Colchicine induces apoptosis in organotypic hippocampal slice cultures

Pumpkin seed oil lessens the colchicine-induced altered sex male hormone balance, testicular oxidative status, sperm abnormalities, and collagen deposition in male rats via Caspase3/Desmin/PCNA modulation

This study examined the efficiency of pumpkin seed oil (PSO) to rescue the colchicine (CHC)-induced adverse impacts on sperm characteristics, male sex hormones, testicular architecture, oxidative status, DNA content, collagen deposition, and immune expression of desmin and PCNA. Male Sprague Dawley rats were divided into four experimental groups (n = 10 each): control (distilled water), CHC (0.6 mg/kg b.wt), PSO (4 mL/kg b.wt), and CHC + PSO. After 60 days of dosing, CHC significantly reduced sperm motility (19%), sperm concentration (38%), estradiol (52%), testosterone (37%), luteinizing hormone (54%), and follicle-stimulating hormone (29%) compared to the control. Yet, the testicular tissues of CHC-administered rats exhibited elevated abnormal sperms (156%), malondialdehyde (354%), lactate dehydrogenase (73%), Caspase-3 (66%), and 8-hydroxyguanosine (65%) but lower reduced glutathione (74%), catalase (73%), and superoxide dismutase (78%) compared to the control group. Moreover, CHC induced testicular degeneration, distorted seminiferous tubules, apoptotic cells, exfoliated spermatogenic cells, reduced DNA content, decreased PCNA and desmin immune-expression, and increased collagen deposition. PSO effectively reversed the CHC-induced alterations in sperm quality and testicular function and architecture, likely through its antioxidant, antifibrotic, anti-apoptotic, and DNA-protective properties. These results suggest that PSO may be a beneficial intervention for long-term CHC users and may protect against CHC-induced male reproductive toxicity.

Stabilizing microtubules aids neurite structure and disrupts syncytia formation in human cytomegalovirus-infected human forebrain neurons

Human cytomegalovirus (HCMV) is a prolific human herpesvirus that infects most individuals by adulthood. While typically asymptomatic in adults, congenital infection can induce serious neurological symptoms including hearing loss, visual deficits, cognitive impairment, and microcephaly in 10-15% of cases. HCMV has been shown to infect most neural cells with our group recently demonstrating this capacity in stem cell-derived forebrain neurons. Infection of neurons induces deleterious effects on calcium dynamics and electrophysiological function paired with gross restructuring of neuronal morphology. Here, we utilize an iPSC-derived model of the human forebrain to demonstrate how HCMV infection induces syncytia, drives neurite retraction, and remodels microtubule networks to promote viral production and release. We establish that HCMV downregulates microtubule associated proteins at 14 days postinfection while simultaneously sparing other cytoskeletal elements, and this includes HCMV-driven alterations to microtubule stability. Further, we pharmacologically modulate microtubule dynamics using paclitaxel (stabilize) and colchicine (destabilize) to examine the effects on neurite structure, syncytial morphology, assembly compartment formation, and viral release. With paclitaxel, we found improvement of neurite outgrowth with a corresponding disruption to HCMV-induced syncytia formation and Golgi network disruptions but with limited impact on viral titers. Together, these data suggest that HCMV infection-induced disruption of microtubules in human cortical neurons can be partially mitigated with microtubule stabilization, suggesting a potential avenue for future neuroprotective therapeutic exploration.

Engineered Nanomaterials: The Challenges and Opportunities for Nanomedicines

The emergence of nanotechnology as a key enabling technology over the past years has opened avenues for new and innovative applications in nanomedicine. From the business aspect, the nanomedicine market was estimated to worth USD 293.1 billion by 2022 with a perception of market growth to USD 350.8 billion in 2025. Despite these opportunities, the underlying challenges for the future of engineered nanomaterials (ENMs) in nanomedicine research became a significant obstacle in bringing ENMs into clinical stages. These challenges include the capability to design bias-free methods in evaluating ENMs' toxicity due to the lack of suitable detection and inconsistent characterization techniques. Therefore, in this literature review, the state-of-the-art of engineered nanomaterials in nanomedicine, their toxicology issues, the working framework in developing a toxicology benchmark and technical characterization techniques in determining the toxicity of ENMs from the reported literature are explored.

Anti-CD133 Antibody-Targeted Therapeutic Immunomagnetic Albumin Microbeads Loaded with Vincristine-Assisted to Enhance Anti-Glioblastoma Treatment

Poor uptake of antitumor drugs by tumor cells is a critical challenge for anticancer therapeutics. Moreover, the deficiency of specific tumor selectivity for tumor sites may further limit the therapeutic efficacy and cause side effects in healthy regions of the body. Vincristine (VCR) is an effective antitumor drug; however, because of its severe nerve toxicity, short half-life, and fast metabolism, its clinical application is limited. Herein, novel anti-CD133 monoclonal antibody (^CD133mAb)-targeted therapeutic immunomagnetic albumin microbeads (^CD133mAb/TMAMbs) are smartly constructed for enhancing antiglioblastoma treatment. Superparamagnetic iron oxide nanoparticles (SPIO NPs) were first fabricated as nanocarrier cores, then encapsulated with human serum albumin (HSA), and loaded antitumor drug VCR. Then ^CD133mAb, which has specific affinity with the cell membrane CD133, was subsequently conjugated to form ^CD133mAb-decorated therapeutic immunomagnetic albumin microbeads (^CD133mAb/TMAMbs). The influence of ^CD133mAb/TMAMbs on the viability, cell cycle, apoptosis, cell cytoskeleton, migration, and invasion of CD133-overexpressing U251 cells was explored. The ^CD133mAb-conjugated magnetic albumin microbeads exhibited a high drug loading capacity, stability and hemocompatibility, and active targeting ability by specific recognition of the CD133 surface antigen by the bioconjugation of ^CD133mAb. More importantly, the constructed therapeutic ^CD133mAb/TMAMbs have a specifically effective uptake via the CD133 transmembrane protein that is overexpressed in U251 glioblastoma cells and displayed an effective antitumor proliferation and invasive ability. Therefore, based on these results, the fabricated ^CD133mAb/TMAMbs demonstrate promising uses in brain cancer-targeted diagnosis and therapy.

Organotypic Brain Slice Cultures: An Efficient and Reliable Method for Neurotoxicological Screening and Mechanistic Studies

This paper reviews the current state of the use of organotypic brain slice cultures for neurotoxicological and neuropharmacological screening and mechanistic studies, as exemplified by excitotoxin application. At present, no in vitro systems have been approved by the regulatory authorities for neurotoxicity testing. For the evaluation of the slice culture method, organotypic hippocampal slice cultures were exposed to toxic doses of the excitotoxins, glutamate, N-methyl-D-aspartate (NMDA), kainic acid and 2-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA), and the glial toxin, DL-alpha-aminoadipic acid (DLAAA). Neuronal cell death was quantified by propidium iodide (PI) uptake, and visualised by Fluoro-Jade (FJ) staining. General cell death was monitored by lactate dehydrogenase (LDH) release into the culture medium. EC50 values for the different compounds, based on PI uptake after exposure for 48 hours in entire cultures, were: glutamate, 3.5 mM; DL-AAA, 2.3 mM; kainic acid, 13 microM; NMDA, 11 microM; and AMPA, 3.7 microM. In the slice cultures, the hippocampal subfields displayed the same differences in vulnerability as those observed in vivo. When subfield analysis was performed on the cultures, the CA1 subfield was most susceptible to glutamate, NMDA and AMPA, while CA3 was most susceptible to kainic acid. The amount of LDH release for DL-AAA was about four times that of L-glutamate, in accordance with the additional toxic effect on glial cells, which was also found by confocal microscopy to stain for FJ. In conclusion, it was found that organotypic brain slice culture, combined with standardised protocols and quantifiable markers, such as PI and FJ staining, is a relevant and feasible in vitro system for neurotoxicity testing. Considering the amount and quality of the available published data, it is recommended that the brain slice culture method could be subjected to pre-validation and formal validation for inclusion in a tiered in vitro neurotoxicity testing scheme to supplement and replace conventional animal tests.

