Changes In PC12 Cells Research Articles

RNA sequencing reveals transcriptomic changes in PC-12 cells following plasminogen activator, tissue type overexpression.

Pheochromocytoma and paraganglioma, collectively known as PPGL, are categorized as neuroendocrine tumors with the potential for malignancy. Plasminogen activator, tissue type (PLAT) is a protein encoding gene that encodes tissue-type plasminogen activator, which converts plasminogen to plasmin. There is limited research on the association between PLAT and PPGL. Previous studies have only found that the expression level of PLAT protein is significantly increased in PPGL with deficient blood supply, and its role in the occurrence and progression of PPGL remains unclear and needs further clarification. The purpose of this study is to provide some new clues to elucidate the role of PLAT in PPGL, in order to better guide future research directions. The PC-12 cell line was selected for this study, and lentivirus transfection technology was used to construct control and PLAT overexpression cell models. Transcriptomic information of PLAT regulation in PC-12 cells was obtained through RNA sequencing, and differentially expressed genes (DEGs) were screened using bioinformatics methods. The physiological functions and related signaling pathways of these genes were analyzed. After validating the overexpression cell model and performing quality control analysis on the transcriptome sequencing data, DEGs were identified. The Gene Ontology (GO) functional enrichment analysis of DEGs revealed significant enrichment in 46 GO functions, while the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis showed significant enrichment in seven pathways. It was found that these genes were significantly enriched in functional pathways associated with mitochondrial respiratory chain and energy metabolism. This study provides some insights into the role of PLAT in pheochromocytoma and suggests directions for further research on its involvement in tumor development and angiogenesis. However, the specific regulatory mechanisms still require further validation.

The structurally diverse phytocannabinoids cannabichromene, cannabigerol and cannabinol significantly inhibit amyloid β-evoked neurotoxicity and changes in cell morphology in PC12 cells.

Phytocannabinoids (pCBs) have been shown to inhibit the aggregation and neurotoxicity of the neurotoxic Alzheimer's disease protein beta amyloid (Aβ). We characterized the capacity of six pCBs-cannabichromene (CBC), cannabigerol (CBG), cannabinol (CBN), cannabidivarin (CBDV), cannabidiol (CBD) and Δ9 -tetrahydrocannabinol (Δ9 -THC)-to disrupt Aβ aggregation and protect against Aβ-evoked neurotoxicity in PC12 cells. Neuroprotection against lipid peroxidation and Aβ-induced cytotoxicity was assessed using the MTT assay. Transmission electron microscopy was used to visualize pCB effects on Aβ aggregation and fluorescence microscopy, with morphometrics and principal component analysis to assess PC12 cell morphology. CBD inhibited lipid peroxidation with no significant effect on Aβ toxicity, whilst CBN, CBDV and CBG provided neuroprotection. CBC, CBG and CBN inhibited Aβ1-42 -induced neurotoxicity in PC12 cells, as did Δ9 -THC, CBD and CBDV. CBC, CBN and CBDV inhibited Aβ aggregation, whilst Δ9 -THC reduced aggregate density. Aβ1-42 induced morphological changes in PC12 cells, including a reduction in neuritic projections and rounded cell morphology. CBC and CBG inhibited this effect, whilst Δ9 -THC, CBD and CBDV did not alter Aβ1-42 effects on cell morphology. These findings highlight the neuroprotective activity of CBC, CBG and CBN as novel pCBs associated with variable effects on Aβ-evoked neurite damage and inhibition of amyloid β aggregation.

Combination of Lutein and DHA Alleviate H2O2 Induced Cytotoxicity in PC12 Cells by Regulating the MAPK Pathway.

