AGA Abstracts the innate immunity related molecule, is playing an important role in gastric epithelial trans-differentiation. 752 Treatment With 17 Beta-Estradiol Prevents the Development of Cancer in Chronically H. pylori Infected INS-GAS Mice by Shifting the Inflammatory Pathways From That of Males to One Resembling Females Alexander Sheh, Nicola M. Parry, Melissa W. Mobley, Amanda F. McCabe, Julia Rager, Arek R. Racynski, Rebecca C. Fry, Timothy C. Wang, James G. Fox Gastric cancer (GC) is a male-predominant cancer associated with Helicobacter pylori (HP). Epidemiological studies suggest that female hormones reduce GC risk and our previous work demonstrated that ovariectomized female mice have increased GC risk. We examined the effect of 17 beta-estradiol (E2) on HP-induced gastric cancer in hypergastrinemic 8 week-old male and female INS-GAS mice inoculated with HP SS1 or vehicle-only. At 16 weeks post-infection (WPI), mice were treated with E2, Tamoxifen, E2 and Tamoxifen or placebo pellets for 12 weeks. Gastric histopathology was evaluated before and after treatment. At 28 WPI, stomachs were evaluated by HP quantitative culture, promoter CpG methylation of 24 tumor suppressors/oncogenes, and gene expression, and serum inflammatory cytokines measured by Luminex. At 16 WPI, HP infection induced robust gastric pathology in mice of both genders (P<0.001). After 12 weeks of E2 treatment, gastric pathology was significantly reduced in infected E2 males compared to infected placebo males (P<0.001). Tamoxifen- treated and dual-treated infected males also showed reduction in gastric pathology compared to infected placebo males (both P<0.01) indicating that Tamoxifen may act agonistically in the stomach. In contrast, Tamoxifen treatment in females did not alter pathology in females. By microarray assessment, infected E2 males differentially expressed 412 probes compared to infected placebo males (Q<0.05). Cancer (115/412 probes) and inflammatory response (38/412) were among the top five differentially expressed biological functions using Ingenuity pathway analysis. Serum keratinocyte chemoattractant (KC) was decreased in infected E2 males and infected placebo females (P<0.05, P<0.001 respectively) compared to infected placebo males. Infected E2 males had significantly higher amounts of IL-6 and IL-10 com- pared to infected placebo males (P<0.01, P<0.05, respectively). MIP1a and MIP1b was significantly lower in infected placebo males compared to infected placebo females (both P<0.01) but these cytokines in infected E2 males did not differ from females. Both KC and MIP1a/b are strong neutrophil activators that were deregulated by E2 in infected males and trended toward the levels in infected females. IL-6 and IL-10 increased in infected E2 males to levels similar to that noted in infected females. Initial CpG methylation results indicate increased promoter methylation in 4 of 24 genes caused by HP infection in male mice. Studies are underway to elucidate the effect of E2 on methylation status. Our results demonstrate that E2 treatment can prevent the progression of HP-induced pathology by shifting the inflammatory response in males to one that resembles a female inflammatory response. 753 Iron Deficiency Amplifies Helicobacter pylori Virulence and Accelerates Gastric Carcinogenesis Jennifer M. Noto, M. Blanca Piazuelo, Judith Romero-Gallo, Alberto G. Delgado, Shumin Tan, Josephine Y. Lee, Pelayo Correa, Manuel R. Amieva, Richard M. Peek Helicobacter pylori colonizes the stomachs of greater than half of the world's population and is the strongest singular risk factor for gastric cancer. However, only a fraction of infected individuals ever develop gastric adenocarcinoma. In conjunction with host and bacterial constituents, environmental factors clearly contribute to the development of gastric cancer. Levels of essential micronutrients, such as iron, affect multiple pathogen-induced processes including expression of microbial virulence factors and severity of inflammatory responses and injury. To more clearly define the role of dietary iron in gastric cancer, we utilized a Mongolian gerbil model of H. pylori-induced carcinogenesis. Gerbils maintained