Immunolocalization of muscarinic M1 receptor in the rat medial prefrontal cortex

The medial prefrontal cortex (mPFC) has been considered to participate in many higher cognitive functions, such as memory formation and spatial navigation. These cognitive functions are modulated by cholinergic afferents via muscarinic acetylcholine receptors. Previous pharmacological studies have strongly suggested that the M1 receptor (M1R) is the most important subtype among muscarinic receptors to perform these cognitive functions. Actually, M1R is abundant in mPFC. However, the proportion of somata containing M1R among cortical cellular types, and the precise intracellular localization of M1R remain unclear. In this study, to clarify the precise immunolocalization of M1R in rat mPFC, we examined three major cellular types, pyramidal neurons, inhibitory neurons, and astrocytes. M1R immunopositivity signals were found in the majority of the somata of both pyramidal neurons and inhibitory neurons. In pyramidal neurons, strong M1R immunopositivity signals were usually found throughout their somata and dendrites including spines. On the other hand, the signal strength of M1R immunopositivity in the somata of inhibitory neurons significantly varied. Some neurons showed strong signals. Whereas about 40% of GAD67‐immunopositive neurons and 30% of parvalbumin‐immunopositive neurons (PV neurons) showed only weak signals. In PV neurons, M1R immunopositivity signals were preferentially distributed in somata. Furthermore, we found that many astrocytes showed substantial M1R immunopositivity signals. These signals were also mainly distributed in their somata. Thus, the distribution pattern of M1R markedly differs between cellular types. This difference might underlie the cholinergic modulation of higher cognitive functions subserved by mPFC.

Synthesis of tumor-targeted folate conjugated fluorescent magnetic albumin nanoparticles for enhanced intracellular dual-modal imaging into human brain tumor cells

Superparamagnetic iron oxide nanoparticles (SPIO NPs), utilized as carriers are attractive materials widely applied in biomedical fields, but target-specific SPIO NPs with lower toxicity and excellent biocompatibility are still lacking for intracellular visualization in human brain tumor diagnosis and therapy. Herein, bovine serum albumin (BSA) coated superparamagnetic iron oxide, i.e. γ-Fe2O3 nanoparticles (BSA-SPIO NPs), are synthesized. Tumor-specific ligand folic acid (FA) is then conjugated onto BSA-SPIO NPs to fabricate tumor-targeted NPs, FA-BSA-SPIO NPs as a contrast agent for MRI imaging. The FA-BSA-SPIO NPs are also labeled with fluorescein isothiocyanate (FITC) for intracellular visualization after cellular uptake and internalization by glioma U251 cells. The biological effects of the FA-BSA-SPIO NPs are investigated in human brain tumor U251 cells in detail. These results show that the prepared FA-BSA-SPIO NPs display undetectable cytotoxicity, excellent biocompatibility, and potent cellular uptake. Moreover, the study shows that the made FA-BSA-SPIO NPs are effectively internalized for MRI imaging and intracellular visualization after FITC labeling in the targeted U251 cells. Therefore, the present study demonstrates that the fabricated FITC-FA-BSA-SPIO NPs hold promising perspectives by providing a dual-modal imaging as non-toxic and target-specific vehicles in human brain tumor treatment in future.

Establishment and Characterization of a Tumor Stem Cell-Based Glioblastoma Invasion Model

Aims

Glioblastoma is the most frequent and malignant brain tumor. Recurrence is inevitable and most likely connected to tumor invasion and presence of therapy resistant stem-like tumor cells. The aim was therefore to establish and characterize a three-dimensional in vivo-like in vitro model taking invasion and tumor stemness into account.

Methods

Glioblastoma stem cell-like containing spheroid (GSS) cultures derived from three different patients were established and characterized. The spheroids were implanted in vitro into rat brain slice cultures grown in stem cell medium and in vivo into brains of immuno-compromised mice. Invasion was followed in the slice cultures by confocal time-lapse microscopy. Using immunohistochemistry, we compared tumor cell invasion as well as expression of proliferation and stem cell markers between the models.

Results

We observed a pronounced invasion into brain slice cultures both by confocal time-lapse microscopy and immunohistochemistry. This invasion closely resembled the invasion in vivo. The Ki-67 proliferation indexes in spheroids implanted into brain slices were lower than in free-floating spheroids. The expression of stem cell markers varied between free-floating spheroids, spheroids implanted into brain slices and tumors in vivo.

Conclusion

The established invasion model kept in stem cell medium closely mimics tumor cell invasion into the brain in vivo preserving also to some extent the expression of stem cell markers. The model is feasible and robust and we suggest the model as an in vivo-like model with a great potential in glioma studies and drug discovery.

Transferrin-conjugated drug/dye-co-encapsulated magnetic nanocarriers for active-targeting fluorescent/magnetic resonance imaging and anti-tumor effects in human brain tumor cells

A combinatorial nanosystem with the advantages of superparamagnetic iron oxide nanoparticles (SPIO NPs) and targeting polymer carriers is expected to improve the therapeutic effects in developing multifunctional delivery systems.

A subset of thalamocortical projections to the retrosplenial cortex possesses two vesicular glutamate transporter isoforms, VGluT1 and VGluT2, in axon terminals and somata

Vesicular glutamate transporter isoforms, VGluT1-VGluT3, accumulate glutamate into synaptic vesicles and are considered to be important molecules in glutamatergic transmission. Among them, VGluT2 mRNA is expressed predominantly throughout the dorsal thalamus, whereas VGluT1 mRNA is expressed in a few thalamic nuclei. In the thalamic nuclei that project to the retrosplenial cortex (RSC), VGluT1 mRNA is expressed strongly in the anterodorsal thalamic nucleus (AD), is expressed moderately in the anteroventral and laterodorsal thalamic nuclei, and is not expressed in the anteromedial thalamic nucleus. Thus, it has been strongly suggested that a subset of thalamocortical projections to RSC possesses both VGluT1 and VGluT2. In this study, double-labeled neuronal somata showing both VGluT1 and VGluT2 immunolabelings were found exclusively in the ventral region of AD (vAD). Many double-labeled axon terminals were also found in two major targets of vAD, the rostral part of the reticular thalamic nucleus and layers Ia and III-IV of the retrosplenial granular b cortex (RSGb). Some were also found in layer Ia of the retrosplenial granular a cortex (RSGa). These axon terminals contain significant amounts of both VGluTs. Because the subset of thalamocortical projections to RSC has a unique molecular basis in the glutamatergic transmission system, it might play an important role in the higher cognitive functions processed in the RSC. Furthermore, double-labeled axon terminals of a different type were distributed in RSGb and RSGa. Because they are small and the immunoreactivity of VGluT2 is significantly weaker than that of VGluT1, they seemed to be a subset of corticocortical terminals.

