Mouse Abdominal Aortic Aneurysm Model Induced by Periarterial Incubation of Papain.

For decades, numerous experimental animal models have been developed to examine the pathophysiologic mechanisms and potential treatments for abdominal aortic aneurysms (AAAs) in diverse species with varying chemical or surgical approaches. This study aimed to create an AAA mouse model by the periarterial incubation with papain, which can mimic human AAA with advantages such as simplicity, convenience, and high efficiency. Eighty C57BL/6J male mice were randomly assigned to 1 of the 4 groups: papain (1.0 or 2.0 mg), porcine pancreatic elastase, and phosphate-buffered solution. The aortic segment was wrapped for 20 minutes, and the diameter was measured using ultrasound preoperatively and postoperative days 7 and 14. Then, the mice were killed for histomorphometric and immunohistochemical analyses. According to ultrasound measurements and histomorphometric analyses, on postoperative day 7, 65% of mice in the 1.0-mg papain group and 60% of mice in the 2.0-mg papain group developed AAA. In both papain groups, 100% of mice developed AAA, and 65% of mice in the porcine pancreatic elastase group developed AAA on postoperative day 14. Furthermore, hematoxylin/eosin, elastin van Gieson, and Masson staining of tissues from the papain group revealed thickened media and intimal hyperplasia, collagen sediments, and elastin destruction, indicating that AAA histochemical alteration was similar to that of humans. In addition, the immunohistochemical analysis was conducted to detect infiltrated inflammatory cells, such as macrophages and leukocytes, in the aortic wall and hyperplasic adventitia. The expression of matrix metalloproteinase 2 and 9 was significantly upregulated in papain and human AAA tissues. Periarterial incubation with 1.0 mg of papain for 20 minutes can successfully create an experimental AAA model in mice for 14 days, which can be used to explore the mechanism and treatment of human AAA.

The modulation of potassium channels by estrogens facilitates neuroprotection.

Estrogens, the sex hormones, have the potential to govern multiple cellular functions, such as proliferation, apoptosis, differentiation, and homeostasis, and to exert numerous beneficial influences for the cardiovascular system, nervous system, and bones in genomic and/or non-genomic ways. Converging evidence indicates that estrogens serve a crucial role in counteracting neurodegeneration and ischemic injury; they are thereby being considered as a potent neuroprotectant for preventing neurological diseases such as Alzheimer's disease and stroke. The underlying mechanism of neuroprotective effects conferred by estrogens is thought to be complex and multifactorial, and it remains obscure. It is well established that the K+ channels broadly expressed in a variety of neural subtypes determine the essential physiological features of neuronal excitability, and dysfunction of these channels is closely associated with diverse brain deficits, such as ataxia and epilepsy. A growing body of evidence supports a neuroprotective role of K+ channels in malfunctions of nervous tissues, with the channels even being a therapeutic target in clinical trials. As multitarget steroid hormones, estrogens also regulate the activity of distinct K+ channels to generate varying biological actions, and accumulated data delineate that some aspects of estrogen-mediated neuroprotection may arise from the impact on multiple K+ channels, including Kv, BK, KATP, and K2P channels. The response of these K+ channels after acute or chronic exposure to estrogens may oppose pathological abnormality in nervous cells, which serves to extend our understanding of these phenomena.

Beneficial effects of carvedilol modulating potassium channels on the control of glucose.

