Journal of Pharmacological Sciences
Online ISSN : 1347-8648
Print ISSN : 1347-8613
ISSN-L : 1347-8613
Volume 121, Issue 1
Displaying 1-10 of 10 articles from this issue
Full Paper
  • Mahoko Asayama, Junko Kurokawa, Kiyoshi Shirakawa, Hisashi Okuyama, To ...
    2013 Volume 121 Issue 1 Pages 1-8
    Published: 2013
    Released on J-STAGE: January 19, 2013
    Advance online publication: December 14, 2012
    JOURNAL FREE ACCESS
    In short QT syndrome, inherited gain-of-function mutations in the human ether a-gogo-related gene (hERG) K+ channel have been associated with development of fatal arrhythmias. This implies that drugs that activate hERG as a side effect may likewise pose significant arrhythmia risk. hERG activators have been found to have diverse mechanisms of activation, which may reflect their distinct binding sites. Recently, the new hERG activator ICA-105574 was introduced, which disables inactivation of the hERG channel with very high potency. We explored characteristics of this new drug in several experimental models. Patch clamp experiments were used to verify activation of hERG channels by ICA-105574 in human embryonic kidney cells stably-expressing hERG channels. ICA-105574 significantly shortened QT and QTc intervals and monophasic action potential duration (MAP90) in Langendorff-perfused guinea-pig hearts. We also administered ICA-105574 to anesthetized dogs while recording ECG and drug plasma concentrations. ICA-105574 (10 mg/kg) significantly shortened QT and QTc intervals, with a free plasma concentration of approximately 1.7 μM at the point of maximal effect. Our data showed that unbound ICA-105574 caused QT shortening in dogs at concentrations comparable to the half maximal effective concentration (EC50, 0.42 μM) of hERG activation in the patch clamp studies.
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  • Shohei Yamamoto, Masahiro Ohsawa, Hideki Ono
    2013 Volume 121 Issue 1 Pages 9-16
    Published: 2013
    Released on J-STAGE: January 19, 2013
    Advance online publication: December 14, 2012
    JOURNAL FREE ACCESS
    Neuropathic pain induces allodynia and hyperalgesia. In the spared nerve injury (SNI) model, marked mechanical hyperalgesia is manifested as prolongation of the duration of paw withdrawal after pin stimulation. We have previously reported that spinal ventral root discharges (after-discharges) after cessation of noxious mechanical stimulation applied to the corresponding hindpaw were prolonged in anesthetized spinalized rats. Since these after-discharges occurred through transient receptor potential (TRP) V1–positive fibers, these fibers could contribute to mechanical hyperalgesia. Therefore, we examined whether selective deletion of TRPV1-positive fibers by resiniferatoxin, an ultrapotent TRPV1 agonist, would affect the behavioral changes and ventral root discharges in SNI rats. Mechanical allodynia in the von Frey test, mechanical hyperalgesia after pin stimulation, and enhancement of ventral root discharges, but not thermal hyperalgesia in the plantar test, appeared in Wistar rats with SNI. Mechanical hyperalgesia was abolished by treatment with resiniferatoxin, whereas mechanical allodynia was not affected. Moreover, resiniferatoxin eliminated after-discharges completely. These results show that TRPV1-positive fibers do not participate in the mechanical allodynia caused by sensitization of Aβ-fibers, but contribute to the enhancement of after-discharges and mechanical hyperalgesia following SNI. It is suggested that the mechanisms responsible for generating mechanical allodynia differ from those for prolongation of mechanical hyperalgesia.
