Astemizole, an inhibitor of ether-à-go-go-1 potassium channel, increases the activity of the tyrosine kinase inhibitor gefitinib in breast cancer cells

Abstract Background Expression and activity of the potassium channel ether-à-go-go-1 (EAG1) are strongly related to carcinogenesis and tumor progression, which can be exploited for therapeutic purposes. EAG1 activity may be reduced by preventing its phosphorylation with epidermal growth factor receptor (EGFR) kinase inhibitors and by astemizole, which blocks the channel pore and downregulates its gene expression. Objective We aimed to study the potential cooperative antiproliferative effect of the EGFR inhibitor gefitinib and the EAG1-blocker astemizole, in breast cancer cells. Materials and Methods The cells were characterized by immunocytochemistry. Inhibitory concentrations were determined by non-linear regression analysis using dose-response curves. The nature of the pharmacological effect was evaluated by the combination index equation while cell cycle analysis was studied by flow cytometry. Results Astemizole and gefitinib inhibited cell proliferation in a concentration-dependent manner, with inhibitory concentrations (IC 50) values of 1.72 µM and 0.51 µM, respectively. All combinations resulted in a synergistic antiproliferative effect. The combination of astemizole and gefitinib diminished the percentage of cells in G2/M and S phases, while increased accumulation in G0/G1 of the cell cycle. Conclusions Astemizole and gefitinib synergistically inhibited proliferation in breast cancer cells expressing both EGFR and EAG1. Our results suggest that the combined treatment increased cell death by targeting the oncogenic activity of EAG1.

Progress in research on defective protein trafficking and functional restoration in HERG-associated long QT syndrome / 中华医学遗传学杂志

The human ether-a-go-go related gene (HERG) encodes the α -subunit of the rapid component of the delayed rectifier K(+) channel, which is essential for the third repolarization of the action potential of human myocardial cells. Mutations of the HERG gene can cause type II hereditary long QT syndrome (LQT2), characterized by prolongation of the QT interval, abnormal T wave, torsade de pointes, syncope and sudden cardiac death. So far more than 300 HERG mutations have been identified, the majority of which can cause LQT2 due to HERG protein trafficking defect. It has been reported that certain drugs can induce acquired long QT syndrome through directly blocking the pore and/or affecting the HERG trafficking. The trafficking defects and K(+) currents can be restored with low temperature and certain drugs. However, the mechanisms underlying defective trafficking caused by HERG mutations and the inhibition/restoration of HERG trafficking by drugs are still unknown. This review summarizes the current understanding of the molecular mechanisms including HERG trafficking under physiological and pathological conditions, and the effects of drugs on the HERG trafficking, in order to provide theoretical evidence for the diagnosis and treatment of long QT syndrome.

Effects of midazolam on hERG K+ channel / 中国应用生理学杂志

<p><b>OBJECTIVE</b>To investigate the effect of midazolam on human ether-a-go-go (hERG) K+ channels exogenously expressed in human embryonic kidney cells (HEK-293) and the underlying molecular mechanisms.</p><p><b>METHODS</b>Whole-cell patch clamp technique was used to record WT, Y652A and F656C hERG K+ current expressed in HEK-293 cells.</p><p><b>RESULTS</b>Midazolam inhibited hERG K+ current in a concentration-dependent manner, the half-maximum block concentrations (IC50) values were (1.31 ± 0.32) µmol/L. The half-activation voltage (V1/2) were (2.32 ± 0.38) mV for the control and (-1.96 ± 0.83) mV for 1.0 µmol/L midazolam. The half-inactivation voltage (V1/2) was slightly shifted towards negative voltages from (-49.25 ± 0.69) mV in control to (-57.53 ± 0.53) mV after 1.0 µmol/L midazolam (P < 0.05). Mutations in drug-binding sites (Y652A or F656C) of the hERG channel significantly attenuated the hERG current blockade by midazolam.</p><p><b>CONCLUSION</b>Midazolam can block hERG K+ channel and cause the speed of inactivation faster. Mutations in the drug-binding sites (Y652 or F656) of the hERG channel were found to attenuate hERG current blockage by midazolam.</p>

