Behavioral Engagement With Playable Objects Resolves Stress-Induced Adaptive Changes by Reshaping the Reward System.

BACKGROUND: The reward system regulates motivated behavior, and repeated practice of specific motivated behavior might conversely modify the reward system. However, the detailed mechanisms by which they reciprocally regulate each other are not clearly understood. METHODS: Mice subjected to chronic restraint stress show long-lasting depressive-like behavior, which is rescued by continual engagement with playable objects. A series of molecular, pharmacological, genetic, and behavioral analyses, combined with microarray, liquid chromatography, and chemogenetic tools, are used to investigate the neural mechanisms of antidepressive effects of playable objects. RESULTS: Here, we show that repeated restraint induces dopamine surges into the nucleus accumbens-lateral shell (NAc-lSh), which cause upregulation of the neuropeptide PACAP in the NAc-lSh. As repeated stress is continued, the dopamine surge by stressors is adaptively suppressed without restoring PACAP upregulation, and the resulting enhanced PACAP inputs from NAc-lSh neurons to the ventral pallidum facilitate depressive-like behaviors. Continual engagement with playable objects in mice subjected to chronic stress remediates reduced dopamine response to new stressors, enhanced PACAP upregulation, and depressive-like behaviors. Overactivation of dopamine D1 receptors over the action of D2 receptors in the NAc-lSh promotes depressive-like behaviors. Conversely, inhibition of D1 receptors or PACAP upregulation in the NAc-lSh confers resilience to chronic stress-induced depressive-like behaviors. Histochemical and chemogenetic analyses reveal that engagement with playable objects produces antidepressive effects by reshaping the ventral tegmental area-to-NAc-lSh and NAc-lSh-to-ventral pallidum circuits. CONCLUSIONS: These results suggest that behavioral engagement with playable objects remediates depressive-like behaviors by resolving stress-induced maladaptive changes in the reward system.

Behavioral stress accelerates plaque pathogenesis in the brain of Tg2576 mice via generation of metabolic oxidative stress.

Alzheimer's disease (AD) is a progressive neurodegenerative disease caused by genetic and non-genetic factors. Most AD cases may be triggered and promoted by non-genetic environmental factors. Clinical studies have reported that patients with AD show enhanced baseline levels of stress hormones in the blood, but their physiological significance with respect to the pathophysiology of AD is not clearly understood. Here we report that AD mouse models exposed to restraints for 2 h daily on 16 consecutive days show increased levels of beta-amyloid (Abeta) plaque deposition and commensurable enhancements in Abeta(1-42), tau hyperphosphorylation, and neuritic atrophy of cortical neurons. Repeated restraints in Tg2576 mice markedly increased metabolic oxidative stress and down-regulated the expression of MMP-2, a potent Abeta-degrading enzyme, in the brain. These stress effects were reversed by blocking the activation of the hypothalamus-pituitary-adrenal gland axis with the corticotropin-releasing factor receptor antagonist NBI 27914, further suggesting that over-activation of the hypothalamic-pituitary-adrenal axis is required for stress-enhanced AD-like pathogenesis. Consistent with these findings, corticosteroid treatments to cultured primary cortical neurons increased metabolic oxidative stress and down-regulated MMP-2 expression, and MMP-2 down-regulation was reversed by inhibition of oxidative stress. These results suggest that behavioral stress aggravates AD pathology via generation of metabolic oxidative stress and MMP-2 down-regulation.

Adenylyl cyclase-5 activity in the nucleus accumbens regulates anxiety-related behavior.

Type 5 adenylyl cyclase (AC5) is highly concentrated in the dorsal striatum and nucleus accumbens (NAc), two brain areas which have been implicated in motor function, reward, and emotion. Here we demonstrate that mice lacking AC5 (AC5-/-) display strong reductions in anxiety-like behavior in several paradigms. This anxiolytic behavior in AC5-/- mice was reduced by the D(1) receptor antagonist SCH23390 and enhanced by the D(1) dopamine receptor agonist, dihydrexidine (DHX). DHX-stimulated c-fos induction in AC5-/- mice was blunted in the dorso-lateral striatum, but it was overactivated in the dorso-medial striatum and NAc. The siRNA-mediated inhibition of AC5 levels within the NAc was sufficient to produce an anxiolytic-like response. Microarray and RT-PCR analyses revealed an up-regulation of prodynorphin and down-regulation of cholecystokinin (CCK) in the NAc of AC5-/- mice. Administration of nor-binaltorphimine (a kappa opioid receptor antagonist) or CCK-8s (a CCK receptor agonist) reversed the anxiolytic-like behavior exhibited by AC5-/- mutants. Taken together, these results suggest an essential role of AC5 in the NAc for maintaining normal levels of anxiety.

