Proteomic Analysis of Hippocampus in a Mouse Model of Depression Reveals Neuroprotective Function of Ubiquitin C-terminal Hydrolase L1 (UCH-L1) via Stress-induced Cysteine Oxidative Modifications.

Chronic physical restraint stress increases oxidative stress in the brain, and dysregulation of oxidative stress can be one of the causes of major depressive disorder. To understand the underlying mechanisms, we undertook a systematic proteomic analysis of hippocampus in a chronic restraint stress mouse model of depression. Combining two-dimensional gel electrophoresis (2D-PAGE) for protein separation with nanoUPLC-ESI-q-TOF tandem mass spectrometry, we identified sixty-three protein spots that changed in the hippocampus of mice subjected to chronic restraint stress. We identified and classified the proteins that changed after chronic stress, into three groups respectively functioning in neural plasticity, metabolic processes and protein aggregation. Of these, 5 proteins including ubiquitin C-terminal hydrolase L1 (UCH-L1), dihydropyrimidinase-related protein 2 (DPYL2), haloacid dehalogenase-like hydrolase domain-containing protein 2 (HDHD2), actin-related protein 2/3 complex subunit 5 (ARPC5) and peroxiredoxin-2 (PRDX2), showed pI shifts attributable to post-translational modifications. Further analysis indicated that UCH-L1 underwent differential oxidations of 2 cysteine residues following chronic stress. We investigated whether the oxidized form of UCH-L1 plays a role in stressed hippocampus, by comparing the effects of UCH-L1 and its Cys mutants on hippocampal cell line HT-22 in response to oxidative stress. This study demonstrated that UCH-L1 wild-type and cysteine to aspartic acid mutants, but not its cysteine to serine mutants, afforded neuroprotective effects against oxidative stress; there were no discernible differences between wild-type UCH-L1 and its mutants in the absence of oxidative stress. These findings suggest that cysteine oxidative modifications of UCH-L1 in the hippocampus play key roles in neuroprotection against oxidative stress caused in major depressive disorder.

Adenylyl cyclase 5 deficiency reduces renal cyclic AMP and cyst growth in an orthologous mouse model of polycystic kidney disease.

Cyclic AMP promotes cyst growth in polycystic kidney disease (PKD) by stimulating cell proliferation and fluid secretion. Previously, we showed that the primary cilium of renal epithelial cells contains a cAMP regulatory complex comprising adenylyl cyclases 5 and 6 (AC5/6), polycystin-2, A-kinase anchoring protein 150, protein kinase A, and phosphodiesterase 4C. In Kif3a mutant cells that lack primary cilia, the formation of this regulatory complex is disrupted and cAMP levels are increased. Inhibition of AC5 reduces cAMP levels in Kif3a mutant cells, suggesting that AC5 may mediate the increase in cAMP in PKD. Here, we examined the role of AC5 in an orthologous mouse model of PKD caused by kidney-specific ablation of Pkd2. Knockdown of AC5 with siRNA attenuated the increase in cAMP levels in Pkd2-deficient renal epithelial cells. Levels of cAMP and AC5 mRNA transcripts were elevated in the kidneys of mice with collecting duct-specific ablation of Pkd2. Compared with Pkd2 single mutant mice, AC5/Pkd2 double mutant mice had less kidney enlargement, lower cyst index, reduced kidney injury, and improved kidney function. Importantly, cAMP levels and cAMP-dependent signaling were reduced in the kidneys of AC5/Pkd2 double mutant compared to the kidneys of Pkd2 single mutant mice. Additionally, we localized endogenous AC5 in the primary cilium of renal epithelial cells and showed that ablation of AC5 reduced ciliary elongation in the kidneys of Pkd2 mutant mice. Thus, AC5 contributes importantly to increased renal cAMP levels and cyst growth in Pkd2 mutant mice, and inhibition of AC5 may be beneficial in the treatment of PKD.

Effects of histone acetyltransferase inhibitors on L-DOPA-induced dyskinesia in a murine model of Parkinson's disease.

