Angiostatin inhibits activation and migration of neutrophils

Abstract

There is a critical need to identify molecules that modulate the biology of neutrophils because activated neutrophils, though necessary for host defense, cause exuberant tissue damage through production of reactive oxygen species and increased lifespan. Angiostatin, an endogenous anti-angiogenic cleavage product of plasminogen, binds to integrin αvβ3, ATP synthase and angiomotin and its expression is increased in inflammatory conditions. We test the hypothesis that angiostatin inhibits neutrophil activation, induces apoptosis and blocks recruitment in vivo and in vitro. The data show immuno-reactivity for plasminogen/angiostatin in resting neutrophils. Angiostatin conjugated to FITC revealed that angiostatin was endocytozed by activated mouse and human neutrophils in a lipid raft-dependent fashion. Co-immunoprecipitation of human neutrophil lysates, confocal microscopy of isolated mouse and human neutrophils and functional blocking experiments showed that angiostatin complexes with flotillin-1 along with integrin αvβ3 and ATP synthase. Angiostatin inhibited fMLP-induced neutrophil polarization, as well as caused inhibition of hsp-27 phosphorylation and stabilization of microtubules. Angiostatin treatment, before or after LPS-induced neutrophil activation, inhibited phosphorylation of p38 and p44/42 MAPKs, abolished reactive oxygen species production and released the neutrophils from suppressed apoptosis, as indicated by expression of activated caspase-3 and morphological evidence of apoptosis. Finally, intravital microscopy and myeloperoxidase assay showed inhibition of neutrophil recruitment in post-capillary venules of TNFα-treated cremaster muscle in mouse. These in vitro and in vivo data demonstrate angiostatin as a broad deactivator and silencer of neutrophils and an inhibitor of their migration. These data potentially open new avenues for the development of anti-inflammatory drugs.

Regulation of tissue infiltration by neutrophils

“…The plasminogen-derived cleavage product angiostatin, which exerts anti-angiogenic properties, was shown to also act as an inhibitor of neutrophil recruitment in vitro and in acute inflammation by interfering with β1- and β2-integrin-dependent adhesion to extracellular matrix proteins and endothelium [66]. More recently, the anti-inflammatory actions of angiostatin were expanded, as it was shown to block neutrophil recruitment by inhibiting MAPK signaling and reactive oxygen species production [67]. Furthermore, in the context of autoimmune arthritis, Blazek et al showed that IFN-λ2/IL-28A can block neutrophil recruitment by acting via its cognate receptor IL-28RA on neutrophils [68].…”

Levels of angiogenic regulators and MMP-2, -9 activities in Martorell ulcer: a case report

“…It can be explained by the fact that angiostatins exhibit potent antagonizing action toward VEGF, resulting in mitochondrial damage and activating apoptotic signaling pathway in endothelial cells [20]. Moreover, angiostatin proteins have been shown to inhibit neutrophil activation, induce apoptosis and block neutrophil recruitment [21]. Meanwhile, neutrophils are known to be the predominant cell type in the early inflammation phase and play very important role in wound healing by regulating inflammation, debridement of necrotic tissue, phagocytosis of infectious agents and producing various mediators and growth factors [22].…”

A Hypothesis Concerning the Biphasic Dose-response of Tumors to Angiostatin and Endostatin

“…It inhibits recruitment of macrophages ( Distler et al 2002 ; Chavakis et al 2005 ; Dineen et al 2008 ; Lee et al 2009; Chen et al 2011 ; Li et al 2011 ; Lin et al 2011 ), which are normally attracted into the stroma by signaling involving VEGFR-1 and VEGFR-2 ( Li et al 2011 ) and which are involved with completing vascular circuits with VEGFR-3 ( Tammela et al 2011 ). Angiostatin has recently been shown to inhibit migration and activation of neutrophils ( Aulakh et al 2014 ).…”