The increased prevalence of hypertensive patients with type 2 diabetes mellitus (T2DM) is evident worldwide, leading to a higher risk of cardiovascular disease onset, which is substantially associated with disabilities and mortality in the clinic. In order to achieve the satisfyingly clinical outcomes and prognosis, the comprehensive therapies have been conducted with a beneficial effect on both blood pressure and glucose homeostasis, and clinical trials reveal that some kind of antihypertensive drugs such as angiotensin converting enzyme inhibitors (ACE-I) may, at least in part, meet the dual requirement during the disease management. As a nonselective ß-blocker, carvedilol is employed for treating many cardiovascular diseases in clinical practice, including hypertension, angina pectoris and heart failure, and also exhibit the effectiveness for glycemic control and insulin resistance. Apart from alleviating sympathetic nervous system activity, several causes, such as lowering oxygen reactive species, may contribute to the effects of carvedilol on controlling plasma glucose levels, suggesting a feature of this drug having multiple targets. Interestingly, numerous distinct K+ channels expressed in pancreatic ß-cells and peripheral insulin-sensitive tissues, which play a sentential role in glucose metabolism, are subjected to extensive modulation of carvdilol, establishing a linkage between K+ channels and drug's effects on the control of glucose. A variety of evidence shows that the impact of carvedilol on different K+ channels, including Kv, KAch, KATP and K2 P, can lead to positive influences for glucose homeostasis, contributing to its clinical beneficial effectiveness in treatment of hypertensive patients with T2DM. This review focus on the control of plasma glucose conferred by carvedilol modulation on K+ channels, providing the novel mechanistic explanation for drug's actions.

Alzheimer's disease therapy based on acetylcholinesterase inhibitor/blocker effects on voltage-gated potassium channels.

Alzheimer's disease (AD) is the most prevalent neurodegenerative disorder with progressive loss of memory and other cognitive functions. The pathogenesis of this disease is complex and multifactorial, and remains obscure until now. To enhance the declined level of acetylcholine (ACh) resulting from loss of cholinergic neurons, acetylcholinesterase (AChE) inhibitors are developed and successfully approved for AD treatment in the clinic, with a limited therapeutic effectiveness. At present, it is generally accepted that multi-target strategy is potently useful for designing novel drugs for AD. Accumulated evidence reveals that Kv channels, which are broadly expressed in brain and possess crucial functions in modulating the neuronal activity, are inhibited by several acetylcholinesterase (AChE) inhibitors, such as tacrine, bis(7)-tacrine, donepezil and galantamine. Inhibition of Kv channels by these AChE inhibitors can generate neuroprotective effects by either mitigating Aß toxicity and neuronal apoptosis, or facilitating cell proliferation. These inhibitory effects provide additional explanations for clinical beneficial effectiveness of AChE inhibitors, meaning that Kv channel is a promising candidate target for novel drugs for AD therapy.

Estrogen-induced downregulation of TASK-1 expression through estrogen receptor ß in N2A cells.

BACKGROUND: Our previous data revealed that reduction of TASK-1 expression, as a consequence of exposure to 17ß-estradiol, could participate in neuroprotective effects in N2A cells. However, it is unclear which estrogen receptor underlies these effects of 17ß-estradiol. METHODS AND RESULTS: In this study, the knockdown experiments are carried out to clarify the estrogen receptor responsible for effects of estrogen on TASK-1 channels. Subsequently, data from QPCR measurements reveal that estrogen receptor ß (ERß), but not estrogen receptor α, serves as a binding target for 17ß-estradiol after a 48-h treatment. CONCLUSIONS: The current result suggests the implication of the ERß-dependent manner in the pro-proliferative action of estrogen via TASK-1 channels.

Effects of Huatan Jiangzhuo decoction on diet-induced hyperlipidemia and gene expressions in rats.

