A novel murine model of esophageal nonerosive reflux disease: from inflammation to impairment in mucosal integrity

Pepsin Inhibitors Prevent Inflammation and Loss of Laryngeal Barrier Function in Mice with Gastroesophageal Reflux

OBJECTIVE

This study aimed to evaluate the role of pepsin inhibitors in the inflammatory response and their effects on laryngeal mucosal integrity during gastroesophageal reflux (GERD) under in vivo conditions.

METHODS

A surgical model of GERD was used, in which mice were treated with pepstatin (0.3 mg/kg) or darunavir (8.6 mg/kg) for 3 days. On the third day after the experimental protocol, the laryngeal samples were collected to assess the severity of inflammation (wet weight and myeloperoxidase activity) and mucosal integrity (transepithelial electrical resistance and paracellular epithelial permeability to fluorescein).

RESULTS

The surgical GERD model was reproduced. It showed features of inflammation and loss of barrier function in the laryngeal mucosa. Pepstatin and darunavir administration suppressed laryngeal inflammation and preserved laryngeal mucosal integrity.

CONCLUSION

Pepsin inhibition by the administration of pepstatin and darunavir improved inflammation and protected the laryngeal mucosa in a mouse experimental model of GERD.

LEVEL OF EVIDENCE

NA Laryngoscope, 134:3080-3085, 2024.

A polyphenol-rich açaí seed extract protects against 5-fluorouracil-induced intestinal mucositis in mice through the TLR-4/MyD88/PI3K/mTOR/NF-κBp65 signaling pathway

Açaí seed extract (ASE) is obtained from Euterpe oleracea Mart. (açaí) plant (Amazon region) has high nutritional and functional value. ASE is rich in polyphenolic compounds, mainly proanthocyanidins. Proanthocyanidins can modulate the immune system and oxidative stress by inhibiting the toll-like receptor-4 (TLR-4)/myeloid differentiation primary response 88 (MyD88)/nuclear factor-κB (NF-κB) pathway. A great deal of evidence suggests that inflammatory cytokines and oxidative stress contribute to the pathogenesis of intestinal mucositis, and these events can lead to intestinal dysmotility. We hypothesized that ASE acts as an anti-inflammatory and antioxidant compound in intestinal mucositis induced by 5-fluorouracil (5-FU) through modulation of the TLR-4/MyD88/phosphatidylinositol-3-kinase α/mechanistic target of rapamycin/NF-κBp65 pathway. The animals were divided into linear 5-FU (450 mg/kg) and 5-FU + ASE (10, 30, and 100 mg/kg) groups. The weight loss of the animals was evaluated daily. Samples from duodenum, jejunum, and ileum were obtained for histopathological, biochemical, and functional analyses. ASE reduced weight loss, inflammatory parameters (interleukin-1β; tumor necrosis factor-α; myeloperoxidase activity) and the gene expression of mediators involved in the TLR-2/MyD88/NF-κB pathway. ASE prevented histopathological changes with beneficial effects on gastrointestinal transit delay, gastric emptying, and intestinal absorption/permeability. In conclusion, ASE protects the integrity of the intestinal epithelial barrier by inhibiting the TLR/MyD88/PI3K/mechanistic target of rapamycin/NF-κBp65 pathway.

Laryngeal and Esophageal Mucosal Protection Using the Angico Gum Biopolymer in a Mouse Model of Reflux

OBJECTIVE

This study aimed to evaluate the in vivo protective effect of the angico gum biopolymer in reducing the inflammatory response and preserving the integrity of the laryngeal and esophageal mucosa.

STUDY DESIGN

Animal study.

METHODS

A murine surgical model of gastroesophageal reflux disease was accomplished and subsequently treated with angico gum or omeprazole. On days 3 and 7 post surgery, samples of the larynx and esophagus, respectively, were collected to measure the level of inflammation (wet weight and myeloperoxidase activity) and mucosal integrity (transepithelial electrical resistance and mucosal permeability to fluorescein).

RESULTS

Angico gum and omeprazole decreased laryngeal inflammation (wet weight and myeloperoxidase activity) and dramatically improved the integrity of the laryngeal mucosa. It also reduced inflammation (decreased wet weight and myeloperoxidase activity) of the esophagus and preserved the barrier function (inferred by assessing the integrity of the mucosa).

