Caspase-3 activation and inflammatory responses in rat hippocampus inoculated with a recombinant adenovirus expressing the Alzheimer amyloid precursor protein

Ojeok-san ameliorates visceral and somatic nociception in a mouse model of colitis induced colorectal cancer

Cancer patients can develop visceral, somatic, and neuropathic pain, largely due to the malignancy itself and its treatments. Often cancer patients and survivors turn to the use of complementary and alternative medicine (CAM) to alleviate pain and fatigue. Thus, it is necessary to investigate how CAM therapies work as novel analgesics to treat cancer pain. Ojeok-san (OJS) is an herbal formula consisting of seventeen herbs. This herbal formula has been shown to possess anti-inflammatory, immunoregulatory, and analgesic properties. In this study, we examined the potential beneficial effects and mechanism of action of OJS in a preclinical model of colitis-associated colorectal cancer. Male and female C57BL/6J mice were exposed to the carcinogen, azoxymethane (AOM, 10 mg/kg) and a chemical inflammatory driver, dextran sulfate sodium (DSS1-2%), to promote tumorigenesis in the colorectum. OJS was given orally (500, 1000, and 2000 mg/kg) to determine its influence on disease activity, tumor burden, nociception, sedation, Erk signaling, and behavioral and metabolic outcomes. In addition, in vitro studies were performed to assess CT-26 cell viability, dorsal root ganglia (DRG) activation, and bone-marrow-derived macrophage (BMDM) inflammatory response to lipopolysaccharide stimulation after OJS treatment. We found that administration of 2000 mg/kg of OJS was able to mitigate mechanical somatic and visceral nociception via Erk signaling without affecting symptom score and polyp number. Moreover, we discovered that OJS has sedative properties and elicits prolonged total sleeping time in AOM/DSS mice. Our in vitro experiments showed that OJS has the capacity to reduce TNFα gene expression in LPS-stimulated BMDM, but no changes were observed in DRG spike number and CT-26 cell proliferation. Taken together, these data suggest that OJS ameliorates nociception in mice and warrants further examination as a potential CAM therapy to promote analgesia.

Dieckol exerts anticancer activity in human osteosarcoma (MG-63) cells through the inhibition of PI3K/AKT/mTOR signaling pathway

Background

Osteosarcoma (OS) is the most common malignant bone cancer with more metastasis and increased occurrence in children and teen-agers and being responsible for more number of morbidity and mortality worldwide.

Objective

The current exploration was planned study the in vitro anticancer actions of dieckol against human OS MG-63 cells via PI3K/AKT/mTOR signaling inhibition.

Methodology

The cytotoxicity of dieckol was scrutinized by MTT assay. Effects of dieckol on the ROS accumulation, apoptotic cell death, and MMP level in the MG-63 cells were studied by respective fluorescence staining assays. The levels of proliferative, inflammatory, and apoptotic markers in the dieckol treated MG-63 cells were scrutinized by marker specific kits. The expressions of PI3K, AKT, and mTOR was assayed by RT-PCR.

Results

The MTT assay revealed that the dieckol dose dependently prevented MG-63 cells viability and the IC50 was found at 15 µM. Dieckol treatment effectively reduced the MMP level and improved the ROS generation and apoptosis in MG-63 cells. Dieckol also regulated the proliferative (cyclin D1), inflammatory (COX-2, IL-6, TNF-α, and NF-κB), and apoptotic (caspase-3, Bax, Bcl-2) markers in the MG-63 cells. The PI3K/AKT/mTOR signaling in the MG-63 cells were effectively inhibited by the dieckol treatment.

Conclusion

In conclusion, our findings from this study recommends that the dieckol could be a talented anticancer candidate for the OS management in the future.

