Atypical antidepressant mirtazapine inhibits 5-hydroxytryptamine3 receptor currents in NCB-20 cells

Mirtazapine, an atypical antidepressant, is known to enhance serotonergic transmission by inhibiting the 5-hydroxytryptamine (5-HT)_1A, 5-HT_2C, and 5-HT₃ receptors. However, the mechanism of action on the 5-HT₃ receptor remains unclear. We investigated the inhibitory mechanisms of mirtazapine on 5-HT₃ receptors of NCB20 neuroblastoma cells using the whole-cell voltage-clamp method. Mirtazapine inhibited the 5-HT₃ receptor currents in a concentration-dependent manner, and the inhibitory effect was influenced by the concentration of 5-HT. When mirtazapine was co-applied to 5-HT, the maximal response of the 5-HT₃ receptor current was reduced and EC₅₀ was increased, suggesting that mirtazapine might act as a non-competitive inhibitor. Inhibition of 5-HT₃ current by mirtazapine was stronger in pre-application than in co-application, which suggests that mirtazapine might act as a closed state inhibitor. This finding was further supported by no use-dependency of the mirtazapine for 5-HT₃ receptor inhibition. Finally, mirtazapine accelerated the desensitization and deactivation process in a concentration-dependent manner. The difference in recovery time showed that mirtazapine drastically influences the desensitization process than the deactivation process. These mechanistic characteristics of mirtazapine support the understanding of the relationship between the 5-HT₃ receptor and atypical antidepressants.

Selective serotonin reuptake inhibitor escitalopram inhibits 5-HT3 receptor currents in NCB-20 cells

Escitalopram is one of selective serotonin reuptake inhibitor antidepressants. As an S-enantiomer of citalopram, it shows better therapeutic outcome in depression and anxiety disorder treatment because it has higher selectivity for serotonin reuptake transporter than citalopram. The objective of this study was to determine the direct inhibitory effect of escitalopram on 5-hydroxytryptamine type 3 (5-HT₃) receptor currents and study its blocking mechanism to explore additional pharmacological effects of escitalopram through 5-HT₃ receptors. Using a whole-cell voltage clamp method, we recorded currents of 5-HT₃ receptors when 5-HT was applied alone or co-applied with escitalopram in cultured NCB-20 neuroblastoma cells known to express 5-HT₃ receptors. 5-HT induced currents were inhibited by escitalopram in a concentration-dependent manner. EC₅₀ of 5-HT on 5-HT₃ receptor currents was increased by escitalopram while the maximal peak amplitude was reduced by escitalopram. The inhibitory effect of escitalopram was voltage independent. Escitalopram worked more effectively when it was co-applied with 5-HT than pre-application of escitalopram. Moreover, escitalopram showed fast association and dissociation to the open state of 5-HT₃ receptor channel with accelerating receptor desensitization. Although escitalopram accelerated 5-HT₃ receptor desensitization, it did not change the time course of desensitization recovery. These results suggest that escitalopram can inhibit 5-HT₃ receptor currents in a non-competitive manner with the mechanism of open channel blocking.

Gastroprokinetic agent, mosapride inhibits 5-HT3 receptor currents in NCB-20 cells

Mosapride accelerates gastric emptying by acting on 5-hydroxytryptamine type 4 (5-HT₄) receptor and is frequently used in the treatment of gastrointestinal (GI) disorders requiring gastroprokinetic efficacy. We tested the effect of mosapride on 5-hydroxytryptamine type 3 (5-HT₃) receptor currents because the 5-HT₃ receptors are also known to be expressed in the GI system and have an important role in the regulation of GI functions. Using the whole-cell voltage clamp method, we compared the currents of the 5-HT₃ receptors when 5-HT was applied alone or was co-applied with mosapride in cultured NCB-20 cells known to express 5-HT₃ receptors. The 5-HT₃ receptor current amplitudes were inhibited by mosapride in a concentration-dependent manner. Mosapride blocked the peak currents evoked by the application of 5-HT in a competitive manner because the EC₅₀ shifted to the right without changing the maximal effect. The rise slopes of 5-HT₃ receptor currents were decreased by mosapride. Pre-application of mosapride before co-application, augmented the inhibitory effect of mosapride, which suggests a closed channel blocking mechanism. Mosapride also blocked the opened 5-HT₃ receptor because it inhibited the 5-HT₃ receptor current in the middle of the application of 5-HT. It accelerated desensitization of the 5-HT₃ receptor but did not change the recovery process from the receptor desensitization. There were no voltage-, or use-dependency in its blocking effects. These results suggest that mosapride inhibited the 5-HT₃ receptor through a competitive blocking mechanism probably by binding to the receptor in closed state, which could be involved in the pharmacological effects of mosapride to treat GI disorders.

Tricyclic antidepressant amitriptyline inhibits 5-hydroxytryptamine 3 receptor currents in NCB-20 cells

Amitriptyline, a tricyclic antidepressant, is commonly used to treat depression and neuropathic pain, but its mechanism is still unclear. We tested the effect of amitriptyline on 5-hydroxytryptamine 3 (5-HT₃) receptor currents and studied its blocking mechanism because the clinical applications of amitriptyline overlapped with 5-HT₃ receptor therapeutic potentials. Using a whole-cell voltage clamp method, we recorded the currents of the 5-HT₃ receptor when 5-HT was applied alone or co-applied with amitriptyline in cultured NCB-20 neuroblastoma cells known to express 5-HT₃ receptors. To elucidate the mechanism of amitriptyline, we simulated the 5-HT₃ receptor currents using Berkeley Madonna® software and calculated the rate constants of the agonist binding and receptor transition steps. The 5-HT₃ receptor currents were inhibited by amitriptyline in a concentration-dependent, voltage-independent manner, and a competitive mode. Amitriptyline accelerated the desensitization of the 5-HT₃ receptor. When amitriptyline was applied before 5-HT treatment, the currents rose slowly until the end of 5-HT treatment. When amitriptyline was co-applied with 5-HT, currents rose and decayed rapidly. Peak current amplitudes were decreased in both applications. All macroscopic currents recorded in whole cell voltage clamping experiments were reproduced by simulation and the changes of rate constants by amitriptyline were correlated with macroscopic current recording data. These results suggest that amitriptyline blocks the 5-HT₃ receptor by close and open state blocking mechanisms, in a competitive manner. We could expand an understanding of pharmacological mechanisms of amitriptyline related to the modulation of a 5-HT₃ receptor, a potential target of neurologic and psychiatric diseases through this study.

Lamotrigine, an antiepileptic drug, inhibits 5-HT3 receptor currents in NCB-20 neuroblastoma cells

Lamotrigine is an antiepileptic drug widely used to treat epileptic seizures. Using whole-cell voltage clamp recordings in combination with a fast drug application approach, we investigated the effects of lamotrigine on 5-hydroxytryptamine (5-HT)₃ receptors in NCB-20 neuroblastoma cells. Co-application of lamotrigine (1~300 µM) resulted in a concentration-dependent reduction in peak amplitude of currents induced by 3 µM of 5-HT for an IC₅₀ value of 28.2±3.6 µM with a Hill coefficient of 1.2±0.1. These peak amplitude decreases were accompanied by the rise slope reduction. In addition, 5-HT₃-mediated currents evoked by 1 mM dopamine, a partial 5-HT₃ receptor agonist, were inhibited by lamotrigine co-application. The EC₅₀ of 5-HT for 5-HT₃ receptor currents were shifted to the right by co-application of lamotrigine without a significant change of maximal effect. Currents activated by 5-HT and lamotrigine co-application in the presence of 1 min pretreatment of lamotrigine were similar to those activated by 5-HT and lamotrigine co-application alone. Moreover, subsequent application of lamotrigine in the presence of 5-HT and 5-hydroxyindole, known to attenuate 5-HT₃ receptor desensitization, inhibited 5-HT₃ receptor currents in a concentration-dependent manner. The deactivation of 5-HT₃ receptor was delayed by washing with an external solution containing lamotrigine. Lamotrigine accelerated the desensitization process of 5-HT₃ receptors. There was no voltage-dependency in the inhibitory effects of lamotrigine on the 5-HT₃ receptor currents. These results indicate that lamotrigine inhibits 5-HT₃-activated currents in a competitive manner by binding to the open state of the channels and blocking channel activation or accelerating receptor desensitization.

