G q / 11 protein-coupled muscarinic receptors are known to regulate the release of soluble amyloid precursor protein (sAPP␣) produced by ␣-secretase processing; however, their signaling mechanisms remain to be elucidated. It has been reported that a muscarinic agonist activates nuclear factor (NF)-B, a transcription factor that has been shown to play an important role in the Alzheimer disease brain, and that NF-B activation is regulated by intracellular Ca 2؉ level. In the present study, we investigated whether NF-B activation plays a role in muscarinic receptor-mediated sAPP␣ release enhancement and contributes to a changed capacitative Ca 2؉ entry (CCE), which was suggested to be involved in the muscarinic receptor-mediated stimulation of sAPP␣ release. Muscarinic receptor-mediated NF-B activation was confirmed by observing the translocation of the active subunit The amyloid precursor protein (APP)4 is a transmembrane protein that produces ␤ amyloid (A␤) by proteolytic cleavage in brains of individuals with Alzheimer disease. APP normally undergoes proteolytic cleavage within the A␤ sequence liberating the ␣-secretase-cleaved APP (sAPP␣). Although evidence indicates that sAPP␣ plays important roles in regulating neuronal survival and plasticity, the mechanisms that mediate these biological activities and the regulation of sAPP␣ secretion have not been established. The transcriptional nuclear factor-B (NF-B) responds to a large number of environmental cues, and in the nervous system, it is modulated under physiological and pathological conditions, which include developmental cell death and acute of chronic neurodegenerative disorders (1, 2). It was proposed that NF-B or other B-binding proteins may be involved in a neuroprotective change in gene expression evoked by various cytokines and by secreted APP in neuronal cells, and therefore, may have a positive effect on Alzheimer disease (3-6).The NF-B/Rel family of dimeric transcriptional factors is involved in the immediate early transcription of a large array of genes induced by mitogenic and antiapoptotic pathogen-associated stimuli (7,8). The eukaryotic NF-B/Rel family of eukaryotic transcription factors, which includes p50, p65, c-Rel, RelB, and p52, bind DNA with high specificity and affinity as homo-or heterodimers to mediate a diverse range of biological processes (9 -11). The most common form of NF-B consists of a heterodimer of p50 (NF-B1) and p65 (Rel A) (12-15). In most resting cells, NF-B is retained in the cytoplasm by its association with inhibitor molecules of the IB family (16). The formation of NF-B-IB complex masks the nuclear localization signal sequence in NF-B and thus prevents its nuclear translocation. In response to various stimuli, NF-B dimers are released from cytoplasmic IB proteins by a process involving site-specific phosphorylation of IB by IB kinase, ubiquitination, and subsequent proteolytic degradation via the 26 S proteasome pathway (6,17,18).The induction of NF-B activity is known to be regulated by the intracellular Ca 2ϩ leve...

Epigallocatechin gallate (EGCG), a major type of green tea polyphenol, has been reported to cause hepatotoxicity when used in excess. MicroRNAs (miRNAs) are small non-coding RNA molecules that functions as negative regulators of gene expression. They play an important role in the regulation of genes involved in the cellular and molecular responses to toxicants. To examine miRNA regulatory effect on global gene expression in EGCG-treated HepG2 cells, we performed pair-wise correlation coefficient analysis on expression levels of 22 miRNA and 27,419 mRNA, and observed negative correlations (r⁄-0.7) between miRNA and mRNA. We identified a total of 234 negative correlated miRNAmRNA pairs. Gene Ontology analysis on the miRNAcorrelated genes revealed significant enrichment in the several biological processes related to organic acid metabolic process, carboxylic acid metabolic process and cellular protein catabolic process. Connectivity map analysis also revealed that the expression signatures of EGCG were very similar to those of polyphenol gossypol which is hepatotoxic to animal and human.

