Bromobenzene-induced hepatotoxicity at the transcriptome level.
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Rats were exposed to three levels of bromobenzene, sampled at 6, 24, and 48 h, and liver gene expression profiles were determined to identify dose and time-related changes. Expression of many genes changed transiently, and dependent on the dose. Few changes were identified after 6 h, but many genes were differentially expressed after 24 h, while after 48 h, only the high dose elicited large effects. Differentially expressed genes were involved in drug metabolism (upregulated GSTs, mEH, NQO1, Mrps, downregulated CYPs, sulfotransferases), oxidative stress (induced HO-1, peroxiredoxin, ferritin), GSH depletion (induced GCS-l, GSTA, GSTM) the acute phase response, and in processes like cholesterol, fatty acid and protein metabolism, and intracellular signaling. Trancriptional regulation via the electrophile and sterol response elements seemed to mediate part of the response to bromobenzene. Recovery of the liver was suggested in response to BB by the altered expression of genes involved in protein synthesis and cytoskeleton rearrangement. Furthermore, after 48 h, rats in the mid dose group showed no toxicity, and gene expression patterns resembled the normal situation. For certain genes (e.g., CYP4A, metallothioneins), intraday variation in expression levels was found, regardless of the treatment. Selected cDNA microarray measurements were confirmed using the specific and sensitive branched DNA signal amplification assay. (+info)
Changes in the gene expression associated with carbon tetrachloride-induced liver fibrosis persist after cessation of dosing in mice.
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Recent studies have shown that gene expression profiles change in the livers of animals treated acutely with toxic chemicals such as carbon tetrachloride (CCl(4)). This study was undertaken to evaluate the changes in gene expression in mouse liver immediately after a long-term treatment with CCl(4) and possible effects of treatment cessation on these changes. Adult 129/Sv(pc)J mice were treated twice a week with CCl(4) at 1 ml/kg in olive oil for 4 weeks. Hepatic pathological changes observed in the CCl(4)-treated mice included necrosis, inflammation, and fibrosis, along with increased serum alanine aminotransferase activities. Consistent with these changes, expression of genes involved in cell death, cell proliferation, metabolism, DNA damage, and fibrogenesis were upregulated as detected by microarray analysis and confirmed by real-time RT-PCR. Four weeks after CCl(4) treatment cessation, the pathological changes were recovered, with the exception of fibrosis, which was not completely reversed. Most of the gene expression profiles also returned to the control level; however, the fibrogenetic genes remained at a high level of expression. These results demonstrate that changes in gene expression profile correlate with pathological alterations in the liver in response to CCl(4) intoxication. Most of these changes are recoverable upon withdrawal of the toxic insult. However, liver fibrosis is a prolonged change both in gene expression and histopathological alterations. (+info)
Gene expression profiling of rat livers reveals indicators of potential adverse effects.
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This study tested the hypothesis that gene expression profiling can reveal indicators of subtle injury to the liver induced by a low dose of a substance that does not cause overt toxicity as defined by conventional criteria of toxicology (e.g., abnormal clinical chemistry and histopathology). For the purpose of this study we defined this low dose as subtoxic, i.e., a dose that elicits effects which are below the detection of conventional toxicological parameters. Acetaminophen (APAP) was selected as a model hepatotoxicant because (1) considerable information exists concerning the mechanism of APAP hepatotoxicity that can occur following high doses, (2) intoxication with APAP is the leading cause of emergency room visits involving acute liver failure within the United States, and (3) conventional clinical markers have poor predictive value. Rats treated with a single dose of 0, 50, 150, or 1500 mg/kg APAP were examined at 6, 24, or 48 h after exposure for conventional toxicological parameters and for gene expression alterations. Patterns of gene expression were found which indicated cellular energy loss as a consequence of APAP toxicity. Elements of these patterns were apparent even after exposure to subtoxic doses. With increasing dose, the magnitude of changes increased and additional members of the same biological pathways were differentially expressed. The energy loss suggested by gene expression changes was confirmed at the 1500 mg/kg dose exposure by measuring ATP levels. Only by ultrastructural examination could any indication of toxicity be identified after exposure to a subtoxic dose of APAP and that was occasional mitochondrial damage. In conclusion, this study provides evidence that supports the hypothesis that gene expression profiling may be a sensitive means of identifying indicators of potential adverse effects in the absence of the occurrence of overt toxicity. (+info)
Match/X, A gene expression pattern recognition algorithm used to identify genes which may be related to CDC2 function and cell cycle regulation.
