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Franz MJ, Wenisch P, Wohlleben P, Rupprecht L, Chubanov V, Gudermann T, Kyheröinen S, Vartiainen MK, Heinrich MR, Muehlich S. Identification of novel inhibitors of the transcriptional coactivator MRTF-A for HCC therapy. MOLECULAR THERAPY. ONCOLOGY 2024; 32:200855. [PMID: 39262570 PMCID: PMC11387234 DOI: 10.1016/j.omton.2024.200855] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2024] [Revised: 07/11/2024] [Accepted: 08/02/2024] [Indexed: 09/13/2024]
Abstract
Myocardin-related transcription factor A (MRTF-A) is a coactivator of serum response factor (SRF), which regulates the expression of genes involved in cell proliferation, migration, and differentiation and has been implicated in hepatocellular carcinoma (HCC) progression. We recently established inhibition of the transcriptional activity of MRTF-A by NS8593 as a novel therapeutic approach for HCC therapy. NS8593 is a negative gating modulator of the transient receptor potential cation channel TRPM7. In this report, we identify an aminobenzimidazole that is highly potent in inhibiting TRPM7 and its interaction with RhoA, leading to decreased SRF transcriptional activity and enhanced nuclear export of MRTF-A, as determined by fluorescence loss in photobleaching (FLIP). This resulted in reduced expression of the MRTF/SRF target genes transforming growth factor β1 (TGF-β1) and tetraspanin 5 (TSPAN5), senescence induction, and growth arrest in HCC cells. Replacement of the tetraline core by a 3-aminophenyl substructure yielded inhibitor 10 with higher potency than inhibitor 5, and further structural modifications yielded highly potent inhibitors of SRF activity, 14 and 16. Both compounds were capable of inhibiting cell proliferation and inducing senescence in HCC cells with improved efficacy compared to NS8593. These inhibitors represent valuable tools for understanding the molecular basis of drug development targeting TRPM7 and MRTFs.
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Affiliation(s)
- Miriam Jasmin Franz
- Department of Chemistry and Pharmacy, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nikolaus-Fiebiger-Straße 10, 91058 Erlangen, Germany
| | - Pia Wenisch
- Department of Chemistry and Pharmacy, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nikolaus-Fiebiger-Straße 10, 91058 Erlangen, Germany
| | - Petra Wohlleben
- Department of Chemistry and Pharmacy, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nikolaus-Fiebiger-Straße 10, 91058 Erlangen, Germany
| | - Laura Rupprecht
- Department of Chemistry and Pharmacy, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nikolaus-Fiebiger-Straße 10, 91058 Erlangen, Germany
| | - Vladimir Chubanov
- Walther-Straub Institute of Pharmacology and Toxicology, Ludwig-Maximilians-Universität München, Goethestraße 33, 80336 München, Germany
| | - Thomas Gudermann
- Walther-Straub Institute of Pharmacology and Toxicology, Ludwig-Maximilians-Universität München, Goethestraße 33, 80336 München, Germany
| | - Salla Kyheröinen
- Institute of Biotechnology, HiLIFE, University of Helsinki, Viikinkaari 5d, 00790 Helsinki, Finland
| | | | - Markus R Heinrich
- Department of Chemistry and Pharmacy, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nikolaus-Fiebiger-Straße 10, 91058 Erlangen, Germany
- FAU NeW-Research Center for New Bioactive Compounds, Nikolaus-Fiebiger-Straße 10, 91058 Erlangen, Germany
| | - Susanne Muehlich
- Department of Chemistry and Pharmacy, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nikolaus-Fiebiger-Straße 10, 91058 Erlangen, Germany
- FAU NeW-Research Center for New Bioactive Compounds, Nikolaus-Fiebiger-Straße 10, 91058 Erlangen, Germany
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Van NTH, Kim WK, Nam JH. Challenges in the Therapeutic Targeting of KCa Channels: From Basic Physiology to Clinical Applications. Int J Mol Sci 2024; 25:2965. [PMID: 38474212 PMCID: PMC10932353 DOI: 10.3390/ijms25052965] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Revised: 01/23/2024] [Accepted: 01/25/2024] [Indexed: 03/14/2024] Open
Abstract
Calcium-activated potassium (KCa) channels are ubiquitously expressed throughout the body and are able to regulate membrane potential and intracellular calcium concentrations, thereby playing key roles in cellular physiology and signal transmission. Consequently, it is unsurprising that KCa channels have been implicated in various diseases, making them potential targets for pharmaceutical interventions. Over the past two decades, numerous studies have been conducted to develop KCa channel-targeting drugs, including those for disorders of the central and peripheral nervous, cardiovascular, and urinary systems and for cancer. In this review, we synthesize recent findings regarding the structure and activating mechanisms of KCa channels. We also discuss the role of KCa channel modulators in therapeutic medicine. Finally, we identify the major reasons behind the delay in bringing these modulators to the pharmaceutical market and propose new strategies to promote their application.
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Affiliation(s)
- Nhung Thi Hong Van
- Department of Physiology, Dongguk University College of Medicine, Gyeongju 38066, Republic of Korea;
- Channelopathy Research Center (CRC), Dongguk University College of Medicine, Goyang 10326, Republic of Korea
| | - Woo Kyung Kim
- Channelopathy Research Center (CRC), Dongguk University College of Medicine, Goyang 10326, Republic of Korea
- Department of Internal Medicine, Graduate School of Medicine, Dongguk University, Goyang 10326, Republic of Korea
| | - Joo Hyun Nam
- Department of Physiology, Dongguk University College of Medicine, Gyeongju 38066, Republic of Korea;
- Channelopathy Research Center (CRC), Dongguk University College of Medicine, Goyang 10326, Republic of Korea
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3
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Giommi A, Gurgel ARB, Smith GL, Workman AJ. Does the small conductance Ca 2+-activated K + current I SK flow under physiological conditions in rabbit and human atrial isolated cardiomyocytes? J Mol Cell Cardiol 2023; 183:70-80. [PMID: 37704101 DOI: 10.1016/j.yjmcc.2023.09.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Revised: 08/16/2023] [Accepted: 09/02/2023] [Indexed: 09/15/2023]
Abstract
BACKGROUND The small conductance Ca2+-activated K+ current (ISK) is a potential therapeutic target for treating atrial fibrillation. AIM To clarify, in rabbit and human atrial cardiomyocytes, the intracellular [Ca2+]-sensitivity of ISK, and its contribution to action potential (AP) repolarisation, under physiological conditions. METHODS Whole-cell-patch clamp, fluorescence microscopy: to record ion currents, APs and [Ca2+]i; 35-37°C. RESULTS In rabbit atrial myocytes, 0.5 mM Ba2+ (positive control) significantly decreased whole-cell current, from -12.8 to -4.9 pA/pF (P < 0.05, n = 17 cells, 8 rabbits). By contrast, the ISK blocker apamin (100 nM) had no effect on whole-cell current, at any set [Ca2+]i (∼100-450 nM). The ISK blocker ICAGEN (1 μM: ≥2 x IC50) also had no effect on current over this [Ca2+]i range. In human atrial myocytes, neither 1 μM ICAGEN (at [Ca2+]i ∼ 100-450 nM), nor 100 nM apamin ([Ca2+]i ∼ 250 nM) affected whole-cell current (5-10 cells, 3-5 patients/group). APs were significantly prolonged (at APD30 and APD70) by 2 mM 4-aminopyridine (positive control) in rabbit atrial myocytes, but 1 μM ICAGEN had no effect on APDs, versus either pre-ICAGEN or time-matched controls. High concentration (10 μM) ICAGEN (potentially ISK-non-selective) moderately increased APD70 and APD90, by 5 and 26 ms, respectively. In human atrial myocytes, 1 μM ICAGEN had no effect on APD30-90, whether stimulated at 1, 2 or 3 Hz (6-9 cells, 2-4 patients/rate). CONCLUSION ISK does not flow in human or rabbit atrial cardiomyocytes with [Ca2+]i set within the global average diastolic-systolic range, nor during APs stimulated at physiological or supra-physiological (≤3 Hz) rates.
