Junichi Kitanaka

Hepatic Oval Cells Have the Side Population Phenotype Defined by Expression of ATP-Binding Cassette Transporter ABCG2/BCRP1

Organ-specific stem cells can be identified by the side population (SP) phenotype, which is defined by the property to effectively exclude the Hoechst 33342 dye. The ATP-binding cassette transporter ABCG2/BCRP1 mediates the SP phenotype. Because hepatic oval cells possess several characteristics of stem cells, we examined whether they have the SP phenotype using the 2-acetylaminofluorene/partial hepatectomy (PH) model. Fluorescence-activated cell sorting analysis showed that a population of non-parenchymal cells containing oval cells, prepared on day 7 after PH, carried a significant number of SP cells, whereas that of non-parenchymal cells without oval cells, prepared on day 0 after PH, did not. Northern blot analysis using total liver RNA obtained on various days after PH showed that the expression of ABCG2/BCRP1 mRNA increased after PH, reaching the highest level on day 7, and then gradually decreased. This pattern of changes in the ABCG2/BCRP1 mRNA level was well correlated to that in the number of oval cells. Furthermore, in situ hybridization revealed that oval cells were the sites of expression of ABCG2/BCRP1 mRNA. These results indicate that oval cells have the SP phenotype defined by expression of ABCG2/BCRP1, suggesting that oval cells may represent stem cells in the liver.

Behavioral sensitization and alteration in monoamine metabolism in mice after single versus repeated methamphetamine administration.

To address the functional alterations of monoaminergic neuronal systems in mice after single and repeated administration of methamphetamine, we examined the tissue contents of monoamines and their metabolites in addition to locomotor activity estimated by horizontal locomotion and rearing measurements. In male ICR mice, the repeated treatment regimen (intraperitoneal administration of 1.0 mg/kg methamphetamine once per day for five consecutive days) induced hyperlocomotion with a plateau level on test day 4. The initial behavioral response (within 5 min after injection) to the drug appeared to include context-dependent sensitization. Mice after the initial repeated treatment regimen showed behavioral sensitization to the same dose of methamphetamine 5 days after the final injection (test day 11). On test day 11, the first 150 min, but not the nocturnal behavior (during the dark hours), were significantly enhanced after the drug challenge. A marked reduction of the content of L-dihydroxyphenylalanine and the ratio of 3,4-dihydroxyphenylacetic acid to dopamine was observed in the striatum+accumbens of mice after single and repeated administration of methamphetamine. As for serotonin metabolism, the ratio of 5-hydroxyindolacetic acid to serotonin significantly increased in mice after single administration of methamphetamine, although it decreased in mice after repeated administration of methamphetamine. Norepinephrine metabolism (the ratio of 3-methoxy-4-hydroxyphenylglycol to norepinephrine) was not affected in the striatum+accumbens or thalamus+hypothalamus of the mice after repeated or single methamphetamine treatment. These results suggest that dopaminergic and serotonergic neuronal activities were altered during the development of behavioral sensitization. The ratio of 3-methoxytyramine to dopamine was not affected, suggesting that the methamphetamine treatment selectively inhibited the monoamine oxidase pathway for dopamine inactivation.

L3, a novel murine LIM-homeodomain transcription factor expressed in the ventral telencephalon and the mesenchyme surrounding the oral cavity

By reverse-transcription polymerase chain reaction method, we isolated a novel murine LIM-homeodomain gene, L3. In situ hybridization analyses revealed that L3 mRNA was localized to the ventral telencephalon and the mesenchyme surrounding the oral cavity of mouse embryo, suggesting that L3 may be involved in the region-specific differentiation of these areas.

Neurochemical Consequences of Dysphoric State During Amphetamine Withdrawal in Animal Models: A Review

Chronic abuse of amphetamines, such as d-amphetamine (AMPH) and d-methamphetamine, results in psychological dependence, a condition in which the drug produces a feeling of satisfaction and a drive that requires periodic or continuous administration of the drug to produce overwhelming pleasure or to avoid discomfort such as dysphoria. The dysphoric state of AMPH withdrawal has been recognized as depressive syndromes, such as anhedonia, depression, anxiety, and social inhibition, in early drug abstinence. Medication for treatment of the dysphoric state is important for AMPH abusers to avoid impulsive self-injurious behavior or acts that are committed with unconscious or uncontrolled suicidal ideation. However, successful treatments for AMPH withdrawal remain elusive, since the exact molecular basis of the expression of dysphoria has not been fully elucidated. This review focuses on the molecular aspects of AMPH withdrawal as indexed by neurochemical parameters under a variety of injection regimens (for example, levels of brain monoamines and their metabolites, and γ-aminobutyric acid, expression of genes and proteins involved in neuronal activity, and monoamine metabolism and availability) in rodent models which exhibit significant phenotypic features relevant to the syndromes of AMPH withdrawal in humans.

