Extracellular chaperones prevent Aβ42-induced toxicity in rat brains

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterised by cognitive decline, formation of the extracellular amyloid β (Aβ₄₂) plaques, neuronal and synapse loss, and activated microglia and astrocytes. Extracellular chaperones, which are known to inhibit amyloid fibril formation and promote clearance of misfolded aggregates, have recently been shown to reduce efficiently the toxicity of HypF-N misfolded oligomers to immortalised cell lines, by binding and clustering them into large species. However, the role of extracellular chaperones on Aβ oligomer toxicity remains unclear, with reports often appearing contradictory. In this study we microinjected into the hippocampus of rat brains Aβ₄₂ oligomers pre-incubated for 1 h with two extracellular chaperones, namely clusterin and α₂-macroglobulin. The chaperones were found to prevent Aβ₄₂-induced learning and memory impairments, as assessed by the Morris Water Maze test, and reduce Aβ₄₂-induced glia inflammation and neuronal degeneration in rat brains, as probed by fluorescent immunohistochemical analyses. Moreover, the chaperones were able to prevent Aβ₄₂ colocalisation with PSD-95 at post-synaptic terminals of rat primary neurons, suppressing oligomer cytotoxicity. All such effects were not effective by adding pre-formed oligomers and chaperones without preincubation. Molecular chaperones have therefore the potential to prevent the early symptoms of AD, not just by inhibiting Aβ₄₂ aggregation, as previously demonstrated, but also by suppressing the toxicity of Aβ₄₂ oligomers after they are formed. These findings elect them as novel neuroprotectors against amyloid-induced injury and excellent candidates for the design of therapeutic strategies against AD.     

Point mutated caveolin-3 form (P104L) impairs myoblast differentiation via Akt and p38 signalling reduction, leading to an immature cell signature

Unbalanced levels of caveolin-3 (Cav3) are involved in muscular disorders. In the present study we show that differentiation of immortalized myoblasts is affected by either lack or overexpression of Cav3. Nevertheless, depletion of Cav3 induced by delivery of the dominant-negative Cav3 (P104L) form elicited a more severe phenotype, characterized by the simultaneous attenuation of the Akt and p38 signalling networks, leading to an immature cell and molecular signature. Accordingly, differentiation of myoblasts harbouring Cav3 (P104L) was improved by countering the reduced Akt and p38 signalling network via administration of IGF-1 or trichostatin A. Furthermore, loss of Cav3 correlated with a deregulation of the TGF-β-induced Smad2 and Erk1/2 pathways, confirming that Cav3 controls TGF-β signalling at the plasma membrane. Overall, these data suggest that loss of Cav3, primarily causing attenuation of both Akt and p38 pathways, contributes to impair myoblast fusion.     

Up‐regulation of β‐amyloidogenesis in neuron‐like human cells by both 24‐ and 27‐hydroxycholesterol: protective effect of N‐acetyl‐cysteine

An abnormal accumulation of cholesterol oxidation products in the brain of patients with Alzheimer's disease (AD) would further link an impaired cholesterol metabolism in the pathogenesis of the disease. The first evidence stemming from the content of oxysterols in autopsy samples from AD and normal brains points to an increase in both 27‐hydroxycholesterol (27‐OH) and 24‐hydroxycholesterol (24‐OH) in the frontal cortex of AD brains, with a trend that appears related to the disease severity. The challenge of differentiated SK‐N‐BE human neuroblastoma cells with patho‐physiologically relevant amounts of 27‐OH and 24‐OH showed that both oxysterols induce a net synthesis of Aβ_1‐42 by up‐regulating expression levels of amyloid precursor protein and β‐secretase, as well as the β‐secretase activity. Interestingly, cell pretreatment with N‐acetyl‐cysteine (NAC) fully prevented the enhancement of β‐amyloidogenesis induced by the two oxysterols. The reported findings link an impaired cholesterol oxidative metabolism to an excessive β‐amyloidogenesis and point to NAC as an efficient inhibitor of oxysterols‐induced Aβ toxic peptide accumulation in the brain.     