Effects of allitridum on rapidly delayed rectifier potassium current in HEK293 cell line / 南方医科大学学报

<p><b>OBJECTIVE</b>To study the effect of allitridum on rapidly delayed rectifier potassium current (IKr) in HEK293 cell line.</p><p><b>METHODS</b>HEK293 cells were transiently transfected with HERG channel cDNA plasmid pcDNA3.1 via Lipofectamine. Allitridum was added to the extracellular solution by partial perfusion after giga seal at the final concentration of 30 µmol/L. Whole-cell patch clamp technique was used to record the HERG currents and gating kinetics before and after allitridum exposure at room temperature.</p><p><b>RESULTS</b>The amplitude and density of IHERG were both suppressed by allitridum in a voltage-dependent manner. In the presence of allitridum, the peak current of IHERG was reduced from 73.5∓4.3 pA/pF to 42.1∓3.6 pA/pF at the test potential of +50 mV (P<0.01). Allitridum also concentration-dependently decreased the density of the IHERG. The IC50 of allitridum was 34.74 µmol/L with a Hill coefficient of 1.01. Allitridum at 30 µmol/L caused a significant positive shift of the steady-state activation curve of IHERG and a markedly negative shift of the steady-state inactivation of IHERG, and significantly shortened the slow time constants of IHERG deactivation.</p><p><b>CONCLUSION</b>Allitridum can potently block IHERG in HEK293 cells, which might be the electrophysiological basis for its anti-arrhythmic action.</p>

Expression of human ether-a-go-go-related gene in laryngeal carcinoma / 临床耳鼻咽喉头颈外科杂志

OBJECTIVE@#To study the expression of human ether-α-go-go-related gene (herg) and hERG protein expressed by the gene in laryngeal carcinoma compared with the control group(mucosa adjacent to cancer of 2 cm).@*METHOD@#Expression of herg and hERG protein was detected by immunohistochemistry (SP) and real-time PCR in resected tissue of laryngeal carcinoma and mucosa adjacent to cancer of 2 cm.@*RESULT@#(1) By immunohistochemistry, the positive expression rate of hERG in laryngeal carcinoma was 76.7% (23/30), while it was 10.0% (2/20) in mucosa adjacent to cancer of 2 cm, the difference between which was statistically significant (P < 0.05). (2) By real-time PCR, the expression level of herg mRNA in laryngeal carcinoma is 2.25 times higher than that in mucosa adjacent to cancer of 2 cm.@*CONCLUSION@#Herg is highly expressed in tissue of laryngeal carcinoma, and it may be have some relevance to the happening and development of laryngeal carcinoma.

Clinical characteristics of patients with congenital long QT syndrome and bigenic mutations / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Congenital long QT syndrome (LQTS) is an ion channelopathy associated with genetic mutations. It is well known that most LQTS patients (91%) have a single mutation. The purpose of this study was to investigate the clinical characteristics of congenital LQTS patients with bigenic mutations in Taiwan, China.</p><p><b>METHODS</b>Congenital LQTS patients were recruited consecutively at Taiwan University Hospital in Taiwan from 2003 to 2009. The diagnosis of LQTS was defined by an LQTS Schwartz score greater than 4. Mutation screening in KCNQ1, KCNH2, KCNE1, and SCN5A was performed using direct sequencing.</p><p><b>RESULTS</b>Three of 16 LQTS patients (18.7%) were identified with bigenic mutations. One patient had missense mutations in KCNQ1 and KCNH2, the second in KCNQ1 and KCNE1, and the third in KCNH2 and SCN5A. The mean age at onset of LQTS for patients with bigenic mutations was (17 ± 3) years, and all of these patients were female. Two of them experienced seizure and one presented with syncope, although one of them had a family history of syncope. The mean QTc interval was (515 ± 17) ms, similar to those with single mutation or SNPs ((536 ± 74) ms, P = 0.63). Compared to those LQTS patients with single mutation or SNPs, a significantly higher percentage of LQTS patients with bigenic mutations presented with seizure and were younger at onset of the first index event (P = 0.03 and 0.001, respectively), but lower percentage of them presented with sudden cardiac death (P = 0.03).</p><p><b>CONCLUSIONS</b>Although the percentage of bigenic mutations in LQTS is less than 10% in Caucasian populations, we identified 3 of 16 LQTS patients (18.7%, 95% confidence interval: 0.04-0.46) with bigenic mutations in Taiwan. However, the severity of their clinical presentations was not higher than those patients with single mutation or SNPs.</p>

