Seung-Ju Yang

Effects of N-adamantyl-4-methylthiazol-2-amine on hyperglycemia, hyperlipidemia and oxidative stress in streptozotocin-induced diabetic rats.

Thiazole derivatives are attractive candidates for drug development because they can be efficiently synthesized and are active against a number of diseases and conditions, including diabetes. In our present study, we investigated the anti-inflammatory and antioxidant properties of N-adamantyl-4-methylthiazol-2-amine (KHG26693), a new thiazole derivative, in a streptozotocin (STZ)-induced model of diabetes mellitus. STZ-induced diabetic rats were intraperitoneally administered KHG26693 (3mg/kg-body weight/day) for 4 weeks. KHG26693 administration significantly decreased blood glucose, triglycerides, and cholesterol and increased insulin. KHG26693 also suppressed several inflammatory responses in STZ-induced diabetic rats, as evidenced by decreased levels of serum tumor necrosis factor-α, interleukin-1β, and nitric oxide. Additionally, KHG26693 significantly modulated hepatic lipid peroxidation, catalase and superoxide dismutase activity, and the nonenzymatic antioxidant status (e.g., vitamins C and E), and reduced the glutathione content. These anti-inflammatory/antioxidative actions occurred as a result of the downregulation of inducible nitric oxide synthase and nuclear factor-kappa B. Taken together, our results suggest that KHG26693 successfully reduces the production of oxidative stress in STZ-induced diabetic rats by regulating the oxidation-reduction system, specifically increasing antioxidant capacity. Furthermore, KHG26693 treatment significantly reverted the key enzymes of glucose metabolism, such as glucokinase, glucose-6-phosphatase, glycogen synthase, glycogen phosphorylase, and fructose-1,6-bisphosphatase, to near-normal levels in liver tissues. These results indicate that KHG26693 normalizes disturbed glucose metabolism by enhancing glucose utilization and decreasing liver glucose production via insulin release, suggesting the possibility of future diabetes treatments.

N-Adamantyl-4-methylthiazol-2-amine suppresses amyloid β-induced neuronal oxidative damage in cortical neurons

Abstract Recently, we have reported that N-adamantyl-4-methylthiazol-2-amine (KHG26693) successfully reduced the production of oxidative stress in streptozotocin-induced diabetic rats and lipopolysaccharide-induced BV-2 microglial cells by increasing their antioxidant capacity. However, antioxidative effects of KHG26693 against Aβ (Aβ)-induced oxidative stress have not yet been reported. In the present study, we further investigated the antioxidative function of KHG26693 in Aβ-mediated primary cultured cortical neurons. We showed here that KHG26693 attenuated Aβ-induced cytotoxicity, increase of Bax/Bcl-2 ratio, elevation of caspase-3 expression, and impairment of mitochondrial membrane potential in cultured primary cortical neurons. KHG26693 also decreases the Aβ-mediated formation of malondialdehyde, reactive oxygen species, and NO production by decreasing nitric oxide synthase (iNOS) and NADPH oxidase level. Moreover, KHG26693 suppress the Aβ-induced oxidative stress through a possible mechanism involving attenuation of GSH and antioxidant enzyme activities such as glutathione reductase and glutathione peroxidase (GPx). Finally, pretreatment of cortical neurons with KHG26693 significantly reduced the Aβ-induced protein oxidation and nitration. To our knowledge, this is the first report, showing that KHG26693 significantly attenuates Aβ-induced oxidative stress in primary cortical neurons, and may prove attractive strategies to reduce Aβ-induced neural cell death.

The azetidine derivative, KHG26792 protects against ATP-induced activation of NFAT and MAPK pathways through P2X7 receptor in microglia.

Azetidine derivatives are of interest for drug development because they may be useful therapeutic agents. However, their mechanisms of action remain to be completely elucidated. Here, we have investigated the effects of 3-(naphthalen-2-yl(propoxy)methyl)azetidine hydrochloride (KHG26792) on ATP-induced activation of NFAT and MAPK through P2X7 receptor in the BV-2 mouse microglial cell line. KHG26792 decreased ATP-induced TNF-α release from BV-2 microglia by suppressing, at least partly, P2X7 receptor stimulation. KHG26792 also inhibited the ATP-induced increase in IL-6, PGE2, NO, ROS, CXCL2, and CCL3. ATP induced NFAT activation through P2X7 receptor, with KHG26792 reducing the ATP-induced NFAT activation. KHG26792 inhibited an ATP-induced increase in iNOS protein and ERK phosphorylation. KHG26792 prevented an ATP-induced increase in MMP-9 activity through the P2X7 receptor as a result of degradation of TIMP-1 by cathepsin B. Our data provide mechanistic insights into the role of KHG26792 in the inhibition of TNF-α produced via P2X7 receptor-mediated activation of NFAT and MAPK pathways in ATP-treated BV-2 cells. This study highlights the potential use of KHG26792 as a therapeutic agent for the many diseases of the CNS related to activated microglia.

