Microglia induce auditory dysfunction after status epilepticus in mice.

Auditory dysfunction and increased neuronal activity in the auditory pathways have been reported in patients with temporal lobe epilepsy, but the cellular mechanisms involved are unknown. Here, we report that microglia play a role in the disinhibition of auditory pathways after status epilepticus in mice. We found that neuronal activity in the auditory pathways, including the primary auditory cortex and the medial geniculate body (MGB), was increased and auditory discrimination was impaired after status epilepticus. We further demonstrated that microglia reduced inhibitory synapses on MGB relay neurons over an 8-week period after status epilepticus, resulting in auditory pathway hyperactivity. In addition, we found that local removal of microglia from the MGB attenuated the increase in c-Fos+ relay neurons and improved auditory discrimination. These findings reveal that thalamic microglia are involved in auditory dysfunction in epilepsy.

Anatomical variability, multi-modal coordinate systems, and precision targeting in the marmoset brain.

Localising accurate brain regions needs careful evaluation in each experimental species due to their individual variability. However, the function and connectivity of brain areas is commonly studied using a single-subject cranial landmark-based stereotactic atlas in animal neuroscience. Here, we address this issue in a small primate, the common marmoset, which is increasingly widely used in systems neuroscience. We developed a non-invasive multi-modal neuroimaging-based targeting pipeline, which accounts for intersubject anatomical variability in cranial and cortical landmarks in marmosets. This methodology allowed creation of multi-modal templates (MarmosetRIKEN20) including head CT and brain MR images, embedded in coordinate systems of anterior and posterior commissures (AC-PC) and CIFTI grayordinates. We found that the horizontal plane of the stereotactic coordinate was significantly rotated in pitch relative to the AC-PC coordinate system (10 degrees, frontal downwards), and had a significant bias and uncertainty due to positioning procedures. We also found that many common cranial and brain landmarks (e.g., bregma, intraparietal sulcus) vary in location across subjects and are substantial relative to average marmoset cortical area dimensions. Combining the neuroimaging-based targeting pipeline with robot-guided surgery enabled proof-of-concept targeting of deep brain structures with an accuracy of 0.2 mm. Altogether, our findings demonstrate substantial intersubject variability in marmoset brain and cranial landmarks, implying that subject-specific neuroimaging-based localization is needed for precision targeting in marmosets. The population-based templates and atlases in grayordinates, created for the first time in marmoset monkeys, should help bridging between macroscale and microscale analyses.

Involvement of Calcium-Dependent Pathway and ß Subunit-Interaction in Neuronal Migration and Callosal Projection Deficits Caused by the Cav1.2 I1166T Mutation in Developing Mouse Neocortex.

Introduction: Gain-of-function mutations in the L-type Ca2+ channel Cav1.2 cause Timothy syndrome (TS), a multisystem disorder associated with neurologic symptoms, including autism spectrum disorder (ASD), seizures, and intellectual disability. Cav1.2 plays key roles in neural development, and its mutation can affect brain development and connectivity through Ca2+-dependent and -independent mechanisms. Recently, a gain-of-function mutation, I1166T, in Cav1.2 was identified in patients with TS-like disorder. Its channel properties have been analyzed in vitro but in vivo effects of this mutation on brain development remain unexplored. Methods: In utero electroporation was performed on ICR mice at embryonic day 15 to express GFP, wild-type, and mutant Cav1.2 channels into cortical layer 2/3 excitatory neurons in the primary somatosensory area. The brain was fixed at postnatal days 14-16, sliced, and scanned using confocal microscopy. Neuronal migration of electroporated neurons was examined in the cortex of the electroporated hemisphere, and callosal projection was examined in the white matter and contralateral hemisphere. Results: Expression of the I1166T mutant in layer 2/3 neurons caused migration deficits in approximately 20% of electroporated neurons and almost completely diminished axonal arborization in the contralateral hemisphere. Axonal projection in the white matter was not affected. We introduced second mutations onto Cav1.2 I1166T; L745P mutation blocks Ca2+ influx through Cav1.2 channels and inhibits the Ca2+-dependent pathway, and the W440A mutation blocks the interaction of the Cav1.2 α1 subunit to the ß subunit. Both second mutations recovered migration and projection. Conclusion: This study demonstrated that the Cav1.2 I1166T mutation could affect two critical steps during cerebrocortical development, migration and axonal projection, in the mouse brain. This is mediated through Ca2+-dependent pathway downstream of Cav1.2 and ß subunit-interaction.

