Relative contribution of ecto-ATPase and ecto-ATPDase pathways to the biphasic effect of ATP on acetylcholine release from myenteric motoneurons

Background and purpose:

The relative contribution of distinct ecto-nucleotidases to the modulation of purinergic signalling may depend on differential tissue distribution and substrate preference.

Experimental approach:

Extracellular ATP catabolism (assessed by high-performance liquid chromatography) and its influence on [³H]acetylcholine ([³H]ACh) release were investigated in the myenteric plexus of rat ileum in vitro.

Key results:

ATP was primarily metabolized via ecto-ATPDase (adenosine 5′-triphosphate diphosphohydrolase) into AMP, which was then dephosphorylated into adenosine by ecto-5′-nucleotidase. Alternative conversion of ATP into ADP by ecto-ATPase (adenosine 5′-triphosphatase) was more relevant at high ATP concentrations. ATP transiently increased basal [³H]ACh outflow in a 2′,3′-O-(2,4,6-trinitrophenyl)adenosine-5′-triphosphate (TNP-ATP)-dependent, tetrodotoxin-independent manner. ATP and ATPγS (adenosine 5′-[γ-thio]triphosphate), but not α,β-methyleneATP, decreased [³H]ACh release induced by electrical stimulation. ADP and ADPβS (adenosine 5′[β-thio]diphosphate) only decreased evoked [³H]ACh release. Inhibition by ADPβS was prevented by MRS 2179 (2′-deoxy-N⁶-methyl adenosine 3′,5′-diphosphate diammonium salt, a selective P2Y₁ antagonist); blockade of ADP inhibition required co-application of MRS 2179 plus adenosine deaminase (which inactivates endogenous adenosine). Blockade of adenosine A₁ receptors with 1,3-dipropyl-8-cyclopentyl xanthine enhanced ADPβS inhibition, indicating that P2Y₁ stimulation is cut short by tonic adenosine A₁ receptor activation. MRS 2179 facilitated evoked [³H]ACh release, an effect reversed by the ecto-ATPase inhibitor, {"type":"entrez-protein","attrs":{"text":"ARL67156","term_id":"1186396857","term_text":"ARL67156"}}ARL67156, which delayed ATP conversion into ADP without affecting adenosine levels.

Conclusions and implications:

ATP transiently facilitated [³H]ACh release from non-stimulated nerve terminals via prejunctional P2X (probably P2X₂) receptors. Hydrolysis of ATP directly into AMP by ecto-ATPDase and subsequent formation of adenosine by ecto-5′-nucleotidase reduced [³H]ACh release via inhibitory adenosine A₁ receptors. Stimulation of inhibitory P2Y₁ receptors by ADP generated alternatively via ecto-ATPase might be relevant in restraining ACh exocytosis when ATP saturates ecto-ATPDase activity.     

Congenital chylothorax: from foetal life to adolescence

Aim: To analyse the main prenatal and postnatal features of congenital chylothorax (CC), and the outcome including mid‐term follow‐up. Methods: We searched our databases for CC diagnosed between 1990 and 2006. Data of 29 cases were retrieved and analysed. Follow‐up until 3 years of age was available for all patients. Results: Most patients were diagnosed prenatally (94%) and most cases were complicated by foetal hydrops (66.7%). The overall survival rate at 3 years was 56%. A significantly poorer outcome was observed when foetal hydrops, preterm birth < 34 weeks, large effusions and/or early‐onset pneumothorax were present. An important but not significant improvement in the survival rate was observed through the study period; while in 1990–1998, the survival rate was 41.7%, from 1999 to 2006 it was 66.7% (p = 0.19). In the mid‐term follow‐up, we did not observe any recurrence of CC and most infants remain asymptomatic. However, 27% of survivors were diagnosed as having asthma in early infancy. Conclusion: CC still carries a significant risk of perinatal mortality. However, continuous advances in foetal and neonatal medicine are improving the prognosis of these patients, and nowadays most of them are likely to survive. Beyond the neonatal period, most survivors have an uneventful outcome.     

The role of free radicals in endogenous adaptation and intracellular signals

Oxidative stress can generate a mass of oxygen free radicals (OFR) in the cells, and these OFRs can induce several acute and chronic symptoms and diseases. If the amount of the generated OFRs overwhelms the antioxidant capacity of the cells, the pathophysiological changes may lead to the death of the cell or the development of chronic degenerative diseases.     

The final destiny of acantholytic cells in pemphigus is Fas mediated

Background  Pemphigus is an autoimmune disease characterized by the formation of intra-epidermal blisters. Patients develop auto-antibodies against desmoglein 1 and 3 proteins and induce acantholysis.
Objective  This work addresses the issue of whether the Fas pathway mediates acantholysis. Furthermore, the possible suppliers of the Fas pathway were investigated.
Methods  Seventeen biopsies of pemphigus patients were studied by haematoxylin and eosin staining, and apoptosis was defined by TUNEL. The expression of Fas, FasL and caspase 3 was studied by in situ hybridization and immunohistochemistry. Cell infiltrates were studied by immunofluorescence with monoclonal anti-CD3, CD4, CD8, CD19 and CD69.
Results  All of the biopsies showed intra-epidermal blisters, acantholytic cells and inflammatory infiltrates. The blisters expressed Fas, FasL and caspase 3. Cell infiltrates were composed of CD8 and a few CD4⁺CD69⁺ cells. Additionally, CD19⁺ cells were detected. Interestingly, the Fas expression was increased in acantholytic cells and perilesional keratinocytes. Incidentally, these cells exhibited apoptotic features. Interestingly, the CD8 cells expressed FasL.
Conclusion  This paper presents the morphological evidence that apoptosis and acantholysis are linked. Therefore, the Fas pathway is associated with CD8 cells in pemphigus lesions.

Conflicts of interest

None declared.     

Factors Affecting the Risk of Blood Bank Specimen Hemolysis

OBJECTIVES: To evaluate simultaneously several possible risk factors for blood bank specimen hemolysis. METHODS: This was a prospective cohort study of emergency department and labor and delivery patients to estimate the effect of various factors on the risk of blood bank specimen hemolysis. Study variables included patient demographics, type and gauge of needle or catheter, anatomic location of venipuncture, and patient care area. Hemolysis was determined by blood bank laboratory technicians. Cox proportional hazards multivariate regression modeling was performed to estimate the adjusted relative risks for hemolysis. RESULTS: Of the 605 subjects with complete data, 194 (32.1%) subjects had blood specimens drawn directly with a steel needle, and 411 (69.1%) had specimens drawn through a Vialon (BD Medical Systems, Inc., Sandy, UT) intravenous (IV) angiocatheter. The overall risk of hemolysis for all was 7%, 10% for Vialon IV angiocatheters and 1.5% for steel needles. In the multivariate analysis, the factors most closely associated with hemolysis were the use of Vialon IV catheters and sampling from an anatomic site other than the antecubital area. CONCLUSIONS: Blood bank specimens drawn from Vialon IV catheters (particularly smaller gauge catheters) and from veins outside the antecubital area are at significantly increased risk to hemolyze.