Cyclin Y regulates spatial learning and memory flexibility through distinct control of the actin pathway.

Spatial learning and memory flexibility are known to require long-term potentiation (LTP) and long-term depression (LTD), respectively, on a cellular basis. We previously showed that cyclin Y (CCNY), a synapse-remodeling cyclin, is a novel actin-binding protein and an inhibitory regulator of functional and structural LTP in vitro. In this study, we report that Ccny knockout (KO) mice exhibit enhanced LTP and weak LTD at Schaffer collateral-CA1 synapses in the hippocampus. In accordance with enhanced LTP, Ccny KO mice showed improved spatial learning and memory. However, although previous studies reported that normal LTD is necessary for memory flexibility, Ccny KO mice intriguingly showed improved memory flexibility, suggesting that weak LTD could exert memory flexibility when combined with enhanced LTP. At the molecular level, CCNY modulated spatial learning and memory flexibility by distinctively affecting the cofilin-actin signaling pathway in the hippocampus. Specifically, CCNY inhibited cofilin activation by original learning, but reversed such inhibition by reversal learning. Furthermore, viral-mediated overexpression of a phosphomimetic cofilin-S3E in hippocampal CA1 regions enhanced LTP, weakened LTD, and improved spatial learning and memory flexibility, thus mirroring the phenotype of Ccny KO mice. In contrast, the overexpression of a non-phosphorylatable cofilin-S3A in hippocampal CA1 regions of Ccny KO mice reversed the synaptic plasticity, spatial learning, and memory flexibility phenotypes observed in Ccny KO mice. Altogether, our findings demonstrate that LTP and LTD cooperatively regulate memory flexibility. Moreover, CCNY suppresses LTP while facilitating LTD in the hippocampus and negatively regulates spatial learning and memory flexibility through the control of cofilin-actin signaling, proposing CCNY as a learning regulator modulating both memorizing and forgetting processes.

Loss of ABCA8B decreases myelination by reducing oligodendrocyte precursor cells in mice.

The myelin sheath, which is wrapped around axons, is a lipid-enriched structure produced by mature oligodendrocytes. Disruption of the myelin sheath is observed in several neurological diseases, such as multiple sclerosis. A crucial component of myelin is sphingomyelin, levels of which can be increased by ABCA8, a member of the ATP-binding cassette transporter family. ABCA8 is highly expressed in the cerebellum, specifically in oligodendroglia. However, whether ABCA8 plays a role in myelination and mechanisms that would underlie this role remain unknown. Here, we found that the absence of Abca8b, a mouse ortholog of ABCA8, led to decreased numbers of cerebellar oligodendrocyte precursor cells (OPCs) and mature oligodendrocytes in mice. We show that in oligodendrocytes, ABCA8 interacts with chondroitin sulfate proteoglycan 4 (CSPG4), a molecule essential for OPC proliferation, migration, and myelination. In the absence of Abca8b, localization of CSPG4 to the plasma membrane was decreased, contributing to reduced cerebellar CSPG4 expression. Cerebellar CSPG4+ OPCs were also diminished, leading to decreased mature myelinating oligodendrocyte numbers and cerebellar myelination levels in Abca8b-/- mice. In addition, electron microscopy analyses showed that the number of nonmyelinated cerebellar axons was increased, whereas cerebellar myelin thickness (g-ratio), myelin sheath periodicity, and axonal diameter were all decreased, indicative of disordered myelin ultrastructure. In line with disrupted cerebellar myelination, Abca8b-/- mice showed lower cerebellar conduction velocity and disturbed locomotion. In summary, ABCA8 modulates cerebellar myelination, in part through functional regulation of the ABCA8-interacting protein CSPG4. Our findings suggest that ABCA8 disruption may contribute to the pathophysiology of myelin disorders.

AIM2 inflammasome mediates hallmark neuropathological alterations and cognitive impairment in a mouse model of vascular dementia.

