Vitronectin-binding PAI-1 protects against the development of cardiac fibrosis through interaction with fibroblasts

Abstract

Plasminogen activator inhibitor-1 (PAI-1) promotes or abates fibrotic processes occurring in different organs. Binding of PAI-1 to vitronectin, an extracellular matrix component, may inhibit vitronectin–integrin complex-mediated cellular responses in pathophysiological conditions. To investigate the importance of plasmin suppression vs vitronectin-binding pathways of PAI-1 in cardiac fibrosis, we studied uninephrectomized mice fed a high salt diet and infused with angiotensin II (Ang II) together with different PAI-1 variants, including PAI-1AK (AK) that inhibits plasminogen activators but does not bind vitronectin, PAI-1RR (RR) that binds vitronectin but does not have protease inhibitory effects or control PAI-1 (CPAI), the control mutant that has similar molecular backbone and half-life as AK and RR while retaining all functions of native PAI-1. Compared with RR and CPAI, non-vitronectin-binding AK significantly increased expression of cardiac fibroblast marker, periostin (Ang + AK 8.40± 3.55 vs Ang RR 2.23 ± 0.44 and Ang CPAI 2.33 ± 0.12% positive area, both P <0.05) and cardiac fibrosis (Ang + AK 1.79 ± 0.26% vs Ang + RR 0.91 + 0.18% and Ang + CPAI 0.81 ± 0.12% fibrotic area, both P <0.05), as well as Col1 mRNA (Ang + AK 12.81 ± 1.84 vs Ang + RR 4.04 ± 1.06 and Ang + CPAI 5.23 ± 1.21 fold increase, both P <0.05). To elucidate mechanisms underlying the protective effects of vitronectin-binding PAI-1 against fibrosis, fibroblasts from normal adult human ventricles were stimulated with Ang and different PAI-1 variants. Protease inhibitory AK and CPAI increased supernatant fibronectin, while decreasing plasminogen activator/plasmin activities and matrix metalloproteinase. RR and CPAI variants significantly reduced fibroblast expression of integrin β3, vitronectin level in the supernatant and fibroblast adhesion to vitronectin compared with the non-vitronectin-binding AK. Further, RR and CPAI preserved apoptotic, decreased anti-apoptotic and proliferative activities in fibroblasts. Thus, PAI-1 promotes or protects against development of cardiac fibrosis differentially through the protease inhibitory pathway or through its binding to vitronectin.

Discovery and characterisation of an antibody that selectively modulates the inhibitory activity of plasminogen activator inhibitor-1

“…To better realise the therapeutic potential of PAI-1 blockade, it is important to understand the relative contribution of these two pathways in each disease setting. Studies reported to define the contribution of vitronectin and/or protease binding roles of PAI-1 in fibrotic or angiogenic disease pathways have been limited to the administration of recombinant mutant PAI-1 molecules 44–46 , which may be impacted by the presence of endogenous PAI-1 or challenges in administering PAI-1 at physiologically relevant levels to specific target cells or tissues. MEDI-579 is effective in a mouse model of diabetic kidney disease 47 – a model demonstrated to be dependent upon the protease-inhibitory activity of PAI-1 alone 48 .…”

<p>Matrilysins and Stromelysins in Pathogenesis and Diagnostics of Cancers</p>

“…The binding of PAI-1 to vitronectin blocks the vitronectin–integrin αVβ3 interaction, and regulates variety of cell activities including adhesion, migration, proliferation and survival. 58 Complex of PAI-1-vitronectin, may inhibit vitronectin–integrin complex, which mediates cellular responses in pathophysiological conditions like cardiac fibrosis, 58 but also in tumor progression thus promotion of angiogenesis in cancer tissue. 59 Data received by Lijnen et al showed that stable PAI-1 bounded to vitronectin was cleaved and inactivated by MMP-3, however, the cleaved protein did not bind to vitronectin.…”

Biomarker Discovery of Acute Coronary Syndrome Using Proteomic Approach

“…Moreover, it has been shown that during the plaque-induced inflammatory reaction, secreted cytokines induce the production of VN [ 41 ] that establishes interaction with coagulation and fibrinolysis-related proteins and binds to and stabilizes the plaque-induced plasminogen activator inhibitor-1 (PAI-1), a protein that suppresses the conversion of plasminogen to active plasmin [ 41 ]. The decomposition of the intra-arterial thrombus is suppressed by the action of the PAI-1/VN complex, which suggests that the decomposition of thrombus produced by the ruptured plaque would also be suppressed [ 46 , 47 ]. Additionally, VN can promote cell adhesion via the ανβ3 integrin in the cell membrane and ECM, which is hindered by PAI-1 to inhibit cell proliferation and induce apoptosis [ 46 , 48 ].…”