Association of aryl hydrocarbon receptor (AhR) serum level and gene rs10247158 polymorphism with anthropometric, biochemical parameters and food consumption in overweight/obese patients

AIM

Aryl hydrocarbon receptor (AhR) plays a role in xenobiotic metabolism, which can be also activated by dietary patterns and components. AhR ligands in circulation are reported to induce weight gain, glucose intolerance and suggested to contribute to the development of obesity. In this study, we aimed to examine the relationship of the AhR gene and its polymorphisms with obesity and food consumption.

METHODS

The study was conducted with 117 individuals of whom 52 had a body mass index (BMI) of <25 (normal weight) and 65 had a BMI of ≥25 (overweight/obese). The distribution of the serum level and polymorphism (rs10247158) of the participants were determined in venous blood samples using the ELISA and PCR method. Body composition and skinfold thickness of the individuals were measured and their food consumption records were analysed in the BeBiS program.

RESULTS

The serum AhR, HOMA-IR, fasting blood glucose and basal insulin levels were found to be significantly higher (P < .001); however, no relationship was found between AhR polymorphisms in the overweight/obese individuals. In the overweight/obese group, the serum AhR level had a negative correlation with potassium, coffee and alcohol consumption and a positive correlation with suprailiac skinfold thickness. Dietary patterns expected to be related with increased serum AhR levels, such as fat and derivatives, were not observed in overweight/obese group; on the other hand, there was a negative correlation in normal group.

CONCLUSION

In our study, the serum AhR levels of the overweight/obese individuals were found to be significantly higher. Some dietary patterns were determined to be correlated with serum AhR levels in overweight/obese group. However, the results need to be confirmed for ethnic differences and larger samples.

Increased AHR Transcripts Correlate With Pro-inflammatory T-Helper Lymphocytes Polarization in Both Metabolically Healthy Obesity and Type 2 Diabetic Patients

Aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor whose transcription activity is regulated by small compounds provided by diet, xenobiotics, and metabolism. It has been proven to be involved in energy homeostasis and inflammation in most recent years. Epidemiologically, exposure to xenobiotic AHR ligands contributes to obesity and type 2 diabetes (T2D). AHR is also the critical transcription factor determining the lineage commitment of pro-inflammatory Th17 and Th22 cells from naïve CD4+ T lymphocytes. It has been well-illustrated in animal models that IL-22, the major effector cytokine of Th17 and Th22 cells, played a major role in the interaction of metabolism and gut microbiota. But there were still missing links between gut microbiota, IL-22, and metabolism in humans. Our previous findings indicated that elevated circulating levels of IL-22 and frequencies of Th22 cells were associated with insulin resistance in both patients with obesity and T2D. Additionally, the hyperactive Th17 and Th22 cells phenotype also correlate with islets β-cell dysfunction in T2D. In this study, we made efforts to determine AHR expressions in peripheral blood mononuclear cells (PBMCs) from patients with T2D and metabolically healthy obesity (MHO). Correlation analyses were conducted to assess the possible link between AHR and the metabolic and inflammatory context. We revealed that mRNA expression of AHR was up-regulated and correlated with the percentage of Th17, Th22 as well as Th1 cells. Elevated plasma levels of IL-22 and IL-17 also correlated with increased AHR transcripts in PBMCs from both MHO and T2D patients. The transcription factor AHR may thus have a plausible role in the interaction between metabolism and pro-inflammatory status of patients in the development of obesity and T2D.

Aryl Hydrocarbon Receptor in Post-Mortem Hippocampus and in Serum from Young, Elder, and Alzheimer's Patients

One of the characteristics of the cerebral aging process is the presence of chronic inflammation through glial cells, which is particularly significant in neurodegeneration. On the other hand, it has been demonstrated that the aryl hydrocarbon receptor (AHR) participates in the inflammatory response. Currently, evidence in animal models shows that the hallmarks of aging are associated with changes in the AHR levels. However, there is no information concerning the behavior and participation of AHR in the human aging brain or in Alzheimer’s disease (AD). We evaluated the expression of AHR in human hippocampal post-mortem tissue and its association with reactive astrocytes by immunohistochemistry. Besides this, we analyzed through ELISA the AHR levels in blood serum from young and elder participants, and from AD patients. The levels of AHR and glial fibrillar acid protein were higher in elder than in young post-mortem brain samples. AHR was localized mainly in the cytosol of astrocytes and displayed a pattern that resembles extracellular vesicles; this latter feature was more conspicuous in AD subjects. We found higher serum levels of AHR in AD patients than in the other participants. These results suggest that AHR participates in the aging process, and probably in the development of neurodegenerative diseases like AD.

