Corticosterone-induced Neurotoxicity Research Articles

Structural elucidation of a non-starch polysaccharides from Lilii Bulbus and its protective effects against corticosterone-induced neurotoxicity in PC12 cells.

Lilii Bulbus is a folk medicine for both culinary and medicinal purpose. In traditional medicine theory, Lilii Bulbus is usually used as an complementary therapy for nourishing the heart and lung, clearing heat in the treatment of mental instability and depression. In this study, NLPS-1a (Mw = 2610 Da, DP = 16), a water-soluble non-starch Lilii Bulbus polysaccharides, was isolated and purified. Structural analysis showed that NLPS-1a mainly contained Man and Glc with a molar ratio of 11.137 and 9.427. The glycosidic linkages of NLPS-1a were 1,3-Manp (59.93%), 1,2-Glcp (37.93%), T-Glcp (1.21%) and T-Manp (0.93%), indicating the highly-linear structures. In addition, NLPS-1a could significantly repair the injury of PC12 cells induced by corticosterone (CORT), reduce Lactate dehydrogenase (LDH) leakage and decrease the cell apoptosis in a dose-dependent manner. Above all, the results indicated that NLPS-1a had protective effects against CORT-induced neurotoxicity in PC12 cells, and might be a natural antidepressant, which enriched the study of the metabolic mechanism between herbal polysaccharides and antidepressant.

Protective effects of camellia oil and gac oil against corticosterone-induced neurotoxicity in Neuro-2a cells

Depression is characterized by the hyperaccumulation of glucocorticoids, such as corticosterone (CORT), which results in oxidative stress, inflammatory responses, and nerve damage. Edible camellia oil (Camellia oleifera Abel.) and gac oil (Momordica cochinchinensis Spreng) contain beneficial bioactive compounds, such as oleic acid, polyphenols, flavonoids, tocopherol, β-carotene, and lycopene, which have neuroprotective effects. However, the underlying mechanisms of camellia oil (CO) and gac oil (GO) in alleviating CORT-induced depressive-like effects are still unclear. Therefore, this study aimed to investigate the effects of CO and GO on CORT-induced damage in Neuro-2a cells. The results revealed that the upregulation of proapoptotic-associated proteins (Bax, cleaved caspase 9, cleaved caspase 3, cytochrome c), cyclooxygenase-2, interleukin-1β, reactive oxygen species, and malondialdehyde levels in CORT-stimulated Neuro-2a cells was significantly counteracted by CO and GO treatment, which enhanced the production of antiapoptotic Bcl-2, the antioxidative enzymes superoxide dismutase, catalase, glutathione peroxidase, glutathione, heat shock proteins (HSP32, HSP 60, HSP 90), and glucocorticoid receptor (GR)/brain-derived neurotrophic factor (BDNF)/tropomyosin receptor kinase B (TrkB)/extracellular signal-regulated kinase (ERK)/cAMP response element-binding protein (CREB). These findings suggest that increasing daily CO and GO consumption may suppress CORT-induced depression.

Hydrangea macrophylla and Thunberginol C Attenuate Stress-Induced Anxiety in Mice.

Stress is an important neurological input for successful life. However, chronic stress and stress hormones could be a cause of various neurological disorders including anxiety disorders. Therefore, there have been many efforts to find effective materials for curing stress-induced neurological disorders. In this study, we examined the effect of Hydrangea macrophylla (HM) on corticosterone-induced neurotoxicity, stress-induced anxiety in mice and suggested a possible active ingredient of HM. HM protected cortical neurons against neurotoxicity of corticosterone (CORT), a stress hormone. HM also blocked CORT-induced hippocampal synaptic deficit via regulating Akt signaling. Oral administration of HM improved chronic restraint stress-induced anxiety in Elevated Plus maze test along with reduction of plasma corticosterone and TNF-α levels. Moreover, HM reduced stress-induced neuroinflammation and oxidative stress. Thunberginol C, an active ingredient of HM, also prevented CORT-induced neuronal cell death and restraint stress-induced anxiety. Moreover, thunberginol C reduced plasma TNF-α level and neuroinflammation and oxidative stress. Collectively, HM could be a good candidate for preventing stress-induced neurological disorders and thunberginol C may be an active ingredient of HM for this purpose.

Sinisan Protects Primary Hippocampal Neurons Against Corticosterone by Inhibiting Autophagy via the PI3K/Akt/mTOR Pathway.

