Emerging therapeutic targets in the short QT syndrome

Introduction: Short QT Syndrome (SQTS) is a rare but dangerous condition characterised by abbreviated repolarisation, atrial and ventricular arrhythmias and risk of sudden death. Implantable cardioverter defibrillators (ICDs) are a first line protection against sudden death, but adjunct pharmacology is beneficial and desirable.

Areas covered: The genetic basis for genotyped SQTS variants (SQT1-SQT8) and evidence for arrhythmia substrates from experimental and simulation studies are discussed. The main ion channel/transporter targets for antiarrhythmic pharmacology are considered in respect of potential genotype-specific and non-specific treatments for the syndrome.

Expert opinion: Potassium channel blockade is valuable for restoring repolarisation and QT interval, though genotype-specific limitations exist in the use of some K⁺ channel inhibitors. A combination of K⁺ current inhibition during the action potential plateau, with sodium channel inhibition that collectively result in delaying repolarisation and post-repolarisation refractoriness is likely to be valuable in prolonging effective refractory period and wavelength for re-entry. Genotype-specific K⁺ channel inhibition is limited by a lack of targeted inhibitors in clinical use, though experimentally available selective inhibitors now exist. The relatively low proportion of successfully genotyped cases justifies an exome or genome sequencing approach, to reveal new mediators and targets, as demonstrated recently for SLC4A3 in SQT8.     

Synthesis and Biological Evaluation of Pyrazolo[1,5-a]pyrimidine Compounds as Potent and Selective Pim-1 Inhibitors

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Genome sequencing in a genetically elusive multigenerational long QT syndrome pedigree identifies a novel LQT2-causative deeply intronic KCNH2 variant

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Investigation of Cardiovascular Effects of Tetrahydro-β-carboline sstr3 antagonists

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药物对hERG钾通道作用机制研究进展

人ether-a-go-go-related gene(hERG)钾通道表达了延迟整流钾电流的快激活成分,对动作电位的复极至关重要。hERG钾电流不仅是抗心律失常作用的主要靶点,也是诸多药物增加尖端扭转型室速和心源性猝死风险的关键位点,而该电流的降低和(或)升高与基因突变或药物阻滞作用密切相关。随着对药物与hERG钾通道相互作用机制研究的深入,药物与通道孔道区蛋白结合位点的作用及其对通道转运的影响逐步被揭示,但这些药物对hERG作用的临床应用仍有待评价。     

A selective blocker of Kv1.2 and Kv1.3 potassium channels from the venom of the scorpion Centruroides suffusus suffusus

A novel potassium channel blocker peptide was purified from the venom of the scorpion Centruroides suffusus suffusus by high-performance liquid chromatography and its amino acid sequence was completed by Edman degradation and mass spectrometry analysis. It contains 38 amino acid residues with a molecular weight of 4000.3 Da, tightly folded by three disulfide bridges. This peptide, named Css20, was shown to block preferentially the currents of the voltage-dependent K⁺-channels Kv1.2 and Kv1.3. It did not affect several other ion channels tested at 10 nM concentration. Concentration-response curves of Css20 yielded an IC50 of 1.3 and 7.2 nM for Kv1.2- and Kv1.3-channels, respectively. Interestingly, despite the similar affinities for the two channels the association and dissociation rates of the toxin were much slower for Kv1.2, implying that different interactions may be involved in binding to the two channel types; an implication further supported by in silico docking analyses. Based on the primary structure of Css20, the systematic nomenclature proposed for this toxin is α-KTx 2.13.     

Synthesis and pharmacological evaluation of a potent and selective σ1 receptor antagonist with high antiallodynic activity

Based on the pharmacophore model of Glennon the conformationally restricted σ(1) receptor ligand 2 with a 1,3-dioxane moiety has been designed and synthesized. The three step synthesis (transacetalization with pentane-1,3,5-triol, tosylation, and nucleophilic substitution with benzylamine) provided diastereoselectively the cis-configured 1,3-dioxane 2 in good yields. The 1,3-dioxane 2 represents a potent σ(1) receptor ligand (K(i) = 19 nM) with moderate selectivity over the σ(2) subtype (K(i) = 92 nM) and excellent selectivity against more than 60 other targets. Additionally the hERG K(+) channel is not affected by 2. In the capsaicin assay 2 showed extraordinarily high analgesic activity with more than 70% analgesia at the very low dose of 0.25 mg/kg body weight, which indicates σ(1) antagonistic activity. Since 2 does only interact with σ(1) receptors, the in-vivo antiallodynic activity of 2 must be attributed to the σ(1) antagonistic activity.     

Mitigating hERG Inhibition: Design of Orally Bioavailable CCR5 Antagonists as Potent Inhibitors of R5 HIV-1 Replication

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A single hERG mutation underlying a spectrum of acquired and congenital long QT syndrome phenotypes

The long QT syndrome (LQTS) is a multi-factorial disorder that predisposes to life-threatening arrhythmias. Both hereditary and acquired subforms have been identified. Here, we present clinical and biophysical evidence that the hERG mutation c.1039 C > T (p.Pro347Ser or P347S) is responsible for both the acquired and the congenital phenotype. In one case the genotype remained silent for years until the administration of several QT-prolonging drugs resulted into a full-blown phenotype, that was reversible upon cessation of these compounds. On the other hand the mutation was responsible for a symptomatic congenital LQTS in a Dutch family, displaying a substantial heterogeneity of the clinical symptoms. Biophysical characterization of the p.Pro347Ser potassium channels using whole-cell patch clamp experiments revealed a novel pathogenic mechanism of reciprocal changes in the inactivation kinetics combined with a dominant-negative reduction of the functional expression in the heterozygous situation, yielding a modest genetic predisposition for LQTS. Our data show that in the context of the multi-factorial aetiology underlying LQTS a modest reduction of the repolarizing power can give rise to a spectrum of phenotypes originating from one mutation. This observation increases the complexity of genotype-phenotype correlations in more lenient manifestations of the disease and underscores the difficulty of predicting the expressivity of the LQTS especially for mutations with a more subtle impact such as p.Pro347Ser.