Displaying all 12 publications

  1. Teah YF, Abduraman MA, Amanah A, Adenan MI, Sulaiman SF, Tan ML
    Food Chem. Toxicol., 2017 Sep;107(Pt A):293-301.
    PMID: 28689918 DOI: 10.1016/j.fct.2017.07.011
    Elephantopus scaber Linn and its major bioactive component, deoxyelephantopin are known for their medicinal properties and are often reported to have various cytotoxic and antitumor activities. This plant is widely used as folk medicine for a plethora of indications although its safety profile remains unknown. Human ether-a-go-go-related gene (hERG) encodes the cardiac IKr current which is a determinant of the duration of ventricular action potentials and QT interval. The hERG potassium channel is an important antitarget in cardiotoxicity evaluation. This study investigated the effects of deoxyelephantopin on the current, mRNA and protein expression of hERG channel in hERG-transfected HEK293 cells. The hERG tail currents following depolarization pulses were insignificantly affected by deoxyelephantopin in the transfected cell line. Current reduction was less than 40% as compared with baseline at the highest concentration of 50 μM. The results were consistent with the molecular docking simulation and hERG surface protein expression. Interestingly, it does not affect the hERG expression at both transcriptional and translational level at most concentrations, although higher concentration at 10 μM caused protein accumulation. In conclusion, deoxyelephantopin is unlikely a clinically significant hERG channel and Ikr blocker.
    Matched MeSH terms: Ether-A-Go-Go Potassium Channels/metabolism; Delayed Rectifier Potassium Channels/metabolism
  2. Tay YL, Amanah A, Adenan MI, Wahab HA, Tan ML
    Sci Rep, 2019 12 24;9(1):19757.
    PMID: 31874991 DOI: 10.1038/s41598-019-56106-6
    Mitragyna speciosa Korth (M. speciosa) has been widely used as a recreational product, however, there are growing concerns on the abuse potentials and toxicity of the plant. Several poisoning and fatal cases involving kratom and mitragynine have been reported but the underlying causes remain unclear. The human ether-a-go-go-related gene 1 (hERG1) encodes the pore-forming subunit underlying cardiac rapidly delayed rectifier potassium current (IKr). Pharmacological blockade of the IKr can cause acquired long QT syndrome, leading to lethal cardiac arrhythmias. This study aims to elucidate the mechanisms of mitragynine-induced inhibition on hERG1a/1b current. Electrophysiology experiments were carried out using Port-a-Patch system. Quantitative RT-PCR, Western blot analysis, immunofluorescence and co-immunoprecipitation methods were used to determine the effects of mitragynine on hERG1a/1b expression and hERG1-cytosolic chaperones interaction. Mitragynine was found to inhibit the IKr current with an IC50 value of 332.70 nM. It causes a significant reduction of the fully-glycosylated (fg) hERG1a protein expression but upregulates both core-glycosylated (cg) expression and hERG1a-Hsp90 complexes, suggesting possible impaired hERG1a trafficking. In conclusion, mitragynine inhibits hERG1a/1b current through direct channel blockade at lower concentration, but at higher concentration, it upregulates the complexation of hERG1a-Hsp90 which may be inhibitory towards channel trafficking.
    Matched MeSH terms: Ether-A-Go-Go Potassium Channels/metabolism*
  3. Nikoui V, Ostadhadi S, Azhand P, Zolfaghari S, Amiri S, Foroohandeh M, et al.
    Eur J Pharmacol, 2016 Nov 15;791:369-376.
    PMID: 27615446 DOI: 10.1016/j.ejphar.2016.09.017
    Evidence show that gamma-aminobutyric acid (GABA) receptors are involved in depression, so the aim of this study was to investigate the effect of nitrazepam as agonist of GABAA receptors on depression and curiosity in male mice and the role of potassium channel in antidepressant-like response. For this purpose, we studied the antidepressant-like properties of fluoxetine, nitrazepam, glibenclamide, and cromakalim by both forced swimming test (FST) and tail suspension test (TST). Animals were injected by various doses of nitrazepam (0.05, 0.1, and 0.5mg/kg). Nitrazepam at dose of 0.5mg/kg significantly decreased the immobility time compared to control group in both FST and TST. Fluoxetine also showed such a response. Co-administration of nitrazepam (0.05mg/kg) with glibenclamide in TST (1mg/kg) and in FST (0.3, 1mg/kg) also showed antidepressant-like response. Beside, cromakalim (0.1mg/kg) could reverse the antidepressant-like effect of nitrazepam (0.5mg/kg) in both FST and TST, while cromakalim and glibenclamide alone could not change the immobility time compared to control group (P>0.05). The hole-board test revealed that nitrazepam at doses of 0.5 and 0.1mg/kg could increase the activity of the animal's head-dipping and boost the curiosity and exploration behavior of mice. The results of this study revealed that nitrazepam may possess antidepressant-like properties and this effect is dependent to potassium channels in both FST and TST.