Polyethylenimine mediated magnetic nanoparticles for combined intracellular imaging, siRNA delivery and anti-tumor therapy

PEI–magnetic γ-Fe₂O₃nanoparticles (MNPs) were modified with fluorescent FITC for intracellular imaging and were also used for survivin siRNA delivery. The results suggested that the fabricated PEI–MNPs are a promising nanovehicle for efficient anti-tumor therapy.

Highly Efficient Labeling of Human Lung Cancer Cells Using Cationic Poly-l-lysine-Assisted Magnetic Iron Oxide Nanoparticles

Cell labeling with magnetic iron oxide nanoparticles (IONPs) is increasingly a routine approach in the cell-based cancer treatment. However, cell labeling with magnetic IONPs and their leading effects on the biological properties of human lung carcinoma cells remain scarcely reported. Therefore, in the present study the magnetic γ-Fe₂O₃ nanoparticles (MNPs) were firstly synthesized and surface-modified with cationic poly-l-lysine (PLL) to construct the PLL-MNPs, which were then used to magnetically label human A549 lung cancer cells. Cell viability and proliferation were evaluated with propidium iodide/fluorescein diacetate double staining and standard 3-(4,5-dimethylthiazol-2-diphenyl-tetrazolium) bromide assay, and the cytoskeleton was immunocytochemically stained. The cell cycle of the PLL-MNP-labeled A549 lung cancer cells was analyzed using flow cytometry. Apoptotic cells were fluorescently analyzed with nuclear-specific staining after the PLL-MNP labeling. The results showed that the constructed PLL-MNPs efficiently magnetically labeled A549 lung cancer cells and that, at low concentrations, labeling did not affect cellular viability, proliferation capability, cell cycle, and apoptosis. Furthermore, the cytoskeleton in the treated cells was detected intact in comparison with the untreated counterparts. However, the results also showed that at high concentration (400 µg mL^-1), the PLL-MNPs would slightly impair cell viability, proliferation, cell cycle, and apoptosis and disrupt the cytoskeleton in the treated A549 lung cancer cells. Therefore, the present results indicated that the PLL-MNPs at adequate concentrations can be efficiently used for labeling A549 lung cancer cells and could be considered as a feasible approach for magnetic targeted anti-cancer drug/gene delivery, targeted diagnosis, and therapy in lung cancer treatment.

p600 stabilizes microtubules to prevent the aggregation of CaMKIIα during photoconductive stimulation

The large microtubule-associated/Ca(2+)-signalling protein p600 (also known as UBR4) is required for hippocampal neuronal survival upon Ca(2+) dyshomeostasis induced by glutamate treatment. During this process, p600 prevents aggregation of the Ca(2+)/calmodulin-dependent kinase IIα (CaMKIIα), a proxy of neuronal death, via direct binding to calmodulin in a microtubuleindependent manner. Using photoconductive stimulation coupled with live imaging of single neurons, we identified a distinct mechanism of prevention of CaMKIIα aggregation by p600. Upon direct depolarization, CaMKIIα translocates to microtubules. In the absence of p600, this translocation is interrupted in favour of a sustained self-aggregation that is prevented by the microtubule-stabilizing drug paclitaxel. Thus, during photoconductive stimulation, p600 prevents the aggregation of CaMKIIα by stabilizing microtubules. The effectiveness of this stabilization for preventing CaMKIIα aggregation during direct depolarization but not during glutamate treatment suggests a model wherein p600 has two modes of action depending on the source of cytosolic Ca(2+).

Effect of staurosporine in the morphology and viability of cerebellar astrocytes: role of reactive oxygen species and NADPH oxidase

Cell death implies morphological changes that may contribute to the progression of this process. In astrocytes, the mechanisms involving the cytoskeletal changes during cell death are not well explored. Although NADPH oxidase (NOX) has been described as being a critical factor in the production of ROS, not much information is available about the participation of NOX-derived ROS in the cell death of astrocytes and their role in the alterations of the cytoskeleton during the death of astrocytes. In this study, we have evaluated the participation of ROS in the death of cultured cerebellar astrocytes using staurosporine (St) as death inductor. We found that astrocytes express NOX1, NOX2, and NOX4. Also, St induced an early ROS production and NOX activation that participate in the death of astrocytes. These findings suggest that ROS produced by St is generated through NOX1 and NOX4. Finally, we showed that the reorganization of tubulin and actin induced by St is ROS independent and that St did not change the level of expression of these cytoskeletal proteins. We conclude that ROS produced by a NOX is required for cell death in astrocytes, but not for the morphological alterations induced by St.

Pharmacological treatment for keloids

INTRODUCTION

Keloids are fibroproliferative disorders that are characterized by histological accumulation of collagens and fibroblasts, refractory clinical symptoms such as itching, topical invasiveness, and frequent postsurgical recurrence. At present, to treat or prevent keloids, new drugs are currently being designed and the pharmaceutical indications of known drugs are being expanded.

AREAS COVERED

The current pharmacological interventions for keloids are mainly described on the basis of the various hypotheses on keloid etiology and the keloid ingredients that are targeted. These interventions include angiotension-converting enzyme inhibitors and calcium-channel blockers (based on hypertension hypothesis), selective estrogen receptor modulator (based on endocrinological hypothesis), vitamins and essential fatty acids (based on immunonutritional hypothesis), and transglutaminase inhibitor (based on metabolic hypothesis). Drugs that directly target the reduction or destruction of the major extracellular matrix or cellular constituents of keloids are also included. Besides, drugs that indirectly modulate the biochemical microenvironment are described. These include growth factors, immunomodulators, and anti-inflammation and anti-allergy drugs.

EXPERT OPINION

Due to the unclear etiology of keloids and the lack of animal models, efficient, reliable, and specific pharmaceutical interventions for keloids continue to be lacking. The reliability of current data and clinical observations must be strengthened by large-scale, randomized, controlled clinical trials.

Graphene oxide induces toll-like receptor 4 (TLR4)-dependent necrosis in macrophages

Graphene and graphene-based nanomaterials display novel and beneficial chemical, electrical, mechanical, and optical characteristics, which endow these nanomaterials with promising applications in a wide spectrum of areas such as electronics and biomedicine. However, its toxicity on health remains unknown and is of great concern. In the present study, we demonstrated that graphene oxide (GO) induced necrotic cell death to macrophages. This toxicity is mediated by activation of toll-like receptor 4 (TLR4) signaling and subsequently in part via autocrine TNF-α production. Inhibition of TLR4 signaling with a selective inhibitor prevented cell death nearly completely. Furthermore, TLR4-deficient bone marrow-derived macrophages were resistant to GO-triggered necrosis. Similarly, GO did not induce necrosis of HEK293T/TLR4-null cells. Macrophagic cell death upon GO treatment was partially attributed to RIP1-RIP3 complex-mediated programmed necrosis downstream of TNF-α induction. Additionally, upon uptake into macrophages, GO accumulated primarily in cytoplasm causing dramatic morphologic alterations and a significant reduction of the macrophagic ability in phagocytosis. However, macrophagic uptake of GO may not be required for induction of necrosis. GO exposure also caused a large increase of intracellular reactive oxygen species (ROS), which contributed to the cause of cell death. The combined data reveal that interaction of GO with TLR4 is the predominant molecular mechanism underlying GO-induced macrophagic necrosis; also, cytoskeletal damage and oxidative stress contribute to decreased viability and function of macrophages upon GO treatment.

