Histone deacetylase-3 regulates the expression of the amyloid precursor protein and its inhibition promotes neuroregenerative pathways in Alzheimer's disease models.

HDAC3 inhibition has been shown to improve memory and reduce amyloid-ß (Aß) in Alzheimer's disease (AD) models, but the underlying mechanisms are unclear. We investigated the molecular effects of HDAC3 inhibition on AD pathology, using in vitro and ex vivo models of AD, based on our finding that HDAC3 expression is increased in AD brains. For this purpose, N2a mouse neuroblastoma cells as well as organotypic brain cultures (OBCSs) of 5XFAD and wild-type mice were incubated with various concentrations of the HDAC3 selective inhibitor RGFP966 (0.1-10 µM) for 24 h. Treatment with RGFP966 or HDAC3 knockdown in N2a cells was associated with an increase on amyloid precursor protein (APP) and mRNA expressions, without alterations in Aß42 secretion. In vitro chromatin immunoprecipitation analysis revealed enriched HDAC3 binding at APP promoter regions. The increase in APP expression was also detected in OBCSs from 5XFAD mice incubated with 1 µM RGFP966, without changes in Aß. In addition, HDAC3 inhibition resulted in a reduction of activated Iba-1-positive microglia and astrocytes in 5XFAD slices, which was not observed in OBCSs from wild-type mice. mRNA sequencing analysis revealed that HDAC3 inhibition modulated neuronal regenerative pathways related to neurogenesis, differentiation, axonogenesis, and dendritic spine density in OBCSs. Our findings highlight the complexity and diversity of the effects of HDAC3 inhibition on AD models and suggest that HDAC3 may have multiple roles in the regulation of APP expression and processing, as well as in the modulation of neuroinflammatory and neuroprotective genes.

WITHDRAWN: Bacteroides thetaiotaomicron necrotizing fasciitis as presentation of colorectal cancer, with subsequent cutaneous exteriorization.

Ahead of Print article withdrawn by publisher. An 80-year-old woman presented necrotizing fasciitis on the right flank, requiring debridement. Tomography reported ascending colon neoplasm fistulized to the skin. Colonoscopy confirms adenocarcinoma. Intervention postponed due to rejection of surgery during the pandemic and SARS-COV-2 infection, producing progression with exteriorization of the neoplasm. A bloc laparotomic right hemicolectomy was performed (pT4bN0).

Traumatic Brain Injury Leads to Alterations in Contusional Cortical miRNAs Involved in Dementia.

There is compelling evidence that head injury is a significant environmental risk factor for Alzheimer's disease (AD) and that a history of traumatic brain injury (TBI) accelerates the onset of AD. Amyloid-ß plaques and tau aggregates have been observed in the post-mortem brains of TBI patients; however, the mechanisms leading to AD neuropathology in TBI are still unknown. In this study, we hypothesized that focal TBI induces changes in miRNA expression in and around affected areas, resulting in the altered expression of genes involved in neurodegeneration and AD pathology. For this purpose, we performed a miRNA array in extracts from rats subjected to experimental TBI, using the controlled cortical impact (CCI) model. In and around the contusion, we observed alterations of miRNAs associated with dementia/AD, compared to the contralateral side. Specifically, the expression of miR-9 was significantly upregulated, while miR-29b, miR-34a, miR-106b, miR-181a and miR-107 were downregulated. Via qPCR, we confirmed these results in an additional group of injured rats when compared to naïve animals. Interestingly, the changes in those miRNAs were concomitant with alterations in the gene expression of mRNAs involved in amyloid generation and tau pathology, such as ß-APP cleaving enzyme (BACE1) and Glycogen synthase-3-ß (GSK3ß). In addition increased levels of neuroinflammatory markers (TNF-α), glial activation, neuronal loss, and tau phosphorylation were observed in pericontusional areas. Therefore, our results suggest that the secondary injury cascade in TBI affects miRNAs regulating the expression of genes involved in AD dementia.

Near-infrared fluorescence cholangiography at a very low dose of indocyanine green: quantification of fluorescence intensity using a colour analysis software based on the RGB color model.

