Hippocampal mRNA Expression Research Articles

Impaired Innate Immunity Mechanisms in the Brain of Alzheimer's Disease.

Among environmental factors likely associated with Alzheimer’s disease (AD), persistent virus infections, and age-related progressive decline of immune competence might play a pivotal role. However, AD antimicrobial brain immune responses are poorly investigated. The present study focused on genes involved in antimicrobial defenses, especially against virus infections, in the AD brain. In particular, mRNA levels of IRF7, MED23, IL28B, and IFN-α genes were analyzed in hippocampus and temporal cortex brain samples from AD and non-demented controls. All subjects were also genotyped for APOE ε, IRF7, MED23, and IL28B gene polymorphisms. Most AD patients showed decreased mRNA levels of all investigated genes in the hippocampus and temporal cortex. However, a small group of AD patients showed increased hippocampal mRNA expression of MED23, IL28B, and IFN-α. mRNA levels of MED23, IL28B, IFN-α from the hippocampus and those of MED23 from the temporal cortex were further decreased in APOE ε4 allele AD carriers. Moreover, rs6598008 polymorphism of IRF7 was significantly associated with decreased hippocampal expression of IRF7, MED23, IL28B, and IFN-α. These findings suggest that AD brains show impaired innate antimicrobial gene expression profiles, and individual genetic makeup, such as positivity for the APOE ε4 and IRF7 A alleles, might affect brain immune efficiency.

Brain-derived Neurotrophic Factor and TrkB Levels in Mice that Lack Vesicular Zinc: Effects of Age and Sex

In certain neurons, zinc ions are stored in synaptic vesicles by zinc transporter 3 (ZnT3). Vesicular zinc can then be released synaptically to modulate myriad targets. In vitro evidence indicates that these targets may include brain-derived neurotrophic factor (BDNF) and its receptor, tropomyosin receptor kinase B (TrkB). But the effects of vesicular zinc on BDNF and TrkB in the intact brain are unclear. Studies of mice that lack ZnT3 – and, as a result, vesicular zinc – have shown abnormalities in BDNF and TrkB levels, but results have been mixed and are therefore difficult to interpret. This might be caused by differences in the age or sex of mice tested. In the present study, we measured BDNF and TrkB levels in the hippocampus and neocortex, comparing wild type and ZnT3 knockout mice of both sexes at two ages (5 and 12 weeks). We also examined BDNF mRNA expression and protein levels at an intermediate age (8–10 weeks). We found that, regardless of age or sex, BDNF and TrkB protein levels did not differ between wild type and ZnT3 knockout mice. There were sex-specific differences in BDNF protein and mRNA expression, however. BDNF protein levels increased with age in female mice but not in males. And in females, but not males, ZnT3 KO mice exhibited great hippocampal BDNF mRNA expression than wild type mice. We conclude that, at least in naïve mice housed under standard laboratory conditions, elimination of vesicular zinc does not affect BDNF or TrkB protein levels.

Inhibition of oxidative stress by testosterone improves synaptic plasticity in senescence accelerated mice

ABSTRACTIt is well known that synaptic plasticity is associated with cognitive performance in Alzheimer’s disease (AD). Testosterone (T) is known to exert protective effects on cognitive deficits in AD, but the underlying mechanisms of androgenic action on synaptic plasticity remain unclear. Thus, the aim of this study was to examine the protective mechanism attributed to T on synaptic plasticity in an AD senescence accelerated mouse prone 8 (SAMP8) model. The following parameters were measured: (1) number of intact pyramidal cells in hippocampal CA1 region (2) phosphorylated N-methyl-D-aspartate receptor-1 (p-NMDAR1) and (3) phosphorylated calmodulin-dependent protein kinase II (p-CaMKII). In addition, the content of whole brain malondialdehyde (MDA) as well as activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) were determined. Treatment with T significantly elevated the number of intact pyramidal cells in hippocampal CA1 region and markedly increased hippocampal protein and mRNA expression levels of p-NMDAR1 and p-CaMK II. Further, T significantly decreased whole brain MDA levels accompanied by elevated activities of SOD and GSH-Px. Data suggest that the protective effects of T on synaptic plasticity in a mouse AD model may be associated with reduction of oxidant stress.

