title: The extracellular isoform of superoxide dismutase has a significant impact on cardiovascular ischaemia and reperfusion injury during cardiopulmonary bypass.
abstract: OBJECTIVE
  Cardiac surgery with cardiopulmonary bypass (CPB) provokes ischaemia and reperfusion injury (IRI). Superoxide is a main mediator of IRI and is detoxified by superoxide dismutases (SODs). Extracellular SOD (SOD3) is the prevailing isoform in the cardiovascular system. Its mutation is associated with elevated risk for ischaemic heart disease as epidemiological and experimental studies suggest. We investigated the influence of SOD3 on IRI in the context of CPB and hypothesized a protective role for this enzyme.
  
  
  METHODS
  Mutant rats with loss of SOD3 function induced by amino acid shift, SOD3-E124D, (SOD3 mutant; n = 9) were examined in a model of CPB with deep hypothermic circulatory arrest provoking global IRI and compared with SOD3 competent controls (n = 8) as well as sham animals (n = 7). SOD3 plasma activity was photometrically measured with a diazo dye-forming reagent. Activation of cardioprotective rescue pathways (p44-42 MAPK and STAT3), cleavage of PARP-1, expression of SOD isoforms (SOD1, 2 and 3) and nitric oxide metabolism were analysed on the protein level by western blot. To evaluate whether SOD3 inactivity directly affects the myocardium, we isolated adult cardiac myocytes, which underwent hypoxia prior to protein analyses.
  
  
  RESULTS
  Relative SOD3 plasma activity in SOD3 mutant rats was significantly decreased by at least 50% compared with that in SOD3 competent controls (prior to euthanasia P = 0.008). Effectively, physiological parameters [heart rate and mean arterial pressure (MAP)] indicated a trend toward impaired handling of ischaemia and reperfusion in SOD3 mutants: after reperfusion, mean heart rate was 46 bpm lower (P = 0.083) and MAP 8 mmHg lower (P = 0.288) than that in SOD competent controls. Decreased SOD3 activity led to reduced activation of cardioprotective rescue pathways in vivo and in vitro: relative activation of p44-42 MAPK (P = 0.074) and STAT3 (P = 0.027) was more than 30% decreased in heart and aortic tissue of SOD3 mutants (activity normalized to sham control as 1). After CPB, cleavage of PARP-1 was doubled in the control group (P = 0.017), but increased 3-fold in SOD3 mutants (P = 0.002). Furthermore, 3-nitrotyrosine as a measure of decreased nitric oxide bioavailability and other SOD isoforms (SOD1 and 2) were increased.
  
  
  CONCLUSIONS
  Collectively, SOD3 has a significant cardioprotective role in cases of IRI and directly affects the myocardium as hypothesized. Exploration of intervention strategies targeting SOD3 may provide therapeutic options against IRI and associated systemic inflammation.
authors.affiliation: Department of Cardiovascular Surgery, Heinrich Heine University Medical School, Duesseldorf, Germany.
authors.forename: Antonio
authors.initials: A
authors.lastname: Pinto
authors.affiliation: Department of Cardiovascular Surgery, Heinrich Heine University Medical School, Duesseldorf, Germany.
authors.forename: Moritz Benjamin
authors.initials: MB
authors.lastname: Immohr
authors.affiliation: Department of Cardiovascular Surgery, Heinrich Heine University Medical School, Duesseldorf, Germany.
authors.forename: Annika
authors.initials: A
authors.lastname: Jahn
authors.affiliation: Department of Cardiovascular Surgery, Heinrich Heine University Medical School, Duesseldorf, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Jenke
authors.affiliation: Department of Cardiovascular Surgery, Heinrich Heine University Medical School, Duesseldorf, Germany.
authors.forename: Udo
authors.initials: U
authors.lastname: Boeken
authors.affiliation: Department of Cardiovascular Surgery, Heinrich Heine University Medical School, Duesseldorf, Germany artur.lichtenberg@med.uni-duesseldorf.de.
authors.forename: Artur
authors.initials: A
authors.lastname: Lichtenberg
authors.affiliation: Department of Cardiovascular Surgery, Heinrich Heine University Medical School, Duesseldorf, Germany.
authors.forename: Payam
authors.initials: P
authors.lastname: Akhyari
mesh_terms: D000818:Animals; D001784:Blood Gas Analysis; D015153:Blotting, Western; D002315:Cardiopulmonary Bypass / Q000009:adverse effects*; D006324:Heart Arrest, Induced / Q000009:adverse effects; D008297:Male; D017202:Myocardial Ischemia / Q000209:etiology*; D015428:Myocardial Reperfusion Injury / Q000209:etiology*; D032383:Myocytes, Cardiac / Q000201:enzymology / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D020033:Protein Isoforms / Q000502:physiology; D051381:Rats; D011922:Rats, Mutant Strains; D013482:Superoxide Dismutase / Q000097:blood / Q000502:physiology*
chemical_list: D020033:Protein Isoforms; D009569:Nitric Oxide; C499089:Sod3 protein, rat; D013482:Superoxide Dismutase
keywords: Cardiopulmonary bypass; Deep hypothermic circulatory arrest; Extracellular superoxide dismutase; Ischaemia; Reperfusion; SOD3; Systemic inflammatory syndrome