Publications by authors named "Jin Bong Park"

75 Publications

Bee venom reduces burn-induced pain via the suppression of peripheral and central substance P expression in mice.

J Vet Sci 2021 Jan;22(1):e9

Department of Physiology and Medical Science, College of Medicine and Brain Research Institute, Chungnam National University, Daejeon 35015, Korea.

Background: Scalding burn injuries can occur in everyday life but occur more frequently in young children. Therefore, it is important to develop more effective burn treatments.

Objectives: This study examined the effects of bee venom (BV) stimulation on scalding burn injury-induced nociception in mice as a new treatment for burn pain.

Methods: To develop a burn injury model, the right hind paw was immersed temporarily in hot water (65°C, 3 seconds). Immediately after the burn, BV (0.01, 0.02, or 0.1 mg/kg) was injected subcutaneously into the ipsilateral knee area once daily for 14 days. A von Frey test was performed to assess the nociceptive response, and the altered walking parameters were evaluated using an automated gait analysis system. In addition, the peripheral and central expression changes in substance P (Sub P) were measured in the dorsal root ganglion and spinal cord by immunofluorescence.

Results: Repeated BV treatment at the 2 higher doses used in this study (0.02 and 0.1 mg/kg) alleviated the pain responses remarkably and recovered the gait performances to the level of acetaminophen (200 mg/kg, intraperitoneal, once daily), which used as the positive control group. Moreover, BV stimulation had an inhibitory effect on the increased expression of Sub P in the peripheral and central nervous systems by a burn injury.

Conclusions: These results suggest that a peripheral BV treatment may have positive potency in treating burn-induced pain.
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http://dx.doi.org/10.4142/jvs.2021.22.e9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7850793PMC
January 2021

High Salt Intake Recruits Tonic Activation of NR2D Subunit-Containing Extrasynaptic NMDARs in Vasopressin Neurons.

J Neurosci 2021 Feb 10;41(6):1145-1156. Epub 2020 Dec 10.

Department of Physiology, Chungnam National University, Daejeon 35015, Republic of Korea

In addition to producing a classical excitatory postsynaptic current via activation of synaptic NMDA receptors (NMDARs), glutamate in the brain also induces a tonic NMDAR current () via activation of extrasynaptic NMDARs (eNMDARs). However, since Mg blocks NMDARs in nondepolarized neurons, the potential contribution of eNMDARs to the overall neuronal excitatory/inhibitory (E/I) balance remains unknown. Here, we demonstrate that chronic (7 d) salt loading (SL) recruited NR2D subunit-containing NMDARs to generate an Mg-resistant tonic in nondepolarized [ (holding potential) -70 mV] vasopressin (VP; but not oxytocin) supraoptic nucleus (SON) neurons in male rodents. Conversely, in euhydrated (EU) and 3 d SL mice, Mg-resistant tonic was not observed. Pharmacological and genetic intervention of NR2D subunits blocked the Mg-resistant tonic in VP neurons under SL conditions, while an NR2B antagonist unveiled Mg-sensitive tonic but not Mg-resistant tonic In the EU group VP neurons, an Mg-resistant tonic was not generated by increased ambient glutamate or treatment with coagonists (e.g., d-serine and glycine). Chronic SL significantly increased NR2D expression but not NR2B expression in the SON relative to the EU group or after 3 d under SL conditions. Finally, Mg-resistant tonic selectively upregulated neuronal excitability in VP neurons under SL conditions, independent of ionotropic GABAergic input. Our results indicate that the activation of NR2D-containing NMDARs constitutes a novel mechanism that generates an Mg-resistant tonic in nondepolarized VP neurons, thus causing an E/I balance shift in VP neurons to compensate for the hormonal demands imposed by a chronic osmotic challenge. The hypothalamic supraoptic nucleus (SON) consists of two different types of magnocellular neurosecretory cells (MNCs) that synthesize and release the following two peptide hormones: vasopressin (VP), which is necessary for regulation of fluid homeostasis; and oxytocin (OT), which plays a major role in lactation and parturition. NMDA receptors (NMDARs) play important roles in shaping neuronal firing patterns and hormone release from the SON MNCs in response to various physiological challenges. Our results show that prolonged (7 d) salt loading generated a Mg-resistant tonic NMDA current mediated by NR2D subunit-containing receptors, which efficiently activated nondepolarized VP (but not OT) neurons. Our findings support the hypothesis that NR2D subunit-containing NMDARs play an important adaptive role in adult brain in response to a sustained osmotic challenge.
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http://dx.doi.org/10.1523/JNEUROSCI.1742-20.2020DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7888215PMC
February 2021

Alpha-Methylacyl-CoA Racemase (AMACR), a Potential New Biomarker for Glioblastoma.

Front Oncol 2020 13;10:550673. Epub 2020 Oct 13.

Department of Pharmacology, Metabolic Syndrome and Cell Signaling Laboratory, Institute for Cancer Research, College of Medicine, Chungnam National University, Daejeon, South Korea.

Alpha-Methylacyl-CoA racemase (AMACR), which was initially discovered as a prostate cancer marker, is critical for the chiral inversion mechanism of branched-chain fatty acids. However, the function of AMACR in brain tumors has not been investigated. In this study, AMACR appeared to be involved in glioblastoma. The protein and mRNA levels of AMACR were highly elevated in glioblastoma. Downregulation of AMACR inhibited cell proliferation. Comprehensive analysis of the public REMBRANDT GBM dataset also confirmed that the level of AMACR expression was correlated with the clinical prognosis of glioma patients. In summary, these findings indicate that AMACR expression is increased in a glioblastoma cell line and glioma patients, suggesting that AMACR might be a potential diagnostic marker and therapeutic target for cancer, including glioma.
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http://dx.doi.org/10.3389/fonc.2020.550673DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7590573PMC
October 2020

Positive allosteric modulation of GABA receptors by a novel antiepileptic drug cenobamate.

Eur J Pharmacol 2020 Jul 20;879:173117. Epub 2020 Apr 20.

