Chairs
Dr Eoin Cummins, University College Dublin, Ireland
Dr Eoin Cummins, University College Dublin, Ireland
Eoin obtained a bachelor’s degree in Pharmacology (2002), and a PhD (2007) from University College Dublin (UCD). His early work focused the role of oxygen sensing hydroxylases in the context of intestinal inflammation. During his post-doctoral career Eoin became interested in the potential role for carbon dioxide as a modulator of inflammatory and immune signaling, in particular in relation to NFkB signaling. The first paper on this work was published in the Journal of Immunology in 2010. Eoin subsequently took up a short-term fellowship in Northwestern University, before returning to UCD and being appointed as an Assistant Professor in Physiology. He currently leads a Science Foundation Ireland funded research group focused on the effects of hypercapnia on inflammation and immunity.
13:15-13:45
CO2 transport
Professor Walter Boron, Case Western Reserve University, USA
Abstract
The dogma had been that all gases cross all membranes by dissolving in and diffusing through the lipid phase. Work over the past two decades shows that some membranes have negligible CO2 permeability, and that some membrane proteins—a subset of aquaporins (AQPs) and rhesus (Rh) proteins—can conduct CO2 or other gases. Preliminary data on Xenopus oocytes expressing AQP5 show that CO2 transport through AQP5 increases markedly with injection into the cytosol of small amounts of carbonic anhydrase II (CAII). The approach is to measure alkaline surface pH (pHS) transients during introduction of extracellular CO2/HCO3−. The alkaline pHS spike is greatest early, when the inward CO2 gradient—and thus the extracellular reaction HCO3− + H+ H2O + CO2—is greatest, and wanes as CO2 equilibrates across the cell membrane. Cytosolic CAII promotes the consumption of incoming CO2, thereby maintaining low cytosolic [CO2], maximizing the gradient for CO2 influx, and increasing pHS—far more so in AQP5-expressing than in control oocytes. In additional pHS experiments, the electrogenic Na/HCO3 cotransporter NBCe1 (or electroneutral NBCn1) replaced the AQP5. Earlier preliminary work based on intracellular-pH measurements had suggested that NBCe1 conducts CO2. Now, exposing oocytes expressing NBCe1 (or NBCn1)—without injected CAII—to CO2/HCO3− produces a small transient pHS increase (due to CO2 influx) followed by a large pHS decrease (CO3= uptake). In oocytes expressing NBCe1 or NBCn1, CAII injection markedly accentuates the early transient pHS increase (as for AQP5-expressing oocytes), supporting the hypothesis that NBCe1 and NBCn1 both conduct CO2.
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Professor Walter Boron, Case Western Reserve University, USA
Professor Walter Boron, Case Western Reserve University, USA
Dr Boron is Myers/Scarpa Professor and Chair of Physiology & Biophysics Department at CWRU. He earned his MD and PhD (Physiology & Biophysics) at Washington University, joined Yale as a postdoctoral fellow with Emile Boulpaep in 1978, and remained until 2007, serving as department chair for three 3-year terms. Boron was President of the American Physiological Society, Secretary-General of the International Union of Physiological Sciences, and editor-in-chief of both Physiological Reviews and Physiology. With Boulpaep, he edits the textbook Medical Physiology. Boron developed his interest in acid-base transport/intracellular-pH regulation with PhD mentors Albert Roos and Paul De Weer, and his interest in renal HCO3¯ transport with Boulpaep. His group focuses on three related areas: molecular physiology of the Na+-coupled HCO3¯transporters, molecular CO2/HCO3¯ sensors, and gas channels. Among Boron’s honors are an honorary doctorate from Aarhus University (2014), and election to the National Academy of Medicine (2014).
13:55-14:25
The Calvin Benson cycle – atmospheric CO2 assimilation and prospects for improvement
Professor Christine Raines, Essex University, UK
Abstract
The photosynthetic carbon reduction (Calvin-Benson) cycle is the primary pathway of atmospheric CO2 assimilation in all photosynthetic organisms. It is the single largest flux of organic carbon in the biosphere, and assimilates about 100 bn tons of carbon a year (15% of the carbon in the atmosphere). Evidence has now accumulated showing that by increasing flow of CO2 through this cycle we can also increase plant yield which has the potential to contribute the future demands of an increasing world population. Analyses of transgenic with altered level of enzymes in the Calvin-Benson cycle has demonstrated the potential for increasing crop productivity through increased rates of photosynthesis and the manipulation of the allocation of photosynthate. This lecture will discuss these approaches and the future potential.