Huatan Jiangzhuo decoction (HJD) is a combination of six traditional Chinese medicines that were used for lipid metabolism-related disorders, but its efficacy and underlying mechanisms have not been explored by modern research strategies. This study aimed to investigate the therapeutic role of HJD in determining the transcriptome level. Hyperlipidemia model was established by feeding Sprague-Dawley rats with high-fat diet. Differentially expressed genes (DEGs) were detected by high-through transcriptome sequencing, followed by gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. The total cholesterol (TC) and triglyceride (TG) levels in hyperlipidemia model rats were significantly increased, whereas high-density lipoprotein (HDL) concentration decreased when compared to normal rats, and HJD significantly downregulated TC concentrations and liver coefficient in the hyperlipidemia rats. Histology staining showed that HDJ greatly recovered the lipid accumulation in rat hepatic stellate cells and aortic arch vascular wall thickness of hyperlipidemia rats. One thousand nine hundred and thirty-six DEGs were identified in the HJD-treated hyperlipidemia rats, which were associated with various biological processes and signaling pathways such as peroxisome proliferator-activated receptors, AMP-activated Protein Kinase , and insulin signaling pathways. Quantitative reverse transcription-polymerase chain reaction further confirmed the downregulated expression of cholesterol 7-α-hydroxylase(CYP7A1), liver orphan receptor(LXRα),peroxisome proliferator-activated receptor gamma(PPARγ),andSterol Response Element-Binding Protein 1c(SREBP1c) genes in hyperlipidemia rats treated with HJD. Our data first elucidated the gene expression profile of high-fat diet-induced hyperlipidemia in rats after HJD treatment, and lipid metabolism-related genes (CYP7A1, LXRα, PPARγ, and SREBP1c) may be potentially biomarkers for HJD-alleviated hyperlipidemia.

A Quantitative Diagnostic Method for Phlegm and Blood Stasis Syndrome in Coronary Heart Disease Using Tongue, Face, and Pulse Indexes: An Exploratory Pilot Study.

Objectives: The aim of this study was to establish a quantitative syndrome differentiation model with logistic regression analysis for phlegm and blood stasis syndrome (PBSS) in coronary heart disease (CHD) to offer methodology guidance for the quantitative syndrome differentiation of Traditional Chinese Medicine (TCM). Design: Tongue, face, and pulse information of each subject was obtained using the TCM-intelligent diagnosis instruments. Logistic regression model was used to construct the syndrome diagnosis model. The area under receiver operating characteristic curve (ROC-AUC) was used to evaluate the diagnostic value of the model. Subjects: Among the 141 subjects, 83 belonged to the PBSS group, and 58 belonged to the non-PBSS group. Results: The independent indexes used to predict PBSS in patients with CHD were length of the crack (LC) (p = 0.002), number of ecchymosis (NE) (p < 0.001), length of philtrum (LEP) (p = 0.022), and right hand pulse h1 (Rh1) (p = 0.021). The expression of combining predictor L in this study was L = LC +57.58 NE +4.53 LEP +2.68 Rh1. The ROC curve analysis indicated that the AUC values of LC, NE, LEP, and Rh1 were 0.646, 0.710, 0.619, and 0.613, respectively. The AUC = 0.825 of the syndrome diagnosis model was the largest. Conclusions: The quantitative study of TCM syndrome based on logistic regression analysis provides a good method for the objective analysis and application of TCM syndrome.

Tacrine modulates Kv2.1 channel gene expression and cell proliferation.

Purpose/Aim: Besides as a cholinesterase (ChE) inhibitor, tacrine is able to act on multiple targets such as nicotinic receptors (nAChRs) and voltage-gated K+ (Kv) channels. Kv2.1, a Kv channel subunit underlying delayed rectifier currents with slow kinetics of inactivation, is highly expressed in the mammalian brain, especially in the hippocampus. Nevertheless, limited data are available concerning the relationship between tacrine and Kv2.1 channels. In the present study, we explore the possible effects of tacrine on Kv2.1 channels in heterologous expression systems and N2A cells.Materials and methods: The change of expression and currents of Kv2.1 after treatment with tacrine was detected by PCR and whole-cell recordings, respectively. WST-8 experiments were performed to reveal the effects of tacrine on cell proliferation.Results: Incubation with tacrine induced a significant reduction of the mRNA level of Kv2.1 channels in HEK293 cells. The decline of corresponding currents carried by Kv2.1 was also observed. Moreover, the proliferation rates of HEK293 cells with Kv2.1 channel were substantially enhanced after treatment with this chemical for 24 h. Similar results were also detected after exposure to tacrine in N2A cells with native expression of Kv2.1 channels.Conclusion: These lines of evidence indicate that application of tacrine downregulates the expression of Kv2.1 channels and increase cell proliferation. The effect of tacrine on Kv2.1 channels may provide an alternative explanation for its neuroprotective action.

