Mitochondrial dysfunction reduces the activity of KIR2.1 K+ channel in myoblasts via impaired oxidative phosphorylation.

Myoblast fusion depends on mitochondrial integrity and intracellular Ca2+ signaling regulated by various ion channels. In this study, we investigated the ionic currents associated with [Ca2+]i regulation in normal and mitochondrial DNA-depleted (ρ0) L6 myoblasts. The ρ0 myoblasts showed impaired myotube formation. The inwardly rectifying K+ current (IKir) was largely decreased with reduced expression of KIR2.1, whereas the voltage-operated Ca2+ channel and Ca2+-activated K+ channel currents were intact. Sustained inhibition of mitochondrial electron transport by antimycin A treatment (24 h) also decreased the IKir. The ρ0 myoblasts showed depolarized resting membrane potential and higher basal [Ca2+]i. Our results demonstrated the specific downregulation of IKir by dysfunctional mitochondria. The resultant depolarization and altered Ca2+ signaling might be associated with impaired myoblast fusion in ρ0 myoblasts.

Activation of transient receptor potential vanilloid 3 by the methanolic extract of Schisandra chinensis fruit and its chemical constituent γ-schisandrin.

Transient receptor potential vanilloid 3 (TRPV3) is a non-selective cation channel with modest permeability to calcium ions. It is involved in intracellular calcium signaling and is therefore important in processes such as thermal sensation, skin barrier formation, and wound healing. TRPV3 was initially proposed as a warm temperature sensor. It is activated by synthetic small-molecule chemicals and plant-derived natural compounds such as camphor and eugenol. Schisandra chinensis (Turcz.) Baill (SC) has diverse pharmacological properties including antiallergic, anti-inflammatory, and wound healing activities. It is extensively used as an oriental herbal medicine for the treatment of various diseases. In this study, we investigated whether SC fruit extracts and seed oil, as well as four compounds isolated from the fruit can activate the TRPV3 channel. By performing whole-cell patch clamp recording in HEK293T cells overexpressing TRPV3, we found that the methanolic extract of SC fruit has an agonistic effect on the TRPV3 channel. Furthermore, electrophysiological analysis revealed that γ-schisandrin, one of the isolated compounds, activated TRPV3 at a concentration of 30 µM. In addition, γ-schisandrin (~100 µM) increased cytoplasmic Ca2+ concentrations by approximately 20% in response to TRPV3 activation. This is the first report to indicate that SC extract and γ-schisandrin can modulate the TRPV3 channel. This report also suggests a mechanism by which γ-schisandrin acts as a therapeutic agent against TRPV3-related diseases.

Selective serotonin reuptake inhibitors facilitate ANO6 (TMEM16F) current activation and phosphatidylserine exposure.

Anoctamin 6 (ANO6) is a member of the recently identified TMEM16/anoctamin protein family comprising Ca(2+)-activated Cl(-) channels that generate outward-rectifying ionic currents in response to intracellular Ca(2+) increase. ANO6 is also essential for Ca(2+)-dependent phospholipid scrambling required for blood coagulation. Selective serotonin reuptake inhibitors (SSRIs)--fluoxetine, sertraline, and paroxetine-that are used for the treatment of major depressive disorders can increase the risk of upper gastrointestinal bleeding after chronic treatment. However, at the earlier stage of intake, which is 1-7 days after the treatment, the possibility of blood coagulation might also increase, but transiently. Therefore, in this study, we investigated whether therapeutic SSRI concentrations affected the Cl(-) current or phospholipid scrambling activity of ANO6 by assessing ANO6 currents (I ANO6), phosphatidylserine (PS) exposure, and platelet aggregation. In the whole-cell patch mode, SSRIs facilitated Ca(2+)-dependent activation of IANO6 in ANO6-transfected cells, as evidenced by a significant decrease in the delay of IANO6 generation. On the other hand, in the inside-out patch clamp configuration, SSRIs showed an inhibitory effect on ANO6 currents, suggesting that SSRIs activate ANO6 via an indirect mechanism in intact cells. SSRIs also facilitated Ca(2+)-dependent PS exposure and α-thrombin-induced platelet aggregation. These results indicate that SSRIs at clinically relevant concentrations promote Ca(2+)-dependent activation of ANO6, which may have potential clinical implications such as the underlying mechanism of SSRI-induced adverse drug reactions.

Regulation of parathyroid hormone type 1 receptor dynamics, traffic, and signaling by the Na+/H+ exchanger regulatory factor-1 in rat osteosarcoma ROS 17/2.8 cells.

