Besides initiating and propagating action potentials in established neuronal circuits, voltage-dependent sodium channels sculpt and bolster the functional neuronal network from early in embryonic development through adulthood (e.g., differentiation of oligodendrocyte precursor cells into oligodendrocytes, myelinating axon; competition between neighboring equipotential neurites for development into a single axon; enhancing and opposing functional interactions with attractive and repulsive molecules for axon pathfinding; extending and retracting terminal arborization of axon for correct synapse formation; experience-driven cognition; neuronal survival; and remyelination of demyelinated axons). Surprisingly, different patterns of action potentials direct homeostasis-based epigenetic selection for neurotransmitter phenotype, thus excitability by sodium channels specifying expression of inhibitory neurotransmitters. Mechanisms for these pleiotropic effects of sodium channels include reciprocal interactions between neurons and glia via neurotransmitters, growth factors, and cytokines at synapses and axons. Sodium channelopathies causing pain (e.g., allodynia) and neurodegeneration (e.g., multiple sclerosis) derive from 1) electrophysiological disturbances by insults (e.g., ischemia/hypoxia, toxins, and antibodies); 2) loss-of-physiological function or gain-of-pathological function of mutant sodium channel proteins; 3) spatiotemporal inappropriate expression of normal sodium channel proteins; or 4) de-repressed expression of otherwise silent sodium channel genes. Nav1.7 proved to account for pain in human erythermalgia and inflammation, being the convincing molecular target of pain treatment.
We report a simple novel rat model that combines prolonged esophagitis and parallel sphincters failure. The anti-ulcer gastric pentadecapeptide BPC 157, which was found to be stable in gastric juice, and is being evaluated in inflammatory bowel disease trials, is an anti-esophagitis therapy that recovers failed sphincters. Twelve or twenty months after the initial challenge (tubes sutured into sphincters for one week and then spontaneously removed by peristalsis), rats exhibit prolonged esophagitis (confluent hemorrhagic and yellowish lesions, thinner epithelium and superficial corneal layer, with stratification derangement); constantly lowered pressure of both sphincters (assessed by using a water manometer connected to the drainage port of a Foley catheter implanted into the stomach either through esophageal or duodenal incision); and both lower esophageal and pyloric sphincter failure. Throughout the esophagitis experiment, BPC 157 was given at either 10 μg/kg, i.p., once a day (last application 24 h before assessment) or alternatively, it was given continuously in drinking water at 0.16 μg/ml (12 ml/rat). This treatment recovers i) esophagitis (macroscopically and microscopically, at either region or investigated time period) and ii) pressure in both sphincters (cmH2O). In addition, BPC 157 (10 μg/kg) or saline (1 ml/rat, 5 ml/kg) was specifically given directly into the stomach; pressure assessment was performed at 5 min thereafter. The effect of BPC 157 is specific because in normal rats, it increases lower esophageal sphincter-pressure, but decreases pyloric sphincter-pressure. Ranitidine, given as the standard drug using the same protocol (50 mg/kg, i.p., once daily; 0.83 mg/ml in drinking water; or 50 mg/kg directly into the stomach) had no effect.
Paroxetine is commonly used as a selective serotonin reuptake inhibitor for the treatment of depression and other psychiatric disorders. However, the molecular mechanisms of the paroxetine effects have not yet been sufficiently clarified. Using Xenopus oocyte expression assays, we investigated the effects of paroxetine on G protein-activated inwardly rectifying K+ (GIRK) channels, which play an important role in reducing neuronal excitability in most brain regions and the heart rate. In oocytes injected with mRNAs for GIRK1/GIRK2, GIRK2, or GIRK1/GIRK4 subunits, paroxetine reversibly reduced inward currents through the expressed GIRK channels. The inhibition was concentration-dependent, but voltage-independent and time-independent during each voltage pulse. However, two structurally different antidepressants: milnacipran and trazodone, caused only a small inhibition of basal GIRK currents. Additionally, Kir1.1 and Kir2.1 channels were insensitive to all of the antidepressants. Furthermore, the GIRK currents induced by activation of A1 adenosine receptors or by ethanol were inhibited by extracellularly applied paroxetine in a concentration-dependent manner, but not affected by intracellularly applied paroxetine. Our results suggest that inhibition of GIRK channels by paroxetine may contribute partly to some of its therapeutic effects and adverse side effects.