Chronic cerebral hypoperfusion is associated with vascular dementia (VaD). Cerebral hypoperfusion may initiate complex molecular and cellular inflammatory pathways that contribute to long-term cognitive impairment and memory loss. Here we used a bilateral common carotid artery stenosis (BCAS) mouse model of VaD to investigate its effect on the innate immune response-particularly the inflammasome signaling pathway. Comprehensive analyses revealed that chronic cerebral hypoperfusion induces a complex temporal expression and activation of inflammasome components and their downstream products (IL-1ß and IL-18) in different brain regions, and promotes activation of apoptotic and pyroptotic cell death pathways. Polarized glial-cell activation, white-matter lesion formation and hippocampal neuronal loss also occurred in a spatiotemporal manner. Moreover, in AIM2 knockout mice we observed attenuated inflammasome-mediated production of proinflammatory cytokines, apoptosis, and pyroptosis, as well as resistance to chronic microglial activation, myelin breakdown, hippocampal neuronal loss, and behavioral and cognitive deficits following BCAS. Hence, we have demonstrated that activation of the AIM2 inflammasome substantially contributes to the pathophysiology of chronic cerebral hypoperfusion-induced brain injury and may therefore represent a promising therapeutic target for attenuating cognitive impairment in VaD.

Site-specific impairment of perivascular adipose tissue on advanced atherosclerotic plaques using multimodal nonlinear optical imaging.

Perivascular adipose tissue (PVAT), as a mechanical support, has been reported to systemically regulate vascular physiology by secreting adipokines and cytokines. How PVAT spatially and locally changes as atherosclerosis progresses is not known, however. We aimed to reveal the molecular changes in PVAT in advanced atherosclerosis based on multimodal nonlinear optical (MNLO) imaging. First, using an atherogenic apolipoprotein E knockout mouse model, we precisely assessed the browning level of thoracic PVAT via a correlative analysis between the size and number of lipid droplets (LDs) of label-free MNLO images. We also biochemically demonstrated the increased level of brown fat markers in the PVAT of atherosclerosis. In the initial stage of atherosclerosis, the PVAT showed a highly activated brown fat feature due to the increased energy expenditure; however, in the advanced stage, only the PVAT in the regions of the atherosclerotic plaques, not that in the nonplaque regions, showed site-specific changes. We found that p-smad2/3 and TGF-ß signaling enhanced the increase in collagen to penetrate the PVAT and the agglomeration of LDs only at the sites of atherosclerotic plaques. Moreover, atherosclerotic thoracic PVAT (tPVAT) was an increased inflammatory response. Taken together, our findings show that PVAT changes differentially from the initial stages to advanced stages of atherosclerosis and undergoes spatial impairment focused on atherosclerotic plaques. Our study may provide insight into the local control of PVAT as a therapeutic target.

NRF2/ARE pathway negatively regulates BACE1 expression and ameliorates cognitive deficits in mouse Alzheimer's models.

BACE1 is the rate-limiting enzyme for amyloid-ß peptides (Aß) generation, a key event in the pathogenesis of Alzheimer's disease (AD). By an unknown mechanism, levels of BACE1 and a BACE1 mRNA-stabilizing antisense RNA (BACE1-AS) are elevated in the brains of AD patients, implicating that dysregulation of BACE1 expression plays an important role in AD pathogenesis. We found that nuclear factor erythroid-derived 2-related factor 2 (NRF2/NFE2L2) represses the expression of BACE1 and BACE1-AS through binding to antioxidant response elements (AREs) in their promoters of mouse and human. NRF2-mediated inhibition of BACE1 and BACE1-AS expression is independent of redox regulation. NRF2 activation decreases production of BACE1 and BACE1-AS transcripts and Aß production and ameliorates cognitive deficits in animal models of AD. Depletion of NRF2 increases BACE1 and BACE1-AS expression and Aß production and worsens cognitive deficits. Our findings suggest that activation of NRF2 can prevent a key early pathogenic process in AD.

