• The Korean Journal of Physiology and Pharmacology
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• v.28 no.5
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• pp.413-422
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• 2024

Group I metabotropic glutamate receptors (mGluRs) modulate postsynaptic neuronal excitability and epileptogenesis. We investigated roles of group I mGluRs on low extracellular Mg²⁺ concentration ([Mg²⁺]_o)-induced epileptiform activity and neuronal cell death in the CA1 regions of isolated rat hippocampal slices without the entorhinal cortex using extracellular recording and propidium iodide staining. Exposure to Mg²⁺-free artificial cerebrospinal fluid can induce interictal epileptiform activity in the CA1 regions of rat hippocampal slices. MPEP, a mGluR 5 antagonist, significantly inhibited the spike firing of the low [Mg²⁺]_o-induced epileptiform activity, whereas LY367385, a mGluR1 antagonist, did not. DHPG, a group 1 mGluR agonist, significantly increased the spike firing of the epileptiform activity. U73122, a PLC inhibitor, inhibited the spike firing. Thapsigargin, an ER Ca²⁺-ATPase antagonist, significantly inhibited the spike firing and amplitude of the epileptiform activity. Both the IP₃ receptor antagonist 2-APB and the ryanodine receptor antagonist dantrolene significantly inhibited the spike firing. The PKC inhibitors such as chelerythrine and GF109203X, significantly increased the spike firing. Flufenamic acid, a relatively specific TRPC 1, 4, 5 channel antagonist, significantly inhibited the spike firing, whereas SKF96365, a relatively non-specific TRPC channel antagonist, did not. MPEP significantly decreased low [Mg²⁺]_o DMEM-induced neuronal cell death in the CA1 regions, but LY367385 did not. We suggest that mGluR 5 is involved in low [Mg²⁺]_o-induced interictal epileptiform activity in the CA1 regions of rat hippocampal slices through PLC, release of Ca²⁺ from intracellular stores and PKC and TRPC channels, which could be involved in neuronal cell death.

• The korean journal of orthodontics
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• v.33 no.3 s.98
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• pp.199-210
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• 2003

Tooth movement is the result of bone metabolism in the periodontium, where various cytokines take important roles. Interleukin-6(II-6) and nitrous oxide (NO) were reported to be secreted from osteoblasts in the process of bone resorption. The mechanism of the process has not been clearly understood, but the activation of mitogen-activated protein kinase (MAPK) was known to be an important process in the release of the inflammatory cytotines in macrophages. In this regard, to prove the role of MAPK in the release of IL-6 and NO in MC3T3E-1 osteoblasts, Northern blot analysis, Western blot analysis and immune complex kinase assay were used. As a result, the treatment of MC3T3E-1 osteoblast cultures with combined $interferon-\gamma(IFN-\gamma)$, lipopolysaccharide (LPS) and tumor necrosis $factor-\alpha(TNF-\alpha)$ induces expressions of inducible nitric oxide synthase (iNOS) and IL-6, resulting in sustained releases of large amounts of NO and IL-6. However, $IFN-\gamma,\;LPS,\;and\;TNF-\alpha$ individually induce a non-detectable or small amount of NO and IL-6 in MC3T3E-1 osteoblasts. The role of MAPK activation in the early intracellular signal transduction involved in iNOS and IL-6 transcription in the combined agents-stimulated osteoblasts has been investigated. The p38 MAPK pathway is specifically involved in the combined agents-induced NO and IL-6 release, since NO and IL-6 release in the presence of a specific inhibitor of p38 MAPK, 4-(4-fluorophenyl)-2-(4-metylsulfinylphenyl)-5-(4-metylsulfinylphenyl)-5-(4-pyridyl)imidazole) (SB203580), were significantly diminished. In contrast, PD98059, a specific inhibitor of MEK1, had no effect on NO and IL-6 release. Northern blot analysis showed that the p3a MAPK pathway controlled the iNOS and IL-6 transcription level. These data suggest that p38 MAPK play an important role in the secretion of NO and IL-6 in $LPS/IFN{\gamma}-or\;TNF-\gamma-treated\;MC3T3E-1$ osteoblasts.

