Matrix metalloproteinase-7 induces E-cadherin cleavage in acid-exposed primary human pharyngeal epithelial cells via the ROS/ERK/c-Jun pathway

Laryngopharyngeal reflux disease (LPRD) is caused by pharyngeal mucosal damage due to the reflux of gastric contents, including acid, pepsin, and bile juice. Our previous study has demonstrated that LPRD is associated with the cleavage of E-cadherin, which is facilitated by the acid-activated matrix metalloproteinase-7 (MMP-7); however, the mechanism by which the acid activates MMP-7 remains unclear. The purpose of this study was to investigate the mechanism by which MMP-7 is activated in the pharyngeal epithelial cells that are exposed to acid. The levels of reactive oxygen species (ROS) were measured in the epithelial cells exposed to acid. To investigate the signaling mechanism of ROS in the expression of MMP-7, the mechanism of action of the mitogen-activated protein kinase was examined. The expression of various signaling factors was determined, according to the presence or absence of each inhibitor in the acid-exposed pharyngeal epithelial cells. To identify changes in the cleavage of E-cadherin, the integrity of the mucosal membrane was assessed using a transepithelial permeability test. We found that acid exposure increased the levels of ROS, phosphorylated-extracellular signal-regulated kinase (p-ERK) 1/2, and phosphorylated-c-Jun (p–c-Jun) in pharyngeal epithelial cells. The ROS inhibitor reduced the expression of p-ERK and MMP-7, while the ERK inhibitor reduced the expression of p–c-Jun and MMP-7. Moreover, the c-Jun inhibitor reduced the expression of MMP-7 and blocked the degradation of E-cadherin. In addition, decrease in the levels of immunostained E-cadherin and increase in transepithelial permeability after acid exposure were collectively alleviated by the inhibitors of ROS, ERK, and c-Jun. The degradation of E-cadherin that occurs after human mucosal cells are exposed to acid appears to be caused by an increase in the expression of MMP-7 via the ROS/ERK/c-Jun pathway, which is thought to be an important mechanism associated with the development of LPRD. Key messages • ROS is triggered when reflux occurs. • ROS regulates the transcription factor c-Jun via the ERK pathway. • The increase in MMP-7 that induces LPRD is induced via the ROS/ERK/c-Jun pathway. • This study revealed for the first time the expression mechanism of MMP-7, which is one of the causes of LPRD.

Phenotyping patients with borderline elevated esophageal acid exposure

Summary Acid exposure time (AET) <4% on ambulatory reflux monitoring definitively rules out pathologic gastroesophageal acid reflux, while AET >6% indicates pathologic reflux per the Lyon Consensus, leaving AET of 4–6% as borderline. We aimed to elucidate the borderline AET population and identify metrics that could help differentiate this group. A total of 50 subjects in each group, AET <4, 4–6, and >6% on pH-impedance monitoring between 2015 and 2019, were retrospectively reviewed. In addition to demographic and clinical information, the extracted data included mean nocturnal baseline impedance (MNBI) on reflux study and high-resolution manometry (HRM) parameters and diagnosis. After excluding patients with prior foregut surgery, major esophageal motility disorder, or unreliable impedance testing, a total of 89 subjects were included in the analysis (25 with normal AET < 4%, 38 with borderline 4–6%, 26 with abnormal >6%). MNBI in borderline AET patients was significantly lower compared to normal AET (1607.7 vs. 2524.0 ohms, P < 0.01), and higher than abnormal AET (951.5 ohms, P < 0.01). Borderline subjects had a greater frequency of ineffective esophageal motility (IEM) diagnosis per Chicago classification v3.0 (42.1 vs. 8.0%, P = 0.01), but did not demonstrate any differences compared to abnormal subjects (34.6%, P = 0.56). Patients with borderline AET had an average MNBI that was in between normal AET and abnormal AET. Borderline AET patients also commonly demonstrate IEM on HRM, similar to those with abnormal AET. Our findings can be potentially useful in assigning higher clinical significance for patients found to have borderline AET with concomitant low MNBI and IEM on manometry.