TGF-beta1 inhibits caspase-3 activation and neuronal apoptosis in rat hippocampal cultures

Neuronal alarmin IL-1α evokes astrocyte-mediated protective signals: Effectiveness in chemotherapy-induced neuropathic pain

The distinction between glial painful and protective pathways is unclear and the possibility to finely modulate the system is lacking. Focusing on painful neuropathies, we studied the role of interleukin 1α (IL-1α), an alarmin belonging to the larger family of damage-associated molecular patterns endogenously secreted to restore homeostasis. The treatment of rat primary neurons with increasing dose of the neurotoxic anticancer drug oxaliplatin (0.3-100μM, 48 h) induced the release of IL-1α. The knockdown of the alarmin in neurons leads to their higher mortality when co-cultured with astrocytes. This toxicity was related to increased extracellular ATP and decreased release of transforming growth factor β1, mostly produced by astrocytes. In a rat model of neuropathy induced by oxaliplatin, the intrathecal treatment with IL-1α was able to reduce mechanical and thermal hypersensitivity both after acute injection and continuous infusion. Ex vivo analysis on spinal purified astrocyte processes (gliosomes) and nerve terminals (synaptosomes) revealed the property of IL-1α to reduce the endogenous glutamate release induced by oxaliplatin. This protective effect paralleled with an increased number of GFAP-positive cells in the spinal cord, suggesting the ability of IL-1α to evoke a positive, conservative astrocyte phenotype. Endogenous IL-1α induces protective signals in the cross-talk between neurons and astrocytes. Exogenously administered in rats, IL-1α prevents neuropathic pain in the presence of spinal glutamate decrease and astrocyte activation.

Neuroprotective effects of Senkyunolide I against glutamate-induced cells death by attenuating JNK/caspase-3 activation and apoptosis

Glutamate-induced neurotoxicity is one of the most important pathogenic mechanisms in neurological diseases and is widely used as an in vitro model for ischemic stroke. Senkyunolide I (SEI), an active constituent derived from traditional Chinese medicine Ligusticum chuanxiong Hort. and Angelica sinensis (Oliv.) Diels, has been shown to have beneficial effects against focal cerebral ischemia-reperfusion in rats. However, the mechanisms underlying SEI-mediated neuroprotection remain not well understood. Thus, we explored the influence of SEI in glutamate-mediated injury to mouse neuroblastoma (Neuro2a) cells and determined the mechanisms involved. Neuro2a cells were treated with SEI under exposure to glutamate for 24 h. Cell viability was assessed by using WST-1 reagents, and apoptosis was evaluated using Annexin V-FITC and a PI double staining kit. The protein expression levels of p-AKT, AKT, p-GSK3β, GSK3β, p-p38, p38, p-ERK, ERK, p-JNK, JNK, Bcl-2, Bax, Bcl-xl, p-Bad, Bad, p53, and cleaved caspase-3 were determined by Western blot analysis. Glutamate significantly decreased cell viability and elevated the level of apoptosis. Treatment with SEI reversed those effects. Furthermore, the expression of p-JNK/JNK and cleaved caspase-3 were also reduced after treatment with SEI. Our findings demonstrate that SEI protected Neuro2a cells against glutamate toxicity by regulating JNK/caspase-3 pathway and apoptosis. Thus, SEI maybe a promising candidate for neuroprotection.

Evaluation of Caspase-3 Activity During Apoptosis with Fluorescence Lifetime-Based Cytometry Measurements and Phasor Analyses

Caspase-3 is a well-described protease with many roles that impact the fate of a cell. During apoptosis, caspase-3 acts as an executioner caspase with important proteolytic functions that lead to the final stages of programmed cell death. Owing to this key role, caspase-3 is exploited intracellularly as a target of control of apoptosis for therapeutic outcomes. Yet the activation of caspase-3 during apoptosis is challenged by other roles and functions (e.g., paracrine signaling). This brief report presents a way to track caspase-3 levels using a flow cytometer that measures excited state fluorescence lifetimes and a signal processing approach that leads to a graphical phasor-based interpretation. An established Förster resonance energy transfer (FRET) bioprobe was used for this test; the connected donor and acceptor fluorophore is cleavable by caspase-3 during apoptosis induction. With the cell-by-cell decay kinetic data and phasor analyses we generate a caspase activation trajectory, which is used to interpret activation throughout apoptosis. When lifetime-based cytometry is combined with a FRET bioprobe and phasor analyses, enzyme activation can be simplified and quantified with phase and modulation data. We envision extrapolating this approach to high content screening, and reinforce the power of phasor approaches with cytometric data. Analyses such as these can be used to cluster cells by their phase and modulation "lifetime fingerprint" when the intracellular fluorescent probe is utilized as a sensor of enzyme activity. © 2020 The Authors. Cytometry Part A published by Wiley Periodicals LLC on behalf of International Society for Advancement of Cytometry.

Cyclosporine-A induces apoptosis in human prostate cancer cells PC3 and DU145 via downregulation of COX-2 and upregulation of TGFβ

Background

Potential targets for prostate cancer therapy are urgently needed for curative of patients. Cyclosporine-A (CsA), an immunosuppressive and a selective cyclooxygenase-2 (COX-2) inhibitor, exerts antitumor activity. However, the molecular effects of CsA is not fully understood in prostate cancer. In this research, we sought to determine role and mechanism of CsA in prostate cancer.

Materials and methods

PC3 and DU145 cells were treated with CsA time (12, 24, 48 h) and dose dependent (2.5, 10, 25 μM) and cell survival, migration, colony formation, expression of apoptosis related proteins/genes using MTT assay, scratch assay, Western blotting/qPCR. At the same time, cells treated with CsA to test on the effects of COX-2 promoter activity using luciferase reporter plasmid. Lastly, functional role in the CsA treatment prostate cancer cells were interrogated for relationship of TGFβ, Akt, caspases and COX-2.

Results

These study findings provided direct evidences that the CsA induced apoptosis and downregulated migration.

Conclusions

CsA downregulated Akt as well as COX-2 and upregulated TGFβ, resulting in the suppression of cell migration which was augmented a potential therapeutic of CsA in prostate cancer cells.

Combined adult neurogenesis and BDNF mimic exercise effects on cognition in an Alzheimer's mouse model

Adult hippocampal neurogenesis (AHN) is impaired before the onset of Alzheimer's disease (AD) pathology. We found that exercise provided cognitive benefit to 5×FAD mice, a mouse model of AD, by inducing AHN and elevating levels of brain-derived neurotrophic factor (BDNF). Neither stimulation of AHN alone, nor exercise, in the absence of increased AHN, ameliorated cognition. We successfully mimicked the beneficial effects of exercise on AD mice by genetically and pharmacologically inducing AHN in combination with elevating BDNF levels. Suppressing AHN later led to worsened cognitive performance and loss of preexisting dentate neurons. Thus, pharmacological mimetics of exercise, enhancing AHN and elevating BDNF levels, may improve cognition in AD. Furthermore, applied at early stages of AD, these mimetics may protect against subsequent neuronal cell death.

Theaflavin alleviates inflammatory response and brain injury induced by cerebral hemorrhage via inhibiting the nuclear transcription factor kappa β-related pathway in rats

OBJECTIVE

Intracerebral hemorrhage (ICH) is one of the most common acute cerebrovascular diseases with high mortality. Numerous studies have shown that inflammatory response played an important role in ICH-induced brain injury. Theaflavin (TF) extracted from black tea has various biological functions including anti-inflammatory activity. In this study, we investigated whether TF could inhibit ICH-induced inflammatory response in rats and explored its mechanism.

MATERIALS AND METHODS

ICH rat models were induced with type VII collagenase and pretreated with TF by gavage in different doses (25 mg/kg-100 mg/kg). Twenty-four hours after ICH attack, we evaluated the rats' behavioral performance, the blood-brain barrier (BBB) integrity, and the formation of cerebral edema. The levels of reactive oxygen species (ROS) and inflammatory cytokines were examined by 2',7'-dichlorofluorescin diacetate and enzyme-linked immunosorbent assay. Nissl staining and transferase dUTP nick end labeling (TUNEL) were aimed to detect the neuron loss and apoptosis, the mechanism of which was explored by Western blot.

RESULTS

It was found that in the pretreated ICH rats TF significantly alleviated the behavioral defects, protected BBB integrity, and decreased the formation of cerebral edema and the levels of ROS as well as inflammatory cytokines (including interleukin-1 beta [IL-1β], IL-18, tumor nectosis factor-alpha, interferon-γ, transforming growth factor beta, and (C-X-C motif) ligand 1 [CXCL1]). Nissl staining and TUNEL displayed TF could protect against the neuron loss and apoptosis via inhibiting the activation of nuclear transcription factor kappa-β-p65 (NF-κβ-p65), caspase-1, and IL-1β. We also found that phorbol 12-myristate 13-acetate, a nonspecific activator of NF-κβ-p65, weakened the positive effect of TF on ICH-induced neural defects and neuron apoptosis by upregulating NF-κβ-related signaling pathway.

