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Gastroduodenal Reflux (GDR) Induces both Expression and Enzyme Activity of Secretory Phospholipase A2 (sPLA2) in a Murine Reflux Model
D. C. Mauchley, X. Meng, A. M. Banerjee, F. Gamboni-Robertson, X. Yang, A. Babu, D. A. Fullerton, M. J. Weyant. University of Colorado, Denver, CO,
BACKGROUND: Exposure of esophageal epithelium to gastric and duodenal contents results in the histologic changes of hyperproliferation and mucosal thickening. We have previously shown that sPLA2 is necessary to produce these histologic changes in a murine model of gastroduodenal reflux. We sought to determine the influence of GDR on sPLA2 protein level and enzyme activity in esophageal tissue.
METHODS: BALB/c (sPLA2 +/+) mice (n=21) underwent side-to-side surgical anastamosis of the first portion of the duodenum and GE junction that resulted in continuous exposure of esophageal mucosa to mixed gastric and duodenal contents. Mice were euthanized at 2 (n=3), 4 (n=9), and 8 (n=9) weeks and esophageal tissue was harvested. Control mice (n=9) consisted of BALB/c mice which were surgically unaltered. Tissue was either frozen in embedding medium or homogenized in mammalian cell lysis buffer. Immunofluorescent staining was quantitated by digital microscopy using a specific antibody to identify and locate sPLA2 protein expression. Measurement of sPLA2 distribution was conducted by computer aided assessment of positive staining areas by a blinded observer. A colorimetric assay was used to quantify sPLA2 activity after standardization of protein levels. Statistical analysis comparing the mean area of positive staining and mean enzyme activity (µmol/min/mg) was determined using student’s t-test.
RESULTS: Secretory phospholipase A2 protein levels were increased at 2, 4, and 8 weeks compared to untreated controls (Fig. 1). Furthermore, sPLA2 enzyme activity was increased significantly at 4 and 8 weeks compared to untreated controls (Fig. 2)
CONCLUSIONS: The expression and enzyme activity of sPLA2 in murine esophageal tissue is induced by GDR. This novel finding indicates that both increased sPLA2 level and activity are involved in the mechanism underlying the histological changes caused by GDR. This protein continues to be of interest as a potential target for chemoprevention and treatment of reflux related esophageal disease.  
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