Green synthesized zinc oxide nanoparticles regulates the apoptotic expression in bone cancer cells MG-63 cells

Management of degenerative spine pathologies frequently leads to the need for bone growth. Rehmanniae Radix (RR), a Chinese herbal formulation was found to exhibit numerous therapeutic properties including its potent effect against cancer cell lines. However, the underlying mechanism through which the Zinc oxide nanoparticles (ZnONPs) synthesized from Rehmanniae Radix exerts its anti-cancer activity against osteosarcoma cell line MG-63 needs to be explored. Therefore, the study was performed to evaluate the anticancer, cytotoxicity and apoptotic effectiveness of ZnONPs from RR against MG-63 cells. Characterization studies such UV-vis spectroscopy, FTIR, TEM and XRD analysis were performed. Cytotoxicity assay, mitochondrial membrane potential (MMP), morphological examination of cells and formation of reactive oxygen species (ROS), and apoptosis inducing ability of RR were evaluated by various procedures. Western blot analysis of apoptotic markers such as Bax, caspase-3 and caspase-9 were also performed. RR was found to inhibit growth of MG-63 cells at increasing dose. AO/EB staining confirmed the apoptotic efficacy of ZnONPs induced by RR in MG-63 cells. ZnONPs was also found to initiate increased generation of ROS and decreased MMP. Decreased MMP has resulted in increased levels of apoptotic proteins Bax, caspase-3 and caspase-9 and induction of apoptosis was substantiated by western blot analysis. The outcomes of the work propose that ZnONPs from RR exhibits strong anticancer action and inducing apoptosis on MG-63 cells via stimulating increased generation of ROS. Thus, ZnONPs from RR might be used as a hopeful drug target against several types of cancer cell lines.

Amyloid-β precursor protein facilitates the regulator of calcineurin 1-mediated apoptosis by downregulating proteasome subunit α type-5 and proteasome subunit β type-7

Individuals with Down syndrome (DS), caused by trisomy of chromosome 21, inevitably develop characteristic Alzheimer's disease (AD) neuropathology, including neuritic plaques, neurofibrillary tangles, and neuronal loss. Amyloid-β protein, the major component of neuritic plaques, is the proteolytic product of amyloid-β precursor protein (APP). APP and the regulator of calcineurin 1 (RCAN1) genes on chromosome 21 play a pivotal role in promoting plaque formation and neuronal apoptosis. However, the mechanism underlying AD pathogenesis in DS is not well defined. In this study, we demonstrated that APP significantly increased RCAN1 level in both cells and transgenic mice. Overexpression of APP significantly reduced the expression of 2 proteasome subunits, proteasome subunit α type-5 and proteasome subunit β type-7, leading to the inhibition of proteasomal degradation of RCAN1. Furthermore, knockdown of RCAN1 expression attenuated APP-induced neuronal apoptosis. Taken together, the results clearly showed that APP has a previously unknown function in regulating RCAN1-mediated neuronal apoptosis through the proteasome pathway. Our study demonstrates a novel mechanism by which overexpression of APP and RCAN1 causes neurodegeneration and AD pathogenesis in DS, and it provides new insights into the potential of targeting APP-induced proteasomal impairment and RCAN1 accumulation for AD and DS treatment.

Beta amyloid-induced upregulation of death receptor 6 accelerates the toxic effect of N-terminal fragment of amyloid precursor protein

Amyloid precursor protein (APP) plays essential roles in the development of the Alzheimer's disease. Although full-length APP has been thoroughly studied, the role of the cleavage fragments especially the N-terminal fragments (N-APPs) in Alzheimer's disease pathogenesis was still elusive. In this study, we demonstrated that application of recombinant APP₁₈₋₂₈₆ could enhance beta amyloid (Aβ)-induced neuronal injuries which were related to the activation of apoptosis proteins. Aβ treatment could induce a slight increase of N-APPs release. In addition, expression of death receptor 6 (DR6) was increased in Aβ-treated neurons and APP transgenic mice. Moreover, the effect of APP₁₈₋₂₈₆ on Aβ-induced injuries could be suppressed by the application of recombinant DR6₄₁₋₃₄₁ and DR6 antibody. Furthermore, pull-down assay revealed that APP₁₈₋₂₈₆ could bind both exogenous and endogenous DR6. Aβ promoted APP₁₈₋₂₈₆ targeting to neuron which was accompanied with the increase of DR6 expression, whereas downregulation of DR6 by interference RNA could alleviate the binding of N-APPs to neuron and also suppressed Aβ-dependent toxic effect with N-APPs. These results suggested that APP N-terminal fragments might play neurotoxic roles in Aβ-induced neuronal injuries through cell surface DR6.