Myeloperoxidase Deficiency Inhibits Cognitive Decline in the 5XFAD Mouse Model of Alzheimer's Disease.

Myeloperoxidase (MPO) is an enzyme expressed mostly by neutrophils and is a primary mediator of neutrophils oxidative stress response. While a profound body of evidence associates neutrophil-derived MPO in the pathogenesis of Alzheimer’s disease (AD), this role has not been assessed in an animal model of AD. Here, we produced hematologic chimerism in the 5XFAD mouse model of AD, with MPO deficient mice, resulting in 5XFAD with hematologic MPO deficiency (5XFAD-MPO KO). Behavioral examinations of 5XFAD-MPO KO showed significant superior performance in spatial learning and memory, associative learning, and anxiety/risk assessment behavior, as compared to 5XFAD mice transplanted with WT cells (5XFAD-WT). Hippocampal immunohistochemical and mRNA expression analyses showed significantly reduced levels of inflammatory mediators in 5XFAD-MPO KO mice with no apparent differences in the numbers of amyloid-β plaques. In addition, immunoblotting and mRNA analyses showed significantly reduced levels of APOE in 5XFAD-MPO KO. Together, these results indicate a substantial involvement of neutrophil-derived MPO in the pathology of 5XFAD model of AD and suggest MPO as a potential therapeutic target in AD.

Timing-Dependent Protection of Swimming Exercise against d-Galactose-Induced Aging-Like Impairments in Spatial Learning/Memory in Rats.

This study was designed to investigate beneficial effects of swimming exercise training on learning/memory, synaptic plasticity and CREB (cAMP response element binding protein) expression in hippocampus in a rat model of d-galactose-induced aging (DGA). Eighty adult male rats were randomly divided into four groups: Saline Control (group C), DGA (group A), Swimming exercise before DGA (group S1), and Swimming during DGA (group S2). These four groups of animals were further divided into Morris water maze training group (M subgroup) and sedentary control group (N subgroup). Spatial learning/memory was tested using Morris water maze training. The number and density of synaptophysin (Syp) and metabotropic glutamate receptor 1 (mGluR1) in hippocampal dentate gyrus area, CREB mRNA and protein expression and DNA methylation levels were determined respectively with immunohistochemistry, western blot, real-time PCR, and MassArray methylation detection platform. We found that compared with group C, DGA rats showed aging-like poor health and weight loss as well as hippocampal neurodegenerative characteristics. Exercise training led to a time-dependent decrease in average escape latency and improved spatial memory. Exercise training group (S2M) had significantly increased swim distance as compared with controls. These functional improvements in S2M group were associated with higher Syp and mGluR1 values in hippocampus (p < 0.01) as well as higher levels of hippocampal CREB protein/mRNA expression and gene methylation. In conclusion, swimming exercise training selectively during drug-induced aging process protected hippocampal neurons against DGA-elicited degenerative changes and in turn maintained neuronal synaptic plasticity and learning/memory function, possibly through upregulation of hippocampal CREB protein/mRNA and reduction of DGA-induced methylation of CREB.

Early-Life Iron Deficiency Alters Glucose Transporter-1 Expression in the Adult Rodent Hippocampus

Early-life iron deficiency (ID) impairs hippocampal energy production. Whether there are changes in glucose transporter (GLUT) expression is not known. The aim of this study was to investigate whether early-life ID and the treatment iron dose alter brain regional GLUT expression in adult rats and mice. In Study 1, ID was induced in male and female Sprague Dawley rat pups by feeding dams a 3-mg/kg iron diet during gestation and the first postnatal week, followed by treatment using low-iron [3-10 mg/kg; formerly iron-deficient (FID)-10 group], standard-iron (40-mg/kg; FID-40 group), or high-iron (400-mg/kg; FID-400 group) diets until weaning. The control group received the 40 mg/kg iron diet. GLUT1, GLUT3, hypoxia-inducible factor (HIF)-1α, and prolyl-hydroxylase-2 (PHD2) mRNA and protein expression in the cerebral cortex, hippocampus, striatum, cerebellum, and hypothalamus were determined at adulthood. In Study 2, the role of hippocampal ID in GLUT expression was examined by comparing the Glut1, Glut3, Hif1α, and Phd2 mRNA expression in adult male and female wild-type (WT) and nonanemic hippocampal iron-deficient and iron-replete dominant negative transferrin receptor 1 (DNTfR1-/-) transgenic mice. In Study 1, Glut1, Glut3, and Hif1α mRNA, and GLUT1 55-kDa protein expression was upregulated 20-33% in the hippocampus of the FID-10 group but not the FID-40 group, relative to the control group. Hippocampal Glut1 mRNA (-39%) and GLUT1 protein (-30%) expression was suppressed in the FID-400 group, relative to the control group. Glut1 and Glut3 mRNA expression was not altered in the other brain regions in the 3 FID groups. In Study 2, hippocampal Glut1 (+14%) and Hif1α (+147%) expression was upregulated in the iron-deficient DNTfR1-/- mice, but not in the iron-replete DNTfR1-/- mice, relative to the WT mice (P<0.05, all). Early-life ID is associated with altered hippocampal GLUT1 expression in adult rodents. The mouse study suggests that tissue ID is potentially responsible.

