Search

The effects of chronic antidepressant (AD) treatment on sleep disturbances in rodent chronic stress models have not been thoroughly investigated. Here, we show that chronic social defeat stress (SDS) in rats induces prolonged social avoidance, alterations in sleep architecture (increased total rapid eye movement [REM] sleep duration, bout, and shortened REM latency), and contextual but not cued fear memory deficits, even 1 month after the last SDS. These abnormalities were associated with changes in electroencephalography (EEG) spectral powers, including reduced REM sleep theta power during the light phase. Chronic treatment with two different classes of antidepressants (ADs), imipramine and fluoxetine, significantly ameliorated these behavioral, sleep, and EEG abnormalities. Interestingly, REM theta power was normalized by chronic (1 month) but not 1 week AD administration and solely correlated with the ratio (an objective indicator) of social interaction 1 month after the last SDS. These data suggest that reductions in REM sleep theta power, an EEG parameter that has never been directly investigated in humans, is a core sleep symptom in socially defeated rats, and, potentially, also in patients with stress-related psychiatric disorders, including major depressive and posttraumatic stress disorders.

The role of oligodendrocyte lineage cells, the largest glial population in the adult central nervous system (CNS), in the pathogenesis of Alzheimer’s disease (AD) remains elusive. Here, we developed a culture method for adult oligodendrocyte progenitor cells (aOPCs). Fibroblast growth factor 2 (FGF2) promotes survival and proliferation of NG2+ aOPCs in a serum-free defined medium; a subpopulation (~5%) of plexin-B3+ aOPCs was also found. FGF2 withdrawal decreased NG2+, but increased plexin-B3+ aOPCs and Aβ1-42 secretion. Plexin-B3+ aOPCs were distributed throughout the adult rat brain, although less densely than NG2+ aOPCs. Spreading depolarization induced delayed cortical plexin-B3+ aOPC gliosis in the ipsilateral remote cortex. Furthermore, extracellular Aβ1-42 accumulation was occasionally found around plexin-B3+ aOPCs near the lesions. In AD brains, virtually all cortical SPs were immunostained for plexin-B3, and plexin-B3 levels increased significantly in the Sarkosyl-soluble fractions. These findings suggest that plexin-B3+ aOPCs may play essential roles in AD pathogenesis, as natural Aβ-secreting cells., In order to investigate the role of oligodendrocyte lineage cells in Alzheimer’s Disease (AD) pathology, Nihonmatsu-Kikuchi et al developed a culture method for adult oligodendrocyte progenitor cells in the rat. Using this method as well as imaging AD patient brain tissue, they found that plexin-B3-expressing cells could be a potential source of amyloid β peptide.

The roles played by oligodendrocyte (OL) lineage cells, the largest glial population in the adult CNS, in the pathogenesis of Alzheimer’s disease (AD) remain elusive. Here, we show a newly developed culture method for adult OL progenitor cells (aOPCs) and identify novel plexin-B3-expressing (plexin-B3+) aOPCs as potential amyloid β peptides (Aβ)-secreting cells. Fibroblast growth factor 2 (FGF2) promotes the survival and proliferation of aOPCs in a serum-free defined medium. Although the whole expression profiles of the expanded aOPCs closely resemble those of in vivo OPCs, we found a subpopulation (up to 5%) of plexin-B3+/olig2+ aOPCs in the cultures growing in FGF2. FGF2 withdrawal decreased NG2+, but increased plexin-B3+ aOPCs with increased APP expression, Aβ1-40, −42 secretions and Aβ1-42/total Aβ ratios in association with cored senile plaque-like morphological changes. In vivo, plexin-B3+ aOPCs are distributed throughout the adult brain, although less densely so than NG2+ aOPCs. Spreading depolarization, a type of brain injury, induced unique delayed cortical plexin-B3+ aOPC gliosis in the ipsilateral, but not in the contralateral, remote cortex. In AD brains, virtually all senile plaques in the cortex were immunostained with plexin-B3 antibodies and the levels of cortical plexin-B3 expression increased significantly in the Salcosyl-soluble fractions. These findings suggest that plexin-B3+ aOPCs play important roles in the pathogenesis of AD most likely as a natural Aβ source.

Although It is widely recognized that virtually all antidepressants (ADs) suppress rapid eye movement (REM) sleep, the effects of chronic AD treatments on sleep abnormalities, especially those of REM sleep, have rarely been investigated comprehensively in animal models of major depressive disorder (MDD). Here, we show that chronic social defeat stress (SDS) in rats induces prolonged social avoidance and MDD-like alterations in sleep architecture (increased REM sleep durations, bouts, and shortened REM latency) even a month after the last SDS. These abnormalities were associated with changes in electroencephalography (EEG) spectra powers, such as reduced REM sleep theta powers during the light phase. Chronic AD treatments significantly ameliorated these behavioral, sleep, and EEG abnormalities, although in some cases not to control levels. Interestingly, the social interaction ratios a month after the last SDS most strongly correlated with the REM sleep theta powers. These results suggest that chronic AD treatments suppress REM sleep durations and bouts as observed in human MDD patients, but, at the same time, increase REM sleep theta power. The latter is an EEG parameter that has never been directly investigated in humans, and which may be responsible for the therapeutic effects of ADs.Significance StatementDisturbed sleep is one of nine diagnostic criteria for major depressive disorder (MDD), which usually resolves with adequate treatment. However, little is known about how antidepressants (AD) work in MDD animal models. Here, we developed a novel rat social defeat stress model demonstrating long-lasting MDD-like sleep disturbances. We found that chronic AD treatments suppressed REM durations and bouts as reported previously, but, at the same time, increased REM sleep theta power. Interestingly, among several sleep parameters, only REM sleep theta power strongly correlated with depressive symptoms at 1M. Thus, REM sleep theta power, an EEG parameter that has never been investigated directly in humans, could be a novel indicator for MDD and/or AD effects.

