These results demonstrate that CA IX expression is sustained in several types of gastric tumors. The variations observed in the CA IX levels support the concept that gastric adenomas and carcinomas are distinct entities and do not represent progressive steps of a single pathway.

−/− ) mice. The expression of Car4, Car12, Car13 and Car14 mRNAs did not show any significant deviations between the three groups of mice, whereas both groups of CA deficient mice showed decreased expression levels of Car1 in the colon and Car3 in the kidney. The Car2 mRNA level was greatly reduced but not completely abolished in all four tissues from the Car2 −/− mice in which no CA II protein was expressed. Sequencing the Car2 cDNA isolated from C57BL6 Car2 −/− mice revealed two nucleotide differences from the wild-type C57BL6 mice. One is a silent polymorphism found in Car2 mRNA from wild-type DBA mice, which is the strain that provided the original mutagenized chromosome. The second change is a mutation that causes prematurely terminated translation at codon 155 (Gln155X). Car9 mRNA and CA IX protein expression levels were up-regulated about 2.5-and 3.6-fold, respectively, in the stomach of the Car2 −/− mice. These results suggest that the loss of function of cytosolic CA II in the stomach of Car2 −/− mice leads to up-regulation of an extracellular CA, namely CA IX, which is expressed on the cell surface of the gastric epithelium.

Carbonic anhydrase (CA) isoenzyme IX is a hypoxia-inducible enzyme, which is expressed in the human and rodent gastrointestinal tract and overexpressed in several different tumors. Functionally, it has probably an effect on proliferation and differentiation of gastrointestinal epithelial cells. It may also participate in gastric morphogenesis, since a recent study has shown gastric pit cell hyperplasia and glandular atrophy in CA IX-knockout mice. However, it is not known whether CA IX produces morphological changes in the gastric mucosa, which can turn into a dysplasia or malignancy in the presence of some carcinogenic factors. High-salt diet is considered such a factor which has been shown to modulate Helicobacter pylori-associated carcinogenesis. We produced two strains of CA IX-knockout mice, C57/BL6 and BALB/c, and the mice ate either standard or high-salt feed for 20 weeks. Stomach samples were collected from 40 Car 9(-/-) knockout mice and 37 wildtype littermates, and the tissue sections were examined for histology. CA IX-deficiency caused gastric pit cell hyperplasia and glandular atrophy in both BALB/c and C57/BL6 strains. Excess dietary salt had no significant effect on the severity of pit cell hyperplasia. No dysplasia was found in any of the groups. In C57/BL6 mice, CA IX-deficiency was associated with gastric submucosal inflammation. The results indicate that CA IX-deficiency provides a useful model to study the mechanisms of gastric morphogenesis and epithelial integrity. Further studies are needed to see whether CA IX has a role in the regulation of immune response. The findings suggest that although CA IX-deficiency is not a tumor-promoting factor per se, it induces glandular atrophy in the body mucosa, a lesion which is considered to be a preneoplastic alteration in the stomach.

Duodenal bicarbonate secretion (DBS) is accepted as the primary mucosal defense against acid discharged from the stomach and is impaired in patients with duodenal ulcer disease. The secretory response to luminal acid is the main physiological stimulus for DBS and involves mediation by PGE 2 produced by mucosal cells. The aim of this investigation is to elucidate the role of carbonic anhydrases (CAs) II and IX in PGE 2-mediated bicarbonate secretion in the murine duodenum. CA II-and IX-deficient mice and different combinations of their heterozygous and WT counterparts were studied. A 10-mm segment of the proximal duodenum with intact blood supply was isolated, and DBS was titrated by pH-stat (TitroLine-easy, Schott, Mainz, Germany). Mean arterial blood pressure (MAP) was continuously recorded, and blood acid͞base balance and gastrointestinal morphology were analyzed. The duodenal segment spontaneously secreted HCO 3 ؊ at a steady basal rate of 5.3 ؎ 0.6 mol⅐cm ؊1 ⅐h ؊1 . Perfusing the duodenal lumen for 20 min with 47 M PGE2 caused a significant increase in DBS to 13.0 ؎ 2.9 mol⅐cm ؊1 ⅐h ؊1 , P < 0.0001. The DBS response to PGE2 was completely absent in Car2 ؊/؊ mice, whereas basal DBS was normal. The CA IX-deficient mice with normal Car2 alleles showed a slight increase in DBS. Histological abnormalities were observed in the gastroduodenal epithelium in both CA II-and IX-deficient mice. Our data demonstrate a gastrointestinal phenotypic abnormality associated with CA II deficiency. The results show that the stimulatory effect of the duodenal secretagogue PGE 2 completely depends on CA II. duodenal mucosal protection ͉ gastroduodenal histological abnormalities ͉ gastrointestinal phenotype

Kindlin-1 is an intracellular focal adhesion protein that regulates actin cytoskeleton. Patients suffering from Kindler syndrome have a homologous mutation of the kindlin-1 gene and develop skin blisters, periodontal disease and intestinal complications because of deficient adhesion of the basal epithelial cells. We investigated kindlin-1 localization in periodontal tissue and its functions in cultured keratinocytes and showed that kindlin-1 co-localizes with migfilin and paxillin in the basal epithelial cells of oral mucosa and in cultured keratinocytes. The kindlin-1 deficient oral mucosal tissue from a Kindler syndrome patient showed a complete lack of paxillin and reduced migfilin immunostaining in the basal keratinocytes. Co-immunoprecipitation showed that migfilin directly interacted with kindlin-1. RNA interference-induced kindlin-1 deficiency in keratinocytes led to an altered distribution of migfilin containing focal adhesions, reduced cell spreading, decreased cell proliferation and decelerated cell migration. Disruption of microtubules in the kindling-1-deficient cells further reduced cell spreading, suggesting that microtubules can partially compensate for kindlin-1 deficiency. Kindlin-1 supported mature cell-extracellular matrix adhesions of keratinocytes, as downregulation of kindlin-1 expression significantly reduced cell adhesion strength. In summary, kindlin-1 interacts with migfilin and plays a crucial role in actin-dependent keratinocyte cell adhesion essential for epidermal and periodontal health.