Ji-n Seo

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 β‐amyloid (Aβ) plaque deposition and commensurable enhancements in Aβ(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 Aβ‐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.

NADPH Oxidase Mediates Depressive Behavior Induced by Chronic Stress in Mice

Stress is a potent risk factor for depression, yet the underlying mechanism is not clearly understood. In the present study, we explored the mechanism of development and maintenance of depression in a stress-induced animal model. Mice restrained for 2 h daily for 14 d showed distinct depressive behavior, and the altered behavior persisted for >3 months in the absence of intervention. Acute restraint induced a surge of oxidative stress in the brain, and stress-induced oxidative stress progressively increased with repetition of stress. In vitro, the stress hormone glucocorticoid generated superoxide via upregulation of NADPH oxidase. Consistently, repeated restraints increased the expression of the key subunits of NADPH oxidase, p47phox and p67phox, in the brain. Moreover, stressed brains markedly upregulated the expression of p47phox to weak restress evoked in the poststress period, and this molecular response was reminiscent of amplified ROS surge to restress. Pharmacological inhibition of NADPH oxidase by the NADPH oxidase inhibitor apocynin during the stress or poststress period completely blocked depressive behavior. Consistently, heterozygous p47phox knock-out mice (p47phox+/−) or molecular inhibition of p47phox with Lenti shRNA-p47phox in the hippocampus suppressed depressive behavior. These results suggest that repeated stress promotes depressive behavior through the upregulation of NADPH oxidase and the resultant metabolic oxidative stress, and that the inhibition of NADPH oxidase provides beneficial antidepression effects.

Fluoxetine attenuates kainic acid-induced neuronal cell death in the mouse hippocampus

Fluoxetine is a selective serotonin reuptake inhibitor (SSRI) and one of the commonly prescribed antidepressants. Numerous clinical observations and animal studies indicate that fluoxetine enhances the anticonvulsant potencies of several antiepileptic drugs. In the previous report, we showed that fluoxetine strongly protects against delayed cerebral ischemic injury. In the present study, the authors investigated whether fluoxetine has a beneficial effect on KA-induced neuronal cell death. An intracerebroventricular (i.c.v.) injection of 0.94 nmol (0.2 microg) of KA produced typical neuronal cell death both in CA1 and CA3 regions of the hippocampus. Although, there was no significant difference in the time course or severity of epileptic behavior, the systemic administration of fluoxetine 30 min before KA administration significantly attenuated this neuronal cell death. Fluoxetine was found to suppress neuronal cell loss when injected at 10 mg/kg and the effect was enhanced at 50 mg/kg. Furthermore, this fluoxetine-induced neuroprotection was accompanied by marked improvements in memory impairment, as determined by passive avoidance tests. KA-induced gliosis and proinflammatory marker (COX-2, IL-1beta, and TNF-alpha) inductions were also suppressed by fluoxetine administration. It is interesting to note here that fluoxetine treatment suppressed NF-kappaB activity dose-dependently in KA-treated mouse brains, suggesting that this explains in part its anti-inflammatory effect. Together, these results suggest that fluoxetine has therapeutic potential in terms of suppressing KA-induced pathogenesis in the brain, and that these neuroprotective effects are associated with its anti-inflammatory effects.

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 Aβ(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 Aβ in SH-SY5Y cells increased the expression of 17β-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 Aβ 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.

Oriental medicine Jangwonhwan reduces Aβ(1-42) level and β-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.

Severe motor neuron degeneration in the spinal cord of the Tg2576 mouse model of Alzheimer disease.

The transgenic mouse Tg2576 is widely used as a murine model of Alzheimers disease (AD) and exhibits plaque pathogenesis in the brain and progressive memory impairments. Here we report that Tg2576 mice also have severe spinal cord deficits. At 10 months of age, Tg2576 mice showed a severe defect in the hindlimb extension reflex test and abnormal body trembling and hindlimb tremors when suspended by the tail. The frequency and severity of these abnormalities were overt at 10 months of age and became gradually worsened. On the foot-printing analysis, Tg2576 mice had shorter and narrower strides than the non-transgenic control. Histological analyses showed that neuronal cells including cholinergic neurons in the lumbar cord of Tg2576 mice were severely reduced in number. At 16 months of age, Tg2576 mice showed high levels of amyloid-beta accumulation in the spinal cord. Consistent with this, Tg2576 mice showed that lipid peroxidation levels were increased and mitochondrial metabolic activity were significantly reduced in the spinal cord. Administration of curcumin, a natural compound that has antioxidant properties, notably reversed motor function deficits of Tg2576 mice. The enhanced lipid peroxidation and neuronal loss in the lumbar cord was also partially suppressed by curcumin. Electron microscopic analysis revealed that the sciatic nerve fibers were severely reduced in number and were demyelinated in Tg2576 mice, which were partially rescued by curcumin. These results showed that Tg2576 mice display severe degeneration of motor neurons in the spinal cord and associated motor function deficits.

SK-PC-B70M confers anti-oxidant activity and reduces Aβ 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 Alzheimers 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.

Role of dopamine D2 receptors in optimizing choice strategy in a dynamic and uncertain environment

In order to investigate roles of dopamine receptor subtypes in reward-based learning, we examined choice behavior of dopamine D1 and D2 receptor-knockout (D1R-KO and D2R-KO, respectively) mice in an instrumental learning task with progressively increasing reversal frequency and a dynamic two-armed bandit task. Performance of D2R-KO mice was progressively impaired in the former as the frequency of reversal increased and profoundly impaired in the latter even with prolonged training, whereas D1R-KO mice showed relatively minor performance deficits. Choice behavior in the dynamic two-armed bandit task was well explained by a hybrid model including win-stay-lose-switch and reinforcement learning terms. A model-based analysis revealed increased win-stay, but impaired value updating and decreased value-dependent action selection in D2R-KO mice, which were detrimental to maximizing rewards in the dynamic two-armed bandit task. These results suggest an important role of dopamine D2 receptors in learning from past choice outcomes for rapid adjustment of choice behavior in a dynamic and uncertain environment.

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 Aβ(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 Aβ 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.

The Nuclear Inclusion a (NIa) Protease of Turnip Mosaic Virus (TuMV) Cleaves Amyloid-β

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, Val12-His-His-Gln15, near the presumptive α-secretase cleavage site of the amyloid-β (Aβ) peptide led us to hypothesize that NIa could possess activity against Aβ. Methodology/Principal Findings Western blotting results showed that oligomeric as well as monomeric forms of Aβ can be degraded by NIa in vitro. The specific cleavage of Aβ 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 Aβ. Moreover, lentiviral-mediated expression of NIa in APPsw/PS1 transgenic mice significantly reduced the levels of Aβ and plaques in the brain. Conclusions/Significance These results indicate that the degradation of Aβ in the cytoplasm could be a novel strategy to control the levels of Aβ, plaque formation, and the associated cell death.