Regulation of the differentiation of PC12 pheochromocytoma cells

Comparison of Neuroprotection and Regulating Properties on Gut Microbiota between Selenopeptide Val-Pro-Arg-Lys-Leu-SeMet and Its Native Peptide Val-Pro-Arg-Lys-Leu-Met In Vitro and In Vivo

Selenopeptides are promising candidates for intervening in neuroinflammation; however, the key role of selenium (Se) in selenopeptides remains poorly understood. To address this gap, we compared the neuroprotective effects of selenopeptide Val-Pro-Arg-Lys-Leu-SeMet (namely, Se-P1) and its native peptide Val-Pro-Arg-Lys-Leu-Met (namely, P1). Our results demonstrate that Se-P1 treatment exhibits superior antioxidant and antineuroinflammatory effects in PC12 cells and lipopolysaccharide (LPS)-injured mice compared to P1. Moreover, the administration of Se-P1 and P1 resulted in a shift in the gut microbiota composition. Notably, during LPS-induced injury, Se-P1 treatment demonstrated greater stability in maintaining gut microbiota composition compared to P1 treatment. Specifically, Se-P1 may have a positive impact on gut microbiota dysbiosis by modulating inflammatory-related bacteria such as enhancing Lactobacillus abundance while reducing that of Lachnospiraceae_NK4A136_group. Furthermore, the alteration of metabolites induced by Se-P1 treatment exhibited a significant correlation with gut microbiota, subsequently modulating the inflammatory-related metabolic pathways including histidine metabolism, lysine degradation, and purine metabolism. These findings suggest that organic Se contributes to the bioactivities of Se-P1 in mitigating neuroinflammation in LPS-injured mice compared to P1. These findings hold significant value for the development of potential preventive or therapeutic strategies against neurodegenerative diseases and introduce novel concepts in selenopeptide nutrition and supplementation recommendations.

Ukgansan Protects Dopaminergic Neurons against MPTP-Induced Neurotoxicity via the Nurr1 Signaling Pathway

Nuclear receptor-related 1 protein (Nurr1) is a nuclear hormone receptor that protects dopaminergic neurons and is a promising therapeutic target for Parkinson’s disease (PD). Parkinson’s disease is a neurodegenerative disorder caused by the destruction of dopaminergic neurons in the substantia nigra pars compacta (SNpc), and the long-term use of conventional dopamine replacement therapies causes many side effects, highlighting the need for new treatments such as complementary and alternative medicine. Ukgansan has been used in East Asia to treat neurological disorders, including neurodegenerative diseases, and has been reported to have strong effects in treating patients with PD. In addition, recent studies have reported that Ukgansan has a neuroprotective potential. However, there are no detailed studies on the mechanism of action of Nurr1. Thus, unlike previous studies, we focused on the Nurr1 pathways. We confirmed neurotoxicity and apoptosis signaling in the differentiated PC12 cells. In addition, to confirm the protective effect of Ukgansan, we conducted behavioral tests (motor coordination and postural balance, and bradykinesia) and tyrosine hydroxylase immunohistochemistry in both the SNpc and striatum. Specifically, this study demonstrated the effect of Ukgansan in protecting dopaminergic neurons and increasing Nurr1 involved in maintaining dopamine levels by activating Nurr1 expression in MPTP-induced PC12 cells and a mouse model of PD. In this mechanism, the loss of dopaminergic neurons and dopamine depletion were suppressed, and motor impairment caused by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine toxicity was improved. These results provide evidence that Ukgansan ameliorates PD’s motor symptoms and progression.

Androgens Regulate Tau Phosphorylation Through Phosphatidylinositol 3-Kinase-Protein Kinase B-Glycogen Synthase Kinase 3β Signaling

Age-related testosterone depletion in men is a risk factor for Alzheimer's disease (AD). How testosterone modulates AD risk remains to be fully elucidated, although regulation of tau phosphorylation has been suggested as a contributing protective action. To investigate the relationship between testosterone and tau phosphorylation, we first evaluated the effect of androgen status on tau phosphorylation in 3xTg-AD mice. Depletion of endogenous androgens via gonadectomy resulted in increased tau phosphorylation that was prevented by acute testosterone treatment. Parallel alterations in the phosphorylation of both glycogen synthase kinase 3β (GSK3β) and protein kinase B (Akt) suggest possible components of the underlying signaling pathway. To further explore mechanism, primary cultured neurons were treated with a physiological concentration of testosterone or its active metabolite dihydrotestosterone (DHT). Results showed that testosterone and DHT induced significant decreases in phosphorylated tau and significant increases in phosphorylation of Akt and GSK3β. Pharmacological inhibition of phosphatidylinositol 3-kinase (PI3K) effectively inhibited androgen-induced increases in Akt and GSK3β phosphorylation, and decreases in tau phosphorylation. In addition, androgen receptor (AR) knock-down by small interfering RNA prevented androgen-induced changes in the phosphorylation of Akt, GSK3β and tau, suggesting an AR-dependent mechanism. Additional experiments demonstrated androgen-induced changes in Akt, GSK3β and tau phosphorylation in AR-expressing PC12 cells but not in AR-negative PC12 cells. Together, these results suggest an AR-dependent pathway involving PI3K-Akt-GSK3β signaling through which androgens can reduce tau phosphorylation. These findings identify an additional protective mechanism of androgens that can improve neural health and inhibit development of AD.

Novel Selenium Peptides Obtained from Selenium-Enriched Cordyceps militaris Alleviate Neuroinflammation and Gut Microbiota Dysbacteriosis in LPS-Injured Mice

Increasing attention focuses on the relationship between neuroinflammation and Alzheimer's disease (AD). The reports on the microbiota-gut-brain axis reveal that the regulation by gut microbiota is an effective way to intervene in neuroinflammation-related AD. In this study, two novel selenium peptides (Se-Ps), VPRKL(Se)M (Se-P1) and RYNA(Se)MNDYT (Se-P2), with neuroprotection effects were obtained from Se-enriched Cordyceps militaris. Se-P1 and Se-P2 pre-protection led to a 30 and 33% increase in the PC-12 cell viability compared to the damage group, respectively. Moreover, Se-Ps exhibited a significant pre-protection against LPS-induced inflammatory and oxidative stress in the colon and brain by inhibiting the production of pro-inflammatory mediators (p < 0.05) and malondialdehyde, as well as promoting anti-inflammatory cytokine level and antioxidant enzyme activity (p < 0.05), which may alleviate the cognitive impairment in LPS-injured mice (p < 0.05). Se-Ps not only repaired the intestinal mucosa damage of LPS-injured mice but also had a positive effect on gut microbiota dysbacteriosis by increasing the abundance of Lactobacillus and Alistipes and decreasing the abundance of Akkermansia and Bacteroides. Collectively, the antioxidant, anti-inflammatory, and regulating properties on gut microflora of Se-Ps contribute to their neuroprotection, supporting that Se-Ps could be a promising dietary supplement in the prevention and/or treatment of AD.

Small phenolic and indolic gut-dependent molecules in the primate central nervous system: levels vs. bioactivity

INTRODUCTION

A rapidly growing body of data documents associations between disease of the brain and small molecules generated by gut-microbiota (GMB). While such metabolites can affect brain function through a variety of mechanisms, the most direct action would be on the central nervous system (CNS) itself.

OBJECTIVE

Identify indolic and phenolic GMB-dependent small molecules that reach bioactive concentrations in primate CNS.

METHODS

We conducted a PubMed search for metabolomic studies of the primate CNS [brain tissue or cerebrospinal fluid (CSF)] and then selected for phenolic or indolic metabolites that (i) had been quantified, (ii) were GMB-dependent. For each chemical we then conducted a search for studies of bioactivity conducted in vitro in human cells of any kind or in CNS cells from the mouse or rat.