Development of a Diagnostic Questionnaire for Damp Phlegm Pattern and Blood Stasis Pattern in Coronary Heart Disease Patients (CHD-DPBSPQ).

BACKGROUND: The aim was to develop a diagnostic questionnaire for damp phlegm pattern and blood stasis pattern in coronary heart disease patients (CHD-DPBSPQ). METHODS: The standard procedures of questionnaire development were carried out to develop and assess CHD-DPBSPQ. The patients were assessed using the CHD-DPBSPQ, CHD-DPPQ, and CHD-BSPQ. Four methods were used to select the items on the CHD-DPBSPQ in a pilot study based on data from a Guizhou tertiary grade A hospital. Cronbach's alpha and the split-half reliability, test-retest reliability, content validity, criterion validity, construct validity, and convergent validity were determined in a validation study using a nationwide sample. RESULTS: After item selection, the CHD-DPBSPQ contained 15 items in two domains: the phlegm domain (9 items) and the blood stasis domain (6 items). For the CHD-DPBSPQ, the alpha coefficient was 0.88, the split-half coefficient was 0.90, and the intraclass correlation coefficient was 0.83. The range of the item-level content validity index (I-CVI) was 0.71 to 1.0 and that of the scale-level content validity index/average (Scale-CVI/Ave) was 0.97. The domain scores on the CHD-DPBSPQ were in close relation to the scores on a questionnaire for damp phlegm pattern in coronary heart disease patients (CHD-DPPQ) and a questionnaire for blood stasis pattern in coronary heart disease patient (CHD-BSPQ) (P < 0.01). The root mean square error of approximation (RMSEA) was equal to 0.05 (90% CI: 0.044, 0.059). Convergent validity was demonstrated with a moderate correlation. CONCLUSION: The CHD-DPBSPQ is a reliable and valid instrument.

Carvedilol blockage of delayed rectifier Kv2.1 channels and its molecular basis.

Previous studies indicated that one of the action targets of carvedilol is the voltage-gated potassium (Kv) channel, which has a fundamental role in the control of electrical properties in excitable cells. It is not clear whether this compound exerts any actions specifically on delayed rectifier Kv2.1 channels. The present study is conducted on Kv2.1 currents heterologously expressed in HEK293 cells to characterize the block by carvedilol in detail, identifying molecular determinants and providing biophysical insights of the block. Macroscopic Kv2.1 currents obtained by whole-cell recording were substantially inhibited after addition of carvedilol with an IC50 value of 5.1 µM. This drug also led to a largely hyperpolarizing shift (30 mV) of the inactivation curve, which may contribute to the blocking action due to more inactivation of Kv2.1 currents occurred in depolarization potentials. Mutations at Y380 (a putative TEA binding site) and K356 (a K+ binding site) in the outer vestibule of Kv2.1 channels significantly eliminated the inhibitory effects of carvedilol and prevented the leftward shift of inactivation. Moreover, mutations at above positions modulated the effects of carvedilol on the deactivation but not activation kinetics of Kv2.1 channels. Collected data indicate that carvedilol can exert a blocking effect on the closed-state of Kv2.1 channels, and specific residues within the S5-P and P-S6 linkers in the outer vestibule may play crucial roles in carvedilol-induced blocking for Kv2.1 channels.

Diagnostic Accuracy of Chinese Medicine Diagnosis Scale of Phlegm and Blood Stasis Syndrome in Coronary Heart Disease: A Study Protocol.

