Antiseizure effects of Lilii Bulbus on pentylenetetrazol kindling-induced seizures in mice: Involvement of Reelin, Netrin-1, and semaphorin

Lilii Bulbus (Lilium lancifolium Thunberg) has a proneurogenic effect on the hippocampus. However, its effects on epilepsy and associated pathological features remain unknown. In this study, we investigated the antiseizure effects of a water extract of Lilii Bulbus (WELB) in mouse model of pentylenetetrazol (PTZ)-induced seizure. Mice were injected with PTZ once every 48 h until full kindling was achieved. WELB (100 and 500 mg/kg) was orally administered once daily before PTZ administration and during the kindling process. We found that WELB treatment protected against PTZ-induced low seizure thresholds and high seizure severity. Further, WELB-treated mice showed attenuated PTZ kindling-induced anxiety and memory impairment. Immunostaining and immunoblots showed that hyperactivation and ectopic migration of dentate granule cells (DGCs) were significantly reduced by WELB treatment in PTZ kindling-induced seizure mice. Staining for mossy fiber sprouting (MFS) using Timm staining and ZnT3 showed that WELB treatment significantly decreased PTZ kindling-induced MFS. Furthermore, the increased or decreased expression of proteins related to ectopic DGCs (Reelin and Dab-1), MFS (Netrin-1, Sema3A, and Sema3F), and their downstream effectors (ERK, AKT, and CREB) in the hippocampus of PTZ kindling mice was significantly restored by WELB treatment. Overall, our findings suggest that WELB is a potential antiseizure drug that acts by reducing ectopic DGCs and MFS and modulating epileptogenesis-related signaling in the hippocampus.

Electroacupuncture modulates glutamate neurotransmission to alleviate PTSD-like behaviors in a PTSD animal model

Post-traumatic stress disorder (PTSD) is a mental disorder that develops after exposure to a traumatic event. Owing to the relatively low rates of response and remission with selective serotonin reuptake inhibitors as the primary treatment for PTSD, there is a recognized need for alternative strategies to effectively address the symptoms of PTSD. Dysregulation of glutamatergic neurotransmission plays a critical role in various disorders, including anxiety, depression, PTSD, and Alzheimer's disease. Therefore, the regulation of glutamate levels holds great promise as a therapeutic target for the treatment of mental disorders. Electroacupuncture (EA) has become increasingly popular as a complementary and alternative medicine approach. It maintains the homeostasis of central nervous system (CNS) function and alleviates symptoms associated with anxiety, depression, and insomnia. This study investigated the effects of EA at the GV29 (Yintang) acupoint three times per week for 2 weeks in an animal model of PTSD. PTSD was induced using single prolonged stress/shock (SPSS) in mice, that is, SPS with additional foot shock stimulation. EA treatment significantly reduced PTSD-like behavior and effectively regulated serum corticosterone and serotonin levels in the PTSD model. Additionally, EA treatment decreased glutamate levels and glutamate neurotransmission-related proteins (pNR1 and NR2B) in the hippocampus of a PTSD model. In addition, neuronal activity and the number of Golgi-impregnated dendritic spines were significantly lower in the EA treatment group than in the SPSS group. Notably, EA treatment effectively reduced glutamate-induced excitotoxicity (caspase-3, Bax, and pJNK). These findings suggest that EA treatment at the GV29 acupoint holds promise as a potential therapeutic approach for PTSD, possibly through the regulation of NR2B receptor-mediated glutamate neurotransmission to reduce PTSD-like behaviors.

Novel Psychopharmacological Herbs Relieve Behavioral Abnormalities and Hippocampal Dysfunctions in an Animal Model of Post-Traumatic Stress Disorder

Post-traumatic stress disorder (PTSD) is an anxiety disorder caused by traumatic or frightening events, with intensified anxiety, fear memories, and cognitive impairment caused by a dysfunctional hippocampus. Owing to its complex phenotype, currently prescribed treatments for PTSD are limited. This study investigated the psychopharmacological effects of novel COMBINATION herbal medicines on the hippocampus of a PTSD murine model induced by combining single prolonged stress (SPS) and foot shock (FS). We designed a novel herbal formula extract (HFE) from Chaenomeles sinensis, Glycyrrhiza uralensis, and Atractylodes macrocephala. SPS+FS mice were administered HFE (500 and 1000 mg/kg) once daily for 14 days. The effects of HFE of HFE on the hippocampus were analyzed using behavioral tests, immunostaining, Golgi staining, and Western blotting. HFE alleviated anxiety-like behavior and fear response, improved short-term memory, and restored hippocampal dysfunction, including hippocampal neurogenesis alteration and aberrant migration and hyperactivation of dentate granule cells in SPS+FS mice. HFE increased phosphorylation of the Kv4.2 potassium channel, extracellular signal-regulated kinase, and cAMP response element-binding protein, which were reduced in the hippocampus of SPS+FS mice. Therefore, our study suggests HFE as a potential therapeutic drug for PTSD by improving behavioral impairment and hippocampal dysfunction and regulating Kv4.2 potassium channel-related pathways in the hippocampus.

Pro-neurogenic effects of Lilii Bulbus on hippocampal neurogenesis and memory

Lilii Bulbus, the bulb of tiger lily, has anti-oxidant and anti-tumorigenic properties. However, the effects of Lilii Bulbus on learning, memory, and hippocampal neurogenesis remain unknown. This study investigated whether water extract of Lilii Bulbus (WELB) affects memory ability and hippocampal neurogenesis. Behavioral analyses (Morris water maze and passive avoidance test), immunohistochemistry, cell proliferation assay, and immunoblot analysis were performed. WELB (50 and 100 mg/kg; for 14 days) enhanced memory retention and spatial memory in normal mice as well as in scopolamine-treated mice with memory deficits. Furthermore, the administration of WELB significantly increased the number of proliferating cells and surviving newborn cells in the dentate gyrus of the hippocampus in normal mice. We found that WELB has a pro-neurogenic effect by increasing the activation of brain-derived neurotrophic factor (BDNF)/cAMP response element-binding protein (CREB) and mitogen-activated protein kinase kinase/extracellular signal-regulated kinase (MEK/ERK) in the hippocampus. Moreover, we confirmed that WELB (100 and 200 μg/ml) significantly increased NE-4 C and primary embryonic NSCs proliferation. Inhibition/knockdown of MEK/ERK blocked WELB-induced MEK/ERK phosphorylation and NSCs proliferation. Hence, MEK/ERK activation was required in WELB-induced NSCs proliferation. Our study demonstrates the first evidence for WELB promoting hippocampal neurogenesis and memory; pro-neurogenic activity may enhance brain plasticity, with implications for treating neurodegenerative diseases.