RESULTS

36 metabolites of interests were identified in primate CNS through targeted metabolomics. Quantification was available for 31/36 and in vitro bioactivity for 23/36. The reported CNS range for 8 metabolites 2-(3-hydroxyphenyl)acetic acid, 2-(4-hydroxyphenyl)acetic acid, 3-(3-hydroxyphenyl)propanoic acid, (E)-3-(3,4-dihydroxyphenyl)prop-2-enoic acid [caffeic acid], 3-hydroxybenzoic acid, 4-hydroxybenzoic acid, 2-acetamido-3-(1H-indol-3-yl)propanoic acid [N-acetyltryptophan], 1H-indol-3-yl hydrogen sulfate [indoxyl-3-sulfate] overlapped with a bioactive concentration. However, the number and quality of relevant studies of CNS neurochemistry as well as of bioactivity were highly limited. Structural isomers, multiple metabolites and potential confounders were inadequately considered.

CONCLUSION

The potential direct bioactivity of GMB-derived indolic and phenolic molecules on primate CNS remains largely unknown. The field requires additional strategies to identify and prioritize screening of the most promising small molecules that enter the CNS.

Single-cell RNA sequencing of the Strongylocentrotus purpuratus larva reveals the blueprint of major cell types and nervous system of a non-chordate deuterostome

Identifying the molecular fingerprint of organismal cell types is key for understanding their function and evolution. Here, we use single-cell RNA sequencing (scRNA-seq) to survey the cell types of the sea urchin early pluteus larva, representing an important developmental transition from non-feeding to feeding larva. We identify 21 distinct cell clusters, representing cells of the digestive, skeletal, immune, and nervous systems. Further subclustering of these reveal a highly detailed portrait of cell diversity across the larva, including the identification of neuronal cell types. We then validate important gene regulatory networks driving sea urchin development and reveal new domains of activity within the larval body. Focusing on neurons that co-express Pdx-1 and Brn1/2/4, we identify an unprecedented number of genes shared by this population of neurons in sea urchin and vertebrate endocrine pancreatic cells. Using differential expression results from Pdx-1 knockdown experiments, we show that Pdx1 is necessary for the acquisition of the neuronal identity of these cells. We hypothesize that a network similar to the one orchestrated by Pdx1 in the sea urchin neurons was active in an ancestral cell type and then inherited by neuronal and pancreatic developmental lineages in sea urchins and vertebrates.

Customizing biohybrid cryogels to serve as ready-to-use delivery systems of signaling proteins

Macroporous cryogels have recently gained increasing interest for the controlled administration of signaling proteins in tissue engineering due to an advantageous combination of material properties. However, most of the previously reported cryogel systems did not allow for tunable, sustained protein release. We therefore designed a set of ready-to-use multi-armed polyethylene glycol (starPEG)-heparin cryogel systems containing different amounts of the protein-affine glycosaminoglycan component heparin to enable systematically tunable long-term delivery of different signaling proteins without affecting other cell-instructive properties. Experimental data and mathematical modeling indicate that the macroporous structure causes local differences in the concentration of proteins released into the pores and in the surrounding of the cryogels. As a proof-of-concept for their ready-to-use potential, cryogels pre-functionalized with signaling proteins and cell adhesion-peptides were demonstrated to induce the neuronal differentiation of colonizing pheochromocytoma cells. The elaborated approach opens up new perspectives for cryogels as easily storable and applicable systems for the precision delivery of signaling proteins.

Protein hydrolysates from Pleurotus geesteranus obtained by simulated gastrointestinal digestion exhibit neuroprotective effects in H2 O2 -injured PC12 cells

Neurodegenerative diseases are considered to be among the diseases most threatening to human beings. Increasing evidence shows that antioxidant hydrolysates/peptides with neuroprotective effects may relieve neurodegenerative diseases. However, related research in mushrooms, one of the richest sources of antioxidant hydrolysates/peptides, is in its infancy. Therefore, the in vitro neuroprotective effects of protein hydrolysates from Pleurotus geesteranus were researched in this study. Proteins were extracted from P. geesteranus and then hydrolyzed by simulated gastrointestinal digestion. The neuroprotective effects of the protein hydrolysates were evaluated by H₂ O₂ -injured PC12 cells. The hydrolysates showed a superior antioxidative ability and had a higher abundance of hydrophobic amino acids (e.g., leucine, alanine, and phenylalanine). Neither cytotoxicity nor the increase of ROS in PC12 cells was observed under treatment with the hydrolysates. However, pre-treatment with the hydrolysates in PC12 cells, which were then injured by H₂ O₂ , markedly attenuated ROS generation and enhanced the activities and mRNA expression of the endogenous antioxidant enzymes (catalase (CAT), glutathione peroxidase (GPx), and superoxide dismutase (SOD)), leading to a 26.68% increase in cell viability. The hydrolysates exhibited strong neuroprotective activity in H₂ O₂ -injured PC12 cells, possibly by reducing ROS generation and enhancing the activity of the antioxidant enzymatic system. PRACTICAL APPLICATIONS: Antioxidant hydrolysates with neuroprotection were obtained from Pleurotus geesteranus proteins by simulating gastrointestinal digestion, which exhibited an excellent pre-protective effect in oxidatively damaged PC12 cells. Further study showed that hydrolysates pre-protection may exert antioxidant activities not only as an exogenous antioxidant to scavenge ROS but also as a gene regulator to modulate the endogenous antioxidant enzymes gene expression. These results indicated that the potential of antioxidant peptides, derived from P. geesteranus through gastrointestinal digestion, could serve as a source of bioactive molecules in the prevention, relief or even treatment of neurodegenerative disorders.

Metabolomics analysis of poly(l-lactic acid) nanofibers' performance on PC12 cell differentiation

The aim of this article is to reveal the influence of aligned/random poly(l-lactic acid) (PLLA) nanofibers on PC12 cell differentiation from the perspective of metabolic level. First, three materials-PLLA aligned nanofibers (PLLA AF), PLLA random nanofibers (PLLA RF) and PLLA films (control)-were prepared by electrospinning and spin coating. Their surface morphologies were characterized. Subsequently, the cell viability, cell morphology and neurite length of PC12 cells on the surface of the three materials were evaluated, indicating more neurites in the PLLA RF groups but the longer average neurite length in the PLLA AF groups. Next, the metabolite profiles of PC12 cells cultured on the surface of the three nanofibers after 12 h, 24 h and 36 h showed that, compared with the control, 51, 48 and 31 types of differential metabolites were detected at the three time points among the AF groups, respectively; and 56, 45 and 41 types among the RF groups, respectively. Furthermore, the bioinformatics analysis of differential metabolites identified two pathways and three metabolites critical to PC12 cell differentiation influenced by the nanofibers. In addition, the verification experiment on critical metabolites and metabolic pathways were performed. The integrative analysis combining cytology, metabolomics and bioinformatics approaches revealed that though both PLLA AF and RF were capable of stimulating the synthesis of neurotransmitters, the PLLA AF were more beneficial for PC12 cell differentiation, whereas the PLLA RF were less effective.

Utilization of GelMA with phosphate glass fibers for glial cell alignment

Glial cell alignment in tissue engineered constructs is essential for achieving functional outcomes in neural recovery. While gelatin methacrylate (GelMA) hydrogel offers superior biocompatibility along with permissive structure and tailorable mechanical properties, phosphate glass fibers (PGFs) can provide physical cues for directionality of neural growth. Aligned PGFs were fabricated by a melt quenching and fiber drawing method and utilized with synthesized GelMA hydrogel. The mechanical properties of GelMA and biocompatibility of the GelMA-PGFs composite were investigated in vitro using rat glial cells. GelMA with 86% methacrylation degree were photo-crosslinked using 0.1%wt photo-initiator (PI). Photocrosslinking under UV exposure for 60 s was used to produce hydrogels (GelMA-60). PGFs were introduced into the GelMA before crosslinking. Storage modulus and loss modulus of GelMA-60 was 24.73 ± 2.52 and 1.08 ± 0.23 kN/m² , respectively. Increased cell alignment was observed in GelMA-PGFs compared with GelMA hydrogel alone. These findings suggest GelMA-PGFs can provide glial cells with physical cues necessary to achieve cell alignment. This approach could further be used to achieve glial cell alignment in bioengineered constructs designed to bridge damaged nerve tissue.