Construction of pcDNA3-HERG-G572R expression vector and establishment of a cell line stably expressing HKE-HERG-G572R / 南方医科大学学报

<p><b>OBJECTIVE</b>To construct the pcDNA3-HERG-G572R expression vector and establish a cell line stably expressing HKE-HERG-G572R.</p><p><b>METHODS</b>HERG-G572R mutant fragment was constructed by over-lap extension PCR and validated by DNA sequencing. The HKE-HERG-G572R expression vector was constructed and transfected into HEK293 cells to obtain a cell line stably expressing HKE-HERG-G572R.</p><p><b>RESULTS</b>The pcDNA3-HERG-G572R expression vector was successfully constructed and the cell line stably expressing HKE-HERG-G572R was established. Real-time PCR and Western blotting revealed a 632-fold HKE-HERG-G572R overexpression in the transfected HEK293 cells as compared with that in control HEK293 cells transfected with pcDNA3 (P<0.01).</p><p><b>CONCLUSION</b>The protocol can be used to construct the cell line stably expressing HKE-HERG-G572R to provide a cell model for studying individualized therapy.</p>

Protein tyrosine phosphatase non-receptor type 12 negatively regulates cardiac HERG channel currents / 南方医科大学学报

<p><b>OBJECTIVE</b>To study the effect of protein tyrosine phosphatase non-receptor type 12 (PTPN12) in regulating cardiac HERG channel currents.</p><p><b>METHODS</b>The plasmids pcDNA3.1-PTPN12-RFP and herg mutant constructed by PCR technique were transfected into HEK293 cells via Lipofectamine 2000, and the cells stably expressing PTPN12 selected with G418 were identified by Western blotting with anti-PTPN12 antibody. HERG channel current in cells expressing HERG alone (HEK293/HERG cells), cells overexpressing PTPN12 (HEK293/HERG cells transfected with pCDNA3.1-PTPN12-RFP), PAO-treated cells (PTPN12/HERG cells treated with PAO), and herg mutant cells (HEK293/HERGY327A-Y700A-Y845A cells transfected with pcDNA3.1-PTPN12-RFP) were recorded by patch-clamp technique.</p><p><b>RESULTS</b>The plasmids pcDNA3.1-PTPN12-RFP and herg mutant were successfully constructed, and the stable expressing cell lines were established. Red fluorescence was obversed in HEK293/HERG cells transfected with pcDNA3.1-PTPN12-RFP, and the protein expression of PTPN12 was detected. Overexpression of PTPN12 significantly decreased HERG current density in HEK293/HERG cells, and this change was significantly weakened in the inhibitor group and herg mutant group.</p><p><b>CONCLUSION</b>PTPN12 negatively regulates cardiac HERG channel cerrent possibly by decreasing the phosphorylation level of HERG tyrosine residues. This finding provides further insight into the regulatory mechanism of HERG channel and the pathogenesis of long QT syndrome.</p>

Expression of Eag1 K(+) channel in prostate cancer and its significance / 中华男科学杂志