Cancer stem cell labeling using poly(L-lysine)-modified iron oxide nanoparticles

Cell labeling using magnetic nanoparticles is an increasingly used approach in noninvasive behavior tracking, in vitro separation of cancer stem cells (CSCs), and CSC-based research in cancer therapy. However, the impact of magnetic labeling on the biological properties of targeted CSCs, such as self-renewal, proliferation, multi-differentiation, cell cycle, and apoptosis, remains elusive. The present study sought to explore the potential effects on biological behavior when CSCs are labeled with superparamagnetic iron oxide (SPIO) nanoparticles in vitro. The glioblastoma CSCs derived from U251 glioblastoma multiforme were labeled with poly(L-lysine) (PLL)-modified γ-Fe(2)O(3) nanoparticles. The iron uptake of glioblastoma CSCs was confirmed through prussian blue staining, and was further quantified using atomic absorption spectrometry. The cellular viability of the SPIO-labeled glioblastoma CSCs was assessed using a fluorescein diacetate and propidium iodide double-staining protocol. The expressed specific markers and multi-differentiation of SPIO-labeled glioblastoma CSCs were comparatively assessed by immunocytochemistry and semi-quantitative RT-PCR. The effects of magnetic labeling on cell cycle and apoptosis rate of glioblastoma CSCs and their differentiated progenies were assayed using a flow cytometer. The results demonstrated that the cell viability and proliferation capacity of glioblastoma CSCs and their differentiated progenies were not affected by SPIO labeling compared with their unlabeled counterparts. Moreover, the magnetically labeled CSCs displayed an intact multi-differentiation potential, and could be sub-cultured to form new tumor spheres, which indicates the CSCs capacity for self-renewal. In addition, cell cycle distribution, apoptosis rate of the magnetically labeled glioblastoma CSCs, and their differentiated progenies were not impaired. Therefore, the SPIO-labeled CSCs could be a feasible approach in conducting further functional analysis of targeted CSCs.

Enhanced neurogenesis in organotypic cultures of rat hippocampus after transient subfield-selective excitotoxic insult induced by domoic acid

New neurons are continuously generated in the hippocampus and may play an important role in many physiological and pathological conditions. Here we present evidence of cell proliferation and neurogenesis after a selective and transient excitotoxic injury to the hippocampal cornu ammonis 1 (CA1) area induced by low concentrations of domoic acid (DOM) in rat organotypic hippocampal slice cultures (OHSC). DOM is an excitatory amino acid analog to kainic acid that acts through glutamate receptors to elicit a rapid and potent excitotoxic response. Exposure of slice cultures to varying concentrations of DOM for 24 h induced dose-dependent neuronal toxicity that was independent of activation of classic apoptotic markers. Treatment with 2 μM DOM for 24 h caused a selective yet transient neurotoxic injury in the CA1 subfield of the hippocampus that appeared recovered after 7 days of incubation in a DOM-free medium and showed significant microgliosis but no sign of astrogliosis. The DOM insult (2 μM, 24 h) resulted in a significant upregulation of cell proliferation, as assessed by 5-bromo-2-deoxyuridine (BrdU) incorporation, and a concurrent increase of the neuronal precursor cell marker doublecortin (DCX) within the subgranular zone of the dentate gyrus and area CA1. Neurogenesis occurred primarily during the first week after termination of the DOM exposure. Our study shows that exposure of OHSC to concentrations of DOM below those required to induce permanent neurotoxicity can induce proliferation and differentiation of neural progenitor cells that may contribute to recovery from mild injury and to develop abnormal circuits relevant to disease.

Colchicine-induced apoptosis in human normal liver L-02 cells by mitochondrial mediated pathways

Colchicine is an alkaloid that has been widely used to treat gout. It also has a curative effect on cancer. Although many studies have shown that its effect on cell apoptosis was mediated by the activation of caspase-3, the pathways involved in the process remained obscure. Here we show some evidence regarding the missing information using human normal liver cells L-02 in our study. The effect of colchicine on apoptosis in L-02 cells and the apoptosis-associated signaling pathways were determined using different tests including cell viability assay, Annexin V and propidium idodide binding, PI staining, Hoechst 33342 staining, mitochondrial membrane potential assay, caspase activity assay and Western blot analysis. We found that colchicine-induced a dose-dependent drop of cell viability in L-02 cells; early apoptosis happened when cells were treated with 0.1μM of colchicine. The colchicine-induced loss of mitochondrial membrane potential, activation of caspase-3 and 9, up-regulation of Bax and down-regulation of Bcl-2 showed an evidence for the colchicine activity on apoptosis, at least, by acting via the intrinsic apoptotic pathway.

Orexin neurons in hypothalamic slice cultures are vulnerable to endoplasmic reticulum stress

Narcolepsy results from disruption of orexin neurons in the hypothalamus that play a key role in maintenance of the arousal state. Underlying mechanisms leading to selective loss of orexin neurons remain unknown. On the other hand, endoplasmic reticulum stress, namely, conditions associated with impairment of endoplasmic reticulum functions such as proper folding and sorting of newly synthesized proteins, is implicated in pathogenesis of several types of neurodegenerative disorders. Here we found that application of endoplasmic reticulum stress inducers such as tunicamycin (that prevents protein N-glycosylation) and thapsigargin (that inhibits Ca²⁺-ATPase) to organotypic slice cultures of the hypothalamus caused preferential loss of orexin-immunoreactive neurons, as compared to melanin-concentrating hormone- or calcitonin gene-related peptide-immunoreactive neurons. The decrease in orexin-immunoreactive neurons at early time points (6-24 h) was not accompanied by induction of cell death as indicated by the absence of caspase-3 activation and no significant change in the number of NeuN-positive cells, whereas sustained treatment with tunicamycin for 72 h induced cell death. At 24-h treatment, tunicamycin and thapsigargin did not decrease expression of prepro-orexin mRNA, suggesting that post-transcriptional mechanisms were responsible for depletion of orexin peptides. In addition, inhibition of axonal transport by colchicine and inhibition of proteasomal activity by MG132 significantly prevented the decrease in orexin immunoreactivity by tunicamycin. Comparative examinations of expression of unfolded protein response-related proteins revealed that C/EBP-homologous protein (a transcription factor that promotes induction of apoptosis) as well as phosphorylated form of RNA-dependent protein kinase-like endoplasmic reticulum kinase (a protein kinase that mediates inhibition of protein translation) was expressed more prominently in orexin neurons than in melanin-concentrating hormone neurons, in response to tunicamycin. These results indicate that orexin neurons are particularly sensitive to endoplasmic reticulum stress, which may be relevant to pathogenic events in narcolepsy.

