Convolamine, a tropane alkaloid extracted from Convolvulus plauricalis, is a potent sigma-1 receptor-positive modulator with cognitive and neuroprotective properties.

BACKGROUND AND AIM: By using an in vivo phenotypic screening assay in zebrafish, we identified Convolamine, a tropane alkaloid from Convulvus plauricalis, as a positive modulator of the sigma-1 receptor (S1R). The wfs1abKO zebrafish larva, a model of Wolfram syndrome, exhibits an increased visual-motor response due to a mutation in Wolframin, a protein involved in endoplasmic reticulum-mitochondria communication. We previously reported that ligand activating S1R, restored the cellular and behavioral deficits in patient fibroblasts and zebrafish and mouse models. EXPERIMENTAL PROCEDURES: We screened a library of 108 repurposing and natural compounds on zebrafish motor response. KEY RESULTS: One hit, the tropane alkaloid Convolamine, restored normal mobility in wfs1abKO larvae without affecting wfs1abWT controls. They did not bind to the S1R agonist/antagonist binding site nor dissociated S1R from BiP, an S1R activity assay in vitro, but behaved as a positive modulator by shifting the IC50 value of the reference agonist PRE-084 to lower values. Convolamine restored learning in Wfs1∆Exon8 , Dizocilpine-treated, and Aß25-35 -treated mice. These effects were observed at low ~1 mg/kg doses, not shared by Convolvine, the desmethyl metabolite, and blocked by an S1R antagonist. CONCLUSION AND IMPLICATIONS: Convolamine therefore acts as an S1R positive modulator and this pharmacological action is relevant to the traditional use of Shankhpushpi in memory and cognitive protection.

Restorative effects of probiotics on memory impairment in sleep-deprived mice.

BACKGROUND: Insufficient sleep is a serious public health epidemic in modern society, impairing memory and other cognitive functions. In this study, partial sleep deprivation (SD) was used to induce cognitive impairment in mice to determine the effects of probiotics on subsequent cognitive deficits. METHODS: Lactiplantibacillus plantarum Lp-115 (Lp-115), Lacticaseibacillus paracasei Lpc-37 (Lpc-37), Bifidobacterium animalis subsp. lactis 420 (B420) and their combination were administered to mice subjected to partial SD and compared with non-SD and SD vehicle groups. Mice were administered a daily oral gavage containing either 1 × 109 colony forming units (CFU) of single-strain, 1.5 × 109 CFU of multi-strain (5 × 108 CFU/strain), or vehicle for thirty days prior to and for nine days during a behavioural test paradigm. The novel object recognition (NOR) test, spontaneous alternation Y-maze (Y-maze), and the step-through passive avoidance (STPA) task were applied to evaluate learning and memory performance following partial SD. RESULTS: Partial SD had a significant impact on cognitive function in vehicle mice. Intervention with Lpc-37 significantly improved recognition memory deficits in the NOR test, spatial working memory deficits in the Y-maze, and contextual long-term memory impairments in the STPA task, in mice subjected to partial SD compared to the SD vehicle group. The multi-strain significantly improved recognition memory deficits in the NOR test and spatial working memory deficits in the Y-maze in mice subjected to partial SD compared to the SD vehicle group. CONCLUSIONS: These findings demonstrate that Lpc-37 and the multi-strain may play a role in alleviating memory impairments and improve cognitive function in partially sleep-deprived mice.

Efficacy of THN201, a Combination of Donepezil and Mefloquine, to Reverse Neurocognitive Deficits in Alzheimer's Disease.

Donepezil (DPZ) is an acetylcholinesterase inhibitor used in Alzheimer's disease to restore cognitive functions but is endowed with limited efficacy. Recent studies pointed out the implication of astroglial networks in cognitive processes, notably via astrocyte connexins (Cxs), proteins involved in gap junction intercellular communications. Hence, we investigated the impact on cognition of pharmacological or genetic modulations of those astrocyte Cxs during DPZ challenge in two rodent models of Alzheimer's disease-like memory deficits. We demonstrated that the Cx modulator mefloquine (MEF) significantly enhanced the procognitive effect of DPZ in both models. In parallel, we determined that MEF potentiated DPZ-induced release of acetylcholine in hippocampus. Finally, local genetic silencing of astrocyte Cxs in the hippocampus was also found to enhance the procognitive effect of DPZ, pointing out the importance of Cx-dependent astrocyte networks in memory processes.

