Ginseng Total Saponins Reverse Corticosterone-Induced Changes in Depression-Like Behavior and Hippocampal Plasticity-Related Proteins by Interfering with GSK-3 β -CREB Signaling Pathway

20(S)-Protopanaxadiol Exerts Antidepressive Effects in Chronic Corticosterone-Induced Rodent Animal Models as an Activator of Brain-Type Creatine Kinase

20(S)-Protopanaxadiol (PPD) is one of the bioactive ingredients in ginseng and possesses neuroprotective properties. Brain-type creatine kinase (CK-BB) is an enzyme involved in brain energy homeostasis via the phosphocreatine-creatine kinase system. We previously identified PPD as directly bound to CK-BB and activated its activity in vitro. In this study, we explored the antidepressive effects of PPD that target CK-BB. First, we conducted time course studies on brain CK-BB, behaviors, and hippocampal structural plasticity responses to corticosterone (CORT) administration. Five weeks of CORT injection reduced CK-BB activity and protein levels and induced depression-like behaviors and hippocampal structural plasticity impairment. Next, a CK inhibitor and an adeno-associated virus-targeting CKB were used to diminish CK-BB activity or its expression in the brain. The loss of CK-BB in the brain led to depressive behaviors and morphological damage to spines in the hippocampus. Then, a polyclonal antibody against PPD was used to determine the distribution of PPD in the brain tissues. PPD was detected in the hippocampus and cortex and observed in astrocytes, neurons, and vascular endotheliocytes. Finally, different PPD doses were used in the chronic CORT-induced depression model. Treatment with a high dose of PPD significantly increased the activity and expression of CK-BB after long-term CORT injection. In addition, PPD alleviated the damage to depressive-like behaviors and structural plasticity induced by repeated CORT injection. Overall, our study revealed the critical role of CK-BB in mediating structural plasticity in CORT-induced depression and identified CK-BB as a therapeutic target for PPD, allowing us to treat stress-related mood disorders.

Total Ginsenoside Extract from Panax ginseng Enhances Neural Stem Cell Proliferation and Neuronal Differentiation by Inactivating GSK-3 β

OBJECTIVE

To study the effects of total ginsenosides (TG) extract from Panax ginseng on neural stem cell (NSC) proliferation and differentiation and their underlying mechanisms.

METHODS

The migration of NSCs after treatment with various concentrations of TG extract (50, 100, or 200 µ g/mL) were monitored. The proliferation of NSCs was examined by a combination of cell counting kit-8 and neurosphere assays. NSC differentiation mediated by TG extract was evaluated by Western blotting and immunofluorescence staining to monitor the expression of nestin and microtubule associated protein 2 (MAP2). The GSK-3 β/β-catenin pathway in TG-treated NSCs was examined by Western blot assay. The NSCs with constitutively active GSK-3 β mutant were made by adenovirus-mediated gene transfection, then the proliferation and differentiation of NSCs mediated by TG were further verified.

RESULTS

TG treatment significantly enhanced NSC migration (P<0.01 or P<0.05) and increased the proliferation of NSCs (P<0.01 or P<0.05). TG mediation also significantly upregulated MAP2 expression but downregulated nestin expression (P<0.01 or P<0.05). TG extract also significantly induced GSK-3 β phosphorylation at Ser9, leading to GSK-3 β inactivation and, consequently, the activation of the GSK-3 β/β-catenin pathway (P<0.01 or P<0.05). In addition, constitutive activation of GSK-3 β in NSCs by the transfection of GSK-3 β S9A mutant was found to significantly suppress TG-mediated NSC proliferation and differentiation (P<0.01 or P<0.05).

CONCLUSION

TG promoted NSC proliferation and neuronal differentiation by inactivating GSK-3β.

Mechanisms of Panax ginseng action as an antidepressant

OBJECTIVES

Panax ginseng, a well-known traditional Chinese medicine with multiple pharmacological activities, plays a crucial role in modulating mood disorders. Several recent studies have identified an underlying role of Panax ginseng in the prevention and treatment of depression. However, the cellular and molecular mechanisms remain unclear.

MATERIALS AND METHODS

In this review, we summarized the recent progress of antidepressant effects and underlying mechanisms of Panax ginseng and its representative herbal formulae.