• Korean Journal of Veterinary Research
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• v.11 no.2
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• pp.123-136
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• 1971

(1) The non-specific inhibitors (NSI) in normal chicken sera were active against all the tested group A and group B arboviruses, but the group B arbovirus were more sensitive than group A arboviruses. (2) The titres of the NSI were distributed nearly uniformly among chickens from seven different age groups to group A arboviruses. In contrast, the NSI titres to group A arboviruses were found to increase with age. (3) No significant difference could be demonstrated between acetone-ether extraction and kaolin adsorption for removal of the NSI in normal chicken sera. (4) After heating, the NSI titres in chicken sera were increased for both group A and group B arboviruses. (5) After heating the sera at $80^{\circ}C$ and $100^{\circ}C$, kaolin adsorption was less efficient for removing the NSI than it, was in unheated serum. Acetone-ether extraction of the NSI was unimpaired after heating at $80^{\circ}C$ but was less efficient after heating at $100^{\circ}C$. (6) The NSI activity was found mainly in the first peak (IgM) and diffused to a part of second peak (IgG) by fractionation of chicken serum by gel filtration through Sephadex G200. After zonal centrifugation of chicken serum in a linear ten to 40 percent sucrose gradient all of the NSI activities were found on the top of the centrifugal tubes. These properties of large molecular size and low density indicated that the NSI in chicken serum were probably lipoproteins. (7) The natural agglutinins for goose erythrocytes in chicken sera were partially destroyed by acetone-ether extraction but not by kaolin adsorption, and were efficiently adsorbed with ten percent goose erythrocytes. No difference of the NA titre was demonstrated with diluents of different pH. (8) The NA in chicken serum was found to possess the properties of IgM by gel filtration through Sephadex G200 and zonal centrifugation in linear ten to 40 percent sucrose gradient.

• Journal of Environmental Science International
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• v.19 no.12
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• pp.1323-1334
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• 2010

The effect of nitric oxide (NO) on antioxidant system and protective mechanism against oxidative stress under UV-B radiation was investigated in leaves of maize (Zea mays L.) seedlings during 3 days growth period. UV-B irradiation caused a decrease of leaf biomass including leaf length, width and weight during growth. Application of NO donor, sodium nitroprusside (SNP), significantly alleviated UV-B stress induced growth suppression. NO donor permitted the survival of more green leaf tissue preventing chlorophyll content reduction and of higher quantum yield for photosystem II than in non-treated controls under UV-B stress, suggesting that NO has protective effect on chloroplast membrane in maize leaves. Flavonoids and anthocyanin, UV-B absorbing compounds, were significantly accumulated in the maize leaves upon UV-B exposure. Moreover, the increase of these compounds was intensified in the NO treated seedlings. UV-B treatment resulted in lipid peroxidation and induced accumulation of hydrogen peroxide ($H_2O_2$) in maize leaves, while NO donor prevented UV-B induced increase in the contents of malondialdehyde (MDA) and $H_2O_2$. These results demonstrate that NO serves as antioxidant agent able to scavenge $H_2O_2$ to protect plant cells from oxidative damage. The activities of two antioxidant enzymes that scavenge reactive oxygen species, catalase (CAT) and ascorbate peroxidase (APX) in maize leaves in the presence of NO donor under UV-B stress were higher than those under UV-B stress alone. Application of 2-(4-carboxyphenyl)-4, 4, 5, 5-tetramethylimidazoline-1-oxyl-3- oxide (PTIO), a specific NO scavenger, to the maize leaves arrested NO donor mediated protective effect on leaf growth, photosynthetic pigment and free radical scavenging activity. However, PTIO had little effect on maize leaves under UV-B stress compared with that of UV-B stress alone. $N^{\omega}$-nitro-L-arginine (LNNA), an inhibitor of nitric oxide synthase (NOS), significantly increased $H_2O_2$ and MDA accumulation and decreased antioxidant enzyme activities in maize leaves under UV-B stress. This demonstrates that NOS inhibitor LNNA has opposite effects on oxidative resistance. From these results it is suggested that NO might act as a signal in activating active oxygen scavenging system that protects plants from oxidative stress induced by UV-B radiation and thus confer UV-B tolerance.

• Asian-Australasian Journal of Animal Sciences
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• v.25 no.12
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• pp.1681-1690
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• 2012