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Large-scale microarray gene expression studies can provide insight into complex genetic networks and biological pathways. A comprehensive gene expression database was constructed using Affymetrix GeneChip microarrays and RNA isolated from more than 6,400 distinct normal and diseased human tissues. These individual patient samples were grouped into over 700 sample sets based on common tissue and disease morphologies, and each set contained averaged expression data for over 45,000 gene probe sets representing more than 33,000 known human genes. Sample sets were compared to each other in more than 750 normal vs. disease pairwise comparisons. Relative up or downregulation patterns of genes across these pairwise comparisons provided unique expression fingerprints that could be compared and matched to a gene of interest using the Match/X trade mark algorithm. This algorithm uses the kappa statistic to compute correlations between genes and calculate a distance score between a gene of interest and all other genes in the database. Using cdc2 as a query gene, we identified several hundred genes that had similar expression patterns and highly correlated distance scores. Most of these genes were known components of the cell cycle involved in G2/M progression, spindle function or chromosome arrangement. Some of the identified genes had unknown biological functions but may be related to cdc2 mediated mechanism based on their closely correlated distance scores. This algorithm may provide novel insights into unknown gene function based on correlation to expression profiles of known genes and can identify elements of cellular pathways and gene interactions in a high throughput fashion. (+info)
Whole genome scanning identifies genotypes associated with recurrence and metastasis in prostate tumors.
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Prostate cancer is the most commonly diagnosed non-cutaneous neoplasm among American males and is the second leading cause of cancer-related death. Prostate specific antigen screening has resulted in earlier disease detection, yet approximately 30% of men will die of metastatic disease. Slow disease progression, an aging population and associated morbidity and mortality underscore the need for improved disease classification and therapies. To address these issues, we analyzed a cohort of patients using array comparative genomic hybridization (aCGH). The cohort comprises 64 patients, half of whom recurred postoperatively. Analysis of the aCGH profiles revealed numerous recurrent genomic copy number aberrations. Specific loss at 8p23.2 was associated with advanced stage disease, and gain at 11q13.1 was found to be predictive of postoperative recurrence independent of stage and grade. Moreover, comparison with an independent set of metastases revealed approximately 40 candidate markers associated with metastatic potential. Copy number aberrations at these loci may define metastatic genotypes. (+info)
The effects of long-term vitamin E treatment on gene expression and oxidative stress damage in the aging Brown Norway rat epididymis.
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The male reproductive tract of the Brown Norway rat is profoundly affected by aging. In the epididymis, the site of sperm maturation and storage, aging results in histological and biochemical changes that are suggestive of oxidative stress. Vitamin E is a potent lipid-soluble antioxidant that ameliorates the oxidative stress load associated with some chronic disease conditions. To determine the effects of long-term (18-mo) vitamin E deficiency and supplementation on aging in the epididymis, we assessed gene expression changes using cDNA microarrays and lipid peroxidation using immunohistochemical detection of 4-hydroxynonenal (4-HNE) in 24-mo-old rats. Plasma vitamin E levels were significantly lower in vitamin E-deficient animals and higher in vitamin E-supplemented animals compared with age-matched controls. Vitamin E deficiency resulted in increased expression of oxidative stress-related transcripts along the epididymis. This effect was most marked in the corpus epididymidis, where expression of glutathione S-transferases pi, 8, and mu, as well as superoxide dismutase, increased by over 50%. The effect of vitamin E supplementation on the expression of oxidative stress-related transcripts was primarily decreased expression; however, the magnitude of the gene expression changes was smaller than that observed for vitamin E deficiency. 4-HNE immunostaining was present throughout the epididymis in control animals. Vitamin E deficiency both increased the intensity and altered the distribution of 4-HNE staining, while vitamin E supplementation had no observable effect. In summary, we found that long-term vitamin E treatment alters the expression of oxidative stress-related transcripts. Moreover, long-term vitamin E deficiency exacerbates the effects of age on the accumulation of oxidative stress damage in the epididymis. (+info)
Hyperactive Wnt signaling changes the developmental potential of embryonic lung endoderm.