Epigallocatechin gallate protects against nitric oxide-induced apoptosis via scavenging ROS and modulating the Bcl-2 family in human dental pulp cells

Nitric oxide (NO) is produced by three different isoforms of the enzyme NO synthase (NOS). NOS isoforms are expressed in many cell types, including human dental pulp cells (HDPC). NO acts as an intracellular messenger at physiological levels although it can be cytotoxic at higher concentrations. Epigallocatechin gallate (EGCG), a major green tea polyphenol, has diverse pharmacological activities in cell growth and death. This study is aimed to investigate the apoptotic mechanism by NO and effects of EGCG on NO-induced apoptosis in HDPC. Sodium nitroprusside (SNP), an NO donor, decreased the cell viability of HDPC in a dose- and time-dependent manner. EGCG was administered for 1 hr before the SNP treatment, resulting in increased cell viability and reactive oxygen species (ROS) production inhibition. Expression of Bax, a pro-apoptotic Bcl-2 family, was upregulated, whereas expression of Bcl-2, an anti-apoptotic Bcl-2 family, was downregulated in SNP-treated HDPC. SNP augmented the release of cytochrome c from mitochondria into cytosol and enhanced caspase-9, and -3 activities, a marker of the apoptotic executing stage. EGCG ameliorated caspase-9 and -3 activities and cytochrome c release increased by SNP. These results suggest that EGCG has a protective effect against NO-induced apoptosis in HDPC by scavenging ROS and modulating the Bcl-2 family.

The effects of cobalt on the development, oxidative stress, and apoptosis in zebrafish embryos

Metal-on-metal hip arthroplasty has been performed with increasing frequency throughout the world, particularly in younger and more active patients, including women of childbearing age. The potential toxicity of cobalt exposure on fetus is concerned since cobalt ions generated by metal-on-metal bearings can traverse the placenta and be detected in fetal blood and amniotic fluid. This study examined the effects of cobalt exposure on early embryonic development and the mechanisms underlying its toxicity. Zebrafish embryos were exposed to a range of cobalt concentrations (0-100 mg/L) between 1 and 144 h postfertilization. The survival and early development of embryos were not significantly affected by cobalt at concentrations <100 μg/L. However, embryos exposed to higher concentrations (>100 μg/L) displayed reduced survival rates and abnormal development, including delayed hatching, aberrant morphology, retarded growth, and bradycardia. Furthermore, this study examined oxidative stress and apoptosis in embryos exposed to cobalt at concentrations of 0-500 μg/L. Lipid peroxidation levels were increased in cobalt-treated embryos at concentrations of 100 and 500 μg/L. The mRNA levels of catalase, superoxide dismutase 2, p53, caspase-3, and caspase-9 genes were upregulated in a dose-dependent manner. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assays also revealed abnormal apoptotic signals in the brain, trunk, and tail when treated with 500 μg/L cobalt. These data suggest that oxidative stress and apoptosis are associated with cobalt toxicity in zebrafish embryos.

In vitro modelling of Alzheimer's disease: degeneration and cell death induced by viral delivery of amyloid and tau

With increasing life expectancy, Alzheimer's disease (AD) and other dementias pose an increasing and as yet unresolved health problem. A variety of cellular models of AD has helped to decipher some key aspects of amyloid and tau related degeneration. The initial approach of extracellular applications of synthetic peptides has now been replaced by the introduction of amyloid precursor protein (APP) and tau genes. In the present study adenoviral transductions were exploited for gene delivery into primary rat hippocampal and dorsal root ganglion (DRG) cultures to enable comparative and mechanistic studies at the cellular level and subsequent drug testing. Time lapse experiments revealed a different pattern of cell death: apoptotic-like for APP whereas tau positive cells joined and formed clusters. Mutated human APP or tau expression caused accelerated neuronal damage and cell death (cf. EGFP: -50% for APP at 5 days; -40% for tau at 3 days). This reduction in viability was preceded by decreased excitability, monitored via responses to depolarising KCl-challenges in Ca(2+) imaging experiments. Additionally, both transgenes reduced neurite outgrowth in DRG neurones. Treatment studies confirmed that APP induced-damage can be ameliorated by β- and γ-secretase inhibitors (providing protection to 60-100% of control levels), clioquinol (80%) and lithium (100%); while anti-aggregation treatments were beneficial for tau-induced damage (60-90% recovery towards controls). Interestingly, caffeine was the most promising drug candidate for therapeutic intervention with high efficacy in both APP (77%) and tau-induced models (72% recovery). Overall, these cellular models offer advantages for mechanistic studies and target identification in AD and related disorders.

