Release of ATP in the ventral medulla during hypoxia in rats: role in hypoxic ventilatory response

P2X2 receptor subunits of the ATP-gated ion channels are expressed by physiologically identified respiratory neurons in the ventral respiratory column, implicating ATP in the control of respiratory activity. We now show that, during hypoxia, release of ATP in the ventrolateral medulla (VLM) plays an important role in the hypoxic ventilatory response in rats. By measuring ATP release in real time at the ventral surface of the medulla with novel amperometric biosensors, we found that hypoxia (10% O2; 5 min) induced a marked increase in the concentration of ATP (~3 µM). This ATP release occurred after the initiation of enhanced respiratory activity but coincided with the later hypoxia-induced slowing of the respiratory rhythm. ATP was also released at the ventral surface of the medulla during hypoxia in peripherally chemodenervated animals (vagi, aortic, and carotid sinus nerve sectioned). By using horizontal slices of the rat medulla, we found that, during hypoxia, ATP is produced throughout the VLM in the locations corresponding to the ventral respiratory column. Blockade of ATP receptors in the VLM (microinjection of P2 receptor antagonist pyridoxal-5'-phosphate-6-azophenyl-2',4'-disulphonic acid; 100 µM) augmented the hypoxia-induced secondary slowing of the respiratory rhythm. Our findings suggest that ATP released within the ventral respiratory column is involved in maintenance of the respiratory activity in conditions when hypoxia-induced slowing of respiration occurs. These data illustrate a new functional role for ATP-mediated purinergic signaling in the medullary mechanisms controlling respiratory activity

A role for TASK-1 (KCNK3) channels in the chemosensory control of breathing

Acid-sensitive K+ channels of the tandem P-domain K+-channel family (TASK-1 and TASK-3) have been implicated in peripheral and central respiratory chemosensitivity; however, because of the lack of decisive pharmacological agents, the final proof of the role of the TASK channel in the chemosensory control of breathing has been missing. In the mouse, TASK-1 and TASK-3 channels are dispensable for central respiratory chemosensitivity (Mulkey et al., 2007Go). Here, we have used knock-out animals to determine whether TASK-1 and TASK-3 channels play a role in the carotid body function and chemosensory control of breathing exerted by the carotid body chemoreceptors. Ventilatory responses to hypoxia (10% O2 in inspired air) and moderate normoxic hypercapnia (3–6% CO2 in inspired air) were significantly reduced in TASK-1 knock-out mice. In contrast, TASK-3-deficient mice showed responses to both stimuli that were similar to those developed by their wild-type counterparts. TASK-1 channel deficiency resulted in a marked reduction of the hypoxia (by 49%)- and CO2 (by 68%)-evoked increases in the carotid sinus nerve chemoafferent discharge recorded in the in vitro superfused carotid body/carotid sinus nerve preparations. Deficiency in both TASK-1 and TASK-3 channels increased baseline chemoafferent activity but did not cause a further reduction of the carotid body chemosensory responses. These observations provide direct evidence that TASK-1 channels contribute significantly to the increases in the carotid body chemoafferent discharge in response to a decrease in arterial PO2 or an increase in PCO2/[H+]. TASK-1 channels therefore play a key role in the control of ventilation by peripheral chemoreceptors

Geoff Burnstock, purinergic signalling, and chemosensory control of breathing.

This article is the authors' contribution to the tribute issue in honour of Geoffrey Burnstock, the founder of this journal and the field of purinergic signalling. We give a brief account of the results of experimental studies which at the beginning received valuable input from Geoff, who both directly and indirectly influenced our research undertaken over the last two decades. Research into the mechanisms controlling breathing identified ATP as the common mediator of the central and peripheral chemosensory transduction. Studies of the sources and mechanisms of chemosensory ATP release in the CNS suggested that this signalling pathway is universally engaged in conditions of increased metabolic demand by brain glial cells - astrocytes. Astrocytes appear to function as versatile CNS metabolic sensors that detect changes in brain tissue pH, CO2, oxygen, and cerebral perfusion pressure. Experimental studies on various aspects of astrocyte biology generated data indicating that the function of these omnipresent glial cells and communication between astrocytes and neurons are governed by purinergic signalling, - first discovered by Geoff Burnstock in the 70's and researched through his entire scientific career

Differential sensitivity of brainstem vs cortical astrocytes to changes in pH reveals functional regional specialization of astroglia