Low-dose curcumin enhances hippocampal neurogenesis and memory retention in young mice

Adult neurogenesis generates new functional neurons from adult neural stem cells in various regions, including the subventricular zone (SVZ) of the lateral ventricles and subgranular zone (SGZ) of hippocampal dentate gyrus (DG). Available evidence shows hippocampal neurogenesis can be negatively or positively regulated by dietary components. In a previous study, we reported that curcumin (diferuloylmethane; a polyphenolic found in curry spice) stimulates the proliferation of embryonic neural stem cells (NSCs) by activating adaptive cellular stress responses. Here, we investigated whether subchronic administration of curcumin (once daily at 0.4, 2, or 10 mg/kg for 14 days) promotes hippocampal neurogenesis and neurocognitive function in young (5-week-old) mice. Oral administration of low-dose curcumin (0.4 mg/kg) increased the proliferation and survival of newly generated cells in hippocampus, but surprisingly, high-dose curcumin (10 mg/kg) did not effectively upregulate the proliferation or survival of newborn cells. Furthermore, hippocampal BDNF levels and phosphorylated CREB activity were elevated in only low-dose curcumin-treated mice. Passive avoidance testing revealed that low-dose curcumin increased cross-over latency times, indicating enhanced memory retention, and an in vitro study showed that low-concentration curcumin increased the proliferative activity of neural progenitor cells (NPCs) by upregulating NF1X levels. Collectively, our findings suggest that low-dose curcumin has neurogenic effects and that it may prevent age and neurodegenerative disease-related cognitive deficits.

Nutraceutical Interventions for Post-Traumatic Stress Disorder in Animal Models: A Focus on the Hypothalamic–Pituitary–Adrenal Axis

Post-traumatic stress disorder (PTSD) occurs after exposure to traumatic events and is characterized by overwhelming fear and anxiety. Disturbances in the hypothalamic–pituitary–adrenal (HPA) axis are involved in the pathogenesis of mood disorders, including anxiety, PTSD, and major depressive disorders. Studies have demonstrated the relationship between the HPA axis response and stress vulnerability, indicating that the HPA axis regulates the immune system, fear memory, and neurotransmission. The selective serotonin reuptake inhibitors (SSRIs), sertraline and paroxetine, are the only drugs that have been approved by the United States Food and Drug Administration for the treatment of PTSD. However, SSRIs require long treatment times and are associated with lower response and remission rates; therefore, additional pharmacological interventions are required. Complementary and alternative medicine therapies ameliorate HPA axis disturbances through regulation of gut dysbiosis, insomnia, chronic stress, and depression. We have described the cellular and molecular mechanisms through which the HPA axis is involved in PTSD pathogenesis and have evaluated the potential of herbal medicines for PTSD treatment. Herbal medicines could comprise a good therapeutic strategy for HPA axis regulation and can simultaneously improve PTSD-related symptoms. Finally, herbal medicines may lead to novel biologically driven approaches for the treatment and prevention of PTSD.

Mitochondrial genome mutations and neuronal dysfunction of induced pluripotent stem cells derived from patients with Alzheimer's disease

OBJECTIVES

Patient-derived induced pluripotent stem cells (iPSCs) are materials that can be used for autologous stem cell therapy. We screened mtDNA mutations in iPSCs and iPSC-derived neuronal cells from patients with Alzheimer's disease (AD). Also, we investigated whether the mutations could affect mitochondrial function and deposition of β-amyloid (Aβ) in differentiated neuronal cells.

MATERIALS AND METHODS

mtDNA mutations were measured and compared among iPSCs and iPSC-derived neuronal cells. The selected iPSCs carrying mtDNA mutations were subcloned, and then their growth rate and neuronal differentiation pattern were analyzed. The differentiated cells were measured for mitochondrial respiration and membrane potential, as well as deposition of Aβ.

RESULTS

Most iPSCs from subjects with AD harbored ≥1 mtDNA mutations, and the number of mutations was significantly higher than that from umbilical cord blood. About 35% and 40% of mutations in iPSCs were shared with isogenic iPSCs and their differentiated neuronal precursor cells, respectively, with similar or different heteroplasmy. Furthermore, the mutations in clonal iPSCs were stable during extended culture and neuronal differentiation. Finally, mtDNA mutations could induce a growth advantage with higher viability and proliferation, lower mitochondrial respiration and membrane potential, as well as increased Aβ deposition.

CONCLUSION

This study demonstrates that mtDNA mutations in patients with AD could lead to mitochondrial dysfunction and accelerated Aβ deposition. Therefore, early screening for mtDNA mutations in iPSC lines would be essential for developing autologous cell therapy or drug screening for patients with AD.

Combined Treatment with Herbal Medicine and Drug Ameliorates Inflammation and Metabolic Abnormalities in the Liver of an Amyotrophic Lateral Sclerosis Mouse Model

To date, no effective drugs exist for amyotrophic lateral sclerosis (ALS), although riluzole (RZ) and edaravone have been approved for treatment. We previously reported that Bojungikgi-tang (BJIGT) improved motor activity through anti-inflammatory effects in the muscle and spinal cord of hSOD1^G93A mice. Therefore, whether combined treatment with BJIGT and RZ synergistically affects liver function in hSOD1^G93A mice was investigated. Two-month-old male hSOD1^G93A mice were treated with BJIGT (1 mg/g) and RZ (8 μg/g) administered orally for 5 weeks. Drug metabolism and liver function tests of serum and liver homogenates were conducted. mRNA expression levels of cytochrome P450 (CYP) isozymes, inflammatory cytokines, metabolic factors, and mitochondrial oxidative phosphorylation (OXPHOS) subunits were examined using qPCR and Western blotting. Combined administration of BJIGT and RZ did not alter mRNA expression levels of drug-metabolism-related isozymes (CYP1A2 and CYP3A4) but significantly decreased the activity of liver-function-related enzymes (AST, ALT, ALP, and LDH). Increased expression of inflammatory cytokines (IL-1β, TNF-α, and IL-6) and of intracellular stress-related proteins (Bax, AMPKα, JNK, and p38) was reduced by the combined treatment in hSOD1^G93A mice compared to that in control mice. Combined administration reduced the mRNA expression of metabolism-related factors and the expression of OXPHOS subunits. Elevated ATP levels and mitochondrial-fusion-associated protein were decreased after co-administration. Co-administration of BJIGT and RZ did not cause liver damage or toxicity but rather restored liver function in hSOD1^G93A mice. This suggests that this combination can be considered a candidate therapeutic agent for ALS.

