• The Korean Journal of Physiology and Pharmacology
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• v.13 no.4
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• pp.265-271
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• 2009

Nitric oxide (NO) has both neuroprotective and neurotoxic effects depending on its concentration and the experimental model. We tested the effects of NG-nitro-L-arginine methyl ester (L-NAME), a nonselective nitric oxide synthase (NOS) inhibitor, and aminoguanidine, a selective inducible NOS (iNOS) inhibitor, on kainic acid (KA)-induced seizures and hippocampal CA3 neuronal death. L-NAME (50 mg/kg, i.p.) and/or aminoguanidine (200 mg/kg, i.p.) were administered 1 h prior to the intracerebroventricular (i.c.v.) injection of KA. Pretreatment with L-NAME significantly increased KA-induced CA3 neuronal death, iNOS expression, and activation of microglia. However, pretreatment with aminoguanidine significantly suppressed both the KA-induced and L-NAME-aggravated hippocampal CA3 neuronal death with concomitant decreases in iNOS expression and microglial activation. The protective effect of aminoguanidine was maintained for up to 2 weeks. Furthermore, iNOS knockout mice ($iNOS^{-1-}$) were resistant to KA-induced neuronal death. The present study demonstrates that aminoguanidine attenuates KA-induced neuronal death, whereas L-NAME aggravates neuronal death, in the CA3 region of the hippocampus, suggesting that NOS isoforms play different roles in KA-induced excitotoxicity.

• Korean Journal of Veterinary Research
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• v.51 no.3
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• pp.185-191
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• 2011

Trimethyltin chloride (TMT) has been used as a neurotoxin for inducing brain dysfunction and neuronal death. Neuronal death in the hippocampus by TMT may generate excessive nitric oxide, but there are few studies about nitric oxide synthase enzyme involved in the synthesis of nitric oxide. The purpose of present study is to analyze the TMT toxicity in each region of rat hippocampus. To evaluate the involvement of nitric oxide, we analyzed the effects of aminoguanidine known as a selective inhibitor for inducible nitric oxide synthase on behavioral changes and the hippocampus of rat by TMT toxicity. 6-week-old male Sprague-Dawley rats were administered with a single dose of TMT (8 mg/kg b.w., i.p.) and the control group was similarly administered with distilled water. TMT + aminoguanidine-treated groups were administered with aminoguanidine (10 mg/kg or 100 mg/kg b.w., i.p.) for 3 days prior to TMT injection. The rats were sacrificed 2 days after TMT administration. In the TMT-treated group, a number of cell losses were seen in CA1, CA3 and the dentate gyrus. In the TMT + aminoguanidine-treated group, neuronal death was seen in CA1 and CA3, but reduced in the dentate gyrus compared to the TMT-treated group. Western blot analysis showed that cleaved caspase-3 expression was increased in the TMT-treated group compared to the control group. However, the expression significantly declined in the TMT + aminoguanidine-treated group. The present findings suggest that inducible nitric oxide synthase is involved in neuronal death induced by TMT.

• The Korean Journal of Physiology and Pharmacology
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• v.8 no.1
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• pp.1-5
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• 2004

Transient forebrain ischemia results in the delayed neuronal death in the CA1 area of the hippo-campus. The present study was performed to determine effects of aminoguanidine, a selective iNOS inhibitor, on the generation of peroxynitrite and delayed neuronal death occurring in the hippocampus following transient forebrain ischemia. Transient forebrain ischemia was produced in the conscious rats by four-vessel occlusion for 10 min. Treatment with aminoguanidine (100 mg/kg or 200 mg/kg, i.p.) or saline (0.4 ml/100 g, i.p.) was started 30 min following ischemia-reperfusion and the animals were then injected twice daily until 12 h before sacrifice. Immunohistochemical method was used to detect 3-nitrotyrosine, a marker of peroxynitrite production. Posttreatment of aminoguanidine (200 mg/kg) significantly attenuated the neuronal death in the hippocampal CA1 area 3 days, but not 7 days, after ischemia-reperfusion. 3-Nitrotyrosine immunoreactivity was enhanced in the hippocampal CA1 area 3 days after reperfusion, which was prevented by the treatment of aminoguanidine (100 mg/kg and 200 mg/kg). Our findings showed that (1) the generation of peroxynitrite in the hippocampal CA1 area 3 days after ischemia-reperfusion was dependent on the iNOS activity; (2) the postischemic delayed neuronal death was attenuated in the early phase through the prevention of peroxynitrite generation by an iNOS inhibitor.