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  • Mingshan Niu, Yan Sun, Xuejiao Liu, Li Tang, Rongguo Qiu
    2013 Volume 121 Issue 1 Pages 17-24
    Published: 2013
    Released on J-STAGE: January 19, 2013
    Advance online publication: December 26, 2012
    JOURNAL FREE ACCESS
    Tautomycetin (TMC), originally isolated from Streptomyces griseochromogenes, has been suggested as a potential drug retaining specificity toward colorectal cancer. However, we found that TMC exhibited inhibitory effects on cell proliferation of many cancer cell lines including adriamycin-resistant human breast adenocarcinoma. We investigated its anti-tumor activity and mechanisms in human breast cancer cells for the first time. In this study, we showed that TMC effectively inhibited breast cancer cell proliferation, migration, and invasion. TMC also induced apoptosis in MCF-7 cells. This apoptotic response was in part mediated by Bcl-2 cleavage, leading to the release of cytochrome c, which facilitates binding of Apaf-1 to caspase-9 in its presence and subsequent activation of caspase-7 in apoptosis induction signaling pathways. Furthermore, we identified that TMC induced apoptosis by suppressing Akt signaling pathway activation, which is independent of protein phosphatase PP1 inhibition. The levels of downstream targets of Akt, including phospho-forkhead transcription factor and Bad, were also reduced after TMC treatment. Overall, our results indicate that TMC could be used as a potential drug candidate for breast cancer therapy. More importantly, our study provides new mechanisms for the anticancer effects of TMC.
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  • Hikaru Yammamoto, Shigeru Tanaka, Anna Tanaka, Izumi Hide, Takahiro Se ...
    2013 Volume 121 Issue 1 Pages 25-38
    Published: 2013
    Released on J-STAGE: January 19, 2013
    Advance online publication: December 26, 2012
    JOURNAL FREE ACCESS
    To examine the functional regulation of serotonin transporter (SERT) by cAMP, we examined whether SERT uptake activity was affected by dibutyryl cAMP (dbcAMP), a cAMP analog, in SERT-transfected RN46A cells derived from embryonic rat raphe neurons. Long-term exposure (> 4 h) of dbcAMP (1 mM) to SERT-expressing RN46A cells significantly up-regulated SERT activity. In addition, a selective PKA activator, but not a selective EPAC activator, increased the serotonin uptake activity of SERT, suggesting that this regulation was mainly mediated via PKA. Time-dependent up-regulation of SERT activity by dbcAMP was accompanied by neural differentiation of RN46A cells. Further investigation of dbcAMP-induced up-regulation of SERT revealed that dbcAMP elevated SERT protein levels without affecting SERT mRNA transcription. The chase assay for residual SERT protein revealed that dbcAMP slowed its degradation rate. Immunohistochemical analysis revealed that plasma membrane–localized SERT was more abundant in dbcAMP-treated cells than in non-treated cells, suggesting that dbcAMP up-regulated SERT by decreasing its degradation and increasing its plasma membrane expression. These results raise the possibility that the elevation of intracellular cAMP up-regulated SERT function through a mechanism linked to the differentiation of RN46A cells and show the importance of SERT function during the developmental process of the serotonergic nervous system.
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  • Babovic Daniela, Luning Jiang, Satoshi Goto, Ilse Gantois, Günter ...
    2013 Volume 121 Issue 1 Pages 39-47
    Published: 2013
    Released on J-STAGE: January 19, 2013
    JOURNAL FREE ACCESS
    Considerable topographic overlap exists between brain opioidergic and dopaminergic neurons. Pharmacological blockade of the dopamine D1 receptor (Drd1a) reverses several behavioural phenomena elicited by opioids. The present study examines the effects of morphine in adult mutant (MUT) mice expressing the attenuated diphtheria toxin-176 gene in Drd1a-expressing cells, a mutant line shown previously to undergo post-natal striatal atrophy and loss of Drd1a-expression. MUT and wild-type mice were assessed behaviourally following acute administration of 10 mg/kg morphine. Treatment with morphine reduced locomotion and rearing similarly in both genotypes but reduced total grooming only in MUT mice. Morphine-induced Straub tail and stillness were heightened in MUT mice. Chewing and sifting were decreased in MUT mice and these effects were not modified by morphine. Loss of striatal Drd1-positive cells and up-regulated D2-expression, as reflected in down-regulated D1-like and up-regulated D2-like binding, respectively, is not uniform along the cranio-caudal extent in this model but appears to be greater in the caudal striatum. Preferential caudal loss of μ-opioid-expression, a marker for the striosomal compartment, was seen. These data indicate that Drd1a-positive cell loss modifies the exploratory behavioural response elicited by morphine, unmasking novel morphine-induced MUT-specific behaviours and generating a hypersensitivity to morphine for others.