Neuronal brain-derived neurotrophic factor manipulates microglial dynamics.

Brain-derived neurotrophic factor (BDNF), a main member of the neurotrophin family that is active in the brain, supports neuronal survival and growth. Microglial BDNF affects both the structural and functional properties of neurons. In contrast, whether and how neuronal BDNF affects microglial dynamics remain largely undetermined. Here, we examined the effects of BDNF on the properties of microglia in the CA3 region of the hippocampus. We chose this site because the axonal boutons of hippocampal mossy fibers, which are mostly formed in the CA3 region, contain the highest levels of BDNF in the rodent brain. We transfected mouse dentate granule cells with an adeno-associated virus that encodes both a BDNF short hairpin RNA (shRNA) and red fluorescent protein to examine the effects of mossy fiber-derived BDNF on microglia. Based on immunohistochemistry, BDNF knockdown with an shRNA resulted in an increase in microglial density in the mossy fiber pathway and increased engulfment of mossy fiber axons by microglia. In addition, we performed time-lapse imaging of microglial processes in hippocampal slice cultures to examine the effects of BDNF on microglial motility. Time-lapse imaging revealed increases in the motility of microglial processes and the engulfment of mossy fiber synapses by microglia when BDNF signaling was pharmacologically blocked. Thus, neuronal BDNF prevents microglia from engulfing mossy fiber synapses in the hippocampus.

Induced neuronal activity does not attenuate amyloid beta-induced synaptic loss in vitro.

AIM: The accumulation of amyloid beta (Aß) is one of the characteristics of Alzheimer's disease. The excessive accumulation of Aß has been suggested to result in a decrease in the number of synapses. Although the number of synapses is generally modulated by neuronal activity, whether neuronal activity affects Aß-induced synapse loss remains unknown. Therefore, we addressed this question using a primary culture of hippocampal neurons. METHOD: The neuronal activity of cultured hippocampal neurons from mouse pups was increased using the chemogenetic technique designer receptors exclusively activated by designer drugs (DREADD). The cultured neurons were treated with Aß, and synapse density was assessed by immunocytochemistry. RESULTS: Aß decreased the synapse density probably by decreasing postsynapse. On the other hand, enhanced neuronal activity did not affect the synapse density significantly. However, there was a trend that enhanced neuronal activity increased especially presynapse density. CONCLUSION: We found that enhanced neuronal activity did not affect Aß-induced synapse loss in vitro.

New screening strategy and analysis for identification of allosteric modulators for glucagon-like peptide-1 receptor using GLP-1 (9-36) amide.

The glucagon-like peptide-1 receptor (GLP-1R) is an important physiologic regulator of insulin secretion and a major therapeutic target for diabetes mellitus. GLP-1 (7-36) amide (active form of GLP-1) is truncated to GLP-1 (9-36) amide, which has been described as a weak agonist of GLP-1R and the major form of GLP-1 in the circulation. New classes of positive allosteric modulators (PAMs) for GLP-1R may offer improved therapeutic profiles. To identify these new classes, we developed novel and robust primary and secondary high-throughput screening (HTS) systems in which PAMs were identified to enhance the GLP-1R signaling induced by GLP-1 (9-36) amide. Screening enabled identification of two compounds, HIT-465 and HIT-736, which possessed new patterns of modulation of GLP-1R. We investigated the ability of these compounds to modify GLP-1R signaling enhanced GLP-1 (9-36) amide- and/or GLP-1 (7-36) amide-mediated cyclic adenosine monophosphate (cAMP) accumulation. These compounds also had unique profiles with regard to allosteric modulation of multiple downstream signaling (PathHunter ß-arrestin signaling, PathHunter internalization signaling, microscopy-based internalization assay). We found allosteric modulation patterns to be obviously different among HIT-465, HIT-736, and Novo Nordisk compound 2. This work may enable the design of new classes of drug candidates by targeting modulation of GLP-1 (7-36) amide and GLP-1 (9-36) amide.