on an iron- deplete diet developed significant reductions in systemic iron levels. To assess the role of iron deficiency on H. pylori-mediated injury, the carcinogenic H. pylori strain 7.13 was used to infect gerbils for 6-12 weeks. Strain 7.13 colonized iron-replete and iron-deplete gerbils to similar levels; however, iron depletion significantly (P < 0.05) increased the frequency and severity of H. pylori-induced gastritis, dysplasia, and gastric carcinoma. Further, H. pylori 7.13 output strains that had been adapted to iron deficient conditions In Vivo induced significantly higher levels of the pro-inflammatory cytokine IL-8 from human gastric epithelial cells In Vitro when compared to 7.13 output strains that had been adapted to iron-replete conditions. To define the effects of the H. pylori oncoprotein CagA, gerbils were also infected with a 7.13 cagA - isogenic mutant. Under iron-replete conditions, the cagA - isogenic mutant colonized gerbils to the same extent as wild-type strain 7.13. In contrast, iron depletion significantly attenuated colonization by the cagA - isogenic mutant, suggesting that CagA may play a role in iron acquisition In Vivo. Under both iron-replete and iron-deplete conditions, loss of CagA attenuated the development of gastritis, dysplasia, and gastric adenocarcinoma, confirming the role of CagA in H. pylori-induced carcinogenesis. Collect- ively, these data demonstrate that iron depletion enhances the carcinogenic potential of cagA + H. pylori strains, likely through iron-dependent regulation of microbial virulence factors. Loss of CagA significantly attenuates colonization and survival of H. pylori in an iron-dependent manner, suggesting that CagA is important for iron acquisition and/or regulation of iron homeostasis In Vivo. S-126 AGA Abstracts 754 Pancreatic Secretory Trypsin Inhibitor 1 Reduces the Severity of Chronic Pancreatitis in Mice Over-Expressing Interleukin-1β in the Pancreas Joelle Romac, Rafiq A. Shahid, Christoph B. Westphalen, Timothy C. Wang, Rodger A. Liddle A major factor in the development of acute pancreatitis is activation of digestive enzymes within the pancreas. By virtue of its ability to activate all pancreatic zymogens, trypsinogen activation is believed to be a key initiating event in pancreatic autodigestion that accompanies pancreatitis. However, the role of trypsin in chronic pancreatitis has come into question. Recently, a novel model of chronic pancreatitis has been produced by expression of human interleukin-1β (IL-1β) in pancreatic acinar cells in transgenic mice [Tg(Cela1-IL1B)L123Tcw] known here after as Tg(IL1β). Mice develop chronic pancreatitis characterized by extensive intrapancreatic inflammation, atrophy and fibrosis. We have previously created a transgenic mouse expressing rat pancreatic secretory trypsin inhibitor-I in pancreatic acinar cells [B6.Cg- g(Cela1-Spink3)#Rali] known hereafter as Tg(Psti1). PSTI-I overexpression increases pancre- atic trypsin inhibitor activity by 190% and confers protection against caerulein-induced pancreatitis. In order to determine if active trypsin is important in the pathogenesis of chronic pancreatitis in an inflammatory model, we crossed Tg(IL1β) mice with Tg(Psti1) mice to generate dual transgenic Tg(IL1β)-Tg(Psti1) mice. Tg(IL1β) mice were found to have marked pancreatic inflammation manifest by histologic changes including acinar cell loss, inflammatory cell infiltration, elevated myeloperoxidase (MPO) levels, and fibrosis as early as six weeks of age. In contrast to Tg(IL1β) mice, dual transgenic Tg(IL1β)-Tg(Psti1) mice expressing both IL-1β and PSTI-I in pancreatic acinar cells had markedly less severe pancreatitis as indicated by significant reductions in all pancreatitis parameters (less histolog- ical pancreatic damage, reduced levels of MPO, and less Sirius red staining indicative of less collagen deposition and fibrosis). These findings indicate that over-expression of PSTI-I reduces the severity of pancreatitis and suggest that pancreatic trypsin activity contributes to the pathogenesis of an inflammatory model of chronic pancreatitis. 