Identification by microarray analysis of aspartate aminotransferase and glutamine synthetase as glucocorticoid target genes in a mouse Schwann cell line.

International audienceSchwann cells have been identified as targets for glucocorticoids. Besides genes implicated in the myelination process, the target genes of glucocorticoids have not been identified in these cells. For that purpose, we performed microarray analysis on MSC80 (mouse Schwann cells) treated with a synthetic glucocorticoid, dexamethasone. These cells express a functional glucocorticoid receptor (GR), but none of the other steroid receptors. This allowed us to identify genes specifically regulated by GR in the absence of the mineralocorticoid receptor. Among the 5000 genes analyzed, 12 were at least two-fold upregulated and 91 genes were at least two-fold down-regulated upon treatment with dexamethasone. Because of their potential role in Schwann cell homeostasis, we selected, for further analysis, the upregulated genes encoding glutamine synthetase (GS) and cytosolic aspartate aminotransferase (cAspAT). These genes play a crucial role in the glutamate cycle which was shown to be vital in neuron-astrocyte cross-talk in the central nervous system. Their activation was confirmed by semi-quantitative and real-time PCR. A detailed analysis of cAspAT promoter activity revealed that the mechanism of regulation by GR in Schwann cells differs from that in hepatoma cells, suggesting a cell-specific regulation. The transactivation potency of the two Glucocorticoid Responsive Units (GRU) present in the cAspAT promoter seems to be dependent on the levels of the GR in MSC80 cells. Furthermore, we show that an increase in GR levels under certain circumstances could considerably potentiate the effects of glucocorticoids on the cAspAT promoter via synergistic activation of both GRU, To the opposite, an enhancement in GR levels did not further potentiate Dex-activation of the GS promoter, showing a differential mechanism of action of GR in the context of both promoters

Cigarette smoke and tumor micro-environment co-promote aggressiveness of human breast cancer cells

International audienceBreast cancer is a major public health issue and the role of pollutants in promoting breast cancer progression has recently been suggested. We aimed to assess if a mixture of pollutants, cigarette smoke, could favor the aggressivity of breast cancer cells. We also evaluated the impact of the tumor microenvironment, largely represented by adipocytes, in mediating this modification of cell phenotype. Breast cancer cells lines, MCF-7 were cultured using a transwell coculture model with preadipocytes hMADS cells or were cultured alone. Cells were treated with cigarette smoke extract (CSE) and the four conditions: control, treated by CSE, coculture, and coexposure (coculture and CSE) were compared. We analyzed morphological changes, cell migration, resistance to anoikis, stemness, epithelial-to-mesenchymal transition (EMT), and the presence of hormonal receptors in each condition. A complete transcriptomic analysis was carried out to highlight certain pathways. We also assessed whether the aryl hydrocarbon receptor (AhR), a receptor involved in the metabolism of xenobiotics, could mediate these modifications. Several hallmarks of metastasis were specific to the coexposure condition (cell migration, resistance to anoikis, stemness characterized by CD24/CD44 ratios and ALDH1A1 and ALDH1A3 rates) whereas others (morphological changes, EMT, loss of hormonal receptors) could be seen in the coculture condition and were aggravated by CSE (coexposure). Moreover, MCF-7 cells presented a decrease in hormonal receptors, suggesting an endocrine treatment resistance. These results were confirmed by the transcriptomic analysis. We suggest that the AhR could mediate the loss of hormonal receptor and the increase in cell migratio

Adverse outcome pathway from activation of the AhR to breast cancer-related death

International audienceAdverse outcome pathways (AOPs) are formalized and structured linear concepts that connect one molecular initiating event (MIE) to an adverse outcome (AO) via different key events (KE) through key event relationships (KER). They are mainly used in ecotoxicology toxicology, and regulatory health issues. AOPs must respond to specific guidelines from the Organization for Economic Cooperation and Development (OECD) to weight the evidence between each KE. Breast cancer is the deadliest cancer in women with a poor prognosis in case of metastatic breast cancer. The role of the environments in the formation of metastasis has been suggested. We hypothesized that activation of the AhR (MIE), a xenobiotic receptor, could lead to breast cancer related death (AO), through different KEs, constituting a new AOP. An artificial intelligence tool (AOP-helpfinder), which screens the available literature, was used to collect all existing scientific abstracts to build a novel AOP, using a list of key words. Four hundred and seven abstracts were found containing at least a word from our MIE list and either one word from our AO or KE list. A manual curation retained 113 pertinent articles, which were also screened using PubTator. From these analyses, an AOP was created linking the activation of the AhR to breast cancer related death through decreased apoptosis, inflammation, endothelial cell migration, angiogenesis, and invasion. These KEs promote an increased tumor growth, angiogenesis and migration which leads to breast cancer metastasis and breast cancer related death. The evidence of the proposed AOP was weighted using the tailored Bradford Hill criteria and the OECD guidelines. The confidence in our AOP was considered strong. An in vitro validation must be carried out, but our review proposes a strong relationship between AhR activation and breast cancer-related death with an innovative use of an artificial intelligence literature search

Low incidence of SARS-CoV-2, risk factors of mortality and the course of illness in the French national cohort of dialysis patients

International audienceThe aim of this study was to estimate the incidence of COVID-19 disease in the French national population of dialysis patients, their course of illness and to identify the risk factors associated with mortality. Our study included all patients on dialysis recorded in the French REIN Registry in April 2020. Clinical characteristics at last follow-up and the evolution of COVID-19 illness severity over time were recorded for diagnosed cases (either suspicious clinical symptoms, characteristic signs on the chest scan or a positive reverse transcription polymerase chain reaction) for SARS-CoV-2. A total of 1,621 infected patients were reported on the REIN registry from March 16th, 2020 to May 4th, 2020. Of these, 344 died. The prevalence of COVID-19 patients varied from less than 1% to 10% between regions. The probability of being a case was higher in males, patients with diabetes, those in need of assistance for transfer or treated at a self-care unit. Dialysis at home was associated with a lower probability of being infected as was being a smoker, a former smoker, having an active malignancy, or peripheral vascular disease. Mortality in diagnosed cases (21%) was associated with the same causes as in the general population. Higher age, hypoalbuminemia and the presence of an ischemic heart disease were statistically independently associated with a higher risk of death. Being treated at a selfcare unit was associated with a lower risk. Thus, our study showed a relatively low frequency of COVID-19 among dialysis patients contrary to what might have been assumed