CONCLUSION

This study demonstrates the protective effect of angico gum in an experimental gastroesophageal reflux disease model. Angico gum attenuates inflammation and impairment of the mucosal barrier function not only in the larynx but also in the esophagus.

LEVEL OF EVIDENCE

NA Laryngoscope, 133:162-168, 2023.

A randomized, double-blind, placebo-controlled pilot study to evaluate the efficacy and tolerability of a novel oral bioadhesive formulation for the treatment of nonerosive reflux disease-related symptoms

OBJECTIVE

The use of antisecretory drugs can provide symptomatic relief in 70-80% of patients suffering from gastro-oesophageal reflux disease (GORD), although this benefit is reduced by 20-30% in the case of nonerosive reflux disease (NERD). The current study evaluates the efficacy and safety of a patented oral formulation (liquid sachets containing hyaluronic acid, a mixture of amino acids including proline, hydroxyl-proline and glutamine, and rice extract dispersed in a bioadhesive polymer matrix) for relieving the symptoms of NERD.

METHODS

A single-centre, randomized, double-blind, parallel group, placebo-controlled clinical study was performed. Patients who experienced at least three episodes of moderate-severity heartburn during the 7-day run-in period were included and treated with three liquid sachets per day for 14 days. The primary objective was to evaluate the proportion of patients with at least a three-point reduction in the total symptom score (TSS).

RESULTS

Overall, 20 patients were randomized to receive the investigational product and 20 to receive the placebo. At the end of treatment, a three-point reduction in the TSS was achieved by 95% of patients treated with the investigational product and by 20% of patients treated with placebo (P < 0.0001). No adverse events were reported.

CONCLUSION

The investigational product showed a statistically significant superiority to the placebo in relieving common symptoms in patients with NERD. Future studies will be aimed at clarifying the hypothesis that this symptomatic benefit is related to the strengthening of the oesophageal barrier against the damage induced by gastric contents.

Euterpe oleracea Mart. (Açaí) attenuates experimental colitis in rats: involvement of TLR4/COX-2/NF-ĸB

Euterpe oleracea Mart., commonly known as açaí, has been demonstrated to exhibit significantly antioxidant and inflammatory activities in experimental models. These effects of the hydroalcoholic extract from the açaí seed (ASE) were investigated in TNBS-induced (2,4,6-trinitrobenzenesulfonic acid) acute colitis model in rats. Wistar rats (180-220 g) were orally pretreated with saline (0.3 mL), ASE (10, 30 and 100 mg/kg) and dexamethasone (control group, 1 mg/kg) once daily for 3 days starting before TNBS instillation. On day 3 after TNBS, the animals were euthanized, the portion of distal colon was collected and washed with 0.9% saline for macroscopy and histological evaluation, glutathione (GSH) and malonyldialdehyde (MDA) levels, myeloperoxidase (MPO) and catalase (CAT) activity, nitrate and nitrite (NO₃/NO₂) concentration, pro-inflammatory cytokines levels and intestinal barrier integrity. We also evaluated Toll-like Receptor 4/cyclooxygenase-2/nuclear factor kappa B expression as a possible mechanism related to the ASE effects. Treatment with ASE 100 mg/kg decreased significantly macroscopic and microscopic damage induced by TNBS. In addition, MPO activity, TNF-α (tumor necrosis factor-alpha) and IL-1β (interleukin 1) levels were reduced in rats with colitis. ASE 100 mg/kg restored GSH and MDA levels, CAT activity, NO₃/NO₂ concentration and improved the intestinal barrier integrity in the TNBS group. ASE 100 mg/kg significantly reduced TNBS-induced expression of the TLR4, COX-2 and NF-κB p65. ASE 100 mg/kg improved macroscopy and histological parameters, inflammation, intestinal barrier integrity and nitric and oxidative stress through the TLR-4/COX-2/NF-κB pathway.

Laryngeal Mucosa Alterations in Mice Model of Gastroesophageal Reflux: Effects of Topical Protection

OBJECTIVES/HYPOTHESIS

The objectives of this study were to evaluate laryngeal inflammation and mucosal integrity in a murine model of reflux disease and to assess the protective effects of topical agents including alginate, hyaluronic acid, and cashew gum.

STUDY DESIGN

Animal study.