CONCLUSION

TF could alleviate ICH-induced inflammatory responses and brain injury in rats via inhibiting NF-κβ-related pathway, which may provide a new way for the therapy of ICH.

Physostigmine Restores Impaired Autophagy in the Rat Hippocampus after Surgery Stress and LPS Treatment

Tissue damage and pathogen invasion during surgical trauma have been identified as contributing factors leading to neuroinflammation in the hippocampus, which can be protected by stimulation of the cholinergic anti-inflammatory pathway using the acetylcholinesterase inhibitor physostigmine. Macroautophagy, an intracellular degradation pathway used to recycle and eliminate damaged proteins and organelles by lysosomal digestion, seems to be important for cell survival under stress conditions. This study aimed to examine the role of autophagy in physostigmine-mediated hippocampal cell protection in a rat model of surgery stress. In the presence or absence of physostigmine, adult Wistar rats underwent surgery in combination with lipopolysaccharide (LPS). Activated microglia, apoptosis-, autophagy-, and anti-inflammatory-related genes and -proteins in the hippocampus were determined by Real-Time PCR, Western blot and fluorescence microscopy after 1 h, 24 h and 3 d. Surgery combined with LPS-treatment led to microglia activation after 1 h and 24 h which was accompanied by apoptotic cell death after 24 h in the hippocampus. Furthermore, it led to a decreased expression of ATG-3 after 24 h and an increased expression of p62/ SQSTM1 after 1 h and 24 h. Administration of physostigmine significantly increased autophagy related markers and restored the autophagic flux after surgery stress, detected by increased degradation of p62/ SQSTM1 in the hippocampus after 1 h and 24 h. Furthermore, physostigmine reduced activated microglia and apoptosis relevant proteins and elevated the increased expression of TGF-beta1 and MFG-E8 after surgery stress. In conclusion, activation of autophagy may be essential in physostigmine-induced neuroprotection against surgery stress.

TGF-β1 Regulation of P-JNK and L-Type Calcium Channel Cav1.2 in Cortical Neurons

Central nervous system (CNS) diseases can cause a series of neuronal lesions, which may be improved by the anti-apoptotic neuroprotection of transforming growth factor-beta 1 (TGF-β1). In neurons, L-type Ca²⁺ channels (LTCC) are mainly composed of Cav1.2 subunits. Given the implication of TGF-β1 in numerous CNS diseases, we examined the neuroprotective effects of TGF-β1 on the Cav1.2 channel in the CNS. To simulate acute mechanical traumatic brain injury (TBI), we used a needle to create parallel scratches across plates, which were cultured for 9 h. Meanwhile, Fluo4-AM-loaded laser scanning confocal microscopy with a dual wavelength of 488 nm/530 nm was employed to determine intracellular calcium concentrations ([Ca²⁺]_i). We found that MAPK inhibitors impede TGF-β1-induced cell viability and that TGF-β1 recovered from the trauma-induced cell viability in neurons. Cav1.2 production was significantly decreased in the TGF-β1-treated (10 ng/mL) neurons. At this TGF-β1 concentration, Cav1.2 was significantly down-regulated in a time-dependent manner after 12 h. Moreover, TGF-β1 partially recovered the protein levels of Cav1.2 that were reduced by TBI. TGF-β1 significantly inhibited the fluorescence intensity of [Ca²⁺]_i increased by KCl and delayed the time of the peak [Ca²⁺]_i. The observed effects of TGF-β1 on Cav1.2 were regulated by MAPK inhibitors. The observed effects of TGF-β1 on P-JNK were also impeded by pre-incubation with the LTCC inhibitor (10 μM) nimodipine in trauma-injured neurons. Altogether, TGF-β1 regulated LTCCs through a mechanism dependent on MEK, JNK1/2 and p38 MAPK signal pathways in cortical neurons. Thus, we suggest the involvement of this mechanism in cell viability.

Sodium butyrate enhanced physical barrier function referring to Nrf2, JNK and MLCK signaling pathways in the intestine of young grass carp (Ctenopharyngodon idella)

This study evaluated the effect of dietary sodium butyrate (SB) supplementation on the intestinal physical barrier function of young grass carp (Ctenopharyngodon idella). The fish were fed one powdery sodium butyrate (PSB) diet (1000.0 mg kg^-1 diet) and five graded levels of microencapsulated sodium butyrate (MSB) diets: 0.0 (control), 500.0, 1000.0, 1500.0 and 2000.0 mg kg^-1 diet for 60 days. Subsequently, a challenge test was conducted by injection of Aeromonas hydrophila to explore the effect of SB supplementation on intestinal physical barrier function and the potential mechanisms in fish. The results showed that optimal SB supplementation: (1) down-regulated the cysteine-aspartic protease-2 (caspase-2), caspase-3 (rather than PI), caspase-7, caspase-8 (rather than PI), caspase-9, fatty acid synthetase ligand (FasL), apoptotic protease activating factor-1 (Apaf-1), B-cell lymphoma 2 associated X protein (Bax) and c-Jun Nterminal protein kinase (JNK) mRNA levels, up-regulated the B-cell lymphoma protein-2 (Bcl-2) (rather than PI), inhibitor of apoptosis proteins (IAP) and myeloid cell leukemia-1 (Mcl-1) mRNA levels in the intestine (P < 0.05), inhibited the intestinal cell apoptosis, maintained the intestine cell structure integrity; (2) increased NF-E2-related factor 2 (Nrf2) mRNA levels and nucleus protein levels, and down-regulated kelch-like-ECH-associated protein (Keap1b) (rather than Keap1a) mRNA levels in the intestine, up-regulated copper/zinc superoxide dismutase (CuZnSOD), manganese superoxide dismutase (MnSOD), catalase (CAT), glutathione peroxidase 1a (GPx1a), GPx1b, GPx4a, GPx4b, glutathione S-transferases R (GSTR), GSTP1, GSTP2, GSTO1, GSTO2 and glutathione reductase (GR) mRNA levels in the intestine, increased the corresponding antioxidant enzymes activity (P < 0.05), thus enhancing the ability of scavenging free radicals and decreasing the reactive oxygen species (ROS) content, decreasing the lipid and protein peroxidation, as well as alleviating oxidative damage; (3) down-regulated the molecule myosin light-chain kinase (MLCK) mRNA levels in the intestine, and up-regulated the occludin, zonula occludens-1 (ZO-1), ZO-2, claudin-b, claudin-c, claudin-f, claudin-3c (rather than PI), claudin-7a, claudin-7b and claudin-11 mRNA levels, down-regulated claudin-12, claudin-15a and claudin-15b mRNA levels (P < 0.05), thus maintaining the structural integrity between cells. This study suggests that SB supplementation could improve fish intestinal physical barrier function. Furthermore, according to the positive effect, MSB was superior to PSB on improving intestinal physical barrier function of fish. Finally, based on protein carbonyl content in the PI, the optimal SB supplementation (MSB as SB source) for young grass carp was estimated to be 338.8 mg kg^-1 diet.

Prolactin-induced neuroprotection against glutamate excitotoxicity is mediated by the reduction of [Ca2+]i overload and NF-κB activation

Prolactin (PRL) is a peptidic hormone that displays pleiotropic functions in the organism including different actions in the brain. PRL exerts a neuroprotective effect against excitotoxicity produced by glutamate (Glu) or kainic acid in both in vitro and in vivo models. It is well known that Glu excitotoxicity causes cell death through apoptotic or necrotic pathways due to intracellular calcium ([Ca²⁺] i) overload. Therefore, the aim of the present study was to assess the molecular mechanisms by which PRL maintains cellular viability of primary cultures of rat hippocampal neurons exposed to Glu excitotoxicity. We determined cell viability by monitoring mitochondrial activity and using fluorescent markers for viable and dead cells. The intracellular calcium level was determined by a fluorometric assay and proteins involved in the apoptotic pathway were determined by immunoblot. Our results demonstrated that PRL afforded neuroprotection against Glu excitotoxicity, as evidenced by a decrease in propidium iodide staining and by the decrease of the LDH activity. In addition, the MTT assay shows that PRL maintains normal mitochondrial activity even in neurons exposed to Glu. Furthermore, the Glu-induced intracellular [Ca²⁺]i overload was attenuated by PRL. These data correlate with the reduction found in the level of active caspase-3 and the pro-apoptotic ratio (Bax/Bcl-2). Concomitantly, PRL elicited the nuclear translocation of the transcriptional factor NF-κB, which was detected by immunofluorescence and confocal microscopy. To our knowledge, this is the first report demonstrating that PRL prevents Glu excitotoxicity by a mechanism involving the restoration of the intracellular calcium homeostasis and mitochondrial activity, as well as an anti-apoptotic action possibly mediated by the activity of NF-κB. Overall, the current results suggest that PRL could be of potential therapeutic advantage in the treatment of neurodegenerative diseases.