Length difference of multi-walled carbon nanotubes generates differential cytotoxic responses.

Carbon nanotubes have recently been rated as an effective biomaterial owing to their functionalization ability. However, the safety of multi-walled carbon nanotubes (MWCNTs) has yet to be clearly understood. To investigate how cells differentially react to minor geometric differences, we prepared well-dispersed and stable long and short MWCNTs showing an approximately 100-nm length difference in an in vitro system. Through an optimal combination of bovine serum albumin (BSA) and fetal bovine serum (FBS) biosurfactants and ultrasonication, we first confirmed that the MWCNTs were maintained without aggregation throughout the experiments. Internalized MWCNTs in human coronary artery smooth muscle cells were then quantified in a label-free manner using coherent anti-Stokes Raman scattering, followed by an analysis of their localization via two-photon excitation fluorescence. Intracellular MWCNTs were found to primarily localize in mitochondria with abnormal morphologies. Mitochondrial dysfunction, which was found to result from early stages of oxidative stress that consequently lead to cell death, was then proved via decreasing mitochondrial membrane potentials, with short MWCNTs showing significantly greater cytotoxicity than long MWCNTs. Our results suggest that even small length differences of MWCNTs may lead to differential responses in cells.

Molecule-Resolved Visualization of Particulate Matter on Human Skin Using Multimodal Nonlinear Optical Imaging.

Precise measurement of particulate matter (PM) on skin is important for managing and preventing PM-related skin diseases. This study aims to directly visualize the deposition and penetration of PM into human skin using a multimodal nonlinear optical (MNLO) imaging system. We successfully obtained PM particle signals by merging two different sources, C-C vibrational frequency and autofluorescence, while simultaneously visualizing the anatomical features of the skin via keratin, collagen, and elastin. As a result, we found morphologically dependent PM deposition, as well as increased deposition following disruption of the skin barrier via tape-stripping. Furthermore, PM penetrated more and deeper into the skin with an increase in the number of tape-strippings, causing a significant increase in the secretion of pro-inflammatory cytokines. Our results suggest that MNLO imaging could be a useful technique for visualizing and quantifying the spatial distribution of PM in ex vivo human skin tissues.

Transcriptome analysis reveals intermittent fasting-induced genetic changes in ischemic stroke.

Genetic changes due to dietary intervention in the form of either calorie restriction (CR) or intermittent fasting (IF) are not reported in detail until now. However, it is well established that both CR and IF extend the lifespan and protect against neurodegenerative diseases and stroke. The current research aims were first to describe the transcriptomic changes in brains of IF mice and, second, to determine whether IF induces extensive transcriptomic changes following ischemic stroke to protect the brain from injury. Mice were randomly assigned to ad libitum feeding (AL), 12 (IF12) or 16 (IF16) h daily fasting. Each diet group was then subjected to sham surgery or middle cerebral artery occlusion and consecutive reperfusion. Mid-coronal sections of ipsilateral cerebral tissue were harvested at the end of the 1 h ischemic period or at 3, 12, 24 or 72 h of reperfusion, and genome-wide mRNA expression was quantified by RNA sequencing. The cerebral transcriptome of mice in AL group exhibited robust, sustained up-regulation of detrimental genetic pathways under ischemic stroke, but activation of these pathways was suppressed in IF16 group. Interestingly, the cerebral transcriptome of AL mice was largely unchanged during the 1 h of ischemia, whereas mice in IF16 group exhibited extensive up-regulation of genetic pathways involved in neuroplasticity and down-regulation of protein synthesis. Our data provide a genetic molecular framework for understanding how IF protects brain cells against damage caused by ischemic stroke, and reveal cellular signaling and bioenergetic pathways to target in the development of clinical interventions.

TOM1 Regulates Neuronal Accumulation of Amyloid-ß Oligomers by FcγRIIb2 Variant in Alzheimer's Disease.