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  • Ayako Moriyama, Daisuke Nishizawa, Shinya Kasai, Junko Hasegawa, Ken-i ...
    2013 Volume 121 Issue 1 Pages 48-57
    Published: 2013
    Released on J-STAGE: January 19, 2013
    Advance online publication: December 21, 2012
    JOURNAL FREE ACCESS
    Individual differences in the sensitivity to fentanyl, a widely used opioid analgesic, can hamper effective pain treatment. The adrenergic system is reportedly involved in the mechanisms of pain and analgesia. Here, we focused on one of the adrenergic receptor genes, ADRB1, and analyzed the influence of single-nucleotide polymorphisms (SNPs) in the ADRB1 gene on individual differences in pain and analgesic sensitivity. We examined associations between pain and fentanyl sensitivity and the two SNPs, A145G and G1165C, in the human ADRB1 gene in 216 Japanese patients who underwent painful orofacial cosmetic surgery, including bone dissection. The patients who carried the A-allele of the A145G SNP were more sensitive to cold pressor– induced pain than those who did not carry this allele, especially in male patients. The analgesic effect was significantly less in females who carried the G-allele of the G1165C SNP than the females who did not carry the G-allele. The haplotype analysis revealed a significant decrease in 24-h postoperative fentanyl use in female 145A/1165C haplotype carriers. These results suggest that SNPs in the ADRB1 gene are associated with individual differences in pain and analgesic sensitivity, and analyzing these SNPs may promote personalized pain treatment in the future.
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  • Yukiko Mine, Seiko Oku, Naoyuki Yoshida
    2013 Volume 121 Issue 1 Pages 58-66
    Published: 2013
    Released on J-STAGE: January 19, 2013
    Advance online publication: December 21, 2012
    JOURNAL FREE ACCESS
    Although selective serotonin reuptake inhibitors (SSRIs) are widely used to treat depression, they frequently cause gastrointestinal adverse effects, such as nausea and emesis. In the present study, we investigated the anti-emetic effect of mosapride, a 5-HT4 receptor agonist, on SSRIs-induced emesis in Suncus murinus and dogs. We also examined the effect of mosapride on SSRIs-induced delay in gastric emptying and increase in gastric vagal afferent activity in rats. Oral administration of paroxetine, but not its subcutaneous administration, dose-dependently caused emesis in both animals. Mosapride inhibited paroxetine-induced emesis in Suncus murinus and dogs with ID50 values of 7.9 and 1.1 mg/kg, respectively. The anti-emetic effect of mosapride was partially inhibited by SB207266, a selective 5-HT4 antagonist. Intragastric administration of paroxetine increased gastric vagal afferent discharge in anesthetized rats. Mosapride failed to suppress this increase. On the other hands, mosapride improved the delay in gastric emptying caused by paroxetine in rats. We have shown in this study that oral administration of SSRIs causes emesis and activates gastric vagal afferent activity in experimental animals and that mosapride inhibits SSRIs-induced emesis, probably via improvement of SSRIs-induced delay in gastric emptying. These findings highlight the promising potential of mosapride as an anti-emetic agent.
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  • Tatsuhiko Ikeda, Kiyo-aki Ishii, Yuria Saito, Masahiro Miura, Aoi Otag ...
