Dioxin affects glucose transport via the arylhydrocarbon receptor signal cascade in pluripotent embryonic carcinoma cells

The potential of aryl hydrocarbon receptor as receptors for metabolic changes in tumors

Cancer cells can alter their metabolism to meet energy and molecular requirements due to unfavorable environments with oxygen and nutritional deficiencies. Therefore, metabolic reprogramming is common in a tumor microenvironment (TME). Aryl hydrocarbon receptor (AhR) is a ligand-activated nuclear transcription factor, which can be activated by many exogenous and endogenous ligands. Multiple AhR ligands can be produced by both TME and tumor cells. By attaching to various ligands, AhR regulates cancer metabolic reprogramming by dysregulating various metabolic pathways, including glycolysis, lipid metabolism, and nucleotide metabolism. These regulated pathways greatly contribute to cancer cell growth, metastasis, and evading cancer therapies; however, the underlying mechanisms remain unclear. Herein, we review the relationship between TME and metabolism and describe the important role of AhR in cancer regulation. We also focus on recent findings to discuss the idea that AhR acts as a receptor for metabolic changes in tumors, which may provide new perspectives on the direction of AhR research in tumor metabolic reprogramming and future therapeutic interventions.

Identification of PCB congeners and their thresholds associated with diabetes using decision tree analysis

Few studies have investigated the potential combined effects of multiple PCB congeners on diabetes. To address this gap, we used data from 1244 adults in the National Health and Nutrition Examination Survey (NHANES) 2003-2004. We used (1) classification trees to identify serum PCB congeners and their thresholds associated with diabetes; and (2) logistic regression to estimate the odds ratios (ORs) and 95% confidence intervals (CIs) of diabetes with combined PCB congeners. Of the 40 PCB congeners examined, PCB 126 has the strongest association with diabetes. The adjusted OR of diabetes comparing PCB 126 > 0.025 to ≤ 0.025 ng/g was 2.14 (95% CI 1.30-3.53). In the subpopulation with PCB 126 > 0.025 ng/g, a lower PCB 101 concentration was associated with an increased risk of diabetes (comparing PCB 101 < 0.72 to ≥ 0.72 ng/g, OR 3.3, 95% CI 1.27-8.55). In the subpopulation with PCB 126 > 0.025 & PCB 101 < 0.72 ng/g, a higher PCB 49 concentration was associated with an increased risk of diabetes (comparing PCB 49 > 0.65 to ≤ 0.65 ng/g, OR 2.79, 95% CI 1.06-7.35). This nationally representative study provided new insights into the combined associations of PCBs with diabetes.

Identification of PCB Congeners and their Thresholds associated with Diabetes using Decision Tree Analysis

Few studies have investigated the potential combined effects of multiple PCB congeners on diabetes. To address this gap, we used data from 1244 adults in the National Health and Nutrition Examination Survey (NHANES) 2003-2004. We used 1) classification trees to identify serum PCB congeners and their thresholds associated with diabetes; and 2) logistic regression to estimate the odds ratios (ORs) and 95% confidence intervals (CIs) of diabetes with combined PCB congeners. Of the 40 PCB congeners examined, PCB 126 has the strongest association with diabetes. The adjusted OR of diabetes comparing PCB 126 > 0.025 to ≤ 0.025 ng/g was 2.14 (95% CI 1.30-3.53). In the subpopulation with PCB 126 > 0.025 ng/g, a lower PCB 101 concentration was associated with an increased risk of diabetes (comparing PCB 101 < 0.72 to ≥ 0.72 ng/g, OR = 3.3, 95% CI: 1.27-8.55). In the subpopulation with PCB 126 > 0.025&PCB 101 < 0.72 ng/g, a higher PCB 49 concentration was associated with an increased risk of diabetes (comparing PCB 49 > 0.65 to ≤ 0.65 ng/g, OR = 2.79, 95% CI: 1.06-7.35). This nationally representative study provided new insights into the combined associations of PCBs with diabetes.

