Validation of precision-cut liver slices to study drug-induced cholestasis:A transcriptomics approach

Hepatotoxicity is one of the major reasons for withdrawal of drugs from the market. Therefore, there is a need to screen new drugs for hepatotoxicity in humans at an earlier stage. The aim of this study was to validate human precision-cut liver slices (PCLS) as an ex vivo model to predict drug-induced cholestasis and identify the possible mechanisms of cholestasis-induced toxicity using gene expression profiles. Five hepatotoxicants, which are known to induce cholestasis (alpha-naphthyl isothiocyanate, chlorpromazine, cyclosporine, ethinyl estradiol and methyl testosterone) were used at concentrations inducing low (<30 %) and medium (30-50 %) toxicity, based on ATP content. Human PCLS were incubated with the drugs in the presence of a non-toxic concentration (60 µM) of a bile acid mixture (portal vein concentration and composition) as model for bile acid-induced cholestasis. Regulated genes include bile acid transporters and cholesterol transporters. Pathway analysis revealed that hepatic cholestasis was among the top ten regulated pathways, and signaling pathways such as farnesoid X receptor- and liver X receptor-mediated responses, which are known to play a role in cholestasis, were significantly affected by all cholestatic compounds. Other significantly affected pathways include unfolded protein response and protein ubiquitination implicating the role of endoplasmic reticulum stress. This study shows that human PCLS incubated in the presence of a physiological bile acid mixture correctly reflect the pathways affected in drug-induced cholestasis in the human liver. In the future, this human PCLS model can be used to identify cholestatic adverse drug reactions of new chemical entities

Why don't we inform patients about the risk of diagnostic errors?

The principles of autonomy and informed consent dictate that patients who undergo a radiological examination should actually be informed about the risk of diagnostic errors. Implementing such a policy could potentially increase the quality of care. However, due to the vast number of radiological examinations that are performed in each hospital each day, financial constraints, and the risk of losing trust, patients, and income if the requirement for informed consent is not imposed by law on a state or national level, it may be challenging to inform patients about the risk of diagnostic errors. Future research is necessary to determine if and how an informed consent procedure for diagnostic errors can be implemented in clinical practice.</p

A transcriptomic approach for evaluating the relative potency and mechanism of action of azoles in the rat Whole Embryo Culture.

We evaluated the effect of six azoles on embryonic development in the rat whole embryo culture (WEC). Using the total morphological scoring system (TMS), we calculated the ID10concentration (effective dose for 10% decrease in TMS). For evaluating gene specific responses, we combined previously and newly collected transcriptomics data of rat WEC exposed to a total of twelve azoles at their ID10for 4h. Results revealed shared expressions responses in genes involved in the retinoic acid (RA) and sterol biosynthesis pathways, which are respectively representatives of developmental toxicity and targeted fungicidal action of the azoles. Azoles with more pronounced effects on the regulation of RA-associated genes were generally characterized as more potent embryotoxicants. Overall, compounds with strong sterol biosynthesis related responses and low RA related responses were considered as more favourable candidates, as they specifically regulated genes related to a desired target response. Among the identified sterol associated genes, we detected that methylsterol monooxygenase 1 (Msmo1) was more sensitively induced compared to Cyp51, a classical biomarker of this pathway. Therefore, we suggest that Msmo1 could be a better biomarker for screening the fungicidal value of azoles. In summary, we conclude that the embryonic regulation of RA and sterol metabolic pathways could be indicators for ranking azoles as embryotoxicants and determining their drug efficacy

Comparison of clastogen-induced gene expression profiles in wild-type and DNA repair-deficient Rad54/Rad54B cells

Background: Previously we found that Rad54/Rad54B cells are more sensitive towards mitomycin C (MMC) as compared to wild-type (WT) cells. This difference in sensitivity was absent upon exposure to other clastogens like bleomycin (BLM) and g-radiation. In order to get further insight into possible underlying mechanisms, gene expression changes in WT and Rad54/Rad54B MEFs (mouse embryonic fibroblasts) after exposure to the clastogens MMC and BLM were investigated. Exposures of these cells to mutagens (N-ac-AAF and ENU) and vehicle were taken as controls. Results: Most exposures resulted in an induction of DNA damage signaling and apoptosis genes and a reduced expression of cell division genes in cells of both genotypes. As expected, responses to N-ac-AAF were very similar in both genotypes. ENU exposure did not lead to significant gene expression changes in cells of both genotypes, presumably due to its short half-life. Gene expression responses to clastogens, however, showed a genotype-dependent effect for BLM and MMC. MMC treated Rad54/Rad54B MEFs showed no induction of p53-signaling, DNA damage response and apoptosis as seen for all the other treatments. Conclusion: These data support our finding that different types of clastogens exist and that responses to these types depend on the DNA repair status of the cells.Toxicogenomics and risk assessmen

