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Vera OD, Wulff H, Braun AP. Endothelial KCa channels: Novel targets to reduce atherosclerosis-driven vascular dysfunction. Front Pharmacol 2023; 14:1151244. [PMID: 37063294 PMCID: PMC10102451 DOI: 10.3389/fphar.2023.1151244] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Accepted: 03/24/2023] [Indexed: 04/03/2023] Open
Abstract
Elevated levels of cholesterol in the blood can induce endothelial dysfunction, a condition characterized by impaired nitric oxide production and decreased vasodilatory capacity. Endothelial dysfunction can promote vascular disease, such as atherosclerosis, where macrophages accumulate in the vascular intima and fatty plaques form that impair normal blood flow in conduit arteries. Current pharmacological strategies to treat atherosclerosis mostly focus on lipid lowering to prevent high levels of plasma cholesterol that induce endothelial dysfunction and atherosclerosis. While this approach is effective for most patients with atherosclerosis, for some, lipid lowering is not enough to reduce their cardiovascular risk factors associated with atherosclerosis (e.g., hypertension, cardiac dysfunction, stroke, etc.). For such patients, additional strategies targeted at reducing endothelial dysfunction may be beneficial. One novel strategy to restore endothelial function and mitigate atherosclerosis risk is to enhance the activity of Ca2+-activated K+ (KCa) channels in the endothelium with positive gating modulator drugs. Here, we review the mechanism of action of these small molecules and discuss their ability to improve endothelial function. We then explore how this strategy could mitigate endothelial dysfunction in the context of atherosclerosis by examining how KCa modulators can improve cardiovascular function in other settings, such as aging and type 2 diabetes. Finally, we consider questions that will need to be addressed to determine whether KCa channel activation could be used as a long-term add-on to lipid lowering to augment atherosclerosis treatment, particularly in patients where lipid-lowering is not adequate to improve their cardiovascular health.
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Affiliation(s)
- O. Daniel Vera
- Department of Physiology and Pharmacology, Libin Cardiovascular Institute, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
| | - Heike Wulff
- Department of Pharmacology, School of Medicine, University of California, Davis, CA, United States
| | - Andrew P. Braun
- Department of Physiology and Pharmacology, Libin Cardiovascular Institute, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
- *Correspondence: Andrew P. Braun,
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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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3
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Mishra RC, Kyle BD, Kendrick DJ, Svystonyuk D, Kieser TM, Fedak PWM, Wulff H, Braun AP. KCa channel activation normalizes endothelial function in Type 2 Diabetic resistance arteries by improving intracellular Ca 2+ mobilization. Metabolism 2021; 114:154390. [PMID: 33039407 PMCID: PMC7736096 DOI: 10.1016/j.metabol.2020.154390] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Revised: 09/28/2020] [Accepted: 09/30/2020] [Indexed: 10/23/2022]
Abstract
BACKGROUND Endothelial dysfunction is an early pathogenic event in the progression of cardiovascular disease in patients with Type 2 Diabetes (T2D). Endothelial KCa2.3 and KCa3.1 K+ channels are important regulators of arterial diameter, and we thus hypothesized that SKA-31, a small molecule activator of KCa2.3 and KCa3.1, would positively influence agonist-evoked dilation in myogenically active resistance arteries in T2D. METHODOLOGY Arterial pressure myography was utilized to investigate endothelium-dependent vasodilation in isolated cremaster skeletal muscle resistance arteries from 22 to 24 week old T2D Goto-Kakizaki rats, age-matched Wistar controls, and small human intra-thoracic resistance arteries from T2D subjects. Agonist stimulated changes in cytosolic free Ca2+ in acutely isolated, single endothelial cells from Wistar and T2D Goto-Kakizaki cremaster and cerebral arteries were examined using Fura-2 fluorescence imaging. MAIN FINDINGS Endothelium-dependent vasodilation in response to acetylcholine (ACh) or bradykinin (BK) was significantly impaired in isolated cremaster arteries from T2D Goto-Kakizaki rats compared with Wistar controls, and similar results were observed in human intra-thoracic arteries. In contrast, inhibition of myogenic tone by sodium nitroprusside, a direct smooth muscle relaxant, was unaltered in both rat and human T2D arteries. Treatment with a threshold concentration of SKA-31 (0.3 μM) significantly enhanced vasodilatory responses to ACh and BK in arteries from T2D Goto-Kakizaki rats and human