Chronic Antidepressant Treatment in Normal Mice Induces Anxiety and Impairs Stress-coping Ability.

Antidepressants are clinically used for patients with major depression. Antidepressant treatments in certain groups of patients are effective for relieving depression as well as anxiety disorder. However, it is not clearly known whether the use of current antidepressants in healthy persons is beneficial for upcoming depression- and anxiety-inducing life events. To address this question, normal mice were intraperitoneally administered with imipramine or fluoxetine for more than 2 weeks, and behaviors related to anxiety and depression were evaluated. Mice treated with imipramine or fluoxetine for more than 14 days exhibited significantly decreased immobility time in the forced swim test and tail suspension test, but these mice exhibited enhanced anxiety in several behavioral tests. Furthermore, chronic antidepressant treatments followed by sub-threshold level of stress in normal mice profoundly aggravated antidepressant-induced anxiety-like behaviors without further affecting depression-related behaviors. Chronic antidepressant treatments followed by sub-threshold level of stress produced swollen vesicles and ulcerations on the lips as well as a watery and inflammatory nose. Mice given chronic antidepressant treatments displayed intestinal abnormalities evidenced by a highly enlarged and inflamed small intestine full of defecation materials. These results suggest that chronic antidepressant treatment in normal mice provokes anxiety-like behaviors and impairs their stress-coping ability.

AAD-2004 Attenuates Progressive Neuronal Loss in the Brain of Tg-betaCTF99/B6 Mouse Model of Alzheimer Disease.

Alzheimer's disease (AD) is a neurodegenerative disease that proceeds with the age-dependent neuronal loss, an irreversible event which causes severe cognitive and psychiatric devastations. In the present study, we investigated whether the compound, AAD-2004 [2-hydroxy-5-[2-(4-trifluoromethylphenyl)-ethylaminobenzoic acid] which has anti-oxidant and anti-inflammatory properties, is beneficial for the brain of Tg-betaCTF99/B6 mice, a murine AD model that was recently developed to display age-dependent neuronal loss and neuritic atrophy in the brain. Administration of AAD-2004 in Tg-betaCTF99/B6 mice from 10 months to 18 months of age completely repressed the accumulation of lipid peroxidation in the brain. AAD-2004 markedly suppressed neuronal loss and neuritic atrophy, and partially reversed depleted expression of calbindin in the brain of Tg-beta-CTF99/B6. These results suggest that AAD-2004 affords neurodegeneration in the brain of AD mouse model.

Repeated Short-term (2h×14d) Emotional Stress Induces Lasting Depression-like Behavior in Mice.

Chronic behavioral stress is a risk factor for depression. To understand chronic stress effects and the mechanism underlying stress-induced emotional changes, various animals model have been developed. We recently reported that mice treated with restraints for 2 h daily for 14 consecutive days (2h-14d or 2h×14d) show lasting depression-like behavior. Restraint provokes emotional stress in the body, but the nature of stress induced by restraints is presumably more complex than emotional stress. So a question remains unsolved whether a similar procedure with "emotional" stress is sufficient to cause depression-like behavior. To address this, we examined whether "emotional" constraints in mice treated for 2h×14d by enforcing them to individually stand on a small stepping platform placed in a water bucket with a quarter full of water, and the stress evoked by this procedure was termed "water-bucket stress". The water-bucket stress activated the hypothalamus-pituitary-adrenal gland (HPA) system in a manner similar to restraint as evidenced by elevation of serum glucocorticoids. After the 2h×14d water-bucket stress, mice showed behavioral changes that were attributed to depression-like behavior, which was stably detected >3 weeks after last water-bucket stress endorsement. Administration of the anti-depressant, imipramine, for 20 days from time after the last emotional constraint completely reversed the stress-induced depression-like behavior. These results suggest that emotional stress evokes for 2h×14d in mice stably induces depression-like behavior in mice, as does the 2h×14d restraint.

Behavioral stress causes mitochondrial dysfunction via ABAD up-regulation and aggravates plaque pathology in the brain of a mouse model of Alzheimer disease.