Oxidative Stress as a Therapeutic Target in Amyotrophic Lateral Sclerosis: Opportunities and Limitations

Amyotrophic lateral sclerosis (ALS), also known as motor neuron disease (MND) and Lou Gehrig’s disease, is characterized by a loss of the lower motor neurons in the spinal cord and the upper motor neurons in the cerebral cortex. Due to the complex and multifactorial nature of the various risk factors and mechanisms that are related to motor neuronal degeneration, the pathological mechanisms of ALS are not fully understood. Oxidative stress is one of the known causes of ALS pathogenesis. This has been observed in patients as well as in cellular and animal models, and is known to induce mitochondrial dysfunction and the loss of motor neurons. Numerous therapeutic agents have been developed to inhibit oxidative stress and neuroinflammation. In this review, we describe the role of oxidative stress in ALS pathogenesis, and discuss several anti-inflammatory and anti-oxidative agents as potential therapeutics for ALS. Although oxidative stress and antioxidant fields are meaningful approaches to delay disease progression and prolong the survival in ALS, it is necessary to investigate various animal models or humans with different subtypes of sporadic and familial ALS.

Periodontal Pathogens Promote Foam Cell Formation by Blocking Lipid Efflux

Foam cells are one of the major cellular components of atherosclerotic plaques, within which the trace of periodontal pathogens has also been identified in recent studies. In line with these findings, the correlation between periodontitis and atherosclerotic cardiovascular incidences has been repetitively supported by evidence from a number of experimental studies. However, the direct role of periodontal pathogens in altered cellular signaling underlying such cardiovascular events has not been clearly defined. To determine the role of periodontal pathogens in the pathogenesis of atherosclerosis, especially in the evolution of macrophages into foam cells, we monitored the pattern of lipid accumulation within macrophages in the presence of periodontal pathogens, followed by characterization of these lipids and investigation of major molecules involved in lipid homeostasis. The cells were stained with the lipophilic fluorescent dye BODIPY 493/503 and Oil Red O to characterize the lipid profile. The amounts of Oil Red O-positive droplets, representing neutral lipids, as well as fluorescent lipid aggregates were prominently increased in periodontal pathogen-infected macrophages. Subsequent analysis allowed us to locate the accumulated lipids in the endoplasmic reticulum. In addition, the levels of cholesteryl ester in periodontal pathogen-infected macrophages were increased, implying disrupted lipid homeostasis. Further investigations to delineate the key messengers and regulatory factors involved in the altered lipid homeostasis have revealed alterations in cholesterol efflux-related enzymes, such as ABCG1 and CYP46A1, as contributors to foam cell formation, and increased Ca²⁺ signaling and reactive oxygen species (ROS) production as key events underlying disrupted lipid homeostasis. Consistently, a treatment of periodontal pathogen-infected macrophages with ROS inhibitors and nifedipine attenuated the accumulation of lipid droplets, further confirming periodontal pathogen-induced alterations in Ca²⁺ and ROS signaling and the subsequent dysregulation of lipid homeostasis as key regulatory events underlying the evolution of macrophages into foam cells.

Neural stem cells derived from the developing forebrain of YAC128 mice exhibit pathological features of Huntington's disease

Objectives

Huntington's disease (HD) is a devastating neurodegenerative disease caused by polyglutamine (polyQ) expansion in the huntingtin (HTT) gene. Mutant huntingtin (mHTT) is the main cause of HD and is associated with impaired mitochondrial dynamics, ubiquitin‐proteasome system and autophagy, as well as tauopathy. In this study, we aimed to establish a new neural stem cell line for HD studies.

Materials and methods

YAC128 mice are a yeast artificial chromosome (YAC)‐based transgenic mouse model of HD. These mice express a full‐length human mutant HTT gene with 128 CAG repeats and exhibit various pathophysiological features of HD. In this study, we isolated a new neural stem cell line from the forebrains of YAC128 mouse embryos (E12.5) and analysed its characteristics using cellular and biochemical methods.

Results

Compared to wild‐type (WT) NSCs, the YAC128 NSC line exhibited greater proliferation and migration capacity. In addition to mHTT expression, increased intracellular Ca²⁺ levels and dysfunctional mitochondrial membrane potential were observed in the YAC128 NSCs. YAC128 NSCs had defects in mitochondrial dynamics, including a deficit in mitochondrial axonal transport and unbalanced fusion and fission processes. YAC128 NSCs also displayed decreased voltage response variability and Na⁺ current amplitude. Additionally, the ubiquitin‐proteasome and autophagy systems were impaired in the YAC128 NSCs.

Conclusions

We have established a new neural stem line from YAC128 transgenic mice, which may serve as a useful resource for studying HD pathogenesis and drug screening.

Activity of hippocampal adult-born neurons regulates alcohol withdrawal seizures

Alcohol withdrawal (AW) after chronic alcohol exposure produces a series of symptoms, with AW-associated seizures being among the most serious and dangerous. However, the mechanism underlying AW seizures has yet to be established. In our mouse model, a sudden AW produced 2 waves of seizures: the first wave includes a surge of multiple seizures that occurs within hours to days of AW, and the second wave consists of sustained expression of epileptiform spikes and wave discharges (SWDs) during a protracted period of abstinence. We revealed that the structural and functional adaptations in newborn dentate granule cells (DGCs) in the hippocampus underlie the second wave of seizures but not the first wave. While the general morphology of newborn DGCs remained unchanged, AW increased the dendritic spine density of newborn DGCs, suggesting that AW induced synaptic connectivity of newborn DGCs with excitatory afferent neurons and enhanced excitability of newborn DGCs. Indeed, specific activation and suppression of newborn DGCs by the chemogenetic DREADD method increased and decreased the expression of epileptiform SWDs, respectively, during abstinence. Thus, our study unveiled that the pathological plasticity of hippocampal newborn DGCs underlies AW seizures during a protracted period of abstinence, providing critical insight into hippocampal neural circuits as a foundation to understand and treat AW seizures.

Enhancement of neuroprotective activity of Sagunja-tang by fermentation with lactobacillus strains

BACKGROUND

Sagunja-tang (SGT) is widely used in traditional herbal medicine to treat immune system and gastrointestinal disorders and reportedly has protective effects against inflammation, cancer, and osteoporosis. In this study, we fermented SGT with different Latobacillus strains and investigated the change in phytochemical compositions in SGT and enhancement of it neuroprotective effects in SH-SY5Y human neuroblastoma.

METHODS

Marker components, including ginsenoside Rg₁, glycyrrhizin, liquiritin, liquiritigenin, atractylenolide I, atractylenolide II, atractylenolide III, and pachymic acid, in SGT, were qualitatively and quantitatively analyzed using high-performance liquid chromatography-diode array detection and liquid chromatography-mass spectrometry. SGT was fermented with eight different Lactobacillus strains to yield eight fermented SGTs (FSGTs). The conversion efficiencies of SGT marker components were determined in each FSGT. To detect the protective effect of SGT and FSGT, reactive oxygen species (ROS) assay and mitochondrial membrane potentials (MMPs) assay were performed in SH-SY5Y cells.

