Sex differences in nucleus accumbens transcriptome profiles associated with susceptibility versus resilience to subchronic variable stress

Depression and anxiety disorders are more prevalent in females, but the majority of research in animal models, the first step in finding new treatments, has focused predominantly on males. Here we report that exposure to subchronic variable stress (SCVS) induces depression-associated behaviors in female mice, whereas males are resilient as they do not develop these behavioral abnormalities. In concert with these different behavioral responses, transcriptional analysis of nucleus accumbens (NAc), a major brain reward region, by use of RNA sequencing (RNA-seq) revealed markedly different patterns of stress regulation of gene expression between the sexes. Among the genes displaying sex differences was DNA methyltransferase 3a (Dnmt3a), which shows a greater induction in females after SCVS. Interestingly, Dnmt3a expression levels were increased in the NAc of depressed humans, an effect seen in both males and females. Local overexpression of Dnmt3a in NAc rendered male mice more susceptible to SCVS, whereas Dnmt3a knock-out in this region rendered females more resilient, directly implicating this gene in stress responses. Associated with this enhanced resilience of female mice upon NAc knock-out of Dnmt3a was a partial shift of the NAc female transcriptome toward the male pattern after SCVS. These data indicate that males and females undergo different patterns of transcriptional regulation in response to stress and that a DNA methyltransferase in NAc contributes to sex differences in stress vulnerability

Papain

Peer reviewed: YesNRC publication: Ye

Peptide aldehydes and nitriles as transition state analog inhibitors of cysteine proteases

Enzymes efficiently catalyze reactions by stabilizing inherently unstable transition states. For cysteine proteases, part of the stabilization is provided by a region of the enzyme termed the oxyanion hole. Site-directed mutagenesis has been used to investigate further the role of the oxyanion hole of papain in the binding of putative transition state analog inhibitors of cysteine proteases. The dissociation constants Kiobs for inhibition of wild-type and mutant enzymes (Gln19Ala, Glnl9Glu , and Glnl9His) by the aldehyde Ac-Phe-Gly-CHO and the nitrile MeOCO-Phe-Gly-CN have been determined in the pH range 3.5-9.0. For the peptide nitrile inhibitor, mutation of Gln19 was found to cause important increases in Kiobs, and thioimidate adducts with the papain mutants Gln19Ala and Gln19Glu are less stable by 1.4-2.4 kcal/mol. However, for the peptide aldehyde inhibitor, the mutations resulted in a small but significant increase in stability of the tetrahedral hemithioacetal adduct (0.4-1.2 kcal/mol). In that respect, the hemithioacetal formed between papain and a peptide aldehyde cannot be considered a good model of the transition state for cysteine protease-catalyzed reactions. The influence of the mutations on the pH dependency of inhibition also indicates that with respect to oxyanion hole interaction, the inhibition of papain by peptide nitriles is a process closer to that of substrate hydrolysis than is the inhibition by the corresponding peptide aldehydes. The nature of the intermediates and transition states in hydrolysis reactions catalyzed by cysteine proteases, as well as the use of enzyme-inhibitor adducts as their models, is discussed.NRC publication: Ye

Critical role of TLR9 in acute graft-versus-host disease

Graft-vs-host disease (GVHD) is a major complication after allogeneic bone marrow transplantation. Different studies have demonstrated that intestinal bacterial breakdown products and loss of gastrointestinal tract integrity, both induced by conditioning regiments, are critical in the pathogenesis of acute GVHD. Using C57BL/6 knockout mice, we evaluated the role of TLR4 and TLR9, which recognize bacterial LPS and DNA, respectively, in the GVHD associated with allogeneic bone marrow transplantation. When myeloablative-irradiated TLR9 knockout (TLR9(-/-)) mice were used as graft recipients, survival and clinical score of acute GVHD were improved as compared with the wild-type recipient mice (18/30 vs 1/31 mice still alive at day 70 in a total of four experiments); while no differences were observed using recipient TLR4 knockout (TLR4(-/-)) mice. The reduced mortality and morbidity in TLR9(-/-) mice related with reduced stimulatory activity of TLR9(-/-) spleen APCs after conditioning and reduced proliferation of allogeneic donor T cells. Experiments using TLR9(+/+) into TLR9(-/-) and TLR9(-/-) into TLR9(+/+) chimeric mice as recipients indicated a critical role for nonhematopoietic TLR9(+/+) cells interacting with bacterial breakdown products released in myeloablated mice. Altogether these data reveal a novel important role of TLR9 in GVHD, a finding that might provide tools to reduce this complication of allogeneic transplantation