<p><b>OBJECTIVE</b>To investigate the expression of the Eag1 K( +) channel in the prostate cancer (PCa) tissue, its correlation with the development and progression of PCa, and whether it could be a target for the diagnosis and treatment of PCa.</p><p><b>METHODS</b>We used RT-PCR and immunohistochemistry to determine the mRNA and protein expressions of the Eag1 K(+) channel in the normal peritumoral tissue of androgen-dependent PCa (ADPCa) (group A) and androgen-independent PCa (AIPCa) (group B) as well as in the tumorous tissue of ADPCa (group C) and AIPCa (group D).</p><p><b>RESULTS</b>The relative coefficients of the mRNA expression of the Eag1 K(+) channel were 0.265 +/- 0.413, 0.167 +/- 0.511, 2.673 +/- 2.988 and 2.815 +/- 2.901 in groups A, B, C and D, respectively, increased significantly in the latter two groups (P < 0.05). The positive rates of the protein expression of the Eag1 K (+) channel were significantly higher in groups C (88.9%) and D (86.7%) than in A (7.4%) and B (6.7%) (P < 0.05).</p><p><b>CONCLUSION</b>The Eag1 K(+) channel might be involved in the pathophysiological processes of PCa, and is expected to be a valuable target for the diagnosis and treatment of PCa.</p>

A novel deletion-frameshift mutation in the S1 region of HERG gene in a Chinese family with long QT syndrome / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>The congenital Long QT syndrome (LQTS) is a hereditary cardiac channelopathy that is characterized by a prolonged QT interval, syncope, ventricular arrhythmias, and sudden death. The chromosome 7-linked type 2 congenital LQTS (LQT2) is caused by gene mutations in the human ether-a-go-go-related gene (HERG).</p><p><b>METHODS</b>A Chinese family diagnosed with LQTS were screened for KCNQ1, HERG and SCN5A, using polymerase chain reaction (PCR), direct sequencing, and clong sequencing. We also investigated the mRNA expression of the HERG gene.</p><p><b>RESULTS</b>We identified a novel I414fs + 98X mutation in the HERG gene. The deletion mutation of 14-bp in the first transmembrane segment (S1) introduced premature termination codons (PTCs) at the end of exon 6. This mutation would result in a serious phenotype if the truncated proteins co-assembled with normal subunit to form the defective channels. But only the proband was symptomatic.</p><p><b>CONCLUSIONS</b>We found that the mRNA level of the HERG gene was significantly lower in I414fs + 98X carriers than in noncarriers. We found a novel I414fs + 98X mutation. The mRNA level supports that NMD mechanism might regulate the novel mutation.</p>

Genetic Mutation in Korean Patients of Sudden Cardiac Arrest as a Surrogating Marker of Idiopathic Ventricular Arrhythmia

Mutation or common intronic variants in cardiac ion channel genes have been suggested to be associated with sudden cardiac death caused by idiopathic ventricular tachyarrhythmia. This study aimed to find mutations in cardiac ion channel genes of Korean sudden cardiac arrest patients with structurally normal heart and to verify association between common genetic variation in cardiac ion channel and sudden cardiac arrest by idiopathic ventricular tachyarrhythmia in Koreans. Study participants were Korean survivors of sudden cardiac arrest caused by idiopathic ventricular tachycardia or fibrillation. All coding exons of the SCN5A, KCNQ1, and KCNH2 genes were analyzed by Sanger sequencing. Fifteen survivors of sudden cardiac arrest were included. Three male patients had mutations in SCN5A gene and none in KCNQ1 and KCNH2 genes. Intronic variant (rs2283222) in KCNQ1 gene showed significant association with sudden cardiac arrest (OR 4.05). Four male sudden cardiac arrest survivors had intronic variant (rs11720524) in SCN5A gene. None of female survivors of sudden cardiac arrest had SCN5A gene mutations despite similar frequencies of intronic variants between males and females in 55 normal controls. Common intronic variant in KCNQ1 gene is associated with sudden cardiac arrest caused by idiopathic ventricular tachyarrhythmia in Koreans.