Characterization of Puma-dependent and Puma-independent neuronal cell death pathways following prolonged proteasomal inhibition

Proteasomal stress and the accumulation of polyubiquitinated proteins are key features of numerous neurodegenerative disorders. Previously we demonstrated that stabilization of p53 and activation of its target gene, puma (p53-upregulated mediator of apoptosis), mediated proteasome inhibitor-induced apoptosis in cancer cells. Here we demonstrated that Puma also contributed to proteasome inhibitor-induced apoptosis in mouse neocortical neurons. Although protection afforded by puma gene deletion was incomplete, we found little evidence indicating contributions from other proapoptotic BH3-only proteins. Attenuation of bax expression did not further reduce Puma-independent apoptosis, suggesting that pathways other than the mitochondrial apoptosis pathway were activated. Real-time imaging experiments in wild-type and puma-deficient neurons using a fluorescence resonance energy transfer (FRET)-based caspase sensor confirmed the involvement of a second cell death pathway characterized by caspase activation prior to mitochondrial permeabilization and, more prominently, a third, caspase-independent and Puma-independent pathway characterized by rapid cell shrinkage and nuclear condensation. This pathway involved lysosomal permeabilization in the absence of autophagy activation and was sensitive to cathepsin but not autophagy inhibition. Our data demonstrate that proteasomal stress activates distinct cell death pathways in neurons, leading to both caspase-dependent and caspase-independent apoptosis, and demonstrate independent roles for Puma and lysosomal permeabilization in this model.

Analyses of neuronal damage in excitotoxically lesioned organotypic hippocampal slice cultures

Organotypic hippocampal slice cultures (OHSCs) are widely used to study the mechanisms of neurodegeneration and neuroprotection. However, there are still controversies about the most appropriate method for quantification of neuronal damage. The response to excitotoxic lesions can be determined by propidium iodide (PI) staining, which labels nuclei of degenerating cells. Semiquantitative measurements of PI staining are based on (1) recording of the propidium iodide (PI) fluorescence intensity or (2) counting of PI positive neuronal nuclei. Here, we investigated OHSCs lesioned by the application of increasing NMDA concentrations (10microM, 50microM and 500microM) at 6 days in vitro (div) for 4h or left untreated, respectively. After 9 div, PI staining was performed and the staining determined in the dentate gyrus and cornu ammonis (CA1) by measurement of PI-fluorescence intensity or by counting PI(+)-nuclei with a confocal laser scanning microscope. The fluorescence intensity of lesioned OHSCs did not show a NMDA concentration dependent difference. In contrast, confocal laser scanning microscopy revealed a significant and dose-dependent increase in the number of PI(+)-nuclei. Linear regression analysis showed a high correlation between NMDA concentration and the number of PI(+)-nuclei. A high correlation was also found between the mean number of PI(+)-nuclei determined in every third optical section and that determined in a single mid-stag optical section. The results show that proper analysis of neuronal damage requires counting of PI(+)-nuclei by confocal laser scanning microscopy.

The use of Organotypic Hippocampal Slice Cultures to Evaluate Protection by Non-competitive NMDA Receptor Antagonists against Excitotoxicity

There is great interest in testing neuroprotectants which inhibit the neurodegeneration that results from excessive activation of N-methyl-D-aspartate (NMDA) receptors. As an alternative to in vivo testing in animal models, we demonstrate here the use of a complex in vitro model to compare the efficacy and toxicity of NMDA receptor inhibitors. Organotypic hippocampal slice cultures were used to compare the effectiveness of the Alzheimer's disease drug, memantine, the Parkinson's disease drug, procyclidine, and the novel neuroprotectant, gacyclidine (GK11), against NMDA-induced toxicity. All three drugs are non-competitive NMDA receptor open-channel blockers that inhibit excitotoxic injury, and their neuroprotective capacities have been extensively investigated in vivo in animal models. They have also been evaluated as potential countermeasure agents against organophosphate poisoning. Quantitative densitometric image analysis of propidium iodide uptake in hippocampal regions CA1, CA3 and DG, showed that, after exposure to 10μM NMDA for 24 hours, GK11 was the most potent of the three drugs, with an IC50 of about 50nM and complete protection at 250nM. When applied at high doses, GK11 was still the more potent neuroprotectant, and also the least cytotoxic. These findings are consistent with those from in vivo tests in rodents. We conclude that the slice culture model provides valuable pre-clinical data, and that applying the model to the screening of neuroprotectants might significantly limit the use of in vivo tests in animals.

Selective vulnerability of hippocampal cornu ammonis 1 pyramidal cells to excitotoxic insult is associated with the expression of polyamine-sensitive N-methyl-D-asparate-type glutamate receptors

Excess glutamate release and stimulation of post-synaptic glutamatergic receptors have been implicated in the pathophysiology of many neurological diseases. The hippocampus, and the pyramidal cell layer of the cornu ammonus 1 (CA1) region in particular, has been noted for its selective sensitivity to excitotoxic insults. The current studies examined the role of N-methyl-D-aspartate (NMDA) receptor subunit composition and sensitivity to stimulatory effects of the polyamine spermidine, an allosteric modulator of NMDA NR2 subunit activity, in hippocampal CA1 region sensitivity to excitotoxic insult. Organotypic hippocampal slice cultures of 8 day-old neonatal rat were obtained and maintained in vitro for 5 days. At this time, immunohistochemical analysis of mature neuron density (NeuN); microtubule associated protein-2(a,b) density (MAP-2); and NMDA receptor NR1 and NR2B subunit density in the primary cell layers of the dentate gyrus (DG), CA3, and CA1 regions, was conducted. Further, autoradiographic analysis of NMDA receptor distribution and density (i.e. [(125)I]MK-801 binding) and spermidine (100 microM)-potentiated [(125)I]MK-801 binding in the primary cell layers of these regions was examined. A final series of studies examined effects of prolonged exposure to NMDA (0.1-10 microM) on neurodegeneration in the primary cell layers of the DG, CA3, and CA1 regions, in the absence and presence of spermidine (100 microM) or ifenprodil (100 microM), an allosteric inhibitor of NR2B polypeptide subunit activity. The pyramidal cell layer of the CA1 region demonstrated significantly greater density of mature neurons, MAP-2, NR1 and NR2B subunits, and [(125)I]MK-801 binding than the CA3 region or DG. Twenty-four hour NMDA (10 microM) exposure produced marked neurodegeneration (approximately 350% of control cultures) in the CA1 pyramidal cell region that was significantly reduced by co-exposure to ifenprodil or DL-2-Amino-5-phosphonopentanoic acid (APV). The addition of spermidine significantly potentiated [(125)I]MK-801 binding and neurodegeneration induced by exposure to a non-toxic concentration of NMDA, exclusively in the CA1 region. This neurodegeneration was markedly reduced with co-exposure to ifenprodil. These data suggest that selective sensitivity of the CA1 region to excitotoxic stimuli may be attributable to the density of mature neurons expressing polyamine-sensitive NR2B polypeptide subunits.

A review of the effectiveness of antimitotic drug injections for hypertrophic scars and keloids

Hypertrophic scars and keloids are common problems after injury and cause functional and cosmetic deformities. A wide variety of treatments have been advocated for hypertrophic scars and keloids regression. Unfortunately, the reported efficacy has been variable. This article explores antimitotic drugs described in the literature such as steroid injection, 5-FU, mitomycin C, and bleomycin, which mainly target the fibroblasts in scar tissue, have been proposed as the effective modalities for scar treatment and scar prevention after surgery, but restricted due to possible side effects. The current accepted treatment for hypertrophic scar and keloid are combination therapy and the early treatment which could achieve better efficacy and less adverse effect.