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Affiliation(s)
- Alessandro Giommi
- School of Cardiovascular and Metabolic Health, University of Glasgow, Glasgow, UK
| | - Aline R B Gurgel
- School of Cardiovascular and Metabolic Health, University of Glasgow, Glasgow, UK
| | - Godfrey L Smith
- School of Cardiovascular and Metabolic Health, University of Glasgow, Glasgow, UK
| | - Antony J Workman
- School of Cardiovascular and Metabolic Health, University of Glasgow, Glasgow, UK.
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Orfali R, AlFaiz A, Rahman MA, Lau L, Nam YW, Zhang M. K Ca2 and K Ca3.1 Channels in the Airways: A New Therapeutic Target. Biomedicines 2023; 11:1780. [PMID: 37509419 PMCID: PMC10376499 DOI: 10.3390/biomedicines11071780] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Revised: 06/08/2023] [Accepted: 06/13/2023] [Indexed: 07/30/2023] Open
Abstract
K+ channels are involved in many critical functions in lung physiology. Recently, the family of Ca2+-activated K+ channels (KCa) has received more attention, and a massive amount of effort has been devoted to developing selective medications targeting these channels. Within the family of KCa channels, three small-conductance Ca2+-activated K+ (KCa2) channel subtypes, together with the intermediate-conductance KCa3.1 channel, are voltage-independent K+ channels, and they mediate Ca2+-induced membrane hyperpolarization. Many KCa2 channel members are involved in crucial roles in physiological and pathological systems throughout the body. In this article, different subtypes of KCa2 and KCa3.1 channels and their functions in respiratory diseases are discussed. Additionally, the pharmacology of the KCa2 and KCa3.1 channels and the link between these channels and respiratory ciliary regulations will be explained in more detail. In the future, specific modulators for small or intermediate Ca2+-activated K+ channels may offer a unique therapeutic opportunity to treat muco-obstructive lung diseases.
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Affiliation(s)
- Razan Orfali
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA 92618, USA
- Biomedical Research Administration, Research Centre, King Fahad Medical City, Riyadh Second Health Cluster, Riyadh 12231, Saudi Arabia
| | - Ali AlFaiz
- Biomedical Research Administration, Research Centre, King Fahad Medical City, Riyadh Second Health Cluster, Riyadh 12231, Saudi Arabia
| | - Mohammad Asikur Rahman
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA 92618, USA
| | - Liz Lau
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA 92618, USA
| | - Young-Woo Nam
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA 92618, USA
| | - Miao Zhang
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA 92618, USA
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van Herck IGM, Seutin V, Bentzen BH, Marrion NV, Edwards AG. Gating kinetics and pharmacological properties of small-conductance Ca 2+-activated potassium channels. Biophys J 2023; 122:1143-1157. [PMID: 36760125 PMCID: PMC10111258 DOI: 10.1016/j.bpj.2023.02.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Revised: 11/20/2022] [Accepted: 02/06/2023] [Indexed: 02/11/2023] Open
Abstract
Small-conductance (SK) calcium-activated potassium channels are a promising treatment target in atrial fibrillation. However, the functional properties that differentiate SK inhibitors remain poorly understood. The objective of this study was to determine how two unrelated SK channel inhibitors, apamin and AP14145, impact SK channel function in excised inside-out single-channel recordings. Surprisingly, both apamin and AP14145 exert much of their inhibition by inducing a class of very-long-lived channel closures (apamin: τc,vl = 11.8 ± 7.1 s, and AP14145: τc,vl = 10.3 ± 7.2 s), which were never observed under control conditions. Both inhibitors also induced changes to the three closed and two open durations typical of normal SK channel gating. AP14145 shifted the open duration distribution to favor longer open durations, whereas apamin did not alter open-state kinetics. AP14145 also prolonged the two shortest channel closed durations (AP14145: τc,s = 3.50 ± 0.81 ms, and τc,i = 32.0 ± 6.76 ms versus control: τc,s = 1.59 ± 0.19 ms, and τc,i = 13.5 ± 1.17 ms), thus slowing overall gating kinetics within bursts of channel activity. In contrast, apamin accelerated intraburst gating kinetics by shortening the two shortest closed durations (τc,s = 0.75 ± 0.10 ms and τc,i = 5.08 ± 0.49 ms) and inducing periods of flickery activity. Finally, AP14145 introduced a unique form of inhibition by decreasing unitary current amplitude. SK channels exhibited two clearly distinguishable amplitudes (control: Ahigh = 0.76 ± 0.03 pA, and Alow = 0.54 ± 0.03 pA). AP14145 both reduced the fraction of patches exhibiting the higher amplitude (AP14145: 4/9 patches versus control: 16/16 patches) and reduced the mean low amplitude (0.38 ± 0.03 pA). Here, we have demonstrated that both inhibitors introduce very long channel closures but that each also exhibits unique effects on other components of SK gating kinetics and unitary current. The combination of these effects is likely to be critical for understanding the functional differences of each inhibitor in the context of cyclical Ca2+-dependent channel activation in vivo.
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Affiliation(s)
- Ilsbeth G M van Herck
- Computational Physiology Department, Simula Research Laboratory, Oslo, Norway; Institute of Informatics, University of Oslo, Oslo, Norway
| | - Vincent Seutin
- Neurophysiology Unit, GIGA Neurosciences, University of Liège, Liège, Belgium
| | - Bo H Bentzen
- Acesion Pharma, Copenhagen, Denmark; Biomedical Institute, University of Copenhagen, Copenhagen, Denmark
| | - Neil V Marrion
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, UK
| | - Andrew G Edwards
- Computational Physiology Department, Simula Research Laboratory, Oslo, Norway; Department of Pharmacology, University of California, Davis, California.
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Nam YW, Downey M, Rahman MA, Cui M, Zhang M. Channelopathy of small- and intermediate-conductance Ca 2+-activated K + channels. Acta Pharmacol Sin 2023; 44:259-267. [PMID: 35715699 PMCID: PMC9889811 DOI: 10.1038/s41401-022-00935-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2022] [Accepted: 05/31/2022] [Indexed: 02/04/2023] Open
Abstract
Small- and intermediate-conductance Ca2+-activated K+ (KCa2.x/KCa3.1 also called SK/IK) channels are gated exclusively by intracellular Ca2+. The Ca2+ binding protein calmodulin confers sub-micromolar Ca2+ sensitivity to the channel-calmodulin complex. The calmodulin C-lobe is constitutively associated with the proximal C-terminus of the channel. Interactions between calmodulin N-lobe and the channel S4-S5 linker are Ca2+-dependent, which subsequently trigger conformational changes in the channel pore and open the gate. KCNN genes encode four subtypes, including KCNN1 for KCa2.1 (SK1), KCNN2 for KCa2.2 (SK2), KCNN3 for KCa2.3 (SK3), and KCNN4 for KCa3.1 (IK). The three KCa2.x channel subtypes are expressed in the central nervous system and the heart. The KCa3.1 subtype is expressed in the erythrocytes and the lymphocytes, among other peripheral tissues. The impact of dysfunctional KCa2.x/KCa3.1 channels on human health has not been well documented. Human loss-of-function KCa2.2 mutations have been linked with neurodevelopmental disorders. Human gain-of-function mutations that increase the apparent Ca2+ sensitivity of KCa2.3 and KCa3.1 channels have been associated with Zimmermann-Laband syndrome and hereditary xerocytosis, respectively. This review article discusses the physiological significance of KCa2.x/KCa3.1 channels, the pathophysiology of the diseases linked with KCa2.x/KCa3.1 mutations, the structure-function relationship of the mutant KCa2.x/KCa3.1 channels, and potential pharmacological therapeutics for the KCa2.x/KCa3.1 channelopathy.
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Affiliation(s)
- Young-Woo Nam
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA, 92618, USA
| | - Myles Downey
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA, 92618, USA
| | - Mohammad Asikur Rahman
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA, 92618, USA
| | - Meng Cui
- Department of Pharmaceutical Sciences, Northeastern University School of Pharmacy, Boston, MA, 02115, USA
| | - Miao Zhang
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA, 92618, USA.