Single Nucleotide Deletion Mutation of KCNH2 Gene is Responsible for LQT Syndrome in a 3-Generation Korean Family

Long QT syndrome (LQTS) is characterized by the prolongation of the QT interval in ECG and manifests predisposition to life threatening arrhythmia which often leads to sudden cardiac death. We encountered a 3-generation family with 5 affected family members in which LQTS was inherited in autosomal dominant manner. The LQTS is considered an ion channel disorder in which the type and location of the genetic mutation determines to a large extent the expression of the clinical syndrome. Upon screening of the genomic sequences of cardiac potassium ion channel genes, we found a single nucleotide C deletion mutation in the exon 3 of KCNH2 gene that co-segregates with the LQTS in this family. This mutation presumably resulted in a frameshift mutation, P151fs+15X. This study added a new genetic cause to the pool of mutations that lead to defected potassium ion channels in the heart.

Effect of berberine, liensinine and neferine on HERG channel expression / 中国中药杂志

<p><b>OBJECTIVE</b>Immunofluorescence and Western blot methods were adopted for qualitative and quantitative detections of the effect of different concentrations of berberine, liensinine and neferine on the expression of stable transfection in HERG potassium channel in HEK-293 cells, as well as the effect of different concentrations of berberine on protein expression of Ikr channel in cardiac muscular tissues, in order to investigate the anti-arrhythmic mechanism of berberine, liensinine and neferine.</p><p><b>METHOD</b>Western blot method was used to detect protein expression of HERG channel in HERG-HEK cells. Immunofluorescence method as well as confocal laser microscope were used to detect the effect of different concentrations of berberine, liensinine and neferine on protein expression of HERG channel. Western blot method was used to detect the effect of different concentrations of berberine on protein expression of Ikr channel in cardiac muscular tissues as well as the effect of berberine, liensinine and neferine on protein expression of stable transfection in HERG potassium channel in HEK-293 cells.</p><p><b>RESULT</b>Western blot experiment manifested that stable transfection of HEK293 cells containing HERG genes could increase protein expression of HERG channel. Berberine (10, 30 micromol x L(-1)) remarkably inhibited protein expression of HERG channel in HERG-HEK cells (P < 0.01). Berberine (10, 20 mg x kg(-1)) also inhibited protein expression of Ikr channel in rat ventricular tissues (P < 0.05). Liensinine (3, 10, 30 micromol x L(-1)) increased protein expression of HERG channel in HERG-HEK cells (P < 0.05). Neferine showed no effect on protein expression of HERG channel in HERG-HEK cells.</p><p><b>CONCLUSION</b>The stably transfection of HERG-HEK cells can increase protein expression of HERG channel. Berberine shows inhibitory effect on protein expressions of in vitro HERG-HEK cells and Ikr channel in rat ventricular tissues. Liensinine improves protein expression of HERG channe in HERG-HEK cells. Neferine shows no effect on protein expression of HERG channel.</p>

Frequency- and state-dependent blockade of human ether-a-go-go-related gene K+ channel by arecoline hydrobromide / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>The rapidly activating delayed rectifier potassium current (I(Kr)), whose pore-forming alpha subunit is encoded by the human ether-a-go-go-related gene (hERG), is a key contributor to the third phase of action potential repolarization. The aim of this study was to investigate the effect and mechanism of arecoline hydrobromide induced inhibition of hERG K(+) current (I(hERG)).</p><p><b>METHODS</b>Transient transfection of hERG channel cDNA plasmid pcDNA3.1 into the cultured HEK293 cells was performed using Lipofectamine. A standard whole-cell patch-clamp technique was used to record the I(hERG) before and after the exposure to arecoline.</p><p><b>RESULTS</b>Arecoline decreased the amplitude and the density of the I(hERG) in a concentration-dependent manner (IC(50) = 9.55 mmol/L). At test potential of +60 mV, the magnitude of I(hERG) tail at test pulse of -40 mV was reduced from (151.7 ± 6.2) pA/pF to (84.4 ± 7.6) pA/pF (P < 0.01, n = 20) and the magnitude of I(hERG) tail at test pulse of -110 mV was reduced from (-187.5 ± 9.8) pA/pF to (-97.6 ± 12.6) pA/pF (P < 0.01, n = 20). The blockade of arecoline in the open and inactivated state was significant in a state-dependent manner. The maximal blockade was achieved in the inactivated state. Studies of gating mechanism showed that the steady-state activation curve of I(hERG) was significantly negatively shifted by arecoline. Time constants of activation were shortened. Steady-state inactivation curve and time constants of fast inactivation were not significantly affected by arecoline. Furthermore, the inhibition of I(hERG) by arecoline was characterized markedly by a frequency-dependent manner from 0.03 to 1.00 Hz pulse.</p><p><b>CONCLUSION</b>Arecoline could potently block I(hERG) in both frequency and state-dependent manner.</p>

