title: Mitogen-activated protein kinase inhibition and cardioplegia-cardiopulmonary bypass reduce coronary myogenic tone.
abstract: BACKGROUND
  Cardioplegia-cardiopulmonary bypass (C/CPB) is associated with coronary microcirculatory dysfunction. Regulation of the microcirculation includes myogenic tone. Mitogen-activated protein kinases (MAPK) have been implicated in coronary vasomotor function. We hypothesized that vasomotor dysfunction of the coronary microcirculation is mediated in part by alterations in extracellular signal regulated kinase 1/2 (ERK1/2) activity following C/CPB in humans.
  
  
  RESULTS
  Atrial myocardium was harvested from patients (n=15) before and after blood cardioplegia and short-term reperfusion under conditions of CPB. Myogenic tone of coronary arterioles was measured by videomicroscopy. Microvessel tone was determined post-C/CPB and after PD98059, a MAPK/ERK kinase 1/2 (MEK1/2) inhibitor. MAPK phosphatase-1 (MKP-1) and activated ERK1/2 were measured by Western blot. MKP-1 gene expression was determined by Northern blot. In situ hybridization and immunohistochemistry were used to localize myocardial MKP-1 and activated ERK1/2, respectively. Myogenic tone was reduced in coronary arterioles post-C/CPB (-10.5+/-0.9%, P<0.01 versus control/pre-C/CPB, n=5). Myogenic tone was decreased in coronary microvessels after 30 micromol/L (n=5) and 50 micromol/L (n=5) PD98059 treatment (-11.0+/-0.8% and -14.6+/-2.0%, respectively, both P<0.01 versus control/pre-C/CPB). Myocardial levels of activated ERK1/2 were reduced post-C/CPB (0.6+/-0.1, post/pre-C/CPB ratio, P<0.05, n=5) while MKP-1 levels increased (4.2+/-0.6, post/pre-C/CPB ratio, P<0.05, n=5). Myocardial MKP-1 gene expression increased post-C/CPB (3.0+/-0.8, post/pre-C/CPB ratio, P<0.05, n=5). MKP-1 and activated ERK1/2 localized to coronary arterioles in myocardial sections.
  
  
  CONCLUSIONS
  Coronary myogenic tone is dependent on ERK1/2 and decreased after C/CPB. C/CPB reduces levels of activated ERK1/2, potentially by increased levels of MKP-1. The ERK1/2 signal transduction pathway in part mediates coronary microvascular dysfunction after C/CPB in humans.
authors.affiliation: Division of Cardiothoracic Surgery, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA 02215, USA.
authors.forename: Tanveer A
authors.initials: TA
authors.lastname: Khan
authors.forename: Cesario
authors.initials: C
authors.lastname: Bianchi
authors.forename: Marc
authors.initials: M
authors.lastname: Ruel
authors.forename: Pierre
authors.initials: P
authors.lastname: Voisine
authors.forename: Jianyi
authors.initials: J
authors.lastname: Li
authors.forename: John R
authors.initials: JR
authors.lastname: Liddicoat
authors.forename: Frank W
authors.initials: FW
authors.lastname: Sellke
mesh_terms: D000368:Aged; D001160:Arterioles / Q000033:anatomy & histology / Q000201:enzymology / Q000502:physiology; D002315:Cardiopulmonary Bypass; D018797:Cell Cycle Proteins; D003331:Coronary Vessels / Q000033:anatomy & histology / Q000201:enzymology* / Q000502:physiology*; D054638:Dual Specificity Phosphatase 1; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005419:Flavonoids / Q000494:pharmacology; D006324:Heart Arrest, Induced; D006801:Humans; D017874:Immediate-Early Proteins / Q000378:metabolism; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; D008297:Male; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors
chemical_list: D018797:Cell Cycle Proteins; D004791:Enzyme Inhibitors; D005419:Flavonoids; D017874:Immediate-Early Proteins; C482128:MAP2K2 protein, human; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D020928:Mitogen-Activated Protein Kinases; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; C482125:MAP2K1 protein, human; D020929:Mitogen-Activated Protein Kinase Kinases; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; C517019:DUSP1 protein, human; D054638:Dual Specificity Phosphatase 1; D017027:Protein Tyrosine Phosphatases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one