Department of Physiology, College of Medicine and Brain Research Institute, Chungnam National University, 6 Munhwa-ro, Jung-gu, Daejeon, 35015, Republic of Korea. Electronic address:

Cenobamate is a novel antiepileptic drug under investigation for use in patients with focal (partial-onset) seizures. To understand its potential molecular mechanism of action, the effects of cenobamate on GABA-mediated currents and GABA receptors in rodent hippocampal neurons were examined. Cenobamate potentiated GABA-induced currents (I) in acutely isolated CA3 pyramidal cells in a concentration-dependent manner (EC, 164 μM), which was not affected by flumazenil, a benzodiazepine receptor antagonist. Cenobamate enhanced tonic GABA currents (I), which is defined as a holding current shift by the GABA receptor antagonist bicuculline (EC, 36.63 μM). At therapeutically relevant concentrations, cenobamate induced minimal changes in the frequency, amplitudes, and decay time of spontaneous inhibitory postsynaptic currents in the CA1 neurons. Flumazenil failed to affect cenobamate-potentiated I and I in CA1 neurons. Cenobamate showed positive allosteric modulation of GABA-induced I mediated by GABA receptors. This effect was similar for all tested hGABA receptors containing six different alpha subunits (αβγ or αβγ), with EC values ranging from 42 to 194 μM. Cenobamate did not displace the binding of flunitrazepam, a benzodiazepine derivative, or flumazenil to GABA receptors. The results showed that cenobamate, a novel antiepileptic drug, acts as a positive allosteric modulator of high-affinity GABA receptors, activated by GABA at a site independent of the benzodiazepine binding site and efficiently enhances I inhibition in hippocampal neurons, which could be an underlying molecular mechanism stabilizing neural circuits of the epileptic hippocampus.
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http://dx.doi.org/10.1016/j.ejphar.2020.173117DOI Listing
July 2020

Author Correction: CD200R/Foxp3-mediated signalling regulates microglial activation.

Sci Rep 2020 Mar 23;10(1):5510. Epub 2020 Mar 23.

Department of Anatomy, Brain Research Institute, Chungnam National University School of Medicine, Daejeon, 301-747, Republic of Korea.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.
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http://dx.doi.org/10.1038/s41598-020-62310-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7090081PMC
March 2020

Bestrophin1-mediated tonic GABA release from reactive astrocytes prevents the development of seizure-prone network in kainate-injected hippocampi.

Glia 2020 05 13;68(5):1065-1080. Epub 2019 Dec 13.

Department of Medical Science, College of Medicine and Brain Research Institute, Chungnam National University, Daejeon, Republic of Korea.

Tonic extrasynaptic GABA receptor (GABA R) activation is under the tight control of tonic GABA release from astrocytes to maintain the brain's excitation/inhibition (E/I) balance; any slight E/I balance disturbance can cause serious pathological conditions including epileptic seizures. However, the pathophysiological role of tonic GABA release from astrocytes has not been tested in epileptic seizures. Here, we report that pharmacological or genetic intervention of the GABA-permeable Bestrophin-1 (Best1) channel prevented the generation of tonic GABA inhibition, disinhibiting CA1 pyramidal neuronal firing and augmenting seizure susceptibility in kainic acid (KA)-induced epileptic mice. Astrocyte-specific Best1 over-expression in KA-injected Best1 knockout mice fully restored the generation of tonic GABA inhibition and effectively suppressed seizure susceptibility. We demonstrate for the first time that tonic GABA from reactive astrocytes strongly contributes to the compensatory shift of E/I balance in epileptic hippocampi, serving as a good therapeutic target against altered E/I balance in epileptic seizures.
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http://dx.doi.org/10.1002/glia.23762DOI Listing
May 2020

Calpain-2 as a Treatment Target in Prenatal Stress-induced Epileptic Spasms in Infant Rats.

Exp Neurobiol 2019 Aug;28(4):529-536

Department of Medical Science, Chungnam National University, Daejeon 35015, Korea.

Stress can induce a serious epileptic encephalopathy that occurs during early infancy. Recent studies have revealed that prenatal stress exposure is a risk factor for the development of infantile spasms. Our previous work demonstrates that prenatal stress with betamethasone-induced alterations to the expression of the K/Cl co-transporter (KCC2) in gamma-aminobutyric acid (GABA) interneurons lowers the seizure threshold in exposed animals. Here, we further investigated the mechanisms involved in this KCC2 dysfunction and explored possible treatment options. We stressed Sprague-Dawley rats prenatally and further treated dams with betamethasone on gestational day 15, which increases seizure susceptibility and NMDA (N-Methyl-D-aspartate)-triggered spasms on postnatal day 15. In this animal model, first, we evaluated baseline calpain activity. Second, we examined the cleavage and dephosphorylation of KCC2. Finally, we checked the effect of a calpain inhibitor on seizure occurrence. The phosphorylated-N-methyl-Daspartate Receptor 2B (NR2B):non-phosphorylated NR2B ratio was found to be higher in the cortex of the prenatally stressed betamethasone model. We further found that the betamethasone model exhibited increased phosphorylation of calpain-2 and decreased phosphorylation of KCC2 and Glutamic acid decarboxylase 67 (GAD67). After using a calpain inhibitor in prenatal-stress rats, the seizure frequency decreased, while latency increased. GABAergic depolarization was further normalized in prenatal-stress rats treated with the calpain inhibitor. Our study suggests that calpain-dependent cleavage and dephosphorylation of KCC2 decreased the seizure threshold of rats under prenatal stress. Calpain-2 functions might, thus, be targeted in the future for the development of treatments for epileptic spasms.
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http://dx.doi.org/10.5607/en.2019.28.4.529DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6751866PMC
August 2019

The extracellular role of Ref-1 as anti-inflammatory function in lipopolysaccharide-induced septic mice.

Free Radic Biol Med 2019 08 15;139:16-23. Epub 2019 May 15.

Research Institute of Medical Sciences, Department of Physiology, School of Medicine, Chungnam National University, Daejeon, South Korea. Electronic address:

