Non-Central Influences of α2-Adrenergic and Imidazoline Agonist Interactions in Isolated ardiomyocytes Cardiac Cells

Aim: to investigate the functional interaction of α₂-adrenergic and imidazoline receptors recently identified on the sarcolemma of isolated cardiomyocytes for regulation of the intracellular calcium and the production of the signal molecule of nitric oxide (NO). Materials and methods: experiments were performed on isolated left ventricular cardiomyocytes of Wistar rats. Potential-dependent Ca²⁺-currents were measured from the whole-cell by the patch-clamp method in “perforated-patch” configuration. The intracellular calcium and the production of nitric oxide were estimated from the changes in fluorescence intensity of the Ca²⁺-specific and NO-sensitive dyes at fluorescent or confocal microscope. Results: It has been shown that α₂‑adrenergic and imidazoline receptor agonists inhibit L-type Ca²⁺-currents by themselves, but their effects do not develop against each other’s background. The blockade of key effector molecules: protein kinase B (Akt kinase) for α₂‑adrenergic receptors, and protein kinase C for imidazoline receptors causes the action of agonists to become additive. Both the selective α₂‑agonist, guanabenz, and the specific agonist of the first type imidazoline receptors, rilmenidine, show an additional inhibition of Ca²⁺-currents against the basal background already reduced by the activation of one of the two receptor systems. Wherein rilmenidine increases the level of free  Ca²⁺ in the cytosol, and guanabenz, on the contrary, decreases it. The action of guanabenz does not develop against the background of rilmenidine, although it, in turn, effectively increases the intracellular level of calcium in guanabenz-pretreated cardiac cells. Activation of α₂‑adrenergic receptors leads to significant stimulation of the endothelial isoform of NO-synthase, and as a result to an increase in the NO level. Activation of imidazoline receptors itself does not affect NO synthesis but it prevents the production of NO induced by α₂‑agonists. Conclusion: obtained data make it possible to formulate a number of useful recommendations for clinical practice, and also to clarify the non-central peripheral effects arising from the activation of α₂‑adrenergic or imidazoline systems under conditions of endogenous hyperactivation on of the two systems.

1. World Health Organization. World health statistics 2016: Monitoring health for the SDGs. 136 с. ISBN 978-92-4-069569-6

2. Selye H. Stress without distress. -Philadelphia: Lippincott; 171 с. ISBN 978-0-397-01026-4

3. William Tank A, Lee Wong D. Peripheral and Central Effects of Circulating Catecholamines. In: Comprehensive Physiology. -Hoboken, NJ, USA: John Wiley & Sons, Inc., 2014. - pp. 1-15. ISBN: 978-0-470-65071-4.

4. Bers DM. Calcium Cycling and Signaling in Cardiac Myocytes. Annual Review of Physiology. 2008;70(1):23–49. DOI: 10.1146/annurev.physiol.70.113006.100455

5. Gustafsson AB, Gottlieb RA. Heart mitochondria: gates of life and death. Cardiovascular Research. 2007;77(2):334–43. DOI: 10.1093/cvr/cvm005

6. Brini M, Ottolini D, Calì T, Carafoli E. Calcium in Health and Disease. In: Interrelations between Essential Metal Ions and Human Diseases. -Dordrecht: Springer Netherlands, 2013. - pp.81-137. ISBN: 978-94-007-7499-5, 978-94-007-7500-8.

7. Foucart S, Nadeau R, de Champlain J. The release of catecholamines from the adrenal medulla and its modulation by alpha 2-adrenoceptors in the anaesthetized dog. Canadian Journal of Physiology and Pharmacology. 1987;65(4):550–7. PMID: 3038285

8. Gadkari TV, Cortes N, Madrasi K, Tsoukias NM, Joshi MS. Agmatine induced NO dependent rat mesenteric artery relaxation and its impairment in salt-sensitive hypertension. Nitric Oxide. 2013;35:65–71. DOI: 10.1016/j.niox.2013.08.005

9. Brede M, Wiesmann F, Jahns R, Hadamek K, Arnolt C, Neubauer S et al. Feedback inhibition of catecholamine release by two different alpha2-adrenoceptor subtypes prevents progression of heart failure. Circulation. 2002;106(19):2491–6. PMID: 12417548

10. MacMillan LB, Hein L, Smith MS, Piascik MT, Limbird LE. Central hypotensive effects of the alpha2A-adrenergic receptor subtype. Science (New York, N.Y.). 1996;273(5276):801–3. PMID: 8670421

11. Link RE, Desai K, Hein L, Stevens ME, Chruscinski A, Bernstein D et al. Cardiovascular regulation in mice lacking alpha2-adrenergic receptor subtypes b and c. Science (New York, N. Y.). 1996;273(5276):803–5. PMID: 8670422

12. Makaritsis KP, Handy DE, Johns C, Kobilka B, Gavras I, Gavras H. Role of the alpha2B-adrenergic receptor in the development of salt-induced hypertension. Hypertension (Dallas, Tex.: 1979). 1999;33(1):14–7. PMID: 9931075

13. Hein L, Altman JD, Kobilka BK. Two functionally distinct α2-adrenergic receptors regulate sympathetic neurotransmission. Nature. 1999;402(6758):181–4. DOI: 10.1038/46040

14. Zefirov TL, Khisamieva LI, Ziyatdinova NI, Zefirov AL. Peculiar Effects of Selective Blockade of α2-Adrenoceptor Subtypes on Cardiac Chronotropy in Newborn Rats. Bulletin of Experimental Biology and Medicine. 2015;160(1):6–8. DOI: 10.1007/s10517-015-3084-5