Objective: Corticosterone causes significant neurotoxicity in primary hippocampal neurons which is associated with depression. Dysfunctional autophagy is implicated in cognitive impairment and depressive-like behavior. The traditional Chinese medicine Sinisan (SNS) is highly effective in clinical treatment of depression. However, the molecular mechanisms underlying therapeutic effects of SNS are unknown.Purpose: The aim of this study was to elucidate the protective effect of SNS and the underlying mechanisms against corticosterone-induced neuronal damage.Study Design: The effects of serum derived from rats containing SNS (or untreated controls) on the expression of autophagy-related molecules in primary rat hippocampal neurons exposed to different concentrations of corticosterone for different intervals were explored.Methods: CCK-8 assay, LDH assay were used to analyze cell viability and LDH activity. Western blot, qRT-PCR, and immunofluorescence assays were used to determine protein and mRNA expression levels of molecules such as LC3, p62, Beclin1, ULK1, PI3K, p-PI3K, Akt p-Akt, mTOR, p-mTOR, p70S6, p-p70S6, 4ebp1 and p-4ebp1.Results: Corticosterone induced a dose- and time-dependent reduction in cellular viability. Moreover, corticosterone (100–400 μM) treatment for 24 h increased LC3-II/LC3-I protein ratio, increased Beclin1 and ULK1 protein expression levels, and decreased p62, PI3K, p-PI3K, p-Akt, p-mTOR, p-p70S6, and p-4ebp1 protein expression levels. Notably, SNS-containing serum reversed corticosterone-induced reduction of neuronal viability, and increased p62, PI3K, p-Akt, p-mTOR, p-p70S6, and p-4ebp1 protein and mRNA expression levels. In addition, SNS-containing serum decreased LC3-II/LC3-I protein ratio, and downregulated Beclin1, and ULK1 protein and mRNA expression in primary hippocampal neurons.Conclusion: SNS protects primary hippocampal neurons against corticosterone-induced neurotoxicity by preventing excessive autophagy through activation of PI3K/AKT/mTOR pathway.

Protective Effects of p-Coumaric Acid Isolated from Vaccinium bracteatum Thunb. Leaf Extract on Corticosterone-Induced Neurotoxicity in SH-SY5Y Cells and Primary Rat Cortical Neurons

Corticosterone (CORT)-induced oxidative stress and neurotoxicity can cause neuronal dysfunction and mental disorders. In the present study, we investigated the effects and mechanism of the HP-20 resin fraction of the water extract of Vaccinium bracteatum leaves (NET-D1602) and its bioactive compound p-coumaric acid on neuronal cell damage in SH-SY5Y cells and primary culture of rat cortical cells. NET-D1602 and p-coumaric acid significantly improved cell viability in CORT-induced neurotoxicity in SH-SY5Y cells and primary cultures of rat cortical cells, and increased the activities of antioxidant enzymes (superoxide dismutase and catalase) against CORT-induced neurotoxicity in SH-SY5Y cells. NET-D1602 and p-coumaric acid increased the phosphorylation levels of ERK1/2 and cAMP response element-binding protein (CREB) in cortical neurons. In addition, CREB phosphorylation by NET-D1602 and p-coumaric acid was dramatically reversed by PKA, c-Raf/ERK, PI3K, and mTOR inhibitors. Lastly, we demonstrated the neuroprotective effects of NET-D1602 (3 and 10 μg/mL) and p-coumaric acid (3 and 10 μM) via increased CREB phosphorylation in CORT-induced neurotoxicity mediated via the ERK1/2, Akt, and mTOR pathways. These results suggest that p-coumaric acid is a potential neuroprotective component of NET-D1602, with the ability to protect against CORT-induced neurotoxicity by regulating ERK1/2, Akt, and mTOR-mediated CREB phosphorylation.

Neuroprotective effects of macamide from maca (Lepidium meyenii Walp.) on corticosterone-induced hippocampal impairments through its anti-inflammatory, neurotrophic, and synaptic protection properties.