The Effect of GLUT1 on Survival Rate and the Immune Cell Infiltration of Lung Adenocarcinoma and Squamous Cell Carcinoma: A Meta and Bioinformatics Analysis

BACKGROUND

Lung adenocarcinoma (LUAD) and squamous cell carcinoma (LUSC) are two major subtypes of non-small cell lung cancer (NSCLC). Studies have shown that abnormal expression of glucose transport type 1 (GLUT1) in NSCLC patients has been associated with progression, aggressiveness, and poor clinical outcome. However, the clinical effect of GLUT1 expression on LUAD and LUSC is unclear.

OBJECTIVE

This study aims to learn more about the character of GLUT1 in LUAD and LUSC.

METHODS

A meta-analysis was performed to evaluate the GLUT1 protein level, and bioinformatics analysis was used to detect the GLUT1 mRNA expression level, survival differences, and the infiltration abundance of immune cells in samples from TCGA. Meanwhile, functional and network analysis was conducted to detect important signaling pathways and key genes with the Gene Expression Omnibus (GEO) dataset.

RESULTS

Our results showed that GLUT1 was over-expressed both in LUAD and LUSC. LUAD patients with high GLUT1 expression had a poor prognosis. Additionally, GLUT1 was related to B cell and neutrophil infiltration of LUAD. In LUSC, GLUT1 was correlated with tumor purity, B cell, CD8⁺ T cell, CD4⁺ T cell, macrophage, neutrophil, and dendritic cell infiltration. The GEO dataset analysis results suggested GLUT1 potentially participated in the p53 signaling pathway and metabolism of xenobiotics by cytochrome P450 and was associated with KDR, TOX3, AGR2, FOXA1, ERBB3, ANGPT1, and COL4A3 gene in LUAD and LUSC.

CONCLUSION

GLUT1 might be a potential biomarker for aggressive progression and poor prognosis in LUAD, and a therapeutic biomarker in LUSC.

Legacy environmental polychlorinated biphenyl contamination attenuates the acute stress response in a cartilaginous fish, the Round Stingray

In a population of Round Stingrays (Urobatis halleri) sampled from mainland California (polychlorinated biphenyl [PCB] exposed site, n = 46), relative to a nearby offshore island (reference site, n = 34), we tested the hypothesis that stingrays from the PCB-exposed site would have a compromised stress response. Adult male and pregnant female (pregnancy = matrotrophic histotrophy), stingrays were captured via hook and line at both locations over a breeding season and plasma was sampled either immediately (Baseline, males = 10, females = 31), or after ∼5 min of struggle on the line followed by a 15 min confinement stressor (Stressed, males = 16, females = 23). Biomarkers of the primary stress response (1α-OH-corticosterone) and the secondary response (energy mobilization; glucose, glycogen, and lactate in liver and muscle) were assessed. Females from both sites demonstrated the expected primary stress response of 1α-OH-corticosterone elevation, but the contaminant-exposed males did not. PCB-exposed stingrays, regardless of sex, failed to produce a plasma glucose increase in response to the applied stress, even though the stressor increased liver glucose as expected. This suggests a dysfunction in glucose transport due to PCB exposure. The Round Stingray accumulates lower PCB loads than other, predatory elasmobranchs, and by extension, the stress axis effects could be more severely impacted in those species as well. Lay summary Legacy polychlorinated biphenyl (PCB) contamination continues to adversely affect marine life. We show that PCB-exposure interferes with the ability of pregnant female and adult male stingrays to mobilize the energy necessary to respond appropriately to an acute stress like capture. Other cartilaginous fish species, such as sharks, accumulate considerably more PCB as a result of their predatory diet, and are likely to be more adversely impacted.

Aryl hydrocarbon receptor mediates the cardiac developmental toxicity of EOM from PM2.5 in P19 embryonic carcinoma cells