MiR-31 promotes Th22 differentiation through targeting Bach2 in coronary heart disease

The aim of the present study was to investigate the role of miR-31 in Th22 differentiation in coronary heart disease (CHD). Th22 frequencies in peripheral blood of CHD patients and controls as well as in CD4+ T cells were detected by flow cytometry. The mRNA expression of Th22-associated transcription factor aryl hydrocarbon receptor (AHR) and Th22-effector cytokine interleukin (IL)-22, as well as miR-31 were examined by quantitative real-time PCR (qRT-PCR). The protein level of BTB domain and CNC homolog 2 (Bach2) was measured by Western blotting. The interaction between miR-31 and Bach2 was verified using dual luciferase reporter assay. The results showed that Th22 frequency and miR-31 expression were elevated in CHD patients. Furthermore, miR-31 mimic and Bach2 silencing significantly promoted Th22 frequency and the levels of AHR and IL-22 in CD4+ T cells from CHD patients. Further studies showed that miR-31 facilitated Th22 cell differentiation by targeting and inhibiting Bach2. Our data indicate that miR-31 promotes Th22 differentiation through targeting Bach2 in CHD.

Negative association between serum aryl hydrocarbon receptor concentrations and β-cell function in patients with no history of diabetes undergoing coronary angiography

BACKGROUND

The aim of the present study was to investigate the association between serum aryl hydrocarbon receptor (AhR) levels and insulin resistance and β-cell function in patients undergoing coronary angiography with no history of diabetes.

METHODS

Patients with no history of diabetes who had undergone coronary angiography underwent an oral glucose tolerance test (OGTT) 2-4 weeks after discharge from hospital; blood samples were collected for measurements of glucose, insulin, and AhR. Patients' glucose regulation status was determined on the basis of the OGTT. Insulin resistance was assessed using the homeostasis model assessment of insulin resistance (HOMA-IR). β-Cell function was assessed using the insulinogenic index (IGI).

RESULTS

The study included 473 patients (mean (±SD) age 61 ±12 years, 81.8% male, mean body mass index 26.1 ±3.6 kg/m² ). Overall, mean serum AhR concentrations were 25.1 ±12.2 pg/mL. Patients with normal glucose tolerance had a lower serum AhR concentrations than patients with prediabetes or newly diagnosed diabetes (23.4 ±10.8 vs 26.2 ±13.2 and 26.9 ±12.3 pg/mL, respectively; P = 0.029). Linear regression analysis revealed that serum AhR concentrations were not associated with HOMA-IR, but were negatively associated with IGI after adjustment for several confounders, including HOMA-IR (β = -0.162; 95% confidence interval - 0.302, -0.022; P = 0.023).

CONCLUSIONS

In patients with no history of diabetes, serum AhR concentrations were negatively associated with β-cell function, independent of several confounders, including insulin resistance.

Serum Levels of Aryl Hydrocarbon Receptor, Cytochromes P450 1A1 and 1B1 in Patients with Exacerbated Psoriasis Vulgaris

The aryl hydrocarbon receptor (AhR) is highly expressed in psoriasis skin lesions. The aim of this study was to investigate serum concentrations of AhR, cytochromes P450 (CYP) 1A1 and 1B1 in patients with exacerbated psoriasis vulgaris treated with combined therapy of ultraviolet radiation (UVR) and crude coal tar. The analyses were performed by using enzyme-linked immunosorbent assays. Before the treatment, the patients had significantly higher serum levels of AhR and CYP1A1 than healthy controls. AhR median noticeably decreased after the therapy; nevertheless, it remained significantly higher compared to the controls. CYP1A1 levels measured before and after the therapy did not differ significantly. Serum CYP1A1 positively correlated with AhR values before and after the treatment. The serum values of CYP1B1 were very low and we did not see any differences between the study group and the control group. The study demonstrated that serum levels of AhR and CYP1A1 could indicate their immunopathological and metabolic roles in exacerbated psoriasis.