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7
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Butler AS, Hancox JC, Marrion NV. Preferential formation of human heteromeric SK2:SK3 channels limits homomeric SK channel assembly and function. J Biol Chem 2022; 299:102783. [PMID: 36502918 PMCID: PMC9841042 DOI: 10.1016/j.jbc.2022.102783] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Revised: 11/29/2022] [Accepted: 12/04/2022] [Indexed: 12/13/2022] Open
Abstract
Three isoforms of small conductance, calcium-activated potassium (SK) channel subunits have been identified (SK1-3) that exhibit a broad and overlapping tissue distribution. SK channels have been implicated in several disease states including hypertension and atrial fibrillation, but therapeutic targeting of SK channels is hampered by a lack of subtype-selective inhibitors. This is further complicated by studies showing that SK1 and SK2 preferentially form heteromeric channels during co-expression, likely limiting the function of homomeric channels in vivo. Here, we utilized a simplified expression system to investigate functional current produced when human (h) SK2 and hSK3 subunits are co-expressed. When expressed alone, hSK3 subunits were more clearly expressed on the cell surface than hSK2 subunits. hSK3 surface expression was reduced by co-transfection with hSK2. Whole-cell recording showed homomeric hSK3 currents were larger than homomeric hSK2 currents or heteromeric hSK2:hSK3 currents. The smaller amplitude of hSK2:hSK3-mediated current when compared with homomeric hSK3-mediated current suggests hSK2 subunits regulate surface expression of heteromers. Co-expression of hSK2 and hSK3 subunits produced a current that arose from a single population of heteromeric channels as exhibited by an intermediate sensitivity to the inhibitors apamin and UCL1684. Co-expression of the apamin-sensitive hSK2 subunit and a mutant, apamin-insensitive hSK3 subunit [hSK3(H485N)], produced an apamin-sensitive current. Concentration-inhibition relationships were best fit by a monophasic Hill equation, confirming preferential formation of heteromers. These data show that co-expressed hSK2 and hSK3 preferentially form heteromeric channels and suggest that the hSK2 subunit acts as a chaperone, limiting membrane expression of hSK2:hSK3 heteromeric channels.
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Affiliation(s)
- Andrew S Butler
- School of Physiology, Pharmacology and Neuroscience, Medical Sciences Building, University of Bristol, University Walk, Bristol, United Kingdom
| | - Jules C Hancox
- School of Physiology, Pharmacology and Neuroscience, Medical Sciences Building, University of Bristol, University Walk, Bristol, United Kingdom.
| | - Neil V Marrion
- School of Physiology, Pharmacology and Neuroscience, Medical Sciences Building, University of Bristol, University Walk, Bristol, United Kingdom.
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Nam YW, Pala R, El-Sayed NS, Larin-Henriquez D, Amirrad F, Yang G, Rahman MA, Orfali R, Downey M, Parang K, Nauli SM, Zhang M. Subtype-Selective Positive Modulation of K Ca2.3 Channels Increases Cilia Length. ACS Chem Biol 2022; 17:2344-2354. [PMID: 35947779 PMCID: PMC9396613 DOI: 10.1021/acschembio.2c00469] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
Small-conductance Ca2+-activated potassium
(KCa2.x) channels are gated exclusively by intracellular
Ca2+. The activation of KCa2.3 channels induces
hyperpolarization,
which augments Ca2+ signaling in endothelial cells. Cilia
are specialized Ca2+ signaling compartments. Here, we identified
compound 4 that potentiates human KCa2.3 channels
selectively. The subtype selectivity of compound 4 for
human KCa2.3 over rat KCa2.2a channels relies
on an isoleucine residue in the HA/HB helices. Positive modulation
of KCa2.3 channels by compound 4 increased
flow-induced Ca2+ signaling and cilia length, while negative
modulation by AP14145 reduced flow-induced Ca2+ signaling
and cilia length. These findings were corroborated by the increased
cilia length due to the expression of Ca2+-hypersensitive
KCa2.3_G351D mutant channels and the reduced cilia length
resulting from the expression of Ca2+-hyposensitive KCa2.3_I438N channels. Collectively, we were able to associate
functions of KCa2.3 channels and cilia, two crucial components
in the flow-induced Ca2+ signaling of endothelial cells,
with potential implications in vasodilation and ciliopathic hypertension.
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Affiliation(s)
- Young-Woo Nam
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, California 92618, USA
| | - Rajasekharreddy Pala
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, California 92618, USA
| | - Naglaa Salem El-Sayed
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, California 92618, USA
| | - Denisse Larin-Henriquez
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, California 92618, USA
| | - Farideh Amirrad
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, California 92618, USA
| | - Grace Yang
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, California 92618, USA
| | - Mohammad Asikur Rahman
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, California 92618, USA
| | - Razan Orfali
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, California 92618, USA
| | - Myles Downey
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, California 92618, USA
| | - Keykavous Parang
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, California 92618, USA
| | - Surya M Nauli
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, California 92618, USA
| | - Miao Zhang
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, California 92618, USA
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Channelopathy-causing mutations in the S 45A/S 45B and HA/HB helices of K Ca2.3 and K Ca3.1 channels alter their apparent Ca 2+ sensitivity. Cell Calcium 2022; 102:102538. [PMID: 35030515 PMCID: PMC8844225 DOI: 10.1016/j.ceca.2022.102538] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Revised: 01/05/2022] [Accepted: 01/06/2022] [Indexed: 12/11/2022]
Abstract
Small- and intermediate-conductance Ca2+-activated potassium (KCa2.x and KCa3.1, also called SK and IK) channels are activated exclusively by a Ca2+-calmodulin gating mechanism. Wild-type KCa2.3 channels have a Ca2+ EC50 value of ∼0.3 μM, while the apparent Ca2+ sensitivity of wild-type KCa3.1 channels is ∼0.27 μM. Heterozygous genetic mutations of KCa2.3 channels have been associated with Zimmermann-Laband syndrome and idiopathic noncirrhotic portal hypertension, while KCa3.1 channel mutations were reported in hereditary xerocytosis patients. KCa2.3_S436C and KCa2.3_V450L channels with mutations in the S45A/S45B helices exhibited hypersensitivity to Ca2+. The corresponding mutations in KCa3.1 channels also elevated the apparent Ca2+ sensitivity. KCa3.1_S314P, KCa3.1_A322V and KCa3.1_R352H channels with mutations in the HA/HB helices are hypersensitive to Ca2+, whereas KCa2.3 channels with the equivalent mutations are not. The different effects of the equivalent mutations in the HA/HB helices on the apparent Ca2+ sensitivity of KCa2.3 and KCa3.1 channels may imply distinct modulation of the two channel subtypes by the HA/HB helices. AP14145 reduced the apparent Ca2+ sensitivity of the hypersensitive mutant KCa2.3 channels, suggesting the potential therapeutic usefulness of negative gating modulators.