Challenges and solutions for fabrication of three-dimensional cocultures of neural cell-loaded biomimetic constructs

Fabrication of three-dimensional (3D) constructs to model body tissues and organs can contribute to research into tissue development and models for studying disease, as well as supporting preclinical drug screening in vitro. Furthermore, 3D constructs can also be used for diagnosis and therapy of disease conditions via lab on a chip and microarrays for diagnosis and engineered products for tissue repair, replacement, and regeneration. While cell culture approaches for studying tissue development and disease in two dimensions are long-established, the translation of this knowledge into 3D environments remains a fertile field of research. In this Tutorial, we specifically focus on the application of biosynthetic hydrogels for neural cell encapsulation. The Tutorial briefly covers background on using biosynthetic hydrogels for cell encapsulation, as well as common fabrication techniques. The Methods section focuses on the hydrogel design and characterization, highlighting key elements and tips for more effective approaches. Coencapsulation of different cell types, and the challenges associated with different growth and maintenance requirements, is the main focus of this Tutorial. Much care is needed to blend different cell types, and this Tutorial provides tips and insights that have proven successful for 3D coculture in biosynthetic hydrogels.

Enhanced Neural Differentiation Using Simultaneous Application of 3D Scaffold Culture, Fluid Flow, and Electrical Stimulation in Bioreactors

Neural differentiation is studied using a simultaneous application of 3D scaffold culture and hydrodynamic and electrical stimuli in purpose-designed recirculation bioreactors operated with continuous fluid flow. Pheochromocytoma (PC12) cells are seeded into nonwoven microfibrous viscose-rayon scaffolds functionalized with poly-l-lysine and laminin. Compared with the results from static control cultures with and without electrical stimulation and bioreactor cultures with the fluid flow without electrical stimulation, expression levels of the differentiation markers β3-tubulin, shootin1, and ephrin type-A receptor 2 are greatest when cells are cultured in bioreactors with fluid flow combined with in-situ electrical stimulus. Immunocytochemical assessment of neurite development and morphology within the scaffolds confirm the beneficial effects of exposing the cells to concurrent hydrodynamic and electrical treatments. Under the conditions tested, electrical stimulation by itself produces more pronounced levels of cell differentiation than fluid flow alone; however, significant additional improvements in differentiation are achieved by combining these treatments. Fluid flow and electrical stimuli exert independent and noninteractive effects on cellular differentiation, suggesting that interference between the mechanisms of differentiation enhancement by these two treatments is minimal during their simultaneous application. This work demonstrates the beneficial effects of combining several different potent physical environmental stimuli in cell culture systems to promote neurogenesis.

Dental pulp stem cells stimulate neuronal differentiation of PC12 cells

Dental pulp stem cells (DPSCs) secrete neurotrophic factors which may play an important therapeutic role in neural development, maintenance and repair. To test this hypothesis, DPSCs-conditioned medium (DPSCs-CM) was collected from 72 hours serum-free DPSCs cultures. The impact of DPSCs-derived factors on PC12 survival, growth, migration and differentiation was investigated. PC12 cells were treated with nerve growth factor (NGF), DPSCs-CM or co-cultured with DPSCs using Transwell inserts for 8 days. The number of surviving cells with neurite outgrowths and the length of neurites were measured by image analysis. Immunocytochemical staining was used to evaluate the expression of neuronal markers NeuN, microtubule associated protein 2 (MAP-2) and cytoskeletal marker βIII-tubulin. Gene expression levels of axonal growth-associated protein 43 and synaptic protein Synapsin-I, NeuN, MAP-2 and βIII-tubulin were analysed by quantitative polymerase chain reaction (qRT-PCR). DPSCs-CM was analysed for the neurotrophic factors (NGF, brain-derived neurotrophic factor [BDNF], neurotrophin-3, and glial cell-derived neurotrophic factor [GDNF]) by specific ELISAs. Specific neutralizing antibodies against the detected neurotrophic factors were used to study their exact role on PC12 neuronal survival and neurite outgrowth extension. DPSCs-CM significantly promoted cell survival and induced the neurite outgrowth confirmed by NeuN, MAP-2 and βIII-tubulin immunostaining. Furthermore, DPSCs-CM was significantly more effective in stimulating PC12 neurite outgrowths than live DPSCs/PC12 co-cultures over the time studied. The morphology of induced PC12 cells in DPSCs-CM was similar to NGF positive controls; however, DPSCs-CM stimulation of cell survival was significantly higher than what was seen in NGF-treated cultures. The number of surviving PC12 cells treated with DPSCs-CM was markedly reduced by the addition of anti-GDNF, whilst PC12 neurite outgrowth was significantly attenuated by anti-NGF, anti-GDNF and anti-BDNF antibodies. These findings demonstrated that DPSCs were able to promote PC12 survival and differentiation. DPSCs-derived NGF, BDNF and GDNF were involved in the stimulatory action on neurite outgrowth, whereas GDNF also had a significant role in promoting PC12 survival. DPSCs-derived factors may be harnessed as a cell-free therapy for peripheral nerve repair. All experiments were conducted on dead animals that were not sacrificed for the purpose of the study. All the methods were carried out in accordance with Birmingham University guidelines and regulations and the ethical approval is not needed.

A human relevant mixture of persistent organic pollutants (POPs) and perfluorooctane sulfonic acid (PFOS) enhance nerve growth factor (NGF)-induced neurite outgrowth in PC12 cells

Disruption of neurite outgrowth is a marker for neurotoxicity. Persistent organic pollutants (POPs) are potential developmental neurotoxicants. We investigated their effect on neurite outgrowth in PC12 rat pheochromocytoma cells, in absence or presence of nerve growth factor (NGF), an inducer of neuronal differentiation. Cells were exposed for 72 h to a defined mixture of POPs with chemical composition and concentrations based on blood levels in the Scandinavian population. We also evaluated perfluorooctane sulfonic acid (PFOS) alone, the most abundant compound in the POP mixture. Only higher concentrations of POP mixture reduced tetrazolium salt (MTT) conversion. High-content analysis showed a decrease in cell number, but no changes for nuclear and mitochondrial cellular health parameters. Robust glutathione levels were observed in NGF-differentiated cells. Live imaging, using the IncuCyte ZOOM platform indicated ongoing cell proliferation over time, but slower in presence of NGF. The pollutants did not inhibit neuritogenesis, but rather increased NGF-induced neurite length. PFOS induced neurite outgrowth to about 50 % of the level seen with the POP mixture. Neither the POP mixture nor PFOS affected neurite length in the absence of NGF. Our observations indicate that realistic complex mixtures of environmental pollutants can affect neuronal connectivity via NGF-induced neurite outgrowth.

In VitroStudies of Acrylamide Neurotoxicity in Rat Pheochromocytoma (PC12) Cells

This review discusses our studies on molecular mechanisms of acrylamide neurotoxicity by using the rat pheochromocytoma (PC12) cell line. The results showed that: a) acrylamide altered the gross morphology of PC12 cells; b) acrylamide induced neurofilament accumulation in PC12 cells; c) the effects of acrylamide on PC12 cells are consistent with its neurotoxicity in vivo; d) acrylamide stimulated neurofilament protein synthesis in PC12 cells; e) acrylamide did not act via nerve growth factor (NGF) receptor gp140trk to regulate neurofilament synthesis in PC12 cells; f) dexamethasone antagonised NGF and/or acrylamide-induced neurofilament protein synthesis and expression; and g) acrylamide differentially regulated the mRNA levels of three neurofilament subunit genes in PC12 cells. These molecular studies provide the first evidence that: a) there are distinctive and convergent signalling pathways for NGF-regulated and acrylamide-regulated neurofilament expression; b) acrylamide may differentially regulate the expression of each subunit, resulting in aberrant accumulation of neurofilament proteins; and c) there is a dexamethasone-sensitive signalling step common to NGF and acrylamide. These results could partially explain the mechanisms of neurofilament accumulation in distal axonal swellings, a pathognomonic feature of acrylamide neurotoxicity.

