Dual mechanisms diminishing tonic GABAA inhibition of dentate gyrus granule cells in Noda epileptic rats.

The Noda epileptic rat (NER), a Wistar colony mutant, spontaneously has tonic-clonic convulsions with paroxysmal discharges. In the present study, we measured phasic and tonic γ-aminobutyric acid A (GABAA) current (I tonic) in NER hippocampal dentate gyrus granule cells and compared the results with those of normal parent strain Wistar rats (WIS). I tonic, revealed by a bicuculline-induced outward shift in holding current, was significantly smaller in NER than in WIS (P < 0.01). The frequency of inhibitory postsynaptic currents (IPSCs) was also significantly lower in NER than in WIS (P < 0.05), without significant differences in the IPSC amplitude or decay time between WIS and NER. I tonic attenuation in NER was further confirmed in the presence of GABA transporter blockers, NO-711 and nipecotic acid, with no difference in neuronal GABA transporter expression between WIS and NER. I tonic responses to extrasynaptic GABAA receptor agonists (THIP and DS-2) were significantly reduced in NER compared with WIS (P < 0.05). Allopregnanolone caused less I tonic increase in NER than in WIS, while it prolonged the IPSC decay time to a similar rate in the two groups. Expression of the GABAA receptor δ-subunit was decreased in the dentate gyrus of NER relative to that of WIS. Taken together, our results showed that a combination of attenuated presynaptic GABA release and extrasynaptic GABAA receptor expression reduced I tonic amplitude and its sensitivity to neurosteroids, which likely diminishes the gating function of dentate gyrus granule cells and renders NER more susceptible to seizure propagation.

Neuroprotective effects of KR-62980, a new PPARγ agonist, against chemical ischemia-reperfusion in SK-N-SH cells.

PPARγ agonists exert neuroprotective effects against various types of brain injuries. In the present study, we investigated the effects of KR-62980, a new PPARγ agonist, and rosiglitazone on the neuronal cell death induced by chemical ischemia-reperfusion in SK-N-SH cells and their underlying molecular mechanisms. Both agonists inhibited chemical ischemia-reperfusion-induced cell death, and the effects were associated with anti-apoptotic action. KR-62980 and rosiglitazone suppressed NO and ROS formation, and N-acetyl-N-acetoxy-4-chlorobenzenesulfonamide, an NO generator, reversed the protective effects of the agonists on cell viability. In the agonist-induced anti-apoptotic process, PTEN expression was suppressed in parallel with increased Akt and ERK phosphorylation, whereas PD98059 (an ERK inhibitor) or wortmannin (a PI-3K inhibitor) abolished the cell survival by KR-62980 and rosiglitazone. All of the effects of KR-62980 and rosiglitazone appeared to be PPARγ-dependent because the effects were reversed by bisphenol A diglycidyl ether, a PPARγ antagonist, or by PPARγ knockdown. Our results demonstrate that two PPARγ agonists, KR-62980 and rosiglitazone, inhibited chemical ischemia-reperfusion-induced neuronal cell death by PPARγ-mediated anti-apoptotic and anti-oxidant mechanisms related to PTEN suppression and ERK phosphorylation.

Phosphatase and tensin homolog deleted on chromosome 10 suppression is an important process in peroxisome proliferator-activated receptor-gamma signaling in adipocytes and myotubes.