Histone acetylation is a key regulatory factor for gene expression in cells. Modulation of histone acetylation by targeting of histone acetyltransferases (HATs) effectively alters many gene expression profiles and synaptic plasticity in the brain. However, the role of HATs on L-DOPA-induced dyskinesia of Parkinson's disease (PD) has not been reported. Our aim was to determine whether HAT inhibitors such as anacardic acid, garcinol, and curcumin from natural plants reduce severity of L-DOPA-induced dyskinesia using a unilaterally 6-hydroxydopamine (6-OHDA)-lesioned PD mouse model. Anacardic acid 2 mg/kg, garcinol 5 mg/kg, or curcumin 100 mg/kg co-treatment with L-DOPA significantly reduced the axial, limb, and orofacial (ALO) score indicating less dyskinesia with administration of HAT inhibitors in 6-OHDA-lesioned mice. Additionally, L-DOPA's efficacy was not altered by the compounds in the early stage of treatment. The expression levels of c-Fos, Fra-2, and Arc were effectively decreased by administration of HAT inhibitors in the ipsilateral striatum. Our findings indicate that HAT inhibitor co-treatment with L-DOPA may have therapeutic potential for management of L-DOPA-induced dyskinesia in patients with PD.

Nitric oxide induction of Parkin translocation in PTEN-induced putative kinase 1 (PINK1) deficiency: functional role of neuronal nitric oxide synthase during mitophagy.

The failure to trigger mitophagy is implicated in the pathogenesis of familial Parkinson disease that is caused by PINK1 or Parkin mutations. According to the prevailing PINK1-Parkin signaling model, mitophagy is promoted by the mitochondrial translocation of Parkin, an essential PINK1-dependent step that occurs via a previously unknown mechanism. Here we determined that critical concentrations of NO was sufficient to induce the mitochondrial translocation of Parkin even in PINK1 deficiency, with apparent increased interaction of full-length PINK1 accumulated during mitophagy, with neuronal nitric oxide synthase (nNOS). Specifically, optimum levels of NO enabled PINK1-null dopaminergic neuronal cells to regain the mitochondrial translocation of Parkin, which appeared to be significantly suppressed by nNOS-null mutation. Moreover, nNOS-null mutation resulted in the same mitochondrial electron transport chain (ETC) enzyme deficits as PINK1-null mutation. The involvement of mitochondrial nNOS activation in mitophagy was further confirmed by the greatly increased interactions of full-length PINK1 with nNOS, accompanied by mitochondrial accumulation of phospho-nNOS (Ser(1412)) during mitophagy. Of great interest is that the L347P PINK1 mutant failed to bind to nNOS. The loss of nNOS phosphorylation and Parkin accumulation on PINK1-deficient mitochondria could be reversed in a PINK1-dependent manner. Finally, non-toxic levels of NO treatment aided in the recovery of PINK1-null dopaminergic neuronal cells from mitochondrial ETC enzyme deficits. In summary, we demonstrated the full-length PINK1-dependent recruitment of nNOS, its activation in the induction of Parkin translocation, and the feasibility of NO-based pharmacotherapy for defective mitophagy and ETC enzyme deficits in Parkinson disease.

Robust neuroprotective effects of intranasally delivered iNOS siRNA encapsulated in gelatin nanoparticles in the postischemic brain.

The therapeutic efficacy of intranasal iNOS siRNA delivery was investigated in the postischemic rat brain after encapsulating on in gelatin nanoparticles (GNPs; diameter 188.0 ± 60.9 nm) cross-linked with 0.0667% glutaraldehyde (GA). Intranasally delivered GNPs were found in extracellular and intracellular compartments of many brain regions, including the olfactory bulb, cerebral cortex, and striatum at 1 hour after infusion and continued to be detected for days. Infarct volumes were markedly suppressed (maximal reduction to 42.1 ± 2.6%) at 2 days after 60 minutes of middle cerebral artery occlusion (MCAO) when iNOS siRNA/GNPs were delivered at 6 hours post-MCAO. In addition, this protective effect was manifested by reductions in neurological and behavioral deficits that were sustained for 2 weeks. Therapeutic potency of iNOS siRNA/GNPs was significantly greater and sustained longer than that of bare siRNA and prolonged and efficient iNOS by iNOS siRNA/GNP is responsible for the robust neuroprotective effect.

Inhibition of adenylyl cyclase type 5 prevents L-DOPA-induced dyskinesia in an animal model of Parkinson's disease.