Oncostatin M Inhibits Proliferation of Rat Oval Cells, OC15-5, Inducing Differentiation into Hepatocytes

Oval cells of the liver participate in liver regeneration when hepatocytes are prevented from proliferating in response to liver damage. To clarify the role of oncostatin M (OSM) in the liver regeneration involving oval cells, we examined the expression of OSM and OSM-specific receptor (OSM-R) in the liver undergoing regeneration in the 2-acetylaminofluorene/partial hepatectomy model. Expression levels of OSM-R changed in correlation to the number of oval cells, and its expression was exclusively observed in oval cells. On the other hand, OSM was expressed in both oval cells and Kupffer cells. To examine the effect of OSM on the growth and differentiation of oval cells, rat oval cells (OC15-5) were incubated in conditioned medium of 293T cells expressing rat OSM cDNA. This resulted in suppression of growth, changes in morphology (microvilli and large cytoplasm with developed organelles), and expression of hepatocyte markers (albumin, tyrosine amino transferase, and tryptophan oxygenase). The effects of the conditioned medium with rat OSM were abrogated by introducing a small interfering RNA specifically targeting rat OSM-R into OC15-5 cells. These results indicate that OSM is a key mediator for inducing differentiation of OC15-5 cells into hepatocytes and suggest that the OSM/OSM-R system is pivotal in the differentiation of oval cells into hepatocytes, thereby promoting liver regeneration.

Inhibition of methamphetamine-induced hyperlocomotion in mice by clorgyline, a monoamine oxidase-a inhibitor, through alteration of the 5-hydroxytriptamine turnover in the striatum

The psychomotor stimulant methamphetamine (METH) has been shown to cause specific behaviors such as hyperlocomotion in rodents. Pretreatment of repeated s.c. administration of clorgyline (1 mg/kg, once per day for 5 consecutive days), a monoamine oxidase (MAO)-A inhibitor, blocked hyperlocomotion induced by a single i.p. administration of METH (1 mg/kg) in male ICR mice, without any effect on spontaneous locomotion. The blockade was also observed when mice were pretreated with a single administration of clorgyline (1 mg/kg, s.c.), without potentiating hyperlocomotion and rearing induced by a single challenge of METH at the range of 0.5-2 mg/kg (i.p.). In contrast, single or repeated pretreatment of selegiline (0.3 mg/kg, s.c.), a MAO-B inhibitor, had no effect on METH-induced hyperlocomotion. Clorgyline pretreatment, both single and repeated, altered the effects of single METH challenges on apparent 5-hydroxytryptamine (serotonin) turnover in the region of the striatum and accumbens. These results suggest that clorgyline tends to oppose METH-induced hyperlocomotion through alteration of the serotonergic system in the region of the striatum and accumbens.

Expression of diamine oxidase (histaminase) in guinea-pig tissues.

The expression of mRNA for diamine oxidase (histaminase) and the enzyme activity in guinea-pig tissues were investigated. Reverse transcription-polymerase chain reaction analysis revealed that the message corresponding to the long form present in humans and rats was expressed abundantly in the small intestine and liver. Small but detectable amounts of diamine oxidase mRNA were observed in the kidney, stomach, cerebellum, thalamus+hypothalamus, and cerebral cortex. Northern blot analysis showed that the message (2.8 kb in size) was observed abundantly in the liver and small intestine and was detectable in the kidney and stomach but not in the brain or lung. In situ hybridization showed that diamine oxidase mRNA was localized throughout the liver and epithelial cells of the small intestine. Diamine oxidase activity was detected at various levels in different tissues of the guinea-pig at the following relative abundance: liver>small intestine>lung, kidney>stomach. Histamine dose-dependently induced the contraction of sections of the guinea-pig small intestine, and the pretreatment of the tissue section with aminoguanidine (100 microM), a diamine oxidase inhibitor, but not with S-[4-(N,N-dimethylamino)butyl]isothiourea (100 microM), an inhibitor of histamine N-methyltransferase, shifted the dose-response curve of histamine-induced contraction to lower concentrations. These results suggest that diamine oxidase has a crucial role in the degradation of histamine in the guinea-pig small intestine and probably in the liver.