The functional neurophysiology of the amyloid precursor protein (APP) processing pathway

Amyloid beta (Abeta) peptides derived from proteolytic cleavage of amyloid precursor protein (APP) are thought to be a pivotal toxic species in the pathogenesis of Alzheimer's disease (AD). Furthermore, evidence has been accumulating that components of APP processing pathway are involved in non-pathological normal function of the CNS. In this review we aim to cover the extensive body of research aimed at understanding how components of this pathway contribute to neurophysiological function of the CNS in health and disease. We briefly outline changes to clinical neurophysiology seen in AD patients before discussing functional changes in mouse models of AD which range from changes to basal synaptic transmission and synaptic plasticity through to abnormal synchronous network activity. We then describe the various neurophysiological actions that are produced by application of exogenous Abeta in various forms, and finally discuss a number or other neurophysiological aspects of the APP pathway, including functional activities of components of secretase complexes other than Abeta production.

Antibody binding to cell surface amyloid precursor protein induces neuronal injury by deregulating the phosphorylation of focal adhesion signaling related proteins

The biological function of full-length amyloid-beta protein precursor (APP), the precursor of Abeta, is not fully understood. Mounting studies reported that antibody binding to cell surface APP causes neuronal injury. However, the mechanism of cell surface APP mediating neuronal injury remains to be determined. Colocalization of APP with integrin on cell surface leads us to suppose that focal adhesion (FA) related mechanism is involved in surface APP-mediated neuronal injury. In the present study, results demonstrated that primary cultured neurons treated with antibody against APP-N-terminal not only caused neuronal injury and aberrant morphologic changes of neurite, but also induced reaction of FA proteins appearing an acute increase then decrease pattern. Moreover, the elevation of tyrosine phosphorylation of FA proteins including paxillin and focal adhesion kinase (FAK), and down-regulated expression of protein tyrosine phosphatase (PTP1B) induced by APP antibody were prevented by inhibitor of Src protein kinases 4-amino-5-(4-chlorophenyl)-7(t-butyl) pyrazol (3,4-D) pyramide (PP2) and G protein inhibitor pertussis toxin (PTX), implying that Src family kinase and G protein play roles in APP-induced FA signals. In addition, pretreatment with PTX and PP2 was able to suppress APP-antibody induced neuronal injury. Taken together, the results suggest a novel mechanism for APP mediating neuronal injury through deregulating FA signals.

Versatile somatic gene transfer for modeling neurodegenerative diseases

A growing variety of technical approaches allow control over the expression of selected genes in living organisms. The ability to deliver functional exogenous genes involved in neurodegenerative diseases has opened pathological processes to experimental analysis and targeted therapeutic development in rodent and primate preclinical models. Biological adaptability, economic animal use, and reduced model development costs complement improved control over spatial and temporal gene expression compared with conventional transgenic models. A review of viral vector studies, typically adeno-associated virus or lentivirus, for expression of three proteins that are central to major neurodegenerative diseases, will illustrate how this approach has powered new advances and opportunities in CNS disease research.

Differential binding and activation of caspase-3 in cultured hippocampal neurons by assembly forms of A beta 1-42

