Su-Yong Eun

6-Hydroxydopamine-Induced PC12 Cell Death is Mediated by MEF2D Down-regulation

Recently, it was reported that in a 4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) model, neuronal cell death is associated with the cdk5-mediated hyperphosphorylation of myocyte enhancer factor 2 (MEF2), a transcription factor that is critically required for neuronal survival. In the present study, we investigated the possible involvement of cdk5-mediated MEF2D down-regulation on 6-hydroxydopamine (6-OHDA)-induced PC12 cell death. 6-OHDA was found to significantly increase nitric oxide (NO) production and to induce apoptosis in a time-dependent manner in PC12 cells. Furthermore, 6-OHDA was found to markedly reduce MEF2D levels under conditions that could induce PC12 cell apoptosis. In addition, PC12 cell death and MEF2D degradation by 6-OHDA were prevented by the cdk5 inhibitor roscovitine, but roscovitine could not restore the 6-OHDA-induced inactivation of Akt. These results suggest that the cell death and MEF2D degradation caused by 6-OHDA are dependent on cdk5 activity. On the other hand, roscovitine enhanced the 6-OHDA-induced activations of ERK1/2 and JNK, but reduced the 6-OHDA-induced activation of p38. These results suggest that PC12 cell death by 6-OHDA appears to be regulated by the down-regulation of MEF2D via some interaction between cdk5 and MAP kinase.

Modulatory effects of aromatherapy massage intervention on electroencephalogram, psychological assessments, salivary cortisol and plasma brain-derived neurotrophic factor

OBJECTIVES Aromatherapy massage is commonly used for the stress management of healthy individuals, and also has been often employed as a therapeutic use for pain control and alleviating psychological distress, such as anxiety and depression, in oncological palliative care patients. However, the exact biological basis of aromatherapy massage is poorly understood. Therefore, we evaluated here the effects of aromatherapy massage interventions on multiple neurobiological indices such as quantitative psychological assessments, electroencephalogram (EEG) power spectrum pattern, salivary cortisol and plasma brain-derived neurotrophic factor (BDNF) levels. DESIGN A control group without treatment (n = 12) and aromatherapy massage group (n = 13) were randomly recruited. They were all females whose children were diagnosed as attention deficit hyperactivity disorder and followed up in the Department of Psychiatry, Jeju National University Hospital. Participants were treated with aromatherapy massage for 40 min twice per week for 4 weeks (8 interventions). RESULTS A 4-week-aromatherapy massage program significantly improved all psychological assessment scores in the Stat-Trait Anxiety Index, Beck Depression Inventory and Short Form of Psychosocial Well-being Index. Interestingly, plasma BDNF levels were significantly increased after a 4 week-aromatherapy massage program. Alpha-brain wave activities were significantly enhanced and delta wave activities were markedly reduced following the one-time aromatherapy massage treatment, as shown in the meditation and neurofeedback training. In addition, salivary cortisol levels were significantly reduced following the one-time aromatherapy massage treatment. CONCLUSIONS These results suggest that aromatherapy massage could exert significant influences on multiple neurobiological indices such as EEG pattern, salivary cortisol and plasma BDNF levels as well as psychological assessments.

Neuroprotective effect of methyl lucidone against microglia-mediated neurotoxicity.

Excessive microglial activation-mediated neurotoxicity has been implicated in playing a crucial role in the pathogenesis of stroke and neurodegenerative diseases. Therefore, much attention has been paid to therapeutic strategies aimed at suppressing neurotoxic microglial activation. The microglial regulatory mechanism of methyl lucidone, a cyclopentenedione isolated from the stem bark of Lindera erythrocarpa Makino, was investigated in the present study. Methyl lucidone treatment (0.1-10 μM) significantly inhibited lipopolysaccharide (LPS, 100 ng/ml, 24 h)-stimulated nitric oxide (NO) production in a dose-dependent manner in both primary cortical microglia and BV-2 cell line. Moreover, it strongly inhibited LPS-stimulated secretion of pro-inflammatory cytokines, such as interleukin 6 (IL-6) and tumor necrosis factor α (TNF-α). Methyl lucidone treatment markedly induced down-regulation of LPS-induced nuclear translocation of nuclear factor κB (NF-κB) through preventing the degradation of the inhibitory protein IκBα. In addition, phosphorylation of Akt and mitogen-activated protein kinases (MAPKs) such as extracellular signal-regulated kinase (ERK) and p38 kinases were also suppressed by methyl lucidone. The cell viabilities of HT-22 neurons were significantly attenuated by treatment of the conditioned media containing neurotoxic secretary molecules from LPS-stimulated microglia. However, methyl lucidone significantly blocked neuronal cell death induced by microglial conditioned media. These neuroprotective effects of methyl lucidone were also confirmed in a neuron-microglia co-culture system using EGFP-transfected B35 neuroblastoma cell line. Taken together, these results suggest that methyl lucidone may have a neuroprotective potential via inhibition of neurotoxic microglial activation implicated in neurodegeneration.