In Vitro and In Vivo Neuroprotective Effects of Etifoxine in ß-Amyloidinduced Toxicity Models.

AIM: The aim of this study is to examine the effect of etifoxine on ß-amyloid-induced toxicity models. BACKGROUND: Etifoxine is an anxiolytic compound with a dual mechanism of action; it is a positive allosteric modulator of GABAergic receptors as well as a ligand for the 18 kDa mitochondrial Translocator Protein (TSPO). TSPO has recently raised interest in Alzheimer's Disease (AD), and experimental studies have shown that some TSPO ligands could induce neuroprotective effects in animal models. OBJECTIVE: In this study, we examined the potential protective effect of etifoxine in an in vitro and an in vivo model of amyloid beta (Aß)-induced toxicity in its oligomeric form, which is a crucial factor in AD pathologic mechanisms. METHODS: Neuronal cultures were intoxicated with Aß1-42, and the effects of etifoxine on oxidative stress, Tau-hyperphosphorylation and synaptic loss were quantified. In a mice model, behavioral deficits induced by intracerebroventricular administration of Aß25-35 were measured in a spatial memory test, the spontaneous alternation and in a contextual memory test, the passive avoidance test. RESULTS: In neuronal cultures intoxicated with Aß1-42, etifoxine dose-dependently decreased oxidative stress (methionine sulfoxide positive neurons), tau-hyperphosphorylation and synaptic loss (ratio PSD95/synaptophysin). In a mice model, memory impairments were fully alleviated by etifoxine administered at anxiolytic doses (12.5-50mg/kg). In addition, markers of oxidative stress and apoptosis were decreased in the hippocampus of these animals. CONCLUSION: Our results have shown that in these two models, etifoxine could fully prevent neurotoxicity and pathological changes induced by Aß. These results confirm that TSPO ligands could offer an interesting therapeutic approach to Alzheimer's disease.

Strain specific stress-modulating effects of candidate probiotics: A systematic screening in a mouse model of chronic restraint stress.

BACKGROUND: Changes in the gut microbiota have been implicated in mood and cognition. In rodents, supplementation with certain bacteria have been shown to alleviate adverse effects of stress on gut microbiota composition and behaviour, but little is known of how the performance of different strains compare to each other. We took a systematic approach to test the efficacy of twelve candidate probiotic strains from ten species/sub-species of Bifidobacterium and Lactobacillus on behaviours and neuroendocrine responses of chronically stressed mice. METHODS: The strains were tested in four screening experiments with non-stressed and chronically stressed vehicle groups. The three most efficacious strains were re-tested to validate the results. Mice were administered a daily oral gavage containing either 1 × 109 colony forming units (CFU) of selected candidate probiotic or saline solution for one week prior to and for three weeks during daily chronic restraint stress. Behavioural tests including the elevated plus maze, open field, novel object recognition, and forced swim test were applied during week five. Corticosterone and adrenocorticotropic hormone (ACTH) were analysed to measure the neuroendocrine response to stress. Plasma and tissue samples were collected for biomarker analyses. RESULTS: Of the twelve candidate probiotics, Lactobacillus paracasei Lpc-37, Lactobacillus plantarum LP12407, Lactobacillus plantarum LP12418 and Lactobacillus plantarum LP12151 prevented stress-associated anxiety and depression-related behaviours from developing compared with chronically stressed vehicle mice. In addition, Lpc-37 improved cognition. CONCLUSION: This systematic screening indicates species- and strain-dependent effects on behavioural outcomes related to stress and further suggests that strains differ from each other in their effects on potential mechanistic outcomes.

N-acetylcysteine Treatment Reduces Age-related Hearing Loss and Memory Impairment in the Senescence-Accelerated Prone 8 (SAMP8) Mouse Model.