RESULTS

Compared with the other FSGTs, SGT166, i.e., SGT fermented with L. plantarum 166, had high conversion efficiency, as indicated by increased amounts of glycyrrhizin, liquiritigenin, and atractylenolides I-III. In SH-SY5Y cells, protection against cell death induced by H₂O₂ and etoposide was high using SGT166 and very low using SGT. Furthermore, ROS production and mitochondrial membrane potential disruption in SH-SY5Y cells were markedly suppressed by SGT166 treatment, which demonstrated that inhibition of ROS generation may be one of the neuroprotective mechanisms of SGT166.

CONCLUSIONS

This study demonstrated that fermentation of SGT with L. plantarum 166 enhanced suppression of oxidative stress and MMP loss. This enhanced neuroprotective effect was thought to be caused by the conversion of SGT phytochemicals by fermentation. SGT166 shows potential for treating neurological damage-related diseases.

Learning, memory deficits, and impaired neuronal maturation attributed to acrylamide

Acrylamide (ACR) is a neurotoxin known to produce neurotoxicity characterized by ataxia, skeletal muscle weakness, cognitive impairment, and numbness of the extremities. Previously, investigators reported that high-dose (50 mg/kg) ACR impaired hippocampal neurogenesis and increased neural progenitor cell death; however, the influence of subchronic environmentally relevant low dose-(2, 20, or 200 μg/kg) ACRs have not been examined in adult neurogenesis or cognitive function in mice. Accordingly, the aim of the present study was to investigate whether low-dose ACR adversely affected mouse hippocampal neurogenesis and neurocognitive functions. Male C57BL/6 mice were orally administered vehicle or ACR at 2, 20, or 200 μg/kg/day for 4 weeks. ACR did not significantly alter the number of newly generated cells or produce neuroinflammation or neuronal loss in hippocampi. However, behavioral studies revealed that 200 μg/kg ACR produced learning and memory impairment. Furthermore, incubation of ACR with primary cultured neurons during the developmental stage was found to delay neuronal maturation without affecting cell viability indicating the presence of developmental neurotoxicity. These findings indicate that although exposure to in vivo low-dose ACR daily for 4 weeks exerted no apparent marked effect on hippocampal neurogenesis, in vitro observations in primary cultured neurons noted adverse effects on learning and memory impairment suggestive of neurotoxic actions.

Berberine reduce allergic inflammation in a house dust mite allergic rhinitis mouse model

BACKGROUND

Berberine (Ber), used widely as an antibacterial, antifungal, and anti-inflammatory drug, has long been used as a gastrointestinal remedy in Chinese traditional medicine. Recent reports have suggested that Ber suppresses Th17 responses that was mediated by direct actions on T cells and thymic stromal lymphopoietin production in primary mast cells. It has been suggested that Ber may be useful in treating allergic response. The purpose of this study was to assess the effects of Ber treatment on allergic inflammation in an allergic rhinitis mouse model and to examine the underlying mechanism(s).

METHODS

BALB/c mice were divided into control, Derf with no treated (Derf), Ber treated, and Ber with anti-C25 monoclonal antibody treated (Ber + anti-CD25) groups. All mice, with the exception of the control group, were sensitized with an intraperitoneal i.p. injection of Dermatophagoides farinae (Derf). Mice in the Ber and Ber + anti-CD25 group were treated intranasally with 10 #181;g/mL. Then, 1 week after sensitization, all mice were challenged intranasally with 20 #181;g Derf for 5 consecutive days. Mice in the anti-CD25 group were treated intraperitoneally with 250 #181;g anti-CD25 monoclonal antibody 1 day before the first intra-nasal challenge with Derf. Allergic symptom scores, eosinophil counts, and serum Derf-specific IgE levels were measured. T-bet, GATA-3, interferon-g (IFN-γ), interleukin (IL)-10, IL-13, and Foxp3 expression was examined by real-time polymerase chain reaction and Western blotting. CD4⁺ CD25⁺ Foxp3⁺ T cells were assessed by flow cytometry.

RESULTS

Symptom scores, serum Derf-specific IgE levels, GATA-3 mRNA levels, T-bet mRNA levels, and tissue eosinophil counts were decreased in the Ber versus the Derf group. In the Ber + anti-CD25 group, serum IL-10 levels were decreased versus the control, Derf, and Ber groups. In the Ber + anti-CD25 mAb groups, Foxp3 mRNA levels were decreased versus the control group. In the Ber group, Foxp3 mRNA levels were increased versus the control group. In the Ber group, the percentage of CD4⁺ CD25⁺ Foxp3⁺ T cells was increased versus the Derf group. The percentage of CD4⁺ CD25⁺ Foxp3+ T cells was increased in the Ber versus the Derf groups.

CONCLUSIONS

In our study, Ber reduced allergic inflammation significantly. Moreover, our findings suggest that the mechanism of action of Ber may be via CD4⁺ CD25⁺ Foxp3⁺ Treg cells, possibly through not only by increasing their numbers but also altering their function.

The mitochondrial uncoupler DNP triggers brain cell mTOR signaling network reprogramming and CREB pathway up-regulation

Mitochondrial metabolism is highly responsive to nutrient availability and ongoing activity in neuronal circuits. The molecular mechanisms by which brain cells respond to an increase in cellular energy expenditure are largely unknown. Mild mitochondrial uncoupling enhances cellular energy expenditure in mitochondria and can be induced with 2,4-dinitrophenol (DNP), a proton ionophore previously used for weight loss. We found that DNP treatment reduces mitochondrial membrane potential, increases intracellular Ca(2+) levels and reduces oxidative stress in cerebral cortical neurons. Gene expression profiling of the cerebral cortex of DNP-treated mice revealed reprogramming of signaling cascades that included suppression of the mammalian target of rapamycin (mTOR) and insulin--PI3K - MAPK pathways, and up-regulation of tuberous sclerosis complex 2, a negative regulator of mTOR. Genes encoding proteins involved in autophagy processes were up-regulated in response to DNP. CREB (cAMP-response element-binding protein) signaling, Arc and brain-derived neurotrophic factor, which play important roles in synaptic plasticity and adaptive cellular stress responses, were up-regulated in response to DNP, and DNP-treated mice exhibited improved performance in a test of learning and memory. Immunoblot analysis verified that key DNP-induced changes in gene expression resulted in corresponding changes at the protein level. Our findings suggest that mild mitochondrial uncoupling triggers an integrated signaling response in brain cells characterized by reprogramming of mTOR and insulin signaling, and up-regulation of pathways involved in adaptive stress responses, molecular waste disposal, and synaptic plasticity. Physiological bioenergetic challenges such as exercise and fasting can enhance neuroplasticity and protect neurons against injury and neurodegeneration. Here, we show that the mitochondrial uncoupling agent 2,4-dinitrophenol (DNP) elicits adaptive signaling responses in the cerebral cortex involving activation of Ca(2+) -CREB and autophagy pathways, and inhibition of mTOR and insulin signaling pathways. The molecular reprogramming induced by DNP, which is similar to that of exercise and fasting, is associated with improved learning and memory, suggesting potential therapeutic applications for DNP.