The aim of this study was to investigate the impact of a reported p53 inhibitor, pifithrin-${\alpha}$ (PFT-${\alpha}$), on preimplantation porcine in vitro fertilized (IVF) embryo development in culture. Treatment of PFT-${\alpha}$ was administered at both early (0 to 48 hpi), and later stages (48 to 168 hpi) of preimplantation development, and its impact upon the expression of five genes related to apoptosis (p53, bak, bcl-xL, p66Shc and caspase3), was assessed in resulting d 7 blastocysts, using real-time quantitative PCR. Total cell numbers, along with the number of apoptotic nuclei, as detected by the in situ cell death detection assay, were also calculated on d 7 in treated and non-treated control embryos. The results indicate that PFT-${\alpha}$, when administered at both early and later stages of porcine IVF embryo development, increases the incidence of apoptosis in resulting blastocysts. When administered at early cleavage stages, PFT-${\alpha}$ treatment was shown to reduce the developmental competence of porcine IVF embryos, as well as reducing the quality of resulting blastocysts in terms of overall cell numbers. In contrast, at later stages, PFT-${\alpha}$ administration resulted in marginally increased blastocyst development rates amongst treated embryos, but did not affect cell numbers. However, PFT-${\alpha}$ treatment induced apoptosis and apoptotic related gene expression, in all treated embryos, irrespective of the timing of treatment. Our results indicate that PFT-${\alpha}$ may severely compromise the developmental potential of porcine IVF embryos, and is a potent apoptotic agent when placed into porcine embryo culture media. Thus, caution should be exercised when using PFT-${\alpha}$ as a specific inhibitor of p53 mediated apoptosis, in the context of porcine IVF embryo culture systems.

• The Korean Journal of Physiology and Pharmacology
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• v.1 no.6
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• pp.731-739
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• 1997

The aim of present study is to investigate the effects of cGMP on hyperpolarization activated inward current ($I_f$), pacemaker current of the heart, in rabbit sino-atrial node cells using the whole-cell patch clamp technique. When sodium nitroprusside (SNP, $80{\mu}M$), which is known to activate guanylyl cyclase, was added, $I_f$ amplitude was increased and its activation was accelerated. However, when $I_f$ was prestimulated by isopreterenol (ISO, $1{\mu}M$), SNP reversed the effect of ISO. In the absence of ISO, SNP shifted activation curve rightward. On the contrary in the presence of ISO, SNP shifted activation curve in opposite direction. $8Br-cGMP(100\;{\mu}M)$, more potent PKG activator and worse PDE activator than cGMP, also increased basal $I_f$ but did not reverse stimulatory effect of ISO. It was probable that PKG activation seemed to be involved in SNP-induced basal $I_f$ increase. The fact that SNP inhibited ISO-stimulated $I_f$ suggested cGMP antagonize cAMP action via the activation of PDE. This possibility was supported by experiment using 3-isobutyl-1-methylxanthine (IBMX), non-specific PDE inhibitor. SNP did not affect $I_f$ when $I_f$ was stimulated by $20{\mu}M$ IBMX. Therefore, cGMP reversed the stimulatory effect of cAMP via cAMP breakdown by activating cGMP-stimulated PDE. These results suggest that PKG and PDE are involved in the modulation of $I_f$ by cGMP: PKG may facilitate $I_f$ and cGMP-stimulated PDE can counteract the stimulatory action of cAMP.

• Biomolecules & Therapeutics
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• v.5 no.2
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• pp.202-210
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• 1997

Protective effect of DA-9601, an extract of Artemisia Herb, against ethanol-induced gastric mucosal injury was evaluated in rats. In the prophylactic study, DA-9601 exhibited total protection (99.4%) against absolute ethanol-induced gastropathy, And the protective effect of DA-9601 lasted up to 2 hours, which was longer than those of other contemporary mucoprotectants. In the treatment study, DA-9601 significantly facilitated the healing of 70% ethanol-induced mucosal damage, which was superior to cetraxate, a commonly used anti-ulcer drug. The mechanisms of mucoprotection of DA-9601 were also assessed. DA-9601 increased the release of prostaglandin E$_2$ from murine neutrophils in a dose-dependent manner in vitro. The cytoprotective effect of DA-9601 against ethanol-induced mucosal damage was significantly diminished by the concommitant injection of N$\omega$-nitro-L-arginine methyl ester (L-NAME, 5 mg/kg, i.v.), a non-specific nitric oxide (NO) synthase inhibitor, while it was not affected by preinjection of indomethacin (5 mg/kg, s.c.), a prostaglandins-depletor. And it was found that DA-9601 significantly enhanced adaptive cytoprotective action of 10% ethanol against absolute ethanol (56.9$\pm$6.5 vs 23.0$\pm$3.3 mm$^2$, p<0.05, mean$\pm$SEM), though its exact underlying mechanism remains to be clarified. The present fin[lings demonstrate that DA-9601 exerts gastroprotecticv actions for the stomach against ethanol through several different underlying mechanisms, in which prostanglandins and NO are involved. In conclusion, the results obtained suggest that DA-9601 can be useful both in prevention and treatment of ethanol-induced gastric damage.