Expression of fibroblast growth factor receptor 3 in the recurrence of non-muscle-invasive urothelial carcinoma of the bladder.

Purpose The fibroblast growth factor receptor 3 (FGFR3) gene is known to be frequently mutated in noninvasive urothelial carcinomas of the bladder. In this study, we investigated the expression of FGFR3, Ki-67, and p53 in bladder cancers and the effects of expression on tumor recurrence. Materials and Methods Fifty-five cases of primary bladder cancer were examined by immunohistochemistry. The relationship of these markers with various clinicopathological factors, including recurrence, was assessed. Results Positivity for cytoplasmic FGFR3 (FGFR3-c) was associated with a lower cancer grade (p=0.022) and stage (p=0.011). Recurrence was more frequent in patients with a higher stage, negative FGFR3-c, and high Ki-67 expression. According to univariate analysis, predictors of recurrence-free survival included the following: age, stage, FGFR-c, Ki-67, and p53. However, none of these was independent from the other parameters in multivariate studies. Conclusions The immunohistochemical expression of FGFR3 is not only one of the characteristic features of lower-grade and lower-stage urothelial carcinoma but also a possible marker in predicting disease recurrence.

Cell type-specific upregulation of myristoylated alanine-rich C kinase substrate and protein kinase C-α, -β I, -β II, and -δ in microglia following kainic acid-induced seizures

Myristoylated alanine-rich C kinase substrate (MARCKS) is a widely distributed protein kinase C (PKC) substrate and has been implicated in actin cytoskeletal rearrangement in response to extracellular stimuli. Although MARCKS was extensively examined in various cell culture systems, the physiological function of MARCKS in the central nervous system has not been clearly understood. We investigated alterations of cellular distribution and phosphorylation of MARCKS in the hippocampus following kainic acid (KA)-induced seizures. KA (25 mg/kg, i.p.) was administered to eight to nine week-old C57BL/6 mice. Behavioral seizure activity was observed for 2 h after the onset of seizures and was terminated with diazepam (8 mg/kg, i.p.). The animals were sacrificed and analyzed at various points in time after the initiation of seizure activity. Using double-labeling immunofluorescence analysis, we demonstrated that the expression and phosphorylation of MARCKS was dramatically upregulated specifically in microglial cells after KA-induced seizures, but not in other types of glial cells. PKC α, β I, β II and δ, from various PKC isoforms examined, also were markedly upregulated, specifically in microglial cells. Moreover, immunoreactivities of phosphorylated MARCKS were co-localized in the activated microglia with those of the above isoforms of PKC. Taken together, our in vivo data suggest that MARCKS is closely linked to microglial activation processes, which are important in pathological conditions, such as neuroinflammation and neurodegeneration.

Mild mitochondrial depolarization is involved in a neuroprotective mechanism of Citrus sunki peel extract.

Mitochondrial membrane potential (∆Ψm) contributes to determining a driving force for calcium to enter the mitochondria. It has been demonstrated that even a small mitochondrial depolarization is sufficient to prevent mitochondrial calcium overload and the subsequent apoptosis. Therefore, mild mitochondrial depolarization has been recently evaluated as a novel mechanism of neuroprotection via inhibiting neurotoxic mitochondrial calcium overload during neuronal insults. In the present study, using both real‐time recording and flow cytometric analyses of ∆Ψm, we demonstrated that ethanolic peel extract of Citrus sunki Hort. ex Tanaka (CPE) and its active compounds are capable of inducing a mild mitochondrial depolarization. Polymethoxylated flavones such as nobiletin and tangeretin were found as the active compounds responsible for CPE effects on ∆Ψm. Neuronal viability was significantly increased in a dose‐dependent manner by CPE treatment in H2O2‐stimulated HT‐22 cells as an in vitro neuronal insult model. CPE treatment significantly inhibited H2O2‐induced apoptotic processes such as chromatin condensation, caspase 3 activation and anti‐poly (ADP‐ribose) polymerase (PARP) cleavage. CPE treatment significantly blocked mitochondrial calcium overload in H2O2‐stimulated HT‐22 neurons as indicated by rhod‐2 acetoxymethyl ester. Taken together, our findings suggest that CPE and its active compounds may be considered as promising neuroprotective agents via inducing a mild mitochondrial depolarization. Copyright

