On the Biomarkers of Alzheimer's Disease.

Nakamura et al. examined the evidence, using a discovery and a validation database, that amyloid-β precursor protein (APP)/amyloid-β (Aβ) and Aβ/Aβ ratios, and composites based on traditional statistics; they concluded that these may be useful as biomarkers of Alzheimer's Disease (AD). We reexamined the same datasets, each of which included cognitively normal individuals (CN), individuals with mild cognitive impairment (MCI) and individuals with AD.

The Mitochondrial Na/Ca Exchanger is Necessary but Not Sufficient for Ca Homeostasis and Viability.

Unlabelled: Luongo et al. found that the mitochondrial Na/Ca exchanger (NCLX) was essential for Ca homeostasis and viability. Here, we re-analyze their data in terms of fractal self-similarity and quantitative difference (QD).

Quantitative Biology of Exercise-Induced Signal Transduction Pathways.

Unlabelled: Exercise is essential in regulating energy metabolism. Exercise activates cellular, molecular, and biochemical pathways with regulatory roles in training response adaptation. Among them, endurance/strength training of an individual has been shown to activate its respective signal transduction pathways in skeletal muscle.

Neuroprotection Mediated through GluN2C-Containing N-methyl-D-aspartate (NMDA) Receptors Following Ischemia.

Post-ischemic activation of NMDA receptors (NMDARs) has been linked to NMDAR subunit-specific signaling that mediates pro-survival or pro-death activity. Although extensive studies have been performed to characterize the role of GluN2A and GluN2B following ischemia, there is less understanding regarding the regulation of GluN2C. Here, we show that GluN2C expression is increased in acute hippocampal slices in response to ischemia.

Increased oligodendrogenesis by humanin promotes axonal remyelination and neurological recovery in hypoxic/ischemic brains.

Oligodendrocytes are the predominant cell type in white matter and are highly vulnerable to ischemic injury. The role of oligodendrocyte dysfunction in ischemic brain injury is unknown. In this study, we used a 24-amino acid peptide S14G-Humanin (HNG) to examine oligodendrogenesis and neurological functional recovery in a hypoxic/ischemic (H/I) neonatal model.

Brain-derived estrogen exerts anti-inflammatory and neuroprotective actions in the rat hippocampus.

17β-estradiol (E2) has been implicated to play a critical role in neuroprotection, synaptic plasticity, and cognitive function. Classically, the role of gonadal-derived E2 in these events is well established, but the role of brain-derived E2 is less clear. To address this issue, we investigated the expression, localization, and modulation of aromatase and local E2 levels in the hippocampus following global cerebral ischemia (GCI) in adult ovariectomized rats.

Premature menopause and risk of neurological disease: basic mechanisms and clinical implications.

Since basic scientific studies in the 1990s revealed dramatic gender differences in neurological damage from cerebral ischemia, significant evidence has accumulated for a neuroprotective role of ovarian-derived 17β-Estradiol (E2). Intriguingly, observational studies have further suggested that early and prolonged loss of ovarian E2 (premature menopause) leads to a doubled lifetime risk for dementia and a fivefold increased risk of mortality from neurological disorders, but some controversy remains. Here, we briefly summarize and analyze clinical cohort studies assessing the detrimental neurological outcomes of premature menopause.

Hypersensitivity of the hippocampal CA3 region to stress-induced neurodegeneration and amyloidogenesis in a rat model of surgical menopause.

Females who enter menopause prematurely via bilateral ovariectomy (surgical menopause) have a significantly increased risk for cognitive decline and dementia. To help elucidate the mechanisms underlying this phenomenon, we used an animal model of surgical menopause, long-term (10-week) bilateral ovariectomy in female rats. Herein, we demonstrate that long-term oestrogen deprivation dramatically increases sensitivity of the normally resistant hippocampal CA3 region to ischaemic stress, an effect that was gender-specific, as it was not observed in long-term orchiectomized males.

Estrogen regulation of spine density and excitatory synapses in rat prefrontal and somatosensory cerebral cortex.

The steroid hormone, 17β-estradiol (E2) has been reported to enhance executive functions that are known to be mediated by the prefrontal cortex (PFC), although the underlying mechanisms remain unclear. To shed light on the potential mechanisms, we examined the effect of E2 in vivo upon spine density in the rat PFC and the somatosensory cortex (SSC), which has been implicated to be a transient storage site for information that can also contribute to working memory. The results revealed that E2 significantly enhanced the number of dendritic spines in both the SSC and PFC, as well as the expression of spinophilin.

KDM1 is a novel therapeutic target for the treatment of gliomas.

Glioma development is a multistep process, involving alterations in genetic and epigenetic mechanisms. Understanding the mechanisms and enzymes that promote epigenetic changes in gliomas are urgently needed to identify novel therapeutic targets. We examined the role of histone demethylase KDM1 in glioma progression.

