Enhanced Hippocampal Neurogenesis in APP/Ps1 Mouse Model of Alzheimer's Disease After Implantation of VEGF-loaded PLGA Nanospheres

During adult life, hippocampus is an important brain region involved in neurogenesis. The generation and cell death of newly generated neuronal cells in this region have critical roles in brain maintenance and alterations in these processes are seen in Alzheimer's disease (AD). For the purpose of carrying out a neuroregenerative strategy, we propose a novel approach based on the encapsulation of vascular endothelial growth factor (VEGF) in poly (lactic co-glycolic acid) (PLGA) biodegradable nanospheres (NS) administered by craniotomy to stimulate the proliferation of neuronal precursors in a transgenic mouse model of AD. VEGF loaded nanospheres were prepared by double emulsion solvent evaporation technique, obtaining 200 nm nanospheres with a biphasic release profile. After demonstrating their efficacy in the proliferation and differentiation of neuronal cell cultures, in vivo studies were carried out. 3 months after VEGF-NS were implanted directly into the cerebral cortex of APP/Ps1 mice, the determination of BrdU(+) cells in the whole hippocampal region and specifically in the dentate gyrus, demonstrated a significantly enhanced cellular proliferation in VEGF-NS treated group. These results were also confirmed showing an increased number of DCX(+) and NeuN(+) cells. Hence, PLGA-VEGF nanospheres may be a potential strategy to modulate proliferative neuronal progenitors in the hippocampal region, and therefore, provide new insight for future therapeutic approaches in AD.

Potential Role of Aminoprocalcitonin in the Pathogenesis of Alzheimer Disease

Increasing evidence suggests that inflammatory responses cause brain atrophy and play a prominent and early role in the progression of Alzheimer disease. Recent findings show that the neuroendocrine peptide aminoprocalcitonin (NPCT) plays a critical role in the development of systemic inflammatory response; however, the presence, possible function, regulation, and mechanisms by which NPCT may be involved in Alzheimer disease neuropathology remain unknown. We explored the expression of NPCT and its interaction with amyloid-β (Aβ), and proinflammatory and neurogenic effects. By using brain samples of Alzheimer disease patients and APP/PS1 transgenic mice, we evaluated the potential role of NPCT on Aβ-related pathology. We found that NPCT is expressed in hippocampal and cortical neurons and Aβ-induced up-regulation of NPCT expression. Peripherally administered antibodies against NPCT decreased microglial activation, decreased circulating levels of proinflammatory cytokines, and prevented Aβ-induced neurotoxicity in experimental models of Alzheimer disease. Remarkably, anti-NPTC therapy resulted in a significant improvement in the behavioral status of APP/PS1 mice. Our results indicate a central role of NPCT in Alzheimer disease pathogenesis and suggest NPCT as a potential biomarker and therapeutic target.

Olfactory Receptors in Non-Chemosensory Organs: The Nervous System in Health and Disease

Olfactory receptors (ORs) and down-stream functional signaling molecules adenylyl cyclase 3 (AC3), olfactory G protein α subunit (Gαolf), OR transporters receptor transporter proteins 1 and 2 (RTP1 and RTP2), receptor expression enhancing protein 1 (REEP1), and UDP-glucuronosyltransferases (UGTs) are expressed in neurons of the human and murine central nervous system (CNS). In vitro studies have shown that these receptors react to external stimuli and therefore are equipped to be functional. However, ORs are not directly related to the detection of odors. Several molecules delivered from the blood, cerebrospinal fluid, neighboring local neurons and glial cells, distant cells through the extracellular space, and the cells’ own self-regulating internal homeostasis can be postulated as possible ligands. Moreover, a single neuron outside the olfactory epithelium expresses more than one receptor, and the mechanism of transcriptional regulation may be different in olfactory epithelia and brain neurons. OR gene expression is altered in several neurodegenerative diseases including Parkinson’s disease (PD), Alzheimer’s disease (AD), progressive supranuclear palsy (PSP) and sporadic Creutzfeldt-Jakob disease (sCJD) subtypes MM1 and VV2 with disease-, region- and subtype-specific patterns. Altered gene expression is also observed in the prefrontal cortex in schizophrenia with a major but not total influence of chlorpromazine treatment. Preliminary parallel observations have also shown the presence of taste receptors (TASRs), mainly of the bitter taste family, in the mammalian brain, whose function is not related to taste. TASRs in brain are also abnormally regulated in neurodegenerative diseases. These seminal observations point to the need for further studies on ORs and TASRs chemoreceptors in the mammalian brain.