Neuroprotective effects of Liriope platyphylla extract against hydrogen peroxide-induced cytotoxicity in human neuroblastoma SH-SY5Y cells

Background

Oxidative stress is involved in neuronal cell death and mitochondrial dysfunction in neurodegenerative diseases. Liriope platyphylla (LP) has been suggested to have anti-inflammation, anti-bacterial, and anti-cancer effects. However, whether LP exerts neuroprotective effects on neuronal cells is unknown.

Methods

The present study was performed to investigate the neuroprotective effects of LP extract (LPE) against hydrogen peroxide (H₂O₂)-induced injury in human neuroblastoma cells SH-SY5Y. To test neuroprotective effects of LPE, we performed cell viability assay, flow cytometry analysis and western blot analysis. In addition, mitochondrial membrane potential (MMP) and oxidative stress were performed to evaluate the anti-apoptotic and anti-oxidant effects.

Results

LPE pretreatment conferred significant protection against the H₂O₂-induced decrease of SH-SY5Y cell viability. H₂O₂-induced increases of intracellular oxidative stress and mitochondrial dysfunction were attenuated by LPE pretreatment. Therefore, LPE pretreatment prevented SH-SY5Y cell injury. Treatment with H₂O₂ significantly induced poly(ADP ribose) polymerase (PARP) and caspase-3 cleavage, which was blocked by LPE. We found that p38 activation was involved in the neuroprotective effects of LPE.

Conclusions

Current findings suggest that LPE exerts neuroprotective effects against H₂O₂-induced apoptotic cell death by modulating p38 activation in SH-SY5Y cells. Therefore, LPE has potential anti-apoptotic effects that may be neuroprotective in neurodegenerative diseases and aging-related dementia.

Lipotoxicity of palmitic Acid on neural progenitor cells and hippocampal neurogenesis

Lipotoxicity involves pathological alterations to cells and tissues in response to elevated fat levels in blood. Furthermore, this process can disturb both cellular homeostasis and viability. In the current study, the authors show that neural progenitor cells (NPCs) are vulnerable to high levels of palmitic acid (PA) a saturated fatty acid. PA was found to cause cell death associated with elevated reactive oxygen species (ROS) levels, and to reduce NPCs proliferation. To evaluate the lipotoxicity of PA in adult NPCs in the hippocampus, male C57BL/6 mice were divided into two groups and maintained on either a normal diet (ND) or PA-rich high fat diet (HFD) for 2 weeks. Interestingly, short-term PA-rich HFD feeding reduced the survival of newly generated cells in the hippocampal dentate gyrus and hippocampal brain-derived neurotrophic factor levels. These findings suggest PA has a potent lipotoxicity in NPCs and that a PA-rich HFD disrupts hippocampal neurogenesis.

Baicalein attenuates impaired hippocampal neurogenesis and the neurocognitive deficits induced by γ-ray radiation

BACKGROUND AND PURPOSE

Whole-brain irradiation (WBI) therapy produces learning and memory deficits in patients with brain tumours. Although the pathological cascade of cognitive deficits remains unknown, it may involve reduced neurogenesis within the hippocampus. Baicalein is a flavonoid derived from the roots of Huangqin, Scutellaria baicalensis Georgi, and has been shown to have antioxidant effects. Here, we have investigated the protective effects of baicalein on irradiation-induced impairments in hippocampal neurogenesis and cognitive function.

EXPERIMENTAL APPROACH

Radioprotective effects of baicalein were evaluated in C17.2 neural progenitor cells and 6-week-old male C57BL/6 mice during hippocampal neurogenesis. Mice were given a single dose of 5 Gy WBI. Changes in hippocampal neurogenesis, oxidative stress and BDNF-pCREB signalling were evaluated. Morris water maze and passive avoidance test were used to assess learning and memory.

KEY RESULTS

Baicalein protected neural progenitor cells against irradiation-induced necrotic cell death. Pretreatment with baicalein attenuated the irradiation-induced impairment of hippocampal neurogenesis by modulating oxidative stress and elevating BDNF-pCREB signalling. Furthermore, baicalein prevented the spatial learning and memory retention deficits follwing WBI.

CONCLUSIONS AND IMPLICATIONS

Our findings suggest that baicalein can be viewed as a potential therapeutic agent that protects against the impaired neurogenesis induced by WBI, and its neurocognitive consequences.

Elevated TRAF2/6 expression in Parkinson's disease is caused by the loss of Parkin E3 ligase activity

Parkinson's disease (PD) is the second leading neurodegenerative disease, and is known to be induced by environmental factors or genetic mutations. Among the verified genetic mutations of PD, Parkin, isolated from the PARK2 locus, shows an autosomal recessive inheritance pattern and is known to be an E3 ligase. However, the physiological target of Parkin and the molecular mechanism of Parkin-deficiency-induced PD have not been clearly demonstrated until now. It has recently been proposed that inflammation, suggesting as a causal factor for PD, is enhanced by Parkin deficiency. Thus, we examined the relationship between inflammation-related factors and Parkin. Here, we provide the evidence that Parkin suppresses inflammation and cytokine-induced cell death by promoting the proteasomal degradation of TRAF2/6 (TNF-α receptor-associated factor 2/6). Overexpression of Parkin can reduce the half-lives of TRAF2 and TRAF6, whereas si-Parkin can extend them. However, mutant Parkins did not alter the expression of TRAF2/6. Thus, loss of Parkin enhances sensitivity to TNF-α- or IL-1β-induced JNK activation and NF-κB activation. Indeed, si-Parkin-induced apoptosis is suppressed by the knockdown of TRAF6 or TRAF2. We also observed elevated expression levels of TRAF6 and a reduction of IκB in an 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced PD mouse model. Moreover, elevated expression levels or aggregation of TRAF6 were detected in approximately half of the human PD tissues (7/15 cases) and 2 cases, respectively. In addition, TRAF6 and Parkin expression levels show a reverse relationship in human PD tissues. Our results strongly suggest that the reduction of Parkin or overexpression of TRAF2/6 by chronic inflammation would be the reason for occurrence of PD.