Endowing carbon nanotubes with biological and biomedical properties by chemical modifications

abstrac

Hippocampal membrane-associated p75 ntr levels are increased in alzheimer's Disease

The pan-specific p75 neurotrophin receptor (p75 NTR) is believed to play an important role in the pathogenesis of Alzheimer's disease (AD). It is involved in mediating amyloid-\u3b2 (A\u3b2) toxicity and stimulating amyloidogenesis. In addition, we have recently shown that stimulating cultured SH-SY5Y human neuroblastoma cells with A\u3b2 42 increases the level of membrane-associated p75 NTR and that A\u3b2 42- accumation in two strains of transgenic AD model mice is accompanied by an increased level of hippocampal membrane-associated p75 NTR (Chakravarthy et al. J Alzheimers Dis 19, 915-925, 2010). This raised an important question whether accumulating A\u3b2 42 in human AD is also accompanied by an increased hippocampal membrane-associated p75 NTR. In this study, using polyclonal and monoclonal antibodies against the p75 NTR receptor's intra-and extracellular domains, we show that indeed the mean level of membrane-associated p75 NTR in the hippocampal formation is significantly higher (~two-fold, p < 0.03) in human AD brains than in identical samples of hippocampal formation in age-matched non-AD human brains. The possible relation of this elevated hippocampal p75 NTR to AD cognitive decline is discussed. \ua9 2012 -IOS Press and the authors.Peer reviewed: YesNRC publication: Ye

Evidence that a synthetic amyloid- f oligomer-binding peptide (ABP) targets amyloid- f deposits in transgenic mouse brain and human Alzheimer's disease brain

The synthetic ~5kDa ABP (amyloid- f binding peptide) consists of a region of the 228kDa human pericentrioloar material-1 (PCM-1) protein that selectively and avidly binds in vitro A\u3b21-42 oligomers, believed to be key co-drivers of Alzheimer's disease (AD), but not monomers (Chakravarthy et al., (2013) [3]). ABP also prevents A f1-42 from triggering the apoptotic death of cultured human SHSY5Y neuroblasts, likely by sequestering A f oligomers, suggesting that it might be a potential AD therapeutic. Here we support this possibility by showing that ABP also recognizes and binds A\u3b21-42 aggregates in sections of cortices and hippocampi from brains of AD transgenic mice and human AD patients. More importantly, ABP targets A\u3b21-42 aggregates when microinjected into the hippocampi of the brains of live AD transgenic mice. \ua9 2014.Peer reviewed: YesNRC publication: Ye

The p75 neurotrophin receptor is localized to primary cilia in adult murine hippocampal dentate gyrus granule cells

The densely ciliated granule cell layer of the adult murine hippocampal dentate gyrus is one of two sites of adult neurogenesis. The granule cells have already been proven to localize their SSTR3 (somatostatin receptor 3) receptors to their so-called primary cilia. Here we show for the first time that 70\u201390% of these cells in 7\u201318 months-old wild-type and 3xTg-AD (Alzheimer disease transgenic) mice also load p75NTR receptors into the structures containing SSTR3, i.e., their primary cilia. On the other hand, p75NTR\u2019s TrkA co-receptors were not localized to cilia but conventionally distributed throughout the cell surface. Significantly fewer cells (20\u201340%) in the hippocampal CA1 and CA3 regions and cerebral cortex have p75NTR containing cilia. While we don\u2019t know what the impact of the cilial localization of p75NTR on dentate gyral adult neurogenesis and memory encoding might be, the cilia\u2019s amyloid beta-activatable p75NTR receptors could be damaging or lethal to the hippocampal functioning of amyloid beta\u2013accumulating Alzheimer brain

Amyloid-beta Peptides Stimulate the Expression of the p75NTR / Neurotrophin Receptor in SHSY5Y Human Neuroblastoma Cells and AD Transgenic Mice.

