Chlorogenic acid alters the voltage-gated potassium channel currents of trigeminal ganglion neurons

Chlorogenic acid（5-caffeoylquinic acid, CGA） is a phenolic compound that is found ubiquitously in plants, fruits and vegetables and is formed via the esterification of caffeic acid and quinic acid. In addition to its notable biological functions against cardiovascular diseases, type-2 diabetes and inflammatory conditions, CGA was recently hypothesized to be an alternative for the treatment of neurological diseases such as Alzheimer＇s disease and neuropathic pain disorders. However, its mechanism of action is unclear.Voltage-gated potassium channel（Kv） is a crucial factor in the electro-physiological processes of sensory neurons. Kv has also been identified as a potential therapeutic target for inflammation and neuropathic pain disorders. In this study, we analysed the effects of CGA on the two main subtypes of Kv in trigeminal ganglion neurons, namely, the IK,Aand IK,Vchannels. Trigeminal ganglion（TRG）neurons were acutely disassociated from the rat TRG, and two different doses of CGA（0.2 and 1 mmol·L21） were applied to the cells.Whole-cell patch-clamp recordings were performed to observe alterations in the activation and inactivation properties of the IK,Aand IK,Vchannels. The results demonstrated that 0.2 mmol·L21CGA decreased the peak current density of IK,A. Both 0.2 mmol·L21and1 mmol·L21CGA also caused a significant reduction in the activation and inactivation thresholds of IK,Aand IK,V. CGA exhibited a strong effect on the activation and inactivation velocities of IK,Aand IK,V. These findings provide novel evidence explaining the biological effects of CGA, especially regarding its neurological effects.

Role of Voltage-gated Potassium Channels in Pathogenesis of Chronic Pulmonary Heart Disease

The influence of hypoxia on the activity of voltage-gated potassium channel in pulmonary artery smooth muscle cells （PASMCs） of rats and its roles in the pathogenesis of chronic pulmonary heart disease were investigated. Eighty male Sprague-Dawley rats were randomly allocated into control group （n=10）, acute hypoxic group （n=10）, and chronic hypoxic groups （n=60）. The chronic hypoxic groups were randomly divided into 6 subgroups （n=10 each） according to the chronic hypoxic periods. The rats in the control group were kept in room air and those in acute hypoxic group in hypoxia envi- ronmental chamber for 8 h. The rats in chronic hypoxic subgroups were kept in hypoxia environmental chamber for 8 h per day for 5, 10, 15, 20, 25, and 30 days, respectively. The mean pulmonary arterial pressure （mPAP）, right ventricular hypertrophy index （RVHI）, and the current of voltage-gated potas- sium channel （IK） in PASMCs were measured. Results showed that both acute and chronic hypoxia could decrease the IK in PASMCs of rats and the I-V relationship downward shifted to the right. And the peak Ir density at ＋60mV decreased with prolongation of hypoxia exposure. No significant difference was noted in the density oflK （at ＋60 mV） and I-V relationship between control group and chronic hy- poxic subgroup exposed to hypoxia for 5 days （P〉0.05）, but there was a significant difference between control group and chronic hypoxic subgroup exposed to hypoxia for 10 days （P〈0.05）. Significant dif- ferences were noted in the IK density （at ＋60 mV） and I-V relationships between control group and chronic hypoxic subgroups exposed to hypoxia for 20 days and 30 days （P〈0.01）. Compared with con- trol rats, the mPAP and RVHI were significantly increased after chronic exposure to hypoxia for 10 days （P〈0.05）, which were further increased with prolongation of hypoxia exposure, and there were signifi- cant differences between control group and chronic hypoxic subgroups exposed to hypoxia for 20 days and 30 days （P〈0.01）. Both the mPAP and the RVHI were negatively correlated with the density OflK （r---0.89769 and -0.94476, respectively, both P〈0.01）. It is concluded that exposure to hypoxia may cause decreased activity of voltage-gated potassium channel, leading to hypoxia pulmonary vasocon- striction （HPV）. Sustained HPV may result in chronic pulmonary hypertension, even chronic pulmonary heart disease, contributing to the pathogenesis of chronic pulmonary heart disease.