Amyloid-beta (A beta) peptides, the primary constituents of amyloid plaques in the brain in Alzheimer's disease (AD), may cause AD, but how they do so is not clear. A beta peptides spontaneously aggregate, or self-assemble, to generate several distinct macromolecular and morphological forms that can differ significantly in their effects on cells. We have compared different assembly forms of A beta(1-42) (A beta 42) for their ability to trigger apoptosis in cultured hippocampal neurons at a submicromolar concentration and for their binding to such neurons. Fibrillar A beta 42 caused both morphological changes indicative of apoptosis and specific activation of caspase-3, a characteristic marker of neurodegeneration in AD, in hippocampal neurons, whereas other preparations tested did not do so under the same conditions. More aggregated forms of A beta 42, including both fibrils and a mixture of assembly forms termed A beta-derived diffusible ligands (ADDLs), bound to neurons much more extensively and at lower concentrations than preparations that contained smaller forms. Fibrillar A beta 42, in particular, bound to neurons at concentrations as low as 1 nM. Colocalization studies showed that fibrillar A beta 42 bound almost exclusively at nonsynaptic sites. These results show differences between assembly forms of A beta 42 in the ability to trigger apoptotic signaling in CNS neurons, and they directly demonstrate differences between assembly forms in the binding to CNS neurons, a possible first step in the pathogenesis of AD. These results suggest that fibrillar A beta 42 contributes to the pathogenesis of AD.

Inhibition by epigallocatechin gallate of CoCl2-induced apoptosis in rat PC12 cells

Epigallocatechin-3-gallate (EGCG) is a major constituent of green tea polyphenols. This study was aimed to investigate the possible mechanisms of EGCG-mediated inhibition against apoptosis in rat pheochromocytoma PC12 cells by exposure to CoCl(2). Exposure to CoCl(2) caused the generation of ROS and induced cell death with appearance of apoptotic morphology and DNA fragmentation. However, EGCG rescued the loss of viability in the cells exposed to CoCl(2) and led the reduction of DNA fragmentation and sub-G(1) fraction of cell cycle. Also, EGCG attenuated the CoCl(2)-induced disruption of mitochondrial membrane potential (DeltaPsim), release of cytochrome c from the mitochondria to cytosol and abolished the CoCl(2)-stimulated activities of the caspase cascades, caspase-9 and caspase-3. In addition, EGCG ameliorated the increase in the Bax to Bcl-2 ratio, a marker of apoptosis proceeding, induced by CoCl(2) treatment. Taken together, the present results suggest that EGCG inhibit the CoCl(2)-induced apoptosis of PC12 cells through the mitochondria-mediated apoptosis pathway involved in modulating the Bcl-2 family.

Amyloid precursor protein regulates differentiation of human neural stem cells

Although amyloid beta (Abeta) deposition has been a hallmark of Alzheimer's disease (AD), the absence of a phenotype in the beta amyloid precursor protein (APP) knockout mouse, tends to detract our attention away from the physiological functions of APP. Although much attention has been focused on the neurotoxicity of Abeta, many studies suggest the involvement of APP in neuroplasticity. We found that secreted amyloid precursor protein (sAPP) increased the differentiation of human neural stem cells (hNSCs) in vitro, while an antibody-recognizing APP dose-dependently inhibited these activities. With a high dose of sAPP treatment or wild-type APP gene transfection, hNSCs were differentiated into astrocytes rather than neurons. In vivo, hNSCs transplanted into APP-transgenic mouse brain exhibited glial differentiation rather than neural differentiation. Our results suggest that APP regulates neural stem cell biology in the adult brain, and that altered APP metabolism in Down syndrome or AD may have implications for the pathophysiology of these diseases.

Suppression of Stat3 promotes neurogenesis in cultured neural stem cells

To investigate the effects of signal transducer and activator of transcription 3 (Stat3) on neural stem cell fate, stem cells were inoculated with an adenovirus vector expressing dominant negative form of Stat3 (Stat3F). One day later, a promoter assay revealed significant reduction of the transcriptional level in the transfected cells. Three days later, Western blot analysis and immunocytochemical analysis revealed that the protein level of microtubule-associated protein (MAP)2 and the number of MAP2-positive cells were increased significantly in the transfected cells whereas the protein level of glial fibrillary acidic protein (GFAP) and the number of GFAP-positive cells were decreased significantly. In addition, mRNA levels of Notch family members (Notch1, 2, and 3) and of inhibitory basic helix-loop-helix (bHLH) factors (Hes5, Id2, and Id3) were significantly downregulated at 3 days after viral inoculation with Stat3F; however, mRNA levels of bHLH determination factors (Math1 and Neurogenin3) and bHLH differentiation factors (NeuroD1 and NeuroD2) were significantly upregulated. These data indicated that suppression of Stat3 directly induced neurogenesis and inhibited astrogliogenesis in neural stem cells.