The present study aims to investigate the protective effects of N-(3-methoxybenzyl)-(9Z,12Z,15Z)-octadecatrienamide (M 18:3) on corticosterone-induced neurotoxicity. A neurotoxic model was established by subcutaneous injection of corticosterone (40 mg per kg bw) for 21 days. Depressive behaviors (the percentage of sucrose consumption, the immobility time in the forced swimming test, and the total distance in the open field test) were observed. The levels of the brain-derived neurotrophic factor, the contents of tumor necrosis factor-α and interleukin-6, and the numbers of positive cells of doublecortin and bromodeoxyuridine in the hippocampus were measured. The density of hippocampal neurons was calculated. The morphological changes of hippocampal neurons (the density of dendritic spines, the dendritic length, and the area and volume of dendritic cell bodies) were observed. The expression levels of synaptophysin, synapsin I, and postsynaptic density protein 95 were measured. Behavioral experiments showed that M 18:3 (5 and 25 mg per kg bw) could remarkably improve the depressive behaviors. The enzyme-linked immunosorbent assay showed that M 18:3 could considerably reduce hippocampal neuroinflammation and increase hippocampal neurotrophy. Nissl staining showed that M 18:3 could remarkably improve the corticosterone-induced decrease in the hippocampal neuron density. Immunofluorescence analysis showed that M 18:3 could considerably promote hippocampal neurogenesis. Golgi staining showed that M 18:3 could remarkably improve the corticosterone-induced changes in the hippocampal dendritic structure. Western blotting showed that M 18:3 could considerably increase the expression levels of synaptic-structure-related proteins in the hippocampus. In conclusion, the protective effects of M 18:3 may be attributed to the anti-inflammatory, neurotrophic, and synaptic protection properties.

Sedum takesimense Protects PC12 Cells against Corticosterone-Induced Neurotoxicity by Inhibiting Neural Apoptosis.

Neuronal cell death induced by chronic stress in the central nervous system is a cause of neurological dysfunction. We investigated the neuroprotective potential of a water extract of S. takesimense (WEST) against corticosterone-induced apoptosis in PC12 cells and the possible underlying mechanisms. Cells were pretreated with 50 µg/mL of WEST to evaluate its neuroprotective effect based on endoplasmic reticulum (ER) stress inhibition and mitochondrial function improvement. Pretreatment with WEST prevented corticosterone-induced injury in PC12 cells, resulting in increased cell survival, decreased lactate dehydrogenase (LDH) release, and potent apoptosis inhibition by a reduction in apoptotic nuclei demonstrated by Hoechst 33342 and propidium iodide (PI) double staining, and TUNEL staining. WEST strongly attenuated calcium (Ca2+) elevation, inducing the closure of mitochondrial permeability transition pores (mPTPs), which were opened by corticosterone. It also stabilized mitochondrial membrane potential (MMP) loss and inhibited the corticosterone-induced decrease in adenosine triphosphate (ATP) levels. Furthermore, the increased reactive oxygen species (ROS) production induced by corticosterone was prevented in PC12 cells treated with WEST. WEST also downregulated the expression of glucose-regulated protein 78 (GRP78), growth arrest- and DNA damage-inducible gene 153 (GADD153), the pro-apoptotic protein Bcl-2-associated X (Bax), cytochrome c, cysteine-aspartic protease (caspase)-9, and caspase-3, and upregulated the expression of the anti-apoptotic protein B-cell lymphoma 2 (Bcl-2). Thus, WEST exerts a neuroprotective effect by inhibiting the apoptosis pathway in ER stress and the mitochondrial dysfunction induced by corticosterone. These results demonstrate that WEST reduces neuronal damage from the neurotoxicity caused by chronic stress.

Liquiritin protects PC12 cells from corticosterone-induced neurotoxicity via regulation of metabolic disorders, attenuation ERK1/2-NF-κB pathway, activation Nrf2-Keap1 pathway, and inhibition mitochondrial apoptosis pathway