Ambient fine particulate matter (PM_2.5) has been found to be associated with congenital heart defects, but the molecular mechanisms remain to be elucidated. Our previous study revealed that extractable organic matter (EOM) from PM_2.5 exerted cardiac developmental toxicity in zebrafish embryos. The aim of the current study is to explore the effects of EOM on cardiac differentiation of P19 mouse embryonic carcinoma stem cells. We found that EOM at 10 μg/ml (a non-cytotoxic dose level) significantly reduced the proportion of cardiac muscle troponin (cTnT) positive cells and the percentage of spontaneously beating embryoid bodies, indicating a severe inhibition of cardiac differentiation. Immunofluorescence and qPCR data demonstrated that EOM increased the expression levels of the aryl hydrocarbon receptor (AhR) and its target gene Cyp1A1 and diminished the expression level of β-catenin. Furthermore, EOM treatment significantly upregulated cell proliferation rate and elevated the percentage of γH2A.X positive cells without affecting apoptosis. It is worth noting that the EOM-induced changes in gene expression, cellular proliferation and DNA double strain breaks were attenuated by the AhR antagonist CH223191. In conclusion, our data indicate that AhR mediates the inhibitory effects of EOM (from PM_2.5) on the cardiac differentiation of P19 cells.

Metabolomics Reveals Aryl Hydrocarbon Receptor Activation Induces Liver and Mammary Gland Metabolic Dysfunction in Lactating Mice

The liver and the mammary gland have complementary metabolic roles during lactation. Substrates synthesized by the liver are released into the circulation and are taken up by the mammary gland for milk production. The aryl hydrocarbon receptor (AHR) has been identified as a lactation regulator in mice, and its activation has been associated with myriad morphological, molecular, and functional defects such as stunted gland development, decreased milk production, and changes in gene expression. In this study, we identified adverse metabolic changes in the lactation network (mammary, liver, and serum) associated with AHR activation using 1H nuclear magnetic resonance (NMR)-based metabolomics. Pregnant mice expressing Ahr d (low affinity) or Ahr b (high affinity) were fed diets containing beta naphthoflavone (BNF), a potent AHR agonist. Mammary, serum, and liver metabolomics analysis identified significant changes in lipid and TCA cycle intermediates in the Ahr b mice. We observed decreased amino acid and glucose levels in the mammary gland extracts of Ahr b mice fed BNF. The serum of BNF fed Ahr b mice had significant changes in LDL/VLDL (increased) and HDL, PC, and GPC (decreased). Quantitative PCR analysis revealed ∼50% reduction in the expression of key lactogenesis mammary genes including whey acid protein, α-lactalbumin, and β-casein. We also observed morphologic and developmental disruptions in the mammary gland that are consistent with previous reports. Our observations support that AHR activity contributes to metabolism regulation in the lactation network.

Genetic dissection of endothelial transcriptional activity of zebrafish aryl hydrocarbon receptors (AHRs)

The aryl hydrocarbon receptor (AHR) is a basic helix-loop-helix transcription factor conserved across phyla from flies to humans. Activated by a number of endogenous ligands and environmental toxins, studies on AHR function and gene regulation have largely focused on a toxicological perspective relating to aromatic hydrocarbons generated by human activities and the often-deleterious effects of exposure on vertebrates mediated by AHR activation. A growing body of work has highlighted the importance of AHR in physiologic processes, including immune cell differentiation and vascular patterning. Here we dissect the contribution of the 3 zebrafish AHRs, ahr1a, ahr1b and ahr2, to endothelial cyp1a1/b1 gene regulation under physiologic conditions and upon exposure to the AHR ligand Beta-naphthoflavone. We show that in fish multiple AHRs are functional in the vasculature, with vessel-specific differences in the ability of ahr1b to compensate for the loss of ahr2 to maintain AHR signaling. We further provide evidence that AHR can regulate the expression of the chemokine receptor cxcr4a in endothelial cells, a regulatory mechanism that may provide insight into AHR function in the endothelium.

α-Lipoic acid potentially targets AMP-activated protein kinase and energy production in the fetal brain to ameliorate dioxin-produced attenuation in fetal steroidogenesis

