Identification of glucosinolates and volatile odor compounds in microwaved radish (Raphanus sativus L.) seeds and the corresponding oils by UPLC-IMS-QTOF-MS and GC × GC-qMS analysis.

The effect of microwave treatment on the content of glucosinolates (GSL) in radish seeds and volatile odor compounds in the microwaved radish seed oils (MRSO) is still unclear. In this study, a total of 13 GSL were identified and quantified in five radish seed varieties by UPLC-IMS-QTOF-MS, among which glucoraphenin, glucoraphasatin, glucoerucin accounting for up to 90 %. Total GSL decreased by 47.39-67.88% after microwave processing. Moreover, 58 odor compounds were identified in MRSO, including 6 sulfides, 12 nitriles, 2 isothiocyanates, 10 alcohols, 12 aldehydes, 5 ketones, 6 acids, and 5 others. The major odor compounds were (methyldisulfanyl)methane, dimethyltrisulfane, (methylsulfinyl)methane, 3-(methylsulfanyl)-1-propanol, methyl thiocyanate, hexanenitrile, 5-(methylsulfanyl)pentanenitrile, and 4-isothiocyanato-1-butene with odor activity value (OAV) higher than 1. The principal components analysis (PCA) results can distinguish MRSO from five different radish seed varieties, three of which (H20-18, H20-19 and H20-28) were in one group and other two (H20-23 and H20-26) were in another group. In addition, aliphatic GSL showed positive correlations with sulfides, isothiocyanates, and nitriles, while negative correlations with alcohols. This work provides a new insight into the odor contribution of GSL degradation products.

Low-field magnetic stimulation improved cuprizone-induced depression-like symptoms and demyelination in female mice.

Depression is a common and disabling comorbidity of multiple sclerosis (MS), with currently no clear guidelines for treatment. Low-field magnetic stimulation (LFMS), a novel non-invasive neuromodulation intervention, has been previously demonstrated to rapidly alleviate mood disorders. The aim of the present study was to investigate the effects of LFMS on depression-like behaviors and demyelination in a well-established mouse model of MS. C57BL/6 female mice were fed a 0.2% cuprizone (CPZ) diet for 3 or 6 weeks to induce acute demyelination. During this time, the mice were treated with either sham or LFMS for 20 min/day, 5 days/week. After 3 or 6 weeks of treatment, behavior was assessed with the open field task, Y-maze and the forced swim test. The prefrontal cortex and hippocampus were then collected to perform immunohistochemistry and western blot analysis to verify myelination status. The CPZ diet did not cause significant locomotor deficits; however, working memory, measured using the Y maze, depression-like behavior and adaptive learning, assayed using the forced swim test, were significantly impaired in these animals. LFMS treatment demonstrated a significant antidepressant-like effect and markedly attenuated the CPZ-induced demyelination in the prefrontal cortex after 3- and 6-weeks of treatment, as observed by changes in myelin basic protein immunostaining and western blot analysis. Therefore, the results of the present study indicated that LFMS may be a promising therapy for demyelinating diseases due to the improvement of depressive symptoms via regulation of myelination in cortical areas.

A Progressive Loss of phosphoSer138-Profilin Aligns with Symptomatic Course in the R6/2 Mouse Model of Huntington's Disease: Possible Sex-Dependent Signaling.

The R6/2 transgenic mouse model of Huntington's disease (HD) carries several copies of exon1 of the huntingtin gene that contains a highly pathogenic 120 CAG-repeat expansion. We used kinome analysis to screen for kinase activity patterns in neural tissues from wildtype (WT) and R6/2 mice at a pre-symptomatic (e.g., embryonic) and symptomatic (e.g., between 3 and 10 weeks postnatal) time points. We identified changes in several signaling cascades, for example, the Akt/FoxO3/CDK2, mTOR/ULK1, and RAF/MEK/CREB pathways. We also identified the Rho-Rac GTPase cascade that contributes to cytoskeleton organization through modulation of the actin-binding proteins, cofilin and profilin. Immunoblotting revealed higher levels of phosphoSer138-profilin in embryonic R6/2 mouse samples (cf. WT mice) that diminish progressively and significantly over the postnatal, symptomatic course of the disease. We detected sex- and genotype-dependent patterns in the phosphorylation of actin-regulators such a ROCK2, PAK, LIMK1, cofilin, and SSH1L, yet none of these aligned consistently with the changing levels of phosphoSer138-profilin. This could be reflecting an imbalance in the sequential influences these regulators are known to exert on actin signaling. The translational potential of these observations was inferred from preliminary observations of changes in LIMK-cofilin signaling and loss of neurite integrity in neural stem cells derived from an HD patient (versus a healthy control). Our observations suggest that a pre-symptomatic, neurodevelopmental onset of change in the phosphorylation of Ser138-profilin, potentially downstream of distinct signaling changes in male and female mice, could be contributing to cytoskeletal phenotypes in the R6/2 mouse model of HD pathology.

