1
|
Newly Discovered Action of HpTx3 from Venom of Heteropoda venatoria on Na v1.7 and Its Pharmacological Implications in Analgesia. Toxins (Basel) 2019; 11:toxins11120680. [PMID: 31757020 PMCID: PMC6950750 DOI: 10.3390/toxins11120680] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2019] [Revised: 11/17/2019] [Accepted: 11/18/2019] [Indexed: 02/07/2023] Open
Abstract
It has been reported that Heteropodatoxin3 (HpTx3), a peptidic neurotoxin purified from the venom of the spider species Heteropoda venatoria, could inhibit Kv4.2 channels. Our present study newly found that HpTx3 also has potent and selective inhibitory action on Nav1.7, with an IC50 of 135.61 ± 12.98 nM. Without effect on the current–voltage (I-V) relationship of Nav1.7, HpTx3 made minor alternation in the voltage-dependence of activation and steady-state inactivation of Nav1.7 (4.15 mV and 7.29 mV, respectively) by interacting with the extracellular S3–S4 loop (S3b–S4 sequence) in domain II and the domain IV of the Nav channel subtype, showing the characteristics of both pore blocker and gate modifier toxin. During the interaction of HpTx3 with the S3b–S4 sequence of Nav1.7, the amino acid residue D in the sequence played a key role. When administered intraperitoneally or intramuscularly, HpTx3 displayed potent analgesic activity in a dose-dependent manner in different mouse pain models induced by formalin, acetic acid, complete Freund’s adjuvant, hot plate, or spared nerve injury, demonstrating that acute, inflammatory, and neuropathic pains were all effectively inhibited by the toxin. In most cases HpTx3 at doses of ≥ 1mg/kg could produce the analgesic effect comparable to that of 1 mg/kg morphine. These results suggest that HpTx3 not only can be used as a molecular probe to investigate ion channel function and pain mechanism, but also has potential in the development of the drugs that treat the Nav1.7 channel-related pain.
Collapse
|
2
|
Alpha-adrenoceptor antagonism by Crassostrea gigas oyster extract inhibits noradrenaline-induced vascular contraction in Wistar rats. JOURNAL OF INTEGRATIVE MEDICINE-JIM 2015; 13:194-200. [PMID: 26006032 DOI: 10.1016/s2095-4964(15)60167-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
OBJECTIVE Crassostrea gigas oyster extract has been reported to have antioxidant, antihypertensive and lipid-lowering properties that may be useful for treating cardiovascular diseases. This study aimed to evaluate the effect of C. gigas oyster extract on cardiovascular function in tissues from healthy rats. METHODS Single-cell microelectrode and isolated thoracic aortic organ bath studies were performed on tissues from 8-week-old healthy Wistar rats, using varying concentrations of C. gigas oyster extract. To elucidate a mechanism of action for the oyster's vasoactive properties, concentration response curves were carried out in the presence of a calcium channel inhibitior (verapamil), a nitric oxide synthase inhibitor (N(G)-nitro-L-arginine methyl ester), a potassium channel inhibitor (4-aminopyridine), in addition to the α-adrenoceptor inhibitor prazosin. RESULTS Oyster solution at 7 500 mg/mL inhibited noradrenaline-induced contraction in isolated aortic rings. Cardiac electrophysiology results showed that neither concentration of oyster solution was able to significantly reduce action potential duration at all phases of repolarisation in left ventricular papillary muscles from healthy animals. CONCLUSION When administered to healthy vascular tissue, C. gigas oyster extract inhibits contraction induced by noradrenaline. This effect is likely to be mediated through α-adrenoceptor inhibition, and to a lesser extent, calcium modulating activity.