Apurinic/apyrimidinic endonuclease/redox factor-1 (Ref-1), a multifunctional protein secreted from stimulated cells, has been identified as a new serological biomarker. Despite recent reports on the role of Ref-1 in inflammation, the biological function of secreted Ref-1 remains unknown, especially in vivo. This study aimed to evaluate the possible roles of secreted Ref-1 in lipopolysaccharide-induced systemic inflammation in vivo. We generated a secretory Ref-1 adenoviral vector system, AdPPT-LS-Ref-1, by conjugation of preprotrypsin leading sequence (PPT-LS) with full-length Ref-1 sequences. Expression of tumor necrosis factor-α (TNF-α)-induced vascular cell adhesion molecule-1 (VCAM-1) in endothelial cells and lipopolysaccharide (LPS)-induced cyclooxygenase-2 in Raw264.7 cells was inhibited by secretory Ref-1, and this inhibitory effect was abrogated following neutralization of Ref-1 with anti-Ref-1 antibody. Plasma Ref-1 levels following administration of AdPPT-LS-Ref-1 (2 × 10 ifu, i.p.) for 24 h were substantially higher than those recorded following administration of Adβgal (84.6 ± 7.2 ng/ml vs. 4.4 ± 1.5 ng/ml). Treatment with LPS (10 mg/kg, i.v. for 6 h) markedly increased VCAM-1 expression, cathepsin or myeloperoxidase activity, which were significantly suppressed by treatment with AdPPT-LS-Ref-1. Furthermore, LPS-induced cytokines, such as TNF-α, interleukin (IL)-1β, IL-6, and monocyte chemoattractant protein 1, were significantly inhibited in AdPPT-LS-Ref-1-treated mice. However, LPS-induced myeloperoxidase activities were not suppressed by treatment with the redox mutant of secretory Ref-1, AdPPT-LS-Ref-1(C65A/C93A), or wild-type AdRef-1. Collectively, these results suggest that secreted Ref-1 has anti-inflammatory properties and that its redox cysteine residue is associated with the anti-inflammatory activity in vivo. Furthermore, our findings indicate that secretory Ref-1 may be useful as a therapeutic biomolecule against systemic inflammation.
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http://dx.doi.org/10.1016/j.freeradbiomed.2019.05.013DOI Listing
August 2019

Exercise training normalizes elevated firing rate of hypothalamic presympathetic neurons in heart failure rats.

Am J Physiol Regul Integr Comp Physiol 2019 02 28;316(2):R110-R120. Epub 2018 Nov 28.

Department of Veterinary Pharmacology, College of Veterinary Medicine and Research Institute for Veterinary Science, Seoul National University , Seoul , Republic of Korea.

Exercise training (ExT) normalizes elevated sympathetic nerve activity in heart failure (HF), but the underlying mechanisms are not well understood. In this study, we examined the effects of 3 wk of ExT on the electrical activity of the hypothalamic presympathetic neurons in the brain slice of HF rats. HF rats were prepared by ligating the left descending coronary artery. The electrophysiological properties of paraventricular nucleus neurons projecting to the rostral ventrolateral medulla (PVN-RVLM) were examined using the slice patch-clamp technique. The neuronal firing rate was elevated in HF rats, and ExT induced a reduction in the firing rate ( P < 0.01). This ExT-induced decrease in the firing rate was associated with an increased frequency of spontaneous and miniature inhibitory postsynaptic current (IPSCs; P < 0.05). There was no significant change in excitatory postsynaptic current. Replacing Ca with Mg in the recording solution reduced the elevated IPSC frequency in HF rats with ExT ( P < 0.01) but not in those without ExT, indicating an increase in the probability of GABA release. In contrast, ExT did not restore the reduced GABA receptor-mediated tonic inhibitory current in HF rats. A GABA receptor blocker (bicuculline, 20 μM) increased the firing rate in HF rats with ExT ( P < 0.01) but not in those without ExT. Collectively, these results show that ExT normalized the elevated firing activity by increasing synaptic GABA release in PVN-RVLM neurons in HF rats. Our findings provide a brain mechanism underlying the beneficial effects of ExT in HF, which may shed light on the pathophysiology of other diseases accompanied by sympathetic hyperactivation.
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http://dx.doi.org/10.1152/ajpregu.00225.2018DOI Listing
February 2019

C-27-carboxylated oleanane triterpenoids up-regulate TRAIL DISC assembly via p38 MAPK and CHOP-mediated DR5 expression in human glioblastoma cells.

Biochem Pharmacol 2018 12 22;158:243-260. Epub 2018 Oct 22.

Department of Pharmacology, College of Medicine, Chungnam National University, 266 Munhwa-ro, Daejeon 35015, Republic of Korea. Electronic address:

Despite recent tremendous progress, targeting of TNF-related apoptosis-inducing ligand (TRAIL) as a cancer therapy has limited success in many clinical trials, in part due to inactivation of death inducing signaling complex (DISC)-mediated caspase-8 signaling cascade in highly malignant tumors such as glioblastoma. In this study, screening of constituents derived from Astilbe rivularis for TRAIL-sensitizing activity identified C-27-carboxylated oleanolic acid derivatives (C27OAs) including 3β-hydroxyolean-12-en-27-oic acid (C27OA-1), 3β,6β,7α-trihydroxyolean-12-en-27-oic acid (C27OA-2), and 3β-trans-p-coumaroyloxy-olean-12-en-27-oic acid (C27OA-3) as novel TRAIL sensitizers. Interestingly, these C27OAs did not affect apoptotic cell death induced by either ligation of other death receptor (DR) types, such as TNF and Fas or DNA damaging agents, which suggests that C27OAs effectively and selectively sensitize TRAIL-mediated caspase-8 activation. Mechanistically, C27OAs upregulate the expression of cell surface DR5 and DISC formation without affecting downstream intracellular apoptosis-related proteins. The upregulation of DR5 expression by C27OAs strictly depends on transactivation of C/EBP homology protein, which is regulated through the p38 MAPK pathway, rather than p53 and intracellular reactive oxygen species status. Taken together, our results identify the novel C27OAs as TRAIL sensitizers targeting the upstream DISC assembly of DR5, and provide a rationale for further development of C27OAs for facilitating TRAIL-based chemotherapy in glioblastoma patients.
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http://dx.doi.org/10.1016/j.bcp.2018.10.019DOI Listing
December 2018

GABAergic signaling linked to autophagy enhances host protection against intracellular bacterial infections.

Nat Commun 2018 10 10;9(1):4184. Epub 2018 Oct 10.

Department of Microbiology, Chungnam National University School of Medicine, Daejeon, 35015, Korea.

Gamma-aminobutyric acid (GABA) is the principal inhibitory neurotransmitter in the brain; however, the roles of GABA in antimicrobial host defenses are largely unknown. Here we demonstrate that GABAergic activation enhances antimicrobial responses against intracellular bacterial infection. Intracellular bacterial infection decreases GABA levels in vitro in macrophages and in vivo in sera. Treatment of macrophages with GABA or GABAergic drugs promotes autophagy activation, enhances phagosomal maturation and antimicrobial responses against mycobacterial infection. In macrophages, the GABAergic defense is mediated via macrophage type A GABA receptor (GABAR), intracellular calcium release, and the GABA type A receptor-associated protein-like 1 (GABARAPL1; an Atg8 homolog). Finally, GABAergic inhibition increases bacterial loads in mice and zebrafish in vivo, suggesting that the GABAergic defense plays an essential function in metazoan host defenses. Our study identified a previously unappreciated role for GABAergic signaling in linking antibacterial autophagy to enhance host innate defense against intracellular bacterial infection.
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http://dx.doi.org/10.1038/s41467-018-06487-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6180030PMC
October 2018

CR6 interacting factor 1 deficiency promotes endothelial inflammation by SIRT1 downregulation.

