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.     

Bradykinin and angiotensin-converting enzyme inhibition in cardioprotection

OBJECTIVES:

To show that angiotensin-converting enzyme (ACE) inhibition potentiates subthreshold ischemic preconditioning (IPC) via the elevation of bradykinin activity, leading to a fully delayed cardioprotective response.

METHODS:

On day 1 of the experiment, pigs were subjected to sham (group 1, controls) or IPC protocols. In groups 2 and 3, 4×5 min and 2×2 min of IPC, respectively, were elicited by occluding the left anterior descending coronary artery with percutaneous transluminal coronary angioplasty inflatable balloon catheter. Group 4 was subjected to the ACE inhibitor perindoprilate only. In group 5, the pigs were pretreated with perindoprilate (0.06 mg/kg) and then subjected to 2×2 min IPC. In group 6, intracoronary HOE 140 (a selective bradykinin B₂ receptor antagonist) was added before the perindoprilateaugmented subthreshold (2×2 min) PC stimulus. On the second day, all animals underwent 40 min left anterior descending coronary artery ligation and 3 h reperfusion, followed by infarct size analysis using triphenyl tetrazolium chloride staining.

RESULTS:

The rates of infarct size and risk zone were the following in the experimental groups: group 1, 42.8%; group 2,19.5% (P<0.05); group 3, ischemia/reperfusion (I/R) 33.4%; group 4, I/R 18.4% (P<0.05); group 5, I/R 31.2%; and group 6, I/R 36.3%. A significant increase of nuclear factor kappa B activation in groups 2 and 4 was seen.

CONCLUSIONS:

Results confirm that ACE inhibitors do not give total pharmacological IPC, but they enhance the induction effect of small ischemic insults, which raises the ischemic tolerance of myocardium. It was determined that enhanced bradykinin activity leads to downstream nuclear factor kappa B activation in this model.     

Assessment of macro‐ and microcirculation in contemporary critical limb ischemia

Objectives : A paucity of data exists regarding manifestations of macro‐ and microcirculation in contemporary critical limb ischemia (CLI). The aim of this study was (1) to evaluate the differences in foot circulation based on angiographic findings, (2) to clarify the relationship between macro‐ and microcirculation, and (3) to investigate the effects of postural changes on micro as well as macrocirculation between the supine position to the dependent position. Methods : A total of 40 critically ischemic limbs in 29 patients were included in this study. Noninvasive evaluation of macrocirculation, based on the ankle brachial index (ABI) and ankle pressure, and microcirculation, using skin perfusion pressure (SPP), was performed in both the supine and dependent positions. Results : There was no significant difference in macro‐ and microcirculations between any angiographical involvements. In the supine position, dorsal SPP correlated significantly with ABI (P = 0.021, r = 0.363) and ankle‐pressure (P = 0.001, r = 0.495), whereas plantar SPP failed to correlate with ABI (P = 0.198, r = 0.208) or ankle‐pressure (P = 0.185, r = 0.214). In the dependent position, however, SPP showed no significant correlation with ABI and ankle pressure. Postural change from the supine to dependent position yielded a significant increase in SPP (dorsal: 37.2 ± 16.2 to 77.9 ± 17.7 mm Hg, P < 0.001; plantar: 33.6 ± 17.3 to 75.7 ± 18.3 mm Hg, P < 0.001) as well as ABI and ankle‐pressure (ABI: 0.70 ± 0.35 to 0.78 ± 0.42, P = 0.003; ankle‐pressure; 108 ± 61 to 111 ± 60 mm Hg, P = 0.038). The effect of postural change on SPP showed no difference between patients with and without any clinical and angiographical complications. Conclusions : Of microcirculation assessed, only dorsal SPP correlated significantly with macrocirculation in the supine position. Furthermore, postural change from the supine to dependent position produced a dramatic improvement in microcirculation due to the effects of gravity. © 2011 Wiley Periodicals, Inc.     

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.     

Protein-losing enteropathy in gastrointestinal sarcoidosis associated with malignant lymphoma.

A patient with disseminated gastrointestinal sarcoidosis and non-Hodgkin's malignant lymphoma developed diarrhea and polyadenopathy. Laboratory analysis revealed the presence of protein-losing enteropathy without biological signs of malabsorption. Gastrointestinal biopsy specimens showed numerous sarcoidosis nodules without neoplastic proliferation in the stomach, small intestine, and rectum. The patient's course was favorable after treatment with prednisone and chlorambucil. Disseminated gastrointestinal sarcoidosis may be a previously unidentified cause of protein-losing enteropathy.     

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.