The effects of the expression of the Na+/H+ exchanger regulatory factor-1 (NHERF1) on the distribution, dynamics, and signaling properties of the PTH type 1 receptor (PTH1R) were studied in rat osteosarcoma cells ROS 17/2.8. NHERF1 had a dramatic effect on the subcellular distribution of PTH1R, promoting a substantial relocation of the receptor to regions of the plasma membrane located in very close proximity to cytoskeletal fibers. Direct interactions of NHERF1 with the PTH1R and the cytoskeleton were required for these effects, because they were abolished by 1) PTH1R mutations that impair NHERF1 binding, and 2) NHERF1 mutations that impair binding to the PTH1R or the cytoskeleton. NHERF1 reduced significantly the diffusion of the PTH1R by a mechanism that was also dependent on a direct association of NHERF1 with the PTH1R and the cytoskeleton. NHERF1 increased ligand-dependent production of cAMP and induced ligand-dependent rises in intracellular calcium. These effects on calcium were due to increased calcium uptake, as they were blocked by calcium channel inhibitors and by the addition of EGTA to the medium. These calcium effects were abolished by protein kinase A inhibition but phospholipase C inhibition was without effect. Based on these analyses, we propose that, in ROS cells, the presence of NHERF1 induces PTH-dependent calcium signaling by a cAMP-mediated mechanism that involves local protein kinase A-dependent activation of calcium channels.

Radix Puerariae modulates glutamatergic synaptic architecture and potentiates functional synaptic plasticity in primary hippocampal neurons.

ETHNOPHARMACOLOGICAL RELEVANCE: Neurologic disorders are frequently characterized by synaptic pathology, including abnormal density and morphology of dendritic spines, synapse loss, and aberrant synaptic signaling and plasticity. Therefore, to promote and/or protect synapses by the use of natural molecules capable of modulating neurodevelopmental events, such as, spinogenesis and synaptic plasticity, could offer a preventive and curative strategy for nervous disorders associated with synaptic pathology. Radix Puerariae, the root of Pueraria monatana var. lobata (Willd.) Sanjappa&Pradeep, is a Chinese ethnomedicine, traditionally used for the treatment of memory-related nervous disorders including Alzheimer's disease. In the previous study, we showed that the ethanolic extracts of Radix Puerariae (RPE) and its prime constituent, puerarin induced neuritogenesis and synapse formation in cultured hippocampal neurons, and thus could improve memory functions. AIMS OF THE STUDY: In the present study, we specifically investigated the abilities of RPE and puerarin to improve memory-related brain disorders through modulating synaptic maturation and functional potentiation. MATERIALS AND METHODS: Rat embryonic (E19) brain neurons were cultured in the absence or presence of RPE or puerarin. At predetermined times, cells were live-stained with DiO or fixed and immunostained to visualize neuronal morphologies, or lysed for protein harvesting. Morphometric analyses of dendritic spines and synaptogenesis were performed using Image J software. Functional pre- and postsynaptic plasticity was measured by FM1-43 staining and whole-cell patch clamping, respectively. RPE or puerarin-mediated changes in actin-related protein 2 were assessed by Western blotting. Neuronal survivals were measured using propidium iodide exclusion assay. RESULTS: RPE and puerarin both: (1) promoted a significant increase in the numbers, and maturation, of dendritic spines; (2) modulated the formation of glutamatergic synapses; (3) potentiated synaptic transmission by increasing the sizes of reserve vesicle pools at presynaptic terminals; (4) enhanced NMDA receptor-mediated postsynaptic currents, and (5) increased cell viability against naturally occurring cell death. Moreover, upregulation of actin-related protein 2 (ARP2) in RPE and puerarin treated brain neurons suggest that RPE and puerarin induced synaptic plasticity might be associated, at least in part, with ARP2-mediated actin-dependent regulation of spinogenesis. CONCLUSIONS: Our findings indicate that RPE and puerarin might play a substantial role in the morphological and functional maturation of brain neurons and suggest that RPE and puerarin are potentially valuable preventative therapeutics for memory-related nervous disorders.

The neuritogenic and synaptogenic effects of the ethanolic extract of radix Puerariae in cultured rat hippocampal neurons.