Expression of regulatory proteins in choroid plexus changes in early stages of Alzheimer disease

Recent studies indicate that the choroid plexus has important physiologic and pathologic roles in Alzheimer disease (AD). To obtain additional insight on choroid plexus function, we performed a proteomic analysis of choroid plexus samples from patients with AD stages I to II (n = 16), III to IV (n = 16), and V to VI (n = 11) and 7 age-matched control subjects. We used 2-dimensional differential gel electrophoresis coupled with mass spectrometry to generate a complete picture of changes in choroid plexus protein expression occurring in AD patients. We identified 6 proteins: 14-3-3 β/α, 14-3-3 ε, moesin, proteasome activator complex subunit 1, annexin V, and aldehyde dehydrogenase, which were significantly regulated in AD patient samples (p < 0.05, >1.5-fold variation in expression vs control samples). These proteins are implicated in major physiologic functions including mitochondrial dysfunction and apoptosis regulation. These findings contribute additional significance to the emerging importance of molecular and functional changes of choroid plexus function in the pathophysiology of AD.

High-fat diet-induced deregulation of hippocampal insulin signaling and mitochondrial homeostasis deficiences contribute to Alzheimer disease pathology in rodents

Global obesity is a pandemic status, estimated to affect over 2 billion people, that has resulted in an enormous strain on healthcare systems worldwide. The situation is compounded by the fact that apart from the direct costs associated with overweight pathology, obesity presents itself with a number of comorbidities, including an increased risk for the development of neurodegenerative disorders. Alzheimer disease (AD), the main cause of senile dementia, is no exception. Spectacular failure of the pharmaceutical industry to come up with effective AD treatment strategies is forcing the broader scientific community to rethink the underlying molecular mechanisms leading to cognitive decline. To this end, the emphasis is once again placed on the experimental animal models of the disease. In the current study, we have focused on the effects of a high-fat diet (HFD) on hippocampal-dependent memory in C57/Bl6 Wild-type (WT) and APPswe/PS1dE9 (APP/PS1) mice, a well-established mouse model of familial AD. Our results indicate that the continuous HFD administration starting at the time of weaning is sufficient to produce β-amyloid-independent, hippocampal-dependent memory deficits measured by a 2-object novel-object recognition test (NOR) in mice as early as 6months of age. Furthermore, the resulting metabolic syndrome appears to have direct effects on brain insulin regulation and mitochondrial function. We have observed pathological changes related to both the proximal and distal insulin signaling pathway in the brains of HFD-fed WT and APP/PS1 mice. These changes are accompanied by a significantly reduced OXPHOS metabolism, suggesting that mitochondria play an important role in hippocampus-dependent memory formation and retention in both the HFD-treated and AD-like rodents at a relatively young age.

Soluble Megalin is Reduced in Cerebrospinal Fluid Samples of Alzheimer's Disease Patients

Megalin or low-density lipoprotein receptor-related protein-2 is a member of the low-density lipoprotein receptor family, which has been linked to Alzheimer’s disease (AD) by clearing brain amyloid β-peptide (Aβ) across the blood–cerebrospinal fluid barrier at the choroid plexus. Here, we found a soluble form of megalin secreted from choroid plexus epithelial cells. Soluble megalin levels were also localized in the human cerebrospinal fluid (CSF), being reduced in AD patients. We have also shown that soluble megalin binding to Aβ is decreased in the CSF of AD patients, suggesting that decreased sequestration of Aβ in the CSF could be associated with defective clearance of Aβ and an increase of brain Aβ levels. Thus, therapies, which increase megalin expression, at the choroid plexus and/or enhance circulating soluble megalin hold potential to control brain Aβ-related pathologies in AD.