Low field magnetic stimulation promotes myelin repair and cognitive recovery in chronic cuprizone mouse model.

BACKGROUND: Multiple sclerosis (MS) is an inflammatory demyelinating disease featured with neuroinflammation, demyelination, and the loss of oligodendrocytes. Cognitive impairment and depression are common neuropsychiatric symptoms in MS that are poorly managed with the present interventions. OBJECTIVE: This study aimed to investigate the effects of low field magnetic stimulation (LFMS), a novel non-invasive neuromodulation technology, on cognitive impairment and depressive symptoms associated with MS using a mouse model of demyelination. METHODS: C57BL female mice were fed with a 0.2% cuprizone diet for 12 weeks to induce a chronic demyelinating model followed by 4 weeks of cuprizone withdrawal with either sham or LFMS treatment. RESULTS: Improved cognition and depression-like behaviour and restored weight gain were observed in mice with LFMS treatment. Immunohistochemical and immunoblotting data showed enhanced myelin basic protein (MBP) and myelin oligodendrocyte glycoprotein expressions (MOG) in the prefrontal cortex of mice with LFMS treatment, supporting that myelin repair was promoted. LFMS also increased the protein expression of mature oligodendrocyte biomarker glutathione-S-transferase (GST-π). In addition, expression of TGF-ß and associated receptors were elevated with LFMS treatment, implicating this pathway in the response. CONCLUSION: Results from the present study revealed LFMS to have neuroprotective effects, suggesting that LFMS has potential therapeutic value for treating cognitive impairment and depression related to demyelination disorders.

Low-Field Magnetic Stimulation Accelerates the Differentiation of Oligodendrocyte Precursor Cells via Non-canonical TGF-ß Signaling Pathways.

Demyelination and oligodendrocyte loss are characteristic changes in demyelinating disorders. Low-field magnetic stimulation (LFMS) is a novel transcranial neuromodulation technology that has shown promising therapeutic potential for a variety of neuropsychiatric conditions. The cellular and molecular mechanisms of magnetic stimulation remain unclear. Previous studies mainly focused on the effects of magnetic stimulation on neuronal cells. Here we aimed to examine the effects of a gamma frequency LFMS on the glial progenitor cells. We used rat central glia-4 (CG4) cell line as an in vitro model. CG4 is a bipotential glial progenitor cell line that can differentiate into either oligodendrocyte or type 2-astrocyte. The cells cultured in a defined differentiation media were exposed to a 40-Hz LFMS 20 min daily for five consecutive days. We found that LFMS transiently elevated the level of TGF-ß1 in the culture media in the first 24 h after the treatment. In correlation with the TGF-ß1 levels, the percentage of cells possessing complex branches and expressing the late oligodendrocyte progenitor marker O4 was increased, indicating the accelerated differentiation of CG4 cells towards oligodendrocyte in LFMS-treated cultures. LFMS increased phosphorylation of Akt and Erk1/2 proteins, but not SMAD2/3. TGF-ß1 receptor I specific inhibitor LY 364947 partially suppressed the effects of LFMS on differentiation and on levels of pAkt and pErk1/2, indicating that LFMS enhances the differentiation of oligodendrocyte progenitor cells via activation of non-canonical TGF-ß-Akt and TGF-ß-Erk1/2 pathways but not the canonical SMAD pathway. The data from this study reveal a novel mechanism of magnetic stimulation as a potential therapy for demyelination disorders.

Cannabinoids as an Emerging Therapy for Posttraumatic Stress Disorder and Substance Use Disorders.