Emerging evidences suggest that intraneuronal Aß correlates with the onset of Alzheimer's disease (AD) and highly contributes to neurodegeneration. However, critical mediator responsible for Aß uptake in AD pathology needs to be clarified. Here, we report that FcγRIIb2, a variant of Fcγ-receptor IIb (FcγRIIb), functions in neuronal uptake of pathogenic Aß. Cellular accumulation of oligomeric Aß1-42, not monomeric Aß1-42 or oligomeric Aß1-40, was blocked by Fcgr2b knock-out in neurons and partially in astrocytes. Aß1-42 internalization was FcγRIIb2 di-leucine motif-dependent and attenuated by TOM1, a FcγRIIb2-binding protein that repressed the receptor recycling. TOM1 expression was downregulated in the hippocampus of male 3xTg-AD mice and AD patients, and regulated by miR-126-3p in neuronal cells after exposure to Aß1-42 In addition, memory impairments in male 3xTg-AD mice were rescued by the lentiviral administration of TOM1 gene. Augmented Aß uptake into lysosome caused its accumulation in cytoplasm and mitochondria. Moreover, neuronal accumulation of Aß in both sexes of 3xTg-AD mice and memory deficits in male 3xTg-AD mice were ameliorated by forebrain-specific expression of Aß-uptake-defective Fcgr2b mutant. Our findings suggest that FcγRIIb2 is essential for neuropathic uptake of Aß in AD.SIGNIFICANCE STATEMENT Accumulating evidences suggest that intraneuronal Aß is found in the early step of AD brain and is implicated in the pathogenesis of AD. However, the critical mediator involved in these processes is uncertain. Here, we describe that the FcγRIIb2 variant is responsible for both neuronal uptake and intraneuronal distribution of pathogenic Aß linked to memory deficits in AD mice, showing a pathologic significance of the internalized Aß. Further, Aß internalization is attenuated by TOM1, a novel FcγRIIb2-binding protein. Together, we provide a molecular mechanism responsible for neuronal uptake of pathogenic Aß found in AD.

Cks1 regulates human hepatocellular carcinoma cell progression through osteopontin expression.

Precise cell cycle regulation is critical to prevent aberrant cell proliferation and cancer progression. Cks1 was reported to be an essential accessory factor for SCFSkp2, the ubiquitin ligase that targets p27Kip1 for proteasomal degradation; these actions drive mammalian cell transition from G1 to S phase. In this study, we investigated the role played by Cks1 in the growth and progression of human hepatocellular carcinoma (HCC) cells. Silencing Cks1 expression abrogated osteopontin (OPN) expression in a p27Kip1-dependent manner in Huh7 HCC cells. OPN increased the proliferation, migration and invasion of Huh7 cells. Pharmacological inhibitor studies demonstrated that ERK1/2 signaling is responsible mainly for Cks1-mediated OPN expression. Cks1 appears to regulate ERK1/2 signaling through the expression of dual-specificity phosphatase 16 (DUSP16) because both Cks1 knockdown, which leads to DUSP16 upregulation, and DUSP16 overexpression decreased ERK1/2 phosphorylation and the resulting OPN expression. The same is true for the Cks1-mediated increases in p27Kip1, suggesting that Cks1 regulates OPN expression through activating ERK1/2 signaling either by suppressing DUSP16 expression or by a p27Kip1-dependent mechanism. Cks1 and OPN expression levels were significantly higher, but DUSP16 expression levels were significantly lower in HCC tissues than in normal liver tissues. Both Cks1 and OPN expression were negatively correlated with DUSP16 expression, whereas Cks1 expression was positively correlated with OPN expression. Moreover, combined panels for the expression levels of Cks1, DUSP16 and OPN showed significant prognostic power for the risk assessment of HCC patient overall survival. In conclusion, our data propose a novel function for Cks1 as a tumor promoter through the expression of the strongly oncogenic protein OPN in HCC.

Cerebral transcriptome analysis reveals age-dependent progression of neuroinflammation in P301S mutant tau transgenic male mice.