Our previous studies demonstrated that treating pregnant rats with dioxins, including 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), targets the pituitary expression of luteinizing hormone (LH) to attenuate testicular steroidogenesis in fetuses, resulting in the imprinting of sexual immaturity of the offspring after reaching maturity. Furthermore, we found that although TCDD disturbs the tricarboxylic acid (TCA) cycle in the fetal hypothalamus, maternal co-treatment with α-lipoic acid (α-LA), a cofactor of the TCA cycle, restores a TCDD-produced reduction in the LH-evoked steroidogenesis as well as the TCA cycle activity in fetuses. However, the mechanism underlying the beneficial effect of α-LA remains to be fully elucidated. To address this issue, we compared the effect of α-LA with that of thiamine, another cofactor of the TCA cycle. As with α-LA, supplying thiamine to dams exposed to TCDD alleviates the reduced level of not only hypothalamic ATP but also pituitary LH and testicular steroidogenic protein in fetuses. However, thiamine had a much weaker effect than α-LA. In agreement with ATP attenuation, TCDD activated AMP-activated protein kinase (AMPK), a negative regulator of LH production, whereas the supplementation of α-LA allowed recovery from this defect. Furthermore, α-LA restored the TCDD-produced reduction in the pituitary expression of the receptor for gonadotropin-releasing hormone (GnRH), an upstream regulator of LH synthesis. These results suggest that α-LA rescues TCDD-produced attenuation during fetal steroidogenesis due not only to facilitation of energy production through the TCA cycle but also through suppression of AMPK activation, and the pituitary GnRH receptor may serve as a mediator of these effects.

Relationship between serum concentrations of persistent organic pollutants and markers of insulin resistance in a cohort of women with a history of gestational diabetes mellitus

The aim of the present study was to assess the relationship between serum concentrations of several persistent organic pollutants and insulin resistance markers in a cohort of women with a history of gestational diabetes mellitus. ∑POPs was computed as the sum of individual serum POP concentrations. No statistically significant associations were found between levels of any POP and fasting glucose. However, polychlorinated biphenyl (PCB) congeners 138 and 180 were positively associated with 2-h glucose levels and PCB 180 also with fasting immunoreactive insulin (IRI). We also found a positive association of p,p'- dichlorodiphenyldichloroethylene (p,p'- DDE), PCBs (138, 153, and 180), hexachlorobenzene, and ∑POPs with 2-h IRI. Serum concentrations of PCBs (138, 153, and 180), hexachlorobenzene, and ∑POPs were also positively associated with homeostasis model assessment (HOMA2-IR) levels. Moreover, p,p'- DDE, PCBs (138, 153 and 180), hexachlorobenzene, and ∑POPs were negatively associated with Insulin Sensitivity Index (ISI-gly) levels. No significant association was found between glycated hemoglobin and the concentrations of any POP. The removal of women under blood glucose lowering treatment from the models strengthened most of the associations previously found for the whole population. Our findings suggest that exposure to certain POPs is a modifiable risk factor contributing to insulin resistance.

Impact of di-ethylhexylphthalate exposure on metabolic programming in P19 ECC-derived cardiomyocytes

Di(2-ethylhexyl)phthalate (DEHP) is the most common plasticizer in plastic devices of everyday use. It is a ubiquitous environmental contaminant and primarily known to impair male gonadal development and fertility. Studies concerning the long-term effects of prenatal DEHP exposure on certain diseases [The Developmental Origins of Health and Disease paradigm (DOHaD) hypothesis] are scarce although it is proven that DEHP crosses the placenta. Rising environmental pollution during the last centuries coincides with an increasing prevalence of cardiovascular and metabolic diseases. We have investigated the effects of an early embryonic DEHP exposure at different developmental stages on cardiomyogenesis. We used an in-vitro model, the murine P19 embryonic carcinoma cell line (P19 ECC), mimicking early embryonic stages up to differentiated beating cardiomyocytes. P19 ECC were exposed to DEHP (5, 50, 100 µg ml(-1)) at the undifferentiated stage for 5 days and subsequently differentiated to beating cardiomyocytes. We analyzed the expression of metabolic (Pparg1, Fabp4 and Glut4), cardiac (Myh6, Gja1) and methylation (Dnmt1, Dnmt3a) marker genes by quantitative real-time PCR (qRT-PCR), beating rate and the differentiation velocity of the cells. The methylation status of Pparg1, Ppara and Glut4 was investigated by pyrosequencing. DEHP significantly altered the expression of all investigated genes. The beating rate and differentiation velocity were accelerated. Exposure to DEHP led to small but statistically significant increases in methylation of specific CpGs within Ppara and Pparg1, which otherwise were generally hypomethylated, but methylation of Glut4 was unaltered. Early DEHP exposure of P19 ECC alters the expression of genes associated with cellular metabolism and the functional features of cardiomyocytes.