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Gatta G, Sobota V, Citerni C, Diness JG, Sørensen US, Jespersen T, Bentzen BH, Zeemering S, Kuiper M, Verheule S, Schotten U, van Hunnik A. Effective termination of atrial fibrillation by SK channel inhibition is associated with a sudden organization of fibrillatory conduction. Europace 2021; 23:1847-1859. [PMID: 34080619 PMCID: PMC8576281 DOI: 10.1093/europace/euab125] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Accepted: 04/22/2021] [Indexed: 11/12/2022] Open
Abstract
AIMS Pharmacological termination of atrial fibrillation (AF) remains a challenge due to limited efficacy and potential ventricular proarrhythmic effects of antiarrhythmic drugs. SK channels are proposed as atrial-specific targets in the treatment of AF. Here, we investigated the effects of the new SK channel inhibitor AP14145. METHODS AND RESULTS Eight goats were implanted with pericardial electrodes for induction of AF (30 days). In an open-chest study, the atrial conduction velocity (CV) and effective refractory period (ERP) were measured during pacing. High-density mapping of both atrial free-walls was performed during AF and conduction properties were assessed. All measurements were performed at baseline and during AP14145 infusion [10 mg/kg/h (n = 1) or 20 mg/kg/h (n = 6)]. At an infusion rate of 20 mg/kg/h, AF terminated in five of six goats. AP14145 profoundly increased ERP and reduced CV during pacing. AP14145 increased spatiotemporal instability of conduction at short pacing cycle lengths. Atrial fibrillation cycle length and pathlength (AF cycle length × CV) underwent a strong dose-dependent prolongation. Conduction velocity during AF remained unchanged and conduction patterns remained complex until the last seconds before AF termination, during which a sudden and profound organization of fibrillatory conduction occurred. CONCLUSION AP14145 provided a successful therapy for termination of persistent AF in goats. During AF, AP14145 caused an ERP and AF cycle length prolongation. AP14145 slowed CV during fast pacing but did not lead to a further decrease during AF. Termination of AF was preceded by an abrupt organization of AF with a decline in the number of fibrillation waves.
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Affiliation(s)
- Giulia Gatta
- Department of Physiology, Maastricht University, P.O. Box 616, 6200 MD Maastricht, The Netherlands
| | - Vladimir Sobota
- Department of Physiology, Maastricht University, P.O. Box 616, 6200 MD Maastricht, The Netherlands
| | - Carlotta Citerni
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | | | | | - Thomas Jespersen
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Bo Hjorth Bentzen
- Acesion Pharma, Copenhagen, Denmark.,Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Stef Zeemering
- Department of Physiology, Maastricht University, P.O. Box 616, 6200 MD Maastricht, The Netherlands
| | - Marion Kuiper
- Department of Physiology, Maastricht University, P.O. Box 616, 6200 MD Maastricht, The Netherlands
| | - Sander Verheule
- Department of Physiology, Maastricht University, P.O. Box 616, 6200 MD Maastricht, The Netherlands
| | - Ulrich Schotten
- Department of Physiology, Maastricht University, P.O. Box 616, 6200 MD Maastricht, The Netherlands
| | - Arne van Hunnik
- Department of Physiology, Maastricht University, P.O. Box 616, 6200 MD Maastricht, The Netherlands
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Qi MM, Qian LL, Wang RX. Modulation of SK Channels: Insight Into Therapeutics of Atrial Fibrillation. Heart Lung Circ 2021; 30:1130-1139. [PMID: 33642173 DOI: 10.1016/j.hlc.2021.01.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Revised: 01/12/2021] [Accepted: 01/31/2021] [Indexed: 11/19/2022]
Abstract
Atrial fibrillation (AF) is the most prevalent cardiac arrhythmia in the world. Although much technological progress in the treatment of AF has been made, there is an urgent need for better treatment of AF due to its high rates of morbidity and mortality. The anti-arrhythmic drugs currently approved for marketing have significant limitations and side effects such as life-threatening ventricular arrhythmias and hypotension. The small conductance Ca2+-activated K+ channels (SK channels) are dependent on intracellular Ca2+ concentrations, which tightly integrate with membrane potential. Given the predominant expression in the atria of many species, including humans, they are now emerging as a therapeutic target for treating AF. This review aimed to illustrate the characteristics and function of SK channels. Moreover, it discussed the regulation of SK channels and their potential as a therapeutic target of AF.
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Affiliation(s)
- Miao-Miao Qi
- Department of Cardiology, Wuxi People's Hospital Affiliated to Nanjing Medical University, Wuxi, Jiangsu, China
| | - Ling-Ling Qian
- Department of Cardiology, Wuxi People's Hospital Affiliated to Nanjing Medical University, Wuxi, Jiangsu, China
| | - Ru-Xing Wang
- Department of Cardiology, Wuxi People's Hospital Affiliated to Nanjing Medical University, Wuxi, Jiangsu, China.
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12
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Fenner MF, Gatta G, Sattler S, Kuiper M, Hesselkilde EM, Adler DMT, Smerup M, Schotten U, Sørensen U, Diness JG, Jespersen T, Verheule S, Van Hunnik A, Buhl R. Inhibition of Small-Conductance Calcium-Activated Potassium Current ( I K,Ca) Leads to Differential Atrial Electrophysiological Effects in a Horse Model of Persistent Atrial Fibrillation. Front Physiol 2021; 12:614483. [PMID: 33633584 PMCID: PMC7900437 DOI: 10.3389/fphys.2021.614483] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Accepted: 01/08/2021] [Indexed: 12/13/2022] Open
Abstract
Background Small-conductance Ca2+-activated K+ (KCa2) channels have been proposed as a possible atrial-selective target to pharmacologically terminate atrial fibrillation (AF) and to maintain sinus rhythm. However, it has been hypothesized that the importance of the KCa2 current—and thereby the efficacy of small-conductance Ca2+-activated K+ current (IK,Ca) inhibition—might be negatively related to AF duration and the extent of AF-induced remodeling. Experimental Approach and Methods To address the hypothesis of the efficacy of IK,Ca inhibition being dependent on AF duration, the anti-arrhythmic properties of the IK,Ca inhibitor NS8593 (5 mg/kg) and its influence on atrial conduction were studied using epicardial high-density contact mapping in horses with persistent AF. Eleven Standardbred mares with tachypacing-induced persistent AF (42 ± 5 days of AF) were studied in an open-chest experiment. Unipolar AF electrograms were recorded and isochronal high-density maps analyzed to allow for the reconstruction of wave patterns and changes in electrophysiological parameters, such as atrial conduction velocity and AF cycle length. Atrial anti-arrhythmic properties and adverse effects of NS8593 on ventricular electrophysiology were evaluated by continuous surface ECG monitoring. Results IK,Ca inhibition by NS8593 administered intravenously had divergent effects on right and left AF complexity and propagation properties in this equine model of persistent AF. Despite global prolongation of AF cycle length, a slowing of conduction in the right atrium led to increased anisotropy and electrical dissociation, thus increasing AF complexity. In contrast, there was no significant change in AF complexity in the LA, and cardioversion of AF was not achieved. Conclusions Intra-atrial heterogeneity in response to IK,Ca inhibition by NS8593 was observed. The investigated dose of NS8593 increased the AF cycle length but was not sufficient to induce cardioversion. In terms of propagation properties during AF, IK,Ca inhibition by NS8593 led to divergent effects in the right and left atrium. This divergent behavior may have impeded the cardioversion success.