The role of oligodendrocyte lineage cells, the largest glial population in the adult central nervous system (CNS), in the pathogenesis of Alzheimer's disease (AD) remains elusive. Here, we developed a culture method for adult oligodendrocyte progenitor cells (aOPCs). Fibroblast growth factor 2 (FGF2) promotes survival and proliferation of NG2

Glyoxalase I catalyses the isomerization of the hemithioacetal formed non-enzymatically from methylglyoxal and glutathione to S-D-lactoylglutathione. The activity of glyoxalase I is conventionally measured spectrophotometrically by following the increase in A240 for which the change in molar absorption coefficient Δε240=2.86 mM−1·cm−1. The hemithioacetal is pre-formed in situ by incubation of methylglyoxal and glutathione in 50 mM sodium phosphate buffer (pH 6.6) at 37°C for 10 min. The cell extract is then added, the A240 is monitored over 5 min, and the initial rate of increase in A240 and hence glyoxalase I activity deduced with correction for blank. Glyoxalase I activity is given in units per mg of protein or cell number where one unit is the amount of enzyme that catalyses the formation of 1 μmol of S-D-lactoylglutathione per min under assay conditions. Glyoxalase II catalyses the hydrolysis of S-D-lactoylglutathione to D-lactate and glutathione. Glyoxalase II activity is also measured spectrophotometrically by following the decrease in A240 for which the change in molar absorption coefficient Δε240=−3.10 mM−1·cm−1. It is given in units per mg of protein or cell number where one unit is the amount of enzyme that catalyses the hydrolysis of 1 μmol of S-D-lactoylglutathione per min under assay conditions. Glyoxalase I and glyoxalase II activity measurements have been modified for use with a UV-transparent microplate for higher sample throughput.

The relationship between depression and Alzheimer's disease (AD) has always been relevant and controversial. Here, we briefly review epidemiological and biological studies that have investigated these disorders and then introduce our recent research about postmortem brains from patients with major depressive disorder (MDD). Our novel methodological approaches have revealed that MDD may be associated with an unknown type of myelin/myelination abnormalities in the frontopolar cortex. Based mainly on our findings, as well as on neuropathological observations by Braak and Braak (Acta Neuropathol 9, 197-201, 1996), we discuss the possible existence of an as yet unknown common mechanism linking the pathophysiologies underlying both depression and AD.

A novel, rapid, quantitative cell-counting method reveals oligodendroglial reduction in the frontopolar cortex in major depressive disorder

Families bearing mutations in the presenilin-1 (PSI) gene develop Alzheimer's disease (AD). However, the mechanism through which PS1 causes AD is unclear. The co-immunoprecipitation with PS1 in transfected COS-7 cells indicates that PSI directly interacts with endogenous beta-catenin, and the interaction requires residues 322450 of PSI and 445-676 of beta-catenin. Both proteins are co-localized in the endoplasmic reticulum. Over-expression of PS1 reduces the level of cytoplasmic beta-catenin, and inhibits beta-catenin-T cell factor-regulated transcription. These results indicate that PSI plays a role as inhibitor of the beta-catenin signal, which may be connected with the AD dysfunction.

Families bearing mutations in the presenilin 1 (PS1) gene develop Alzheimer’s disease. Previous studies have shown that the Alzheimer-associated mutations in PS1 increase production of amyloid β protein (Aβ 1–42 ). We now show that PS1 also regulates phosphorylation of the microtubule-associated protein tau. PS1 directly binds tau and a tau kinase, glycogen synthase kinase 3β (GSK-3β). Deletion studies show that both tau and GSK-3β bind to the same region of PS1, residues 250–298, whereas the binding domain on tau is the microtubule-binding repeat region. The ability of PS1 to bring tau and GSK-3β into close proximity suggests that PS1 may regulate the interaction of tau with GSK-3β. Mutations in PS1 that cause Alzheimer’s disease increase the ability of PS1 to bind GSK-3β and, correspondingly, increase its tau-directed kinase activity. We propose that the increased association of GSK-3β with mutant PS1 leads to increased phosphorylation of tau.

