E. V. Parfenova

Urokinase induces ROS production in vascular smooth muscle cells

Urokinase stimulates the production of superoxide radical in cultured aortal smooth muscle cells simultaneously with activation of the expression of NAD(F)H-oxidases nox1, nox4, and phox22. Antioxidant ebselen abolishes the stimulating effect of urokinase on smooth muscle cell proliferation. The data showed that urokinase can potentiate oxidative stress in the arterial wall and can play an important role in the development of adverse arterial remodeling.

Urokinase stimulates production of matrix metalloproteinase-9 in fibroblasts with involvement of reactive oxygen species.

In cultured fibroblasts, urokinase stimulated expression of MMP-9 and generation of ROS, while antioxidant ebselen abolished the stimulating effect of urokinase on MMP-9 expression. sTNF-α produced similar and more pronounced stimulating effect. The data showed that urokinase could regulate MMP-9 expression via ROS generation in fibroblasts, which can play an important role in stimulation of their migration and development of constrictor (negative) vascular remodeling due to thickening of the adventitia.

Structural investigations of recombinant urokinase growth factor-like domain

Urokinase-type plasminogen activator (uPA) is a serine protease that converts the plasminogen zymogen into the enzymatically active plasmin. uPA is synthesized and secreted as the single-chain molecule (scuPA) composed of an N-terminal domain (GFD) and kringle (KD) and C-terminal proteolytic (PD) domains. Earlier, the structure of ATF (which consists of GFD and KD) was solved by NMR (A. P. Hansen et al. (1994) Biochemistry, 33, 4847–4864) and by X-ray crystallography alone and in a complex with the soluble form of the urokinase receptor (uPAR, CD87) lacking GPI (C. Barinka et al. (2006) J. Mol. Biol., 363, 482–495). According to these data, GFD contains two β-sheet regions oriented perpendicularly to each other. The area in the GFD responsible for binding to uPAR is localized in the flexible Ω-loop, which consists of seven amino acid residues connecting two strings of antiparallel β-sheet. It was shown by site-directed mutagenesis that shortening of the Ω-loop length by one amino acid residue leads to the inability of GFD to bind to uPAR (V. Magdolen et al. (1996) Eur. J. Biochem., 237, 743–751). Here we show that, in contrast to the above-mentioned studies, we found no sign of the β-sheet regions in GFD in our uPA preparations either free or in a complex with uPAR. The GFD seems to be a rather flexible and unstructured domain, demonstrating in spite of its apparent flexibility highly specific interaction with uPAR both in vitro and in cell culture experiments. Circular dichroism, tryptophan fluorescence during thermal denaturation of the protein, and heteronuclear NMR spectroscopy of 15N/13C-labeled ATF both free and in complex with urokinase receptor were used to judge the secondary structure of GFD of uPA.

Modulation of the Inflammatory Status of Macrophages and Their Paracrine Effect on the Sensitivity of Adipocytes to Insulin with Sirtuin and PPARγ Receptor Activators

We studied the effect of SIRT1 deacetylase and PPARγ receptor activators on proinflammatory (M1), anti-inflammatory (M2) polarization of RAW264.7 macrophages and their modulating effects on insulin sensitivity of adipocytes. In M1 macrophages, the expression of TNFα and CXCL9, secretion of CXCL11, ROS generation, and content of dendritic-like cells were elevated. In M2 macrophages, expression of IGF-1 and ALOX15 factors was enhanced. SIRT1 activator (DCHC) and PPARγ receptor ligand (rosiglitazone) reduced expression of inflammatory markers TNFα and CXCL9 and increased expression of IGF-1 and ALOX15. SIRT1 inhibitor Ex527 increased the proportion of dendritic cells in macrophage populations. The paracrine effect of M1-macrophage-conditioned media attenuated insulin-dependent phosphorylation of threonine (Thr308) in Akt kinase and enhanced phosphorylation of serine (Ser473). This effect was attenuated by DCHC and rosiglitazone.

Regulatory Effects of Urokinase on Mesenchymal Stromal Cell Migration, Proliferation, and Matrix Metalloproteinase Secretion

We studied the effect of urokinase, its recombinant forms, and domain fragments on migration and proliferation of adipose tissue mesenchymal stromal cells (MSCs) and MMP secretion by these cells. Urokinase, but not its recombinant forms, slightly induced directed migration of MSCs. Spontaneous migration of MSCs increased under the action of urokinase or its isolated kringle domain. Migration induced by platelet-derived growth factor was inhibited by proteolytically inactive form of urokinase, the kringle domain, and blocking antibody to urokinase receptor. Urokinase, its proteolytically inactive form, and kringle domain produced no effect on MSC proliferation. In contrast to platelet-derived growth factor, all urokinase forms induced secretion of MMP-9 by MSCs.

Proteolytically Inactive Recombinant Forms of Urokinase Suppress Migration of Endothelial Cells

Proteolytically inactive recombinant forms of urokinase (uPAHQ and amino-terminal fragment) inhibit spontaneous migration of endothelial cells; amino-terminal fragment also suppresses angiogenesis stimulated by basic fi broblast growth factor in vitro. These fi ndings suggest the possibility of using synthesized proteolytically inactive recombinant forms of urokinase for the regulation of endothelial cell migration and suppression of neoangiogenesis.

Urokinase stimulates differentiation of fibroblasts into myofibroblasts and their proliferation in damaged adventitia.

Urokinase expression in the adventitia of rat common carotid artery increased on the 4th day after periadventitial damage. Periadventitial application of recombinant urokinase increased the area of the adventitia and the content of contractile and proliferating cells, while proteolytically inactive recombinant urokinase was ineffective.