A 50-gene biomarker identifies estrogen receptor-modulating chemicals in a microarray compendium

High throughput transcriptomics (HTTr) profiling has the potential to rapidly and comprehensively identify molecular targets of environmental chemicals that can be linked to adverse outcomes. We describe here the construction and characterization of a 50-gene expression biomarker designed to identify estrogen receptor (ER) active chemicals in HTTr datasets. Using microarray comparisons, the genes in the biomarker were identified as those that exhibited consistent directional changes when ER was activated (4 ER agonists; 4 ESR1 gene constitutively active mutants) and opposite directional changes when ER was suppressed (4 antagonist treatments; 4 ESR1 knockdown experiments). The biomarker was evaluated as a predictive tool using the Running Fisher algorithm by comparison to annotated gene expression microarray datasets including those evaluating the transcriptional effects of hormones and chemicals in MCF-7 cells. Depending on the reference dataset used, the biomarker had a predictive accuracy for activation of up to 96%. To demonstrate applicability for HTTr data analysis, the biomarker was used to identify ER activators in a set of 15 chemicals that are considered potential bisphenol A (BPA) alternatives examined at up to 10 concentrations in MCF-7 cells and analyzed by full-genome TempO-Seq. Using benchmark dose (BMD) modeling, the biomarker genes stratified the ER potency of BPA alternatives consistent with previous studies. These results demonstrate that the ER biomarker can be used to accurately identify ER activators in transcript profile data derived from MCF-7 cells.

From vision toward best practices: Evaluating in vitro transcriptomic points of departure for application in risk assessment using a uniform workflow

The growing number of chemicals in the current consumer and industrial markets presents a major challenge for regulatory programs faced with the need to assess the potential risks they pose to human and ecological health. The increasing demand for hazard and risk assessment of chemicals currently exceeds the capacity to produce the toxicity data necessary for regulatory decision making, and the applied data is commonly generated using traditional approaches with animal models that have limited context in terms of human relevance. This scenario provides the opportunity to implement novel, more efficient strategies for risk assessment purposes. This study aims to increase confidence in the implementation of new approach methods in a risk assessment context by using a parallel analysis to identify data gaps in current experimental designs, reveal the limitations of common approaches deriving transcriptomic points of departure, and demonstrate the strengths in using high-throughput transcriptomics (HTTr) to derive practical endpoints. A uniform workflow was applied across six curated gene expression datasets from concentration-response studies containing 117 diverse chemicals, three cell types, and a range of exposure durations, to determine tPODs based on gene expression profiles. After benchmark concentration modeling, a range of approaches was used to determine consistent and reliable tPODs. High-throughput toxicokinetics were employed to translate in vitro tPODs (µM) to human-relevant administered equivalent doses (AEDs, mg/kg-bw/day). The tPODs from most chemicals had AEDs that were lower (i.e., more conservative) than apical PODs in the US EPA CompTox chemical dashboard, suggesting in vitro tPODs would be protective of potential effects on human health. An assessment of multiple data points for single chemicals revealed that longer exposure duration and varied cell culture systems (e.g., 3D vs. 2D) lead to a decreased tPOD value that indicated increased chemical potency. Seven chemicals were flagged as outliers when comparing the ratio of tPOD to traditional POD, thus indicating they require further assessment to better understand their hazard potential. Our findings build confidence in the use of tPODs but also reveal data gaps that must be addressed prior to their adoption to support risk assessment applications.

In vitro transcriptomic analyses reveal pathway perturbations, estrogenic activities, and potencies of data-poor BPA alternative chemicals

Since initial regulatory action in 2010 in Canada, bisphenol A (BPA) has been progressively replaced by structurally related alternative chemicals. Unfortunately, many of these chemicals are data-poor, limiting toxicological risk assessment. We used high-throughput transcriptomics to evaluate potential hazards and compare potencies of BPA and 15 BPA alternative chemicals in cultured breast cancer cells. MCF-7 cells were exposed to BPA and 15 alternative chemicals (0.0005-100 µM) for 48 h. TempO-Seq (BioSpyder Inc) was used to examine global transcriptomic changes and estrogen receptor alpha (ERα)-associated transcriptional changes. Benchmark concentration (BMC) analysis was conducted to identify 2 global transcriptomic points of departure: (1) the lowest pathway median gene BMC and (2) the 25th lowest rank-ordered gene BMC. ERα activation was evaluated using a published transcriptomic biomarker and an ERα-specific transcriptomic point of departure was derived. Genes fitting BMC models were subjected to upstream regulator and canonical pathway analysis in Ingenuity Pathway Analysis. Biomarker analysis identified BPA and 8 alternative chemicals as ERα active. Global and ERα transcriptomic points of departure produced highly similar potency rankings with bisphenol AF as the most potent chemical tested, followed by BPA and bisphenol C. Further, BPA and transcriptionally active alternative chemicals enriched similar gene sets associated with increased cell division and cancer-related processes. These data provide support for future read-across applications of transcriptomic profiling for risk assessment of data-poor chemicals and suggest that several BPA alternative chemicals may cause hazards at similar concentrations to BPA.

