Hyperpolarization-Activated Cyclic Nucleotide-Gated Ion (HCN) Channels Regulate PC12 Cell Differentiation Toward Sympathetic Neuron.

Hyperpolarization-activated cyclic nucleotide-gated ion channels (HCN channels) are widely expressed in the central and peripheral nervous systems and organs, while their functions are not well elucidated especially in the sympathetic nerve. The present study aimed to investigate the roles of HCN channel isoforms in the differentiation of sympathetic neurons using PC12 cell as a model. PC12 cells derived from rat pheochromocytoma were cultured and induced by nerve growth factor (NGF) (25 ng/ml) to differentiate to sympathetic neuron-like cells. Sympathetic directional differentiation of PC12 cells were evaluated by expressions of growth-associated protein 43 (GAP-43) (a growth cone marker), tyrosine hydroxylase (TH) (a sympathetic neuron marker) and neurite outgrowth. Results show that the HCN channel isoforms (HCN1-4) were all expressed in PC12 cells; blocking HCN channels with ivabradine suppressed NGF-induced GAP-43 expression and neurite outgrowth; silencing the expression of HCN2 and HCN4 using silenced using small interfering RNAs (siRNA), rather than HCN1 and HCN3, restrained GAP-43 expression and neurite outgrowth, while overexpression of HCN2 and HCN4 channels with gene transfer promoted GAP-43 expression and neurite outgrowth. Patch clamp experiments show that PC12 cells exhibited resting potentials (RP) of about -65 to -70 mV, and also presented inward HCN channel currents and outward (K+) currents, but no inward voltage-gated Na+ current was induced; NGF did not significantly affect the RP but promoted the establishment of excitability as indicated by the increased ability to depolarize and repolarize in the evoked suspicious action potentials (AP). We conclude that HCN2 and HCN4 channel isoforms, but not HCN1 and HCN3, promote the differentiation of PC12 cells toward sympathetic neurons. NGF potentiates the establishment of excitability during PC12 cell differentiation.

Sodium Tanshinone II-A Sulfonate (DS-201) Induces Vasorelaxation of Rat Mesenteric Arteries via Inhibition of L-Type Ca2+ Channel.

Background: We previously have proved that sodium tanshinone II-A sulfonate (DS-201), a derivative of traditional Chinese medicinal herb Danshen (Salvia miltiorrhiza), is an opener and vasodilator of BKCa channel in the vascular smooth muscle cells (VSMCs). Vascular tension is closely associated with Ca2+ dynamics and activation of BKCa channel may not be the sole mechanism for the relaxation of the vascular tension by DS-201. Therefore, we hypothesized that the vasorelaxing effect of DS-20 may be also related to Ca2+ channel and cytoplasmic Ca2+ level in the VSMCs. Methods: Arterial tension was measured by Danish Myo Technology (DMT) myograph system in the mesentery vessels of rats, intracellular Ca2+ level by fluorescence imaging system in the VSMCs of rats, and L-type Ca2+ current by patch clamp technique in Ca2+ channels transfected human embryonic kidney 293 (HEK-293) cells. Results: DS-201 relaxed the endothelium-denuded artery rings pre-constricted with PE or high K+ and the vasorelaxation was reversible. Blockade of K+ channel did not totally block the effect of DS-201 on vasorelaxation. DS-201 suppressed [Ca2+]i transient induced by high K+ in a concentration-dependent manner in the VSMCs, including the amplitude of Ca2+ transient, the time for Ca2+ transient reaching to the [Ca2+]i peak and the time to remove Ca2+ from the cytoplasm. DS-201 inhibited L-type Ca2+ channel with an EC50 of 59.5 µM and at about 40% efficacy of inhibition. However, DS-201did not significantly affect the kinetics of Ca2+ channel. The effect of DS-201 on L-type Ca2+ channel was rate-independent. Conclusion: The effect of DS-201 on vasorelaxation was not only via activating BKCa channel, but also blocking Ca2+ channel and inhibiting Ca2+ influx in the VSMCs of rats. The results favor the use of DS-201 and Danshen in the treatment of cardiovascular diseases clinically.

[Reconstitution of large conductance calcium-activated potassium channels into artificial planar lipid bilayers].

