Neuroinflammation alters cellular proteostasis by producing endoplasmic reticulum stress, autophagy activation and disrupting ERAD activation

Proteostasis alteration and neuroinflammation are typical features of normal aging. We have previously shown that neuroinflammation alters cellular proteostasis through immunoproteasome induction, leading to a transient decrease of proteasome activity. Here, we further investigated the role of acute lipopolysaccharide (LPS)-induced hippocampal neuroinflammation in cellular proteostasis. In particular, we focused on macroautophagy (hereinafter called autophagy) and endoplasmic reticulum-associated protein degradation (ERAD). We demonstrate that LPS injection induced autophagy activation that was dependent, at least in part, on glycogen synthase kinase (GSK)-3β activity but independent of mammalian target of rapamycin (mTOR) inhibition. Neuroinflammation also produced endoplasmic reticulum (ER) stress leading to canonical unfolded protein response (UPR) activation with a rapid activating transcription factor (ATF) 6α attenuation that resulted in a time-dependent down-regulation of ERAD markers. In this regard, the time-dependent accumulation of unspliced X-box binding protein (XBP) 1, likely because of decreased inositol-requiring enzyme (IRE) 1α-mediated splicing activity, might underlie in vivo ATF6α attenuation. Importantly, lactacystin-induced activation of ERAD was abolished in both the acute neuroinflammation model and in aged rats. Therefore, we provide a cellular pathway through which neuroinflammation might sensitize cells to neurodegeneration under stress situations, being relevant in normal aging and other disorders where neuroinflammation is a characteristic featureUnión Europea PI12/00445Unión Europea ERDF PI12/0044

Neuroprotective antibiotics in Alzheimer´s disease

Alzheimer´s disease (AD) is an irreversible neurodegenerative disorder and one of the main agingdependent maladies of the 21st century. Currently, around 46 million people suffer from AD worldwide and this is projected to double within the next 20 years. Due to the progressive aging of the population and the prediction of an increase in the incidence of this disease, AD constitutes a serious familial and social health problem. Therefore, it is essential to find therapeutic strategies which are aim to prevent, delay the onset, slow the progression and/or improve the symptoms of AD. Nowadays, the research is focused on finding and identifying new drugs for achieving these goals. In this article we have focused on a thorough review of the neuroprotective role the antibiotics rifampicin, rapamycin and minocycline play in the treatment of AD as these medications reach the brain quickly and are relatively inexpensive. Likewise, we have found evidence in both “in vitro” and “in vivo” studies and also some clinical trials. In an overview, all the reviewed antibiotics exert neuroprotection because they act as anti-inflammatory and anti-amyloidogenic agent

Could antibiotics be therapeutic agents in Alzheimer´s disease?

Alzheimer´s disease (AD) is an irreversible neurodegenerative disorder and one of the main aging-dependent maladies of the 21st century. Around 46 million people suffer from AD worldwide and this is projected to double within the next 20 years. Due to the progressive aging of the population and the prediction of an increase in the incidence of this disease, AD constitutes a serious familial and social health problem. Therefore, it is necessary to find new therapeutic strategies which are aimed to prevent, delay the onset, slow the progression and/or improve the symptoms of AD. Currently, the research is focused on finding and identifying new drugs for achieving these goals. In this chapter of the book, we widely review the neuroprotective role that some antibiotics could play in AD, because these drugs reach the brain quickly and are relatively inexpensive. Likewise, we have found evidence in both in vitro and in vivo studies and also in some clinical trials. In summary, all the reviewed antibiotics exert neuroprotection because they act on the main pathophysiological features of AD. Nevertheless, it must be taken into account that a long-term treatment with antibiotics could cause adverse effects including antibiotic resistance. Thus, properly clinical trials should be carried out in order to corroborate benefits of these antibiotics in people with AD

Hydroxytyrosol improves mitochondrial energetics of a cellular model of Alzheimer’s disease