Basic and clinical studies have reported that behavioral stress worsens the pathology of Alzheimer disease (AD), but the underlying mechanism has not been clearly understood. In this study, we determined the mechanism by which behavioral stress affects the pathogenesis of AD using Tg-APPswe/PS1dE9 mice, a murine model of AD. Tg-APPswe/PS1dE9 mice that were restrained for 2h daily for 16 consecutive days (2-h/16-day stress) from 6.5months of age had significantly increased Aß(1-42) levels and plaque deposition in the brain. The 2-h/16-day stress increased oxidative stress and induced mitochondrial dysfunction in the brain. Treatment with glucocorticoid (corticosterone) and Aß in SH-SY5Y cells increased the expression of 17ß-hydroxysteroid dehydrogenase (ABAD), mitochondrial dysfunction, and levels of ROS, whereas blockade of ABAD expression by siRNA-ABAD in SH-SY5Y cells suppressed glucocorticoid-enhanced mitochondrial dysfunction and ROS accumulation. The 2-h/16-day stress up-regulated ABAD expression in mitochondria in the brain of Tg-APPswe/PS1dE9 mice. Moreover, all visible Aß plaques were costained with anti-ABAD in the brains of Tg-APPswe/PS1dE9 mice. Together, these results suggest that behavioral stress aggravates plaque pathology and mitochondrial dysfunction via up-regulation of ABAD in the brain of a mouse model of AD.

Mice lacking adenylyl cyclase type 5 (AC5) show increased ethanol consumption and reduced ethanol sensitivity.

RATIONALE: The adenylyl cyclase (AC)/cAMP system is believed to be a key component in regulating alcohol-drinking behavior. It was reported that adenylyl cyclase-5 (AC5) is expressed widely in the brain, with a preferential concentration in the dorsal striatum and nucleus accumbens, brain regions which are important for addiction and emotion. AC5 has been shown to be an essential mediator of morphine addiction and dopamine receptor function; however, it remains unknown whether or not AC5 plays a role in ethanol preference and sensitivity in animals. OBJECTIVE: This work was carried out to determine the role of AC5 in alcohol consumption and the hypnotic response to alcohol using AC5 knockout (KO) mice. RESULTS: In the test for ethanol preference employing a two-bottle free-choice paradigm, AC5 KO mice showed increased ethanol consumption and preference compared with the wild-type mice. Ethanol-induced hypothermia was weakly reduced in AC5 KO mice. AC5 KO mice exhibited sedation/behavioral sleep to high-dose ethanol, but their responses were greatly suppressed compared with the wild-type mice. CONCLUSIONS: These results suggest that AC5 is an important signaling molecule regulating alcohol sensitivity and preference in animals. These data provide critical information for AC5 activation as a candidate target for the treatment of alcoholism.

SK-PC-B70M alleviates neurologic symptoms in G93A-SOD1 amyotrophic lateral sclerosis mice.

SK-PC-B70M, an oleanolic-glycoside saponins fraction extracted from the root of Pulsatilla koreana, carries active ingredient(s) that protects the cytotoxicity induced by Aß(1-42) in SK-N-SH cells. It was recently demonstrated that SK-PC-B70M improved scopolamine-induced deficits of memory consolidation and spatial working memory in rats, and reduced Aß levels and plaque deposition in the brains of the Tg2576 mouse model of Alzheimer disease. In the present study, we investigated whether SK-PC-B70M produces helpful effects on the pathology of the G93A-SOD1 transgenic mouse model of amyotrophic lateral sclerosis (ALS). Administration of SK-PC-B70M (100 or 400 mg/kg/day) from 8 weeks to 16 weeks of age attenuated neurological deficits of G93A-SOD1 mice in several motor-function-related behavioral tests. SK-PC-B70M treatment significantly suppressed the accumulation of the by-products of lipid peroxidation, malonedialdehyde (MDA) and 4-hydroxy-2-nonenal (HNE), in the spinal cord of G93A-SOD1 mice. Moreover, histologic analysis stained with cresyl violet or anti-choline acetyltransferase (ChAT) revealed that SK-PC-B70M suppressed neuronal loss in the ventral horn of the spinal cords of G93A-SOD1 mice. These results suggest that SK-PC-B70M affords a beneficial effect on neurologic deficits of G93A-SOD1 ALS mice.

Oriental medicine Jangwonhwan reduces Abeta(1-42) level and beta-amyloid deposition in the brain of Tg-APPswe/PS1dE9 mouse model of Alzheimer disease.