Flavonoids enhance melanogenesis in human melanoma cells.

Flavonoids are pigmentary compounds existing widely in plants. We have reported that quercetin (3, 3', 4', 5, 7-pentahydroxylflavone), one of the typical flavonoids, strongly promotes melanogenesis by melanocytes. Meanwhile, there are 8000 or more flavonoids having a chemical structure different from each other in the natural world. Their distinctive chemical properties suggest that they may be different in melanogenic actions. In the present study, the melanogenic actions of 14 flavonoids were analyzed to correlate their chemical structures with melanogenic actions. To evaluate the effects of flavonoids on melanogenesis, the HMV II cell line derived from human malignant melanoma was used. Flavonols including quercetin, kaempferol, rhamnetin and fisetin, flavones including apigenin, luteolin and chrysin, and isoflavones including genestein showed melanogenesis-promoting actions but rutin, robinetin, myricetin, ipriflavone, epigalocatechin gallate (EGCg) and naringin did not. From analyses of the relationships between the chemical structures of flavonoids and their melanogenesis-promoting actions, it was inferred that a hydroxyl group bound to the phenyl group plays an important role in stimulating melanogenesis. From the above results, 8 flavonoids were identified as melanogenesis promoters. Also, correlations were established between the melanogenesis-promoting actions of flavonoids and their chemical structures.

Stimulation of melanogenesis by nordihydroguaiaretic Acid in human melanoma cells.

Nordihydroguaiaretic acid (NDGA), a lignan found in vegetables, fruits and legumin, has been shown to possess antineoplastic, antiviral and antioxidant characteristics. In this study, we examined the effect of NDGA on melanogenesis in human melanoma cells (HMVII). In vitro, NDGA does not alter mushroom tyrosinase activity. However, in NDGA-treated HMVII cells, cellular tyrosinase activity increased in both a time- and dose-dependent manner. The concomitant increases in melanin content in NDGA-treated cells indicated an elevation of melanin synthesis by tyrosinase activation. In addition, after a 7-day incubation, melanin content in 20 µM NDGA-treated cells increased 5.02 fold. Tyrosinase protein also increased by treatment with NDGA. Nevertheless, tyrosinase mRNA was not altered in NDGA-treated cells. Our results suggest that NDGA can increase tyrosinase activity and de novo synthesis of melanin in human melanoma cells. We found that NDGA is a novel potent stimulator of melanogenesis in human melanoma cells.

7-Phenyl-imidazoquinolin-4(5H)-one derivatives as selective and orally available mPGES-1 inhibitors.

To identify compounds with strong mPGES-1 inhibitory activity and clear in vitro ADME profile, we optimized the lead compound 1 by carrying our substitutions at the C(7)- and C(8)-positions. Replacement of the bromine atom of 1 with various substituents led to identification of the phenyl group as the best C(7)-substituent giving strong inhibitory activity with good in vitro ADME profile. Further SAR examination on both the C(2)- and the C(7)-phenyl groups provided compound 39 as the best candidate for further development. Compound 39 exhibited strong mPGES-1 inhibitory activity (IC50=4.1 nM), potent cell-based functional activity (IC50=33 nM) with good mPGES-1 selectivity (over 700-fold), excellent in vitro ADME profile, and good oral absorption in rat PK study.

Synthesis and biological evaluation of substituted imidazoquinoline derivatives as mPGES-1 inhibitors.