Collapse
|
3
|
Ma D, Wei H, Lu J, Huang D, Liu Z, Loh LJ, Islam O, Liew R, Shim W, Cook SA. Characterization of a novel KCNQ1 mutation for type 1 long QT syndrome and assessment of the therapeutic potential of a novel IKs activator using patient-specific induced pluripotent stem cell-derived cardiomyocytes. Stem Cell Res Ther 2015; 6:39. [PMID: 25889101 PMCID: PMC4396080 DOI: 10.1186/s13287-015-0027-z] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2014] [Revised: 02/27/2015] [Accepted: 02/27/2015] [Indexed: 12/14/2022] Open
Abstract
Introduction Type 1 long QT syndrome (LQT1) is a common type of cardiac channelopathy associated with loss-of-function mutations of KCNQ1. Currently there is a lack of drugs that target the defected slowly activating delayed rectifier potassium channel (IKs). With LQT1 patient-specific human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes (hiPSC-CMs), we tested the effects of a selective IKs activator ML277 on reversing the disease phenotypes. Methods A LQT1 family with a novel heterozygous exon 7 deletion in the KCNQ1 gene was identified. Dermal fibroblasts from the proband and her healthy father were reprogrammed to hiPSCs and subsequently differentiated into hiPSC-CMs. Results Compared with the control, LQT1 patient hiPSC-CMs showed reduced levels of wild type KCNQ1 mRNA accompanied by multiple exon skipping mRNAs and a ~50% reduction of the full length Kv7.1 protein. Patient hiPSC-CMs showed reduced IKs current (tail current density at 30 mV: 0.33 ± 0.02 vs. 0.92 ± 0.21, P < 0.05) and prolonged action potential duration (APD) (APD 50 and APD90: 603.9 ± 39.2 vs. 319.3 ± 13.8 ms, P < 0.005; and 671.0 ± 41.1 vs. 372.9 ± 14.2 ms, P < 0.005). ML277, a small molecule recently identified to selectively activate KV7.1, reversed the decreased IKs and partially restored APDs in patient hiPSC-CMs. Conclusions From a LQT1 patient carrying a novel heterozygous exon7 deletion mutation of KCNQ1, we generated hiPSC-CMs that faithfully recapitulated the LQT1 phenotypes that are likely associated with haploinsufficiency and trafficking defect of KCNQ1/Kv7.1. The small molecule ML277 restored IKs function in hiPSC-CMs and could have therapeutic value for LQT1 patients. Electronic supplementary material The online version of this article (doi:10.1186/s13287-015-0027-z) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Dongrui Ma
- National Heart Research Institute Singapore, National Heart Centre Singapore, 5th Hospital Drive, Singapore, 169609, Singapore.
| | - Heming Wei
- National Heart Research Institute Singapore, National Heart Centre Singapore, 5th Hospital Drive, Singapore, 169609, Singapore. .,Cardiovascular & Metabolic Disorders Program, Duke-NUS Graduate Medical School Singapore, 8 College Road, Singapore, 169857, Singapore.
| | - Jun Lu
- National Heart Research Institute Singapore, National Heart Centre Singapore, 5th Hospital Drive, Singapore, 169609, Singapore.
| | - Dou Huang
- National Heart Research Institute Singapore, National Heart Centre Singapore, 5th Hospital Drive, Singapore, 169609, Singapore.
| | - Zhenfeng Liu
- National Heart Research Institute Singapore, National Heart Centre Singapore, 5th Hospital Drive, Singapore, 169609, Singapore.
| | - Li Jun Loh
- National Heart Research Institute Singapore, National Heart Centre Singapore, 5th Hospital Drive, Singapore, 169609, Singapore.
| | - Omedul Islam
- National Heart Research Institute Singapore, National Heart Centre Singapore, 5th Hospital Drive, Singapore, 169609, Singapore.
| | - Reginald Liew
- Cardiovascular & Metabolic Disorders Program, Duke-NUS Graduate Medical School Singapore, 8 College Road, Singapore, 169857, Singapore.
| | - Winston Shim
- National Heart Research Institute Singapore, National Heart Centre Singapore, 5th Hospital Drive, Singapore, 169609, Singapore. .,Cardiovascular & Metabolic Disorders Program, Duke-NUS Graduate Medical School Singapore, 8 College Road, Singapore, 169857, Singapore.
| | - Stuart A Cook
- National Heart Research Institute Singapore, National Heart Centre Singapore, 5th Hospital Drive, Singapore, 169609, Singapore. .,Cardiovascular & Metabolic Disorders Program, Duke-NUS Graduate Medical School Singapore, 8 College Road, Singapore, 169857, Singapore. .,National Heart and Lung Institute, Imperial College, South Kensington Campus, London, SW7 2AZ, UK.