This study was aimed to establish a method to create a stable planar lipid bilayer membranes (PLBMs), in which large conductance calcium-activated potassium channels (BKCa) were reconstituted. Using spreading method, PLBMs were prepared by decane lipid fluid consisting of N2-weathered mixture of phosphatidylcholine and cholesterol at 3:1 ratio. After successful incorporation of BKCa channel into PLBMs, single channel characteristics of BKCa were studied by patch clamp method. The results showed that i) the single channel conductance of BKCa was (206.8 ± 16.9) pS; ii) the activities of BKCa channel were voltage dependent; iii) in the bath solution without Ca2+, there was almost no BKCa channel activities regardless of under hyperpolarization or repolarization conditions; iv) under the condition of +40 mV membrane potential, BKCa channels were activated in a Ca2+ concentration dependent manner; v) when [Ca2+] was increased from 1 µmol/L to 100 µmol/L, both the channel open probability and the average open time were increased, and the average close time was decreased from (32.2 ± 2.8) ms to (2.1 ± 1.8) ms; vi) the reverse potential of the reconstituted BKCa was -30 mV when [K+] was at 40/140 mmol/L (Cis/Trans). These results suggest that the spreading method could serve as a new method for preparing PLBMs and the reconstituted BKCa into PLBMs showed similar electrophysiological characteristics to natural BKCa channels, so the PLBMs with incorporated BKCa can be used in the studies of pharmacology and dynamics of BKCa channel.

The phosphoinositide-3 kinase signaling is involved in neuroinflammation in hypertensive rats.

AIMS: It has been demonstrated that neuroinflammation is associated with cardiovascular dysfunction. The phosphoinositide-3 kinase (PI3K) signaling in the rostral ventrolateral medulla (RVLM), a key region for sympathetic outflow, is upregulated and contributes to increased blood pressure (BP) and sympathetic outflow in hypertension. This study was designed to determine the role of the PI3K signaling in neuroinflammation in the RVLM of hypertension. METHODS: The normotensive WKY rats were performed by intracisternal infusion of lipopolysaccharide (LPS) or angiotensin II (Ang II) for inducing neuroinflammation. Elisa was used to determine the level of proinflammatory cytokines. Western blot was employed to detect the protein expression of PI3K signaling pathway. Gene silencing of PI3K p110δ subunit and overexpression of angiotensin-converting enzyme 2 (ACE2) were realized by injecting related lentivirus into the RVLM. RESULTS: In the spontaneously hypertensive rats (SHR), the PI3K signaling in the RVLM was upregulated compared with WKY, gene silencing of PI3K in the RVLM significantly reduced BP and renal sympathetic nerve activity (RSNA), but also decreased the levels of proinflammatory cytokines. In the WKY rats, central infusion of LPS and Ang II significantly elevated BP and RSNA, but also increased the levels of proinflammatory cytokines and PI3K signaling activation in the RVLM. These changes in the Ang II-induced hypertension were effectively prevented by gene silencing of PI3K in the RVLM. Furthermore, overexpression of ACE2 in the RVLM significantly attenuated high BP and neuroinflammation, as well as decreased the activation of PI3K signaling in hypertensive rats. CONCLUSION: This study suggests that the PI3K signaling in the RVLM is involved in neuroinflammation in hypertension and plays an important role in the renin-angiotensin system-mediated changes in neuroinflammation in the RVLM.

Different Effects of Hypertension and Age on the Function of Large Conductance Calcium- and Voltage-Activated Potassium Channels in Human Mesentery Artery Smooth Muscle Cells.

BACKGROUND: Large-conductance calcium- and voltage-activated potassium channels (BKC a channels) play important roles in the maintenance of vascular tone, and their dysregulation is associated with abnormal vascular relaxation and contraction. We tested the changes in BKC a channel properties in patients at different ages to assess the effects of hypertension and aging on the functional changes of BKC a channels. METHODS AND RESULTS: Patch clamp was performed to detect the activities of BKC a channels in freshly isolated human mesenteric artery smooth muscle cells from younger patients (aged ≤45 years) without hypertension, older patients (aged ≥65 years) without hypertension, and older patients with hypertension. The expression of mRNA and protein from BKC a channels was evaluated by reverse transcription polymerase chain reaction and Western blot analysis, respectively. Results showed that the whole-cell current density, spontaneous transient outward current, and Ca(2+) sensitivity of the artery smooth muscle cells were significantly decreased in the older patients with hypertension; the decreases were insignificant in the older patients without hypertension, although a clear tendency to have spontaneous transient outward current was detected in these patients. The expression of both mRNA and protein of BKC a subunits α and ß1 was significantly decreased in the older patients with hypertension but not in the older patients without hypertension compared with the younger patients without hypertension. CONCLUSIONS: Our findings demonstrate for the first time that hypertension is an important factor for the pathological alteration of the properties of BKC a channels in human mesenteric artery smooth muscle cells, and aging itself may also be a factor in these changes in the cells.