Modeling the effect of cigarette smoke on hexose utilization in spermatocytes

We set out to determine whether the addition of an aryl hydrocarbon receptor (AHR) antagonist has an effect on glucose/fructose utilization in the spermatocyte when exposed to cigarette smoke condensate (CSC). We exposed male germ cells to 5 and 40 μg/mL of CSC ± 10 μmol/L of AHR antagonist at various time points. Immunoblot expression of specific glucose/fructose transporters was compared to control. Radiolabeled uptake of 2-deoxyglucose (2-DG) and fructose was also performed. Spermatocytes utilized fructose nearly 50-fold more than 2-DG. Uptake of 2-DG decreased after CSC + AHR antagonist exposure. Glucose transporters (GLUTs) 9a and 12 declined after CSC + AHR antagonist exposure. Synergy between CSC and the AHR antagonist in spermatocytes may disrupt the metabolic profile in vitro. Toxic exposures alter energy homeostasis in early stages of male germ cell development, which could contribute to later effects explaining decreases in sperm motility in smokers.

Association of dioxin and other persistent organic pollutants (POPs) with diabetes: epidemiological evidence and new mechanisms of beta cell dysfunction

The worldwide explosion of the rates of diabetes and other metabolic diseases in the last few decades cannot be fully explained only by changes in the prevalence of classical lifestyle-related risk factors, such as physical inactivity and poor diet. For this reason, it has been recently proposed that other "nontraditional" risk factors could contribute to the diabetes epidemics. In particular, an increasing number of reports indicate that chronic exposure to and accumulation of a low concentration of environmental pollutants (especially the so-called persistent organic pollutants (POPs)) within the body might be associated with diabetogenesis. In this review, the epidemiological evidence suggesting a relationship between dioxin and other POPs exposure and diabetes incidence will be summarized, and some recent developments on the possible underlying mechanisms, with particular reference to dioxin, will be presented and discussed.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) increases bilirubin formation but hampers quantitative hepatic conversion of biliverdin to bilirubin in rats with wild-type AH receptor

In haem degradation, haem oxygenase-1 (HO-1) first cleaves haem to biliverdin, which is reduced to bilirubin by biliverdin IXα reductase (BVR-A). The environmental pollutant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) causes hepatic accumulation of biliverdin in moderately TCDD-resistant line B (Kuopio) rats. Using line B and two TCDD-sensitive rat strains, the present study set out to probe the dose-response and biochemical mechanisms of this accumulation. At 28 days after exposure to 3-300 μg/kg TCDD in line B rats, already the lowest dose of TCDD tested, 3 μg/kg, affected serum bilirubin conjugates, and after doses ≥100 μg/kg, the liver content of bilirubin, biliverdin and their conjugates (collectively 'bile pigments') as well as HO-1 was elevated. BVR-A activity and serum bile acids were increased only by the doses of 100 and 300 μg/kg TCDD, respectively. Biliverdin conjugates correlated best with biliverdin suggesting it to be their immediate precursor. TCDD (100 μg/kg, 10 days) increased hepatic bilirubin and biliverdin levels also in TCDD-sensitive Long-Evans (Turku/AB; L-E) rats. Hepatic bilirubin and bile acids, but not biliverdin, were increased in feed-restricted L-E control rats. In TCDD-sensitive line C (Kuopio) rats, 10 μg/kg of TCDD increased the body-weight-normalized biliary excretion of bilirubin. Altogether, the results suggest that at acutely toxic doses, TCDD induces the formation of bilirubin in rats. However, concurrently, TCDD seems to hamper the quantitative conversion of biliverdin to bilirubin in line B and L-E rats' liver. Biliverdin conjugates are most likely formed as secondary products of biliverdin.

