Naringin exerts antiarrhythmic effects by inhibiting channel currents in mouse cardiomyocytes.

INTRODUCTION: Naringin, a flavonoid extracted from citrus plants, has a variety of biological effects. Studies have shown that increasing the consumption of flavonoid-rich foods can reduce the incidence of cardiac arrhythmia. Naringin has been reported to have beneficial cardiovascular effects and thus can be used to prevent cardiovascular diseases, but the electrophysiological mechanism through which it prevents arrhythmias has not been elucidated. This study was conducted to investigate the effect of naringin on the transmembrane ion channel currents in mouse ventricular myocytes and the antiarrhythmic effect of this compound on Langendorff-perfused mouse hearts. METHODS: Action potentials (APs) and ionic currents were recorded in isolated ventricular myocytes using the whole-cell patch-clamp technique. Anemone toxin II (ATX II) and CaCl2 were used to induce early afterdepolarizations (EADs) and delayed afterdepolarizations (DADs), respectively. Electrocardiogram (ECG) recordings were conducted in Langendorff-perfused mouse hearts with a BL-420F biological signal acquisition and analysis system. RESULTS: At the cellular level, naringin shortened the action potential duration (APD) of ventricular myocytes and decreased the maximum depolarization velocity (Vmax) of APs.Naringin inhibited the L-type calcium current (ICa.L) and ATX II enhanced the late sodium current (INa.L) in a concentration-dependent manner with IC50 values of 508.5 µmol/L (n = 9) and 311.6 µmol/L (n = 10), respectively. In addition, naringin also inhibited the peak sodium current (INa·P) and delayed the rectifier potassium current (IK) and the transient outward potassium current (Ito). Moreover, naringin reduced ATX II-induced APD prolongation and EADs and had a significant inhibitory effect on CaCl2-induced DADs as well. At the organ level, naringin reduced the incidence of ventricular tachycardia (VT) and ventricular fibrillation (VF) induced by ATX II and shortened the duration of both in isolated hearts. CONCLUSION: Naringin can inhibit the occurrence of EADs and DADs at the cellular level; furthermore, it can inhibit INa.L, ICa.L, INa·P, IK, and Ito in ventricular myocytes. Naringin also inhibits arrhythmias induced by ATX II in hearts. By investigating naringin with this electrophysiological method for the first time, we determined that this flavonoid may be a multichannel blocker with antiarrhythmic effects.

Eleutheroside B, a selective late sodium current inhibitor, suppresses atrial fibrillation induced by sea anemone toxin II in rabbit hearts.

Eleutheroside B (EB) is the main active constituent derived from the Chinese herb Acanthopanax senticosus (AS) that has been reported to possess cardioprotective effects. In this study we investigated the effects of EB on cardiac electrophysiology and its suppression on atrial fibrillation (AF). Whole-cell recording was conducted in isolated rabbit atrial myocytes. The intracellular calcium ([Ca2+]i) concentration was measured using calcium indicator Fura-2/AM fluorescence. Monophasic action potential (MAP) and electrocardiogram (ECG) synchronous recordings were conducted in Langendorff-perfused rabbit hearts using ECG signal sampling and analysis system. We showed that EB dose-dependently inhibited late sodium current (INaL), transient sodium current (INaT), and sea anemone toxin II (ATX II)-increased INaL with IC50 values of 167, 1582, and 181 µM, respectively. On the other hand, EB (800 µM) did not affect L-type calcium current (ICaL), inward rectifier potassium channel current (IK), and action potential duration (APD). Furthermore, EB (300 µM) markedly decreased ATX II-prolonged the APD at 90% repolarization (APD90) and eliminated ATX II-induced early afterdepolarizations (EADs), delayed afterdepolarizations (DADs), and triggered activities (TAs). Moreover, EB (200 µM) significantly suppressed ATX II-induced Na+-dependent [Ca2+]i overload in atrial myocytes. In the Langendorff-perfused rabbit hearts, application of EB (200 µM) or TTX (2 µM) substantially decreased ATX II-induced incidences of atrial fibrillation (AF), ventricular fibrillation (VF), and heart death. These results suggest that augmented INaL alone is sufficient to induce AF, and EB exerts anti-AF actions mainly via blocking INaL, which put forward the basis of pharmacology for new clinical application of EB.