Astrocytes might function as brain interoceptors capable of detecting different (chemo)sensory modalities and transmitting sensory information to the relevant neural networks controlling vital functions. For example, astrocytes which reside near the ventral surface of the brainstem (central respiratory chemosensitive area) respond to physiological decreases in pH with vigorous elevations in intracellular Ca(2+) and release of ATP. ATP transmits astroglial excitation to the brainstem respiratory network and contributes to adaptive changes in lung ventilation. Here we show that in terms of pH-sensitivity ventral brainstem astrocytes are clearly distinct from astrocytes residing in the cerebral cortex. We monitored vesicular fusion in cultured rat brainstem astrocytes using total internal reflection fluorescence microscopy and found that approximately 35% of them respond to acidification with an increased rate of exocytosis of ATP-containing vesicular compartments. These fusion events require intracellular Ca(2+) signaling and are independent of autocrine ATP actions. In contrast, the rate of vesicular fusion in cultured cortical astrocytes is not affected by changes in pH. Compared to cortical astrocytes, ventral brainstem astrocytes display higher levels of expression of genes encoding proteins associated with ATP vesicular transport and fusion, including vesicle-associated membrane protein-3 and vesicular nucleotide transporter. These results suggest that astrocytes residing in different parts of the rat brain are functionally specialized. In contrast to cortical astrocytes, astrocytes of the brainstem chemosensitive area(s) possess signaling properties which are functionally relevant – they are able to sense changes in pH and respond to acidification with enhanced vesicular release of ATP

Glucagon-like peptide-1 (GLP-1) mediates cardioprotection by remote ischaemic conditioning

This work was supported by the British Heart Foundation (Ref: RG/14/4/30736), Medical Research Council (MR/N02589X/1) and The Wellcome Trust (Ref: 200893/Z/16/Z). A.V.G. is a Wellcome Trust Senior Research Fellow. S.M. is a Marie Skłodowska-Curie Research Fellow (Ref: 654691)

Impaired CO2 sensitivity of astrocytes in a mouse model of Rett syndrome

Rett syndrome is a prototypical neurological disorder characterised by abnormal breathing pattern and reduced ventilatory CO2 sensitivity. Medullary astrocytes are a crucial component of central CO2 /pH chemosensitivity. This study tested the hypotheses that methyl-CpG-binding protein 2 (MeCP2) deficient medullary astrocytes are (i) unable to produce/release appropriate amounts of lactate, and/or (ii) unable to sense changes in PCO2/[H(+) ]. We found no differences in tonic or hypoxia-induced release of lactate from the ventral surface of the medulla oblongata or cerebral cortex between MeCP2-knockout and wild-type mice. Respiratory acidosis triggered robust [Ca(2+) ]i responses in wild-type astrocytes residing near the ventral surface of the medulla oblongata. CO2 -induced [Ca(2+) ]i responses in astrocytes were dramatically reduced in conditions of MeCP2 deficiency. These data suggest that (i) 'metabolic' function of astrocytes in releasing lactate into the extracellular space is not affected by MeCP2 deficiency, and (ii) MeCP2 deficiency impairs the ability of medullary astrocytes to sense changes in PCO2/[H(+) ]

Cardioprotection evoked by remote ischaemic preconditioning is critically dependent on the activity of vagal pre-ganglionic neurones

AIMS: Innate mechanisms of inter-organ protection underlie the phenomenon of remote ischaemic preconditioning (RPc) in which episode(s) of ischaemia and reperfusion in tissues remote from the heart reduce myocardial ischaemia/reperfusion injury. The uncertainty surrounding the mechanism(s) underlying RPc centres on whether humoral factor(s) produced during ischaemia/reperfusion of remote tissue and released into the systemic circulation mediate RPc, or whether a neural signal is required. While these two hypotheses may not be incompatible, one approach to clarify the potential role of a neural pathway requires targeted disruption or activation of discrete central nervous substrate(s). METHODS AND RESULTS: Using a rat model of myocardial ischaemia/reperfusion injury in combination with viral gene transfer, pharmaco-, and optogenetics, we tested the hypothesis that RPc cardioprotection depends on the activity of vagal pre-ganglionic neurones and consequently an intact parasympathetic drive. For cell-specific silencing or activation, neurones of the brainstem dorsal motor nucleus of the vagus nerve (DVMN) were targeted using viral vectors to express a Drosophila allatostatin receptor (AlstR) or light-sensitive fast channelrhodopsin variant (ChIEF), respectively. RPc cardioprotection, elicited by ischaemia/reperfusion of the limbs, was abolished when DVMN neurones transduced to express AlstR were silenced by selective ligand allatostatin or in conditions of systemic muscarinic receptor blockade with atropine. In the absence of remote ischaemia/reperfusion, optogenetic activation of DVMN neurones transduced to express ChIEF reduced infarct size, mimicking the effect of RPc. CONCLUSION: These data indicate a crucial dependence of RPc cardioprotection against ischaemia/reperfusion injury upon the activity of a distinct population of vagal pre-ganglionic neurones