Long-term estrogen deprivation leads to elevation of Dickkopf-1 and dysregulation of Wnt/β-Catenin signaling in hippocampal CA1 neurons.

Surgically menopausal women incur a 2- to 5-fold increased risk for dementia and mortality from neurological diseases, but the mechanisms underlying these increased risks remain unclear. Previously, we demonstrated that after global cerebral ischemia (GCI), 17β-estradiol (E2 or estrogen) suppresses hippocampal elevation of the Wnt antagonist Dickkopf-1 (Dkk1), a neurodegenerative factor. We, thus, hypothesized that prolonged loss of E2 may lead to dysregulation of neural Dkk1 and Wnt/β-Catenin signaling, which could contribute to an increased risk of neurodegeneration.

Critical role of NADPH oxidase in neuronal oxidative damage and microglia activation following traumatic brain injury.

Background: Oxidative stress is known to play an important role in the pathology of traumatic brain injury. Mitochondria are thought to be the major source of the damaging reactive oxygen species (ROS) following TBI. However, recent work has revealed that the membrane, via the enzyme NADPH oxidase can also generate the superoxide radical (O(2)(-)), and thereby potentially contribute to the oxidative stress following TBI.

Therapeutic significance of estrogen receptor β agonists in gliomas.

Gliomas are the most common and devastating central nervous system neoplasms. A gender bias exists in their development: females are at lower risk than males, implicating estrogen-mediated protective effects. Estrogen functions are mediated by two estrogen receptor (ER) subtypes: ERα, which functions as tumor promoter, and ERβ, which functions as tumor suppressor.

VPS35 haploinsufficiency increases Alzheimer's disease neuropathology.

VPS35, a major component of the retromer complex, is important for endosome-to-Golgi retrieval of membrane proteins. Although implicated in Alzheimer's disease (AD), how VPS35 regulates AD-associated pathology is unknown. In this paper, we show that hemizygous deletion of Vps35 in the Tg2576 mouse model of AD led to earlier-onset AD-like phenotypes, including cognitive memory deficits, defective long-term potentiation, and impaired postsynaptic glutamatergic neurotransmission in young adult age.

Estrogen neuroprotection and the critical period hypothesis.

17β-Estradiol (estradiol or E2) is implicated as a neuroprotective factor in a variety of neurodegenerative disorders. This review focuses on the mechanisms underlying E2 neuroprotection in cerebral ischemia, as well as emerging evidence from basic science and clinical studies, which suggests that there is a "critical period" for estradiol's beneficial effect in the brain. Potential mechanisms underlying the critical period are discussed, as are the neurological consequences of long-term E2 deprivation (LTED) in animals and in humans after natural menopause or surgical menopause.

Acetylation of the pro-apoptotic factor, p53 in the hippocampus following cerebral ischemia and modulation by estrogen.

Background: Recent studies demonstrate that acetylation of the transcription factor, p53 on lysine(373) leads to its enhanced stabilization/activity and increased susceptibility of cells to stress. However, it is not known whether acetylation of p53 is altered in the hippocampus following global cerebral ischemia (GCI) or is regulated by the hormone, 17β-estradiol (17β-E(2)), and thus, this study examined these issues.

Methodology/principal Findings: The study revealed that Acetyl p53-Lysine(373) levels were markedly increased in the hippocampal CA1 region after GCI at 3 h, 6 h and 24 h after reperfusion, an effect strongly attenuated by 17β-E(2).

C terminus of Hsc70-interacting protein (CHIP)-mediated degradation of hippocampal estrogen receptor-alpha and the critical period hypothesis of estrogen neuroprotection.

Recent work suggests that timing of 17β-estradiol (E2) therapy may be critical for observing a beneficial neural effect. Along these lines, E2 neuroprotection, but not its uterotropic effect, was shown to be lost following long-term E2 deprivation (LTED), and this effect was associated with a significant decrease of estrogen receptor-α (ERα) in the hippocampus but not the uterus. The purpose of the current study was to determine the mechanism underlying the ERα decrease and to determine whether aging leads to a similar loss of hippocampal ERα and E2 sensitivity.

Role of Rac1 GTPase in NADPH oxidase activation and cognitive impairment following cerebral ischemia in the rat.

Background: Recent work by our laboratory and others has implicated NADPH oxidase as having an important role in reactive oxygen species (ROS) generation and neuronal damage following cerebral ischemia, although the mechanisms controlling NADPH oxidase in the brain remain poorly understood. The purpose of the current study was to examine the regulatory and functional role of the Rho GTPase, Rac1 in NADPH oxidase activation, ROS generation and neuronal cell death/cognitive dysfunction following global cerebral ischemia in the male rat.

Methodology/principal Findings: Our studies revealed that NADPH oxidase activity and superoxide (O(2)(-)) production in the hippocampal CA1 region increased rapidly after cerebral ischemia to reach a peak at 3 h post-reperfusion, followed by a fall in levels by 24 h post-reperfusion.