Acepromazine inhibits hERG potassium ion channels expressed in human embryonic kidney 293 cells

The effects of acepromazine on human ether-à-go-go-related gene (hERG) potassium channels were investigated using whole-cell voltage-clamp technique in human embryonic kidney (HEK293) cells transfected with hERG. The hERG currents were recorded with or without acepromazine, and the steady-state and peak tail currents were analyzed for the evaluating the drug effects. Acepromazine inhibited the hERG currents in a concentration-dependent manner with an IC₅₀ value of 1.5 µM and Hill coefficient of 1.1. Acepromazine blocked hERG currents in a voltage-dependent manner between –40 and +10 mV. Before and after application of acepromazine, the half activation potentials of hERG currents changed to hyperpolarizing direction. Acepromazine blocked both the steady-state hERG currents by depolarizing pulse and the peak tail currents by repolarizing pulse; however, the extent of blocking by acepromazine in the repolarizing pulse was more profound than that in the depolarizing pulse, indicating that acepromazine has a high affinity for the open state of the channels, with a relatively lower affinity for the closed state of hERG channels. A fast application of acepromazine during the tail currents inhibited the open state of hERG channels in a concentration-dependent. The steady-state inactivation of hERG currents shifted to the hyperpolarized direction by acepromazine. These results suggest that acepromazine inhibits the hERG channels probably by an open- and inactivated-channel blocking mechanism. Regarding to the fact that the hERG channels are the potential target of drug-induced long QT syndrome, our results suggest that acepromazine can possibly induce a cardiac arrhythmia through the inhibition of hERG channels.

Immunosuppressive therapy versus alternative donor hematopoietic stem cell transplantation for children with severe aplastic anemia who lack an HLA-matched familial donor

We compared the outcomes of immunosuppressive treatment (IST) with those of alternative donor hematopoietic stem cell transplantation (HSCT) in children and adolescents with severe aplastic anemia (SAA). The medical records of 42 patients with SAA who received frontline IST (N=19) or frontline HSCT with an alternative donor (N=23) between 1998 and 2012 were analyzed retrospectively. Six patients responded in the frontline IST group, whereas 11 underwent salvage HSCT after IST failure. Twenty-one of 23 patients who underwent frontline HSCT survived without treatment failure. The estimated failure-free survival rate of the frontline HSCT group was higher than that of the frontline IST group (91.3% vs 30.7% respectively, P<0.001). Six of 11 patients who underwent salvage HSCT experienced event-free survival (EFS). The estimated EFS of the frontline HSCT group was higher than that of the salvage HSCT group (91.3% vs 50.9% respectively, P=0.015). The outcome of alternative donor HSCT was better than commonly reported rates, especially in patients who underwent frontline HSCT. These results suggest that frontline alternative donor HSCT may be a better treatment option than IST for children and adolescents with SAA who lack a human leukocyte Ag-matched familial donor.

Endoxifen, the active metabolite of tamoxifen, inhibits cloned hERG potassium channels

The effects of tamoxifen, and its active metabolite endoxifen (4-hydroxy-N-desmethyl-tamoxifen), on hERG currents stably expressed in HEK cells were investigated using the whole-cell patch-clamp technique and an immunoblot assay. Tamoxifen and endoxifen inhibited hERG tail currents at -50mV in a concentration-dependent manner with IC50 values of 1.2 and 1.6μM, respectively. The steady-state activation curve of the hERG currents was shifted to the hyperpolarizing direction in the presence of endoxifen. The voltage-dependent inhibition of hERG currents by endoxifen increased steeply in the voltage range of channel activation. The inhibition by endoxifen displayed a shallow voltage dependence (δ=0.18) in the full activation voltage range. A fast application of endoxifen induced a reversible block of hERG tail currents during repolarization in a concentration-dependent manner, which suggested an interaction with the open state of the channel. Endoxifen also decreased the hERG current elicited by a 5s depolarizing pulse to +60mV to inactivate the hERG currents, suggesting an interaction with the activated (open and/or inactivated) states of the channels. Tamoxifen and endoxifen inhibited the hERG channel protein trafficking to the plasma membrane in a concentration-dependent manner with endoxifen being more potent than tamoxifen. These results indicated that tamoxifen and endoxifen inhibited the hERG current by direct channel blockage and by the disruption of channel trafficking to the plasma membrane in a concentration-dependent manner. A therapeutic concentration of endoxifen inhibited the hERG current by preferentially interacting with the activated (open and/or inactivated) states of the channel.

Effects of donepezil on hERG potassium channels

Donepezil is a potent, selective inhibitor of acetylcholinesterase, which is used for the treatment of Alzheimer's disease. Whole-cell patch-clamp technique and Western blot analyses were used to study the effects of donepezil on the human ether-a-go-go-related gene (hERG) channel. Donepezil inhibited the tail current of the hERG in a concentration-dependent manner with an IC50 of 1.3 μM. The metabolites of donepezil, 6-ODD and 5-ODD, inhibited the hERG currents in a similar concentration-dependent manner; the IC50 values were 1.0 and 1.5 μM, respectively. A fast drug perfusion system demonstrated that donepezil interacted with both the open and inactivated states of the hERG. A fast application of donepezil during the tail currents inhibited the open state of the hERG in a concentration-dependent manner with an IC50 of 2.7 μM. Kinetic analysis of donepezil in an open state of the hERG yielded blocking and unblocking rate constants of 0.54 µM(-1)s(-1) and 1.82 s(-1), respectively. The block of the hERG by donepezil was voltage-dependent with a steep increase across the voltage range of channel activation. Donepezil caused a reduction in the hERG channel protein trafficking to the plasma membrane at low concentration, but decreased the channel protein expression at higher concentrations. These results suggest that donepezil inhibited the hERG at a supratherapeutic concentration, and that it did so by preferentially binding to the activated (open and/or inactivated) states of the channels and by inhibiting the trafficking and expression of the hERG channel protein in the plasma membrane.

Raloxifene inhibits cloned Kv4.3 channels in an estrogen receptor-independent manner

Raloxifene is widely used for the treatment and prevention of postmenopausal osteoporosis. We examined the effects of raloxifene on the Kv4.3 currents expressed in Chinese hamster ovary (CHO) cells using the whole-cell patch-clamp technique and on the long-term modulation of Kv4.3 messenger RNA (mRNA) by real-time PCR analysis. Raloxifene decreased the Kv4.3 currents with an IC50 of 2.0 μM and accelerated the inactivation and activation kinetics in a concentration-dependent manner. The inhibitory effects of raloxifene on Kv4.3 were time-dependent: the association and dissociation rate constants for raloxifene were 9.5 μM(-1) s(-1) and 23.0 s(-1), respectively. The inhibition by raloxifene was voltage-dependent (δ = 0.13). Raloxifene shifted the steady-state inactivation curves in a hyperpolarizing direction and accelerated the closed-state inactivation of Kv4.3. Raloxifene slowed the time course of recovery from inactivation, thus producing a use-dependent inhibition of Kv4.3. β-Estradiol and tamoxifen had little effect on Kv4.3. A preincubation of ICI 182,780, an estrogen receptor antagonist, for 1 h had no effect on the inhibitory effect of raloxifene on Kv4.3. The metabolites of raloxifene, raloxifene-4'-glucuronide and raloxifene-6'-glucuronide, had little or no effect on Kv4.3. Coexpression of KChIP2 subunits did not alter the drug potency and steady-state inactivation of Kv4.3 channels. Long-term exposure to raloxifene (24 h) significantly decreased the expression level of Kv4.3 mRNA. This effect was not abolished by the coincubation with ICI 182,780. Raloxifene inhibited Kv4.3 channels by interacting with their open state during depolarization and with the closed state at subthreshold potentials. This effect was not mediated via an estrogen receptor.