PLoS One 2018 23;13(2):e0192693. Epub 2018 Feb 23.

Department of physiology & Medical Science, School of Medicine, Chungnam National University, Daejeon, Republic of Korea.

Aims: CR6 interacting factor 1 (CRIF1) deficiency impairs mitochondrial oxidative phosphorylation complexes, contributing to increased mitochondrial and cellular reactive oxygen species (ROS) production. CRIF1 downregulation has also been revealed to decrease sirtuin 1 (SIRT1) expression and impair vascular function. Inhibition of SIRT1 disturbs oxidative energy metabolism and stimulates nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB)-induced inflammation. Therefore, we hypothesized that both CRIF1 deficiency-induced mitochondrial ROS production and SIRT1 reduction play stimulatory roles in vascular inflammation.

Methods And Results: Plasma levels and mRNA expression of proinflammatory cytokines (tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6) were markedly elevated in endothelium-specific CRIF1-knockout mice and CRIF1-silenced endothelial cells, respectively. Moreover, CRIF1 deficiency-induced vascular adhesion molecule-1 (VCAM-1) expression was consistently attenuated by the antioxidant N-acetyl-cysteine and NF-κB inhibitor (BAY11). We next showed that siRNA-mediated CRIF1 downregulation markedly activated NF-κB. SIRT1 overexpression not only rescued CRIF1 deficiency-induced NF-κB activation but also decreased inflammatory cytokines (TNF-α, IL-1β, and IL-6) and VCAM-1 expression levels in endothelial cells.

Conclusions: These results strongly suggest that CRIF1 deficiency promotes endothelial cell inflammation by increasing VCAM-1 expression, elevating inflammatory cytokines levels, and activating the transcription factor NF-κB, all of which were inhibited by SIRT1 overexpression.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0192693PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5825004PMC
April 2018

Developmental changes in GABA tonic inhibition are compromised by multiple mechanisms in preadolescent dentate gyrus granule cells.

Korean J Physiol Pharmacol 2017 Nov 30;21(6):695-702. Epub 2017 Oct 30.

Department of Physiology, School of Medicine and Brain Research Institute, Chungnam National University, Daejeon 35015, Korea.

The sustained tonic currents (I) generated by γ-aminobutyric acid A receptors (GABARs) are implicated in diverse age-dependent brain functions. While various mechanisms regulating I in the hippocampus are known, their combined role in I regulation is not well understood in different age groups. In this study, we demonstrated that a developmental increase in GABA transporter (GAT) expression, combined with gradual decrease in GABAR α subunit, resulted in various I in the dentate gyrus granule cells (DGGCs) of preadolescent rats. Both GAT-1 and GAT-3 expression gradually increased at infantile (P and P) and juvenile (P and P) stages, with stabilization observed thereafter in adolescents (P) and young adults (P). I facilitation of a selective GAT-1 blocker (NO-711) was significantly less at P than after P. The facilitation of I by SNAP-5114, a GAT-3 inhibitor, was negligible in the absence of exogenous GABA at all tested ages. In contrast, I in the presence of a nonselective GAT blocker (nipecotic acid, NPA) gradually decreased with age during the preadolescent period, which was mimicked by I changes in the presence of exogenous GABA. I sensitivity to L-655,708, a GABAR α subunit inverse agonist, gradually decreased during the preadolescent period in the presence of NPA or exogenous GABA. Finally, Western blot analysis showed that the expression of the GABAR α subunit in the dentate gyrus gradually decreased with age. Collectively, our results suggested that the I regulation of altered GATs is under the final tune of GABAR α subunit activation in DGGCs at different ages.
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http://dx.doi.org/10.4196/kjpp.2017.21.6.695DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5709487PMC
November 2017

Automated Gait Analysis in Mice with Chronic Constriction Injury.

J Vis Exp 2017 10 17(128). Epub 2017 Oct 17.

Department of Physiology and Medical Science, College of Medicine and Brain Research Institute, Chungnam National University; Department of Neuroscience and Cell Biology, University of Texas Medical Branch at Galveston;

The von Frey test is a classical method that has been widely used to examine the sensory function of neuropathic pain animals. However, it has some disadvantages such as subjective data and the requirement of a skilled, experienced experimenter. To date, a variety of modifications have improved the von Frey method, but it still has a few limitations. Recent reports have suggested that gait analysis produces more accurate and objective data from the neuropathic animals. This protocol demonstrates how to perform the automated gait analysis to determine the degree of neuropathic pain in mice. After several days of acclimation, the mice were allowed to walk freely on the glass floor to illuminate footprints. Then, quantification of the footprints and gait were performed through video clips with automatic analysis of various walking parameters, such as area of paw print, swing time, angle of paw, etc. The main purpose of this study is to describe the methodology of automated gait analysis and briefly compare it with data from the classical sensory test using von Frey filament.
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http://dx.doi.org/10.3791/56402DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5752418PMC
October 2017

The anti-inflammatory role of extranuclear apurinic/apyrimidinic endonuclease 1/redox effector factor-1 in reactive astrocytes.

Mol Brain 2016 12 16;9(1):99. Epub 2016 Dec 16.

Department of Physiology and Department of Medical Science, School of Medicine, Chungnam National University, 266 Munhwa-Ro, Jung-gu, Daejeon, 30501, Republic of Korea.

Apurinic/apyrimidinic endonuclease 1 (APE1), a ubiquitous multipurpose protein, is also known as redox effector factor-1 (Ref-1). It is involved in DNA repair and redox signaling and, in turn, oxidative stress-induced neurodegeneration. Although previous studies have demonstrated that APE1/Ref-1 functions as a negative regulator of inflammatory response via several mechanisms in neuronal cells, little is known about the roles of APE1/Ref-1 in glial cells. In this study, we found that cytoplasmic APE1/Ref-1 expression was upregulated in reactive astrocytes of the kainic acid- or lipopolysaccharide (LPS)-injected hippocampus. Analysis of the inflammatory response induced by extranuclear APE1/Ref-1 (ΔNLS-Ref-1) in cultured primary astrocytes revealed that it markedly suppressed inducible nitric oxide synthase (iNOS) expression and tumor necrosis factor-α (TNF-α) secretion induced by LPS to a similar extent as did wild type APE1/Ref-1 (WT-Ref-1), supporting the concept an anti-inflammatory role of extranuclear APE1/Ref-1 in astrocytes. Additionally, overexpression of WT- and ΔNLS-Ref-1 suppressed the transcriptional activity of nuclear factor-κB (NF-κB), although it effectively enhanced activator protein 1 (AP-1) activity. The blunting effect of APE1/Ref-1 on LPS-induced NF-κB activation was not mediated by IκB kinase (IKK) activity. Instead, APE1/Ref-1 inhibited p300-mediated acetylation of p65 by suppressing intracellular reactive oxygen species (ROS) levels following LPS treatment. Taken together, our results showed that altered expression and/or subcellular distribution of APE1/Ref-1 in activated astrocytes regulated the neuroinflammatory response to excitotoxin and endotoxin insults used in model of neurodegenerative brain diseases.
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http://dx.doi.org/10.1186/s13041-016-0280-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5162091PMC
December 2016