Posttraumatic Stress Disorder (PTSD) is a leading psychiatric disorder that mainly affects military and veteran populations but can occur in anyone affected by trauma. PTSD treatment remains difficult for physicians because most patients with PTSD do not respond to current pharmacological treatment. Psychotherapy is effective, but time consuming and expensive. Substance use disorder is often concurrent with PTSD, which leads to a significant challenge for PTSD treatment. Cannabis has recently received widespread attention for the potential to help many patient populations. Cannabis has been reported as a coping tool for patients with PTSD and preliminary legalization data indicate Cannabis use may reduce the use of more harmful drugs, such as opioids. Rigorous clinical studies of Cannabis could establish whether Cannabis-based medicines can be integrated into treatment regimens for both PTSD and substance use disorder patients.

Minocycline Ameliorates Depressive-Like Behavior and Demyelination Induced by Transient Global Cerebral Ischemia by Inhibiting Microglial Activation.

Global cerebral ischemia (GCI) commonly occurs in the elderly. Subcortical white matter lesions and oligodendrocyte (OLG) loss caused by cerebral ischemia have been implicated in the development of post-ischemic depression and cognitive impairment. OLGs are necessary for axonal myelination; the disrupted differentiation of OLG progenitor cells (OPCs) is associated with impaired remyelination. Evidence has indicated that increased levels of inflammatory cytokines released from activated microglia induce depression-like behaviors by affecting neurotransmitter pathways, but the mechanisms remain elusive. We explored the potential mechanisms that link microglia activation with GCI-induced depression and cognitive dysfunction by studying effects of minocycline on white matter damage, cytokine levels, and the monoaminergic neurotransmitters. An acute GCI animal model was generated through bilateral common carotid artery occlusion to induce ischemic inflammation and subcortical white matter damage. Minocycline, an inhibitor of microglia activation, was intraperitoneally administrated immediately after surgery and continued daily for additional six days. Minocycline shortened the immobile duration in tail suspension test and forced swimming test, while no improvement was found in Morris water maze test. The plasma levels of IL-1ß, IL-6, TNF-α, HMGB1, and netrin-1 were significantly reduced with the treatment of minocycline. Minocycline treatment substantially reversed demyelination in corpus callosum and hippocampus, alleviated hippocampal microglia activation, and promoted OPCs maturation, while no effect was found on hippocampal neurodegeneration. Besides, the content of dopamine (DA) in the hippocampus was upregulated by minocycline treatment after GCI. Collectively, our data demonstrated that minocycline exerts an anti-depressant effect by inhibiting microglia activation, promoting OPCs maturation and remyelination. Increased DA in hippocampus may also play a role in ameliorating depressive behavior with minocycline treatment.

Venlafaxine Improves the Cognitive Impairment and Depression-Like Behaviors in a Cuprizone Mouse Model by Alleviating Demyelination and Neuroinflammation in the Brain.

Growing evidence has implicated that myelin deficits and neuroinflammation are the coexisted pathological features that contribute to the mood swing and cognitive decline in major depressive disorder (MDD) and multiple sclerosis (MS). Therefore, attenuation of neuroinflammation and reduction of demyelination became newly emerging treatment strategies for the mood and cognitive symptoms. Antidepressant venlafaxine has been used in depression and anxiety through its multiple neuroprotective effects. However, it is unclear whether venlafaxine can improve myelin integrity and alter inflammation status in the brain. By using a well-established cuprizone-induced acute mouse model of demyelination, we investigated the protective effects of venlafaxine on these facets. The cuprizone-fed animals exhibited cognitive impairment and mood disturbances together with myelin loss and prominent neuroinflammation in the brain. Our present study showed that a high dose of venlafaxine alleviated the loss of myelin and oligodendrocytes (OLs), mitigated depression-like behaviors, and improved cognitive function in cuprizone-fed animals. Data from the present study also showed that venlafaxine reduced microglia-mediated inflammation in the brains of cuprizone-fed animals. These findings suggest that venlafaxine may exert its therapeutic effects via facilitating myelin integrity and controlling neuroinflammation, which may provide extra benefits to MS patients with depression and anxiety beyond the symptom management.

Age- and sex-dependent profiles of APP fragments and key secretases align with changes in despair-like behavior and cognition in young APPSwe/Ind mice.