Liquiritin, a flavone derived from the medicine food homology plant liquorice, possesses neuroprotective. However, the neuroprotective mechanism is not clear. In this study, metabolomics based LC-MS was performed to discover the metabolite changes in PC12 cells treated with corticosterone-induced neurotoxicity after liquiritin treatment. A total of 30 metabolites were identified as differential metabolites. Among them, 11 metabolites were regulated by liquiritin, and involved in the D-glutamine and D-glutamate metabolism, and glutathione metabolism, etc. Based on the results of metabolomics, three cell signaling pathways related to these metabolic pathways were verified. The results showed that the ERK1/2-NF-κB pathway related to the D-glutamine and D-glutamate metabolism was attenuated by liquiritin via down-regulation phospho-ERK1/2, phospho-IκBα, phospho–NF–κB protein expression levels. Furthermore, the Nrf2-Keap1 pathway related to glutathione metabolism was activated by liquiritin via up-regulation Nrf2, Keap1, HO-1, NQO1 protein expression levels, and increased SOD, CAT, GSH-PX enzyme activity, thus exerting antioxidant activity. Additionally, liquiritin inhibited the mitochondrial apoptosis by decreasing the Ca2+ concentration, improving MMP, up-regulating Bcl-2, and down-regulating Bax, cytochrome C, cleaved-Caspase-3 expression levels. These results suggest that the neuroprotective mechanisms of liquiritin are connected to the regulation of metabolic disorders, activation Nrf2/Keap1 pathway, attenuation ERK1/2/NF-κB pathway, and inhibition mitochondrial apoptosis pathway.

Phosphodiesterase 2 inhibitor Hcyb1 reverses corticosterone-induced neurotoxicity and depression-like behavior.

Currently available PDE2 inhibitors have poor brain penetration that limits their therapeutic utility in the treatment of depression. Hcyb1 is a novel selective PDE2 inhibitor that was introduced more lipophilic groups with polar functionality to the scaffold pyrazolopyrimidinone to improve the blood-brain barrier (BBB) penetration. Our previous study suggested that Hcyb1 increased the neuronal cell viability and exhibited antidepressant-like effects, which were parallel to the currently available PDE2 inhibitor Bay 60-7550. The present study investigated whether Hcyb1 protected HT-22 cells against corticosterone-induced neurotoxicity and produced antidepressant-like effects in behavioral tests in stressed mice. The neuroprotective effects of Hcyb1 against corticosterone-induced cell lesion were examined by cell viability (MTS) assay. The enzyme-linked immunosorbent assay (ELISA) and immunoblot analysis were used to determine the levels of cAMP or cGMP and expression of pCREB or BDNF, respectively, in the corticosterone-treated HT-22 cells. The antidepressant-like effects of Hcyb1 were determined in the tail suspension and novelty suppressed feeding tests in stressed mice. In the cell-based assay, Hcyb1 significantly increased cell viability of HT-22 cells against corticosterone-induced neurotoxicity in a time- and dose-dependent manner. Hcyb1 also rescued corticosterone-induced decreases in both cGMP and cAMP levels, pCREB/CREB and BDNF expression. These protective effects of Hcyb1 were prevented by pretreatment with either the PKA inhibitor H89 or the PKG inhibitor KT5823. Moreover, Hcyb1 reversed acute stress-induced increases in immobility time and the latency to feed in the tail suspension and novelty suppressed feeding tests, respectively, which were prevented by pretreatment with H89 or KT5823. These findings provide evidence that the neuroprotective effects of Hcyb1 are mediated by PDE2-dependent cAMP/cGMP signaling.

Effect of Different Processing Methods on Phytochemical Contents and Neuroprotective Activity of Camellia euphlebia Leaves Extract.

Camellia euphlebia is a new food source and traditional folk medicine in China. Previous studies have demonstrated the antidepressant activity of Camellia euphlebia extract by both in vivo and in vitro experiments. The effects of different pretreatments on phytochemical contents and neuroprotective activity of Camellia euphlebia extract were further investigated in order to develop an optimal processing method that makes the extraction more efficient. Six different powders of Camellia euphlebia leaves were prepared by different pretreatments. The particle size and morphology were examined by using a Malvern particle size analyzer and scanning electron microscopy, respectively. The results showed that the percentage of powder particle size within a range of 0.2∼40 μm was up to 79.18% after press-shear assisted interaction technology pretreatment by 2% addition of shellfish shell powder, and the cells were broken completely. Additionally, the contents of flavonoids, polysaccharides, polyphenols, saponins, and catechin in the extract were 11.78 ± 0.62%, 34.60 ± 3.37%, 6.15 ± 0.29%, 9.43 ± 1.19%, and 1.99 ± 0.11%, respectively, which were higher than those of the other five extracts. Moreover, the extract had the strongest neuroprotective activity by comparing the neuroprotective effect of different extracts on corticosterone-induced neurotoxicity in differentiated PC12 cells. It is concluded that press-shear assisted interaction technology with 2% addition of shellfish shell powder pretreatment, to a great extent, improved the dissolution of bioactive ingredients in Camellia euphlebia.