Recently, obesity has become a worldwide public health concern and the use of anorectic drugs has drastically increased. In this study, sibutramine and phendimetrazine, representative marketed anorectics, were repeatedly administered per os on a daily basis into C57BL/6 mice and the effects of these drugs on food intakes, body weight changes and gene expression profiles were monitored for up to following 7 days. Methamphetamine, which has a potent anorectic effect, was used as a positive control. Anorectic effects were sustained only for two days by phendimetrazine or methamphetamine, but for six days by sibutramine. The modulations of gene expressions in the hypothalamus and the striatum were investigated using microarrays on day 2 and day 7 post-administration, which corresponded to the anorectic period and a return of appetite respectively, for all three drugs tested. Differences in overall gene expression profiles in the stratum on day 2 for sibutramine and phendimetrazine seems to reflect difference between the two in terms of the onsets of drug tolerance. According to microarray findings, the Ankrd26 gene appears to have an important anorectic role, whereas the up-regulation of the olfaction system appeared to be involved in the drug tolerance of anorectics. The microarray data presented in this study demonstrates the usefulness of gene expression analysis for gathering information on the efficacy and safety of anorectic drugs.

The differentiation of neural precursor cells (NPCs) into neurons and astrocytes is a process that is tightly controlled by complicated and ill-defined gene networks. To extend our knowledge to gene networks, we performed a temporal analysis of gene expression during the differentiation (2, 4, and 8 days) of spinal cord-derived NPCs using oligonucleotide microarray technology. Out of 32,996 genes analyzed, 1878 exhibited significant changes in expression level (fold change＞2, p＜0.05) at least once throughout the differentiation process. These 1878 genes were classified into 12 groups by k-means clustering, based on their expression patterns. K-means clustering analysis revealed that the genes involved in astrogenesis were categorized into the clusters containing constantly upregulated genes, whereas the genes involved in neurogenesis were grouped to the cluster showing a sudden decrease in gene expression on Day 8. Functional analysis of the differentially expressed genes indicated the enrichment of genes for Pax6-NeuroD signaling−TGFb-SMAD and BMP-SMAD−which suggest the implication of these genes in the differentiation of NPCs and, in particular, key roles for Nova1 and TGFBR1 in the neurogenesis/astrogenesis of mouse spinal cord.

Statins are competitive inhibitors of hydroxy-3-methyl glutaryl coenzyme A (HMG-CoA) reductase and used most frequently to reduce plasma cholesterol levels and to decrease cardiovascular events. However, statins also have been reported to have undesirable side effects such as myotoxicity and hepatotoxicity associated with their intrinsic efficacy mechanisms. Clinical studies recurrently reported that statin therapy elevated the level of liver enzymes such as ALT and AST in patients suggesting possible liver toxicity due to statins. This observation has been drawn great attention since statins are the most prescribed drugs and statin-therapy was extended to a larger number of high-risk patients. Here we employed rat primary hepatocytes and microarray technique to understand underlying mechanism responsible for statin-induced liver toxicity on cell level. We isolated genes whose expressions were commonly modulated by statin treatments and examined their biological functions. It is of interest that those genes have function related to response to stress in particular immunity and defense in cells. Our study provided the basic information on cellular mechanism of statin-induced cytotoxicity and may serve for finding indicator genes of statin -induced toxicity in rat primary hepatocytes.

Mercuric chloride, a model nephrotoxicant was used to elucidate time-and dose-dependent global gene expression changes associated with proximal tubular toxicity. Rat kidney cell lines NRK-52E cells were exposed for 2, 6 and 12 hours and with 3 different doses of mercuric chloride. Cell viability assay showed that mercuric chloride had toxic effects on NRK-52E cells causing 20% cell death (IC20) at 40μM concentration. We set this IC20 as high dose concentration and 1/5 and 1/25 concentration of LC20 were used as mid and low concentration, respectively. Analyses of microarray data revealed that 738 genes were differentially expressed (more than two-fold change and p＜0.05) by low concentration of mercuric chloride at least one time point in NRK-52E cells. 317 and 2,499 genes were differentially expressed at mid and high concentration of mercuric chloride, respectively. These deregulated genes showed a primary involvement with protein trafficking (CAV2, CANX, CORO1B), detoxification (GSTs) and immunity and defense (HMOX1, NQO1). Several of these genes were previously reported to be up-regulated in proximal tubule cells treated with nephrotoxicants and might be aid in promoting the predictive biomarkers for nephrotoxicity.

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