Epigenetic aging is accelerated in alcohol use disorder and regulated by genetic variation in APOL2

To investigate the potential role of alcohol use disorder (AUD) in aging processes, we employed Levine’s epigenetic clock (DNAm PhenoAge) to estimate DNA methylation age in 331 individuals with AUD and 201 healthy controls (HC). We evaluated the effects of heavy, chronic alcohol consumption on epigenetic age acceleration (EAA) using clinical biomarkers, including liver function test enzymes (LFTs) and clinical measures. To characterize potential underlying genetic variation contributing to EAA in AUD, we performed genome-wide association studies (GWAS) on EAA, including pathway analyses. We followed up on relevant top findings with in silico expression quantitative trait loci (eQTL) analyses for biological function using the BRAINEAC database. There was a 2.22-year age acceleration in AUD compared to controls after adjusting for gender and blood cell composition (p = 1.85 × 10−5). This association remained significant after adjusting for race, body mass index, and smoking status (1.38 years, p = 0.02). Secondary analyses showed more pronounced EAA in individuals with more severe AUD-associated phenotypes, including elevated gamma-glutamyl transferase (GGT) and alanine aminotransferase (ALT), and higher number of heavy drinking days (all ps < 0.05). The genome-wide meta-analysis of EAA in AUD revealed a significant single nucleotide polymorphism (SNP), rs916264 (p = 5.43 × 10−8), in apolipoprotein L2 (APOL2) at the genome-wide level. The minor allele A of rs916264 was associated with EAA and with increased mRNA expression in hippocampus (p = 0.0015). Our data demonstrate EAA in AUD and suggest that disease severity further accelerates epigenetic aging. EAA was associated with genetic variation in APOL2, suggesting potential novel biological mechanisms for age acceleration in AUD.

Differential Expression Profiles and Functional Prediction of Circular RNAs and Long Non-coding RNAs in the Hippocampus of Nrf2-Knockout Mice.

BackgroundNrf2 (nuclear factor, erythroid 2 like 2) is believed to play a major role in neurodegenerative diseases. The present study attempts to investigate the hippocampal circRNA and lncRNA expression profiles associated with Nrf2-mediated neuroprotection.MethodsThe hippocampal mRNA, circRNA and lncRNA expression profiles of Nrf2 (−/−) mice were determined by a microarray analysis. Bioinformatics analyses, including identification of differentially expressed mRNAs (DEmRNAs), circRNAs (DEcircRNAs) and lncRNAs (DElncRNAs), DEcircRNA-miRNA-DEmRNA interaction network construction, DElncRNA-DEmRNA co-expression network construction, and biological function annotation, were conducted. Quantitative real-time polymerase chain reaction (qRT-PCR) was performed to validate the dysregulated expression of circRNAs and lncRNAs derived from the microarray data of the hippocampus of Nrf2 (−/−) mice.ResultsCompared to wild-type Nrf2 (+/+) mice, 412 DEmRNAs (109 up- and 303 down-regulated mRNAs), 1279 DEcircRNAs (632 up- and 647 down-regulated circRNAs), and 303 DElncRNAs (50 up- and 253 down-regulated lncRNAs) were identified in the hippocampus of Nrf2 (−/−) mice. Additionally, in the qRT-PCR validation results, the expression patterns of selected DEcircRNAs and DElncRNAs were generally consistent with results in the microarray data. The DEcircRNA-miRNA-DEmRNA interaction networks revealed that mmu_circRNA_44531, mmu_circRNA_34132, mmu_circRNA_000903, mmu_circRNA_018676, mmu_circRNA_45901, mmu_circRNA_33836, mmu_circRNA_ 34137, mmu_circRNA_34106, mmu_circRNA_008691, and mmu_circRNA_003237 were predicted to compete with 47, 54, 45, 57, 63, 81, 121, 85, 181, and 43 DEmRNAs, respectively. ENSMUST00000125413, NR_028123, uc008nfy.1, AK076764, AK142725, AK080547, and AK035903 were co-expressed with 178, 89, 149, 179, 142, 55, and 112 DEmRNAs in the Nrf2 (−/−) hippocampus, respectively.ConclusionOur study might contribute to exploring the key circRNAs and lncRNAs associated with Nrf2-mediated neuroprotection.