Chlorogenic acid protects PC12 cells against corticosterone-induced neurotoxicity related to inhibition of autophagy and apoptosis

BackgroundThere are evidences that chlorogenic acid (CGA) has antidepressant effects, however the underlying molecular mechanism has not been well understood. The aim of the study was to explore the neuroprotective effect of CGA on corticosterone (CORT)-induced PC 12 cells and its mechanism, especially the autophagy pathway.MethodsPC12 cells were incubated with CORT (0, 100, 200, 400 or 800 μM) for 24 h, cell viability was measured by MTT assay. PC12 cells were cultured with 400 μM of CORT in the absence or presence of CGA (25 μg/ml) for 24 h, morphologies and specific marker of autophagosome were observed by transmission electron microscope (TEM) and confocal immunofluorescence microscopy, respectively. In addition, PC12 cells were treated with different doses of CGA (0, 6.25, 12.5, 25 or 50 μg/ml) with or without CORT (400 μM) for 24 h, cell viability and changes in the morphology were observed, and further analysis of apoptotic and autophagic proteins, and expression of AKT/mTOR signaling pathway were carried out by Western blot. Specific inhibitors of autophagy 3-Methyladenine (3-MA) and chloroquine (CQ) were added to the PC12 cells cultures to explore the potential role of autophagy in CORT-induced neuronal cell apoptosis.ResultsBesides decreasing PC12 cell activity, CORT could also induce autophagy and apoptosis of PC12 cells, while CGA could reverse these effects. In addition, CGA treatment regulated AKT/mTOR signaling pathway in PC12 cells. CGA, similar to 3-MA and QC, significantly inhibited CORT-induced apoptosis in PC12 cells.ConclusionsOur results provide a new molecular mechanism for the treatment of CORT-induced neurotoxicity by CGA, and suggest CGA may be a potential substance which is can alleviate depression.

Protective Effect of Resveratrol Against Corticosterone-induced Neurotoxicity in PC12 Cells.

ObjectiveResveratrol(RES) is a natural polyphenol which possesses an anti-depressant effect. However, the mechanisms of its anti-depressant effect remain unclear. The aim of the study is to investigate the potential mechanisms in the neuro-protective efficiency in the corticosterone-induced pheochromacytoma 12 (PC12) cells.MethodsPC12 cells were treated with 200 μM of corticosterone in the absence or presence of different concentrations of RES for 24 h. Then, cell viability was measured by Cell Counting Kit-8 assay. Apoptosis of PC12 cells was measured by Annexin V-FITC and Propidium iodide (PI) labelling. The expression of apoptosis-related proteins including Bax, Bcl-2, caspase-3 was determined by western blotting.ResultsThe results showed that treatment with 200 μM of corticosterone induced cytotoxicity in PC12 cells. However, different concentrations of RES (2.5μmol/L, 5μmol/L and 10 μmol/L) significantly increased the cell viability, suppressed the apoptosis of PC12 cells, down-regulated Bax and caspase-3 protein expression, and up-regulated Bcl-2 protein expression, compared to the model group (p<0.05).ConclusionResveratrol has a protective effect on corticosterone-induced neurotoxicity in PC12 cells, which may be related to the apoptosis via inhibition of apoptosis-related proteins and displays the antidepressant-like effect.

D-Limonene protects PC12 cells against corticosterone-induced neurotoxicity by activating the AMPK pathway