BACKGROUND: Phlegm and blood stasis syndrome (PBSS) is one of the main syndromes in coronary heart disease (CHD). Syndromes of Chinese medicine (CM) are lack of quantitative and easy-implementation diagnosis standards. To quantify and standardize the diagnosis of PBSS, scales are usually applied. OBJECTIVE: To evaluate the diagnostic accuracy of CM diagnosis scale of PBSS in CHD. METHODS: Six hundred patients with stable angina pectoris of CHD, 300 in case group and 300 in control group, will be recruited from 5 hospitals across China. Diagnosis from 2 experts will be considered as the "gold standard". The study design consists of 2 phases: pilot test is used to evaluate the reliability and validity, and diagnostic test is used to assess the diagnostic accuracy of the scale, including sensitivity, specificity, likelihood ratio and area under the receiver operator characteristic (ROC) curve. DISCUSSION: This study will evaluate the diagnostic accuracy of CM diagnosis scale of PBSS in CHD. The consensus of 2 experts may not be ideal as a "gold standard", and itself still requires further study. (No. ChiCTR-OOC-15006599).

Assessment of Intermingled Phlegm and Blood Stasis Syndrome in Coronary Heart Disease: Development of a Diagnostic Scale.

BACKGROUND: Intermingled Phlegm and Blood Stasis Syndrome (IPBSS) is a common feature in patients with coronary heart disease (CHD). In clinical practice, the diagnostic agreement of clinical doctor of Chinese Medicine (CM) is poor. We previously developed a IPBSS diagnostic scale for use by general practitioner. OBJECTIVES: To assess a IPBSS diagnostic scale that we previously developed for use by non-experts. METHODS: This is a multicenter, prospective study involving eight study sites across China. Eligible patients were adults (≥18 years) with CHD as demonstrated by a history of myocardial infarction, stenosis, or past coronary revascularization. IPBSS was assessed using a scale that consisted of 14 items in two domains (e.g., phlegm and blood stasis). The score range for each item was 0 to 3 points. Maximum total score was 72 points. Diagnostic accuracy was verified using consensus opinion by two independent experts as reference. RESULTS: A total of 1,142 CHD patients were included. IPBSS was established in 729 subjects using the IPBSS diagnostic scale. In ROC curve analyses, at the optimal cut-off of 25.5, the sensitivity and specificity of the IPBSS scale were 67.6% and 72.4%, respectively. The area under the ROC curve was 0.741 (95%CI: 0.711-0.772). CONCLUSIONS: The newly developed IPBSS scoring system showed moderate performance in diagnosing IPBSS in CHD patients. Data from further large-scale diagnostic test accuracy studies are warranted. This trial is registered with ChiCTR-OOC-15006599.

Characterization and molecular basis for the block of Kv1.3 channels induced by carvedilol in HEK293 cells.

Carvedilol is a non-selective ß-adrenoreceptor antagonist and exhibits a wide range of biological activities. The voltage-gated K+ (Kv) channel is one of the target ion channels of this compound. The rapidly activating Kv1.3 channel is expressed in several different tissues and plays an important role in the regulation of physiological functions, including cell proliferation and apoptosis. However, little is known about the possible action of carvedilol on Kv1.3 currents. Using the whole-cell configuration of the patch-clamp technique, we have revealed that exposure to carvedilol produced a concentration-dependent blocking of Kv1.3 channels heterologously expressed in HEK293 cells, with an IC50 value of 9.7 µM. This chemical decelerated the deactivation tail current of Kv1.3 currents, resulting in a tail crossover phenomenon. In addition, carvedilol generated a markedly hyperpolarizing shift (20 mV) of the inactivation curve, but failed to affect the activation curve. Mutagenesis experiments of Kv1.3 channels identified G427 and H451, two related sites of TEA block, as important residues for carvedilol-mediated blocking. The present results suggest that carvedilol acts directly on Kv1.3 currents by inducing closed- and open-channel block and helps to elucidate the mechanisms of action of this compound on Kv channels.

Methological quality of systematic reviews and meta-analyses on acupuncture for stroke: A review of review.