Age-related hearing loss (ARHL) is the most common sensory disorder in the elderly population. SAMP8 mouse model presents accelerated senescence and has been identified as a model of gerontological research. SAMP8 displays a progressive age-related decline in brain function associated with a progressive hearing loss mimicking human aging memory deficits and ARHL. The molecular mechanisms associated with SAMP8 senescence process involve oxidative stress leading to chronic inflammation and apoptosis. Here, we studied the effect of N-acetylcysteine (NAC), an antioxidant, on SAMP8 hearing loss and memory to determine the potential interest of this model in the study of new antioxidant therapies. We observed a strong decrease of auditory brainstem response thresholds from 45 to 75 days of age and an increase of distortion product amplitudes from 60 to 75 days in NAC treated group compared to vehicle. Moreover, NAC treated group presented also an increase of memory performance at 60 and 105 days of age. These results confirm that NAC delays the senescence process by slowing the age-related hearing loss, protecting the cochlear hair cells and improving memory, suggesting that antioxidants could be a pharmacological target for age-related hearing and memory loss.

Neuroprotective effect of a new photobiomodulation technique against Aß25-35 peptide-induced toxicity in mice: Novel hypothesis for therapeutic approach of Alzheimer's disease suggested.

INTRODUCTION: Photobiomodulation was assessed as a novel treatment of Alzheimer's disease (AD) by the use of a new device RGn500 combining photonic and magnetic emissions in a mouse model of AD. METHODS: Following the injection of amyloid ß 25-35 peptide in male Swiss mice, RGn500 was applied once a day for 7 days either on the top of the head or the center of abdomen or both. RESULTS: RGn500 daily application for 10 min produced a neuroprotective effect on the neurotoxic effects of amyloid ß 25-35 peptide injection when this type of photobiomodulation was applied both on the head and on the abdomen. Protection was demonstrated by memory restoration and on the normalization of key markers of AD (amyloid ß 1-42, pTau), oxidative stress (lipid peroxidation), apoptosis (Bax/Bcl2) and neuroinflammation. DISCUSSION: RGn500 displays therapeutic efficacy similar to other pharmacological approaches evaluated in this model of AD.

In Vivo Characterization of ARN14140, a Memantine/Galantamine-Based Multi-Target Compound for Alzheimer's Disease.

Alzheimer's disease (AD) is a chronic pathological condition that leads to neurodegeneration, loss of intellectual abilities, including cognition and memory, and ultimately to death. It is widely recognized that AD is a multifactorial disease, where different pathological cascades (mainly amyloid and tau) contribute to neural death and to the clinical outcome related to the disease. The currently available drugs for AD were developed according to the one-target, one-drug paradigm. In recent times, multi-target strategies have begun to play an increasingly central role in the discovery of more efficacious candidates for complex neurological conditions, including AD. In this study, we report on the in vivo pharmacological characterization of ARN14140, a new chemical entity, which was obtained through a multi-target structure-activity relationship campaign, and which showed a balanced inhibiting profile against the acetylcholinesterase enzyme and the NMDA receptor. Based on the initial promising biochemical data, ARN14140 is here studied in mice treated with the amyloidogenic fragment 25-35 of the amyloid-ß peptide, a consolidated non-transgenic AD model. Sub-chronically treating animals with ARN14140 leads to a prevention of the cognitive impairment and of biomarker levels connected to neurodegeneration, demonstrating its neuroprotective potential as new AD agent.

Leucettine L41, a DYRK1A-preferential DYRKs/CLKs inhibitor, prevents memory impairments and neurotoxicity induced by oligomeric Aß25-35 peptide administration in mice.

