Miaoling Li

Activation of high conductance Ca2+-activated K+ channels by sodium tanshinoneII-A sulfonate (DS-201) in porcine coronary artery smooth muscle cells

High conductance Ca(2+) activated K(+) channels (BK(Ca)) in vascular smooth muscles play important roles in controlling the vascular tone by determining the level of membrane potential and Ca(2+) influx through voltage gated Ca(2+) channels. Agents that alter the activity of Ca(2+) channels or BK(Ca) thus affect the vascular tone in both physiological and pathological conditions. Danshen, the dried root of Salvia miltiorrhiza, is a commonly used traditional Chinese medicine and is widely used as an effective remedy for cardiovascular and cerebral vascular diseases partly by its vasodilatation. Sodium tanshinoneII-A sulfonate (DS-201) is a water-soluble derivative of Tanshinone IIA, the main active component of Danshen. The purpose of this study was to explore possible mechanisms of vasodilative effects of DS-201 using porcine coronary artery smooth muscle. DS-201 induced relaxation of the coronary smooth muscle which had been contracted with 30 mM KCl, and the relaxation was inhibited by 100 nM iberiotoxin (IbTX), a specific BK(Ca) channel blocker. Using perforated whole-cell recordings and single channel recordings, effects of DS-201 on BK(Ca) were examined. The results showed that DS-201 activated BK(Ca). Extracellular application of DS-201 at 40, 80 microM under the whole-cell configuration induced increases of the BK(Ca) macroscopic currents by 43.6%, 42.1% respectively, and the spontaneous transient outward K(+) currents (STOCs) by 48.7%, 47.4% respectively. In inside-out patches, bath application of 20-150 muM of DS-201 activated BK(Ca) by 5.4-173.2 fold. These results indicate that the vasodilatation by DS-201 is related to activation of BK(Ca).

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.

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.

Sodium Tanshinone IIA Sulfonate Prevents Angiotensin II-Induced Differentiation of Human Atrial Fibroblasts into Myofibroblasts

Differentiation of atrial fibroblasts into myofibroblasts plays a critical role in atrial fibrosis. Sodium tanshinone IIA sulfonate (DS-201), a water-soluble derivative of tanshinone IIA, has been shown to have potent antifibrotic properties. However, the protective effects of DS-201 on angiotensin II- (Ang II-) induced differentiation of atrial fibroblasts into myofibroblasts remain to be elucidated. In this study, human atrial fibroblasts were stimulated with Ang II in the presence or absence of DS-201. Then, α-smooth muscle actin (α-SMA), collagen I, and collagen III expression and reactive oxygen species (ROS) generation were measured. The expression of transforming growth factor-β1 (TGF-β1) and the downstream signaling of TGF-β1, such as phosphorylation of Smad2/3, were also determined. The results demonstrated that DS-201 significantly prevented Ang II-induced human atrial fibroblast migration and decreased Ang II-induced α-SMA, collagen I, and collagen III expression. Furthermore, increased production of ROS and expression of TGF-β1 stimulated by Ang II were also significantly inhibited by DS-201. Consistent with these results, DS-201 significantly inhibited Ang II-evoked Smad2/3 phosphorylation and periostin expression. These results and the experiments involving N-acetyl cysteine (antioxidant) and an anti-TGF-β1 antibody suggest that DS-201 prevent Ang II-induced differentiation of atrial fibroblasts to myofibroblasts, at least in part, through suppressing oxidative stress and inhibiting the activation of TGF-β1 signaling pathway. All of these data indicate the potential utility of DS-201 for the treatment of cardiac fibrosis.

Myricetin inhibits Kv1.5 channels in HEK293 cells

Myricetin (Myr) is a flavonoid that exerts anti-arrhythmic effects. However, its potential effects on ion channels have remained elusive. The aim of the present study was to investigate the effects of Myr on Kv1.5 channels in HEK293 cells. The current of Kv1.5 channels (Ikur) in HEK293 cells was recorded using the whole-cell patch-clamp technique and the expression of the Kv1.5 protein was measured using western blot analysis 24 h after treatment with Myr. The results showed that 5 µM Myr significantly reduced Ikur from 215.04 ± 40.59 to 77.72 ± 17.94 pA/pF (P<0.05; n=5). Myr increased the current suppression from 0 to 0.31 ± 0.12 and 0.55 ± 0.11 over 5 or 20 min, respectively. In addition, Ikur decreased from 376.23 ± 1.30 to 270.19 ± 4.28 pA/pF when the frequency was increased from 0.5 to 4 Hz in HEK293 cells treated with 10 µM Myr for 5 min. Furthermore, Myr reduced hKv1.5 protein expression in a dose-dependent manner. These results demonstrated that Myr inhibited Ikur and the expression of hKv1.5 in HEK293 cells in a dose-, time- and frequency-dependent manner. These observations partly explained the mechanisms by which Myr exerts anti-arrhythmic effect.

GW24-e1858 The expression of SKCa channel in human mesenteric artery from Chinese patients with hypertension

Objectives The small conductance calcium-activated potassium (SKCa) channel is a key factor in the regulation of vessel tone and blood pressure. It has been proposed that activation of endothelial SK3 channel plays an important role in the arteriolar dilation through EDHF signal pathway. Nowdays, the expression of SK3 channel has been researched in a variety of hypertensive rat models. However, the results are not completely identical and the expression of SK3 channel in human with hypertension is undefined. To clarify the alteration of SK3 channel in human with hypertension, we quantified the expression of SK3 mRNA and protein in mesenteric artery of hypertension patients. Methods Mesenteric arterial tissues were collected from the removed tissues by abdominal operations in Han Chinese normotensive and primary hypertensive patients. The human tissue collection protocol was approved by the Ethics Committee of Luzhou medical College. Informed consent was obtained from the patients for the use of vascular tissue (which is usually discarded). The expression of mRNA was detected using quantitative Real-time PCR and analyzed with 2-ΔΔCT method. The artery protein extractions were detected using western blot with SK3 antibody (alomone labs, APC-025). The statistical analysis was done using independent-samples T test by SPSS 19.0. Results Average age of hypertension group (HP) used in this research was 55.0000 ± 10.2425 (n = 12), while the age of normotensive group (NP) was 58.5000 ± 12.2808 (n = 12). The value of ΔCt in HP was 10.6808 ± 1.4035 (n = 12), while it was 12.1015 ± 1.3541 (n = 12) in NP. The expression of SK3 mRNA in HP was 2.36 times higher than in NP. The relative expression of SK3 protein in HP was 1.0748 ± 0.4089 (n = 12), while it was 0.7671 ± 0.1643 (n = 12) in NP, P<0.05. Expression levels of SK3 mRNA and protein were significant up-regulation in hypertension patients. Conclusions The alteration of SK3 channel in human with hypertension is obvious enhancement but not decrease. This is contrary to results which were reported in spontaneously hypertensive rats. The nosogenesis of hypertension is quite complex, it is a result of synergism involving a series of factors and pathways. The up-regulation of SK3 channel maybe compensate deficient activity of other factors in the vasculature of hypertensive patients.