Lydia E. Wroblewski

Gastrin-stimulated gastric epithelial cell invasion: the role and mechanism of increased matrix metalloproteinase 9 expression

The gastric hormone gastrin regulates the organization of the gastric epithelium, but the cellular control mechanisms are yet unknown. Epithelial remodelling typically involves extracellular proteolysis mediated by the matrix metalloproteinases (MMPs). Since a gene-array analysis of the gastric cancer cell line AGS-G(R) suggested that gastrin increased MMP-9 expression, we examined the control of MMP-9 expression by gastrin. Gelatin zymography confirmed gastrin induction of MMP-9 in AGS-G(R) cells, but showed a small inhibition of MMP-2. Immunocytochemical studies showed that MMP-9 was localized to vesicles that appeared to traffic along the processes that were extended in response to gastrin. Gastrin stimulated the invasion of AGS-G(R) cells through artificial basement membrane, which was reduced by an inhibitor of MMP-2/-9. There was also an increase in MMP-9 in the stomach of patients with elevated plasma gastrin and multiple-endocrine neoplasia type 1 (MEN-1) syndrome, suggesting in vivo regulation of MMP-9 expression by gastrin. Finally, we showed that the expression of 1.9 kb of human MMP-9 gene promoter coupled with luciferase (MMP-9-luc) was increased 7.65+/-1.2-fold by gastrin, via a pathway which includes stimulation of protein kinase C, and activation of Raf and the mitogen-activated protein (MAP) kinase pathway. The tumour suppressor menin (which is mutated in MEN-1 syndrome) inhibited the expression of MMP-9-luc by gastrin. These results suggest that gastrin increases MMP-9 expression, which is associated with increased invasion, and this is a putative mechanism regulating remodelling of the gastric epithelium.

Gastrin-cholecystokinin(B) receptor expression in AGS cells is associated with direct inhibition and indirect stimulation of cell proliferation via paracrine activation of the epidermal growth factor receptor.

Background: Activation of the gastrin-cholecystokininB (CCKB) receptor stimulates cell proliferation and increases production of ligands for the epidermal growth factor receptor (EGF-R). Aims: To determine the role of gastrin-CCKB activation in stimulation of cell proliferation via paracrine activation of EGF-R. Methods: AGS cells were transfected with the gastrin-CCKB receptor (AGS-GR cells) or with green fluorescent protein (AGS-GFP cells). Proliferation was determined by [3H] thymidine incorporation, flow cytometry, and cell counting. Results: Gastrin inhibited proliferation of AGS-GR cells by delaying entry into S phase. However, when AGS-GR cells were cocultured with AGS-GFP cells, gastrin stimulated proliferation of the latter. Immunoneutralisation and pharmacological studies using metalloproteinase and kinase inhibitors indicated that the proliferative response was mediated by paracrine stimulation of EGF-R and activation of the mitogen activated protein kinase pathway through release of heparin binding EGF. Conclusions: Gastrin can directly inhibit, and indirectly stimulate, proliferation of gastric AGS cells.

Helicobacter pylori: Pathogenic enablers [mdash] toxic relationships in the stomach

Chronic infection with Helicobacter pylori is the strongest known risk factor for the development of gastric cancer. Saju et al. shed new light on mechanisms by which Epstein–Barr virus, a viral initiator of gastric cancer, potentiates the oncogenic effects of Helicobacter pylori in the stomach.

“H. pylori in gastric carcinogenesis-mechanisms”

Helicobacter pylori infection induces chronic inflammation and is the strongest known risk factor for gastric cancer. The genomes of H pylori are highly diverse and therefore bacterial virulence factors play an important role in determining the outcome of H pylori infection, in combination with host responses that are augmented by environmental and dietary risk factors. It is important to gain further understanding of the pathogenesis of H pylori infection to develop more effective treatments for this common but deadly malignancy. This review focuses on the specific mechanisms used by H pylori to drive gastric carcinogenesis.

Pathogenic enablers — toxic relationships in the stomach: Helicobacter pylori

Chronic infection with Helicobacter pylori is the strongest known risk factor for the development of gastric cancer. Saju et al. shed new light on mechanisms by which Epstein–Barr virus, a viral initiator of gastric cancer, potentiates the oncogenic effects of Helicobacter pylori in the stomach.

523 Helicobacter pylori cag+ Strains Stimulate Expansion of Lrig1+ Progenitor Cells Within the Gastric Mucosa in a Strain-Specific Manner

Background & Aims. Despite the preponderance of stress-related diseases and inflammatory bowel disease (IBD) in women, the role of the corticotropin-releasing factor (CRF) system in mediating sex-specific effects on cellular signaling and immune function has not been systematically investigated. In this study, we determined the contribution of CRF receptor 2 (CRF2) in mediating sex-specific responses during colitis in mice. Methods. Colitis was induced by 2,4,6-trinitrobenzenesulfonic acid (TNBS) in wild-type, CRF2, and CRF2 mice of both sexes and treated with the CRF2 agonist urocortin1 (Ucn1) or saline. Changes in gastrointestinal permeability were detected using Evans blue dye method to measure plasma extravasation. Changes in immune cell infiltration were determined using flow cytometry and changes in the MAPK signaling pathway were assessed by western blot analysis. Results. Baseline plasma extravasation in the gastrointestinal tract was ~1.4-1.74fold higher in females than in males in all three different genotypes. Colitis increased plasma extravasation in the distal colon in both sexes in all three different genotypes. Interestingly, the sex-specific difference in plasma extravasation was maintained in Wt, but lost in CRF2 and CRF2 mice during colitis. Colitis resulted in greater thymus atrophy, loss of spleen mass, adrenal hypertrophy, and neutrophil infiltration in the blood and in the colon in Wt female mice than in Wt males. Wt females showed a ~4-fold higher neutrophil infiltration in the colon than Wt males and this sex-specific difference was lost in CRF2 and CRF2 mice. Surprisingly, colitis-induced mortality was abolished in male CRF2 mice, but exceeded 25% in female CRF2 mice. Although Ucn1 intervention rescued colitis-induced mortality in male CRF2 mice, female CRF2 mice showed increased mortality and worsened inflammation after Ucn1 intervention. The p38 MAPK signaling pathway regulates inflammatory responses and is altered in IBD. We found dysregulated p38 MAPK signaling in CRF2 mice of both sexes, accompanied by decreased phosphorylation of downstream target heat shock protein 27 (Hsp27) during colitis. Ucn1 restored the phosphorylation levels of Hsp27 back to baseline levels in male, but not female CRF2 mice. Conclusions. Ucn1 and CRF2 mediate contextand sex-dependent inflammatory responses at the molecular, cellular and organ levels during IBD. Our observations suggest that Ucn1 intervention can rescue colitisinduced mortality in males alone. In males, Ucn1 ameliorates inflammation by mechanisms that involve the MAPK signaling pathway and phosphorylation of Hsp27 that regulates stabilization and formation of tight junctions in the gut epithelium.