Docosahexaenoic acid (DHA) and lutein are important nutrients for brain health. Whether there were synergistic effects of DHA and lutein on the protection against neuronal cell damage induced by oxidative stress remained unclear. The present study was designed to investigate the synergistic effects of DHA and lutein against hydrogen peroxide (H2O2)-induced oxidative challenge in PC12 cells. PC12 cells were divided into different groups and received H2O2 (80 μM), lutein (20 μM)+H2O2 (80 μM), DHA (25 μM)+H2O2 (80 μM), and lutein (20 μM)+DHA (25 μM)+H2O2 (80 μM), respectively. The results indicated that pre-treatment of cells with lutein, DHA and DHA+lutein could significantly antagonize the H2O2-mediated growth inhibition and morphological changes in PC12 cells (p<0.05). Molecularlevel studies indicated that the DHA+lutein combination can significantly inhibit the mRNA expression of AMAD10 and BAX. Furthermore, Western blot analysis demonstrated that DHA+lutein synergistically inhibits the phosphorylation of JNK1/2. The results of the present study suggest that DHA and lutein in combination may be utilized as potent antioxidative compounds, with potential preventative or palliative effects on age-related neurodegenerative diseases.

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.

Anemarrhenae asphodeloides rhizoma Extract Enriched in Mangiferin Protects PC12 Cells against a Neurotoxic Agent-3-Nitropropionic Acid.

The rhizome of Anemarrhena asphodeloides Bunge, used in Traditional Chinese Medicine as a brain function-improving herb, is a promising source of neuroprotective substances. The aim of this study was to evaluate the protective action of xanthones from A. asphodeloides rhizomes on the PC12 cell line exposed to the neurotoxic agent—3-nitropropionic acid (3-NP). The xanthone-enriched fraction of the ethanolic extract of A. asphodeloides (abbreviated from now on as XF, for the Xanthone Fraction), rich in polyphenolic xanthone glycosides, in concentrations from 5 to 100 μg/mL, and 3-NP in concentrations from 2.5 to 15 mM, were examined. After 8, 16, 24, 48, and 72 h of exposure of cells to various combinations of 3-NP and XF, the MTT viability assay was performed and morphological changes were estimated by confocal fluorescence microscopy. The obtained results showed a significant increase in the number of cells surviving after treatment with XF with exposure to neurotoxic 3-NP and decreased morphological changes in PC12 cells in a dose and time dependent manner. The most effective protective action was observed when PC12 cells were pre-incubated with the XF. This effect may contribute to the traditional indications of this herb for neurological and cognitive complaints. However, a significant cytotoxicity observed at higher XF concentrations (over 10 µg/mL) and longer incubation time (48 h) requires caution in future research and thorough investigation into potential adverse effects.

MiR-124-5p/NOX2 Axis Modulates the ROS Production and the Inflammatory Microenvironment to Protect Against the Cerebral I/R Injury.

The reperfusion after an acute ischemic stroke can lead to a secondary injury, which is ischemia-reperfusion (I/R) injury. During ischemia, the reactive oxygen species (ROS) is over-produced, mostly from nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX). Besides, miRNAs are also associated with neuronal death in ischemic stroke. MiR-124-5p is selectively expressed within central nervous system (CNS) and is predicted to bind to NOX2 directly. Herein, we successfully set up cerebral I/R injury model in rats through middle cerebral artery occlusion (MCAO) surgery. After 12 h or 24 h of refusion, the superoxide dismutase (SOD) activity was significantly inhibited, accompanied by NOX2 protein increase within MCAO rat infarct area. In vitro, oxygen-glucose deprivation/refusion (OGD/R) stimulation on PC-12 cells significantly increased NOX2 protein levels, ROS production, and the cell apoptosis, while a significant suppression on SOD activity; OGD/R stimulation-induced changes in PC-12 cells described above could be significantly attenuated by NOX2 silence. In vivo, miR-124 overexpression improved, whereas miR-124 inhibition aggravated I/R injury in MCAO rats. miR-124-5p directly bound to the CYBB 3'-untranslated region (UTR) to negatively regulate CYBB expression and NOX2 protein level. In vitro, miR-124 overexpression improved, while NOX2 overexpression aggravated OGD/R-induced cellular injuries; NOX2 overexpression significantly attenuated the effects of miR-124 overexpression. Besides, miR-124 overexpression significantly repressed NF-κB signaling activation and TNFα and IL-6 production through regulating NOX2. In conclusion, miR-124-5p/NOX2 axis modulates NOX-mediated ROS production, the inflammatory microenvironment, subsequently the apoptosis of neurons, finally affecting the cerebral I/R injury.

