The aim of this study was to investigate the inhibitory effect and the underlying mechanism of ethacrynic acid (EA) on the contraction in mice. BL-420S force measuring system was used to measure the tension of mouse tracheal rings. The whole cell patch clamp technique was utilized to record the channel currents of airway smooth muscle (ASM) cells. The calcium imaging system was used to determine the intracellular Ca concentration ([Ca]) in ASM cells. The results showed that EA significantly inhibited the high K (80 mmol/L) and acetylcholine (ACh, 100 µmol/L)-induced contraction of mouse tracheal rings in a dose-dependent manner. The maximal relaxation percentages were (97.02 ± 1.56)% and (85.21 ± 0.03)%, and the median effective concentrations were (40.28 ± 2.20) μmol/L and (56.22 ± 7.62) μmol/L, respectively. EA decreased the K and ACh-induced elevation of [Ca] from 0.40 ± 0.04 to 0.16 ± 0.01 and from 0.50 ± 0.01 to 0.39 ± 0.01, respectively. In addition, EA inhibited L-type voltage-dependent calcium channel (LVDCC) and store-operated calcium channel (SOCC) currents in ASM cells, and Ca influx. Moreover, EA decreased the resistance of the respiratory system (Rrs) in vivo in mice. These results indicated that EA inhibits LVDCC and SOCC, which results in termination of Ca influx and decreases of [Ca], leading to relaxation of ASM. Taken together, EA might be a potential bronchodilator.
Animals ; Calcium ; metabolism ; Calcium Channels, L-Type ; Enzyme Inhibitors ; pharmacology ; Ethacrynic Acid ; pharmacology ; Mice ; Muscle Contraction ; drug effects ; Muscle, Smooth ; drug effects ; Respiratory System ; cytology ; drug effects

The aim of this study was to investigate the effect of interleukin 6 (IL-6) on the contraction of colon longitudinal muscle strips in rats with acute pancreatitis (AP) and its underlying mechanism. Rat AP model was established by combined injection (i. p.) of ceruletide and lipopolysaccharide. The effect of IL-6 on spontaneous contraction of longitudinal smooth muscle strips of rat colon was observed by biological function experiment system. The level of serum IL-6 was detected by ELISA, the expression and distribution of IL-6 in colon were observed by histochemical staining, and the effect of IL-6 on L-type calcium channel in colon smooth muscle cells was observed by whole cell patch clamp technique. The results showed that, compared with the control group, AP group exhibited reduced contractile amplitude and longer contraction cycle of colon smooth muscle strips. IL-6 prolonged the contraction cycle of colon smooth muscle strips, but did not affect their spontaneous contraction amplitude. Serum IL-6 concentration in AP group was significantly higher than that in control group (P > 0.05). IL-6 was diffusely distributed in the colon of the control group, but the expression of IL-6 was significantly up-regulated in the colon gland, mucosa and submucosa of the AP group. IL-6 significantly decreased the peak current density of L-type calcium channel in rat colon smooth muscle cells. These results suggest that the colon motility of AP rats is weakened, and the mechanism may be that up-regulated IL-6 inactivates L-type voltage-dependent calcium channels, and then inhibits the contraction of colon longitudinal smooth muscle.
Animals ; Calcium Channels, L-Type ; metabolism ; Colon ; Interleukin-6 ; metabolism ; Muscle Contraction ; Muscle, Smooth ; physiopathology ; Pancreatitis ; physiopathology ; Rats

Anoctamin 5 (ANO5)/TMEM16E belongs to a member of the ANO/TMEM16 family member of anion channels. However, it is a matter of debate whether ANO5 functions as a genuine plasma membrane chloride channel. It has been recognized that mutations in the ANO5 gene cause many skeletal muscle diseases such as limb girdle muscular dystrophy type 2L (LGMD2L) and Miyoshi muscular dystrophy type 3 (MMD3) in human. However, the molecular mechanisms of the skeletal myopathies caused by ANO5 defects are poorly understood. To understand the role of ANO5 in skeletal muscle development and function, we silenced the ANO5 gene in C2C12 myoblasts and evaluated whether it impairs myogenesis and myotube function. ANO5 knockdown (ANO5-KD) by shRNA resulted in clustered or aggregated nuclei at the body of myotubes without affecting differentiation or myotube formation. Nuclear positioning defect of ANO5-KD myotubes was accompanied with reduced expression of Kif5b protein, a kinesin-related motor protein that controls nuclear transport during myogenesis. ANO5-KD impaired depolarization-induced [Ca²⁺]i transient and reduced sarcoplasmic reticulum (SR) Ca²⁺ storage. ANO5-KD resulted in reduced protein expression of the dihydropyridine receptor (DHPR) and SR Ca²⁺-ATPase subtype 1. In addition, ANO5-KD compromised co-localization between DHPR and ryanodine receptor subtype 1. It is concluded that ANO5-KD causes nuclear positioning defect by reduction of Kif5b expression, and compromises Ca²⁺ signaling by downregulating the expression of DHPR and SERCA proteins.
Active Transport, Cell Nucleus ; Calcium Channels, L-Type ; Cell Membrane ; Chloride Channels ; Humans ; Muscle Development ; Muscle Fibers, Skeletal ; Muscle, Skeletal ; Muscular Diseases ; Muscular Dystrophies ; Muscular Dystrophies, Limb-Girdle ; Myoblasts ; RNA, Small Interfering ; Ryanodine Receptor Calcium Release Channel ; Sarcoplasmic Reticulum