BACKGROUND: Indocyanine green (ICG) near-infrared fluorescence cholangiography (NIRF-C) is widely used to visualize the biliary tract during laparoscopic cholecystectomy (LC). However, the ICG dose and its dosing time vary in the literature so there is not a standard ICG protocol. The objectives of this descriptive prospective study were to demonstrate that NIRF-C at a very low dose of ICG provides good visualization of the extrahepatic biliary tree while avoiding hepatic hyperluminescence and to assess the surgeon-perceived benefit. Furthermore, another additional aim was quantifying the amount of ICG dye in the liver tissue and biliary tract through a green colour intensity (GCI) analysis according to red green blue (RGB) color model and correlating it to surgeon-perceived benefit. METHOD: Forty-four patients were scheduled for LC. We recorded demographics, surgical indication, intraoperative details, adverse reactions to ICG, hepatic hyperluminescence, visualization of the cystic duct (CD), the common bile duct (CBD) and the cystic duct-bile duct junction (CDBDJ) before and after dissection of Calot's triangle, operation time, surgical complications and subjective surgeon data. For all procedures, a unique dose of 0.25 mg of ICG was administered intravenously during the anaesthetic induction. ICG NIRF-C was performed using the overlay mode of the VISERA ELITE II Surgical Endoscope in all surgeries. Video recordings of all 44 LC were reviewed. Using a color analysis software, the GCI of CBD versus adjacent liver tissue was calculated using RGB color model. RESULTS: ICG NIRF-C was performed in all 44 cases. The mean operation time was 45 ± 15 min. There were no bile duct injuries (BDIs) or allergic reactions to ICG. The postoperative course was uneventful in all of cases. The mean postoperative hospital stay was 28 ± 4 h. ICG NIRF-C identified the CBD in 100% of the patients, the CD in 71% and the CDBDJ in 84%, with a surgeon satisfaction of 4/5 or 5/5 in almost 90% of surgeries based on a visual analogue scale (VAS). No statistically significant differences were found in the visualization of the biliary structures after the dissection of Calot's triangle in obese patients or with gallbladder inflammation. Furthermore, 25% of patients with a BMI ≥ 30, 27% of patients with a Nassar grade ≥ 3 and 21% of patients with gallbladder inflammation had a VAS score 5/5 compared to 6% of patients with a BMI < 30 (p = 0.215), 6% of patients with a Nassar grade < 3 (p = 0.083) and none of the patients without gallbladder inflammation (p = 0.037). Measured pixel GCI of CBD was higher than adjacent hepatic tissue for all cases regardless of the degree of gallbladder inflammation, the Nassar scale grades or the patient's BMI (p < 0.0001). In addition, a significant correlation was observed between surgeon-perceived benefit and the amount of ICG dye into the CBD according the RGB color model (p < 0.0001). CONCLUSION: ICG NIRF-C at a very low dose of ICG (0.25 mg of ICG 20 min before surgery) enables the real-time identification of biliary ducts, thereby avoiding the hepatic hyperluminescence even in cases of obese patients or those with gallbladder inflammation.

Astrocyte Reactivity in Alzheimer's Disease: Therapeutic Opportunities to Promote Repair.

Astrocytes are fast climbing the ladder of importance in neurodegenerative disorders, particularly in Alzheimer's Disease (AD), with the prominent presence of reactive astrocytes surrounding amyloid-ß plaques, together with activated microglia. Reactive astrogliosis, implying morphological and molecular transformations in astrocytes, seems to precede neurodegeneration, suggesting a role in the development of the disease. Single-cell transcriptomics has recently demonstrated that astrocytes from AD brains are different from "normal" healthy astrocytes, showing dysregulations in areas such as neurotransmitter recycling, including glutamate and GABA, and impaired homeostatic functions. However, recent data suggest that the ablation of astrocytes in mouse models of amyloidosis results in an increase in amyloid pathology, worsening of the inflammatory profile, and reduced synaptic density, indicating that astrocytes mediate neuroprotective effects. The idea that interventions targeting astrocytes may have great potential for AD has therefore emerged, supported by a range of drugs and stem cell transplantation studies that have successfully shown a therapeutic effect in mouse models of AD. In this article, we review the latest reports on the role and profile of astrocytes in AD brains and how manipulation of astrocytes in animal models has paved the way for the use of treatments enhancing astrocytic function as future therapeutic avenues for AD.

Selective Detection of Cu+ Ions in Live Cells via Fluorescence Lifetime Imaging Microscopy.

