Integrin alpha4beta1 mediates leukocyte recruitment, activation, mediator release, and apoptosis inhibition, and it plays a central role in inflammatory pathophysiology. High-affinity, selective inhibitors of alpha4beta1, based on the Leu-Asp-Val (LDV) sequence from the alternatively spliced connecting segment-1 (CS-1) peptide of cellular fibronectin, are described that employ a novel N-terminal peptide "cap" strategy. One inhibitor, BIO-1211, was approximately 10(6)-fold more potent than the starting peptide and exhibited tight-binding properties (koff = 1.4 x 10(-4) s-1, KD = 70 pM), a remarkable finding for a noncovalent, small-molecule inhibitor of a protein receptor. BIO-1211 was also 200-fold selective for the activated form of alpha4beta1, and it stimulated expression of ligand-induced epitopes on the integrin beta1 subunit, a property consistent with occupancy of the receptor's ligand-binding site. Pretreatment of allergic sheep with a 3-mg nebulized dose of BIO-1211 inhibited early and late airway responses following antigen challenge and prevented development of nonspecific airway hyperresponsiveness to carbachol. These results show that highly selective and potent small-molecule antagonists can be identified to integrins with primary specificity for peptide domains other than Arg-Gly-Asp (RGD); they confirm the generality of integrins as small molecule targets; and they validate alpha4beta1 as a therapeutic target for asthma.

Background & Aims Infection with H. pylori represses expression of the gastric H, K-ATPase α subunit (HKα), which could contribute to transient hypochlorhydria. CagL, a pilus protein component of the H. pylori type IV secretion system, binds to the integrin α5β1 to mediate translocation of virulence factors into the host cell and initiate signaling. α5β1 binds ADAM17, a metalloenzyme that catalyzes ectodomain shedding of receptor tyrosine kinase ligands. We investigated whether H. pylori-induced repression of HKα is mediated by CagL activation of ADAM17 and release of heparin-binding epidermal growth factor (HB-EGF). Methods HKα promoter and ADAM17 activity were measured in AGS gastric epithelial cells transfected with HKα promoter-reporter constructs or ADAM17-specific small interfering (si)RNAs and infected with H. pylori. HB-EGF secretion was measured by ELISA analysis and ADAM17 interaction with integrins were investigated by co-immunoprecipitation analyses. Results Infection of AGS cells with wild-type H. pylori or an H. pylori cagL-deficient isogenic mutant that also contained a wild-type version of cagL (P12ΔcagL/cagL) repressed HKα promoter-Luc reporter activity and stimulated ADAM17 activity. Both responses were inhibited by point mutations in the NF-κB binding site of HKα or by infection with P12ΔcagL. siRNA-mediated silencing of ADAM17 in AGS cells inhibited the repression of wild-type HKα promoter and reduced ADAM17 activity and HB-EGF production, compared to controls. Coimmunoprecipitation studies of AGS lysates showed that wild-type H. pylori disrupted ADAM17–α5β1 complexes. Conclusions During acute H. pylori infection, CagL dissociates ADAM17 from the integrin α5β1 and activates ADAM17-dependent, NF-κB–mediated repression of HKα. This might contribute to transient hypochlorhydria in patients with H. pylori infection.

No abstract

Background and aims-Helicobacter pylori infection of gastric mucosa causes gastritis and transient hypochlorhydria, which may provoke emergence of a mucosal precancer phenotype; H pylori strains containing a cag pathogenicity island (PAI) augment cancer risk. Acid secretion is mediated by the catalytic α subunit of parietal cell H,K-ATPase (HKα). In AGS gastric epithelial cells, H pylori induces nuclear factor-κB (NF-κB) binding to and repression of transfected HKα promoter activity. This study sought to identify bacterial genes involved in HKα repression and to assess their impact on acid secretion.