Antinociceptive Profile of Levo-tetrahydropalmatine in Acute and Chronic Pain Mice Models: Role of spinal sigma-1 receptor.

Sci Rep 2016 12 2;6:37850. Epub 2016 Dec 2.

Department of Physiology and Medical Science, College of Medicine and Brain Research Institute, Chungnam National University, Daejeon 35015, South Korea.

We have recently reported that repeated systemic treatments of extract from Corydalis yanhusuo alleviate neuropathic pain and levo-tetrahydropalmatine (l-THP) is one of active components from Corydalis. We designed this study to investigate antinociceptive effect of l-THP in acute and chronic pain models and related mechanism within the spinal cord. We found that intraperitoneal pretreatment with l-THP significantly inhibited the second phase of formalin-induced pain behavior. In addition, intrathecal as well as intraperitoneal pretreatment with l-THP reduced the mechanical allodynia (MA) induced by direct activation of sigma-1 receptor (Sig-1). In chronic constriction injury mice, these treatments remarkably suppressed the increase in MA and spinal phosphorylation of the NMDA receptor NR1 subunit expression on day 7 after surgery. Intrathecal treatment with l-THP combined with the Sig-1R antagonist, BD1047 synergistically blocked MA suggesting that l-THP modulates spinal Sig-1R activation. CatWalk gait analysis also supported that antinociceptive effect of l-THP as demonstrated by restoration of percentages of print area and single stance. Meanwhile, intrathecal pretreatment with naloxone, non-selective opioid receptor antagonist, did not affect the effect of l-THP. In conclusion, these results demonstrate that l-THP possesses antinociceptive effects through spinal Sig-1R mechanism and may be a useful analgesic in the management of neuropathic pain.
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http://dx.doi.org/10.1038/srep37850DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5133565PMC
December 2016

TonEBP suppresses adipocyte differentiation via modulation of early signaling in 3T3-L1 cells.

Korean J Physiol Pharmacol 2016 Nov 28;20(6):649-655. Epub 2016 Oct 28.

Department of Physiology, Chungnam National University School of Medicine, Daejeon 35015, Korea.

TonEBP belongs to the Rel family of transcription factors and plays important roles in inflammation as well as kidney homeostasis. Recent studies suggest that TonEBP expression is also involved in differentiation of several cell types such as myocytes, chondrocytes, and osteocytes. In this study, we investigated the roles of TonEBP during adipocyte differentiation in 3T3-L1 cells. TonEBP mRNA and protein expression was dramatically reduced during adipocyte differentiation. Sustained expression of TonEBP using an adenovirus suppressed the formation of lipid droplets as well as the expression of FABP4, a marker of differentiated adipocytes. TonEBP also inhibited the expression of PPARγ, a known master regulator of adipocytes. RNAi-mediated knock down of TonEBP promoted adipocyte differentiation. However, overexpression of TonEBP did not affect adipogenesis after the initiation of differentiation. Furthermore, TonEBP expression suppressed mitotic clonal expansion and insulin signaling, which are required early for adipocyte differentiation of 3T3-L1 cells. These results suggest that TonEBP may be an important regulatory factor in the early phase of adipocyte differentiation.
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http://dx.doi.org/10.4196/kjpp.2016.20.6.649DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5106399PMC
November 2016

CD200R/Foxp3-mediated signalling regulates microglial activation.

Sci Rep 2016 10 12;6:34901. Epub 2016 Oct 12.

Department of Anatomy, Brain Research Institute, Chungnam National University School of Medicine, Daejeon, 301-747, Republic of Korea.

The heterogeneity of microglial functions have either beneficial or detrimental roles in specific physiological or pathological environments. However, the details of what transcriptional mechanisms induce microglia to take beneficial phenotypes remain unknown. Here, we report that Foxp3 is essential for beneficial outcome of the microglial response and depends upon signalling by the immunoglobulin CD200 through its receptor (CD200R). Foxp3 expression was up-regulated in microglia activated by excitotoxicity-induced hippocampal neuroinflammation. Suppression of CD200R prevented anti-inflammatory phenotype of microglia, but over-expression of Foxp3 enhanced it. Phosphorylation of STAT6, a downstream effector of CD200R, modulated transcription of Foxp3. Finally, CD200R/Foxp3-mediated signalling enhanced hippocampal neuronal viability and conferred a degree of neuroprotection, presumably by counteracting inducible nitric oxide synthase. We conclude that enhancement of Foxp3 through CD200R could be neuroprotective by targeting the microglia.
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http://dx.doi.org/10.1038/srep34901DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5059636PMC
October 2016

Inoculation of Lewis lung carcinoma cells enhances formalin-induced pain behavior and spinal Fos expression in mice.

J Vet Sci 2017 Sep;18(3):267-272

Department of Physiology and Medical Science and Brain Research Institute, College of Medicine, Chungnam National University, Daejeon 35015, Korea.

The incidence of lung cancer has rapidly increased and cancer patients at a later cancer stage frequently suffer from unbearable cancer-associated pain. However, the pathophysiology of lung cancer pain has not been fully described due to a lack of appropriate animal models. This study was designed to determine the effect of Lewis lung carcinoma (LLC) cell inoculation on formalin-induced pain behavior and spinal Fos expression in C57BL/6 mice. LLC cells (1.5 × 10, 2.5 × 10, 3.0 × 10 or 5.0 × 10) were inoculated into back or peri-sciatic nerve areas. Back area inoculation was adopted to determine the effect of cancer cell circulating factors and the peri-sciatic nerve area was used to evaluate the possible effects of cancer cell contacting and circulating factors on formalin-induced pain. At postinoculation day 7, LLC cell (5.0 × 10) inoculations in both back and peri-sciatic nerve area significantly increased formalin-induced paw-licking time and spinal Fos expression over those in cell-media-inoculated (control) mice. Enhanced pain behavior and spinal Fos expression were significantly suppressed by ibuprofen pretreatment (250 mg/kg). The results of this study suggest that LLC cell circulating factors and inflammatory responses may be critical in enhancing pain sensation in the early stage of lung cancer cell inoculation.
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http://dx.doi.org/10.4142/jvs.2017.18.3.267DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5639078PMC
September 2017

Facilitation of AMPA receptor-mediated steady-state current by extrasynaptic NMDA receptors in supraoptic magnocellular neurosecretory cells.

