Exposure to chronic stress is frequently accompanied by cognitive and affective disorders in association with neurostructural adaptations. Chronic stress was previously shown to trigger Alzheimer's-like neuropathology, which is characterized by Tau hyperphosphorylation and missorting into dendritic spines followed by memory deficits. Here, we demonstrate that stress-driven hippocampal deficits in wild-type mice are accompanied by synaptic missorting of Tau and enhanced Fyn/GluN2B-driven synaptic signaling. In contrast, mice lacking Tau [Tau knockout (Tau-KO) mice] do not exhibit stress-induced pathological behaviors and atrophy of hippocampal dendrites or deficits of hippocampal connectivity. These findings implicate Tau as an essential mediator of the adverse effects of stress on brain structure and function.Tau | stress | hippocampus | depression | memory deficits T he cytoskeletal protein Tau is implicated in the establishment of Alzheimer's disease (AD) (1) as well as excitotoxicity (1) and, more recently, epilepsy (2, 3). Exposure to stressful conditions induces depressive behavior and memory deficits in both rodents and humans (4-8). Studies in rodents have shown that chronic stress triggers Tau hyperphosphorylation, a key pathogenic mechanism in AD, and results in cognitive and mood deficits (9-13); however, those studies do not provide direct evidence for a role of Tau in stress-evoked brain pathology. Given that Tau plays an important role in regulating neuronal architecture and function through its interaction with various cellular targets (e.g., tubulin and Fyn) (14), we hypothesized that Tau mediates the deleterious actions of stress on brain structure and function.To test the above hypothesis, we compared the impact of chronic unpredictable stress (CUS) (11, 15) in mice carrying a null mutation of the mapt gene [Tau knockout (Tau-KO) mice] (16) with their wild-type (WT) littermates. Three well-characterized behavioral endpoints (cognition, coping styles, and anxiety) that are disrupted by CUS served as the primary assay endpoints; these were complemented with measures of hippocampal structural and functional integrity. The hippocampus is a central component of the neurocircuitries that control these behaviors and displays overt lesions in both stress-and Tau-related pathologies; in the latter, the hippocampus is one of the earliest brain regions to show signs of neurodegeneration (1,4,7,(10)(11)(12)(13)17). ResultsDeleterious Effects of Stress on Memory and Mood Are Abrogated in the Absence of Tau Protein. Cognition, mood, and anxiety are interdependent behavioral domains that exhibit complex interactions (5). Different forms of memory were assessed after exposure of WT and Tau-KO mice to the CUS paradigm; the test battery included the Y-maze, Morris water maze (MWM), and the novel object recognition test (NOR). Anxiety was evaluated using the elevated plus maze (EPM), and coping styles and anhedonia were assessed using the forced swim test (FST) and the sucrose consumption test (SCT).Two-way ANOVA ...

Angiotensin (Ang)-(1-7) is one of the major active components of the renin-angiotensin system, produced from cleavage of Ang II by angiotensin-converting-enzyme type 2 (ACE2), which acts through a specific G protein-coupled receptor, Mas. We have investigated whether the human endometrium expresses these components during menstrual cycle. By radioimmunoassay, Ang-(1-7) was detected in endometrial wash fluid at picomolar concentrations. Using immunofluorescence, both the peptide and its receptor were identified in cultured endometrial epithelial and stromal cells. By immunohistochemistry, Ang(1-7) was localized in the endometrium throughout menstrual cycle, being more concentrated in the glandular epithelium of mid- and late secretory phase. This pattern corresponded to the ACE2 mRNA, which was more abundant in epithelial cells than in stromal cells (2-fold increase, p < 0.05) and in the secretory vs. proliferative phase (6.6-fold increase, p < 0.01). The receptor Mas was equally distributed between epithelial and stromal cells and did not change during menstrual cycle. The physiological role of this peptide system in normal and pathological endometrium warrants further investigation.