RESULTS

The molecular and cellular mechanisms of Panax ginseng and its herbal formulae include modulating monoamine neurotransmitter system, upregulating the expression of neurotrophic factors, regulating the function of HPA axis, and anti-inflammatory action.

CONCLUSIONS

Therefore, this review may provide theoretical bases and clinical applications for the treatment of depression by Panax ginseng and its representative herbal formulae.

Excessive corticosterone induces excitotoxicity of hippocampal neurons and sensitivity of potassium channels via insulin-signaling pathway

Corticosterone (CORT) is a kind of corticosteroid produced by cortex of adrenal glands. Hypothalamic-pituitary-adrenal (HPA) axis hyperfunction leads to excessive CORT, which is associated with depression. Few studies have investigated the role of CORT in voltage-gated ion channels and its upstream signaling pathway in central nervous system. In this study, we investigated the mechanism of excessive CORT resulting in brain impairment on voltage-gated ion channels, and its upstream signaling effectors in hippocampal CA1 neurons. The action potential (AP) and voltage-gated potassium currents were determined by using whole-cell patch-clamp. Insulin and CORT improved the neuronal excitability. Independent effects existed in transient potassium channel (I_A) and delay rectifier potassium channel (I_K). The inhibition of potassium currents, I_A in our experiment, could increase neuronal excitability. CORT led to the excitotoxicity of hippocampal neurons via phosphatidylinositol 3 kinase (PI3K)-mediated insulin-signaling pathway. Therefore, the stimulation of excessive CORT induces excitotoxicity of hippocampal neurons and sensitivity of potassium channels via PI3K-mediated insulin-signaling pathway, which indicates one possible way of depression treatment.

Botanicals as Modulators of Neuroplasticity: Focus on BDNF

The involvement of brain-derived neurotrophic factor (BDNF) in different central nervous system (CNS) diseases suggests that this neurotrophin may represent an interesting and reliable therapeutic target. Accordingly, the search for new compounds, also from natural sources, able to modulate BDNF has been increasingly explored. The present review considers the literature on the effects of botanicals on BDNF. Botanicals considered were Bacopa monnieri (L.) Pennell, Coffea arabica L., Crocus sativus L., Eleutherococcus senticosus Maxim., Camellia sinensis (L.) Kuntze (green tea), Ginkgo biloba L., Hypericum perforatum L., Olea europaea L. (olive oil), Panax ginseng C.A. Meyer, Rhodiola rosea L., Salvia miltiorrhiza Bunge, Vitis vinifera L., Withania somnifera (L.) Dunal, and Perilla frutescens (L.) Britton. The effect of the active principles responsible for the efficacy of the extracts is reviewed and discussed as well. The high number of articles published (more than one hundred manuscripts for 14 botanicals) supports the growing interest in the use of natural products as BDNF modulators. The studies reported strengthen the hypothesis that botanicals may be considered useful modulators of BDNF in CNS diseases, without high side effects. Further clinical studies are mandatory to confirm botanicals as preventive agents or as useful adjuvant to the pharmacological treatment.

The potential benefit of combined versus monotherapy of coenzyme Q10 and fluoxetine on depressive-like behaviors and intermediates coupled to Gsk-3β in rats

As a part of the serotoninergic dysfunction implicated in neurobiology of depression, evidence has focused on serotonin (5-HT) receptors downstream signaling intermediates including glycogen synthase kinase-3β (GSK-3β), cAMP response element binding protein (CREB) and brain derived neurotrophic factor (BDNF). Our team previously reported that coenzyme Q10 (CoQ10) exerted antidepressant-like effect in rats exposed to chronic unpredictable mid stress (CUMS) via elevating serotonin levels. However, the effect of CoQ10 has not been elucidated in downstream signaling molecules mediating 5HT receptors' effect involved in depressive disorder hitherto. In the present study, we focused on 5-HT_1A and 5-HT_2A receptors (activation of 5-HT_1A receptor and inhibition of 5-HT_2A receptors reduce depressive like-behaviors). We investigated the role of these 5-HT receptors and their linked GSK-3β signaling intermediates as an underlying mechanism of CoQ10 as monotherapy or combined with fluoxetine, a selective serotonin reuptake inhibitor, to alleviate depressive-like phenotype. Effects of CoQ10 (100mg/kg/day) or/and fluoxetine (10mg/kg/day) were determined on 5-HT_1A, 5-HT_2A receptors mRNA expression, GSK-3β and phosphorylated (p)GSK-3β, CREB, pCREB and BDNF protein expression in rats subjected to CUMS for 6weeks. CUMS rats exhibited obvious depressive-like behaviors (anhedonia-like behavior, negative alterations in social interaction, open field and forced swimming tests) with increased corticosterone and adrenal glands weight, decreased hippocampal levels of pGSK-3β, pCREB and BDNF protein expressions. Additionally, they exhibited decreased hippocampal 5-HT_1A and increased 5-HT_2A receptor mRNA expression. CoQ10 or fluoxetine significantly attenuated the behavioral and neurochemical alterations in stressed rats with more significance with combined treatment. These findings imply that CoQ10 or/and fluoxetine attenuated CUMS-induced depressive-like behavior partly through modulating dysfunctional regulation of post-serotonergic receptor signaling pathway focusing on GSK-3β, CREB and BDNF.