Korean J Physiol Pharmacol 2016 Jul 23;20(4):425-32. Epub 2016 Jun 23.

Department of Physiology, Brain Research Institute, School of Medicine, Chungnam National University, Daejeon 35015, Korea.

In addition to classical synaptic transmission, information is transmitted between cells via the activation of extrasynaptic receptors that generate persistent tonic current in the brain. While growing evidence supports the presence of tonic NMDA current (INMDA) generated by extrasynaptic NMDA receptors (eNMDARs), the functional significance of tonic INMDA in various brain regions remains poorly understood. Here, we demonstrate that activation of eNMDARs that generate INMDA facilitates the α-amino-3-hydroxy-5-methylisoxazole-4-proprionate receptor (AMPAR)-mediated steady-state current in supraoptic nucleus (SON) magnocellular neurosecretory cells (MNCs). In low-Mg(2+) artificial cerebrospinal fluid (aCSF), glutamate induced an inward shift in Iho lding (IGLU) at a holding potential (Vholding) of -70 mV which was partly blocked by an AMPAR antagonist, NBQX. NBQX-sensitive IGLU was observed even in normal aCSF at Vholding of -40 mV or -20 mV. IGLU was completely abolished by pretreatment with an NMDAR blocker, AP5, under all tested conditions. AMPA induced a reproducible inward shift in Iholding (IAMPA) in SON MNCs. Pretreatment with AP5 attenuated IAMPA amplitudes to ~60% of the control levels in low-Mg(2+) aCSF, but not in normal aCSF at Vholding of -70 mV. IAMPA attenuation by AP5 was also prominent in normal aCSF at depolarized holding potentials. Memantine, an eNMDAR blocker, mimicked the AP5-induced IAMPA attenuation in SON MNCs. Finally, chronic dehydration did not affect IAMPA attenuation by AP5 in the neurons. These results suggest that tonic INMDA, mediated by eNMDAR, facilitates AMPAR function, changing the postsynaptic response to its agonists in normal and osmotically challenged SON MNCs.
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http://dx.doi.org/10.4196/kjpp.2016.20.4.425DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4930911PMC
July 2016

Altered expression of KCC2 in GABAergic interneuron contributes prenatal stress-induced epileptic spasms in infant rat.

Neurochem Int 2016 07 12;97:57-64. Epub 2016 May 12.

Department of Pediatrics, Chungnam National University Hospital, Brain Research Institute, Chungnam National University School of Medicine, Munwha-ro 282, Jung-gu, Daejeon, 301-721, Republic of Korea. Electronic address:

Long-term stress during pregnancy causes neurologic deficits to offspring with altered gamma-aminobutyric acid (GABA) system in the brain. However, it is not clear how prenatal stress affects the maturing GABAergic interneurons and the resulting abnormalities in infantile seizures. Here, we showed that prenatal stress alters the maturation of GABA inhibitory system using a seizure model induced by prenatal stress. Prenatal stress with betamethasone or acute immobilization stress (AIS) on gestational day 15 increased the seizure susceptibility to N-methyl-d-aspartate-triggered spasms on postnatal day 15. The expression of GABA was lower in the prenatally stressed group, which compromise the decrease of glutamate decarboxylase 67-immunopositive cells. Prenatal stress markedly decreased the expression of K(+)/Cl(-) co-transporter (KCC2) in the cortex. GABA induced membrane depolarization demonstrated prenatal stress models had significant higher membrane depolarization compared to control. GABA increased KCC2 expression in cultured cortex-containing slices. Taken together, our results showed that prenatal stress with betamethasone or AIS altered the maturation of GABAergic progenitors and resulted in the lack of GABA input, which in turn, decreased KCC2 expression and lowered seizure threshold. We conclude that delayed GABA excitatory/inhibitory shift would render the cortical neuronal circuit more susceptible to excitatory input in prenatal stress induced seizure.
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http://dx.doi.org/10.1016/j.neuint.2016.05.006DOI Listing
July 2016

The 18-kDa Translocator Protein Inhibits Vascular Cell Adhesion Molecule-1 Expression via Inhibition of Mitochondrial Reactive Oxygen Species.

Mol Cells 2015 Dec 25;38(12):1064-70. Epub 2015 Nov 25.

Infectious Signaling Network Research Center and Research Institute for Medical Sciences, Department of Physiology, School of Medicine, Chungnam National University, Daejeon 301-747, Korea.

Translocator protein 18 kDa (TSPO) is a mitochondrial outer membrane protein and is abundantly expressed in a variety of organ and tissues. To date, the functional role of TSPO on vascular endothelial cell activation has yet to be fully elucidated. In the present study, the phorbol 12-myristate 13-acetate (PMA, 250 nM), an activator of protein kinase C (PKC), was used to induce vascular endothelial activation. Adenoviral TSPO overexpression (10-100 MOI) inhibited PMA-induced vascular cell adhesion molecule-1 (VCAM-1) and intracellular cell adhesion molecule-1 (ICAM-1) expression in a dose dependent manner. PMA-induced VCAM-1 expressions were inhibited by Mito-TEMPO (0.1-0.5 μM), a specific mitochondrial antioxidants, and cyclosporin A (1-5 μM), a mitochondrial permeability transition pore inhibitor, implying on an important role of mitochondrial reactive oxygen species (ROS) on the endothelial activation. Moreover, adenoviral TSPO overexpression inhibited mitochondrial ROS production and manganese superoxide dismutase expression. On contrasts, gene silencing of TSPO with siRNA increased PMA-induced VCAM-1 expression and mitochondrial ROS production. Midazolam (1-50 μM), TSPO ligands, inhibited PMA-induced VCAM-1 and mitochondrial ROS production in endothelial cells. These results suggest that mitochondrial TSPO can inhibit PMA-induced endothelial inflammation via suppression of VCAM-1 and mitochondrial ROS production in endothelial cells.
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http://dx.doi.org/10.14348/molcells.2015.0165DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4696997PMC
December 2015

Enhanced astroglial GABA uptake in heart failure.