Investigating the mechanisms underlying neuronal death in ischemia using in vitro oxygen-glucose deprivation: potential involvement of protein SUMOylation

It is well established that brain ischemia can cause neuronal death via different signaling cascades. The relative importance and interrelationships between these pathways, however, remain poorly understood. Here is presented an overview of studies using oxygen-glucose deprivation of organotypic hippocampal slice cultures to investigate the molecular mechanisms involved in ischemia. The culturing techniques, setup of the oxygen-glucose deprivation model, and analytical tools are reviewed. The authors focus on SUMOylation, a posttranslational protein modification that has recently been implicated in ischemia from whole animal studies as an example of how these powerful tools can be applied and could be of interest to investigate the molecular pathways underlying ischemic cell death.

Necrostatin-1 reduces histopathology and improves functional outcome after controlled cortical impact in mice

Necroptosis is a newly identified type of programmed necrosis initiated by the activation of tumor necrosis factor alpha (TNFalpha)/Fas. Necrostatin-1 is a specific inhibitor of necroptosis that reduces ischemic tissue damage in experimental stroke models. We previously reported decreased tissue damage and improved functional outcome after controlled cortical impact (CCI) in mice deficient in TNFalpha and Fas. Hence, we hypothesized that necrostatin-1 would reduce histopathology and improve functional outcome after CCI in mice. Compared with vehicle-/inactive analog-treated controls, mice administered necrostatin-1 before CCI had decreased propidium iodide-positive cells in the injured cortex and dentate gyrus (6 h), decreased brain tissue damage (days 14, 35), improved motor (days 1 to 7), and Morris water maze performance (days 8 to 14) after CCI. Improved spatial memory was observed even when drug was administered 15 mins after CCI. Necrostatin-1 treatment did not reduce caspase-3-positive cells in the dentate gyrus or cortex, consistent with a known caspase-independent mechanism of necrostatin-1. However, necrostatin-1 reduced brain neutrophil influx and microglial activation at 48 h, suggesting a novel anti-inflammatory effect in traumatic brain injury (TBI). The data suggest that necroptosis plays a significant role in the pathogenesis of cell death and functional outcome after TBI and that necrostatin-1 may have therapeutic potential for patients with TBI.

Neuronal maturation-associated resistance of neurite degeneration caused by trophic factor deprivation or microtubule-disrupting agents

Neurite (axon and dendrite) degeneration requires self-destructive programs independent of cell death programs to segregate neurite degeneration from cell soma demise. We have here addressed the question of whether neuritic degeneration is delayed or occurs normally under conditions in which sympathetic neurons acquire resistance to somal apoptosis upon maturation. For this purpose, we have examined both beading formation and fragmentation, two hall-marks of neurite degeneration, caused by three experimental paradigms including NGF deprivation, treatment with microtubule-disrupting agents, and in vitro Wallerian degeneration. Sympathetic neurons from 1-day-old mice or newborn rats were grown for 5-6 days (young) or 3 weeks (mature). Mature neurons acquired resistance to apoptosis caused by colchicine as well as NGF withdrawal. Neither cytochrome c release nor DNA fragmentation occurred. Both beading formation and subsequent fragmentation were delayed in mature neurons following NGF deprivation, treatment with colchicine, or in vitro Wallerian degeneration. Neuritic ATP levels of young ganglia decreased rapidly, while those of mature ganglia did so slowly during degeneration, although the basal levels of neuritic ATP of both ganglia were similar. Notably, mature neurites were resistant to fragmentation caused by NGF deprivation and capable of growing again after replenishment of NGF. This development of resistance to neurite degeneration in mature neurons may be thought as an important protective mechanism for the maintenance of the adult nervous system.

Acute plasmalemma permeability and protracted clearance of injured cells after controlled cortical impact in mice

Cell death after traumatic brain injury (TBI) evolves over days to weeks. Despite advances in understanding biochemical mechanisms that contribute to posttraumatic brain cell death, the time course of cell injury, death, and removal remains incompletely characterized in experimental TBI models. In a mouse controlled cortical impact (CCI) model, plasmalemma permeability to propidium iodide (PI) was an early and persistent feature of posttraumatic cellular injury in cortex and hippocampus. In cortical and hippocampal brain regions known to be vulnerable to traumatic cell death, the number of PI+ cells peaked early after CCI, and increased with increasing injury severity in hippocampus but not cortex (P<0.05). Propidium iodide labeling correlated strongly with hematoxylin and eosin staining in injured cells (r=0.99, P<0.001), suggesting that plasmalemma damage portends fatal cellular injury. Using PI pulse labeling to identify and follow the fate of a cohort of injured cells, we found that many PI+ cells recovered plasmalemma integrity by 24 h and were terminal deoxynucleotidyl transferase-mediated biotinylated UTP nick end labeling negative, but nonetheless disappeared from injured brain by 7 days. Propidium iodide-positive cells in dentate gyrus showed significant ultrastructural damage, including plasmalemma and nuclear membrane damage or overt membrane loss, in all cells when examined by laser capture microdissection and transmission electron microscopy 1 to 24 h after CCI. The data suggest that plasmalemma damage is a fundamental marker of cellular injury after CCI; some injured cells might have an extended window for potential rescue by neuroprotective strategies.

The developmental expression of fluorescent proteins in organotypic hippocampal slice cultures from transgenic mice and its use in the determination of excitotoxic neurodegeneration

Transgenic mice, expressing fluorescent proteins in neurons and glia, provide new opportunities for real-time microscopic monitoring of degenerative and regenerative structural changes. We have previously validated and compared a number of quantifiable markers for neuronal damage and cell death in organotypic brain slice cultures, such as cellular uptake of propidium iodide (PI), loss of microtubule-associated protein 2 (MAP2), Fluoro-Jade (FJ) cell staining, and the release of cytosolic lactate dehydrogenase (LDH). An important supplement to these markers would be data on corresponding morphological changes, as well as the opportunity to monitor reversible changes or long-term effects in the event of minor damage. As a first step, we present: a) the developmental expression in organotypic hippocampal brain slice cultures of transgenic fluorescent proteins, useful for the visualisation of neuronal subpopulations and astroglial cells; and b) examples of excitotoxic, glutamate receptor-induced degeneration of hippocampal CA1 pyramidal cells, with corresponding astroglial reactivity in such cultures. The slice cultures were set up according to standard techniques, by using one-week old pups from four transgenic mouse strains which express fluorescent proteins in their neurons and/or astroglial cells. From the time of explantation, and subsequently for up to nine weeks in culture, the transgenic neuronal fluorescence displayed the expected characteristics of a developmental, in vivo-like increase, including both the number and localisation of cells, as well as the intensity of fluorescence. At that stage and later, the transgenic fluorescence clearly permitted the visualisation of cell bodies, larger and smaller dendritic branches, spines and axons. In separate experiments, with a 24-hour exposure of matured sliced cultures to 100 microM of the glutamate agonist, N-methyl-D-aspartate (NMDA), we observed, by time-lapse recording, a gradual, but rapid loss of fluorescent CA1 pyramidal cells, accompanied by astrogliosis of transgene fluorescent astroglial cells. Based on these results, we consider that organotypic brain slice cultures from transgenic mice, with fluorescent neurons and glia, combined with detailed visualisation by time-lapse fluorescence microscopy, have great potential for investigating both major irreversible and minor reversible structural changes in neurons and glia, induced by neurotoxins and other neurodegenerative compounds and conditions.