    Matched MeSH terms: Potassium Channels/metabolism*
  4. Jeevaratnam K, Chadda KR, Huang CL, Camm AJ
    J. Cardiovasc. Pharmacol. Ther., 2018 03;23(2):119-129.
    PMID: 28946759 DOI: 10.1177/1074248417729880
    The development of novel drugs specifically directed at the ion channels underlying particular features of cardiac action potential (AP) initiation, recovery, and refractoriness would contribute to an optimized approach to antiarrhythmic therapy that minimizes potential cardiac and extracardiac toxicity. Of these, K+ channels contribute numerous and diverse currents with specific actions on different phases in the time course of AP repolarization. These features and their site-specific distribution make particular K+ channel types attractive therapeutic targets for the development of pharmacological agents attempting antiarrhythmic therapy in conditions such as atrial fibrillation. However, progress in the development of such temporally and spatially selective antiarrhythmic drugs against particular ion channels has been relatively limited, particularly in view of our incomplete understanding of the complex physiological roles and interactions of the various ionic currents. This review summarizes the physiological properties of the main cardiac potassium channels and the way in which they modulate cardiac electrical activity and then critiques a number of available potential antiarrhythmic drugs directed at them.
    Matched MeSH terms: Potassium Channels/metabolism*
  5. Lu J, Wei H, Wu J, Jamil MF, Tan ML, Adenan MI, et al.
    PLoS One, 2014;9(12):e115648.
    PMID: 25535742 DOI: 10.1371/journal.pone.0115648
    INTRODUCTION: Mitragynine is a major bioactive compound of Kratom, which is derived from the leave extracts of Mitragyna speciosa Korth or Mitragyna speciosa (M. speciosa), a medicinal plant from South East Asia used legally in many countries as stimulant with opioid-like effects for the treatment of chronic pain and opioid-withdrawal symptoms. Fatal incidents with Mitragynine have been associated with cardiac arrest. In this study, we determined the cardiotoxicity of Mitragynine and other chemical constituents isolated using human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs).

    METHODS AND RESULTS: The rapid delayed rectifier potassium current (IKr), L-type Ca2+ current (ICa,L) and action potential duration (APD) were measured by whole cell patch-clamp. The expression of KCNH2 and cytotoxicity was determined by real-time PCR and Caspase activity measurements. After significant IKr suppression by Mitragynine (10 µM) was confirmed in hERG-HEK cells, we systematically examined the effects of Mitragynine and other chemical constituents in hiPSC-CMs. Mitragynine, Paynantheine, Speciogynine and Speciociliatine, dosage-dependently (0.1∼100 µM) suppressed IKr in hiPSC-CMs by 67%∼84% with IC50 ranged from 0.91 to 2.47 µM. Moreover, Mitragynine (10 µM) significantly prolonged APD at 50 and 90% repolarization (APD50 and APD90) (439.0±11.6 vs. 585.2±45.5 ms and 536.0±22.6 vs. 705.9±46.1 ms, respectively) and induced arrhythmia, without altering the L-type Ca2+ current. Neither the expression, and intracellular distribution of KCNH2/Kv11.1, nor the Caspase 3 activity were significantly affected by Mitragynine.

    CONCLUSIONS: Our study indicates that Mitragynine and its analogues may potentiate Torsade de Pointes through inhibition of IKr in human cardiomyocytes.

    Matched MeSH terms: Delayed Rectifier Potassium Channels/metabolism
  6. Kamaldin MN, Akhtar MN, Mohamad AS, Lajis N, Perimal EK, Akira A, et al.
    Molecules, 2013 Apr 10;18(4):4209-20.
