Euteum Park

Rosmarinic acid protects human dopaminergic neuronal cells against hydrogen peroxide-induced apoptosis.

In this study, we investigated the protective effects of rosmarinic acid (RA) on H(2)O(2)-induced neurotoxicity in human dopaminergic cell line, SH-SY5Y. Results showed that RA significantly attenuated H(2)O(2)-induced reactive oxygen species (ROS) generation and apoptotic cell death. Rosmarinic acid effectively suppressed the up-regulation of Bax and down-regulation of Bcl-2. Furthermore, RA stimulated the antioxidant enzyme heme oxygenase-1 (HO-1). We also demonstrated that the HO-1 induction by RA was associated with the protein kinase A (PKA) and phosphatidylinositiol-3-kinase (PI3K) signaling pathways. These results suggest that RA can protect SH-SY5Y cells under oxidative stress conditions by regulating apoptotic process. Thus, RA should be clinically evaluated for the prevention of neurodegenerative diseases.

MicroRNA-205 Directly Regulates the Tumor Suppressor, Interleukin-24, in Human KB Oral Cancer Cells

MicroRNA (miRNA) is a form of small noncoding RNA that regulates the expression of genes either by inhibiting mRNA translation or by inducing its degradation. Small microRNA play important roles in regulating a large number of cellular processes, including development, proliferation and apoptosis. This study examined the biological functions of miR-205 as a tumor suppressor in KB oral cancer cells. The results showed that miR-205 expression was significantly lower in KB oral cancer cells than in human normal oral keratinocytes. Furthermore, the miR-205 over-expressed in KB oral cancer cells increased the cell cytotoxicity and induced apoptosis through the activation of caspase-3/-7. The transfection of miR-205 into KB oral cancer cells strongly induced IL-24, a well known cytokine that acts as a tumor suppressor in a range of tumor tissues. In addition, miR-205 targeted the IL-24 promoter directly to induce gene expression. Overall, miR-205 has significant therapeutic potential to turn on silenced tumor suppressor genes by targeting them with miRNA.

The plant phenolic diterpene carnosol suppresses sodium nitroprusside-induced toxicity in c6 glial cells.

Carnosol, a naturally occurring bioactive phenolic diterpene originating from rosemary and sage, has been shown to exert antioxidant and anti-inflammatory effects. This study examined possible protective effects of carnosol on sodium nitroprusside (SNP)-induced cytotoxicity in C6 glial cells. Carnosol (1-10 microM) dose-dependently attenuated SNP (100 microM)-induced cell death and NO production. SNP-induced apoptotic characteristics, including DNA fragmentation, caspase-3 activation, and c-jun N-terminal protein kinase (JNK) phosphorylation, were significantly suppressed by carnosol (10 microM). In addition, carnosol pretreatment restored the level of reduced glutathione (GSH), which was diminished by SNP treatment. Although both SNP (100 microM) and carnosol (10 microM) stimulated the HO-1 expression time-dependently, SNP caused a temporal increase in HO-1 in early time periods (3-6 h) before cell death occurred. In contrast, carnosol induced the sustained expression of HO-1 until a late time point (24 h). The addition of 1 microM zinc protoporphyrin IX (ZnPP), a specific HO inhibitor, with SNP or carnosol further reduced cell viability. Also, the addition of ZnPP inhibited the protective effect of carnosol against SNP-induced cytotoxicity in C6 cells. These results suggest that carnosol possesses abilities to inhibit SNP-mediated glial cell death through modulation of apoptotic events and induction of HO-1 expression.

Protective effects of N-acetylcysteine against monosodium glutamate-induced astrocytic cell death

Monosodium glutamate (MSG) is a flavor enhancer, largely used in the food industry and it was reported to have excitotoxic effects. Higher amounts of MSG consumption have been related with increased risk of many diseases, including Chinese restaurant syndrome and metabolic syndromes in human. This study investigated the protective effects of N-acetylcysteine (NAC) on MSG-induced cytotoxicity in C6 astrocytic cells. MSG (20 mM)-induced reactive oxygen species (ROS) generation and apoptotic cell death were significantly attenuated by NAC (500 μM) pretreatment. NAC effectively inhibited the MSG-induced mitochondrial membrane potential (MMP) loss and intracellular reduced glutathione (GSH) depletion. In addition, NAC significantly attenuated MSG-induced endoplasmic reticulum (ER) stress markers, such as XBP1 splicing and CHOP, PERK, and GRP78 up-regulation. Furthermore, NAC prevented the changes of MSG-induced Bcl-2 expression level. These results suggest that NAC can protect C6 astrocytic cells against MSG-induced oxidative stress, mitochondrial dysfunction, and ER stress.

Anticancer activities of diphenyl difluoroketone, a novel curcumin analog, on KB human oral cancer cells

Effects of diphenyl difluoroketone (EF-24) and curcumin on cell growth and apoptosis induction in KB human oral cancer cells were examined. EF-24 and curcumin inhibited the growth of KB cells in a dose-dependent manner, and the potency of EF-24 was 30 times greater than that of curcumin. Treatment with EF-24 or curcumin resulted in nuclear condensation and fragmentation. EF-24 and curcumin promoted the proteolytic cleavage of procaspases-3, -7, and -9. Activities of caspases-3 and -7 were detected in living KB cells treated with EF-24 or curcumin. These results suggest that EF-24 and curcumin inhibit cell proliferation and induce apoptosis in KB human oral cancer cells, and have potential properties for development of anti oral cancer drug.

