Enhanced apoptosis, oxidative stress and mitochondrial dysfunction in lymphocytes as potential biomarkers for Alzheimer's disease

Alzheimer's disease (AD) is the most common progressive neurodegenerative disease. Today, AD affects millions of people worldwide and the number of AD cases will increase with increased life expectancy. The AD brain is marked by severe neurodegeneration like the loss of synapses and neurons, atrophy and depletion of neurotransmitter systems in the hippocampus and cerebral cortex. Recent findings suggest that these pathological changes are causally induced by mitochondrial dysfunction, increased oxidative stress and elevated apoptosis. Until now, AD cannot be diagnosed by a valid clinical method or a biomarker before the disease has progressed so far that dementia is present. Furthermore, no valid method is available to determine which patient with mild cognitive impairment (MCI) will progress to AD. Therefore, a correct diagnosis in the early stage of AD is not only of importance considering that early drug treatment is more effective but also that the psychological burden of the patients and relatives could be decreased. In this review, we discuss the potential role of elevated apoptosis, increased oxidative stress and mitochondrial dysfunction as biomarker for AD in a peripheral cell model, the lymphocytes.

Estrogen Receptor Dependent Inhibitors of NF-κB Transcriptional Activation-1 Synthesis and Biological Evaluation of Substituted 2-Cyanopropanoic Acid Derivatives: Pathway Selective Inhibitors of NF-κB, a Potential Treatment for Rheumatoid Arthritis

Pathway selective ligands of the estrogen receptor inhibit transcriptional activation of proinflammatory genes mediated by NF-kappaB. Substituted 2-cyanopropanoic acid derivatives were developed leading to the discovery of WAY-204688, an orally active, pathway selective, estrogen receptor dependent anti-inflammatory agent. This propanamide was shown to be orally active in preclinical models of inflammatory diseases, such as rheumatoid arthritis, without the proliferative effect associated with traditional estrogens.

The PEA-15/PED protein protects glioblastoma cells from glucose deprivation-induced apoptosis via the ERK/MAP kinase pathway

PEA-15 (phosphoprotein enriched in astrocytes 15 kDa) is a death effector domain-containing protein, which is involved in the regulation of apoptotic cell death. Since PEA-15 is highly expressed in cells of glial origin, we studied the role of PEA-15 in human malignant brain tumors. Immunohistochemical analysis of PEA-15 expression shows strong immunoreactivity in astrocytomas and glioblastomas. Phosphorylation of PEA-15 at Ser(116) is found in vivo in perinecrotic areas in glioblastomas and in vitro after glucose deprivation of glioblastoma cells. Overexpression of PEA-15 induces a marked resistance against glucose deprivation-induced apoptosis, whereas small interfering RNA (siRNA)-mediated downregulation of endogenous PEA-15 results in the sensitization to glucose withdrawal-mediated cell death. This antiapoptotic activity of PEA-15 under low glucose conditions depends on its phosphorylation at Ser(116). Moreover, siRNA-mediated knockdown of PEA-15 abolishes the tumorigenicity of U87MG glioblastoma cells in vivo. PEA-15 regulates the level of phosphorylated extracellular-regulated kinase (ERK)1/2 in glioblastoma cells and the PEA-15-dependent protection from glucose deprivation-induced cell death requires ERK1/2 signaling. PEA-15 transcriptionally upregulates the Glucose Transporter 3, which is abrogated by the inhibition of ERK1/2 phosphorylation. Taken together, our findings suggest that Ser(116)-phosphorylated PEA-15 renders glioma cells resistant to glucose deprivation-mediated cell death as encountered in poor microenvironments, for example in perinecrotic areas of glioblastomas.

[The PEA-15 protein induces resistance against glucose deprivation-induced cell death via the ERK/MAP kinase pathway]

PEA-15 (Phosphoprotein enriched in astrocytes 15 kD) is a death effector domain-containing protein, which is involved in the regulation of apoptotic cell death. Since PEA-15 is highly expressed in cells of glial origin, we studied the role of PEA-15 in human malignant brain tumors. Immunohistochemical analysis of PEA-15 expression shows strong immunoreactivity in astrocytomas and glioblastomas. Phosphorylation of PEA-15 at Ser116 is found in vivo in perinecrotic areas in glioblastomas and in vitro after glucose deprivation of glioblastoma cells. Overexpression of PEA-15 induces a marked resistance against glucose deprivation-induced apoptosis, whereas siRNA-mediated down-regulation of endogenous PEA-15 results in the sensitization to glucose withdrawal-mediated cell death. This anti-apoptotic activity of PEA-15 under low glucose conditions depends on its phosphorylation at Ser116 Moreover, siRNA-mediated knockdown of PEA-15 abolishes the tumorigenicity of U87MG glioblastoma cells in vivo. PEA-15 regulates the level of phosphorylated ERK1/2 in glioblastoma cells and the PEA-15-dependent protection from glucose deprivation-induced cell death requires ERK1/2 signaling. PEA-15 transcriptionally up-regulates the glucose transporter 3, which is abrogated by the inhibition of ERK1/2 phosphorylation. Taken together, our findings suggest that Ser116-phosphorylated PEA-15 renders glioma cells resistant to glucose deprivation-mediated cell death as encountered in poor microenvironments, e.g. in perinecrotic areas of glioblastomas.

