1. Thrombin peptide (TP508) promotes adipose tissue-derived stem cell proliferation via PI3 kinase/Akt pathway
Yao-Hua Song, Eckhard Alt, Fabian Muehlberg, Susanne Freyberg J Vasc Res . 2009;46(2):98-102. doi: 10.1159/000142727.
A synthetic peptide representing the receptor-binding domain of human thrombin (TP508) promotes angiogenesis and accelerates wound healing in animal models. However, the mechanisms underlying the therapeutic effects of TP508 have not been clearly defined. In this study, we set out to determine whether TP508 could stimulate stem cell proliferation. Adipose tissue-derived stem cells (ASCs) were incubated with TP508 (5 microg/ml) and cell proliferation was determined by bromodeoxyuridine (BrdU) incorporation. Our data showed that TP508 treatment significantly stimulated BrdU incorporation in ASCs (p < 0.01). The increased BrdU incorporation induced by TP508 was abolished by the PI3 kinase (PI3K) inhibitor LY294002 at 50 microM. Western blot analysis of ASCs revealed increased phosphorylation of Akt in response to TP508 when compared to unstimulated controls. These results indicate that TP508 exerts proliferative effects on ASCs via the PI3K/Akt pathway.
2. TP508 (Chrysalin) reverses endothelial dysfunction and increases perfusion and myocardial function in hearts with chronic ischemia
Gerald M Fuller, Darrell H Carney, Matthew W Miller, Barbara Olszewska-Pazdrak, Lih Kuo, Travis W Hein, Michelle M Mertens, Lori A Makarski, Theresa W Fossum, Fred Clubb J Cardiovasc Pharmacol Ther . 2008 Sep;13(3):214-25. doi: 10.1177/1074248408321468.
Endothelial dysfunction (ED) is characterized by impaired nitric oxide (NO) signaling, decreased NO-dependent vasodilatation, increased vascular inflammation, and diminished response to angiogenic factors. TP508 (Chrysalin), an angiogenic tissue repair peptide, was tested for potential effects on myocardial revascularization and ED using a porcine model of chronic myocardial ischemia. TP508 increased perfusion in ischemic regions up to16-fold (P < .02) and doubled myocardial wall thickening (P < .02) relative to placebo controls. Ischemic arterioles exhibited impaired NO-mediated vasodilation and diminished NO production. TP508 reversed ischemic effects, increasing NO-mediated vasodilation (P < .05), endothelial nitric oxide synthase (eNOS) expression, and NO production. In human endothelial cells, TP508 stimulated eNOS activation (1.84 +/- 0.2-fold; P < .02), increased NO production (85 +/- 18%; P < .02), and prevented hypoxia-induced eNOS downregulation (P < .01). Thus, TP508 reverses ED both in porcine ischemic hearts and cultured human endothelial cells. These results suggest potential therapeutic benefit of TP508 in myocardial revascularization and treatment of ED-related diseases.
3. Systemic administration of thrombin peptide TP508 enhances VEGF-stimulated angiogenesis and attenuates effects of chronic hypoxia
Barbara Olszewska-Pazdrak, Darrell H Carney J Vasc Res . 2013;50(3):186-96. doi: 10.1159/000348250.
Revascularization of chronic wounds and ischemic tissue is attenuated by endothelial dysfunction and the inability of angiogenic factors to stimulate angiogenesis. We recently showed that TP508, a nonproteolytic thrombin peptide, increases perfusion and NO-dependent vasodilation in hearts with chronic ischemia and stimulates NO production by endothelial cells. In this study, we investigated systemic in vivo effects of TP508 on VEGF-stimulated angiogenesis in vitro using aortic explants in normoxic and hypoxic conditions. Mice were injected with saline or TP508 and 24 h later aortas were removed and cultured to quantify endothelial sprouting. TP508 injection increased endothelial sprouting and potentiated the in vitro response to VEGF. Exposure of control explants to hypoxia inhibited basal and VEGF-stimulated endothelial cell sprouting. This effect of hypoxia was significantly prevented by TP508 injection. Thus, TP508 systemic administration increases responsiveness of aortic endothelial cells to VEGF and diminishes the effect of chronic hypoxia on endothelial cell sprouting. Studies using human endothelial cells in culture suggest that protective effects of TP508 during hypoxia may involve stimulation of endothelial cell NO production. These data suggest potential clinical benefit of using a combination of systemic TP508 and local VEGF as a therapy for revascularization of ischemic tissue.