Biological sex exerts distinct influences on brain levels of the ß-amyloid (Aß) peptide in both clinical depression and Alzheimer disease (AD), yet studies in animal models focus primarily on males. We examined behavioral 'despair'/depression (using the tail-suspension test) and memory (using the novel object recognition task) in J20 (hAPPSwe/Ind) mice. Three month-old male (but not female) J20 mice exhibited less despair-like behavior, but more evidence of cognitive deficits. In young J20 mice, only soluble Aß peptides -primarily Aß(1-40)- were detected. There was no evidence of an effect on despair-like behavior in the six month-old J20 mice, although cognitive deficits were now evident in both sexes, and coincided with a greater proportion of the neurotoxic Aß(1-42) species (in soluble as well as insoluble fractions). This age-dependent shift in Aß peptide profile coincided with reduced expression of glycosylated species of ADAM-10 (α-secretase) and BACE1 (ß-secretase), and an increased co-immunoprecipitation of presenilin-1 with nicastrin (components of the γ-secretase complex). Sex-dependent changes in depression-related monoaminergic, e.g. serotonin and dopamine (but not noradrenaline), systems were evident already in young J20 mice. It is critical to acknowledge that sex-dependent APP-related phenotypes might differentially influence modifiable depression-related monoaminergic signalling at some of the earliest pathological stages of clinical AD.

Perampanel but Not Amantadine Prevents Behavioral Alterations and Epileptogenesis in Pilocarpine Rat Model of Status Epilepticus.

Pilocarpine-induced status epilepticus (SE), which results in the development of spontaneous recurrent seizures (SRSs) activates glutamatergic receptors that contribute to seizure sustenance and neuronal cell death. In the current study, we evaluate whether the exposure to perampanel, an α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor blocker, or amantadine, a N-methyl-D-aspartic acid (NMDA) receptor blocker would reduce the SE-induced long-term consequences. SE was induced in adult male Sprague Dawley rats with pilocarpine. Perampanel or amantadine was injected 10 or 60 min after SE onset. The efficacy of either, in overcoming pilocarpine-induced SE was assessed using electroencephalogram (EEG) recordings. In addition, alterations in cognitive function, development of spontaneous recurrent seizures (SRSs), and hippocampal damage that are generally encountered after SE were also assessed at 72 h and 5 weeks after the induction of SE. Our results indicate that both early and late treatment with perampanel but not amantadine significantly reduced seizure activity. Furthermore, perampanel but not amantadine, reversed the memory deficits in Y-maze and novel object recognition (NOR) tests and retarded the appearance of SRSs. Moreover, perampanel treatment led to reduced SE-induced caspase-3 activation in the hippocampal lysates. Taken together, the data obtained from the study reveals that blocking AMPA receptors by perampanel can modify SE-induced long-term consequences. Our results may provide a proof of principle for the potential therapeutic application of perampanel in clinical use for status epilepticus in future.

Humanin attenuates Alzheimer-like cognitive deficits and pathological changes induced by amyloid ß-peptide in rats.

Amyloid ß-peptide (Aß) has been implicated as a key molecule in the neurodegenerative cascades of Alzheimer's disease (AD). Humanin (HN) is a secretory peptide that inhibits the neurotoxicity of Aß. However, the mechanism(s) by which HN exerts its neuroprotection against Aß-induced AD-like pathological changes and memory deficits are yet to be completely defined. In the present study, we provided evidence that treatment of rats with HN increases the number of dendritic branches and the density of dendritic spines, and upregulates pre- and post-synaptic protein levels; these effects lead to enhanced long-term potentiation and amelioration of the memory deficits induced by Aß(1-42). HN also attenuated Aß(1-42)-induced tau hyperphosphorylation, apparently by inhibiting the phosphorylation of Tyr307 on the inhibitory protein phosphatase-2A (PP2A) catalytic subunit and thereby activating PP2A. HN also inhibited apoptosis and reduced the oxidative stress induced by Aß(1-42). These findings provide novel mechanisms of action for the ability of HN to protect against Aß(1-42)-induced AD-like pathological changes and memory deficits.

Aspartic acid substitutions in monoamine oxidase-A reveal both catalytic-dependent and -independent influences on cell viability and proliferation.