Apoptosis of CD4+ T and Natural Killer Cells in Alzheimer's Disease

BACKGROUND

Immunotherapy appears to be a potent treatment against Alzheimer's disease (AD), but the mechanisms underlying neural-immune interaction are still not known.

METHODS

Here, we determined cell death and distribution of lymphocyte subsets of peripheral blood mononuclear cells (PBMC) in AD and aging, e.g. T (CD4+ CD3+, CD8+ CD3+), B (CD19+) and NK (CD16++CD56+) cells.

RESULTS

Increased apoptosis was found in CD4+ T and NK cells in AD, while in aging all subsets were affected. The expression of anti-apoptotic Bcl2 correlated with observed cell death in T-helper and B cells irrespective of dementia. The levels of Bcl2 in T-cells were significantly increased in mild AD. Apoptosis and Bcl2 levels were also elevated in the APP (751SL)xPS1 (M146L) transgenic mouse model.

CONCLUSION

The mechanisms triggering apoptosis and activation of lymphocytes in AD appear therefore to be different than those in immunosenescence and possibly bear an important biomarker to monitor immunotherapy in AD.

Pineal and cortical melatonin receptors MT1 and MT2 are decreased in Alzheimer's disease

The pineal hormone melatonin is involved in physiological transduction of temporal information from the light dark cycle to circadian and seasonal behavioural rhythms, as well as possessing neuroprotective properties. Melatonin and its receptors MT1 and MT2, which belong to the family of G protein-coupled receptors, are impaired in Alzheimer's disease (AD) with severe consequences to neuropathology and clinical symptoms. The present data provides the first immunohistochemical evidence for the cellular localization of the both melatonin receptors in the human pineal gland and occipital cortex, and demonstrates their alterations in AD. We localized MT1 and MT2 in the pineal gland and occipital cortex of 7 elderly controls and 11 AD patients using immunohistochemistry with peroxidase-staining. In the pineal gland both MT1 and MT2 were localized to pinealocytes, whereas in the cortex both receptors were expressed in some pyramidal and non-pyramidal cells. In patients with AD, parallel to degenerative tissue changes, there was an overall decrease in the intensity of receptors in both brain regions. In line with our previous findings, melatonin receptor expression in AD is impaired in two additional brain areas, and may contribute to disease pathology.

Apolipoprotein E epsilon 4 is associated with an increased vulnerability to cell death in Alzheimer’s disease

The presumption to suffer from Alzheimer's disease (AD) accelerates with aging. One important risk factor seems to be the isoform epsilon 4 of the apolipoprotein E gene (Apo epsilon 4), which increases the risk to develop AD at an earlier age. Furthermore, convincing evidence is provided that apoptotic cell death mechanisms play an important role in neuronal cell death in AD. In the present study, we investigated whether abnormalities in apoptosis and caspase-3 activity can be found at the level of lymphocytes and a T cell subtype, CD4 T cells, from AD patients compared to aged sex- and ApoE genotype-matched non-demented controls. Under different experimental conditions (at baseline or after in vitro incubation in the presence of proapoptotic stimuli) increased levels of apoptosis and enhanced caspase-3 activity were detected in lymphocytes from AD patients. This difference was most pronounced in the CD4(+) T cell subtype. Notably, we found a significant increase of apoptotic cells and caspase-3 activity in lymphocytes from AD patients bearing one or two alleles of the ApoE4 compared to non-E4 carriers. Again, these effects were strongest in CD4(+) T cells. Circulating amyloid-beta (A beta) levels did not differ between AD patients bearing ApoE4 and non-ApoE4 and age-matched controls. Therefore, it is likely that circulating A beta is not responsible for the observed effects, which might rather reflect an ongoing systemic response in AD, e.g. an increase in CD95 expression.

Control of chronic inflammation with pathway selective estrogen receptor ligands

The discovery of novel intervention points in the inflammatory pathway has been a focus of drug development in recent years. We have identified pathway selective ligands for the estrogen receptor (ER) that inhibit NF-kappaB mediated inflammatory gene expression causing a reduction of cytokines, chemokines, adhesion molecules and inflammatory enzymes. SAR development of a series of 4-(Indazol-3-yl)-phenols has led to the identification of WAY-169916 an orally active non-steroidal ligand with the potential use in the treatment of inflammatory diseases without the classical proliferative effects associated with non-selective estrogens.

