Cognitive Decline, Cerebral-Spleen Tryptophan Metabolism, Oxidative Stress, Cytokine Production, and Regulation of the Txnip Gene in a Triple Transgenic Mouse Model of Alzheimer Disease.

Pathologic inflammation in response to injury, infection, or oxidative stress is a proposed mechanism relating cognitive decline to dementia. The kynurenine pathway and thioredoxin-interacting protein (TXNIP) activity regulate inflammation and neurotoxicity in Alzheimer disease (AD). We examined cognitive deficits, kynurenine pathway mediators, TXNIP, and oxidative damage in the cerebrum and spleen, including inflammatory cytokine production by stimulated splenocytes, from female triple transgenic (3xTg-AD) mice in early and late stages of disease progression, and characterized tissue-specific epigenetic regulation of Txnip gene expression. We show that cognitive deficits in 7-month-old 3xTg-AD mice are associated with a stable increase in cerebrum and spleen tryptophan metabolites, with a concomitant increase in amyloid ß 40 (Aß40)/Aß42 and tau/hyperphosphorylated tau pathologies and a coordinated reduction in spleen proinflammatory cytokine production in 17-month-old mice. The enhanced cerebrum TXNIP expression is associated with increased histone acetylation, transcription factor [Aß42 or CCCTC-binding factor (CTCF)] binding, and Txnip promoter hypomethylation, whereas the attenuated spleen TXNIP expression is associated with increased histone methylation, reduced CTCF binding, and Txnip promoter hypermethylation. These results suggest a causal relationship among epigenomic state, TXNIP expression, cerebral-spleen tryptophan metabolism, inflammatory cytokine production, and cognitive decline; and they provide a potential mechanism for Txnip gene regulation in normal and pathologic conditions, suggesting TXNIP levels may be a useful predictive or diagnostic biomarker for Aß40/Aß42 targeted AD therapies.

Stress and the Emerging Roles of Chromatin Remodeling in Signal Integration and Stable Transmission of Reversible Phenotypes.

The influence of early life experience and degree of parental-infant attachment on emotional development in children and adolescents has been comprehensively studied. Structural and mechanistic insight into the biological foundation and maintenance of mammalian defensive systems (metabolic, immune, nervous and behavioral) is slowly advancing through the emerging field of developmental molecular (epi)genetics. Initial evidence revealed that differential nurture early in life generates stable differences in offspring hypothalamic-pituitary-adrenal (HPA) regulation, in part, through chromatin remodeling and changes in DNA methylation of specific genes expressed in the brain, revealing physical, biochemical and molecular paths for the epidemiological concept of gene-environment interactions. Herein, a primary molecular mechanism underpinning the early developmental programming and lifelong maintenance of defensive (emotional) responses in the offspring is the alteration of chromatin domains of specific genomic regions from a condensed state (heterochromatin) to a transcriptionally accessible state (euchromatin). Conversely, DNA methylation promotes the formation of heterochromatin, which is essential for gene silencing, genomic integrity and chromosome segregation. Therefore, inter-individual differences in chromatin modifications and DNA methylation marks hold great potential for assessing the impact of both early life experience and effectiveness of intervention programs-from guided psychosocial strategies focused on changing behavior to pharmacological treatments that target chromatin remodeling and DNA methylation enzymes to dietary approaches that alter cellular pools of metabolic intermediates and methyl donors to affect nutrient bioavailability and metabolism. In this review article, we discuss the potential molecular mechanism(s) of gene regulation associated with chromatin modeling and programming of endocrine (e.g., HPA and metabolic or cardiovascular) and behavioral (e.g., fearfulness, vigilance) responses to stress, including alterations in DNA methylation and the role of DNA repair machinery. From parental history (e.g., drugs, housing, illness, nutrition, socialization) to maternal-offspring exchanges of nutrition, microbiota, antibodies and stimulation, the nature of nurture provides not only mechanistic insight into how experiences propagate from external to internal variables, but also identifies a composite therapeutic target, chromatin modeling, for gestational/prenatal stress, adolescent anxiety/depression and adult-onset neuropsychiatric disease.

Presymptomatic Alterations in Amino Acid Metabolism and DNA Methylation in the Cerebellum of a Murine Model of Niemann-Pick Type C Disease.