Remodeling of Kv1.5 channel in right atria from Han Chinese patients with atrial fibrillation.

BACKGROUND: The incidence of atrial fibrillation (AF) in rheumatic heart diseases (RHD) is very high and increases with age. Occurrence and maintenance of AF are very complicated process accompanied by many different mechanisms. Ion-channel remodeling, including the voltage-gated potassium channel Kv1.5, plays an important role in the pathophysiology of AF. However, the changes of Kv1.5 channel expression in Han Chinese patients with RHD and AF remain poorly understood. The aim of the present study was to investigate whether the Kv1.5 channels of the right atria may be altered with RHD, age, and sex to contribute to AF. MATERIAL/METHODS: Right atrial appendages were obtained from 20 patients with normal cardiac functions who had undergone surgery, and 26 patients with AF. Subjects were picked from 4 groups: adult and aged patients in normal sinus rhythm (SR) and AF. Patients were divided into non-RHD and RHD groups or men and women groups in normal SR and AF, respectively. The expression of Kv1.5 protein and messenger RNA (mRNA) were measured using Western blotting and polymerase chain reaction (PCR) method, respectively. RESULTS: Compared with the SR group, the expression of Kv1.5 protein decreased significantly in the AF group. However, neither Kv1.5 protein nor KCNA5 mRNA had significant differences in adult and aged groups, non-RHD and RHD group, and men and women group of AF. CONCLUSIONS: The expression of Kv1.5 channel protein changes with AF but not with age, RHD, and sex in AF.

[Effects of intracellular calcium alteration on SK currents in atrial cardiomyocytes from patients with atrial fibrillation].

OBJECTIVE: SK channels are existed in hearts of mouse, rat, and human. Biochemical evidence indicates that SK2 channels are expressed more in atrial than in ventricular tissue. SK channels are highly sensitive to the calcium concentration of the pipette solution. In the present study, performed whole-cell patch clamp was used to detect the calcium sensitivity of small conductance Ca(2+)-activated K+ channels (SK) currents between sinus ryhthm (SR) and auricular fibrillation (AF). METHODS: The patients who accepted cardiopulmonary bypass were divided into two groups: 21 patients with SR and 8 patients with AF. The enzymatic dissociation method was improved according to the previous research by our lab. The performed whole cell patch-clamp technique was used to record SK2 currents in both SR and AF groups at room temperature. RESULTS: The SK2 current density was (-2.92 +/- 0.35) pA/pF in SR group (n = 6) vs (-6.83 +/- 0.19) pA/pF in AF group at -130 mV (n = 3, P < 0.05). In SR group, the SK2 current densities in calcium concentration of the pipette solution are (-1.43 +/- 0.33) pA/pF (n = 7), (-2.92 +/- 0.35) pA/pF (n = 6), (-10.11 +/- 2.15) pA/pF (n = 8, P < 0.05); In AF group, the SK2 current densities are (-2.17 +/- 0.40) pA/pF (n = 4), (-6.83 +/- 0.19) pA/pF (n = 3), (-14.47 +/- 2.89 pA/pF) (n = 4, P < 0.05). CONCLUSION: The SK2 currents recorded in this experiment are voltage-independent, inwardly rectifying and apamin-sensitive. When the calcium concentration of the pipette solution is 5 x 10(-7) mol/L, SK2 current density in AF group are significantly larger than those in SR group. It suggests that SK currents involve the cardiomyocytes electric remodeling in AF. In AF group, the SK2 currents are more sensitive to free calcium ion. It shows that the increased sensitivity of SK2 currents to the calcium contribute to the occurrence and maintenance of AF.

Tanshinone II-A sodium sulfonate (DS-201) enhances human BKCa channel activity by selectively targeting the pore-forming α subunit.