Dual-specificity tyrosine phosphorylation-regulated kinases (DYRKs) and cdc2-like kinases (CLKs) are implicated in the onset and progression of Down syndrome (DS) and Alzheimer's disease (AD). DYRK1A has emerged as a possible link between amyloid-ß (Aß) and Tau, the major pathological proteins in AD. We here assessed the neuroprotective potential of a novel inhibitor of DYRKs/CLKs. The Leucettine L41, acting preferentially on DYRK1A, was tested in Aß25-35-treated mice, a nontransgenic model of AD-like toxicity. We co-injected intracerebroventricularly oligomeric Aß25-35 peptide and L41 in Swiss male mice. After 7 days, they were submitted to behavioral tests addressing spatial and non-spatial, short- and long-term memories. The oxidative stress, apoptotic markers, kinases involved in Tau phosphorylation, and synaptic integrity were analyzed by Western blot and ELISA in the hippocampus. L41, tested at 0.4, 1.2, 4 µg, prevented the Aß25-35-induced memory deficits in the Y-maze, passive avoidance and water-maze tests, with the most active dose being 4 µg. The inhibitor prevented the Aß25-35-induced oxidative stress, as revealed by measures of lipid peroxidation levels and reactive oxygen species accumulation, and abolished Aß25-35-induced expression of pro-apoptotic markers. L41 prevented the Aß25-35-induced decrease of AKT activation and increase of glycogen synthase kinase-3ß (GSK-3ß) activation, resulting in a decrease of Tau phosphorylation. Finally, L41 restored Aß25-35-reduced levels of synaptic markers. The novel DYRK1A-preferential inhibitor L41 therefore prevented Aß25-35-induced memory impairments and neurotoxicity in the mouse hippocampus. These in vivo data highlighted particularly DYRK1A as a major kinase involved in Aß pathology and suggested therapeutic developments for DYRK1A inhibitors in AD.

The effects of sigma (σ1) receptor-selective ligands on muscarinic receptor antagonist-induced cognitive deficits in mice.

BACKGROUND AND PURPOSE: Cognitive deficits in patients with Alzheimer's disease, Parkinson's disease, traumatic brain injury and stroke often involve alterations in cholinergic signalling. Currently available therapeutic drugs provide only symptomatic relief. Therefore, novel therapeutic strategies are needed to retard and/or arrest the progressive loss of memory. EXPERIMENTAL APPROACH: Scopolamine-induced memory impairment provides a rapid and reversible phenotypic screening paradigm for cognition enhancement drug discovery. Male C57BL/6J mice given scopolamine (1 mg·kg(-1) ) were used to evaluate the ability of LS-1-137, a novel sigma (σ1) receptor-selective agonist, to improve the cognitive deficits associated with muscarinic antagonist administration. KEY RESULTS: LS-1-137 is a high-affinity (Ki = 3.2 nM) σ1 receptor agonist that is 80-fold selective for σ1, compared with σ2 receptors. LS-1-137 binds with low affinity at D2-like (D2, D3 and D4) dopamine and muscarinic receptors. LS-1-137 was found to partially reverse the learning deficits associated with scopolamine administration using a water maze test and an active avoidance task. LS-1-137 treatment was also found to trigger the release of brain-derived neurotrophic factor from rat astrocytes. CONCLUSIONS AND IMPLICATIONS: The σ1 receptor-selective compound LS-1-137 may represent a novel candidate cognitive enhancer for the treatment of muscarinic receptor-dependent cognitive deficits.

Brain toxicity and inflammation induced in vivo in mice by the amyloid-ß forty-two inducer aftin-4, a roscovitine derivative.

Aftins (amyloid forty-two inducers) represent a novel class of tri-substituted purines derived from roscovitine, able to promote the generation of amyloid-ß (Aß)1-42 from amyloid-ß protein precursor through γ-secretase activation in cell cultures. We here examined whether aftin-4 could provoke an amyloid-like toxicity in vivo in mice. The intracerebroventricular administration of aftin-4 (3-20 nmol) increased Aß1-42, but not Aß1-40, content in the mouse hippocampus, between 5 and 14 days after injection. Aftin-4 injection increased lipid peroxidation levels in the hippocampus, an index of oxidative stress. It increased brain contents in pro-inflammatory cytokines, IL-1ß, IL-6, and TNFα, and GFAP immunolabeling, showing astrocytic reaction. Expression of the synaptic marker synaptophysin was decreased by aftin-4. Finally, the treatment provoked marked learning deficits, observed using different memory procedures: Spontaneous alternation in the Y-maze, place learning in the water-maze, and passive avoidance response. The systemic intraperitoneal injection of aftin-4 in the 3-30 mg/kg dose range also induced oxidative stress and learning deficits. All these alterations could be blocked by pre-treatment with the γ-secretase inhibitor BMS-299,897, confirming that the mechanism of action of aftin-4 involves secretase activity. Furthermore, we examined if the cholinesterase inhibitor donepezil and the non-steroidal anti-inflammatory drug ibuprofen could prevent aftin-4-induced memory impairments, cytokine release, and lipid peroxidation. Donepezil prevented all alterations, whereas ibuprofen prevented the increases in cytokine release and lipid peroxidation, but only marginally the memory impairments. As a whole, this study showed that in vivo injection of aftin-4 results in a rapid, acute Alzheimer's disease-like toxicity in the rodent brain.