Cyfip1 Haploinsufficiency Does Not Alter GABAA Receptor δ-Subunit Expression and Tonic Inhibition in Dentate Gyrus PV+ Interneurons and Granule Cells.

Copy number variation (CNV) at chromosomal region 15q11.2 is linked to increased risk of neurodevelopmental disorders including autism and schizophrenia. A significant gene at this locus is cytoplasmic fragile X mental retardation protein (FMRP) interacting protein 1 (CYFIP1). CYFIP1 protein interacts with FMRP, whose monogenic absence causes fragile X syndrome (FXS). Fmrp knock-out has been shown to reduce tonic GABAergic inhibition by interacting with the δ-subunit of the GABAA receptor (GABAAR). Using in situ hybridization (ISH), qPCR, Western blotting techniques, and patch clamp electrophysiology in brain slices from a Cyfip1 haploinsufficient mouse, we examined δ-subunit mediated tonic inhibition in the dentate gyrus (DG). In wild-type (WT) mice, DG granule cells (DGGCs) responded to the δ-subunit-selective agonist THIP with significantly increased tonic currents. In heterozygous mice, no significant difference was observed in THIP-evoked currents in DGGCs. Phasic GABAergic inhibition in DGGC was also unaltered with no difference in properties of spontaneous IPSCs (sIPSCs). Additionally, we demonstrate that DG granule cell layer (GCL) parvalbumin-positive interneurons (PV+-INs) have functional δ-subunit-mediated tonic GABAergic currents which, unlike DGGC, are also modulated by the α1-selective drug zolpidem. Similar to DGGC, both IPSCs and THIP-evoked currents in PV+-INs were not different between Cyfip1 heterozygous and WT mice. Supporting our electrophysiological data, we found no significant change in hippocampal δ-subunit mRNA expression or protein level and no change in α1/α4-subunit mRNA expression. Thus, Cyfip1 haploinsufficiency, mimicking human 15q11.2 microdeletion syndrome, does not alter hippocampal phasic or tonic GABAergic inhibition, substantially differing from the Fmrp knock-out mouse model.

Dexmedetomidine alleviates cognitive dysfunction induced by tibial fracture in rats

To study the effect of dexmedetomidine (Dex) on cognitive dysfunction induced by tibial fracture in rats. Sixteen male SD rats were randomized into control group and tibial fracture group, and the behavior indicators were measured on days 1, 3, 5 and 7 after tibial fracture and the expressions of CX3L1 protein and mRNA in the hippocampus were detected. Another 24 male SD rats were randomly divided into control group, tibial fracture group, and tibia fracture with CX3CL1 antibody group, and the behavior indicators and hippocampal CX3L1 protein expression were evaluated after corresponding treatments. In another experiment, we randomized 24 male SD rats into control group, tibial fracture group and tibial fracture with Dex treatment, and tested their hippocampal CX3L1 protein and mRNA expressions as well as the behavior indicators after the treatments. Compared with the control rats, the rats with tibial fracture spent significantly less time in the novel arm on days 1, 3, 5 and 7 after the fracture (P &lt; 0.05) with obviously lowered expressions of CX3L1 protein and mRNA in the hippocampus (P &lt; 0.05). In the rats with tibial fracture, treatment with CX3CL1 antibody further decreased the time spent in the novel arm (P &lt; 0.05) and the expression level of CX3L1 protein in the hippocampus (P &lt; 0.05); In contrast, treatment with Dex significantly increased the time spent time in the novel arm (P &lt; 0.05) and enhanced the hippocampal expressions of CX3L1 protein and mRNA in rats with tibial fractures (P &lt; 0.05). Dex can alleviate cognitive dysfunction induced by tibial fracture in rats by increasing the expression of CX3CL1 in the hippocampus.