OBJECTIVE: To assess the methodological quality of systematic reviews and meta-analyses regarding acupuncture intervention for stroke and the primary studies within them. METHODS: Two researchers searched PubMed, Cumulative index to Nursing and Allied Health Literature, Embase, ISI Web of Knowledge, Cochrane, Allied and Complementary Medicine, Ovid Medline, Chinese Biomedical Literature Database, China National Knowledge Infrastructure, Wanfang and Traditional Chinese Medical Database to identify systematic reviews and meta-analyses about acupuncture for stroke published from the inception to December 2016. Review characteristics and the criteria for assessing the primary studies within reviews were extracted. The methodological quality of the reviews was assessed using adapted Oxman and Guyatt Scale. The methodological quality of primary studies was also assessed. RESULTS: Thirty-two eligible reviews were identified, 15 in English and 17 in Chinese. The English reviews were scored higher than the Chinese reviews (P=0.025), especially in criteria for avoiding bias and the scope of search. All reviews used the quality criteria to evaluate the methodological quality of primary studies, but some criteria were not comprehensive. The primary studies, in particular the Chinese reviews, had problems with randomization, allocation concealment, blinding, dropouts and withdrawals, intent-to-treat analysis and adverse events. CONCLUSIONS: Important methodological flaws were found in Chinese systematic reviews and primary studies. It was necessary to improve the methodological quality and reporting quality of both the systematic reviews published in China and primary studies on acupuncture for stroke.

The inhibitory effects of levo-tetrahydropalmatine on rat Kv1.5 channels expressed in HEK293 cells.

Levo-tetrahydropalmatine (l-THP) exerts various pharmacological effects on neural and cardiac tissues and K+ channel can be one of its multiple targets. The rapidly activating Kv1.5 channel is expressed in a variety of tissues including atrial cells and hippocampal neurons, and has an essential role in tuning the action potential and excitability in those cells. The aim of current study is to explore whether there are the possible effects of l-THP on Kv1.5 channels expressed in HEK293 cells. Superfusion of l-THP led to a dose-dependent blockage of Kv1.5 currents with an IC50 value of 53.2µM. This blocking effect was substantially attenuated in mutant H452G rather than R476V and R476Y, suggesting a specific binding site in the outer mouth region. In addition, the properties of Kv1.5 channel kinetics were markedly altered by l-THP. Treatment with l-THP resulted in a potential left shift of the inactivation curve, with the half-maximum inactivation potential (V1/2) of 4.5mV in control and -12.8mV in 50µM l-THP. Our data reveal that l-THP can exert an inhibitory effect on the delayed rectifier Kv1.5 channels expressed in HEK293 cells. These lines of evidence provided an insight to understand the possible effects exerted by l-THP on relative tissues.

Inhibitory effects of cholinesterase inhibitor donepezil on the Kv1.5 potassium channel.

Kv1.5 channels carry ultra-rapid delayed rectifier K+ currents in excitable cells, including neurons and cardiac myocytes. In the current study, the effects of cholinesterase inhibitor donepezil on cloned Kv1.5 channels expressed in HEK29 cells were explored using whole-cell recording technique. Exposure to donepezil resulted in a rapid and reversible block of Kv1.5 currents, with an IC50 value of 72.5 µM. The mutant R476V significantly reduced the binding affinity of donepezil to Kv1.5 channels, showing the target site in the outer mouth region. Donepezil produced a significant delay in the duration of activation and deactivation, and mutant R476V potentiated these effects without altering activation curves. In response to slowed deactivation time course, a typical crossover of Kv1.5 tail currents was clearly evident after bath application of donepezil. In addition, both this chemical and mutant R476V accelerated current decay during channel inactivation in a voltage-dependent way, but barely changed the inactivation and recovery curves. The presence of donepezil exhibited the use-dependent block of Kv1.5 currents in response to a series of depolarizing pulses. Our data indicate that donepezil can directly block Kv1.5 channels in its open and closed states.

The inhibitory effects of nifedipine on outward voltage-gated potassium currents in mouse neuroblastoma N2A cells.

