Preventive Effect of Betaine Against Cognitive Impairments in Amyloid ß Peptide-Injected Mice Through Sirtuin1 in Hippocampus.

In the pathophysiology of Alzheimer's disease, the deposition of amyloid ß peptide (Aß) is associated with oxidative stress, leading to cognitive impairment and neurodegeneration. We have already reported that betaine (glycine betaine), an osmolyte and methyl donor in cells, prevents the development of cognitive impairment in mice with intracerebroventricular injection of Aß25-35, an active fragment of Aß, associated with oxidative stress in the hippocampus, but molecular mechanisms of betaine remain to be determined. Here, to investigate a key molecule underlying the preventive effect of betaine against cognitive impairments in Aß25-35-injected mice, cognitive tests and qPCR assays were performed in Aß25-35-injected mice with continuous betaine intake, in which intake was started a day before Aß25-35 injection, and then continued for 8 days. The Aß25-35 injection impaired short-term and object recognition memories in the Y-maze and object recognition tests, respectively. PCR assays revealed the down-regulation of Sirtuin1 (SIRT1), a NAD+-dependent deacetylase that mediates metabolic responses, in the hippocampus of Aß25-35-injected mice, whereas betaine intake prevented memory deficits as well as the decrease of hippocampal SIRT1 expression in Aß25-35-injected mice. Further, sirtinol, an inhibitor of the Sirtuin family, blocked the preventive effect of betaine against memory deficits. On the other hand, resveratrol, the potent compound that activates SIRT1, also prevented memory impairments in Aß25-35-injected mice, suggesting that SIRT1 plays a causative role in the preventive effect of betaine against memory deficits caused by Aß exposure.

Preventive Effects of Continuous Betaine Intake on Cognitive Impairment and Aberrant Gene Expression in Hippocampus of 3xTg Mouse Model of Alzheimer's Disease.

BACKGROUND: The deposition of amyloid-ß (Aß) and hyperphosphorylation of tau are well-known as the pathophysiological features of Alzheimer's disease (AD), leading to oxidative stress and synaptic deficits followed by cognitive symptoms. We already demonstrated that betaine (glycine betaine) prevented cognitive impairment and hippocampal oxidative stress in mice intracerebroventricularly injected with an active fragment of Aß, whereas the effect of betaine in chronic models of AD remains unknown. OBJECTIVE: Our objective was to investigate the effects of chronic betaine intake on cognitive impairment and aberrant expression of genes involved in synapse and antioxidant activity in the hippocampus of a genetic AD model. METHODS: We performed cognitive tests and RT-PCR in the hippocampus in 3xTg mice, a genetic AD model. RESULTS: Cognitive impairment in the Y-maze and novel object recognition tests became evident in 3xTg mice at 9 months old, and not earlier, indicating that cognitive impairment in 3xTg mice developed age-dependently. To examine the preventive effect of betaine on such cognitive impairment, 3xTg mice were fed betaine-containing water for 3 months from 6 to 9 months old, and subsequently subjected to behavioral tests, in which betaine intake prevented the development of cognitive impairment in 3xTg mice. Additionally, the expression levels of genes involved in synapse and antioxidant activity were downregulated in hippocampus of 3xTg mice at 9 months old compared with age-matched wild-type mice, which were suppressed by betaine intake. CONCLUSION: Betaine may be applicable as an agent preventing the progression of AD by improving the synaptic structure/function and/or antioxidant activity.

Involvement of GAT2/BGT-1 in the preventive effects of betaine on cognitive impairment and brain oxidative stress in amyloid ß peptide-injected mice.

In the pathophysiology of Alzheimer's disease (AD), the deposition of amyloid ß protein (Aß) is associated with oxidative stress, leading to cognitive impairment and neurodegeneration. Betaine (glycine betaine or trimethylglycine), known as an osmolyte and methyl donor in mammalian cells, has been reported to suppress the proinflammatory response and oxidative stress in the kidneys, but the effects of betaine on brain diseases remain to be determined. Here, to investigate the effects of betaine treatment on cognitive impairment and the increase in oxidative stress in the brain of an AD animal model, we performed a novel object recognition test and measured the malondialdehyde (MDA; a marker of oxidative stress) levels in the frontal cortex and hippocampus of mice intracerebroventricularly injected with Aß25-35, an active fragment of Aß. Betaine prevented cognitive impairment as well as increases of the cortical and hippocampal MDA levels in Aß25-35-injected mice. Of note, NNC 05-2090, a selective inhibitor of betaine/GABA transporter-1 (GAT2/BGT-1), reduced the preventive effects of betaine on Aß25-35-induced cognitive impairment without affecting the increased MDA levels in the brain of Aß25-35-injected mice. As betaine is used as a substrate of GAT2/BGT-1, these results suggest that betaine is transported through GAT2/BGT-1 and prevents cognitive impairment in Aß25-35-injected mice, but GAT2/BGT-1 function is not required for the antioxidant effects of betaine.