The progression toward end-stage Alzheimer's disease (AD) in the aging brain is driven by accumulating amyloid-beta (Abeta)1-42 oligomers that is accompanied by the downregulation of the Trk A neurotrophin receptor and by either upregulation or at least maintenance of the p75 neurotrophin receptor (p75NTR), which can be stimulated by the accumulating Abeta1-42 peptides. Here we show that Abetae fragment Abeta25-35, but not Abeta42-1, can at least double the level of p75NTR receptors in the membranes of model SH-SY5Y human neuroblastoma cells. We also show that p75NTR is upregulated in the hippocampi of two strains of AD transgenic mice. Specifically, the level of the p75NTR receptor in the hippocampal membranes from 12-15 monthold AD-triple transgenic mice (3xTg-AD) harboring PS1_M146V, AbetaPP_Swe, and tau_P301L was nearly twice that in hippocampal membranes from age-matched wild-type mice. Similarly, the level of p75NTR receptor in 7 month-old B6.Cg-Tg AD mice harboring PSEN1dE9 and AbetaPP_Swe was also increased above the level in the corresponding wild-type mice. This increase correlated with the age-dependent rise in Abeta1-42 levels in the AD mice. Thus, it appears that it could be the accumulating Abeta1-42 that increases or at least prevents the downregulation of p75NTR receptors in key parts of AD brains. It is possible that when the Abeta1-42 accumulation reaches a critical level in the brain on the way to late-onset AD, the Abeta1-42-induced p75NTR receptor signaling starts a vicious cycle that accelerates AD development because of the activated receptors' recently shown ability to stimulate Abeta1-42 production. PMID: 19920315 [P

Involvement of insulin-like growth factor 1 receptor signaling in the amyloid-\u3b2 peptide oligomers-induced p75 neurotrophin receptor protein expression in mouse hippocampus

The p75 neurotrophin receptor (p75NTR) has been thought to play a critical role in amyloid-\u3b2 peptide (A\u3b2)-mediated neurodegeneration and A\u3b2 metabolism in Alzheimer's disease (AD) brains. Our previous report showed that membrane-associated p75NTR protein expression was significantly increased in the hippocampi of two different strains of transgenic AD mice and was associated with the age-dependent elevation of A\u3b21-42 levels. Here, we provide evidence that the A\u3b21-42 oligomers known as ADDLs (A\u3b2-derived diffusible ligands) induce p75NTR protein expression through insulin-like growth factor 1 receptor (IGF-1R) phosphorylation in SH-SY5Y human neuroblastoma cells. An in vivo microinjection study demonstrated that microinjected ADDLs increased the p75NTR protein expression by 1.4-fold in the ipsilateral hippocampus compared to the contralateral hippocampus. In addition, ADDLs microinjected into mouse hippocampi facilitated IGF-1R phosphorylation within 30 min and the co-administration of picropodophyllin, an IGF-1R kinase inhibitor, blocked ADDLs-induced p75NTR expression. We examined the possible involvement of IGF-1R in the increased p75NTR protein expression in the hippocampi of 6-month-old A\u3b2PPswe/PS1dE9 AD model mice that had accumulated significant amounts of A\u3b21-42 and showed significantly higher p75NTR expression than age-matched wild-type mice. We found that IGF-1R phosphorylation in these transgenic mice was higher than that in the wild-type mice. These findings indicate that A\u3b21-42 oligomers stimulate the p75NTR protein expression in the hippocampus through IGF-1R signaling. Thus, A\u3b21-42 oligomers-mediated IGF-1R activation may trigger an increase in p75NTR protein expression in the hippocampus of AD brain during the early stages of disease development. \ua9 2012-IOS Press and the authors. All rights reserved.Peer reviewed: YesNRC publication: Ye