Long-term Synaptic Plasticity: Circuit Perturbation and Stabilization

At central synapses, activity-dependent synaptic plasticity has a crucial role in information processing, storage, learning, and memory under both physiological and pathological conditions. One widely accepted model of learning mechanism and information processing in the brain is Hebbian Plasticity: long-term potentiation (LTP) and long-term depression (LTD). LTP and LTD are respectively activity-dependent enhancement and reduction in the efficacy of the synapses, which are rapid and synapse-specific processes. A number of recent studies have a strong focal point on the critical importance of another distinct form of synaptic plasticity, non-Hebbian plasticity. Non-Hebbian plasticity dynamically adjusts synaptic strength to maintain stability. This process may be very slow and occur cell-widely. By putting them all together, this mini review defines an important conceptual difference between Hebbian and non-Hebbian plasticity.

Kv4.2 block of long-term potentiation is partially dependent on synaptic NMDA receptor remodeling.

Proper expression of synaptic NMDA receptors (NMDARs) is necessary to regulate synaptic Ca²(+) influx and the induction the long-term potentiation (LTP) in the mammalian hippocampus. Previously we reported that expressing the A-type K(+) channel subunit Kv4.2 in CA1 neurons of organotypic slice cultures reduced synaptic NR2B-containing NMDAR expression and completely blocked LTP induced by a pairing protocol. As pretreatment with an NMDAR antagonist (APV) overnight blocked the reduction of NR2B-containing receptors in neurons expressing EGFP-labeled Kv4.2 (Kv4.2g), we hypothesized that LTP would be rescued in Kv4.2g neurons by overnight treatment with APV. We report here that the overnight APV pretreatment in Kv4.2g-expressing neurons only partially restored potentiation. This partial potentiation was completely blocked by inhibition of the CAMKII kinase. These results indicate that A-type K(+) channels must regulate synaptic integration and plasticity through another mechanism in addition to their regulation of synaptic NR2 subunit composition. We suggest that dendritic excitability, which is regulated by Kv4.2 expression, also contributes to synaptic plasticity.

Dieckol Attenuates Microglia-mediated Neuronal Cell Death via ERK, Akt and NADPH Oxidase-mediated Pathways

Excessive microglial activation and subsequent neuroinflammation lead to synaptic loss and dysfunction as well as neuronal cell death, which are involved in the pathogenesis and progression of several neurodegenerative diseases. Thus, the regulation of microglial activation has been evaluated as effective therapeutic strategies. Although dieckol (DEK), one of the phlorotannins isolated from marine brown alga Ecklonia cava, has been previously reported to inhibit microglial activation, the molecular mechanism is still unclear. Therefore, we investigated here molecular mechanism of DEK via extracellular signal-regulated kinase (ERK), Akt and nicotinamide adenine dinuclelotide phosphate (NADPH) oxidase-mediated pathways. In addition, the neuroprotective mechanism of DEK was investigated in microglia-mediated neurotoxicity models such as neuron-microglia co-culture and microglial conditioned media system. Our results demonstrated that treatment of anti-oxidant DEK potently suppressed phosphorylation of ERK in lipopolysaccharide (LPS, 1 µg/ml)-stimulated BV-2 microglia. In addition, DEK markedly attenuated Akt phosphorylation and increased expression of gp91phox, which is the catalytic component of NADPH oxidase complex responsible for microglial reactive oxygen species (ROS) generation. Finally, DEK significantly attenuated neuronal cell death that is induced by treatment of microglial conditioned media containing neurotoxic secretary molecules. These neuroprotective effects of DEK were also confirmed in a neuron-microglia co-culture system using enhanced green fluorescent protein (EGFP)-transfected B35 neuroblastoma cell line. Taken together, these results suggest that DEK suppresses excessive microglial activation and microglia-mediated neuronal cell death via downregulation of ERK, Akt and NADPH oxidase-mediated pathways.

Quercetagetin inhibits macrophage‐derived chemokine in HaCaT human keratinocytes via the regulation of signal transducer and activator of transcription 1, suppressor of cytokine signalling 1 and transforming growth factor‐β1

Inflammatory chemokines, such as macrophage‐derived chemokine (MDC/CCL22), are elevated in the serum and lesioned skin of patients with atopic dermatitis (AD), and are ligands for C‐C chemokine receptor 4, which is predominantly expressed on T helper 2 lymphocytes, basophils and natural killer cells. We have previously reported that quercetagetin has an inhibitory activity on inflammatory chemokines, which is induced by interferon (IFN)‐γ and tumour necrosis factor (TNF)‐α, occurring via inhibition of the signal transducer and activator of transcription 1 (STAT1) signal.