Hyperthermia-induced seizures followed by repetitive stress are associated with age-dependent changes in specific aspects of the mouse stress system.

Stress is among the most frequently self-reported factors provoking epileptic seizures in children and adults. It is still unclear, however, why some people display stress-sensitive seizures and others do not. Recently, we showed that young epilepsy patients with stress-sensitive seizures exhibit a dysregulated hypothalamic-pituitary-adrenal (HPA)-axis. Most likely, this dysregulation gradually develops, and is triggered by stressors occurring early in life (early-life stress [ELS]). ELS may be particularly impactful when overlapping with the period of epileptogenesis. To examine this in a controlled and prospective manner, the present study investigated the effect of repetitive variable stressors or control treatment between postnatal day (PND) 12 and 24 in male mice exposed on PND10 to hyperthermia (HT)-induced prolonged seizures (control: normothermia). A number of peripheral and central indices of HPA-axis activity were evaluated at pre-adolescent and young adult age (ie, at PND25 and 90, respectively). At PND25 but not at PND90, body weight gain and absolute as well as relative (to body weight) thymus weight were reduced by ELS (vs control), whereas relative adrenal weight was enhanced, confirming the effectiveness of the stress treatment. Basal and stress-induced corticosterone levels were unaffected, though, by ELS at both ages. HT by itself did not affect any of these peripheral markers of HPA-axis activity, nor did it interact with ELS. However, centrally we did observe age-specific interaction effects of HT and ELS with regard to hippocampal glucocorticoid receptor mRNA expression, neurogenesis with the immature neurone marker doublecortin and the number of hilar (ectopic) granule cells using Prox1 staining. This lends some support to the notion that exposure to repetitive stress after HT-induced seizures may dysregulate central components of the stress system in an age-dependent manner. Such dysregulation could be one of the mechanisms conferring higher vulnerability of individuals with epilepsy to develop seizures in the face of stress.

Exploring the involvement of Tac2 in the mouse hippocampal stress response through gene networking

Tachykinin 2 (Tac2) is expressed in a number of areas throughout the brain, including the hippocampus. However, knowledge about its function has been only well explored in the hypothalamus in the context of reproductive health. In this study, we identified and validated increased hippocampal Tac2 mRNA expression in response to chronic mild stress in mice. Expression quantitative trait locus (eQTL) analysis showed Tac2 is cis-regulated in the hippocampus. Using a systems genetics approach, we constructed a Tac2 co-expression network to better understand the relationship between Tac2 and the hippocampal stress response. Our network identified 69 total genes associated with Tac2, several of which encode major neuropeptides involved in hippocampal stress signaling as well as critical genes for producing neural plasticity, indicating that Tac2 is involved in these processes. Pathway analysis for the member of Tac2 gene network revealed a strong connection between Tac2 and neuroactive ligand-receptor interaction, calcium signaling pathway, as well as cardiac muscle contraction. In addition, we also identified 46 stress-related phenotypes, specifically fear conditioning response, that were significantly correlated with Tac2 expression. Our results provide evidence for Tac2 as a strong candidate gene who likely plays a role in hippocampal stress processing and neural plasticity.

Ojayeonjonghwan, an oriental medicine composed of five seeds, protects against vasomotor and neurological disorders in estrogen-deficient rats.

Menopausal symptoms impair the quality of life of many women, and although conventional treatments are often effective, their use is limited by adverse effects. Ojayeonjonghwan, OJa, is a traditional Oriental medicine that is used for both male and female reproductive health and has a long history of safe use. We evaluated the effectiveness of two variations of OJa (OJa1 and OJa2) for treating menopausal symptoms in ovariectomized (OVX) rats. Both OJa preparations were effective for relieving indicators of hot flashes and depression, and for preventing loss of bone mineral density and lean body mass. Only OJa 2 prevented memory dysfunction. These results show that the traditional Oriental medicine, Ojayeonjonghwan, has the potential to relieve menopausal symptoms in women and should be further evaluated in human clinical trials as an alternative to convention therapies in women for whom conventional therapies are not indicated or found to be ineffective.