Discrimination of cellular developmental states focusing on glycan transformation and membrane dynamics by using BODIPY-tagged lactosyl ceramides

Glycosphingolipids (GSLs) are a group of molecules composed of a hydrophilic glycan part and a hydrophobic ceramide creating a diverse family. GSLs are de novo synthesised from ceramides at the endoplasmic reticulum and Golgi apparatus, and transported to the outer surface of the plasma membrane. It has been known that the glycan structures of GSLs change reflecting disease states. We envisioned that analysing the glycan pattern of GSLs enables distinguishing diseases. For this purpose, we utilised a fluorescently tagged compound, LacCerBODIPY (1). At first, compound 1 was taken up by cultured PC12D cells and transformed into various GSLs. As a result, changes in the GSL patterns of differentiation states of the cells were successfully observed by using an analysis platform, nano-liquid chromatography (LC)-fluorescence detection (FLD)-electrospray ionisation (ESI)-mass spectrometry (MS), which could quantify and provide molecular ions simultaneously. We found that compound 1 remained for about 10 min on the plasma membrane before it was converted into other GSLs. We therefore investigated a more rapid way to discriminate different cellular states by fluorescence recovery after photobleaching, which revealed that it is possible to distinguish the differentiation states as well.

Nicotinic Acetylcholine Receptors of PC12 Cells

Nicotinic acetylcholine receptors (nAChRs) have gained much attention in the scientific community since they play a significant role in multiple physiological and pathophysiological processes. Multiple approaches to study the receptors exist, with characterization of the receptors' functionality at a single cellular level using cell culturing being one of them. Derived from an adrenal medulla tumor, PC12 cells express nicotinic receptor subunits and form functional nicotinic receptors. Thus, the cells offer a convenient environment to address questions related to the functionality of the receptors. The review summarizes the findings on nicotinic receptors' expression and functions which were conducted using PC12 cells. Specific focus is given to α3-containing receptors as well as α7 receptor. Critical evaluation of findings is provided alongside insights into what can still be learned about nAChRs, using PC12 cells.

PC12 Cell Line: Cell Types, Coating of Culture Vessels, Differentiation and Other Culture Conditions

The PC12 cell line is one of the most commonly used in neuroscience research, including studies on neurotoxicity, neuroprotection, neurosecretion, neuroinflammation, and synaptogenesis. Two types of this line are available in the ATCC collection: traditional PC12 cells grown in suspension and well-attached adherent phenotype. PC12 cells grown in suspension tend to aggregate and adhere poorly to non-coated surfaces. Therefore, it is necessary to modify the surface of culture vessels. This paper aims to characterise the use of two distinct variants of PC12 cells as well as describe their differentiation and neuronal outgrowth with diverse NGF concentrations (rat or human origin) on various surfaces. In our study, we evaluated cell morphology, neurite length, density and outgrowth (measured spectrofluorimetrically), and expression of neuronal biomarkers (doublecortin and NeuN). We found that the collagen coating was the most versatile method of surface modification for both cell lines. For adherent cells, the coating was definitely less important, and the poly-d-lysine surface was as good as collagen. We also demonstrated that the concentration of NGF is of great importance for the degree of differentiation of cells. For suspension cells, we achieved the best neuronal characteristics (length and density of neurites) after 14 days of incubation with 100 ng/mL NGF (change every 48 h), while for adherent cells after 3-5 days, after which they began to proliferate. In the PC12 cell line, doublecortin (DCX) expression in the cytoplasm and NeuN in the cell nucleus were found. In turn, in the PC12 Adh line, DCX was not expressed, and NeuN expression was located in the entire cell (both in the nucleus and cytoplasm). Only the traditional PC12 line grown in suspension after differentiation with NGF should be used for neurobiological studies, especially until the role of the NeuN protein, whose expression has also been noted in the cytoplasm of adherent cells, is well understood.

Dopamine, a key factor of mitochondrial damage and neuronal toxicity on rotenone exposure and also parkinsonic motor dysfunction-Impact of asiaticoside with a probable vesicular involvement

Persuasive evidence propose that the toxicity of dopamine in parkinsonism and the loss of dopaminergic neurons are the earliest events during the pathogenesis of Parkinson's disease (PD). In our earlier study, Asiaticoside (AS), a triterpenoid saponin isolated from Centella asiatica was shown to exert a neuroprotective effect against hemiparkinsonism, purportedly due to phosphoinositides (PI)-assisted cytodynamics and synaptic function. Here, we evaluate AS in the modulation of dopamine (DA), mitochondrial integrity and neurite variations in vitro and motor dysfunctions in vivo. PC12 cells challenged with rotenone-(ROT) (0.1 μM/mL) were exposed to AS and l-DOPA (10 mM and 20 μM/mL respectively). The protein expressions of Bax and Bcl-2 that regulate cell death were assessed following neurite length assays. Rats were distributed into 6 groups (6 rats/group): Sham, Vehicle controls, ROT-infused (6 μg/μl/kg), AS- treated (50 mg/kg/day), Drug control, and ROT + L-DOPA-treated (6 mg/kg/day) groups. At the end of the experimental period, the rats were sacrificed after performing motor behavioral analysis, and the striatum was dissected out. The contents of synaptic vesicular and cytosolic DA were analyzed. Further, the levels of striatal PI were also measured. ROT had caused significant reduction in the neurite outgrowth in the exposed PC12 cells while the tested concentrations of AS and l-DOPA can exert their protective effect on the stunted neurite growth. The levels of Bax, Bcl-2, and cytochrome c which were significantly disturbed by ROT, could also be affected by AS thereby suggesting its effect on neurons. AS treatment caused an improved motor performance, vesicular and cytosolic DA, and striatal PI. These pre-clinical findings force us to speculate that AS could be a potential drug candidate in combating ROT-induced variations that are possibly precipitated by varied vesicular trafficking of DA.

GSK3β Regulates Brain Energy Metabolism

GSK3β is a serine threonine kinase implicated in the progression of Alzheimer’s disease. Although the role of GSK3β in growth and pathology has been extensively studied, little is known about the metabolic consequences of GSK3β manipulation, particularly in the brain. Here, we show that GSK3β regulates mitochondrial energy metabolism in human H4 neuroglioma cells and rat PC12-derived neuronal cells and that inhibition of GSK3β in mice in vivo alters metabolism in the hippocampus in a region-specific manner. We demonstrate that GSK3β inhibition increases mitochondrial respiration and membrane potential and alters NAD(P)H metabolism. These metabolic effects are associated with increased PGC-1α protein stabilization, enhanced nuclear localization, and increased transcriptional co-activation. In mice treated with the GSK3β inhibitor lithium carbonate, changes in hippocampal energy metabolism are linked to increased PGC-1α. These data highlight a metabolic role for brain GSK3β and suggest that the GSK3β/PGC-1α axis may be important in neuronal metabolic integrity.

Electrical stimulation of cell growth and neurogenesis using conductive and nonconductive microfibrous scaffolds

The effect of exogenous electrical stimulation on cell viability, attachment, growth, and neurogenesis was examined using PC12 cells in microfibrous viscose-rayon scaffolds immersed in culture medium. The scaffolds were applied either in their nonconductive state or after coating the fibres with 200 nm of gold to give a scaffold sheet resistivity of (13 ± 1.3) Ω square−1. The cells were treated for 12 days using direct current electrical stimulation of 2 h per day. No cytotoxic effects were observed when up to 500 mV (8.3 mV mm−1) was applied to the scaffolds without gold, or when up to 100 mV (1.7 mV mm−1) was applied to the scaffolds with gold. Compared with unstimulated cells, whereas electrical stimulation significantly enhanced cell growth and attachment in the nonconductive scaffolds without gold, similar effects were not found for the conductive scaffolds with gold. Neural differentiation in the presence of nerve growth factor was improved by electrical stimulation in both scaffolds; however, neurite development and the expression of key differentiation markers were greater in the nonconductive scaffolds without gold than in the scaffolds with gold. Application of the same current to scaffolds with and without gold led to much higher levels of neurogenesis in the scaffolds without gold. This work demonstrates that substantial benefits in terms of cell growth and neural differentiation can be obtained using electric fields exerted across nonconductive microfibrous scaffolds, and that this approach to electrical stimulation can be more effective than when the stimulus is applied to cells on conductive scaffolds.