The transcriptomic response to irinotecan in colon carcinoma bearing mice preconditioned by fasting

Background: Irinotecan use is limited due to severe toxicity. Preconditioning by fasting (PBF) protects against side effects of irinotecan while preserving its antitumor activity. The mechanisms underlying the effects of PBF still need to be elucidated. Here, we investigated the transcriptional responses of PBF on irinotecan in both tumor and healthy liver tissue. Experimental approach: Male BALB/c mice were subcutaneously injected with C26 colon carcinoma cells. Twelve days after tumor inoculation, two groups were fasted for three days and two groups were allowed food ad libitum (AL). Subsequently, both groups received one dose of irinotecan. Twelve hours after administration mice were sacrificed and blood, tumor and liver tissue were harvested. Blood samples were analyzed to determine liver, kidney and bone marrow function, tissues were used for transcriptome analyses. Key results: The AL irinotecan group showed worsened organ function and decreased leukocyte numbers. These effects were abated in PBF animals. PBF led to an altered transcriptional response in the liver of irinotecan-treated mice, including decreased cellular injury and increased stress resistance. Hepatic metabolism of irinotecan was also significantly changed due to PBF. The transcriptional response of tumor tissue observed after PBF was hardly affected compared to AL fed animals. Conclusions: Transcriptional changes after PBF to irinotecan treatment showed an improved protective stress response in healthy liver but not in tumor tissue, including changes in irinotecan metabolism. These data help to unravel the mechanisms underlying the effects of fasting on irinotecan and help to improve outcome of chemotherapeutic treatment in cancer patients

Benzo(a)pyrene induces similar gene expression changes in testis of DNA repair proficient and deficient mice

<p>Abstract</p> <p>Background</p> <p>Benzo [a]pyrene (B[a]P) exposure induces DNA adducts at all stages of spermatogenesis and in testis, and removal of these lesions is less efficient in nucleotide excision repair deficient <it>Xpc</it>^-/-mice than in wild type mice. In this study, we investigated by using microarray technology whether compromised DNA repair in <it>Xpc</it>^-/-mice may lead to a transcriptional reaction of the testis to cope with increased levels of B[a]P induced DNA damage.</p> <p>Results</p> <p>Two-Way ANOVA revealed only 4 genes differentially expressed between wild type and <it>Xpc</it>^-/-mice, and 984 genes between testes of B[a]P treated and untreated mice irrespective of the mouse genotype. However, the level in which these B[a]P regulated genes are expressed differs between Wt and <it>Xpc</it>^-/-mice (p = 0.000000141), and were predominantly involved in the regulation of cell cycle, translation, chromatin structure and spermatogenesis, indicating a general stress response. In addition, analysis of cell cycle phase dependent gene expression revealed that expression of genes involved in G1-S and G2-M phase arrest was increased after B[a]P exposure in both genotypes. A slightly higher induction of average gene expression was observed at the G2-M checkpoint in <it>Xpc</it>^-/-mice, but this did not reach statistical significance (P = 0.086). Other processes that were expected to have changed by exposure, like apoptosis and DNA repair, were not found to be modulated at the level of gene expression.</p> <p>Conclusion</p> <p>Gene expression in testis of untreated <it>Xpc</it>^-/-and wild type mice were very similar, with only 4 genes differentially expressed. Exposure to benzo(a)pyrene affected the expression of genes that are involved in cell cycle regulation in both genotypes, indicating that the presence of unrepaired DNA damage in testis blocks cell proliferation to protect DNA integrity in both DNA repair proficient and deficient animals.</p

Biomarkers for circadian rhythm disruption independent of time of day

Frequent shift work causes disruption of the circadian rhythm and might on the long-term result in increased health risk. Current biomarkers evaluating the presence of circadian rhythm disturbance (CRD), including melatonin, cortisol and body temperature, require 24-hr ("around the clock") measurements, which is tedious. Therefore, these markers are not eligible to be used in large-scale (human) studies.

Comparative genomic profiling of Dutch clinical Bordetella pertussis isolates using DNA microarrays: Identification of genes absent from epidemic strains

Contains fulltext : 72769.pdf (publisher's version ) (Open Access)14 p

Correction: Comparative genomic profiling of Dutch clinical Bordetella pertussis isolates using DNA microarrays: identification of genes absent from epidemic strains

<p><b>Copyright information:</b></p><p>Taken from "Comparative genomic profiling of Dutch clinical isolates using DNA microarrays: Identification of genes absent from epidemic strains"</p><p>http://www.biomedcentral.com/1471-2164/9/311</p><p>BMC Genomics 2008;9():311-311.</p><p>Published online 30 Jun 2008</p><p>PMCID:PMC2481270.</p><p></p