Intranasal PRGF-Endoret enhances neuronal survival and attenuates NF-κB-dependent inflammation process in a mouse model of Parkinson's disease

Parkinson's disease is a common neurodegenerative disorder of unknown pathogenesis characterized by the loss of nigrostriatal dopaminergic neurons. Oxidative stress, microglial activation and inflammatory responses seem to contribute to the pathogenesis. Recent data showed that growth factors mediate neuroprotection in rodent models of Parkinson's disease, modulating pro-inflammatory processes. Based on our recent studies showing that plasma rich in growth factors (PRGF-Endoret) mediates neuroprotection as inflammatory moderator in Alzheimer's disease, in the present study we examined the effects of plasma rich in growth factors (PRGF-Endoret) in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned mouse as a translational therapeutic approach for Parkinson's disease. We found substantial neuroprotection by PRGF-Endoret in our model of Parkinson's disease, which resulted in diminished inflammatory responses and improved motor performance. Additionally, these effects were associated with robust reduction in nuclear transcription factor-κB (NF-κB) activation, and nitric oxide (NO), cyclooxygenase-2 (COX-2), and tumor necrosis factor-alpha (TNF-α) expression in the substantia nigra. We propose that PRGF-Endoret can prevent dopaminergic degeneration via an NF-κB-dependent signaling process. As the clinical safety profile of PRGF-Endoret is already established, these data suggest that PRGF-Endoret provides a novel neuroprotective strategy for Parkinson's disease.

Alzheimer's disease-like impaired cognition in endothelial-specific megalin-null mice

Megalin has been suggested to be involved in Alzheimer's disease (AD), mediating blood-brain barrier (BBB) transport of multiple ligands, including amyloid-β peptide (Aβ), but also neuroprotective factors. Because no transgenic model is currently available to study this concept, we have obtained transgenic mice blocking megalin expression at the BBB. These endothelial megalin deficient (EMD) mice developed increased anxiety behavior and impaired learning ability and recognition memory, similar to symptoms described in AD. Degenerating neurons were also observed in the cerebral cortex of EMD mice. In view of our findings we suggest that, in mice, megalin deficiency at the BBB leads to neurodegeneration.

Choroid plexus implants rescue Alzheimer's disease-like pathologies by modulating amyloid-β degradation

The choroid plexuses (CP) release numerous biologically active enzymes and neurotrophic factors, and contain a subpopulation of neural progenitor cells providing the capacity to proliferate and differentiate into other types of cells. These characteristics make CP epithelial cells (CPECs) excellent candidates for cell therapy aiming at restoring brain tissue in neurodegenerative illnesses, including Alzheimer's disease (AD). In the present study, using in vitro approaches, we demonstrated that CP were able to diminish amyloid-β (Aβ) levels in cell cultures, reducing Aβ-induced neurotoxicity. For in vivo studies, CPECs were transplanted into the brain of the APP/PS1 murine model of AD that exhibits advanced Aβ accumulation and memory impairment. Brain examination after cell implantation revealed a significant reduction in brain Aβ deposits, hyperphosphorylation of tau, and astrocytic reactivity. Remarkably, the transplantation of CPECs was accompanied by a total behavioral recovery in APP/PS1 mice, improving spatial and non-spatial memory. These findings reinforce the neuroprotective potential of CPECs and the use of cell therapies as useful tools in AD.