Nicotine attenuates beta-amyloid peptide-induced neurotoxicity, free radical and calcium accumulation in hippocampal neuronal cultures

1. Recent studies indicate that neuronal loss in Alzheimer's disease (AD) is accompanied by the deposition of beta-amyloid protein (A beta) in senile plaques. Nicotine as a major component of cigarette smoke has been suggested to have a protective effect for neurons against A beta neurotoxicity. 2. Our present study demonstrates that nicotine protected cultured hippocampal neurons against the A beta-induced apoptosis. Nicotine effectively inhibits apoptosis in hippocampal cultures caused by A beta(25-35) or A beta(1-40) treatment and increase of caspase activity induced by A beta(25-35) or A beta(1-40). 3. Measurements of cellular oxidation and intracellular free Ca(2+) showed that nicotine suppressed A beta-induced accumulation of free radical and increase of intracellular free Ca(2+). 4. Cholinergic antagonist mecamylamine inhibited nicotine-induced protection against A beta-induced caspase-3 activation and ROS accumulation. 5. The data show that the protection of nicotine is partly via nicotinic receptors. Our results suggest that nicotine may be beneficial in retarding the neurodegenerative diseases such as AD.

Green tea polyphenols enhance sodium nitroprusside-induced neurotoxicity in human neuroblastoma SH-SY5Y cells

Oxidative stress is a main mediator in nitric oxide (NO) -induced neurotoxicity and has been implicated in the pathogenesis of many neurodegenerative disorders. Green tea polyphenols are usually expected as potent chemo-preventive agents due to their ability of scavenging free radicals and chelating metal ions. However, not all the actions of green tea polyphenols are necessarily beneficial. In the present study, we demonstrated that higher-concentration green tea ployphenols significantly enhanced the neurotoxicity by treatment of sodium nitroprusside (SNP), a nitric oxide donor. SNP induced apoptosis in human neuroblastoma SH-SY5Y cells in a concentration and time-dependent manner, as estimated by cell viability assessment, FACScan analysis and DNA fragmentation assay, whereas treatment with green tea polyphenols alone had no effect on cell viability. Pre-treatment with lower-dose green tea polyphenols (50 and 100 microm) had only a slightly deleterious effect in the presence of SNP, while higher-dose green tea polyphenols (200 and 500 microm) synergistically damaged the cells severely. Further research showed that co-incubation of green tea polyphenols and SNP caused loss of mitochondrial membrane potential, depletion of intracellular GSH and accumulation of reactive oxygen species, and exacerbated NO-induced neuronal apoptosis via a Bcl-2 sensitive pathway.

Late Simian virus 40 transcription factor is a target of the phosphoinositide 3-kinase/Akt pathway in anti-apoptotic Alzheimer's amyloid precursor protein signalling

The association of familial Alzheimer's disease (FAD) with mutations in Alzheimer's amyloid precursor protein (APP) suggests important functions for APP in the central nervous system. Mutations in APP impair its function to confer resistance to apoptosis in cells under stress, and this may contribute to neurodegeneration in Alzheimer's disease (AD) brain, but the mechanisms involved are unknown. We examined the role of the late Simian virus 40 transcription factor (LSF), in anti-apoptotic APP pathways. We show that in APP-deficient B103 cells, expression of wild-type human APP (hAPPwt), but not of FAD-mutant APP, inhibited staurosporine (STS)-induced apoptosis. This inhibition was further enhanced by expression of LSFwt, although LSFwt alone was not sufficient to inhibit STS-induced apoptosis. In contrast, expression of dominant-negative LSF led to a marked increase in STS-induced cell death that was significantly blocked by hAPPwt. These effects of APP were accompanied by LSF nuclear translocation and dependent gene transcription. The activation of LSF is dependent on the expression of hAPPwt and is inhibited by the expression of dominant-negative forms of either phosphoinositide 3-kinase or Akt. These results demonstrate that LSF activation is required for the neuroprotective effects of APP via phosphoinositide 3-kinase/Akt signalling. Alterations in this pathway by aberrations in APP and/or LSF could promote neuronal loss in AD brain, due to secondary insults. Thus a link is established between APP and LSF and AD.