The Efficacy of Electrospun PAN/Kefiran Nanofiber and Kefir in Mammalian Cell Culture: Promotion of PC12 Cell Growth, Anti-MCF7 Breast Cancer Cells Activities, and Cytokine Production of PBMC.

BackgroundKefiran is a useful polysaccharide made of branched glucogalactose which is produced by microorganisms. Here the anti-MCF-7 breast cancer cells activity of kefiran and cytokine productions (IL-6) of peripheral blood mononuclear cells (PBMC) treated by kefiran was studied. Also, the effect of using kefiran as a useful and cost-effective scaffold in neural stem cell culture (PC12 cell culture) was investigated.Material and MethodsKefiran was produced from raw milk with 0.5% fat and 10 g of kefir grains. After incubation for 48 hrs at room temperature, the solvent collected (crude kefiran). These samples were kept at 100°C for 1 hr (boiled kefiran) and the supernatant was precipitated by ethanol (pure kefiran). Then, the electrospun nanofibers, pure polyacrylonitrile (PAN), PAN/kefiran 5%, and PAN/kefiran 10% were fabricated and used as scaffolds in the cell culture. The structure of fabricated was studied by SEM and the cytokine production (IL-6) in vitro in the cell culture supernatant of PBMC line after treatment with kefiran (1mg/mL, 5 mg/mL) and kefiran-PAN 5% and 10% were carried out by enzyme-linked immunosorbent assay (ELISA). The attachment of PC12 cells was examined by inverted microscope. Also, cytotoxicity of kefiran for PC12 and MCF7 cells and morphological changes of PC12 cells were evaluated by MTT and Cresyl violet staining (Nissl staining) respectively.ResultsThe mean diameter of fabricated PAN/kefiran 5% and 10% nanofibers were 310.2±43.97 nm. The contact angle measurement results (26.9± 1.9 for the pure PAN scaffold vs 12.3± 1.13 for the PAN/kefiran) revealed enhanced hydrophilicity of scaffolds upon the incorporation of kefiran and PAN. Seeding of PC12 cells on the scaffolds showed that fabrication of kefiran into PAN led to the enhancement of cell attachment, proliferation, and morphological changes. Also, the promotion of PBMC growth and decreasing of MCF7 cell lines viability were shown through MTT assay. No significant changes were measured for the level of IL-6 in PAN/kefiran 5% treated cells compared to the control (p ≥ 0.05).ConclusionThese results suggest superior properties of kefiran/PAN nanofibrous scaffolds for the neural stem cell culture especially for repairing injured spinal cord. Also, the pure kefiran could be used for the enhancement of PBMC growth and reducing the MCF7 cancerous cells growth. So, using biocompatible, anti-bacterial, and anti-tumor kefiran/PAN nanofibers for regenerative medicine seems promising.

Protective effect of nitronyl nitroxide against hypoxia-induced damage in PC12 cells.