The dopamine precursor L-3,4-dihydroxyphenylalanine (L-DOPA) is widely used as a therapeutic choice for the treatment of patients with Parkinson's disease. However, the long-term use of L-DOPA leads to the development of debilitating involuntary movements, called L-DOPA-induced dyskinesia (LID). The cAMP/protein kinase A (PKA) signaling in the striatum is known to play a role in LID. However, from among the nine known adenylyl cyclases (ACs) present in the striatum, the AC that mediates LID remains unknown. To address this issue, we prepared an animal model with unilateral 6-hydroxydopamine lesions in the substantia nigra in wild-type and AC5-knock-out (KO) mice, and examined behavioral responses to short-term or long-term treatment with L-DOPA. Compared with the behavioral responses of wild-type mice, LID was profoundly reduced in AC5-KO mice. The behavioral protection of long-term treatment with L-DOPA in AC5-KO mice was preceded by a decrease in the phosphorylation levels of PKA substrates ERK (extracellular signal-regulated kinase) 1/2, MSK1 (mitogen- and stress-activated protein kinase 1), and histone H3, levels of which were all increased in the lesioned striatum of wild-type mice. Consistently, FosB/ΔFosB expression, which was induced by long-term L-DOPA treatment in the lesioned striatum, was also decreased in AC5-KO mice. Moreover, suppression of AC5 in the dorsal striatum with lentivirus-shRNA-AC5 was sufficient to attenuate LID, suggesting that the AC5-regulated signaling cascade in the striatum mediates LID. These results identify the AC5/cAMP system in the dorsal striatum as a therapeutic target for the treatment of LID in patients with Parkinson's disease.

Antidepressant effects of exercise are produced via suppression of hypocretin/orexin and melanin-concentrating hormone in the basolateral amygdala.

Physical exercise is considered beneficial in the treatment of depression, but the underlying mechanism is not clearly understood. In the present study, we investigated the mechanism regulating antidepressant effects of exercise by focusing on the role of the amygdala using a well-defined animal model of depression. C57BL/6 mice treated with repeated restraint showed depression-like behaviors, which was counteracted by post-stress treatment with physical exercise. The two neuropeptides hypocretin/orexin (Hcrt/Orx) and melanin-concentrating hormone (MCH) were transcriptionally upregulated in the BLA after repeated stress, and their enhanced expression was downregulated by treatment with exercise, mirroring stress-induced depression-like behaviors and their reversal by exercise. Stereotaxic injection of either Hcrt/Orx peptide or MCH peptide within the BLA commonly increased phospho-CaMKIIα level and produced depression-like behaviors, mimicking the neural states in the BLA of mice subjected to repeated stress. In contrast, siRNA-mediated suppression of Hcrt/Orx or MCH in the BLA blocked stress-induced depression-like behaviors. Furthermore, siRNA-mediated inhibition of CaMKIIα in the BLA also counteracted stress-induced depression-like behaviors. Local injection of Hcrt/Orx peptide or MCH peptide within the BLA in exercise-treated animals blocked antidepressant-like effects of exercise. Together these results suggest that exercise produces antidepressant effects via suppression of Hcrt/Orx and MCH neural systems in the BLA.

Ethyl pyruvate inhibits HMGB1 phosphorylation and release by chelating calcium.

Ethyl pyruvate (EP), a simple aliphatic ester of pyruvic acid, has been shown to have antiinflammatory effects and to confer protective effects in various pathological conditions. Recently, a number of studies have reported EP inhibits high mobility group box 1 (HMGB1) secretion and suggest this might contribute to its antiinflammatory effect. Since EP is used in a calcium-containing balanced salt solution (Ringer solution), we wondered if EP directly chelates Ca(2+) and if it is related to the EP-mediated suppression of HMGB1 release. Calcium imaging assays revealed that EP significantly and dose-dependently suppressed high K(+)-induced transient [Ca(2+)]i surges in primary cortical neurons and, similarly, fluorometric assays showed that EP directly scavenges Ca(2+) as the peak of fluorescence emission intensities of Mag-Fura-2 (a low-affinity Ca(2+) indicator) was shifted in the presence of EP at concentrations of ≥7 mmol/L. Furthermore, EP markedly suppressed the A23187-induced intracellular Ca(2+) surge in BV2 cells and, under this condition, A23187-induced activations of Ca(2+)-mediated kinases (protein kinase Cα and calcium/calmodulin-dependent protein kinase IV), HMGB1 phosphorylation and subsequent secretion of HMGB1 also were suppressed. (A23187 is a calcium ionophore and BV2 cells are a microglia cell line.) Moreover, the above-mentioned EP-mediated effects were obtained independent of cell death or survival, which suggests that they are direct effects of EP. Together, these results indicate that EP directly chelates Ca(2+), and that it is, at least in part, responsible for the suppression of HMGB1 release by EP.