Neuroinflammation and anti-inflammatory therapy for Alzheimer's disease

Neuroinflammation is now recognized as a prominent feature in Alzheimer's pathology and a potential target for therapy aimed at treatment and prevention of disease. This review provides a synopsis of current information about cellular and molecular mediators involved in Alzheimer's neuroinflammation as well as interactions between these mediators that influence pathology. Anti-inflammatory therapies, particularly nonsteroidal anti-inflammatory drugs, are considered from experimental and clinical perspectives and potential mechanisms underlying their apparent benefits are discussed. Finally, possible protective effects of the inflammatory response in Alzheimer's are described. Taken all together, evidence presented in this review suggests a scheme for Alzheimer's pathogenesis, with neuroinflammation playing a crucial role influencing and linking beta-amyloid deposition to neuronal damage and clinical disease.

Anti-apoptotic wild-type Alzheimer amyloid precursor protein signaling involves the p38 mitogen-activated protein kinase/MEF2 pathway

Alzheimer amyloid precursor protein (APP) effectively protects against apoptosis in neuronal cells under stress, but the mechanisms of this anti-apoptotic effect remain largely unknown. Transcription factors act as critical molecular switches in promoting neuronal survival. The myocyte enhancer factor-2 (MEF2) is a transcription factor, and is known to be necessary for neurogenesis and activity-dependent neuronal survival. This study examined the possible role of MEF2 in the anti-apoptotic signaling pathways activated by APP. We report that expression of wild-type human APP (hAPPwt) but not familial Alzheimer's disease mutant APP (FAD-hAPPmut) in APP-deficient rat B103 cells led to a significant increase in the level of phosphorylated MEF2. This differential phosphorylation was dependent on enhanced activation of p38 mitogen-activated protein kinase (p38 MAPK). Also, expression of hAPPwt mediated an increase in MEF2 DNA binding affinity that correlated with p38 MAPK-dependent trans-activation of a MEF2-responsive reporter gene. Furthermore, over-expression of dominant negative MEF2 in hAPPwt-expressing cells enhanced staurosporine-induced apoptosis, in contrast MEF2wt enhanced the capacity of hAPPwt to confer resistance to apoptosis. Thus, MEF2 plays a critical role in APP-mediated signaling pathways that inhibit neuronal apoptosis. A model of anti-apoptotic APP signaling is proposed where APP mediates p38 MAPK-dependent phosphorylation and activation of MEF2. Once activated MEF2 regulates neuronal survival by stimulation of MEF2-dependent gene transcriptions. Alteration of this function by mutations in APP and aberrant APP processing could contribute to neuronal degeneration seen in AD.

Activation of calpain in cultured neurons overexpressing Alzheimer amyloid precursor protein

We have previously reported that overexpression of wild-type amyloid precursor protein (APP) in postmitotic neurons induces cleavage-dependent activation of caspase-3 both in vivo and in vitro. In this study, we investigated the mechanism underlying APP-induced caspase-3 activation using adenovirus-mediated gene transfer into postmitotic neurons derived from human embryonal carcinoma NT2 cells. Overexpression of wild-type APP significantly increased intracellular (45)Ca(2+) content prior to the activation of caspase-3 in NT2-derived neurons. Chelation of intracellular Ca(2+) markedly suppressed APP-induced activation of caspase-3. Furthermore, calpain, a Ca(2+)-dependent cysteine protease, was activated in neurons overexpressing APP as assessed by increased levels of calpain-cleaved alpha-fodrin and autolytic mu-calpain fragments. Neither calpain nor caspase-3 was activated in neurons expressing an APP mutant defective in the Abeta(1-20) domain. Calpain inhibitors almost completely suppressed APP-induced activation of neuronal caspase-3. E64d, a membrane permeable inhibitor of calpain, significantly suppressed APP-induced neuronal death. These results suggest that overexpression of wild-type APP activates calpain that mediates caspase-3 activation in postmitotic neurons.

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.