Mitochondrial energetic deficit is one of the hallmarks of neurodegenerative disorders, e.g. Alzheimer´s disease (AD). Adherence to a Mediterranean diet is associated with lower incidence of cognitive decline and AD and extra virgin olive oil’s (poly)phenols such as oleuropein and hydroxytyrosol (HT) are being actively studied in this respect. In this study, we assessed the effects of HT on mitochondrial energetic dysfunction in the 7PA2 cells cellular model, i.e. one of the best cellular models of Aβ toxicity with a well-characterized mitochondrial dysfunction typically observed in AD. We report an increase of new mitochondria at 8 h post HT-treatment, which was followed by higher mitochondrial fusion. Further, ATP concentrations were significantly increased after 24 h of treatment with HT as compared with controls. Our data suggest that HT may revert the energetic deficit of a cellular model of AD by potentiating mitochondrial activity. Because HT is being proposed as dietary supplement or component of functional foods, future studies in appropriate animal models and – eventually – humans are warranted to further investigate its potential neuroprotective actions in AD

Dysfunction of the unfolded protein response increases neurodegeneration in aged rat hippocampus following proteasome inhibition

Dysfunctions of the ubiquitin proteasome system (UPS) have been proposed to be involved in the aetiology and/or progression of several age-related neurodegenerative disorders. However, the mechanisms linking proteasome dysfunction to cell degeneration are poorly understood. We examined in young and aged rat hippocampus the activation of the unfolded protein response (UPR) under cellular stress induced by proteasome inhibition. Lactacystin injection blocked proteasome activity in young and aged animals in a similar extent and increased the amount of ubiquitinated proteins. Young animals activated the three UPR arms, IRE1α, ATF6α and PERK, whereas aged rats failed to induce the IRE1α and ATF6α pathways. In consequence, aged animals did not induce the expression of pro-survival factors (chaperones, Bcl-XL and Bcl-2), displayed a more sustained expression of proapoptotic markers (CHOP, Bax, Bak and JKN), an increased caspase-3 processing. At the cellular level, proteasome inhibition induced neuronal damage in young and aged animals as assayed using Fluorojade-B staining. However, degenerating neurons were evident as soon as 24 h postinjection in aged rats, but it was delayed up to 3 days in young animals. Our findings show evidence supporting age-related dysfunctions in the UPR activation as a potential mechanism linking protein accumulation to cell degeneration. An imbalance between pro-survival and pro-apoptotic proteins, because of noncanonical activation of the UPR in aged rats, would increase the susceptibility to cell degeneration. These findings add a new molecular vision that might be relevant in the aetiology of several age-related neurodegenerative disorders

Lipopolysacharide-induced neuroinflammation leads to the accumulation of ubiquitinated proteins and increases susceptibility to neurodegeneration induced by proteasome inhibition in rat hippocampus

BACKGROUND: Neuroinflammation and protein accumulation are characteristic hallmarks of both normal aging and age-related neurodegenerative diseases. However, the relationship between these factors in neurodegenerative processes is poorly understood. We have previously shown that proteasome inhibition produced higher neurodegeneration in aged than in young rats, suggesting that other additional age-related events could be involved in neurodegeneration. We evaluated the role of lipopolysaccharide (LPS)-induced neuroinflammation as a potential synergic risk factor for hippocampal neurodegeneration induced by proteasome inhibition. METHODS: Young male Wistar rats were injected with 1 μL of saline or LPS (5 mg/mL) into the hippocampus to evaluate the effect of LPS-induced neuroinflammation on protein homeostasis. The synergic effect of LPS and proteasome inhibition was analyzed in young rats that first received 1 μL of LPS and 24 h later 1 μL (5 mg/mL) of the proteasome inhibitor lactacystin. Animals were sacrificed at different times post-injection and hippocampi isolated and processed for gene expression analysis by real-time polymerase chain reaction; protein expression analysis by western blots; proteasome activity by fluorescence spectroscopy; immunofluorescence analysis by confocal microscopy; and degeneration assay by Fluoro-Jade B staining. RESULTS: LPS injection produced the accumulation of ubiquitinated proteins in hippocampal neurons, increased expression of the E2 ubiquitin-conjugating enzyme UB2L6, decreased proteasome activity and increased immunoproteasome content. However, LPS injection was not sufficient to produce neurodegeneration. The combination of neuroinflammation and proteasome inhibition leads to higher neuronal accumulation of ubiquitinated proteins, predominant expression of pro-apoptotic markers and increased neurodegeneration, when compared with LPS or lactacystin (LT) injection alone. CONCLUSIONS: Our results identify neuroinflammation as a risk factor that increases susceptibility to neurodegeneration induced by proteasome inhibition. These results highlight the modulation of neuroinflammation as a mechanism for neuronal protection that could be relevant in situations where both factors are present, such as aging and neurodegenerative diseases