subjects, whereas only modest effects were observed in non-diabetic arteries of both species. Mechanistically, SKA-31 enhancement of evoked dilation was independent of vascular NO synthase and COX activities. Remarkably, SKA-31 treatment improved agonist-stimulated Ca2+ elevation in acutely isolated endothelial cells from T2D Goto-Kakizaki cremaster and cerebral arteries, but not from Wistar control vessels. In contrast, SKA-31 treatment did not affect intracellular Ca2+ release by the sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) inhibitor cyclopiazonic acid. CONCLUSIONS Collectively, our data demonstrate that KCa channel modulation can acutely restore endothelium-dependent vasodilatory responses in T2D resistance arteries from rats and humans, which appears to involve improved endothelial Ca2+ mobilization.
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Affiliation(s)
- Ramesh C Mishra
- Dept. of Physiology and Pharmacology, Libin Cardiovascular Institute of Alberta, University of Calgary, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Canada
| | - Barry D Kyle
- Dept. of Physiology and Pharmacology, Libin Cardiovascular Institute of Alberta, University of Calgary, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Canada
| | - Dylan J Kendrick
- Dept. of Physiology and Pharmacology, Libin Cardiovascular Institute of Alberta, University of Calgary, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Canada
| | - Daniyil Svystonyuk
- Dept. of Cardiac Sciences, Libin Cardiovascular Institute of Alberta, University of Calgary, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Canada
| | - Teresa M Kieser
- Dept. of Cardiac Sciences, Libin Cardiovascular Institute of Alberta, University of Calgary, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Canada
| | - Paul W M Fedak
- Dept. of Cardiac Sciences, Libin Cardiovascular Institute of Alberta, University of Calgary, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Canada
| | - Heike Wulff
- Dept of Pharmacology, University of California Davis, 451 Health Sciences Drive, Davis, CA 95616, USA
| | - Andrew P Braun
- Dept. of Physiology and Pharmacology, Libin Cardiovascular Institute of Alberta, University of Calgary, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Canada.
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4
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John CM, Khaddaj Mallat R, Mishra RC, George G, Singh V, Turnbull JD, Umeshappa CS, Kendrick DJ, Kim T, Fauzi FM, Visser F, Fedak PWM, Wulff H, Braun AP. SKA-31, an activator of Ca 2+-activated K + channels, improves cardiovascular function in aging. Pharmacol Res 2019; 151:104539. [PMID: 31707036 DOI: 10.1016/j.phrs.2019.104539] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Revised: 10/22/2019] [Accepted: 11/06/2019] [Indexed: 12/16/2022]
Abstract
Aging represents an independent risk factor for the development of cardiovascular disease, and is associated with complex structural and functional alterations in the vasculature, such as endothelial dysfunction. Small- and intermediate-conductance, Ca2+-activated K+ channels (KCa2.3 and KCa3.1, respectively) are prominently expressed in the vascular endothelium, and pharmacological activators of these channels induce robust vasodilation upon acute exposure in isolated arteries and intact animals. However, the effects of prolonged in vivo administration of such compounds are unknown. In our study, we hypothesized that such treatment would ameliorate aging-related cardiovascular deficits. Aged (∼18 months) male Sprague Dawley rats were treated daily with either vehicle or the KCa channel activator SKA-31 (10 mg/kg, intraperitoneal injection; n = 6/group) for 8 weeks, followed by echocardiography, arterial pressure myography, immune cell and plasma cytokine characterization, and tissue histology. Our results show that SKA-31 administration improved endothelium-dependent vasodilation, reduced agonist-induced vascular contractility, and prevented the aging-associated declines in cardiac ejection fraction, stroke volume and fractional shortening, and further improved the expression of endothelial KCa channels and associated cell signalling components to levels similar to those observed in young male rats (∼5 months at end of study). SKA-31 administration did not promote pro-inflammatory changes in either T cell populations or plasma cytokines/chemokines, and we observed no overt tissue histopathology in heart, kidney, aorta, brain, liver and spleen. SKA-31 treatment in young rats had little to no effect on vascular reactivity, select protein expression, tissue histology, plasma cytokines/chemokines or immune cell properties. Collectively, these data demonstrate that administration of the KCa channel activator SKA-31 improved aging-related cardiovascular function, without adversely affecting the immune system or promoting tissue toxicity.