Channels (Austin) 2015 11;9(5):225-6. Epub 2015 Aug 11.

a Department of Physiology ; Brain Research Institute and School of Medicine, Chungnam National University ; Daejeon , Republic of Korea.

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http://dx.doi.org/10.1080/19336950.2015.1074475DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4826118PMC
April 2016

Enhanced astroglial GABA uptake attenuates tonic GABAA inhibition of the presympathetic hypothalamic paraventricular nucleus neurons in heart failure.

J Neurophysiol 2015 Aug 10;114(2):914-26. Epub 2015 Jun 10.

Department of Physiology, School of Medicine, Chungnam National University, Daejeon, Republic of Korea;

γ-Aminobutyric acid (GABA) generates persistent tonic inhibitory currents (Itonic) and conventional inhibitory postsynaptic currents in the hypothalamic paraventricular nucleus (PVN) via activation of GABAA receptors (GABAARs). We investigated the pathophysiological significance of astroglial GABA uptake in the regulation of Itonic in the PVN neurons projecting to the rostral ventrolateral medulla (PVN-RVLM). The Itonic of PVN-RVLM neurons were significantly reduced in heart failure (HF) compared with sham-operated (SHAM) rats. Reduced Itonic sensitivity to THIP argued for the decreased function of GABAAR δ subunits in HF, whereas similar Itonic sensitivity to benzodiazepines argued against the difference of γ2 subunit-containing GABAARs in SHAM and HF rats. HF Itonic attenuation was reversed by a nonselective GABA transporter (GAT) blocker (nipecotic acid, NPA) and a GAT-3 selective blocker, but not by a GAT-1 blocker, suggesting that astroglial GABA clearance increased in HF. Similar and minimal Itonic responses to bestrophin-1 blockade in SHAM and HF neurons further argued against a role for astroglial GABA release in HF Itonic attenuation. Finally, the NPA-induced inhibition of spontaneous firing was greater in HF than in SHAM PVN-RVLM neurons, whereas diazepam induced less inhibition of spontaneous firing in HF than in SHAM neurons. Overall, our results showed that combined with reduced GABAARs function, the enhanced astroglial GABA uptake-induced attenuation of Itonic in HF PVN-RVLM neurons explains the deficit in tonic GABAergic inhibition and increased sympathetic outflow from the PVN during heart failure.
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http://dx.doi.org/10.1152/jn.00080.2015DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4533111PMC
August 2015

Nuclear localization and functional characteristics of voltage-gated potassium channel Kv1.3.

J Biol Chem 2015 May 31;290(20):12547-57. Epub 2015 Mar 31.

From the Laboratories of Veterinary Pharmacology and

It is widely known that ion channels are expressed in the plasma membrane. However, a few studies have suggested that several ion channels including voltage-gated K(+) (Kv) channels also exist in intracellular organelles where they are involved in the biochemical events associated with cell signaling. In the present study, Western blot analysis using fractionated protein clearly indicates that Kv1.3 channels are expressed in the nuclei of MCF7, A549, and SNU-484 cancer cells and human brain tissues. In addition, Kv1.3 is located in the plasma membrane and the nucleus of Jurkat T cells. Nuclear membrane hyperpolarization after treatment with margatoxin (MgTX), a specific blocker of Kv1.3 channels, provides evidence for functional channels at the nuclear membrane of A549 cells. MgTX-induced hyperpolarization is abolished in the nuclei of Kv1.3 silenced cells, and the effects of MgTX are dependent on the magnitude of the K(+) gradient across the nuclear membrane. Selective Kv1.3 blockers induce the phosphorylation of cAMP response element-binding protein (CREB) and c-Fos activation. Moreover, Kv1.3 is shown to form a complex with the upstream binding factor 1 in the nucleus. Chromatin immunoprecipitation assay reveals that Sp1 transcription factor is directly bound to the promoter region of the Kv1.3 gene, and the Sp1 regulates Kv1.3 expression in the nucleus of A549 cells. These results demonstrate that Kv1.3 channels are primarily localized in the nucleus of several types of cancer cells and human brain tissues where they are capable of regulating nuclear membrane potential and activation of transcription factors, such as phosphorylated CREB and c-Fos.
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http://dx.doi.org/10.1074/jbc.M114.561324DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4432276PMC
May 2015

Adenine suppresses IgE-mediated mast cell activation.

Mol Immunol 2015 Jun 17;65(2):242-9. Epub 2015 Feb 17.

Department of Biochemistry, College of Medicine, Chungnam National University, Daejeon 301-747, Republic of Korea; Research Institute for Medical Sciences, College of Medicine, Chungnam National University, Daejeon 301-747, Republic of Korea. Electronic address:

Nucleobase adenine is produced by dividing human lymphoblasts mainly from polyamine synthesis and inhibits immunological functions of lymphocytes. We investigated the anti-allergic effect of adenine on IgE-mediated mast cell activation in vitro and passive cutaneous anaphylaxis (PCA) in mice. Intraperitoneal injection of adenine to IgE-sensitized mice attenuated IgE-mediated PCA reaction in a dose dependent manner, resulting in a median effective concentration of 4.21 mg/kg. In mast cell cultures, only adenine among cytosine, adenine, adenosine, ADP and ATP dose-dependently suppressed FcɛRI (a high affinity receptor for IgE)-mediated degranulation with a median inhibitory concentration of 1.6mM. It also blocked the production of LTB4, an inflammatory lipid mediator, and inflammatory cytokines TNF-α and IL-4. In addition, adenine blocked thapsigargin-induced degranulation which is FcɛRI-independent but shares FcɛRI-dependent signaling events. Adenine inhibited the phosphorylation of signaling molecules important to FcɛRI-mediated allergic reactions such as Syk, PLCγ2, Gab2, Akt, and mitogen activated protein kinases ERK and JNK. From this result, we report for the first time that adenine inhibits PCA in mice and allergic reaction by inhibiting FcɛRI-mediated signaling events in mast cells. Therefore, adenine may be useful for the treatment of mast cell-mediated allergic diseases. Also, the upregulation of adenine production may provide another mechanism for suppressing mast cell activity especially at inflammatory sites.
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http://dx.doi.org/10.1016/j.molimm.2015.01.021DOI Listing
June 2015

APE1/Ref-1 as a Serological Biomarker for the Detection of Bladder Cancer.

Cancer Res Treat 2015 Oct 2;47(4):823-33. Epub 2015 Jan 2.