KCNQ1, KCNH2, KCNE1 and KCNE2 potassium channels gene variants in sudden manhood death syndrome / 法医学杂志

OBJECTIVE@#To investigate KCNQ1, KCNH2, KCNE1 and KCNE2 gene variants in the cases of sudden manhood death syndrome (SMDS).@*METHODS@#One hundred and sixteen sporadic cases of SMDS and one hundred and twenty-five healthy controlled samples were enrolled. Genomic DNA was extracted from blood samples. Gene variants of KCNQ1, KCNH2, KCNE1 and KCNE2 were screened by direct sequencing.@*RESULTS@#A total of 14 mutations and 14 SNP were detected. Two non-synonymous mutations of them were newfound. There was no non-synonymous mutation found in the control group.@*CONCLUSION@#There are KCNQ1, KCNH2, KCNE1 and KCNE2 gene variants found in Chinese SMDS cases. KCNQ1, KCNH2, KCNE1 and KCNE2 gene mutation may correlate partly with the occurrence of some cases of the SMDS in China.

Investigação de variantes gênicas de canais iônicos em pacientes com síndrome do QT longo / Investigation of ion channel gene variants in patients with long QT syndrome / Investigación de variantes génicas de canales iónicos en pacientes con síndrome del QT largo

FUNDAMENTO: A síndrome do QT longo (SQTL) é uma síndrome arrítmica herdada com aumento do intervalo QT e risco de morte súbita. Mutações nos genes KCNQ1, KCNH2 e SCN5A respondem por 90 por cento dos casos com genótipo determinado, e a genotipagem é informativa para aconselhamento genético e melhor manejo da doença. OBJETIVO: Investigação molecular e análise computacional de variantes gênicas de KCNQ1, KCNH2 e SCN5A associadas à SQTL em famílias portadoras da doença. MÉTODOS: As regiões codificantes dos genes KCNQ1, KCNH2 e SCN5A de pacientes com SQTL e familiares foram sequenciadas e analisadas utilizando o software Geneious ProTM. RESULTADOS: Foram investigadas duas famílias com critérios clínicos para SQTL. A probanda da Família A apresentava QTC = 562 ms, Escore de Schwartz = 5,5. A genotipagem identificou a mutação G1714A no gene KCNH2. Foi observado QTC = 521 ± 42 ms nos familiares portadores da mutação contra QTC = 391 ± 21 ms de não portadores. A probanda da Família B apresentava QTc = 551 ms, Escore de Schwartz = 5. A genotipagem identificou a mutação G1600T, no mesmo gene. A análise dos familiares revelou QTC = 497 ± 42 ms nos portadores da mutação, contra QTC = 404 ± 29 ms nos não portadores. CONCLUSÃO: Foram encontradas duas variantes gênicas previamente associadas à SQTL em duas famílias com diagnóstico clínico de SQTL. Em todos os familiares portadores das mutações foi observado o prolongamento do intervalo QT. Foi desenvolvida uma estratégia para identificação de variantes dos genes KCNQ1, KCNH2 e SCN5A, possibilitando o treinamento de pessoal técnico para futura aplicação na rotina diagnóstica.