Preventive Effects of Ginseng Total Saponins on Chronic Corticosterone-Induced Impairment in Astrocyte Structural Plasticity and Hippocampal Atrophy

To further explore the underlying antidepressant mechanism of ginseng total saponins (GTS), this study observed the effects on hippocampal astrocyte structural plasticity and hippocampal volume in the corticosterone-induced mouse depression model. Corticosterone (20 mg/kg/day) was administered subcutaneously for 5 weeks, and GTS (12.5, 25, and 50 mg/kg/day; namely GTSL, GTSM, and GTSH) or fluoxetine (10 mg/kg/day) were given intragastrically during the last 3 weeks. On day 33 and day 34, depression-like behavior was observed via a forced swimming test and a tail suspension test, respectively. At 6 h after the last dose of corticosterone (day 35), all mice were sacrificed followed by serum corticosterone assays, stereological analysis of hippocampal glial fibrillary acidic protein-positive (GFAP⁺ ) astroctyes and hippocampal volume, and hippocampal glycogen tests. Results showed that all doses of GTS ameliorated depression-like behavior and the decrease in hippocampal glycogen without normalizing hypercortisolism. Moreover, GTSH and GTSM reversed the corticosterone-induced reduction in the total number of hippocampal GFAP⁺ astrocytes and hippocampal volume. Additionally, GTSH alleviated the diminished protrusion length and somal volume of GFAP⁺ astrocytes induced by corticosterone. These findings imply that the effects of GTS on corticosterone-induced depression-like behavior may be mediated partly through the protection to hippocampal astrocyte structural plasticity. Copyright © 2017 John Wiley & Sons, Ltd.

Individual Differences in Behavioural Despair Predict Brain GSK-3beta Expression in Mice: The Power of a Modified Swim Test

While deficient brain plasticity is a well-established pathophysiologic feature of depression, little is known about disorder-associated enhanced cognitive processing. Here, we studied a novel mouse paradigm that potentially models augmented learning of adverse memories during development of a depressive-like state. We used a modification of the classic two-day protocol of a mouse Porsolt test with an additional session occurring on Day 5 following the initial exposure. Unexpectedly, floating behaviour and brain glycogen synthase kinase-3 beta (GSK-3beta) mRNA levels, a factor of synaptic plasticity as well as a marker of distress and depression, were increased during the additional swimming session that was prevented by imipramine. Observed increases of GSK-3beta mRNA in prefrontal cortex during delayed testing session correlated with individual parameters of behavioural despair that was not found in the classic Porsolt test. Repeated swim exposure was accompanied by a lower pGSK-3beta/GSK-3beta ratio. A replacement of the second or the final swim sessions with exposure to the context of testing resulted in increased GSK-3beta mRNA level similar to the effects of swimming, while exclusion of the second testing prevented these changes. Together, our findings implicate the activation of brain GSK-3beta expression in enhanced contextual conditioning of adverse memories, which is associated with an individual susceptibility to a depressive syndrome.