| |
Collapse
|
4
|
de Menezes-Filho JER, Gondim ANS, Cruz JS, de Souza AA, Santos JNAD, Conde-Garcia EA, de Sousa DP, Santos MS, de Oliveira ED, de Vasconcelos CML. Geraniol blocks calcium and potassium channels in the mammalian myocardium: useful effects to treat arrhythmias. Basic Clin Pharmacol Toxicol 2014; 115:534-44. [PMID: 24862086 DOI: 10.1111/bcpt.12274] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2014] [Accepted: 05/14/2014] [Indexed: 11/28/2022]
Abstract
Geraniol is a monoterpene present in several essential oils, and it is known to have a plethora of pharmacological activities. In this study, we explored the contractile and electrophysiological properties of geraniol and its antiarrhythmic effects in the heart. The geraniol effects on atrial contractility, L-type Ca(2+) current, K(+) currents, action potential (AP) parameters, ECG profile and on the arrhythmia induced by ouabain were evaluated. In the atrium, geraniol reduced the contractile force (~98%, EC = 1,510 ± 160 μM) and diminished the positive inotropism of CaCl2 and BAY K8644. In cardiomyocytes, the IC a,L was reduced by 50.7% (n = 5) after perfusion with 300 μM geraniol. Moreover, geraniol prolonged the AP duration (APD) measured at 50% (n = 5) after repolarization, without changing the resting potential. The increased APD could be attributed to the blockade of the transient outward K(+) current (Ito ) (59.7%, n = 4), the non-inactivation K(+) current (Iss ) (39.2%, n = 4) and the inward rectifier K(+) current (IK 1 ) (33.7%, n = 4). In isolated hearts, geraniol increased PRi and QTi without affecting the QRS complex (n = 6), and it reduced both the left ventricular pressure (83%) and heart rate (16.5%). Geraniol delayed the time to onset of ouabain-induced arrhythmias by 128%, preventing 30% of the increase in resting tension (n = 6). Geraniol exerts its negative inotropic and chronotropic responses in the heart by decreasing both L-type Ca(2+) and voltage-gated K(+) currents, ultimately acting against ouabain-induced arrhythmias.
Collapse
|
5
|
A systematic review for anti-inflammatory property of clusiaceae family: a preclinical approach. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE 2014; 2014:960258. [PMID: 24976853 PMCID: PMC4058220 DOI: 10.1155/2014/960258] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/29/2014] [Revised: 04/23/2014] [Accepted: 04/24/2014] [Indexed: 11/17/2022]
Abstract
Background. Clusiaceae family (sensu lato) is extensively used in ethnomedicine for treating a number of disease conditions which include cancer, inflammation, and infection. The aim of this review is to report the pharmacological potential of plants of Clusiaceae family with the anti-inflammatory activity in animal experiments. Methods. A systematic review about experiments investigating anti-inflammatory activity of Clusiaceae family was carried out by searching bibliographic databases such as Medline, Scopus and Embase. In this update, the search terms were "anti-inflammatory agents," "Clusiaceae," and "animals, laboratory." Results. A total of 255 publications with plants this family were identified. From the initial 255 studies, a total of 21 studies were selected for the final analysis. Studies with genera Allanblackia, Clusia, Garcinia or Rheedia, and Hypericum showed significant anti-inflammatory activity. The findings include a decrease of total leukocytes, a number of neutrophils, total protein concentration, granuloma formation, and paw or ear edema formation. Other interesting findings included decreased of the MPO activity, and inflammatory mediators such as NF- κ B and iNOS expression, PGE2 and Il-1 β levels and a decrease in chronic inflammation. Conclusion. The data reported suggests the anti-inflammatory effect potential of Clusiaceae family in animal experiments.