Copper is an essential trace element in living organisms with its levels and localisation being carefully managed by the cellular machinery. However, if misregulated, deficiency or excess of copper ions can lead to several diseases. Therefore, it is important to have reliable methods to detect, monitor and visualise this metal in cells. Herein we report a new optical probe based on BODIPY, which shows a switch-on in its fluorescence intensity upon binding to copper(I), but not in the presence of high concentration of other physiologically relevant metal ions. More interestingly, binding to copper(I) leads to significant changes in the fluorescence lifetime of the new probe, which can be used to visualize copper(I) pools in lysosomes of live cells via fluorescence lifetime imaging microscopy (FLIM).

The Role of PGC1α in Alzheimer's Disease and Therapeutic Interventions.

The peroxisome proliferator-activated receptor co-activator-1α (PGC1α) belongs to a family of transcriptional regulators, which act as co-activators for a number of transcription factors, including PPARs, NRFs, oestrogen receptors, etc. PGC1α has been implicated in the control of mitochondrial biogenesis, the regulation of the synthesis of ROS and inflammatory cytokines, as well as genes controlling metabolic processes. The levels of PGC1α have been shown to be altered in neurodegenerative disorders. In the brains of Alzheimer's disease (AD) patients and animal models of amyloidosis, PGC1α expression was reduced compared with healthy individuals. Recently, it was shown that overexpression of PGC1α resulted in reduced amyloid-ß (Aß) generation, particularly by regulating the expression of BACE1, the rate-limiting enzyme involved in the production of Aß. These results provide evidence pointing toward PGC1α activation as a new therapeutic avenue for AD, which has been supported by the promising observations of treatments with drugs that enhance the expression of PGC1α and gene therapy studies in animal models of AD. This review summarizes the different ways and mechanisms whereby PGC1α can be neuroprotective in AD and the pre-clinical treatments that have been explored so far.

Annexin A1 restores cerebrovascular integrity concomitant with reduced amyloid-ß and tau pathology.

Alzheimer's disease, characterized by brain deposits of amyloid-ß plaques and neurofibrillary tangles, is also linked to neurovascular dysfunction and blood-brain barrier breakdown, affecting the passage of substances into and out of the brain. We hypothesized that treatment of neurovascular alterations could be beneficial in Alzheimer's disease. Annexin A1 (ANXA1) is a mediator of glucocorticoid anti-inflammatory action that can suppress microglial activation and reduce blood-brain barrier leakage. We have reported recently that treatment with recombinant human ANXA1 (hrANXA1) reduced amyloid-ß levels by increased degradation in neuroblastoma cells and phagocytosis by microglia. Here, we show the beneficial effects of hrANXA1 in vivo by restoring efficient blood-brain barrier function and decreasing amyloid-ß and tau pathology in 5xFAD mice and Tau-P301L mice. We demonstrate that young 5xFAD mice already suffer cerebrovascular damage, while acute pre-administration of hrANXA1 rescued the vascular defects. Interestingly, the ameliorated blood-brain barrier permeability in young 5xFAD mice by hrANXA1 correlated with reduced brain amyloid-ß load, due to increased clearance and degradation of amyloid-ß by insulin degrading enzyme (IDE). The systemic anti-inflammatory properties of hrANXA1 were also observed in 5xFAD mice, increasing IL-10 and reducing TNF-α expression. Additionally, the prolonged treatment with hrANXA1 reduced the memory deficits and increased synaptic density in young 5xFAD mice. Similarly, in Tau-P301L mice, acute hrANXA1 administration restored vascular architecture integrity, affecting the distribution of tight junctions, and reduced tau phosphorylation. The combined data support the hypothesis that blood-brain barrier breakdown early in Alzheimer's disease can be restored by hrANXA1 as a potential therapeutic approach.

Pharmacological ablation of astrocytes reduces Aß degradation and synaptic connectivity in an ex vivo model of Alzheimer's disease.