Isorhamnetin inhibits Prevotella intermedia lipopolysaccharide-induced production of interleukin-6 in murine macrophages via anti-inflammatory heme oxygenase-1 induction and inhibition of nuclear factor-κB and signal transducer and activator of transcription 1 activation

BACKGROUND AND OBJECTIVE

Interleukin-6 (IL-6) is a key proinflammatory cytokine that has been considered to be important in the pathogenesis of periodontal disease. Therefore, host-modulatory agents directed at inhibiting IL-6 appear to be beneficial in terms of attenuating periodontal disease progression and potentially improving disease susceptibility. In the current study, we investigated the effect of the flavonoid isorhamnetin on the production of IL-6 in murine macrophages stimulated with lipopolysaccharide (LPS) from Prevotella intermedia, a pathogen implicated in inflammatory periodontal disease, and its mechanisms of action.

MATERIAL AND METHODS

Lipopolysaccharide from P. intermedia ATCC 25611 was isolated using the standard hot phenol-water method. Culture supernatants were collected and assayed for IL-6. We used real-time PCR to quantify IL-6 and heme oxygenase-1 (HO-1) mRNA expression. The expression of HO-1 protein and the levels of signaling proteins were monitored using immunoblot analyses. The DNA-binding activity of nuclear factor-κB (NF-κB) was analyzed using ELISA-based assay kits.

RESULTS

Isorhamnetin significantly down-regulated P. intermedia LPS-induced production of IL-6 as well as its mRNA expression in RAW264.7 cells. Isorhamnetin up-regulated the expression of HO-1 at both gene transcription and translation levels in cells stimulated with P. intermedia LPS. In addition, inhibition of HO-1 activity by tin protoporphyrin IX blocked the inhibitory effect of isorhamnetin on IL-6 production. Isorhamnetin failed to prevent LPS from activating either c-Jun N-terminal kinase or p38 pathways. Isorhamnetin did not inhibit NF-κB transcriptional activity at the level of inhibitory κB-α degradation. Isorhamnetin suppressed NF-κB signaling through inhibition of nuclear translocation and DNA binding activity of NF-κB p50 subunit and attenuated signal transducer and activator of transcription 1 signaling.

CONCLUSION

Although further research is required to clarify the detailed mechanism of action, we propose that isorhamnetin may contribute to blockade of the host-destructive processes mediated by IL-6 and could be a highly efficient modulator of the host response in the treatment of inflammatory periodontal disease. Further research in animal models of periodontitis is required to better evaluate, the potential of isorhamnetin as a novel agent for treating periodontal disease.

Identifying genes related to radiation resistance in oral squamous cell carcinoma cell lines

Radioresistance is one of the main determinants of treatment outcome in oral cancer, but the prediction of radioresistance is difficult. The authors aimed to establish radioresistant oral squamous cell carcinoma (OSCC) cell lines to identify genes with altered expression in response to radioresistance. To induce radioresistant cell lines, the authors treated OSCC cell lines with an accumulated dosage of 60Gy over 30 cycles of radiotherapy. They compared the results from cDNA arrays and proteomics between non-radiated and radioresistant cell lines in order to identify changes in gene expression. Western blot analysis was used to validate the results. The cDNA array revealed 265 commonly up-regulated genes and 268 commonly down-regulated genes in radioresistant cell lines, 30 of which were cancer-related genes. Proteomics identified 51 proteins with commonly altered expression in radioresistant cell lines, 18 of which were cancer-related proteins. Both the cDNA array and proteomics indicated that NM23-H1 and PA2G4 were over-expressed. Western blot analysis showed increased expression of NM23-H1, but not PA2G4, in radioresistant cell lines. The authors concluded that NM23-H1 may be a radioresistance-related gene and over-expression of NM23-H1 could serve as a biomarker to predict radioresistance in OSCC.

Senescence marker protein 30 deficiency increases Parkinson's pathology by impairing astrocyte activation

Senescence marker protein 30 (SMP30) was recently identified as gluconolactonase, which is involved in vitamin C (VC) biosynthesis. Therefore, the antioxidant property of SMP30 is thought to be mediated by its gluconolactonase function. However, pathologic effects of SMP30 deficiency independent of VC biosynthesis have not been studied in models of neurodegenerative diseases. In the present study, we evaluated the effect of SMP30 deficiency on Parkinson's disease (PD) in SMP30 knockout (KO) mice. Wild type and SMP30 KO mice supplemented with VC were treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Our results showed that MPTP-induced dopaminergic neuronal loss and motor function impairment were more significant in the SMP30 KO mice. Reactive oxygen species generation and microglia activation were higher in MPTP-treated SMP30 KO mice. However, SMP30 deficiency mitigated MPTP-induced astrocyte activation and glia-derived neurotrophic factor production. Cultures of astrocytes recovered from wild type and SMP30 KO mice revealed that SMP30 deficiency abolished 1-methyl-4-phenyl-pyridinium-induced astroglial activation by blocking the extracellular signal-regulated kinase pathway. Taken together, our findings demonstrate for the first time that SMP30 deficiency increases the severity of PD and suggest a beneficial role of SMP30 in protective astrocyte activation in response to neurodegeneration. The present study shows that modulation of astrocytic SMP30 can be a promising target for treating PD.

Resveratrol inhibits the proliferation of neural progenitor cells and hippocampal neurogenesis

Resveratrol is a phytoalexin and natural phenol that is present at relatively high concentrations in peanuts and red grapes and wine. Based upon studies of yeast and invertebrate models, it has been proposed that ingestion of resveratrol may also have anti-aging actions in mammals including humans. It has been suggested that resveratrol exerts its beneficial effects on health by activating the same cellular signaling pathways that are activated by dietary energy restriction (DR). Some studies have reported therapeutic actions of resveratrol in animal models of metabolic and neurodegenerative disorders. However, the effects of resveratrol on cell, tissue and organ function in healthy subjects are largely unknown. In the present study, we evaluated the potential effects of resveratrol on the proliferation and survival of neural progenitor cells (NPCs) in culture, and in the hippocampus of healthy young adult mice. Resveratrol reduced the proliferation of cultured mouse multi-potent NPCs, and activated AMP-activated protein kinase (AMPK), in a concentration-dependent manner. Administration of resveratrol to mice (1-10 mg/kg) resulted in activation of AMPK, and reduced the proliferation and survival of NPCs in the dentate gyrus of the hippocampus. Resveratrol down-regulated the levels of the phosphorylated form of cyclic AMP response element-binding protein (pCREB) and brain-derived neurotrophic factor (BDNF) in the hippocampus. Finally, resveratrol-treated mice exhibited deficits in hippocampus-dependent spatial learning and memory. Our findings suggest that resveratrol, unlike DR, adversely affects hippocampal neurogenesis and cognitive function by a mechanism involving activation of AMPK and suppression of CREB and BDNF signaling.