Periconceptional maternal alcohol consumption leads to behavioural changes in adult and aged offspring and alters the expression of hippocampal genes associated with learning and memory and regulators of the epigenome

Maternal alcohol consumption throughout pregnancy can result in long term behavioural deficits in offspring. However, less is known about the impact of alcohol during the periconceptional period (PC). The aim of this study was to examine the effect of PC ethanol (PC:EtOH) exposure on long term cognitive function; including memory and anxiety. Rats were exposed to a liquid diet containing ethanol (EtOH) (12.5% vol;vol) or a control diet from 4 days prior to mating until day 4 of pregnancy.Separate cohorts of animals were tested at 6 months (adult) or 15–18 months of age (aged). Offspring underwent a series of behavioural tests to assess anxiety, spatial and recognition memory. The hippocampus was collected, and mRNA expression of epigenetic modifiers and genes implicated in learning and memory were examined. PC:EtOH exposure resulted in a subtle anxiety like behaviour in adult female offspring with a significant reduction in directed exploring/head dipping behaviour during holeboard testing. In aged male offspring, PC:EtOH exposure resulted in a tendency for increased directed exploring/head dipping behaviour during holeboard testing. No differences between treatments were observed in the elevated plus maze. Aged female offspring exposed to PC:EtOH demonstrated short term spatial memory impairment (P < 0.05). PC:EtOH resulted in an upregulation of hippocampal mRNA expression of bdnf, grin2a and grin2b at 18 months of age along with increased expression of epigenetic modifiers (dnmt1, dnmt3a and hdac2). In conclusion, PC:EtOH can lead to sex specific anxiety-like behaviour and impairments in spatial memory and altered hippocampal gene expression.

Mammary tumor and mastectomy synergistically promote neuroinflammation in a breast cancer survivor model

Understanding why breast cancer survivors are at an increased risk for cognitive and affective disorders is essential for developing targeted treatment plans and improving quality of life. Microglia priming results in chronic neuroinflammation and can contribute to neuronal degeneration and dysfunction, thereby offering a potential mechanism for altered brain function that persists after tumor removal. This study examined whether mammary tumors alter microglia and augment the inflammatory profile and behavior of mice. To test this, non-metastatic mammary tumor cells (67NR) were injected orthotopically into the mammary glands of BALB/c mice, allowed to grow for 16 days, and then the tumors were removed via mastectomy. Following a 14-day surgical recovery, the mice were challenged with lipopolysaccharide (LPS), and then central and peripheral inflammation, anxiety, and depressive-like behavior were evaluated. Here we show that major central and peripheral inflammatory markers were not altered by tumor growth nor mastectomy surgery alone. However, hippocampal mRNA expression of major proinflammatory cytokines IL-1β and TNFα was increased in tumor removal animals, persisting past surgical recovery. Nonetheless, the immune and behavioral responses following LPS administration were comparable among groups. In sum, these data demonstrate that the combination of tumor and mastectomy promotes neuroinflammation; however, immune challenge did not elucidate this inflammation as maladaptive for the host.

Hemisphere-dependent Changes in mRNA Expression of GABAA Receptor Subunits and BDNF after Intra-prefrontal Cortex Allopregnanolone Infusion in Rats