Resveratrol Induces Apoptosis of KB Human Oral Cancer Cells

Resveratrol (trans-3,4′s,5,-trihydroxystilbene), a phytoalexin present in grape skin and red wine, suppresses many types of cancers by regulating cell proliferation and apoptosis through a variety of mechanisms. However, the effects of resveratrol on oral cancer are not completely understood. Thus, effects of resveratrol on cell growth and apoptosis induction were examined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, DNA fragmentation, immunoblotting, and determination of caspase activation in KB human oral cancer cells. Treatment with resveratrol induced inhibition of cell growth depending on the resveratrol treatment time and concentration in KB cells. Treatment with resveratrol induced DNA ladder formation in KB cells and promoted proteolytic cleavage of procaspase-3 and procaspase-7 with increases in the amount of cleaved caspases-3 and -7. Proteolytic processing of caspase-9 in KB cells was increased by resveratrol treatment. Activation of caspase-3/-7 was detected in living KB cells by fluorescence microscopy. These results suggest that the resveratrol can suppress cell growth and induce cell apoptosis in KB human oral cancer cells, and may have potential as an anti-cancer drug.

Resveratrol inhibits lipopolysaccharide-induced phagocytotic activity in BV2 cells

The inhibitory effects of resveratrol, a natural bioactive polyphenolic phytoalexin rich in grape, on lipopolysaccharide (LPS)-induced microglial activation and its beneficial effects on dopaminergic neurodegeneration were studied. Resveratrol dosedependently suppressed LPS-induced nitric oxide production and the expression of inducible NO synthase (iNOS) in BV-2 microglial cells. Furthermore, resveratrol (1 μM) significantly blocked BV2 microglial phagocytosis induced by LPS (0.1 μg/mL). Although the conditioned media from LPS-stimulated BV2 cells caused the SN4741 dopaminergic neuronal cell death, that from resveratrolpretreated BV2 cells did not diminish the viability of SN4741 cells. These results suggest that resveratrol can prevent neuronal death possibly through the modulation of phagocytosis and microglial activation.

Nargenicin attenuates lipopolysaccharide-induced inflammatory responses in BV-2 cells

Microglia activation has been considered as a major factor associated with neurodegenerative diseases. In this study, we investigated the inhibitory effects of nargenicin, a natural antibiotic from soil bacterium Nocardia, on lipopolysaccharide (LPS)-induced inflammatory activation of microglia. Nargenicin significantly attenuated LPS-induced nitric oxide production in BV-2 microglial cells. Furthermore, nargenicin effectively suppressed the upregulation of interleukin-1&bgr;, tumor necrosis factor &agr;, and inducible nitric oxide synthase at both mRNA and protein levels in LPS-stimulated BV-2 microglia. In addition, nargenicin blocked LPS-induced degradation of IκB-&agr;, indicating that the initial molecular target of nargenicin is the transcription factor nuclear factor-κB. These results suggest that nargenicin should be evaluated as a therapeutic agent for inflammatory neurodegenerative diseases.

Protective effects of quercetin on dieldrin-induced endoplasmic reticulum stress and apoptosis in dopaminergic neuronal cells.

Dieldrin, an organochlorine pesticide still used in several developing countries, has been proposed as a risk factor for Parkinson’s disease. Quercetin is one of the potent bioactive flavonoids present in numerous plants. In this study, we investigated the protective effects of quercetin on neurotoxicity induced by dieldrin in cultured dopaminergic SN4741 cells. Our initial experiments showed that quercetin (10–40 &mgr;M) dose dependently prevented dieldrin (20 &mgr;M)-induced cytotoxicity in SN4741 cells. Pretreatment for 1 h with quercetin before dieldrin application could significantly suppress dieldrin-induced apoptotic characteristics, including nuclear condensation, DNA fragmentation, and caspase-3/7 activation. Results showed that dieldrin-induced markers of endoplasmic reticulum (ER) stress response such as chaperone GRP78, heme oxygenase-1, and phosphorylation of the &agr; subunit of eukaryotic initiation factor 2. In addition, dieldrin reduced antiapoptotic Bcl-2 expression, but significantly elevated a proapoptotic transcription factor CHOP. Furthermore, RNA interference to CHOP almost completely repressed dieldrin-induced apoptotic cell death. Interestingly, quercetin prevented the changes in dieldrin-induced ER stress markers. These results suggest that quercetin may suppress the ER stress-CHOP pathway and dieldrin-induced apoptosis in dopaminergic neurons.

Protective Effects of Curcumin on Manganese-Induced BV-2 Microglial Cell Death

Curcumin, a bioactive component in tumeric, has been shown to exert antioxidant, anti-inflammatory, anticarcinogenic, hepatoprotective, and neuroprotective effects, but the effects of curcumin against manganese (Mn)-mediated neurotoxicity have not been studied. This study examined the protective effects of curcumin on Mn-induced cytotoxicity in BV-2 microglial cells. Curcumin (0.1-10 µM) dose-dependently prevented Mn (250 µM)-induced cell death. Mn-induced mitochondria-related apoptotic characteristics, such as caspase-3 and -9 activation, cytochrome c release, Bax increase, and Bcl-2 decrease, were significantly suppressed by curcumin. In addition, curcumin significantly increased intracellular glutathione (GSH) and moderately potentiated superoxide dismutase (SOD), both which were diminished by Mn treatment. Curcumin pretreatment effectively suppressed Mn-induced upregulation of malondialdehyde (MDA), total reactive oxygen species (ROS). Moreover, curcumin markedly inhibited the Mn-induced mitochondrial membrane potential (MMP) loss. Furthermore, curcumin was able to induce heme oxygenase (HO)-1 expression. Curcumin-mediated inhibition of ROS, down-regulation of caspases, restoration of MMP, and recovery of cell viability were partially reversed by HO-1 inhibitor (SnPP). These results suggest the first evidence that curcumin can prevent Mn-induced microglial cell death through the induction of HO-1 and regulation of oxidative stress, mitochondrial dysfunction, and apoptotic events.