Crowd-Sourced Verification of Computational Methods and Data in Systems Toxicology: A Case Study with a Heat-Not-Burn Candidate Modified Risk Tobacco Product

Systems toxicology intends to quantify the effect of toxic molecules in biological systems and unravel their mechanisms of toxicity. The development of advanced computational methods is required for analyzing and integrating high throughput data generated for this purpose as well as for extrapolating predictive toxicological outcomes and risk estimates. To ensure the performance and reliability of the methods and verify conclusions from systems toxicology data analysis, it is important to conduct unbiased evaluations by independent third parties. As a case study, we report here the results of an independent verification of methods and data in systems toxicology by crowdsourcing. The sbv IMPROVER systems toxicology computational challenge aimed to evaluate computational methods for the development of blood-based gene expression signature classification models with the ability to predict smoking exposure status. Participants created/trained models on blood gene expression data sets including smokers/mice exposed to 3R4F (a reference cigarette) or noncurrent smokers/Sham (mice exposed to air). Participants applied their models on unseen data to predict whether subjects classify closer to smoke-exposed or nonsmoke exposed groups. The data sets also included data from subjects that had been exposed to potential modified risk tobacco products (MRTPs) or that had switched to a MRTP after exposure to conventional cigarette smoke. The scoring of anonymized participants' predictions was done using predefined metrics. The top 3 performers' methods predicted class labels with area under the precision recall scores above 0.9. Furthermore, although various computational approaches were used, the crowd's results confirmed our own data analysis outcomes with regards to the classification of MRTP-related samples. Mice exposed directly to a MRTP were classified closer to the Sham group. After switching to a MRTP, the confidence that subjects belonged to the smoke-exposed group decreased significantly. Smoking exposure gene signatures that contributed to the group separation included a core set of genes highly consistent across teams such as AHRR, LRRN3, SASH1, and P2RY6. In conclusion, crowdsourcing constitutes a pertinent approach, in complement to the classical peer review process, to independently and unbiasedly verify computational methods and data for risk assessment using systems toxicology.

Genetic association of aromatic hydrocarbon receptor and its repressor gene polymorphisms with risk of rheumatoid arthritis in Han Chinese populations

The goal of this study was to evaluate the potential relationship among polymorphisms of aromatic hydrocarbon receptor, aromatic hydrocarbon receptor repressor, and rheumatoid arthritis (RA) susceptibility as well as the association among the polymorphisms of aromatic hydrocarbon receptor, aromatic hydrocarbon receptor repressor, and their expression.We performed a hospital-based, case-control study of 400 patients with RA and 726 healthy controls in Han Chinese populations. Two single-nucleotide polymorphisms were selected for genotyping including aromatic hydrocarbon receptor (rs2066853) and aromatic hydrocarbon receptor repressor (rs2292596).To single-nucleotide polymorphism rs2292596, a statistically significantly increased risk of RA was found to be associated with the G allele of rs2292596; the odds ratio was 2.170 (95% confidence interval: 1.820-2.587). Unfortunately, no significant differences exhibited in the allelic and the genotype frequencies of rs2066853 between 2 groups. We failed to find any association between rs2066853, rs2292596 genotypes and their expression of patients, respectively. No statistical relationship was found between aromatic hydrocarbon receptor, aromatic hydrocarbon receptor repressor at messenger Ribonucleic acid levels and clinical data, either.This study demonstrated that the polymorphisms of rs2292596 was significant with genetic susceptibility to RA patients; furthermore, it suggests the G allele of rs2292596 might be associated with a dangerous effect on RA in Han Chinese populations.

Unbalanced expression of aryl hydrocarbon receptor in peripheral blood CCR6+CD4+ and CD4+CD25+T cells of rheumatoid arthritis

OBJECTIVE

The goal of this study was to analyze the role of aryl hydrocarbon receptor in peripheral blood CCR6⁺CD4⁺ and CD4⁺CD25⁺T cells of patients with rheumatoid arthritis.

METHODS

Flow cytometry was applied to determine the proportion of AhR positive cells in CCR6⁺CD4⁺T, CD4⁺CD25⁺T and peripheral blood peripheral mononuclear cells from each subject. AhR mRNA and CYP1A1 mRNA relative expression levels were tested by real-time PCR.