Post-translational influences could underlie the ambiguous roles of monoamine oxidase-A (MAO-A) in pathologies such as depression, cancer and Alzheimer disease. In support of this, we recently demonstrated that the Ca²âº-sensitive component of MAO-A catalytic activity is inhibited by a pro-survival p38 (MAPK)-dependent mechanism. We substituted three aspartic acid (D) residues in human MAO-A that reside in putative Ca²âº-binding motifs and overexpressed the individual proteins in the human HEK293 cell line. We assayed the overexpressed proteins for catalytic activity and for their influence on cell viability (using MTT conversion and trypan blue exclusion) and proliferation/DNA synthesis [using bromodeoxyuridine (BrdU) incorporation]. Innate MAO-A catalytic activity (and the capacity for generating hydrogen peroxide) was unaffected by the D61A substitution, but inhibited moderately or completely by the D248A and D328G substitutions, respectively. The Ca²âº-sensitive activities of wild-type and D248A MAO-A proteins were enhanced by treatment with the selective p38(MAPK) inhibitor, SB203580, but was completely abrogated by the D61A substitution. Monoamine oxidase-A(D61A) was toxic to cells and exerted no effect on cell proliferation, while MAO-A(D248A) was generally comparable to wild-type MAO-A. As expected, the catalytic-dead MAO-A(D328G) was not cytotoxic, but unexpectedly enhanced both MTT conversion and BrdU staining. Variant-dependent changes in Bax and Bcl-2/Bcl-XL protein expression were observed. A different pattern of effects in N2-a cells suggests cell line-dependent roles for MAO-A. A catalytic-dependent mechanism influences MAO-A-mediated cytotoxicity, whereas a catalytic-independent mechanism contributes to proliferation. Context-dependent inputs by either mechanism could underlie the ambiguous pathological contributions of MAO-A.

Monoamine oxidase-A physically interacts with presenilin-1(M146V) in the mouse cortex.

The concentration of presenilin-1 (PS-1) protein at the mitochondrial-associated aspect of the endoplasmic reticulum supports the potential for a mitochondrial influence of PS-1. Given that carriers of certain Alzheimer's disease (AD)-related PS-1 variants are predisposed to clinical depression and that depression has been historically associated with the mitochondrial enzyme, monoamine oxidase-A (MAO-A), we investigated cortical MAO-A function in the AD-related PS-1(M146V) knock-in mouse. The MAO-A system was clearly altered in the PS-1(M146V) mouse as revealed by (a) a mismatch between MAO-A protein expression and MAO-A activity; (b) changes in MAO-A-mediated monoaminergic neurotransmitter metabolism; (c) changes in non-cognitive behavior following treatment with the irreversible MAO-A inhibitor clorgyline; and (d) an increase in the potency of clorgyline in these same mice. We next investigated whether PS-1(M146V) could be influencing MAO-A directly. We observed (a) an enhanced MAO-A activity in necropsied PS-1(M146V) mouse cortical extracts incubated with DAPT (a PS-1 substrate-competitor); (b) the proximity of PS-1 with MAO-A and mitochondrial markers in cortical sections and in primary cortical neurons; (c) the co-segregation and co-immunoprecipitation of PS-1 and MAO-A within the mitochondrial fraction; and (d) the co-immunoprecipitation of overexpressed PS-1(M146V) and MAO-A proteins from N2a lysates. The PS-1(ΔEx9) and PS-1(D257A) variants, known to have low substrate-binding capacity, co-immunoprecipitated weakly with MAO-A. These combined data support a physical interaction between PS-1 and MAO-A that could influence MAO-A activity and contribute to the monoaminergic disruptions common to disorders as seemingly diverse as depression and AD.

Chronic nicotine administration impairs activation of cyclic AMP-response element binding protein and survival of newborn cells in the dentate gyrus.

Chronic intake of nicotine can impair hippocampal plasticity, but the underlying mechanism is poorly understood. Here, we demonstrate that chronic nicotine administration in adult rats inactivates the cyclic AMP-response element binding protein (CREB), a transcription factor that regulates neurogenesis and other plasticity-related processes necessary for learning and memory. Consequently, we showed that impaired CREB signaling is associated with a significant decline in the production of new neurons in the dentate gyrus. Combining retrovirus labeling with gene expression approaches, we found that chronic nicotine administration reduces the number of adult-generated granule neurons by decreasing the survival of newborn cells but not the proliferation of progenitor cells. Additionally, we found that retroviral-mediated expression of a constitutively active CREB in the dentate gyrus rescues survival of newborn cells and reverses the nicotine-induced decline in the number of mature granule neurons. Prolonged nicotine exposure also compromises CREB activation and reduces the viability of progenitor cells in vitro, thereby suggesting that nicotine may exert its adverse effects directly on immature cells in vivo. Taken together, these data demonstrate that inhibition of CREB activation is responsible for the nicotine-induced impairment of hippocampal plasticity.