Depending on the intracellular buffering of calcium by chelation, zinc has the following two apparent effects on neuronal excitability: enhancement or reduction. Zinc increased tonic activity in the depolarized state when neurons were intracellularly dialyzed with EGTA but attenuated the neuronal activity when BAPTA was used as an intracellular calcium buffer. This suggests that neuronal excitability can be modulated by zinc, depending on the internal calcium buffering capacity. In this study, we elucidated the mechanisms of zinc-mediated alterations in neuronal excitability and determined the effect of calcium-related channels on zinc-mediated alterations in excitability. The zinc-induced augmentation of firing activity was mediated via the inhibition of small-conductance calcium-activated potassium (SK) channels with not only the contribution of voltage-gated L-type calcium channels (VGCCs) and ryanodine receptors (RyRs), but also through the activation of VGCCs via melastatin-like transient receptor potential channels. We suggest that zinc modulates the dopaminergic neuronal activity by regulating not only SK channels as calcium sensors, but also VGCCs or RyRs as calcium sources. Our results suggest that the cytosolic calcium-buffering capacity can tightly regulate zinc-induced neuronal firing patterns and that local calcium-signaling domains can determine the physiological and pathological state of synaptic activity in the dopaminergic system.
Animals ; Calcium ; Calcium Channels, L-Type ; Cytosol ; Dopaminergic Neurons ; Egtazic Acid ; Electrophysiology ; Fires ; Neurons ; Potassium ; Rats ; Ryanodine Receptor Calcium Release Channel ; Transient Receptor Potential Channels ; Zinc

To investigate the relationship between single nucleotide polymorphisms (SNPs) of CACNA1C (SNPs rs58619945, rs7316246 and rs216008) and susceptibility of chronic spontaneous urticaria (CSU) as well as the curative effect of non-sedating antihistamine drugs.
 Methods: Peripheral blood were extracted from 191 CSU patients to collect DNA. Urticaria Activity Score 7 (UAS7) and Dermatology Life Quality Index (DLQI) changes were collected from these patients with different non-sedating antihistamine drugs. PubMed retrieval system was used to select the 3 SNPs (rs58619945, rs7316246 and rs216008) of CACNA1C. Susceptibility of CSU and curative effect of non-sedating antihistamine drugs (desloratadine, mizolastine, fisofenadine) in 189 CSU patients and 105 controls with different SNPs were compared with Chi-squared test. Data of 105 southern Chinese controls were extracted from the 1 000 genome database.
 Results: Frequency of rs58619945 G allele in the CSU patients was significantly higher than that in the controls [OR(95%CI)=0.660(0.470-0.925), P=0.016]. However, there was no significant differences in rs7316246 and rs216008 between the CSU patients and the controls. Meanwhile there was no significant difference in general curative effect of the 3 drugs in the 3 SNPs (rs58619945: OR=0.843, P=0.454; rs7316246: OR=2.103, P=0.102; rs216008: OR=0.237, P=0.363). There was significant difference in different alleles of rs216008 in the patients administered by desloratadine [OR(95%CI)=0.480(0.247-0.933), P=0.029]. No difference was shown in the 3 SNPs in patients administered by mizolastine.
 Conclusion: The rs58619945 A/G might be related to susceptibility of CSU, and the rs216008 mutation might affect drug response of desloratadine.
Calcium Channels, L-Type ; genetics ; Chronic Disease ; Genetic Predisposition to Disease ; Histamine H1 Antagonists, Non-Sedating ; therapeutic use ; Humans ; Loratadine ; analogs & derivatives ; therapeutic use ; Polymorphism, Single Nucleotide ; Prognosis ; Retrospective Studies ; Urticaria ; drug therapy ; genetics

Calcium Channels, L-Type ; genetics ; metabolism ; Esophageal Achalasia ; genetics ; metabolism ; Esophagus ; metabolism ; Humans ; Nitric Oxide Synthase ; metabolism ; Nitric Oxide Synthase Type I ; genetics ; metabolism ; RNA, Messenger ; metabolism ; Real-Time Polymerase Chain Reaction ; Receptors, Calcium-Sensing ; genetics ; metabolism

