Early Molecular Events in Murine Gastric Epithelial Cells Mediated by Helicobacter pylori CagA.

BACKGROUND: Murine models of Helicobacter pylori infection are used to study host-pathogen interactions, but lack of severe gastritis in this model has limited its usefulness in studying pathogenesis. We compared the murine gastric epithelial cell line GSM06 to the human gastric epithelial AGS cell line to determine whether similar events occur when cultured with H. pylori. MATERIALS AND METHODS: The lysates of cells infected with H. pylori isolates or an isogenic cagA-deficient mutant were assessed for translocation and phosphorylation of CagA and for activation of stress pathway kinases by immunoblot. RESULTS: Phosphorylated CagA was detected in both cell lines within 60 minutes. Phospho-ERK 1/2 was present within several minutes and distinctly present in GSM06 cells at 60 minutes. Similar results were obtained for phospho-JNK, although the 54 kDa phosphoprotein signal was dominant in AGS, whereas the lower molecular weight band was dominant in GSM06 cells. CONCLUSION: These results demonstrate that early events in H. pylori pathogenesis occur within mouse epithelial cells similar to human cells and therefore support the use of the mouse model for the study of acute CagA-associated host cell responses. These results also indicate that reduced disease in H. pylori-infected mice may be due to lack of the Cag PAI, or by differences in the mouse response downstream of the initial activation events.

Identification and characterization of noncalcemic, tissue-selective, nonsecosteroidal vitamin D receptor modulators.

Vitamin D receptor (VDR) ligands are therapeutic agents for the treatment of psoriasis, osteoporosis, and secondary hyperparathyroidism. VDR ligands also show immense potential as therapeutic agents for autoimmune diseases and cancers of skin, prostate, colon, and breast as well as leukemia. However, the major side effect of VDR ligands that limits their expanded use and clinical development is hypercalcemia that develops as a result of the action of these compounds mainly on intestine. In order to discover VDR ligands with less hypercalcemia liability, we sought to identify tissue-selective VDR modulators (VDRMs) that act as agonists in some cell types and lack activity in others. Here, we describe LY2108491 and LY2109866 as nonsecosteroidal VDRMs that function as potent agonists in keratinocytes, osteoblasts, and peripheral blood mononuclear cells but show poor activity in intestinal cells. Finally, these nonsecosteroidal VDRMs were less calcemic in vivo, and LY2108491 exhibited more than 270-fold improved therapeutic index over the naturally occurring VDR ligand 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] in an in vivo preclinical surrogate model of psoriasis.

Vitamin D receptor modulators for inflammation and cancer.

1alpha, 25-Dihydroxyvitamin D3 [1,25-(OH)2D3], the biologically active form of vitamin D, is an important hormone that is critically required for the maintenance of mineral homeostasis and structural integrity of bones. 1,25-(OH)2D3 accomplishes this by facilitating calcium absorption from the gut and by a direct action on osteoblasts, the bone forming cells. Apart form its classical actions on the gut and bone, 1,25-(OH)2D3 and its synthetic analogs also possess potent anti-proliferative, differentiative and immunomodulatory activities. 1,25-(OH)2D3 exerts these effects through vitamin D receptor (VDR), a ligand-dependent transcription factor that belongs to the superfamily of steroid/thyroid hormone/retinoid nuclear receptors. The presence of VDR in various tissues other than gut and bone, along with their ability to exert differentiation, growth inhibitory and anti-inflammatory action, has set the stage for therapeutic exploitation of VDR ligands for the treatment of various inflammatory indications and cancer. However, the use of VDR ligands in clinic is limited by their major dose-related side effect, namely hypercalcemia/hypercalciuria. Efforts are being undertaken to develop vitamin D receptor modulators (VDRMs) that are tissue-selective and/or gene-selective in their action and these ligands may exhibit increased therapeutic indices. This review explores the recent advances in VDR biology, non-secosteroidal VDR ligands and the current and potential clinical applications of VDR ligands in inflammation and cancer.