Age-Dependent and Aß-Induced Dynamic Changes in the Subcellular Localization of HMGB1 in Neurons and Microglia in the Brains of an Animal Model of Alzheimer's Disease.

HMGB1 is a prototypical danger-associated molecular pattern (DAMP) molecule that co-localizes with amyloid beta (Aß) in the brains of patients with Alzheimer's disease. HMGB1 levels are significantly higher in the cerebrospinal fluid of patients. However, the cellular and subcellular distribution of HMGB1 in relation to the pathology of Alzheimer's disease has not yet been studied in detail. Here, we investigated whether HMGB1 protein levels in brain tissue homogenates (frontal cortex and striatum) and sera from Tg-APP/PS1 mice, along with its cellular and subcellular localization in those regions, differed. Total HMGB1 levels were increased in the frontal cortices of aged wildtype (7.5 M) mice compared to young (3.5 M) mice, whereas total HMGB1 levels in the frontal cortices of Tg-APP/PS1 mice (7.5 M) were significantly lower than those in age-matched wildtype mice. In contrast, total serum HMGB1 levels were enhanced in aged wildtype (7.5 M) mice and Tg-APP/PS1 mice (7.5 M). Further analysis indicated that nuclear HMGB1 levels in the frontal cortices of Tg-APP/PS1 mice were significantly reduced compared to those in age-matched wildtype controls, and cytosolic HMGB1 levels were also significantly decreased. Triple-fluorescence immunohistochemical analysis indicated that HMGB1 appeared as a ring shape in the cytoplasm of most neurons and microglia in the frontal cortices of 9.5 M Tg-APP/PS1 mice, indicating that nuclear HMGB1 is reduced by aging and in Tg-APP/PS1 mice. Consistent with these observations, Aß treatment of both primary cortical neuron and primary microglial cultures increased HMGB1 secretion in the media, in an Aß-dose-dependent manner. Our results indicate that nuclear HMGB1 might be translocated from the nucleus to the cytoplasm in both neurons and microglia in the brains of Tg-APP/PS1 mice, and that it may subsequently be secreted extracellularly.

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.

Intranasal delivery of HMGB1 siRNA confers target gene knockdown and robust neuroprotection in the postischemic brain.

Noninvasive intranasal drug administration has been noted to allow direct delivery of drugs to the brain. In the present study, the therapeutic efficacy of intranasal small interfering RNA (siRNA) delivery was investigated in the postischemic rat brain. Fluorescein isothiocyanate (FITC)-labeled control siRNA was delivered intranasally in normal adult rats using e-PAM-R, a biodegradable PAMAM dendrimer, as gene carrier. Florescence-tagged siRNA was found in the cytoplasm and processes of neurons and of glial cells in many brain regions, including the hypothalamus, amygdala, cerebral cortex, and striatum, in 1 hour after infusion, and the FITC-fluorescence was continuously detected for at least 12 hours. When siRNA for high mobility group box 1 (HMGB1), which functions as an endogenous danger molecule and aggravates inflammation, was delivered intranasally, the target gene was significantly depleted in many brain regions, including the prefrontal cortex and striatum. More importantly, intranasal delivery of HMGB1 siRNA markedly suppressed infarct volume in the postischemic rat brain (maximal reduction to 42.8 ± 5.6% at 48 hours after 60 minutes middle cerebral artery occlusion (MCAO)) and this protective effect was manifested by recoveries from neurological and behavioral deficits. These results indicate that the intranasal delivery of HMGB1 siRNA offers an efficient means of gene knockdown-mediated therapy in the ischemic brain.

Extracellular Vesicles Released by Lactobacillus paracasei Mitigate Stress-induced Transcriptional Changes and Depression-like Behavior in Mice.