Extranuclear estrogen receptors mediate the neuroprotective effects of estrogen in the rat hippocampus.

Background: 17beta-estradiol (E2) has been implicated to exert neuroprotective effects in the brain following cerebral ischemia. Classically, E2 is thought to exert its effects via genomic signaling mediated by interaction with nuclear estrogen receptors. However, the role and contribution of extranuclear estrogen receptors (ER) is unclear and was the subject of the current study.

Estrogen attenuates ischemic oxidative damage via an estrogen receptor alpha-mediated inhibition of NADPH oxidase activation.

The goal of this study was to elucidate the mechanisms of 17beta-estradiol (E(2)) antioxidant and neuroprotective actions in stroke. The results reveal a novel extranuclear receptor-mediated antioxidant mechanism for E(2) during stroke, as well as a hypersensitivity of the CA3/CA4 region to ischemic injury after prolonged hypoestrogenicity. E(2) neuroprotection was shown to involve a profound attenuation of NADPH oxidase activation and superoxide production in hippocampal CA1 pyramidal neurons after stroke, an effect mediated by extranuclear estrogen receptor alpha (ERalpha)-mediated nongenomic signaling, involving Akt activation and subsequent phosphorylation/inactivation of Rac1, a factor critical for activation of NOX2 NADPH oxidase.

Preconditioning neuroprotection in global cerebral ischemia involves NMDA receptor-mediated ERK-JNK3 crosstalk.

Previous work has demonstrated that ischemic preconditioning neuroprotection is associated with inhibition of JNK pathway activation. The present study was designed to examine the hypothesis that the suppression of JNK3 activation by preconditioning is mediated by NMDA receptors and crosstalk between ERK1/2 and JNK3. Preconditioning (3 min ischemia) 2 days before global cerebral ischemia (8-min) markedly decreased neuronal degeneration in hippocampus CA1, an effect abolished by pretreatment with the NMDA receptor antagonist, MK-801.

Role of Rac1 GTPase in JNK signaling and delayed neuronal cell death following global cerebral ischemia.

The overall goal of this study was to determine the role of Rac1 in POSH/MLK/JNK signaling and delayed neuronal cell death following cerebral ischemia. Temporal studies revealed that Rac1 GTPase activation was significantly elevated in hippocampus CA1 at 10 min to 72 h after cerebral ischemia reperfusion, with peak levels 30 min to 6 h after reperfusion. Total Rac1 protein levels were not significantly changed following cerebral ischemia.

Positive modulation of AMPA receptors prevents downregulation of GluR2 expression and activates the Lyn-ERK1/2-CREB signaling in rat brain ischemia.

alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) are responsible for excitotoxicity induced by ischemic injury in hippocampal CA1 neurons, whereas the molecular mechanisms responsible for their neurotrophic activities are much less studied. Here, we examined the neuroprotective effect of positive modeulation of AMPARs by coapplication of AMPA with PEPA, an allosteric potentiator of AMPARs. We showed that coapplication of AMPA with PEPA protected hippocampal CA1 neurons from brain ischemia-induced death.

The ERK5-MEF2C transcription factor pathway contributes to anti-apoptotic effect of cerebral ischemia preconditioning in the hippocampal CA1 region of rats.

The purpose of the present study was to investigate the role of myocyte enhancer binding factor 2C (MEF2C), a common substrate of p38 kinase and extracellular signal-regulated kinase 5 (ERK5) in the hippocampal CA1 region following cerebral ischemia preconditioning (CIP) and without CIP. In animals that did not undergo preconditioning, MEF2C was significantly activated with an early peak at 30 min of reperfusion, which was followed by a pronounced decrease of MEF2C protein levels in the late phase of reperfusion (3-5 d). Co-immunoprecipitation studies failed to show an interaction between ERK5 and MEF2C, and ERK5-antisense oligonucleotide (ERK5-AS) had no effect on MEF2C activation, suggesting that the MEF2C activation is mediated by a kinase other than ERK5.

Role of Dickkopf-1, an antagonist of the Wnt/beta-catenin signaling pathway, in estrogen-induced neuroprotection and attenuation of tau phosphorylation.

17beta-Estradiol (E2) has been implicated to be neuroprotective in a variety of neurodegenerative disorders, although the mechanism remains poorly understood. The current study sheds light on this issue by demonstrating that low physiological levels of E2 protects the hippocampus CA1 against global cerebral ischemia by preventing elevation of dickkopf-1 (Dkk1), an antagonist of the Wnt/beta-catenin signaling pathway, which is a principal mediator of neurodegeneration in cerebral ischemia and Alzheimer's disease. E2 inhibition of Dkk1 elevation correlated with a reduction of phospho-beta-catenin and elevation of nuclear beta-catenin levels, as well as enhancement of Wnt-3, suggesting E2 activation of the Wnt/beta-catenin signaling pathway.