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Professor Christine Raines, Essex University, UK
Professor Christine Raines, Essex University, UK
Christine Raines graduated with a BSc (Hons) Agricultural Botany, Glasgow University. Following which she was awarded a Glasgow University Scholarship and studied for a PhD in Photosynthetic electron transport graduating in 1986. Christine’s post-doctoral research started in late 1985 at the Institute of Plant Science Research, Cambridge where she initiated a project cloning nuclear genes encoding enzymes of the C3 cycle. In 1988 Christine was appointed to a faculty position at the University of Essex being promoted to Professor in 2004. Christine was Head of the School of Life Sciences at Essex (2011-2017) and is now Pro-Vice Chancellor Research for the University of Essex. Christine has also held a number of external roles; Editor in Chief, Journal of Experimental Botany (2011- ), Chair of Plant Section, Society of Experimental Biology (2009- ) and SEB President (2017-2019).
Christine’s research interests are in the area of plant molecular physiology including the isolation and characterisation of photosynthetic genes, analysis of gene expression and production and analysis of transgenic plants. Currently Christine leads a research group funded through BBSRC and the Bill and Melinda Gates foundation through the University of Illinois (RIPE) focused on improving photosynthesis by re-engineering the CO2 assimilatory pathway (the Calvin Benson cycle) and electron transport.
15:00-15:30
CO2 and lung airway function
Dr Masahiko Shigemura, Northwestern University, USA
Abstract
Carbon dioxide (CO2), a primary product of oxidative metabolism, can be sensed by eukaryotic cells eliciting specific responses via specific signaling pathways. The physiological and pathophysiological effects of high CO2 conditions (hypercapnia) on the lungs and specific lung cells, which are the primary site of CO2 elimination, are incompletely understood. Dr Shigemura’s group has recently reported using combined unbiased molecular approaches with studies in mice and cell culture systems on the mechanisms by which hypercapnia increased airway smooth muscle contractility. The group described that high CO2 levels cause non-apoptotic caspase-7 activation via the calcium-calpain signal, which cleaves the transcription factor myocyte-specific enhancer factor 2D and in turn downregulates miR-133a that increases RhoA protein abundance and myosin light chain phosphorylation, and thus leads to airway smooth muscle contraction. In demonstration of the clinical relevance of this signaling, the group determined that patients with severe chronic obstructive pulmonary disease (COPD) and hypercapnia had elevated airway resistance, which improved after correction of hypercapnia. These data suggest that hypercapnia is not only a manifestation of severe COPD, but it can also worsen the airflow obstruction. Dr Shigemura will provide a pathophysiological and mechanistic perspective on the effects of hypercapnia on the lung airways and discuss the recent understanding of high CO2 modulation of the airway function.
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Dr Masahiko Shigemura, Northwestern University, USA
Dr Masahiko Shigemura, Northwestern University, USA
Masahiko Shigemura is a Research Assistant Professor of Medicine at Northwestern University (USA). He obtained his PhD in Medicine from Hokkaido University (Japan). Afterwards, he carried out post-doctoral research work in the laboratory of Dr Jacob I Sznajder at Northwestern University. During his postdoctoral training, he concentrated on the biology of hypercapnia (an elevation of CO2 in the blood) in lungs and meanwhile, he developed a keen interest in the molecular mechanisms by which hypercapnia activates specific signal transduction pathways in the lung airways. His primary research includes airway smooth muscle contractility during hypercapnia, which is potentially clinically relevant to patients with obstructive lung diseases such as chronic obstructive pulmonary disease (COPD). As a Research Assistant Professor, he has been expanding his scientific repertoire and has been conducting research to address airway pathobiology in hypercapnia.
15:40-16:10
CO2 sensing and signal transduction in stomatal guard cells
Professor Julian Schroeder, University of Calfornia, San Diego, USA
Abstract
Plants control CO2 exchange and water loss via stomatal pores. Previous research has suggested that bicarbonate (HCO3-) may directly up-regulate reconstituted SLAC1 channel activity in vitro. However, whether this HCO3- regulation is relevant in planta remains unknown. We have computationally predicted candidate bicarbonate-binding sites within SLAC1 through long-timescale Gaussian-accelerated molecular dynamics (GaMD) simulations. Gas exchange and patch clamp experiments with complemented slac1 mutant plants expressing mutated SLAC1 proteins revealed that in plants one of these SLAC1 residues is specifically required for the stomatal CO2 response, but not for ABA responses. These findings suggest that SLAC1 not only mediates anion efflux from guard cells, but also that SLAC1 could contribute as a CO2/HCO3- sensing in guard cells. These analyses suggest that SLAC1 can function as a “secondary” bicarbonate/CO2 sensor, but not as the primary CO2/bicarbonate sensor.