METHODS

A surgical murine model of reflux disease was evaluated at 3 or 7 days postsurgery, and laryngeal samples were collected to measure inflammation (wet weight and myeloperoxidase [MPO]) and mucosal integrity (transepithelial resistance [TER] and mucosal permeability to fluorescein). Additional groups of animals were administered one of several topical agents (alginate, hyaluronic acid, or cashew gum) daily, and laryngeal inflammation and mucosal integrity were evaluated at 3 days postsurgery.

RESULTS

At 3 days, and not 7 days postsurgery, we observed increased laryngeal wet weight and MPO, decreased laryngeal TER, and increased laryngeal mucosa permeability. Alginate partially decreased laryngeal inflammation (wet weight and not MPO) and dramatically improved laryngeal mucosal integrity. Conversely, hyaluronic acid eliminated the inflammation; however, it had no effect on laryngeal mucosal integrity impairment. Cashew gum eliminated laryngeal inflammation as well as the impairment in laryngeal mucosal integrity.

CONCLUSIONS

This study shows that a surgical model of reflux disease induced laryngeal inflammation and impairment in laryngeal barrier function. These observed alterations were partially attenuated by alginate and hyaluronic acid and completely reversed by cashew gum.

LEVEL OF EVIDENCE

NA Laryngoscope, 2020.

Role of TRPV1 receptor in inflammation and impairment of esophageal mucosal integrity in a murine model of nonerosive reflux disease

BACKGROUND

Microscopic inflammation and impairment of the esophageal epithelial barrier are considered relevant for perception of symptoms in patients with nonerosive reflux disease (NERD). In these patients, the receptor transient receptor potential vanilloid 1 (TRPV1) is overexpressed in the esophageal mucosa, but its role is not yet fully understood. We evaluated the role of TRPV1 in esophageal inflammation and mucosal barrier impairment in a murine model of NERD.

METHODS

Nonerosive reflux disease was surgically induced in Swiss mice by pyloric substenosis and ligature of the gastric fundus, and the mice were killed 7 days post surgery. The experimental groups were: I, sham surgery (negative control); II, NERD untreated; III and IV, NERD + SB366791 or capsazepine (TRPV1 antagonists); and V, NERD + resiniferatoxin (for long-term desensitization of TRPV1). The esophagus was collected for western blotting and histopathology and for evaluation of wet weight, myeloperoxidase (MPO), keratinocyte-derived chemokine (KC), transepithelial electrical resistance (TEER), and basal permeability to fluorescein.

KEY RESULTS

Compared to sham, NERD mice had increased esophageal wet weight and MPO and KC levels. The mucosa had no ulcers but exhibited inflammation. NERD mice showed mucosal TRPV1 overexpression, a more pronounced decrease in TEER at pH 0.5 (containing pepsin and taurodeoxycholic acid), and increased basal permeability. Pharmacological modulation of TRPV1 prevented esophageal inflammation development, TEER changes by acidic exposure, and increase in esophageal permeability.

CONCLUSIONS & INFERENCES

The TRPV1 receptor has a critical role in esophageal inflammation and mucosal barrier impairment in NERD mice, suggesting that TRPV1 might be a pharmacological target in patients with NERD.

A review of pharmacotherapy for treating gastroesophageal reflux disease (GERD)

INTRODUCTION

Medical therapy of gastroesophageal reflux disease (GERD) is based on the use of proton pump inhibitors (PPIs) as first choice treatment. Despite their effectiveness, about 20-30% of patients report an inadequate response and alternative drugs are required. Areas covered: This review provides an overview of current pharmacotherapy for treating GERD by showing the results of PPIs, reflux inhibitors, antidepressants and mucosa protective medications. Expert opinion: Medical therapy of GERD does not definitely cure the disease, because even PPIs are not able to change the key factors responsible for it. However, they remain the mainstay of medical treatment, allowing us to alleviate symptoms, heal esophagitis and prevent complications in the majority of cases. Nevertheless, many patients do not respond, because acid does not play any pathogenetic role. Prokinetics and reflux inhibitors have the potential to control motor abnormalities, but the results of clinical trials are inconsistent. Antidepressant drugs are effective in specific subgroups of NERD patients with visceral hypersensitivity, but larger, controlled clinical studies are necessary. Protective drugs or medical devices have been recently adopted to reinforce mucosal resistance and preliminary trials have confirmed their efficacy either combined with or as add-on medication to PPIs in refractory patients.