Collapse
|
6
|
Mustroph J, Maier LS, Wagner S. CaMKII regulation of cardiac K channels. Front Pharmacol 2014; 5:20. [PMID: 24600393 PMCID: PMC3930912 DOI: 10.3389/fphar.2014.00020] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Accepted: 01/31/2014] [Indexed: 11/23/2022] Open
Abstract
Cardiac K channels are critical determinants of cardiac excitability. In hypertrophied and failing myocardium, alterations in the expression and activity of voltage-gated K channels are frequently observed and contribute to the increased propensity for life-threatening arrhythmias. Thus, understanding the mechanisms of disturbed K channel regulation in heart failure (HF) is of critical importance. Amongst others, Ca/calmodulin-dependent protein kinase II (CaMKII) has been identified as an important regulator of K channel activity. In human HF but also various animal models, increased CaMKII expression and activity has been linked to deteriorated contractile function and arrhythmias. This review will discuss the current knowledge about CaMKII regulation of several K channels, its influence on action potential properties, dispersion of repolarization, and arrhythmias with special focus on HF.
Collapse
Affiliation(s)
- Julian Mustroph
- Department of Cardiology, University Medical Center Göttingen Göttingen, Germany
| | - Lars S Maier
- Department of Cardiology, University Medical Center Göttingen Göttingen, Germany
| | - Stefan Wagner
- Department of Cardiology, University Medical Center Göttingen Göttingen, Germany
| |
Collapse
|
7
|
Anderson ME, Brown JH, Bers DM. CaMKII in myocardial hypertrophy and heart failure. J Mol Cell Cardiol 2011; 51:468-73. [PMID: 21276796 DOI: 10.1016/j.yjmcc.2011.01.012] [Citation(s) in RCA: 338] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/22/2010] [Revised: 01/13/2011] [Accepted: 01/13/2011] [Indexed: 02/08/2023]
Abstract
Many signals have risen and fallen in the tide of investigation into mechanisms of myocardial hypertrophy and heart failure (HF). In our opinion, the multifunctional Ca and calmodulin-dependent protein kinase II (CaMKII) has emerged as a molecule to watch, in part because a solid body of accumulated data essentially satisfy Koch's postulates, showing that the CaMKII pathway is a core mechanism for promoting myocardial hypertrophy and heart failure. Multiple groups have now confirmed the following: (1) that CaMKII activity is increased in hypertrophied and failing myocardium from animal models and patients; (2) CaMKII overexpression causes myocardial hypertrophy and HF and (3) CaMKII inhibition (by drugs, inhibitory peptides and gene deletion) improves myocardial hypertrophy and HF. Patients with myocardial disease die in equal proportion from HF and arrhythmias, and a major therapeutic obstacle is that drugs designed to enhance myocardial contraction promote arrhythmias. In contrast, inhibiting the CaMKII pathway appears to reduce arrhythmias and improve myocardial responses to pathological stimuli. This brief paper will introduce the molecular physiology of CaMKII and discuss the impact of CaMKII on ion channels, Ca handling proteins and transcription in myocardium. This article is part of a special issue entitled "Key Signaling Molecules in Hypertrophy and Heart Failure".
Collapse
Affiliation(s)
- Mark E Anderson
- Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, IA, USA.
| | | | | |
Collapse
|
8
|
Keskanokwong T, Lim HJ, Zhang P, Cheng J, Xu L, Lai D, Wang Y. Dynamic Kv4.3-CaMKII unit in heart: an intrinsic negative regulator for CaMKII activation. Eur Heart J 2010; 32:305-15. [PMID: 21148163 DOI: 10.1093/eurheartj/ehq469] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
AIMS Reduction of transient outward current (I(to)) and excessive activation of Ca(2+)/Calmodulin-dependent kinase II (CaMKII) are general features of ventricular myocytes in heart failure. We hypothesize that alterations of I(to) directly regulate CaMKII activation in cardiomyocytes. METHODS AND RESULTS A dynamic coupling of I(to) channel subunit Kv4.3 and inactive CaMKII was discovered in cardiomyocytes with the membrane predominant distribution by co-immunoprecipitation and fluorescence resonance energy transfer techniques. CaMKII dissociation from Kv4.3-CaMKII units caused a significant increase in CaMKII autophosphorylation and L-type calcium current (I(Ca)) facilitation. I(Ca) facilitation was blunted by the compartmental Ca²(+) chelator BAPTA but unaffected by bulk Ca²(+) chelator EGTA, implicating membrane-localized CaMKII. Kv4.3 overexpression reduced basal CaMKII autophosphorylation in myocytes and eliminated Ca²(+)-induced CaMKII activation. Kv4.3 blocks CaMKII activation by binding to the calmodulin binding sites, whereas Kv4.3 uncoupling releases these sites and leads to a substantial CaMKII activation. CONCLUSION Our results uncovered an important mechanism that regulates CaMKII activation in the heart and implicate I(to) channel alteration in pathological CaMKII activation.
