OBJECTIVETo review the recent developments in the mechanisms of epithelium sodium channels (ENaCs) induced bone formation and regulation.

DATA SOURCESStudies written in English or Chinese were searched using Medline, PubMed and the index of Chinese-language literature with time restriction from 2005 to 2014. Keywords included ENaC, bone, bone formation, osteonecrosis, estrogen, and osteoporosis. Data from published articles about the structure of ENaC, mechanism of ENaC in bone formation in recent domestic and foreign literature were selected.

STUDY SELECTIONAbstract and full text of all studies were required to obtain. Studies those were not accessible and those did not focus on the keywords were excluded.

RESULTSENaCs are tripolymer ion channels which are assembled from homologous α, β, and γ subunits. Crystal structure of ENaCs suggests that ENaC has a central ion-channel located in the central symmetry axis of the three subunits. ENaCs are protease sensitive channels whose iron-channel activity is regulated by the proteolytic reaction. Channel opening probability of ENaCs is regulated by proteinases, mechanical force, and shear stress. Several molecules are involved in regulation of ENaCs in bone formation, including nitride oxide synthases, voltage-sensitive calcium channels, and cyclooxygenase-2.

CONCLUSIONThe pathway of ENaC involved in shear stress has an effect on stimulating osteoblasts even bone formation by estrogen interference.

Calcium Channels ; physiology ; Epithelial Sodium Channels ; chemistry ; physiology ; Estrogens ; pharmacology ; Humans ; Osteogenesis ; physiology

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 (BK) were reconstituted. Using spreading method, PLBMs were prepared by decane lipid fluid consisting of N-weathered mixture of phosphatidylcholine and cholesterol at 3:1 ratio. After successful incorporation of BKchannel into PLBMs, single channel characteristics of BKwere studied by patch clamp method. The results showed that i) the single channel conductance of BKwas (206.8 ± 16.9) pS; ii) the activities of BKchannel were voltage dependent; iii) in the bath solution without Ca, there was almost no BKchannel activities regardless of under hyperpolarization or repolarization conditions; iv) under the condition of +40 mV membrane potential, BKchannels were activated in a Caconcentration dependent manner; v) when [Ca] 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 BKwas -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 BKinto PLBMs showed similar electrophysiological characteristics to natural BKchannels, so the PLBMs with incorporated BKcan be used in the studies of pharmacology and dynamics of BKchannel.
Animals ; Calcium ; chemistry ; Electrophysiological Phenomena ; Large-Conductance Calcium-Activated Potassium Channels ; chemistry ; Lipid Bilayers ; chemistry ; Membrane Potentials ; Patch-Clamp Techniques

Small conductance Ca(2+)-activated potassium channels (SK channels) distributing in the nervous system play an important role in learning, memory and synaptic plasticity. Most pharmacological properties of them are determined by short-chain scorpion toxins. Different from most voltage-gated potassium channels and large-conductance Ca(2+)-activated potassium channels, SK channels are only inhibited by a small quantity of scorpion toxins. Recently, a novel peptide screener in the extracellular pore entryway of SK channels was considered as the structural basis of toxin selective recognition. In this review, we summarized the unique interactions between scorpion toxins and SK channels, which is crucial not only in deep-researching for physiological function of SK channels, but also in developing drugs for SK channel-related diseases.
Animals ; Memory ; Neuronal Plasticity ; Scorpion Venoms ; chemistry ; Scorpions ; Small-Conductance Calcium-Activated Potassium Channels ; antagonists & inhibitors

Animals ; Asthma ; physiopathology ; Bronchi ; metabolism ; Bronchial Hyperreactivity ; etiology ; Humans ; Muscle, Smooth ; metabolism ; Potassium Channels ; chemistry ; physiology ; Potassium Channels, Calcium-Activated ; physiology ; Potassium Channels, Voltage-Gated ; physiology

BACKGROUNDThe contractility of hepatic stellate cells (HSCs) may play an important role in the pathogenesis of cirrhosis with portal hypertension. The aim of this study was to research the effects of octreotide, an analogue of somatostatin, on intracellular Ca2+ and on the expression of L-type voltage-operated calcium channels (L-VOCCs) in activated HSCs, and to try to survey the use of octreotide in treatment and prevention of cirrhosis with portal hypertension complications.

METHODSHSC-T6, an activated HSCs line, was plated on small glass coverslips in 35-mm culture dishes at a density of 1 x 10(5)/ml, and incubated in DMEM media for 24 hours. After the cells were loaded with Fluo-3/AM, intracellular Ca2+ was measured by Laser Scanning Confocal Microscopy (LSCM). The dynamic changes in activated HSCs of intracellular Ca2+, stimulated by octreotide, endothelin-1, and KCl, respectively, were also determined by LSCM. Each experiment was repeated six times. L-VOCC expression in HSCs was estimated by immunocytochemistry.