2,3,7,8-Tetrachlorodibenzo-p-dioxin-mediated production of reactive oxygen species is an essential step in the mechanism of action to accelerate human keratinocyte differentiation

Chloracne is commonly observed in humans exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD); yet, the mechanism of toxicity is not well understood. Using normal human epidermal keratinocytes, we investigated the mechanism of TCDD-mediated enhancement of epidermal differentiation by integrating functional genomic, metabolomic, and biochemical analyses. TCDD increased the expression of 40% of the genes of the epidermal differentiation complex found on chromosome 1q21 and 75% of the genes required for de novo ceramide biosynthesis. Lipid analysis demonstrated that eight of the nine classes of ceramides were increased by TCDD, altering the ratio of ceramides to free fatty acids. TCDD decreased the expression of the glucose transporter, SLC2A1, and most of the glycolytic transcripts, followed by decreases in glycolytic intermediates, including pyruvate. NADH and Krebs cycle intermediates were decreased, whereas NAD(+) was increased. Mitochondrial glutathione (GSH) reductase activity and the GSH/glutathione disulfide ratio were decreased by TCDD, ultimately leading to mitochondrial dysfunction, characterized by decreased inner mitochondrial membrane potential and ATP production, and increased production of the reactive oxygen species (ROS), hydrogen peroxide. Aryl hydrocarbon receptor (AHR) antagonists blocked the response of many transcripts to TCDD, and the endpoints of decreased ATP production and differentiation, suggesting regulation by the AHR. Cotreatment of cells with chemical antioxidants or the enzyme catalase blocked the TCDD-mediated acceleration of keratinocyte cornified envelope formation, an endpoint of terminal differentiation. Thus, TCDD-mediated ROS production is a critical step in the mechanism of this chemical to accelerate keratinocyte differentiation.

Impact of endocrine-disrupting compounds (EDCs) on female reproductive health

Evidence is accumulating that environmental chemicals (ECs) including endocrine-disrupting compounds (EDCs) can alter female reproductive development, fertility and onset of menopause. While not as clearly defined as in the male, this set of abnormalities may constitute an Ovarian Dysgenesis Syndrome with at least some origins of the syndrome arising during foetal development. ECs/EDCs have been shown to affect trophoblast and placental function, the female hypothalamo-pituitary-gonadal axis, onset of puberty and adult ovarian function. The effects of ECs/EDCs are complex, not least because it is emerging that low-level, 'real-life' mixtures of ECs/EDCs may carry significant biological potency. In addition, there is evidence that ECs/EDCs can alter the epigenome in a sexually dimorphic manner, which may lead to changes in the germ line and perhaps even to transgenerational effects. This review summarises the evidence for EC, including EDC, involvement in female reproductive dysfunction, it highlights potential mechanisms of EC action in the female and emphasises the need for further research into EC effects on female development and reproductive function.

Polychlorinated biphenyl (PCB) exposure and diabetes: results from the Anniston Community Health Survey

BACKGROUND

Polychlorinated biphenyls (PCBs) manufactured in Anniston, Alabama, from 1929 to 1971 caused significant environmental contamination. The Anniston population remains one of the most highly exposed in the world.

OBJECTIVES

Reports of increased diabetes in PCB-exposed populations led us to examine possible associations in Anniston residents.

METHODS

Volunteers (n = 774) from a cross-sectional study of randomly selected households and adults who completed the Anniston Community Health Survey also underwent measurements of height, weight, fasting glucose, lipid, and PCB congener levels and verification of medications. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to assess the relationships between PCBs and diabetes, adjusting for diabetes risk factors. Participants with prediabetes were excluded from the logistic regression analyses.

RESULTS

Participants were 47% African American, 70% female, with a mean age of 54.8 years. The prevalence of diabetes was 27% in the study population, corresponding to an estimated prevalence of 16% for Anniston overall; the PCB body burden of 35 major congeners ranged from 0.11 to 170.42 ppb, wet weight. The adjusted OR comparing the prevalence of diabetes in the fifth versus first quintile of serum PCB was 2.78 (95% CI: 1.00, 7.73), with similar associations estimated for second through fourth quintiles. In participants < 55 years of age, the adjusted OR for diabetes for the highest versus lowest quintile was 4.78 (95% CI: 1.11, 20.6), whereas in those ≥ 55 years of age, we observed no significant associations with PCBs. Elevated diabetes prevalence was observed with a 1 SD increase in log PCB levels in women (OR = 1.52; 95% CI: 1.01, 2.28); a decreased prevalence was observed in men (OR = 0.68; 95% CI: 0.33, 1.41).