Glucagon-Like Peptide-1 (GLP-1) Mediates Cardioprotection by Remote Ischaemic Conditioning

AIMS: Although the nature of the humoral factor which mediates cardioprotection established by remote ischaemic conditioning (RIc) remains unknown, parasympathetic (vagal) mechanisms appear to play a critical role. As the production and release of many gut hormones is modulated by the vagus nerve, here we tested the hypothesis that RIc cardioprotection is mediated by the actions of glucagon-like peptide-1 (GLP-1). METHODS AND RESULTS: A rat model of myocardial infarction (coronary artery occlusion followed by reperfusion) was used. Remote ischaemic pre- (RIPre) and perconditioning (RIPer) was induced by 15 min occlusion of femoral arteries applied prior to or during the myocardial ischaemia. The degree of RIPre and RIPer cardioprotection was determined in conditions of cervical or subdiaphragmatic vagotomy, or following blockade of GLP-1 receptors (GLP-1R) using specific antagonist Exendin(9-39). Phosphorylation of PI3K/AKT and STAT3 was assessed. RIPre and RIPer reduced infarct size by ~50%. In conditions of bilateral cervical or subdiaphragmatic vagotomy RIPer failed to establish cardioprotection. GLP-1R blockade abolished cardioprotection induced by either RIPre or RIPer. Exendin(9-39) also prevented RIPre-induced AKT phosphorylation. Cardioprotection induced by GLP-1R agonist Exendin-4 was preserved following cervical vagotomy, but was abolished in conditions of M3 muscarinic receptor blockade. CONCLUSIONS: These data strongly suggest that GLP-1 functions as a humoral factor of remote ischaemic conditioning cardioprotection. This phenomenon requires intact vagal innervation of the visceral organs and recruitment of GLP-1R-mediated signalling. Cardioprotection induced by GLP-1R agonism is mediated by a mechanism involving M3 muscarinic receptors

A transition towards transparency through branding to achieve a competitive advantage in the industrial B2B market:Case European nonwovens market