Effects of haloperidol on Kv4.3 potassium channels

Haloperidol is commonly used in clinical practice to treat acute and chronic psychosis, but it also has been associated with adverse cardiovascular events. We investigated the effects of haloperidol on Kv4.3 currents stably expressed in CHO cells using a whole-cell patch-clamp technique. Haloperidol did not significantly inhibit the peak amplitude of Kv4.3, but accelerated the decay rate of inactivation of Kv4.3 in a concentration-dependent manner. Thus, the effects of haloperidol on Kv4.3 were estimated from the integral of the Kv4.3 currents during the depolarization pulse. The Kv4.3 was decreased by haloperidol in a concentration-dependent manner with an IC50 value of 3.6 μM. Haloperidol accelerated the decay rate of Kv4.3 inactivation and activation kinetics in a concentration-dependent manner, thereby decreasing the time-to-peak. Haloperidol shifted the voltage dependence of the steady-state activation and inactivation of Kv4.3 in a hyperpolarizing direction. Haloperidol also caused an acceleration of the closed-state inactivation of Kv4.3. Haloperidol produced a use-dependent block of Kv4.3, which was accompanied by a slowing of recovery from the inactivation of Kv4.3. These results suggest that haloperidol blocks Kv4.3 by both interacting with the open state of Kv4.3 channels during depolarization and accelerating the closed-state inactivation at subthreshold membrane potentials.

Quality of functional haematopoietic stem/progenitor cells from cryopreserved human umbilical cord blood

BACKGROUND AND OBJECTIVES

Transplantation of cryopreserved umbilical cord blood (UCB) can be used to treat a multitude of haematologic and immunological diseases. In this study, we examined the quality of UCB cryopreserved for 2 (group I), 4 (group II) and 6 (group III) years.

METHODS

The following parameters and procedures were used to test individual units of cryopreserved UCB: the number of total nucleated cells (TNC), cell viability, CFU-GM assay, T-cell activation in vitro and haematopoietic stem cell engraftment in NOD/SCID mice in vivo.

RESULTS

The TNC recovery rates for groups I, II and III were 106·2 ± 6·17%, 96·69 ± 6·39% and 100·38 ± 5·27%, respectively, and the mean percentages of viable cells after thawing were 86·88%, 86·38% and 87·43%. When TNC were plated at 5 × 10(3), the number of CFU-GM was 13·6 (group I), 13·8 (group II), 14·2 (group III) and 14·7 (fresh UCB). We confirmed that the huCD4(+) and huCD8(+) T cells within cryopreserved UCB are functionally responsive by assessment of activated huCD25(+) cells. Moreover, the percentage of huCD45(+) cells in the bone marrow was 4·32 ± 1·29% (group I), 4·48 ± 1·11% (group II), 4·40% ± 1·12% (group III) and 4·50% ± 0·66% (fresh UCB), and that in the peripheral blood was 14·69 ± 3·08% (group I), 15·24 ± 4·05% (group II), 15·74 ± 3·43% (group III) and 17·48 ± 3·74% (fresh UCB) in NOD/SCID mice infused with isolated huCD34(+) cells.

CONCLUSION

These results indicated that cryopreserved UCB units efficiently retrieve in functionally competent form and are suitable for transplantation.

Fluoxetine suppresses synaptically induced [Ca²⁺]i spikes and excitotoxicity in cultured rat hippocampal neurons

Fluoxetine is a widely used antidepressant with an action that is primarily attributed to the inhibition of serotonin re-uptake into the synaptic terminals of the central nervous system. Fluoxetine also has blocking effects on various ion channels, including Ca(2+) channels. It remains unclear, however, how fluoxetine may affect synaptically induced [Ca(2+)](i) spikes. We investigated the effects of fluoxetine on [Ca(2+)](i) spikes, along with the subsequent neurotoxicity that is synaptically evoked by lowering extracellular Mg(2+) in cultured rat hippocampal neurons. Fluoxetine inhibited the synaptically induced [Ca(2+)](i) spikes in p-chloroamphetamine-treated and non-treated neurons, in a concentration-dependent manner. However, other selective serotonin reuptake inhibitors, such as paroxetine and citalopram, did not significantly affect the spikes. Pretreatment with fluoxetine for 5 min inhibited [Ca(2+)](i) increases induced by glutamate, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, and N-methyl-d-aspartate. Fluoxetine also inhibited α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-induced currents. In addition, fluoxetine decreased the [Ca(2+)](i) responses induced by the metabotrophic glutamate receptor agonist (S)-3,5-dihydroxyphenylglycine or the ryanodine receptor agonist caffeine. Fluoxetine inhibited [Ca(2+)](i) responses induced by 20mM KCl. Fluoxetine decreased the release of FM1-43 induced by electric field stimulation. Furthermore, fluoxetine inhibited 0.1mM [Mg(2+)](o)-induced cell death. Collectively, our results suggest that fluoxetine suppresses the spikes and protects neurons against excitotoxicity, particularly in cultured rat hippocampal neurons, presumably due to both direct inhibition of presynaptic glutamate release and postsynaptic glutamate receptor-mediated [Ca(2+)](i) signaling. In addition to an indirect inhibitory effect via 5-HT levels, these data suggest a new, possibly direct inhibitory action of fluoxetine on synaptically induced [Ca(2+)](i) spikes and neuronal cell death.

Evaluation of overnight storage conditions for autologous peripheral blood stem cell products: comparison of three different conditions

BACKGROUND

Overnight (ON) storage of peripheral blood stem cell (PBSC) occurs frequently in clinical settings. However, there are no standard guidelines for optimal storage conditions of freshly harvested PBSC. The aim of this study was to investigate the influence of storage temperatures on the quality of autologous PBSC and establish optimal storage conditions before cryopreservation.

METHODS

A retrospective analysis was performed on 260 PBSC harvests according to pre-cryopreservation conditions: immediate processing or ON storage at room temperature (RT). For direct comparison, 30 autologous PBSC products were collected prospectively and prepared under three different pre-cryopreservation conditions: immediate processing, ON storage at 4°C and ON storage at RT. The recovery of CD34(+) cells, post-thaw CFU-GM count and viability were analysed.

RESULTS

Retrospective analysis revealed that post-thaw CFU-GM count was significantly lower when PBSC were stored ON at RT compared to when immediately processed (136·4 vs. 409·6/μl). Prospective analysis showed a mean recovery of CD34(+) cells of 65·5 ± 25·1%, 70·5 ± 27·4% and 35·9 ± 25·1% for immediate processing, ON storage at 4°C and ON storage at RT, respectively. Similarly, mean viability and CFU-GM counts were significantly reduced when stored ON at RT compared to when immediately processed or stored ON at 4°C (60·4 ± 25·6 vs. 84·1 ± 12·9 vs. 82·7 ± 12·6%, 15·7 ± 25·7 vs. 398·5 ± 906·2 vs. 350·0 ± 847·9/μl, respectively).

CONCLUSIONS

ON storage of autologous PBSC at RT significantly decreased the quality of HPCs. These data indicate that ON storage of autologous PBSC at 4°C would be the most reasonable approach for maintaining the quality of HPCs when immediate processing is not possible.