CONCLUSIONS

We observed significant associations between elevated PCB levels and diabetes mostly due to associations in women and in individuals < 55 years of age.

Effects of environmental pollutants on the reproduction and welfare of ruminants

Anthropogenic pollutants comprise a wide range of synthetic organic compounds and heavy metals, which are dispersed throughout the environment, usually at low concentrations. Exposure of ruminants, as for all other animals, is unavoidable and while the levels of exposure to most chemicals are usually too low to induce any physiological effects, combinations of pollutants can act additively or synergistically to perturb multiple physiological systems at all ages but particularly in the developing foetus. In sheep, organs affected by pollutant exposure include the ovary, testis, hypothalamus and pituitary gland and bone. Reported effects of exposure include changes in organ weight and gross structure, histology and gene and protein expression but these changes are not reflected in changes in reproductive performance under the conditions tested. These results illustrate the complexity of the effects of endocrine disrupting compounds on the reproductive axis, which make it difficult to extrapolate between, or even within, species. Effects of pollutant exposure on the thyroid gland, immune, cardiovascular and obesogenic systems have not been shown explicitly, in ruminants, but work on other species suggests that these systems can also be perturbed. It is concluded that exposure to a mixture of anthropogenic pollutants has significant effects on a wide variety of physiological systems, including the reproductive system. Although this physiological insult has not yet been shown to lead to a reduction in ruminant gross performance, there are already reports indicating that anthropogenic pollutant exposure can compromise several physiological systems and may pose a significant threat to both reproductive performance and welfare in the longer term. At present, many potential mechanisms of action for individual chemicals have been identified but knowledge of factors affecting the rate of tissue exposure and of the effects of combinations of chemicals on physiological systems is poor. Nevertheless, both are vital for the identification of risks to animal productivity and welfare.

GLUT1 as a therapeutic target in hepatocellular carcinoma

Primary hepatocellular carcinoma (HCC) is one of the most fatal cancers in humans with rising incidence in many regions around the world. Currently, no satisfactory curative pharmacological treatment is available, and the outcome is mostly poor. Recently, we have shown that the glucose transporter GLUT1 is increased in a subset of patients with HCC and functionally affects tumorigenicity. GLUT1 is a rate-limiting transporter for glucose uptake, and its expression correlates with anaerobic glycolysis. This phenomenon is also known as the Warburg effect and recently became of great interest, since it affects not only glucose uptake and utilization but also has an influence on tumorigenic features like metastasis, chemoresistance and escape from immune surveillance. Consistent with this, RNA-interference-mediated inhibition of GLUT1 expression in HCC cells resulted in reduced tumorigenicity. Together, these findings indicate that GLUT1 is a novel and attractive therapeutic target for HCC. This review summarizes our current knowledge on the expression and function of GLUT1 in HCC, available drugs/strategies to inhibit GLUT1 expression or function, and potential side effects of such therapeutic strategies.

Aromatic hydrocarbons upregulate glyceraldehyde-3-phosphate dehydrogenase and induce changes in actin cytoskeleton. Role of the aryl hydrocarbon receptor (AhR)

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a multifunctional enzyme involved in several cellular functions including glycolysis, membrane transport, microtubule assembly, DNA replication and repair, nuclear RNA export, apoptosis, and the detection of nitric oxide stress. Therefore, modifications in the regulatory ability and function of GAPDH may alter cellular homeostasis. We report here that 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and beta-naphthoflavone, which are well-known ligands for the aryl hydrocarbon receptor (AhR), increase GAPDH mRNA levels in vivo and in vitro, respectively. These compounds fail to induce GAPDH transcription in an AhR-null mouse model, suggesting that the increase in GAPDH level is dependent upon AhR activation. To analyse the consequences of AhR ligands on GAPDH function, mice were treated with TCDD and the level of liver activity of GAPDH was determined. The results showed that TCDD treatment increased GAPDH activity. On the other hand, treatment of Hepa-1 cells with beta-naphthoflavone leads to an increase in microfilament density when compared to untreated cultures. Collectively, these results suggest that AhR ligands, such as polycyclic hydrocarbons, can modify GAPDH expression and, therefore, have the potential to alter the multiple functions of this enzyme.