AIM: Tanshinone II-A sodium sulfonate (DS-201), a water-soluble derivative of Tanshinone II-A, has been found to induce vascular relaxation and activate BKCa channels. The aim of this study was to explore the mechanisms underlying the action of DS-201 on BKCa channels. METHODS: Human BKCa channels containing α subunit alone or α plus ß1 subunits were expressed in HEK293 cells. BKCa currents were recorded from the cells using patch-clamp technique. The expression and trafficking of BKCa subunits in HEK293 cells or vascular smooth muscle cells (VSMCs) were detected by Western blotting, flow cytometry and confocal microscopy. RESULTS: DS-201 (40-160 µmol/L) concentration-dependently increased the total open probability of BKCa channels in HEK293 cells, associated with enhancements of Ca(2+) and voltage dependence as well as a delay in deactivation. Coexpression of ß1 subunit did not affect the action of DS-201: the values of EC50 for BKCa channels containing α subunit alone and α plus ß1 subunit were 66.6±1.5 and 62.0±1.1 µmol/L, respectively. In both HEK293 cells and VSMCs, DS-201 (80 µmol/L) markedly increased the expression of α subunit without affecting ß1 subunit. In HEK293 cells, DS-201 enriched the membranous level of α subunit, likely by accelerating the trafficking and suppressing the internalization of α subunit. In both HEK293 cells and VSMCs, DS-201 (≥320 µmol/L) induced significant cytotoxicity. CONCLUSION: DS-201 selectively targets the pore-forming α subunit of human BKCa channels, thus enhancing the channel activities and increasing the subunit expression and trafficking, whereas the ß1 subunit does not contribute to the action of DS-201.

[The measurement of the third-order branches of the mesenteric artery tone by microvascular ring technique].

OBJECTIVE: In our study, the function of the third-order branches of the mesentenc artery was measured by microvascular ring technique, which can be used to detect microvascular function in some disease related to microvascular dysfunction. METHODS: Isolated, fixed, standardized and then activated the third-order branches of rat mesenteric artery. Microvascular tone was measured by systolic and diastolic drags respectively, with the help of DMT tension apparatus and PowerLab data acquisition system. RESULTS: The third-order branches of rat mesenteric artery showed excellent response to vasoactive drugs. The contraction effect of norepinephrine (NE) reached 19 in mN. When acetylcholine (Ach) or sodium nitroprusside (SNP) of 10(9)-10(5)mol/L was added, vascular tones showed gradient drop: 80% of maximal relaxation when adding ACh, while 95% of maximal relaxation when adding SNP. CONCLUSION: The third-order branches of the mesenteric artery function was successfully detected by using microvascular ring technique.

IP3 decreases coronary artery tone via activating the BKCa channel of coronary artery smooth muscle cells in pigs.

Large conductance Ca(2+)-activated K(+) channel (BKCa) is a potential target for coronary artery-relaxing medication, but its functional regulation is largely unknown. Here, we report that inositol trisphosphate (IP3) activated BKCa channels in isolated porcine coronary artery smooth muscle cells and by which decreased the coronary artery tone. Both endogenous and exogenous IP3 increased the spontaneous transient outward K(+) currents (STOC, a component pattern of BKCa currents) in perforated and regular whole-cell recordings, which was dependent on the activity of IP3 receptors. IP3 also increased the macroscopic currents (MC, another component pattern of BKCa currents) via an IP3 receptor- and sarcoplasmic Ca(2+) mobilization-independent pathway. In inside-out patch recordings, direct application of IP3 to the cytosolic side increased the open probability of single BKCa channel in an IP3 receptor-independent manner. We conclude that IP3 is an activator of BKCa channels in porcine coronary smooth muscle cells and exerts a coronary artery-relaxing effect. The activation of BKCa channels by IP3 involves the enhancement of STOCs via IP3 receptors and stimulation of MC by increasing the Ca(2+) sensitivity of the channels.

Rhynchophylline-induced vasodilation in human mesenteric artery is mainly due to blockage of L-type calcium channels in vascular smooth muscle cells.