Allopregnanolone is a neurosteroid implicated in mood disorders such as depression and anxiety. It acts as a GABAA receptor (GABAAR)-positive allosteric modulator and changes the expression of GABAAR subunits and of brain-derived neurotrophic factor (BDNF) in different brain regions. It has been demonstrated that such neurochemical changes may have an asymmetrical pattern regarding brain hemispheres. The aim of this study was to verify the behavioral and hemisphere-specific neurochemical effects of the bilateral intra-prefrontal cortex (intra-PFC) infusion of allopregnanolone in rats. Rats were exposed to the forced swim test and to the grooming microstructure test, followed by the right and left hemisphere-specific quantification of mRNA expression by Real-Time PCR of δ and γ2 GABAAR subunits and BDNF in the PFC and in the hippocampus. Though we did not observe any significant effects in the behavioral tests, intra-PFC allopregnanolone infusion bilaterally increased the mRNA expression of the δ subunit in the same area and of BDNF in the hippocampus. Both mRNA expressions of the γ2 subunit and BDNF were higher in the right than in the left PFC of control animals, and the hemisphere differences were not seen after allopregnanolone infusion. Overall hippocampal BDNF expression was also higher in the right hemisphere, but this asymmetry was not normalized by allopregnanolone. No asymmetries or changes were observed in the hippocampal mRNA expression of GABAAR subunits. These results point to a hemisphere-dependent regulation of GABAAR subunits and BDNF that can be modulated by intra-PFC allopregnanolone infusion, even in the absence of associated behavioral effects.

Activation of TRPV1 receptors affects memory function and hippocampal TRPV1 and CREB mRNA expression in a rat model of biliary cirrhosis

ABSTRACTObjective: Memory impairment induced by biliary cirrhosis is associated with abnormalities in the function of different neurotransmitter systems. However, the exact molecular mechanisms involved in the learning and memory dysfunctions following biliary cirrhosis is largely unknown. This study set out to determine whether activation of transient receptor potential vanilloid type 1 (TRPV1) in the CA1 area of the hippocampus in rats improve memory impairment induced by biliary cirrhosis.Methods: To assess learning and memory, passive avoidance task was carried out using a shuttle box. The mRNA expression of TRPV1 and cAMP response element binding (CREB) protein in the hippocampus were also evaluated by qT-PCR.Results: Our results indicated that activation of TRPV1 channels by capsaicin significantly decreased memory impairment and increased mRNA expression of the TRPV1 and CREB in the hippocampus of rats with biliary cirrhosis. Our findings also demonstrated that a positive correlation existed between mRNA expression of TRPV1 and CREB, and between memory function and TRPV1 expression.Discussion: Taken together, the results of this study support the view that TRPV1 receptor may play an important role in the regulation of learning and memory functions, and suggest that activation of TRPV1 channels seems to be a promising therapeutic target for learning and memory impairments following biliary cirrhosis.

Minocycline ameliorates depressive behaviors and neuro-immune dysfunction induced by chronic unpredictable mild stress in the rat

Activated microglia-induced neuroinflammation can stimulate the hypothalamic- pituitary-adrenal (HPA) axis to release glucocorticoids and suppress astrocyte functions, such as reducing neurotrophin production, which occur in depression. However, the balance between M1 (pro-inflammation) and M2 (anti-inflammation) microglial phenotypes and the interaction between these two glial cells are unclear in the depression. Hence, the chronic unpredictable mild stress (CUMS)-induced depression model was chosen to study depression- and anxiety-like behaviors, the concentration of corticosterone and relevant hippocampal cytokines, mRNA and protein expressions of microglial and astrocyte markers. To demonstrate the role of M1 phenotype activation in depression, the effect of microglial inhibitor minocycline on these aspects was also evaluated. Six weeks after CUMS exposure, behaviors were tested. Compared to the control group, CUMS increased serum corticosterone concentration and depression-like behaviors, like anhedonia, helplessness and anxiety. Moreover, CUMS increased microglia M1 marker CD11b expression and tumor necrosis factor (TNF)-α, interferon (INF)-γ, interleukin (IL)-1β and IL-17 concentrations, but decreased the concentration of M2 cytokines, IL-4, IL-10 and IL-13. Meanwhile, CUMS inhibited the expressions of astrocyte marker glial fibrillary acidic protein (GFAP), brain-derived neurotrophic factor (BDNF) and TrKB. Minocycline (40 mg/kg, 45 days) treatment significantly attenuated CUMS-induced behavioral abnormalities, which were associated with the suppressed M1 response, restored GFAP, BDNF and its receptor expression. In conclusion, CUMS-induced depression- and anxiety-like behavior may result from an imbalance between M1 and M2 and suppressed astrocyte function. Minocycline treatment reversed M1 response, which was associated with behavioral normalization.