The stress-induced hormone corticosterone initiates oxidative stress and inflammatory responses, culminating in cell apoptosis and neurological changes. We assessed the effects of d-Limonene on a PC12 cellular model of corticosterone-induced neurotoxicity, and whether these effects involved the AMP-activated protein kinase (AMPKα) pathway. PC12 cells were treated with corticosterone with or without d-limonene for 24 h. Western blots were performed to measure activation of AMPK pathway members [Silent mating type information regulation 2 homolog-1 (SIRT1), AMPKα, and nuclear factor (NFκB)], reactive oxygen species, inflammatory cytokines, and markers of apoptosis. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) was used to measure cell death after treatment. d-Limonene reversed the effects of corticosterone on PC12 cells: it decreased the levels of malondialdehyde (MDA) and nitric oxide (NO), activities of NADPH oxidase (p67-phox and p47-phox), expression of pro-inflammatory markers [inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), interleukin 6 (IL-6), interleukin 1β (IL-1β), and tumor necrosis factor α (TNF-α)], and expression of pro-apoptotic proteins [Bcl2 associated with X protein (Bax) and cleaved caspase-3)]. d-Limonene also increased levels of the antioxidant enzymes superoxide dismutase 1 (SOD1) and heme oxygenase 1 (HO-1) and the anti-apoptotic protein Bcl-2 while decreasing the number of TUNEL-positive cells. d-limonene significantly activated AMPKα and suppressed NF-κB nuclear translocation through up-regulation of SIRT1. Addition of compound C, an AMPK inhibitor, severely weakened these neuroprotective effects of d-limonene. d-Limonene has a neuroprotective effect on corticosterone-induced PC12 cell injury induced by activating the AMPKα signaling pathway, and thereby inhibiting reactive oxygen species and inflammatory factors. These data suggest that d-limonene might protect against neuronal death to improve depressive symptoms.

Protective effect of liquiritin on corticosterone-induced neurotoxicity in PC12 cells

Purpose: To determine the protective effects of liquiritin on corticosterone-induced neurotoxicity in rat pheochromocytoma (PC12) cells.Methods: Neurotoxicity in PC12 cells was induced by different concentrations of corticosterone. Proliferation of PC12 cells was evaluated using CCK8 assay kits, while apoptosis was determined by flow cytometry.Results: The results indicate that corticosterone inhibited the proliferation of PC12 cells time- and dosedependently. The inhibitory effect (0.2 mM) was ameliorated by liquiritin. Furthermore, the cell apoptosis rate and protein level of caspase 3 in PC12 cells induced by corticosterone were ameliorated by liquiritin (1 and 2 mg/mL) treatment. Moreover, the protective effect of liquiritin (2 mg/mL) on corticosterone induced neurotoxicity in PC12 cells was weakened by K252a (the specific TrkB inhibitor) treatment. In addition, the protein level of brain-derived neurotrophic factor (BDNF) and (tyrosine-kinase receptor) TrkB showed a reverse trend to caspase 3.Conclusion: Liquiritin shows protective effects against neurotoxicity induced by corticosterone in PC12 cells, and these effects are exerted via up-regulating BDNF/TrkB signaling.Keywords: Liquiritin, Antidepressant, Corticosterone, Neuroprotection, PC12 cells, BDNF/TrkB signaling

Protective effects of macamides from Lepidium meyenii Walp. against corticosterone-induced neurotoxicity in PC12 cells.

Maca has attracted considerable attention owing to its neuroprotective effects in vitro and vivo. Macamides, a series of nonpolar and long-chain fatty acid N-benzylamides, are considered unique constituents in maca. This study investigated the protective effects of ethanol extracts of maca (EEM) and macamides on corticosterone-induced (CORT) neurotoxicity in rat pheochromocytoma (PC12) cells. CORT reduced cell viability and increased LDH release, intracellular ROS levels, and MMP decline rate, and induced mitochondrial apoptosis. However, pretreatment with EEM and macamides ameliorated CORT-induced neurotoxicity. EEM increased the cell viability and reduced the LDH release. M 18:1, M 18:2, and M 18:3 increased cell viability and reduced LDH release and intracellular ROS generation. M 18:2 and M 18:3 inhibited MMP reduction and reduced the Bax/Bcl-2 ratios. M 18:1 reduced the intracellular ROS without affecting other factors. Moreover, M 18:3 prevented CORT-induced mitochondrial apoptosis, restrained the expression levels of pro-apoptotic proteins, namely, Bax, cytochrome C, cleaved-caspase-3, and cleaved-PARP, and increased the expression levels of Bcl-2. In addition, M 18:3 increased Akt phosphorylation and the ability of M 18:3 to protect against CORT-induced cytotoxicity was remarkably reduced by LY294002, a PI3K phosphorylation inhibitor. M 18:3 also elevated the phosphorylation of CREB and activated the BDNF protein levels in CORT-induced PC12 cells. In conclusion, macamides, especially M 18:3, exert protective effects on CORT-induced PC12 cells. The cellular mechanism of M 18:3 against CORT-induced cytotoxicity may involve inhibition of mitochondrial apoptosis, and activation of Akt and CREB phosphorylation. Overall, macamides may potentially treat neuronal damage induced by CORT.