Transcriptome profiles of corticosterone-induced cytotoxicity reveals the involvement of neurite growth-related genes in depression

Corticosterone (CORT), the main HPA-axis glucocorticoid hormone in rodents, is involved in the regulation of animal stress responses. However, the neural mechanisms underlying the effects of corticosteroids on depression are yet to be elucidated. We found that fluoxetine reversed neurite growth inhibition induced by CORT in PC12 cells, a widely used model system for neurobiological and neurotoxicological studies. Transcriptome profiling showed that 1,609 genes were up-regulated, whereas 1,764 genes were down-regulated significantly in the CORT group in comparison with the Control group. Of them, the expression of 589 DEGs was reversed after fluoxetine treatment, and genes related to cell morphogenesis, neurite growth, and immune function were involved in the neuroprotective effect of fluoxetine against CORT. Furthermore, expression of neurite growth-related genes, such as such as Calpain 2 (Capn2), vesicle-associated membrane protein 7 (Vamp7) and C-type natriuretic peptide (Cnp), altered in a brain region- or treatment-specific manner in the animal models of depression. Therefore, the interaction between stress, glucocorticoids, and neurite growth inhibition may be a candidate pathophysiology underlying major depressive disorder (MDD), and the identification of Capn2, Vamp7 and Cnp might provide insight into treatment of MDD.

Tuftelin Is Required for NGF-Induced Differentiation of PC12 Cells

Nerve growth factor (NGF) promotes pleiotropic gene transcription-dependent biological effects, in neuronal and non-neuronal cells, including survival, proliferation, differentiation, neuroprotection, pain, and angiogenesis. It is hypothesized that during odontogenesis, NGF may be implicated in morphogenetic and mineralization events by affecting proliferation and/or differentiation of dental cells. Tuftelin belongs to the enamel associated teeth proteins and is thought to play a role in enamel mineralization. We previously reported that tuftelin transcript and protein, which are ubiquitously expressed in various tissues of embryos, adults, and tumors, were significantly upregulated during NGF-induced PC12 differentiation. To further confirm the involvement of tuftelin in the differentiation process, we established a tuftelin-knockdown neuronal PC12 cell model, using a non-cytotoxic siRNA directed towards sequences at the 3' UTR of the tuftelin gene. Using real-time PCR, we quantified tuftelin mRNA expression and found that tuftelin siRNA, but not scrambled siRNA or transfection reagents, efficiently depleted about 60% of NGF-induced tuftelin mRNA transcripts. The effect of tuftelin siRNA was quantified up to 6 days of NGF-induced differentiation. Using immunofluorescence and western blot analyses, we also found a direct correlation between reduction of 60-80% in tuftelin protein expression and inhibition of about 50-70% in NGF-induced differentiation of the cells, as was detected after 3-6 days of treatment. These results demonstrate an important role for tuftelin in NGF-induced differentiation of PC12 cells. Tuftelin could be a useful target for drug development in disease where neurotrophin therapy is required.

Differential gene expression profile analysis in corticosterone-treated PC12 cells

Major depressive disorder (MDD) is a highly prevalent psychiatric disorder that has been ranked as the 4th leading cause of disability worldwide. Past clinical and laboratory evidence has confirmed that abnormalities of the hypothalamic-pituitary-adrenal (HPA)-axis are involved in MDD development. In this study, we took advantage of corticosterone treatment of PC12 cells as a model to identify genes regulated by HPA-axis hormones. Next-generation RNA-Seq technology was utilized to explore genome-wide differentially expressed gene profiles between control and corticosterone treated PC12 cells. 1,274 genes with at least two-fold expression level change were identified. Gene ontology analysis showed that the top enriched biological processes included response to glucocorticoid signaling, apoptosis, cell division/DNA replication, and neuron projection/axon guidance, highly consistent with phenotypes of PC12 cells treated with corticosterone. Taken together, RNA-seq data is reliable and comprehensive, thus providing a valuable resource for understanding underlying mechanisms of glucocorticoid-induced neuron malfunction.

Methylene-Cycloalkylacetate (MCA) Scaffold-Based Compounds as Novel Neurotropic Agents

One of the main symptoms in degenerative diseases is death of neuronal cell followed by the loss of neuronal pathways. In neuronal cultures, neurite outgrowths are cell sprouts capable of transforming into either axons or dendrites, to further form functional neuronal synaptic connections. Such connections have an important role in brain cognition, neuronal plasticity, neuronal survival, and regeneration. Therefore, drugs that stimulate neurite outgrowth may be found beneficial in ameliorating neural degeneration. Here, we establish the existence of a unique family of methylene-cycloalkylacetate-based molecules (MCAs) that interface with neuronal cell properties and operate as acceptable pharmacophores for a novel neurotropic (neurite outgrowth inducing) lead compounds. Using an established PC12 cell bioassay, we investigated the neurotropic effect of methylene-cycloalkylacetate compounds by comparison to NGF, a known neurotropic factor. Micrographs of the cells were collected by using a light microscope camera, and digitized photographs were analyzed for compound-induced neurotropic activity using an NIH image protocol. The results indicate that the alkene element, integrated within the cycloalkylacetate core, is indispensable for neurotropic activity. The discovered lead compounds need further mechanistic investigation and may be improved toward development of a neurotropic drug.

Design and validation of an ontology-driven animal-free testing strategy for developmental neurotoxicity testing

Developmental neurotoxicity entails one of the most complex areas in toxicology. Animal studies provide only limited information as to human relevance. A multitude of alternative models have been developed over the years, providing insights into mechanisms of action. We give an overview of fundamental processes in neural tube formation, brain development and neural specification, aiming at illustrating complexity rather than comprehensiveness. We also give a flavor of the wealth of alternative methods in this area. Given the impressive progress in mechanistic knowledge of human biology and toxicology, the time is right for a conceptual approach for designing testing strategies that cover the integral mechanistic landscape of developmental neurotoxicity. The ontology approach provides a framework for defining this landscape, upon which an integral in silico model for predicting toxicity can be built. It subsequently directs the selection of in vitro assays for rate-limiting events in the biological network, to feed parameter tuning in the model, leading to prediction of the toxicological outcome. Validation of such models requires primary attention to coverage of the biological domain, rather than classical predictive value of individual tests. Proofs of concept for such an approach are already available. The challenge is in mining modern biology, toxicology and chemical information to feed intelligent designs, which will define testing strategies for neurodevelopmental toxicity testing.

Developmental neurotoxicity resulting from pharmacotherapy of preterm labor, modeled in vitro: Terbutaline and dexamethasone, separately and together

Terbutaline and dexamethasone are used in the management of preterm labor, often for durations of treatment exceeding those recommended, and both have been implicated in increased risk of neurodevelopmental disorders. We used a variety of cell models to establish the critical stages at which neurodifferentiation is vulnerable to these agents and to determine whether combined exposures produce a worsened outcome. Terbutaline selectively promoted the initial emergence of glia from embryonic neural stem cells (NSCs). The target for terbutaline shifted with developmental stage: at later developmental stages modeled with C6 and PC12 cells, terbutaline had little effect on glial differentiation (C6 cells) but impaired the differentiation of neuronotypic PC12 cells into neurotransmitter phenotypes. In contrast to the specificity shown by terbutaline, dexamethasone affected both neuronal and glial differentiation at all stages, impairing the emergence of both cell types in NSCs but with a much greater impairment for glia. At later stages, dexamethasone promoted glial cell differentiation (C6 cells), while shifting neuronal cell differentiation so as to distort the balance of neurotransmitter phenotypes (PC12 cells). Finally, terbutaline and dexamethasone interacted synergistically at the level of late stage glial cell differentiation, with dexamethasone boosting the ability of terbutaline to enhance indices of glial cell growth and neurite formation while producing further decrements in glial cell numbers. Our results support the conclusion that terbutaline and dexamethasone are directly-acting neuroteratogens, and further indicate the potential for their combined use in preterm labor to worsen neurodevelopmental outcomes.