Motor Neuron Disease Associated with Voltage-Gated Potassium Channel Antibodies

Introduction: Antibodies to voltage-gated potassium channels have been implicated in causing a host of peripheral and central nervous system disorders. However, the presence of these antibodies has not been previously associated with motor neuropathy. We describe the first case of acquired motor neuron disease associated with voltage-gated potas-sium channel antibodies. Case Report: The patient is an 81-year-old female who developed signs and symptoms of an idiopathic motor neuron disease. The patient was found to have increased antibodies to voltage-gated potassium chan-nels in the absence of a known metastatic or autoimmune process. Magnetic resonance imaging of the cervical spine demonstrated increased signal in the anterior horn regions of the cervical and upper thoracic spinal cord on T2-weighted imaging. The patient’s disease progression was refractory to both intravenous immunoglobulin and ster-oid therapy. Conclusion: Voltage-gated potassium channels may be causal or simply associated with motor neuron disease;this relationship needs to be elucidated. Testing for these antibodies may be warranted in cases of idiopathic rapidly progressing motor neuron disease.

Effect of genistein on voltage-gated potassium channels in guinea pig proximal colon smooth muscle cells

瞄准：调查 genistein (GST ) 的行动，一个广谱酷氨酸激酶禁止者，在在畿尼猪的电压门钾隧道上近似冒号平滑肌房间。方法：在畿尼猪的平滑肌房间近似冒号酶的联盟者被孤立。穿孔制霉菌素的整个房间补丁 clamp 技术被用来包括快短暂外面的电流(IKto ) 记录钾水流并且推迟了整流器电流(IKdr ) 。钙依赖者钾水流的污染在一个外部答案没有钙和 0.2 mmol/L CdCl2 被最小化。结果：GST (10-100 micromol/L ) reversibly 并且 dose-dependently 与 22.0+/-6.9 micromol/L 的 IC50 价值减少了 IKto 的山峰振幅。到更小的程度， IKdr 也在两山峰水流被禁止并且支撑了电流。GST 不能完全堵住是的外面的钾水流很少的外面的钾水流，它对 GST 感觉迟钝。GST 没在不变的激活(n=6 ) 上并且在 IKto 的激活动力学(n=6 ) 有效果。正钒酸钠(1 mmol/L ) ，酷氨酸磷酸酶的一个有势力禁止者，显著地禁止的导致 GST 的抑制(P【0.05 ) 。结论：GST 能 dose-dependently 并且 reversibly 在畿尼猪堵住电压门钾隧道近似冒号平滑肌房间。

Diabetes-induced changes in cardiac voltage-gated ion channels

Diabetes mellitus affects the heart through various mechanisms such as microvascular defects,metabolic abnormalities,autonomic dysfunction and incompatible immune response.Furthermore,it can also cause functional and structural changes in the myocardium by a disease known as diabetic cardiomyopathy(DCM)in the absence of coronary artery disease.As DCM progresses it causes electrical remodeling of the heart,left ventricular dysfunction and heart failure.Electrophysiological changes in the diabetic heart contribute significantly to the incidence of arrhythmias and sudden cardiac death in diabetes mellitus patients.In recent studies,significant changes in repolarizing K+currents,Na+currents and L-type Ca^(2+)currents along with impaired Ca^(2+ )homeostasis and defective contractile function have been identified in the diabetic heart.In addition,insulin levels and other trophic factors change significantly to maintain the ionic channel expression in diabetic patients.There are many diagnostic tools and management options for DCM,but it is difficult to detect its development and to effectively prevent its progress.In this review,diabetes-associated alterations in voltage-sensitive cardiac ion channels are comprehensively assessed to understand their potential role in the pathophysiology and pathogenesis of DCM.

