Interaction between 24-hydroxycholesterol, oxidative stress, and amyloid-β in amplifying neuronal damage in Alzheimer's disease: three partners in crime

All three cholesterol oxidation products implicated thus far in the pathogenesis of Alzheimer's disease, 7β-hydroxycholesterol, 24-hydroxycholesterol, and 27-hydroxycholesterol, markedly enhance the binding of amyloid-beta (Aβ) to human differentiated neuronal cell lines (SK-N-BE and NT-2) by up-regulating net expression and synthesis of CD36 and β1-integrin receptors. However, only 24-hydroxycholesterol markedly potentiates the pro-apoptotic and pro-necrogenic effects of Aβ(1-42) peptide on these cells: 7β-hydroxycholesterol and 27-hydroxycholesterol, like unoxidized cholesterol, show no potentiating effect. This peculiar behavior of 24-hydroxycholesterol at physiologic concentrations (1 μm) depends on its strong enhancement of the intracellular generation of NADPH oxidase-dependent reactive oxygen species (ROS), mainly H(2) O(2) , and the consequent impairment of neuronal cell redox equilibrium, measured in terms of the GSSG/GSH ratio. Cell incubation with antioxidants quercetin or genistein prevents 24-hydroxycholesterol's pro-oxidant effect and potentiation of Aβ-induced necrosis and apoptosis. Thus, the presence of 24-hydroxycholesterol in the close vicinity of amyloid plaques appears to enhance the adhesion of large amounts of Aβ to the plasma membrane of neurons and then to amplify the neurotoxic action of Aβ by locally increasing ROS steady-state levels. This report further supports a primary involvement of altered brain cholesterol metabolism in the complex pathogenesis of Alzheimer's disease.     

Inflammation-related gene expression by lipid oxidation-derived products in the progression of atherosclerosis

Vascular areas of atherosclerotic development persist in a state of inflammation, and any further inflammatory stimulus in the subintimal area elicits a proatherogenic response; this alters the behavior of the artery wall cells and recruits further inflammatory cells. In association with the inflammatory response, oxidative events are also involved in the development of atherosclerotic plaques. It is now unanimously recognized that lipid oxidation-derived products are key players in the initiation and progression of atherosclerotic lesions. Oxidized lipids, derived from oxidatively modified low-density lipoproteins (LDLs), which accumulate in the intima, strongly modulate inflammation-related gene expression, through involvement of various signaling pathways. In addition, considerable evidence supports a proatherogenic role of a large group of potent bioactive lipids called eicosanoids, which derive from oxidation of arachidonic acid, a component of membrane phospholipids. Of note, LDL lipid oxidation products might regulate eicosanoid production, modulating the enzymatic degradation of arachidonic acid by cyclooxygenases and lipoxygenases; these enzymes might also directly contribute to LDL oxidation. This review provides a comprehensive overview of current knowledge on signal transduction pathways and inflammatory gene expression, modulated by lipid oxidation-derived products, in the progression of atherosclerosis.     

Inhibition of receptor-dependent urokinase signaling by specific Ser to Glu substitutions

We have previously reported that phosphorylation of human urokinase on Ser138/303 abolishes its catalytic-independent motogen and proadhesive abilities, whereas receptor binding is not affected. Here we show that substitution of the two relevant serines with glutamic acid residues impairs the ability of urokinase to mobilize a variety of human and mouse cell lines as well as human primary T lymphocytes. Accordingly, urokinase receptor-dependent signaling, leading to cytoskeletal rearrangements and paxillin re-distribution, does not occur in MCF-7 breast carcinoma cells exposed to 'phosphorylation-like' urokinase. Unlike the wild-type form, di-substituted urokinase is unable to induce the physical association of urokinase receptor with alphavbeta5 vitronectin receptor, which is required for MCF-7 urokinase-dependent cell migration. Finally, the di-substituted variant fails to activate p55fgr, a member of the Src tyrosine kinase family, which mediates cell migration and adhesion of U937 myelomonocytic cells. In conclusion, the finding that specific amino acid substitutions strongly interfere with the ability of urokinase to stimulate cell migration, and the associated intracellular events uncover a novel way to regulate urokinase receptor-dependent signaling.     