• Biomolecules & Therapeutics
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• v.13 no.3
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• pp.190-197
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• 2005

Advanced glycation end products (AGE) have been implicated in the pathogenesis of diabetic complications including nephropathy. However, the role of AGE in the activation of mesangial cells cultured under high glucose has not been elucidated. The effects of aminoguanidine, which prevents formation of AGE and protein cross-linking, on the synthesis of $TGF-{\beta}1$ and fibronectin by rat mesangial cells cultured under high glucose for 2 weeks were examined and compared with the effects of $N^G$-nitro-L-arginine methyl ester (NAME), a selective nitric oxide synthase inhibitor, because aminoguanidine also inhibits the inducible nitric oxide synthase. Culture of mesangial cells in 30 mM (high) glucose for 2 weeks induced 1.5-fold (ELISA) and 1.9-fold (Western blot analysis) increase in AGE in the culture media compared to 5.6 mM (control) glucose. Northern blot analysis revealed 1.5-fold increase in $TGF-{\beta}1$ and 1.7-fold increase in fibronectin mRNA expression in cells cultured under high glucose compared to control glucose. Increases in mRNA expression were followed by increased protein synthesis. Mink lung epithelial cell growth inhibition assay revealed 1.4-fold increase in $TGF-{\beta}1$ protein in high glucose media compared to control. Fibronectin protein also increased 2.1-fold that of control glucose by Western blot analysis. Administration of aminoguanidine suppressed AGE formation in a dose dependent manner and at the same time suppressed $TGF-{\beta}1$ and fibronectin synthesis by mesangial cells cultured in both control and high glucose. In contrast, NAME did not affect high glucose-induced changes. These findings support a role for AGE in high glucose-induced upregulation of $TGF-{\beta}1$ and fibronectin synthesis by mesangial cells.

• The Korean Journal of Pharmacology
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• v.32 no.1
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• pp.113-123
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• 1996

It has been well known that polyamines ensure the stability of chromatin structure and the fidelity of DNA transcription. This study was carried out to evaluate the effect of polyamines on the apoptosis of mouse thymocytes induced by dexamethasone and polyamine synthesis inhibitors. 1) In the histological death findings of thymocytes double-stained with acridine orange and ethidium bromide, the apoptotic and the necrotic fractions (AF; NF) in the control group were $9.4{\pm}4.2%$ and $4.5{\pm}5.3%$, respectively. Dexamethasone $(3\;{\times}\;10^{-8}\;M:\;DX)$ in creased AF upto $52.0{\pm}8.1%$ and did not change NF, but A23187 $(5\;{\times}\;10^{-7}\;M:\;A2)$ increased AF and NF upto $45.0{\pm}8.9%$ and $20.5{\pm}10.6%$, respectively. 2) The thymocyte viability was significantly reduced by DX, DHEA $(1\;{\times}\;10^{-4}\;M)$, A2, DFMO $(1\;{\times}\;10^{-4}\;M)$, and $MGBG\;(1\;{\times}\;10^{-4}\;M)$, respectively. It was, however, little affected by $aminoguanidine\;(1\;{\times}\;10^{-4}\;M:\;AG)$, $putrescine\;(1\;{\times}\;10^{-5}\;M:\;PT)$, $spermidine\;(1\;{\times}\;10^{-5}\;M:\;SD)$, and $spermine\;(1\;{\times}\;10^{-5}\;M:\;SM)$. 3) The genomic DNA of mouse thymocyte was markedly fragmented by DX and A2, respectively, and to a lesser extent, by DHEA, but was little affected by MGBG, DFMO, AG, and each of polyamines. 4) The DX induced reduction of thymocyte viability was moderately attenuated by DHEA, but little affected by DFMO, MGBC, and AG. However, SM significantly attenuated the viability reduction induced by A2 as well as DX. 5) The thymocyte viability reduction by MGBG and DFMO was significantly attenuated by only SM among three polyamines applied in this study. 6) The thymocyte viability redution by combined treatments of DX with DFMO and MGBG, respectively, was significantly attenuated by SM, and moderately by PT. But the viability reduction by combined treatment of DX with AG or DHEA was not affected by polyamines. These results suggest that polyamines, particularly spermine, might play the inhibitory role in thymocyte apoptosis and the inhibitory effect can be ascribed in part to the increase of polyamine uptake by thymocytes pretreated with DFMO and MGBG.