Plasma rich in growth factors (PRGF-Endoret) reduces neuropathologic hallmarks and improves cognitive functions in an Alzheimer's disease mouse model

Impaired growth factor function is thought to drive many of the alterations observed in Alzheimer's disease (AD) patients. Endogenous regenerative technology, PRGF (plasma rich in growth factor)-Endoret, is designed for the delivery of a complex pool of patient's own active morphogens that may stimulate tissue regeneration. We obtained and characterized PRGF-Endoret preparations from human blood. We used, as experimental approach in vivo, APP/PS1 mice, characterized by age-dependent brain amyloid-β (Aβ) accumulation. Intranasal administration of PRGF-Endoret to APP/PS1 mice resulted in an important decrease in brain Aβ deposition and tau phosphorylation. PRGF-Endoret-treated APP/PS1 mice also showed decreased astrocyte reactivity, and prevented protein synaptic loss. In vitro approaches demonstrated that PRGF-Endoret treatment modulated astrocyte activation, reducing inflammatory responses, and promoted Aβ degradation. Furthermore, PRGF-Endoret stimulated global improvements in anxiety, learning, and memory behaviors. Our findings show that PRGF-Endoret exerts multifunctional and complementary effects that result in the reversal of the broad range of cognitive deficits in AD, suggesting that PRGF-Endoret may hold promise as an innovative therapy in AD.

Insulin-like growth factor I and Alzheimer´s disease: therapeutic prospects?

The search for a cure of Alzheimer's dementia is restless. In recent years, unexpected epidemiological data showing a protective effect of anti-inflammatory and cholesterol-lowering drugs gave way to clinical trials with these compounds. Now, a newly described mechanism indicating that brain amyloid clearance is modulated by serum insulin-like growth factor I may also lead to new trials with this growth factor. Insulin-like growth factor I is an abundant circulating hormone with potent central actions whose levels in serum appear to be altered in Alzheimer's patients. Amyloid clearance, a potential therapeutic target in Alzheimer's disease was mostly neglected until recent antiamyloid therapies proved to involve a peripheral amyloid sink. Although more work in animal models are required, the evidence available strongly indicates that insulin-like growth factor I therapy in Alzheimer's dementia may be addressing pathogenic processes.

Neurogenic effects of β-amyloid in the choroid plexus epithelial cells in Alzheimer's disease

β-amyloid (Aβ) can promote neurogenesis, both in vitro and in vivo, by inducing neural progenitor cells to differentiate into neurons. The choroid plexus in Alzheimer's disease (AD) is burdened with amyloid deposits and hosts neuronal progenitor cells. However, neurogenesis in this brain tissue is not firmly established. To investigate this issue further, we examined the effect of Aβ on the neuronal differentiation of choroid plexus epithelial cells in several experimental models of AD. Here we show that Aβ regulates neurogenesis in vitro in cultured choroid plexus epithelial cells as well as in vivo in the choroid plexus of APP/Ps1 mice. Treatment with oligomeric Aβ increased proliferation and differentiation of neuronal progenitor cells in cultured choroid plexus epithelial cells, but decreased survival of newly born neurons. These Aβ-induced neurogenic effects were also observed in choroid plexus of APP/PS1 mice, and detected also in autopsy tissue from AD patients. Analysis of signaling pathways revealed that pre-treating the choroid plexus epithelial cells with specific inhibitors of TyrK or MAPK diminished Aβ-induced neuronal proliferation. Taken together, our results support a role of Aβ in proliferation and differentiation in the choroid plexus epithelial cells in Alzheimer's disease.

Phosphodiesterase 7 inhibitor reduced cognitive impairment and pathological hallmarks in a mouse model of Alzheimer's disease

Elevated levels of amyloid beta (Aβ) peptide, hyperphosphorylation of tau protein, and inflammation are pathological hallmarks in Alzheimer's disease (AD). Phosphodiesterase 7 (PDE7) regulates the inflammatory response through the cyclic adenosine monophosphate signaling cascade, and thus plays a central role in AD. The aim of this study was to evaluate the efficacy of an inhibitor of PDE7, named S14, in a mouse model of AD. We report that APP/Ps1 mice treated daily for 4 weeks with S14 show: (1) significant attenuation in behavioral impairment; (2) decreased brain Aβ deposition; (3) enhanced astrocyte-mediated Aβ degradation; and (4) decreased tau phosphorylation. These effects are mediated via the cyclic adenosine monophosphate/cyclic adenosine monophosphate response element-binding protein signaling pathway, and inactivation of glycogen synthase kinase (GSK)3. Our data support the use of PDE7 inhibitors, and specifically S14, as effective therapeutic agents for the prevention and treatment of AD.