Infection Signaling Network Research Center, Research Institute of Medical Sciences, Department of Physiology, Chungnam National University School of Medicine, Daejeon, Korea.

Purpose: Apurinic/apyrimidinic endonuclease 1/redox factor-1 (APE1/Ref-1) is a multifunctional protein that shows elevated expression in a number of cancers. We attempted to determine whether serum APE1/Ref-1 is elevated in patients with bladder cancer.

Materials And Methods: Serum APE1/Ref-1 levels were determined using enzyme-linked immunosorbent assay in serum from patients with bladder cancer who had not received chemotherapy or radiotherapy (n=51) and non-tumor controls (n=55). The area under the receiver operating characteristic area under the curve was applied to determine the correlation between clinical factors and the serum levels of APE1/Ref-1.

Results: Serum levels of APE1/Ref-1 in bladder cancer patients were significantly elevated compared to those of the control group (3.548 ± 0.333 ng/100 μL [n=51] for bladder cancer vs. 1.547 ± 0.319 ng/100 μL [n=55] for the control group), with a sensitivity and specificity of 93% and 59%, respectively. Serum APE1/Ref-1 levels are associated with tumor stage, grade, muscle invasion, and recurrence.

Conclusion: Serum APE1/Ref-1 might be useful as a potential serologic biomarker for bladder cancer.
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http://dx.doi.org/10.4143/crt.2014.074DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4614188PMC
October 2015

Analgesic effect of electroacupuncture on paclitaxel-induced neuropathic pain via spinal opioidergic and adrenergic mechanisms in mice.

Am J Chin Med 2015 2;43(1):57-70. Epub 2015 Feb 2.

Department of Physiology and Brain Research Institute, Chungnam National University, School of Medicine, Daejeon 301-747, South Korea.

This study was designed to determine the antinociceptive effect and related neuronal mechanism of electroacupuncture (EA) on paclitaxel (PTX)-induced neuropathic pain in mice. PTX (4 mg/kg, i.p.) was administered once a day for 5 consecutive days to induce neuropathic pain. EA stimulation (2 mA, 2 Hz, 30 min) was applied at the ST36 acupoint bilaterally once in every 2 days. Repeated EA stimulation significantly attenuated PTX-induced mechanical allodynia and thermal hyperalgesia. In a separate set of experiment, the antinociceptive effect of a single EA stimulation 8 days after PTX treatment was reduced by intrathecal pretreatment with naloxone (opioid receptor antagonist), idazoxan (alpha2-adrenoceptor antagonist) or propranolol (beta-adrenoceptor antagonist), but not prazosin (alpha1-adrenoceptor antagonist). Moreover, EA remarkably suppressed the PTX-enhanced phosphorylation of the NMDA receptor NR2B subunit in the spinal dorsal horn, and intrathecal pretreatment of naloxone, idazoxan (IDA) or propranolol blocked the effect of EA. In conclusion, EA stimulation at the ST36 acupoint significantly diminished PTX-induced neuropathic pain in mice via the mediation of spinal opioid receptor, alpha2- and beta-adrenoceptors.
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http://dx.doi.org/10.1142/S0192415X15500044DOI Listing
September 2015

Mitochondrial APE1/Ref-1 suppressed protein kinase C-induced mitochondrial dysfunction in mouse endothelial cells.

Mitochondrion 2014 Jul 23;17:42-9. Epub 2014 May 23.

Department of Physiology, School of Medicine, Chungnam National University, Daejeon 301-747, Republic of Korea; Infection Signaling Network Research Center, College of Medicine, Chungnam National University, Daejeon 301-747, Republic of Korea.

Protein kinase C (PKC) induces mitochondrial dysfunction, which is an important pathological factor in cardiovascular diseases. The role of apurinic/apyrimidinic endonuclease-1/redox factor-1 (APE1/Ref-1) on PKC-induced mitochondrial dysfunction has not been variously investigated. In this study, phorbol 12-myristate 13-acetate (PMA), an activator of protein kinase C, induced mitochondrial hyperpolarization and reactive oxygen species generation and also increased mitochondrial translocation of APE1/Ref-1. APE1/Ref-1 overexpression suppressed PMA-induced mitochondrial dysfunction. In contrast, gene silencing of APE1/Ref-1 increased the sensitivity of mitochondrial dysfunction. Moreover, mitochondrial targeting sequence (MTS)-fused APE1/Ref-1 more effectively suppressed PMA-induced mitochondrial dysfunctions. These results suggest that mitochondrial APE1/Ref-1 is contributed to the protective role to protein kinase C-induced mitochondrial dysfunction in endothelial cells.
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http://dx.doi.org/10.1016/j.mito.2014.05.006DOI Listing
July 2014

Cytoplasmic localization and redox cysteine residue of APE1/Ref-1 are associated with its anti-inflammatory activity in cultured endothelial cells.

Mol Cells 2013 Nov 6;36(5):439-45. Epub 2013 Nov 6.

Department of Physiology, School of Medicine, Chungnam National University, Daejeon, 301-747, Korea.

Apurinic/apyrimidinic endonuclease1/redox factor-1 (APE1/Ref-1) is a multifunctional protein involved in base excision DNA repair and transcriptional regulation of gene expression. APE1/Ref-1 is mainly localized in the nucleus, but cytoplasmic localization has also been reported. However, the functional role of cytoplasmic APE1/Ref-1 and its redox cysteine residue are still unknown. We investigated the role of cytoplasmic APE1/Ref-1 on tumor necrosis factor-α (TNF-α)-induced vascular cell adhesion molecule-1 (VCAM-1) expressions in endothelial cells. Endogenous APE1/Ref-1 was mainly observed in the nucleus, however, cytoplasmic APE1/Ref-1 was increased by TNF-α. Cytoplasmic APE1/Ref-1 expression was not blunted by cycloheximide, a protein synthesis inhibitor, suggesting cytoplasmic translocation of APE1/Ref-1. Transfection of an N-terminus deletion mutant APE1/Ref-1(29-318) inhibited TNF-α-induced VCAM-1 expression, indicating an anti-inflammatory role for APE1/Ref-1 in the cytoplasm. In contrast, redox mutant of APE1/Ref-1 (C65A/C93A) transfection led to increased TNF-α-induced VCAM-1 expression. Our findings suggest cytoplasmic APE1/Ref-1 localization and redox cysteine residues of APE1/Ref-1 are associated with its anti-inflammatory activity in endothelial cells.
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http://dx.doi.org/10.1007/s10059-013-0195-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3887937PMC
November 2013