Effects of grape seed proanthocyanidin on 5-hydroxytryptamine(3) receptors in NCB-20 neuroblastoma cells

Proanthocyanidin is a phenolic compound present in plants, that has antioxidant, antinociceptive, anti-emetic, and neuroprotective properties. We investigated the actions of proanthocyanidin from grape seeds on 5-hydroxytryptamine (5-HT)(3) receptors in NCB-20 neuroblastoma cells using a whole-cell voltage clamp technique. Co-treatment of proanthocyanidin (0.3-100 µg/ml) and 3 µM 5-HT (near EC(50)) produced a slight inhibition of 5-HT-induced inward peak current (I(5-HT)) in NCB-20 cells, but pretreatment with proanthocyanidin for 30 s before application of 5-HT induced a much larger inhibition of I(5-HT) in an irreversible, concentration- and time-dependent manner (IC(50)=6.5±0.4 µg/ml, Hill coefficient=2.5±0.1). Proanthocyanidin also produced a concentration-dependent inhibition of currents induced by 30 µM 5-HT, near-maximal concentration (IC(50)=22.1±0.4 µg/ml, Hill coefficient=2.4±0.1). High concentrations (≧30 µg/ml) of proanthocyanidin caused a concentration-dependent inhibition of the activation and desensitization of currents induced by 30 µM 5-HT. Further studies showed that pretreatment of 20 µg/ml proanthocyanidin caused not only a rightward shift of the dose-response curve for 5-HT (EC(50) shift from 2.7±0.4 to 6.2±0.5 µM), but also a decreased E(max) (inhibition by 37.5±1.3%). The proanthocyanidin-induced inhibition of 5-HT(3) receptors did not show a significant difference within the testing holding potential ranges (-50-+30 mV). These results suggest that proanthocyanidin inhibits 5-HT(3) receptor function in NCB-20 cells in a noncompetitive mode, and that this inhibitory effect of proanthocyanidin probably contributes to the pharmacological actions of proanthocyanidin.

Correlation between the immature characteristics of umbilical cord blood-derived mesenchymal stem cells and engraftment of hematopoietic stem cells in NOD/SCID mice

Umbilical cord blood (UCB)-derived mesenchymal stem cells (MSC) facilitate the engraftment of human (h) hematopoietic stem cells when transplanted simultaneously in animal and human studies. However, the type of MSCs that preferentially enhance the engraftment of HSCs is unknown. Recent studies have shown that MSCs derived from a single source are heterogeneous in terms of cell size, morphology, proliferation rate, and differentiation potential. This study was designed to investigate the properties of UCB-MSCs, which influence the engraftment of hHSCs in a NOD/SCID mouse model. We categorized MSCs as being the most effective (UCB-352 MSCs) or the least effective (UCB-156 MSCs) at promoting the homing and engraftment of HSCs, and compared the characteristics of these 2 MSC populations. We observed that the 2 populations showed differences in characteristics typical of immature MSCs, and related to proliferation potential. We showed that UCB-352 MSCs, which proliferate quickly, preferentially enhanced the engraftment of HSCs in NOD/SCID mice. In addition, we observed differences in the pattern of both PODXL and Oct4 expression, and in the levels of cytokines such as SDF-1 and SCF using flow cytometry and membrane arrays. The more effective UCB-352 MSCs expressed higher levels of PODXL and Oct4, which were associated with immaturity, than did the UCB-156 MSCs. Furthermore, UCB-352 cells secreted greater levels of SDF-1 and SCF, both of which are required for hematopoiesis. We propose that the proliferation potential of UCB-MSCs, coupled with their immature characteristics, may serve as a novel standard to promote the homing and engraftment of HSCs.

Hepatic veno-occlusive disease in children after hematopoietic stem cell transplantation: incidence, risk factors, and outcome

Four hundred and sixty-seven hematopoietic stem cell transplantations (HSCTs) (217 autologous and 250 allogeneic HSCT) were performed in 374 children at four pediatric HSCT centers in Korea from January 2005 to December 2007. Among 467 transplants, veno-occlusive disease (VOD) developed in 72 transplants (15.4%) at a median of 10 days after HSCT. Multivariate analysis showed that BU or TBI-containing regimen (P=0.002), VOD prophylaxis without lipo-prostaglandin E1 (PGE1) (P=0.012), number of previous HSCT (P=0.014), and pretransplant serum ferritin (P=0.018) were independent risk factors for developing VOD. Mean serum ferritin levels were significantly higher in HSCT with VOD (2109.6+/-2842.5 ng/ml) than in HSCT without VOD (1315.9+/-1094.4 ng/ml) (P<0.001). The relative risk of death within 100 days of HSCT in transplants with VOD compared with transplants without VOD was 3.39 (confidence interval: 1.78-6.45). Our results suggest that lipo-PGE1 might have a protective effect against the development of VOD, and pretransplant serum ferritin could act as a risk factor for VOD. A larger prospective study is needed to confirm a possible role of lipo-PGE1 and iron chelation therapy in reducing the incidence of VOD.

Electrophysiological Characterization of AMPA and NMDA Receptors in Rat Dorsal Striatum

The striatum receives glutamatergic afferents from the cortex and thalamus, and these synaptic transmissions are mediated by alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) and N-methyl-D-aspartate (NMDA) receptors. The purpose of this study was to characterize glutamate receptors by analyzing NMDA/AMPA ratio and rectification of AMPA and NMDA excitatory postsynaptic currents (EPSCs) using a whole-cell voltage-clamp method in the dorsal striatum. Receptor antagonists were used to isolate receptor or subunit specific EPSC, such as (DL)-2-amino-5-phosphonovaleric acid (APV), an NMDA receptor antagonist, ifenprodil, an NR2B antagonist, CNQX, an AMPA receptor antagonist and IEM-1460, a GluR2-lacking AMPA receptor blocker. AMPA and NMDA EPSCs were recorded at -70 and +40 mV, respectively. Rectification index was calculated by current ratio of EPSCs between +50 and -50 mV. NMDA/AMPA ratio was 0.20+/-0.05, AMPA receptor ratio of GluR2-lacking/GluR2-containing subunit was 0.26+/-0.05 and NMDA receptor ratio of NR2B/NR2A subunit was 0.32+/-0.03. The rectification index (control 2.39+/-0.27) was decreased in the presence of both APV and combination of APV and IEM-1460 (1.02+/-0.11 and 0.93+/-0.09, respectively). These results suggest that the major components of the striatal glutamate receptors are GluR2-containing AMPA receptors and NR2A-containing NMDA receptors. Our results may provide useful information for corticostriatal synaptic transmission and plasticity studies.

Forskolin Enhances Synaptic Transmission in Rat Dorsal Striatum through NMDA Receptors and PKA in Different Phases

The effect of forskolin on corticostriatal synaptic transmission was examined by recording excitatory postsynaptic currents (EPSCs) in rat brain slices using the whole-cell voltage-clamp technique. Forskolin produced a dose-dependent increase of corticostriatal EPSCs (1, 3, 10, and 30 microM) immediately after its treatment, and the increase at 10 and 30 microM was maintained even after its washout. When the brain slices were pre-treated with (DL)-2-amino-5-phosphonovaleric acid (AP-V, 100 microM), an NMDA receptor antagonist, the acute effect of forskolin (10 microM) was blocked. However, after washout of forskolin, an increase of corticostriatal EPSCs was still observed even in the presence of AP-V. When KT 5720 (5 microM), a protein kinase A (PKA) inhibitor, was applied through the patch pipette, forskolin (10 microM) increased corticostriatal EPSCs, but this increase was not maintained. When forskolin was applied together with AP-V and KT 5720, both the increase and maintenance of the corticostriatal EPSCs were blocked. These results suggest that forskolin activates both NMDA receptors and PKA, however, in a different manner.

Direct effects of riluzole on 5-hydroxytryptamine (5-HT)3 receptor-activated ion currents in NCB-20 neuroblastoma cells

The pharmacological action of riluzole, a drug that has been approved as a neuroprotective agent for the treatment of amyotrophic lateral sclerosis, has not yet been established. We examined the effects of riluzole on 5-hydroxytryptamine (5-HT)3) receptors in NCB-20 neuroblastoma cells using the whole-cell voltage clamp technique combined with a fast drug application method. Co-application of riluzole (1 - 300 microM, 5 s) produced a dose-dependent reduction in peak amplitudes and in the rise slope of the currents induced by 2 microM 5-HT. In addition, 5-HT3-mediated currents evoked by dopamine, a partial 5-HT3-receptor agonist, were inhibited by riluzole co-application. These inhibitory effects were clearly shown at low concentrations of 5-HT. The decay time constants of the receptor desensitization and deactivation were also significantly attenuated by riluzole. G-protein inhibitors (pertussis toxin and guanosine 5'-[beta-thio] diphosphate) did not completely block these inhibitory actions of riluzole. These results indicate that riluzole inhibits 5-HT3-induced ion currents directly by slowing channel activation in NCB-20 neuroblastoma cells.

