cAMP- and Ca²(+) /calmodulin-dependent protein kinases mediate inotropic, lusitropic and arrhythmogenic effects of urocortin 2 in mouse ventricular myocytes.

Abstract

BACKGROUND AND PURPOSE:

Urocortin 2 is beneficial in heart failure, but the underlying cellular mechanisms are not completely understood. Here we have characterized the functional effects of urocortin 2 on mouse cardiomyocytes and elucidated the underlying signalling pathways and mechanisms.

EXPERIMENTAL APPROACH:

Mouse ventricular myocytes were field-stimulated at 0.5 Hz at room temperature. Fractional shortening and [Ca²(+)](i) transients were measured by an edge detection and epifluorescence system respectively. Western blots were carried out on myocyte extracts with antibodies against total phospholamban (PLN) and PLN phosphorylated at serine-16.

KEY RESULTS:

Urocortin 2 elicited time- and concentration-dependent positive inotropic and lusitropic effects (EC₅₀ : 19 nM) that were abolished by antisauvagine-30 (10 nM, n= 6), a specific antagonist of corticotrophin releasing factor (CRF) CRF₂ receptors. Urocortin 2 (100 nM) increased the amplitude and decreased the time constant of decay of the underlying [Ca²(+)](i) transients. Urocortin 2 also increased PLN phosphorylation at serine-16. H89 (2 µM) or KT5720 (1 µM), two inhibitors of protein kinase A (PKA), as well as KN93 (1 µM), an inhibitor of Ca²(+)/calmodulin-dependent protein kinase II (CaMKII), suppressed the urocortin 2 effects on shortening and [Ca²(+)](i) transients. In addition, urocortin 2 also elicited arrhythmogenic events consisting of extra cell shortenings and extra [Ca²(+)](i) increases in diastole. Urocortin 2-induced arrhythmogenic events were significantly reduced in cells pretreated with KT5720 or KN93.

CONCLUSIONS AND IMPLICATIONS:

Urocortin 2 enhanced contractility in mouse ventricular myocytes via activation of CRF₂ receptors in a cAMP/PKA- and Ca²(+)/CaMKII-dependent manner. This enhancement was accompanied by Ca²(+)-dependent arrhythmogenic effects mediated by PKA and CaMKII.

• Authors: Li-Zhen Yang, Jens Kockskämper, Shelina Khan, Jorge Suarez, Stefanie Walther, Bernhard Doleschal, Gregor Unterer, Mounir Khafaga, Heinrich Mächler, Frank R Heinzel, Wolfgang H Dillmann, Burkert Pieske, Joachim Spiess
• Journal: British journal of pharmacology (Br J Pharmacol) Vol. 162 Issue 2 Pg. 544-56 (Jan 2011) ISSN: 1476-5381 [Electronic] England
• PMID: 20942811 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: © 2010 The Authors. British Journal of Pharmacology © 2010 The British Pharmacological Society.

Chemical References

• CRF receptor type 2
• Cardiotonic Agents
• Receptors, Corticotropin-Releasing Hormone
• Urocortins
• Cyclic AMP
• Cyclic AMP-Dependent Protein Kinases
• Calcium-Calmodulin-Dependent Protein Kinases
• Calcium

Topics

• Aged
• Aged, 80 and over
• Animals
• Arrhythmias, Cardiac (chemically induced, metabolism)
• Calcium (metabolism)
• Calcium-Calmodulin-Dependent Protein Kinases (metabolism)
• Cardiotonic Agents (pharmacology)
• Cyclic AMP (metabolism)
• Cyclic AMP-Dependent Protein Kinases (metabolism)
• Female
• Heart Atria (drug effects, metabolism)
• Heart Ventricles
• Humans
• Male
• Mice
• Mice, Inbred C57BL
• Middle Aged
• Muscle Relaxation (drug effects)
• Myocardial Contraction (drug effects)
• Myocytes, Cardiac (drug effects, enzymology, physiology)
• Receptors, Corticotropin-Releasing Hormone (metabolism)
• Urocortins (pharmacology)