Isoprenylated Flavonoids as Cav3.1 Low Voltage-Gated Ca^(2+)Channel Inhibitors from Salvia digitaloides

Saldigones A-C(1,3,4),three new isoprenylated flavonoids with diverse flavanone,pterocarpan,and isoflavanone architec-tures,were characterized from the roots of Salvia digitaloides,together with a known isoprenylated flavanone(2).Notably,it’s the first report of isoprenylated flavonoids from Salvia species.The structures of these isolates were elucidated by extensive spectroscopic analysis.All of the compounds were evaluated for their activities on Cav3.1 low voltage-gated Ca^(2+)channel(LVGCC),of which 2 strongly and dose-dependently inhibited Cav3.1 peak current.

Frequency Switches at Transition Temperature in Voltage-Gated Ion Channel Dynamics of Neural Oscillators

Understanding of the mechanisms of neural phase transitions is crucial for clarifying cognitive processes in the brain. We investigate a neural oscillator that undergoes different bifurcation transitions from the big saddle homoclinic orbit type to the saddle node on an invariant circle type, and the saddle node on an invariant circle type to the small saddle homoclinic orbit type. The bifurcation transitions are accompanied by an increase in thermodynamic temperature that affects the voltage-gated ion channel in the neural oscillator. We show that nonlinear and thermodynamical mechanisms are responsible for different switches of the frequency in the neural oscillator. We report a dynamical role of the phase response curve in switches of the frequency, in terms of slopes of frequency-temperature curve at each bifurcation transition. Adopting the transition state theory of voltagegated ion channel dynamics, we confirm that switches of the frequency occur in the first-order phase transition temperature states and exhibit different features of their potential energy derivatives in the ion channel. Each bifurcation transition also creates a discontinuity in the Arrhenius plot used to compute the time constant of the ion channel.

Do age-associated changes of voltage-gated sodium channel isoforms expressed in the mammalian heart predispose the elderly to atrial fibrillation?

Atrial fibrillation(AF)is the most common cardiac arrhythmia worldwide.The prevalence of the disease increases with age,strongly implying an age-related process underlying the pathology.At a time when people are living longer than ever before,an exponential increase in disease prevalence is predicted worldwide.Hence unraveling the underlying mechanics of the disease is paramount for the development of innovative treatment and prevention strategies.The role of voltage-gated sodium channels is fundamental in cardiac electrophysiology and may provide novel insights into the arrhythmogenesis of AF.Na_v1.5 is the predominant cardiac isoform,responsible for the action potential upstroke.Recent studies have demonstrated that Na_v1.8(an isoform predominantly expressed within the peripheral nervous system)is responsible for cellular arrhythmogenesis through the enhancement of pro-arrhythmogenic currents.Animal studies have shown a decline in Na_v1.5 leading to a diminished action potential upstroke during phase 0.Furthermore,the study of human tissue demonstrates an inverse expression of sodium channel isoforms;reduction of Na_v1.5 and increase of Na_v1.8 in both heart failure and ventricular hypertrophy.This strongly suggests that the expression of voltage-gated sodium channels play a crucial role in the development of arrhythmias in the diseased heart.Targeting aberrant sodium currents has led to novel therapeutic approaches in tackling AF and continues to be an area of emerging research.This review will explore how voltage-gated sodium channels may predispose the elderly heart to AF through the examination of laboratory and clinical based evidence.

Functional Expression of Voltage-Gated Sodium Channels Nav1.5 in Human Breast Caner Cell Line MDA-MB-231

Voltage-gated sodium channels （VGSCs） are known to be involved in the initiation and progression of many malignancies, and the different subtypes of VGSCs play important roles in the metastasis cascade of many tumors. This study investigated the functional expression of Nav1.5 and its effect on invasion behavior of human breast cancer cell line MDA-MB-231. The mRNA and protein expression of Nav1.5 was detected by real time PCR, Western Blot and immunofluorescence. The effects of Nav1.5 on cell proliferation, migration and invasion were respectively assessed by MTT and Transwell. The effects of Nav1.5 on the secretion of matrix metalloproteases （MMPs） by MDA-MB-231 were analyzed by RT-PCR. The over-expressed Nav 1.5 was present on the membrane of MDA-MB-231 cells. The invasion ability in vitro and the MMP-9 mRNA expression were respectively decreased to （47.82±0.53）% and （43.97±0.64）% （P〈0.05） respectively in MDA-MB-23 t cells treated with VGSCs specific inhibitor tetrodotoxin （TTX） by blocking Navl.5 activity. It was concluded that Navl.5 functional expression potentiated the invasive behavior of human breast cancer cell line MDA-MB-231 by increasing the secretion of MMP-9.