Various probiotic strains have been reported to affect emotional behavior. However, the underlying mechanisms by which specific probiotic strains change brain function are not clearly understood. Here, we report that extracellular vesicles derived from Lactobacillus paracasei (Lpc-EV) have an ability to produce genome-wide changes against glucocorticoid (GC)-induced transcriptional responses in HT22 hippocampal neuronal cells. Genome-wide analysis using microarray assay followed by Rank-Rank Hypergeometric Overlap (RRHO) method leads to identify the top 20%-ranked 1,754 genes up- or down-regulated following GC treatment and their altered expressions are reversed by Lpc-EV in HT22 cells. Serial k-means clustering combined with Gene Ontology enrichment analyses indicate that the identified genes can be grouped into multiple functional clusters that contain functional modules of "responses to stress or steroid hormones", "histone modification", and "regulating MAPK signaling pathways". While all the selected genes respond to GC and Lpc-EV at certain levels, the present study focuses on the clusters that contain Mkp-1, Fkbp5, and Mecp2, the genes characterized to respond to GC and Lpc-EV in opposite directions in HT22 cells. A translational study indicates that the expression levels of Mkp-1, Fkbp5, and Mecp2 are changed in the hippocampus of mice exposed to chronic stress in the same directions as those following GC treatment in HT22 cells, whereas Lpc-EV treatment restored stress-induced changes of those factors, and alleviated stress-induced depressive-like behavior. These results suggest that Lpc-EV cargo contains bioactive components that directly induce genome-wide transcriptional responses against GC-induced transcriptional and behavioral changes.

Lactobacillus-derived extracellular vesicles counteract Aß42-induced abnormal transcriptional changes through the upregulation of MeCP2 and Sirt1 and improve Aß pathology in Tg-APP/PS1 mice.

Mounting evidence suggests that probiotics are beneficial for treating Alzheimer's disease (AD). However, the mechanisms by which specific probiotics modify AD pathophysiology are not clearly understood. In this study, we investigated whether Lactobacillus paracasei-derived extracellular vesicles (Lpc-EV) can directly act on neuronal cells to modify amyloid-beta (Aß)-induced transcriptional changes and Aß pathology in the brains of Tg-APP/PS1 mice. Lpc-EV treatment in HT22 neuronal cells counteracts Aß-induced downregulation of Brain-derived neurotrophic factor (Bdnf), Neurotrophin 3 (Nt3), Nt4/5, and TrkB receptor, and reverses Aß-induced altered expression of diverse nuclear factors, including the downregulation of Methyl-CpG binding protein 2 (Mecp2) and Sirtuin 1 (Sirt1). Systematic siRNA-mediated knockdown experiments indicate that the upregulation of Bdnf, Nt3, Nt4/5, and TrkB by Lpc-EV is mediated via multiple epigenetic factors whose activation converges on Mecp2 and Sirt1. In addition, Lpc-EV reverses Aß-induced downregulation of the Aß-degrading proteases Matrix metalloproteinase 2 (Mmp-2), Mmp-9, and Neprilysin (Nep), whose upregulation is also controlled by MeCP2 and Sirt1. Lpc-EV treatment restores the downregulated expression of Bdnf, Nt4/5, TrkB, Mmp-2, Mmp-9, and Nep; induces the upregulation of MeCP2 and Sirt1 in the hippocampus; alleviates Aß accumulation and neuroinflammatory responses in the brain; and mitigates cognitive decline in Tg-APP/PS1 mice. These results suggest that Lpc-EV cargo contains a neuroactive component that upregulates the expression of neurotrophic factors and Aß-degrading proteases (Mmp-2, Mmp-9, and Nep) through the upregulation of MeCP2 and Sirt1, and ameliorates Aß pathology and cognitive deficits in Tg-APP/PS1 mice.

Glycyrrhizic acid affords robust neuroprotection in the postischemic brain via anti-inflammatory effect by inhibiting HMGB1 phosphorylation and secretion.

High mobility group box 1 (HMGB1) is an endogenous danger signal molecule. In a previous report, we showed that HMGB1 is massively released during NMDA-induced acute damaging process in the postischemic brain and triggers inflammatory processes, like microglial activation. siRNA-mediated HMGB1 knockdown markedly reduced infarct volumes, confirming the crucial role played by HMGB1 in the postischemic brain. In the present study, we showed neuroprotective effects of glycyrrhizin (GL) in the postischemic rat brain after middle cerebral artery occlusion (MCAO). GL, a triterpene present in the roots and rhizomes of licorice, Glycyrrhiza glabra, has been shown to have anti-inflammatory and anti-viral effects. It has been reported that GL binds directly to HMGB1, and inhibits its chemoattractant and mitogenic activities. The administration of GL (10mg/kg) intravenously at 3 or 6h after MCAO reduced infarct volumes to 12.9±4.2% and 46.2±9.9%, respectively, of untreated control. This neuroprotective effect was accompanied by improvements in motor impairment and neurological deficits and suppressions of microglia activation and proinflammatory cytokine induction. Interestingly, GL almost completely blocked HMGB1 secretion in the postischemic brain and in lipopolysaccharide (LPS)-treated microglia cells. Furthermore, HMGB1 phosphorylation, which is the initial step for HMGB1 secretion, and the interaction between HMGB1 and protein kinase C (PKC) or calcium/calmodulin-dependent protein kinase IV (CaMKIV) were suppressed dose-dependently by GL. Here, we hypothesized that the blockage for the putative phosphorylation sites in HMGB1 by GL might be attributed to this suppression. In addition to the anti-inflammatory effects, we found that GL has anti-excitotoxic and anti-oxidative effects in neurons. Together these results indicate that GL has neuroprotective efficacy in the postischemic brain via its anti-inflammatory, anti-excitotoxic, and anti-oxidative effects and in particular, it exerts anti-inflammatory effect, at least in part, by inhibiting HMGB1 secretion.

