The role of the NO/cGMP/cGMP-dependent protein kinase I (cGKI) pathway in myocardial protection and pre-/postconditioning has been intensively investigated. Drugs that block the activity of cGMP-degrading enzymes, such as the phosphodiesterase 5 inhibitor sildenafil, have a pre-conditioning-like effect on the survival of cardiomyocytes after ischaemia/reperfusion (I/R) injury and reduce infarction area. In cardiac myocytes, accumulation of cGMP leads to several protective events including stimulation of mitochondrial ATP-dependent potassium channels (mitoKATP) at the inner mitochondrial membrane (IMM). Increased K+ fluxes into the mitochondrial matrix causes a rise in reactive oxygen species production via the electron transport chain and an activation of the epsilon isoform of protein kinase C. Ca2+-activated K+ channels of the BK type, in cardiomyocytes exclusively present at the IMM, play also a role in protection against I/R injury. MitoBK channels significantly contribute to mitochondrial K+ uptake, and mitoBK openers have been shown to protect hearts against infarction. Importantly, knockdown of the accessory b1-subunit of the BK channel abolished the infarct limiting effects of the cGMP-elevating drug sildenafil. These findings indicate that mitoBK activation confers cardioprotection in a manner similar to but independent of mitoKATP activation and, together with the well-established signalling of NO/cGMP/cGKI to plasma membrane BK channels in smooth muscle cells and neurons, suggest a direct link between cGMP- and mitoBK-mediated effects in ischaemic conditioning. To investigate the role of mitoBK as a target of cGMP signalling in cardiac cells in vivo, we aim to study BK-/- mice with a global deletion in addition to mice with cardiomyocyte-specific inactivation of BK. The protection against I/R injury will be tested by ischaemic pre- and postconditioning, ligands of particulate guanylyl cyclase receptors, NO-stimulated guanylyl cyclases, and compounds that directly modulate BK activity. We will also assess the long-term outcome after occlusion and reperfusion of the left coronary artery by comparing infarct size and survival of BK knockout and litter-matched control mice. Analyses of cGMP pools at I/R and effects of cGMP on functional characteristics of mitochondria isolated from cardiomyocytes of gene-targeted BK mouse mutants together with approaches to reveal electro-pharmacological properties of mitoBK will corroborate the in vivo studies, and will finally improve our understanding of cGMP signalling to K+ channels at the IMM.
PIs of this project; PIs of other FOR 2060 projects are in bold.
1. Straubinger J, Schöttle V, Bork N, Subramanian H, Dünnes H, Russwurm M, Gawaz M, Friebe A, Nemer M, Nikolaev VO, Lukowski R. Sildenafil does not prevent heart hypertrophy and fibrosis induced by cardiomyocyte AT1R signalling. J Pharmacol Exp Ther. 2015;354:406-16. [Project 3, Project 4, and Project 5] [pubmed]
2. Brennenstuhl C, Tanimoto N, Burkard M, Wagner R, Bolz S, Trifunovic D, Kabagema-Bilan C, Paquet-Durand F, Beck SC, Huber G, Seeliger MW, Ruth P, Wissinger B, Lukowski R. Targeted ablation of the Pde6h gene in mice reveals cross-species differences in cone and rod phototransduction protein isoform inventory. J Biol Chem. 2015;290:10242-55. [Project 5 and Project 9] [pubmed]
3. Lu R, Bausch AE, Kallenborn-Gerhardt W, Stoetzer C, Debruin N, Ruth P, Geisslinger G, Leffler A, Lukowski R*, Schmidtko A*. Slack channels expressed in sensory neurons control neuropathic pain in mice. J Neurosci. 2015;35:1125-35. (*equal contribution) [Project 5] [pubmed]
4. Feil S, Fehrenbacher B, Lukowski R, Essmann F, Schulze-Osthoff K, Schaller M, Feil R. Transdifferentiation of vascular smooth muscle cells to macrophage-like cells during atherogenesis. Circ Res. 2014;115:662-7. [Project 1 and Project 5] [pubmed]
5. Lu R, Lukowski R, Sausbier M, Zhang DD, Sisignano M, Schuh CD, Kuner R, Ruth P, Geisslinger G, Schmidtko A. BKCa channels expressed in sensory neurons modulate inflammatory pain in mice. Pain. 2014;155:556-65. [Project 5] [pubmed]
7. Patrucco E, Domes K, Sbroggio M, Blaich A, Schlossmann J, Desch M, Rybalkin SD, Beavo JA, Lukowski R, Hofmann F. Roles of cGMP-dependent protein kinase I (cGKI) and PDE5 in the regulation of Ang II-induced cardiac hypertrophy and fibrosis. Proc Natl Acad Sci U S A. 2014;111:12925-9. [Project 5] [pubmed]
8. Soltysinska E, Bentzen BH, Barthmes M, Hattel H, Thrush AB, Harper ME, Qvortrup K, Larsen FJ, Schiffer TA, Losa-Reyna J, Straubinger J, Kniess A, Thomsen MB, Bruggemann A, Fenske S, Biel M, Ruth P, Wahl-Schott C, Boushel RC, Olesen SP, Lukowski R. KCNMA1 encoded cardiac BK channels afford protection against ischaemia-reperfusion injury. PLoS One. 2014;9:e103402. [Project 5] [pubmed]
9. Zhang L*, Lukowski R*, Gaertner F, Lorenz M, Legate KR, Domes K, Angermeier E, Hofmann F, Massberg S. Thrombocytosis as a response to high interleukin-6 levels in cGMP-dependent protein kinase I mutant mice. Arterioscler Thromb Vasc Biol. 2013;33:1820-8. (*equal contribution) [Project 5] [pubmed]
10. Methner C, Lukowski R, Grube K, Loga F, Smith RA, Murphy MP, Hofmann F, Krieg T. Protection through postconditioning or a mitochondria-targeted S-nitrosothiol is unaffected by cardiomyocyte-selective ablation of protein kinase G. Basic Res Cardiol. 2013;108:337. [Project 5] [pubmed]