Collapse
Affiliation(s)
- Thitima Keskanokwong
- Department of Pediatrics and Children's Healthcare of Atlanta, Emory University, Atlanta, GA 30322, USA
| | | | | | | | | | | | | |
Collapse
|
9
|
Abstract
Calcium/calmodulin-dependent kinase II (CaMKII) is a multifunctional serine/threonine kinase expressed abundantly in the heart. CaMKII targets numerous proteins involved in excitation-contraction coupling and excitability, and its activation may simultaneously contribute to heart failure and cardiac arrhythmias. In this review, we summarize the modulatory effects of CaMKII on cardiac ion channel function and expression and illustrate potential implications in the onset of arrhythmias via a computer model.
Collapse
|
10
|
Wang Y, Hill JA. Electrophysiological remodeling in heart failure. J Mol Cell Cardiol 2010; 48:619-32. [PMID: 20096285 DOI: 10.1016/j.yjmcc.2010.01.009] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/14/2008] [Revised: 01/11/2010] [Accepted: 01/12/2010] [Indexed: 11/25/2022]
Abstract
Heart failure affects nearly 6 million Americans, with a half-million new cases emerging each year. Whereas up to 50% of heart failure patients die of arrhythmia, the diverse mechanisms underlying heart failure-associated arrhythmia are poorly understood. As a consequence, effectiveness of antiarrhythmic pharmacotherapy remains elusive. Here, we review recent advances in our understanding of heart failure-associated molecular events impacting the electrical function of the myocardium. We approach this from an anatomical standpoint, summarizing recent insights gleaned from pre-clinical models and discussing their relevance to human heart failure.
Collapse
Affiliation(s)
- Yanggan Wang
- Department of Pediatrics, Emory University, Atlanta, GA, USA.
| | | |
Collapse
|
11
|
Wu ZZ, Li DP, Chen SR, Pan HL. Aminopyridines potentiate synaptic and neuromuscular transmission by targeting the voltage-activated calcium channel beta subunit. J Biol Chem 2009; 284:36453-36461. [PMID: 19850918 DOI: 10.1074/jbc.m109.075523] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Aminopyridines such as 4-aminopyridine (4-AP) are widely used as voltage-activated K(+) (Kv) channel blockers and can improve neuromuscular function in patients with spinal cord injury, myasthenia gravis, or multiple sclerosis. Here, we present novel evidence that 4-AP and several of its analogs directly stimulate high voltage-activated Ca(2+) channels (HVACCs) in acutely dissociated neurons. 4-AP, 4-(aminomethyl)pyridine, 4-(methylamino)pyridine, and 4-di(methylamino)pyridine profoundly increased HVACC, but not T-type, currents in dissociated neurons from the rat dorsal root ganglion, superior cervical ganglion, and hippocampus. The widely used Kv channel blockers, including tetraethylammonium, alpha-dendrotoxin, phrixotoxin-2, and BDS-I, did not mimic or alter the effect of 4-AP on HVACCs. In HEK293 cells expressing various combinations of N-type (Cav2.2) channel subunits, 4-AP potentiated Ca(2+) currents primarily through the intracellular beta(3) subunit. In contrast, 4-AP had no effect on Cav3.2 channels expressed in HEK293 cells. Furthermore, blocking Kv channels did not mimic or change the potentiating effects of 4-AP on neurotransmitter release from sensory and motor nerve terminals. Thus, our findings challenge the conventional view that 4-AP facilitates synaptic and neuromuscular transmission by blocking Kv channels. Aminopyridines can directly target presynaptic HVACCs to potentiate neurotransmitter release independent of Kv channels.
