Altered E-NTPDase/E-ADA activities and CD39 expression in platelets of sickle cell anemia patients.

Sickle cell anemia (SCA) is a hemoglobinopathy characterized by hemolysis and vaso-occlusions caused by rigidly distorted red blood cells. Sickle cell crisis is associated with extracellular release of nucleotides and platelets, which are critical mediators of hemostasis participating actively in purinergic thromboregulatory enzymes system.This study aimed to investigate the activities of purinergic system ecto-enzymes present on the platelet surface as well as CD39 and CD73 expressions on platelets of SCA treated patients. Fifteen SCA treated patients and 30 health subjects (control group) were selected. Ecto-nucleoside triphosphate diphosphohydrolase (E-NTPDase), ecto-5'-nucleotidase (E-5'-NT) and ecto-adenosine deaminase (E-ADA) activities were measured in platelets isolated from these individuals. Results demonstrated an increase of 41 % in the E-NTPDase for ATP hydrolysis, 52% for ADP hydrolysis and 60 % in the E-ADA activity in SCA patients (P<0.05); however, a two folds decrease in the CD39 expression in platelets was observed in the same group (P<0.01). The increased E-NTPDase activity could be a compensatory mechanism associated with the low expression of CD39 in platelets. Besides, alteration of these enzymes activities suggests that the purinergic system could be involved in the thromboregulatory process in SCA patients.

NTPDase and 5'-nucleotidase activities from synaptosomes and platelets of rats exposed to cadmium and treated with N-acetylcysteine.

The purpose of the present investigation was to evaluate the hydrolysis of adenine nucleotides on synaptosomes and platelets obtained from rats exposed to cadmium (Cd) and treated with N-acetylcysteine (NAC). Rats received Cd (2 mg/kg) and NAC (150 mg/kg) by gavage every other day for 30 days. Animals were divided into four groups (n = 4-6): control/saline, NAC, Cd, and Cd/NAC. The results of this study demonstrated that NTPDase and 5'-nucleotidase activities were increased in the cerebral cortex synaptosomes of Cd-poisoned rats, and NAC co-treatment reversed these activities to the control levels. In relation to hippocampus synaptosomes, no differences on the NTPDase and 5'-nucleotidase activities of Cd-poisoned rats were observed and only the 5'-nucleotidase activity was increased by the administration of NAC per se. In platelets, Cd-intoxicated rats showed a decreased NTPDase activity and no difference in the 5'-nucleotidase activity; NAC co-treatment was inefficient in counteracting this undesirable effect. Our findings reveal that adenine nucleotide hydrolysis in synaptosomes and platelets of rats were altered after Cd exposure leading to a compensatory response in the central nervous system and acting as a modulator of the platelet activity. NAC was able to modulate the purinergic system which is interesting since the regulation of these enzymes could have potential therapeutic importance. Thus, our results reinforce the importance of the study of the ecto-nucleotidases pathway in poisoning conditions and highlight the possibility of using antioxidants such as NAC as adjuvant against toxicological conditions.

Enzymes that hydrolyze adenine nucleotides in patients with ischemic heart disease.

BACKGROUND: The extracellular nucleotides, ATP and ADP, as well as the nucleoside adenosine have been implicated in a great number of pathologic and physiological functions. However, extracellular adenine nucleotide levels are controlled by a complex cell surface-located group of enzymes called ectonucleotidases. We evaluated activities of enzymes that hydrolyze adenine nucleotides and nucleosides in platelets from patients with ischemic heart disease (IHD). METHODS: Sixty IHD patients were selected for the study. The activities of ectonucleoside triphosphate diphosphohydrolase (NTPDase, CD39), ectonucleotide pyrophosphatase/phosphodiesterase (E-NPP), ecto-5'-nucleotidase and adenosine deaminase (ADA) were studied in isolated platelets of these patients, as well as the platelet aggregation and NTPDase expression. RESULTS: The results show that NTPDase, ecto-5'-nucleotidase, E-NPP activities and NTPDase expression were increased in platelets of IHD patients when compared with the control group (p < 0.05). On the other hand, ADA activity and platelet aggregation were decreased in IHD patients, when compared with the control group (p < 0.05). CONCLUSIONS: The pathological condition in IHD generates alterations in ectonucleotidase activities as a compensatory organic response to thrombotic events that occur in IHD.

Activities of enzymes that hydrolyze adenine nucleotides in platelets from patients with rheumatoid arthritis.

OBJECTIVES: To investigate whether there are changes in the activity of the enzymes NTPDase, 5'-nucleotidase, E-NPP and ADA in platelets from patients with rheumatoid arthritis (RA). DESIGN AND METHODS: Thirty-five RA patients diagnosed with RA through American College of Rheumatology criteria, as well as 35 healthy patients were selected. NTPDase, 5'-nucleotidase, E-NPP and ADA activities were verified in platelets isolated from these patients. RESULTS: The results demonstrate that an increase in NTPDase (approximately 100%), 5'-nucleotidase (170%), E-NPP (approximately 100%) and ADA (approximately 45%) activities occurred in RA patients when compared to the control group. CONCLUSIONS: Ours results suggest an increase in the NTPDase, 5'-nucleotidase and E-NPP activities, which could be related to a compensatory organic response to excessive platelet aggregation which occurs during the inflammation. The increased ADA activity found in this work could lead to a decrease in the adenosine concentration in the circulation, which could explain the accelerated atherosclerosis found in patients with RA.