Aggregation of the microtubule-associated protein, tau, can lead to neurofibrillary tangle formation in neurons and glia which is the hallmark of tauopathy. The cellular damage induced by the formation of neurofibrillary tangles leads to neuroinflammation and consecutive neuronal death. However, detailed observation of transcriptomic changes under tauopathy together with the comparison of age-dependent progression of neuroinflammatory gene expressions mediated by tau overexpression is required. Employing RNA sequencing on PS19 transgenic mice that overexpress human mutant tau harboring the P301S mutation, we have examined the effects of age-dependent tau overexpression on transcriptomic changes of immune and inflammatory responses in the cerebral cortex. Compared to age-matched wild type control, P301S transgenic mice exhibit significant transcriptomic alterations. We have observed age-dependent neuroinflammatory gene expression changes in both wild type and P301S transgenic mice where tau overexpression further promoted the expression of neuroinflammatory genes in 10-month old P301S transgenic mice. Moreover, functional gene network analyses (gene ontology and pathway enrichment) and prospective target protein interactions predicted the potential involvement of multiple immune and inflammatory pathways that may contribute to tau-mediated neuronal pathology. Our current study on P301S transgenic mice model revealed for the first time, the differences of gene expression patterns in both early and late stage of tau pathology in cerebral cortex. Our analyses also revealed that tau overexpression alone induces multiple inflammatory and immune transcriptomic changes and may provide a roadmap to elucidate the targets of anti-inflammatory therapeutic strategy focused on tau pathology and related neurodegenerative diseases.

Inhibition of Drp1 Ameliorates Synaptic Depression, Aß Deposition, and Cognitive Impairment in an Alzheimer's Disease Model.

Excessive mitochondrial fission is a prominent early event and contributes to mitochondrial dysfunction, synaptic failure, and neuronal cell death in the progression of Alzheimer's disease (AD). However, it remains to be determined whether inhibition of excessive mitochondrial fission is beneficial in mammal models of AD. To determine whether dynamin-related protein 1 (Drp1), a key regulator of mitochondrial fragmentation, can be a disease-modifying therapeutic target for AD, we examined the effects of Drp1 inhibitor on mitochondrial and synaptic dysfunctions induced by oligomeric amyloid-ß (Aß) in neurons and neuropathology and cognitive functions in Aß precursor protein/presenilin 1 double-transgenic AD mice. Inhibition of Drp1 alleviates mitochondrial fragmentation, loss of mitochondrial membrane potential, reactive oxygen species production, ATP reduction, and synaptic depression in Aß-treated neurons. Furthermore, Drp1 inhibition significantly improves learning and memory and prevents mitochondrial fragmentation, lipid peroxidation, BACE1 expression, and Aß deposition in the brain in the AD model. These results provide evidence that Drp1 plays an important role in Aß-mediated and AD-related neuropathology and in cognitive decline in an AD animal model. Therefore, inhibiting excessive Drp1-mediated mitochondrial fission may be an efficient therapeutic avenue for AD.SIGNIFICANCE STATEMENT Mitochondrial fission relies on the evolutionary conserved dynamin-related protein 1 (Drp1). Drp1 activity and mitochondria fragmentation are significantly elevated in the brains of sporadic Alzheimer's disease (AD) cases. In the present study, we first demonstrated that the inhibition of Drp1 restored amyloid-ß (Aß)-mediated mitochondrial dysfunctions and synaptic depression in neurons and significantly reduced lipid peroxidation, BACE1 expression, and Aß deposition in the brain of AD mice. As a result, memory deficits in AD mice were rescued by Drp1 inhibition. These results suggest that neuropathology and combined cognitive decline can be attributed to hyperactivation of Drp1 in the pathogenesis of AD. Therefore, inhibitors of excessive mitochondrial fission, such as Drp1 inhibitors, may be a new strategy for AD.

S6K1 controls epigenetic plasticity for the expression of pancreatic α/ß cell marker genes.