RESULTSAfter octreotide stimulation, a significant decrease in the intracellular Ca2+ of activated HSCs was observed. However, octreotide did not inhibit the increases in intracellular Ca2+ after stimulation by KCl and endothelin-1. Moreover, octreotide did not significantly affect L-VOCC expression. These results suggest that neither L-VOCC nor endothelin-1 receptors in activated HSCs are inhibited by octreotide.

CONCLUSIONSOctreotide may decrease portal hypertension and intrahepatic vascular tension by inhibiting activated HSCs contractility through decreases in intracellular Ca2+. The somatostatin receptors in activated HSCs may be inhibited by octreotide.

Calcium ; analysis ; Calcium Channels, L-Type ; analysis ; Cells, Cultured ; Hepatocytes ; chemistry ; cytology ; drug effects ; Microscopy, Confocal ; Octreotide ; pharmacology

BACKGROUND: The primary mode of conduction bldegrees Ckade by ldegrees Cal anesthetics degrees Ccurs through the inhibition of voltage-dependent sodium current and, inhibitory potency of ldegrees Cal anesthetics are correlated with their hydrophobicity, expressed as degrees Ctanol/buffer partition coefficients(PC). The homologous structural bidegrees Chemistry and analogous physiology of voltage-dependent sodium and calcium channels prompted us to examine the relationship between potency of various ldegrees Cal anesthetics for the inhibition of voltage-dependent calcium channels(VDCC) and their PC values. METHODS: Whole cell patch clamp recordings were made from acutely dissdegrees Ciated rat dorsal root ganglion neurons, and voltage dependent calcium current(ICa) was evoked by depolarizing pulse. The concentrations of various ldegrees Cal anesthetics(bupivacaine, liddegrees Caine, prildegrees Caine, prdegrees Caine, tetracaine) that bldegrees Ck 50% of the control ICa(IC50) were calculated from dose-response curves. The relationship between IC50 and PC values of various ldegrees Cal anesthetics were investigated. RESULTS: Ldegrees Cal anesthetics inhibited ICa with neglegible effect on the current- voltage relatonship. IC50 values of tetracaine, bupivacaine, liddegrees Caine, prildegrees Caine and prdegrees Caine were 98, 142, 2710, 10400, 16900 uM respectively, and linear regression of the plot of log(IC50) against log(PC) was statistically significant (p<0.001). CONCLUSIONS: It is speculated that inhibitory effects of ldegrees Cal anesthetics on the VDCC when used in epidural and spinal anesthesia may contribute to their analgesic and anesthetic actions. Inhibitory potency of ldegrees Cal anesthetics on the VDCC, as for voltage-dependent sodium channels, was correlated with their hydrophobicity.
Anesthesia, Spinal ; Anesthetics* ; Animals ; Bupivacaine ; Calcium Channels ; Calcium* ; Chemistry ; Ganglia, Spinal ; Hydrophobic and Hydrophilic Interactions* ; Inhibitory Concentration 50 ; Linear Models ; Neurons ; Physiology ; Rats ; Sodium ; Sodium Channels ; Tetracaine

The large-conductance calcium-activated potassium (BK) channels distributed in both excitable and non-excitable cells are key participants in a variety of physiological functions. By employing numerous high-affinity natural toxins originated from scorpion venoms the pharmacological and structural characteristics of these channels tend to be approached. A 37-residue short-chain peptide, named as martentoxin, arising from the venom of the East-Asian scorpion (Buthus martensi Karsch) has been investigated with a comparatively higher preference for BK channels over other voltage-gated potassium (Kv) channels. Up to now, since the specific drug tool probing for clarifying structure-function of BK channel subtypes and related pathology remain scarce, it is of importance to illuminate the underlying mechanism of molecular interaction between martentoxin and BK channels. As for it, the current review will address the recent progress on the studies of pharmacological characterizations and molecular determinants of martentoxin targeting on BK channels.
Amino Acid Sequence ; Humans ; Large-Conductance Calcium-Activated Potassium Channels ; antagonists & inhibitors ; Ligands ; Peptides ; chemistry ; Scorpion Venoms ; chemistry