Neuroprotective effect of interleukin-6 regulation of voltage-gated Na^+ channels of cortical neurons is time-and dose-dependent

Interleukin-6 has been shown to be involved in nerve injury and nerve regeneration, but the effects of long-term administration of high concentrations of interleukin-6 on neurons in the central nervous system is poorly understood. This study investigated the effects of 24 hour expo-sure of interleukin-6 on cortical neurons at various concentrations （0.1, 1, 5 and 10 ng/mL） and the effects of 10 ng/mL interleukin-6 exposure to cortical neurons for various durations （2, 4, 8, 24 and 48 hours） by studying voltage-gated Na＋ channels using a patch-clamp technique. Volt-age-clamp recording results demonstrated that interleukin-6 suppressed Na＋ currents through its receptor in a time- and dose-dependent manner, but did not alter voltage-dependent activation and inactivation. Current-clamp recording results were consistent with voltage-clamp recording results. Interleukin-6 reduced the action potential amplitude of cortical neurons, but did not change the action potential threshold. The regulation of voltage-gated Na＋channels in rat corti-cal neurons by interleukin-6 is time- and dose-dependent.

Whole-cell recordings of voltage-gated Calcium,Potassium and Sodium currents in acutely isolated hippocampal pyramidal neurons

Objective：To record Calcium, Potassium and Sodium currents in acutely isolated hippocampal pyramidal neurons. Methods：Hippocampal CA3 neurons were freshly isolated by 1 mg protease/3 ml SES and mechanical trituration with polished pipettes of progressively smaller tip diameters. Patch clamp technique in whole-cell mode was employed to record voltage-gated channel currents. Results：The procedure dissociated hippocampal neurons, preserving apical dendrites and several basal dendrites, without impairing the electrical characteristics of the neurons. Whole-cell patch clamp configuration was successfully used to record voltage-gated Ca^2＋ currents, delayed rectifier K^＋ current and voltage-gated Na^＋ currents. Conclusion：Protease combined with mechanical trituration may be used for the dissociation of neurons from rat hippocampus. Voltage-gated channels currents could be recorded using a patch clamp technique.

Molecular Docking Studies on Anticonvulsant Enaminones Inhibiting Voltage-Gated Sodium Channels

Epilepsy is described as the most common chronic brain disorder. A typical symptom of epilepsy results in uncontrolled convulsions caused by temporary excessive neuronal discharges. Although several new anticon-vulsants have been introduced, some types of seizures have still not been adequately controlled with these new and current therapies. There is an urgent need to develop new anticonvulsant drugs to control the many different types of seizures. Many studies have shown that the epilepsies involve more than one mechanism and therefore may be responsible for the various types of observed seizures. Recently reported studies have shown that a group of newly synthesized 6 Hz active anticonvulsant fluorinated N-benzamide enaminones exhibited selective inhibitions of voltage-gated sodium (Nav) channels. Nav channels are responsible for the initial inward currents during the depolarization phases of the action potential in excitable cells. The activation and opening of Nav channels result in the initial phases of action potentials. We hypothesize that there is an essential pharmacophore model for the interactions between these enaminones and the active sites of Nav channels. The research reported here is focused on molecular docking studies of the interactions that occur between the fluorinated N-benzamide enaminones and the Nav channels. These studies may open an avenue for designing anticonvulsant drugs by inhibiting Nav channels.