The failure of insulin production by pancreatic ß cells is a common hallmark of type 1 diabetes mellitus (T1DM). Because administration of exogenous insulin is associated with diabetes-derived complications, endogenous α to ß cell transition can be an attractive alternative. Although decreased ß cell size and hypoinsulinaemia have been observed in S6K1-deficient mice, the molecular mechanism underlying the involvement of S6K1 in the transcriptional regulation of insulin remains elusive. Here, we show that the hypoinsulinaemic phenotype of S6K1-deficient mice stems from the dysregulated transcription of a set of genes required for insulin and glucagon production. First, we observed that increased expression of α cell marker genes and decreased expression of ß cell marker genes in pancreas tissues from S6K1-deficient mice. Furthermore, S6K1 was highly activated in murine ß cell line, ßTC6, compared to murine α cell line αTC1. In both α and ß cells, active S6K1 promoted the transcription of ß cell marker genes, including insulin, whereas S6K1 inhibition increased the transcription of α cell marker genes. Moreover, S6K1 mediated pancreatic gene regulation by modifying two histone marks (activating H3K4me3 and repressing H3K27me3) on gene promoters. These results suggest that S6K1 drives the α to ß transition through the epigenetic regulation of cell-specific genes, including insulin and glucagon. This novel role of S6K1 in islet cells provides basic clues to establish therapeutic strategies against T1DM.

Atf3 induction is a therapeutic target for obesity and metabolic diseases.

Activating transcription factor 3 (Atf3) has been previously demonstrated to impact obesity and metabolism. However, a metabolic role of Atf3 in mice remains debatable. We investigated the role of Atf3 in mice and further investigated Atf3 expression as a therapeutic target for obesity and metabolic diseases. Atf3 knockout (KO) mice fed with a high fat diet (HFD) aggravated weight gain and impaired glucose metabolism compared to littermate control wild type (WT) mice. Atf3 KO aged mice fed with a chow diet (CD) for longer than 10 months also displayed increased body weight and fat mass compared to WT aged mice. We also assessed requirements of Atf3 in a phytochemical mediated anti-obese effect. Effect of sulfuretin, a previously known phytochemical Atf3 inducer, in counteracting weight gain and improving glucose tolerance was almost completely abolished in the absence of Atf3, indicating that Atf3 induction can be a molecular target for preventing obesity and metabolic diseases. We further identified other Atf3 small molecule inducers that exhibit inhibitory effects on lipid accumulation in adipocytes. These data highlight the role of Atf3 in obesity and further suggest the use of chemical Atf3 inducers for prevention of obesity and metabolic diseases.

Modelling APOE ɛ3/4 allele-associated sporadic Alzheimer's disease in an induced neuron.

The recent generation of induced neurons by direct lineage conversion holds promise for in vitro modelling of sporadic Alzheimer's disease. Here, we report the generation of induced neuron-based model of sporadic Alzheimer's disease in mice and humans, and used this system to explore the pathogenic mechanisms resulting from the sporadic Alzheimer's disease risk factor apolipoprotein E (APOE) ɛ3/4 allele. We show that mouse and human induced neurons overexpressing mutant amyloid precursor protein in the background of APOE ɛ3/4 allele exhibit altered amyloid precursor protein (APP) processing, abnormally increased production of amyloid-ß42 and hyperphosphorylation of tau. Importantly, we demonstrate that APOE ɛ3/4 patient induced neuron culture models can faithfully recapitulate molecular signatures seen in APOE ɛ3/4-associated sporadic Alzheimer's disease patients. Moreover, analysis of the gene network derived from APOE ɛ3/4 patient induced neurons reveals a strong interaction between APOE ɛ3/4 and another Alzheimer's disease risk factor, desmoglein 2 (DSG2). Knockdown of DSG2 in APOE ɛ3/4 induced neurons effectively rescued defective APP processing, demonstrating the functional importance of this interaction. These data provide a direct connection between APOE ɛ3/4 and another Alzheimer's disease susceptibility gene and demonstrate in proof of principle the utility of induced neuron-based modelling of Alzheimer's disease for therapeutic discovery.