Protective effects of vacuolar H+-ATPase c on hydrogen peroxide-induced cell death in C6 glioma cells

We have isolated a gene, the c subunit (ATP6L) of vacuolar H(+)-ATPase, involved in oxidative stress response. In this study, we examined the role of ATP6L and its molecular mechanisms in glial cell death induced by H(2)O(2). Expression of the ATP6L gene was increased by H(2)O(2) treatment in C6 glial cells. ATP6L siRNA-transfected C6 cells treated with H(2)O(2) showed a significant decrease in viability. ATP6L siRNA-transfected cells that were pretreated with MEK1/2 inhibitor completely recovered cell viability. Pretreatment of the transfected cells with zVAD-fmk, a pan-specific caspase inhibitor, did not result in the recovery of cell viability, as determined by a H(2)O(2)-induced cytotoxicity assay. The ultrastructural morphology of the transfected cells as seen by the use of transmission electron microscopy showed numerous cytoplasmic autophagic vacuoles with double membrane. These results suggest that ATP6L has a protective role against H(2)O(2)-induced cytotoxicity via an inhibition of the Erk1/2 signaling pathway, leading to inhibition of autophagic cell death.

Chronic 3,4-methylenedioxymethamphetamine treatment suppresses cell proliferation in the adult mouse dentate gyrus

We investigated the influence of chronic 3,4-methylenedioxymethamphetamine (MDMA) treatment on cell proliferation in the adult dentate gyrus. Mice were orally treated with MDMA (1.25 mg/kg-40 mg/kg) or saline for 30 days. To label dividing cells, mice were given 5-bromo-2'-deoxyuridine (BrdU) for 4 days from the day after the last administration of MDMA, and their brains were examined 24 h later. MDMA dose-dependently induced a decrease in the number of BrdU-positive cells in the male and female dentate gyrus. Our results suggest that chronic exposure to MDMA suppresses cell proliferation in the dentate gyrus.

Calcineurin-independent inhibition of KV1.3 by FK-506 (tacrolimus): a novel pharmacological property

The interaction of FK-506 with KV1.3, stably expressed in Chinese hamster ovary cells, was investigated with the whole cell patch-clamp technique. FK-506 inhibited KV1.3 in a reversible, concentration-dependent manner with an IC50of 5.6 μM. Rapamycin, another immunosuppressant, produced effects that were similar to those of FK-506 (IC50= 6.7 μM). Other calcineurin inhibitors (cypermethrin or calcineurin autoinhibitory peptide) alone had no effect on the amplitude or kinetics of KV1.3. In addition, the inhibitory action of FK-506 continued, even after the inhibition of calcineurin activity. The inhibition produced by FK-506 was voltage dependent, increasing in the voltage range for channel activation. At potentials positive to 0 mV (where maximal conductance is reached), however, no voltage-dependent inhibition was found. FK-506 exhibited a strong use-dependent inhibition of KV1.3. FK-506 shifted the steady-state inactivation curves of KV1.3 in the hyperpolarizing direction in a concentration-dependent manner. The apparent dissociation constant for FK-506 to inhibit KV1.3 in the inactivated state was estimated from the concentration-dependent shift in the steady-state inactivation curve and was calculated to be 0.37 μM. Moreover, the rate of recovery from inactivation of KV1.3 was decreased. In inside-out patches, FK-506 not only reduced the current amplitude but also accelerated the rate of inactivation during depolarization. FK-506 also inhibited KV1.5 and KV4.3 in a concentration-dependent manner with IC50of 4.6 and 53.9 μM, respectively. The present results indicate that FK-506 inhibits KV1.3 directly and that this effect is not mediated via the inhibition of the phosphatase activity of calcineurin.

Tandem high-dose chemotherapy and autologous stem cell rescue in patients over 1 year of age with stage 4 neuroblastoma

From June 1997 to August 2005, 52 consecutive newly diagnosed stage 4 neuroblastoma patients over 1 year of age were assigned to receive tandem high-dose chemotherapy and autologous stem cell rescue (HDCT/ASCR) as consolidation therapy. Fifty of the 52 patients underwent a first HDCT/ASCR and 44 patients underwent a second HDCT/ASCR. Eight patients (15.4%) died from treatment-related toxicity (seven during the second HDCT/ASCR). Total body irradiation (TBI) in the first HDCT/ASCR and a shorter interval (< 12 weeks) between the first and second HDCT/ASCR were associated with a higher rate of treatment-related death in the second HDCT/ASCR (P = 0.032 and 0.095, respectively). The tumor relapsed or progressed in 11 patients, and 33 patients remained event free with a median follow-up of 53 months (range 19-117) from diagnosis. The 5-year event-free survival (EFS) (+/- 95% confidence interval) for all 52 patients was 62.1+/-13.7%. The application of TBI and local radiotherapy, and a longer interval between the first and second HDCT/ASCR were independently associated with a better EFS (P = 0.026, 0.007 and 0.020, respectively). However, further studies will be needed to decrease the toxic death rate in the second HDCT/ASCR while reducing the relapse rate.

Regional differences in the neuroprotective effect of minocycline in a mouse model of global forebrain ischemia

We investigated the effect of minocycline on neuronal damage in the hippocampus and striatum in a mouse model of transient global forebrain ischemia. Male C57BL/6 mice were anesthetized with halothane and subjected to bilateral occlusion of the common carotid artery (BCCAO) for 30 min. Minocycline (90 mg/kg, i.p., qd) or saline was injected immediately after BCCAO and daily for the next two days (45 mg/kg, i.p., bid). In order to reduce the variability in ischemic neuronal damage, we applied selection criteria based on regional cerebral blood flow (rCBF), evaluated using laser Doppler flowmetry, and the plasticity of the posterior communicating artery (PcomA), evaluated using India ink solution. In animals with rCBF that was less than 15% of the baseline value and with a smaller PcomA, of diameter less than one-third that of the basilar artery, we consistently observed neuronal damage in the striatum and hippocampal subfields, including medial CA1, CA2, and CA4. When the effect of minocycline was assessed with cresyl violet staining, neuronal damage in the medial part of the CA1 subfield and the striatum was found to be significantly attenuated, although minocycline did not protect against neuronal damage in the remaining hippocampal subfields. Immunohistochemistry for NeuN, adenosine A1 receptor, and SCIP/Oct-6 confirmed the region-specific effect of minocycline in the hippocampus. In summary, our results suggest that minocycline protects neurons against global forebrain ischemia in a subregion-specific manner.

The impact of post-thaw colony-forming units-granulocyte/macrophage on engraftment following unrelated cord blood transplantation in pediatric recipients

We retrospectively reviewed the engraftment kinetics following unrelated cord blood transplantation (CBT) in association with the post-thaw colony-forming units-granulocyte/macrophage (CFU-GM) number along with the numbers of total nucleated cells (TNC), CD34(+) cells and CD3(+) cells. A total of 71 cord blood units prepared for 53 patients (double-unit CBT in 18 patients) were evaluated. Either the number of infused CFU-GM or CD34(+) cells was significantly lower in patients who failed to achieve engraftment (P=0.028 and 0.005, respectively). Post-thaw CFU-GM, TNC and CD34(+) cells correlated with the speed of neutrophil engraftment (P=0.004, 0.037 and 0.004, respectively), whereas only CFU-GM showed a significant correlation with platelet engraftment (r=-0.385, P=0.024). In double-unit transplants, the number of CFU-GM was the only significant factor predicting engraftment of the predominating unit (P=0.006). We conclude that the post-thaw CFU-GM number is a reliable predictor of rapid engraftment after CBT as well as of the predominating unit in double-unit transplants. Thus, it would be important to perform post-thaw CFU-GM assay on cryopreserved aliquots from several candidate cord blood units in advance before CBT to avoid selecting the unit that might possess a low clonogenic potential.