Therapeutic Targets for Neurodevelopmental Disorders Emerging from Animal Models with Perinatal Immune Activation.

Increasing epidemiological evidence indicates that perinatal infection with various viral pathogens enhances the risk for several psychiatric disorders. The pathophysiological significance of astrocyte interactions with neurons and/or gut microbiomes has been reported in neurodevelopmental disorders triggered by pre- and postnatal immune insults. Recent studies with the maternal immune activation or neonatal polyriboinosinic polyribocytidylic acid models of neurodevelopmental disorders have identified various candidate molecules that could be responsible for brain dysfunction. Here, we review the functions of several candidate molecules in neurodevelopment and brain function and discuss their potential as therapeutic targets for psychiatric disorders.

FUS regulates AMPA receptor function and FTLD/ALS-associated behaviour via GluA1 mRNA stabilization.

FUS is an RNA/DNA-binding protein involved in multiple steps of gene expression and is associated with amyotrophic lateral sclerosis (ALS) and fronto-temporal lobar degeneration (FTLD). However, the specific disease-causing and/or modifying mechanism mediated by FUS is largely unknown. Here we evaluate intrinsic roles of FUS on synaptic functions and animal behaviours. We find that FUS depletion downregulates GluA1, a subunit of AMPA receptor. FUS binds GluA1 mRNA in the vicinity of the 3' terminus and controls poly (A) tail maintenance, thus regulating stability. GluA1 reduction upon FUS knockdown reduces miniature EPSC amplitude both in cultured neurons and in vivo. FUS knockdown in hippocampus attenuates dendritic spine maturation and causes behavioural aberrations including hyperactivity, disinhibition and social interaction defects, which are partly ameliorated by GluA1 reintroduction. These results highlight the pivotal role of FUS in regulating GluA1 mRNA stability, post-synaptic function and FTLD-like animal behaviours.

Induction of interferon-induced transmembrane protein 3 gene expression by lipopolysaccharide in astrocytes.

Astrocytes are important modulators of the immune and inflammatory reactions in the central nervous system. We have recently demonstrated the role of interferon-induced transmembrane protein 3 (IFITM3) in long-lasting neuronal impairments in mice following neonatal immune challenge by injections of the double-stranded RNA analog polyriboinosinic polyribocytidylic acid. Here, we show that IFITM3 is induced after lipopolysaccharide (LPS) treatment in cultured astrocytes. The induction of IFITM3 by LPS was completely suppressed by the addition of anti-interferon-ß (IFN-ß) antibody. In addition, neutralization of tumor necrosis factor-α (TNF-α) with its antibody partially inhibited the induction of IFITM3, suggesting that LPS induces IFITM3 through autocrine secretion of IFN-ß and TNF-α. Furthermore, experiments using pharmacological inhibitors suggest that LPS induces IFITM3 through activation of TANK-binding kinase 1, p38 mitogen-activated protein kinase, and nuclear factor-κB pathways. Together, these findings may provide new insight into the role of IFITM3 in the pathogenesis of neurodevelopmental diseases associated with immune activation.

Nicotine ameliorates impairment of working memory in methamphetamine-treated rats.

Nicotine is hypothesized to have therapeutic effects on attentional and cognitive abnormalities in psychosis. In this study, we investigated the effect of nicotine on impaired spatial working memory in repeated methamphetamine (METH)-treated rats. Rats were administered METH (4 mg/kg, s.c.) once a day for 7 days, and their working memory was assessed with a delayed spatial win-shift task in a radial arm maze. The task consisted of two phases, a training phase and a test phase, separated by a delay. Control animals showed impaired performance in the test phase when the delay time was increased to 120 min or longer, while METH-treated rats showed impaired performance with a shorter delay time of 90 min. Memory impairment in METH-treated rats persisted for at least 14 days after drug withdrawal. METH-induced impairment of working memory was reversed by nicotine (0.3mg/kg, p.o., for 7 days), but the effect was diminished 7 days after the withdrawal. In control rats, nicotine decreased the number of working memory errors in the test with delay time of 120 min when administered before the training phase. Neither post-training nor pre-test administration of nicotine had any effect on working memory. These findings suggest that nicotine may have some protective effect against the impairment of working memory.

The hydrophobic dipeptide Leu-Ile inhibits immobility induced by repeated forced swimming via the induction of BDNF.