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Affiliation(s)
- Cini Mathew John
- Dept. of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Canada; Libin Cardiovascular Institute, Cumming School of Medicine, University of Calgary, Canada
| | - Rayan Khaddaj Mallat
- Dept. of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Canada; Libin Cardiovascular Institute, Cumming School of Medicine, University of Calgary, Canada
| | - Ramesh C Mishra
- Dept. of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Canada; Libin Cardiovascular Institute, Cumming School of Medicine, University of Calgary, Canada
| | - Grace George
- Dept. of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Canada; Libin Cardiovascular Institute, Cumming School of Medicine, University of Calgary, Canada
| | - Vikrant Singh
- Dept. of Pharmacology, University of California, Davis, USA
| | - Jeannine D Turnbull
- Dept. of Cardiac Sciences, Cumming School of Medicine, University of Calgary, Canada; Libin Cardiovascular Institute, Cumming School of Medicine, University of Calgary, Canada
| | - Channakeshava S Umeshappa
- Dept. of Microbiology, Immunology and Infectious Diseases, Cumming School of Medicine, University of Calgary, Canada
| | - Dylan J Kendrick
- Dept. of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Canada; Libin Cardiovascular Institute, Cumming School of Medicine, University of Calgary, Canada
| | - Taeyeob Kim
- Dept. of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Canada; Libin Cardiovascular Institute, Cumming School of Medicine, University of Calgary, Canada
| | - Fazlin M Fauzi
- Dept. of Pharmacology and Chemistry, Universiti Teknologi MARA, Malaysia
| | - Frank Visser
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Canada
| | - Paul W M Fedak
- Dept. of Cardiac Sciences, Cumming School of Medicine, University of Calgary, Canada; Libin Cardiovascular Institute, Cumming School of Medicine, University of Calgary, Canada
| | - Heike Wulff
- Dept. of Pharmacology, University of California, Davis, USA
| | - Andrew P Braun
- Dept. of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Canada; Libin Cardiovascular Institute, Cumming School of Medicine, University of Calgary, Canada.