BACKGROUND: Astrocytes provide a vital support to neurons in normal and pathological conditions. In Alzheimer's disease (AD) brains, reactive astrocytes have been found surrounding amyloid plaques, forming an astrocytic scar. However, their role and potential mechanisms whereby they affect neuroinflammation, amyloid pathology, and synaptic density in AD remain unclear. METHODS: To explore the role of astrocytes on Aß pathology and neuroinflammatory markers, we pharmacologically ablated them in organotypic brain culture slices (OBCSs) from 5XFAD mouse model of AD and wild-type (WT) littermates with the selective astrocytic toxin L-alpha-aminoadipate (L-AAA). To examine the effects on synaptic circuitry, we measured dendritic spine number and size in OBCSs from Thy-1-GFP transgenic mice incubated with synthetic Aß42 or double transgenics Thy-1-GFP/5XFAD mice treated with LAAA or vehicle for 24 h. RESULTS: Treatment of OBCSs with L-AAA resulted in an increased expression of pro-inflammatory cytokine IL-6 in conditioned media of WTs and 5XFAD slices, associated with changes in microglia morphology but not in density. The profile of inflammatory markers following astrocytic loss was different in WT and transgenic cultures, showing reductions in inflammatory mediators produced in astrocytes only in WT sections. In addition, pharmacological ablation of astrocytes led to an increase in Aß levels in homogenates of OBCS from 5XFAD mice compared with vehicle controls, with reduced enzymatic degradation of Aß due to lower neprilysin and insulin-degrading enzyme (IDE) expression. Furthermore, OBSCs from wild-type mice treated with L-AAA and synthetic amyloid presented 56% higher levels of Aß in culture media compared to sections treated with Aß alone, concomitant with reduced expression of IDE in culture medium, suggesting that astrocytes contribute to Aß clearance and degradation. Quantification of hippocampal dendritic spines revealed a reduction in their density following L-AAA treatment in all groups analyzed. In addition, pharmacological ablation of astrocytes resulted in a decrease in spine size in 5XFAD OBCSs but not in OBCSs from WT treated with synthetic Aß compared to vehicle control. CONCLUSIONS: Astrocytes play a protective role in AD by aiding Aß clearance and supporting synaptic plasticity.

Imidazoline ligand BU224 reverses cognitive deficits, reduces microgliosis and enhances synaptic connectivity in a mouse model of Alzheimer's disease.

BACKGROUND AND PURPOSE: Activation of type 2 imidazoline receptors has been shown to exhibit neuroprotective properties including anti-apoptotic and anti-inflammatory effects, suggesting a potential therapeutic value in Alzheimer's disease (AD). Here, we explored the effects of the imidazoline-2 ligand BU224 in a model of amyloidosis. EXPERIMENTAL APPROACH: Six-month-old female transgenic 5XFAD and wild-type (WT) mice were treated intraperitoneally with 5-mg·kg-1 BU224 or vehicle twice a day for 10 days. Behavioural tests were performed for cognitive functions and neuropathological changes were investigated by immunohistochemistry, Western blot, elisa and qPCR. Effects of BU224 on amyloid precursor protein (APP) processing, spine density and calcium imaging were analysed in brain organotypic cultures and N2a cells. KEY RESULTS: BU224 treatment attenuated spatial and perirhinal cortex-dependent recognition memory deficits in 5XFAD mice. Fear-conditioning testing revealed that BU224 also improved both associative learning and hippocampal- and amygdala-dependent memory in transgenic but not in WT mice. In the brain, BU224 reduced levels of the microglial marker Iba1 and pro-inflammatory cytokines IL-1ß and TNF-α and increased the expression of astrocytic marker GFAP in 5XFAD mice. These beneficial effects were not associated with changes in amyloid pathology, neuronal apoptosis, mitochondrial density, oxidative stress or autophagy markers. Interestingly, ex vivo and in vitro studies suggested that BU224 treatment increased the size of dendritic spines and induced a threefold reduction in amyloid-ß (Aß)-induced functional changes in NMDA receptors. CONCLUSION AND IMPLICATIONS: Sub-chronic treatment with BU224 restores memory and reduces inflammation in transgenic AD mice, at stages when animals display severe pathology.

[Gallbladder volvulus: Diagnostic and surgical challenges]. / Vólvulo de vesícula biliar: retos diagnósticos y quirúrgicos.