Emerging studies implicate Tau as an essential mediator of neuronal atrophy and cognitive impairment in Alzheimer's disease (AD), yet the factors that precipitate Tau dysfunction in AD are poorly understood. Chronic environmental stress and elevated glucocorticoids (GC), the major stress hormones, are associated with increased risk of AD and have been shown to trigger intracellular Tau accumulation and downstream Tau-dependent neuronal dysfunction. However, the mechanisms through which stress and GC disrupt Tau clearance and degradation in neurons remain unclear. Here, we demonstrate that Tau undergoes degradation via endolysosomal sorting in a pathway requiring the small GTPase Rab35 and the endosomal sorting complex required for transport (ESCRT) machinery. Furthermore, we find that GC impair Tau degradation by decreasing Rab35 levels, and that AAV-mediated expression of Rab35 in the hippocampus rescues GC-induced Tau accumulation and related neurostructural deficits. These studies indicate that the Rab35/ESCRT pathway is essential for Tau clearance and part of the mechanism through which GC precipitate brain pathology.

Tau protein in dendrites and synapses has been recently implicated in synaptic degeneration and neuronal malfunction. Chronic stress, a well-known inducer of neuronal/synaptic atrophy, triggers hyperphosphorylation of Tau protein and cognitive deficits. However, the cause-effect relationship between these events remains to be established. To test the involvement of Tau in stress-induced impairments of cognition, we investigated the impact of stress on cognitive behavior, neuronal structure, and the synaptic proteome in the prefrontal cortex (PFC) of Tau knock-out (Tau-KO) and wild-type (WT) mice. Whereas exposure to chronic stress resulted in atrophy of apical dendrites and spine loss in PFC neurons as well as significant impairments in working memory in WT mice, such changes were absent in Tau-KO animals. Quantitative proteomic analysis of PFC synaptosomal fractions, combined with transmission electron microscopy analysis, suggested a prominent role for mitochondria in the regulation of the effects of stress. Specifically, chronically stressed animals exhibit Tau-dependent alterations in the levels of proteins involved in mitochondrial transport and oxidative phosphorylation as well as in the synaptic localization of mitochondria in PFC. These findings provide evidence for a causal role of Tau in mediating stress-elicited neuronal atrophy and cognitive impairment and indicate that Tau may exert its effects through synaptic mitochondria.

The exposure to high glucocorticoids (GC) triggers neuronal atrophy and cognitive deficits, but the exact cellular mechanisms underlying the GC-associated dendritic remodeling and spine loss are still poorly understood. Previous studies have implicated sustained GC elevations in neurodegenerative mechanisms through GC-evoked hyperphosphorylation of the cytoskeletal protein Tau while Tau mislocation has recently been proposed as relevant in Alzheimer's disease (AD) pathology. In light of the dual cytoplasmic and synaptic role of Tau, this study monitored the impact of prolonged GC treatment on Tau intracellular localization and its phosphorylation status in different cellular compartments. We demonstrate, both by biochemical and ultrastructural analysis, that GC administration led to cytosolic and dendritic Tau accumulation in rat hippocampus, and triggered Tau hyperphosphorylation in epitopes related to its malfunction (Ser396/404) and cytoskeletal pathology (e.g., Thr231 and Ser262). In addition, we show, for the first time, that chronic GC administration also increased Tau levels in synaptic compartment; however, at the synapse, there was an increase in phosphorylation of Ser396/404, but a decrease of Thr231. These GC-triggered Tau changes were paralleled by reduced levels of synaptic scaffolding proteins such as PSD-95 and Shank proteins as well as reduced dendritic branching and spine loss. These in vivo findings add to our limited knowledge about the underlying mechanisms of GC-evoked synaptic atrophy and neuronal disconnection implicating Tau missorting in mechanism(s) of synaptic damage, beyond AD pathology.