Antidepressant-Like and Neuroprotective Effects of Ethanol Extract from the Root Bark of Hibiscus syriacus L.

Hibiscus syriacus L. (Malvaceae) is an important ornamental shrub in horticulture and has been widely used as a medical material in Asia. The aim of this study was to assess the antidepressant and neuroprotective effects of a root bark extract of H. syriacus (HSR) and to investigate the underlying molecular mechanisms. Using an animal model of restraint stress, we investigated the effects of HSR on depressive-like behaviors and on the expression levels of serotonin, corticosterone, and neurotrophic factors in the brain. The mice were exposed to restraint stress for 2 h per day over a period of 3 weeks and orally treated with HSR (100, 200, or 400 mg/kg/day). We also examined the neuroprotective effect of HSR using corticosterone-treated human neuroblastoma SK-N-SH cells. The cells were incubated with the extract for 24 h, followed by corticosterone stimulation for 1 h, and then cell viability assay, cellular ATP assay, mitochondrial membrane potential (MMP) assay, cellular reactive oxygen species (ROS) assay, and western blotting were used to investigate the neuroprotective effects of HSR. Administration of HSR not only reduced the immobility times of the restraint-stressed mice in the forced swimming and tail suspension tests, but also significantly increased sucrose preference in the sucrose preference test. In addition, HSR significantly reduced the plasma levels of corticosterone and increased the brain levels of serotonin. The extract also increased the phosphorylation level of cyclic AMP response element-binding (CREB) protein and the expression level of brain-derived neurotrophic factor (BDNF). The in vitro assays showed that HSR pretreatment increased cell viability and ATP levels, recovered MMP, decreased ROS levels, and increased the expression of CREB and BDNF in corticosterone-induced neurotoxicity. Taken together, our data suggest that HSR may have the potential to control neuronal cell damage and depressive behaviors caused by chronic stress.

Standardized Citrus unshiu peel extract ameliorates dexamethasone-induced neurotoxicity and depressive-like behaviors in mice.

Dried Citrus unshiu peel, also known as Chinpi, have been commonly used as a traditional medicine to improve for allergy, inflammation and hepatopathy. Many previously studies have reported that citrus flavonoids show neuroprotective activities. However, the antidepressant-related effects of C. unshiu peels have not been well characterized. Here, the antidepressant-like effects of standardized C. unshiu peel extract (SCP) were evaluated in in vivo and in vitro depression models induced by dexamethasone (DEX), a synthetic glucocorticoid. Male ICR mice (9-week-old) were injected the DEX (40mg/kg) and were orally given SCP daily (30, 100, and 300mg/kg) for 14 consecutive days. The depressive-like behaviors were determined by use of open filed test (OFT), sucrose preference test (SPT), tail suspension test (TST), and forced swim test (FST). We show that treatment with SCP significantly alleviated DEX-induced depressive-like behaviors and reduced neurotoxicity in a concentration dependent manner in SH-SY5Y cells. Additionally, repeated DEX injection markedly decreased brain derived neurotrophic factor (BDNF) level, tropomyosin receptor kinase B (TrkB), and cyclic AMP-response element-binding protein (CREB), while SCP treatment improved these levels in the cerebral cortex and hippocampus regions. Our findings suggest that SCP exhibits significant antidepressant-like effects in the DEX-induced depressive animal model, and this activity may be mediated by preventing corticosterone-induced neurotoxicity.

Glycyrrhizic Acid Alleviates 6-Hydroxydopamine and Corticosterone-Induced Neurotoxicity in SH-SY5Y Cells Through Modulating Autophagy.