Open channel block of A-type, kv4.3, and delayed rectifier K+ channels, Kv1.3 and Kv3.1, by sibutramine

The effects of sibutramine on voltage-gated K+ channel (Kv)4.3, Kv1.3, and Kv3.1, stably expressed in Chinese hamster ovary cells, were investigated using the whole-cell patch-clamp technique. Sibutramine did not significantly decrease the peak Kv4.3 currents, but it accelerated the rate of decay of current inactivation in a concentration-dependent manner. This phenomenon was effectively characterized by integrating the total current over the duration of a depolarizing pulse to +40 mV. The IC50 value for the sibutramine block of Kv4.3 was 17.3 microM. Under control conditions, the inactivation of Kv4.3 currents could be fit to a biexponential function, and the time constants for the fast and slow components were significantly decreased after the application of sibutramine. The association (k+1) and dissociation (k-1) rate constants for the sibutramine block of Kv 4.3 were 1.51 microM-1s-1 and 27.35 s-1, respectively. The theoretical KD value, derived from k-1/k+1, yielded a value of 18.11 microM. The block of Kv4.3 by sibutramine displayed a weak voltage dependence, increasing at more positive potentials, and it was use-dependent at 2 Hz. Sibutramine did not affect the time course for the deactivating tail currents. Neither steady-state activation and inactivation nor the recovery from inactivation was affected by sibutramine. Sibutramine caused the concentration-dependent block of the Kv1.3 and Kv3.1 currents with an IC50 value of 3.7 and 32.7 microM, respectively. In addition, sibutramine reduced the tail current amplitude and slowed the deactivation of the tail currents of Kv1.3 and Kv3.1, resulting in a crossover phenomenon. These results indicate that sibutramine acts on Kv4.3, Kv1.3, and Kv3.1 as an open channel blocker.

Open channel block of Kv1.3 by rosiglitazone and troglitazone: Kv1.3 as the pharmacological target for rosiglitazone

The effects of rosiglitazone and troglitazone were examined on cloned Kv1.3 channels stably expressed in Chinese hamster ovary cells using the whole-cell configuration of the patch-clamp technique. Rosiglitazone decreased the Kv1.3 currents and accelerated the decay rate of current inactivation in a concentration-dependent manner with an IC(50) of 18.6 microM. These effects were reversible after washout of the drug. Troglitazone caused the block of Kv1.3 with a similar pattern but was five times more potent than rosiglitazone with an IC(50) of 3.5 microM. The block of Kv1.3 by rosiglitazone and troglitazone was voltage-dependent at a membrane potential coinciding with the activation of the channels. Both drugs decreased the tail current amplitude and slowed the deactivation process of Kv1.3, resulting in a tail crossover phenomenon. These results indicate that rosiglitazone and troglitazone block the open state of Kv1.3 channels, suggesting that it is an important pharmacological target for rosiglitazone as a potent blocker of Kv1.3 channels.

Acute inhibition of corticostriatal synaptic transmission in the rat dorsal striatum by ethanol

The purpose of this study was to examine the effects of ethanol on synaptic transmission in the dorsal striatum in rat brain slices. The effects of ethanol on corticostriatal synaptic transmission were tested by whole-cell voltage-clamp recording. Ethanol significantly decreased corticostriatal excitatory postsynaptic currents (EPSCs) in a dose-dependent manner (10-200 mM). However, the paired-pulse ratio was not affected by the ethanol (100 mM) treatment. The amplitude of miniature EPSCs (mEPSCs) from these neurons, recorded without cortical stimulation, was decreased, but the frequency of the mEPSCs remained unchanged. Ethanol also decreased currents induced by the local pressure injection of glutamate into dorsal striatal neurons. These results suggest that ethanol inhibits glutamatergic synaptic transmission in the dorsal striatum, possibly through a postsynaptic mechanism.

Increased leptin and decreased ghrelin level after smoking cessation

Smoking cessation is associated with transient increases in body weight. Leptin and ghrelin are known to be major mediators of appetite, weight and the reward pathway. Therefore, this study assessed the changes in the plasma leptin and ghrelin level and their relationship with the body weight and appetite after smoking cessation in the Korean population. Eighteen subjects, who had stopped smoking for 2 months were enrolled in this study. The body mass index (BMI), body fat mass (BFM), waist-hip ratio (WHR), weight and appetite were measured before and after smoking cessation. In addition, the plasma leptin and ghrelin levels were measured. The BMI, BFM, WHR, weight and appetite were significantly higher than baseline in those who had gave up smoking for 2 months (p<0.05). The plasma leptin concentration increased and the plasma ghrelin level decreased after smoking cessation. The change in the leptin level was positively correlated with the change in the body mass index and body fat mass. These results do not support the direct mediation of the leptin-ghrelin-neuropeptide Y (NPY) system on weight gain after smoking cessation. It appears that weight and appetite is regulated by a more complicated mechanism after smoking cessation.

Interaction of riluzole with the closed inactivated state of Kv4.3 channels

The effect of riluzole on Kv4.3 was examined using the whole-cell patch-clamp technique. Riluzole inhibited the peak amplitude of Kv4.3 in a reversible, concentration-dependent manner with an IC(50) of 115.6 microM. Under control conditions, a good fit for the inactivation of Kv4.3 currents to a double exponential function, with the time constants of the fast component (tau(f)) and the slow component (tau(s)), was obtained. tau(f) was not altered by riluzole at concentrations up to 100 microM, but tau(s) became slower with increasing riluzole concentration, resulting in the crossover of the currents. The inhibition increased steeply with increasing channel activation at more positive potentials. In the full activation voltage range positive to (+)30 mV, however, no voltage-dependent inhibition was found. Riluzole shifted the voltage dependence of the steady-state inactivation of Kv4.3 in the hyperpolarizing direction in a concentration-dependent manner. However, the slope factor was not affected by riluzole. The K(i) for riluzole for interacting with the inactivated state of Kv4.3 was estimated from the concentration-dependent shift in the steady-state inactivation curve and was determined to be 1.2 muM. Under control conditions, closed state inactivation was fitted to a single exponential function. Riluzole caused a substantial acceleration in the closed state inactivation. In the presence of riluzole, the recovery from inactivation was slower than under control conditions. Riluzole induced a significant use-dependent inhibition of Kv4.3. These results suggest that riluzole inhibits Kv4.3 by binding to the closed inactivated state of the channels and that the unbinding of riluzole occurs from the closed state during depolarization.

Assessment of converting from intravenous to oral administration of cyclosporin A in pediatric allogeneic hematopoietic stem cell transplant recipients

We studied the administration method during a transition period from continuous intravenous (i.v.) infusion to oral administration of cyclosporin A (CsA). Thirty-two pediatric hematopoietic stem cell transplant (HSCT) recipients, between the ages of 8 months and 15.6 years (median 7.1 years) participated in this study. The pharmacokinetic properties of CsA was evaluated during the transition period from i.v. to oral CsA. The daily oral dose of CsA was three times higher than the i.v. dose. Oral dosing began immediately after the continuous infusion was discontinued. Whole-blood CsA concentrations were measured by a monoclonal fluorescence polarization immunoassay (FPIA). The mean+/-s.d. value of bioavailability (F), maximum concentration (C(max)), half-life (t(1/2)) of CsA were 43.1+/-14.4%, 1135.3+/-340.6 ng/ml and 3.1+/-1.2 h, respectively. Mean clearance (CL)+/-s.d. was 480.9+/-103.7, 414.9+/-137.1 and 320+/-51.8 ml/h/kg in patients <20, 20-40 and >40 kg of body weight, respectively. The CsA CL of younger children was significantly greater than for older children (P=0.044). CsA trough levels were maintained within the therapeutic range throughout the transition period. Therefore, our findings suggest that the immediate administration of an oral formulation, after discontinuation of the continuous infusion, would be practical and effective for routine clinical use.

