of E-cadherin and the resultant weakness in the cell-cell links in the laryngeal epithelium lining is induced by exposure to acidic contents of the refluxate. Herein, we aimed to evaluate the role of matrix metalloproteinases (MMPs) in inducing E-cadherin level changes following acid exposure to the human pharyngeal mucosal cells. E-cadherin levels were inversely correlated with the duration of acid exposure. Treatment with actinonin, a broad MMP inhibitor, inhibited this change. Immunocytochemical staining and transepithelial permeability test revealed that the cell surface staining of E-cadherin decreased and transepithelial permeability increased after acid exposure, which was significantly inhibited by the MMP inhibitor. Among the various MMPs analyzed, the mRNA for MMP-7 in the cellular component was upregulated, and the secretion and enzymatic activity of MMP-7 in the culture media increased with the acid treatment. Consequently, MMP-7 plays a significant role in the degradation of E-cadherin after exposure to a relatively weak acidic condition that would be similar to the physiologic condition that occurs in Laryngopharyngeal reflux disease patients.

Tissue specific human fibroblast differential expression based on RNAsequencing analysis

Background

Physical forces, such as mechanical stress, are essential for tissue homeostasis and influence gene expression of cells. In particular, the fibroblast has demonstrated sensitivity to extracellular matrices with assumed adaptation upon various mechanical loads. The purpose of this study was to compare the vocal fold fibroblast genotype, known for its unique mechanically stressful tissue environment, with cellular counterparts at various other anatomic locales to identify differences in functional gene expression profiles.

Results

By using RNA-seq technology, we identified differentially expressed gene programs (DEseq2) among seven normal human fibroblast primary cell lines from healthy cadavers, which included: vocal fold, trachea, lung, abdomen, scalp, upper gingiva, and soft palate. Unsupervised gene expression analysis yielded 6216 genes differentially expressed across all anatomic sites. Hierarchical cluster analysis revealed grouping based on anatomic site origin rather than donor, suggesting global fibroblast phenotype heterogeneity. Sex and age-related effects were negligible. Functional enrichment analyses based on separate post-hoc 2-group comparisons revealed several functional themes within the vocal fold fibroblast related to transcription factors for signaling pathways regulating pluripotency of stem cells and extracellular matrix components such as cell signaling, migration, proliferation, and differentiation potential.

Conclusions

Human fibroblasts display a phenomenon of global topographic differentiation, which is maintained in isolation via in vitro assays. Epigenetic mechanical influences on vocal fold tissue may play a role in uniquely modelling and maintaining the local environmental cellular niche during homeostasis with vocal fold fibroblasts distinctly specialized related to their anatomic positional and developmental origins established during embryogenesis.

Electronic supplementary material

The online version of this article (10.1186/s12864-019-5682-5) contains supplementary material, which is available to authorized users.

Approach to the patient with presumed extraoesophageal GERD

Reflux related cough, asthma and laryngitis are frequently encountered and are considered part of extraoesophageal syndromes. The diagnosis of extraoesophageal reflux is difficult due to the lack of gold standard diagnostic criteria. Esophagogastroduodenoscopy and esophageal pH monitoring are inadequate diagnostic tools for due to poor sensitivity and specificity. For this reason, empirical PPI therapy is recommended as an initial approach to diagnose and treat the potential underlying cause of these symptoms in patients without alarm symptoms. Diagnostic testing with esophageal pH and/or impedance monitoring and esophageal motility testing is usually reserved for those who continue to be symptomatic despite a trial of therapy with PPIs. Recent developments have increased our understanding of this difficult to treat group of patients but more research into reflux related extraoesophageal symptoms are needed to better diagnose and treat this group.

