In vivo – in vitro toxicogenomic comparison of TCDD-elicited gene expression in Hepa1c1c7 mouse hepatoma cells and C57BL/6 hepatic tissue

BACKGROUND: In vitro systems have inherent limitations in their ability to model whole organism gene responses, which must be identified and appropriately considered when developing predictive biomarkers of in vivo toxicity. Systematic comparison of in vitro and in vivo temporal gene expression profiles were conducted to assess the ability of Hepa1c1c7 mouse hepatoma cells to model hepatic responses in C57BL/6 mice following treatment with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). RESULTS: Gene expression analysis and functional gene annotation indicate that Hepa1c1c7 cells appropriately modeled the induction of xenobiotic metabolism genes in vivo. However, responses associated with cell cycle progression and proliferation were unique to Hepa1c1c7 cells, consistent with the cell cycle arrest effects of TCDD on rapidly dividing cells. In contrast, lipid metabolism and immune responses, representative of whole organism effects in vivo, were not replicated in Hepa1c1c7 cells. CONCLUSION: These results identified inherent differences in TCDD-mediated gene expression responses between these models and highlighted the limitations of in vitro systems in modeling whole organism responses, and additionally identified potential predictive biomarkers of toxicity

Differences in TCDD-elicited gene expression profiles in human HepG2, mouse Hepa1c1c7 and rat H4IIE hepatoma cells

<p>Abstract</p> <p>Background</p> <p>2,3,7,8-Tetrachlorodibenzo-<it>p</it>-dioxin (TCDD) is an environmental contaminant that elicits a broad spectrum of toxic effects in a species-specific manner. Current risk assessment practices routinely extrapolate results from <it>in vivo </it>and <it>in vitro </it>rodent models to assess human risk. In order to further investigate the species-specific responses elicited by TCDD, temporal gene expression responses in human HepG2, mouse Hepa1c1c7 and rat H4IIE cells were compared.</p> <p>Results</p> <p>Microarray analysis identified a core set of conserved gene expression responses across species consistent with the role of AhR in mediating adaptive metabolic responses. However, significant species-specific as well as species-divergent responses were identified. Computational analysis of the regulatory regions of species-specific and -divergent responses suggests that dioxin response elements (DREs) are involved. These results are consistent with <it>in vivo </it>rat vs. mouse species-specific differential gene expression, and more comprehensive comparative DRE searches.</p> <p>Conclusions</p> <p>Comparative analysis of human HepG2, mouse Hepa1c1c7 and rat H4IIE TCDD-elicited gene expression responses is consistent with <it>in vivo </it>rat-mouse comparative gene expression studies, and more comprehensive comparative DRE searches, suggesting that AhR-mediated gene expression is species-specific.</p

Integration of Genome-Wide Computation DRE Search, AhR ChIP-chip and Gene Expression Analyses of TCDD-Elicited Responses in the Mouse Liver

<p>Abstract</p> <p>Background</p> <p>The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor (TF) that mediates responses to 2,3,7,8-tetrachlorodibenzo-<it>p</it>-dioxin (TCDD). Integration of TCDD-induced genome-wide AhR enrichment, differential gene expression and computational dioxin response element (DRE) analyses further elucidate the hepatic AhR regulatory network.</p> <p>Results</p> <p>Global ChIP-chip and gene expression analyses were performed on hepatic tissue from immature ovariectomized mice orally gavaged with 30 μg/kg TCDD. ChIP-chip analysis identified 14,446 and 974 AhR enriched regions (1% false discovery rate) at 2 and 24 hrs, respectively. Enrichment density was greatest in the proximal promoter, and more specifically, within ± 1.5 kb of a transcriptional start site (TSS). AhR enrichment also occurred distal to a TSS (e.g. intergenic DNA and 3' UTR), extending the potential gene expression regulatory roles of the AhR. Although TF binding site analyses identified over-represented DRE sequences within enriched regions, approximately 50% of all AhR enriched regions lacked a DRE core (5'-GCGTG-3'). Microarray analysis identified 1,896 number of TCDD-responsive genes (|fold change| ≥ 1.5, P1(t) > 0.999). Integrating this gene expression data with our ChIP-chip and DRE analyses only identified 625 differentially expressed genes that involved an AhR interaction at a DRE. Functional annotation analysis of differentially regulated genes associated with AhR enrichment identified overrepresented processes related to fatty acid and lipid metabolism and transport, and xenobiotic metabolism, which are consistent with TCDD-elicited steatosis in the mouse liver.</p> <p>Conclusions</p> <p>Details of the AhR regulatory network have been expanded to include AhR-DNA interactions within intragenic and intergenic genomic regions. Moreover, the AhR can interact with DNA independent of a DRE core suggesting there are alternative mechanisms of AhR-mediated gene regulation.</p