Ageing alters the lipid sensing process in the hypothalamus of Wistar rats. Effect of food restriction

Lipids regulate a wide range of biological processes. The mechanisms by which fatty acids (FA) and its metabolites influence the hypothalamic regulation of energy homeostasis have been highly studied. However, the effect of ageing and food restriction (FR) on this process is unknown. Herein, we analyzed the gene expression, protein and phosphorylation levels of hypothalamic enzymes and transcription factors related to lipid metabolism. Experiments were performed in male Wistar rats of 3-, 8- and 24-month-old Wistar rats fed ad libitum (AL), as ageing model. Besides, 5- and 21-month-old rats were subjected to a moderate FR protocol (equivalent to ≈ 80% of normal food intake) for three months before the sacrifice. Aged Wistar rats showed a situation of chronic lipid excess as a result of an increase in de novo FA synthesis and FA levels that reach the brain, contributing likely to the development of central leptin and insulin resistance. We observe a hypothalamic downregulation of AMP-activated protein kinase (AMPK) and stearoyl-CoA desaturase (SCD1) and an increase of carnitine palmitoyltransferase-1c (CPT1c) expression

Regional difference in inflammatory response to LPS-injection in the brain: Role of microglia cell density

To elucidate whether density of cells could contribute to the extent of microglial activation, we performed in vitro assays using three different densities of N13 microglia stimulated with LPS. Our results showed that induction of pro-inflammatory factors as TNF-α and iNOS was directly related to cell density, meanwhile the induction of the anti-inflammatory IL-10 was inversely related to cell density. Accordingly, in vivo assays showed that after LPS-injection, iNOS expression was more intense in substantia nigra, a brain area showing specific susceptibility to neurodegeneration after microglia activation, whereas IL-10 expression was more sustained in striatum, an area resistant to damage. These results support that microglia density is pivotal to control the balance between pro- and anti-inflammatory factors release.Instituto de Salud Carlos III PI060781, PI060567Junta de Andalucía CVI-90

Capítulo 4. Restricción calórica y ayuno intermitente ¿tienen efecto neuroprotector?

La restricción calórica moderada o el ayuno intermitente han sido propuestas como estrategias para la prevención de enfermedades asociadas al envejecimiento, como son las enfermedades neurodegenerativas. Sin embargo, es importante tener en cuenta tanto la composición de la dieta como la edad a la que comienza la restricción y el ayuno, ya que los mecanismos de adaptación a una situación de bajo aporte calórico podrían estar afectados en el proceso de envejecimiento. Por otro lado, la alteración en los mecanismos de control de la ingesta a nivel cerebral y la existencia de un riesgo de malnutrición en las personas mayores pueden comprometer, de igual forma, el correcto aporte de nutrientes al cerebro. Este déficit energético podría estar asociado a la presencia de muerte neuronal por mecanismos de excitotoxicidad y al aumento de la neurotransmisión de glutamato