Single nucleotide polymorphisms in the matrix metalloproteinase gene family and the frequency and duration of gastroesophageal reflux disease influence the risk of esophageal adenocarcinoma

The matrix metalloproteinase (MMP) family of proteins mediates various cellular pathways, including apoptosis and angiogenesis. Polymorphisms of MMP genes are associated with increased esophageal adenocarcinoma (EAC) risk. Gastroesophageal reflux disease (GERD) is an established EAC risk factor. We examined whether MMP polymorphism-EAC risk is modified by GERD. In total, 309 EAC patients and 279 frequency-matched healthy controls underwent MMP1 1G/2G, MMP3 6A/5A, MMP12 -82A/G and MMP12 1082A/G genotyping. Questionnaires collected GERD history. EAC risk was analyzed using logistic regression, adjusted for key covariates and stratified by GERD. Joint effects models explored GERD severity and duration, whereas additional models explored genotype-GERD interactions in EAC risk. We determined that each MMP1 and MMP3 minor (variant) allele was independently associated with increased EAC risk (adjusted odds ratio (AOR) 3.2, 95% confidence interval (CI) 2.0-5.1, p < 0.001 and AOR 1.8, 95% CI 1.1-2.7, p = 0.01, respectively) only among those with GERD but not in GERD-free individuals (all p = nonsignificant). There were significant interactions between the MMP1 variants and the presence of GERD (p = 0.002) and between MMP3 variants and GERD (p = 0.04). There was an equally strong interaction between cumulative GERD severity and MMP1 (p = 0.002). The AOR of each variant allele was 14.9 (95% CI 1.6-136) for individuals with severe GERD, 1.7 (95% CI 1.0-2.7) for mild-moderate GERD and 0.98 (95% CI 0.7-1.4) for those without GERD. This was further reflected in separate analyses of frequency and duration of GERD. In conclusion, MMP1 1G/2G (and possibly MMP3 6A/5A) polymorphisms alter EAC risk differentially for GERD and GERD-free individuals.

Biomarkers and laryngopharyngeal reflux

Laryngopharyngeal reflux is a controversial but increasingly made diagnosis used in patients with a collection of often non-specific laryngeal symptoms. It is a clinical diagnosis, and its pathophysiology is currently poorly understood. Previous reflux research has focused on injurious agents, acid, pepsin and biomarker expression. Failure of intrinsic defences in the larynx may cause changes in laryngeal epithelia, particularly alterations in carbonic anhydrases and E-cadherin. Carbonic anhydrase III levels vary in the larynx in response to laryngopharyngeal reflux, depending on location. Expression of E-cadherin, a known tumour suppressor, is reduced in the presence of reflux. Mucin expression also varies according to the severity of reflux. Further research is required to define the clinical entity of laryngopharyngeal reflux, and to identify a definitive mechanism for mucosal injury. Understanding this mechanism should allow the development of a comprehensive model, which would enable future diagnostic and therapeutic interventions to be developed.

Effects of transforming growth factor-beta1 on human vocal fold fibroblasts

OBJECTIVES

We studied the effect of transforming growth factor (TGF)-beta on immortalized human vocal fold fibroblasts.

METHODS

Normal human vocal fold fibroblasts were subjected to sequential lentiviral transduction with genes for human telomerase (hTERT) and SV40 large T antigen in order to produce an "immortalized" cell line of normal phenotype. After confirmation of vocal fold fibroblast transfection, these cells, referred to as HVOX, were treated with various concentrations of exogenous TGF-beta1 and assayed for collagen secretion, migration, and proliferation. In addition, components of the TGF-beta signaling pathway were examined in this cell line.

RESULTS

TGF-beta stimulated collagen secretion and migration without altering proliferation of HVOX. HVOX constitutively expressed type I and II TGF-beta receptors, as well as messenger RNA for the Smad signaling proteins and for all TGF-beta isoforms. Exogenous TGF-beta1 induced temporally dependent alterations in Smad2 and Smad3 gene expression. TGF-beta increased Smad7 expression at both 4 and 24 hours. Prolonged exposure to TGF-beta decreased TGF-beta1 gene expression.