    PMID: 23612473 DOI: 10.3390/molecules18044209
    Previous studies have shown that systemic administration of 6'-hydroxy-2',4'-dimethoxychalcone (flavokawin B, FKB) exerts significant peripheral and central antinociceptive effects in laboratory animals. However, the mechanisms underlying these peripheral and central antinociceptive effects have yet to be elucidated. Therefore, the objective of the present study was to evaluate the participation of nitric oxide (NO)/cyclic guanosine monophosphate (cGMP)/potassium (K+) channels pathway in the peripheral antinociception induced by FKB. It was demonstrated that intraplantar (i.pl.) administration of FKB (150, 250, 375 and 500 µg/paw) resulted in dose-dependent peripheral antinociception against mechanical hyperalgesia in carrageenan-induced hyperalgesia test model in rats. The possibility of FKB having either a central or a systemic effect was excluded since administration of FKB into the right paw did not elicit antinociception in the contralateral paw. Furthermore, peripheral antinociception induced by FKB (500 µg/paw) was significantly reduced when L-arginine (25 µg/paw, i.pl.), Oxadiazolo[4,3-a]quinoxalin-1-one (ODQ; 50 µg/paw, i.pl.), glibenclamide (300 µg/paw, i.pl.), tetraethylammonium (300 µg/paw, i.pl.) and charybdotoxin (3 µg/paw, i.pl.) were injected before treatment. Taken together, our present data suggest that FKB elicits peripheral antinociception when assessed in the mechanical hyperalgesia induced by carrageenan. In addition, it was also demonstrated that this effect was mediated through interaction of the NO/cGMP/K+ channels signaling pathway.
    Matched MeSH terms: Potassium Channels/metabolism*
  7. Lee MK, Lim KH, Millns P, Mohankumar SK, Ng ST, Tan CS, et al.
    Phytomedicine, 2018 Mar 15;42:172-179.
    PMID: 29655683 DOI: 10.1016/j.phymed.2018.03.025
    BACKGROUND: Lignosus rhinocerotis (Cooke) Ryvarden is a popular medicinal mushroom used for centuries in Southeast Asia to treat asthma and chronic cough. The present study aimed to investigate the effect of this mushroom on airways patency.

    MATERIALS AND METHODS: The composition of L. rhinocerotis TM02 cultivar was analyzed. Organ bath experiment was employed to study the bronchodilator effect of Lignosus rhinocerotis cold water extract (CWE) on rat isolated airways. Trachea and bronchus were removed from male Sprague-Dawley rats, cut into rings of 2 mm, pre-contracted with carbachol before adding CWE into the bath in increasing concentrations. To investigate the influence of incubation time, tissues were exposed to intervals of 5, 15 and 30 min between CWE concentrations after pre-contraction with carbachol in subsequent protocol. Next, tissues were pre-incubated with CWE before the addition of different contractile agents, carbachol and 5-hydroxytrptamine (5-HT). The bronchodilator effect of CWE was compared with salmeterol and ipratropium. In order to uncover the mechanism of action of CWE, the role of beta-adrenoceptor, potassium and calcium channels was investigated.

    RESULTS: Composition analysis of TM02 cultivar revealed the presence of β-glucans and derivatives of adenosine. The extract fully relaxed the trachea at 3.75 mg/ml (p potassium channel in CWE-mediated airway relaxation is ruled out, but the bronchodilator effect was unequivocally affected by influx of calcium.

    CONCLUSIONS: The bronchodilator effect of L. rhinocerotis on airways is mediated by calcium signalling pathway downstream of Gαq-coupled protein receptors. The airway relaxation effect is both concentration- and incubation time-dependent. Our findings provide unequivocal evidence to support its traditional use to relieve asthma and cough.

    Matched MeSH terms: Potassium Channels/metabolism
  8. Loganathan K, Moriya S, Parhar IS
    Zebrafish, 2018 10;15(5):473-483.
    PMID: 30102584 DOI: 10.1089/zeb.2018.1594
    Ambient light and temperature affect reproductive function by regulating kisspeptin and gonadotrophin-releasing hormone (GnRH) in vertebrates. Melatonin and melatonin receptors, as well as the two-pore domain K+ channel-related K+ (TREK) channels, are affected by light and/or temperature; therefore, these molecules could modulate kisspeptin and GnRH against ambient light and temperature. In this study, we investigated the effect of light and temperature, which affect melatonin levels in gene expression levels of TREK channels, kisspeptin, and GnRH. We first investigated the effects of different light and temperature conditions on brain melatonin concentrations by ELISA. Fish were exposed to either constant darkness, constant light, high temperature (35°C), or low temperature (20°C) for 72 h. Brain melatonin levels were significantly high under constant darkness and high temperature. We further investigated the effects of high brain melatonin levels by constant darkness and high temperature on gene expression levels of melatonin receptors (mt1, mt2, and mel1c), TREK channels (trek1b, trek2a, and trek2b), gnrh3, and kiss2 in the adult zebrafish brain by real-time polymerase chain reaction. Fish were exposed to constant darkness or elevated temperatures (35°C) for 72 h. trek2a, kiss2, and gnrh3 levels were increased under constant darkness. High temperature decreased gene expression levels of mt1, mt2, mel1c, and gnrh3 in the preoptic area, whereas other genes remained unchanged. Melatonin receptors, TREK channels, gnrh3, and kiss2 responded differently under high melatonin conditions. The melatonin receptors and the TREK channels could play roles in the regulation of reproduction by environmental cues, especially ambient light and temperature.