Collapse
Affiliation(s)
- Zi-Zhen Wu
- Division of Anesthesiology and Critical Care, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030
| | - De-Pei Li
- Division of Anesthesiology and Critical Care, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030
| | - Shao-Rui Chen
- Division of Anesthesiology and Critical Care, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030
| | - Hui-Lin Pan
- Division of Anesthesiology and Critical Care, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030; Program in Neuroscience, The University of Texas Graduate School of Biomedical Sciences, Houston, Texas 77225.
| |
Collapse
|
12
|
DeSimone CV, Lu Y, Bondarenko VE, Morales MJ. S3b amino acid substitutions and ancillary subunits alter the affinity of Heteropoda venatoria toxin 2 for Kv4.3. Mol Pharmacol 2009; 76:125-33. [PMID: 19357248 DOI: 10.1124/mol.109.055657] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Heteropoda venatoria toxin 2 (HpTx2) is an inhibitor cystine knot (ICK)-gating modifier toxin that selectively inhibits Kv4 channels. To characterize the molecular determinants of interaction, we performed alanine scanning of the Kv4.3 S3b region. HpTx2-Kv4.3 interaction had an apparent K(d) value of 2.3 microM. Two alanine mutants in Kv4.3 increased K(d) values to 6.4 microM for V276A and 25 microM for L275A. Simultaneous mutation of both amino acids to alanine nearly eliminated toxin interaction. Unlike Hanatoxin and other well characterized ICK toxins, HpTx2 binding does not require a charged amino acid for interaction. To determine whether the identity of the S3b binding site amino acids altered HpTx2 specificity, we constructed Kv4.3 [LV275IF]. This mutation decreased the K(d) value to 0.54 microM, suggesting that the hydrophobic character of the putative binding site is the most important property for interaction with HpTx2. One mutant, N280A, caused stronger interaction of HpTx2 with Kv4.3; the K(d) value for Kv4.3 [N280A] was 0.26 microM. To understand Kv4.3-based transient outward currents in native tissues, we tested the affinity of HpTx2 for Kv4.3 coexpressed with KChIP2b. The toxin's K(d) value for Kv4.3 + KChIP2b was 0.95 microM. KChIP2b stabilizes the closed state of Kv4.3, suggesting that the increased toxin affinity is due to increased stabilization of the closed state. These data show that HpTx2 binding to Kv4.3 has aspects in common with other ICK gating modifier toxins but that the interventions that increase toxin affinity suggest flexibility toward channel binding that belies its unusual specificity for Kv4 channels.
Collapse
Affiliation(s)
- Christopher V DeSimone
- Department of Physiology and Biophysics, University at Buffalo, The State University of New York, Buffalo, NY 14214, USA
| | | | | | | |
Collapse
|
13
|
Wang YJ, Chen BS, Lin MW, Lin AA, Peng H, Sung RJ, Wu SN. Time-Dependent Block of Ultrarapid-Delayed Rectifier K+ Currents by Aconitine, a Potent Cardiotoxin, in Heart-Derived H9c2 Myoblasts and in Neonatal Rat Ventricular Myocytes. Toxicol Sci 2008; 106:454-63. [DOI: 10.1093/toxsci/kfn189] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
|
14
|
Wang Y, Tandan S, Cheng J, Yang C, Nguyen L, Sugianto J, Johnstone JL, Sun Y, Hill JA. Ca2+/calmodulin-dependent protein kinase II-dependent remodeling of Ca2+ current in pressure overload heart failure. J Biol Chem 2008; 283:25524-25532. [PMID: 18622016 DOI: 10.1074/jbc.m803043200] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) activity is increased in heart failure (HF), a syndrome characterized by markedly increased risk of arrhythmia. Activation of CaMKII increases peak L-type Ca(2+) current (I(Ca)) and slows I(Ca) inactivation. Whether these events are linked mechanistically is unknown. I(Ca) was recorded in acutely dissociated subepicardial and subendocardial murine left ventricular (LV) myocytes using the whole cell patch clamp method. Pressure overload heart failure was induced by surgical constriction of the thoracic aorta. I(Ca) density was significantly larger in subepicardial myocytes than in subendocardial/myocytes. Similar patterns were observed in the cell surface expression of alpha1c, the channel pore-forming subunit. In failing LV, I(Ca) density was increased proportionately in both cell types, and the time course of I(Ca) inactivation was slowed. This typical pattern of changes suggested a role of CaMKII. Consistent with this, measurements of CaMKII activity revealed a 2-3-fold increase (p < 0.05) in failing LV. To test for a causal link, we measured frequency-dependent I(Ca) facilitation. In HF myocytes, this CaMKII-dependent process could not be induced, suggesting already maximal activation. Internal application of active CaMKII in failing myocytes did not elicit changes in I(Ca). Finally, CaMKII inhibition by internal diffusion of a specific peptide inhibitor reduced I(Ca) density and inactivation time course to similar levels in control and HF myocytes. I(Ca) density manifests a significant transmural gradient, and this gradient is preserved in heart failure. Activation of CaMKII, a known pro-arrhythmic molecule, is a major contributor to I(Ca) remodeling in load-induced heart failure.
