Naoki Ito

FERULIC ACID INDUCES NEURAL PROGENITOR CELL PROLIFERATION IN VITRO AND IN VIVO

Ferulic acid (4-hydroxy-3-methoxycinnamic acid; FA) is a plant constituent and is contained in several medicinal plants for clinical use. In this paper, we investigated the effects of FA on the proliferation of neural stem/progenitor cells (NSC/NPCs) in vitro and in vivo. FA significantly increased the proliferation of NSC/NPCs cultured from the telencephalon of embryonic day-14 rats, and increased the number and size of secondary formed neurospheres. An in vitro differentiation assay showed that FA did not affect the percentage of either neuron-specific class III beta-tubulin (Tuj-1)-positive cells or glial fibrillary acidic protein (GFAP)-positive cells in the total cell population. Oral administration of FA increased the number of newly generated cells in the dentate gyrus (DG) of the hippocampus of corticosterone (CORT)-treated mice, indicating that FA enhances the proliferation of adult NSC/NPCs in vivo. We also found that oral administration of FA increased cAMP response element binding protein (CREB) phosphorylation and brain-derived neurotrophic factor (BDNF) mRNA level in the hippocampus of CORT-treated mice, and ameliorated the stress-induced depression-like behavior of mice. These novel pharmacological effects of FA may be useful for the treatment of mood disorders such as depression.

I.c.v. administration of orexin-A induces an antidepressive-like effect through hippocampal cell proliferation.

A decrease in orexin-A (OX-A) levels has been reported to be associated with depression. It is also well known that stress and depression can disrupt neurogenesis in the dentate gyrus of the hippocampus; however, it is unclear how OX-A is involved in depression and/or neurogenesis. In the present study, we investigated the effect of i.c.v. administration of OX-A on the forced swimming test (FST), an accepted behavioral screen of antidepressant-like activity, and on the cell proliferation with bromodeoxyuridine (BrdU) in the dentate gyrus at 4 days after i.c.v. administration of OX-A. OX-A administration (140 pmol/mouse) led to a significant reduction in animal immobility in the FST, without affecting spontaneous locomotor activities or serum corticosterone levels. In addition, the number of BrdU-positive cells in the dentate gyrus was significantly increased in OX-A-treated mice in vivo; however, OX-A did not affect the percentage of doublecortin-positive cells in the dentate gyrus. The proliferation of neural progenitor cells derived from rat fetal brain was not affected by OX-A treatment in vitro, and the orexin receptor 1 (OXR1) protein was not expressed in these cells. Treatment with the OXR1 antagonist SB-334867 (30 mg/kg, i.p.) blocked both the OX-A-induced decrease in the immobility of FST and increase in BrdU-positive. Moreover, the OX-A-induced increase in neuropeptide Y (NPY)-positive cells in the hilus of the dentate gyrus was blocked by SB-334867. These results suggest that OX-A induces an antidepressive-like effect, at least in part, via the enhancement of cell proliferation in the dentate gyrus. These effects of OX-A also may be partly relevant to the regulation of the NPY system in the hilus of the dentate gyrus.

Kososan, a Kampo medicine, prevents a social avoidance behavior and attenuates neuroinflammation in socially defeated mice

BackgroundKososan, a Kampo (traditional Japanese herbal) medicine, has been used for the therapy of depressive mood in humans. However, evidence for the antidepressant efficacy of kososan and potential mechanisms are lacking. Recently, it has been recognized that stress triggers neuroinflammation and suppresses adult neurogenesis, leading to depression and anxiety. Here, we examined whether kososan extract affected social behavior in mice exposed to chronic social defeat stress (CSDS), an animal model of prolonged psychosocial stress, and neuroinflammation induced by CSDS.MethodsIn the CSDS paradigm, C57BL/6J mice were exposed to 10xa0min of social defeat stress from an aggressive CD-1 mouse for 10 consecutive days (days 1–10). Kososan extract (1.0xa0g/kg) was administered orally once daily for 12xa0days (days 1–12). On day 11, the social avoidance test was performed to examine depressive- and anxious-like behaviors. To characterize the impacts of kososan on neuroinflammation and adult neurogenesis, immunochemical analyses and ex vivo microglial stimulation assay with lipopolysaccharide (LPS) were performed on days 13–15.ResultsOral administration of kososan extract alleviated social avoidance, depression- and anxiety-like behaviors, caused by CSDS exposure. CSDS exposure resulted in neuroinflammation, as indicated by the increased accumulation of microglia, the resident immune cells of the brain, and their activation in the hippocampus, which was reversed to normal levels by treatment with kososan extract. Additionally, in ex vivo studies, CSDS exposure potentiated the microglial pro-inflammatory response to a subsequent LPS challenge, an effect that was also blunted by kososan extract treatment. Indeed, the modulatory effect of kososan extract on neuroinflammation appears to be due to a hippocampal increase in an anti-inflammatory phenotype of microglia while sparing an increased pro-inflammatory phenotype of microglia caused by CSDS. Moreover, reduced adult hippocampal neurogenesis in defeated mice was recovered by kososan extract treatment.ConclusionsOur findings suggest that kososan extract prevents a social avoidant behavior in socially defeated mice that is partially mediated by the downregulation of hippocampal neuroinflammation, presumably by the relative increased anti-inflammatory microglia and regulation of adult hippocampal neurogenesis. Our present study also provides novel evidence for the beneficial effects of kososan on depression/anxiety and the possible underlying mechanisms.

Kososan, but not milnacipran, elicits antidepressant‐like effects in a novel psychological stress‐induced mouse model of depression

Mild or moderate depressive symptoms are often resistant to treatment with currently available antidepressants. We constructed a novel animal model of depression induced by the exposure of mice to psychological stress and evaluated the antidepressant efficacy of kososan and milnacipran.

Antidepressive‐like effect of a Kampo (traditional Japanese) medicine, kososan (Xiang Su San) in a stress‐induced depression‐like mouse model: Proteomic analysis of hypothalamus

A Kampo medicine, kososan (KS), has been used clinically for the treatment of certain depression‐like symptoms. Our previous studies using the stress‐induced depression‐like model mice, showed that oral KS treatment leads to an antidepressive‐like effect via the normalization of dysfunction of hypothalamic‐pituitary‐adrenal axis. In the present study, proteomic analysis was used to identify brain hypothalamus proteins that are affected by KS treatment.

Antidepressive‐like effect of volatile components of kososan in a mouse model of stress‐induced depression

Kososan (Xiang‐Su‐San in Chinese), a kampo (traditional Japanese herbal) medicine, contains large amounts of unique volatile components (termed KSv). This study evaluated the antidepressive‐like effects of KSv alone or in combination with the water‐soluble extracts of kososan (termed KSw), neither of which is fully known, in a mouse model of stress‐induced depression.