Melanins and melanosomes from llama (Lama glama L.)

Analysis of melanins and melanosomes in eight hair and skin samples taken of adult pigmented Argentine llamas (Lama glama L.) has been carried out. In each sample, eumelanins, pheomelanins and alkali-soluble melanins were identified. The total amount of melanins and the amount of eumelanins both decreased from black to reddish brown colour, while pheomelanins were found to be present in small quantities in each sample. Eumelanosomes were round and oval-shaped, displaying transverse striations clearly visible at low magnification. Dark brown samples revealed all four melanosomes stages. Stages I and II melanosomes appeared as large, asymmetrical vacuoles containing numerous microvesicles randomly scattered within an amorphous proteinaceous material (vesiculo-globular bodies). Stage III melanosomes had microgranular melanin deposits in the microvesicles and in the matrix. The fully melanized melanosomes (stage IV) were primarily round-shaped, showing an irregular outline and the electron-dense pigment was arranged to form large clusters. In light brown melanocytes, numerous melanosomes at different maturation stages could be found. Premelanosomes appeared ovoid, containing amorphous proteinaceous material and spotty and microgranular deposits. Mature melanosomes were fully melanized, homogeneously electron-dense, ovoid granules.     

Short-Term Exposure to Enriched Environment in Adult Rats Restores MK-801-Induced Cognitive Deficits and GABAergic Interneuron Immunoreactivity Loss

Perinatal injections of N-methyl-D-aspartate (NMDA) receptor antagonist in rodents emulate some cognitive impairments and neurochemical alterations, such as decreased GABAergic (gamma aminobutyric acid) interneuron immunoreactivity, also found in schizophrenia. These features are pervasive, and developing neuroprotective or neurorestorative strategies is of special interest. In this work, we aimed to investigate if a short exposure to enriched environment (EE) in early adulthood (P55–P73) was an effective strategy to improve cognitive dysfunction and to restore interneuron expression in medial prefrontal cortex (mPFC) and hippocampus (HPC). For that purpose, we administered MK-801 intraperitoneally to Long Evans rats from postnatal days 10 to 20. Twenty-four hours after the last injection, MK-801 produced a transient decrease in spontaneous motor activity and exploration, but those abnormalities were absent at P24 and P55. The open field test on P73 manifested that EE reduced anxiety-like behavior. In addition, MK-801-treated rats showed cognitive impairment in novel object recognition test that was reversed by EE. We quantified different interneuron populations based on their calcium-binding protein expression (parvalbumin, calretinin, and calbindin), glutamic acid decarboxylase 67, and neuronal nuclei-positive cells by means of unbiased stereology and found that EE enhanced interneuron immunoreactivity up to normal values in MK-801-treated rats. Our results demonstrate that a timely intervention with EE is a powerful tool to reverse long-lasting changes in cognition and neurochemical markers of interneurons in an animal model of schizophrenia.     

Filamin A is mutated in X-linked chronic idiopathic intestinal pseudo-obstruction with central nervous system involvement

We have previously reported that an X-linked recessive form of chronic idiopathic intestinal pseudo-obstruction (CIIPX) maps to Xq28. To select candidate genes for the disease, we analyzed the expression in murine fetal brain and intestine of 56 genes from the critical region. We selected and sequenced seven genes and found that one affected male from a large CIIPX-affected kindred bears a 2-bp deletion in exon 2 of the FLNA gene that is present at the heterozygous state in the carrier females of the family. The frameshift mutation is located between two close methionines at the filamin N terminus and is predicted to produce a protein truncated shortly after the first predicted methionine. Loss-of-function FLNA mutations have been associated with X-linked dominant nodular ventricular heterotopia (PVNH), a central nervous system (CNS) migration defect that presents with seizures in females and lethality in males. Notably, the affected male bearing the FLNA deletion had signs of CNS involvement and potentially has PVNH. To understand how the severe frameshift mutation we found can explain the CIIPX phenotype and its X-linked recessive inheritance, we transiently expressed both the wild- type and mutant filamin in cell culture and found that filamin translation can start from either of the two initial methionines in these conditions. Therefore, translation of a normal shorter filamin can occur in vitro from the second methionine downstream of the 2-bp insertion we found. We confirmed this, demonstrating that the filamin protein is present in the patient's lymphoblastoid cell line that shows abnormal cytoskeletal actin organization compared with normal lymphoblasts. We conclude that the filamin N terminal region between the initial two methionines is crucial for proper enteric neuron development.     