Collapse
Affiliation(s)
- Yanggan Wang
- Department of Internal Medicine (Cardiology), Dallas, Texas 75390-8573
| | - Samvit Tandan
- Department of Internal Medicine (Cardiology), Dallas, Texas 75390-8573
| | - Jun Cheng
- Department of Internal Medicine (Cardiology), Dallas, Texas 75390-8573
| | - Chunmei Yang
- Department of Internal Medicine (Cardiology), Dallas, Texas 75390-8573
| | - Lan Nguyen
- Department of Internal Medicine (Cardiology), Dallas, Texas 75390-8573
| | - Jessica Sugianto
- Department of Internal Medicine (Cardiology), Dallas, Texas 75390-8573
| | - Janet L Johnstone
- Department of Internal Medicine (Cardiology), Dallas, Texas 75390-8573
| | - Yuyang Sun
- Department of Pediatrics, Emory University, Atlanta, Georgia 30322
| | - Joseph A Hill
- Department of Internal Medicine (Cardiology), Dallas, Texas 75390-8573; Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-8573 and the.
| |
Collapse
|
15
|
Sun H, Xu B, Sheveleva E, Chen QM. LY294002 inhibits glucocorticoid-induced COX-2 gene expression in cardiomyocytes through a phosphatidylinositol 3 kinase-independent mechanism. Toxicol Appl Pharmacol 2008; 232:25-32. [PMID: 18657281 DOI: 10.1016/j.taap.2008.05.024] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2008] [Revised: 05/19/2008] [Accepted: 05/27/2008] [Indexed: 01/08/2023]
Abstract
Glucocorticoids induce COX-2 expression in rat cardiomyocytes. While investigating whether phosphatidylinositol 3 kinase (PI3K) plays a role in corticosterone (CT)-induced COX-2, we found that LY294002 (LY29) but not wortmannin (WM) attenuates CT from inducing COX-2 gene expression. Expression of a dominant-negative mutant of p85 subunit of PI3K failed to inhibit CT from inducing COX-2 expression. CT did not activate PI3K/AKT signaling pathway whereas LY29 and WM decreased the activity of PI3K. LY303511 (LY30), a structural analogue and a negative control for PI3K inhibitory activity of LY29, also suppressed COX-2 induction. These data suggest PI3K-independent mechanisms in regulating CT-induced COX-2 expression. LY29 and LY30 do not inhibit glucocorticoid receptor transactivity. Both compounds have been reported to inhibit Casein Kinase 2 activity and modulate potassium and calcium levels independent of PI3K, while LY29 has been reported to inhibit mammalian Target of Rapamycin (mTOR), and DNA-dependent Protein Kinase (DNA-PK). Inhibitor of Casein Kinase 2 (CK2), mTOR or DNA-PK failed to prevent CT from inducing COX-2 expression. Tetraethylammonium (TEA), a potassium channel blocker, and nimodipine, a calcium channel blocker, both attenuated CT from inducing COX-2 gene expression. CT was found to increase intracellular Ca(2+) concentration, which can be inhibited by LY29, TEA or nimodipine. These data suggest a possible role of calcium instead of PI3K in CT-induced COX-2 expression in cardiomyocytes.