ETHNOPHARMACOLOGICAL RELEVANCE: Jangwonhwan, a boiled extract of 12 medicinal plants/mushroom including Korean red ginseng (Panax ginseng C.A. Meyer), has been prescribed for patients with cognitive dysfunction and are believed to induce brain activity enhancement, provide light sedation, and facilitate sound sleep. AIM OF THE STUDY: The present study was carried out to investigate whether Jangwonhwan has a beneficial effect on the brain of Alzheimer disease. MATERIALS AND METHODS: The transgenic mice of Alzheimer disease, Tg-APPswe/PS1dE9, were fed a modified recipe of Jangwonhwan consisting of a boiled extract of 7 herbs/mushroom (called LMK02-Jangwonhwan) at 400mg/kg/day of dose for 3 months from 4.5 months of age. Immunohistological and ELISA analyses were used to assess the Abeta accumulation and plaque deposition in the brain. Other in vitro and in vivo works were performed to understand the underlying mechanism. RESULTS: LMK02-Jangwonhwan notably reduced Abeta(1-42) and Abeta(1-40) levels, concomitantly with a reduction of plaque deposition, in the brain of Tg-APPswe/PS1dE9 mice. LMK02-Jangwonhwan partially suppressed oxidative stress accumulation, and prevented the down-regulation of phospho-CREB and calbindin typically seen in the hippocampus of AD-like brains. In vitro study with SH-SY5Y neuroblastoma cells showed that LMK02-Jangwonhwan inhibited oxidative stress and Abeta-induced neurotoxicity. CONCLUSION: The present study suggests that LMK02-Jangwonhwan confers a therapeutic potential to ameliorate AD-like pathology in the brain of Tg-APPswe/PS1dE9 mice.

The nuclear inclusion a (NIa) protease of turnip mosaic virus (TuMV) cleaves amyloid-ß.

BACKGROUND: The nuclear inclusion a (NIa) protease of turnip mosaic virus (TuMV) is responsible for the processing of the viral polyprotein into functional proteins. NIa was previously shown to possess a relatively strict substrate specificity with a preference for Val-Xaa-His-Gln↓, with the scissile bond located after Gln. The presence of the same consensus sequence, Val(12)-His-His-Gln(15), near the presumptive α-secretase cleavage site of the amyloid-ß (Aß) peptide led us to hypothesize that NIa could possess activity against Aß. METHODOLOGY/PRINCIPAL FINDINGS: Western blotting results showed that oligomeric as well as monomeric forms of Aß can be degraded by NIa in vitro. The specific cleavage of Aß was further confirmed by mass spectrometry analysis. NIa was shown to exist predominantly in the cytoplasm as observed by immunofluorescence microscopy. The overexpression of NIa in B103 neuroblastoma cells resulted in a significant reduction in cell death caused by both intracellularly generated and exogenously added Aß. Moreover, lentiviral-mediated expression of NIa in APP(sw)/PS1 transgenic mice significantly reduced the levels of Aß and plaques in the brain. CONCLUSIONS/SIGNIFICANCE: These results indicate that the degradation of Aß in the cytoplasm could be a novel strategy to control the levels of Aß, plaque formation, and the associated cell death.

SK-PC-B70M confers anti-oxidant activity and reduces Abeta levels in the brain of Tg2576 mice.

SK-PC-B70M is an oleanolic-glycoside saponin-enriched fraction derived from the root of Pulsatilla koreana. Recently, it was reported that hederacolchiside-E is an active ingredient of SK-PC-B70M that confers a neuroprotective effect against the cytotoxicity induced by Abeta(1-42) in SK-N-SH neuroblastoma cells. SK-PC-B70M improves scopolamine-induced impairments of spatial working memory in rats. In the present study, we investigated whether SK-PC-B70M has a beneficial effect on the Tg2576 murine model of Alzheimer's disease. ELISA analysis revealed that the levels of soluble and insoluble forms of Abeta(1-42) in Tg2576 mice fed SK-PC-B70M (2000 ppm) from 11 months to 16 months of age were reduced to, respectively, 66% and 79% of the control Tg2576 mice. Anti-Abeta antibody-stained brain sections of Tg2576 mice with SK-PC-B70M (2000 ppm) consistently showed a reduction in plaque formation in the brain. Western blot analyses showed altered expressions of various cellular factors, such as up-regulation of transthyretin, phospho-ERK, and phospho-CREB in the brain treated with SK-PC-B70M. SK-PC-B70M suppressed the neuronal toxicity induced by H(2)O(2) in primary cortical culture. Moreover, biochemical and immunohistochemical analyses showed that the levels of malondialdehyde (MDA) and 4-hydroxy-2-nonenal (HNE), oxidized by-products of lipid peroxidation, were notably reduced in the hippocampus of Tg2576 mice treated with SK-PC-B70M compared with the Tg2576 control. These results suggest that SK-PC-B70M attenuates AD-like pathology in the brain of Tg2576 mice.