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BACKGROUND: Studies in many model systems have shown that canonical signaling through the pathway downstream of ligands of the Wnt family can regulate multiple steps in organogenesis, including cell proliferation, differentiation, and lineage specification. In addition, misexpression of the Wnt-family member Wingless in Drosophila imaginal disc cells can lead to transdetermination of progenitors from one lineage to another. Conditional deletion of the beta-catenin component of the Wnt signaling pathway has indicated a role for Wnt signaling in mouse lung endoderm development. The full range of effects of this pathway, which includes the transcription factor Lef1, has not been explored, however. RESULTS: To explore this issue, we expressed a constitutively active beta-catenin-Lef1 fusion protein in transgenic embryos using a lung-endoderm-specific promoter from the surfactant protein C gene. Transgenic lungs appeared grossly normal, but internally they contained highly proliferative, cuboidal epithelium lacking fully differentiated lung cell types. Unexpectedly, microarray analysis and in situ hybridization revealed a mosaic of cells expressing marker genes characteristic of intestinal Paneth and goblet cells and other non-lung secretory cell types. In addition, there was strong ectopic expression of genes such as Cdx1 and Atoh1 that normally regulate gut development and early allocation of cells to intestinal secretory lineages. CONCLUSIONS: Our results show that hyperactive Wnt signaling in lung progenitors expressing a lung-specific gene can induce a dramatic switch in lineage commitment and the generation of intestinal cell types. We discuss the relevance of our findings to the poorly understood pathological condition of intestinal metaplasia in humans. (+info)
Regulation of IL-8 and IL-1beta expression in Crohn's disease associated NOD2/CARD15 mutations.
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Crohn's disease (CD) is a chronic inflammation affecting the gastrointestinal tract. Three mutations (Arg702Trp, Gly908Arg and Leu1007fsinsC) within the NOD2/CARD15 gene increase CD susceptibility. Here, we define cytokine regulation in primary human mononuclear cells, with muramyl dipeptide (MDP), the minimal NOD2/CARD15 activating component of peptidoglycan. By microarray, MDP induces a broad array of transcripts, including interleukin 1beta (IL-1beta) and interleukin 8 (IL-8). Leu1007fsinsC homozygotes demonstrated decreased transcriptional response to MDP. Electromobility shift assay demonstrated that MDP-induced NF-kappaB activation is mediated via p50 and p65 subunits, but not RelB or c-Rel. In wild-type individuals, MDP-induced IL-8 protein expression with a greater response to high dose (1 micro g/ml) compared with low-dose (10 ng/ml) MDP. At low MDP doses, in all homozygotes, we observed no induction of IL-8 protein. With high doses of MDP, Leu1007fsinsC homozygotes showed no induction. Modest induction of IL-8 protein was observed in Gly908Arg and Arg702Trp homozygotes, indicating varying MDP sensitivity of the CD-associated mutations. In wild-type healthy control, CD and ulcerative colitis individuals, low-dose MDP and TNFalpha alone results in only modest IL-1beta protein induction. With MDP plus TNFalpha, there is a synergistic induction of IL-1beta secretion. In Leu1007fsinsC homozygotes, there is a profound defect in IL-1beta secretion, despite marked induction of IL-1beta mRNA. These findings demonstrate post-transcriptional dependency on the NOD2/CARD15 pathway for IL-1beta secretion with MDP and TNFalpha treatment. Taken together, these studies suggest that a signaling defect of innate immunity to MDP may be an essential underlying defect in the pathogenesis of some CD patients. (+info)