RESULTS

The percentage of AhR positive cells in peripheral blood mononuclear cells was higher in RA group than that in healthy cases [(35.23±10.71)% vs. (18.83±7.32)%, p<0.01]. The expression levels of AhR and CYP1A1 were both increased in patients with RA while compared to controls [(3.71±1.63) vs. (2.00±1.27), p=0.002; (2.62±2.08) vs. (0.62±0.29), p<0.01, respectively]. In RA patients, the percentage of AhR positive cells in CD4⁺CD25⁺T cells was significantly lower than that from controls [17.90 (6.10±80.10)% vs. (52.49±19.18)%, p<0.01]; In healthy controls, the percentage of AhR positive cells in CD4⁺CD25⁺T cells was significantly higher than that in CCR6⁺CD4⁺T cells, and was also significantly higher than that in PBMCs [(52.49±19.18)% vs. (23.18±5.62)% vs. (18.06±7.80)%, X²=24.03, p<0.01]; in RA patients, the percentage of AhR positive cells in CCR6⁺CD4⁺T cells was significantly increased than that in CD4⁺CD25⁺T cells and PBMCs [(46.02±14.68)% vs. 17.90 (6.10±80.10)% vs. (34.22±10.33)%, X²=38.29, p<0.01]; Nevertheless, no statistically significant relationship was found between clinical data and AhR positive cells in CCR6⁺CD4⁺T and CD4⁺CD25⁺T cells.

CONCLUSION

AhR may participate in the pathological progress of RA by controlling the differentiation of Th17 and Treg cells in peripheral blood.

The alteration and clinical significance of Th22/Th17/Th1 cells in patients with chronic myeloid leukemia

T helper- (Th-) cell immunodeficiency plays important roles in tumor development and their effects in chronic myeloid leukemia (CML) remain unclear. In the present study, we mainly investigated the role of Th22, Th17, and Th1 cell and their related cytokines (IL-22, IL-17, and IFN-r) in the pathophysiology of CML. Bone marrow (BM) and peripheral blood (PB) were extracted from newly diagnosed (ND), chronic phase- (CP-) CML patients, and controls. Th subsets were examined by flow cytometry. Plasma IL-22, IL-17, and IFN-r concentrations were measured by ELISA. AHR and RORC mRNA expressions were examined by RT-PCR. The frequencies of Th22, Th17, and Th1 cells, along with the expression of specific transcription factors RORC and AHR, were significantly decreased in ND patients compared with healthy controls, while all these abnormality recovered in CP patients. In addition, there existed a significantly positive relationship between Th22 and Th17 cells in PB or BM. A significantly negative relationship was found between Th cells (Th22, Th17, or Th1) and BCR-ABL (%) IS or the number of PB white blood cells. All these results demonstrated that Th22, Th17, and Th1 cells might be important therapeutic targets in CML and could facilitate a better outcome for tumor immunotherapy.

Increased aryl hydrocarbon receptor expression in patients with allergic rhinitis

BACKGROUND

A predominant Th17 population is a marker of allergic rhinitis (AR). As a ligand-activated transcription factor, the aryl hydrocarbon receptor (AhR) plays a vital role in promoting or inhibiting the development of specific Th cells. However, its role in AR remains undefined.

OBJECTIVE

To analyze the potential role of AhR in the pathogenesis of AR.

METHODS

In total, 30 AR patients and 13 healthy controls were recruited for this study and AR patients had clinical features, as demonstrated by rhinoconjunctivitis quality of life questionnaires, total symptom scores and visual analog scale scores. The expression of AhR, IL-17 and IL-22 and the presence of Th17 cells in peripheral blood mononuclear cells were measured before and after treatment with the nontoxic AhR ligand 2-(1'H-indole-3'-carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE).

RESULTS

Pretreatment ITE studies revealed that all AR patients had a significant increase in AhR expression compared with controls and AhR expression positively correlated with clinical parameters. After ITE intervention, a severe reduction in the differentiation of Th17 cells and the production of IL-17 and IL-22 was noted in both AR patients and normal subjects. Simultaneously, a dramatic enhancement of AhR expression was also observed in all healthy controls, but not in AR patients.

CONCLUSION

The results suggested that the AhR may be one of the mechanisms underlying the Th17 response during the pathogenesis of AR and AhR levels were closely related to clinical severity in all AR patients. Additionally, ITE may represent a new drug candidate in the treatment of AR.

Immune-relevant and new xenobiotic molecular biomarkers to assess anthropogenic stress in seals

Harbour seals as top predators and indicators for ecosystem health are exposed to increasing pressure caused by anthropogenic activities in their marine environment. After their lactation period of about 24 days pups are weaned and left to hunt on their own. Little is known about the development of their immune system and a better understanding of anthropogenic impacts on the general health and immune system of harbour seal pups is needed. mRNA transcription of six immuno-relevant biomarkers was analysed in 13 abandoned harbour seal pups from the North Sea, fostered at the Seal Centre Friedrichskoog, Germany. RNAlater blood samples were taken at admission, day 22 and before release and analysed using RT-qPCR. Significant differences in HSP70, cytokine IL-2 and xenobiotic biomarkers AHR, ARNT and PPARα transcription were found between admission, during rehabilitation and before release. Highest levels at admission may result from dehydration, handling, transport and contaminant exposure via lactation. The significant decrease is linked to health improvement, feeding and adaptation. The increase before release is suspected to be due to infection pressure and contaminant exposure from feeding on fish. Molecular biomarkers are a sensitive tool to evaluate health and pollutant exposure and useful to serve as early warning indicators, monitoring and case-by-case tool for marine mammals in human care and the wild.

