title: Levosimendan preserves the contractile responsiveness of hypoxic human myocardium via mitochondrial K(ATP) channel and potential pERK 1/2 activation.
abstract: This study investigated the role of levosimendan, a mitochondrial K(ATP) channel opener, during hypoxia-reoxygenation injury in human isolated tissue. The activation of preconditioning pathways, and the release of mitochondrial cytochrome c were determined. Human right atrial trabeculae were mounted in an organ bath, electrically paced and contractile force measured. Tissue was subjected to hypoxia-reoxygenation, and isoproterenol concentration-response experiments were performed as an index of contractile viability. The intracellular activities of Akt, ERK 1/2, P38, caspase 3, and cytochrome c were assayed by western blot. Following hypoxia-reoxygenation, the maximal contractile response of trabeculae to isoproterenol was significantly increased with levosimendan pretreatment compared to the hypoxia-reoxygenation control (0.88±0.02 versus 0.60±0.01g, P<0.01). This enhanced response was blocked by 5-hydroxydecoanate (0.54±0.09g, P<0.01). A significant increase in both phosphorylated and total ERK 1/2 and P38 occurred at 60min reoxygenation, compared to control tissue. No difference was observed in phosphorylated or total Akt, though there was a trend for increased levels in hypoxic tissue. Cytochrome c was detected at 60min post reoxygenation, in both levosimendan treated and untreated tissue. No increase in cleaved-caspase 3 activity was observed. Our findings suggest that levosimendan preserves the contractile force to isoproterenol after hypoxia-reoxygenation, a response mediated via mK(ATP) channel activation. The significant increase in the activity of prosurvival mediators ERK 1/2 and P38 following hypoxia indicates a potential mechanism of action for levosimendan-induced cardioprotection.
authors.affiliation: Cardiovascular Therapeutics Unit, Department of Pharmacology, University of Melbourne, Parkville, Australia. paulsoeding@bigpond.com.au
authors.forename: Paul F
authors.initials: PF
authors.lastname: Soeding
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Crack
authors.forename: Christine E
authors.initials: CE
authors.lastname: Wright
authors.forename: James A
authors.initials: JA
authors.lastname: Angus
authors.forename: Colin F
authors.initials: CF
authors.lastname: Royse
mesh_terms: D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D053148:Caspase 3 / Q000378:metabolism; D015687:Cell Hypoxia / Q000187:drug effects; D045304:Cytochromes c / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D006325:Heart Atria / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D006801:Humans; D006835:Hydrazones / Q000494:pharmacology*; D066298:In Vitro Techniques; D019157:Ischemic Preconditioning, Myocardial; D007545:Isoproterenol / Q000494:pharmacology; D008928:Mitochondria / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D009119:Muscle Contraction / Q000187:drug effects*; D009206:Myocardium / Q000201:enzymology* / Q000378:metabolism / Q000473:pathology; D010100:Oxygen / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism*; D015221:Potassium Channels / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D011724:Pyridazines / Q000494:pharmacology*; D000077464:Simendan; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D000318:Adrenergic beta-Agonists; D006835:Hydrazones; D010750:Phosphoproteins; D015221:Potassium Channels; D011724:Pyridazines; C117780:mitochondrial K(ATP) channel; D000077464:Simendan; D045304:Cytochromes c; D051057:Proto-Oncogene Proteins c-akt; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048051:p38 Mitogen-Activated Protein Kinases; D053148:Caspase 3; D007545:Isoproterenol; D010100:Oxygen