HYPERTENSION AND AGEING LEAD TO IMPAIRMENT OF MYOGENIC VASOMOTOR MECHANISM, HIPPOCAMPAL EXPRESSION OF GENES INVOLVED IN BETA-AMYLOID GENERATION AND COGNITIVE DYSFUNCTION

Objective: Hypertension in the elderly can lead to dysfunctional autoregulation of cerebral blood flow (CBF), leading to increased risk of stroke and the development of Alzheimer's disease (AD), but the underlying mechanisms are still unknown. We hypothesized that hypertension and aging synergistically impair the myogenic constrictor response of cerebral arteries (CA), known to be involved in the autoregulation of CBF and as a consequence, an altered gene expression in the hippocampus will be observable. Design and method: Hypertension was induced in young (3 mo) and aged (24 mo) C57BL/6 mice with chronic (4 wk) infusion of angiotensin II and changes in myogenic response of CA) and hippocampal mRNA expression of genes involved in amyloid precursor protein (APP)-dependent signaling, APP cleavage, A-beta processing and A-beta-degradation, synaptic function were assessed. Results: In MCAs from young hypertensive mice, pressure-induced increases in SMC Ca-signal and myogenic tone were increased, both of which were inhibited by the cytochrome P-450 omega-hydroxylase inhibitor HET0016 and the transient receptor potential (TRP) channel blocker SKF96365. MCAs from aged hypertensive mice did not show adaptive increases in pressure-induced Ca-signal and myogenic tone and responses to HET0016 and SKF96365 were blunted. Aged hypertensive mice exhibited spatial memory impairments in the Y-maze and impaired performance in the novel object recognition assay. Hypertension in aging was associated with changes in hippocampal expression of APP-binding proteins, e.g., [Mint3/amyloid beta A4 precursor protein-binding family. A member 3 (APBA3), Fe65/amyloid beta A4 precursor protein-binding family B member 1 (APBB1)], amyloid beta (A4) precursor-like protein 1 (APLP1), muscarinic M1 receptor, and serum amyloid P component, all of which may have a role in the pathogenesis of late-onset AD. Conclusions: Thus functional maladaptation of aged cerebral arteries to hypertension is due to the dysregulation of pressure-induced 20-HETE and TRP channel-mediated SMC calcium signaling, whereas the hippocampal gene expression signature observed in aged hypertensive mice provides important clues for future studies to elucidate the mechanisms by which hypertension may contribute to the pathogenesis of Alzheimer's disease.

Indomethacin promotes survival of new neurons in the adult murine hippocampus accompanied by anti-inflammatory effects following MPTP-induced dopamine depletion

BackgroundParkinson’s disease (PD) is characterized by dopaminergic cell loss and inflammation in the substantia nigra (SN) leading to motor deficits but also to hippocampus-associated non-motor symptoms such as spatial learning and memory deficits. The cognitive decline is correlated with impaired adult hippocampal neurogenesis resulting from dopamine deficit and inflammation, represented in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine hydrochloride (MPTP) mouse model of PD. In the inflammatory tissue, cyclooxygenase (COX) is upregulated leading to an ongoing inflammatory process such as prostaglandin-mediated increased cytokine levels. Therefore, inhibition of COX by indomethacin may prevent the inflammatory response and the impairment of adult hippocampal neurogenesis.MethodsWildtype C57Bl/6 and transgenic Nestin-GFP mice were treated with MPTP followed by short-term or long-term indomethacin treatment. Then, aspects of inflammation and neurogenesis were evaluated by cell counts using immunofluorescence and immunohistochemical stainings in the SN and dentate gyrus (DG). Furthermore, hippocampal mRNA expression of neurogenesis-related genes of the Notch, Wnt, and sonic hedgehog signaling pathways and neurogenic factors were assessed, and protein levels of serum cytokines were measured.ResultsIndomethacin restored the reduction of the survival rate of new mature neurons and reduced the amount of amoeboid CD68+ cells in the DG after MPTP treatment. Indomethacin downregulated genes of the Wnt and Notch signaling pathways and increased neuroD6 expression. In the SN, indomethacin reduced the pro-inflammatory cellular response without reversing dopaminergic cell loss.ConclusionIndomethacin has a pro-neurogenic and thereby restorative effect and an anti-inflammatory effect on the cellular level in the DG following MPTP treatment. Therefore, COX inhibitors such as indomethacin may represent a therapeutic option to restore adult neurogenesis in PD.