Extracellular ATP hydrolysis in Caco-2 human intestinal cell line.

Extracellular nucleotides and nucleosides activate signaling pathways that play major roles in the physiology and pathophysiology of the gastrointestinal tract. Ectonucleotidases hydrolyze extracellular nucleotides and thus regulate ligand exposure to purinergic receptors. In this study, we investigated the expression, localization and activities of ectonucleotidases using Caco-2 cells, a model of human intestinal epithelial cells. In addition, by studying ATP release and the rates of extracellular ATP (eATP) hydrolysis, we analyzed the contribution of these processes to the regulation of eATP in these cells. Results show that Caco-2 cells regulate the metabolism of eATP and by-products by ecto-nucleoside triphosphate diphosphohydrolase-1 and -2, a neutral ecto-phosphatase and ecto-5'-nucleotidase. All these ectoenzymes were kinetically characterized using intact cells, and their presence confirmed by denatured and native gels, western blot and cytoimmunofluorescence techniques. In addition, regulation of eATP was studied by monitoring the dynamic balance between intracellular ATP release and ectoATPase activity. Following mechanical and hypotonic stimuli, Caco-2 cells triggered a strong but transient release of intracellular ATP, with almost no energy cost, leading to a steep increase of eATP concentration, which was later reduced by ectoATPase activity. A data-driven algorithm allowed quantifying and predicting the rates of ATP release and ATP consumption contributing to the dynamic accumulation of ATP at the cell surface.

Regulation of extracellular ATP of human erythrocytes treated with α-hemolysin. Effects of cell volume, morphology, rheology and hemolysis.

Alpha-hemolysin (HlyA) of uropathogenic strains of Escherichia coli irreversibly binds to human erythrocytes (RBCs) and triggers activation of ATP release and metabolic changes ultimately leading to hemolysis. We studied the regulation of extracellular ATP (ATPe) of RBCs exposed to HlyA. Luminometry was used to assess ATP release and ATPe hydrolysis, whereas changes in cell volume and morphology were determined by electrical impedance, ektacytometry and aggregometry. Exposure of RBCs to HlyA induced a strong increase of [ATPe] (3-36-fold) and hemolysis (1-44-fold), partially compensated by [ATPe] hydrolysis by ectoATPases and intracellular ATPases released by dead cells. Carbenoxolone, a pannexin 1 inhibitor, partially inhibited ATP release (43-67%). The un-acylated toxin ProHlyA and the deletion analog HlyA∆914-936 were unable to induce ATP release or hemolysis. For HlyA treated RBCs, a data driven mathematical model showed that simultaneous lytic and non-lytic release mainly governed ATPe kinetics, while ATPe hydrolysis became important after prolonged toxin exposure. HlyA induced a 1.5-fold swelling, while blocking this swelling reduced ATP release by 77%. Blocking ATPe activation of purinergic P2X receptors reduced swelling by 60-80%. HlyA-RBCs showed an acute 1.3-2.2-fold increase of Ca2+i, increased crenation and externalization of phosphatidylserine. Perfusion of HlyA-RBCs through adhesion platforms showed strong adhesion to activated HMEC cells, followed by rapid detachment. HlyA exposed RBCs exhibited increased sphericity under osmotic stress, reduced elongation under shear stress, and very low aggregation in viscous media. Overall results showed that HlyA-RBCs displayed activated ATP release, high but weak adhesivity, low deformability and aggregability and high sphericity.

[Cystic adrenal lesion. Incidental finding]. / Lesión quística adrenal. Hallazgo incidental.

We report a case of a non functioning cystic adrenal mass. It was incidentally found in an abdominal ultrasound carried out for unrelated symptoms. According to the classification of adrenal cysts it is a multilocular pseudocyst with wall fibrosis and calcification. The pseudocyst lining expresses Factor VIII suggesting a vascular origin.

[Catastrophic antiphospholipid syndrome. Communication of 2 forms of presentation]. / Síndrome antifosfolipídico catastrófico. Comunicación de dos formas de presentación.

Antiphospholipid syndrome is characterized by recurrent fetal loss, arterial and venous thromboses, thrombocytopenia and circulating antiphospholipid antibodies. Few patients have a rapidly progressive, fatal outcome. We report two young patients with systemic lupus erythematosus and antiphospholipid antibodies who died after a short course of disease. Although clinical and laboratory findings differed in both patients--small vessel thromboses and microangiopathic hemolytic anemia mimicking thrombotic thrombocytopenic purpura predominated in one of the patients while small and medium size vessel thromboses without hemolysis were present in the other case--autopsy revealed widespread visceral thromboses in both of them, features consistent with a diagnosis of catastrophic antiphospholipid syndrome. This syndrome has not been reported to occur in association with Pneumocistis carinii pneumonia as we describe in one of our patients.

[Primary laryngeal tuberculosis caused by Mycobacterium bovis]. / Tuberculosis laríngea primaria por Mycobacterium bovis.

It is suggested that laryngeal tuberculosis is a common complication of pulmonary tuberculosis. The most frequent germ is Mycobacterium tuberculosis. We present a case in which a infrequent bacillus, Mycobacterium bovis, was isolated without lung afectation. Considerations about morphologic and microbiologic findings are discussed.

[Aphthous ulcers and their syndromes]. / Las aftas y sus síndromes.

With the object to clarify the different aphthous syndromes, their clinical manifestations, histopathological and radiological patterns and their evolution, the authors report three patients (26 year old woman with a bipolar aphthosis, Neumann type; 47 year old man with a Behcet's syndrome, and a 53 year old woman with a recurrent necrotic mucous periadenitis), pointing out that these entities are as important for dermatologists as for the other specialists.