Rhynchophylline (Rhy) is a pharmacologically active substance isolated from Uncaria rhynchophylla which has been used to treat cardiovascular diseases and has drawn considerable attention in recent years for its antihypertensive activities. We investigated the actions of Rhy on endothelium-denuded human mesenteric artery by tension measurement and its actions on high conductance Ca(2+)-activated K(+) channels (BKCa) currents and calcium currents (ICa) in freshly isolated smooth muscle cells using perforated patch clamp technique. Intracellular Ca(2+) level was measured in Fura-2-loaded cells. Rhy inhibited both the KCl and BayK-evoked mesenteric artery constrictions in a dose-dependent manner. K(+) channel blockers (TEA, glibenclamide, IbTX, and 4-AP) did not affect the vasorelaxing effect of Rhy. Rhy inhibited L-type voltage-gated Ca(2+) current (ICa,L) but had no significant effect on macroscopic BKCa current. Rhy preincubation markedly reduced the elevation of [Ca(2+)]i level induced by KCl depolarization. Caffeine-stimulated [Ca(2+)]i elevation was also decreased to some extent by pretreatment with Rhy for 20 min. Our results show that Rhy relaxes smooth muscles of human mesenteric resistance arteries, mainly due to inhibition of Ca(2+) influx by blockage of L-type Ca(2+) channels and thereby the decrease in [Ca(2+)]i.

Function of BKCa channels is reduced in human vascular smooth muscle cells from Han Chinese patients with hypertension.

Chronic hypertension is associated with an impaired vascular relaxation caused by an increased vascular tone; however, the underlying mechanisms are not fully understood in human patients. The present study was to investigate whether large-conductance Ca(2+)- and voltage-activated K(+) (BK(Ca)) channels are involved in dysfunctional relaxation of artery in Han Chinese patients with hypertension using the perforated patch clamp, inside-out single-channel, and macromembrane patch recording techniques to determine whole-cell current, spontaneous transient outward current, open probability, and Ca(2+) sensitivity and the reverse transcription polymerase chain reaction and Western blot analysis to examine the gene and protein expression of α-subunit (KCa1.1) and ß1-subunit (KCNMB1) of BK(Ca) channels in isolated human vascular smooth muscle cells and mesenteric arteries from normotensive and hypertensive patients. It was found that whole-cell current density, spontaneous transient outward current, and Ca(2+) sensitivity, but not single-channel open probability and slope conductance, were significantly decreased in vascular smooth muscle cells from patients with hypertension. Interestingly, mRNA and protein levels of KCNMB1, but not KCa1.1, were reduced in the arterial tissue from patients with hypertension. These results demonstrate for the first time that whole-cell current, spontaneous transient outward current, and Ca(2+) sensitivity of BK(Ca) channels are reduced in human vascular smooth muscle cells, which resulted from downregulation of ß1-subunit of the channel. This may account, at least in part, for the dysfunction of artery relaxation in Han Chinese patients with primary hypertension.

[Construction and identification of the expression plasmid of SK2 (KCNN2) gene from human atrial myocytes with overlapping PCR].

OBJECTIVE: Small conductance calcium activated potassium channels type 2 (SK2) play a crucial role in atrial repolarization. It is difficult to acquire the full-length of its coded gene KCNN2 by RT-PCR with one step. We aim to get the full-length of KCNN2 gene and construct the plasmid by Overlapping PCR, and further more discuss the application of Overlapping PCR. METHODS: Total RNA was extracted from human right atrial tissue and cDNA was acquired with reverse transcription. Overlapping PCR was conducted with three pairs of primers which were designed according to the sequence of KCNN2 (AY258141) gene. The expression plasmid of pIRES-hrGFP-SK2 was constructed by directed cloning with restriction enzyme site and identified by enzyme cutting and sequencing. RESULTS: Three parts of PCR amplification were consistent with predicted size. The sequence of the plasmid was consistent with the gene-bank data except two sites, however, which were the same as gene in different tissues. CONCLUSION: The expression plasmid pIRES-hrGFP-SK2 was constructed successfully. Overlapping PCR is a good choice for amplifying these genes with long size or low expression.

[Application of recording SK2 current in human atrial myocytes by perforated patch clamp techniques with the mix of beta-escin and amphotericin B].

OBJECTIVE: To establish a perforated patch-clamp technology with amphotericin B and beta-escin and to research the regulation of small conductance calcium-activated potassium channel SK2 currents by calcium ions. METHODS: Single human atrial myocytes were enzymatically isolated from the right atrial appendage. Amphotericin B and / or beta-escin were used by perforated electrode liquid. The regulation of SK2 current by calcium ions in human atrial myocytes was performed with the perforated patch-clamp technique. The intracellular calcium changes were measured by the intracellular calcium test system. RESULTS: Mixed perforated electrode liquid compared with 150 microg/ml amphotericin B or 6.88 microg/ml beta-escin alone, it was easy to seal cells and activate SK2 current by the former method. Moreover, the ration of F340/380 was consistent with the change of intracellular free calcium ion concentration increase after the formation of perforation. The ration of F340/380 was measured by intracellular calcium test system. CONCLUSION: The appropriate concentration of amphotericin B mixed with beta-escin can form a stable whole-cell patch recording technology that is appropriate for the research of SK2 current regulation by intracellular calcium.