CONCLUSIONS

Insight into the underlying pathophysiology of vocal fold fibrosis is likely to yield improved therapeutic strategies to mitigate vocal fold scarring. Our data suggest that TGF-beta signaling may be both paracrine and autocrine in this vocal fold fibroblast cell line, and we therefore propose that TGF-beta may be a reasonable target for therapies to prevent and/or treat vocal fold fibrosis, given its putative role in both acute and chronic vocal fold injury, as well as its effects on vocal fold fibroblasts.

A method for identification of vocal fold lamina propria fibroblasts in culture

OBJECTIVE

Vocal fold biology research is emerging as a vital area of study in laryngology. One impediment is the lack of both commercially available vocal fold lamina propria fibroblasts and a constitutively expressed specific marker for fibroblasts. We present an in vitro technique that allows for identification of fibroblasts by ruling out the possibility of the cells belonging to other lineages that are found in vocal fold tissue.

STUDY DESIGN

An in vitro study.

METHODS

Two primary vocal fold fibroblast cell lines and one immortalized vocal fold fibroblast cell line were cultured. Immunohistologic staining for alpha-actinin, cytokeratin 19, and von Willebrand factor was completed for the three fibroblast lines in addition to skeletal, endothelial, and epithelial cell lines. Cell type was differentiated by positive staining for alpha-actinin, cytokeratin 19, and von Willebrand factor.

RESULTS

Fibroblast cultures did not express alpha-actinin, cytokeratin 19, and von Willebrand factor, whereas skeletal muscle, endothelial, and epithelial cultured cells expressed each respectively.

CONCLUSIONS

This simple rule-out methodology for fibroblast confirmation is an important step when establishing cell culture, and it establishes sound internal validity particularly in the early stages of this emerging area of study.

Mucin Gene Expression in Human Laryngeal Epithelia: Effect of Laryngopharyngeal Reflux

Objectives:

We sought to document the mucin gene profile in normal human laryngeal epithelium and compare it with that in patients with reflux-attributed laryngeal injury or disease. We also investigated the effect of low pH with or without pepsin on mucin messenger RNA levels in vitro.

Methods:

Laryngeal biopsy specimens were obtained from 3 patients with clinically diagnosed laryngopharyngeal reflux and from 2 control subjects who had no signs or symptoms of reflux. Signs and symptoms were assessed by the Reflux Finding Score and the Reflux Symptom Index, respectively. Reverse transcription–polymerase chain reaction (RT-PCR) was performed to establish the mucin gene profile. Human hypopharyngeal epithelial cells were exposed to pH 7, 5, 4, and 2 with and without pepsin (0.1 mg/mL) for 20 minutes at 37°C, and expression of selected mucins was analyzed via real-time RT-PCR.

Results:

Mucin 1–5, 7, 9, 13, 15, 16, and 18–20 transcripts were detected in normal laryngeal epithelium, whereas mucin 6, 8, and 17 transcripts were not. Mucins 2, 3, and 5 were expressed at reduced levels in patients with reflux-attributed laryngeal injury or disease. These mucin genes were up-regulated after exposure to low pH in vitro (p < 0.005). Pepsin inhibited this up-regulation (p < 0.001).

Conclusions:

Reflux laryngitis is associated with down-regulation of mucin gene expression.

Vocal hygiene education, voice production therapy, and the role of patient adherence: a treatment effectiveness study in women with phonotrauma

PURPOSE

To assess the effectiveness of vocal hygiene education (VHE) and voice production therapy (VP) in altering patient perception of vocal handicap in adult women with benign, bilateral phonotraumatic vocal fold lesions and the role of adherence in that perception.

METHOD

Sixty-two women were randomly assigned to 6 weeks of VP (n = 31) or VHE (n = 31), followed by 4 weeks of self-study. The primary outcome measure was the Voice Handicap Index (VHI) score, assessed at baseline, post-therapy, and post-self-study. Patient adherence was assessed as a cofactor.

RESULTS

Both groups achieved a decrease in VHI scores from baseline to completion of the study, although the improvement was significantly greater for the VP group. The treatment effect size was large for the VP group and small for the VHE group. More participants adhered to VP than to VHE. Only adherent participants achieved significant improvement. Only adherent participants in the VP group improved with self-study. More than two thirds of the VP group achieved final VHI scores within normal limits, compared with approximately one third of those in the VHE group.