Neuroprotection by the synthetic neurosteroid enantiomers ent-PREGS and ent-DHEAS against Aß25₋35 peptide-induced toxicity in vitro and in vivo in mice.

RATIONALE: Pregnenolone sulfate (PREGS) and dehydroepiandrosterone sulphate (DHEAS) are pro-amnesic, anti-amnesic and neuroprotective steroids in rodents. In Alzheimer's disease (AD) patient's brains, their low concentrations are correlated with high levels of Aß and tau proteins. The unnatural enantiomer ent-PREGS enhanced memory in rodents. We investigated here whether ent-PREGS and ent-DHEAS could be neuroprotective in AD models. OBJECTIVE: The effects of PREGS, ent-PREGS, DHEAS and ent-DHEAS against Aß25-35 peptide-induced toxicity were examined in vitro on B104 neuroblastoma cells and in vivo in mice. METHODS: B104 cells pretreated with the steroids before Aß25-35 were analysed by flow cytometry measuring cell viability and death processes. Mice injected intracerebroventricularly with Aß25-35 and the steroids were analysed for their memory abilities. Additionally, lipid peroxidation levels in the hippocampus were measured. RESULTS: ent-PREGS and PREGS significantly attenuated the Aß25-35-induced decrease in cell viability. Both steroids prevented the Aß25-35-induced increase in late apoptotic cells. PREGS further attenuated the ratio of necrotic cells. ent-DHEAS and DHEAS significantly reduced the Aß25-35-induced toxicity and prevented the cells from entering late apoptosis and necrosis. All steroids stimulated neurite outgrowth per se and prevented the Aß25-35-induced decrease. In vivo, ent-PREGS and ent-DHEAS significantly attenuated the Aß25-35-induced decrease in memory (spontaneous alternation and passive avoidance) and an increase in lipid peroxidation levels. In contrast to the natural steroids, both enantiomers prevented amnesia when injected 6 h before Aß25-35 in contrast to the natural steroids. CONCLUSION: The unnatural steroids ent-PREGS and ent-DHEAS are potent neuroprotective agents and could be effective therapeutical tools in AD.

Blockade of Tau hyperphosphorylation and Aß1₋42 generation by the aminotetrahydrofuran derivative ANAVEX2-73, a mixed muscarinic and σ1 receptor agonist, in a nontransgenic mouse model of Alzheimer's disease.

The main objective of the present study was to establish whether the mixed σ1/muscarinic ligand ANAVEX2-73, shown to be neuroprotective in Alzheimer's disease (AD) models in vivo and currently in clinical phase I/IIa, could have the ability to reduce the appearance of hyperphosphorylated Tau and amyloid-ß1₋42 (Aß1₋42 in the Aß25₋35 mouse model of AD. We therefore first confirmed that Aß25₋35 injection induced hyperphosphorylation of Tau protein, by showing that it rapidly decreased Akt activity and activated glycogen synthase kinase-3ß (GSK-3ß) in the mouse hippocampus. Second, we showed that the kinase activation, and resulting Tau alteration, directly contributed to the amyloid toxicity, as co-administration of the selective GSK-3ß inhibitor 2-thio(3-iodobenzyl)-5-(1-pyridyl)-[1,3,4]-oxidiazole blocked both Tau phosphorylation and Aß25₋35-induced memory impairments. Third, we analyzed the ANAVEX2-73 effect on Tau phosphorylation and activation of the related kinase pathways (Akt and GSK-3ß). And fourth, we also addressed the impact of the drug on Aß25₋35-induced Aß1₋42 seeding and observed that the compound significantly blocked the increase in Aß1₋42 and C99 levels in the hippocampus, suggesting that it may alleviate amyloid load in AD models. The comparison with PRE-084, a selective and reference σ1 receptor agonist, and xanomeline, a muscarinic ligand presenting similar profile as ANAVEX2-73 on M1 and M2 subtypes, confirmed that both muscarinic and σ1 targets are involved in the ANAVEX2-73 effects. The drug, acting synergistically on both targets, but with moderate affinity, presents a promising pharmacological profile.