Differential expression of SUMO-specific protease 7 variants regulates epithelial–mesenchymal transition

Two Sentrin/small ubiquitin-like modifier (SUMO)-specific protease 7 (SENP7) variants are naturally expressed in breast epithelia. Breast cancer (BCa) onset down-regulates the short SENP7 splice variant (SENP7S) and enhances the long transcript (SENP7L). Here, we show that SENP7L induction promotes gene expression profiles that favor aberrant proliferation and initiate epithelial–mesenchymal transition (EMT). SENP7L exhibits an interaction domain for the epigenetic remodeler heterochromatin protein 1 α (HP1α) and isopeptidase activity against SUMO-modified HP1α. Loss of this interaction domain, as observed with SENP7S, favors HP1α SUMOylation. SUMOylated HP1α is enriched at E2F-responsive and mesenchymal gene promoters, silences transcription of these genes, and promotes cellular senescence. Elevated SENP7L renders HP1α hypo-SUMOylated, which relieves transcriptional repression of the same genes and concurrently decreases transcription of epithelial-promoting genes via an HP1α-independent mechanism. Consequently, SENP7L levels correlate with EMT, motility, and invasiveness of BCa cells. Stable knockdown of elevated SENP7L levels lessens the dissemination of highly metastatic BCa cells to the lungs from primary implantation sites in in vivo studies. Thus, differential splicing of the SENP7 regulates either tumor suppression or progression

Burnout among surgeons before and during the SARS-CoV-2 pandemic: an international survey

Background: SARS-CoV-2 pandemic has had many significant impacts within the surgical realm, and surgeons have been obligated to reconsider almost every aspect of daily clinical practice. Methods: This is a cross-sectional study reported in compliance with the CHERRIES guidelines and conducted through an online platform from June 14th to July 15th, 2020. The primary outcome was the burden of burnout during the pandemic indicated by the validated Shirom-Melamed Burnout Measure. Results: Nine hundred fifty-four surgeons completed the survey. The median length of practice was 10&nbsp;years; 78.2% included were male with a median age of 37&nbsp;years old, 39.5% were consultants, 68.9% were general surgeons, and 55.7% were affiliated with an academic institution. Overall, there was a significant increase in the mean burnout score during the pandemic; longer years of practice and older age were significantly associated with less burnout. There were significant reductions in the median number of outpatient visits, operated cases, on-call hours, emergency visits, and research work, so, 48.2% of respondents felt that the training resources were insufficient. The majority (81.3%) of respondents reported that their hospitals were included in the management of COVID-19, 66.5% felt their roles had been minimized; 41% were asked to assist in non-surgical medical practices, and 37.6% of respondents were included in COVID-19 management. Conclusions: There was a significant burnout among trainees. Almost all aspects of clinical and research activities were affected with a significant reduction in the volume of research, outpatient clinic visits, surgical procedures, on-call hours, and emergency cases hindering the training. Trial registration: The study was registered on clicaltrials.gov "NCT04433286" on 16/06/2020

Data from: All-trans retinoic acid disrupts development in ex vivo cultured fetal rat testes. I: altered seminiferous cord maturation and testicular cell fate

Exposure to excess retinoic acid disrupts the development of the mammalian testicular seminiferous cord. However, the molecular events surrounding retinoic acid-driven loss of cord structure have not previously been examined. To investigate the mechanisms associated with this adverse developmental effect, fetal rat testes were isolated on gestational day 15, after testis determination and the initiation of cord development, and cultured in media containing all-trans retinoic acid (ATRA; 10-8 to 10-6 M) or vehicle for 3 days. ATRA exposure resulted in a concentration-dependent decrease in the number of seminiferous cords per testis section and number of germ cells, assessed by histopathology and immunohistochemistry. Following 1 day of culture, genome-wide expression profiling by microarray demonstrated that ATRA exposure altered biological processes related to retinoid metabolism and gonadal sex determination. Real-time RT-PCR analysis confirmed that ATRA enhanced the expression of the key ovarian development gene Wnt4 and the anti-testis gene Nr0b1 in a concentration-dependent manner. After 3 days of culture, ATRA-treated testes contained both immunohistochemically DMRT1-positive and FOXL2-positive somatic cells, providing evidence of disrupted testicular cell fate maintenance following ATRA exposure. We conclude that exogenous retinoic acid disrupts seminiferous cord development in ex vivo cultured fetal rat testes, resulting in a reduction in seminiferous cord number, and interferes with maintenance of somatic cell fate by enhancing expression of factors that promote ovarian development