Immunohistochemical evaluation of intermediate filament nestin in dog hair follicles

Hair follicles (HFs) are self-renewing structures that reconstitute themselves through the hair cycle. They maintain reservoirs of stem cells (SC) that are thought to reside in the bulge area, a region localized in the lowermost permanent portion of HFs. In mice and humans, HF bulge cells express nestin and present stem features as pluripotency. Nestin is a class VI intermediate filament protein; it was first described as a specific marker of CNS stem cells, but recent studies suggest that it may represent a more general stem cell marker (Wiese et al., 2004; Hoffman, 2006). Bulge cell characteristics have mainly been studied in mice and humans, but recently, a bulge-like region was identified also in dog HFs (Pascucci et al., 2006). In this work we investigate the presence and localization of nestin in dog HFs with the aim of evaluating its expression and to correlate it with the location of the bulge-like region. Immunostaining of skin samples collected from healthy dogs was performed by using a rabbit anti-nestin polyclonal antibody. The presence of a population of immunoreactive cells was revealed in the hair follicle middle region, at the arrector pili muscle insertion level. An immunohistochemical signal was detected only in primary hair follicles throughout the hair cycle. These observations led us to conclude that nestin positive cells are located in the bulge-like region of dog HFs and strengthen our hypothesis regarding the correlation between this region and the dog HF stem compartment.     

A molecular survey concerning the origin of Cyperus esculentus (Cyperaceae,Poales): two sides of the same coin (weed vs. crop)

Background and AimsCyperus esculentus is widespread in tropical and temperate zones and is also present in cooler regions. It is used as a crop plant, but it also occurs in the wild and as a weed. As a consequence of its ecological plasticity, C. esculentus has remarkable variability, with several morphotypes. Four wild-type varieties are presently recognized, in addition to the cultivated form. This study investigates the phylogenetic position and biogeography of C. esculentus with the objective of contributing new data to increase the understanding of its evolutionary history.Methods Genealogical relationships among genotypes were inferred by using plastid DNA haplotype and nuclear ribosomal (nr) DNA ribotype sequences for 70 specimens either collected in the field or obtained from herbaria. Statistical dispersal–vicariance (S-DIVA) and Bayesian binary method (BBM) analyses were used to reconstruct the possible ancestral ranges of C. esculentus. In order to determine the age of C. esculentus, a time-measured phylogenetic analysis was performed.Key Results Considerable variation between the chosen nuclear and plastid markers was detected (27 ribotypes vs. six haplotypes). No geographical structure was displayed among the haplotypes, but information on the dispersal pattern may be deduced. Two types of ribotypes were detected in nrDNA, with an evident geographical segregation into an Old World group and a polymorphic New World group. Both S-DIVA and BBM analyses suggested a biogeographical history in which dispersal from the African region has been crucial in shaping the current distribution pattern of C. esculentus. The most recent common ancestor between C. esculentus races has an age of 5.1 million years (95 % highest posterior density 2.5–10.2).Conclusions The molecular analysis provides novel insights into the evolutionary history of C. esculentus. The results have various taxonomic and phylogenetic implications, including a hypothesis on the origin and phylogeography of this species, which probably originated in the late Cenozoic in Africa, and reached the Americas repeatedly, independently of Columbian exchanges.