Minocycline attenuates white matter damage in a rat model of chronic cerebral hypoperfusion

White matter lesions are thought to result from chronic cerebral ischemia and constitute a core pathology of subcortical vascular dementia. This rarefaction has been known to be associated with microglial activation. We investigated whether minocycline, a microglial inhibitor, attenuates the white matter damage induced by chronic cerebral hypoperfusion that is used as a model of vascular dementia. Male Wistar rats were subjected to bilateral, permanent occlusion of the common carotid arteries (BCCAO) to induce chronic cerebral hypoperfusion. Minocycline or saline was injected daily for 2 weeks after BCCAO. In the corpus callosum and the optic tract, white matter damage observed with Klüver-Barrera staining was significantly attenuated in the minocycline-treated group compared to saline-treated controls. In control rats, immunoreactivities of major basic protein (MBP), Ox-42 as a microglial marker, and matrix metalloproteinase (MMP)-2 were increased in the corpus callosum. Minocycline significantly reduced these changes. Co-expression of Ox-42 and MMP-2 was confirmed by double immunofluorescence histochemistry. Our results suggest that chronic treatment with minocycline could be protective against at least some ischemic white matter damage, and its mechanism may be related to suppressing microglial activation.

Differential Expression of Phospholipase D Isozymes in the Hippocampus Following Kainic Acid-Induced Seizures

To investigate the pathophysiological role of phospholipase D (PLD)-mediated signaling, changes in the expression of the PLD isozymes PLD1 and PLD2 were investigated in the rat kainic acid (KA) model of human temporal lobe epilepsy. Western blot analysis showed a significant increase in the expression of PLD1 and PLD2 in the postictal hippocampus. PLD1 immunoreactivity increased preferentially in the CA3 and CA1 regions, where pyramidal neurons are susceptible to temporal lobe epilepsy. Experiments employing double immunofluorescence revealed that the cells expressing PLD1 were GFAP-expressing reactive astrocytes. By contrast, PLD2 immunoreactivity increased strikingly in infrapyramidal, but not in suprapyramidal granule cells of the postictal dentate gyrus, fitting well with results of the PLD activity assay. Considering that PLD belongs to a key signaling pathway, this result suggests that changes in granule cell activity in the dentate gyrus after seizures occurs specifically between the supra- and infrapyramidal blades. In addition, enhanced immunoreactivity of PLD2 was observed in the reactive astrocytes of the CA1, CA3, and hilar subregions, but its temporal pattern is different from that of PLD1. Taken together, our results suggest that PLD1 and PLD2 exercise their unique pathophysiological functions in the rat hippocampus after KA-induced seizures.

Mechanism of block by fluoxetine of 5-hydroxytryptamine3 (5-HT3)-mediated currents in NCB-20 neuroblastoma cells

The effect of fluoxetine (Prozac) on 5-hydroxytryptamine(3) (5-HT(3))-mediated currents in NCB-20 neuroblastoma cells was examined using the whole-cell patch-clamp technique. Fluoxetine produced a significant reduction of peak amplitude without altering the activation time course of 5-HT(3)-mediated currents. These effects were concentration-dependent, with an IC(50) value of 4.15 microM. No voltage dependence was evident in fluoxetine's block of 5-HT(3)-mediated currents over the entire voltage range tested. The extent of block by pre-application of fluoxetine was significantly greater than that by co-application. Fluoxetine also increased the apparent rate of current desensitization to 5-HT application. Using a first-order kinetics analysis, the open-channel blocking rate constants were 0.06 microM(-1)s(-1) (k(+1), association rate constant) and 0.05 s(-1) (k(-1), dissociation rate constant), with an apparent K(d) (=k(-1)/k(+1)) of 0.83 microM. This value is close to an IC(50) of 1.11 microM obtained from the reduction in tau, the time constant of desensitization. Intracellular application of fluoxetine for long durations had no effect on the amplitude or kinetics of 5-HT(3)-mediated currents. Similarly, norfluoxetine, the major metabolite of fluoxetine, reduced the peak current, and enhanced the rate of current desensitization in a concentration-dependent manner with an IC(50) of 2.66 microM, indicating that norfluoxetine is more potent than fluoxetine in blocking 5-HT(3)-mediated currents. These results indicate that, at clinically relevant concentrations, fluoxetine and its metabolite, norfluoxetine, block 5-HT(3)-mediated currents in NCB-20 neuroblastoma cells.

Regional differences in enhanced neurogenesis in the dentate gyrus of adult rats after transient forebrain ischemia

Neurogenesis in the dentate gyrus occurs throughout life. We observed regional differences in neurogenesis in the dentate gyrus of adult rats following transient forebrain ischemia. Nine days after ischemic-reperfusion or sham manipulation, rats were given 5-bromo-2'-deoxyuridine-5'-monophosphate (BrdU), a marker for dividing cells. They were killed 1 or 28 days later to distinguish between cell proliferation and survival. Neurogenesis was evaluated by BrdU incorporation as well by identifying neuronal and glial markers in six regions of the dentate gyrus: rostral, middle and caudal along the rostrocaudal axis, each further divided into suprapyramidal and infrapyramidal blade subregions. In control rats BrdU-positive cells in the rostral subregions were significantly lower in the suprapyramidal than in the infrapyramidal blades at both 1 and 28 days after BrdU injection. One day after injection, BrdU-positive cells had increased more in five of the subregions in the ischemic rats than in the controls, the exception being the suprapyramidal blade of the rostral subregion. At 28 days after BrdU injection, numbers of BrdU-positive cells were higher in four subregions in the ischemic group, the exceptions being the rostral suprapyramidal and middle infrapyramidal blades. At 28 days after BrdU injection, the percentages of BrdU positive cells that expressed a neuronal marker (NeuN) were the same in the dentate granule cell layers of ischemic and control rats. Our data thus demonstrate regional differences in enhanced neurogenesis in the dentate gyrus of adult rats after transient forebrain ischemia.

Alterations in mRNA expression of ribosomal protein S9 in hydrogen peroxide-treated neurotumor cells and in rat hippocampus after transient ischemia

This study was designed to isolate new genes related to apoptosis in rat pheochromocytoma (PC12) cells treated with hydrogen peroxide (H2O2), and to characterize the roles of the genes using both in vitro and in vivo models of oxidative injury. cDNA libraries were prepared from H2O2-treated and -untreated PC12 cells, and a ribosomal protein S9 (RPS9) clone was isolated by a differential screening method. Increase of RPS9 expression in both H2O2-treated PC12 and neuroblastoma (Neuro-2A) cells was shown by Northern blot analysis. Viability of the antisense-transfected Neuro-2A (RPS9-AS) cells following H2O2 treatment was significantly reduced in a dose-dependent manner. In an in vivo model of transient forebrain ischemia, an increase in RPS9 expression was prominent by 1 day postischemia in the granule cell layer neurons of the dentate gyrus. Both activation of caspase-3 and significant recovery of viability following pretreatment with cycloheximide were shown in RPS9-AS cells treated with H2O2. These data suggest that RPS9 plays a protective role in oxidative injury of neuronal cells.