Voltage-gated sodium (Na) channels are essential for the rapid upstroke of action potentials and the propagation of electrical signals in nerves and muscles. Defects of Na channels are associated with a variety of channelopathies. More than 1000 disease-related mutations have been identified in Na channels, with Na1.1 and Na1.5 each harboring more than 400 mutations. Na channels represent major targets for a wide array of neurotoxins and drugs. Atomic structures of Na channels are required to understand their function and disease mechanisms. The recently determined atomic structure of the rabbit voltage-gated calcium (Ca) channel Ca1.1 provides a template for homology-based structural modeling of the evolutionarily related Na channels. In this Resource article, we summarized all the reported disease-related mutations in human Na channels, generated a homologous model of human Na1.7, and structurally mapped disease-associated mutations. Before the determination of structures of human Na channels, the analysis presented here serves as the base framework for mechanistic investigation of Na channelopathies and for potential structure-based drug discovery.
Animals ; Calcium Channels, L-Type ; chemistry ; genetics ; metabolism ; Channelopathies ; genetics ; metabolism ; Humans ; Mutation ; NAV1.1 Voltage-Gated Sodium Channel ; chemistry ; genetics ; metabolism ; NAV1.5 Voltage-Gated Sodium Channel ; chemistry ; genetics ; metabolism ; NAV1.7 Voltage-Gated Sodium Channel ; chemistry ; genetics ; metabolism ; Protein Domains ; Rabbits ; Structure-Activity Relationship

BACKGROUND/AIMS: Chronic intestinal pseudo-obstruction (CIPO) is a disorder characterized by recurrent symptoms suggestive of obstruction such as abdominal pain, proximal distension with extremely suppressed motility in the absence of lumen-occluding lesion, whose etiology/pathophysiology is poorly understood. In this study we investigated a functionally obstructive lesion that could underlie symptoms of CIPO. METHODS: We studied colons surgically removed from 13 patients exhibiting clinical/pathological features of pseudo-obstruction but were unresponsive to standard medical treatments. The colons were characterized morphologically, functionally and molecularly, which were compared between regions and to 28 region-matched controls obtained from colon cancer patients. RESULTS: The colons with pseudo-obstruction exhibited persistent luminal distension proximally, where the smooth muscle was hypertrophied with changes in the cell phenotypes. Distinct luminal narrowing was observed near the distal end of the dilated region, close to the splenic flexure, previously referred to as the "transition zone (TZ)" between the dilated and non-dilated loops. Circular muscles from the TZ responded less to depolarization and cholinergic stimulation, which was associated with down-regulation of L-type calcium channel expression. Smooth muscle contractile protein was also downregulated. Myenteric ganglia and neuronal nitric oxide synthase (nNOS) positive cells were deficient, more severely in the TZ region. Interstitial cells of Cajal was relatively less affected. CONCLUSIONS: The TZ may be the principal site of functional obstruction, leading to proximal distension and smooth muscle hypertrophy, in which partial nNOS depletion could play a key role. The neuromuscular abnormalities probably synergistically contributed to the extremely suppressed motility observed in the colonic pseudo-obstruction.
Abdominal Pain ; Calcium Channels, L-Type ; Colon* ; Colon, Transverse ; Colonic Neoplasms ; Colonic Pseudo-Obstruction* ; Constipation* ; Down-Regulation ; Ganglia ; Humans ; Hypertrophy ; Interstitial Cells of Cajal ; Intestinal Pseudo-Obstruction ; Muscle, Smooth ; Muscles ; Nitric Oxide ; Nitric Oxide Synthase Type I ; Phenobarbital ; Phenotype

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

This study is aimed to investigate the effects of high intracellular Mg²⁺ on L-type calcium channel in guinea-pig ventricular myocytes. The cardiomyocytes were acutely isolated with enzyme digestion method. By adopting inside-out configuration of patch clamp technique, single channel currents of the L-type calcium channel were recorded under different intracellular Mg²⁺ concentrations ([Mg²⁺]i). In control group, which was treated with 0.9 mmol/L Mg²⁺, the relative activity of calcium channel was (176.5 ± 34.1)% (n = 7). When [Mg²⁺]i was increased from 0.9 to 8.1 mmol/L (high Mg²⁺ group), the relative activities of calcium channel decreased to (64.8 ± 18.1)% (n = 6, P < 0.05). Moreover, under 8.1 mmol/L Mg²⁺, the mean open time of calcium channel was shortened to about 25% of that under control condition (P < 0.05), but the mean close time of calcium channel was not altered. These results suggest that high intracellular Mg²⁺ may inhibit the activities of L-type calcium channel, which is mainly due to the shortening of the mean open time of single L-type calcium channel.
Animals ; Calcium Channels, L-Type ; physiology ; Guinea Pigs ; Magnesium ; physiology ; Myocytes, Cardiac ; physiology ; Patch-Clamp Techniques