Hypoxia induces cellular oxidative stress that is associated with neurodegenerative diseases. HPN (4'-hydroxyl-2-substituted phenyl nitronyl nitroxide), a stable nitronyl nitroxide, has excellent free radical scavenging properties. The purpose of this study was to investigate the protective effects of HPN on hypoxia-induced damage in PC12 cells. It was shown that HPN significantly attenuated hypoxia-induced loss of cell viability, release of lactate dehydrogenase (LDH), and morphological changes in PC12 cells. Moreover, hypoxic PC12 cells had increased levels of reactive oxygen species (ROS), malondialdehyde (MDA), and expression of HIF-1α and VEGF, but had reduced levels of superoxide dismutase (SOD) and catalase (CAT), and HPN reversed these changes. HPN also inhibited hypoxia-induced cell apoptosis via suppressing the expression of Bax, cytochrome c, and caspase-3, and inducing the expression of Bcl-2. These results indicate that the protective effects of HPN on hypoxia-induced damage in PC12 cells is associated with the suppression of hypoxia-induced oxidative stress and cell apoptosis. HPN could be a promising candidate for the development of a novel neuroprotective agent.

Acetate Mediates Alcohol Excitotoxicity in Dopaminergic-like PC12 Cells.

Neuronal excitotoxicity is the major cause of alcohol-related brain damage, yet the underlying mechanism remains poorly understood. Using dopaminergic-like PC12 cells, we evaluated the effect of N-methyl-d-aspartate receptors (NMDAR) on acetate-induced changes in PC12 cells: cell death, cytosolic calcium, and expression levels of the pro-inflammatory cytokine tumor necrosis factor alpha (TNFα). Treatment of PC12 cells with increasing concentrations of acetate for 4 h caused a dose-dependent increase in the percentage of cells staining positive for cell death using propidium iodide (PI) exclusion and cytosolic reactive oxygen species (ROS) using cell ROX detection analyzed via flow cytometry. The EC50 value for acetate was calculated and found to be 4.40 mM for PI and 1.81 mM for ROS. Ethanol up to 100 mM had no apparent changes in the percent of cells staining positive for PI or ROS. Acetate (6 mM) treatment caused an increase in cytosolic calcium measured in real-time with Fluo-4AM, which was abolished by coapplication with the NMDAR blocker memantine (10 μM). Furthermore, cells treated with acetate (6 mM) for 4 h had increased expression levels of TNFα relative to control, which was abolished by coapplication of memantine (10 μM). Co-application of acetate (6 mM) and memantine had no apparent reduction in acetate-induced cell death. These findings suggest that acetate is capable of increasing cytosolic calcium concentrations and expression levels of the pro-inflammatory cytokine TNFα through an NMDAR-dependent mechanism. Cell death from acetate was not reduced through NMDAR blockade, suggesting alternative pathways independent of NMDAR activation for excitotoxicity.

Vitamin K3 Regulates Reactive Oxygen Species and Extracellular-Regulated Protein Kinase in Differentiated PC-12 Cells within a Safe Dose Range

Objective: Acupuncture can relieve pain by acting on the mitogen-activated protein kinase (MAPK) signal pathway, which plays a critical role in the balance between hyperalgesia and inflammation. Our previous studies have suggested that acupoint injection of Vitamin K3 (Vit K3) had an intensive analgesic effect on primary dyspareunia. However, the mechanism by which Vit K3 worked on nerve cells has not been elucidated. Methods: Cell apoptosis, mitochondrial membrane potential (MMP), and reactive oxygen species (ROS) changes of PC-12 cells with Vit K3 treatment, for which the concentration gradient was 0, 5, 10, 20, 40, and 60 μmol/L, were quantified by flow cytometry. The expression and phosphorylation of c-Jun N-terminal kinase, p38, and extracellular-regulated protein kinase (ERK), the three critical molecules of the MAPK pathway, were further assessed using Western blotting. Results: The level of ROS first decreased and then increased with Vit K3 at 20 μmol/L, but no change in neither apoptosis nor MMP was evident. In addition, only ERK level decreased at 20 μmol/L and the relative phosphorylation level increased. Changes in ROS were negatively correlated with the expression of ERK. Conclusions: The rapid analgesic effect of Vit K3 acupoint injection may be through the reduction of ROS in nerve cells with a small dose of Vit K3 or by influencing the expression of ERK but without damaging the nerve cells themselves.