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5
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Kloza M, Baranowska-Kuczko M, Toczek M, Kusaczuk M, Sadowska O, Kasacka I, Kozłowska H. Modulation of Cardiovascular Function in Primary Hypertension in Rat by SKA-31, an Activator of KCa2.x and KCa3.1 Channels. Int J Mol Sci 2019; 20:ijms20174118. [PMID: 31450834 PMCID: PMC6747311 DOI: 10.3390/ijms20174118] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Revised: 08/17/2019] [Accepted: 08/21/2019] [Indexed: 12/11/2022] Open
Abstract
The aim of this study was to investigate the hemodynamic effects of SKA-31, an activator of the small (KCa2.x) and intermediate (KCa3.1) conductance calcium-activated potassium channels, and to evaluate its influence on endothelium-derived hyperpolarization (EDH)-KCa2.3/KCa3.1 type relaxation in isolated endothelium-intact small mesenteric arteries (sMAs) from spontaneously hypertensive rats (SHRs). Functional in vivo and in vitro experiments were performed on SHRs or their normotensive controls, Wistar-Kyoto rats (WKY). SKA-31 (1, 3 and 10 mg/kg) caused a brief decrease in blood pressure and bradycardia in both SHR and WKY rats. In phenylephrine-pre-constricted sMAs of SHRs, SKA-31 (0.01–10 µM)-mediated relaxation was reduced and SKA-31 potentiated acetylcholine-evoked endothelium-dependent relaxation. Endothelium denudation and inhibition of nitric oxide synthase (eNOS) and cyclooxygenase (COX) by the respective inhibitors l-NAME or indomethacin, attenuated SKA-31-mediated vasorelaxation. The inhibition of KCa3.1, KCa2.3, KIR and Na+/K+-ATPase by TRAM-34, UCL1684, Ba2+ and ouabain, respectively, reduced the potency and efficacy of the EDH-response evoked by SKA-31. The mRNA expression of eNOS, prostacyclin synthase, KCa2.3, KCa3.1 and KIR were decreased, while Na+/K+-ATPase expression was increased. Collectively, SKA-31 promoted hypotension and vasodilatation, potentiated agonist-stimulated vasodilation, and maintained KCa2.3/KCa3.1-EDH-response in sMAs of SHR with downstream signaling that involved KIR and Na+/K+-ATPase channels. In view of the importance of the dysfunction of endothelium-mediated vasodilatation in the mechanism of hypertension, application of activators of KCa2.3/KCa3.1 channels such as SKA-31 seem to be a promising avenue in pharmacotherapy of hypertension.
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Affiliation(s)
- Monika Kloza
- Department of Experimental Physiology and Pathophysiology, Medical University of Białystok, 15-222 Białystok, Poland
| | - Marta Baranowska-Kuczko
- Department of Experimental Physiology and Pathophysiology, Medical University of Białystok, 15-222 Białystok, Poland
- Department of Clinical Pharmacy, Medical University of Białystok, 15-222 Białystok, Poland
| | - Marek Toczek
- Department of Experimental Physiology and Pathophysiology, Medical University of Białystok, 15-222 Białystok, Poland
| | - Magdalena Kusaczuk
- Department of Pharmaceutical Biochemistry, Medical University of Białystok, 15-222 Białystok, Poland
| | - Olga Sadowska
- Department of Experimental Physiology and Pathophysiology, Medical University of Białystok, 15-222 Białystok, Poland
| | - Irena Kasacka
- Department of Histology and Cytophysiology, Medical University of Białystok, 15-222 Białystok, Poland
| | - Hanna Kozłowska
- Department of Experimental Physiology and Pathophysiology, Medical University of Białystok, 15-222 Białystok, Poland.
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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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7
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Khaddaj Mallat R, Mathew John C, Mishra RC, Kendrick DJ, Braun AP. Pharmacological Targeting of KCa Channels to Improve Endothelial Function in the Spontaneously Hypertensive Rat. Int J Mol Sci 2019; 20:ijms20143481. [PMID: 31315169 PMCID: PMC6678254 DOI: 10.3390/ijms20143481] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2019] [Revised: 07/05/2019] [Accepted: 07/12/2019] [Indexed: 01/01/2023] Open
Abstract
Systemic hypertension is a major risk factor for the development of cardiovascular disease and is often associated with endothelial dysfunction. KCa2.3 and KCa3.1 channels are expressed in the vascular endothelium and contribute to stimulus-evoked vasodilation. We hypothesized that acute treatment with SKA-31, a selective activator of KCa2.x and KCa3.1 channels, would improve endothelium-dependent vasodilation and transiently lower mean arterial pressure (MAP) in male, spontaneously hypertensive rats (SHRs). Isolated vascular preparations exhibited impaired vasodilation in response to bradykinin (i.e., endothelial dysfunction) compared with Wistar controls, which was associated with decreased bradykinin receptor expression in mesenteric arteries. In contrast, similar levels of endothelial KCa channel expression were observed, and SKA-31 evoked vasodilation was comparable in vascular preparations from both strains. Addition of a low concentration of SKA-31 (i.e., 0.2–0.3 μM) failed to augment bradykinin-induced vasodilation in arteries from SHRs. However, responses to acetylcholine were enhanced. Surprisingly, acute bolus administration of SKA-31 in vivo (30 mg/kg, i.p. injection) modestly elevated MAP compared with vehicle injection. In summary, pharmacological targeting of endothelial KCa channels in SHRs did not readily reverse endothelial dysfunction in situ, or lower MAP in vivo. SHRs thus appear to be less responsive to endothelial KCa channel activators, which may be related to their vascular pathology.