The fatal neurodegenerative disorder Niemann-Pick type C (NPC) is caused in most cases by mutations in NPC1, which encodes the late endosomal NPC1 protein. Loss of NPC1 disrupts cholesterol trafficking from late endosomes to the endoplasmic reticulum and plasma membrane, causing cholesterol accumulation in late endosomes/lysosomes. Neurons are particularly vulnerable to this cholesterol trafficking defect, but the pathogenic mechanisms through which NPC1 deficiency causes neuronal dysfunction remain largely unknown. Herein, we have investigated amino acid metabolism in cerebella of NPC1-deficient mice at different stages of NPC disease. Imbalances in amino acid metabolism were evident from increased branched chain amino acid and asparagine levels and altered expression of key enzymes of glutamine/glutamate metabolism in presymptomatic and early symptomatic NPC1-deficient cerebellum. Increased levels of several amino acid intermediates of one-carbon metabolism indicated disturbances in folate and methylation pathways. Alterations in DNA methylation were apparent in decreased expression of DNA methyltransferase 3a and methyl-5'-cytosine-phosphodiester-guanine-domain binding proteins, reduced 5-methylcytosine immunoreactivity in the molecular and Purkinje cell layers, demethylation of genome-wide repetitive LINE-1 elements, and hypermethylation in specific promoter regions of single-copy genes in NPC1-deficient cerebellum at early stages of the disease. Alterations in amino acid metabolism and epigenetic changes in the cerebellum at presymptomatic stages of NPC disease represent previously unrecognized mechanisms of NPC pathogenesis.

Pre-clinical study of drug combinations that reduce breast cancer burden due to aberrant mTOR and metabolism promoted by LKB1 loss.

Cancer therapies that simultaneously target activated mammalian target of rapamycin (mTOR) and cell metabolism are urgently needed. The goal of our study was to identify therapies that effectively inhibited both mTOR activity and cancer cell metabolism in primary tumors in vivo. Using our mouse model of spontaneous breast cancer promoted by loss of LKB1 expression in an ErbB2 activated model; referred to as LKB1-/-NIC mice, we evaluated the effect of novel therapies in vivo on primary tumors. Treatment of LKB1-/-NIC mice with AZD8055 and 2-DG mono-therapies significantly reduced mammary gland tumorigenesis by inhibiting mTOR pathways and glycolytic metabolism; however simultaneous inhibition of these pathways with AZD8055/2-DG combination was significantly more effective at reducing tumor volume and burden. At the molecular level, combination treatment inhibited mTORC1/mTORC2 activity, selectively inhibited mitochondria function and blocked MAPK pro-survival signaling responsible for the ERK-p90RSK feedback loop. Our findings suggest that loss of LKB1 expression be considered a marker for metabolic dysfunction given its role in regulating AMPK and mTOR function. Finally, the outcome of our pre-clinical study confirms therapies that simultaneously target mTORC1/mTORC2 and glycolytic metabolism in cancer produce the best therapeutic outcome for the treatment of patients harboring metabolically active HER2 positive breast cancers.

Gastrin-releasing peptide induces c-Fos in the hamster suprachiasmatic nucleus.

The suprachiasmatic nuclei (SCN) contain the dominant circadian pacemaker in the mammalian brain. Retinal illumination at specific circadian phases resets the circadian pacemaker and induces the expression of several transcription factors, including c-Fos, in SCN neurons. Gastrin-releasing peptide (GRP) is made by SCN neurons and exogenous GRP mimics the resetting actions of photic stimuli on behavioural and cellular rhythms. We assessed the effects of microinjection of GRP into the SCN region at three phases of the circadian cycle on c-Fos immunoreactivity (-ir) in this structure. Microinjections of GRP increased levels of c-Fos-ir in the SCN. A distinct pattern of c-Fos-ir was seen following GRP administration in the early subjective night, with immunostaining localized to a dorsolateral region of the SCN. Pre-treatment with a GRP receptor antagonist failed to block GRP-evoked increases in c-Fos-ir and the antagonist alone was found to increase c-Fos-ir in the dorsolateral SCN. These results indicate that a subpopulation of SCN neurons is particularly sensitive to microinjection of GRP; activation of these neurons may be important for GRP's phase-delaying actions. Future studies using GRP receptor antagonists that lack intrinsic agonist activity will be needed to fully evaluate the role of these cells in photic entrainment.