Persistent organic pollutants and β-cell toxicity: a comprehensive review

Persistent organic pollutants (POPs) are a diverse family of contaminants that show widespread global dispersion and bioaccumulation. Humans are continuously exposed to POPs through diet, air particles, and household and commercial products; POPs are consistently detected in human tissues, including the pancreas. Epidemiological studies show a modest but consistent correlation between exposure to POPs and increased diabetes risk. The goal of this review is to provide an overview of epidemiological evidence and an in-depth evaluation of the in vivo and in vitro evidence that POPs cause β-cell toxicity. We review evidence for six classes of POPs: dioxins, polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), organophosphate pesticides (OPPs), flame retardants, and per- and polyfluoroalkyl substances (PFAS). The available data provide convincing evidence implicating POPs as a contributing factor driving impaired glucose homeostasis, β-cell dysfunction, and altered metabolic and oxidative stress pathways in islets. These findings support epidemiological data showing that POPs increase diabetes risk and emphasize the need to consider the endocrine pancreas in toxicity assessments. Our review also highlights significant gaps in the literature assessing islet-specific endpoints after both in vivo and in vitro POP exposure. In addition, most rodent studies do not consider the impact of biological sex or secondary metabolic stressors in mediating the effects of POPs on glucose homeostasis and β-cell function. We discuss key gaps and limitations that should be assessed in future studies.

Prolonged Low-Dose Dioxin Exposure Impairs Metabolic Adaptability to High-Fat Diet Feeding in Female but Not Male Mice

CONTEXT

Human studies consistently show an association between exposure to persistent organic pollutants, including 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, aka "dioxin"), and increased diabetes risk. We previously showed that a single high-dose TCDD exposure (20 µg/kg) decreased plasma insulin levels in male and female mice in vivo, but effects on glucose homeostasis were sex-dependent.

OBJECTIVE

The current study assessed whether prolonged exposure to a physiologically relevant low-dose of TCDD impacts glucose homeostasis and/or the islet phenotype in a sex-dependent manner in chow-fed or high-fat diet (HFD)-fed mice.

METHODS

Male and female mice were exposed to 20 ng/kg/d TCDD 2×/week for 12 weeks and simultaneously fed standard chow or a 45% HFD. Glucose homeostasis was assessed by glucose and insulin tolerance tests, and glucose-induced plasma insulin levels were measured in vivo. Histological analysis was performed on pancreas from male and female mice, and islets were isolated from females for TempO-Seq transcriptomic analysis.

RESULTS

Low-dose TCDD exposure did not lead to adverse metabolic consequences in chow-fed male or female mice, or in HFD-fed males. However, TCDD accelerated the onset of HFD-induced hyperglycemia and impaired glucose-induced plasma insulin levels in females. TCDD caused a modest increase in islet area in males but reduced the percent beta cell area within islets in females. TempO-Seq analysis suggested abnormal changes to endocrine and metabolic pathways in female TCDDHFD islets.

CONCLUSION

Our data suggest that prolonged low-dose TCDD exposure has minimal effects on glucose homeostasis and islet morphology in chow-fed male and female mice but promotes maladaptive metabolic responses in HFD-fed females.

Long-term metabolic consequences of acute dioxin exposure differ between male and female mice

Epidemiological studies have consistently shown an association between exposure to environmental pollutants and diabetes risk in humans. We have previously shown that direct exposure of mouse and human islets (endocrine pancreas) to the highly persistent pollutant TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) causes reduced insulin secretion ex vivo. Furthermore, a single high-dose of TCDD (200 µg/kg) suppressed both fasting and glucose-induced plasma insulin levels and promoted beta-cell apoptosis after 7 days in male mice. The current study investigated the longer-term effects of a single high-dose TCDD injection (20 µg/kg) on glucose metabolism and beta cell function in male and female C57Bl/6 mice. TCDD-exposed males displayed modest fasting hypoglycemia for ~4 weeks post-injection, reduced fasting insulin levels for up to 6 weeks, increased insulin sensitivity, decreased beta cell area, and increased delta cell area. TCDD-exposed females also had long-term suppressed basal plasma insulin levels, and abnormal insulin secretion for up to 6 weeks. Unlike males, TCDD did not impact insulin sensitivity or islet composition in females, but did cause transient glucose intolerance 4 weeks post-exposure. Our results show that a single exposure to dioxin can suppress basal insulin levels long-term in both sexes, but effects on glucose homeostasis are sex-dependent.