Peroxisome proliferator-activated receptor-gamma (PPARgamma) activation enhances insulin sensitivity in type 2 diabetes mellitus. However, downstream mediators of PPARgamma activation in adipocytes and myotubes, the most important cell types involved in glucose homeostasis, remained unclear. Here we show by using two synthetic PPARgamma agonists (rosiglitazone and KR-62776, a novel PPARgamma agonist) that phosphatase and tensin homolog deleted on chromosome 10 (PTEN) is a key downstream mediator of PPARgamma signaling. The PPARgamma agonists down-regulated PTEN expression, resulting in glucose uptake increase in differentiated 3T3-L1 adipocytes and C2C12 skeletal muscle cells. In both cells, PTEN knockdown increased glucose uptake, whereas overexpression abolished the agonist-induced effects. The effects of PPARgamma agonists on PTEN expression and glucose uptake disappeared by pretreatment with a PPARgamma antagonist or by knockdown of PPARgamma expression. In vivo treatment of the agonists to C57BL/6J-ob/ob mice resulted in the reduction of PTEN level in both adipose and skeletal muscle tissues and decreased plasma glucose levels. Thus, these results suggest that PTEN suppression is a key mechanism of the PPARgamma-mediated glucose uptake stimulation in insulin-sensitive cells such as adipocytes and skeletal muscle cells, thereby restoring glucose homeostasis in type 2 diabetes.

Development and clinical evaluation of a highly sensitive DNA microarray for detection and genotyping of human papillomaviruses.

Human papillomavirus (HPV) has been found in cervical cancer, tonsillar cancer, and certain types of head and neck cancers. We report on a DNA microarray-based method for the simultaneous detection and typing of HPVs. The genotype spectrum discriminated by this HPV DNA microarray includes 15 high-risk HPV genotypes and 12 low-risk HPV genotypes. The HPV DNA microarray showed high degrees of specificity and reproducibility. We evaluated the performance of the HPV DNA microarray by application to three HPV-positive cell lines (HeLa, Caski, and SiHa cells) and two HPV-negative cell lines (C33A and A549 cells). The HPV DNA microarray successfully identified the known types of HPV present in the cell lines. The detection limit of the HPV DNA microarray was at least 100-fold higher than that of PCR. To assess the clinical applicability of the HPV DNA microarray, we performed the HPV genotyping assay with 73 nonmalignant and malignant samples from 39 tonsillar cancer patients. Twenty-five of the 39 (64.1%) malignant samples were positive for HPV, whereas 3 of 34 (8.8%) nonmalignant samples were positive for HPV. This result shows a preferential association of HPV with tonsillar carcinomas. The correlations of the presence of HPV with the grade of differentiation and risk factors were not significant. Our data show that the HPV DNA microarray may be useful for the diagnosis and typing of HPV in large-scale epidemiological studies.

Genome-scale analysis of resveratrol-induced gene expression profile in human ovarian cancer cells using a cDNA microarray.

Resveratrol (3,5,4'-trihydroxy-trans-stilbene) is a natural compound found in large quantities, most notably in grapes and red wine, which has been shown to have anti-inflammatory, chemopreventive and anti-angiogenic effects. We examined whether resveratrol has any effect on growth and gene expression in the human ovarian cancer PA-1 cells. We show that resveratrol inhibits cell growth and induces apoptosis in PA-1 human ovarian cancer cells. We also investigated the effect of resveratrol on changes of global gene expression during resveratrol-induced growth inhibition and apoptosis in PA-1 cells using a human cDNA microarray with 7,448 sequence-verified clones. Out of the 7,448 genes screened, 118 genes were founded to be affected in their expression levels by more than 2-fold after 24-h treatment with 50 micro M resveratrol. Resveratrol treatment of PA-1 cells at the final concentration of 50 micro M for 6, 12, 24 and 48 h and gene expression patterns were analyzed by microarray. Clustering of the genes modulated more than 2-fold at three of the above times points divided the genes into 2 groups. Within these groups, there were specific subgroups of genes whose expressions were substantially changed at the specified time points. One of the most highly up-regulated genes found in this study was NAD(P)H quinone oxidoreductase 1(NQO-1), which has recently been shown to be involved in p53 regulation. Although the precise roles of genes whose expression levels were found to fluctuate after resveratrol treatment remain to be elucidated, we hope that the new view of gene expression in human ovarian cancer cells following resveratrol exposure, as offered by this study, provides clues for the mechanism of resveratrol action.