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Affiliation(s)
- Rayan Khaddaj Mallat
- Department of Physiology and Pharmacology and Libin Cardiovascular Institute of Alberta, Cumming School of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Canada
| | - Cini Mathew John
- Department of Physiology and Pharmacology and Libin Cardiovascular Institute of Alberta, Cumming School of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Canada
| | - Ramesh C Mishra
- Department of Physiology and Pharmacology and Libin Cardiovascular Institute of Alberta, Cumming School of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Canada
| | - Dylan J Kendrick
- Department of Physiology and Pharmacology and Libin Cardiovascular Institute of Alberta, Cumming School of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Canada
| | - Andrew P Braun
- Department of Physiology and Pharmacology and Libin Cardiovascular Institute of Alberta, Cumming School of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Canada.
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8
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SKA-31, an activator of endothelial Ca 2+-activated K + channels evokes robust vasodilation in rat mesenteric arteries. Eur J Pharmacol 2018; 831:60-67. [PMID: 29753043 DOI: 10.1016/j.ejphar.2018.05.006] [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: 01/31/2018] [Revised: 05/04/2018] [Accepted: 05/08/2018] [Indexed: 12/17/2022]
Abstract
It is now well recognized that endothelial KCa2.3 and KCa3.1 channel activities contribute to dilation of resistance arteries via endothelium-mediated hyperpolarization and vascular smooth muscle relaxation. In this study, we have investigated the functional effect of the KCa channel activator SKA-31 in third order rat mesenteric arteries using arterial pressure myography. Isolated arteries were cannulated, pressurized intraluminally to 70 mmHg at 36 °C and then constricted with 1 μM phenylephrine. Acute bath exposure to SKA-31 evoked a robust and reversible inhibition of developed tone (IC50 = 0.22 μM). The vasodilatory effects of SKA-31 and acetylcholine were blunted in the presence of KCa2.3 and KCa3.1 channel antagonists, and were largely prevented following endothelial denudation. Western blot and q-PCR analyses of isolated mesenteric arteries revealed KCa2.3 and KCa3.1 channel expression at the protein and mRNA levels, respectively. Penitrem-A, an inhibitor of KCa1.1 channels, decreased vasodilatory responses to acetylcholine, sodium nitroprusside and NS-1619, but had little effect on SKA-31. Similarly, bath exposure to the eNOS inhibitor L-NAME did not alter SKA-31 and acetylcholine-mediated vasodilation. Collectively, these data highlight the major cellular mechanisms by which the endothelial KCa channel activator SKA-31 inhibits agonist-evoked vasoconstriction in rat small mesenteric arteries.
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9
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Mathew John C, Khaddaj Mallat R, George G, Kim T, Mishra RC, Braun AP. Pharmacologic targeting of endothelial Ca 2+-activated K + channels: A strategy to improve cardiovascular function. Channels (Austin) 2018; 12:126-136. [PMID: 29577810 PMCID: PMC5972810 DOI: 10.1080/19336950.2018.1454814] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Accepted: 03/15/2018] [Indexed: 12/17/2022] Open
Abstract
Endothelial small and intermediate-conductance, Ca2+-activated K+ channels (KCa2.3 and KCa3.1, respectively) play an important role in the regulation of vascular function and systemic blood pressure. Growing evidence indicates that they are intimately involved in agonist-evoked vasodilation of small resistance arteries throughout the circulation. Small molecule activators of KCa2.x and 3.1 channels, such as SKA-31, can acutely inhibit myogenic tone in isolated resistance arteries, induce effective vasodilation in intact vascular beds, such as the coronary circulation, and acutely decrease systemic blood pressure in vivo. The blood pressure-lowering effect of SKA-31, and early indications of improvement in endothelial dysfunction suggest that endothelial KCa channel activators could eventually be developed into a new class of endothelial targeted agents to combat hypertension or atherosclerosis. This review summarises recent insights into the activation of endothelial Ca2+ activated K+ channels in various vascular beds, and how tools, such as SKA-31, may be beneficial in disease-related conditions.