Differential expression of LIM-homeodomain genes in the embryonic murine brain☆

Homeobox-containing genes are associated with the control of various stages in embryogenesis. LIM-homeodomain genes have been implicated in the control of differentiation of specific cell types in both neuronal and non-neuronal tissues, yet there have been few studies comparing the expression domains of these genes in the developing brain of a single species. In the present study, we isolated murine LIM-homeodomain genes (LH-2, lim-1, and L3) by reverse transcription-polymerase chain reaction (RT-PCR) method and investigated their expression domains in the embryonic brain by in situ hybridization analysis. These mRNAs showed mutually exclusive expression patterns suggesting that these factors may be involved in region-specific differentiation in the developing brain.

Blockade of brain histamine metabolism alters methamphetamine-induced expression pattern of stereotypy in mice via histamine H1 receptors.

The administration of methamphetamine (METH, 10 mg/kg, i.p.) to male ICR mice induced stereotyped behavior consisting of nail and/or wood chip biting (86.0%), continuous sniffing (12.0%), head bobbing (1.1%), and circling (1.0%) during the observation period of 1 h. Pretreatment of the mice with metoprine (2, 10, and 20 mg/kg, i.p.), a selective inhibitor of histamine N-methyltransferase (HMT), which metabolizes histamine in the brain, significantly increased and decreased METH-induced continuous sniffing (20.5, 51.3, and 80.3%) and nail and/or wood chip biting (77.4, 45.3, and 14.2%), respectively, in a dose-dependent manner. The hypothalamic contents of histamine and its metabolite N(tau)-methylhistamine were significantly increased and decreased by metoprine (10 mg/kg, i.p.), respectively. The metoprine action on METH-induced behavior was completely abolished by pyrilamine (10 and 20 mg/kg) and ketotifen (10 mg/kg), selective, centrally acting histamine H(1) receptor antagonists, but not by fexofenadine (20 mg/kg), zolantidine (10 mg/kg) and thioperamide (10 mg/kg), a peripherally acting histamine H(1) receptor antagonist and a selective, brain-penetrating antagonist for histamine H(2) and H(3) receptors, respectively. The metoprine action was mimicked by SKF 91488 (100 microg/animal, i.c.v.), another HMT inhibitor, and the action of SKF 91488 was also blocked by pyrilamine. The frequency of the expression of METH-induced total stereotypic patterns was unchanged after metoprine pretreatment. Mice pretreated with metoprine displayed no anxiety-like behavior in the elevated plus maze test. These results suggest that brain histamine, increased by agents such as metoprine and SKF 91488, binds to histamine H(1) receptors in the brain, resulting in the modulation of dopaminergic transmission associated with stereotyped behavioral patterns induced by METH.

Lack of effect of anticonvulsant topiramate on methamphetamine-induced stereotypy and rewarding property in mice.

The effects of topiramate, a structurally novel anticonvulsant, on the methamphetamine (METH)-induced expression of stereotypy and conditioned place preference (CPP) in male ICR mice were investigated. After a single administration of METH (10 mg/kg, i.p.), mice showed stereotyped behaviors with a plateau level 25 min after drug challenge. Pretreatment with topiramate (1, 10, and 100 mg/kg, i.p.) 30 min prior to METH challenge had no effect on the expression frequency of stereotypy, compared with saline challenge. No differential effects of topiramate on METH-induced stereotyped behavior (that is, head-bobbing, circling, continuous sniffing, nail and/or wood-chip biting, and vigorous and compulsive grooming) were observed. In saline-challenged groups, the doses of topiramate examined did not induce any stereotyped behaviors. Although mice showed a significant CPP for METH (0.5 mg/kg, i.p.), pretreatment with subchronic topiramate did not affect the magnitude of CPP. Locomotor activity was not affected by the doses of topiramate tested. Conditioned rewarding or aversive effects of topiramate were not observed as indexed by the place preference procedure. These results suggested the lack of effect of topiramate on METH-induced stereotypy and rewarding property in mice.