BACKGROUND: Voltage-gated K(+) (Kv) channels have a pivotal role in tuning the action potential duration and excitability in neuronal cells. Although Ca(2+) channel antagonist nifedipine exhibited an inhibitory effect on cardiac Kv currents, a possible action of nifedipine on neuronal Kv currents has not been fully investigated. METHODS: The effects of nifedipine on elicited Kv currents were characterized using whole-cell recording in mouse neuroblastoma N2A cells. RESULTS: Exposure to nifedipine induced a dose-dependent inhibition of Kv currents with an IC50 value of 22.3±4.2µM and prolonged the time course of activation. The half-maximum activation potential was 1.6±1.7mV in control conditions and became 13.5±1.5mV in 50µM nifedipine. In addition, the decay rate of Kv currents was substantially accelerated by 39.5% at +60mV. For the voltage-dependent inactivation, the half-maximum inactivation potential was -13.8±0.8mV and strongly shifted to the left following treatment with 50µM nifedipine. CONCLUSION: Treatment with nifedipine exerted a strong influence on the activation and inactivation rate of Kv currents as well as an obvious leftward shift in the inactivation curve. These data indicated that nifedipine exerted an inhibitory effect on Kv currents in N2A cells.

[Study on Macrocosmic Diagnostic Criteria for Coronary Heart Disease with Intermingled Phlegm- Blood Stasis Syndrome].

Macrocosmic diagnostic criteria for coronary heart disease (CHD) with phlegm-damp- ness syndrome (PDS) were established after screening based on macrocosmic indices of CHD with PDS after previous literature analyses and experts consultations. The weights of macrocosmic indices of PDS were compared using analytic hierarchy process (AHP). Macrocosmic diagnostic criteria for CHD with intermingled phlegmblood stasis syndrome were studied by combining with diagnostic criteria for CHD patients with blood stasis syndrome (BSS) set by Academician CHEN Ke-ji group.

The Tau-Induced Reduction of mRNA Levels of Kv Channels in Human Neuroblastoma SK-N-SH Cells.

Previous findings indicated that microtubule-binding protein tau and voltage-gated K(+) (Kv) channels exhibit a regulatory role in cell proliferation. However, the possible interaction of tau with Kv channels remained obscure. In this report, transfection of tau plasmids into human neuroblastoma SK-N-SH cells caused a significant reduction in the messenger RNA (mRNA) levels of several Kv channels, including Kv2.1, Kv3.1, Kv5.1, Kv9.2, and KCNH4. Correspondingly, the Kv currents recorded using patch-clamp techniques were substantially declined in the tau-transfected SK-N-SH cells. Moreover, tau induction and treatment with the Kv channel blocker TEA (tetraethylammonium) were able to improve proliferation rates of SK-N-SH cells by 43.1 and 66.2%, respectively. These data suggested that the tau-mediated alteration of Kv channels could be involved in its action on neural proliferation.

The Inhibitory Effects of Ca2+ Channel Blocker Nifedipine on Rat Kv2.1 Potassium Channels.

It is well documented that nifedipine, a commonly used dihydropyridine Ca2+ channel blocker, has also significant interactions with voltage-gated K+ (Kv) channels. But to date, little is known whether nifedipine exerted an action on Kv2.1 channels, a member of the Shab subfamily with slow inactivation. In the present study, we explored the effects of nifedipine on rat Kv2.1 channels expressed in HEK293 cells. Data from whole-cell recording showed that nifedipine substantially reduced Kv2.1 currents with the IC50 value of 37.5 ± 5.7 µM and delayed the time course of activation without effects on the activation curve. Moreover, this drug also significantly shortened the duration of inactivation and deactivation of Kv2.1 currents in a voltage-dependent manner. Interestingly, the half-maximum inactivation potential (V1/2) of Kv2.1 currents was -11.4 ± 0.9 mV in control and became -38.5 ± 0.4 mV after application of 50 µM nifedipine. The large hyperpolarizing shift (27 mV) of the inactivation curve has not been reported previously and may result in more inactivation for outward delayed rectifier K+ currents mediated by Kv2.1 channels at repolarization phases. The Y380R mutant significantly increased the binding affinity of nifedipine to Kv2.1 channels, suggesting an interaction of nifedipine with the outer mouth region of this channel. The data present here will be helpful to understand the diverse effects exerted by nifedipine on various Kv channels.