Loading into Nanoparticles Improves Quercetin's Efficacy in Preventing Neuroinflammation Induced by Oxysterols

Chronic inflammatory events appear to play a fundamental role in Alzheimer''s disease (AD)-related neuropathological changes, and to result in neuronal dysfunction and death. The inflammatory responses observed in the AD brain include activation and proliferation of glial cells, together with up-regulation of inflammatory mediators and of free radicals. Along with glial cells, neurons themselves can also react and contribute to neuroinflammatory changes in the AD brain, by serving as sources of inflammatory mediators. Because excess cholesterol cannot be degraded in the brain, it must be excreted from that organ as cholesterol oxidation products (oxysterols), in order to prevent its accumulation. Among risk factors for this neurodegenerative disease, a mechanistic link between altered cholesterol metabolism and AD has been suggested; oxysterols appear to be the missing linkers between the two, because of their neurotoxic effects. This study shows that 24-hydroxycholesterol, 27-hydroxycholesterol, and 7β-hydroxycholesterol, the three oxysterols potentially implicated in AD pathogenesis, induce some pro-inflammatory mediator expression in human neuroblastoma SH-SY5Y cells, via Toll-like receptor-4/cyclooxygenase-2/membrane bound prostaglandin E synthase (TLR4/COX-2/mPGES-1); this clearly indicates that oxysterols may promote neuroinflammatory changes in AD. To confirm this evidence, cells were incubated with the anti-inflammatory flavonoid quercetin; remarkably, its anti-inflammatory effects in SH-SY5Y cells were enhanced when it was loaded into β-cyclodextrin-dodecylcarbonate nanoparticles, versus cells pretreated with free quercetin. The goal of loading quercetin into nanoparticles was to improve its permeation across the blood-brain barrier into the brain, and its bioavailability to reach target cells. The findings show that this drug delivery system might be a new therapeutic strategy for preventing or reducing AD progression.     

Localization of Ras signaling complex in budding yeast

In Saccharomyces cerevisiae, cAMP/pKA pathway plays a major role in metabolism, stress resistance and proliferation control. cAMP is produced by adenylate cyclase, which is activated both by Gpr1/Gpa2 system and Ras proteins, regulated by Cdc25/Sdc25 guanine exchange factors and Ira GTPase activator proteins. Recently, both Ras2 and Cdc25 RasGEF were reported to localize not only in plasma membrane but also in internal membranes. Here, the subcellular localization of Ras signaling complex proteins was investigated both by fluorescent tagging and by biochemical cell membrane fractionation on sucrose gradients. Although a consistent minor fraction of Ras signaling complex components was found in plasma membrane during exponential growth on glucose, Cdc25 appears to localize mainly on ER membranes, while Ira2 and Cyr1 are also significantly present on mitochondria. Moreover, PKA Tpk1 catalytic subunit overexpression induces Ira2 protein to move from mitochondria to ER membranes. These data confirm the hypothesis that different branches of Ras signaling pathways could involve different subcellular compartments, and that relocalization of Ras signaling complex components is subject to PKA control.     

Rhabdomyosarcomas: an overview on the experimental animal models

Rhabdomyosarcomas (RMS) are aggressive childhood soft-tissue malignancies deriving from mesenchymal progenitors that are committed to muscle-specific lineages. Despite the histopathological signatures associated with three main histological variants, termed embryonal, alveolar and pleomorphic, a plethora of genetic and molecular changes are recognized in RMS. Over the years, exposure to carcinogens or ionizing radiations and gene-targeting approaches in vivo have greatly contributed to disclose some of the mechanisms underlying RMS onset. In this review, we describe the principal distinct features associated with RMS variants and focus on the current available experimental animal models to point out the molecular determinants cooperating with RMS development and progression.     

Landscape genetic structure of chestnut (Castanea sativa Mill.) in Spain

The current need for forest conservation and management has driven a rapid expansion of landscape genetics approach. This discipline combines tools from molecular genetics, landscape ecology and spatial statistics and is decisive for improving not only ecological knowledge but also for properly managing population genetic resources. This approach could be appropriate to sweet chestnut (Castanea sativa Mill.), a multipurpose species of great economic importance in the Mediterranean basin and a species considered to be a good model of integration between natural and human-driven distribution of diversity. Sixteen chestnut populations, covering the distribution range of the species in Spain, were analysed using seven microsatellite markers. Results revealed a high level of genetic diversity in Spanish chestnut populations, which in part followed a geographical pattern, although distribution was not homogeneous. Likewise, areas particularly rich in diversity were detected, facilitating the development of a hypothesis about the history of chestnut in Spain. In conclusion, these results provide valuable baseline data for more in-depth studies on chestnut landscape genetics that can contribute to its conservation.