We have previously reported 7-bromo-2-(2-chrolophenyl)-imidazoquinolin-4(5H)-one (1) as a novel potent mPGES-1 inhibitor. To clarify the essential functional groups of 1 for inhibition of mPGES-1, we investigated this compound structure-activity relationship following substitution at the C(4)-position and N-alkylation at the N(1)-, the N(3)-, and the N(5)-positions of 1. To prepare the target compounds, we established a good methodology for selective N-alkylation of the imidazoquinolin-4-one, that is, selective alkylation of 1 at the N(3)- and N(5)-positions was achieved by use of an appropriate base and introduction of a protecting group at the nitrogen atom in the imidazole part, respectively. Replacement of the C(4)-oxo group with nitrogen- or sulfur- linked substituents gave decreased inhibitory activity for mPGES-1, and introduction of alkyl groups on the nitrogen atom at the N(1)-, the N(3)-, and the N(5)-positions resulted in even larger loss of inhibitory activity. These results revealed that the C(4)-oxo group, and the hydrogen atoms at the N(5)-position and the imidazole part were the best substituents.

Screening for adiponectin secretion regulators.

Adiponectin is an adipokine secreted from adipocytes and plays important roles in the suppression of metabolic syndromes that can result in type 2 diabetes, obesity, and atherosclerosis. Adiponectin is a promising drug target because a number of studies have shown that upregulation of adiponectin has a number of therapeutic benefits. Extensive efforts have revealed various adiponectin regulators, such as cytokines, transcription factors, and drugs. Cytokines, such as tumor necrosis factor α, IL-6, and IL-18, downregulate adiponectin production. On the other hand, transcription factors such as peroxisome proliferator-activated receptor-γ (PPARγ), CCAAT-enhancer-binding protein α, and forkhead box O1 (FoxO1) upregulate adiponectin expression, although the activating transcription factor 3 and cAMP response element-binding protein downregulate it. Although a number of therapeutic drugs have been reported as adiponectin secretion regulators, most of them act through PPARγ-dependent mechanisms, leaving PPARγ-derived side effects as a concern. Using high-throughput screening, we have identified PPARγ-independent adiponectin secretion regulators as potential drug candidates with a novel mechanism of action.

Synthesis and SAR study of imidazoquinolines as a novel structural class of microsomal prostaglandin E2 synthase-1 inhibitors.

The imidazoquinoline derivative 1 was found as a novel mPGES-1 inhibitor. Optimization of 1 led to the identification of the 2-chlorophenyl group at the C(2)-position and the quinolone structure at the C(4)-position. Compound 33, the most potent synthesized compound, showed excellent mPGES-1 inhibition (IC(50)=9.1nM) with high selectivity (>1000-fold) over both COX-1 and COX-2.

High-throughput screening for small-molecule adiponectin secretion modulators.

Adiponectin is an adipokine secreted by adipocytes and plays a role in the suppression of metabolic disorders that can result in type 2 diabetes, obesity, and atherosclerosis. Several studies have shown that upregulation of adiponectin has a number of therapeutic benefits. Although peroxisome proliferator-activated receptor γ (PPARγ) agonists are known to increase adiponectin secretion both in cultured adipocytes and humans, they have several side effects, such as weight gain, congestive heart failure, and edema. Therefore, adiponectin secretion modulators that do not possess PPARγ agonistic activity seem to promising for a number of conditions. Here, the authors report on the development of a reporter-based high-throughput screening (HTS) assay using insulin-resistant-mimic 3T3-L1 adipocytes for discovery of adiponectin secretion modulators. They screened a library of approximately 100 000 small-molecule compounds using this model, performed several follow-up screens, and identified six hit compounds that increase adiponectin secretion without having PPARγ agonistic activity. These compounds may be useful drug candidates for diabetes, obesity, atherosclerosis, and other metabolic syndromes. This HTS assay might be applicable to screening for other adipokine modulators that can be useful for the treatment of other conditions.

A homogeneous time-resolved fluorescence-based high-throughput screening system for discovery of inhibitors of IKKbeta-NEMO interaction.