As industrial markets have become more competitive, and pressure from stakeholders such as consumers, policymakers, legislators, and partners has increased, businesses have changed their core values and activities. At the same time, branding has taken on a more comprehensive meaning to differentiate the company from the competition. Transparency is widely considered to attract consumers, and its importance has also increased within the business-to-business market. This study focuses on the European nonwovens market, which is undergoing a lot of changes from a sustainability and consumer behaviour standpoint. A change in the market has resulted in the need for better branding and a better understanding of consumer needs, which reflect the business-to-business market and relationships within the value chain. This study consists of an integrative literature review, in which theory and previous studies are used to deepen the knowledge to answer the research questions designed for this study, as well as three objectives supporting the main research question. The literature review focused on brand management, competitive advantage, and transparency disruption in business. In addition to comprehensive secondary-data review, this case study completed with eight in-depth interviews with professionals of the European nonwovens market. These interviews complement the reliability of the study and underlines the findings of the study. This study answers the main research question: How to achieve a competitive advantage in the European nonwovens market by transitioning to transparency through branding? Based on the results, in order to gain a competitive advantage in the European nonwovens market, it is necessary to increase transparency in communication, internally and externally. In addition, it will be necessary to establish better partnerships within the value chain. It is also critical to fulfil promises and maintain strong relationships with stakeholders, by implementing strategic actions and considering the effects throughout the entire value chain. As a result of interacting with all parties involved and creating reliable buyer-supplier relationships, it becomes evident the importance of creating a strong brand with targets aligned with partners and consumer’s values and preferences. By creating a strong brand in the name of sustainability and transparency, as well as creating more effective messages for a market, and involving internal stakeholders in the process, a competitive advantage is likely to be achieved.Teollisuusmarkkinoista on tullut entistä kilpailukykyisempiä ja sidosryhmien, kuten kuluttajien, poliittisten päättäjien, lainsäätäjien ja kumppaneiden paine on markkinaa kohtaan lisääntynyt. Tämä paine on saanut yritykset muuttamaan ydinarvojaan ja toimintaansa. Muutokset ovat antaneet brändäykselle laajemman merkityksen erilaistaa yritys kilpailijoista. Avoimuuden katsotaan laajalti houkuttelevan kuluttajia, ja sen merkitys on kasvanut myös yritysten välisillä markkinoilla. Tässä tutkimuksessa keskitytään Euroopan kuitukangas -markkinoihin, jotka ovat käymässä läpi muutoksia kestävyyden ja kuluttajakäyttäytymisen näkökulmasta. Markkinoiden muutos on johtanut tarpeeseen parantaa brändäystä ja ymmärtää paremmin kuluttajien tarpeita, jotka heijastavat yritysten välisiin markkinoihin ja suhteisiin koko arvoketjussa. Tutkimus toteutettiin laadullisin menetelmin ja se koostuu integroivasta kirjallisuuskatsauksesta, jossa teoriaa ja aiempia tutkimuksia käytetään syventämään tietoa vastaamaan tätä tutkimusta varten suunniteltuun tutkimuskysymykseen sekä kolmeen tutkimuskysymystä tukevaan tavoitteeseen. Kirjallisuuskatsaus keskittyi brändinhallintaan, kilpailuetuun ja läpinäkyvyyteen liiketoiminnassa. Kattavan kirjallisuuskatsauksen lisäksi tämä tapaustutkimus haastattelee kahdeksaa kuitukangas -markkinoiden asiantuntijaa, joiden osaaminen sijoittuu arvoketjun eri osiin. Nämä haastattelut täydentävät tutkimuksen reliabiliteettia sekä vahvistavat tutkimuksen löydöksiä. Tutkimus vastaa tutkimuskysymykseen: Kuinka saavuttaa kilpailuetu Euroopan kuitukangas -markkinoilla siirtymällä avoimuuteen brändäyksen avulla? Tulosten perusteella kilpailuedun saavuttamiseksi Euroopan kuitukangas -markkinoilla on tarpeen lisätä viestinnän avoimuutta sekä sisäisesti että ulkoisesti. Viestinnän lisäksi on tarpeen luoda parempia kumppanuuksia sekä suhteita arvoketjun sisällä. On myös ratkaisevan tärkeää täyttää lupaukset ja ylläpitää vahvoja suhteita sidosryhmiin toteuttamalla strategisia toimia ja ottamalla huomioon toimintojen vaikutukset koko arvoketjussa. Vuorovaikutuksen tuloksena kaikkien osapuolten kanssa ja luotettavien ostaja-toimittaja-suhteiden luomisen seurauksena käy selväksi, kuinka tärkeää on luoda vahva brändi, jonka tavoitteet ovat linjassa kumppaneiden ja kuluttajien arvojen sekä mieltymysten kanssa. Luomalla vahva brändi kestävyyden ja läpinäkyvyyden nimissä, viestimällä tehokkaammin markkinoille, sekä ottamalla yrityksen työntekijät mukaan prosessiin, kilpailuetu voidaan todennäköisesti saavuttaa

The potential for autonomic neuromodulation to reduce perioperative complications and pain: a systematic review and meta-analysis

BACKGROUND: Autonomic dysfunction promotes organ injury after major surgery through numerous pathological mechanisms. Vagal withdrawal is a key feature of autonomic dysfunction, and it may increase the severity of pain. We systematically evaluated studies that examined whether vagal neuromodulation can reduce perioperative complications and pain. METHODS: Two independent reviewers searched PubMed, EMBASE, and the Cochrane Register of Controlled Clinical Trials for studies of vagal neuromodulation in humans. Risk of bias was assessed; I2 index quantified heterogeneity. Primary outcomes were organ dysfunction (assessed by measures of cognition, cardiovascular function, and inflammation) and pain. Secondary outcomes were autonomic measures. Standardised mean difference (SMD) using the inverse variance random-effects model with 95% confidence interval (CI) summarised effect sizes for continuous outcomes. RESULTS: From 1258 records, 166 full-text articles were retrieved, of which 31 studies involving patients (n=721) or volunteers (n=679) met the inclusion criteria. Six studies involved interventional cardiology or surgical patients. Indirect stimulation modalities (auricular [n=23] or cervical transcutaneous [n=5]) were most common. Vagal neuromodulation reduced pain (n=10 studies; SMD=2.29 [95% CI, 1.08-3.50]; P=0.0002; I2=97%) and inflammation (n=6 studies; SMD=1.31 [0.45-2.18]; P=0.003; I2=91%), and improved cognition (n=11 studies; SMD=1.74 [0.96-2.52]; P<0.0001; I2=94%) and cardiovascular function (n=6 studies; SMD=3.28 [1.96-4.59]; P<0.00001; I2=96%). Five of six studies demonstrated autonomic changes after vagal neuromodulation by measuring heart rate variability, muscle sympathetic nerve activity, or both. CONCLUSIONS: Indirect vagal neuromodulation improves physiological measures associated with limiting organ dysfunction, although studies are of low quality, are susceptible to bias and lack specific focus on perioperative patients