Anti-apoptotic signaling and failure of apoptosis in the ischemic rat hippocampus

Several anti-apoptotic proteins are induced in CA1 neurons after transient forebrain ischemia (TFI), but fail to protect the majority of these cells from demise. Correlating cell death morphologies (apoptosis-like and necrosis-like death) with immunohistochemistry (IHC), we investigated whether anti-apoptosis contributes to survival, compromises apoptosis effector functions and/or delays death in CA1 neurons 1-7 days after TFI. As surrogate markers for bioenergetic failure, the IHC of respiratory chain complex (RCC) subunits was investigated. Dentate granule cell (DGC) apoptosis following colchicine injection severed as a reference for classical apoptosis. Heat shock protein 70 (Hsp70), neuronal apoptosis inhibitory protein (NAIP) and manganese superoxide dismutase (MnSOD) were upregulated in the majority of intact CA1 neurons paralleling the occurrence of CA1 neuronal death (days 3-7) as well as in a proportion of apoptosis-(<50%) and necrosis-like (<30%) CA1 neurons. Colchicine did not provoke an anti-apoptotic response in DGC at all. In addition, more than 70% of apoptosis- and necrosis-like CA1 neurons had completely lost their RCC subunits suggesting bioenergetic failure; by contrast, following colchicine injection, 88% of all apoptotic DGC presented RCC subunits. Thus, anti-apoptotic proteins may, in a subset of ischemic CA1 neurons, prevent cell death, while in others, affected by pronounced energy failure, they may cause secondary necrosis.

Executive dysfunctions and depression in Behçet's disease without explicit neurological involvement

This study aims to assess the executive functions and depression status in patients with Behçet's disease without explicit neurological involvement and to evaluate cognitive functions in this group of patients independent of accompanying depression. In the present study, 30 patients with Behçet's disease in the non-active phase of their illness and 30 healthy volunteers were included. In the evaluation of depression levels, Beck Depression Inventory was employed. The executive functions of the patients were evaluated by Wisconsin Card Sorting Test (WCST) and Stroop Test (ST). Beck Depression Inventory scores measured in the Behçet's disease group, in which no clinically serious depression was observed, were higher than the control group. Then, it was observed that the scores of neuropsychological tests of the Behçet's disease group were found to be significantly lower, especially in WCST, while significant relations were revealed between Beck Depression Inventory scores and WCST, ST scores. The authors' findings suggest that there may be factors other than depression causing executive impairment in patients with Behçet's disease without explicit neurological symptoms. Executive dysfunctions may occur in association with mild depressive states due to chronic disease stress or silent and/or future neurological involvement of Behçet's disease, especially in the frontal lobes.

Retigabine and flupirtine exert neuroprotective actions in organotypic hippocampal cultures

Retigabine and flupirtine are two structurally related molecules provided of anticonvulsant and analgesic actions. The present study has investigated the neuroprotective potential, as well as the possible underlying molecular mechanisms, exerted by retigabine and flupirtine in rat organotypic hippocampal slice cultures (OHSCs) exposed to N-methyl-D-aspartate (NMDA), oxygen and glucose deprivation followed by reoxygenation (OGD), or serum withdrawal (SW). Region-specific vulnerability of hippocampal subfields occurred with each of these injury models. Specifically, CA1 was the most susceptible region to both NMDA and OGD-induced neurodegeneration, whereas selective cell death in the dentate gyrus (DG) occurred upon OHSCs exposure to SW. The NMDA antagonist MK-801 (10-30 microM), despite blocking NMDA- and OGD-induced cell death, failed to prevent SW-induced neurodegeneration. Interestingly, retigabine (0.01-10 microM) and flupirtine (0.01-10 microM) dose-dependently prevented DG neuronal death induced by SW, with IC50 s of 0.4 microM and 0.7 microM, respectively. By contrast, retigabine and flupirtine (each at 10 microM) were less effective in counteracting NMDA- or OGD-induced toxicity in the CA1 region. Both retigabine and flupirtine (0.1-10 microM) reduced SW-induced ROS production in the DG with IC50 s of approximately 1 microM. This suggested that antioxidant actions of these compounds participated in OHSC neuroprotection during SW. By contrast, activation of KCNQ K+ channels seemed not to be involved in retigabine-induced OHSCs neuroprotection during SW, since linopirdine (20 microM) and XE-991 (10 microM), two KCNQ blockers, failed to reverse retigabine-induced neuronal rescue.

Ionotropic glutamate receptors and glutamate transporters are involved in necrotic neuronal cell death induced by oxygen-glucose deprivation of hippocampal slice cultures

Organotypic hippocampal slice cultures represent a feasible model for studies of cerebral ischemia and the role of ionotropic glutamate receptors in oxygen-glucose deprivation-induced neurodegeneration. New results and a review of existing data are presented in the first part of this paper. The role of glutamate transporters, with special reference to recent results on inhibition of glutamate transporters under normal and energy-failure (ischemia-like) conditions is reviewed in the last part of the paper. The experimental work is based on hippocampal slice cultures derived from 7 day old rats and grown for about 3 weeks. In such cultures we investigated the subfield neuronal susceptibility to oxygen-glucose deprivation, the type of induced cell death and the involvement of ionotropic glutamate receptors. Hippocampal slice cultures were also used in our studies on glutamate transporters reviewed in the last part of this paper. Neurodegeneration was monitored and/or shown by cellular uptake of propidium iodide, loss of immunocytochemical staining for microtubule-associated protein 2 and staining with Fluoro-Jade B. To distinguish between necrotic vs. apoptotic neuronal cell death we used immunocytochemical staining for active caspase-3 (apoptosis indicator) and Hoechst 33342 staining of nuclear chromatin. Our experimental studies on oxygen-glucose deprivation confirmed that CA1 pyramidal cells were the most susceptible to this ischemia-like condition. Judged by propidium iodide uptake, a selective CA1 lesion, with only minor affection on CA3, occurred in cultures exposed to oxygen-glucose deprivation for 30 min. Nuclear chromatin staining by Hoechst 33342 and staining for active caspase-3 showed that oxygen-glucose deprivation induced necrotic cell death only. Addition of 10 microM of the N-methyl-D-aspartate glutamate receptor antagonist MK-801, and 20 microM of the non-N-methyl-D-aspartate glutamate receptor antagonist 2,3-dihyroxy-6-nitro-7-sulfamoyl-benzo(F)quinoxaline to the culture medium confirmed that both N-methyl-D-aspartate and non-N-methyl-D-aspartate ionotropic glutamate receptors were involved in the oxygen-glucose deprivation-induced cell death. Glutamate is normally quickly removed, from the extracellular space by sodium-dependent glutamate transporters. Effects of blocking the transporters by addition of the DL-threo-beta-benzyloxyaspartate are reviewed in the last part of the paper. Under normal conditions addition of DL-threo-beta-benzyloxyaspartate in concentrations of 25 microM or more to otherwise untreated hippocampal slice cultures induced neuronal cell death, which was prevented by addition of 2,3-dihyroxy-6-nitro-7-sulfamoyl-benzo(F)quinoxaline and MK-801. In energy failure situations, like cerebral ischemia and oxygen-glucose deprivation, the transporters are believed to reverse and release glutamate to the extracellular space. Blockade of the transporters by a subtoxic (10 microM) dose of DL-threo-beta-benzyloxyaspartate during oxygen-glucose deprivation (but not during the next 48 h after oxygen-glucose deprivation) significantly reduced the oxygen-glucose deprivation-induced propidium iodide uptake, suggesting a neuroprotective inhibition of reverse transporter activity by DL-threo-beta-benzyloxyaspartate during oxygen-glucose deprivation under these conditions. Adding to this, other results from our laboratory have demonstrated that pre-treatment of the slice cultures with glial cell-line derived neurotrophic factor upregulates glutamate transporters. As a logical, but in some glial cell-line derived neurotrophic factor therapy-related conditions clearly unwanted consequence the susceptibility for oxygen-glucose deprivation-induced glutamate receptor-mediated cell death is increased after glial cell-line derived neurotrophic factor treatment. In summary, we conclude that both ionotropic glutamate receptors and glutamate transporters are involved in oxygen-glucose deprivation-induced necrotic cell death in hippocampal slice cultures, which have proven to be a feasible tool in experimental studies on this topic.