Signaling Cross Talk between TGF-β/Smad and Other Signaling Pathways

Cytokines of the transforming growth factor β (TGF-β) family, including TGF-βs, bone morphogenic proteins (BMPs), activins, and Nodal, play crucial roles in embryonic development and adult tissue homeostasis by regulating cell proliferation, survival, and differentiation, as well as stem-cell self-renewal and lineage-specific differentiation. Smad proteins are critical downstream mediators of these signaling activities. In addition to regulating the transcription of direct target genes of TGF-β, BMP, activin, or Nodal, Smad proteins also participate in extensive cross talk with other signaling pathways, often in a cell-type- or developmental stage-specific manner. These combinatorial signals often produce context-, time-, and location-dependent biological outcomes that are critical for development. This review discusses recent progress in our understanding of the cross talk between Smad proteins and signaling pathways of Wnt, Notch, Hippo, Hedgehog (Hh), mitogen-activated protein (MAP), kinase, phosphoinositide 3-kinase (PI3K)-Akt, nuclear factor κB (NF-κB), and Janus kinase/signal transducers and activators of transcription (JAK/STAT) pathways.

Signaling Cross Talk between TGF-β/Smad and Other Signaling Pathways

Cytokines of the transforming growth factor β (TGF-β) family, including TGF-βs, bone morphogenic proteins (BMPs), activins, and Nodal, play crucial roles in embryonic development and adult tissue homeostasis by regulating cell proliferation, survival, and differentiation, as well as stem-cell self-renewal and lineage-specific differentiation. Smad proteins are critical downstream mediators of these signaling activities. In addition to regulating the transcription of direct target genes of TGF-β, BMP, activin, or Nodal, Smad proteins also participate in extensive cross talk with other signaling pathways, often in a cell-type- or developmental stage-specific manner. These combinatorial signals often produce context-, time-, and location-dependent biological outcomes that are critical for development. This review discusses recent progress in our understanding of the cross talk between Smad proteins and signaling pathways of Wnt, Notch, Hippo, Hedgehog (Hh), mitogen-activated protein (MAP), kinase, phosphoinositide 3-kinase (PI3K)-Akt, nuclear factor κB (NF-κB), and Janus kinase/signal transducers and activators of transcription (JAK/STAT) pathways.

Differential regional responsiveness of astroglia in mild hepatic encephalopathy: An Immunohistochemical approach in bile duct ligated rat

Hepatic encephalopathy (HE) is a neuropsychiatric disorder that occurs in both acute and chronic liver failure. However, the pathomechanisms of the disease remains obscure. Neuropathological studies have demonstrated a primary gliopathy in humans as well as in animal models of chronic and acute liver failure. Here, we have investigated in an animal model of mild HE: the bile duct ligated rat (BDL) at the cirrhotic stage (4 weeks after surgery), the expression of the key marker of mature astrocytes; the glial fibrillary acidic protein (GFAP) in different brain areas such as: Substantia nigra pars compacta (SNc), Ventral tegmental area (VTA), hippocampus, dorsal striatum and brain cortex by means of immunohistochemistry. The immunohistochemical study showed, in BDL compared to the operated controls (shams), a diminished astrocyte reactivity corresponding to a loss of GFAP expression within SNc, VTA, hippocampus and dorsal striatum (p<0.05),whereas in the brain cortex astrocytes appeared strongly immunoreactive with increased GFAP expression (p<0.05) as compared to shams. Our finding demonstrated differential astroglial responses which depend to the specificity of the area investigated and its particular neuronal neighboring environment, and could have possible outcomes on the diverse neuronal functions especially those observed during the different episodes of hepatic encephalopathy.

α7 Nicotinic Receptor Promotes the Neuroprotective Functions of Astrocytes against Oxaliplatin Neurotoxicity

Neuropathies are characterized by a complex response of the central nervous system to injuries. Glial cells are recruited to maintain neuronal homeostasis but dysregulated activation leads to pain signaling amplification and reduces the glial neuroprotective power. Recently, we highlighted the property of α7 nicotinic-acetylcholine-receptor (nAChR) agonists to relieve pain and induce neuroprotection simultaneously with a strong increase in astrocyte density. Aimed to study the role of α7 nAChR in the neuron-glia cross-talk, we treated primary rat neurons and astrocytes with the neurotoxic anticancer drug oxaliplatin evaluating the effect of the α7 nAChR agonist PNU-282987 (PNU). Oxaliplatin (1 μM, 48 h) reduced cell viability and increased caspase-3 activity of neuron monocultures without damaging astrocytes. In cocultures, astrocytes were not able to protect neurons by oxaliplatin even if glial cell metabolism was stimulated (pyruvate increase). On the contrary, the coculture incubation with 10 μM PNU improved neuron viability and inhibited apoptosis. In the absence of astrocytes, the protection disappeared. Furthermore, PNU promoted the release of the anti-inflammatory cytokine TGF-β1 and the expression of the glutamate-detoxifying enzyme glutamine synthetase. The α7 nAChR stimulation protects neurons from oxaliplatin toxicity through an astrocyte-mediated mechanism. α7 nAChR is suggested for recovering the homeostatic role of astrocytes.

Expression of caspase-3 predicts prognosis in advanced noncardia gastric cancer

There is strong evidence that tumor growth is not only a result of uncontrolled cell proliferation but also of decreased apoptosis. Caspase-3 is a member of interleukin-1 beta-converting enzyme which is involved in the induction of apoptosis. Data on the expression of caspase-3 in patients with gastric cancer and its association with patient outcome are somewhat contradictory. We aimed to investigate the potential relation of the expression of caspase-3 protein with response to therapy and overall survival in patients with advanced noncardia gastric cancer. Tumor tissue samples collected from 359 consecutive patients with gastric cancer stage IV were retrospectively analyzed for the expression of caspase-3 in the primary tumor. The DNA apoptotic index assessed by the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end labeling method. All patients were followed up until death. Caspase-3 was expressed in 43.5 % of tumors. Caspase-3 expression compared to no expression was related with a higher DNA apoptotic index (p < 0.05). In multivariate analysis, tumor expression of caspase-3 was found to be an independent predictor of poor treatment response and survival (p < 0.05). Expression of caspase-3 in advanced gastric cancer is a predictor of poor response to treatment and survival. Further studies are needed to fully elucidate the prognostic value of caspase-3 expression in these patients.

TGF-beta signalling in the adult neurogenic niche promotes stem cell quiescence as well as generation of new neurons

Members of the transforming growth factor (TGF)-β family govern a wide range of mechanisms in brain development and in the adult, in particular neuronal/glial differentiation and survival, but also cell cycle regulation and neural stem cell maintenance. This clearly created some discrepancies in the field with some studies favouring neuronal differentiation/survival of progenitors and others favouring cell cycle exit and neural stem cell quiescence/maintenance. Here, we provide a unifying hypothesis claiming that through its regulation of neural progenitor cell (NPC) proliferation, TGF-β signalling might be responsible for (i) maintaining stem cells in a quiescent stage, and (ii) promoting survival of newly generated neurons and their functional differentiation. Therefore, we performed a detailed histological analysis of TGF-β1 signalling in the hippocampal neural stem cell niche of a transgenic mouse that was previously generated to express TGF-β1 under a tetracycline regulatable Ca-Calmodulin kinase promoter. We also analysed NPC proliferation, quiescence, neuronal survival and differentiation in relation to elevated levels of TGF-β1 in vitro and in vivo conditions. Finally, we performed a gene expression profiling to identify the targets of TGF-β1 signalling in adult NPCs. The results demonstrate that TGF-β1 promotes stem cell quiescence on one side, but also neuronal survival on the other side. Thus, considering the elevated levels of TGF-β1 in ageing and neurodegenerative diseases, TGF-β1 signalling presents a molecular target for future interventions in such conditions.

A systems toxicology approach to the surface functionality control of graphene-cell interactions

The raised considerable concerns about the possible environmental health and safety impacts of graphene nanomaterials and their derivatives originated from their potential widespread applications. We performed a comprehensive study about biological interaction of grapheme nanomaterials, specifically in regard to its differential surface functionalization (oxidation status), by using OMICS in graphene oxide (GO) and reduced graphene oxide (rGO) treated HepG2 cells. Differential surface chemistry (particularly, oxidation - O/C ratio) modulates hydrophobicity/philicity of GO/rGO which in turn governs their biological interaction potentiality. Similar toxic responses (cytotoxicity, DNA damage, oxidative stress) with differential dose dependency were observed for both GO and rGO but they exhibited distinct mechanism, such as, hydrophilic GO showed cellular uptake, NADPH oxidase dependent ROS formation, high deregulation of antioxidant/DNA repair/apoptosis related genes, conversely, hydrophobic rGO was found to mostly adsorbed at cell surface without internalization, ROS generation by physical interaction, poor gene regulation etc. Global gene expression and pathway analysis displayed that TGFβ1 mediated signaling played the central role in GO induced biological/toxicological effect whereas rGO might elicited host-pathogen (viral) interaction and innate immune response through TLR4-NFkB pathway. In brief, the distinct biological and molecular mechanisms of GO/rGO were attributed to their differential surface oxidation status.