The hepatoprotective effects of adenine nucleotide translocator-2 against aging and oxidative stress

Mitochondrial adenine nucleotide translocator (ANT) plays important roles in the regulation of mitochondrial permeability transition and cell bioenergetics. The mouse has three ANT isoforms (1, 2 and 4) showing tissue-specific expression patterns. Although ANT1 is known to have a pro-apoptotic property, the specific functions of ANT2 have not been well determined. In the present study, ANT2 expression was significantly lower in the aged rat liver and in a liver fibrosis model. To explore the protective role of ANT2 in the liver, we established a hepa1c1c7 cell line overexpressing ANT2. Overexpression of ANT2 caused hepa1c1c7 cells to be more resistant to oxidative stress, and mitochondrial membrane potential (MMP, ∆Ψm) was relatively intact in ANT2-overexpressing cells under oxidative stress. In addition, ANT2 was found to increase ATP production by influencing mitochondrial bioenergetics. These results imply that the hepatoprotective effect of ANT2 is due to the stabilization of MMP and enhanced ATP production, and thus, maintaining ANT2 levels in the liver might be important to enhance resistance to aging and oxidative stress.

Organic solvent metabolite, 1,2-diacetylbenzene, impairs neural progenitor cells and hippocampal neurogenesis

1,2-Diacetylbenzene (DAB) is a neurotoxic minor metabolite of 1,2-diethylbenzene or naphthalene reaction product with OH radical. DAB causes central and peripheral neuropathies that lead to motor neuronal deficits. However, the potent effects and molecular mechanisms of DAB on neural progenitor cells and hippocampus are unknown. In the current study, we report the DAB damage at lower doses (less than 50 μM) to neural progenitor cell (NPC) invitro and hippocampal neurogenesis invivo. DAB significantly suppressed NPC proliferation with increased reactive oxygen species (ROS) production in a dose-dependent manner. The suppression of NPC proliferation was effectively blunted by the action of an antioxidant, N-acetyl cysteine. Six-week-old male C57BL/6 mice were treated with 1 or 5 mg/kg DAB for 2 weeks. DAB significantly suppressed NPC proliferation in the dentate gyrus of the hippocampus, indicating impaired hippocampal neurogenesis. Increased ROS production and the formation of oxidative stress-associated dinitrophenyl adducts were detected in the hippocampal homogenates of DAB-treated mice. DAB activated Mac-1-positive immune cells which are involved in inflammatory process in the hippocampus. Taken together, these results confirm that oxidative stress by DAB might be cause of adverse effects in NPC proliferation and hippocampal neurogenesis.

Exposure to bisphenol A appears to impair hippocampal neurogenesis and spatial learning and memory

Bisphenol A (BPA) is widely used in the manufacture of plastics and epoxy resins, and is known to affect reproductive organ growth and development. However, the effects of BPA on hippocampal neurogenesis are unclear in young adult mice. Therefore, the present study was conducted to examine the effects of BPA on hippocampal neurogenesis and learning as well as memory performance in young adult mice. BPA (1, 5, and 20 mg/kg/day) was administered orally to mice for 2 weeks. It was found that high-dose BPA (20 mg/kg/day) decreased the number of newly generated cells in hippocampus, but that low-dose BPA (1 mg/kg) increased the survival of newly generated cells in hippocampi of young mice. Furthermore, high-dose BPA (20mg/kg/day) was found to impair learning and memory performance significantly. However, no significant differences were observed between high- and low-dose treated mice in terms of levels of brain-derived neurotrophic factor (BDNF) or reactive oxygen species production in hippocampus. In addition, BPA treatment did not induce neuronal loss or damage or astrocyte activation. These data suggest that exposure to BPA causes fluctuations in hippocampal neurogenesis in young adult mice that result in spatial learning and memory impairment via a BDNF-independent pathway.

Morin attenuates tau hyperphosphorylation by inhibiting GSK3β

Alzheimer's disease (AD) is the major form of age-related dementia and is characterized by progressive cognitive impairment, the accumulation of extracellular amyloid β-peptide (Aβ), and intracellular hyperphosphorylated tau aggregates in affected brain regions. Tau hyperphosphorylation and accumulation in neurofibrillary tangles is strongly correlated with cognitive deficits, and is apparently a critical event in the dementia process because mutations in tau can cause a tangle-only form of dementia called frontotemporal lobe dementia. Among kinases that phosphorylate tau, glycogen synthase kinase 3β (GSK3β) is strongly implicated in AD pathogenesis. In the present study, we established an ELISA to screen for agents that inhibit GSK3β activity and found that the flavonoid morin effectively inhibited GSK3β activity and blocked GSK3β-induced tau phosphorylation in vitro. In addition, morin attenuated Aβ-induced tau phosphorylation and protected human neuroblastoma cells against Aβ cytotoxicity. Furthermore, treatment of 3xTg-AD mice with morin resulted in reductions in tau hyperphosphorylation and paired helical filament-like immunoreactivity in hippocampal neurons. Morin is a novel inhibitor of GSK3β that can reduce tau pathology in vivo and may have potential as a therapeutic agent in tauopathies.

Anomalous band formation in arrays of terahertz nanoresonators

We investigate band formation in one-dimensional periodic arrays of rectangular holes which have a nanoscale width but a length of 100 μm. These holes are tailored to work as resonators in the terahertz frequency regime. We study the evolution of the electromagnetic response with the period of the array, showing that this dependence is not monotonic due to both the oscillating behavior of the coupling between holes and its long-range character.

Senescence marker protein 30 is up-regulated in kainate-induced hippocampal damage through ERK-mediated astrocytosis

Senescence maker protein 30 (SMP30) is decreased in an androgen-independent manner in kidney and liver with age. However, regulation of SMP30 expression in the brain has not been examined in aging and neurodegenerative diseases. To investigate SMP30 expression in the brain, we utilized aging and kainate (KA)-induced neurodegenerative disease models. Interestingly, expression of SMP30 was unlikely to decrease in the aged brain, but total levels of SMP30 protein were increased at 4 weeks after KA injury. Increased glial fibrillary acidic protein (GFAP) with elevated SMP30 expression was observed at the same time post-KA, indicating that regulation of SMP30 expression in the brain may be associated with astrocytosis. We confirmed that KA induced GFAP expression with increased SMP30 in rat astrocyte cells. Moreover, we found that ERK1/2 activation was involved in the up-regulation of SMP30 in astrocytes. Our results suggest that elevated SMP30 in activated astrocytes plays an important supportive role after brain damage.

Capsaicin impairs proliferation of neural progenitor cells and hippocampal neurogenesis in young mice

Capsaicin (N-vanillyl-8-methyl-1-nonenamide) is a major pungent ingredient in hot peppers and induces apoptosis in malignant carcinoma cell lines. However, the adverse effects of capsaicin on neuronal development have not been fully explored. The aim of this study was to determine whether capsaicin affected murine-derived cerebellar multi-potent neural progenitor cells (NPC) or adult hippocampal neurogenesis in vivo. Capsaicin dose-dependently suppressed NPC proliferation, and higher concentrations were cytotoxic. Capsaicin decreased the activation of extracellular signal-regulated kinases (ERK) without markedly affecting p38 kinases. Capsaicin reduced the number of newly generated cells in the dentate gyrus of the hippocampus but did not significantly alter learning and memory performance in young adult mice. Interestingly, capsaicin decreased ERK activation in the hippocampus, suggesting that reduced ERK signaling may be involved in the capsaicin-mediated regulation of hippocampal neurogenesis.