• The Korean Journal of Physiology and Pharmacology
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• v.12 no.2
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• pp.37-41
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• 2008

Melatonin has been reported to protect neurons from a variety of neurotoxicity. However, the underlying mechanism by which melatonin exerts its neuroprotective property has not yet been clearly understood. We previously demonstrated that melatonin protected kainic acid-induced neuronal cell death in mouse hippocampus, accompanied by sustained activation of Akt, a critical mediator of neuronal survival. To further elucidate the neuroprotective action of melatonin, we examined in the present study the causal mechanism how Akt signaling pathway is regulated by melatonin in a rat primary astrocyte culture model. Melatonin resulted in increased astrocytic Akt phosphorylation, which was significantly decreased with wortmannin, a specific inhibitor of PI3K, suggesting that activation of Akt by melatonin is mediated through the PI3K-Akt signaling pathway. Furthermore, increased Akt activation was also significantly decreased with luzindole, a non-selective melatonin receptor antagonist. As downstream signaling pathway of Akt activation, increased levels of CREB phoshorylation and GDNF expression were observed, which were also attenuated with wortmannin and luzindole. These results strongly suggest that melatonin exerts its neuroprotective property in astrocytes through the activation of plasma membrane receptors and then PI3K-Akt signaling pathway.

• Molecular & Cellular Toxicology
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• v.2 no.2
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• pp.141-149
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• 2006

Tamoxifen (TAM), a non-steroidal anti estrogen anticancer drug and chemopreventive agent for breast cancer, have caused cholestasis in liver. The potent hepatocarcinogenicity of this drug has been reported. Methotrexate (MTX) is dihydrofolate reductase inhibitor which interfaces with the synthesis for urine nucleotide and dTMP. And it may cause atrophy, necrosis and steatosis in liver. These two anticancer drug have well-known hepatotoxicity. So, in this study we compare the gene expression pattern of antitumor agent TAM and MTX, using the cDNA microarray. We have used 4.8 K cDNA microarray to identify hepatotoxicity-related genes in 5-week-old male Sprague-Dawley (SD) rats. Confirm the pattern of gene expression, we have used Real time PCR for targeted gene. In the case of MTX, Protease related gene (Ctse, Ctsk) and Protein kinase (Pctk 1) have shown specific expression pattern. And in the case of TAM, apoptosis related gene (Pdcd 8) and signal transduction related gene (kdr) have significantly up regulated during treatment time. Gene related with growth factor, lipid synthesis, chemokins were significantly changed. From the result of this study, the information about influence of TAM and MTX to hepatoxicity will provide.

• The Korean Journal of Physiology and Pharmacology
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• v.3 no.3
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• pp.263-273
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• 1999

The role of phospholipase $A_2\;(PLA_2)$ in acute lung leak induced by intestinal ischemia was investigated in association with neutrophilic respiratory burst. To induce lung leak, we generated intestinal ischemia for 60 min prior to the 120 min reperfusion by clamping superior mesenteric artery in Sprague-Dawley rats. Acute lung leak was confirmed by the increased lung leak index and protein content in bronchoalveolar fluid. These changes were inhibited by mepacrine, the non-specific $PLA_2$ inhibitor. The lung myeloperoxidase (MPO) activity denoting the pulmonary recruitment of neutrophils was increased by intestinal I/R, but decreased by mepacrine. Simultaneously, the number of leukocytes in bronchoalveolar fluid was increased by intestinal ischemia/reperfusion (I/R) and decreased by mepacrine. Gamma glutamyl transferase activity, an index of oxidative stress in the lung, was increased after intestinal I/R but decreased by mepacrine, which implicates that $PLA_2$ increases oxidative stress caused by intestinal I/R. The $PLA_2$ activity was increased after intestinal I/R not only in the intestine but also in the lung. These changes were diminished by mepacrine. In the cytochemical electron microscopy to detect hydrogen peroxide, intestinal I/R increased the generation of the hydrogen peroxide in the lung as well as in the intestine. Expression of interleukin-1 (IL-1) in the lung was investigated through RT-PCR. The expression of IL-1 after intestinal I/R was enhanced, and again, the inhibition of $PLA_2$ suppressed the expression of IL-1 in the lung. Taken together, intestinal I/R seems to induce acute lung leak through the activation of $PLA_2$, the increase of IL-1 expression associated with increased oxidative stress by neutrophilic respiratory burst.