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Affiliation(s)
- Cini Mathew John
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Rayan Khaddaj Mallat
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Grace George
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Taeyeob Kim
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Ramesh C. Mishra
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Andrew P. Braun
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
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10
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Khaddaj Mallat R, Mathew John C, Kendrick DJ, Braun AP. The vascular endothelium: A regulator of arterial tone and interface for the immune system. Crit Rev Clin Lab Sci 2017; 54:458-470. [PMID: 29084470 DOI: 10.1080/10408363.2017.1394267] [Citation(s) in RCA: 83] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
As the primary interface between the blood and various tissues of the body, the vascular endothelium exhibits a diverse range of roles and activities, all of which contribute to the overall health and function of the cardiovascular system. In this focused review, we discuss several key aspects of endothelial function, how this may be compromised and subsequent consequences. Specifically, we examine the dynamic regulation of arterial contractility and distribution of blood flow through the generation of chemical and electrical signaling events that impinge upon vascular smooth muscle. The endothelium can generate a diverse range of vasoactive compounds and signals, most of which act locally to adjust blood flow in a dynamic fashion to match tissue metabolism. Disruption of these vascular signaling processes (e.g. reduced nitric oxide bioavailability) is typically referred to as endothelial dysfunction, which is a recognized risk factor for cardiovascular disease in patients and occurs early in the development and progression of hypertension, atherosclerosis and tissue ischemia. Endothelial dysfunction is also associated with type-2 Diabetes and aging and increased mechanistic knowledge of the cellular changes contributing to these effects may provide important clues for interventional strategies. The endothelium also serves as the initial site of interaction for immune cells entering tissues in response to damage and acts to facilitate the actions of both the innate and acquired immune systems to interact with the vascular wall. In addition to representing the main cell type responsible for the formation of new blood vessels (i.e. angiogenesis) within the vasculature, the endothelium is also emerging as a source of extracellular vesicle or microparticles for the transport of signaling molecules and other cellular materials to nearby, or remote, sites in the body. The characteristics of released microparticles appear to change with the functional status of the endothelium; thus, these microparticles may represent novel biomarkers of endothelial health and more serious cardiovascular disease.