Successive double high-dose chemotherapy with peripheral blood stem cell rescue collected during a single leukapheresis round in patients with high-risk pediatric solid tumors: a pilot study in a single center

In total, 18 of 26 double high-dose chemotherapies (HDCT) in pediatric solid tumors were rescued with peripheral blood stem cells collected during a single leukapheresis round (single-harvest group, SHG). In the remaining eight HDCT, additional leukapheresis were necessary after the first HDCT (HDCT1) to rescue the second HDCT (HDCT2) (double-harvest group, DHG). Stem cell collection after HDCT1 was inefficient and delayed in patients who had received prior chemotherapy before HDCT1. The interval between HDCT1 and HDCT2 was shorter in SHG than in DHG (median 62.5 days vs 178.5 days, P-value=0.002). Hematologic recovery in HDCT2 was delayed compared to HDCT1. However, there was no difference in hematologic recovery between SHG and DHG. A high rate of treatment-related mortality (TRM) was recorded during HDCT2, but there was no evidence that the shorter interval caused a higher rate of TRM (P-value=0.454). The probability of disease-free survival at 2 years after HDCT2 in the SHG and DHG were 66.7 and 25.0%, respectively (P-value=0.031). Therefore, to administer the second HDCT earlier in double HDCT, and thus to improve the survival of patients with high-risk solid tumors, the single-harvest approach is recommended rather than the double-harvest approach.

Effect of 5-hydroxyindole on ethanol potentiation of 5-hydroxytryptamine (5-HT)3 receptor-activated ion current in NCB-20 neuroblastoma cells

We examined the effect of 5-hydroxyindole (5-HI) on the potentiation of 5-hydroytryptamine (5-HT)(3) receptor function by ethanol (EtOH) so as to study whether EtOH potentiates channel function through increasing activation or blocking desensitization. We measured 5-HT(3) receptor current using a whole-cell voltage clamp technique with a method of rapid drug application in NCB-20 neuroblastoma cells. The 5-HI, an agent that block receptor desensitization, increased the decay time constant (tau), not the peak of 5-HT(3) receptor-mediated currents induced by 10 microM 5-HT. EtOH did not change the peak amplitude and tau of the current induced by 10 microM 5-HT. Coapplication of EtOH and 5-HI with 5-HT caused no increase in the peak currents, but tau was further increased. Therefore, a further block in desensitization could be induced by 5-HI, despite the presence of EtOH. These results indicate that EtOH potentiates 5-HT(3) receptor function, with these effects due at least in part by increasing channel activation rather than by blocking desensitization.

Upregulation of gp130 and STAT3 activation in the rat hippocampus following transient forebrain ischemia

To determine whether the pathophysiological processes after transient forebrain ischemia are mediated via a signal pathway involving gp130 (a signal transducer for the interleukin-6 family), we analyzed changes in the expression of gp130 and its downstream transcription factor, signal transducer and activator of transcription factor 3 (STAT3), in the rat hippocampus of a four-vessel occlusive ischemia model. Expression of gp130 mRNA was restricted to neurons of the pyramidal cell and granule cell layers in control animals. Four hours after ischemic injury, astrocytes expressed gp130 mRNA. Expression of gp130 increased preferentially in the CA1 and dentate hilar regions, and was maintained for at least 2 weeks. Increase in gp130 expression was accompanied by the activation of STAT3 following ischemic injury. Four hours after injury, STAT3 and phosphorylated STAT3 (pSTAT3) were observed in the nuclei of the dentate hilar region, and sequentially in the CA1 region at day 1. By day 3, STAT3 immunoreactivity markedly increased in these areas, where small cells with the morphology of astrocytes showed nuclear and cytoplasmic STAT3 and nuclear pSTAT3 immunoreactivities. These patterns were especially maintained in the CA1 area until 14 days of reperfusion. Double-labeling experiments revealed that the cells expressing STAT3 and pSTAT3 were glial fibrillary acidic protein-expressing reactive astrocytes. These results show a coordinated and long-lasting upregulation of gp130 mRNA and STAT3 activation in reactive astrocytes of the postischemic hippocampus, indicating that they may be involved in the astrocytic response to an ischemic insult.

Upregulation of haptoglobin in reactive astrocytes after transient forebrain ischemia in rats

Immunohistochemistry for haptoglobin (Hp) in the postischemic hippocampus demonstrated an immunoreactivity visible one day after reperfusion and continuing to increase until 14 days after ischemia. The immunoreactivity was most prominent in CA1 and the dentate hilar region, especially in cells with astroglial morphology. Double immunofluorescence histochemistry confirmed colocalization of the Hp and glial fibrillary acidic protein. Furthermore, a reverse transcription-polymerase chain reaction study confirmed an elevated Hp mRNA level in the postischemic hippocampus. The Hp gene expression was also upregulated in C6 and A-172 glioblastoma cell lines after H O treatment. These findings suggest that Hp is synthesized in reactive astrocytes in response to ischemia-reperfusion injury.

Activation of group I mGluRs is necessary for induction of long-term depression at striatal synapses

Activation of metabotropic glutamate receptors (mGluRs), which are coupled to G proteins, has important roles in certain forms of synaptic plasticity including corticostriatal long-term depression (LTD). In the present study, extracellular field potential and whole cell voltage-clamp recording techniques were used to investigate the effect of mGluR antagonists with different subtype specificity on high-frequency stimulation (HFS)-induced LTD of synaptic transmission in the striatum of brain slices obtained from 15-to 25-day-old rats. Induction of LTD was prevented during exposure to the nonselective mGluR antagonist (RS)-alpha-methyl-4-carboxyphenylglycine (500 microM). The group I mGluR-selective antagonists (S)-4-carboxy-phenylglycine (50 microM) and (RS)-1-aminoindan-1,5-dicarboxylic acid (100 microM) prevented induction of LTD when applied before and during HFS. The mGluR1-selective antagonist 7-(Hydroxyimino) cyclopropa[b]chromen-1a-carboxylate ethyl ester (80 microM) also blocked LTD induction. Unexpectedly, the mGluR5-selective antagonist 2-methyl-6-(phenylethyl)-pyridine (10 microM) also prevented LTD induction. The group II mGluR antagonist LY307452 (10 microM) did not block LTD induction at corticostriatal synapses, but LY307452 was able to block transient synaptic depression induced by the group II agonist LY314593. None of the antagonists had any effect on basal synaptic transmission at the concentrations used, and mGluR antagonists did not reverse LTD when applied beginning 20 min after HFS. These results suggest that both group I mGluR subtypes contribute to the induction of LTD at corticostriatal synapses.

Abnormal GABAA receptor-mediated currents in dorsal root ganglion neurons isolated from Na-K-2Cl cotransporter null mice

We have recently disrupted Slc12a2, the gene encoding the secretory Na-K-2Cl cotransporter in mice (NKCC1) (Delpire et al., 1999). Gramicidin perforated-patch and whole-cell recordings were performed to study GABA-induced currents in dorsal root ganglion (DRG) neurons isolated from wild-type and homozygote NKCC1 knock-out mice. In wild-type DRG neurons, strong GABA-evoked inward current was observed at the resting membrane potential, suggesting active accumulation of Cl(-) in these cells. This GABA-induced current was blocked by picrotoxin, a GABA(A) receptor blocker. The strong Cl(-) accumulation that gives rise to depolarizing GABA responses is caused by Na-K-2Cl cotransport because reduction of external Cl(-) or application of bumetanide induced a decrease in [Cl(-)](i), whereas an increase in external K(+) caused an apparent [Cl(-)](i) accumulation. In contrast to control neurons, little or no net current was observed at the resting membrane potential in homozygote NKCC1 mutant DRG neurons. E(GABA) was significantly more negative, demonstrating the absence of Cl(-) accumulation in these cells. Application of bumetanide induced a positive shift of E(GABA), suggesting the presence of an outward Cl(-) transport mechanism. In agreement with an absence of GABA depolarization in DRG neurons, behavioral analysis revealed significant alterations in locomotion and pain perception in the knock-out mouse. Our results clearly demonstrate that the Na-K-2Cl cotransporter is responsible for [Cl(-)](i) accumulation in DRG neurons and that via regulation of intracellular Cl(-), the Na-K-2Cl cotransporter participates in the modulation of GABA neurotransmission and sensory perception.