755 Trypsinogen Activation is Not Required for the Pathogenesis of Chronic Pancreatitis Raghuwansh P. Sah, Rajinder Dawra, Ashley Bekolay, Vikas Dudeja, Ashok Saluja BACKGROUND AND AIMS: Trypsinogen activation is considered to be the central event in the current paradigm of pancreatitis. This is based on consistent demonstration of trypsinogen activation early during acute pancreatitis in animal models. Further evidence comes from association of mutations leading to pathologic trypsinogen activation with hereditary pancre- atitis, a form of chronic pancreatitis. We aimed to evaluate the role of intra-acinar trypsinogen activation in the pathogenesis of CP. METHODS: The mouse model of CP induced by caerulein (50μg/kg i.p. every hour x 6) twice a week for 10 weeks was employed in this study. This commonly used model, based on repeated episodes of acute pancreatitis, is a robust and reproducible model replicating the histopathological features of clinical CP. We induced CP in wild type (WT) and Cathepsin B knockout (CB-/-) mice. Cathepsin B is involved in intra-acinar trypsinogen activation during pancreatitis and CB-/- mice lack pathologic trypsinogen activation. The histopathological features of CP were compared between mice with (WT) and without (CB-/-) pathologic trypsinogen activation with saline- injected mice serving as controls. Two independent experiments each with 7-8 mice/group were carried out. RESULTS: The pancreas weight measured 39±1% and 37±3% of that of controls in WT and CB-/- respectively. On histology, comparable decline in acinar density was seen in both groups with 500% increase in fibrosis measured by Sirius Red stained area. Marked stellate cell proliferation (desmin, vimentin stain) and activation (α-smooth muscle actin stain) was seen which was similar in both groups. Cytokeratin 19 positive tubular structures increased from 3/field to 28±2 in WT and 31±2 in CB-/- groups indicating acinar to ductal metaplasia. Overexpression of Aquaporin 1, signifying impaired duct func- tion, was noted in WT and CB-/- groups to a similar degree. Proliferating cells (Ki-67 positive) increased from 3/field to 108±5 in WT vs 98±6 in CB-/- group. CD3 staining revealed similar extent of T-cell infiltration in both groups. Further, 3 fold increase in protein level of COX-2 was noted in both groups. Staining for p65 subunit of NF-kB revealed nuclear translocation of p65 in significantly higher number of acinar cells in WT and CB-/- groups vs. controls, suggesting chronic NF-kB activation in CP. CONCLUSION: Chronic Pancreatitis in the presence (WT) and absence of trypsinogen activation (CB-/-) is similar suggesting that intra-acinar trypsinogen activation is not required for the pathogenesis of chronic pancreatitis. This is an important finding and a major paradigm-shift in our current understanding of the pathogenesis of chronic pancreatitis. Furthermore, independent of trypsinogen activation, chronic ongoing inflammation is seen in chronic pancreatitis and may be responsible for its pathogenesis. 756 Milk Fat Globule-EGF Factor 8 is Required for Recovery of Pancreas From Cerulein-Induced Pancreatitis Heng-Fu Bu, Pauline M. Chou, Xiao Wang, Sambasiva Rao, Xiao-Di Tan Pancreatitis is the most common disease of the exocrine pancreas, occurring in acute, recurrent acute, and chronic manifestations. Previous studies have shown that repeated episodes of acute pancreatitis can progress to chronic pancreatitis and subsequently lead to destruction of exocrine pancreas, glandular atrophy, and extensive parenchymal fibrosis in pancreas. Milk fat globule-EGF factor 8 (MFG-E8) is a soluble glycoprotein secreted by macrophages. Previously, we and others have shown that MFG-E8 plays a critical role in resolution of inflammation and normal repair in organs which are largely comprised of epithelial cells including the gut, lung, and kidney. Here, we further examined the role of MFG-E8 in the resolution of pancreatic inflammation using a murine model of cerulein- induced pancreatitis. First, we determined histological alteration of pancreas during the entire course of cerulein-induced acute pancreatitis ranging from the acute phase (i.e. 1 h after the final injection of cerulein) to recovery phase (i.e. up to 7 days after cerulein