Encapsulated VEGF-secreting cells enhance proliferation of neuronal progenitors in the hippocampus of AβPP/Ps1 mice

Vascular endothelial growth factor (VEGF) promotes neurogenesis in the adult hippocampus, but the way in which this process occurs in the Alzheimer's disease (AD) brain is still unknown. We examined the proliferation of neuronal precursors with an ex vivo approach, using encapsulated VEGF secreting cells, in AβPP/PS1 mice, a mouse model of AD. Overexpression of VEGF and VEGF receptor flk-1 was observed in the cerebral cortex from VEGF microcapsules-treated AβPP/PS1 mice at 1, 3 and 6 months after VEGF-microcapsule implantation. Stereological counting of 5-bromodeoxyuridine positive cells revealed that encapsulated VEGF secreting cells significantly enhanced cellular proliferation in the hippocampal dentate gyrus (DG). The number of neuronal precursors in VEGF microcapsules-treated AβPP/PS1 mice was also greater, and this effect remains after 6 months. We also confirmed that encapsulated VEGF secreting cells also stimulated angiogenesis in the cerebral cortex and hippocampal dentate gyrus. In addition, we found that VEGF-microcapsule treatment was associated with a depressed expression and activity of acetylcholinesterase in the hippocampus of AβPP/PS1 mice, a similar pattern as first-line medications for the treatment of AD. We conclude that stereologically-implanted VEGF-microcapsules exert an acute and long-standing neurotrophic effects, and could be utilized to improve potential therapies to control the progression of AD.

Systematic evaluation of magnetic resonance imaging and spectroscopy techniques for imaging a transgenic model of Alzheimer's disease (AβPP/PS1)

Murine models of Alzheimer's disease (AD) provide means to detect and follow biomarker changes similar to those observed in humans. Non-invasive biomarkers, such as those provided by magnetic resonance imaging (MRI) and spectroscopy (MRS) methods are highly desirable, however, systematic studies of in vivo MRI/MRS methods to characterize the cerebral morphology and metabolic pattern of these mice remain scarce. We investigated sixteen consecutive slices from the brain of wild-type and AβPP/PS1 mice, obtaining a collection of T2 weighted, diffusion weighted and magnetization transfer weighted images as well as 1H PRESS spectra from the cortical and subcortical areas. Compared to controls, AβPP/PS1 mice show significant regional hyperintensities in T2 weighted images of the cerebral cortex, significant ventricular enlargement, and decreased hippocampal area and fractional magnetization transfer. MRS demonstrated an increase in the ratio of choline (Cho) to creatine (Cr) in the cortical and subcortical areas of the transgenic animals. A logistic regression classifier was implemented considering all parameters investigated, and revealed the most characteristic changes and allowed for the correct classification of control and AβPP/PS1 mice. In summary, the present results provide a useful frame to evaluate optimal MRI/MRS biomarkers for the characterization of AD models, potentially applicable in drug discovery processes, because of their non-invasive and repeatable nature in longitudinal studies.