    Matched MeSH terms: Potassium Channels/metabolism*
  9. Yam MF, Tan CS, Shibao R
    Hypertens. Res., 2018 Oct;41(10):787-797.
    PMID: 30111856 DOI: 10.1038/s41440-018-0083-8
    Orthosiphon stamineus Benth. (Lambiaceae) is an important traditional plant for the treatment of hypertension. Previous studies have demonstrated that the sinensetin content in O. stamineus is correlated with its vasorelaxant activity. However, there is still very little information regarding the vasorelaxant effect of sinensetin due to a lack of scientific studies. Therefore, the present study was designed to investigate the underlying mechanism of action of sinensetin in vasorelaxation using an in vitro precontraction aortic ring assay. The changes in the tension of the aortic ring preparations were recorded using a force-displacement transducer and the PowerLab system. The mechanisms of the vasorelaxant effect of sinensetin were determined in the presence of antagonists. Sinensetin caused relaxation of the aortic ring precontracted with PE in the presence and absence of the endothelium and with potassium chloride in endothelium-intact aortic rings. In the presence of Nω-nitro-L-arginine methyl ester (nitric oxide synthase inhibitor), methylene blue (cyclic guanosine monophosphate lowering agent), ODQ (selective soluble guanylate cyclase inhibitor), indomethacin (a nonselective cyclooxygenase inhibitor), tetraethylammonium (nonselective calcium activator K+ channel blocker), 4-aminopyridine (voltage-dependent K+ channel blocker), barium chloride (inwardly rectifying Kir channel blocker), glibenclamide (nonspecific ATP-sensitive K+ channel blocker), atropine (muscarinic receptor blocker), or propranolol (β-adrenergic receptor blocker), the relaxation stimulated by sinensetin was significantly reduced. Sinensetin was also active in reducing Ca2+ release from the sarcoplasmic reticulum (via IP3R) and in blocking calcium channels (VOCC). The present study demonstrates the vasorelaxant effect of sinensetin, which involves the NO/sGC/cGMP and indomethacin pathways, calcium and potassium channels, and muscarinic and beta-adrenergic receptors.
    Matched MeSH terms: Potassium Channels/metabolism*
  10. Loganathan K, Moriya S, Sivalingam M, Ng KW, Parhar IS
    J. Chem. Neuroanat., 2017 Dec;86:92-99.
    PMID: 29074372 DOI: 10.1016/j.jchemneu.2017.10.004
    kcnk10a has been predicted in zebrafish to be a member of the two-pore domain potassium ion (K+) channel-related K+ (TREK) channel family known as a thermoreceptor. Since reproduction is affected by temperature, Kcnk10a could be involved in the regulation of reproduction. However, expression of kcnk10a in the zebrafish brain and association with reproduction has not been identified. In this study, the full length sequence and localization of kcnk10a in the brain was investigated and gene expressions of the TREK channel family were examined to investigate association with reproduction. We initially identified the full length cDNA sequence of kcnk10a using Rapid Amplification of cDNA Ends and localization in the zebrafish brain using in situ hybridization. Furthermore, we examined the gene expression differences of kcnk2b, kcnk10a and kcnk10b mRNA between genders as well as developmental stages by real-time PCR. The deduced amino acid sequence of the identified kcnk10a mRNA contains highly conserved two pore domains and four transmembrane regions and was higher similarity to zebrafish Kcnk10b than zebrafish Kcnk2a and 2b. kcnk10a mRNA was widely distributed in the brain such as the preoptic area, hypothalamus and the midbrain. kcnk10a mRNA expression exhibited significant difference between mature male and female, and increase during puberty. Kcnk10a could be involved in the regulation of reproductive function.