Chronic over-expression of TGFβ1 alters hippocampal structure and causes learning deficits

The cytokine transforming growth factor β1 (TGFβ1) is chronically upregulated in several neurodegenerative conditions, including Alzheimer's disease, Parkinson's disease, Creutzfeldt-Jacob disease, amyotrophic lateral sclerosis and multiple sclerosis, and following stroke. Although previous studies have shown that TGFβ1 may be neuroprotective, chronic exposure to elevated levels of this cytokine may contribute to disease pathology on its own. In order to study the effects of chronic exposure to TGFβ1 in isolation, we used transgenic mice that over-express a constitutively active porcine TGFβ1 in astrocytes. We found that TGFβ1 over-expression altered brain structure, with the most pronounced volumetric increases localized to the hippocampus. Within the dentate gyrus (DG) of the hippocampus, increases in granule cell number and astrocyte size were responsible for volumetric expansion, with the increased granule cell number primarily related to a marked reduction in death of new granule cells generated in adulthood. Finally, these cumulative changes in DG microstructure and macrostructure were associated with the age-dependent emergence of spatial learning deficits in TGFβ1 over-expressing mice. Together, our data indicate that chronic upregulation of TGFβ1 negatively impacts hippocampal structure and, even in the absence of disease, impairs hippocampus-dependent learning.

Characterization of the secretome of human tooth germ stem cells (hTGSCs) reveals neuro-protection by fine-tuning micro-environment

Bone-marrow-derived mesenchymal stem cells (MSCs) demonstrate neuro-protective effects in several disease models. By producing growth-factors, cytokines and chemokines, they promote survival of neurons in damaged brain areas. Alternative MSC sources, such as human tooth germ stem cells (hTGSCs), have been investigated for their neuro-protective properties. They ameliorate effects of neuro-toxic agents by paracrine mechanisms, however these secreted bio-active molecules are not yet characterized. Therefore, the current study aimed to provide a detailed analysis of the secretome of hTGSCs. Brain cells were exposed to various toxic materials, including Alzheimer's β-amyloid peptide (β-AP) and 6-hydroxy-dopamine (6-OHDA). When co-cultured with hTGSCs, the activity of a number of anti-oxidant enzymes (catalase, glutathione-s-transferase, glutathione-peroxidase, superoxide-dismutase) was increased and neuronal death/apoptosis was subsequently reduced. The composition of the secreted bio-active materials is influenced by various pre-existing factors such as oxygen and glucose deprivation and the age of cells (passage number). This report reveals for the first time that the neuro-protective secretome of hTGSCs and the micro-environment of cells have a mutual and dynamic impact on one another.

Decreasing loss of cryopreserved-thawed rat islets by coculture with Sertoli cells

OBJECTIVE

Cryopreserved-thawed rat islets were cocultured with Sertoli cells to examine whether they could decrease the loss and improve islet function.

METHODS

Islets and Sertoli cells were harvested from the pancreas and the testis of Sprague-Dawley rats, respectively. Cryopreserved, stored islets were thawed and divided into groups of coculture with Sertoli cells versus single cells. We measured islets recovery rate and function. Apoptotic-related proteins and gene expressions were detected by Western blot and reverse-transcriptase polymerase chain reaction. Soluble factors secreted by Sertoli cells in to the supernate were detected by enzyme-linked immunosorbent assay. We compared islet graft survival times in diabetic mice.

RESULTS

In contrast to the single culture controls, thawed islets cocultured with Sertoli cells exhibited improved morphology. Recovery rates and insulin secretion were significantly higher among coculture cells. Four soluble factors were detected in supernates from Sertoli cell cultures including transforming growth factor-β, insulin-like growth factor-1, epidermal growth factor, and basic fibroblast growth factor. Expression of proapoptotic Bax and caspase 3, 7 were down-regulated while that of antiapoptotic Bcl-2 was up-regulated. Cotransplantation with Sertoli cells significantly prolonged islet graft survival.

CONCLUSION

These results suggested that coculture with Sertoli cells significantly improved islet yields and function after thawing and depressed islet apoptosis.

The neuroprotective functions of transforming growth factor beta proteins

Transforming growth factor beta (TGF-β) proteins are multifunctional cytokines whose neural functions are increasingly recognized. The machinery of TGF-β signaling, including the serine kinase type transmembrane receptors, is present in the central nervous system. However, the 3 mammalian TGF-β subtypes have distinct distributions in the brain suggesting different neural functions. Evidence of their involvement in the development and plasticity of the nervous system as well as their functions in peripheral organs suggested that they also exhibit neuroprotective functions. Indeed, TGF-β expression is induced following a variety of types of brain tissue injury. The neuroprotective function of TGF-βs is most established following brain ischemia. Damage in experimental animal models of global and focal ischemia was shown to be attenuated by TGF-βs. In addition, support for their neuroprotective actions following trauma, sclerosis multiplex, neurodegenerative diseases, infections, and brain tumors is also accumulating. The review will also describe the potential mechanisms of neuroprotection exerted by TGF-βs including anti-inflammatory, -apoptotic, -excitotoxic actions as well as the promotion of scar formation, angiogenesis, and neuroregeneration. The participation of these mechanisms in the neuroprotective effects of TGF-βs during different brain lesions will also be discussed.

Transforming growth factor β and apoptosis in leprosy skin lesions: possible relationship with the control of the tissue immune response in the Mycobacterium leprae infection

The course of leprosy depends of the host immune response which ranges from the lepromatous pole (LL) to the tuberculoid pole (TT). A comparative study was conducted in 60 patients with the LL and TT. The results showed a mean expression of TGF-β of 339 ± 99.4 cells/field for TT and of 519.2 ± 68.2 cells/field for LL. Frequency of apoptosis was 6.3 ± 1.8 in TT and 14.0 ± 6.1 in LL. A correlation (p = 0.0251) between TGF-β and caspase-3 in the LL was found. This finding indicates a role of TGF-β and apoptosis in the immune response in leprosy.

Dysfunction of TGF-β1 signaling in Alzheimer's disease: perspectives for neuroprotection

Alzheimer's disease (AD) is a neurodegenerative disorder that affects about 35 million people worldwide. Current drugs for AD only treat the symptoms and do not interfere with the underlying pathogenic mechanisms of the disease. AD is characterized by the presence of β-amyloid (Aβ) plaques, neurofibrillary tangles, and neuronal loss. Identification of the molecular determinants underlying Aβ-induced neurodegeneration is an essential step for the development of disease-modifying drugs. Recently, an impairment of the transforming growth factor-β1 (TGF-β1) signaling pathway has been demonstrated to be specific to the AD brain and, particularly, to the early phase of the disease. TGF-β1 is a neurotrophic factor responsible for the initiation and maintenance of neuronal differentiation and synaptic plasticity. The deficiency of TGF-β1 signaling is associated with Aβ pathology and neurofibrillary tangle formation in AD animal models. Reduced TGF-β1 signaling seems to contribute both to microglial activation and to ectopic cell-cycle re-activation in neurons, two events that contribute to neurodegeneration in the AD brain. The neuroprotective features of TGF-β1 indicate the advantage of rescuing TGF-β1 signaling as a means to slow down the neurodegenerative process in AD.

Early defect of transforming growth factor β1 formation in Huntington's disease

A defective expression or activity of neurotrophic factors, such as brain- and glial-derived neurotrophic factors, contributes to neuronal damage in Huntington’s disease (HD). Here, we focused on transforming growth factor-β (TGF-β₁), a pleiotropic cytokine with an established role in mechanisms of neuroprotection. Asymptomatic HD patients showed a reduction in TGF-β₁ levels in the peripheral blood, which was related to trinucleotide mutation length and glucose hypometabolism in the caudate nucleus. Immunohistochemical analysis in post-mortem brain tissues showed that TGF-β₁ was reduced in cortical neurons of asymptomatic and symptomatic HD patients. Both YAC128 and R6/2 HD mutant mice showed a reduced expression of TGF-β₁ in the cerebral cortex, localized in neurons, but not in astrocytes. We examined the pharmacological regulation of TGF-β₁ formation in asymptomatic R6/2 mice, where blood TGF-β₁ levels were also reduced. In these R6/2 mice, both the mGlu2/3 metabotropic glutamate receptor agonist, LY379268, and riluzole failed to increase TGF-β₁ formation in the cerebral cortex and corpus striatum, suggesting that a defect in the regulation of TGF-β₁ production is associated with HD. Accordingly, reduced TGF-β₁ mRNA and protein levels were found in cultured astrocytes transfected with mutated exon 1 of the human huntingtin gene, and in striatal knock-in cell lines expressing full-length huntingtin with an expanded glutamine repeat. Taken together, our data suggest that serum TGF-β₁ levels are potential biomarkers of HD development during the asymptomatic phase of the disease, and raise the possibility that strategies aimed at rescuing TGF-β₁ levels in the brain may influence the progression of HD.