Molecular mechanism of hepatocellular carcinoma-specific antitumor activity of the novel thienopyridine derivative TP58.

Despite progress made in the treatment of hepatocellular carcinoma (HCC), there is no curable treatment. Novel therapies are therefore needed. In our previous study on the design and synthesis of a small molecular inhibitor targeting Aurora kinase, we discovered a novel thienopyridine derivative compound (1g, TP58) which displayed the most potent and relatively specific inhibition of the proliferation of HepG2 human hepatoma cells in vitro. However, the molecular mechanism remains to be elucidated. Herein, in vitro and in vivo studies were conducted to further verify its antitumor activity against HCC. cDNA microarray and two-dimensional protein gel electrophoresis technology were utilized to elucidate the mechanism of HCC-specific inhibition of TP58. Flow cytometry analysis displayed that TP58 can significantly induce G0/G1 arrest in HepG2 cells. Sixteen genes involved in cell cycle regulation were found to be dysregulated following TP58 treatment using microarray technology. Nine proteins whose expression was altered (corresponding to 10 spots identified as differentially expressed) were identified by proteomic analysis. Further study showed that TP58 can modulate the expression of some liver-enriched transcription factors (LETFs) and liver-specific marker genes, such as hepatic nuclear factor (HNF-4) and α-fetoprotein (AFP). These findings may help explain the mechanism of HCC-specific antitumor activity of TP58 and provide some useful insight for anti-HCC drug design and future use of thienopyridine derivatives in HCC therapy.

[ß-estradiol activates BK(Ca) in mesenteric artery smooth muscle cells of post-menopause women].

The aim of the present study was to study the effect of ß-estradiol (ß-E(2)) on the large-conductance Ca(2+)-activated potassium (BK(Ca)) channel in mesenteric artery smooth muscle cells (SMCs). The mesenteric arteries were obtained from post-menopause female patients with abdominal surgery, and the SMCs were isolated from the arteries using an enzymatic disassociation. According to the sources, the SMCs were divided into non-hypertension (NH) and essential hypertension (EH) groups. Single channel patch clamp technique was used to investigate the effect of ß-E(2) and ICI 182780 (a specific blocker of estrogen receptor) on BK(Ca) in the SMCs. The results showed the opening of BK(Ca) in the SMCs was voltage and calcium dependent, and could be blocked by IbTX. ß-E(2) (100 µmol/L) significantly increased open probability (Po) of BK(Ca) in both NH and EH groups. After ß-E(2) treatment, NH group showed higher Po of BK(Ca) compared with EH group. ICI 182780 could inhibit the activating effect of ß-E(2) on BK(Ca) in no matter NH or EH groups. These results suggest ß-E(2) activates BK(Ca) in mesenteric artery SMCs from post-menopause women via estrogen receptor, but hypertension may decline the activating effect of ß-E(2) on BK(Ca).

Propofol increases the Ca2+ sensitivity of BKCa in the cerebral arterial smooth muscle cells of mice.

AIM: Propofol has the side effect of hypotension especially in the elderly and patients with hypertension. Previous studies suggest propofol-caused hypotension results from activation of large conductance Ca(2+)-sensitive K channels (BKCa). In this study, the effects of propofol on the Ca(2+) sensitivity of BKCa were investigated in mice cerebral arterial smooth muscle cells. METHODS: Single smooth muscle cells were prepared from the cerebral arteries of mice. Perforated whole-cell recoding was conducted to investigate the whole-cell BKCa current and spontaneous transient outward K(+) current (STOC). Inside-out patch configuration was used to record the single channel current and to study the Ca(2+)- and voltage-dependence of BKCa. RESULTS: Propofol (56 and 112 µmol/L) increased the macroscopic BKCa and STOC currents in a concentration-dependent manner. It markedly increased the total open probability (NPo) of single BKCa channel with an EC(50) value of 76 µmol/L. Furthermore, propofol significantly decreased the equilibrium dissociation constant (K(d)) of Ca(2+) for BKCa channel. The K(d) value of Ca(2+) was 0.881 µmol/L in control, and decreased to 0.694, 0.599 and 0.177 µmol/L, respectively, in the presence of propofol 28, 56 and 112 µmol/L. An analysis of the channel kinetics revealed that propofol (112 µmol/L) significantly increased the open dwell time and decreased the closed dwell time, which stabilized BKCa channel in the open state. CONCLUSION: Propofol increases the Ca(2+) sensitivity of BKCa channels, thus lowering the Ca(2+) threshold of the channel activation in arterial smooth muscle cells, which causes greater vasodilating effects.