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Affiliation(s)
- Rayan Khaddaj Mallat
- a Department of Physiology and Pharmacology, Cumming School of Medicine , University of Calgary, and Libin Cardiovascular Institute of Alberta , Calgary , Canada
| | - Cini Mathew John
- a Department of Physiology and Pharmacology, Cumming School of Medicine , University of Calgary, and Libin Cardiovascular Institute of Alberta , Calgary , Canada
| | - Dylan J Kendrick
- a Department of Physiology and Pharmacology, Cumming School of Medicine , University of Calgary, and Libin Cardiovascular Institute of Alberta , Calgary , Canada
| | - Andrew P Braun
- a Department of Physiology and Pharmacology, Cumming School of Medicine , University of Calgary, and Libin Cardiovascular Institute of Alberta , Calgary , Canada
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Protective role of ACE2-Ang-(1-7)-Mas in myocardial fibrosis by downregulating K Ca3.1 channel via ERK1/2 pathway. Pflugers Arch 2016; 468:2041-2051. [PMID: 27592222 DOI: 10.1007/s00424-016-1875-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2016] [Revised: 08/27/2016] [Accepted: 08/29/2016] [Indexed: 01/18/2023]
Abstract
The intermediate-conductance Ca2+-activated K+ (KCa3.1) channel plays a vital role in myocardial fibrosis induced by angiotensin (Ang) II. However, as the antagonists of Ang II, the effect of angiotensin-converting enzyme 2 (ACE2)-angiotensin-(1-7)-Mas axis on KCa3.1 channel during myocardial fibrosis remains unknown. This study was designed to explore the function of KCa3.1 channel in the cardioprotective role of ACE2-Ang-(1-7)-Mas. Wild-type (WT) mice, hACE2 transgenic mice (Tg), and ACE2 deficiency mice (ACE2-/-) were administrated with Ang II by osmotic mini-pumps. As the activator of ACE2, diminazene aceturate (DIZE) inhibited increase of blood pressure, collagen deposition, and KCa3.1 protein expression in myocardium of WT mice induced by Ang II. In Tg and ACE2-/- mice, besides the elevation of blood pressure, Ang II induced transformation of cardiac fibroblast into myofibroblast and resulted in augmentation of hydroxyproline concentration and collagen deposition, as well as KCa3.1 protein expression, but the changes in ACE2-/- mice were more obvious than those in Tg mice. Mas antagonist A779 reduced blood pressure, myocardium fibrosis, and myocardium KCa3.1 protein expression by Ang II in Tg mice, but activation of KCa3.1 with SKA-31 in Tg mice promoted the pro-fibrogenic effects of Ang II. Respectively, in ACE2-/- mice, TRAM-34, the KCa3.1 blocker, and Ang-(1-7) inhibited increase of blood pressure, collagen deposition, and KCa3.1 protein expression by Ang II. Moreover, DIZE and Ang-(1-7) depressed p-ERK1/2/t-ERK increases by Ang II in WT mice, and after blockage of ERK1/2 pathway with PD98059, the KCa3.1 protein expression was reduced in WT mice. In conclusion, the present study demonstrates that ACE2-Ang-(1-7)-Mas protects the myocardium from hypertension-induced injury, which is related to its inhibiting effect on KCa3.1 channels through ERK1/2 pathway. Our results reveal that KCa3.1 channel is likely to be a critical target on the ACE2-Ang-(1-7)-Mas axis for its protective role in myocardial fibrosis and changes of KCa3.1 induced by homeostasis of ACE-Ang II-AT1 axis and ACE2-Ang-(1-7)-Mas axis may be a new therapeutic target in myocardial fibrosis.
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Oliván-Viguera A, Valero MS, Pinilla E, Amor S, García-Villalón ÁL, Coleman N, Laría C, Calvín-Tienza V, García-Otín ÁL, Fernández-Fernández JM, Murillo MD, Gálvez JA, Díaz-de-Villegas MD, Badorrey R, Simonsen U, Rivera L, Wulff H, Köhler R. Vascular Reactivity Profile of Novel KCa 3.1-Selective Positive-Gating Modulators in the Coronary Vascular Bed. Basic Clin Pharmacol Toxicol 2016; 119:184-92. [PMID: 26821335 DOI: 10.1111/bcpt.12560] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Accepted: 01/17/2016] [Indexed: 12/12/2022]
Abstract
Opening of intermediate-conductance calcium-activated potassium channels (KC a 3.1) produces membrane hyperpolarization in the vascular endothelium. Here, we studied the ability of two new KC a 3.1-selective positive-gating modulators, SKA-111 and SKA-121, to (1) evoke porcine endothelial cell KC a 3.1 membrane hyperpolarization, (2) induce endothelium-dependent and, particularly, endothelium-derived hyperpolarization (EDH)-type relaxation in porcine coronary arteries (PCA) and (3) influence coronary artery tone in isolated rat hearts. In whole-cell patch-clamp experiments on endothelial cells of PCA (PCAEC), KC a currents evoked by bradykinin (BK) were potentiated ≈7-fold by either SKA-111 or SKA-121 (both at 1 μM) and were blocked by a KC a 3.1 blocker, TRAM-34. In membrane potential measurements, SKA-111 and SKA-121 augmented bradykinin-induced hyperpolarization. Isometric tension measurements in large- and small-calibre PCA showed that SKA-111 and SKA-121 potentiated endothelium-dependent relaxation with intact NO synthesis and EDH-type relaxation to BK by ≈2-fold. Potentiation of the BK response was prevented by KC a 3.1 inhibition. In Langendorff-perfused rat hearts, SKA-111 potentiated coronary vasodilation elicited by BK. In conclusion, our data show that positive-gating modulation of KC a 3.1 channels improves BK-induced membrane hyperpolarization and endothelium-dependent relaxation in small and large PCA as well as in the coronary circulation of rats. Positive-gating modulators of KC a 3.1 could be therapeutically useful to improve coronary blood flow and counteract impaired coronary endothelial dysfunction in cardiovascular disease.