Adult rat hippocampal slices as in vitro models for neurodegeneration: Studies on cell viability and apoptotic processes

Adult hippocampal slice cultures were used in the modeling of apoptotic aspects of neurodegeneration. Slice viability was determined by the use of trypan blue (TB) staining, and apoptosis was assessed by caspase-3 immunohistochemistry. A large number of pyramidal cells showed signs of degeneration 30 min after sectioning (58.4% of the total number of pyramidal cells), as they exhibited TB uptake, and about 71.6% of these neurons became stained by the third day in culture, when patches in the stratum oriens also demonstrated distinct TB staining. By the sixth day of culturing, almost all cells in the pyramidal cell layer became TB positive (88.4%). The caspase-3 immunoreactivity displayed a different pattern, as the most intense immunoreactivity, detected mainly in the pyramidal cells, peaked 6 h after culturing, and then decreased steadily. The present data show that in adult hippocampal slices a large number of pyramidal cells initiate apoptotic processes as a result of irreparable damage sustained during slice preparation and culture maintenance, and support the notion that apoptosis is an integral part of the neurodegenerative processes not only in vivo but also in vitro. Elucidation of mechanisms for the apoptotic processes in adult hippocampal slice cultures could lead to the development of new therapeutic strategies; moreover, the utilization of adult hippocampal slice cultures could be a viable alternative technique to in vivo experiments in studying the mechanisms responsible for neurodegeneration.

TGF-β1 pathway as a new target for neuroprotection in Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disorder that affects more than 37 million people worldwide. Current drugs for AD are only symptomatic, but do not interfere with the underlying pathogenic mechanisms of the disease. AD is characterized by the presence of ß-amyloid (Aβ) plaques, neurofibrillary tangles, and neuronal loss. The identification of the molecular determinants underlying AD pathogenesis is a fundamental step to design new disease-modifying drugs. Recently, a specific impairment of transforming-growth-factor-β1 (TGF-β1) signaling pathway has been demonstrated in AD brain. The deficiency of TGF-β1 signaling has been shown to increase both Aβ accumulation and Aβ-induced neurodegeneration in AD models. The loss of function of TGF-ß1 pathway seems also to contribute to tau pathology and neurofibrillary tangle formation. Growing evidence suggests a neuroprotective role for TGF-β1 against Aβ toxicity both in vitro and in vivo models of AD. Different drugs, such as lithium or group II mGlu receptor agonists are able to increase TGF-β1 levels in the central nervous system (CNS), and might be considered as new neuroprotective tools against Aβ-induced neurodegeneration. In the present review, we examine the evidence for a neuroprotective role of TGF-β1 in AD, and discuss the TGF-β1 signaling pathway as a new pharmacological target for the treatment of AD.

Proinflammatory cytokine gene induction by human T-cell leukemia virus type 1 (HTLV-1) and HTLV-2 Tax in primary human glial cells

Infection with human T-cell leukemia virus type 1 (HTLV-1) can result in the development of HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP), a chronic inflammatory disease of the central nervous system (CNS). HTLV-2 is highly related to HTLV-1 at the genetic level and shares a high degree of sequence homology, but infection with HTLV-2 is relatively nonpathogenic compared to HTLV-1. Although the pathogenesis of HAM/TSP remains to be fully elucidated, previous evidence suggests that elevated levels of the proinflammatory cytokines in the CNS are associated with neuropathogenesis. We demonstrate that HTLV-1 infection in astrogliomas results in a robust induction of interleukin-1beta (IL-1beta), IL-1alpha, tumor necrosis factor alpha (TNF-alpha), TNF-beta, and IL-6 expression. HTLV encodes for a viral transcriptional transactivator protein named Tax that also induces the transcription of cellular genes. To investigate and compare the effects of Tax1 and Tax2 expression on the dysregulation of proinflammatory cytokines, lentivirus vectors were used to transduce primary human astrocytomas and oligodendrogliomas. The expression of Tax1 in primary human astrocytomas and oligodendrogliomas resulted in significantly higher levels of proinflammatory cytokine gene expression compared to Tax2. Notably, Tax1 expression uniquely sensitized primary human astrocytomas to apoptosis. A Tax2/Tax1 chimera encoding the C-terminal 53 amino acids of the Tax1 fused to the Tax2 gene (Tax(221)) demonstrated a phenotype that resembled Tax1, with respect to proinflammatory cytokine gene expression and sensitization to apoptosis. The patterns of differential cytokine induction and sensitization to apoptosis displayed by Tax1 and Tax2 may reflect differences relating to the heightened neuropathogenicity associated with HTLV-1 infection and the development of HAM/TSP.

Implication of PTEN in production of reactive oxygen species and neuronal death in in vitro models of stroke and Parkinson's disease

Oxidative stress plays crucial role in the pathogenesis of neurodegenerative diseases. However, the precise mechanism for an increased production of reactive oxygen species (ROS) under pathological conditions is not yet fully understood. We have recently demonstrated an implication of phosphatase and tensin homologue deleted on chromosome 10 (PTEN), a tumor suppressor, in ROS generation and neuronal apoptosis induced by staurosporine. These findings raised further interest whether PTEN functions as a common mediator of oxidative stress in neurodegenerative processes. To address this issue, neural cells were exposed to oxygen-glucose deprivation (OGD) and to the neurotoxin 1-methyl-4-phenylpyridinium iodide (MPP(+)), which mimic cerebral ischemia and Parkinson's disease, respectively. OGD for 4 h followed by 16 h of reoxygenation or incubation with MPP(+) (250 microM) for 48 h induced 33% and 45% neuronal death in rat hippocampal and in human dopaminergic SH-SY5Y neurons, respectively, accompanied by a gradual increase in the intracellular level of ROS. The increase in ROS by OGD and by MPP(+) did not cause oxidative inactivation of PTEN and thus, PTEN remains constitutively active. In support, the protein level of PTEN was not reduced in both cell cultures after challenging with OGD or MPP(+). Importantly, the elevated intracellular ROS levels and the neuronal death caused by OGD or by MPP(+) toxicity were significantly inhibited when PTEN was downregulated by a specific antisense oligonucleotide or by siRNA. Because SOD2 protein level is not altered either by knockdown of PTEN nor by an inhibition of the PI3K/Akt signalling, we suggest that SOD2 do not contribute to the pathomechanism of oxidative stress induced by PTEN or by inhibiting the related Akt signalling. The present study highlights PTEN as a crucial and common mediator of ROS generation and neuronal death and suggests that PTEN could become a potential therapeutic target for interfering with neurodegeneration.

Protection of ischemic brain cells is dependent on astrocyte-derived growth factors and their receptors

An in vitro ischemia model (oxygen, glucose, and serum deprivation) is used to investigate the possible cellular and molecular mechanisms responsible for cerebral ischemia. We have previously demonstrated that supernatants derived from ischemic microglia can protect ischemic brain cells by releasing GDNF and TGF-beta1. In the present study, we investigate whether products of ischemic astrocytes can also protect ischemic microglia, astrocytes, and neurons in a similar manner. Supernatants from ischemic astrocytes were collected after various periods of ischemia and incubated with microglia, astrocytes, or neurons individually, under in vitro ischemic conditions. The components responsible for the protective effects of astrocyte-derived supernatants were then identified by Western blot, ELISA, trypan blue dye exclusion, and immunoblocking assays. Results showed that under conditions of in vitro ischemia the number of surviving microglia, astrocytes, and neurons was significantly increased by the incorporation of the astrocyte-derived supernatants. Astrocyte supernatant-mediated protection of ischemic microglia was dependent on TGF-beta1 and NT-3, ischemic astrocytes were protected by GDNF, and ischemic neurons were protected by NT-3. In addition, protein expression of TGF-beta1 and NT-3 receptors in microglia, GDNF receptors in astrocytes, and NT-3 receptors in neurons was increased by in vitro ischemia. These results suggest that astrocyte-derived protection of ischemic brain cells is dependent not only on factors released from the ischemic astrocytes, but also on the type of receptor present on the responding cells. Therapeutic potential of TGF-beta1, GDNF, and NT-3 in the control of cerebral ischemia is further suggested.

Adrenalectomy promotes a permanent decrease of plasma corticoid levels and a transient increase of apoptosis and the expression of Transforming Growth Factor beta1 (TGF-beta1) in hippocampus: effect of a TGF-beta1 oligo-antisense

BACKGROUND

Corticosterone reduction produced by adrenalectomy (ADX) induces apoptosis in dentate gyrus (DG) of the hippocampus, an effect related to an increase in the expression of the pro-apoptotic gene bax. However it has been reported that there is also an increase of the anti-apoptotic gene bcl-2, suggesting the promotion of a neuroprotective phenomenon, perhaps related to the expression of transforming growth factor beta1 (TGF-beta1). Thus, we have investigated whether TGF-beta1 levels are induced by ADX, and whether apoptosis is increased by blocking the expression of TGF-beta1 with an antisense oligonucleotide (ASO) administered intracerebrally in corticosterone depleted rats.