Systemic PEGylated TRAIL treatment ameliorates liver cirrhosis in rats by eliminating activated hepatic stellate cells.

UNLABELLED: Liver fibrosis is a common outcome of chronic liver disease that leads to liver cirrhosis and hepatocellular carcinoma. No US Food and Drug Administration-approved targeted antifibrotic therapy exists. Activated hepatic stellate cells (aHSCs) are the major cell types responsible for liver fibrosis; therefore, eradication of aHSCs, while preserving quiescent HSCs and other normal cells, is a logical strategy to stop and/or reverse liver fibrogenesis/fibrosis. However, there are no effective approaches to specifically deplete aHSCs during fibrosis without systemic toxicity. aHSCs are associated with elevated expression of death receptors and become sensitive to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced cell death. Treatment with recombinant TRAIL could be a potential strategy to ameliorate liver fibrosis; however, the therapeutic application of recombinant TRAIL is halted due to its very short half-life. To overcome this problem, we previously generated PEGylated TRAIL (TRAILPEG ) that has a much longer half-life in rodents than native-type TRAIL. In this study, we demonstrate that intravenous TRAILPEG has a markedly extended half-life over native-type TRAIL in nonhuman primates and has no toxicity in primary human hepatocytes. Intravenous injection of TRAILPEG directly induces apoptosis of aHSCs in vivo and ameliorates carbon tetrachloride-induced fibrosis/cirrhosis in rats by simultaneously down-regulating multiple key fibrotic markers that are associated with aHSCs. CONCLUSION: TRAIL-based therapies could serve as new therapeutics for liver fibrosis/cirrhosis and possibly other fibrotic diseases. (Hepatology 2016;64:209-223).

Adaptive cellular stress pathways as therapeutic targets of dietary phytochemicals: focus on the nervous system.

During the past 5 decades, it has been widely promulgated that the chemicals in plants that are good for health act as direct scavengers of free radicals. Here we review evidence that favors a different hypothesis for the health benefits of plant consumption, namely, that some phytochemicals exert disease-preventive and therapeutic actions by engaging one or more adaptive cellular response pathways in cells. The evolutionary basis for the latter mechanism is grounded in the fact that plants produce natural antifeedant/noxious chemicals that discourage insects and other organisms from eating them. However, in the amounts typically consumed by humans, the phytochemicals activate one or more conserved adaptive cellular stress response pathways and thereby enhance the ability of cells to resist injury and disease. Examplesof such pathways include those involving the transcription factors nuclear factor erythroid 2-related factor 2, nuclear factor-κB, hypoxia-inducible factor 1α, peroxisome proliferator-activated receptor γ, and forkhead box subgroup O, as well as the production and action of trophic factors and hormones. Translational research to develop interventions that target these pathways may lead to new classes of therapeutic agents that act by stimulating adaptive stress response pathways to bolster endogenous defenses against tissue injury and disease. Because neurons are particularly sensitive to potentially noxious phytochemicals, we focus on the nervous system but also include findings from other cell types in which actions of phytochemicals on specific signal transduction pathways have been more thoroughly studied.

Pin1 promotes neuronal death in stroke by stabilizing Notch intracellular domain.