Small‐interfering‐RNA‐mediated silencing of human glutamate dehydrogenase induces apoptosis in neuroblastoma cells

In the nervous system, GDH (glutamate dehydrogenase) is enriched in astrocytes and is important for recycling glutamate, a major excitatory neurotransmitter. The function of hGDH (human GDH) may be important in neurodegenerative diseases such as Parkinsons disease. To test the effect of decreased hGDH expression, several vector‐based plasmidlinked hGDH siRNAs (small interfering RNAs) were expressed intracellularly in BE(2)C human neuroblastoma cells. Immunoblotting and reverse‐transcription–PCR confirmed that expression of hGDH protein and mRNA was knocked down by co‐transfection with phGDH‐siRNA vectors in BE(2)C human neuroblastoma cells. TUNEL (terminal uridine deoxynucleotidyl transferase dUTP nick‐end labelling) and DNA fragmentation assays 48 h after transfection of phGDH‐siRNAs revealed that inhibition of hGDH expression induced cellular apoptosis and activated phospho‐ERK1/2 (phospho‐extracellular‐signal‐regulated kinase 1/2). These findings show that inhibition of hGDH expression by siRNA is related to apoptosis in neuronal cells.

N -Adamantyl-4-Methylthiazol-2-Amine Attenuates Glutamate-Induced Oxidative Stress and Inflammation in the Brain

In this study, we explored the possible mechanisms underlying the neuroprotective and anti-oxidative effects of N-adamantyl-4-methylthiazol-2-amine (KHG26693) against in vivo glutamate-induced toxicity in the rat cerebral cortex. Our results showed that pretreatment with KHG26693 significantly attenuated glutamate-induced elevation of lipid peroxidation, tumor necrosis factor-α, interferon gamma, IFN-γ, interleukin-1β, nitric oxide, reactive oxygen species, NADPH oxidase, caspase-3, calpain activity, and Bax. Furthermore, KHG26693 pretreatment attenuated key antioxidant parameters such as levels of superoxide dismutase, catalase, glutathione, and glutathione reductase. KHG26693 also attenuated the protein levels of inducible nitric oxide synthase, neuronal nitric oxide synthase, nuclear factor erythroid 2-related factor 2, heme oxygenase-1, and glutamate cysteine ligase catalytic subunit caused by glutamate toxicity. Finally, KHG26693 mitigated glutamate-induced changes in mitochondrial ATP level and cytochrome oxidase c. Thus, KHG26693 functions as neuroprotective and anti-oxidative agent against glutamate-induced toxicity through its antioxidant and anti-inflammatory activities in rat brain at least in part.

Anti-inflammatory and anti-oxidative effects of 3-(naphthalen-2-yl(propoxy)methyl)azetidine hydrochloride on β-amyloid-induced microglial activation

We aimed to assess the anti-inflammatory and antioxidative properties of KHG26792, a novel azetidine derivative, in amyloid β (Aβ)-treated primary microglial cells. KHG26792 attenuated the Aβ-induced production of inflammatory mediators such as IL-6, IL-1β, TNF-α, and nitric oxide. The levels of protein oxidation, lipid peroxidation, ROS, and NADHP oxidase enhanced by Aβ were also downregulated by KHG26792 treatment. The effects of KHG26792 against the Aβ-induced increases in inflammatory cytokine levels and oxidative stress were achieved by increasing the phosphorylation of Akt/GSK-3β signaling and by decreasing the Aβ-induced translocation of NF-κB. Our results provide novel insights into the use of KHG26792 as a potential agent against Aβ toxicity, including its role in the reduction of inflammation and oxidative stress. Nevertheless, further investigations of cellular signaling are required to clarify the in vivo effects of KHG26792 against Aβ-induced toxicity.

S100A8 Induces Secretion of MCP-1, IL-6, and IL-8 via TLR4 in Jurkat T Cells

In the pathogenesis of inflammatory diseases such as allergies, S100A8 acts as an important molecule and T lymphocytes are essential cytokine-releasing cells. In this study, we investigated the effect of S100A8 on release of cytokines, specifically MCP-1, IL-6, and IL-8 in T cells, and its associated signaling mechanism. S100A8 increased secretion of MCP-1, IL-6, and IL-8 in a time- and dose-dependent manner. Elevated secretion of MCP-1, IL-6, and IL-8 due to S100A8 was inhibited by the TLR4 inhibitor TLR4i, the PI3K inhibitor LY294002, the PKCδ inhibitor rottlerin, the ERK inhibitor PD98059, the p38 MAPK inhibitor SB202190, the JNK inhibitor SP600125, and the NF-κB inhibitor BAY-11-7085. S100A8 induced phosphorylation of ERK, p38 MAPK, and JNK in a time-dependent manner, and activation was suppressed by TLR4i, LY294002, and rottlerin. S100A8 induced NF-κB activation by Iκ-Bα degradation, and NF-κB activity was suppressed by PD98059, SB202190, and SP600125. These results indicate that S100A8 induces cytokine release via TLR4. Study of PI3K, PKCδ, MAPKs, and NF-κB will contribute to elucidation of the S100A8-invovled mechanism.