Neurological diseases associated with autoantibodies targeting the voltage-gated potassium channel complex:immunobiology and clinical characteristics

Voltage-gated potassium channels(VGKCs)represent a group of tetrameric signaling proteins with several functions,including modulation of neuronal excitability and neurotransmitter release.Moreover,VGKCs give a key contribution to the generation of the action potential.VGKCs are complexed with other neuronal proteins,and it is now widely known that serum autoantibodies directed against VGKCs are actually directed against the potassium channel subunits only in a minority of patients.By contrast,these autoantibodies more commonly target three proteins that are complexed with alpha-dendrotoxin-labeled potassium channels in brain extracts.These three proteins are contactin-associated protein-2(Caspr-2),leucine-rich,glioma inactivated 1(LGI-1)protein and the protein Tag-1/contactin-2.Neoplasms are detected only in a minority of seropositive patients for VGKC complex-IgG and do not significantly associate with Caspr-2 or LGI-1.Among all the cancers described in association with VGKC complex-IgG,lung carcinoma,thymoma,and hematologic malignancies are the most commonly detected.We will review all the major neurological conditions associated with VGKC complex-IgG.These include Isaacs’syndrome,Morvan syndrome,limbic encephalitis,facio-brachial dystonic seizures,chorea and other movement disorders,epilepsy,psychosis,gastrointestinal neuromuscular diseases,a subacute encephalopathy that mimics Creutzfeldt-Jakob prion disease both clinically and radiologically and autoimmune chronic pain.The vast majority of these conditions are reversible by immunotherapy,and it is becoming increasingly recognized that early diagnosis and detection of VGKC complex-IgG is critical in order to rapidly start the treatment.As a result,VGKC complex-IgG are now part of the investigation of patients with unexplained subacute onset of epilepsy,memory or cognitive problems,or peripheral nerve hyperexcitability syndromes.

Effects Of ATP Sensitive potassium channel opener on the mRNA and pro- tein expressions of caspase-12 after cerebral ischemia-reperfusion in rats

Objective To investigate effects of K_ATP opener on the expressions of caspase-12 mRNA and protein, and to explore the role of endoplasmic reticulum （ER） stress pathway in the mechanism of K_ATP opener protecting against neuronal apoptosis after cerebral ischemia-reperfusion. Methods Two hundred rats were randomly divided into four groups： sham operation group, ischemia-reperfusion group, K_ATP opener group, and K_ATP blocker group. The middle cerebral artery occlusion （MCAO） model was established by intraluminal suture occlusion method; neuronal apoptosis was detected by TUNEL staining. The mRNA and protein expressions of caspase-12 were detected by semi-quantitative RT-PCR and immunohisto-chemical staining, respectively. Results In ischemia-reperfusion group, K_ATP opener group and K_ATP blocker group, the number of apoptotic cells and the mRNA and protein expressions of caspase-12 gradually increased following cerebral reperfusion, and reached the peak at 24 h. In K_ATP opener group, The number of apoptotic cells was significantly less than that in ischemia-reperfusion group and K_ATP blocker group at 12 h, 24 h, 48 h and 72 h （P 〈 0.05 or P 〈 0.01）; while the mRNA and protein levels of caspase-12 were significantly less than those in ischemia-reperfusion group and K_ATP blocker group at all times （P 〈 0.05 or P〈0.01）. There were no differences between the ischemia-reperfusion group and K_ATP blocker group at each time （P〉 0.05）. Conclusion K_ATP opener may protect neurons from apoptosis following the cerebral ischemia-reperfusion by inhibiting ER stress pathway.

Bisoprolol reverses down-regulation of potassium channel proteins in ventricular tissues of rabbits with heart failure

Remodeling of ion channels is an important mechanism of arrhythmia induced by heart failure （HF）. We investigated the expression of potassium channel encoding genes in the ventricles of rabbit established by volumeoverload operation followed with pressure-overload. The reversible effect of these changes with bisoprolol was also evaluated. The HF group exhibited left ventricular enlargement, systolic dysfunction, prolongation of corrected QT interval （QTc）, and increased plasma brain natriuretic peptide levels in the HF rabbits. Several potassium channel subunit encoding genes were consistently down-regulated in the HF rabbits. After bisoprolol treatment, heart function was improved significantly and QTc was shortened. Additionally, the mRNA expression of potassium channel subunit genes could be partially reversed. The down-regulated expression of potassium channel subunits Kv4.3, Kv1.4, KvLQT1, minK and Kir 2.1 may contribute to the prolongation of action potential duration in the heart of rabbits induced by volume combined with pressure overload HF. Bisoprolol could partially reverse these down-regulations and improve heart function.