BACKGROUND: The gallbladder volvulus is defined as the rotation of the gallbladder on its mesentery along the axis of the cystic duct and cystic artery. It is an extremely rare surgical disease and definitive diagnosis is usually made during surgery. CASE REPORT: A 78 year old woman presented with upper right quadrant abdominal pain, with no comorbidities and no other accompanying symptoms. Analysis revealed haemodynamic instability and leukocytosis. Computed tomography of abdomen showed an acute cholecystitis. During emergency right hypochondrium laparotomy, the gallbladder was found to be twisted counterclockwise with huge gangrenous gallbladder distal. Open cholecystectomy was performed and after the surgery, the patient was discharged in a few days. CONCLUSION: Gallbladder volvulus, or gallbladder torsion, is a rare condition and should be considered when clinical and imaging findings of complicated cholecystitis are present. The performance of urgent laparoscopic surgery would be first option to avoid perforation, peritonitis and haemodynamic instability.

The nuclear cofactor receptor interacting protein-140 (RIP140) regulates the expression of genes involved in Aß generation.

The receptor interacting protein-140 (RIP140) is a cofactor for several nuclear receptors and has been involved in the regulation of metabolic and inflammatory genes. We hypothesize that RIP140 may also affect Aß generation because it modulates the activity of transcription factors previously implicated in amyloid precursor protein (APP) processing, such as peroxisome proliferator-activated receptor-γ (PPARγ). We found that the levels of RIP140 are reduced in Alzheimer's disease (AD) postmortem brains compared with healthy controls. In addition, in situ hybridization experiments revealed that RIP140 expression is enriched in the same brain areas involved in AD pathology, such as cortex and hippocampus. Furthermore, we provide evidence using cell lines and genetically modified mice that RIP140 is able to modulate the transcription of certain genes involved in AD pathology, such as ß-APP cleaving enzyme (BACE1) and GSK3. Consequently, we found that RIP140 overexpression reduced the generation of Aß in a neuroblastoma cell line by decreasing the transcription of ß-APP cleaving enzyme via a PPARγ-dependent mechanism. The results of this study therefore provide molecular insights into common signaling pathways linking metabolic disease with AD.

The anti-inflammatory Annexin A1 induces the clearance and degradation of the amyloid-ß peptide.

BACKGROUND: The toxicity of amyloid-ß (Aß) peptide present in the brain of Alzheimer's disease (AD) patients is thought to be mediated via the increased secretion of pro-inflammatory mediators, which can lead to neuronal dysfunction and cell death. In addition, we have previously shown that inflammation can affect Aß generation. More recently, we have reported that in vitro administration of the anti-inflammatory mediator Annexin A1 (ANXA1) following an inflammatory challenge suppressed microglial activation and this effect was mediated through formyl peptide receptor-like 1 (FPRL1/FPR2) signalling. The aim of this study was to determine the potential role of ANXA1 in the generation and clearance of Aß. METHODS: We first compared ANXA1 protein expression in the brains of AD patients and healthy controls as well as in the 5XFAD model of AD. To determine the role of ANXA1 in the processing of amyloid precursor protein (APP) and the degradation of Aß, N2a neuroblastoma cells were treated with human recombinant ANXA1 or transfected with ANXA1 siRNA. We also investigated the effect of ANXA1 on Aß phagocytosis and microglial activation in BV2 cells treated with synthetic Aß. RESULTS: Our data show that ANXA1 is increased in the brains of AD patients and animal models of AD at early stages. ANXA1 was able to reduce the levels of Aß by increasing its enzymatic degradation by neprilysin in N2a cells and to stimulate Aß phagocytosis by microglia. These effects were mediated through FPRL1 receptors. In addition, ANXA1 inhibited the Aß-stimulated secretion of inflammatory mediators by microglia. CONCLUSIONS: These data suggest that ANXA1 plays a pivotal role in Aß clearance and supports the use of ANXA1 as potential pharmacological tool for AD therapeutics.

Systemic administration of fibroblast growth factor-2 (FGF2) reduces BACE1 expression and amyloid pathology in APP23 mice.