• Archives of Pharmacal Research
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• v.25 no.5
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• pp.697-703
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• 2002

We investigated that the role of nitric oxide (NO) on ischemic rats in brain and heart. Ischemia was induced by both common carotid arteries (CCA) occlusion for 24h following reperfusion. Then tissue samples were removed and measured NOx. In brain, NOx was increased by about 40% vs. normal and it was significantly inhibited by aminoguanidine, selective iNOS inhibitor. This result showed that NOx concentration was increased by iNOS. We investigated the role of $Ca^{2+}$ during ischemia. Nimodipine, L-type calcium channel blocker, didn't inhibit the increases of NOx concentration during ischemia. It suggested that increased NOx was due to calcium-independent NOS. MK-801, which N-methyl-D-aspartate (NMDA) receptor antagonist, didn't significantly prevent the increases of NOx. In heart, ischemia caused NOx decrease and it is inconsistent with NOx increase in brain. Aminoguanidine and nimodipine didnt affect on NOx decrease. But MK-801 more lowered NOx concentration than those of ischemia control group. It seemed that $Ca^{2+}$ influx in heart partially occurred via NMDA receptor and inhibited by NMDA receptor antagonist. The mean arterial pressure (MAP) in ischemic rats after 24h of CCA occlusion was decreased when compared to normal value, whereas the heart rates (HR) was not different between two groups. Aminoguanidine or MK801 had no effect on MAP or HR, but nimodipine reduced MAP. There was no difference the effects of aminoguanidine, nimodipine, or MK-801, on MAP and HR between normal rats and ischemic rats. In summary, ischemic model caused an increase of NOx concentration, suggesting that this may be produced via iNOS, which is calcium independent in brain. However in heart, ischemia decreased NOx concentration and NMDA receptor was partially involved. The basal MAP was decreased in ischemic rats but HR was not different from normal control, suggesting that increased NOx in brain of ischemic rat may result in the hypotension.

• The Korean Journal of Pharmacology
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• v.28 no.2
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• pp.115-128
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• 1992

The training of male wistar rats for active conditioned response (ACR) was performed by one daily training session of 30 consecutive trials for 10 successive days using a two-way shuttle box, and the rats that showed 10 or more ACRs on the last day were treated for further 10 days with electroconvulsive shock (ECS : 50 mA, 0.5 msec; 100 Hz; 1.5 sec) and the following compounds. On the 20th day, all the rats were tested for the ACR rention. The ECS regimens were one ECS per day for 10 days with one day interval $(5{\times}ECS)$, one ECS at 3 hrs (ECS-3h), and one ECS at 24 hrs (ECS-24h), respectively, before the ACR retention test. And CDP-choline (cc: 250 mg/kg), spermine (SM: 10 mg/kg), ${\alpha}-difluoromethylornithine$ (DO: 250 mg/kg), or aminoguanidine (AG: 100 mg/kg) was administered by one daily i.p. injection for 10 days. The ACR number $(13.7{\pm}1.0)$ obtained on the last training day was increased by 37.23% on the 20th day in the control rats. And the ACR increase was significantly suppressed by 5-ECS, ECS-3h, CC, or SM but was little affected by ECS-24h, DO, or AG. However, the 5-ECS induced impairment of ACR retention was significantly suppressed by AG, SM, and CC in the order of potency but was little affected by DFMO. And the ECS-3h induced impairment was moderately worsened by SM or AG. The acetylcholine (ACh) of the rat hypothalamus (HT), hippocampus (HC), and entorhinal cortex (EC) was markedly increased by CC and moderately increased by SM, but little affected by ECS-3h, ECS-24h, DO, or AG. But $5{\times}ECS$ slightly increased the ACh content. The brain putrescine (Pt) content was significantly increased by AG and little affected by CC, SM, or DO. But the $5{\times}ECS$ markedy decreased the brain Pt content, and the decrease was significantly suppressed by CC, SM, or AG. CC induced the marked increases of the spermidine (Sd) and spermine (Sm) contents of all the areas. SM increased the Sd contents of all the areas and the EC-Sm content. DO decreased the brain Sd and Sm contents. And AG increased the HT-Sd content and the Sm contents of all the brain areas. The $5{\times}ECS$ induced decrease of the HC-Sm content was suppressed by CC, SM and AG. These results suggest that the improving effect of aminoguanidine on the $5{\times}ECS$ induced impairment of ACR retention may be ascribed in part to its activity as a diamine oxidase inhibitor.