Previously, we reported that spironolactone reduced cytokine production in cultured human peripheral blood mononuclear cells (PBMCs) with angiotensin (Ang) II stimulation. To address the mechanisms underlying this effect, we examined the contribution of aldosterone to cytokine production in cultured human PBMCs with Ang II stimulation. PBMCs expressed the messenger RNA (mRNA) of Ang II type 1 receptor (AT1R) and mineralocorticoid receptor (MR) both spontaneously and after Ang II stimulation, but expressed Ang II type 2 receptor (AT2R) under neither condition. After 24 h of incubation, exogenous Ang II induced the expression of CYP11B2 (a key enzyme of aldosterone synthesis) mRNA and caused aldosterone synthesis. CV-11974 (an AT1R antagonist) reduced Ang II-induced aldosterone synthesis, whereas PD-123319 (an AT2R antagonist) had no effect. The concentration of aldosterone peaked earlier than those of monocyte chemoattractant protein-1 (MCP-1) and tumor necrosis factor-α (TNF-α). After 48 h of incubation (under the influence of synthesized aldosterone), CV-11974 and spironolactone significantly reduced the Ang II-enhanced production of MCP-1 and TNF-α, whereas PD-123319 also had no effect. In conclusion, Ang II induces aldosterone synthesis through AT1R and enhances cytokine production through an AT1R-dependent mechanism and, at least partly, through a MR-dependent mechanism in human PBMCs.
We characterized [methyl-3H]thymidine ([3H]thymidine) and [5-3H]uridine ([3H]uridine) incorporation into cultured astrocytes and neurons in the presence and absence of hydrogen peroxide (H2O2) in order to define the response to oxidative stress in the central nervous system. [3H]Thymidine incorporation into cultured astrocytes was remarkably decreased by N6,2'-O-dibutyryladenosine 3',5'-cyclic monophosphate (DBcAMP), a permeable analogue of cAMP, which induced a morphological change from the polygonal form (undifferentiated astrocytes) to the process-bearing one (differentiated astrocytes). H2O2 induced [3H]thymidine, but not [3H]uridine, incorporation into cultured astrocytes at only an early time from 24 h after DBcAMP treatment, although the absolute quantities of [3H]thymidine incorporation into astrocytes pretreated with DBcAMP were less than those into astrocytes pretreated without DBcAMP. Hydroxyurea, a replicative DNA synthesis inhibitor, suppressed dose-dependently and completely [3H]thymidine incorporation into astrocytes pretreated without DBcAMP, but not astrocytes pretreated with DBcAMP. H2O2 did not stimulate [3H]thymidine or [3H]uridine incorporation into astrocytes pretreated without DBcAMP and neurons. These findings indicate that only astrocytes pretreated with DBcAMP are able to increase thymidine incorporation specifically in the presence of H2O2 for a purpose other than proliferation, including the repair of H2O2-induced DNA injury, for example.
Oridonin, isolated from Rabdosia rubescences, has been reported to exert cytotoxic effects on L929 cells. In this study, we investigated the mechanisms of FGF-2 protection of L929 cells from oridonin-induced apoptosis. Phosphatidylinositol 3-kinase (PI3K)/protein kinase B (PKB) signal did not mediate this effect because the PI3K inhibitor wortmannin failed to reverse this protection and PKB activation was not observed in this process. In contrast, the extracellular signal-regulated kinase (ERK) was responsible for this rescue because its inhibition abolished the protective effect of fibroblast growth factor (FGF)-2. ERK had dual regulatory functions: mediating cell apoptosis or preventing cells from initiating the apoptotic response by phosphorylation or promoting expression of Bcl-2 in dependence of different stimuli. In L929 cells treated with oridonin alone, the activated ERK decreased the ratio of Bcl-2/Bax by mediating the phosphorylation of Bcl-2, resulting in apoptosis; the Ras inhibitor manumycin A and Raf inhibitor GW5074 failed to inhibit this apoptosis, indicating that there is a signal other than Ras/Raf pathway activated ERK. However, in the presence of FGF-2, Bcl-2 phosphorylation was blocked, and the Ras/Raf/ERK signal pathway was activated and protected against the oridonin-induced apoptosis by the alternative function of promoting of Bcl-2 expression.
Clinically, hemorrhoidal bleeding and prolapse disappeared immediately after injection of the sclerosing agent OC-108 into submucosa of hemorrhoids. The aim of this study was to elucidate the mechanism of action responsible for the immediate hemostatic effect of OC-108 using anesthetized rats. Subcutaneous injection of OC-108 in rats decreased blood flow at the injection site within 5 min. Aluminum potassium sulfate, one of the main ingredients of OC-108, reduced the skin blood flow. However, tannic acid, another main ingredient, did not. By perfusion of OC-108 on the mesenteric surface, microcirculatory blood flow was arrested without remarkable change in blood vessel diameter, accompanied by increased vascular permeability and venous hematocrit. These results indicate that OC-108 induces regional blood flow arrest with rapid onset, this effect being attributed to the action of aluminum potassium sulfate, and that hemoconcentration due to increased vascular permeability (plasma extravasation), an acute inflammatory reaction, is involved in the mechanisms of the immediate hemostatic action of OC-108.
