title: Inflammation, glucose, and vascular cell damage: the role of the pentose phosphate pathway.
abstract: BACKGROUND
  Hyperglycemia is acknowledged as a pro-inflammatory condition and a major cause of vascular damage. Nevertheless, we have previously described that high glucose only promotes inflammation in human vascular cells previously primed with pro-inflammatory stimuli, such as the cytokine interleukin (IL)1β. Here, we aimed to identify the cellular mechanisms by which high glucose exacerbates the vascular inflammation induced by IL1β.
  
  
  METHODS
  Cultured human aortic smooth muscle cells (HASMC) and isolated rat mesenteric microvessels were treated with IL1β in medium containing 5.5-22 mmol/L glucose. Glucose uptake and consumption, lactate production, GLUT1 levels, NADPH oxidase activity and inflammatory signalling (nuclear factor-κB activation and inducible nitric oxide synthase expression) were measured in HASMC, while endothelium-dependent relaxations to acetylcholine were determined in rat microvessels. Pharmacological inhibition of IL1 receptors, NADPH oxidase and glucose-6-phosphate dehydrogenase (G6PD), as well as silencing of G6PD, were also performed. Moreover, the pentose phosphate pathway (PPP) activity and the levels of reduced glutathione were determined.
  
  
  RESULTS
  We found that excess glucose uptake in HASMC cultured in 22 mM glucose only occurred following activation with IL1β. However, the simple entry of glucose was not enough to be deleterious since over-expression of the glucose transporter GLUT1 or increased glucose uptake following inhibition of mitochondrial respiration by sodium azide was not sufficient to trigger inflammatory mechanisms. In fact, besides allowing glucose entry, IL1β activated the PPP, thus permitting some of the excess glucose to be metabolized via this route. This in turn led to an over-activation NADPH oxidase, resulting in increased generation of free radicals and the subsequent downstream pro-inflammatory signalling. Moreover, in rat mesenteric microvessels high glucose incubation enhanced the endothelial dysfunction induced by IL1β by a mechanism which was abrogated by the inhibition of the PPP.
  
  
  CONCLUSIONS
  A pro-inflammatory stimulus like IL1β transforms excess glucose into a vascular deleterious agent by causing an increase in glucose uptake and its subsequent diversion into the PPP, promoting the pro-oxidant conditions required for the exacerbation of pro-oxidant and pro-inflammatory pathways. We propose that over-activation of the PPP is a crucial mechanism for the vascular damage associated to hyperglycemia.
authors.affiliation: Departamento de Farmacología, Facultad de Medicina, Universidad Autónoma de Madrid, 29029, Madrid, Spain.
authors.forename: Concepción
authors.initials: C
authors.lastname: Peiró
authors.affiliation: Departamento de Farmacología, Facultad de Medicina, Universidad Autónoma de Madrid, 29029, Madrid, Spain.|Paul Langerhans-Group, Integrative Physiology, German Diabetes Center, Auf'm Hennekamp 65, 40225, Düsseldorf, Germany.
authors.forename: Tania
authors.initials: T
authors.lastname: Romacho
authors.affiliation: Departamento de Farmacología, Facultad de Medicina, Universidad Autónoma de Madrid, 29029, Madrid, Spain.|Department of Pathology, University of Michigan, Ann Arbor, MI, 48109, USA.
authors.forename: Verónica
authors.initials: V
authors.lastname: Azcutia
authors.affiliation: Departamento de Farmacología, Facultad de Medicina, Universidad Autónoma de Madrid, 29029, Madrid, Spain.
authors.forename: Laura
authors.initials: L
authors.lastname: Villalobos
authors.affiliation: Instituto de Biología Funcional y Genómica, Universidad de Salamanca-CSIC, 37007, Salamanca, Spain.
authors.forename: Emilio
authors.initials: E
authors.lastname: Fernández
authors.affiliation: Instituto de Biología Funcional y Genómica, Universidad de Salamanca-CSIC, 37007, Salamanca, Spain.
authors.forename: Juan P
authors.initials: JP
authors.lastname: Bolaños
authors.affiliation: Wolfson Institute for Biomedical Research, University College London, London, WC1E 6BT, UK. salvador.moncada@manchester.ac.uk.|Institute of Cancer Sciences, Manchester Cancer Research Centre, University of Manchester, Wilmslow Road, Manchester, M20 4QL, UK. salvador.moncada@manchester.ac.uk.
authors.forename: Salvador
authors.initials: S
authors.lastname: Moncada
authors.affiliation: Departamento de Farmacología, Facultad de Medicina, Universidad Autónoma de Madrid, 29029, Madrid, Spain. carlosf.sanchezferrer@uam.es.
authors.forename: Carlos F
authors.initials: CF
authors.lastname: Sánchez-Ferrer
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism; D005947:Glucose / Q000378:metabolism*; D005978:Glutathione; D006801:Humans; D006943:Hyperglycemia / Q000378:metabolism; D007249:Inflammation / Q000378:metabolism*; D053583:Interleukin-1beta / Q000494:pharmacology; D008297:Male; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism*; D019255:NADPH Oxidases / Q000378:metabolism; D010084:Oxidation-Reduction / Q000187:drug effects; D010427:Pentose Phosphate Pathway / Q000187:drug effects; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D053583:Interleukin-1beta; D017382:Reactive Oxygen Species; D019255:NADPH Oxidases; D005978:Glutathione; D005947:Glucose
keywords: High glucose; Inflammation; Oxidative stress; Pentose phosphate pathway; Vascular cells