Gene modulation in total brain induced by exposure to the bicyclic phosphorus ester trimethylolpropane phosphate (TMPP)

Protection of adult mouse progenitor cells and human glioma cells by de novo decorin expression in an oxygen- and glucose-deprived cell culture model system

We employed an in vitro hypoxia cell culture model system and gene transfer technology to examine the effect of the decorin gene on cell survival against oxygen and glucose deprivation (OGD). Ectopic expression of decorin in subventricular zone (SVZ) cells from adult male mouse brain and human glioblastoma U-87 cells kept the cells viable against 24 h of OGD. Fewer than 1% of decorin-synthesizing cells were apoptotic after 12 h of OGD. In contrast, 100% of the control cells were apoptotic even after 4 h of OGD. De novo decorin synthesis in SVZ and U-87 cells induced expression of p21, p27 and Ras, AKT (acutely transforming retrovirus AKT8 in rodent T-cell lymphoma), and phosphorylated AKT. Blocking of phosphoinositide 3-kinase (PI-3K), Ras, and the epidermal growth factor receptor with specific inhibitors had no effect on induction of Ras, p21, and p27 at the messenger RNA level in decorin-synthesizing SVZ and U-87 cells. PI-3K inhibitors significantly increased apoptosis in decorin-expressing cells. Our data indicate that induction of p21, p27, Ras, AKT, and phosphorylated AKT by decorin inhibits apoptosis and protects U-87 and SVZ cells against OGD. Therefore, our data suggest that decorin is a potent trophic factor that protects neuronal progenitor cells and glioma cells from OGD.

Characteristic expression profiles induced by genotoxic carcinogens in rat liver

When applied in toxicological studies, the recently developed gene expression profiling techniques using microarrays, which brought forth the new field of toxicogenomics, facilitate the interpretation of a toxic compound's mechanism of action. In this study, we investigated whether genotoxic carcinogens at doses known to induce liver tumors in the 2-year rat bioassay deregulate a common set of genes in a short-term in vivo study and, if so, whether these deregulated genes represent defined biological pathways. Rats were dosed with the four genotoxic hepatocarcinogens dimethylnitrosamine (4 mg/kg/day), 2-nitrofluorene (44 mg/kg/day), aflatoxin B1 (0.24 mg/kg/day), and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK, 20 mg/kg/day). After treatment for up to 14 days, the expression profiles of the livers were analyzed on Affymetrix RG_U34A microarrays. Among the significantly upregulated genes were a set of target genes of the tumor suppressor protein p53, indicating a DNA damage response. Such a response was expected and, therefore, confirmed the validity of our approach. In addition, the gene expression changes suggest a specific detoxification response, the activation of proliferative and survival signaling pathways, and some cell structural changes. These responses were strong throughout the 14 day time course for 2-nitrofluorene and aflatoxin B1; in the case of dimethylnitrosamine and NNK, the effects were weakly detectable at day 1 and then increased with time. For dimethylnitrosamine and aflatoxin B1, which caused observable inflammation in vivo, we found a corresponding upregulation of inflammatory genes at the same time points. Thus, by the toxicogenomic analysis of short-term in vivo studies, we identified genes and pathways commonly deregulated by genotoxic carcinogens, which may be indicative for the early events in tumorigenesis and, thus, predictive of later tumor development.

Treatment of spontaneous and chemically induced EEG paroxysms in the Fischer-344 rat with traditional antiepileptic drugs or AED+CGP 35348 polytherapy

Twenty-four Fischer-344 rats implanted with cortical electroencephalograph (EEG) electrodes were evaluated for frequency, duration, and mean duration (duration/frequency) of both spontaneous and chemically induced spike-and-wave discharges (SWDs) during earlier and later adulthood. Fischer-344 rats, exhibiting a low level of spontaneous SWDs during earlier adulthood, progressed to exhibit a significantly larger number and duration of SWDs during later adulthood. The convulsant trimethylolpropane phosphate (TMPP), known to antagonize the GABAA inhibitory system through blockade of the chloride channel, induced or increased SWDs in every rat tested. Spontaneous or chemically induced SWDs in Fischer-344 rats were eliminated or reduced by several drugs used to control human absence seizures. The gamma-aminobutyric acid (GABA)B antagonist CGP 35348 reduced spontaneous EEG paroxysms; CGP 35348 as a polytherapy with several traditional antiabsence treatments improved control of TMPP-induced seizures. It would appear that the Fischer-344 rat provides an excellent research alternative to use of genetically selected rodent strains for investigation of progression of absencelike epilepsy with aging, induction of SWDs by toxicant exposures, and treatment of spontaneous and chemically induced paroxysms.