STUDIES OF IRON DEPOSITS, INDUCIBLE NITRIC-OXIDE SYNTHASE AND NITROTYROSINE IN A RAT MODEL FOR ESOPHAGEAL ADENOCARCINOMA

A rat model was developed recently in our laboratory to study the path ogenesis of Barrett's esophagus (BE) and its progression to esophageal adenocarcinoma (FAC). Eight-week-old male Sprague-Dawley rats underwe nt esophagoduodenal anastomosis (EDA) to produce gastric and duodenal reflux in their distal esophagi, The rats were given iron dextran (50 mg of Fe/kg, i.p.) starting 2 weeks after surgery and this was continu ed once a month. BE was observed as early as week 3 and the incidence of BE and EAC increased with time: 58 and 17% at week 23; 91 and 73% a t week 31, There was a progression in epithelial cell proliferation an d inflammation from mild to severe in the distal one-third of the esop hagus, Iron deposition in the esophagus also increased with time. Iron deposits in the stromal tissue adjacent to the epithelium in the dist al one-third of the esophagus were associated with areas of severe inf lammation. Immunohistochemical analysis showed positive inducible nitr ic oxide synthase (iNOS) expression in the stromal macrophages directl y beneath the epithelium in the distal one-third of the esophagus in 3 6, 83 and 100% of the rats at weeks 17, 23 and 31, respectively. A sig nificant increasing linear trend (P = 0.001) was seen in nitrotyrosine immunostaining (number of positive cells/high power field) in the dis tal esophagus, Strong positive nitrotyrosine staining was seen in the macrophages and weaker positive staining was seen in the adjacent epit helium starting at week 17, Furthermore, iron supplemented rats killed at week 31 had significantly higher (P < 0.05) levels of inflammation , cell proliferation, iNOS and nitrotyrosine as well as more tumors in their distal esophagi than did rats that received no iron supplement. These results suggest that iron supplementation enhanced inflammation and the production of reactive oxygen and nitrogen species in the eso phageal epithelium. These processes could contribute to the formation of BE and its progression to EAC.