Altered cell cycle-related gene expression in brain and lymphocytes from a transgenic mouse model of Alzheimer's disease [amyloid precursor protein/presenilin 1 (PS1)]

Cumulative evidence indicates that aberrant re-expression of many cell cycle-related proteins and inappropriate neuronal cell cycle control are critical events in Alzheimer's disease (AD) pathogenesis. Evidence of cell cycle activation in post-mitotic neurons has also been observed in murine models of AD, despite the fact that most of these mice do not show massive loss of neuronal bodies. Dysfunction of the cell cycle appears to affect cells other than neurons, as peripheral cells, such as lymphocytes and fibroblasts from patients with AD, show an altered response to mitogenic stimulation. We sought to determine whether cell cycle disturbances are present simultaneously in both brain and peripheral cells from the amyloid precursor protein (APP)/presenilin 1 (PS1) mouse model of AD, in order to validate the use of peripheral cells from patients not only to study cell cycle abnormalities as a pathogenic feature of AD, but also as a means to test novel therapeutic approaches. By using cell cycle pathway-specific RT(2)Profiler™ PCR Arrays, we detected changes in a number of cell cycle-related genes in brain as well as in lymphocytes from APP/PS1 mice. Moreover, we found enhanced 5'-bromo-2'-deoxyuridine incorporation into DNA in lymphocytes from APP/PS1 mice, and increased expression of the cell proliferation marker proliferating cell nuclear antigen (PCNA), and the cyclin-dependent kinase (CDK) inhibitor Cdkn2a, as detected by immunohistochemistry in cortical neurons of the APP/PS1 mice. Taken together, the cell cycle-related changes in brain and blood cells reported here support the mitosis failure hypothesis in AD and validate the use of peripheral cells as surrogate tissue to study the molecular basis of AD pathogenesis.

Pathological alteration in the choroid plexus of Alzheimer's disease: implication for new therapy approaches

Morphological alterations of choroid plexus in Alzheimer’s disease (AD) have been extensively investigated. These changes include epithelial atrophy, thickening of the basement membrane, and stroma fibrosis. As a result, synthesis, secretory, and transportation functions are significantly altered resulting in decreased cerebrospinal fluid (CSF) turnover. Recent studies discuss the potential impacts of these changes, including the possibility of reduced resistance to stress insults and slow clearance of toxic compounds from CSF with specific reference to the amyloid peptide. Here, we review new evidences for AD-related changes in the choroid plexus. The data suggest that the significantly altered functions of the choroid plexus contribute to the multiparametric pathogenesis of late-onset AD.

Effects of a tacrine-8-hydroxyquinoline hybrid (IQM-622) on Aβ accumulation and cell death: involvement in hippocampal neuronal loss in Alzheimer's disease

Several studies have implicated the enzyme acetylcholinesterase (AChE) as well as several biometals in the pathogenesis of Alzheimer's disease (AD). A multifunctional molecule, the hybrid tacrine-8-hydroxyquinoline (named IQM-622), displays cholinergic, antioxidant, copper-complexing and neuroprotective properties. Using in vitro and in vivo models, we investigated the modulating effects of IQM-622 on amyloid β-protein (Aβ)-induced pathology as well as on chemically induced neurodegeneration by domoic acid. In the first experimental model, we observed a significant decrease in brain Aβ deposits in IQM-622-treated APP/Ps1 mice for four weeks. Moreover, IQM-622 promoted the degradation of intracellular Aβ in astrocytes, and protected against Aβ toxicity in cultured astrocytes and neurons. These findings suggest that the neuroprotective effect of IQM-622 is not only related to AChE inhibition, but also involves other mechanisms, including the modulation of Aβ-degradation pathways in AD brain. In this study we also compare the neuronal loss in CA1 hippocampal field of AD patients and of mice treated with domoic acid, giving similar patterns. Thus, we used a second experimental model by killing hippocampal neurons by domoic acid damage, in which IQM-622 increased survival in the CA1 and dentate gyrus regions of the hippocampus. Our observations suggest that administration of IQM-622 may have significant beneficial effects in neurodegenerative diseases, including AD, which course with acute or progressive neuronal death.