Comparative proteomic analysis of atrial appendages from rheumatic heart disease patients with sinus rhythm and atrial fibrillation.

Atrial fibrillation (AF) is the most common form of arrhythmia encountered in clinical practice, and contributes to cardiovascular morbidity and mortality. Despite significant advances in the understanding of the mechanisms associated with AF, the number of effective biomarkers and viable therapeutic targets remains relatively limited. In this study, 2-DE and MS/MS analysis was used to identify differentially expressed proteins in human atrial appendage tissues from patients with AF (n=4) compared to controls with sinus rhythm (SR; n=5). All subjects had rheumatic heart disease. Following 2-DE analysis, Coomassie Brilliant Blue staining and MS/MS identification, a total of 19 protein spots were found to be differentially expressed between the AF and SR groups. By cluster and metabolic/signaling pathway analysis, these proteins were divided into three major groups: proteins involved in the cytoskeleton and myofilament, energy metabolism associated proteins, and proteins associated with oxidative stress. The proteins identified in this study may enable a better understanding of the molecular mechanisms of AF, and may provide useful biomarkers and novel targets for drug development.

[Increased small conductance calcium-activated potassium channel (SK2 channel) current in atrial myocytes of patients with persistent atrial fibrillation].

OBJECTIVE: To compare the amplitude of the SK2 current (small conductance calcium-activated potassium channel) in human atrial myocytes with or without persistent atrial fibrillation (AF). METHODS: Right atrial appendage was obtained from 15 patients with sinus rate (SR) and 7 patients with AF underwent surgical valve replacement. Single myocyte was isolated by enzymatic dissociation method and the SK2 channel current density was recorded using whole-cell patch clamp techniques to detect the changes. Immunofluorescence was used to observe SK2 channel protein distribution on right atrial appendage. RESULTS: Using the whole cell patch-clamp recording techniques, an inward rectifier K(+) mix currents could be obtained from both SR (n = 15) and AF (n = 7) samples, I(K1) mix currents density in single myocyte of AF group was significantly increased than in SR group [(-16.42 ± 5.32) pA/pF vs (-6.59 ± 2.24) pA/pF, P < 0.01], which could be partially inhibited by apamin (100 nmol/L). The apamin-sensitive current was obtained by subtraction of the currents before and after treatment with apamin. SK2 current density was significantly increased in AF group than that of SR group [(-9.81 ± 2.54) pA/pF vs (-3.67 ± 0.37) pA/pF, P < 0.01]. SK2 channel protein was evidenced with immunofluorescence method in right atrial appendage from AF group and SR group. CONCLUSION: SK2 channel protein and current were present in atrial myocytes. The SK2 current density was significantly increased in AF group than in SR group suggesting that the increase of SK2 current might contribute to the electrical remodeling in AF patients.

The technique of simultaneous recording calcium transients and spontaneous transient outward currents in arterial smooth muscle cells.

Laser scanning confocal microscopy (LSCM) and whole-cell perforated patch-clamp techniques were combined to study simultaneously the changes of intracellular signal molecules and membrane currents. Intracellular calcium transients and spontaneous transient outward currents (STOCs) were recorded simultaneously in freshly isolated mouse cerebral artery smooth muscle cells. The cells loaded with fluo-4/AM were scanned with the confocal line-scan mode. Triggering voltage pulses derived from an EPC-10 patch clamp amplifier triggered the confocal line scan. The results showed that STOCs and intracellular calcium transients could be simultaneously recorded in the same cell. This technique will be useful in studies of diseases caused by impairments of intracellular Ca(2+) signaling and related ionic channel activities, or vice versa.