The objectives of this study were to define the pharmacokinetics of recombinant human interleukin-1 receptor antagonist (rhIL-1ra) and its effects on allergic asthma, cell adhesion molecules, and upper respiratory tract following non-parenteral administration in animals. Pharmacokinetics and immunomodulating effects of rhIL-1ra were investigated in Sprague-Dawley rats and asthmatic guinea pigs, respectively. Effects on the upper respiratory tract following the applications of rhIL-1ra were investigated on the ex vivo nasal mucosa of Sprague-Dawley rats and in situ in the upper palate of Chinese toads. Absolute bioavailabilities after intratracheal and intranasal administrations of rhIL-1ra were 94.3% and 24.8%, respectively. After administration of rhIL-1ra solution as ultrasonic spraying, the asthmatic symptom in guinea pigs was obviously attenuated. The plasma soluble intercellular cell adhesion molecule (sICAM-1) and P-selectin levels in asthmatic guinea pigs were each dose-dependently reduced with the increase of rhIL-1ra dose. The rhIL-1ra solution after administration via the airway seemed to have no impact on the integrity of nasal mucosa and mucocilia clearance in the upper respiratory tract. The present study provides evidence that rhIL-1ra effectively suppresses allergen-induced asthmatic symptoms through spraying, which corresponds to nasal and pulmonary absorption or both, and the efficacy is associated with downregulation of sICAM-1 and P-selectin expressions.
The previous Northern blot analysis and in situ hybridization studies showed that histamine H1-receptor (H1R) mRNA is expressed in human placenta and suggested that H1R plays some roles in the function of placenta in pregnancy. To investigate further, it is essential to show the precise location of H1R in the placenta. In the present study, we investigated H1R expression in human placenta by radioligand binding assay and immunohistochemical study using an antibody against human H1R. Placentas were obtained from normal uncomplicated deliveries. Membranes prepared from the tissue exhibited saturable [3H]mepyramine binding (Kd = 4.0 ± 0.6 nM and Bmax = 91.4 ± 4.9 fmol/mg of protein). Stereoisomers of chlorpheniramine inhibited [3H]mepyramine binding; d-chlorpheniramine inhibited more potently than l-chlorpheniramine, Ki values being 1.1 ± 0.4 and 270 ± 170 nM, respectively. The placenta tissues were positively immunostained with anti-H1R antibody only in the region of the syncytiotrophoblast of chorionic villus. The tissues were double stained with anti-H1R antibody and an antibody against human chorionic gonadotoropin (hCG) that is solely expressed in placental syncytiotrophoblast cells. The results showed that H1R and hCG were expressed on the same cells, that is, syncytiotrophoblast cells. These results indicate that H1Rs are specifically expressed in syncytiotrophoblast cells of human placenta organ.
We prepared a cell-populated collagen-gel fiber including GbaSM-4 cells derived from the basilar artery of guinea pigs. This fiber tended to be a differentiated contractile phenotype in electron-microscope observations. Sphingosylphosphorylcholine (SPC) can induce contraction of the fiber (EC50 = 0.70 ± 0.05 μM), and blebbistatin can inhibit the SPC-induced contraction (IC50 = 22.8 ± 1.26 μM). Phosphorylation of the 20 kD myosin light chain (MLC20) significantly increased in GbaSM-4 cells provided with 1 μM SPC (P<0.05), which was maintained in the presence of 1 to 100 μM blebbistatin. These results suggest that vascular smooth muscle can relax even if MLC20 is phosphorylated.
The effects of docosahexaenoic acid (DHA) and other fatty acids on P2X-receptor-mediated inward currents in rat nodose ganglion neurons were studied using the nystatin perforated patch-clamp technique. DHA accelerated the desensitization rate of the ATP-induced current. DHA showed use-dependent inhibition of the peak ATP-induced current. Other polyunsaturated fatty acids, such as arachidonic acid and eicosapentaenoic acid, displayed a similar use-dependent inhibition. The inhibitory effects of saturated fatty acids including palmitic acid and arachidic acid were weaker than those of polyunsaturated fatty acids. The results suggest that fatty acids may modulate the P2X receptor-mediated response when the channel is in the open-state.
The influence of direct single pulse and subtetanic electrical stimulation (ES) on isolated rat hemidiaphragm response to adrenoceptor antagonists and calcium channel blockers was investigated. Muscle contractility was stimulated by cumulative micromolar noradrenaline. Noradrenaline effects on developed tension (Td) in the presence of various α- and β-adrenoceptor antagonists (e.g., prazosin and ICI 118551) were qualitatively different during different types of ES. Also, intact L-voltage calcium channels were necessary for noradrenaline-induced potentiation of Td during both types of ES, while the balance between ryanodine receptors- and inositol triphosphate (IP3)-related calcium events in the muscle was influenced by the pattern of the ES.
Presenilin 1 (PS1) is a multifunctional protein, and its mutations are highly related to familial Alzheimer’s disease (AD). In this study, we examined the effects of PS1 overexpression on neuronal morphology using SH-SY5Y cells. Overexpression of dominant-negative D385A PS1 induced morphological change and impairment of neurite formation, while those of wild-type and pathogenic P117L mutant PS1 did not change cellular morphology compared with native cells. Moreover, filopodium-formation-related proteins were decreased only in cells overexpressing D385A PS1. Therefore, PS1 may be involved in neuritogenesis and morphological change in SH-SY5Y cells, and P117L mutation may linked to AD by different mechanisms.