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Affiliation(s)
| | - Marta Sofía Valero
- Department of Pharmacy, Faculty of Health Sciences, Universidad San Jorge, Villanueva de Gállego, Spain
| | - Estéfano Pinilla
- Department of Biomedicine, Pulmonary and Cardiovascular Pharmacology, Aarhus University, Aarhus, Denmark
| | - Sara Amor
- Department of Physiology, Faculty of Medicine, Universidad Autónoma de Madrid, Madrid, Spain
| | | | - Nichole Coleman
- Department of Pharmacology, University of California, Davis, CA, USA
| | - Celia Laría
- Department of Pharmacy, Faculty of Health Sciences, Universidad San Jorge, Villanueva de Gállego, Spain
| | - Víctor Calvín-Tienza
- Department of Pharmacy, Faculty of Health Sciences, Universidad San Jorge, Villanueva de Gállego, Spain
| | - Ángel-Luis García-Otín
- Department of Pharmacy, Faculty of Health Sciences, Universidad San Jorge, Villanueva de Gállego, Spain
| | - José M Fernández-Fernández
- Laboratori de Fisiologia Molecular i Canalopaties, Departament de Ciències Experimentals i de la Salut, Universitat Pompeu Fabra, Barcelona, Spain
| | - M Divina Murillo
- Department of Pharmacology and Physiology, Veterinary Faculty, University of Zaragoza, Zaragoza, Spain
| | - José A Gálvez
- Departamento de Catálisis y Procesos Catalíticos, Instituto de Síntesis Química y Catálisis Homogénea (ISQCH), CSIC - Universidad de Zaragoza, Zaragoza, Spain
| | - María D Díaz-de-Villegas
- Departamento de Catálisis y Procesos Catalíticos, Instituto de Síntesis Química y Catálisis Homogénea (ISQCH), CSIC - Universidad de Zaragoza, Zaragoza, Spain
| | - Ramón Badorrey
- Departamento de Catálisis y Procesos Catalíticos, Instituto de Síntesis Química y Catálisis Homogénea (ISQCH), CSIC - Universidad de Zaragoza, Zaragoza, Spain
| | - Ulf Simonsen
- Department of Biomedicine, Pulmonary and Cardiovascular Pharmacology, Aarhus University, Aarhus, Denmark
| | - Luis Rivera
- Department of Physiology, Faculty of Pharmacy, Universidad Complutense de Madrid, Madrid, Spain
| | - Heike Wulff
- Department of Pharmacology, University of California, Davis, CA, USA
| | - Ralf Köhler
- Aragon Institute of Health Sciences & IIS, Zaragoza, Spain.,Aragon Agency for Research and Development (ARAID), Zaragoza, Spain
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Köhler R, Oliván-Viguera A, Wulff H. Endothelial Small- and Intermediate-Conductance K Channels and Endothelium-Dependent Hyperpolarization as Drug Targets in Cardiovascular Disease. ADVANCES IN PHARMACOLOGY 2016; 77:65-104. [DOI: 10.1016/bs.apha.2016.04.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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