Recent researches have shown that autophagy is associated with the pathogenesis of neurodegenerative disorders, but there is no paper to investigate the effects of autophagy modulation on Parkinson's disease depression (PDD). In addition, glycyrrhizic acid (GA), the major bioactive ingredient of Radix glycyrrhizae, can induce autophagy and ease rotenone-induced Parkinson's disease (PD). However, there is also no paper to study the action and molecular mechanisms of GA on PDD. In this research, we built the injury model of SH-SY5Y cells through 6-hydroxydopamine (6-OHDA) and corticosterone (CORT). Then, our results showed that GA markedly increased the viability and decreased the apoptosis in SH-SY5Y cells after pre-treating with 6-OHDA and CORT. Moreover, GA notably decreased the expressions of α-Syn and p-S1292-LRRK2 proteins, and significantly increased the levels of CREB and BDNF proteins. Previous papers have suggested that CORT contributed to dopaminergic neurodegeneration via the glucocorticoid (GC)/glucocorticoid receptor (GR) interaction, and our results showed that GA reduced GC level and hypothalamic-pituitary-adrenal (HPA) activity in SH-SY5Y cells by regulating GR signaling pathway. Furthermore, mechanism investigations also showed that GA had the ability to up-regulate the conversion of LC3B II/I and the expression of Beclin-1, and induce autophagy in SH-SY5Y cells, which were reversed by the autophagy inhibitor 3-methyladenine (3-MA). Collectively, these findings proved that GA exerted efficient activity against neurotoxicity in SH-SY5Y cells induced by 6-OHDA and CORT via activation of autophagy, which should be developed as an efficient candidate for treating PDD in the future.

A novel PDE9 inhibitor WYQ-C36D ameliorates corticosterone-induced neurotoxicity and depression-like behaviors by cGMP-CREB-related signaling.

Major depressive disorder (MDD) is a mental disease characterized by depressed mood, lifetime anxiety, and deficits of learning and memory. Inhibition of phosphodiesterase 9 (PDE9) has been reported to improve rodent cognitive and memory function. However, the role of PDE9 in MDD, in particular its manifestations of depression and anxiety, has not been investigated. We examined the protective effects of WYQ-C36D (C36D), a novel PDE9 inhibitor, against corticosterone-induced cytotoxicity, pCREB/CREB and BDNF expression by cell viability, and immunoblot assays in HT-22 cells. The potential effects of C36D at doses of 0.1, 0.5, and 1mg/kg on stress-induced depression- and anxiety-like behaviors and memory deficits were also examined in mice. C36D significantly protected HT-22 cells against corticosterone-induced cytotoxicity and rescued corticosterone-induced decreases in cGMP, CREB phosphorylation, and BDNF expression. All these effects were otherwise blocked by the PKG inhibitor Rp-8-Br-PET-cGMPS (Rp8). In addition, when tested in vivo in stressed mice, C36D produced antidepressant-like effects on behavior, as shown by decreased immobility time both in the forced swimming and tail suspension tests. C36D also showed anxiolytic-like and memory-enhancing effects in the elevated plus-maze and novel object recognition tests. Our results show that inhibition of PDE9 by C36D produces antidepressant- and anxiolytic-like behavioral effects and memory enhancement by activating cGMP/PKG signaling pathway. PDE9 inhibitors may have the potential as a novel class of drug to treat MDD.

(-)-Epigallocatechin-3-gallate protects PC12 cells against corticosterone-induced neurotoxicity via the hedgehog signaling pathway.

It has been acknowledged that environmental stress is a risk factor for developing mental disorders. Chronic stress may contribute to the hyperactivation of the hypothalamic-pituitary-adrenal (HPA) axis and a sustained rise in the levels of glucocorticoids (GCs). A high concentration of corticosterone (CORT) damages neuronal PC12 cells. It has been reported that (−)-Epigallocatechin-3-gallate (EGCG), a major component of green tea, exhibits neuroprotective activity. However, the protective effect of EGCG on neuronal cells injured by CORT remains to be elucidated. The present study aimed to identify the effects of EGCG on CORT-injured neuronal PC12 cells and its associated mechanisms of action. CORT-injured PC12 cells were pretreated with EGCG with or without cyclopamine. Cell viability was assessed using an MTT assay, changes in cell morphology were observed using phase-contrast microscopy, cellular apoptosis was assessed by Hoechst 33342 staining, cell proliferation was measured using a cell counting kit-8 assay, mRNA levels were measured by reverse transcription-quantitative polymerase chain reaction and protein expression was assessed using western blot analysis. The current study demonstrated that exposure to high concentrations of CORT induced cytotoxicity and downregulated the Sonic hedgehog pathway (Shh) in PC12 cells. These effects were attenuated by EGCG. However, the EGCG-mediated neuroprotective effects, as well as upregulation of the Shh pathway were all attenuated by the Shh signaling inhibitor cyclopamine. These results indicate that EGCG protects PC12 cells from CORT-induced neurotoxicity via activation of the Shh signaling pathway.