Effect of carbaryl on some biochemical changes in PC12 cells: the protective effect of soy isoflavone genistein, and daidzein, and their mixed solution

ABSTRACTWe planned to investigate the protective effect of soy isoflavone (SIF) genistein (GEN), and daidzein (DAI), and their mixed solution against carbaryl-induced toxicity in PC12 cells. PC12 cells were exposed to carbaryl, pretreated, co-treatment, or posttreatment with three different SIF solutions for indicated times. Exposure to SIF resulted a better survival and cell morphology which were subjected to carbaryl toxicity. Treatment with SIF was also found to reduce malondialdehyde content, superoxide dismutase inhibitory rate, reactive oxygen species generation, acetylcholine levels in medium, and maintain the integrity of mitochondrial membrane potential. It was also found to increase GSH level. In conclusion, SIF can effectively mitigate adverse effects induced by carbaryl. GEN and DAI have a combined effect that is greater than the effect obtained with each isoflavone alone, although they have different effects against carbaryl-induced damage. SIF enhances metabolism of choline and plays a role as both antioxidant and neuroprotectant.

Cyanidin suppresses amyloid beta-induced neurotoxicity by inhibiting reactive oxygen species-mediated DNA damage and apoptosis in PC12 cells.

Amyloid beta (Aβ)-induced oxidative stress is a major pathologic hallmark of Alzheimer's disease. Cyanidin, a natural flavonoid compound, is neuroprotective against oxidative damage-mediated degeneration. However, its molecular mechanism remains unclear. Here, we investigated the effects of cyanidin pretreatment against Aβ-induced neurotoxicity in PC12 cells, and explored the underlying mechanisms. Cyanidin pretreatment significantly attenuated Aβ-induced cell mortality and morphological changes in PC12 cells. Mechanistically, cyanidin effectively blocked apoptosis induced by Aβ, by restoring the mitochondrial membrane potential via upregulation of Bcl-2 protein expression. Moreover, cyanidin markedly protected PC12 cells from Aβ-induced DNA damage by blocking reactive oxide species and superoxide accumulation. These results provide evidence that cyanidin suppresses Aβ-induced cytotoxicity, by preventing oxidative damage mediated by reactive oxide species, which in turn inhibits mitochondrial apoptosis. Our study demonstrates the therapeutic potential of cyanidin in the prevention of oxidative stress-mediated Aβ neurotoxicity.

Chemogenomic analysis of neuronal differentiation with pathway changes in PC12 cells.

The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway database creates networks from interrelations between molecular biology and underlying chemical elements. This allows for analysis of biologic networks, genomic information, and higher-order functional information at a system level. Through high throughput experiments and system biology analysis, we investigated the genes and pathways associated with NGF induced neuronal differentiation. We performed microarray experiments and used the KEGG database, system biology analysis, and annotation of pathway functions to study NGF-induced differentiation in PC12 cells. We identified 2020 NGF-induced genes with altered expressions over time. Cross-matching with the KEGG database revealed 830 genes; among which, 395 altered genes were found to have a 2-fold increase in gene expression over a two-hour period. We then identified 191 associated biologic pathways in the KEGG database; the top 15 pathways showed correlation with neural differentiation. These included the neurotrophin pathways, mitogen-activated protein kinase (MAPK) pathways, genes associated with axonal guidance and the Wnt pathways. The activation of these pathways synchronized with nerve growth factor (NGF)-induced differentiation in PC12 cells. In summary, we have established a model system that allows one to systematically characterize the functional pathway changes in a group of neuronal population after an external stimulus.

Neuroprotective effects of 20(S)-protopanaxadiol against glutamate-induced mitochondrial dysfunction in PC12 cells.