BACKGROUND: The long QT syndrome (LQTS) is an inherited arrhythmia syndrome with increased QT interval and risk of sudden death. Mutations in genes KCNQ1, KCNH2 and SCN5A account for 90 percent of cases with genotype determined, and genotyping is informative for genetic counseling and better disease management. OBJECTIVE: Molecular investigation and computational analysis of gene variants of KCNQ1, KCNH2 and SCN5A associated with LQTS, in families with the disease. METHODS: The coding regions of genes KCNQ1, KCNH2 and SCN5A in patients with LQTS and their family members were sequenced and analyzed using Geneious ProTM software. RESULTS: Two families with clinical criteria for LQTS were investigated. The proband of Family A had QTC = 562 ms, Schwartz Score = 5.5. The genotyping identified the G1714A mutation in the KCNH2 gene. QTC = 521 ± 42 ms was observed in family members carrying the mutation against QTC = 391 ± 21 ms for non-carriers. The proband of Family B had QTc = 551 ms, Schwartz Score = 5.5. The genotyping identified the G1600T mutation, in the same gene. The analysis of family members revealed QTC = 497 ± 42 ms in mutation carriers, compared with QTC = 404 ± 29 ms in non-carriers. CONCLUSION: Two gene variants previously associated with LQTS were found in two families clinically diagnosed with LQTS. The prolongation of the QT interval was observed in all family members carrying the mutations. A strategy was developed to identify variants of genes KCNQ1, KCNH2 and SCN5A, making it possible to train technical staff for future application to diagnosis routine.

FUNDAMENTO: El síndrome del QT largo (SQTL) es un síndrome arrítmico heredado con aumento del intervalo QT y riesgo de muerte súbita. Mutaciones en los genes KCNQ1, KCNH2 y SCN5A responden por 90 por ciento de los casos con genotipo determinado, y el genotipaje es informativo para aconsejamiento genético y mejor manejo de la enfermedad. OBJETIVO: Investigación molecular y análisis computacional de variantes génicas de KCNQ1, KCNH2 y SCN5A asociadas a la SQTL en familias portadoras de la enfermedad. MÉTODOS: Las regiones codificantes de los genes KCNQ1, KCNH2 y SCN5A de pacientes con SQTL y familiares fueron secuenciadas y analizadas utilizando el software Geneious Pro®. RESULTADOS: Fueron investigadas dos familias con criterios clínicos para SQTL. La probanda de la Familia A presentaba QT C = 562 ms, Escore de Schwartz = 5,5. El genotipaje identificó la mutación G1714A en el gen KCNH2. Fue observado QT C = 521 ± 42 ms en los familiares portadores de la mutación contra QT C = 391 ± 21 ms de no portadores. La probanda de la Familia B presentaba QT C = 551 ms, Escore de Schwartz = 5. El genotipaje identificó la mutación G1600T, en el mismo gen. El análisis de los familiares reveló QT C = 497 ± 42 ms en los portadores de la mutación, contra QT C = 404 ± 29 ms en los no portadores. CONCLUSIÓN: Fueron encontradas dos variantes génicas previamente asociadas a la SQTL en dos familias con diagnóstico clínico de SQTL. En todos los familiares portadores de las mutaciones fue observada la prolongación del intervalo QT. Fue desarrollada una estrategia para identificación de variantes de los genes KCNQ1, KCNH2 y SCN5A, posibilitando el entrenamiento de personal técnico para futura aplicación en la rutina diagnóstica.

Lidamycin inhibits the proliferation of HERG K+ channel highly expressing cancer cells and shows synergy with anticancer drugs / 药学学报