This study was amid to construct the pharmacophore model of L-type calcium channel antagonist in the application of screening Drugbank and TCMD. This paper repositions the approved drugs resulting from virtual screening and discusses the relocation-based drug discovery methods, screening antihypertensive drugs with L-type calcium channel function from TCMD. Qualitative hypotheses wre generated by HipHop separately on the basis of 12 compounds with antagonistic action on L-type calcium channel expressed in rabbit cardiac muscle. Datebase searching method was used to evaluate the generated hypotheses. The optimum hypothesis was used to search Drugbank and TCMD. This paper repositions the approved drugs and evaluates the antihypertensive effect of the chemical constituent of traditional Chinese medicine resulting from virtual screening by the matching score and literature. The results showed that optimum qualitative hypothesis is with six features, which were two hydrogen-bond acceptors, four hydrophobic groups, and the CAI value of 2.78. Screening Drugbank achieves 93 approved drugs. Screening TCMD achieves 285 chemical constituents of traditional Chinese medicine. It was concluded that the hypothesis is reliable and can be used to screen datebase. The approved drugs resulting from virtual screening, such as pravastatin, are potentially L-type calcium channels inhibitors. The chemical constituents of traditional Chinese medicine, such as Arctigenin III and Arctigenin are potentially antihypertensive drugs. It indicates that Drug Repositioning based on hypothesis is possible.
Animals ; Antihypertensive Agents ; chemistry ; pharmacology ; Calcium Channel Blockers ; chemistry ; pharmacology ; Calcium Channels, L-Type ; genetics ; metabolism ; Drug Repositioning ; methods ; Molecular Structure ; Myocardium ; metabolism ; Rabbits

Large-conductance Ca²⁺-activated K⁺ channels (BK channels) constitute an key physiological link between cellular Ca²⁺ signaling and electrical signaling at the plasma membrane. Thus these channels are critical to the control of action potential firing and neurotransmitter release in several types of neurons, as well as the dynamic control of smooth muscle tone in resistance arteries, airway, and bladder. Recent advances in our understanding of K⁺ channel structure and function have led to new insight toward the molecular mechanisms of opening and closing (gating) of these channels. Here we will focus on mechanisms of BK channel gating by Ca²⁺, transmembrane voltage, and auxiliary subunit proteins.
Animals ; Calcium Signaling ; Cytoplasm ; metabolism ; Electric Conductivity ; Electrophysiological Phenomena ; Humans ; Ion Channel Gating ; Large-Conductance Calcium-Activated Potassium Channels ; chemistry ; metabolism ; Protein Subunits ; chemistry ; metabolism

It has been shown that oxidative stress correlates with atrial fibrillation (AF). The purpose of the present study was to investigate the effects of reactive oxygen species (ROS) on the electrophysiological activity of human atrial myocytes. Right atrial appendages were obtained from patients with AF (AF group, n=12) and without AF (non-AF group, n=12). Single human atrial myocytes were isolated through enzymatic dissociation with type XXIV protease and type V collagenase, then divided into three subgroups: control group (n=12), H2O2 group (0.1, 0.2, 0.5, 0.75, 1, 2, 5, 10 mumol/L, n=7 at each concentration) and vitamin C (antioxidant) group (1 mumol/L, n=7). Ultrarapid delayed rectifier K(+) current (I(Kur)), L-type calcium current (I(Ca,L)) and action potential duration (APD) were recorded by whole-cell patch clamp. In AF control group, the maximum current densities of I(Kur) and I(Ca,L) were significantly lower than that in non-AF control group (both P<0.05) and APD(90) was significantly shorter as well (P<0.05). In both non-AF and AF groups, H2O2 showed two-way concentration-dependent effect on I(Kur) and I(Ca,L). The maximum current densities of I(Kur) and I(Ca,L) was significantly increased at lower H2O2 concentration, but was decreased at higher H2O2 concentration. In non-AF group, 0.2 mumol/L H2O2 caused a peak increase in the maximum current identities of I(Kur) [(8.92+/-0.51) pA/pF, P<0.05] and I(Ca,L) [(9.32+/-0.67) pA/pF, P<0.05]. H2O2 at a concentration higher than 0.75 mumol/L decreased I(Kur) and I(Ca,L). When the H2O2 concentrations were 0.2, 1, 2, 5 and 10 mumol/L, APD(90) was significantly shorter compared with that in non-AF control group (P<0.05), meanwhile it had no significant difference from that in AF control group. In AF group, the peak effective concentration of H2O2 was 0.5 mumol/L, and the turning concentration was 1 mumol/L. The H2O2 concentration-current density curve in AF group was similar to that in non-AF group, but the turning point shifted to the right, indicating that the way that H2O2 acted on ion channels in AF was the same as that in non-AF, however, the sensitivity of ion channels to H2O2 was decreased in AF. Vitamin C reversed these changes induced by H2O2, and did not affect the characteristics of ion channels. H2O2-induced electrophysiological changes in human atrial myocytes were similar to atrial electrical remodeling (AER) in AF, suggesting that ROS might induce AF. Meanwhile, H2O2 also could aggravate AER in AF, contributing to the maintenance of AF. The results suggest that antioxidants might play a significant role in the prevention and treatment of AF.
Action Potentials ; Atrial Fibrillation ; physiopathology ; Calcium ; physiology ; Calcium Channels, L-Type ; physiology ; Delayed Rectifier Potassium Channels ; physiology ; Heart Atria ; cytology ; Humans ; Hydrogen Peroxide ; chemistry ; Myocytes, Cardiac ; physiology ; Patch-Clamp Techniques ; Potassium ; physiology ; Reactive Oxygen Species ; chemistry