Ginseng (Panax ginseng C.A. Mey.) is commonly used in traditional oriental medicine for its wide spectrum of medicinal properties, including anti-inflammatory, antitumorigenic, adaptogenic and anti-aging properties. 20(S)-Protopanaxadiol (PPD), the main intestinal metabolite of ginsenosides, is one of the active ingredients in ginseng. In this study, we aimed to investigate the neuroprotective effects of PPD on PC12 cells; however, the underlying mechanisms remain elusive. We examined cell viability by MTT assay and the morphological changes of PC12 cells following glutamate-induced cell damage and evaluated the anti-apoptotic effects of PPD using Hoechst 33258 staining, western blot analysis and Muse™ Cell Analyzer and the antioxidant effects of PPD using FACS analysis and immunofluorescence. Furthermore, PPD exerted protective effects on PC12 cells via the inhibition of mitochondrial damage against glutamate-induced excitotoxicity using immunofluorescence, electron microscopy and FACS analysis. We demonstrate that treatment with PPD suppresses apoptosis, which contributes to the neuroprotective effects of PPD against glutamate-induced excitotoxicity in PC12 cells. Treatment with PPD inhibited nuclear condensation and decreased the number of Annexin V-positive cells. In addition, PPD increased antioxidant activity and mitochondrial homeostasis in the glutamate-exposed cells. These antioxidant effects were responsible for the neuroprotection and enhanced mitochondrial function following treatment with PPD. Furthermore, PD inhibited the glutamate-induced morphological changes in the mitochondria and scavenged the mitochondrial and cytosolic reactive oxygen species (ROS) induced by glutamate. In addition, mitochondrial function was significantly improved in terms of mitochondrial membrane potential (MMP) and enhanced mitochondrial mass compared with the cells exposed to glutamate and not treated with PPD. Taken together, the findings of our study indicate that the antioxidant effects and the enhanced mitochondrial function triggered by PPD contribute to the inhibition of apoptosis, thus leading to a neuroprotective response, as a novel survival mechanism.

Insulin-like growth factor binding protein 5 (IGFBP5) mediates methamphetamine-induced dopaminergic neuron apoptosis

Overexposure to methamphetamine (METH), a psychoactive drug, induces a variety of adverse effects to the nervous system, including apoptosis of dopaminergic neurons. Insulin-like growth factor binding protein 5 (IGFBP5), a member of insulin-like growth factor (IGF) system, is a pro-apoptotic factor that plays important roles in neuronal apoptosis. To test the hypothesis that IGFBP5 can mediate METH-induced neuronal apoptosis, we examined IGFBP5 mRNA and protein expression changes in PC12 cells exposed to METH (3.0mM) for 24h and in the striatum of rats following 15mg/kg×8 intraperitoneal injections of METH at 12h interval. We also checked the effect on neuronal apoptosis after silencing IGFBP5 expression with TUNEL staining and flow cytometry; Western blot was used for detecting the expression of apoptotic markers active-caspase3 and PARP. To elucidate the mechanisms underlying IGFBP5-mediated neuronal apoptosis, we determined the release of cytochrome c (cyto c), an apoptogenic factor, from the mitochondria after METH treatment with or without IGFBP5 knockdown. Our results showed that IGFBP5 expression was increased significantly after METH exposure in PC12 cells and in the METH-treated rats’ striatum. Further, METH-exposed PC12 cells exhibited higher apoptosis-positive cell number and activity of caspase3 and PARP compared with control cells, while these changes can be blocked by silencing IGFBP5 expression. In addition, a significant increase of cyto c release from mitochondria after METH exposure was observed and it was inhibited after silencing IGFBP5 expression in PC12 cells. These results indicate that IGFBP5 plays key roles in METH-induced neuronal apoptosis and may be a potential gene target for therapeutics in METH-caused neurotoxicity.