Functional cytochrome P450 1A enzymes are induced in mouse and human islets following pollutant exposure

AIMS/HYPOTHESIS

Exposure to environmental pollution has been consistently linked to diabetes incidence in humans, but the potential causative mechanisms remain unclear. Given the critical role of regulated insulin secretion in maintaining glucose homeostasis, environmental chemicals that reach the endocrine pancreas and cause beta cell injury are of particular concern. We propose that cytochrome P450 (CYP) enzymes, which are involved in metabolising xenobiotics, could serve as a useful biomarker for direct exposure of islets to pollutants. Moreover, functional CYP enzymes in islets could also impact beta cell physiology. The aim of this study was to determine whether CYP1A enzymes are activated in islets following direct or systemic exposure to environmental pollutants.

METHODS

Immortalised liver (HepG2) and rodent pancreatic endocrine cell lines (MIN6, βTC-6, INS1, α-TC1, α-TC3), as well as human islets, were treated in vitro with known CYP1A inducers 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and 3-methylcholanthrene (3-MC). In addition, mice were injected with either a single high dose of TCDD or multiple low doses of TCDD in vivo, and islets were isolated 1, 7 or 14 days later.

RESULTS

CYP1A enzymes were not activated in any of the immortalised beta or alpha cell lines tested. However, both 3-MC and TCDD potently induced CYP1A1 gene expression and modestly increased CYP1A1 enzyme activity in human islets after 48 h. The induction of CYP1A1 in human islets by TCDD was prevented by cotreatment with a cytokine mixture. After a systemic single high-dose TCDD injection, CYP1A1 enzyme activity was induced in mouse islets ~2-fold, ~40-fold and ~80-fold compared with controls after 1, 7 and 14 days, respectively, in vivo. Multiple low-dose TCDD exposure in vivo also caused significant upregulation of Cyp1a1 in mouse islets. Direct TCDD exposure to human and mouse islets in vitro resulted in suppressed glucose-induced insulin secretion. A single high-dose TCDD injection resulted in lower plasma insulin levels, as well as a pronounced increase in beta cell death.

CONCLUSIONS/INTERPRETATION

Transient exposure to TCDD results in long-term upregulation of CYP1A1 enzyme activity in islets. This provides evidence for direct exposure of islets to lipophilic pollutants in vivo and may have implications for islet physiology.

Intraoperative effects of combined versus general anesthesia during major liver surgery

AIM

The study compares the intraoperative effects of combined versus general anesthesia during major liver surgery.

METHODS

In this prospective randomized study, 70 patients were divided into 2 group of 35 subjects. Group A received general anesthesia (thiopentone, fentanyl, vecuronium, sevoflurane in a closed circuit) 15 minutes after placement of an epidural catheter (D9-D10) and induction of epidural anesthesia (6 ml 2% naropine). Continuous epidural infusion was initiated before surgical incision and continued with 0.2% naropine (7 ml/h) until the end of the operation. Group B received combined intraoperative anesthesia wit fentanyl doses according to hemodynamic parameters and 0.1 mg/kg morphine 30-4 minutes before cutaneous suture. Hemodynamic values were measured at base line (T0), and then at 15, 30, 60, 120 and 180 minutes after induction of general anesthesia (T1, T2, T3, T4 and T5, respectively). On recovery, patients were assessed for pain at rest and on movement reported on a visual analog scale; degree of motor blockade according to the Bromage scale; appearance of side effects; use af analgesic.

RESULTS

A statistically significant decrease in the mean arterial blood pressure (ABP) and heart rate (HR) was noted within each group at 15 minutes after induction of general anesthesia. Significant differences in ABP were found between the 2 groups at T1 to T5, whereas HR values were substantially similar. The mean intraoperative use of fentanyl was significantly higher in Group B than in Group A, as was that of vecuronium. Pain intensity on recovery in patients who received epidural anesthesia was lower both at rest and on movement; only the patients in Group B required additional analgesics. No motor blockade was observed in either group. Nausea and vomiting were more frequent in Group B; hypotension was more frequent in Group A.