[CO2] elevation and the plant hormone abscisic acid (ABA) both trigger rapid stomatal closure via regulation of ion channels in guard cells. Abscisic acid is known to enhance CO2 responses. However, it has remained unknown whether [CO2]-triggered stomatal closure is directly mediated via activation of the early ABA synthesis and signal transduction pathway and how these pathways converge. To address these questions, stomatal CO2 responses were analyzed in ABA synthesis mutants and ABA receptor mutants. Experiments using higher order mutants show that abscisic acid synthesis and signaling components are essential for robust CO2 responses. Furthermore, direct biochemical and patch clamp analyses of guard cell CO2 and ABA signal transduction were pursued. Moreover, newly developed real-time ABA FRET nano-reporter expressing plants were generated to determine whether CO2 elevation causes rapid ABA concentration changes in guard cells. Taken together these interdisciplinary analyses provide strong evidence for a requirement of basal ABA signal transduction for CO2 signaling and point to a new and unexpected understanding of how CO2 signaling and ABA signaling merge downstream of early ABA and CO2 signaling mechanisms that both close stomata.
New findings on CO2 sensing mechanisms and on dissecting CO2-specific signaling in grasses will be presented. A model for early CO2 signal transduction mechanisms that control stomatal movements will be discussed.
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Professor Julian Schroeder, University of Calfornia, San Diego, USA
Professor Julian Schroeder, University of Calfornia, San Diego, USA
Julian Schroeder is Novartis Chair and Distinguished Professor at the University of California San Diego. Schroeder identified and characterized of ion channels in higher plants and identified their functions and regulation mechanisms, in particular in stomatal guard cell signal transduction and abiotic stress resistance. His recent research is focused on uncovering the fundamental mechanisms by which plants regulate their stomata in response to drought, abscisic acid and the continuing rise in the atmospheric CO2 concentration. He has received awards, including the Presidential Young Investigator Award (NSF), the ASPB Charles Albert Shull Award (1997), the Blasker Award in Environmental Science and is Churchill Overseas Fellow at Cambridge University. Julian is a member of the U.S. National Academy of Sciences, Fellow of the American Association for the Advancement of Science and member of the German National Academy of Sciences Leopoldina.
16:20-16:50
The effects of carbon dioxide on pulmonary inflammatory processes arising from septic and aseptic aetiologies
Professor Daniel O'Toole, National University of Ireland, Galway, Ireland
Abstract
Acute respiratory distress syndrome (ARDS), a lung disease with rapid onset and high mortality, is characterised by inflammatory signalling pathway activation, infiltration of peripheral leukocytes into the pulmonary space and resultant systemic hypoxia and hypercapnia. Aetiology is typically pathogenic, but also arises due to factors including ventilator induced lung injury (VILI). Permissive or therapeutic hypercapnia are useful anti-inflammatory approaches to ARDS management, but molecular mechanisms are only slowly being revealed. In a series of experiments, rats were buffered renally or ventilated with 5% CO2 and received caecal puncture, E.coli instillation or increased volume ventilation. Assessment was through blood gas analysis, biochemical markers and lung tissue histology. In vitro, lung epithelial and other cells were exposed to increasing CO2 and subject to scratch wound, cytokine, endotoxin or cyclic mechanical stretch injury. Transfection and immunoprecipitation studies examined the influence of CO2 on various points along the NFκB signalling pathway. Hypercapnia attenuated systemic sepsis, though unbuffered alone reduced lung complications. CO2 related benefit was observed in both early and prolonged sepsis. VILI was attenuated by hypercapnia, reflected in a mechanical stretch model of lung epithelium. Hypercapnia diminished the NFκB inflammatory response in multiple cell lines independently of cytoplasmic pH, suggesting direct control by CO2. IKK2 enzymatic activity, IκBα degradation and NFκB translocation were all impaired, as was healing of epithelial scratch wounds, by elevated CO2. In conclusion, hypercapnia is anti-inflammatory in a range of pulmonary injury models, and is inhibitory across many points of the central NFκB inflammatory pathway.
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Professor Daniel O'Toole, National University of Ireland, Galway, Ireland
Professor Daniel O'Toole, National University of Ireland, Galway, Ireland
Dr Daniel O’Toole graduated in biochemistry at the National University of Ireland, Galway, and following a PhD in Biochemistry at Trinity College Dublin and postdoctoral work in immunology at University College Dublin, returned to Galway as a senior research lecturer in the Discipline of Anaesthesia. His work covers pathological processes and therapeutics for a range of conditions including pneumonia, sepsis and other inflammatory diseases and invokes ventilation, gene and cell therapy approaches. He is particularly interested in carbon dioxide as a potential anti-inflammatory agent in acute respiratory distress syndrome (ARDS).