This study is to investigate inhibitory effects of lidamycin (LDM) on the proliferation of HERG K+ channel highly expressing cancer cells and its synergy with anticancer drugs. MTT assay was used to examine the inhibitory effects of lidamycin combined with various anticancer drugs on the proliferation of human lung cancer A549 cells, human colon cancer HT-29 cells and herg-stably-transfected A549 cells. Using the xenograft model of subcutaneously transplanted HT-29 in nude mice, inhibitory effect was appraised in vivo. The coefficient of drug interaction (CDI) was used to evaluate the synergistic effect of drug combination. LDM significantly inhibited the proliferation ofA549 cells and HT-29 cells with IC50 values of 2.14 and 4.64 ng mL(-1), respectively. The efficacy in HT-29 cells with high HERG potassium expression level is less potent than that in A549 cells with low expression level. In terms of IC50 values, LDM suppressed the growth of herg-stably-transfected A549 cells less potently than pCDNA3.1-stably-transfected A549 cells. There existed synergistic effects in the combinations of fluorouracil (5-FU) and LDM, doxorubicin (DOX) and LDM, or hydroxycamptothecine (HCPT) and LDM. CDI values of the combinations of 5-FU and LDM were more than 0.75. CDI values of LDM and DOX were more than 0.70, but some CDI values of LDM and HCPT were less than 0.70. As for the CDI values, synergistic effects of the combination of LDM and HCPT were the most potent of the three groups. There is no relationship between the inhibitory effect of the growth of cancer cells by 5-FU and HERG potassium expression level. HERG expression level negatively correlated with inhibitory effect on the proliferation of cancer cells by DOX. HERG expression levels and chemosensitivity were positively correlated for HCPT. In the model of subcutaneously xenograft transplanted HT-29 in vivo, LDM and/or HCPT effectively inhibited the growth of HT-29 in nude mice, and the optimum CDI of the combination of LDM and HCPT was less than 1. HERG expression level negatively correlates the chemosensitivity of cancer cells to LDM. There exist synergistic effects in vitro and in vivo in the combination of LDM and HCPT, which inhibitory effects of the proliferation of cancer cells positively modulated by HERG potassium expression level. HERG K+ channel may become a target of combined therapy for choosing anticancer drugs.

Effect of matrine on human ether à go-go related gene (HERG) channels expressed in Chinese hamster ovary cells / 中国结合医学杂志

<p><b>OBJECTIVE</b>To observe the effect of matrine on human ether à go-go related gene (HERG) potassium channels expressed in Chinese hamster ovary (CHO) cells and investigate whether HERG channel is a new target of the pharmacological effect of matrine on arrhythmia and tumor</p><p><b>METHODS</b>HERG channel potassium current in CHO cell was recorded using whole-cell patch-clamp technique, and the influence of matrine on the current was explored.</p><p><b>RESULTS</b>Matrine inhibited HERG potassium current in a dose-dependent manner, and the 50% inhibitory concentration (IC IC(50)) was 411±23 μmol/L. Matrine had no significant effect on the activation kinetics, and mainly blocked HERG channels in their closed state.</p><p><b>CONCLUSIONS</b>The blocking effect of matrine on HERG channels might be one of the mechanisms against arrythmias and tumors. Unlike most other blockers exerting blocking effect at the intracellular sites by entering the cell with the opening of HERG channel, matrine blocked HERG channels at the extracellular sites.</p>

A novel mutation of the KCNH2 gene in a family with congenital long QT syndrome / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To perform mutation analysis in a family with long QT syndrome.</p><p><b>METHODS</b>The medical record of the affected child and his parents were collected. The locus of gene associated with the long QT syndrome was mapped by linkage analysis. Mutation analysis was done by PCR-single strand conformation polymorphism (SSCP) and direct sequencing.</p><p><b>RESULTS</b>A mutation (L539fs/47) and a SNP (L564L) were found in exon 7 of the KCNH2 gene of the proband. The mutation was from the father.</p><p><b>CONCLUSION</b>A novel mutation of L539fs/47 in the KCNH2 gene was identified in the LQTS family, which might be the disease-causing mutation for the family.</p>

Chinfloxacin hydrochloride inhibits HERG potassium channel at open state / 药学学报

This study is designed to investigate the effects of chinfloxacin hydrochloride (CFX) on the kinetics of HERG K+ channel. Whole cell patch clamp technique was used to record HERG K+ currents from HEK293 cells transiently transfected with cgi-HERG-GFP plasmids and channel kinetics were assessed in the absence and presence of CFX and moxifloxacin hydrochloride (MOX). Results demonstrated that the open state of HERG K+ channel was inhibited by CFX in a concentration- and time-dependent manner, with an IC50 of 162.1 +/- 14.2 micromol x L(-1), two folds higher than its positive control MOX. But there were no significant effects on channel kinetics. In addition, the inhibitory effect of CFX on HERG was enhanced when cells were subjected to altered extracellular K+ concentration.