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Affiliation(s)
- Merle Friederike Fenner
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Taastrup, Denmark
| | - Giulia Gatta
- Department of Physiology, Cardiovascular Research Institute Maastricht, Maastricht, Netherlands
| | - Stefan Sattler
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Marion Kuiper
- Department of Physiology, Cardiovascular Research Institute Maastricht, Maastricht, Netherlands
| | - Eva Melis Hesselkilde
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Taastrup, Denmark.,Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Ditte M T Adler
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Taastrup, Denmark
| | - Morten Smerup
- Department of Cardiothoracic Surgery, The Heart Centre, Copenhagen University Hospital, Copenhagen, Denmark
| | - Ulrich Schotten
- Department of Physiology, Cardiovascular Research Institute Maastricht, Maastricht, Netherlands
| | | | | | - Thomas Jespersen
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Sander Verheule
- Department of Physiology, Cardiovascular Research Institute Maastricht, Maastricht, Netherlands
| | - Arne Van Hunnik
- Department of Physiology, Cardiovascular Research Institute Maastricht, Maastricht, Netherlands
| | - Rikke Buhl
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Taastrup, Denmark
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13
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Nam YW, Cui M, Orfali R, Viegas A, Nguyen M, Mohammed EHM, Zoghebi KA, Rahighi S, Parang K, Zhang M. Hydrophobic interactions between the HA helix and S4-S5 linker modulate apparent Ca 2+ sensitivity of SK2 channels. Acta Physiol (Oxf) 2021; 231:e13552. [PMID: 32865319 PMCID: PMC7736289 DOI: 10.1111/apha.13552] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Revised: 08/09/2020] [Accepted: 08/20/2020] [Indexed: 12/11/2022]
Abstract
AIM Small-conductance Ca2+ -activated potassium (SK) channels are activated exclusively by increases in intracellular Ca2+ that binds to calmodulin constitutively associated with the channel. Wild-type SK2 channels are activated by Ca2+ with an EC50 value of ~0.3 μmol/L. Here, we investigate hydrophobic interactions between the HA helix and the S4-S5 linker as a major determinant of channel apparent Ca2+ sensitivity. METHODS Site-directed mutagenesis, electrophysiological recordings and molecular dynamic (MD) simulations were utilized. RESULTS Mutations that decrease hydrophobicity at the HA-S4-S5 interface lead to Ca2+ hyposensitivity of SK2 channels. Mutations that increase hydrophobicity result in hypersensitivity to Ca2+ . The Ca2+ hypersensitivity of the V407F mutant relies on the interaction of the cognate phenylalanine with the S4-S5 linker in the SK2 channel. Replacing the S4-S5 linker of the SK2 channel with the S4-S5 linker of the SK4 channel results in loss of the hypersensitivity caused by V407F. This difference between the S4-S5 linkers of SK2 and SK4 channels can be partially attributed to I295 equivalent to a valine in the SK4 channel. A N293A mutation in the S4-S5 linker also increases hydrophobicity at the HA-S4-S5 interface and elevates the channel apparent Ca2+ sensitivity. The double N293A/V407F mutations generate a highly Ca2+ sensitive channel, with an EC50 of 0.02 μmol/L. The MD simulations of this double-mutant channel revealed a larger channel cytoplasmic gate. CONCLUSION The electrophysiological data and MD simulations collectively suggest a crucial role of the interactions between the HA helix and S4-S5 linker in the apparent Ca2+ sensitivity of SK2 channels.
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Affiliation(s)
- Young-Woo Nam
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA, USA
| | - Meng Cui
- Department of Pharmaceutical Sciences, Northeastern University School of Pharmacy, Boston, MA, USA
| | - Razan Orfali
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA, USA
| | - Adam Viegas
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA, USA
| | - Misa Nguyen
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA, USA
| | - Eman H M Mohammed
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA, USA
| | - Khalid A Zoghebi
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA, USA
| | - Simin Rahighi
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA, USA
| | - Keykavous Parang
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA, USA
| | - Miao Zhang
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA, USA
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14
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Bentzen BH, Bomholtz SH, Simó-Vicens R, Folkersen L, Abildgaard L, Speerschneider T, Muthukumarasamy KM, Edvardsson N, Sørensen US, Grunnet M, Diness JG. Mechanisms of Action of the KCa2-Negative Modulator AP30663, a Novel Compound in Development for Treatment of Atrial Fibrillation in Man. Front Pharmacol 2020; 11:610. [PMID: 32477117 PMCID: PMC7232560 DOI: 10.3389/fphar.2020.00610] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Accepted: 04/20/2020] [Indexed: 12/17/2022] Open
Abstract
Aims Small conductance Ca2+-activated K+ channels (SK channels, KCa2) are a new target for treatment of atrial fibrillation (AF). AP30663 is a small molecule inhibitor of KCa2 channels that is currently in clinical development for treatment of AF. The aim of this study is to present the electrophysiological profile and mechanism of action of AP30663 and its efficacy in prolonging atrial refractoriness in rodents, and by bioinformatic analysis investigate if genetic variants in KCNN2 or KCNN3 influence the expression level of these in human heart tissue. Methods and Results Whole-cell and inside-out patch-clamp recordings of heterologously expressed KCa2 channels revealed that AP30663 inhibits KCa2 channels with minor effects on other relevant cardiac ion channels. AP30663 modulates the KCa2.3 channel by right-shifting the Ca2+-activation curve. In isolated guinea pig hearts AP30663 significantly prolonged the atrial effective refractory period (AERP) with minor effects on the QT-interval corrected for heart rate. Similarly, in anaesthetized rats 5 and 10 mg/kg of AP30663 changed the AERP to 130.7±5.4% and 189.9±18.6 of baseline values. The expression quantitative trait loci analyses revealed that the genome wide association studies for AF SNP rs13376333 in KCNN3 is associated with increased mRNA expression of KCNN3 in human atrial appendage tissue. Conclusions AP30663 is a novel negative allosteric modulator of KCa2 channels that concentration-dependently prolonged rodent atrial refractoriness with minor effects on the QT-interval. Moreover, AF associated SNPs in KCNN3 influence KCNN3 mRNA expression in human atrial tissue. These properties support continued development of AP30663 for treatment of AF in man.
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Affiliation(s)
- Bo Hjorth Bentzen
- Acesion Pharma, Copenhagen, Denmark.,Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Sofia Hammami Bomholtz
- Acesion Pharma, Copenhagen, Denmark.,Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Rafel Simó-Vicens
- Acesion Pharma, Copenhagen, Denmark.,Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Lasse Folkersen
- Institute of Biological Psychiatry, Sankt Hans Hospital, Roskilde, Denmark
| | | | - Tobias Speerschneider
- Acesion Pharma, Copenhagen, Denmark.,Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Kalai Mangai Muthukumarasamy
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Nils Edvardsson
- Acesion Pharma, Copenhagen, Denmark.,Department of Molecular and Clinical Medicine/Cardiology, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
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15
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Citerni C, Kirchhoff J, Olsen LH, Sattler SM, Grunnet M, Edvardsson N, Bentzen BH, Diness JG. Inhibition of K Ca2 and K v11.1 Channels in Pigs With Left Ventricular Dysfunction. Front Pharmacol 2020; 11:556. [PMID: 32435191 PMCID: PMC7219273 DOI: 10.3389/fphar.2020.00556] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Accepted: 04/14/2020] [Indexed: 12/17/2022] Open
Abstract
Background Inhibition of KCa2 channels, conducting IKCa, can convert atrial fibrillation (AF) to sinus rhythm and protect against its induction. IKCa inhibition has been shown to possess functional atrial selectivity with minor effects on ventricles. Under pathophysiological conditions with ventricular remodeling, however, inhibiting IKCa can exhibit both proarrhythmic and antiarrhythmic ventricular effects. The aim of this study was to evaluate the effects of the IKCa inhibitor AP14145, when given before or after the IKr blocker dofetilide, on cardiac function and ventricular proarrhythmia markers in pigs with or without left ventricular dysfunction (LVD). Methods Landrace pigs were randomized into an AF group (n = 6) and two control groups: SHAM1 (n = 8) and SHAM2 (n = 4). AF pigs were atrially tachypaced (A-TP) for 43 ± 4 days until sustained AF and LVD developed. A-TP and SHAM1 pigs received 20 mg/kg AP14145 followed by 100 µg/kg dofetilide whereas SHAM2 pigs received the same drugs in the opposite order. Proarrhythmic markers such as short-term variability of QT (STVQT) and RR (STVRR) intervals, and the number of premature ventricular complexes (PVCs) were measured at baseline and after administration of drugs. The influence on cardiac function was assessed by measuring cardiac output, stroke volume, and relevant echocardiographic parameters. Results IKCa inhibition by AP14145 did not increase STVQT or STVRR in any of the pigs. IKr inhibition by dofetilide markedly increased STVQT in the A-TP pigs, but not in SHAM operated pigs. Upon infusion of AP14145 the number of PVCs decreased or remained unchanged both when AP14145 was infused after baseline and after dofetilide. Conversely, the number of PVCs increased or remained unchanged upon dofetilide infusion. Neither AP14145 nor dofetilide affected relevant echocardiographic parameters, cardiac output, or stroke volume in any of the groups. Conclusion IKCa inhibition with AP14145 was not proarrhythmic in healthy pigs, or in the presence of LVD resulting from A-TP. In pigs already challenged with 100 µg/kg dofetilide there were no signs of proarrhythmia when 20 mg/kg AP14145 were infused. KCa2 channel inhibition did not affect cardiac function, implying that KCa2 inhibitors can be administered safely also in the presence of LV dysfunction.