OBJECTIVE: Stroke is a leading cause of mortality and disability. The peptidyl-prolyl cis/trans isomerase Pin1 regulates factors involved in cell growth. Recent evidence has shown that Pin1 plays a major role in apoptosis. However, the role of Pin1 in ischemic stroke remains to be investigated. METHODS: We used Pin1 overexpression and knockdown to manipulate Pin1 expression and explore the effects of Pin1 in cell death on ischemic stress in vitro and in a mouse stroke model. We also used Pin 1 inhibitor, γ-secretase inhibitor, Notch1 intracellular domain (NICD1)-deleted mutant cells, and Pin1 mutant cells to investigate the underlying mechanisms of Pin1-NICD1-mediated cell death. RESULTS: Our findings indicate that Pin1 facilitates NICD1 stability and its proapoptotic function following ischemic stroke. Thus, overexpression of Pin1 increased NICD1 levels and enhanced its potentiation of neuronal death in simulated ischemia. By contrast, depletion or knockout of Pin1 reduced the NICD1 level, which in turn desensitized neurons to ischemic conditions. Pin1 interacted with NICD1 and increased its stability by inhibiting FBW7-induced polyubiquitination. We also demonstrate that Pin1 and NICD1 levels increase following stroke. Pin1 heterozygous (+/-) and knockout (-/-) mice, and also wild-type mice treated with an inhibitor of Pin1, each showed reduced brain damage and improved functional outcomes in a model of focal ischemic stroke. INTERPRETATION: These results suggest that Pin1 contributes to the pathogenesis of ischemic stroke by promoting Notch signaling, and that inhibition of Pin1 is a novel approach for treating ischemic stroke.

Down-regulation of mortalin exacerbates Aß-mediated mitochondrial fragmentation and dysfunction.

Mitochondrial dynamics greatly influence the biogenesis and morphology of mitochondria. Mitochondria are particularly important in neurons, which have a high demand for energy. Therefore, mitochondrial dysfunction is strongly associated with neurodegenerative diseases. Until now various post-translational modifications for mitochondrial dynamic proteins and several regulatory proteins have explained complex mitochondrial dynamics. However, the precise mechanism that coordinates these complex processes remains unclear. To further understand the regulatory machinery of mitochondrial dynamics, we screened a mitochondrial siRNA library and identified mortalin as a potential regulatory protein. Both genetic and chemical inhibition of mortalin strongly induced mitochondrial fragmentation and synergistically increased Aß-mediated cytotoxicity as well as mitochondrial dysfunction. Importantly we determined that the expression of mortalin in Alzheimer disease (AD) patients and in the triple transgenic-AD mouse model was considerably decreased. In contrast, overexpression of mortalin significantly suppressed Aß-mediated mitochondrial fragmentation and cell death. Taken together, our results suggest that down-regulation of mortalin may potentiate Aß-mediated mitochondrial fragmentation and dysfunction in AD.

miR-195a inhibits adipocyte differentiation by targeting the preadipogenic determinator Zfp423.

MicroRNAs (miRNAs) play essential roles in various cellular processes including proliferation and differentiation. In this study, we identified miRNA-195a (miR-195a) as a regulator of adipocyte differentiation. Differential expression of miR-195a in preadipocytes and adipocytes suggests its role in lipid accumulation and adipocyte differentiation. Forced expression of miR-195a mimics suppressed lipid accumulation and inhibited expression of adipocyte markers such as PPARγ and aP2 in 3T3-L1 and C3H10T1/2 cells. Conversely, downregulation of miR-195a by anti-miR-195a increased lipid accumulation and expression of adipocyte markers. Target prediction analysis suggested zinc finger protein 423 (Zfp423), a preadipogenic determinator, as a potential gene recognized by miR-195a. In line with this, mimicked expression of miR-195a reduced the expression of Zfp423, whereas anti-miR-195a increased its expression. Predicted targeting sequences in Zfp423 3'UTR, but not mutated sequences fused to luciferase, were regulated by miR-195a. Ectopic Zfp423 expression in 3T3-L1 cells increased lipid accumulation and expression of adipocyte markers, consistent with the observation that miR-195a targets Zfp423, resulting in suppressed adipocyte differentiation. In addition, miR-195a and Zfp423 were inversely correlated in obese fat tissues, raising the possibility of miRNA's role in obesity. Together, our data show that miR-195a is an anti-adipogenic regulator, which acts by targeting Zfp423, and further suggest the roles of miR-195a in obesity and metabolic diseases.