CONCLUSIONS

VP therapy may be more effective than VHE in addressing patient perception of vocal handicap in adult women with phonotrauma, and self-study may be an important component of therapy. However, adherence is a critical mediator of outcome.

Gene expression changes of inflammatory mediators in posterior laryngitis due to laryngopharyngeal reflux and evolution with PPI treatment: a preliminary study

HYPOTHESIS

Standard of care in laryngopharyngeal reflux (LPR) is acid suppression therapy. Its treatment efficacy and mechanism of action are not well documented. No objective study investigating the molecular patterns of inflammation in LPR or in response to proton pump inhibitor (PPI) treatment has been accomplished. We hypothesized that gene expression levels of mediators of inflammation -- interleukin 6 (IL6), interleukin 8 (IL8), interleukin 1a (IL1a), interleukin 1b (IL1b), transforming growth factor beta 1 (TGFbeta1), vascular endothelial growth factor (VEGF), fibroblast growth factor-2 (FGF2), and tumor necrosis factor alpha (TNFalpha) -- in posterior larynx tissue would be increased in those with diagnosed LPR and would be then reduced with PPI treatment.

STUDY DESIGN

Prospective uncontrolled trial.

METHODS

Biopsies from the posterior larynx were taken from 25 participants with LPR before and after a 10-week period with rabeprazole (40 mg). RNA isolation and real-time PCR was used to measure gene expression levels.

RESULTS

No significant differences were measured for any of the cytokines, either for the entire participant group (n = 25) or for the subset of participants who did not have a previous history of PPI usage (n = 15). In those participants who had a history of PPI usage (n = 10), a significant increase in gene expression levels post medication was measured for TGFbeta1 (P = .0396), VEGF (P = .0216), IL8 (P = .0297), after adjusting for compliance, subjective improvement, and reflux severity.

CONCLUSIONS

Our findings are provocative and speak to the unresolved understanding of the pathophysiology of LPR, its diagnosis, and its differences from gastroesophageal reflux disease.

Effect of a synthetic extracellular matrix on vocal fold lamina propria gene expression in early wound healing

An improved understanding of molecular response in the vocal folds to a synthetic extracellular matrix (sECM) during early wound repair is essential for understanding functional improvement of the tissue and implementation of future tissue-engineering strategies. The present study used real-time reverse transcriptase polymerase chain reaction to measure transcript expression of selected markers (procollagen alpha 2 type I, fibronectin, fibromodulin, hyaluronan synthase 2, and hyaluronidase 2) in 20 rabbits that underwent vocal fold biopsy bilaterally. After the biopsy, Carbylan-GSX 5% was injected immediately into the left vocal fold, and saline was injected into the right vocal fold. Two unwounded normal rabbit larynges were also harvested. Animals were sacrificed at days 1, 3, 5, and 10 post-surgery. At days 1, 3, and 10, no significant differences were found between the Carbylan-GSX-treated and saline-treated groups. At day 5, significant differences in procollagen (p = 0.02), fibronectin (p = 0.02), and transforming growth factor beta1 (p = 0.02) between the Carbylan-GSX-treated and saline-treated groups were measured. The presence of a sECM in the wound bed during the early stages of repair amplified the normal rabbit vocal fold wound-healing response over a short period of time. This amplification provided an optimal environment for tissue regeneration and may lead to the recovery of the functional biomechanical properties of the vocal folds necessary for voice production.