Neuroprotective Effects of Bioactive Compounds and MAPK Pathway Modulation in "Ischemia"-Stressed PC12 Pheochromocytoma Cells

This review surveys the efforts taken to investigate in vitro neuroprotective features of synthetic compounds and cell-released growth factors on PC12 clonal cell line temporarily deprived of oxygen and glucose followed by reoxygenation (OGD/R). These cells have been used previously to mimic some of the properties of in vivo brain ischemia-reperfusion-injury (IRI) and have been instrumental in identifying common mechanisms such as calcium overload, redox potential, lipid peroxidation and MAPKs modulation. In addition, they were useful for establishing the role of certain membrane penetrable cocktails of antioxidants as well as potential growth factors which may act in neuroprotection. Pharmacological mechanisms of neuroprotection addressing modulation of the MAPK cascade and increased redox potential by natural products, drugs and growth factors secreted by stem cells, in either undifferentiated or nerve growth factor-differentiated PC12 cells exposed to ischemic conditions are discussed for future prospects in neuroprotection studies.

Brominated and organophosphate flame retardants target different neurodevelopmental stages, characterized with embryonic neural stem cells and neuronotypic PC12 cells

In addition to their activity as endocrine disruptors, brominated and organophosphate flame retardants are suspected to be developmental neurotoxicants, although identifying their specific mechanisms for that activity has been elusive. In the current study, we evaluated the effects of several flame retardants on neurodifferentiation using two in vitro models that assess distinct "decision nodes" in neural cell development: embryonic rat neural stem cells (NSCs), which evaluate the origination of neurons and glia from precursors, and rat neuronotypic PC12 cells, which characterize a later stage where cells committed to a neuronal phenotype undergo neurite outgrowth and neurotransmitter specification. In NSCs, both brominated and organophosphate flame retardants diverted the phenotype in favor of glia and away from formation of neurons, leading to an increased glia/neuron ratio, a common hallmark of the in vivo effects of neurotoxicants. For this early decision node, the brominated flame retardants were far more potent than the organophosphates. In PC12 cells, the brominated flame retardants were far less effective, whereas tris (1,3-dichloro-2-propyl) phosphate, an organophosphate, was more effective. Thus, the two classes of flame retardants differentially impact the two distinct vulnerable periods of neurodifferentiation. Furthermore, the effects on neurodifferentiation were separable from outright cytotoxicity, an important requirement in establishing a specific effect of these agents on neural cell development. These results reinforce the likelihood that flame retardants act as developmental neurotoxicants via direct effects on neural cell differentiation, over and above other activities that can impact nervous system development, such as endocrine disruption.

In vitro biocompatibility and electrical stability of thick-film platinum/gold alloy electrodes printed on alumina

OBJECTIVE

High-density electrode arrays are a powerful tool in both clinical neuroscience and basic research. However, current manufacturing techniques require the use of specialised techniques and equipment, which are available to few labs. We have developed a high-density electrode array with customisable design, manufactured using simple printing techniques and with commercially available materials.

APPROACH

Electrode arrays were manufactured by thick-film printing a platinum-gold alloy (Pt/Au) and an insulating dielectric on 96% alumina ceramic plates. Arrays were conditioned in serum and serum-free conditions, with and without 1 kHz, 200 µA, charge balanced stimulation for up to 21 d. Array biocompatibility was assessed using an extract assay and a PC-12 cell contact assay. Electrode impedance, charge storage capacity and charge injection capacity were before and after array conditioning.

MAIN RESULTS

The manufactured Pt/Au electrodes have a highly porous surface and exhibit electrical properties comparable to arrays manufactured using alternative techniques. Materials used in array manufacture were found to be non-toxic to L929 fibroblasts by extract assay, and neuronal-like PC-12 cells adhered and extended neurites on the array surfaces. Arrays remained functional after long-term delivery of electrical pulses while exposed to protein-rich environments. Charge storage capacities and charge injection capacities increased following stimulation accounted for by an increase in surface index (real surface area) observed by vertical scanning interferometry. Further, we observed accumulation of proteins at the electrode sites following conditioning in the presence of serum.

SIGNIFICANCE

This study demonstrates the in vitro biocompatibility of commercially available thick-film printing materials. The printing technique is both simple and versatile, with layouts readily modified to produce customized electrode arrays. Thick-film electrode arrays are an attractive tool that may be implemented for general tissue engineering and neuroscience research.

Probing the response of human osteoblasts following exposure to sympathetic neuron-like PC-12 cells in a 3D coculture model

Understanding the capacity of the sympathetic nervous system (SNS) to regulate bone homeostasis has implications for a number of metabolic diseases and may help establish connections between certain neurological conditions and bone quality. The goal of the present work was to gain a deeper understanding of the influence of the SNS on the phenotype of osteoblasts, a major cell type in bone. An in vitro coculture model with human osteoblasts and sympathetic-like, neuroendocrine pheochromocytoma-12 (PC-12) cells encapsulated within separate 3D poly(ethylene glycol) diacrylate (PEGDA) hydrogels was utilized to assess markers involved with bone ECM formation and osteoclast formation. In terms of bone ECM proteins, only osteopontin (OPN) was significantly increased in osteoblasts exposed to PC-12 cells relative to osteoblast mono-culture controls. In contrast, all bone resorption markers investigated (IL-6, TNF, IL-1β, VEGF-A) were enhanced at the gene level and the ratio of osteoprotegerin (OPG) to RANKL was significantly decreased in osteoblasts exposed to PC-12 cells. Cumulatively, these data indicate that the SNS may substantially influence bone resorption. Because of the context-dependent nature of the SNS, future studies will characterize the secretion profile of neurotransmitters and neuropeptides from the PC-12 cells in our model. Additionally, various SNS modulating pharmacologic agents will be examined for their capacity to reduce expression of bone resorption/inflammatory markers. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 984-990, 2017.

In vitro models reveal differences in the developmental neurotoxicity of an environmental polycylic aromatic hydrocarbon mixture compared to benzo[a]pyrene: Neuronotypic PC12 Cells and embryonic neural stem cells

In addition to their carcinogenic activity, polycyclic aromatic hydrocarbons (PAHs) are suspected to be developmental neurotoxicants. We evaluated the effects of PAHs with two in vitro models that assess distinct "decision nodes" in neurodifferentiation: neuronotypic PC12 cells, which characterize the transition from cell replication to neurodifferentiation, neurite outgrowth and neurotransmitter specification; and embryonic neural stem cells (NSCs), which evaluate the origination of neurons and glia from precursors. We compared an environmentally-derived PAH mixture from a Superfund contamination site (Elizabeth River Sediment Extract, ERSE) to those of a single PAH, benzo[a]pyrene (BaP). In PC12 cells, BaP impaired the transition from cell replication to neurodifferentiation, resulting in higher numbers of cells, but with reduced cell size and deficits in all indices of neuronal features (neurite formation, development of dopamine and acetylcholine phenotypes). ERSE was far less effective, causing only modest changes in cell numbers and size and no impairment of neurite formation or neurotransmitter specification; in fact, ERSE evoked a slight increase in emergence of the acetylcholine phenotype. In the NSC model, this relationship was entirely reversed, with far greater sensitivity to ERSE than to BaP. Furthermore, ERSE, but not BaP, enhanced NSC differentiation into neurons, whereas both ERSE and BaP suppressed the glial phenotype. Our studies provide a cause-and-effect relationship for the observed association of developmental PAH exposure to behavioral deficits. Further, PAH sensitivity occurs over developmental stages corresponding to rudimentary brain formation through terminal neurodifferentiation, suggesting that vulnerability likely extends throughout fetal brain development and into early childhood.