CONCLUSION

The study confirms the safety of locoregional anesthesia in liver surgery, with good hemodynamic stability and absence of major side effects. The lower intraoperative use of opioids and muscle relaxants in patients who received epidural anesthesia confirms the neurovegetative protection this method provides. The data support the hypothesis that greater intraoperative use of opioids may be responsible for the higher incidence of side effects. Therefore, the intraoperative use of combined low-concentration anesthetic agents alone appears to offer a reasonable treatment option that provides adequate pain control at recovery from general anesthesia, with only minor side effects typically associated with analgesic (motor blockade) and opioids (nausea and vomiting). Given the complications associated with the technique, it should be performed by an expert anesthetist.

Acute effects of transdermal estradiol administration on plasma levels of nitric oxide in postmenopausal women

OBJECTIVE

To investigate the acute effects of transdermal E2 administration on nitric oxide (NO) plasma levels in postmenopausal women.

DESIGN

Randomized, placebo-controlled trial.

SETTING

Normal human volunteers in an academic research environment.

PATIENT(S)

Twenty healthy postmenopausal women.

INTERVENTION(S)

Transdermal administration of 100 micrograms/d E2 or placebo.

MAIN OUTCOME MEASURE(S)

Plasma concentrations of NO stable oxidation products and serum concentrations of E2 were assessed before and 24 hours after the administration.

RESULT(S)

In the group treated with E2 mean concentration of NO metabolites 24 hours after patch application (37.31 +/- 7.62 mumol/L) resulted significantly higher than baseline (21.04 +/- 5.71 mumol/L) and the control group (23.50 +/- 4.03 mumol/L). The correlation between the mean percent increase in NO metabolites and absolute E2 concentrations 24 hours after the E2 administration was statistically significant.

CONCLUSION(S)

Transdermal administration of E2 to healthy postmenopausal women increases the plasma levels of NO and this supports the hypothesis that a NO-related mechanisms may contribute to the cardiovascular protective effect of estrogens in postmenopause.

Nasal spray administration of bromocriptine: pharmacology and effect on serum prolactin level in puerperal women

This study was aimed at investigating the absorption of nasally administered bromocriptine and its effect on serum prolactin level. Fifteen physiologically hyperprolactinemia women who had asked to discontinue breast feeding received a single nasal spray administration of 0.8 mg bromocriptine. Serum prolactin levels were measured by radioimmunoassay at 30 and 15 min before drug administration, at the time of administration and at 15, 30, 60, 120, 240, 480 and 720 min after administration; bromocriptine was radioimmunoassayed in only five of the patients from time 0 to 720 min after administration. Serum bromocriptine levels increased rapidly after administration, reached a maximum at 120 min and thereafter declined slowly over the subsequent 10 h. As the bromocriptine level increased there was a decline in the serum prolactin level. The first significant decline in serum prolactin level compared with the baseline level occurred at 30 min after administration and the level continued to decrease significantly until time 120 min. Four hours after administration the mean serum prolactin level was within the normal assay range. The maximum decline in serum prolactin level was reached at 720 min after administration. Correlation analysis between serum bromocriptine and prolactin concentrations yielded a significant negative value between times 0 and 120 min after administration. There was no significant change in mean orthostatic systolic or diastolic blood pressure or in mean heart rate. Only one patient complained of headache and dizziness; another experienced mild transient nausea, and none had vomiting. Ten patients (66.67%) reported light endonasal burning and an unpleasant taste which subsided after a few minutes; no patient showed nasal irritation at nasal examination. In conclusion, nasal administration of 0.8 mg bromocriptine was effective in reducing the serum prolactin level for more than 12 h after administration without inducing significant side-effects.

Nasal spray bromocriptine: effects on serum prolactin in puerperal women

BACKGROUND

The objective of this study was to investigate the effectiveness of a single nasal spray administration of 0.8 mg bromocriptine in reducing PRL serum levels.

METHODS

Eighteen physiologically hyperprolactemic women in the early days of puerperium were randomized to receive nasal bromocriptine or placebo; PRL serum levels were measured by RIA at 45, 30 and 15 minutes before the administration and after the following times: 15, 30, 45, 60, 120, 180, 240, 300, and 480 minutes.

RESULTS

After the administration of bromocriptine serum levels of PRL decreased rapidly; the reduction was statistically significant after 45 minutes. Four hours after the administration mean serum levels of PRL resulted in the normal range (< 20 micrograms/l); at the eighth hour the PRL levels were still normal. No one patient complained of any local or systemic side-effects.

CONCLUSION

Nasal route seems to be an effective and probably safe administration route for bromocriptine.