A 24 h corticosterone exposure exacerbates excitotoxic insult in rat hippocampal slice cultures independently of glucocorticoid receptor activation or protein synthesis

Elevations in circulating concentrations of glucocorticoids (GC) may increase the expression and/or sensitivity of ionotropic transmitter receptors in brain. For example, recent evidence suggests that acute and chronic GC exposure may alter the number and/or function of N-methyl-D-aspartate (NMDA)-type glutamate receptors, effects that may sensitize the brain to excitotoxic insults. The present studies examined the ability of short-term (24 h) corticosterone (CORT) exposure to potentiate NMDA-induced cytotoxicity in rat hippocampal slice cultures. Additional studies evaluated the role of mineralocorticoid (MR) and glucocorticoid receptor (GR) function, as well as de novo protein synthesis, in potentiation of toxicity by corticosterone exposure. Hippocampal slice cultures were exposed to NMDA (20 microM) for 24 h with cytotoxicity assessed by fluorescent detection of propidium iodide uptake. Exposure to NMDA caused significant propidium iodide uptake in each hippocampal region, while 24 h CORT (0.001-1 microM) exposure alone did not significantly increase propidium iodide uptake. Co-exposure of cultures to CORT and NMDA synergistically increased propidium iodide uptake in each hippocampal region, effects that were prevented by co-exposure to a non-toxic concentration of MK-801 (20 microM). In contrast, 24 h exposure with the MR antagonist spironolactone (1-10 microM), the GR antagonist RU-486 (1-10 microM), or the protein synthesis inhibitor cycloheximide (1 microM) failed to reduce the significant increase in propidium iodide uptake. These data suggest that relatively brief elevations in CORT levels may sensitize the hippocampus to injury independently of GC receptor activity and protein synthesis.

Ciliary neurotrophic factor-immunoreactivity in olfactory sensory neurons

Ciliary neurotrophic factor (CNTF) has been implicated in processes of neuroprotection, axonal regeneration and synaptogenesis in the lesioned CNS. In the olfactory system, which is characterized by particularly robust neuroplasticity throughout life, the concentration of CNTF is high even under physiological conditions. In the present study, the cellular localization of CNTF-immunoreactivity was studied in the rat and mouse olfactory epithelium. In both species, individual olfactory sensory neurons (ONs) displayed intense CNTF-immunoreactivity. The number of CNTF-ir ONs varied interindividually in rats and was lower in mice than in rats. In olfactory epithelia of mice expressing beta-galactosidase under control of the CNTF promoter, cells of the ON layer were immunoreactive for the reporter protein. CNTF-ir ONs were olfactory marker protein-positive and growth associated protein 43-negative. CNTF-ir ONs lacked apoptotic markers, and the number of specifically labeled ONs was apparently unchanged after light chemical lesioning of the epithelium, indicating that CNTF-immunoreactivity was not associated with ON death. Electron microscopy of CNTF-ir ON axons in innervated olfactory bulb glomeruli documented that they formed typical ON axonal synapses with target neurons. Three dimensional reconstructions of bulb pairs showed a striking similarity of the positions of glomeruli innervated by CNTF-ir ON axons in left and right bulbs of individual animals and interindividually. The number of innervated glomeruli differed interindividually in rats and was lower in mice than in rats. The results show that in rodents CNTF-immunoreactivity occurs in a subset of mature, functionally competent ONs. The localization of target glomeruli suggests that CNTF-immunoreactivity may be associated with the expression and/or activation of specific olfactory receptor proteins.

The temperature dependence and involvement of mitochondria permeability transition and caspase activation in damage to organotypic hippocampal slices following in vitro ischemia

The aggravating effect of hyperglycemia on ischemic brain injury can be mimicked in a model of in vitro ischemia (IVI) using murine hippocampal slice cultures. Using this model, we found that the damage in the CA1 region following IVI in the absence or presence of 40 mm glucose (hyperglycemia) is highly temperature dependent. Decreasing the temperature from 35 to 31 degrees C during IVI prevented cell death, whereas increasing the temperature by 2 degrees C markedly aggravated damage. As blockade of the mitochondrial permeability transition (MPT) is equally effective as hypothermia in preventing ischemic cell death in vivo, we investigated whether inhibition of MPT or of caspases was protective following IVI. In the absence of glucose, the MPT blockers cyclosporin A and MeIle4-CsA but not the immunosuppressive compound FK506 diminished cell death. In contrast, following hyperglycemic IVI, MPT blockade was ineffective. Also, the pan-caspase inhibitor Boc-Asp(OMe)fluoromethyl ketone did not decrease cell death in the CA1 region following IVI or hyperglycemic IVI. We conclude that cell death in the CA1 region of organotypic murine hippocampal slices following IVI is highly temperature dependent and involves MPT. In contrast, cell death following hyperglycemic IVI, although completely prevented by hypothermia, is not mediated by mechanisms that involve MPT or caspase activation.

Characterization of organotypic ventral mesencephalic cultures from embryonic mice and protection against MPP toxicity by GDNF

We characterized organotypic ventral mesencephalic (VM) cultures derived from embryonic day 12 (E12) mice (CBL57/bL6) in terms of number of dopaminergic neurons, cell soma size and dopamine production in relation to time in vitro and tested the effects of 1-methyl-4-phenylpyridinium (MPP(+)) and glial derived neurotrophic factor (GDNF) to validate this novel culture model. Dopamine production and dopaminergic neuron soma size increased dramatically with time in vitro, whereas the number of dopamine neurons declined by approximately 30% between week 1 and week 2, which was further reduced after week 4. GDNF treatment (100 ng/mL) increased dopaminergic neuron soma size (up to 43%) and DOPAC production (approximately three-fold), but not the number of dopamine neurons in control cultures. One-week-old cultures were more vulnerable to MPP(+), than three-week-old cultures. The EC(50) for dopamine depletion after 2 days exposure and 15 days of recovery were 0.6 and 7 microm, respectively. Both pre-treatment and post-treatment with GDNF are important to obtain maximal protection against MPP(+) toxicity. In one-week-old cultures (5 microm MPP(+), 2 days) GDNF provided potent neuroprotection with dopamine contents reaching control levels and number of tyrosine hydroxylase (TH)(+) cells up to 80% of control, but in three-week-old cultures (10 microm MPP(+), 2 days) the protective potential of GDNF was markedly reduced. Long recovery periods after MPP(+) exposure are required to distinguish between reversible or irreversible toxic and/or trophic effects.