ABSTRACT
Objective To investigate the role of c-Jun NH2-terminal kinase (c-JNK) signaling pathway on voltage-gated potassium channel (Kv) remodeling in left ventricular myocytes of diabetic rats,and explore the intrinsic regulatory mechanism.Methods Forty-five SD rats were randomly divided into DM group (n=25,modeling with streptozotocin induction) and control group (n=20,fed with normal diet).Transient outward potassium current (Ito) of rats' ventricular myocytes in DM group and control group was recorded by whole-cell patch-clamp method.The c-Jun activity was detected using a non-radioactive JNK kinase assay kit (Cell Signaling Technology).JNK inhibitor SP600125 was used to incubate the cardiomyocytes of diabetes rats in vitro,and then the changes of I,o in cardiomyocytes were observed.Thioredoxin reductase (TrxR) inhibitor--auranofin (AF) was used to treat the rats' cardiomyocytes incubated with SP600125,and then the changes of Ito in cardiomyocytes were observed.The content of Kv4.2 was tested using anti-Kv4.2 antibody,and the results were analyzed using a UVP bioimaging system.Results The JNK activity in DM group rose more than 1 times compared with control group,while the density of Ito decreased significantly (Control:30.2 ± 3.3pA/pF,n=16;DM:15.3 ± 2.1pA/pF,n=17;P＜0.05).The ventricular myocytes of DM rats were treated with SP600125 (10μmol/Lol/L) for 4 hours,then the Ito density increased to control group level (DM+SP600125:32.3 ± 3.7pA/pF,n=18;Control:30.2 ± 3.3pA/pF,n=16;P＜0.05).There was no significant difference in the maximum Ito density between the treated with SP600125 (Control+SP600125:31.6 ± 3.4pA/pF,n=18) and untreated control groups.The Ito density in DM myocardial cells significantly increased after treatment with the membrane permeable protein inhibitor JNKI-1 (10μmol/L),and no changes were found in control group after the same treatment.The augmentation effect of SP600125 on Ito current in DM myocytes was significantly inhibited by TrxR inhibitor auranofin (lμmol/L) (DM+SP600125+AF:15.7 ± 3.3pA/pF,n=15),while AF did not change the Ito density in control group.The expression of Kv4.2 protein was significantly increased in DM rats after administration of SP600125,which was consistent with the changes of Ito current observed in the myocardium of DM rats,although not fully restored to the level of control group myocardium.JNK inhibitor did not markedly alter the expression of Kv4.2 protein in control group myocardium.Conclusions Kv channel remodeling in DM rat's myocardium is redox-regulated,and the Ito remodeling might be assisted with the persistent activation of c-JNK signaling pathway.It has showed that c-JNK activity is significantly increased in DM rat heart and the current density of Kv channels is reduced.The inhibition of JNK signaling pathway can markedly improve Kv channel reconstruction and the process may be regulated by thioredoxin system.
ABSTRACT
Female gender is an independent risk factor for the development of torsade de pointes (TdP) arrhythmias not only in congenital long QT syndromes(LQTs)but also in acquired long QT syndromes. Clinical evidences imply that sex steroid hormones appear to play important roles in gender differences by affecting the cardiac repolarization process of action potential. This review summarizes the effects of sex hormones on cardiac ion channel currents and the effects of gender differences on drug-induced long QT syndromes, and reveals the mechanism of sex hormone induced arrhythmia by computer simulation
ABSTRACT
Both chronic obstructive pulmonary disease (COPD) and sudden cardiac death (SCD) are major health burdens.In conclusion,cumulating evidence associates COPD with an increased risk of SCD.First,it is found that asystole and pulseless electric activity(PEA)are more common than ventricular tachycardia/ventricular fibrillation(VT/VF)in deaths associated with COPD in studying interrelationship between COPD and ventricul ararrhythmias and cardiac arrest. The underlying mechanism explaining this association requires further investigation.Second,it is found that COPD is associated with a prolonged and shortened QT interval in studying the role of ECG markers between SCD and COPD.Finally,studies of the potential impact of respiratory treatment on the occurrence of SCD showed conflicting results.Accurate prediction of SCD in the general population is still a challenge. The risk assessment of SCD might be guided by studying the link between COPD and SCD.