Folate/vitamin-B12 prevents chronic hyperhomocysteinemia-induced tau hyperphosphorylation and memory deficits in aged rats.

Hyperhomocysteinemia is associated with an increased risk of Alzheimer's disease (AD). Our previous work has demonstrated that combined folate and vitamin B12 (vit-B12) supplementation prevents tau hyperphosphorylation and memory deficits induced by acute administration of homocysteine in young rats. Here, we further investigated whether folate/vit-B12 supplementation is also effective in aged rats with a chronically high level of homocysteine. 18-month-old rats were injected with homocysteine via the vena caudalis with or without a concurrent folate/vit-B12 supplementation for 28 weeks. We found that hyperhomocysteinemia induced tau hyperphosphorylation and accumulation in hippocampus and cortex. Concurrent signaling changes included the activation of glycogen synthase kinases-3ß, cyclin-dependent kinase-5, c-Jun N-terminal kinase, extracellular signal-regulated kinase, and p38MAPK, and inhibition of protein phosphatase 2A. Although the ability to learn was not affected, the aged rats exhibited significant memory deficits. Folate/vit-B12 supplementation attenuated these biochemical and behavioral correlates. These data demonstrate that folate/vit-B12 supplementation is also effective in a chronic hyperhomocysteinemia model in reversing the AD-like tau pathologies and memory deficits.

Notch activation enhances the microglia-mediated inflammatory response associated with focal cerebral ischemia.

BACKGROUND AND PURPOSE: Activation of Notch worsens ischemic brain damage as antisense knockdown or pharmacological inhibition of the Notch pathway reduces the infarct size and improves the functional outcome in a mouse model of stroke. We sought to determine whether Notch activation contributes to postischemic inflammation by directly modulating the microglial innate response. METHODS: The microglial response and the attendant inflammatory reaction were evaluated in Notch1 antisense transgenic (Tg) and in nontransgenic (non-Tg) mice subjected to middle cerebral artery occlusion with or without treatment with a γ-secretase inhibitor (GSI). To investigate the impact of Notch on microglial effector functions, primary mouse microglia and murine BV-2 microglial cell line were exposed to oxygen glucose deprivation or lipopolysaccharide in the presence or absence of GSI. Immunofluorescence labeling, Western blotting, and reverse-transcription polymerase chain reaction were performed to measure microglial activation and production of inflammatory cytokines. The nuclear translocation of nuclear factor-κB in microglia was assessed by immunohistochemistry. The neurotoxic potential of microglia was determined in cocultures. RESULTS: Notch1 antisense mice exhibit significantly lower numbers of activated microglia and reduced proinflammatory cytokine expression in the ipsilateral ischemic cortices compared to non-Tg mice. Microglial activation also was attenuated in Notch1 antisense cultures and in non-Tg cultures treated with GSI. GSI significantly reduced nuclear factor-κB activation and expression of proinflammatory mediators and markedly attenuated the neurotoxic activity of microglia in cocultures. CONCLUSIONS: These findings establish a role for Notch signaling in modulating the microglia innate response and suggest that inhibition of Notch might represent a complementary therapeutic approach to prevent reactive gliosis in stroke and neuroinflammation-related degenerative disorders.

Alzheimer disease-related presenilin-1 variants exert distinct effects on monoamine oxidase-A activity in vitro.

Monoamine oxidase-A (MAO-A) has been associated with both depression and Alzheimer disease (AD). Recently, carriers of AD-related presenilin-1 (PS-1) alleles have been found to be at higher risk for developing clinical depression. We chose to examine whether PS-1 could influence MAO-A function in vitro. Overexpression of selected AD-related PS-1 variants (wildtype, Y115H, ΔEx9 and M146V) in mouse hippocampal HT-22 cells affects MAO-A catalytic activity in a variant-specific manner. The ability of the PS-1 substrate-competitor DAPT to induce MAO-A activity in cells expressing either PS-1 wildtype or PS-1(M146V) suggests the potential for a direct influence of PS-1 on MAO-A function. In support of this, we were able to co-immunoprecipitate MAO-A with FLAG-tagged PS-1 wildtype and M146V proteins. This potential for a direct protein-protein interaction between PS-1 and MAO-A is not specific for HT-22 cells as we were also able to co-immunoprecipitate MAO-A with FLAG-PS-1 variants in N2a mouse neuroblastoma cells and in HEK293 human embryonic kidney cells. Finally, we demonstrate that the two PS-1 variants reported to be associated with an increased incidence of clinical depression [e.g., A431E and L235V] both induce MAO-A activity in HT-22 cells. A direct influence of PS-1 variants on MAO-A function could provide an explanation for the changes in monoaminergic tone observed in several neurodegenerative processes including AD. The ability to induce MAO-A catalytic activity with a PS-1/γ-secretase inhibitor should also be considered when designing secretase inhibitor-based therapeutics.

