Secretory phospholipase A₂ is required to produce histologic changes associated with gastroduodenal reflux in a murine model

Objective

The earliest response of esophageal mucosa to gastric reflux is the development of oxidative damage and inflammation. These processes contribute to the development of metaplasia known as Barrett's esophagus, as well as the progression to malignancy. Secretory phospholipase A₂ is a mediator of inflammation with levels that are increased in Barrett's metaplasia and carcinoma when compared with levels in normal samples. Our goal is to determine the role of secretory phospholipase A₂ in the development of reflux-associated changes in the esophageal mucosa.

Methods

Secretory phospholipase A₂–deficient mice (C57BL/6, n = 5) and mice known to express high levels of secretory phospholipase A₂ (BALB/c, n = 5) underwent side-to-side surgical anastomosis of the first portion of the duodenum and gastroesophageal junction, allowing exposure of esophageal mucosa to duodenal and gastric contents duodeno-gastroesophageal anastomosis. Control animals (n = 5) of each strain underwent laparotomy with esophagotomy and repair. Tissue was frozen in embedding medium. Hematoxylin and eosin staining and Ki67 and secretory phospholipase A₂ immunohistochemistry were used to evaluate esophageal tissue and its response to duodeno-gastroesophageal anastomosis.

Results

Immunofluorescent staining confirmed the absence of secretory phospholipase A₂ in C57BL/6 mice and its presence in BALB/c mice. Hematoxylin and eosin staining demonstrated significant thickening of the esophageal mucosa in response to gastroesophageal reflux in the presence of secretory phospholipase A₂. Mice known to express high levels of secretory phospholipase A₂ also demonstrated increased numbers of proliferating cells. Secretory phospholipase A₂–deficient mice were immune to the early changes induced by mixed reflux.

Conclusions

The presence of secretory phospholipase A₂ appears necessary for early histologic changes produced by exposure of the esophagus to gastroduodenal contents. This enzyme is identified as a promising target for evaluation of mechanisms of carcinogenesis and chemoprevention of esophageal carcinoma.

Abbreviations and Acronyms: ANOVA, analysis of variance, DGEA, duodeno-gastroesophageal anastomosis, EGF, epidermal growth factor, GERD, gastroesophageal reflux disease, PBS, phosphate-buffered saline, sPLA₂, secretory phospholipase A₂

CTSNet classification: 7