Increased amyloid-ß peptide-induced memory deficits in phospholipid transfer protein (PLTP) gene knockout mice.

Oxidative stress is recognized as one of the earliest and most intense pathological processes in Alzheimer's disease (AD), and the antioxidant vitamin E has been shown to efficiently prevent amyloid plaque formation and neurodegeneration. Plasma phospholipid transfer protein (PLTP) has a major role in vitamin E transfers in vivo, and PLTP deficiency in mice is associated with reduced brain vitamin E levels. To determine the impact of PLTP on amyloid pathology in vivo, we analyzed the vulnerability of PLTP-deficient (PLTP-KO) mice to the toxic effects induced by intracerebroventricular injection of oligomeric amyloid-ß 25-35 (Aß 25-35) peptide, a non-transgenic model of AD. Under basal conditions, PLTP-KO mice showed increased cerebral oxidative stress, increased brain Aß 1-42 levels, and a lower expression of the synaptic function marker synaptophysin, as compared with wild-type mice. This PLTP-KO phenotype was associated with increased memory impairment 1 week after Aß25-35 peptide injection. Restoration of brain vitamin E levels in PLTP-KO mice through a chronic dietary supplementation prevented Aß 25-35-induced memory deficits and reduced cerebral oxidative stress and toxicity. We conclude that PLTP, through its ability to deliver vitamin E to the brain, constitutes an endogenous neuroprotective agent. Increasing PLTP activity may offer a new way to develop neuroprotective therapies.

The γ-secretase inhibitor 2-[(1R)-1-[(4-chlorophenyl)sulfonyl](2,5-difluorophenyl) amino]ethyl-5-fluorobenzenebutanoic acid (BMS-299897) alleviates Aß1-42 seeding and short-term memory deficits in the Aß25-35 mouse model of Alzheimer's disease.

Alzheimer's disease pathomimetic toxicity could be induced in mice within one week after the intracerebroventricular (i.c.v.) injection of an aggregated preparation of the highly toxic and endogenous amyloid-ß fragment Aß(25-35). It was recently reported that Aß(25-35) also provokes a modification of APP processing with accumulation of endogenous Aß(1-42). We here analyzed whether a γ-secretase inhibitor, BMS-299897, attenuated this Aß(25-35)-induced Aß(1-42) seeding and toxicity. The compound was administered at 0.1-1 nmol/mouse, concomittantly with Aß(25-35) (9 nmol) in male Swiss mice. After one week, the contents in Aß(1-42) and Aß(1-40), and the levels in lipid peroxidation were analyzed in the mouse hippocampus. Mice were submitted to spontaneous alternation, passive avoidance and object recognition to analyze their short- and long-term memory abilities. Aß(25-35) increased Aß(1-42) content (+240%) but failed to affect Aß(1-40). BMS-299897 blocked the increase in Aß(1-42) content and decreased Aß(1-40) levels significantly. The compound did not affect Aß(25-35)-induced increase in hippocampal lipid peroxidation. Behaviorally, BMS-299897 blocked the Aß(25-35)-induced deficits in spontaneous alternation or novel object recognition, using a 1h intertrial time interval. BMS-299896 failed to affect the passive avoidance impairments or novel object recognition, using a 24h intertrial time interval. These results confirmed that Aß(25-35) injection provoked an accumulation in endogenous Aß(1-42), an effect blocked by γ-secretase inhibition. This Aß(1-42) accumulation marginally contributed to the toxicity or long-term memory deficits. However, since the seeded Aß(1-42) affected short-term memory, the rapid Aß(25-35) injection Alzheimer's disease model could be used to screen the activity of new secretase inhibitors.

Time-course and regional analyses of the physiopathological changes induced after cerebral injection of an amyloid ß fragment in rats.