Evidence for altered Numb isoform levels in Alzheimer's disease patients and a triple transgenic mouse model.

The cell fate determinant Numb exists in four alternatively spliced variants that differ in the length of their PTB (phosphotyrosine-binding domain, either lacking or containing an 11 amino acid insertion) and PRR (proline-rich region, either lacking or containing a 48 amino acid insertion). We previously reported that Numb switches from isoforms containing the PTB insertion to isoforms lacking this insertion in neural cultures subjected to stress induced by trophic factor withdrawal. The switch in Numb isoforms enhances the generation of amyloid-ß peptide (Aß), the principle component of senile plaques in Alzheimer's disease (AD). Here we examine the expression of the Numb isoforms in brains from AD patients and triple transgenic (3xTg) AD mice. We found that levels of the Numb isoforms lacking the PTB insertion are significantly elevated in the parietal cortex but not in the cerebellum of AD patients when compared to control subjects. Levels of Numb isoforms lacking the PTB insertion were also elevated in the cortex but not cerebellum of 12 month-old 3xTg AD mice with Aß deposits compared to younger 3xTg-AD mice and to non-transgenic mice. Exposure of cultured neurons to Aß resulted in an increase in the levels of Numb isoforms lacking the PTB domain, consistent with a role for Aß in the aberrant expression of Numb in vulnerable brain regions of AD patients and mice. Collectively, the data show that altered expression of Numb isoforms in vulnerable neurons occurs during AD pathogenesis and suggest a role for Numb in the disease process.

Compromised respiratory adaptation and thermoregulation in aging and age-related diseases.

Mitochondrial dysfunction and reactive oxygen species (ROS) production are at the heart of the aging process and are thought to underpin age-related diseases. Mitochondria are not only the primary energy-generating system but also the dominant cellular source of metabolically derived ROS. Recent studies unravel the existence of mechanisms that serve to modulate the balance between energy metabolism and ROS production. Among these is the regulation of proton conductance across the inner mitochondrial membrane that affects the efficiency of respiration and heat production. The field of mitochondrial respiration research has provided important insight into the role of altered energy balance in obesity and diabetes. The notion that respiration and oxidative capacity are mechanistically linked is making significant headway into the field of aging and age-related diseases. Here we review the regulation of cellular energy and ROS balance in biological systems and survey some of the recent relevant studies that suggest that respiratory adaptation and thermodynamics are important in aging and age-related diseases.

Stress-induced switch in Numb isoforms enhances Notch-dependent expression of subtype-specific transient receptor potential channel.

The Notch signaling pathway plays an essential role in the regulation of cell specification by controlling differentiation, proliferation, and apoptosis. Numb is an intrinsic regulator of the Notch pathway and exists in four alternative splice variants that differ in the length of their phosphotyrosine-binding domain (PTB) and proline-rich region domains. The physiological relevance of the existence of the Numb splice variants and their exact regulation are still poorly understood. We previously reported that Numb switches from isoforms containing the insertion in PTB to isoforms lacking this insertion in neuronal cells subjected to trophic factor withdrawal (TFW). The functional relevance of the TFW-induced switch in Numb isoforms is not known. Here we provide evidence that the TFW-induced switch in Numb isoforms regulates Notch signaling strength and Notch target gene expression. PC12 cells stably overexpressing Numb isoforms lacking the PTB insertion exhibited higher basal Notch activity and Notch-dependent transcription of the transient receptor potential channel 6 (TRPC6) when compared with those overexpressing Numb isoforms with the PTB insertion. The differential regulation of TRPC6 expression is correlated with perturbed calcium signaling and increased neuronal vulnerability to TFW-induced death. Pharmacological inhibition of the Notch pathway or knockdown of TRPC6 function ameliorates the adverse effects caused by the TFW-induced switch in Numb isoforms. Taken together, our results indicate that Notch and Numb interaction may influence the sensitivity of neuronal cells to injurious stimuli by modulating calcium-dependent apoptotic signaling cascades.