Increased expression of aryl hydrocarbon receptor and interleukin 22 in patients with allergic asthma

OBJECTIVES

We sought to determine whether the aryl hydrocarbon receptor (AhR) and interleukin (IL)-22 may be involved in the pathogenesis of the peripheral blood mononuclear cells (PBMCs) in allergic asthmatic patients and whether their expression may be related to the severity of the disease.

METHODS

Blood samples were obtained from each subject with allergic asthma (n =18), controlled asthma (n = 17) and healthy controls (n = 12) respectively. The PBMCs were collected for AhR mRNA detection by real-time quantitative polymerase chain reaction (PCR). The plasma was collected for IL-22 protein detection by enzyme-linked immunosorbent assay (ELISA).

RESULTS

The expression of AhR mRNA in PBMCs and IL-22 protein in plasma of patients with allergic asthma were higher than those in controlled asthma cases and healthy controls. The plasma concentrations of IL-22 had negative correlation with the predicted percentage of forced expiratory volume in the first second (FEV1%) and the percentage of FEV1 and forced vital capacity (FEV1/FVC%) and it was positively correlated with the asthma severity score (ASS) of the asthmatics.

CONCLUSION

Our results suggested that both AhR and IL-22 might be involved in the pathogenesis of allergic asthma in human and the level of IL-22 might have some relationship with the severity of the disease.

Characterization of the avian aryl hydrocarbon receptor 1 from blood using non-lethal sampling methods

The amino acid sequence of the aryl hydrocarbon receptor 1 ligand binding domain (AHR1 LBD) is an important determinant of sensitivity to dioxin-like compounds in avian species. We are interested in surveying AHR1 LBD sequences in a large number of birds as a means of identifying species that are particularly sensitive to dioxin-like compounds. Our original method for determining AHR1 LBD genotype used liver tissue and required lethal sampling. Here we present two alternate methods for determining AHR1 LBD genotype which use non-lethal sampling and are more appropriate for ecologically sensitive species. First, we establish that AHR1 LBD mRNA is expressed in avian blood and test a variety of blood collection and handling protocols in order to establish a method that is convenient for field collections. Our findings also identify which types of archival blood samples might be appropriate for AHR1 LBD sequence determination. Second, we present a method for obtaining AHR1 LBD coding sequences from DNA. A DNA-based method is advantageous because DNA can be isolated from many tissue types, is more stable than RNA, and requires less specific sample handling and preservation. This work extends applicability of a genetic screen for dioxin sensitivity to a larger number of species and sample types including endangered species and potentially museum specimens.

Direct assessment of cumulative aryl hydrocarbon receptor agonist activity in sera from experimentally exposed mice and environmentally exposed humans

BACKGROUND

Aryl hydrocarbon receptor (AhR) ligands adversely affect many biological processes. However, assessment of the significance of human exposures is hampered by an incomplete understanding of how complex mixtures affect AhR activation/inactivation.

OBJECTIVES

These studies used biological readouts to provide a broader context for estimating human risk than that obtained with serum extraction and gas chromatography/mass spectroscopy (GC/MS)-based assays alone.

METHODS

AhR agonist activity was quantified in sera from dioxin-treated mice, commercial human sources, and polychlorinated biphenyl (PCB)-exposed Faroe Islanders using an AhR-driven reporter cell line. To validate relationships between serum AhR agonist levels and biological outcomes, AhR agonist activity in mouse sera correlated with toxic end points. AhR agonist activity in unmanipulated ("neat") human sera was compared with these biologically relevant doses and with GC/MS-assayed PCB levels.

RESULTS

Mouse serum AhR agonist activity correlated with injected dioxin dose, thymic atrophy, and heptomegaly, validating the use of neat serum to assess AhR agonist activity. AhR agonist activity in sera from Faroe Islanders varied widely, was associated with the frequency of recent pilot whale dinners, but did not correlate with levels of PCBs quantified by GC/MS. Surprisingly, significant "baseline" AhR activity was found in commercial human sera.