Depression has recently become a serious problem in society worldwide. However, we lack appropriate therapeutic tools, since the causes of depression remain unclear. Degeneration of neuronal cells and a decrease in neurogenesis have been suggested recently as two of the factors responsible for depression-like behavior. Furthermore, brain-derived neurotrophic factor (BDNF) is also suggested to be an important factor in recovering from such behavior. We have previously demonstrated that the hydrophobic dipeptide leucyl-isoleucine (Leu-Ile) induces BDNF in cultured neuronal cells. We therefore investigated possible antidepressant-like effects of Leu-Ile in an animal model using the repeated forced swim test (FST). Mice were forced to swim for 6 min once a day in a cylinder containing water. The mice were treated with Leu-Ile s.c. or p.o. immediately after each FST. Five-day repeated Leu-Ile treatment significantly increased BDNF mRNA levels and activated the BDNF/Akt/mTOR signaling pathway in the hippocampi of the mice. While 2-week repeated FST increased immobility time, Leu-Ile treatment for 2 weeks offset this increase. In C57BL/6J-BDNF heterozygous knockout (BDNF(+/-)) mice, Leu-Ile failed to reduce the immobility time increased by repeated FST. We next investigated the extent of cell proliferation in the hippocampus as 5-bromo-2'-deoxy-uridine (BrdU) uptake into hippocampal cells. Repeated FST significantly reduced the number of BrdU-positive cells in the hippocampal dentate gyrus, while this deficit was prevented by repeated Leu-Ile treatment. These results suggest that Leu-Ile has an antidepressant-like effect, at least in part by supporting cell proliferation through the BDNF signaling pathway.

Therapeutic potential of nicotine for methamphetamine-induced impairment of sensorimotor gating: involvement of pallidotegmental neurons.

INTRODUCTION: We have previously found that a disruption to prepulse inhibiton (PPI) induced by methamphetamine (METH) is associated with impaired functioning of pallidotegmental neurons, which play a crucial role in PPI of the startle reflex, through the activation of gamma-aminobutyric acid type B receptors in pedunculopontine tegmental neurons in mice. OBJECTIVES: Here, we examined the effect of nicotine on METH-induced impairment of PPI of the startle reflex focusing on dysfunctional pallidotegmental neurons and the neural system. RESULTS: Nicotine (0.15-0.5 mg/kg) ameliorated the deficit in PPI induced by acute METH, and the ameliorating effect of nicotine was antagonized by nicotinic receptor antagonists such as methyllycaconitine and dihydro-beta-erythroidine. The acute METH-induced disruption of PPI was accompanied by suppression of c-Fos expression in the lateral globus pallidus (LGP) as well as its induction in the caudal pontine reticular nucleus (PnC) in mice subjected to the PPI test. Nicotine-induced amelioration of PPI deficits in METH-treated mice was accompanied by a reversal of the changes in c-Fos expression in both the LGP and PnC to the basal level. CONCLUSIONS: Nicotine is effective in ameliorating the impairment of PPI caused by METH, which may be associated with normalization of the pallidotegmental neurons.

Ovariectomy increases neuronal amyloid-beta binding alcohol dehydrogenase level in the mouse hippocampus.

Ovarian hormone decline after menopause may influence cognitive performance and increase the risk for Alzheimer's disease (AD) in women. Amyloid-beta peptide (Abeta) has been proposed to be the primary cause of AD. In this study, we examined whether ovariectomy (OVX) could affect the levels of cofactors Abeta-binding alcohol dehydrogenase (ABAD) and receptor for advanced glycation endproducts (RAGE), which have been reported to potentiate Abeta-mediated neuronal perturbation, in mouse hippocampus, correlating with estrogen and Abeta levels. Female ICR mice were randomly divided into ovariectomized or sham-operated groups, and biochemical analyses were carried out at 5 weeks after the operation. OVX for 5 weeks significantly decreased hippocampal 17beta-estradiol level, while it tended to reduce the hormone level in serum, compared with the sham-operated control. In contrast, OVX did not affect hippocampal Abeta(1-40) level, although it significantly increased serum Abeta(1-40) level. Furthermore, we demonstrated that OVX increased hippocampal ABAD level in neurons, but not astrocytes, while it did not affect RAGE level. These findings suggest that the expression of neuronal ABAD depends on estrogen level in the hippocampus and the increase in serum Abeta and hippocampal ABAD induced by ovarian hormone decline may be associated with pre-stage of memory deficit in postmenopausal women and Abeta-mediated AD pathology.

Involvement of pallidotegmental neurons in methamphetamine- and MK-801-induced impairment of prepulse inhibition of the acoustic startle reflex in mice: reversal by GABAB receptor agonist baclofen.