The nuclear transcription factor NF-kappaB is crucial to the expression of numerous cytokines, enzymes, and cell adhesion molecules, all of which can drive inflammatory and autoimmune disorders such as rheumatoid arthritis. The IKK complex plays the most important role in the signal cascade leading to NF-kappaB activation. Recently, inhibition of the interaction between NEMO (NF-kappaB essential modulator) and the catalytic subunits of IKK, especially IKKbeta, has received particular attention as a possible new therapeutic approach to treatment of inflammatory disorders, and several reports have shown the efficacy of cell permeable NEMO binding domain (NBD)-containing peptides in blocking the IKK/NF-kappaB pathway. In this article, we describe in detail the development and validation of two novel binding assays, a homogeneous time-resolved fluorescence (HTRF)-based assay and an enzyme-linked immunosorbent assay (ELISA)-based assay, suitable for the discovery of small molecules that inhibit IKKbeta-NEMO interaction. Using the HTRF-based assay, we screened approximately 15,000 compounds from our chemical library and eliminated false positive hits by the ELISA-based assay and IKK complex kinase assay. As a result, seven positive hit compounds that inhibit IKK complex activity through inhibition of IKKbeta-NEMO interaction were identified. These hit compounds may have a good potential in the treatment of inflammatory and autoimmune disorders such as rheumatoid arthritis.

Sevoflurane stimulates MAP kinase signal transduction through the activation of PKC alpha and betaII in fetal rat cerebral cortex cultured neuron.

Protein kinase C (PKC) is a key enzyme that participates in various neuronal functions. PKC has also been identified as a target molecule for general anesthetic actions. Raf, mitogen-activated protein kinase (MEK) and extracellular signal-regulated kinase (ERK1/2) have been thought to be target effectors of PKC. In the present study, we attempted to evaluate the effect of sevoflurane on PKC/MAPK cascade signaling in cultured fetal rat cerebral -cortex neurons, prepared from embryonic day 18 fetuses. The effects of sevoflurane on the translocation of 7 PKC isoforms (alpha, betaI, betaII, gamma, delta, varepsilon and zeta) were observed by immunoblotting using isoform-selective antibodies to PKCs. The treatment of neurons with sevoflurane induced the translocation of PKC alpha and PKC betaII species from the cytosol to the membrane fraction, which indicated the activation of these PKC isoforms. In contrast, there was no clear change in the distribution of other PKC isoforms. We next examined whether the specific activation of PKC alpha and betaII by sevoflurane could stimulate the MAP kinase signaling pathway in cultured neurons. Raf phosphorylation was increased by the administration of 0.25 mM sevoflurane. The phosphorylation of Raf proteins reached a maximum at 5-10 min. Subsequently, the phosphorylation of MEK proteins was increased at 10-15 min after sevoflurane treatments. That of ERK proteins was induced at 15-60 min. Moreover, the phosphorylation of ERK induced by sevoflurane was significantly decreased by the treatment of PKC inhibitor (staurosporine) and MEK inhibitor (PD98059). On the other hand, the contents of total Raf, MEK and ERK proteins were relatively constant at all times examined. To examine the -localization of phosphorylated-ERK protein, immunohistochemical staining of sevoflurane-treated cultured neurons was performed. The phosphorylated-ERK proteins were markedly accumulated in both the cytosol of the cell body and the neurites in the neuronal cells with time after 0.25 mM sevoflurane-treatment. These results demonstrated that sevoflurane induced the phosphorylation of the MAP kinase cascade through the activation of the PKC alpha and PKC betaII species.

Quercetin-induced melanogenesis in a reconstituted three-dimensional human epidermal model.

Quercetin (3,5,7,3',4'-pentahydroxyflavone) is one of the most abundant natural flavonoids. It is present in various common vegetables and fruits. In this report, we examined the effect of quercetin on melanogenesis using a three-dimensional reconstituted human epidermal culture model, MelanoDerm, which is a new commercially-available cultured human epidermis containing functional melanocytes. Treatment with 10 microM quercetin induced an increase of tyrosinase activity in cultured epidermis after 3-5 days in time-dependent manner. In the quercetin-treated epidermis, furthermore, melanin content and tyrosinase expression were markedly increased, as shown by immunohistochemistry after a 7-day culture period. Ultrastructural studies clearly indicated an accumulation of mature melanosomes (stages III and IV) inside the basal layer of the cultured epidermis after the quercetin treatment. In addition, the dendrites of melanocytes extended further towards the adjacent keratinocytes after quercetin treatment. These results suggest that quercetin has an effect on maturation of melanosomes and that quercetin has the potential to induced melanogenesis in human epidermis.