Presenilin 1 (PS 1) shows missense mutations in most early-onset familial Alzheimer's disease (FAD). Transfection of cDNA for wild type PS 1 into rat pheochromocytoma PC12 cells generated a 47 kDa full-size PS 1 protein, which was processed into a 28 kDa N-terminal fragment and a 19 kDa C-terminal fragment. We prepared selected Alzheimer-associated mutations (Gly384Ala, Leu392Val, and Cys410Tyr) of PS 1, which localized after a possible cleavage site. By transient expression in PC12 cells and rat glioma cell line, C6, we examined their influence on the processing of PS 1. Cys410Tyr inhibited proteolytic processing of PS 1, while Gly384Ala and Leu392Val did not. Thus, the Alzheimer related mutations can be divided into two groups in terms of their effect on the proteolytic cleavage of PS 1.

Families bearing mutations in the presenilin 1 (PS1) gene develop early onset familial Alzheimer's disease (FAD). Further, some PS1 mutants enhance secretion of the longer form of amyloid beta protein (Abeta42). We constructed cDNAs encoding human PS1 harboring 28 FAD-linked mutations, and examined the effects of the expressed PS1 mutants on Abeta42 secretion in beta amyloid precursor producing COS-1 cells. All the mutants significantly enhanced the ratio of Abeta42 to total Abeta compared with wild-type PS1. However, the increase in Abeta42 ratio in cells with each PS1 mutation did not correlate with the reported age of onset of FAD caused by that mutation. These results suggest that increased Abeta42 secretion is important for the development of Alzheimer's disease (AD), but may not be the only factor contributing to the onset of AD.

Several 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acids were synthesized and found to have a transiently increasing effect on the locomotor activity of mice after peripheral injection. Three of the active compounds were detected in the brain after intraperitoneal administration. Two of them, the 7-hydroxy and 7-hydroxy-6-methoxy derivatives, were found as endogenous compounds in untreated rat brain and may play a physiological role. The effects of some of these compounds on the level of various endogenous amines, amino acids and metabolites were examined.

Bipolar and major depressive disorders are essentially relapsing and remitting disorders of affect with nearly full recovery between episodes. Although the underlying molecular mechanisms remain unclear, myelin-related abnormalities have long been suspected. Here, using novel statistical analysis, we show that subtle but significant abnormalities exist in the composition of fatty acids (FAs), including docosapentaenoic acid (22:5n-3), one of the omega-3 polyunsaturated FAs, found in the post-mortem frontopolar cortex (FPC) of subjects with bipolar or major depressive disorders, although not in those with schizophrenia. These abnormalities were all aggravated in a myelin level-dependent manner, suggesting their close relationship with myelination. Animal studies have further revealed that chronic antidepressant treatment induces robust changes in brain FA metabolism, but contributes only part of the abnormalities found in the affective disorder brains. These findings indicate that the pathophysiology of affective disorders involves an unknown type of perturbed myelination in the FPC that may serve as a novel diagnostic and therapeutic target.

Recent studies suggest that schizophrenia (SCH) and bipolar disorder (BPD) may share a similar etiopathology. However, their precise neuropathological natures have rarely been characterized in a comprehensive and quantitative fashion. We have recently developed a rapid, quantitative cell-counting method for frozen unfixed postmortem brains using a flow cytometer. In the present study, we not only counted stained nuclei, but also measured their sizes in the gray matter of frontopolar cortices (FPCs) and inferior temporal cortices (ITCs) from patients with SCH or BPD, as well as in that from normal controls. In terms of NeuN(+) neuronal nuclei size, particularly in the reduced densities of small NeuN(+) nuclei, we found abnormal distributions present in the ITC gray matter of both patient groups. These same abnormalities were also found in the FPCs of SCH patients, whereas in the FPCs of BPD patients, a reduction in oligodendrocyte lineage (olig2(+)) cells was much more common. Surprisingly, in the SCH FPC, normal left-greater-than-right asymmetry in neural nuclei densities was almost completely reversed. In the BPD FPC, this asymmetry, though not obvious, differed significantly from that in the SCH FPC. These findings indicate that while similar neuropathological abnormalities are shared by patients with SCH or BPD, differences also exist, mainly in the FPC, which may at least partially explain the differences observed in many aspects in these disorders.

A novel, rapid, cell-counting method for unfixed frozen brains comprehensively quantifies at least four neural cell populations

Genetic variations in the gene encoding dysbindin has consistently been associated with schizophrenia and bipolar disorder, although little is known about the neural functions carried out by dysbindin. To gain some insight into this area, we took advantage of the readily available dysbindin-null mouse sandy (sdy-/-) and studied hippocampal neurogenesis using thymidine analogue bromodeoxuridine (BrdU). No significant differences were found in the proliferation (4 hours) or survival (1, 4 and 8 weeks after the last BrdU injection) of progenitors in the subgranular regions of the dentate gyrus between sdy-/- and sdy+/+ (control) mice. However, 4 weeks after the last BrdU injection, a significant reduction was observed in the ratio of neuronal differentiation in sdy-/- when compared to that of sdy+/+ (sdy+/+ = 87.0 ± 5.3% vs. sdy-/- = 71.3 ± 8.3%, p = 0.01). These findings suggest that dysbindin plays a role during differentiation process in the adult hippocampal neurogenesis and that its deficit may negatively affect neurogenesis-related functions such as cognition and mood.