Alzheimer's disease (AD) is a neurodegenerative pathology characterized by the presence of senile plaques and neurofibrillary tangles, accompanied by synaptic and neuronal loss. The major component of senile plaques is an amyloid ß protein (Aß) formed by pathological processing of the Aß precursor protein. We assessed the time-course and regional effects of a single intracerebroventricular injection of aggregated Aß fragment 25-35 (Aß(25-35)) in rats. Using a combined biochemical, behavioral, and morphological approach, we analyzed the peptide effects after 1, 2, and 3 weeks in the hippocampus, cortex, amygdala, and hypothalamus. The scrambled Aß(25-35) peptide was used as negative control. The aggregated forms of Aß peptides were first characterized using electron microscopy, infrared spectroscopy, and Congo Red staining. Intracerebroventricular injection of Aß(25-35) decreased body weight, induced short- and long-term memory impairments, increased endocrine stress, cerebral oxidative and cellular stress, neuroinflammation, and neuroprotective reactions, and modified endogenous amyloid processing, with specific time-course and regional responses. Moreover, Aß(25-35), the presence of which was shown in the different brain structures and over 3 weeks, provoked a rapid glial activation, acetylcholine homeostasis perturbation, and hippocampal morphological alterations. In conclusion, the acute intracerebroventricular Aß(25-35) injection induced substantial central modifications in rats, highly reminiscent of the human physiopathology, that could contribute to physiological and cognitive deficits observed in AD.

Pharmacological interaction with the sigma1 (σ1)-receptor in the acute behavioral effects of antidepressants.

Selective agonists of the sigma-1 (σ(1)) ligand-operated chaperone protein, like igmesine or PRE-084, are antidepressants in preclinical depression models. σ(1)-Protein activation may contribute to the antidepressant efficacy of drugs known to act as selective serotonin-reuptake inhibitors (SSRI) or noradrenaline reuptake inhibitors through direct or indirect involvement of the σ(1)-receptor in the drug effect. We here compared antidepressant effects in two behavioral procedures, the forced swimming test (FST) and conditioned fear stress (CFS). The involvement of the σ(1)-receptor was examined using a co-treatment with the σ(1)-antagonist BD1047 or using σ(1)-knockout (KO) mice. Igmesine but not PRE-084 decreased FST immobility. The SSRI fluoxetine and sertraline, but not fluvoxamine, and the tricyclic antidepressants imipramine, desipramine, and amitriptyline were also effective. Only the effect of igmesine was blocked by BD1047 or in σ(1)-KO mice. Igmesine, PRE-084, fluvoxamine, and sertraline decreased the CFS immobility in a BD1047- and σ(1)-KO-sensitive manner. Among tricyclics, only amitriptyline was effective and its effect was unaffected by BD1047 or in σ(1)-KO mice. The behavioral effects induced by mixed σ(1)-receptor/SSRI antidepressants, like fluvoxamine or sertraline, may therefore involve a non-selective action at both targets. Moreover, the CFS appears to more reliably uncover a σ(1) pharmacological component in antidepressant screening.

Sigma-1 receptors regulate Bcl-2 expression by reactive oxygen species-dependent transcriptional regulation of nuclear factor kappaB.

The expression of Bcl-2, the major antiapoptotic member of the Bcl-2 family, is under complex controls of several factors, including reactive oxygen species (ROS). The sigma-1 receptor (Sig-1R), which was recently identified as a novel molecular chaperone at the mitochondria-associated endoplasmic reticulum membrane (MAM), has been shown to exert robust cellular protective actions. However, mechanisms underlying the antiapoptotic action of the Sig-1R remain to be clarified. Here, we found that the Sig-1R promotes cellular survival by regulating the Bcl-2 expression in Chinese hamster ovary cells. Although both Sig-1Rs and Bcl-2 are highly enriched at the MAM, Sig-1Rs neither associate physically with Bcl-2 nor regulate stability of Bcl-2 proteins. However, Sig-1Rs tonically regulate the expression of Bcl-2 proteins. Knockdown of Sig-1Rs down-regulates whereas overexpression of Sig-1Rs up-regulates bcl-2 mRNA, indicating that the Sig-1R transcriptionally regulates the expression of Bcl-2. The effect of Sig-1R small interfering RNA down-regulating Bcl-2 was blocked by ROS scavengers and by the inhibitor of the ROS-inducible transcription factor nuclear factor kappaB (NF-kappaB). Knockdown of Sig-1Rs up-regulates p105, the precursor of NF-kappaB, while concomitantly decreasing inhibitor of nuclear factor-kappaBalpha. Sig-1R knockdown also accelerates the conversion of p105 to the active form p50. Lastly, we showed that knockdown of Sig-1Rs potentiates H(2)O(2)-induced apoptosis; the action is blocked by either the NF-kappaB inhibitor oridonin or overexpression of Bcl-2. Thus, these findings suggest that Sig-1Rs promote cell survival, at least in part, by transcriptionally regulating Bcl-2 expression via the ROS/NF-kappaB pathway.