Epidermal growth factor prevents thallium(I)- and thallium(III)-mediated rat pheochromocytoma (PC12) cell apoptosis

We have reported recently that the proliferation of PC12 cells exposed to micromolar concentrations of Tl(I) or Tl(III) has different outcomes, depending on the absence (EGF^- cells) or the presence (EGF⁺ cells) of epidermal growth factor (EGF) added to the media. In the current work, we investigated whether EGF supplementation could also modulate the extent of Tl(I)- or Tl(III)-induced cell apoptosis. Tl(I) and Tl(III) (25-100 μM) decreased cell viability in EGF^- but not in EGF⁺ cells. In EGF^- cells, Tl(I) decreased mitochondrial potential, enhanced H₂O₂ generation, and activated mitochondrial-dependent apoptosis. In addition, Tl(III) increased nitric oxide production and caused a misbalance between the anti- and pro-apoptotic members of Bcl-2 family. Tl(I) increased ERK1/2, JNK, p38, and p53 phosphorylation in EGF^- cells. In these cells, Tl(III) did not affect ERK1/2 and JNK phosphorylation but increased p53 phosphorylation that was related to the promotion of cell senescence. In addition, this cation significantly activated p38 in both EGF^- and EGF⁺ cells. The specific inhibition of ERK1/2, JNK, p38, or p53 abolished Tl(I)-mediated EGF^- cell apoptosis. Only when p38 activity was inhibited, Tl(III)-mediated apoptosis was prevented in EGF^- and EGF⁺ cells. Together, current results indicate that EGF partially prevents the noxious effects of Tl by preventing the sustained activation of MAPKs signaling cascade that lead cells to apoptosis and point to p38 as a key mediator of Tl(III)-induced PC12 cell apoptosis.

Effects of striatal transplantation of cells transfected with GDNF gene without pre- and pro-regions in mouse model of Parkinson's disease

Background

Previously, we have shown that transgenic cells bearing the GDNF gene with deleted pre- and pro-regions (mGDNF) can release transgenic GDNF. The medium conditioned by transgenic cells with mGDNF induced axonal growth in rat embryonic spinal ganglion in vitro. Here we demonstrate a neurotrophic effect of mGDNF on PC12 cells in vitro as well as its neuroprotective effect on dopaminergic neurons in the substantia nigra pars compacta in vivo as indicated by improved motor coordination and sleep-wakefulness cycle in the MPTP mouse model of Parkinson’s disease.

Results

HEK293 cells were transfected with a vector encoding an isoform of the human GDNF gene with deleted pre- and pro-regions (mGDNF). This factor in the medium conditioned by the transfected cells was shown to induce axonal growth in PC12 cells. The early Parkinson’s disease model was established by injection of the dopaminergic pro-neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) into C57Bl/6 mice. Transgenic HEK293/mGDNF/GFP cells were transplanted into the striatum (caudate-putamen) of experimental mice. The sleep-wakefulness cycle was studied by continuous EEG and motor activity monitoring 1 and 2 weeks after MPTP injection. After the experiment, the motor coordination of experimental animals was evaluated in the rotarod test, and dopaminergic neurons in the substantia nigra pars compacta were counted in cross-sections of the midbrain. MPTP administration lowered the number of tyrosine hydroxylase immunopositive cells in the substantia nigra pars compacta, decreased motor coordination, and increased the total wake time during the dark period. The transplantation of HEK293/mGDNF cells into the caudate-putamen 3 days prior to MPTP injection smoothed these effects, while the control transplantation of HEK293 cells showed no notable impact.

Conclusions

Transplantation of transgenic cells with the GDNF gene lacking the pre- and pro-sequences can protect dopaminergic neurons in the mouse midbrain from the subsequent administration of the pro-neurotoxin MPTP, which is confirmed by polysomnographic, behavioral and histochemical data. Hence it is released from transfected cells and preserves the differentiation activity and neuroprotective properties.

Target genes involved in corticosterone-induced PC12 cell viability and neurite disorders: A potential molecular mechanism of major depressive disorder

Past studies confirmed that hypothalamic-pituitary-adrenal (HPA)-axis hormones involved in major depressive disorder (MDD) development. This study used corticosterone treated PC12 cells to explore the potential role of MAPK signal transduction pathway in response to corticosterone stimulation. The results showed that both live cell numbers and cellular neurite outgrowth were remarkably reduced in response to corticosterone treatments. qPCR results demonstrated that the expression levels of four MAPK pathway genes were significantly increased after corticosterone stimulation. In conclusion, glucocorticoids stimulation can affect neuronal cell viability and neurite outgrowth due to the over expression of a group of MAPK pathway genes.

Possible involvement of basic FGF in the upregulation of PDGFRβ in pericytes after ischemic stroke

Central nervous system (CNS) pericytes have been recognized as an indispensable component of the neurovascular unit. The expression of platelet-derived growth factor receptor β (PDGFRβ) is markedly increased in CNS pericytes after brain ischemia. It has been elucidated that PDGFRβ, expressed in pericytes and pericyte-derived fibroblast-like cells, plays important roles in the maintenance of the blood-brain barrier (BBB) and in the repair process in infarct areas. The aim of this study was to uncover how the PDGFRβ expression is regulated in pericytes after brain ischemia. We found that basic fibroblast growth factor (bFGF), but neither hypoxia at 1% O2 nor acidification at pH 6.5, significantly upregulated the PDGFRβ expression in human cultured CNS pericytes. SU5402, an inhibitor of FGF receptor (FGFR), and inhibitors of its downstream effectors Akt and Erk abolished the bFGF-induced upregulation of PDGFRβ. On the other hand, acidification significantly upregulated the expression of bFGF, while hypoxia upregulated the expression of FGFR1 in the pericytes. The expression of bFGF and FGFR1 was markedly induced in the ischemic hemisphere after ischemic insult in a middle cerebral artery occlusion stroke model. Immunofluorescent double labeling demonstrated that the expression of bFGF and FGFR1 was co-localized with PDGFRβ-positive cells in peri-infarct areas. Moreover, treatment with bFGF enhanced cell growth and the PDGF-BB-induced migratory activity of cultured pericytes, which were significantly suppressed by SU5402 or Sunitinib, an inhibitor of PDGFR. These data suggested that increased bFGF upregulates the expression of PDGFRβ and may enhance PDGFRβ-mediated pericyte functions after brain ischemia.

Toxic and transcriptional responses of PC12 cells to soluble tungsten alloy surrogates

There is increasing evidence that metals have a role in the etiology of diverse neurological diseases. This study used PC12 cells as an in vitro model to examine the toxicity of tungsten alloys that have important military applications. Initially, the relative concentrations of tungsten (W), nickel (Ni), and cobalt (Co) mobilized from pellets of a weapons-grade tungsten alloy incubated in physiologically relevant solutions were determined. Dosing solutions of soluble metal salts that were equivalent in ratio to those mobilized from these alloy pellets were used to treat nerve growth factor (NGF) differentiated PC12 cells. Treatments consisted of single (W, Ni or Co), paired (W/Ni, W/Co or Ni/Co) or complete (W/Ni/Co) metal exposures for 24 h followed by measurement of cytotoxicity, viability, and microarray analysis to examine their impact on survival and viability, global gene expression, and biological processes. Gene expression changed dramatically with addition of NGF. Addition of Ni or Co either singly or in combination further impacted gene expression. An observed additive effect of Ni and Co on gene expression was unaffected by the addition of W. The work showed that tungsten, as found in this tungsten alloy, had minimal relative toxicity as compared to the other alloy components when used either alone or in combination.

Growth factor choice is critical for successful functionalization of nanoparticles

Nanoparticles (NPs) show new characteristics compared to the corresponding bulk material. These nanoscale properties make them interesting for various applications in biomedicine and life sciences. One field of application is the use of magnetic NPs to support regeneration in the nervous system. Drug delivery requires a functionalization of NPs with bio-functional molecules. In our study, we functionalized self-made PEI-coated iron oxide NPs with nerve growth factor (NGF) and glial cell-line derived neurotrophic factor (GDNF). Next, we tested the bio-functionality of NGF in a rat pheochromocytoma cell line (PC12) and the bio-functionality of GDNF in an organotypic spinal cord culture. Covalent binding of NGF to PEI-NPs impaired bio-functionality of NGF, but non-covalent approach differentiated PC12 cells reliably. Non-covalent binding of GDNF showed a satisfying bio-functionality of GDNF:PEI-NPs, but turned out to be unstable in conjugation to the PEI-NPs. Taken together, our study showed the importance of assessing bio-functionality and binding stability of functionalized growth factors using proper biological models. It also shows that successful functionalization of magnetic NPs with growth factors is dependent on the used binding chemistry and that it is hardly predictable. For use as therapeutics, functionalization strategies have to be reproducible and future studies are needed.