2-Cyclopropylimino-3-methyl-1,3-thiazoline hydrochloride alters lipopolysaccharide-induced proinflammatory cytokines and neuronal morphology in mouse fetal brain

It is well documented that a maternal immune response to infection during pregnancy can cause neurodevelopmental damage. We demonstrate in our current study that maternally administered 2-cyclopropylimino-3-methyl-1,3-thiazoline hydrochloride (KHG26377), a novel thiazole derivative, prevents fetal malformations and neurodevelopmental deficits in offspring by blocking lipopolysaccharide (LPS)-induced inflammation. Administration of KHG26377 effectively regulated LPS-induced inflammatory markers and mediators such as soluble intercellular adhesion molecule-1, se-Selectin, macrophage chemoattractant protein-1, and cytokine-induced neutrophil chemoattractant-1 in the maternal serum. Furthermore, maternally administered KHG26377 showed an inhibitory effect on the LPS-induced developmental toxicity by selectively suppressing the TNF-α level in maternal serum, amniotic fluid, placenta, fetal liver, and fetal brain as well as by suppression of LPS-induced nitric oxide synthase (iNOS), cyclooxygenase 2 (COX-2), and myelin basic protein (MBP) levels in the fetal brain. In addition, pretreatment of neuronal cells with KHG26377 effectively reestablished the cell body morphology and microtubule-associated protein 2 (MAP2) staining compared to the LPS-treated group in cortex primary neuronal cultures. Although the clinical relevance of our findings remains to be determined, our results provide novel insights into KHG26377 as a possible therapeutic agent to protect fetuses against various inflammatory responses.

The ABCG2 Polymorphism rs2725220 Is Associated with Hyperuricemia in the Korean Population

Elevated serum uric acid levels are associated with a variety of adverse health outcomes, including gout, hypertension, diabetes mellitus, metabolic syndrome, and cardiovascular diseases. Several genome-wide association studies on uric acid levels have implicated the ATP-binding cassette, subfamily G, member 2 (ABCG2) gene as being possibly causal. We investigated an association between the single-nucleotide polymorphism (SNP) rs2725220 in the ABCG2 gene and uric acid levels in the Korean population. A total of 991 subjects in Seoul City were used for a replication study with ABCG2 SNP rs2725220. The rs2725220 SNP in the ABCG2 gene was associated with mean uric acid levels (effect per allele 0.25 mg/dL, p < 0.0001). Subjects with the GC/CC genotype had a 1.78-fold (range, 1.22- to 2.62-fold) higher risk of having abnormal uric acid levels (≥7.0 mg/dL) than subjects with the GG genotype. When analyzed by gender, the association with ABCG2 was stronger in men than in women. The association with ABCG2 was much stronger in male subjects with body mass index (BMI) ≥ 26.4 (odds ratio, 5.09; 95% confidence interval, 2.41 to 10.8) than in male subjects with BMI < 26.4. This study clearly demonstrates that genetic variations in ABCG2 influence uric acid levels in Korean adults.

3-(Naphthalen-2-yl(propoxy)methyl)azetidine hydrochloride attenuates NLRP3 inflammasome-mediated signaling pathway in lipopolysaccharide-stimulated BV2 microglial cells.

The nucleotide-binding and oligomerization domain-like receptor containing a pyrin domain 3 (NLRP3) inflammasome is a multiprotein complex with a role in innate immune responses. NLRP3 inflammasome dysfunction is a common feature of chronic inflammatory diseases. Microglia activation is also associated with neuroinflammatory pathologies. We previously reported that 3-(naphthalen-2-yl(propoxy)methyl)azetidine hydrochloride (KHG26792) reduced hypoxia-induced toxicity by modulating inflammation. However, no studies have elucidated the precise mechanisms for the anti-inflammatory action of KHG26792, in particular via inflammasome mediation. This study investigated the effects of KHG26792 on the inflammasome-mediated signaling pathway in lipopolysaccharide (LPS)-stimulated BV2 microglial cells. KHG26792 significantly attenuated several inflammatory responses including tumor necrosis factor-α, interleukin-1β, interleukin-6, reactive oxygen species, and mitochondrial potential in these cells. KHG26792 also suppressed LPS-induced increase NLRP3, activated caspase-1, and apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) levels. Furthermore, KHG26792 successfully blocked LPS-activated adenosine triphosphate (ATP) level, likely through the purinergic receptor P2X ligand-gated ion channel 7 (P2X7) receptor. Our results suggest that the anti-inflammatory functions of KHG26792 may be, at least in part, due to regulation of the P2X7R/NLRP3-mediated signaling pathway during microglial activation.