15. Bousquet P, Feldman J, Atlas D. An endogenous, non-catecholamine clonidine antagonist increases mean arterial blood pressure. European Journal of Pharmacology. 1986;124(1–2):167–70. PMID: 3720837

16. Maltsev AV, Kokoz YM, Evdokimovskii EV, Pimenov OY, Reyes S, Alekseev AE. Alpha-2 adrenoceptors and imidazoline receptors in cardiomyocytes mediate counterbalancing effect of agmatine on NO synthesis and intracellular calcium handling. Journal of Molecular and Cellular Cardiology. 2014;68:66–74. DOI: 10.1016/j.yjmcc.2013.12.030

17. Maltsev A.V., Nenov M.N., Pimenov O. Yu., Kokoz Yu. M. Modulation of L-type Ca2+ currents and intracellular calcium by agmatine in rat cardiomyocytes. Biological membranes: journal of membrane and cell biology. 2013;30(2):92–104. DOI: 10.7868/S0233475513020059

18. Kokoz YM, Evdokimovskii EV, Maltsev AV, Nenov MN, Nakipova OV, Averin AS et al. Sarcolemmal α2-adrenoceptors control protective cardiomyocyte-delimited sympathoadrenal response. Journal of Molecular and Cellular Cardiology. 2016;100:9–20. DOI: 10.1016/j.yjmcc.2016.09.006

19. Alekseev AE, Korystova AF, Mavlyutova DA, Kokoz YM. Potential-dependent Ca2+ currents in isolated heart cells of hibernators. Biochemistry and Molecular Biology International. 1994;33(2):365–75. PMID: 7951054

20. Nagano T, Yoshimura T. Bioimaging of nitric oxide. Chemical Reviews. 2002;102(4):1235–70. PMID: 11942795

21. Edwards L, Fishman D, Horowitz P, Bourbon N, Kester M, Ernsberger P. The I1-imidazoline receptor in PC12 pheochromocytoma cells activates protein kinases C, extracellular signal-regulated kinase (ERK) and c-jun N-terminal kinase ( JNK). Journal of Neurochemistry. 2001;79(5):931–40. PMID: 11739604

22. Nenov M.N., Berezhnov A.V., Fedotova E.I., Grushin K.S., Pimenov O.Yu., Murashev A.N. et al. “Arginine paradox” in cardyomyocites of Sprague-Dawley and Spontaneously Hypertensive Rats: α2-adrenoreceptor-mediated regulation of L-type Ca2+ currents by L-arginine. Biological Membranes: Journal Of Membrane And Cell Biology. 2010;27(5):440–8.

23. Blaustein MP, Lederer WJ. Sodium/Calcium Exchange: Its Physiological Implications. Physiological Reviews. 1999;79(3):763–854. DOI: 10.1152/physrev.1999.79.3.763

24. Sipido KR, Maes M, Van de Werf F. Low efficiency of Ca2+ entry through the Na(+)-Ca2+ exchanger as trigger for Ca2+ release from the sarcoplasmic reticulum. A comparison between L-type Ca2+ current and reverse-mode Na(+)-Ca2+ exchange. Circulation Research. 1997;81(6):1034–44. PMID: 9400385

25. Michell BJ, Chen Z, Tiganis T, Stapleton D, Katsis F, Power DA et al. Coordinated Control of Endothelial Nitric-oxide Synthase Phosphorylation by Protein Kinase C and the cAMPdependent Protein Kinase. Journal of Biological Chemistry. 2001;276(21):17625–8. DOI: 10.1074/jbc.C100122200

26. Schümann HJ, Endoh S, Brodde OE. The time course of the effects of beta- and alpha-adrenoceptor stimulation by isoprenaline and methoxamine on the contractile force and cAMP level of the isolated rabbit papillary muscle. Naunyn-Schmiedeberg’s Archives of Pharmacology. 1975;289(3):291–302. PMID: 169486

27. Terzic A, Pucéat M, Clément O, Scamps F, Vassort G. Alpha1-adrenergic effects on intracellular pH and calcium and on myofilaments in single rat cardiac cells. The Journal of Physiology. 1992;447:275–92. PMID: 1317431

28. Ranek MJ, Kost CK, Hu C, Martin DS, Wang X. Muscarinic2 receptors modulate cardiac proteasome function in a protein kinase G-dependent manner. Journal of Molecular and Cellular Cardiology. 2014;69:43–51. DOI: 10.1016/j.yjmcc.2014.01.017

29. Lee N, Jeong S, Kim K-C, Kim J-A, Park J-Y, Kang H-W et al. Ca2+ Regulation of Cav 3.3 T-type Ca2+ Channel Is Mediated by Calmodulin. Molecular Pharmacology. 2017;92(3):347–57. DOI: 10.1124/mol.117.108530

30. Cohn JN, Pfeffer MA, Rouleau J, Sharpe N, Swedberg K, Straub M et al. Adverse mortality effect of central sympathetic inhibition with sustained-release moxonidine in patients with heart failure (MOXCON). European Journal of Heart Failure. 2003;5(5):659–67. PMID: 14607206

31. Kang M, Chung KY. PKC-ε mediates multiple endothelin-1 actions on systolic Ca2+ and contractility in ventricular myocytes. Biochemical and Biophysical Research Communications. 2012;423(3):600–5. DOI: 10.1016/j.bbrc.2012.06.024