There is an emerging evidence that growth factors may have a potential beneficial use in the treatment of Alzheimer's disease (AD) because of their neuroprotective properties and effects on neuronal proliferation. Basic fibroblast growth factor or fibroblast growth factor-2 (FGF2) is an anti-inflammatory, angiogenic, and neurotrophic factor that is expressed in many cell types, including neurons and glial cells. Here, we explored whether subcutaneous administration of FGF2 could have therapeutic effects in the APP 23 transgenic mouse, a model of amyloid pathology. FGF2 treatment attenuated spatial memory deficits, reduced amyloid-ß (Aß) and tau pathologies, decreased inducible nitric oxide synthase expression, and increased the number of astrocytes in the dentate gyrus in APP 23 mice compared with the vehicle-treated controls. The decrease in Aß deposition was associated with a reduction in the expression of BACE1, the main enzyme responsible for Aß generation. These results were confirmed in a neuroblastoma cell line, which demonstrated that incubation with FGF2 regulates BACE1 transcription. In addition, and in contrast with what has been previously published, the levels of FGF2 were reduced in postmortem brains from AD patients compared with controls. These data, therefore, suggest that systemic administration of FGF2 could have a potential therapeutic application in AD.

Activation of the Wnt/ß-catenin pathway represses the transcription of the ß-amyloid precursor protein cleaving enzyme (BACE1) via binding of T-cell factor-4 to BACE1 promoter.

Alterations in the Wnt signaling pathway have been implicated in Alzheimer's disease; however, its role in the processing of the amyloid precursor protein remains unknown. In this study, activation of the Wnt pathway by overexpression of the agonist Wnt3a or ß-catenin or by inhibition of glycogen kinase synthase-3 in N2a cells resulted in a reduction in Aß levels and in the activity and expression of BACE1 (ß-APP cleaving enzyme). Conversely, inhibition of the pathway by transfection of the antagonists secreted frizzled receptor protein-1 or dickkopf-1 produced the opposite effects. Chromatin immunoprecipitation analysis demonstrated that ß-catenin binds specifically to regions within the promoter of BACE1 containing putative T-cell factor/lymphoid enhancer binding factor-1 (TCF/LEF) motifs, consistent with canonical Wnt target regulation. Furthermore, cells transfected with ß-catenin mutants incapable of binding to TCF/LEF increased BACE1 gene promoter activity. Interestingly, TCF4 knockdown reversed the effects of Wnt3a activation on BACE1 transcription. We found that TCF4 binds to the same region on BACE1 promoter following Wnt3a stimulation, indicating that TCF4 functions as a transcriptional repressor of BACE1 gene. In conclusion, Wnt/ß-catenin stimulation may repress BACE1 transcription via binding of TCF4 to BACE1 gene, and therefore, activation of the Wnt pathway may hold the key to new treatments of Alzheimer disease.-Parr, C., Mirzaei, N., Christian, M., and Sastre, M. Activation of the Wnt/ß-catenin pathway represses the transcription of the ß-amyloid precursor protein cleaving enzyme (BACE1) via binding of T-cell factor-4 to BACE1 promoter.

Membrane lipid modifications and therapeutic effects mediated by hydroxydocosahexaenoic acid on Alzheimer's disease.

Alzheimer's disease (AD) is a neurodegenerative pathology with relevant unmet therapeutic needs. Both natural aging and AD have been associated with a significant decline in the omega-3 polyunsaturated fatty acid docosahexaenoic acid (DHA), and accordingly, administration of DHA has been proposed as a possible treatment for this pathology. However, recent clinical trials in mild-to-moderately affected patients have been inconclusive regarding the real efficacy of DHA in halting this disease. Here, we show that the novel hydroxyl-derivative of DHA (2-hydroxydocosahexaenoic acid - OHDHA) has a strong therapeutic potential to treat AD. We demonstrate that OHDHA administration increases DHA levels in the brain of a transgenic mouse model of AD (5xFAD), as well as those of phosphatidylethanolamine (PE) species that carry long polyunsaturated fatty acids (PUFAs). In 5xFAD mice, administration of OHDHA induced lipid modifications that were paralleled with a reduction in amyloid-ß (Αß) accumulation and full recovery of cognitive scores. OHDHA administration also reduced Aß levels in cellular models of AD, in association with alterations in the subcellular distribution of secretases and reduced Aß-induced tau protein phosphorylation as well. Furthermore, OHDHA enhanced the survival of neuron-like differentiated cells exposed to different insults, such as oligomeric Aß and NMDA-mediated neurotoxicity. These results were supported by model membrane studies in which incorporation of OHDHA into lipid-raft-like vesicles was shown to reduce the binding affinity of oligomeric and fibrillar Aß to membranes. Finally, the OHDHA concentrations used here did not produce relevant toxicity in zebrafish embryos in vivo. In conclusion, we demonstrate the pleitropic effects of OHDHA that might prove beneficial to treat AD, which suggests that an upstream event, probably the modulation of the membrane lipid composition and structure, influences cellular homeostasis reversing the neurodegenerative process. This Article is Part of a Special Issue Entitled: Membrane Structure and Function: Relevance in the Cell's Physiology, Pathology and Therapy.

