Activities of enzymes that hydrolyze adenine nucleotides in platelets from rats experimentally demyelinated with ethidium bromide and treated with interferon-beta.
ABSTRACT The activities of the enzymes NTPDase (EC 220.127.116.11, apyrase, CD39) and 5'-nucleotidase (EC 18.104.22.168, CD73) were analyzed in platelets from rats submitted to demyelination by ethidium bromide (EB) and treated with interferon beta (IFN-beta). The following groups were studied: I - control (saline), II - (saline and IFN-beta), III - (EB) and IV - (EB and IFN-beta). After 7, 15 and 30 days, the animals (n=7) were sacrificed and the platelets were separated by the method of Lunkes et al. [Lunkes, G., Lunkes D., Morsch, V., Mazzanti, C., Morsch, A., Miron, V., Schetinger, M.R.C., 2004. NTPDase and 5'-nucleotidase in rats alloxan- induced diabetes. Diabetes Research and Clinical Practice 65, 1-6]. NTPDase activity for ATP and ADP substrates was significantly lower in groups II and III after seven days, when compared to control (p<0.001). At fifteen days, ATP hydrolysis was significantly lower in group III and IV and higher in group II (p<0.001), while there was an activation of ADP hydrolysis in group II (p<0.001), when compared with the control. 5'-nucleotidase activity was significantly higher in group IV (p<0.001) after seven days, and lower in the groups III and IV (p<0.001) after fifteen days in relation to the control. No significant differences were observed in NTPDase and 5'-nucleotidase activities after thirty days. In conclusion, our study demonstrated that the hydrolysis of adenine nucleotides is modified in platelets of rats demyelinated and treated with IFN-beta.
Article: Platelet physiology and thrombosis.[show abstract] [hide abstract]
ABSTRACT: Glycoprotein (GP) Ibalpha of the GPIb-IX-V complex and GPVI bind von Willebrand factor (vWF) and collagen, respectively, and are critical for the initial interaction of circulating platelets with the injured vessel wall under high shear conditions. These interactions act together to facilitate stable thrombus formation in vivo. Ligand binding to GPIb-IX-V of the leucine-rich repeat family or GPVI of the immunoglobulin superfamily initiates platelet activation, and inside-out activation of the platelet integrin, alphaIIbbeta3, that binds vWF or fibrinogen and mediates platelet aggregation. The binding site for GPIbalpha on vWF resides in the conserved A1 domain, encompassing the disulfide bond at Cys509-Cys695. This domain may be activated to bind platelet GPIbalpha under shear stress by anchoring of the downstream A3 domain to collagen and conformational distortion of the intervening A2 domain. The N-terminal, 282 residues, of GPIbalpha contains the binding site for vWF-A1, as well as the conserved A-type domain of the leukocyte integrin alphaMbeta2 (alphaM I domain) and P-selectin expressed on activated platelets or endothelial cells. Endothelial P-selectin also supports surface expression of vWF multimers, enabling platelet vessel wall interaction by at least two mechanisms. Recent evidence suggests GPVI that binds collagen, and GPIb-IX-V that binds collagen-bound vWF are physically associated on the platelet surface. This review will focus on the structure-function of primary platelet adhesion receptors, GPIb-IX-V and GPVI, and how they act together to regulate platelet thrombus formation in pathophysiology.Thrombosis Research 02/2004; 114(5-6):447-53. · 3.13 Impact Factor
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ABSTRACT: Oligodendrocytes and Schwann cells are engaged in myelin production, maintenance and repairing respectively in the central nervous system (CNS) and the peripheral nervous system (PNS). Whereas oligodendrocytes act only within the CNS, Schwann cells are able to invade the CNS in order to make new myelin sheaths around demyelinated axons. Both cells have some limitations in their activities, i.e. oligodendrocytes are post-mitotic cells and Schwann cells only get into the CNS in the absence of astrocytes. Ethidium bromide (EB) is a gliotoxic chemical that when injected locally within the CNS, induce demyelination. In the EB model of demyelination, glial cells are destroyed early after intoxication and Schwann cells are free to approach the naked central axons. In normal Wistar rats, regeneration of lost myelin sheaths can be achieved as early as thirteen days after intoxication; in Wistar rats immunosuppressed with cyclophosphamide the process is delayed and in rats administered cyclosporine it may be accelerated. Aiming the enlightening of those complex processes, all events concerning the myelinating cells in an experimental model are herein presented and discussed.Arquivos de Neuro-Psiquiatria. 01/2001;
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ABSTRACT: Bovine myelin basic protein (BP) induced a shape change and endogenous phosphorylation of a 45,000 (45K) molecular weight protein of intact human platelets. This effect occurred rapidly over an effective concentration range of 5-100 microM BP. BP peptides encompassing residues 1-42, 43-88, and 89-169 from the BP molecule of 169 residues, neither induced phosphorylation of platelets nor blocked the effect of intact BP. Subfractionation of disrupted platelets demonstrated the phosphorylated 45K protein in the 100,000 xg supernate. When isolated platelet membranes were used, no BP induced phosphorylation of a 45K protein could be detected. The amino acid composition of the purified, phosphorylated 45K protein differed from those of other known platelet proteins. BP itself was also phosphorylated by an endogenous platelet protein kinase(s) present both in the 100,000 xg supernatant and in the isolated membrane fraction of platelets. These results indicate that the normal or pathological release of BP from myelin may lead to phosphorylation of an internal protein of platelets and possibly other tissue elements with resultant metabolic and functional changes.Thrombosis Research 04/1982; 25(6):487-99. · 3.13 Impact Factor