ETHNOPHARMACOLOGICAL RELEVANCE: Radix Puerariae, the root of Pueraria montana var. lobata (Willd.) Sanjappa & Pradeep, is used in Korean traditional medicine to treat neuronal disorders including Parkinson's disease, and its active constituent, puerarin has been reported to have a neuroprotective effect in experimental models of Parkinson's and Alzheimer's disease. AIMS OF THE STUDY: To investigate the neurotrophic effects of these ethnomedicines on the development of central nervous system neurons and the molecular bases of these activities. MATERIALS AND METHODS: Rat embryonic (E19) brain neurons were cultured in the absence or presence of the ethanolic extract of Radix Puerariae (RPE) or puerarin. At predetermined times, cells were fixed and immunostained to visualize neuronal morphologies, or lysed for protein harvesting. Morphometric analyses of neurite outgrowths and synaptogenesis were performed using Image J software. RPE or puerarin-mediated changes in the protein profiles of cultured neurons were assessed by MALDI-TOF-MS/PMF and measuring immunofluorescent intensities. RESULTS: RPE and puerarin alone promoted maximum neurite outgrowths at concentrations of 1µg/ml and 5µM, respectively. At these optimal concentrations, RPE and puerarin provided neurotrophic support by promoting axo-dendritic arbors and synapse formation in cultured neurons. Proteomic study revealed that RPE and puerarin both up-regulated a number of proteins, including dynein light chain 2 (DLC2) and elongation factor 2 (EF2), which are associated with neuritogenesis and synaptic potentiation, respectively. Immunofluorescence intensity measurements confirmed the expressions of the DLC2 and Dync1h1 subunits of dynein in RPE or puerarin treated hippocampal neurons were up-regulated when RPE or puerarin induced changes in neuronal cytoarchitecture. CONCLUSIONS: Our study demonstrates that RPE and puerarin should be considered potentially valuable preventative therapeutics for brain disorders due to their abilities to promote the neuronal cytoarchitecture and the synaptic functionality, which are possibly associated with dynein-dependent regulation of cytoskeletal structures and up-regulation of translation machinery.

Can medical drama motivate students to have an interest in the healthcare professionalism?

PURPOSE: This study was planned to evaluate that a lecture employing medical drama could motivate students to have an interest in the professionalism of healthcare personnel, which has currently become a critical subject in the field of medical education. METHODS: We analyzed subject headings, learning objectives, and further plans developed by students and their responses after two drama modules, 'car crash' and 'refusal of instruction', which were selected based on the conditions made by our faculty members, were given through video or paper to our 121 second-grade medical and nursing students in year 2012. RESULTS: Meaningful subject headings and learning objectives developed by students were 58.2%~60.0% and 36.8%~38.0% and significantly more in the 'refusal of instruction' than the 'car crash' (p=0.000). According to the students' major, medical students developed significantly more than nursing students (p=0.000). In the analysis of responses, 91.7% of students reported as impressive to the educational modules and 55.3% of them described their ideas associated with healthcare professionalism. CONCLUSION: Our study results suggest a possibility that the educational module employing selected medical drama could motivate students' healthcare professionalism.

Simvastatin, sildenafil and their combination in monocrotaline induced pulmonary arterial hypertension.

BACKGROUND AND OBJECTIVES: Pulmonary arterial hypertension (PAH) is a life threatening disease characterized by progressive pulmonary arterial occlusion which may ultimately result in death. Currently, the available treatments are diverse, but no therapy alone can reverse the disease process although they may have some clinical benefits. This study was designed to investigate single and combination therapy of simvastatin and sildenafil, which have different mechanisms of action, in monocrotaline (MCT)-induced PAH. MATERIALS AND METHODS: [corrected] Rats were randomized to receive saline (control, n=8) or MCT treatment (n=32). MCT treated rats were randomized to vehicle, simvastatin (2 mg/kg/day), sildenafil (25 mg/kg/day) and a combination simvastatin and sildenafil (n=8, respectively). Three weeks later, hemodynamic study and histologic changes of pulmonary arterioles were measured. Proliferating cell nuclear antigen (PCNA) as well as Western blot for endothelial nitric oxide synthase (eNOS) were performed. RESULTS: Systolic right ventricular pressure was significantly decreased in monotherapy groups (simvastatin and sildenafil) and the combination group compared to MCT group (p<0.05). Right ventricular hypertrophy and medial wall thickness of pulmonary arterioles were significantly attenuated with sole and combination therapy (p<0.05). However, combination therapy did not confer additive benefits over monotherapy. Altered PCNA or eNOS in lung tissue was normalized by either monotherapy or combination therapy. CONCLUSION: The results suggest that either simvastatin or sildenafil has the therapeutic potential in MCT-induced PAH, although combination therapy of these two drugs has failed to show greater benefits in the study.

Conformational changes of pore helix coupled to gating of TRPV5 by protons.

The transient receptor potential channel TRPV5 constitutes the apical entry pathway for transepithelial Ca2+ transport. We showed that TRPV5 was inhibited by both physiological intra- and extracellular acid pH. Inhibition of TRPV5 by internal protons was enhanced by extracellular acidification. Similarly, inhibition by external protons was enhanced by intracellular acidification. Mutation of either an extra- or an intracellular pH sensor blunted the cross-inhibition by internal and external protons. Both internal and external protons regulated the selectivity filter gate. Using the substituted cysteine accessibility method, we found that intracellular acidification of TRPV5 caused a conformational change of the pore helix consistent with clockwise rotation along its long axis. Thus, rotation of pore helix caused by internal protons facilitates closing of TRPV5 by external protons. This regulation by protons likely contributes to pathogenesis of disturbances of Ca2+ transport in many diseased states. Rotation of pore helix may be a common mechanism for cross-regulation of ion channels by extra- and intracellular signals.