    2013 Volume 121 Issue 1 Pages 67-73
    Published: 2013
    Released on J-STAGE: January 19, 2013
    Advance online publication: December 26, 2012
    JOURNAL FREE ACCESS
    Sunitinib is an oral multitargeted receptor tyrosine kinase inhibitor with antiangiogenic and antitumor activity that mainly targets vascular endothelial growth factor receptors, and recently, it has been shown to be an active agent for the treatment of malignant pheochromocytomas. Previously, we demonstrated that sunitinib directly inhibited mTORC1 signaling in rat pheochromocytoma PC12 cells. Although autophagy is a highly regulated cellular process, its relevance to cancer seems to be complicated. It is of note that inhibition of mTORC1 is a prerequisite for autophagy induction. Indeed, direct mTORC1 inhibition initiates ULK1/2 autophosphorylation and subsequent Atg13 and FIP200 phosphorylation, inducing autophagy. Here, we demonstrated that sunitinib significantly increased the levels of LC3-II, concomitant with a decrease of p62 in PC12 cells. Following sunitinib treatment, immunofluorescent imaging revealed a marked increased punctate LC3-II distribution. Furthermore, Atg13 knockdown significantly reduced its protein level, which in turn abolished sunitinib-induced autophagy. Moreover, inhibition of autophagy by siRNAs targeting Atg13 or by pharmacological inhibition with ammonium chloride, enhanced both sunitinib-induced apoptosis and anti-proliferation. Thus, sunitinib-induced autophagy is dependent on the suppression of mTORC1 signaling and the formation of ULK1/2–Atg13–FIP200 complexes. Inhibition of autophagy may be a promising therapeutic option for improving the anti-tumor effect of sunitinib.
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  • Maho Kikuta, Tatsuo Shiba, Masanori Yoneyama, Koichi Kawada, Taro Yama ...
    2013 Volume 121 Issue 1 Pages 74-83
    Published: 2013
    Released on J-STAGE: January 19, 2013
    Advance online publication: December 26, 2012
    JOURNAL FREE ACCESS
    Edaravone is clinically used in Japan for treatment of patients with acute cerebral infarction. To clarify the effect of edaravone on neurogenesis in the hippocampus following neuronal injury in the hippocampal dentate gyrus, we investigated the effect of in vitro and in vivo treatment with edaravone on the proliferation of neural stem/progenitor cells prepared from the mouse dentate gyrus damaged by trimethyltin (TMT). Histological assessment revealed the presence of large number of nestin(+) cells in the dentate gyrus on days 3 – 5 post-TMT treatment. We prepared cells from the dentate gyrus of naïve, TMT-treated mice or TMT/edaravone-treated mice. The cells obtained from the dentate gyrus of TMT-treated animals were capable of BrdU incorporation and neurosphere formation when cultured in the presence of growth factors. The TMT-treated group had a larger number of nestin(+) cells and nestin(+)GFAP(+) cells than the naïve one. Under the culture condition used, sustained exposure of the cells from the damaged dentate gyrus to edaravone at 10−11 and 10−8 M promoted the proliferation of nestin(+) cells. The systemic in vivo treatment with edaravone for 2 days produced a significant increase in the number of nestin(+) cells among the cells prepared from the dentate gyrus on day 4 post-TMT treatment, and as well as one in the number of neurospheres formed from these cells in the culture. Taken together, our data indicated that edaravone had the ability to promote the proliferation of neural stem/progenitor cells generated following neuronal damage in the dentate gyrus.
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Short Communication
  • Keisuke Migita, Junko Yamada, Yoshikazu Nikaido, XiuYu Shi, Sunao Kane ...
    2013 Volume 121 Issue 1 Pages 84-87
    Published: 2013
    Released on J-STAGE: January 19, 2013
    Advance online publication: December 21, 2012
    JOURNAL FREE ACCESS
    We recently identified a novel missense mutation of the γ2 subunit at position 40 with serine (N40S) of the GABAA receptor from a patient with epilepsy. Here, we report properties of the mutant receptor using the whole cell patch clamp technique. The Hill coefficient for the N40S receptor was greater than for the wild-type (WT) receptor, while the EC50 and kinetics did not differ. Furthermore, the effects of diazepam, Zn2+, bicuculline, and pH were indistinguishable between WT and N40S receptors. These results suggest that the changes in the steepness of the concentration–response relationship for GABA in the N40S receptor may trigger epilepsy.
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