words)Emerging studies implicate Tau as an essential mediator of neuronal atrophy and cognitive impairment in Alzheimer's disease (AD), yet the factors that precipitate Tau dysfunction in AD are poorly understood. Chronic environmental stress and elevated glucocorticoids (GC), the major stress hormones, are associated with increased risk of AD, and have been shown to trigger intracellular Tau accumulation and downstream Tau-dependent neuronal dysfunction. However, the mechanisms through which stress and GC disrupt Tau clearance and degradation in neurons remain unclear. Here, we demonstrate that Tau undergoes degradation via endo-lysosomal sorting in a pathway requiring the small GTPase Rab35 and the endosomal sorting complex required for transport (ESCRT) machinery.Furthermore, we find that GC impair Tau degradation by decreasing Rab35 levels, and that AAVmediated expression of Rab35 in the hippocampus rescues GC-induced Tau accumulation and related neurostructural deficits. These studies indicate that the Rab35/ESCRT pathway is essential for Tau clearance and part of the mechanism through which GC precipitate brain pathology.

The vasoactive peptide angiotensin (Ang)-(1-7) has vasodilator, antifibrotic and antihypertrophic properties, but little is known about its regulation in the uterus. The aim of this study was to evaluate Ang-(1-7) and its receptor Mas expression throughout rat uterine tissues, in ovariectomized animals treated with estrogen alone or combined with progestin. Adult Wistar rats (n = 19) were ovariectomized and randomly assigned into three different groups 1 week later. One group received a single dose of estradiol benzoate (1.5 mg/kg, i.m. injection, n = 6). Another group received estradiol associated with depot medroxyprogesterone acetate (3 mg/kg, i.m. injection, n = 6). Control group (n = 7) received oil injection. One week later, the rats were euthanized and their uteri were fixed and stained by immunohistochemistry, using a polyclonal antibody specific to Ang-(1-7) and its receptor Mas. Ang-(1-7) was detected in all uterine tissues, but it was weak or absent in the circular myometrium of treated animals. The intensity of the immunostaining decreased in the glandular epithelium of hormonally treated animals when compared to controls. In estrogen treated rats, Ang-(1-7) labeling was scattered and sometimes included the nuclei of glandular cells. We also detected Ang-(1-7) expression in longitudinal myometrium and uterine serosa. Mas receptor was present in all tissues with similar intensity among the tissue types in the control and estrogen plus progestin groups. In the estrogen group, Mas staining was stronger in the luminal and glandular epithelium when compared with stroma or circular myometrium. In conclusion, ovarian steroids are not required to allow endometrial expression of Ang-(1-7) and its receptor Mas in rats, as it remains abundant in ovariectomized animals. However, estrogen and progestin may modulate the distribution pattern of this peptide in the endometrium, especially in the glandular compartment.

Chronic stress and elevated glucocorticoids (GCs), the major stress hormones, are risk factors for Alzheimer’s disease (AD) and promote AD pathomechanisms, including overproduction of toxic amyloid-β (Aβ) peptides and intraneuronal accumulation of hyperphosphorylated Tau protein. The latter is linked to downregulation of the small GTPase Rab35, which mediates Tau degradation via the endolysosomal pathway. Whether Rab35 is also involved in Aβ overproduction remains an open question. Here, we find that hippocampal Rab35 levels are decreased not only by stress/GC but also by aging, another AD risk factor. Moreover, we show that Rab35 negatively regulates Aβ production by sorting amyloid precursor protein (APP) and β-secretase (BACE1) out of the endosomal network, where they interact to produce Aβ. Interestingly, Rab35 coordinates distinct intracellular trafficking steps for BACE1 and APP, mediated by its effectors OCRL and ACAP2, respectively. Finally, we demonstrate that Rab35 overexpression prevents the amyloidogenic trafficking of APP and BACE1 induced by high GC levels. These studies identify Rab35 as a key regulator of APP processing and suggest that its downregulation may contribute to stress-related and AD-related amyloidogenesis.