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Affiliation(s)
- Carlotta Citerni
- Biomedical Institute, University of Copenhagen, Copenhagen, Denmark.,Acesion Pharma, Copenhagen, Denmark
| | | | - Lisbeth Høier Olsen
- Department of Veterinary Disease Biology, University of Copenhagen, Frederiksberg, Denmark
| | - Stefan Michael Sattler
- Biomedical Institute, University of Copenhagen, Copenhagen, Denmark.,Department of Cardiology, Heart Center, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark
| | | | - Nils Edvardsson
- Acesion Pharma, Copenhagen, Denmark.,Department of Molecular and Clinical Medicine, Sahlgrenska Academy at Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Bo Hjorth Bentzen
- Biomedical Institute, University of Copenhagen, Copenhagen, Denmark.,Acesion Pharma, Copenhagen, Denmark
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16
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Yao L, Zhou B, You L, Hu H, Xie R. LncRNA MIAT/miR-133a-3p axis regulates atrial fibrillation and atrial fibrillation-induced myocardial fibrosis. Mol Biol Rep 2020; 47:2605-2617. [DOI: 10.1007/s11033-020-05347-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2019] [Accepted: 02/25/2020] [Indexed: 02/07/2023]
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17
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Diness JG, Kirchhoff JE, Speerschneider T, Abildgaard L, Edvardsson N, Sørensen US, Grunnet M, Bentzen BH. The K Ca2 Channel Inhibitor AP30663 Selectively Increases Atrial Refractoriness, Converts Vernakalant-Resistant Atrial Fibrillation and Prevents Its Reinduction in Conscious Pigs. Front Pharmacol 2020; 11:159. [PMID: 32180722 PMCID: PMC7059611 DOI: 10.3389/fphar.2020.00159] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Accepted: 02/07/2020] [Indexed: 12/20/2022] Open
Abstract
AIMS To describe the effects of the KCa2 channel inhibitor AP30663 in pigs regarding tolerability, cardiac electrophysiology, pharmacokinetics, atrial functional selectivity, effectiveness in cardioversion of tachy-pacing induced vernakalant-resistant atrial fibrillation (AF), and prevention of reinduction of AF. METHODS AND RESULTS Six healthy pigs with implanted pacemakers and equipped with a Holter monitor were used to compare the effects of increasing doses (0, 5, 10, 15, 20, and 25 mg/kg) of AP30663 on the right atrial effective refractory period (AERP) and on various ECG parameters, including the QT interval. Ten pigs with implanted neurostimulators were long-term atrially tachypaced (A-TP) until sustained vernakalant-resistant AF was present. 20 mg/kg AP30663 was tested to discover if it could successfully convert vernakalant-resistant AF to sinus rhythm (SR) and protect against reinduction of AF. Seven anesthetized pigs were used for pharmacokinetic experiments. Two pigs received an infusion of 20 mg/kg AP30663 over 60 min while five pigs received 5 mg/kg AP30663 over 30 min. Blood samples were collected before, during, and after infusion on AP30663. AP30663 was well-tolerated and prominently increased the AERP in pigs with little effect on ventricular repolarization. Furthermore, it converted A-TP induced AF that had become unresponsive to vernakalant, and it prevented reinduction of AF in pigs. Both a >30 ms increase of the AERP and conversion of AF occurred in different pigs at a free plasma concentration level of around 1.0-1.4 µM of AP30663, which was achieved at a dose level of 5 mg/kg. CONCLUSION AP30663 has shown properties in animals that would be of clinical interest in man.
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Affiliation(s)
| | | | - Tobias Speerschneider
- Department of In Vivo Pharmacology, Acesion Pharma, Copenhagen, Denmark
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Lea Abildgaard
- Department of In Vivo Pharmacology, Acesion Pharma, Copenhagen, Denmark
| | - Nils Edvardsson
- Department of In Vivo Pharmacology, Acesion Pharma, Copenhagen, Denmark
- Department of Molecular and Clinical Medicine/Cardiology, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Ulrik S. Sørensen
- Department of In Vivo Pharmacology, Acesion Pharma, Copenhagen, Denmark
| | - Morten Grunnet
- Department of In Vivo Pharmacology, Acesion Pharma, Copenhagen, Denmark
| | - Bo Hjorth Bentzen
- Department of In Vivo Pharmacology, Acesion Pharma, Copenhagen, Denmark
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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18
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Kalstø SM, Siland JE, Rienstra M, Christophersen IE. Atrial Fibrillation Genetics Update: Toward Clinical Implementation. Front Cardiovasc Med 2019; 6:127. [PMID: 31552271 PMCID: PMC6743416 DOI: 10.3389/fcvm.2019.00127] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Accepted: 08/12/2019] [Indexed: 12/16/2022] Open
Abstract
Atrial fibrillation (AF) is the most common heart rhythm disorder worldwide and may have serious cardiovascular health consequences. AF is associated with increased risk of stroke, dementia, heart failure, and death. There are several known robust, clinical risk predictors for AF, such as male sex, increasing age, and hypertension; however, during the last couple of decades, a substantive genetic component has also been established. Over the last 10 years, the discovery of novel AF-related genetic variants has accelerated, increasing our understanding of mechanisms behind AF. Current studies are focusing on mapping the polygenic structure of AF, improving risk prediction, therapeutic development, and patient-specific management. Nevertheless, it is still difficult for clinicians to interpret the role of genetics in AF prediction and management. Here, we provide an overview of relevant topics within the genetics of AF and attempt to provide some guidance on how to interpret genetic advances and their implementation into clinical decision-making.
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Affiliation(s)
- Silje Madeleine Kalstø
- Department of Medical Research, Bærum Hospital, Vestre Viken Hospital Trust, Rud, Norway
| | - Joylene Elisabeth Siland
- Department of Cardiology, University of Groningen, University Medical Center Groningen, Groningen, Netherlands
| | - Michiel Rienstra
- Department of Cardiology, University of Groningen, University Medical Center Groningen, Groningen, Netherlands
| | - Ingrid E Christophersen
- Department of Medical Research, Bærum Hospital, Vestre Viken Hospital Trust, Rud, Norway.,The Department of Medical Genetics, Oslo University Hospital, Oslo, Norway
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19
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Lubberding AF, Sattler SM, Grunnet M, Sørensen US, Tfelt-Hansen J, Jespersen T. Arrhythmia development during inhibition of small-conductance calcium-activated potassium channels in acute myocardial infarction in a porcine model. Europace 2019; 21:1584-1593. [DOI: 10.1093/europace/euz223] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2019] [Accepted: 07/22/2019] [Indexed: 12/19/2022] Open
Abstract
AbstractAims Acute myocardial infarction (AMI) is associated with intracellular Ca2+ build-up. In healthy ventricles, small conductance Ca2+-activated K+ (SK) channels are present but do not participate in repolarization. However, SK current is increased in chronic myocardial infarction and heart failure, and recently, SK channel inhibition was demonstrated to reduce arrhythmias in AMI rats. Hence, we hypothesized that SK channel inhibitors (NS8593 and AP14145) could reduce arrhythmia development during AMI in a porcine model.Methods and results Twenty-seven pigs were randomized 1:1:1 to control, NS8593, or AP14145. Haemodynamic and electrophysiological parameters [electrocardiogram (ECG) and monophasic action potentials (MAP)] were continuously recorded. A balloon was placed in the mid-left anterior descending artery, blinded to treatment. Infusion lasted from 10 min before occlusion until 30 min after. Occlusion was maintained for 1 h, followed by 2 h of reperfusion. Upon occlusion, cardiac output dropped similarly in all groups, while blood pressure remained stable. Heart rate decreased in the NS8593 and AP14145 groups. QRS duration increased upon occlusion in all groups but more prominently in AP14145-treated pigs. Inhibition of SK channels did not affect QT interval. Infarct MAP duration shortened comparably in all groups. Ventricular fibrillation developed in 4/9 control-, 4/9 AP14145-, and 2/9 NS8593-treated pigs. Ventricular tachycardia was rarely observed in either group, whereas ventricular extrasystoles occurred comparably in all groups.Conclusion Inhibition of SK channels was neither beneficial nor detrimental to ventricular arrhythmia development in the setting of AMI in this porcine model.