Glycogen synthase kinase 3 inhibition promotes lysosomal biogenesis and autophagic degradation of the amyloid-ß precursor protein.

Alzheimer's disease (AD) has been associated with altered activity of glycogen synthase kinase 3 (GSK3) isozymes, which are proposed to contribute to both neurofibrillary tangles and amyloid plaque formation. However, the molecular basis by which GSK3 affects the formation of Aß remains unknown. Our aim was to identify the underlying mechanisms of GSK3-dependent effects on the processing of amyloid precursor protein (APP). For this purpose, N2a cells stably expressing APP carrying the Swedish mutation were treated with specific GSK3 inhibitors or transfected with GSK3α/ß short interfering RNA. We show that inhibition of GSK3 leads to decreased expression of APP by enhancing its degradation via an increase in the number of lysosomes. This induction of the lysosomal/autophagy pathway was associated with nuclear translocation of transcription factor EB (TFEB), a master regulator of lysosomal biogenesis. Our data indicate that GSK3 inhibition reduces Aß through an increase of the degradation of APP and its carboxy-terminal fragment (CTF) by activation of the lysosomal/autophagy pathway. These results suggest that an increased propensity toward autophagic/lysosomal alterations in AD patients could have consequences for neuronal function.

PPARγ co-activator-1α (PGC-1α) reduces amyloid-ß generation through a PPARγ-dependent mechanism.

We have previously reported that the nuclear receptor peroxisome proliferator activated receptor-γ (PPARγ) regulates the transcription of ß-secretase (BACE1), a key enzyme involved in amyloid-ß (Aß) generation. Here, we aimed to investigate the role of PPARγ coactivator-1α (PGC-1α), which controls major metabolic functions through the co-activation of PPARγ and other transcription factors. Western blotting experiments with nuclear extracts from brain cortex of AD cases and controls showed a reduction in the levels of PGC-1α in AD patients. PGC-1α overexpression in N2a neuroblastoma cells induced a decrease in the levels of secreted Aß and an increase in the levels of non-amyloidogenic soluble AßPPα. The decrease in Aß after exogenous expression of PGC-1α was a consequence of reduced BACE1 expression and transcription, together with a decrease in BACE1 promoter activity. In addition, we detected a significant reduction in ß-secretase activity by measuring the levels of ß-carboxy terminus fragment (ß-CTFs) and by using a commercial assay for ß-secretase. In contrast, down-regulation of PGC-1α levels by transfection with PGC-1α siRNA increased BACE1 expression. These effects appeared to be dependent on PPARγ, because PGC-1α did not affect Aß and BACE1 levels in N2a cells transfected with PPARγ siRNA or in PPARγ knockout fibroblasts. In conclusion, since PGC-1α appears to decrease Aß generation, therapeutic modulation of PGC-1α could have real potential as a treatment for AD.

Interactions between APP secretases and inflammatory mediators.

There is now a large body of evidence linking inflammation to Alzheimer's disease (AD). This association manifests itself neuropathologically in the presence of activated microglia and astrocytes around neuritic plaques and increased levels of inflammatory mediators in the brains of AD patients. It is considered that amyloid-beta peptide (Abeta), which is derived from the processing of the longer amyloid precursor protein (APP), could be the most important stimulator of this response, and therefore determining the role of the different secretases involved in its generation is essential for a better understanding of the regulation of inflammation in AD. The finding that certain non-steroidal anti-inflammatory drugs (NSAIDs) can affect the processing of APP by inhibiting beta- and gamma-secretases, together with recent revelations that these enzymes may be regulated by inflammation, suggest that they could be an interesting target for anti-inflammatory drugs. In this review we will discuss some of these issues and the role of the secretases in inflammation, independent of their effect on Abeta formation.