• The Korean Journal of Physiology and Pharmacology
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• v.1 no.6
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• pp.665-672
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• 1997

This study aimed to investigate the mechanism of cerebroprotection of platelet-activating factor(PAF) antagonists in transient cerebral ischemia of rat. Right middle cerebral artery(MCA) of Sprague-Dawley rat was occluded for 2 hours using an intraluminal filament technique. After 22 hours of reperfusion, morphometrically detectable infarct was developed in the cortex and striatum identical to the territory of MCA. The infarct size was significantly reduced by PAF antagonists, BN 52021 and CV-6209, as well as an inducible nitric oxide synthase(iNOS) inhibitor aminoguanidine(1 mg/kg, i.p., respectively) administered 5 min after MCA occlusion. PAF antagonists significantly inhibited the enzymatic activities of both myeloperoxidase and iNOS in the cerebral hemisphere ipsilateral to ischemia, whereas aminoguanidine did not inhibit myeloperoxidase activity but significantly inhibited the iNOS activity. These results suggest that PAF antagonists exert a cerebroprotective effect against ischemic brain damage through inhibition of leukocyte infiltration and iNOS activity in the postischemic brain.

• Korean Journal of Pharmacognosy
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• v.40 no.4
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• pp.388-393
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• 2009

Advanced glycation end products (AGEs) have been implicated in the development of diabetic complications. The AGEs inhibitors or cross-link breakers attenuate various functional and structural manifestations of diabetic complications. In this study, 64 herbal medicines from China and Vietnam have been investigated with an in vitro evaluation system using AGEs inhibitory activity. Of these, eight herbal medicines ($IC_{50}$<50 ${\mu}g$/ml) were found to have strong AGEs inhibitory activity compared with aminoguanidine (14 days, $IC_{50}$=75.98 ${\mu}g$/ml; 28 days, $IC_{50}$=88.27 ${\mu}g$/ml). Particularly, four herbal medicines, Buddleja officinalis (whole plant), Syzygium cuminii (leaf), Eugenia caryophyllate (seed), and Paeonia suffruticosa (root) showed more potent inhibitory activity (approximately 5-6 fold) than the positive control aminoguanidine.

• Korean Journal of Pharmacognosy
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• v.33 no.4 s.131
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• pp.308-311
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• 2002

Advanced glycation end products(AGEs) are largly involved in the pathogenesis of diabetic nephropathy. It is obvious that inhibition of AGEs formation is important in preventing the occurrence and progression of diabetic nephropathy. In diabetes, this reaction is greatly accerated and is important in the pathogenesis of diabetic complications, especially diabetic nephropathy. Therefore, to seek possible AGEs inhibitors in herbal medicines, unprocessed - and processed Magnolia Bark were examined in vitro as basic data for aniaml experiment. The content of magnolol in unprocessed Magnolia Bark was $0.796{\pm}0.072%$, and after processing was decreased to $0.586{\pm}0.101%(p<0.01)$. The content of AGEs was measured by their intrinsic fluorescence. The $IC_{50}({\mu}g/ml)$ values of aminoguanidine, unprocessed- and procesled Magnolia Bark are $38.845{\pm}8.36{\mu}g/ml$, $54.264{\pm}3.153{\mu}g/ml$ and $27.882{\pm}1.836{\mu}g/ml$, respectively. This result means that prcessed Magnolia Bark was more effective than aminoguanidine, as positive control.