The brain in Down syndrome

Down syndrome (trisomy 21) is a genetic disease with developmental brain abnormalities resulting in early mental retardation and precocious, age dependent Alzheimer-type neurodegeneration. We tried to discuss the role of neurodevelopmental abnormalities in connection with aberrant expression of genes on chromosome 21 including amyloid precursor protein (APP), CuZn superoxide dismutase (SOD1) and glial-derived S100 beta protein for neurodegeneration in DS. In this model, alterations in developmental pathways due to aberrant gene expression can impair cellular homeostasis and predispose to neurodegeneration of certain brain regions and types of nerve cells, involving cholinergic, serotonergic and catecholaminergic transmission, by shifting balance toward a pro-apoptotic state.

Amyloid precursor protein family-induced neuronal death is mediated by impairment of the neuroprotective calcium/calmodulin protein kinase IV-dependent signaling pathway

The aberrant metabolism of beta-amyloid precursor protein (APP) and the progressive deposition of its derived fragment beta-amyloid peptide are early and constant pathological hallmarks of Alzheimer's disease. Because APP is able to function as a cell surface receptor, we investigated here whether a disruption of the normal function of APP may contribute to the pathogenic mechanisms in Alzheimer's disease. To this aim, we generated a specific chicken polyclonal antibody directed against the extracellular domain of APP, which is common with the beta-amyloid precursor-like protein type 2. Exposure of cultured cortical neurons to this antibody (APP-Ab) induced cell death preceded by neurite degeneration, oxidative stress, and nuclear condensation. Interestingly, caspase-3-like protease was not activated in this neurotoxic action suggesting a different mode of cell death than classical apoptosis. Further analysis of the molecular mechanisms revealed a calpain- and calcineurin-dependent proteolysis of the neuroprotective calcium/calmodulin-dependent protein kinase IV and its nuclear target protein cAMP responsive element binding protein. These effects were abolished by the G protein inhibitor pertussis toxin, strongly suggesting that APP binding operates via a GTPase-dependent pathway to cause neuronal death.

Cell death induced by a caspase-cleaved transmembrane fragment of the Alzheimer amyloid precursor protein

The Alzheimer amyloid precursor protein (APP) is a transmembrane protein whose abnormal processing is associated with the pathogenesis of Alzheimer's disease. Activated caspases cleave APP and generate its carboxyl-terminally truncated fragment (APPdeltaC31). We have previously reported that overexpression of wild-type APP induces caspase-3 activation and apoptosis in postmitotic neurons. We now report that APPdeltaC31 potentially plays pathophysiological roles in neuronal death. Adenovirus-mediated overexpression of wild-type APP695 induced activation of caspase-3 and accumulation of APPdeltaC31 in postmitotic neurons derived from human NT2 embryonal carcinoma cells, whereas an APP mutant lacking the Abeta(1-20) region induced neither caspase-3 activation nor APPdeltaC31 generation. Inhibition of caspase-3 suppressed the generation of APPdeltaC31 in APP-overexpressing neurons. Forced expression of APPdeltaC31 induced apoptotic changes of neurons and non-neuronal cells, but failed to activate caspase-3. The cytotoxicity of APPdeltaC31 was also dependent on the Abeta(1-20) region. These results suggest that accumulation of wild-type APP activates neuronal caspase-3 to generate APPdeltaC31 that mediates caspase-3-independent cell death.

In vivo gene transfer to cerebral white matter lesions with a recombinant adenovirus vector

Ischemic white matter lesions have been reported in rats after bilateral common carotid ligation (BCAL). Previously, comparing normotensive rats (WKY) with spontaneously hypertensive rats (SHR), we too found that sustained moderate ischemia with spontaneous hypertension accelerated the formation of ischemic white matter lesions. In this study, we explored the feasibility of gene therapy for lesioned white matter by means of an adenovirus vector expressing a reporter gene, LacZ. Using sham-operated and hypoperfused SHR as well as sham-operated and hypoperfused WKY, we demonstrated that (i) adenovirus vectors could deliver a foreign gene into oligodendrocytes and astrocytes in the cerebral white matter; (ii) the transduction efficiency was most effective in SHR after BCAL; and (iii) the level of alpha(V)-integrin was significantly correlated with adenoviral transduction efficiency.