Collapse
Affiliation(s)
- Haipeng Sun
- Interdisciplinary Graduate Program of Pharmacology and Toxicology, University of Arizona, Tucson, AZ 85724, USA
| | | | | | | |
Collapse
|
16
|
Shi J, Miles DK, Orr BA, Massa SM, Kernie SG. Injury-induced neurogenesis in Bax-deficient mice: evidence for regulation by voltage-gated potassium channels. Eur J Neurosci 2007; 25:3499-512. [PMID: 17610570 DOI: 10.1111/j.1460-9568.2007.05624.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Adult neural stem and progenitor cells may help remodel the brain in response to injury. The pro-apoptotic molecule Bax has recently been identified as a key player in adult neural stem cell survival. In Bax-deficient mice that have undergone traumatic brain injury, we find increased numbers of neural progenitor cells in the dentate gyrus and improved remodeling of the hippocampus. Exogenous potassium chloride mimics spreading depression (SD)-like events in vitro, and Bax-deficient neural stem cells proliferate in response to these events more robustly than wild-type neural stem cells. Selective potassium channel blockers interrupt SD-mediated stimulation of stem cells. In addition, the potassium channel Kv4.1 is expressed within neural stem and progenitor cells in the dentate gyrus and is increased in Bax-deficiency. These data suggest that the neuroprotection observed after injury in Bax-deficiency may be due to increased neurogenesis via activation of the Kv4 family of potassium channels.
Collapse
Affiliation(s)
- Jian Shi
- Department of Pediatrics, The University of Texas Southwestern Medical Center, Dallas, TX 75390-9133, USA
| | | | | | | | | |
Collapse
|
17
|
London B, Baker LC, Petkova-Kirova P, Nerbonne JM, Choi BR, Salama G. Dispersion of repolarization and refractoriness are determinants of arrhythmia phenotype in transgenic mice with long QT. J Physiol 2006; 578:115-29. [PMID: 17110412 PMCID: PMC2075135 DOI: 10.1113/jphysiol.2006.122622] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Enhanced dispersion of repolarization (DR) and refractoriness may be a unifying mechanism central to arrhythmia genesis in the long QT (LQT) syndrome. The role of DR in promoting arrhythmias was investigated in several strains of molecularly engineered mice: (a) Kv4.2 dominant negative transgenic (Kv4.2DN) that lacks the fast component of the transient outward current, I(to,f), have action potential (AP) and QT prolongation, but no spontaneous arrhythmias, (b) Kv1.4 targeted mice (Kv1.4-/-) that lack the slow component of I(to) (I(to,s)), have no QT prolongation and no spontaneous arrhythmias, and (c) double transgenic (Kv4.2DN x Kv1.4-/-) mice that lack both I(to,f) and I(to,s), have AP and QT prolongation, and spontaneous ventricular tachyarrhythmias. Hearts were perfused, stained with di-4-ANEPPS and optically mapped. Activation patterns and conduction velocities were similar between the strains but AP duration at 75% recovery (APD75) was longer in Kv4.2DN (28.0 +/- 2.5 ms, P < 0.01, n = 6), Kv1.4-/- (28.4 +/- 0.4 ms, P < 0.01, n = 5) and Kv4.2DN x Kv1.4-/- (34.3 +/- 2.6 ms, P < 0.01, n = 6) mice than controls (20.3 +/- 1.0 ms, n = 5). Dispersion of refractoriness between apex and base was markedly reduced in Kv4.2DN (0.3 +/- 0.5 ms, n = 6, P < 0.05) but enhanced in Kv1.4-/- (14.2 +/- 2.0 ms, n = 5, P < 0.05) and Kv4.2DN x Kv1.4(-/-) (15.0 +/- 3 ms, n = 5, P < 0.5) mice compared with controls (10 +/- 2 ms, n = 5). A premature pulse elicited ventricular tachycardia (VT) in Kv1.4-/- (n = 4/5) and Kv4.2DN x Kv1.4-/- hearts (n = 5/5) but not Kv4.2DN hearts (n = 0/6). Voltage-clamp recordings showed that I(to,f) was 30% greater in myocytes from the apex than base which may account for the absence of DR in Kv4.2DN mice. Thus, dispersion of repolarization (DR) appears to be an important determinant of arrhythmia vulnerability.
Collapse
Affiliation(s)
- Barry London
- University of Pittsburgh, Cardiovascular Institute, Pittsburgh, PA 15213, USA
| | | | | | | | | | | |
Collapse
|