Tau Protein Phosphorylated at Threonine-231 is Expressed Abundantly in the Cerebellum in Prion Encephalopathies.

BACKGROUND: Transmissible spongiform encephalopathies (TSEs) are rare neurodegenerative disorders that affect animals and humans. Bovine spongiform encephalopathy (BSE) in cattle, and Creutzfeld-Jakob Disease (CJD) in humans belong to this group. The causative agent of TSEs is called "prion", which corresponds to a pathological form (PrPSc) of a normal cellular protein (PrPC) expressed in nerve cells. PrPSc is resistant to degradation and can induce abnormal folding of PrPC, and TSEs are characterized by extensive spongiosis and gliosis and the presence of PrPSc amyloid plaques. CJD presents initially with clinical symptoms similar to Alzheimer's disease (AD). In AD, tau aggregates and amyloid-ß protein plaques are associated with memory loss and cognitive impairment in patients. OBJECTIVE: In this work, we study the role of tau and its relationship with PrPSc plaques in CJD. METHODS: Multiple immunostainings with specific antibodies were carried out and analyzed by confocal microscopy. RESULTS: We found increased expression of the glial fibrillary acidic protein (GFAP) and matrix metalloproteinase (MMP-9), and an exacerbated apoptosis in the granular layer in cases with prion disease. In these cases, tau protein phosphorylated at Thr-231 was overexpressed in the axons and dendrites of Purkinje cells and the extensions of parallel fibers in the cerebellum. CONCLUSION: We conclude that phosphorylation of tau may be a response to a toxic and inflammatory environment generated by the pathological form of prion.

Insoluble Vascular Amyloid Deposits Trigger Disruption of the Neurovascular Unit in Alzheimer's Disease Brains.

Alzheimer's disease (AD) is a neurodegenerative disease, characterized histopathologically by intra-neuronal tau-related lesions and by the accumulation of amyloid ß-peptide (Aß) in the brain parenchyma and around cerebral blood vessels. According to the vascular hypothesis of AD, an alteration in the neurovascular unit (NVU) could lead to Aß vascular accumulation and promote neuronal dysfunction, accelerating neurodegeneration and dementia. To date, the effects of insoluble vascular Aß deposits on the NVU and the blood-brain barrier (BBB) are unknown. In this study, we analyze different Aß species and their association with the cells that make up the NVU. We evaluated post-mortem AD brain tissue. Multiple immunofluorescence assays were performed against different species of Aß and the main elements that constitute the NVU. Our results showed that there are insoluble vascular deposits of both full-length and truncated Aß species. Besides, insoluble aggregates are associated with a decrease in the phenotype of the cellular components that constitute the NVU and with BBB disruption. This approach could help identify new therapeutic targets against key molecules and receptors in the NVU that can prevent the accumulation of vascular fibrillar Aß in AD.

In vitro effects of citral on the human myometrium: Potential adjunct therapy to prevent preterm births.

BACKGROUND: Premature infants contribute to infant morbidity and mortality especially in low resource settings. Information on tocolytic and/or anti-inflammatory effects of several plant extracts, such as citral, could help prevent preterm birth cases and reduce the number of preterm infants. The aim of this study was to evaluate the in vitro tocolytic and anti-inflammatory effect of citral on myometrial tissues of the human uterus. METHODS: Myometrial samples from uteri obtained after hysterectomy were used in functional tests to evaluate the inhibitory effect of citral on PGF-2α induced contractions. The intracellular cyclic adenosine monophosphate (cAMP) levels generated in response to citral in human myometrial homogenates were measured by ELISAs. Forskolin was used as a positive control. The anti-inflammatory effect of citral was determined through the measurement of two pro-inflammatory cytokines, tumor necrosis factor-α (TNFα) and interleukin (IL)-1ß, and the anti-inflammatory cytokine IL-10, in human myometrial explants stimulated with lipopolysaccharide (LPS). RESULTS: Citral was able to induce a significant inhibition of PGF-2α induced contractions at the highest concentration level (p < .05). Citral caused a concentration-dependent increase in myometrial cAMP levels (p < .05) and a concentration-dependent decrease in LPS-induced TNFα and IL-1ß production, while IL-10 production increased significantly (p < .05). The anti-inflammatory and tocolytic effects induced by citral could be associated with an increase in cAMP levels in human myometrial samples. CONCLUSION: These properties place citral as a potentially safe and effective adjuvant agent in preterm birth cases, an obstetric and gynecological problem that requires urgent attention.

PHF-Core Tau as the Potential Initiating Event for Tau Pathology in Alzheimer's Disease.