TRPC6 channel‐mediated neurite outgrowth in PC12 cells and hippocampal neurons involves activation of RAS/MEK/ERK, PI3K, and CAMKIV signaling

The non-selective cationic transient receptor canonical 6 (TRPC6) channels are involved in synaptic plasticity changes ranging from dendritic growth, spine morphology changes and increase in excitatory synapses. We previously showed that the TRPC6 activator hyperforin, the active antidepressant component of St. John's wort, induces neuritic outgrowth and spine morphology changes in PC12 cells and hippocampal CA1 neurons. However, the signaling cascade that transmits the hyperforin-induced transient rise in intracellular calcium into neuritic outgrowth is not yet fully understood. Several signaling pathways are involved in calcium transient-mediated changes in synaptic plasticity, ranging from calmodulin-mediated Ras-induced signaling cascades comprising the mitogen-activated protein kinase, PI3K signal transduction pathways as well as Ca(2+) /calmodulin-dependent protein kinase II (CAMKII) and CAMKIV. We show that several mechanisms are involved in TRPC6-mediated synaptic plasticity changes in PC12 cells and primary hippocampal neurons. Influx of calcium via TRPC6 channels activates different pathways including Ras/mitogen-activated protein kinase/extracellular signal-regulated kinases, phosphatidylinositide 3-kinase/protein kinase B, and CAMKIV in both cell types, leading to cAMP-response element binding protein phosphorylation. These findings are interesting not only in terms of the downstream targets of TRPC6 channels but also because of their potential to facilitate further understanding of St. John's wort extract-mediated antidepressant activity. Alterations in synaptic plasticity are considered to play an important role in the pathogenesis of depression. Beside several other proteins, TRPC6 channels regulate synaptic plasticity. This study demonstrates that different pathways including Ras/MEK/ERK, PI3K/Akt, and CAMKIV are involved in the improvement of synaptic plasticity by the TRPC6 activator hyperforin, the antidepressant active constituent of St. John's wort extract.

Short-term exposure of 4-hydroxynonenal induces mitochondria-mediated apoptosis in PC12 cells

4-Hydroxynonenal (4-HNE) is one of the most reactive aldehydic by-products of lipid peroxidation. The role of 4-HNE in the etiology of various neurodegenerative disorders including cerebral ischemia/reperfusion, Alzheimer's disease, Parkinson's disease, etc. has been documented. We and others have reported that long-term toxic insults of 4-HNE triggers apoptotic signals and oxidative stress in various cells. However, the status of apoptosis following short-term exposure and underlying mechanisms has not been explored so far. We studied the apoptotic changes in PC12 cells receiving short-term exposure of 4-HNE. A significant dose-dependent induction in reactive oxygen species (ROS) and early response markers (c-Fos, c-Jun, and GAP-43) were observed in cells exposed to 4-HNE (10, 25, and 50 µM) for 1h. Following the exposure of PC12 cells to 4-HNE, the levels of protein and messenger RNA expressions of P(53), Bax, and caspase 3 were significantly upregulated, whereas the levels of Bcl(2) was downregulated. We could record the apoptotic signals and ROS generation in PC12 cells receiving 4-HNE exposure for such a short period of time. Induction in the expression and activity of caspase 3 has also indicated the mitochondrial mediation in the apoptosis induction.

Ischemic insult induced apoptotic changes in PC12 cells: Protection by trans resveratrol

In this study, we determined the protective potential of trans resveratrol against oxygen–glucose deprivation (OGD) induced reactive oxygen species mediated apoptotic damages in PC12 cells. In vitro model of ischemic cerebral stroke was created by keeping cells in an OGD condition for 6 h followed by 24 h reoxygenation. Cells received biologically safe doses (5, 10, and 25 μM) of trans resveratrol in the following schedules for 24 h prior to OGD; during 6 h of OGD; for 24 h post OGD and whole treatment group which starts from 24 h before OGD and lasted to 24 h post OGD. Anti-ischemic potential of trans resveratrol was assessed by measuring the regulation of lipid peroxidation, reactive oxygen species production, glutathione content, and expression (mRNA and protein) of apoptotic markers such as Bax, Bcl 2 and Caspase-3. Hypoxia inducible factor-1α (HIF-1α) was also assessed to correlate the changes with ischemic injuries. Significant (P < 0.05) restoration in lipid peroxidation, reactive oxygen species, and glutathione content were observed following the treatment of trans resveratrol in cells receiving OGD and re-oxygenation. Changes induced by trans resveratrol could be correlated well with alterations in the expression of Bax, Bcl 2, Caspase-3 and HIF-1α. These results indicate that trans resveratrol administration attenuates free radical formation and mitochondria mediated apoptosis perhaps by regulating the expressions of Bax, Bcl 2, and Caspase-3 in PC12 cells receiving OGD and re-oxygenation insult.