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Affiliation(s)
- Anniek F Lubberding
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Norre Alle 14, Copenhagen, Denmark
| | - Stefan M Sattler
- Department of Cardiology, Heart Centre, Copenhagen University Hospital, Rigshospitalet, Blegdamsvej 9, Copenhagen, Denmark
- Medical Department I, University Hospital Grosshadern, LMU, Marchioninistraße 15, Munich, Germany
| | | | | | - Jacob Tfelt-Hansen
- Department of Cardiology, Heart Centre, Copenhagen University Hospital, Rigshospitalet, Blegdamsvej 9, Copenhagen, Denmark
- Department of Forensic Medicine, Faculty of Medical Sciences, University of Copenhagen, Frederik V's Vej, Copenhagen, Denmark
| | - Thomas Jespersen
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Norre Alle 14, Copenhagen, Denmark
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20
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Brown BM, Shim H, Christophersen P, Wulff H. Pharmacology of Small- and Intermediate-Conductance Calcium-Activated Potassium Channels. Annu Rev Pharmacol Toxicol 2019; 60:219-240. [PMID: 31337271 DOI: 10.1146/annurev-pharmtox-010919-023420] [Citation(s) in RCA: 65] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The three small-conductance calcium-activated potassium (KCa2) channels and the related intermediate-conductance KCa3.1 channel are voltage-independent K+ channels that mediate calcium-induced membrane hyperpolarization. When intracellular calcium increases in the channel vicinity, it calcifies the flexible N lobe of the channel-bound calmodulin, which then swings over to the S4-S5 linker and opens the channel. KCa2 and KCa3.1 channels are highly druggable and offer multiple binding sites for venom peptides and small-molecule blockers as well as for positive- and negative-gating modulators. In this review, we briefly summarize the physiological role of KCa channels and then discuss the pharmacophores and the mechanism of action of the most commonly used peptidic and small-molecule KCa2 and KCa3.1 modulators. Finally, we describe the progress that has been made in advancing KCa3.1 blockers and KCa2.2 negative- and positive-gating modulators toward the clinic for neurological and cardiovascular diseases and discuss the remaining challenges.
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Affiliation(s)
- Brandon M Brown
- Department of Pharmacology, University of California, Davis, California 95616, USA;
| | - Heesung Shim
- Department of Pharmacology, University of California, Davis, California 95616, USA;
| | | | - Heike Wulff
- Department of Pharmacology, University of California, Davis, California 95616, USA;
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21
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Kirchhoff JE, Skarsfeldt MA, Muthukumarasamy KM, Simó-Vicens R, Bomholtz SH, Abildgaard L, Jespersen T, Sørensen US, Grunnet M, Bentzen BH, Diness JG. The K Ca2 Channel Inhibitor AP14145, But Not Dofetilide or Ondansetron, Provides Functional Atrial Selectivity in Guinea Pig Hearts. Front Pharmacol 2019; 10:668. [PMID: 31275147 PMCID: PMC6593233 DOI: 10.3389/fphar.2019.00668] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Accepted: 05/23/2019] [Indexed: 11/13/2022] Open
Abstract
Background and Purpose: Prolongation of cardiac action potentials is considered antiarrhythmic in the atria but can be proarrhythmic in ventricles if the current carried by Kv11.1-channels (IKr) is inhibited. The current mediated by KCa2-channels, IKCa, is considered a promising new target for treatment of atrial fibrillation (AF). Selective inhibitors of IKr (dofetilide) and IKCa (AP14145) were used to compare the effects on ventricular and atrial repolarization. Ondansetron, which has been reported to be a potent blocker of both IKr and IKCa, was included to examine its potential atrial antiarrhythmic properties. Experimental Approach: The expression of KCa2- and Kv11.1-channels in the guinea pig heart was investigated using quantitative polymerase chain reaction (qPCR). Whole-cell patch clamp technique was used to investigate the effects of dofetilide, AP14145, and ondansetron on IKCa and/or IKr. The effect of dofetilide, AP14145, and ondansetron on atrial and ventricular repolarization was investigated in isolated hearts. A novel atrial paced in vivo guinea pig model was further validated using AP14145 and dofetilide. Key Results: AP14145 increased the atrial effective refractory period (AERP) without prolonging the QT interval with Bazett's correction for heart rate (QTcB) both ex vivo and in vivo. In contrast, dofetilide increased QTcB and, to a lesser extent, AERP in isolated hearts and prolonged QTcB with no effects on AERP in the in vivo guinea pig model. Ondansetron did not inhibit IKCa, but did inhibit IKr in vitro. Ondansetron prolonged ventricular, but not atrial repolarization ex vivo. Conclusion and Implications: IKCa inhibition by AP14145 selectively increases atrial repolarization, whereas IKr inhibition by dofetilide and ondansetron increases ventricular repolarization to a larger extent than atrial repolarization.
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Affiliation(s)
| | - Mark Alexander Skarsfeldt
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Kalai Mangai Muthukumarasamy
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Rafel Simó-Vicens
- Acesion Pharma, Copenhagen, Denmark.,Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Sofia Hammami Bomholtz
- Acesion Pharma, Copenhagen, Denmark.,Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | | | - Thomas Jespersen
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | | | | | - Bo Hjorth Bentzen
- Acesion Pharma, Copenhagen, Denmark.,Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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22
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Simó-Vicens R, Bomholtz SH, Sørensen US, Bentzen BH. 2,6-Bis(2-Benzimidazolyl)Pyridine (BBP) Is a Potent and Selective Inhibitor of Small Conductance Calcium-Activated Potassium (SK) Channels. Front Pharmacol 2018; 9:1409. [PMID: 30559671 PMCID: PMC6287599 DOI: 10.3389/fphar.2018.01409] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2018] [Accepted: 11/16/2018] [Indexed: 11/13/2022] Open
Abstract
A variety of polycyclic pyridines have been proposed as inhibitors of the small conductance calcium-activated potassium (SK) channel. To this group belongs 2,6-bis(2-benzimidazolyl)pyridine (BBP), a commercially and readily available small organic compound which has earlier been described in a broad range of chemical and biological uses. Here, we show how BBP can also be used as a potent and specific SK channel blocker in vitro. The potency of BBP was measured using automatic patch clamp on all three SK channel subtypes, resulting in similar IC50 of 0.4 μM. We also assessed the selectivity of BBP on a panel of calcium-activated and voltage-activated potassium channels using two-electrode voltage clamp, automatic and manual patch clamp. BBP did not have any effect on IK, Kir2.1, Kir3.1+Kir3.4, Kv1.5, Kv4.3/KCHIP2 and Kv7.1/KCNE1 currents and was 4.8-fold and 46-fold more potent on all SK channel subtypes vs. BK and hERG channels, respectively. Moreover, we were able to identify H491 as a critical amino acid for the pharmacological effect of BBP on the SK channel. From a medicinal chemistry perspective, BBP could be used as a starting point for the design of new and improved SK inhibitors.