RESULTS

It was observed an increase of apoptosis in DG, 2 and 5 days after ADX, in agreement with a reduction of corticosterone levels. However, the effect of ADX on the number of apoptotic positive cells in DG was decreased 5 days after the lesion. In CA1-CA3 regions, the effect was only observed 2 days after ADX. TGF-beta1 mRNA levels were increased 2 days after ADX. The sustained intracerebro-ventricular administration of a TGF-beta1 ASO via an osmotic mini pump increased apoptosis levels in CA and DG regions 5 days after ADX as well as sham-operated control animals. No significant effect was observed following a scrambled-oligodeoxynucleotide treatment.

CONCLUSION

The changes in both the pattern and the magnitude of apoptotic-cell morphology observed 2 and 5 days after ADX suggest that, as a consequence of the reduction of corticosteroids, some trophic mechanisms restricting cell death to a particular time window are elicited. Sustained intracerebral administration of TGF-beta1 ASO increased the apoptosis promoted by ADX, suggesting that TGF-beta1 plays an anti-apoptotic role in vivo in hippocampus.

Transforming growth factor beta 1 promotes cell cycle exit through the cyclin-dependent kinase inhibitor p21 in the developing cerebral cortex

During cortical neurogenesis, cell proliferation and cell cycle exit are carefully regulated to ensure that the appropriate numbers of cells are produced. The antiproliferative agent transforming growth factor beta1 (TGFbeta1) and its receptors are endogenously expressed in proliferative zones of the developing cerebral cortex, thus implicating the growth factor in cell cycle regulation. The present study tested the hypothesis that TGFbeta1 promotes cell cycle exit in the cortical ventricular zone (VZ) through modulation of cell cycle protein expression, in particular cyclin D1 and the cyclin-dependent kinase inhibitors p27 and p21. Although it did not affect the length of the cell cycle, TGFbeta1 decreased the fraction of VZ-cycling cells by 21% and increased the number of VZ cells exiting the cell cycle a commensurate 24%. TGFbeta1 selectively increased the expression of p21 in the VZ. In addition, high p21 expression levels were observed in VZ cells as they exited the cell cycle, and TGFbeta1 increased the number p21-positive cells exiting the cell cycle. Collectively, these data show the following: (1) TGFbeta1 promotes cell cycle exit, (2) p21 upregulation is correlated with cell cycle exit, and (3) TGFbeta1-induced cell cycle exit is mediated by p21.

Role of c-Fos protein on glutamate toxicity in primary neural hippocampal cells

The hippocampus is extremely sensitive to microenvironmental signals and toxic events, including massive glutamate release. Despite the extensive literature related to the cascade of molecular events triggered in postsynaptic neurons, the distinction between proapoptotic and survival pathways is still being discussed. In this study, we have investigated the role of c-Fos in glutamate-induced toxicity in primary cultures of hippocampal neurons by using antisense oligonucleotide (ASO) technology. Exposure of cells (5 days in vitro; DIV) to glutamate 0.5 mM for 24 hr caused massive nuclear alteration. An increase in the number of caspase-3-positive cells was also observed 24 hr after glutamate treatment. The expression of c-fos and c-jun immediate-early genes was increased 30 min after glutamate exposure. The study of c-Fos and c-Jun protein expression revealed an increase in the number of cells positive for both antibodies. To investigate whether the expression of c-Fos protein after glutamate treatment was related to cell death activation or cell survival pathways, cells were exposed to 5 microM of c-fos ASO at 4 DIV, 24 hr before glutamate treatment. The presence of the ASO in the medium significantly decreased the number of altered nuclei, and this was associated with a significant reduction in the number of c-Fos-positive cells after glutamate treatment. Exposure of cells to the c-fos ASO under the conditions described above decreased caspase-3 immunostaining induced by glutamate. These results suggest that the synthesis of c-Fos protein after glutamate exposure favors cell death pathway activation in which caspase-3 is also involved.

PTEN: A crucial mediator of mitochondria-dependent apoptosis

The highly frequent mutation of phosphatase and tensin homologue deleted on chromosome 10 (PTEN) in various cancers has attracted much attention to study its role in tumorigenesis. As an important tumor suppressor, the pro-apoptotic function of PTEN has been linked to its capacity antagonizing the PI3K/Akt signaling pathway. However, less data are available concerning its role in neurodegeneration in which apoptotic processes are also involved. In the present study, we attempted to study the role and the underlying mechanism of PTEN in neuronal apoptosis. Using primary rat hippocampal cultures, staurosporine (STS, 100 nM) induced a time-dependent apoptosis, accompanied by a marked production of reactive oxygen species (ROS), release of cytochrome c and activation of caspase 9 and 3. However, the expression of PTEN, and the levels of phospho-PTEN and phospho-Akt were not changed at all time points tested (0.5-24 h) after STS stimulation, suggesting that the protein level as well as the phosphorylation status of PTEN were not related to the procession of apoptosis. Interestingly, immunostaining revealed a punctate intracellular distribution of PTEN from 2 to 8 h after adding STS. Double labeling and Western blotting of mitochondrial fraction demonstrated a mitochondrial location and accumulation of PTEN, respectively, after challenging with STS. Furthermore, we provide evidence for the first time that PTEN was associated with Bax in the absence and the presence of STS. Of note, the STS-induced marked increase in the cellular ROS level, release of cytochrome c and activation of caspase 3 were inhibited in cultured hippocampal cells when PTEN was knocked down by a specific antisense. Moreover, knockdown of PTEN significantly protected hippocampal cells from apoptotic damage. These findings demonstrated that PTEN is a crucial mediator of mitochondria-dependent apoptosis, and thus could become a molecular target for interfering with neurodegenerative diseases.

Ectopic expression of phospho-Smad2 in Alzheimer's disease: Uncoupling of the transforming growth factor-β pathway?

Transforming growth factor-beta (TGF-beta), a multifunctional cytokine, has been widely suggested to play a role in the pathogenesis of Alzheimer's disease. Supporting this, levels of TGF-beta are elevated in the cerebrospinal fluid, sera, and brain of patients with Alzheimer's disease. Since TGF-beta is neuroprotective, whereas Alzheimer's disease is typified by neurodegeneration, we speculated that defects in TGF-beta signaling might abrogate its neuroprotective properties. Consistently with an increase in TGF-beta in Alzheimer's disease, we found significant increases in phospho-Smad2, a major downstream signaling molecule of TGF-beta, in hippocampal neurons of Alzheimer's disease compared with age-matched control patients. However, in contrast to an expected nuclear localization, phosphorylated Smad2 in Alzheimer's disease was predominantly, and ectopically, found in the neuronal cytoplasm, specifically colocalized with neurofibrillary tangles and granulovacuolar degeneration. Given that a nuclear localization is required to regulate the transcription of TGF-beta target genes to afford neuroprotection, the ectopic localization of phosphorylated Smad2 suggests a defect in the Smad-mediated signaling pathway of TGF-beta in Alzheimer's disease and consequent loss of neuroprotective function.

Apoptosis of mink lung epithelial cells by co-treatment of low-dose staurosporine and transforming growth factor-beta1 depends on the enhanced TGF-beta signaling and requires the decreased phosphorylation of PKB/Akt

We demonstrate how co-treatment of low-dose staurosporine (STS) and TGF-beta1, which alone have little effect on cell death, markedly induces apoptosis in Mv1Lu mink lung epithelial cells, but not in its clonal variant R1B cells lacking functional TGF-beta signaling. This process was associated with mitochondria-dependent apoptosis and the enhanced TGF-beta/Smad signaling in Mv1Lu cells. When R1B cells were infected with adenovirus carrying wild-type ALK5, a functional TGF-beta type I receptor gene, the apoptotic cell death was significantly restored in these cells following co-treatment of low-dose STS and TGF-beta1. Treatment of Mv1Lu cells with both low-dose STS and TGF-beta1 decreased the activity of phospho-Akt, which is involved in cell survival signal. In addition, pre-treatments of PI3 kinase inhibitors, LY294002 and wortmannin, further increased the apoptosis of MvlLu cells induced by co-treatment of low-dose STS and TGF-beta1. And overexpression of constitutively active Akt (myr-Akt) using adenoviral expression system inhibited the apoptotic cell death of Mv1Lu cells by about 50% upon co-treatment of low-dose STS and TGF-beta1. These results suggest that co-treatment of low-dose STS and TGF-beta1 induces apoptosis of mink lung epithelial cells by enhancing TGF-beta signaling and in part suppressing cytoprotective signaling.