Vocal fold tissue repair in vivo using a synthetic extracellular matrix

Chemically modified hyaluronic acid (HA)-gelatin hydrogels have been documented to support attachment, growth, and proliferation of fibroblasts in vitro and to facilitate repair and engineering of tissues in vivo. The objective of this study was to determine the optimal composition of a synthetic extracellular matrix (sECM) that would promote wound repair and induce tissue regeneration in a rabbit vocal fold wound healing model. The sECM was formed using a thiol-modified semisynthetic glycosaminoglycan (GAG) derived of HA (Carbylan-SX) mixed with a thiolated gelatin derivative, co-cross-linked with poly(ethylene glycol) diacrylate to form Carbylan-GSX. Forty rabbits underwent vocal fold biopsy bilaterally. Rabbits were treated with Carbylan-SX, which lacks gelatin, or with Carbylan-GSX with different gelatin concentrations (2.5%, 5%, 10%, and 20%) via unilateral injection of the vocal fold at the time of biopsy. Saline was injected in the contralateral vocal fold as a control. Three weeks after biopsy and injection, animals were euthanized and mRNA levels of procollagen type 1, fibronectin, transforming growth factor beta 1 (TGF-beta1), fibromodulin, HA synthase 2, hyaluronidase 2, and tissue biomechanics were evaluated. Hyaluronidase mRNA levels were found to be significantly elevated in for Carbylan-GSX 20% w/w gelatin compared to controls. Both Carbylan-SX and Carbylan-GSX significantly improved tissue elasticity and viscosity. Carbylan-GSX containing 5% w/w gelatin showed the most promise as a scaffold material for vocal fold tissue regeneration.

Relationship between time of exposure of laryngopharyngeal reflux and gene expression in laryngeal fibroblasts

OBJECTIVES

Acid reflux is damaging to the laryngeal mucosa; however, the significance of the duration of reflux episodes has not been evaluated. The purpose of this study was to determine whether varying the exposure times at low pH with or without pepsin alters gene expression in laryngeal fibroblasts.

METHODS

Human false vocal fold and postcricoidal cultures were exposed to pH 4 or pH 5 media with and without pepsin for 10, 30, 60, and 240 seconds. Using a real-time polymerase chain reaction, we determined the messenger RNA expression of TGFbeta-1, VEGF, FGF-2, EGR-1, ATF-3, CTGF, MMP-1, MMP-2, and decorin.

RESULTS

Molecular responses were initiated at pH 5. Postcricoidal fibroblasts were more sensitive than false vocal fold fibroblasts to the presence of pepsin. Changes in transcript levels were dependent on acid exposure time, and the most significant changes were measured during the first 60 seconds after exposure.

CONCLUSIONS

Time of exposure to acid and pepsin needs to be taken into consideration when determining limit of pathology in pharyngeal reflux. Genes are identified that are induced by low pH and that may be of potential importance in the pathogenesis of reflux laryngitis.

Pharyngeal reflux episodes at pH 5 in healthy volunteers

OBJECTIVE

The clinically used cut-off limit in reflux disease is pH 4. Yet, earlier studies have shown a poor correlation between pharyngeal reflux episodes and symptoms or laryngeal findings, and treatment results have been suboptimal. Moreover, recent data suggest that pepsin is still active at pH 5. The aim of this study was to evaluate the occurrence of pharyngeal pH 5 reflux episodes in healthy controls and to correlate these to the pH monitoring results with a cut-off limit of pH 4.

MATERIAL AND METHODS

The results of double-probe 24-h pH monitoring from 35 healthy controls were reanalysed concerning the occurrence of pH decreases to pH 5.

RESULTS

Pharyngeal pH 5 reflux episodes occurred in 32 healthy controls (91%). The median number of pharyngeal reflux episodes at pH 5 was 4.0. The vast majority of these reflux episodes (92%) occurred in the upright position, especially in the postprandial period. The median time pH < 5 in the pharynx was 0.1% while the upper limit of normality was 1.5%. Pharyngeal pH 5 reflux episodes were 5 times more common than pH 4 reflux episodes. There was a significant positive correlation between hypopharyngeal and oesophageal acid exposure time at both pH 4 and 5 (p<0.01).

CONCLUSIONS

Pharyngeal pH 5 reflux episodes are present in most healthy adults, mainly in upright position and in the postprandial period. The importance of these episodes for the occurrence of laryngeal symptoms and signs and for treatment response needs to be prospectively assessed.