Worldwide, around 50 million people have dementia. Alzheimer's disease (AD) is the most common type of dementia and one of the major causes of disability and dependency among the elderly worldwide. Clinically, AD is characterized by impaired memory accompanied by other deficiencies in the cognitive domain. Neuritic plaques (NPs) and neurofibrillary tangles (NFTs) are histopathological lesions that define brains with AD. NFTs consist of abundant intracellular paired helical filaments (PHFs) whose main constituent is tau protein. Tau undergoes posttranslational changes including hyperphosphorylation and truncation, both of which favor conformational changes in the protein. The sequential pathological processing of tau is illustrated with the following specific markers: pT231, TG3, AT8, AT100, and Alz50. Two proteolysis sites for tau have been described-truncation at glutamate 391 and at aspartate 421-and which can be demonstrated by reactivity with the antibodies 423 and TauC-3, respectively. In this review, we describe the molecular changes in tau protein as pre-NFTs progress to extracellular NFTs and during which the formation of a minimal nucleus of the filament, as the PHF core, occurs. We also analyzed the PHF core as the initiator of PHFs and tau phosphorylation as a protective neuronal mechanism against the assembly of the PHF core.

Analysis of the Relationship Between Metalloprotease-9 and Tau Protein in Alzheimer's Disease.

BACKGROUND: Neurofibrillary tangles (NFTs) and amyloid plaques are the neuropathological hallmarks in brains with Alzheimer's disease (AD). Post-translational modifications of tau, such as phosphorylation and truncation, have been proposed as initiators in the assembly of the abnormal paired helical filaments that constitute the NFTs. Neurons and NFTs are sites of matrix metalloproteinases (MMPs). OBJECTIVE: The aim of this study was to analyze the relationship of MMP-9 and tau protein in brain samples with AD. METHODS: This study was performed on brain tissue samples from patients with early, moderate, and late AD. MMPs and tau levels were analyzed by western blot and gelatin-substrate zymography. Immunofluorescence techniques and confocal microscopy were used to analyze the presence of both proteins in NFTs. Further, molecular dynamics simulations (MDS) and protein-protein docking were conducted to predict interaction between MMP-9 and tau protein. RESULTS: MMP-9 expression was greatest in moderate and late AD, whereas MMP-2 expression was only increased in late-stage AD. Interestingly, confocal microscopy revealed NFTs in which there was co-localization of MMP-9 and tau protein. MDS and protein-protein docking predictions indicate that a high-affinity complex can be formed between MMP-9 and full-length tau protein. CONCLUSION: These observations provide preliminary evidence of an interaction between these two proteins. Post-translational modifications of tau protein, such as C-terminal truncation or phosphorylation of amino acid residues in the MMP-9 recognition site and conformational changes in the protein, such as folding of the N-terminal sequence over the three-repeat domain, could preclude the interaction between MMP-9 and tau protein during stages of NFT development.

A putative calcium-ATPase of the secretory pathway family may regulate calcium/manganese levels in the Golgi apparatus of Entamoeba histolytica.

Calcium regulates many cellular processes in protozoa, including growth, differentiation, programmed cell death, exocytosis, endocytosis, phagocytosis, fusion of the endosomes of distinct stages with phagosomes, fusion of phagosomes with lysosomes, and recycling the membrane. In Entamoeba histolytica, the protozoa responsible for human amoebiasis, calcium ions are essential for signaling pathways that lead to growth and development. In addition, calcium is crucial in the modulation of gene expression in this microorganism. However, there is scant information about the proteins responsible for regulating calcium levels in this parasite. In this work, we characterized a protein of E. histolytica that shows a close phylogenetic relationship with Ca2+ pumps that belong to the family of secretory pathway calcium ATPases (SPCA), which for several organisms are located in the Golgi apparatus. The amoeba protein analyzed herein has several amino acid residues that are characteristic of SPCA members. By an immunofluorescent technique using specific antibodies and immunoelectron microscopy, the protein was detected on the membrane of some cytoplasmic vacuoles. Moreover, this putative calcium-ATPase was located in vacuoles stained with NBD C6-ceramide, a Golgi marker. Overall, the current findings support the hypothesis that the presently analyzed protein corresponds to the SPCA of E. histolytica.

The small GTPase EhRabB of Entamoeba histolytica is differentially expressed during phagocytosis.

It has been described that the pathogenicity of Entamoeba histolytica is influenced by environmental conditions and that transcription profile changes occur during invasion, suggesting that gene expression may be involved in the virulence of this parasite. However, the molecular mechanisms that are implicated in the control of gene expression in this microorganism are poorly understood. Here, we showed that the expression of the EhRabB protein, a small GTPase involved in phagocytosis, is modified through the interaction with red blood cells. By ELISA, Western blot, and immunofluorescence assays, we observed that the expression of EhRabB diminished after 5 min of the interaction of trophozoites with red blood cells, but protein level was recovered at subsequent times. In the EhRabB amino acid sequence, we found two lysine residues that could be target for ubiquitin modification and trigger the degradation of this GTPase at early times of phagocytosis. The analysis of the expression of the EhrabB mRNA showed that the interaction of trophozoites with red blood cells produces a drastic diminishing in its half-life. In addition, promoter assays using the chloramphenicol acetyltransferase reporter gene and electrophoretic mobility shift assays experiments showed that the URE1 motif located in the promoter region of EhrabB is involved in the expression regulation of this gene during phagocytosis. Moreover, the immunolocalization of the URE1-binding protein during phagocytosis indicated that the transcription of the EhrabB gene is determined, at least in part, by the translocation of this transcription factor to nuclei. These results suggested that the expression of particular genes of this parasite is controlled at several stages.