Potencies of bisphenol A on the neuronal differentiation and hippocampal neurogenesis

Endocrine-disrupting chemicals (EDC) produce adverse effects on reproductive and immune function or neurological behavior, and may also induce cancer. The environmental EDC bisphenol A (BPA) is widely used in the manufacture of plastics and epoxy resins. BPA affects reproductive organ growth and development, but the potential adverse effects of BPA on neuronal development are not fully understood. Here, BPA concentration-dependently decreased proliferation of murine-derived multipotent neural progenitor cells (NPC), and high concentrations produced cytotoxicity. In contrast, low concentrations of BPA, which possess estrogenic activity, stimulated NPC differentiation into a neuronal phenotype. BPA treatment did not affect neonatal brain development in F1 mice. However, BPA treatment (20 mg/kg) accelerated formation of the dentate gyrus in postnatal day 1 mice. Prenatal and postnatal BPA treatment did not affect adult hippocampal neurogenesis in the dentate gyrus in 8-wk-old mice. Data indicate that BPA stimulates neuronal differentiation and might disrupt neonatal brain development.

Risk assessment for the combinational effects of food color additives: neural progenitor cells and hippocampal neurogenesis

In 2006, the Korea Food and Drug Administration reported that combinations of dietary colors such as allura red AC (R40), tartrazine (Y4), sunset yellow FCF (Y5), amaranth (R2), and brilliant blue FCF (B1) are widely used in food manufacturing. Although individual tar food colors are controlled based on acceptable daily intake (ADI), there is no apparent information available for how combinations of these additives affect food safety. In the current study, the potencies of single and combination use of R40, Y4, Y5, R2, and B1 were examined on neural progenitor cell (NPC) toxicity, a biomarker for developmental stage, and neurogenesis, indicative of adult central nervous system (CNS) functions. R40 and R2 reduced NPC proliferation and viability in mouse multipotent NPC, in the developing CNS model. Among several combinations tested in mouse model, combination of Y4 and B1 at 1000-fold higher than average daily intake in Korea significantly decreased numbers of newly generated cells in adult mouse hippocampus, indicating potent adverse actions on hippocampal neurogenesis. However, other combinations including R40 and R2 did not affect adult hippocampal neurogenesis in the dentate gyrus. Evidence indicates that single and combination use of most tar food colors may be safe with respect to risk using developmental NPC and adult hippocampal neurogenesis. However, the response to excessively high dose combination of Y4 and B1 is suggestive of synergistic effects to suppress proliferation of NPC in adult hippocampus. Data indicated that combinations of tar colors may adversely affect both developmental and adult hippocampal neurogenesis; thus, further extensive studies are required to assess the safety of these additive combinations.

Molecular Mechanism of Dietary Restriction in Neuroprevention and Neurogenesis: Involvement of Neurotrophic Factors

Dietary restriction (DR) is the most efficacious intervention for retarding the deleterious effects of aging. DR increases longevity, decreases the occurrence and severity of age-related diseases, and retards the physiological decline associated with aging. The beneficial effects of DR have been mostly studied in non-neuronal tissues. However, several studies have showed that DR attenuate neuronal loss after several different insults including exposure to kainate, ischemia, and MPTR Moreover, administration of the non-metabolizable glucose analog 2-deoxy-D-glucose (2DG) could mimic the neuroprotective effect of DR in rodent, presumably by limiting glucose availability at the cellular level. Based on the studies of chemically induced D.R., it has been proposed that the mechanism whereby DR and 2DG protect neurons is largely mediated by stress response proteins such as HSP70 and GRP78 which are increased in neurons of rats and mice fed a DR regimen. In addition, D.R., as mild metabolic stress, could lead to the increased activity in neuronal circuits and thus induce expression of neurotrophic factors. Interestingly, such increased neuronal activities also enhance neurogenesis in the brains of adult rodents. In this review, we focus on what is known regarding molecular mechanisms of the protective role of DR in neurodegenerative diseases and aging process. Also, we propose that DR is a mild cellular stress that stimulates production of neurotrophic factors, which are major regulators of neuronal survival, as well as neurogenesis in adult brain.

Curcumin stimulates proliferation of embryonic neural progenitor cells and neurogenesis in the adult hippocampus

Curcumin is a natural phenolic component of yellow curry spice, which is used in some cultures for the treatment of diseases associated with oxidative stress and inflammation. Curcumin has been reported to be capable of preventing the death of neurons in animal models of neurodegenerative disorders, but its possible effects on developmental and adult neuroplasticity are unknown. In the present study, we investigated the effects of curcumin on mouse multi-potent neural progenitor cells (NPC) and adult hippocampal neurogenesis. Curcumin exerted biphasic effects on cultured NPC; low concentrations stimulated cell proliferation, whereas high concentrations were cytotoxic. Curcumin activated extracellular signal-regulated kinases (ERKs) and p38 kinases, cellular signal transduction pathways known to be involved in the regulation of neuronal plasticity and stress responses. Inhibitors of ERKs and p38 kinases effectively blocked the mitogenic effect of curcumin in NPC. Administration of curcumin to adult mice resulted in a significant increase in the number of newly generated cells in the dentate gyrus of hippocampus, indicating that curcumin enhances adult hippocampal neurogenesis. Our findings suggest that curcumin can stimulate developmental and adult hippocampal neurogenesis, and a biological activity that may enhance neural plasticity and repair.

Interferon-gamma promotes differentiation of neural progenitor cells via the JNK pathway

It has been reported that interferon-gamma (IFN-gamma) facilitates differentiation of PC-12 cells and murine adult neural stem cells. Here we show that IFN-gamma promotes the differentiation of C17.2 neural progenitor cells (NPC) into a neuronal phenotype characterized by neurite outgrowth and the expression of the neuronal marker protein beta-III tubulin. IFN-gamma induced an increase in the activity c-jun N-terminal kinase (JNK) without affecting activities of extracellular signal-regulated kinases (ERKs 1 and 2). An inhibitor of JNK blocked the ability of IFN-gamma to promote differentiation of NPC into neurons, whereas an inhibitor of ERKs 1 and 2 did not. Our findings show that the pro-inflammatory cytokine, IFN-gamma has the potential to stimulate neurogenesis, suggesting roles for this cytokine in development and repair of the nervous system.