Extracellular Vesicles from Gram-positive and Gram-negative Probiotics Remediate Stress-Induced Depressive Behavior in Mice.

Chronic stress causes maladaptive changes in the brain that lead to depressive behavior. In the present study, we investigate whether chronic stress alters gut microbiota compositions that are related to stress-induced maladaptive changes in the brain. Mice treated with daily 2-h restraint for 14 days (CRST) exhibit depressive-like behavior. Sequence readings of 16S rRNA genes prepared from fecal samples taken from CRST-treated mice suggest that chronic stress induces gut microbiota changes that are pronounced in the post-stress period, relative to those that occur in the 14-day stress phase. The genus Lactobacillus is one such microbiota substantially changed following chronic stress. In contrast, intraperitoneal injection of extracellular vesicles (EVs) isolated from culture media of the Gram-positive probiotic Lactobacillus plantarum is sufficient to ameliorate stress-induced depressive-like behavior. Interestingly, EVs from the Gram-positive probiotic Bacillus subtilis and EVs from the Gram-negative probiotic Akkermansia muciniphila also produce anti-depressive-like effects. While chronic stress decreases the expression of MeCP2, Sirt1, and/or neurotrophic factors in the hippocampus, EVs from the three selected probiotics differentially restore stress-induced changes of these factors. These results suggest that chronic stress produces persistent changes in gut microbiota composition, whereas purified EVs of certain probiotics can be used for treatment of stress-induced depressive-like behavior.

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.

Robust protective effects of a novel multimodal neuroprotectant oxopropanoyloxy benzoic acid (a salicylic acid/pyruvate ester) in the postischemic brain.

Cerebral ischemia leads to brain injury via a complex series of pathophysiological events. Therefore, multidrug treatments or multitargeting drug treatments are attractive options in efficiently limiting brain damage. Here, we report a novel multifunctional compound oxopropanoyloxy benzoic acid (OBA-09), a simple ester of pyruvate and salicylic acid. This protective effect was manifested by recoveries from neurological and behavioral deficits. OBA-09 exhibited antioxidative effects in the postischemic brain, which was evidenced by remarkable reduction of lipid peroxidation and 4-hydroxy-2-nonenal staining in OBA-09-administered animals. Reactive oxygen species generation was markedly suppressed in primary cortical cultures under oxygen-glucose deprivation. More interestingly, OBA-09 was capable of scavenging hydroxyl radical in cell-free assays. High-performance liquid chromatography results demonstrated that OBA-09 was hydrolyzed to salicylic acid and pyruvate with t(1/2) = 43 min in serum and 4.2 h in brain parenchyma, indicating that antioxidative function of OBA-09 is executed by itself and also by salicylic acid after the hydrolysis. In addition to antioxidative function, OBA-09 exerts anti-excitotoxic and anti-Zn(2+)-toxic functions, which might be attributed to attenuation of ATP and nicotinamide adenine dinucleotide depletion and to the suppression of nuclear factor-κB activity induction. Together these results indicate that OBA-09 has a potent therapeutic potential as a multimodal neuroprotectant in the postischemic brain and these effects were conferred by OBA-09 itself and subsequently its hydrolyzed products.

Zinc-triggered induction of tissue plasminogen activator by brain-derived neurotrophic factor and metalloproteinases.