Deletion of the Neurotrophic Factor neudesin Prevents Diet-induced Obesity by Increased Sympathetic Activity

Some neurotrophic factors, which are potent regulators of neuronal development and function, have recently been implicated in the control of energy balance by increasing energy expenditure. We previously identified neudesin as a novel neurotrophic factor with potential roles in the central nervous system. Although neudesin is also expressed in various peripheral tissues including adipose tissue, its physiological roles have not yet been elucidated. We found that neudesin knockout (KO) mice were resistant to high-fat diet-induced obesity and obesity-related metabolic dysfunctions. neudesin KO mice exhibited increased energy expenditure due to increased sympathetic activity, which resulted in increased heat production and fatty acid oxidation in brown adipose tissue and enhanced lipolysis in white adipose tissue. Thus, neudesin, which may be a negative regulator of sympathetic activity, could represent a novel regulator of the development of obesity and obesity-related metabolic dysfunctions.

Amelioration strategies fail to prevent tobacco smoke effects on neurodifferentiation: Nicotinic receptor blockade, antioxidants, methyl donors

Tobacco smoke exposure is associated with neurodevelopmental disorders. We used neuronotypic PC12 cells to evaluate the mechanisms by which tobacco smoke extract (TSE) affects neurodifferentiation. In undifferentiated cells, TSE impaired DNA synthesis and cell numbers to a much greater extent than nicotine alone; TSE also impaired cell viability to a small extent. In differentiating cells, TSE enhanced cell growth at the expense of cell numbers and promoted emergence of the dopaminergic phenotype. Nicotinic receptor blockade with mecamylamine was ineffective in preventing the adverse effects of TSE and actually enhanced the effect of TSE on the dopamine phenotype. A mixture of antioxidants (vitamin C, vitamin E, N-acetyl-l-cysteine) provided partial protection against cell loss but also promoted loss of the cholinergic phenotype in response to TSE. Notably, the antioxidants themselves altered neurodifferentiation, reducing cell numbers and promoting the cholinergic phenotype at the expense of the dopaminergic phenotype, an effect that was most prominent for N-acetyl-l-cysteine. Treatment with methyl donors (vitamin B12, folic acid, choline) had no protectant effect and actually enhanced the cell loss evoked by TSE; they did have a minor, synergistic interaction with antioxidants protecting against TSE effects on growth. Thus, components of tobacco smoke perturb neurodifferentiation through mechanisms that cannot be attributed to the individual effects of nicotine, oxidative stress or interference with one-carbon metabolism. Consequently, attempted amelioration strategies may be partially effective at best, or, as seen here, can actually aggravate injury by interfering with normal developmental signals and/or by sensitizing cells to TSE effects on neurodifferentiation.

Protosappanin B protects PC12 cells against oxygen-glucose deprivation-induced neuronal death by maintaining mitochondrial homeostasis via induction of ubiquitin-dependent p53 protein degradation

Protosappanin B (PTB) is a bioactive dibenzoxocin derivative isolated from Caesalpinia sappan L. Here, we investigated the neuroprotective effects and the potential mechanisms of PTB on oxygen-glucose deprivation (OGD)-injured PC12 cells. Results showed that PTB significantly increased cell viability, inhibited cell apoptosis and up-regulated the expression of growth-associated protein 43 (a marker of neural outgrowth). Moreover, our study revealed that PTB effectively maintained mitochondrial homeostasis by up-regulation of mitochondrial membrane potential (MMP), inhibition of cytochrome c release from mitochondria and inactivation of mitochondrial caspase-9/3 apoptosis pathway. Further study showed that PTB significantly promoted cytoplasmic component degradation of p53 protein, a key negative regulator for mitochondrial function, resulting in a release of Bcl-2 from p53-Bcl-2 complex and an enhancing translocation of Bcl-2 to mitochondrial outer membrane. Finally, we found the degradation of p53 protein was induced by PTB via activation of a MDM2-dependent ubiquitination process. Taken together, our findings provided a new viewpoint of neuronal protection strategy for anoxia and ischemic injury with natural small molecular dibenzoxocin derivative by activating ubiquitin-dependent p53 protein degradation as well as increasing mitochondrial function.

Carbon-nanotube-interfaced glass fiber scaffold for regeneration of transected sciatic nerve

Carbon nanotubes (CNTs), with their unique and unprecedented properties, have become very popular for the repair of tissues, particularly for those requiring electrical stimuli. Whilst most reports have demonstrated in vitro neural cell responses of the CNTs, few studies have been performed on the in vivo efficacy of CNT-interfaced biomaterials in the repair and regeneration of neural tissues. Thus, we report here for the first time the in vivo functions of CNT-interfaced nerve conduits in the regeneration of transected rat sciatic nerve. Aminated CNTs were chemically tethered onto the surface of aligned phosphate glass microfibers (PGFs) and CNT-interfaced PGFs (CNT-PGFs) were successfully placed into three-dimensional poly(L/D-lactic acid) (PLDLA) tubes. An in vitro study confirmed that neurites of dorsal root ganglion outgrew actively along the aligned CNT-PGFs and that the CNT interfacing significantly increased the maximal neurite length. Sixteen weeks after implantation of a CNT-PGF nerve conduit into the 10 mm gap of a transected rat sciatic nerve, the number of regenerating axons crossing the scaffold, the cross-sectional area of the re-innervated muscles and the electrophysiological findings were all significantly improved by the interfacing with CNTs. This first in vivo effect of using a CNT-interfaced scaffold in the regeneration process of a transected rat sciatic nerve strongly supports the potential use of CNT-interfaced PGFs at the interface between the nerve conduit and peripheral neural tissues.

Producing 3D neuronal networks in hydrogels for living bionic device interfaces

Hydrogels hold significant promise for supporting cell based therapies in the field of bioelectrodes. It has been proposed that tissue engineering principles can be used to improve the integration of neural interfacing electrodes. Degradable hydrogels based on poly (vinyl alcohol) functionalised with tyramine (PVA-Tyr) have been shown to support covalent incorporation of non-modified tyrosine rich proteins within synthetic hydrogels. PVA-Tyr crosslinked with such proteins, were explored as a scaffold for supporting development of neural tissue in a three dimensional (3D) environment. In this study a model neural cell line (PC12) and glial accessory cell line, Schwann cell (SC) were encapsulated in PVA-Tyr crosslinked with gelatin and sericin. Specifically, this study aimed to examine the growth and function of SC and PC12 co-cultures when translated from a two dimensional (2D) environment to a 3D environment. PC12 differentiation was successfully promoted in both 2D and 3D at 25 days post-culture. SC encapsulated as a single cell line and in co-culture were able to produce both laminin and collagen-IV which are required to support neuronal development. Neurite outgrowth in the 3D environment was confirmed by immunocytochemical staining. PVA-Tyr/sericin/gelatin hydrogel showed mechanical properties similar to nerve tissue elastic modulus. It is suggested that the mechanical properties of the PVA-Tyr hydrogels with native protein components are providing with a compliant substrate that can be used to support the survival and differentiation of neural networks.

Transactivation of P53 by cypermethrin induced miR-200 and apoptosis in neuronal cells

Cypermethrin, a pyrethroid pesticide, has been shown to induce neurotoxicity in adult mammals. However, studies are also needed to explore its toxicity in developing brains and understand its mechanism of action in neurons.

In vitro models for neurotoxicology research

The nervous system has a highly complex organization, including many cell types with multiple functions, with an intricate anatomy and unique structural and functional characteristics; the study of its (dys)functionality following exposure to xenobiotics, neurotoxicology, constitutes an important issue in neurosciences.