Tag Archives: angiostatins
Plasminogen modulates formation and release of platelet angiogenic regulators
A. A. Tykhomyrov, D. D. Zhernosekov, T. V. Grinenko
Palladin Institute of Biochemistry, National Academy of Sciences of Ukraine, Kyiv;
e-mail: artem_tykhomyrov@ukr.net
Received: 19 July 2019; Accepted: 29 November 2019
Platelets store, produce and release a variety of angiogenesis regulators, which can contribute to both normal tissue repair and angiopathy-associated pathologies. Plasminogen has been earlier shown to regulate some platelet functions, but if it is able to modulate angiogenic capacities of platelets is still poorly studied. Thus, the aim of the present study was to evaluate the effects of different plasminogen forms on the formation and secretion of angiogenic protein regulators by platelets. Human washed platelets were obtained by gel-filtration on Sepharose-2B. The levels of P-selectin (CD-62P) exposed on the plasma membrane of untreated and activated platelets was monitored by flow cytometry. Secretion of platelet-derived vascular endothelial growth factor (VEGF) as well as plasminogen fragmentation and angiostatin formation by intact platelets and platelet plasma membranes were analyzed by immunoblotting. It was shown that thrombin or collagen exposure resulted in enhanced P-selectin surface expression by platelets, while Lys-form of plasminogen reduced agonist-induced platelet secretion. Lys-plasminogen, but not Glu-form, inhibited agonist-induced VEGF release from platelets. Activation of platelets significantly accelerated plasminogen cleavage and angiostatin formation. Anti-actin antibodies inhibited plasminogen fragmentation during incubation with platelet plasma membranes indicating surface-exposed actin participation in plasminogen conversion to angiostatins. The present study uncovers a novel function of plasminogen to limit angiogenic potential of platelets via angiostatin formation and inhibition of VEGF secretion.
Levels of angiogenic regulators and MMP-2, -9 activities in Martorell ulcer: a case report
O. M. Petrenko1, A. A. Tykhomyrov2
1Bogomolets National Medical University, Kyiv, Ukraine;
2Palladin Institute of Biochemistry, National Academy of Sciences of Ukraine, Kyiv, Ukraine;
e-mail: artem_tykhomyrov@ukr.net
Received: 27 July 2018; Accepted: 13 December 2018
Martorell hypertensive ischemic leg ulcers (HYTILU) represent a unique form of lower extremity non-healing ulcers that develop in association with poorly controlled high blood pressure. The present study was performed in order to assess levels of protein regulators of angiogenesis (vascular endothelial growth factor, or VEGF, and angiostatins) and to evaluate activities of matrix metalloproteinases (MMPs) (gelatinases MMP-2 and -9) in wound cutaneous tissue in the case of patient with 2-years HYTILU history. VEGF and angiostatin levels were analyzed by Western blot, MMP activities were evaluated by gelatin zymography. We report here for the first time that wound tissue in HYTILU is characterized with increased levels of VEGF (by 75 folds vs. histologically normal tissue, P < 0.01) and dramatic overproduction of angiostatin levels, which are undetectable in healthy cutaneous tissue. Approximately 10-fold elevation in MMP-2 and -9 activities is observed in wound tissue as compared with uninjured cutaneous tissue. Obtained results indicate that increased production of angiogenic inhibitors, angiostatins, may counteract VEGF-induced pro-angiogenic signaling, and together with MMP overactivation, contributes to failed healing of ischemic ulcer. Further extended studies are needed to clarify how changes of angiogenic profile and imbalance of proteolytic activities in non-healing Martorell ulcers can be considered during their management procedures to improve efficacy of surgery debridement and/or skin grafting.
Plasminogen and its fragments in rat brain: a plausible role for astrocytes in angiostatin generation
A. A. Tykhomyrov1, V. S. Nedzvetsky2,3, C. A. Ağca3,
V. V. Korsa1, T. V. Grinenko1
1Palladin Institute of Biochemistry, National Academy of Sciences of Ukraine, Kyiv;
2Dnipropetrovsk National University, Dnipro, Ukraine;
3Bingöl University, Bingöl, Turkey;
e-mail: artem_tykhomyrov@ukr.net
The purpose of the present study was to examine the plasminogen localization and to detect levels of its fragments (angiostatins) in various regions of rat brain as well as to establish whether rat brain astrocytes could be involved in angiostatin production. It was shown immunohistochemically that plasminogen is distributed broadly in the various brain regions, with predominant expression in meningeal layer and IV, V, and VI layers or cerebral cortex, dentate gyrus, meningeal and Purkinje cells, molecular and granular layers of cerebellum, as well as vessel walls. Angiostatin polypeptides were detected by Western blot analysis mostly in the cerebral cortex and were represented by 50 and 40-30 kDa polypeptides. In the whole cell lysates from primary cultures of rat astrocytes, immunoreactive polypeptides with Mm ~ 92, 84, 65-60, 50, 40, 38-30 kDa, corresponding to native plasminogen and a variety of its truncated products, including angiostatin polypeptides, were revealed. Incubation of astrocytes with exogenous plasminogen resulted in gradual increasing levels of some plasminogen fragments, particularly 30 kDa protein. Moreover, this polypeptide appeared to be the single angiostatin released by astrocytes in vitro. We report here for the first time that astrocytes are one of the cell types in CNS that could be responsible for angiostatin formation and releasing.