H2S protects PC12 cells against toxicity of corticosterone by modulation of BDNF-TrkB pathway

Corticosterone, one of the glucocorticoids, is toxic to neurons and plays an important role in depressive-like behavior and depression. We previously showed that hydrogen sulfide (H2S), a novel physiological mediator, plays an inhibitory role in depression. However, the mechanism underlying H2S-triggered antidepressant-like role is not clearly known. Brain-derived neurotrophic factor (BDNF), a neurotrophic factor, plays a neuroprotective role that is mediated by its high-affinity tropomysin-related kinase B (TrkB) receptor. In this study, to investigate the underlying mechanism of H2S-induced antidepressant-like role, we explored whether H2S could protect neurons against corticosterone-mediated cyctotoxicity and whether this protective role of H2S was involved in the regulation of BDNF-TrkB pathway. Our data demonstrated that sodium hydrosulfide (NaHS), the donor of H2S, could prevent corticosterone-induced cytotoxicity, apoptosis, accumulation of intracellular reactive oxygen species (ROS) and loss of mitochondrial membrane potential (MMP) in PC12 cells. NaHS not only induced the up-regulation of BDNF but also prevented the down-regulation of BDNF by corticosterone. It was also found that blocking BDNF-TrkB pathway by K252a, an inhibitor of TrkB, abolished the protection of H2S against corticosterone-induced cytotoxicity, apoptosis, accumulation of ROS, and loss of MMP. These results suggest that H2S protects against the neurotoxicity of corticosterone by modulation of the BDNF-TrkB pathway.

Neuroprotective effect of water extract of Panax ginseng on corticosterone-induced apoptosis in PC12 cells and its underlying molecule mechanisms

ETHNOPHARMACOLOGICAL RELEVANCE

The root of Panax ginseng C.A. Meyer (Family Araliaceae) is an important medicinal plant which has been employed as a panacea for more than 2,000 years in China. It has the actions of invigorating primordial qi, recovering pulse and desertion, engendering liquid, and calming spirit. The water extract of Panax ginseng (WEG) has been used to treat kinds of central nervous system disorders, such as depression, insomnia, Alzheimer׳s disease and Parkinson׳s disease. Our previous work has demonstrated that WEG possessed antidepressant-like activities in both acute and chronic stress models of depression. Nevertheless, there are no studies on the cytoprotection and potential mechanisms of WEG on corticosterone-induced apoptosis. The present study focuses on cytoprotection against corticosterone-induced neurotoxicity in PC12 cells and its underlying molecule mechanisms of the antidepressant-like effect of WEG.

MATERIALS AND METHODS

The PC12 cells were treated with 250 μmol/L corticosterone in the absence or presence of WEG for 24h, then 3-(4,5-dimethy thiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, lactate dehydrogenase (LDH) detection, Hoechst33342 staining and TUNEL staining were investigated to confirm the neuroprotection of WEG. Then, mitochondrial permeability transition pore (mPTP), mitochondrial membrane potential (MMP), intracellular Ca(2+) ([Ca(2+)]i), reactive oxygen species (ROS) concentration, and the expression level of glucocorticoid receptor (GR), heat shock protein 90 (Hsp90), histone deactylase 6 (HDAC6), glucose-regulated protein 78 (GRP78), growth arrest and DNA damage inducible protein 153 (GADD153), X-box DNA-binding protein-1 (XBP-1), caspase-12, cytochrome C, inhibitor of caspase-activated deoxyribonuclease (ICAD), caspase-3 and caspase-9 were assessed by Western Blot analysis to understand the molecule mechanisms of neuroprotection of WEG.

RESULTS

WEG partly reversed corticosterone-induced damage in PC12 cells, which increased cell viability, decreased LDH release, and attenuated corticosterone-induced apoptosis as compared with the corticosterone-treated group. Mechanistically, compared with the corticosterone-treated group, WEG strongly attenuated [Ca(2+)]i overload and ROS level, and restored mitochondrial function, including mPTP and MMP. Furthermore, WEG strongly up-regulated the expression of GR and HDAC6, and down-regulated the expression of Hsp90, cytochrome C, ICAD, caspase-3, caspase-9 as well as endoplasmic reticulum (ER) stress-related proteins, such as GADD153, GRP78, XBP-1, and caspase-12.

CONCLUSION

WEG possessed neuroprotection against corticosterone-induced damage in PC12 cells, and the underlying molecule mechanisms was depended on the intervening of HDAC6 and HSP90 of the GR-related function proteins, and subsequent restoration of ER and mitochondria functions.