Integrins as targets in therapy

Identification of N-acyl 4-(3-pyridonyl)phenylalanine derivatives and their orally active prodrug esters as dual acting α4β1 and α4β7 receptor antagonists

From a series of N-acyl 4-(3-pyridonyl)phenylalanine derivatives of 4, the trifluoromethyl derivative 28 was identified as a potent, dual acting alpha4 integrin antagonist with activity in primate models of allergic asthma. Investigation of a series of prodrug esters led to the discovery of the morpholinopropyl derivative 48 that demonstrated good intestinal fluid stability, solubility and permeability. Compound 48 gave high blood levels of 28 when dosed orally in cynomolgus monkeys. Surprisingly, hydrolysis of 48 was rapid in liver microsomes from the pharmacological species, mouse, rat and monkey, but slow in dog and human; in vivo studies also indicated there was prolonged exposure to unchanged prodrug in dogs.

The biomechanical integrin

The integrin lies at the center of our efforts to understand mechanotransduction in the human body. Over the past two decades, a wealth of information has yielded important insights into integrin structure and functioning in biochemical pathways; however, relatively little emphasis has been placed on mechanics. In this article, we review the current knowledge base of integrin mechanobiology by examining the role of integrins in stabilizing tissue structure, the mechanisms of integrin force transfer, the process of cell migration, and the pathology of cancer. In order to successfully address the gaps in cancer and other disease research going forward, future efforts of integrin mechanobiology must focus on examining cells in 3D environments and integrating our current understanding into computational models that predict the behavior of integrins in non-equilibrium interactions.

Integrins and the activation of latent transforming growth factor beta1 - an intimate relationship

Integrins are crucial for the ability of cells to sense mechanical perturbations and to transmit intracellular stress to their environment. We here review the more recently discovered role of integrins in activating the pleiotrophic cytokine transforming growth factor beta 1 (TGF-beta1). TGF-beta1 controls tissue homeostasis in embryonic and normal adult tissues and contributes to the development of fibrosis, cancer, autoimmune and vascular diseases when being mis-regulated. In most of these conditions, active TGF-beta1 is generated by dissociation from a large latent protein complex that sequesters latent TGF-beta1 in the extracellular matrix (ECM). Two main models are proposed how integrins contribute to latent TGF-beta1 activation: (1) In a protease-dependent mechanism, integrins alphavbeta8 and alphavbeta3 are suggested to simultaneously bind the latent TGF-beta1 complex and proteinases. This close vicinity at the cell surface improves enzymatic cleavage of the latent complex to release active TGF-beta1. (2) Integrins alphavbeta3, alphavbeta5, alphavbeta6, and alphavbeta8 appear to change the conformation of the latent TGF-beta1 complex by transmitting cell traction forces. This action requires association of the latent complex with a mechanically resistant ECM and is independent from proteolysis. Understanding that different integrins use different mechanisms to activate latent TGF-beta1 opens new possibilities to develop cell-specific therapeutic strategies for TGF-beta1-induced pathologies.