    Matched MeSH terms: Potassium Channels/metabolism*
  11. Hall DA, Ray J, Watson J, Sharman A, Hutchison J, Harris P, et al.
    Hear Res, 2019 06;377:153-166.
    PMID: 30939361 DOI: 10.1016/j.heares.2019.03.018
    AUT00063 is an experimental new medicine that has been demonstrated to suppress spontaneous hyperactivity by modulating the action of voltage-gated potassium-channels in central auditory cortical neurons of a rodent model. This neurobiological property makes it a good candidate for treating the central component of subjective tinnitus but this has not yet been tested in humans. The main purpose of the QUIET-1 (QUest In Eliminating Tinnitus) trial was to examine the effect of AUT00063 on the severity of tinnitus symptoms in people with subjective tinnitus. The trial was a randomised, placebo-controlled, observer, physician and participant blinded multi-centre superiority trial with two parallel groups and a primary endpoint of functional impact on tinnitus 28 days after the first drug dosing day. The trial design overcame the scale and logistical challenges of delivering a scientifically robust, statistically powered multi-centre study for subjective tinnitus within the National Health Service in England. The trial was terminated early for futility. Overall, 212 participants consented across 18 sites with 91 participants randomised to groups using age, gender, tinnitus symptom severity and hearing status as minimisation factors. While the pharmacokinetic markers confirm the uptake of AUT00063 in the body, within the expected therapeutic range, with respect to clinical benefit findings indicated that AUT00063 was not effective in alleviating tinnitus symptoms (1.56 point change in Tinnitus Functional Index). In terms of clinical harms, results indicated that a daily dose of 800 mg capsules of AUT00063 taken for 28 days was safe and well tolerated. These findings provide significant advances in the drug development field for hearing sciences, but raise questions about the predictive validity of certain rodent models of noise-induced hearing loss and tinnitus, as least for the mechanism evaluated in the present study. Trial Registration: (EudraCT) 2014-002179-27; NCT02315508.
    Matched MeSH terms: Shaw Potassium Channels/metabolism
  12. Zakaria ZA, Abdul Rahim MH, Roosli RAJ, Mohd Sani MH, Omar MH, Mohd Tohid SF, et al.
    Pain Res Manag, 2018;2018:9536406.
    PMID: 29686743 DOI: 10.1155/2018/9536406
    Methanolic extract of Clinacanthus nutans Lindau leaves (MECN) has been proven to possess antinociceptive activity that works via the opioid and NO-dependent/cGMP-independent pathways. In the present study, we aimed to further determine the possible mechanisms of antinociception of MECN using various nociceptive assays. The antinociceptive activity of MECN was (i) tested against capsaicin-, glutamate-, phorbol 12-myristate 13-acetate-, bradykinin-induced nociception model; (ii) prechallenged against selective antagonist of opioid receptor subtypes (β-funaltrexamine, naltrindole, and nor-binaltorphimine); (iii) prechallenged against antagonist of nonopioid systems, namely, α2-noradrenergic (yohimbine), β-adrenergic (pindolol), adenosinergic (caffeine), dopaminergic (haloperidol), and cholinergic (atropine) receptors; (iv) prechallenged with inhibitors of various potassium channels (glibenclamide, apamin, charybdotoxin, and tetraethylammonium chloride). The results demonstrated that the orally administered MECN (100, 250, and 500 mg/kg) significantly (p < 0.05) reversed the nociceptive effect of all models in a dose-dependent manner. Moreover, the antinociceptive activity of 500 mg/kg MECN was significantly (p < 0.05) inhibited by (i) antagonists of μ-, δ-, and κ-opioid receptors; (ii) antagonists of α2-noradrenergic, β-adrenergic, adenosinergic, dopaminergic, and cholinergic receptors; and (iii) blockers of different K+ channels (voltage-activated-, Ca2+-activated, and ATP-sensitive-K+ channels, resp.). In conclusion, MECN-induced antinociception involves modulation of protein kinase C-, bradykinin-, TRVP1 receptors-, and glutamatergic-signaling pathways; opioidergic, α2-noradrenergic, β-adrenergic, adenosinergic, dopaminergic, and cholinergic receptors; and nonopioidergic receptors as well as the opening of various K+ channels. The antinociceptive activity could be associated with the presence of several flavonoid-based bioactive compounds and their synergistic action with nonvolatile bioactive compounds.
    Matched MeSH terms: Potassium Channels/metabolism
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