Effect of vimentin on activation of NLRP3 inflammasome in the brain of mice with EV71 infection / 南方医科大学学报

<p><b>OBJECTIVE</b>To explore whether vimentin (VIM) mediates the activation of inflammasome in mice with EV71 infection in the central nervous system.</p><p><b>METHODS</b>Forty VIM knockout mice (VIM, 3 to 5 days old) were randomly divided into control group and infection group. The infection group was intraperitoneally injected with EV71 (10 TCID), while the control group was injected with PBS (10 µL); another 40 wild-type mice (WT, 3 to 5 days old) were grouped in the same manner. The general conditions of mice were observed each day. Western blotting, ELISA, and RT-PCR were used to measure the levels of IL-1β and casepase-1 in the brain or cerebrospinal fluid. The pathological changes in the cerebella and brain were observed using immunohistochemistry.</p><p><b>RESULTS</b>Compared with the control group, the VIM mice infected with EV71 showed no significant changes in NLRP3, IL-1β or caspase-1 expression. The WT mice infected with EV71 showed obviously increased NLRP3, IL-1β, and caspase-1 expressions in the central nervous system. The neurons of infected VIM mice exhibited milder cell damage than the those in WT mice.</p><p><b>CONCLUSION</b>VIM mediates the activation of inflammasome and promotes brain inflammation and neuronal damage in mice with EV71 infection in the central nervous system.</p>

Complete genomic sequence analysis on human enterovirus 71 strain in Guangzhou,in 2008 and 2010 / 中华流行病学杂志

Objective To study the genomic genotypes and variation of human enterovirus 71(EV71)infected infants in Guangzhou city,in 2008 and 2010.Methods Primers were designed on the basis of the genomic sequence of EV71 SHZH03 strain(AY465356)in the GenBank,and EV71genome amplified by RT-PCR.PCR-products were directly sequenced and the genomic nucleotide sequences were analyzed with the programs of Clustal W/X,DNASTAR and MEGA 4.1.Results 9strains of EV71 genome appeared to be 7405 bp in length.The genomic sequences of EV71Guangzhou strains were compared with those of EV71 in GenBank,which revealed that the homology with EV71 genotype C4a Fuyang strains ranged between 98%-99%.Homology with genotype C4b were 92%-94%,with genotypes C1,C2,C3 as 82%-83%,with genotypes B3,B4,B5 as 81%-83%and the homology with genotype A was 80%.When compared the VP1 genes of EV71 Guangzhou strains with genotypes A,B,C virus,we revealed that the highest homology was also with genotype C4a.When compared the VP1 amino acid sequences of EV71 Guangzhou strains with genotype A,B,C virus by Clustal W program,the results revealed that the amino acid residue Q at position 22 in VP1gene was transformed to H,while 213(S→T)and 1764(V→(Ⅰ))mutations in polyprotein were discovered.Conclusion Data from the sequences and phylogenetics analysis on those Guangzhou strains in 2008 and 2010 revealed that those isolates belong to genotype C4a,with the homology with Fuyang strains as 98%-99%.Mutation of amino acid residue H at position 22 in VP1 gene was discovered and the neutralizing antibody of EV71 might have been conversed by this residue.213(S→T)and 1764(V→Ⅰ)mutations in polyprotein were also discovered.

