Doerte Vossmeyer

Suppression and Regression of Choroidal Neovascularization by Systemic Administration of an α5β1 Integrin Antagonist

Integrin α5β1 plays an important role in developmental angiogenesis, but its role in various types of pathologic neovascularization has not been completely defined. In this study, we found strong up-regulation of α5β1 in choroidal neovascularization. Implantation of an osmotic pump delivering 1.5 or 10 μg/h (∼1.8 or 12 mg/kg/day) of 3-(2-{1-alkyl-5-[(pyridin-2-ylamino)-methyl]-pyrrolidin-3-yloxy}-acetylamino)-2-(alkylamino)-propionic acid (JSM6427), a selective α5β1 antagonist, caused significant suppression of choroidal neovascularization; the area of neovascularization was reduced by 33 to 40%. When an osmotic pump delivering 10 μg/h of JSM6427 was implanted 7 days after rupture of Bruchs membrane, there was terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) staining in vascular cells within the neovascularization and significant regression of the neovascularization over the next week. JSM6427 also induced apoptosis of cultured vascular endothelial cells. Fibronectin stimulates phosphorylation of extracellular signal-regulated kinase (ERK) in α5β1-expressing cells that is blocked by JSM6427. These data suggest that α5β1 plays a role in the development and maintenance of choroidal neovascularization and provides a target for therapeutic intervention.

α5β1 Integrin Blockade Inhibits Lymphangiogenesis in Airway Inflammation

The integrin alpha5beta1 has been previously implicated in tumor angiogenesis, but its role in the remodeling of both blood vessels and lymphatics during inflammation is at an early stage of understanding. We examined this issue using a selective, small-molecule inhibitor of alpha5beta1 integrin, 2-aroylamino-3-{4-[(pyridin-2-ylaminomethyl)heterocyclyl]phenyl}propionic acid (JSM8757), in a model of sustained airway inflammation in mice with Mycoplasma pulmonis infection, which is known to be accompanied by robust blood vessel remodeling and lymphangiogenesis. The inhibitor significantly decreased the proliferation of lymphatic endothelial cells in culture and the number of lymphatic sprouts and new lymphatics in airways of mice infected for 2 weeks but did not reduce remodeling of blood vessels in the same airways. In inflamed airways, alpha5 integrin immunoreactivity was present on lymphatic sprouts, but not on collecting lymphatics or blood vessels, and was not found on any lymphatics of normal airways. Macrophages, potential targets of the inhibitor, did not have alpha5 integrin immunoreactivity in inflamed airways. In addition, macrophage recruitment, assessed in infected airways by quantitative reverse transcription-polymerase chain reaction measurements of expression of the marker protein ionized calcium-binding adapter molecule 1 (Iba1), was not reduced by JSM8757. We conclude that inhibition of the alpha5beta1 integrin reduces lymphangiogenesis in inflamed airways after M. pulmonis infection because expression of the integrin is selectively increased on lymphatic sprouts and plays an essential role in lymphatic growth.

Integrin α5β1 mediates attachment, migration, and proliferation in human retinal pigment epithelium: relevance for proliferative retinal disease.

PURPOSE The aim of this study was to determine the expression and localization of integrin alpha5beta1 in human retinal pigment epithelium (RPE) and its ability to modulate RPE cell attachment, proliferation, migration, and F-actin cytoskeleton distribution. METHODS Expression and localization of alpha5beta1 were analyzed on human RPE by immunoblot/immunofluorescence. Polarized secretion of fibronectin was measured. RPE attachments to different substrates were determined using cell attachment screening kits. BrdU incorporation and wound-healing assays were used to test hfRPE proliferation and migration. F-actin cytoskeleton was visualized with phalloidin. RESULTS Integrin alpha5beta1 was detected in native adult and fetal human RPE. The alpha5-subunit is predominantly localized at the apical membrane of hfRPE, whereas the beta1-subunit is uniformly detected at the apical/basolateral membranes. The authors also found that hfRPE cultures secrete significant amounts of fibronectin to the apical bath. JSM6427, a specific integrin alpha5beta1 antagonist, significantly inhibited hfRPE cell attachment to fibronectin, but not laminin, or collagen I or IV. JSM6427 also showed a strong inhibitory effect on bFGF, PDGF-BB, and serum-induced cell migration and proliferation. Furthermore, JSM6427 induced significant disruption of the F-actin cytoskeleton of dividing RPE cells but had no effect on quiescent cells. CONCLUSIONS The apical localization of alpha5beta1 and the secretion of fibronectin to the apical bath suggest the presence of an autocrine loop that can guide the migration of RPE. The strong inhibitory effects of JSM6427 on human RPE cell attachment, proliferation, and migration is probably mediated by F-actin cytoskeletal disruption in proliferating cells and suggests a potential clinical use of this compound in proliferative retinopathies.

Inflammation-dependent α5β1 (very late antigen-5) expression on leukocytes reveals a functional role for this integrin in acute peritonitis

The potential role of α5β1 (VLA‐5) in leukocyte trafficking in zymosan‐induced acute peritonitis was determined. In naïve mice, ∼98% of Gr1high cells (PMN) in bone marrow and circulation were α5β1‐negative; these profiles were modestly affected by peritoneal injection of zymosan. In contrast, ∼30% of Gr1high cells recruited by zymosan (24 h) to the peritoneal cavity expressed α5β1. With respect to F4/80+ cells, ∼60% of bone marrow and peripheral blood populations expressed α5β1, with ∼90% positivity in resident cells of noninflamed peritoneum. Analysis of α5β1 expression revealed inflammation‐dependent increased expression on Gr1high and F4/80+ cells in bone marrow, blood, and peritoneal cavity. Blockade of α5β1, by an anti‐α5 mAb, attenuated zymosan‐induced 24 h recruitment of Gr1high and F4/80+ cells. At least one underlying mechanism of this action was reduction of cell adhesion and transmigration across microvascular vessels, as revealed by intravital microscopy. Confocal analyses indicated that deposition of fibronectin, the principal ligand for α5β1, was up‐regulated significantly on and around the inflamed mesenteric microvasculature. These data suggest that the effects of α5‐blockade may be a result of inhibition of α5β1‐dependent leukocyte adhesion to and migration along the fibronectin matrix. This is the first report that identifies a functional role for α5β1 in leukocyte trafficking during acute inflammation.

SAR of N-phenyl piperidine based oral integrin α5β1 antagonists

Recently, a new class of selective integrin alpha5beta1inhibitors consisting of a heterocyclic based scaffold was published. Herein the SAR and pharmacokinetic profiles of N-phenyl piperidine derivatives are described.

Discovery of orally available integrin α5β1 antagonists

Previous research within our laboratories identified the 3-hydroxypyrrolidine scaffold 1 as a new and selective integrin alpha5beta1 inhibitor class which was designed for local administration. Herein the discovery of new orally available integrin alpha5beta1 inhibitor scaffolds for potential systemic treatment is described.