Glucocorticoid regulation of glial responses during hippocampal neurodegeneration and regeneration

Glucocorticoids can prevent or accelerate neurodegeneration in the adult rat hippocampus. To investigate these actions of glucocorticoids, we previously cloned genes from the hippocampus. Adrenalectomy specifically increased glial fibrillary acidic protein and transforming growth factor (TGF)-beta1 mRNAs in the dentate gyrus and these effects were dependent on induced apoptosis. Corticosterone treatment prevented apoptosis, and decreased glial activation and the influx of activated microglia. Since these effects are opposite to injury and neurodegeneration, we propose that they represent adaptive actions of glucocorticoids, preventing cellular defense mechanisms from overshooting. We used adrenalectomy as a model to investigate how adult granule neurons die in vivo and the effects of neurotrophic factors in protecting against apoptosis. Neurotrophin-4/5 and TGF-beta1 protected granule neurons against adrenalectomy-induced apoptosis. Since neurogenesis is also greatly increased in the dentate gyrus following adrenalectomy, we compared the time course of birth and death with glial responses. TGF-beta1 mRNA increased before the detection of dying cells in the dentate gyrus, which was coincident with increased proliferation in the neurogenic zone. Glucocorticoids also increased Ndrg2 mRNA in glia in the neurogenic zone; Ndrg2 is a member of a novel gene family involved in neural differentiation and synapse formation. Therefore, studying the effects of glucocorticoid manipulation on the dentate gyrus is increasing our understanding of how mature neurons die by apoptosis and the role of glia in induced apoptosis and neurogenesis. Discovering how endocrine and inflammatory responses regulate neuron birth and survival is important for developing successful neuron replacement strategies to treat neurodegenerative diseases.

Oleic acid causes apoptosis and dephosphorylates Bad

There is increasing evidence showing the involvement of unsaturated free fatty acids in cell death pathways, particularly in the context of apoptotic signalling. Our previous in vitro study has demonstrated that oleic acid, a monounsaturated fatty acid, reduces phosphorylation of proapoptotic Bad through activation of protein phosphatase type 2Cbeta. In the present study, we attempted to investigate the role of oleic acid in neuronal apoptosis using different types of cell cultures, and, furthermore, to explore the underlying mechanism with regard to its effect on Bad expression. As revealed by nuclear staining, oleic acid caused a concentration- and time-dependent damage with typical apoptotic features in cortical and hippocampal cultures from embryonic and neonatal rats, respectively, as well as in human neuroblastoma SH-SY5Y cells. In mixed hippocampal cultures, nearly all neurons were damaged at 24 h after the treatment, while damage of astrocytes was detected 48 h after adding this fatty acid, suggesting that neurons were more vulnerable than astrocytes. Nile blue staining showed that oleic acid and oleic acid methyl ester were both taken up by the neurons within 30 min. In contrast to oleic acid, oleic acid methyl ester did not change cell viability demonstrating that oleic acid-induced cell death was not due to an overload of the cells with lipids. Caspase-3 activity was not increased by oleic acid in cultured hippocampal cells. Western blot analysis of phospho-Ser112 Bad and the total Bad in cultured hippocampal cells revealed a significant decrease in the ratio of phospho-Ser112 Bad to total Bad in a time- and concentration-dependent manner after the exposure with oleic acid. We conclude that oleic acid induces neuronal apoptosis through a caspase-3-independent mechanism involving dephosphorylation of Bad.

Caspase-3 expression in human gastric carcinoma and its clinical significance

OBJECTIVES

Caspase-3 is one of the most important molecules in the apoptosis cascade, and the relationship between caspase-3 expression and prognosis has been reported in many types of malignancies. However, the involvement of caspase-3 in human gastric carcinoma is not fully understood. We evaluated caspase-3 expression in human gastric carcinoma to clarify the clinicopathological importance and investigated the apoptosis avoidance mechanism by an immunohistological method.

METHODS

Specimens from 151 patients who underwent gastrectomy at the Department of Surgery and Surgical Basic Science of Kyoto University Hospital were investigated. Caspase-3 expression in cancer cells was evaluated by comparing its expression in the germinal center of the lymphoid follicle, and was quantified as the caspase-3 expression index (C3EI). C3EI was compared with the expression of Bcl-2 and the TdT-mediated dUTP biotin nick-end labeling (TUNEL) in 80 randomly selected cases. Actual activation of caspase-3 was determined by immunohistochemistry using monoclonal antibody that recognizes only activated caspase-3.

RESULTS

C3EI correlated significantly with lymph node metastasis (negative 105.5-78.7, positive 153.8 +/- 66.1 p = 0.001) and the lower C3EI group had a better prognosis than the higher group (log-rank test, p = 0.0001). Cox multivariate analysis showed that age, operation curability, tumor invasion and C3EI were significant independent determinants of overall survival. Bcl-2 and TUNEL staining had no significant correlations with C3EI. Immunohistochemistry of activated caspase-3 revealed that most caspase-3 in gastric cancer cells was not activated, in accordance with TUNEL assay.

CONCLUSIONS

Our results show that C3EI is a novel, independent prognostic factor in gastric cancer patients and cancer cells may avoid apoptosis by inhibiting caspase-3 activation.

Neuroprotection by transforming growth factor-beta1 involves activation of nuclear factor-kappaB through phosphatidylinositol-3-OH kinase/Akt and mitogen-activated protein kinase-extracellular-signal regulated kinase1,2 signaling pathways

Prevention of neuronal apoptosis has been introduced as a new therapeutic strategy for neurodegenerative disorders. We have previously reported anti-apoptotic effects of transforming growth factor-beta1 (TGF-beta1), a multifunctional cytokine, in models of cerebral ischemia and in cultured neurons and recently focused on the mechanisms underlying the anti-apoptotic effect of TGF-beta1. The anti-apoptotic transcriptional factor nuclear factor kappa B (NF-kappaB) shows high impact in the cell survival function of multiple cytokines and growth factors. The present study explored whether NF-kappabeta is a target of TGF-beta1 and which signaling pathways involved in the activation of NF-kappabeta are triggered by TGF-beta1. We demonstrated that TGF-beta1 increased the transcriptional activity of NF-kappabeta in cultured hippocampal neurons in a time- and concentration-dependent manner. Furthermore, TGF-beta1 induced translocation of p65/NF-kappabeta to the nucleus and enhanced NF-kappabeta transcriptional activity in the presence of apoptotic stimuli. TGF-beta1-mediated NF-kappabeta activation was blocked by wortmannin and U0126, indicating the involvement of both phosphatidylinositol-3-OH kinase (PI3k)/Akt and mitogen-activated protein kinase (MAPK)/extracellular-signal regulated kinase (Erk)1,2 pathways in the action of TGF-beta1. TGF-beta1 produced a concomitant increase in the phosphorylations of Ikappabeta kinase (IKKalpha/beta) and Ikappabetaalpha with a subsequent degradation of Ikappabetaalpha. Interestingly, the increased phosphorylation of IKKalpha/beta and Ikappabetaalpha was abrogated by wortmannin, but not by U0126, suggesting that PI3k/Akt and MAPK/Erk1,2 pathways triggered by TGF-beta1 regulated the activation of NF-kappabeta through different mechanisms. Of note, wortmannin and U0126, as well as kappabeta-decoy DNA, abolished the anti-apoptotic effect of TGF-beta1, corroborating the notion that both PI3k/Akt and MAPK/Erk1,2 pathways, and NF-kappabeta activity are necessary for the anti-apoptotic activity of TGF-beta1.

TGFβ-1 and neurological function after hypoxia-ischemia in adult rats

The present study compared the short-term and long-term neuroprotective and neurobehavioral effects of transforming growth factor beta-1 (TGF beta-1) after hypoxic-ischemic injury in adult rats. TGF beta-1 (10 ng) or vehicle were administered intracerebroventricularly (i.c.v.) 2 h after hypoxia-ischemia. Adhesive removal test was assessed after 10 or 40 days, and the neuronal outcome then determined. TGF beta-1 significantly increased the area of intact cortex compared with vehicle 10 days after the injury, with a significant improvement in neurological function. In contrast, after 40 days recovery TGFbeta-1 neither improved neuronal outcome nor neurological function, suggesting TGFbeta-1 can transiently improve functional and histological recovery from hypoxia-ischemia.