Prolonged oral cannabinoid administration prevents neuroinflammation, lowers β-amyloid levels and improves cognitive performance in Tg APP 2576 mice

Background

Alzheimer's disease (AD) brain shows an ongoing inflammatory condition and non-steroidal anti-inflammatories diminish the risk of suffering the neurologic disease. Cannabinoids are neuroprotective and anti-inflammatory agents with therapeutic potential.

Methods

We have studied the effects of prolonged oral administration of transgenic amyloid precursor protein (APP) mice with two pharmacologically different cannabinoids (WIN 55,212-2 and JWH-133, 0.2 mg/kg/day in the drinking water during 4 months) on inflammatory and cognitive parameters, and on ¹⁸F-fluoro-deoxyglucose (¹⁸FDG) uptake by positron emission tomography (PET).

Results

Novel object recognition was significantly reduced in 11 month old Tg APP mice and 4 month administration of JWH was able to normalize this cognitive deficit, although WIN was ineffective. Wild type mice cognitive performance was unaltered by cannabinoid administration. Tg APP mice showed decreased ¹⁸FDG uptake in hippocampus and cortical regions, which was counteracted by oral JWH treatment. Hippocampal GFAP immunoreactivity and cortical protein expression was unaffected by genotype or treatment. In contrast, the density of Iba1 positive microglia was increased in Tg APP mice, and normalized following JWH chronic treatment. Both cannabinoids were effective at reducing the enhancement of COX-2 protein levels and TNF-α mRNA expression found in the AD model. Increased cortical β-amyloid (Aβ) levels were significantly reduced in the mouse model by both cannabinoids. Noteworthy both cannabinoids enhanced Aβ transport across choroid plexus cells in vitro.

Conclusions

In summary we have shown that chronically administered cannabinoid showed marked beneficial effects concomitant with inflammation reduction and increased Aβ clearance.

Leptin induces proliferation of neuronal progenitors and neuroprotection in a mouse model of Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease associated with senile amyloid-β (Aβ) plaques, neuronal death, and cognitive decline. Neurogenesis in the adult hippocampus, which is notably affected by progressive neurodegeneration and Aβ pathology, is implicated in learning and memory regulation. Human postmortem brains of AD patients and AβPP/PS1 double transgenic mice show increased neurodegeneration. Leptin, an adipose-derived hormone, promotes neurogenesis in the adult hippocampus, but the way in which this process occurs in the AD brain is still unknown. Thus, we sought to determine if leptin stimulated the proliferation of neuronal precursors in AβPP/PS1 mice. We estimated the number proliferating hippocampal cells after intracerebroventricular administration of a lentiviral vector encoding leptin. After 3 months of treatment with leptin we observed an increase in the number of BrdU-positive cells in the subgranular zone of the dentate gyrus, as shown by morphometric analysis. This increase resulted mainly from an increased proliferation of neuronal precursors. Additionally, leptin led to an attenuation of Aβ-induced neurodegeneration, as revealed by Fluoro-Jade staining. Our results suggest that in AβPP/PS1 mice, leptin exerts changes resembling acute neurotrophic and neuroprotective effects. These effects could serve as the basis for the design of future treatment strategies in AD.

PLA2G3, a gene involved in oxidative stress induced death, is associated with Alzheimer's disease

Oxidative stress, which plays a critical role in the pathogenesis of neurodegenerative diseases such as Alzheimer's disease (AD), is intimately linked to aging, the best established risk factor for AD. Studies in neuronal cells subjected to oxidative stress, mimicking such stress in AD brains, are therefore of great interest. PLA2G3 is the most overexpressed gene in a human neuronal model of oxidative stress induced by the free radical-generating xanthine/xanthine oxidase (X-XOD) system, which provokes apoptotic cell death. In this work, we describe that PLA2G3 gene silencing produced a marked inhibition of X-XOD induced cell death, and that PLA2G3 polymorphisms are associated with AD in a Spanish case-control sample. The capacity to respond to oxidative stress may therefore modulate the risk of AD, and PLA2G3 is a potential target to regulate neuronal damage induced by free radicals.