Enhanced ROS-Generation in Lymphocytes from Alzheimer’s Patients

INTRODUCTION

Reactive oxygen species (ROS) have been implicated in neurodegeneration and seem to be involved in the physiology and pathophysiology of several diseases, including normal aging and Alzheimer's disease (AD). Enhanced ROS production in aging or AD is not restricted to the brain, but can also been seen in several peripheral tissues. The objective of the present study was to evaluate whether the mechanisms involved in the generation of oxidative stress in normal senescence and Alzheimer's disease are identical or not.

METHODS

We analysed intracellular basal levels of ROS in lymphocytes from AD patients and healthy young and aged not-demented subjects as well as ROS levels following stimulation with d-ribose and staurosporine in all three groups. ROS levels were measured by flow cytometry using the intracellular fluorescence dye dihydrorhodamine123 (DHR123).

RESULTS

Our study shows that AD lymphocytes have increased basal levels of ROS, low susceptibility to ROS stimulation by 2-deoxy- D-ribose (dRib) and an increased response to staurosporine when compared with age-matched controls.

DISCUSSION

The data suggest that the defect(s) responsible for enhanced ROS production in AD may involve different or additional biological pathways than those involved in enhanced ROS generation during aging.

Nitric oxide alters arachidonic acid turnover in brain cortex synaptoneurosomes

Nitric oxide (NO) and arachidonic acid (AA) and also its metabolites are very important inter- and intracellular second messengers. They are involved in mechanisms of learning and memory. However, liberated in excessive amount in brain ischemia, Parkinson and Alzheimer diseases they are responsible for cell degeneration and death. Previously, we could show that Alzheimer disease's amyloid-beta protein enhanced nitric oxide liberation. The role of NO in AA metabolism is till now not well understood. Therefore, the aim of the present study was to investigate the mechanisms of NO-evoked activation of AA release and inhibition of AA incorporation into phospholipids of cortical rat brain synaptoneurosomes. The studies were carried out using NO donors, butyryl-cGMP (b-cGMP) and H2O2. All these compounds enhanced AA liberation from phosphatydilinositol (PI) and phosphatidylcholine (PC). Protein kinase ERK1/2, protein kinase C (PKC), cGMP-dependent protein kinase G (PKG) were involved in basal and NO-induced cytosolic phospholipase A2 (cPLA2) activation. Moreover, NO donors, b-cGMP and hydrogen peroxide (H2O2) exerted inhibitory effect on AA incorporation into PI and PC influencing arachidonyl-CoA transferase (AA-CoA-T) activity. AA-CoA synthase (AA-CoA-S) activity did not change. Specific inhibitors of protein kinase ERK1/2 (UO126), PKC (GF109203X), PKG (KT5823) had no effect on NO-mediated lowering of AA incorporation into PI and PC but inhibited the basal AA-CoA-S activity. Our data indicated that AA (10 microM) itself markedly decreased AA incorporation by about 50% into phospholipids of synaptoneurosomes membranes. Increasing release of AA and its metabolites causes the lowering of AA incorporation evoked by NO, b-cGMP and H2O2. Antioxidant, Resveratrol (100 microM) prevented NO- and cGMP-evoked inhibition of AA incorporation. These results suggest that NO affects the intracellular level of AA through alteration of cPLA2 and AA-CoA acyltransferase activities and may have an important implication in alterations of nerve endings properties and function.

Synthesis and activity of substituted 4-(indazol-3-yl)phenols as pathway-selective estrogen receptor ligands useful in the treatment of rheumatoid arthritis

Pathway-selective ligands for the estrogen receptor (ER) inhibit NF-kappaB-mediated inflammatory gene expression causing a reduction of cytokines, chemokines, adhesion molecules, and inflammatory enzymes. SAR development of a series of 4-(indazol-3-yl)phenols has led to the identification of WAY-169916 an orally active nonsteroidal ligand with the potential use in the treatment of rheumatoid arthritis without the classical proliferative effects associated with estrogens.

Synthesis and activity of substituted 4-(indazol-3-yl)phenols as pathway-selective estrogen receptor ligands useful in the treatment of rheumatoid arthritis

Pathway-selective ligands for the estrogen receptor (ER) inhibit NF-kappaB-mediated inflammatory gene expression causing a reduction of cytokines, chemokines, adhesion molecules, and inflammatory enzymes. SAR development of a series of 4-(indazol-3-yl)phenols has led to the identification of WAY-169916 an orally active nonsteroidal ligand with the potential use in the treatment of rheumatoid arthritis without the classical proliferative effects associated with estrogens.