Gene expression profile analyses of cortical dysplasia by cDNA arrays

Cortical dysplasia (CD) is a well-recognized cause of intractable epilepsy, especially in children and is characterized histologically by derangements in cortical development and organization. The objective of this study was to expand the current knowledge of altered gene expression in CD as a first step towards in the identification of additional genes operative in the evolution of CD. Surgical specimens were obtained from eight patients (4 males and 4 females; age range 2-38 years; mean 15 years) with a pathologic diagnosis of CD. Nondysplastic temporal neocortex was obtained from a 2-year-old boy with intractable epilepsy and medial temporal lobe ganglioglioma. After total RNA isolation from frozen brain tissues, we carried out gene expression profiling using a cDNA expression array. Differences in gene expressions between CD and the nondysplastic neocortex were confirmed by semi-quantitative conventional reverse transcription-PCR. Three genes (recombination activating gene 1 (RAG1), heat shock 60 kDa protein 1 (HSP-60), and transforming growth factor beta1 (TGF beta1)) were found to be up-regulated more than two-fold in CD, whereas four genes (phosphoinositide-3-kinase regulatory subunit polypeptide 1 [p85 alpha] (PI3K), frizzled homolog 2 [Drosophila], Bcl-2/adenovirus E1B 19 kDa interacting protein (NIP3), and glia maturation factor beta (GMF beta)) were down-regulated to less than 50% of their normal levels. Interestingly, the majority of genes showing altered expression were associated with apoptosis. Our study demonstrates diverse changes in gene expression in CD. However, it remains to be shown which of these are causally related to the evolution of CD.

Astrocyte protection of neurons: role of transforming growth factor-beta signaling via a c-Jun-AP-1 protective pathway

Astrocytes have become a focal point for research in neurobiology, especially regarding their purported ability to regulate neuronal communication and survival. The present study addressed a poorly understood but important focus in this area, the mechanism(s) underlying astrocyte-induced survival of neurons. The results of the study show that soluble factors in astrocyte-conditioned media (ACM) protect murine GT1-7 neurons from serum deprivation-induced cell death and that this neuroprotection is correlated with enhanced activation/phosphorylation of the AP-1 transcription factor, c-JunSer-63. A parallel and correlated activation of the upstream kinases, c-Jun N-terminal kinase (JNK) and mitogen-activated protein kinase kinase-4 (MKK4) was also demonstrated. Furthermore, co-administration of JNK inhibitors, but not a MEK inhibitor, significantly attenuated ACM-induced phosphorylation of c-JunSer-63 and blocked its neuroprotective action. Gel shift analysis demonstrated that ACM enhanced AP-1 binding, an effect that appears functionally important, since an AP-1 binding inhibitor significantly attenuated the neuroprotective action of ACM. Further studies implicated transforming growth factor (TGF)-beta1 and TGF-beta2 as critical active soluble factors released by astrocytes, since both were demonstrated in ACM, and immunoneutralization of the conditioned media with a panspecific TGF-beta antibody significantly attenuated the enhanced AP-1 binding and neuroprotective action of the ACM. Furthermore, exogenous application of TGF-beta1 and TGF-beta2 was found to enhance c-JunSer-63 phosphorylation and to be neuroprotective, and co-administration of JNK inhibitors or an AP-1 binding inhibitor blocked TGF-beta-induced neuroprotection. Taken together, these studies suggest that astrocytes can protect neurons from serum deprivation-induced cell death, at least in part, by release of TGF-beta and activation of a c-Jun/AP-1 protective pathway.

Stimulus-dependent activation of NF-kappaB specifies apoptosis or neuroprotection in cerebellar granule cells

Oxidative stress is believed to play an important role in neuronal cell death associated with several neurodegenerative diseases (e.g., Alzheimer disease, Parkinson disease, and cerebral ischemia). Neuronal cell death might be one of the crucial mediators of these diseases. The transcription factor NF-kappaB is well-known for its roles in preventing apoptotic cell death. Data indicated that NF-kappaB activation by pre-conditioning is part of a general brain tolerance program. Here we show that pre-conditioning leading to NF-kappaB activation also protects against oxidative insults generated by Fe2+ ions. Protection was accompanied by a long-lasting (more than 24 h) NF-kappaB activation. Using this paradigm of oxidative insult, we analyzed the effect of hypericin, one of the active principles of St. John's Wort. Hypericin alone was able to induce short-time activation of NF-kappaB, which declined to basal levels after 24 h. Cell death was induced by hypericin at a concentration of 10 microM. A profound synergistic action in inducing apoptosis was detected in co-treatment of hypericin together with FeSO4. In contrast, hypericin in low concentrations was able to partly prevent cell death induced by amyloid-beta-peptide (Abeta). Hypericin (10 microM) synergistically enhanced Abeta neurotoxicity. Since hypericin is a described inhibitor of protein kinase C, we compared its action to staurosporine, another natural neuronal death-promoting PKC inhibitor. Staurosporine induced cell death and activates NF-kappaB. Molecular inhibition of NF-kappaB activation with a transdominant negative IkappaB-alpha protected against staurosporine-induced cell death. In summary, the data describe NF-kappaB in the same primary neuronal culture as stimulus-dependent, anti-apoptotic, or pro-apoptotic factor.

Macrophage colony stimulating factor prevents NMDA-induced neuronal death in hippocampal organotypic cultures

Macrophage colony stimulating factor (M-CSF) and its receptor are up-regulated in the brain in Alzheimer's disease (AD), in transgenic mouse models for AD, and experimental models for traumatic and ischemic brain injury. M-CSF induces activation and proliferation of microglial cells and expression of proinflammatory cytokines. We examined the role of M-CSF in excitotoxic neuronal cell death in organotypic hippocampal cultures. NMDA treatment induced neuronal apoptosis and caspase-3 activation in organotypic hippocampal cultures, whereas treatment with M-CSF protected hippocampal neurons from NMDA-induced apoptosis. Caspase-3 activation was inhibited by M-CSF treatment to the same degree as with the caspase inhibitor Z-VAD-FMK. These results suggest that M-CSF has neuroprotective properties through inhibition of caspase-3 that could promote neuronal survival after excitotoxic insult. The role of M-CSF in neurological disease should be reevaluated as a microglial activator with potentially neuroprotective effects.

Transforming growth factor-beta 1 increases bad phosphorylation and protects neurons against damage

Despite the characterization of neuroprotection by transforming growth factor-beta1 (TGF-beta1), the signaling pathway mediating its protective effect is unclear. Bad is a proapoptotic member of the Bcl-2 family and is inactivated on phosphorylation via mitogen-activated protein kinase (MAPK). This study attempted to address whether MAPK signaling and Bad phosphorylation were influenced by TGF-beta1 and, furthermore, whether these two events were involved in the antiapoptotic effect of TGF-beta1. We found a gradual activation of extracellular signal-regulated kinase 1/2 (Erk1/2) and MAPK-activated protein kinase-1 (also called Rsk1) and a concomitant increase in Bad phosphorylation at Ser(112) in mouse brains after adenovirus-mediated TGF-beta1 transduction under nonischemic and ischemic conditions induced by transient middle cerebral artery occlusion. Consistent with these effects, the ischemia-induced increase in Bad protein level and caspase-3 activation were suppressed in TGF-beta1-transduced brain. Consequently, DNA fragmentation, ischemic lesions, and neurological deficiency were significantly reduced. In cultured rat hippocampal cells, TGF-beta1 inhibited the increase in Bad expression caused by staurosporine. TGF-beta1 concentration- and time-dependently activated Erk1/2 and Rsk1 accompanied by an increase in Bad phosphorylation. These effects were blocked by U0126, a mitogen-activated protein kinase/Erk kinase 1/2 inhibitor, suggesting an association between Bad phosphorylation and MAPK activation. Notably, U0126 and a Rsk1 inhibitor (Ro318220) abolished the neuroprotective activity of TGF-beta1 in staurosporine-induced apoptosis, indicating that activation of MAPK is necessary for the antiapoptotic effect of TGF-beta1 in cultured hippocampal cells. Together, we demonstrate that TGF-beta1 suppresses Bad expression under lesion conditions, increases Bad phosphorylation, and activates the MAPK/Erk pathway, which may contribute to its neuroprotective activity.

Transforming growth factor beta1, the dominant cytokine in murine prion disease: influence on inflammatory cytokine synthesis and alteration of vascular extracellular matrix

Previous studies from our laboratory have shown the ME7 model of murine scrapie to be accompanied by an atypical inflammatory response that is characterized by marked astroglial and microglial activation but also by the lack of significant expression of the pro-inflammatory cytokines interleukin (IL)-1beta and IL-6. The aim of this study was to determine whether, in the absence of IL-1beta and IL-6, tumour necrosis factor (TNF)-alpha may play an equivalent pro-inflammatory role, or if an anti-inflammatory cytokine profile dominates. We have used competitive polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA) to determine the levels of TNF-alpha, IL-10 and transforming growth factor (TGF)-beta1 in the ME7 model, using their expression in lipopolysaccharide (LPS)-induced acute inflammation as a positive control. Levels of mRNA were elevated for all three cytokines during acute inflammation, while TGF-beta1 mRNA alone was significantly elevated in ME7-injected brains. Similarly, by ELISA, we detected elevated IL-10, TNF-alpha and TGF-beta1 in LPS-injected animals but only significant elevation of TGF-beta1 in ME7-injected animals. An increase in laminin and collagen IV deposition around blood vessels was also observed and is consistent with up-regulation by active TGF-beta1. These findings suggest that TGF-beta1 may play a central role in maintenance of an atypical microglial phenotype and may also be involved in vascular and extracellular matrix changes.