Antiangiogenic plasma activity in patients with systemic sclerosis

Abstract

Objective. Systemic sclerosis (SSc; scleroderma) is a systemic connective tissue disease with an extensive vascular component that includes aberrant microvasculature and impaired wound healing. The aim of this study was to investigate the presence of antiangiogenic factors in patients with SSc.Methods. Plasma samples were obtained from 30 patients with SSc and from 10 control patients without SSc. The samples were analyzed for the ability of plasma to affect endothelial cell migration and vascular structure formation and for the presence of antiangiogenic activity.Results. Exposure of normal human microvascular dermal endothelial cells to plasma from patients with SSc resulted in decreased cell migration (mean ؎ SEM 52 ؎ 5%) and tube formation (34 ؎ 6%) compared with that in plasma from control patients (P < 0.001 for both). SSc plasma contained 2.9-fold more plasminogen kringle 1-3 fragments (angiostatin) than that in control plasma. The addition of angiostatin to control plasma resulted in inhibition of endothelial cell migration and proliferation similar to that observed in SSc plasma. In vitro studies demonstrated that granzyme B and other proteases contained in T cell granule content cleave plasminogen and plasmin into angiostatin fragments.Conclusion. Plasminogen conformation in patients with SSc enables granzyme B and granule content protease to limit the proangiogenic effects of plasmin and increase the levels of antiangiogenic angiostatin. This increase in angiostatin production may account for some of the vascular defects observed in patients with SSc.

Intracellular versus extracellular granzyme B in immunity and disease: challenging the dogma

“…Plasma from SSc patients shows reduced endothelial cell migration and tube formation in vitro. The serum sample was found to contain higher levels of the antiangiogenic protein angiostatin, which Mulligan-Kehoe et al 130 found to be synthesized by GrB through the cleavage of plasminogen (in the presence of another granule protein) as well as from plasmin. As plasmin is proangiogenic in nature, GrB may also be responsible for decreasing levels of plasmin in SSc serum, thereby decreasing angiogenesis through the synthesis of angiostatin and the degradation of plasmin.…”

“…134 In addition to ECM proteolysis, GrB can act on extracellular substrates involved in the clotting cascade such as plasmin, plasminogen, von Willebrand Factor (VWF), and the matrix form of fibrinogen. 129,130 GrB cleaves VWF in domains that are necessary for platelet interaction and cleavage prevents platelet aggregation, spreading, tethering, and adhesion to the VWF multimer. 129 As GrB has a high affinity for ECM binding, Buzza et al 129 suggest that it would accumulate in areas of inflammation and prevent/delay thrombosis in these areas.…”

“…GrB-dependent cleavage of plasmin and plasminogen has implications outside clotting as degradation of these proteins may also inhibit angiogenesis. 130 GrB can cleave cell surface receptors such as the neuronal glutamate receptor, Notch1, and FGFR1. 131,132 The cleavage of these cell surface receptors may have implications in cell …”

“…As plasmin is proangiogenic in nature, GrB may also be responsible for decreasing levels of plasmin in SSc serum, thereby decreasing angiogenesis through the synthesis of angiostatin and the degradation of plasmin. 130 Interestingly, autoantigen release may be dependent on cell type in SSc. B23 is resistant to GrB-mediated cleavage in many cell types but appears to be exclusively cleaved in vascular SMCs.…”

A quarter century of granzymes

“…Other substrates have included proteins involved in blood clotting, and angiogenesis. 94,97 Additionally, GrB cleaves a number of cell receptors, which may influence their ability to respond to growth and survival signals, as well as promote the production of autoantigens. 98,99 Several studies have suggested an inflammatory role for GrA.…”