We have previously demonstrated that pallidotegmental GABAergic neurons play a crucial role in prepulse inhibition (PPI) of the startle reflex in mice through the activation of GABA(B) receptors in pedunculopontine tegmental neurons. In this study, we investigated whether PPI disruption induced by methamphetamine (METH) or MK-801 is associated with the dysfunction of pallidotegmental neurons. Furthermore, we examined the effects of baclofen, a GABA(B) receptor agonist, on METH- and MK-801-induced PPI impairment. Acute treatment with METH (3 mg/kg, subcutaneouly (s.c.)) and MK-801 (>0.3 mg/kg, s.c.) significantly disrupted PPI, accompanied by the suppression of c-Fos expression in lateral globus pallidus induced by PPI. Furthermore, acute treatment with METH and MK-801 stimulated c-Fos expression in the caudal pontine reticular nucleus (PnC) in mice subjected to the PPT test, although PPI alone had no effect on c-Fos expression. Repeated treatment with 1 mg/kg METH for 7 days, which did not affect PPI acutely, showed similar effects on PPI and c-Fos expression to acute treatment with METH (3 mg/kg). Baclofen dose-dependently ameliorated PPI impairment induced by acute treatment with METH (3 mg/kg) and MK-801 (1 mg/kg), and decreased METH- and MK-801-stimulated c-Fos expression in PnC to the basal level. These results suggest that dysfunction of pallidotegmental neurons is involved in PPI disruption caused by METH and MK-801 in mice. GABA(B) receptor may constitute a putative target in treating neuropsychiatric disorders with sensorimotor gating deficits, such as schizophrenia and METH psychosis.

Dopamine D1 receptors regulate protein synthesis-dependent long-term recognition memory via extracellular signal-regulated kinase 1/2 in the prefrontal cortex.

Several lines of evidence suggest that extracellular signal-regulated kinase1/2 (ERK1/2) and dopaminergic system is involved in learning and memory. However, it remains to be determined if the dopaminergic system and ERK1/2 pathway contribute to cognitive function in the prefrontal cortex (PFC). The amount of phosphorylated ERK1/2 was increased in the PFC immediately after exposure to novel objects in the training session of the novel object recognition test. An inhibitor of ERK kinase impaired long-term recognition memory 24 h after the training although short-term memory tested 1 h after the training was not affected by the treatment. The dopamine D1 receptor agonist increased ERK1/2 phosphorylation in the PFC in vivo as well as in cortical neurons in vitro. Microinjection of the dopamine D1 receptor antagonist into the PFC impaired long-term recognition memory whereas the D2 receptor antagonist had no effect. Immunohistochemistry revealed that exposure to novel objects resulted in an increase in c-Fos expression in the PFC. Microinjection of the protein synthesis inhibitor anisomycin into the PFC impaired the long-term recognition memory. These results suggest that the activation of ERK1/2 following the stimulation of dopamine D1 receptors is necessary for the protein synthesis-dependent long-term retention of recognition memory in the PFC.

An analog of a dipeptide-like structure of FK506 increases glial cell line-derived neurotrophic factor expression through cAMP response element-binding protein activated by heat shock protein 90/Akt signaling pathway.

Glial cell line-derived neurotrophic factor (GDNF) is an important neurotrophic factor that has therapeutic implications for neurodegenerative disorders. We previously showed that leucine-isoleucine (Leu-Ile), an analog of a dipeptide-like structure of FK506 (tacrolimus), induces GDNF expression both in vivo and in vitro. In this investigation, we sought to clarify the cellular mechanisms underlying the GDNF-inducing effect of this dipeptide. Leu-Ile transport was investigated using fluorescein isothiocyanate-Leu-Ile in cultured neurons, and the results showed the transmembrane mobility of this dipeptide. By liquid chromatography-mass spectrometry and quartz crystal microbalance assay, we identified heat shock cognate protein 70 as a protein binding specifically to Leu-Ile, and molecular modeling showed that the ATPase domain is the predicted binding site. Leu-Ile stimulated Akt phosphorylation, which was attenuated significantly by heat shock protein 90 (Hsp90) inhibitor geldanamycin (GA). Moreover, enhanced interaction between phosphorylated Akt and Hsp90 was detected by immunoprecipitation. Leu-Ile elicited an increase in cAMP response element binding protein (CREB) phosphorylation, which was inhibited by GA, indicating that CREB is a downstream target of Hsp90/Akt signaling. Leu-Ile elevated the levels of GDNF mRNA and protein expression, whereas inhibition of CREB blocked such effects. Leu-Ile promoted the binding activity of phosphorylated CREB with cAMP response element. These findings show that CREB plays a key role in transcriptional regulation of GDNF expression induced by Leu-Ile. In conclusion, Leu-Ile activates Hsp90/Akt/CREB signaling, which contributes to the upregulation of GDNF expression. It may represent a novel lead compound for the treatment of dopaminergic neurons or motoneuron diseases.