Extract from Buthus martensii Karsch is associated with potassium channels on glioma cells

Catilan extracted from Leiurus quinquestriatus is a specific ion channel blocker.It can specifically bind chloride channels of glioma cells and kill these tumor cells.The questions remain as to whether antigliomatin,the extract from scorpion venom of Buthus martensii Karsch in China,can inhibit glioma growth,and whether this inhibition is correlated with ion channels of tumor cells.The present study treated rat C6 glioma cells with 0.8,1.2,and 1.6 μg/mL antigliomatin for 20 hours.Whole-cell patch clamp technique showed that antigliomatin delayed rectifier potassium channels of C6 glioma cells.Antigliomatin inhibited tumor growth,which could potentially involve potassium channels of tumor cells.

Effects of Ginkgo biloba extracts with mirodenafil on the relaxation of corpus cavernosal smooth muscle and the potassium channel activity of corporal smooth muscle cells

In this study, we investigated the effects of a combination of Ginkgo biloba extracts （GBE） and phosphodiesterase type 5 （PDE-5） inhibitors on the muscular tone of the corpus cavernosum and potassium channel activity of corporal smooth muscle cells. Strips of corpus cavernosum from male New Zealand white rabbits were mounted in organ baths for isometric tension studies. After contraction with 1 × 10^-5 mol I^-1 norepinephrine, GBE （0.01-1 mg ml^-1） and mirodenafil （0.01-100 nmol I^-1） were added together into the organ bath. In electrophysiological studies, whole-cell currents were recorded by the conventional patch-clamp technique in cultured smooth muscle cells of the human corpus cavernosum. The corpus cavemosum was relaxed in response to GBE in a dose-dependent manner （from 0.64%±8.35% at 0.01 mg ml^-1 to 52.28%±11.42% at 1 mg ml^-1）. After pre-treatment with 0.03 mg ml^-1 of GBE, the relaxant effects of mirodenafil were increased at all concentrations, After tetraethylammonium （TEA） （1 mmol I^-1） administration, the increased effects were inhibited （P〈0.01）. Extracellular administration of GBE increased the whole-cell K^＋ outward currents in a dose-dependent fashion. The increase of the outward current was inhibited by I mmol 1-1 TEA. These results suggest that GBE could increase the relaxant potency of mirodenafil even at a minimally effective dose. The K＋ flow through potassium channels might be one of the mechanisms involved in this synergistic relaxation.

Changes of Expression of Stretch-activated Potassium Channel TREK-1 mRNA and Protein in Hypertrophic Myocardium

The expression of stretch activated potassium channel TREK-1 mRNA and protein of hypertrophic myocardium was measured. Using a model of hypertrophy induced by coarctation of abdominal aorta in male Wistar rats, the expression of TREK-1 mRNA and protein was detected by using semi quantitative RT-PCR and Western blot respectively. At 4th and 8th week after constriction of the abdominal aorta , rats developed significant left ventricular hypertrophy. As compared to sham-operated group, stretch-activated potassium channel TREK-1 mRNA was strongly expressed and protein was up regulated in operation groups （P〈0.05）. It was concluded that the expression of TREK-1 was up-regulated in hypertrophic myocardium induced by chronic pressure overload in Wistar rats.

Astrocytic Kir4.1 potassium channels as a novel therapeutic target for epilepsy and mood disorders

Astrocytic Kir4.1 channels and spatial potassium buffering：Astrocytes play a crucial role in maintaining the structural and functional integrity of the brain,which includes formation of the blood-brain barrier,maintenance of water and ion homeostasis,metabolism of neurotransmitters and secretion of various neuroactive molecules.