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Affiliation(s)
- Rafel Simó-Vicens
- Cardiovascular Pharmacology, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,Acesion Pharma, Copenhagen, Denmark
| | - Sofia H Bomholtz
- Cardiovascular Pharmacology, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,Acesion Pharma, Copenhagen, Denmark
| | | | - Bo H Bentzen
- Cardiovascular Pharmacology, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,Acesion Pharma, Copenhagen, Denmark
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23
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Chen M, Xu DZ, Wu AZ, Guo S, Wan J, Yin D, Lin SF, Chen Z, Rubart-von der Lohe M, Everett TH, Qu Z, Weiss JN, Chen PS. Concomitant SK current activation and sodium current inhibition cause J wave syndrome. JCI Insight 2018; 3:122329. [PMID: 30429367 PMCID: PMC6302939 DOI: 10.1172/jci.insight.122329] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Accepted: 07/17/2018] [Indexed: 12/18/2022] Open
Abstract
The mechanisms of J wave syndrome (JWS) are incompletely understood. Here, we showed that the concomitant activation of small-conductance calcium-activated potassium (SK) current (IKAS) and inhibition of sodium current by cyclohexyl-[2-(3,5-dimethyl-pyrazol-1-yl)-6-methyl-pyrimidin-4-yl]-amine (CyPPA) recapitulate the phenotypes of JWS in Langendorff-perfused rabbit hearts. CyPPA induced significant J wave elevation and frequent spontaneous ventricular fibrillation (SVF), as well as sinus bradycardia, atrioventricular block, and intraventricular conduction delay. IKAS activation by CyPPA resulted in heterogeneous shortening of action potential (AP) duration (APD) and repolarization alternans. CyPPA inhibited cardiac sodium current (INa) and decelerated AP upstroke and intracellular calcium transient. SVFs were typically triggered by short-coupled premature ventricular contractions, initiated with phase 2 reentry and originated more frequently from the right than the left ventricles. Subsequent IKAS blockade by apamin reduced J wave elevation and eliminated SVF. β-Adrenergic stimulation was antiarrhythmic in CyPPA-induced electrical storm. Like CyPPA, hypothermia (32.0°C) also induced J wave elevation and SVF. It facilitated negative calcium-voltage coupling and phase 2 repolarization alternans with spatial and electromechanical discordance, which were ameliorated by apamin. These findings suggest that IKAS activation contributes to the development of JWS in rabbit ventricles.
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Affiliation(s)
- Mu Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
- Department of Cardiology, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Dong-Zhu Xu
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
- Cardiovascular Division, Institute of Clinical Medicine, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
| | - Adonis Z. Wu
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Shuai Guo
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
- Department of Cardiology, First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Juyi Wan
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
- Department of Cardiothoracic Surgery, Affiliated Hospital of Southwest Medical University, Luzhou, China
| | - Dechun Yin
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
- Department of Cardiology, First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Shien-Fong Lin
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
- Institute of Biomedical Engineering, College of Electrical and Computer Engineering, National Chiao Tung University, Hsin-Chu, Taiwan
| | - Zhenhui Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Michael Rubart-von der Lohe
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Thomas H. Everett
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Zhilin Qu
- Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles, California, USA
| | - James N. Weiss
- Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles, California, USA
| | - Peng-Sheng Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
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24
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Skarsfeldt MA, Bomholtz SH, Lundegaard PR, Lopez-Izquierdo A, Tristani-Firouzi M, Bentzen BH. Atrium-specific ion channels in the zebrafish-A role of I KACh in atrial repolarization. Acta Physiol (Oxf) 2018; 223:e13049. [PMID: 29412518 DOI: 10.1111/apha.13049] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2017] [Revised: 01/26/2018] [Accepted: 01/29/2018] [Indexed: 12/16/2022]
Abstract
AIM The zebrafish has emerged as a novel model for investigating cardiac physiology and pathology. The aim of this study was to investigate the atrium-specific ion channels responsible for shaping the atrial cardiac action potential in zebrafish. METHODS Using quantitative polymerase chain reaction, we assessed the expression level of atrium-specific potassium channels. The functional role of these channels was studied by patch clamp experiments on isolated atrial and ventricular cardiomyocytes and by optical mapping of explanted adult zebrafish hearts. Finally, surface ECGs were recorded to establish possible in vivo roles of atrial ion channels. RESULTS In isolated adult zebrafish hearts, we identified the expression of kcnk3, kcnk9, kcnn1, kcnn2, kcnn3, kcnj3 and kcnj5, the genes that encode the atrium-specific K2P , KCa 2.x and Kir 3.1/4 (KACh ) ion channels. The electrophysiological data indicate that the acetylcholine-activated inward-rectifying current, IKACh, plays a major role in the zebrafish atrium, whereas K2P 3.1/9.1 and KCa 2.x channels do not appear to be involved in regulating the action potential in the zebrafish heart. CONCLUSION We demonstrate that the acetylcholine-activated inward-rectifying current (IKACh ) current plays a major role in the zebrafish atrium and that the zebrafish could potentially be a cost-effective and reliable model for pharmacological testing of atrium-specific IKACh modulating compounds.
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Affiliation(s)
- M. A. Skarsfeldt
- Department of Biomedical Sciences; Faculty of Health and Medical Sciences; University of Copenhagen; Copenhagen N Denmark
- Nora Eccles Harrison Cardiovascular Research and Training Institute; University of Utah; Salt Lake City UT USA
| | - S. H. Bomholtz
- Department of Biomedical Sciences; Faculty of Health and Medical Sciences; University of Copenhagen; Copenhagen N Denmark
| | - P. R. Lundegaard
- Department of Biomedical Sciences; Faculty of Health and Medical Sciences; University of Copenhagen; Copenhagen N Denmark
| | - A. Lopez-Izquierdo
- Nora Eccles Harrison Cardiovascular Research and Training Institute; University of Utah; Salt Lake City UT USA
| | - M. Tristani-Firouzi
- Nora Eccles Harrison Cardiovascular Research and Training Institute; University of Utah; Salt Lake City UT USA
| | - B. H. Bentzen
- Department of Biomedical Sciences; Faculty of Health and Medical Sciences; University of Copenhagen; Copenhagen N Denmark
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25
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Simó-Vicens R, Kirchhoff JE, Dolce B, Abildgaard L, Speerschneider T, Sørensen US, Grunnet M, Diness JG, Bentzen BH. A new negative allosteric modulator, AP14145, for the study of small conductance calcium-activated potassium (K Ca 2) channels. Br J Pharmacol 2017; 174:4396-4408. [PMID: 28925012 DOI: 10.1111/bph.14043] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Revised: 09/08/2017] [Accepted: 09/13/2017] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND AND PURPOSE Small conductance calcium-activated potassium (KCa 2) channels represent a promising atrial-selective target for treatment of atrial fibrillation. Here, we establish the mechanism of KCa 2 channel inhibition by the new compound AP14145. EXPERIMENTAL APPROACH Using site-directed mutagenesis, binding determinants for AP14145 inhibition were explored. AP14145 selectivity and mechanism of action were investigated by patch-clamp recordings of heterologously expressed KCa 2 channels. The biological efficacy of AP14145 was assessed by measuring atrial effective refractory period (AERP) prolongation in anaesthetized rats, and a beam walk test was performed in mice to determine acute CNS-related effects of the drug. KEY RESULTS AP14145 was found to be an equipotent negative allosteric modulator of KCa 2.2 and KCa 2.3 channels (IC50 = 1.1 ± 0.3 μM). The presence of AP14145 (10 μM) increased the EC50 of Ca2+ on KCa 2.3 channels from 0.36 ± 0.02 to 1.2 ± 0.1 μM. The inhibitory effect strongly depended on two amino acids, S508 and A533 in the channel. AP14145 concentration-dependently prolonged AERP in rats. Moreover, AP14145 (10 mg·kg-1 ) did not trigger any apparent CNS effects in mice. CONCLUSIONS AND IMPLICATIONS AP14145 is a negative allosteric modulator of KCa 2.2 and KCa 2.3 channels that shifted the calcium dependence of channel activation, an effect strongly dependent on two identified amino acids. AP14145 prolonged AERP in rats and did not trigger any acute CNS effects in mice. The understanding of how KCa 2 channels are inhibited, at the molecular level, will help further development of drugs targeting KCa 2 channels.
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Affiliation(s)
- Rafel Simó-Vicens
- Biomedical Institute, University of Copenhagen, Copenhagen, Denmark.,Acesion Pharma, Copenhagen, Denmark
| | | | - Bernardo Dolce
- Department of Experimental Pharmacology and Toxicology, University Medical Center Hamburg-Eppendorf, DZHK (German Center for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, Hamburg, Germany
| | | | | | | | | | | | - Bo H Bentzen
- Biomedical Institute, University of Copenhagen, Copenhagen, Denmark.,Acesion Pharma, Copenhagen, Denmark
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