Late N-acetylcysteine treatment prevents the deficits induced in the offspring of dams exposed to an immune stress during gestation.

Prenatal infection is a major stressful experience leading to enhanced susceptibility for mental illnesses in humans. We recently reported in rats, that oxidative stress and glutathione (GSH) shortage occurred in fetal male brain after lipopolysaccharide (LPS) to the dams and that these responses might be involved in the neurodevelopmental deficits observed in adolescent offspring. Furthermore, pretreatment with N-acetylcysteine (NAC) before LPS avoided both delayed synaptic plasticity and mnesic performance deficits. Since NAC is one of the few medications permitted in pregnant women, this study evaluated the ability of NAC to serve as a protective therapy even after the LPS challenge. Pregnant rats received a single ip injection of E. coli LPS, two days before delivery, and were given NAC in their tap water after the LPS. GSH was evaluated at the time of its expected drop in the hippocampus of male fetuses, whereas long-term potentiation (LTP) in the CA1 area of the hippocampus and spatial memory in the water-maze were recorded in 28-day-old male offspring. Post-treatment with NAC, four hours after the LPS challenge fully prevented the drop in the GSH hippocampal content. LTP, as well as spatial learning were completely protected. NAC administration at delivery also partially restored the LTP whereas post-treatment two days later was inefficient. Another set of dams were supplemented with alpha-tocopherol prior to LPS exposure, enhancing the alpha-tocopherol levels in fetal hippocampus. This treatment did not prevent the LPS-induced synaptic plasticity impairment. These results point to fetal hippocampal GSH as a major target of the detrimental effects of in utero LPS challenge. The therapeutic window of NAC extends up to birth, suggesting that this drug might be clinically useful even after an immuno-inflammatory episode.

Altered memory capacities and response to stress in p300/CBP-associated factor (PCAF) histone acetylase knockout mice.

Chromatin remodeling by posttranslational modification of histones plays an important role in brain plasticity, including memory, response to stress and depression. The importance of H3/4 histones acetylation by CREB-binding protein (CBP) or related histone acetyltransferase, including p300, was specifically demonstrated using knockout (KO) mouse models. The physiological role of a related protein that also acts as a transcriptional coactivator with intrinsic histone acetylase activity, the p300/CBP-associated factor (PCAF), is poorly documented. We analyzed the behavioral phenotype of homozygous male and female PCAF KO mice and report a marked impact of PCAF deletion on memory processes and stress response. PCAF KO animals showed short-term memory deficits at 2 months of age, measured using spontaneous alternation, object recognition, or acquisition of a daily changing platform position in the water maze. Acquisition of a fixed platform location was delayed, but preserved, and no passive avoidance deficit was noted. No gender-related difference was observed. These deficits were associated with hippocampal alterations in pyramidal cell layer organization, basal levels of Fos immunoreactivity, and MAP kinase activation. PCAF KO mice also showed an exaggerated response to acute stress, forced swimming, and conditioned fear, associated with increased plasma corticosterone levels. Moreover, learning and memory impairments worsened at 6 and 12 months of age, when animals failed to acquire the fixed platform location in the water maze and showed passive avoidance deficits. These observations demonstrate that PCAF histone acetylase is involved lifelong in the chromatin remodeling necessary for memory formation and response to stress.