Quercetin enhances melanogenesis by increasing the activity and synthesis of tyrosinase in human melanoma cells and in normal human melanocytes.

Quercetin (3,3',4',5,7-pentahydroxyflavone) is a diphenyl propanoid widely distributed in edible plants. In this study, we examined the effect of quercetin on melanogenesis in human HMVII melanoma cells and in normal human epidermal melanocytes (NHEM) in the absence of ultraviolet radiation. Upon the addition of quercetin to the culture medium, the melanin content in melanoma cells (HMVII) increased remarkably in time- and dose-dependent manners. In addition, quercetin induced melanogenesis in cultured NHEM. As compared with controls, melanin content was increased about sevenfold by treatment with 20 microM (HMVII) or 1 microM (NHEM) quercetin for 7 d. Tyrosinase activity was also increased, to 61.8-fold higher than the control. The expression of tyrosinase protein was slightly increased by the addition of quercetin. However, quercetin did not affect the expression of tyrosinase mRNA. Tyrosinase activation by quercetin was blocked by actinomycin-D or by cycloheximide demonstrating that its actions in stimulating melanogenesis may involve both transcriptional and translational events. Tyrosinase activity was increased dramatically whereas the level of melanogenic inhibitor was remarkably decreased following quercetin treatment. Taken together, these results demonstrate that in human melanoma cells and in NHEM, quercetin stimulates melanogenesis by increasing tyrosinase activity and decreasing other factors such as melanogenic inhibitors.

A novel and potent biological antioxidant, Kinobeon A, from cell culture of safflower.

Kinobeon A was originally isolated from cultured cells of safflower (Carthamus tinctorius L., Compositae). It had never previously been directly isolated from safflower or other plants, animals or microorganisms. In this report, we demonstrate the anti-oxidative effects of kinobeon A and compare the results with those two known natural antioxidants, lignan (nordihydroguaiaretic acid) and quercetin. The NADPH-induced microsomal lipid peroxidation system was employed to assess anti-oxidative effects of kinobeon A. Addition of kinobeon A to the system significantly decreased the formation of thiobarbituric acid reactive substances (TBARS) in a dose-dependent manner with effects similar to those of lignan and quercetin. Formation of TBARS was completely inhibited at 10 microM of kinobeon A. Employing the xanthine/xanthine oxidase/nitroblue tetrazolium system and the KO2/XTT system, the superoxide anion scavenging activity of kinobeon A was greater than that of lignan or quercetin. IC50 values calculated for kinobeon A in these two systems were 1 microM and 0.8 microM, respectively. Kinobeon A exerted cytoprotective effects following oxidative treatments with hydrogen peroxide, cumene hydroperoxide, menadione and xanthine oxidase (XOD). Addition of kinobeon A to the systems markedly enhanced survival ratios of Madin-Darby bovine kidney cells, while their survival significantly decreased with the oxidative treatment alone. Kinobeon A exhibited stronger effect on the cell viability than lignan or quercetin when menadion or XOD were used as inducing reagents of oxidative stress. The present study demonstrates for the first time that kinobeon A prevents oxidative stresses and could be a useful cytoprotective reagent.

Kinobeon A as a potent tyrosinase inhibitor from cell culture of safflower: in vitro comparisons of kinobeon A with other putative inhibitors.

Kinobeon A is produced from cell cultures of the medicinal plant, safflower. Mushroom tyrosinase activity was inhibited in a concentration-dependent manner when treated with kinobeon A using L-tyrosine or L-3,4-dihydroxyphenylalannine (L-DOPA) as substrates. IC50 values were 22 microM (substrate: L-tyrosine) and 27 microM (L-DOPA). Inhibition of human tyrosinase activity also increased with increasing concentrations of kinobeon A using L-DOPA as the substrate, with an IC50 value of 2.5 microM. Kinobeon A was a more potent competitive inhibitor than kojic acid, arbutin or L-ascorbic acid for both mushroom and human tyrosinase as determined from Lineweaver-Burk plots. These results suggested that kinobeon A could be a potent natural tyrosinase inhibitor.