Tissue plasminogen activator (tPA) is necessary for hippocampal long-term potentiation. Synaptically released zinc also contributes to long-term potentiation, especially in the hippocampal CA3 region. Using cortical cultures, we examined whether zinc increased the concentration and/or activity of tPA. Two hours after a 10-min exposure to 300 µM zinc, expression of tPA and its substrate, plasminogen, were significantly increased, as was the proteolytic activity of tPA. In contrast, increasing extracellular or intracellular calcium levels did not affect the expression or secretion of tPA. Changing zinc influx or chelating intracellular zinc also failed to alter tPA/plasminogen induction by zinc, indicating that zinc acts extracellularly. Zinc-mediated extracellular activation of matrix metalloproteinase (MMP) underlies the up-regulation of brain-derived neurotrophic factor (BDNF) and tropomyosin receptor kinase (Trk) signaling. Consistent with these findings, co-treatment with a neutralizing antibody against BDNF or specific inhibitors of MMPs or Trk largely reversed tPA/plasminogen induction by zinc. Treatment of cortical cultures with p-aminophenylmercuric acetate, an MMP activator, MMP-2, or BDNF alone induced tPA/plasminogen expression. BDNF mRNA and protein expression was also increased by zinc and mediated by MMPs. Thus, an extracellular zinc-dependent, MMP- and BDNF-mediated synaptic mechanism may regulate the levels and activity of tPA.

Hyperoxygenation Treatment Reduces Beta-amyloid Deposition via MeCP2-dependent Upregulation of MMP-2 and MMP-9 in the Hippocampus of Tg-APP/PS1 Mice.

Recently we reported that hyperoxygenation treatment reduces amyloid-beta accumulation and rescues cognitive impairment in the Tg-APP/PS1 mouse model of Alzheimer's disease. In the present study, we continue to investigate the mechanism by which hyperoxygenation reduces amyloid-beta deposition in the brain. Hyperoxygenation treatment induces upregulation of matrix metalloproteinase-2 (MMP-2), MMP-9, and tissue plasminogen activator (tPA), the endopeptidases that can degrade amyloid-beta, in the hippocampus of Tg-APP/PS1 mice. The promoter regions of the three proteinase genes all contain potential binding sites for MeCP2 and Pea3, which are upregulated in the hippocampus after hyperoxygenation. Hyperoxygenation treatment in HT22 neuronal cells increases MeCP2 but not Pea3 expression. In HT22 cells, siRNA-mediated knockdown of Mecp2 decreases Mmp-9 expression and to a lesser extent, Mmp-2 and tPA expression. In mice, siRNA-mediated Mecp2 knockdown in the hippocampus reduces Mmp-9 expression, but not significantly Mmp-2 and tPA expression. The ChIP assay indicates that hyperoxygenation treatment in Tg-APP/PS1 mice increases MeCP2 binding to the promoter regions of Mmp-2 , Mmp-9 and tPA genes in the hippocampus. Together, these results suggest that hyperoxygenation increases the expression of MMP-2, MMP-9, and tPA, of which MMP-9 is upregulated via MeCP2 in neuronal cells, and MMP-2 and tPA are upregulated through MeCP2 and other nuclear factors.

Aging-Dependent Downregulation of SUV39H1 Histone Methyltransferase Increases Susceptibility to Stress-Induced Depressive Behavior.

Aging induces cellular and molecular changes including gene expression alteration in the brain, which might be associated with aging-induced decrease in stress coping ability. In the present study, we investigate how aging changes the ability to cope with stress and increases sensitivity to stress. Aged mice show decreased expression of SUV39H1 histone methyltransferase and increased expression of Mkp-1 in the hippocampus. The siRNA-mediated knockdown of SUV39H1 increases Mkp-1 expression and suppresses p-CREB and Bdnf expression in HT22 cells and in the hippocampus of mice. Chromatin immunoprecipitation assays indicate that the levels of SUV39H1 and methylated histone-H3 bound to the promoter of the Mkp-1 in the hippocampus are reduced in aged mice. Aged mice exhibit depression-like behavior following weak stress that does not induce depressive behavior in young mice. Rosmarinic acid, a phenolic compound that increases SUV39H1 expression, reverses stress-induced changes of SUV39H1, Mkp-1, and Bdnf expression in the hippocampus via an overlapping but distinct mechanism from those of fluoxetine and imipramine and produces anti-depressive effects. These results suggest that aging increases susceptibility to stress via downregulation of SUV39H1 and resulting changes in SUV39H1-regulated signaling pathways in the hippocampus.