NAD+ treatment can prevent multiple rotenone‐induced apoptotic changes of PC12 cells

NAD+ plays critical roles in various biological functions. A number of studies have also indicated that NAD+ treatment can prevent the necrosis of primary neurons and astrocytes, which are induced by multiple insults such as oxidative stress. NAD+ administration has also been shown to decrease ischemic brain damage. However, there, there has been little information regarding the effects of NAD+ treatment on apoptotic changes, which are critical pathological changes in such neurological diseases as brain ischemia. In this study we determined the effects of NAD+ on multiple rotenone‐induced pathological changes by applying flow cytometry‐based Annexin V assay, TUNEL say, Hoechst staining and immunostaining of apoptosis‐inducing factor (AIF). We found that NAD+ treatment, but not nicotinamide, can markedly prevent all of these apoptotic changes, suggesting that NAD+ can prevent cell apoptosis by mechanisms that are independent of its degradation product nicotinamide. Our study using propidium staining assay and lactate dehydrogenase (LDH) assay also showed that NAD+ treatment can block rotenone‐induced cell necrosis. We further found that NAD+ treatment can prevent rotenone‐induced ATP depletion, which could in part underlie the protective effects of NAD+. In summary, our study has provided first evidence that NAD+ treatment can prevent multiple rotenone‐induced apoptotic changes, in addition to its reported preventive effects on cell necrosis. Because mitochondrial impairments belong to a key pathological change in multiple neurological diseases, our study has suggested that NAD+ may be used to prevent mitochondrial impairment‐induced cell death (Supported by a Key Research Grant of Shanghai Municipal Scientific Committee #08JC1415400 (to W. Y.)).

Caspase Cascade Regulated Mitochondria Mediated Apoptosis in Monocrotophos Exposed PC12 Cells

Monocrotophos (MCP) is a commonly used organophosphorus (OP) pesticide. We studied apoptotic changes in PC12 cells exposed to MCP. A significant induction in reactive oxygen species (ROS), lipid peroxide (LPO), and the ratio of glutathione disulfide (GSSG)/reduced glutathione (GSH) was observed in cells exposed to selected doses of MCP. Following the exposure of PC12 cells to MCP, the levels of protein and mRNA expressions of Caspase-3, Caspase-9, Bax, p53, P(21), Puma, and cytochrome-c were significantly upregulated, whereas the levels of Bcl(2), Bcl(w), and Mcl1 were downregulated. TUNEL assay, DNA laddering, and micronuclei induction show that long-term exposure of PC12 cells to MCP at higher concentration (10(-5) M) decreases the number of apoptotic events due to an increase in the number of necrotic cells. MCP-induced translocation of Bax and cytochrome-c proteins between the cytoplasm and mitochondria confirmed the role of p53 and Puma in mitochondrial membrane permeability. Mitochondria mediated apoptosis induction was confirmed by the increased activity of caspase cascade. We believe that this is the first report showing MCP-induced apoptosis in PC12 cells, which is mitochondria mediated and regulated through the caspase cascade. Our data demonstrates that MCP induced the apoptotic cell death in neuronal cells and identifies the possible cellular and molecular mechanisms of organophosphate pesticide-induced apoptosis in neuronal cells.