Etiology of hand, foot and mouth disease in Guangzhou in 2008 / 中华儿科杂志

<p><b>OBJECTIVE</b>To understand the etiology of hand, foot and mouth disease (HFMD) in Guangzhou area in 2008.</p><p><b>METHOD</b>Totally 1023 clinical specimens were collected from pediatric patients suspected of HFMD in 2008. TaqMan real-time RT-PCR were used for detection of enterovirus 71 (EV71), Coxsackievirus A16 (CA16) and other enteroviruses. The specimens which were enterovirus positive by RT-PCR method with universal primer but EV71 and CA16 negative, were amplified and sequenced for 5'untranslated region.</p><p><b>RESULT</b>Enterovirus was identified from 434 of 1023 samples and detection rate of enterovirus was 42.42%; of the 434 samples, 276 were positive for EV71 (63.6%), 126 for CA16 (29%), 4 samples for enterovirus 84, 3 for Echovirus 11, 2 for Echovirus 9, 3 for Coxsackievirus B3, 4 for Coxsackievirus A10, 3 for Coxsackievirus A6, 6 for Coxsackievirus A12 or A5, and for 7 samples typing was difficult.</p><p><b>CONCLUSION</b>The major causative agents of HFMD in Guangzhou were EV71 and CA16 in 2008, and EV84, CA10, CA12, CA6, COSB3, ECHV11, ECHV9 were also the pathogens for smaller proportions of patients.</p>

Molecular epidemiological study on norovirus among children with acute diarrhea in Guangzhou / 中华儿科杂志

<p><b>OBJECTIVE</b>To study molecular epidemiology of norovirus (NV) infections, stool specimens collected from children with acute diarrhea were tested by TaqMan real-time reverse transcription polymerase chain reaction (RT-PCR) for the viral specific nucleic acid segments.</p><p><b>METHODS</b>Fecal samples from a total of 1260 children who had watery diarrhea seen from December 2006 to December 2007 in Guangzhou were analyzed by real-time RT-PCR. The primers and probes used for rapid detection and typing of NV strain target NV sequences were at the ORF1-ORF2 junction, a highly conserved region of the NoV genome. The positive specimens were determined by nested PCR and sequenced.</p><p><b>RESULTS</b>Totally 257 specimens were positive for NV with a positive rate of 20.40%. Shedding of NV type GI was detected in 6.90%, type GII in 16.98% respectively, while the positive number of mixed infection with GI and GII was 44. Of the NV strains that were cloned and sequenced, GI was GI-3, GI-2 and GI-4 detected in positive specimens respectively; meanwhile, GII-4 was most commonly seen in genome II, followed by GII-3 and GII-7. In addition, the average age of children infected with NV was less than 2 years. An epidemic occurred during the winter and early spring (December through the next March).</p><p><b>CONCLUSION</b>NV was one of the important pathogens for acute diarrhea among children in Guangzhou, which suggested GII-4 was the prevalent strain.</p>

Cloning, expression and immunocharacterization of the capsid protein of human Norwalk virus Guangzhou strain NVgz01 / 南方医科大学学报

<p><b>OBJECTIVE</b>To clone, express and characterize the capsid protein of human Norwalk virus Guangzhou strain NVgz01.</p><p><b>METHODS</b>On the basis of successful construction of full-genome clones and sequence analysis of human norovirus Guangzhou strain NVgz01, the full capsid gene was ligated into pET28a (+) for expression. After IPTG induction, the recombinant protein was purified through metal (Ni(2+)) chelating affinity chromatography. Western blotting and enzyme-linked immunosorbent assay (ELISA) were used to determine the antigenicity of the recombinant protein.</p><p><b>RESULTS</b>The recombinant capsid gene was overexpressed in E.coli, yielding the recombinant protein with relative molecular mass of 62x10(3) that was highly purified through metal (Ni(2+)) chelating affinity chromatography. IDEIA Norovirus Kit and immunoassay showed that the recombinant protein had good antigenicity.</p><p><b>CONCLUSION</b>The capsid gene of norovirus Guangzhou strain has been cloned and expressed, which can be useful for developing diagnostic reagents or vaccine of norovirus.</p>