CONCLUSIONS

An AhR reporter assay revealed cumulative levels of AhR activation potential in neat serum, whereas extraction may preclude detection of important non-dioxin-like biological activity. Significant levels of AhR agonist activity in commercial sera and in Faroe Islander sera, compared with that from experimentally exposed mice, suggest human exposures that are biologically relevant in both populations.

AH receptor agonist activity in human blood measured with a cell-based bioassay: evidence for naturally occurring AH receptor ligands in vivo

In the present study, an aryl hydrocarbon receptor (AHR)-driven reporter gene bioassay was used to measure the activity, measured as an induction equivalent (IEQ) as compared to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), or IEQ concentration in human blood samples from 10 volunteers under different dietary regimens. Blood concentrations of polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs) and polychlorinated biphenyls (PCBs), as determined by analytical chemistry (HR-GC/MS), and expressed as toxic equivalents (TEQs) with the use of TCDD equivalency factors (TEFs), were within a range that has been reported in the general US population, ranging from 0.022 to 0.119 ppt (whole blood basis). However, the human blood IEQ measured directly via bioassay ranged from 13.4 to 218 ppt (whole blood basis). These order of magnitude greater IEQs compared to the TEQs for dioxins, furans, and certain PCBs suggests that human blood contains a relatively high level of AHR agonists able to activate the CYP1A1 dioxin response element (DRE)-linked reporter gene bioassay and that this AHR activity is not accounted for by PCDDs/Fs and dioxin-like PCBs based on standard HR-GC/MS and TEF analysis. When study participants switched from a "baseline" to a high-vegetable diet, increases in bioassay IEQ were observed that were statistically significant (P<0.05). In addition, IEQ activity was elevated above levels observed following dietary intervention in two subjects given indole-3-carbinol (I3C) supplements. We conclude that a substantial portion of the IEQ activity occurred as a result of the increased intake of natural AHR agonists (NAHRAs) present in many fruits, vegetables. and herbs. Our findings also suggest that dietary NAHRAs constitute a substantial daily dietary intake of AHR-active compounds, and these NAHRAs could influence AHR status in humans and play a role in a basal level of AHR activation.

Relation between serum xenobiotic-induced receptor activities and sperm DNA damage and sperm apoptotic markers in European and Inuit populations

Persistent organic pollutants (POPs) can interfere with hormone activities and are suspected as endocrine disrupters involved in disorders, e.g. reproductive disorders. We investigated the possible relation between the actual integrated serum xenoestrogenic, xenoandrogenic and aryl hydrocarbon receptor (AhR) activities, and the sperm DNA damage and sperm apoptotic markers of 262 adult males (54 Inuits from Greenland, 69 from Warsaw (Poland), 81 from Sweden, and 58 from Kharkiv (Ukraine)) exposed to different levels of POPs. Xenobiotic-induced receptor activities were determined by receptor-mediated luciferase reporter gene expression. Sperm DNA damage was measured using terminal deoxynucleotidyl transferase-driven dUTP nick labeling assay (TUNEL) and pro- (Fas) and anti-apoptotic (Bcl-xL) markers were determined by immune methods. Different features of xenobiotic-induced receptor activity in serum and sperm DNA fragmentation and apoptotic markers existed between the Inuits and the European Caucasians. Negative correlations between xenobiotic-induced receptor activities and DNA damage were found for Inuits having relatively lower xenoestrogenic, lower dioxin-like activity, and lower sperm DNA damage, but higher xenoandrogenic activity. In contrast, in the European groups, xenobiotic-induced receptor activities were found to be positively correlated with the DNA damage. Further research must elucidate whether altered receptor activities in concerted action with genetic and/or nutrient factors may have protecting effect on sperm DNA damage of the Inuit population.

Dioxin-like activities in serum across European and Inuit populations

BACKGROUND

Persistent organic pollutants (POPs) such as polychlorinated dibenzo-p-dioxins/furans, polychlorinated biphenyls (PCBs) and organochlorine pesticides can cause a series of adverse effects on e.g. reproduction in animals and humans, many of which involve the aryl hydrocarbon receptor (AhR). The aim of the present study was to compare the integrated serum level of AhR mediated activity among European and Inuit populations, and evaluate whether the activity was associated to the selected POP markers, 2,2',4,4',5,5'-hexachlorobiphenyl (CB-153) and 1,1-dichloro-2,2-bis(p-chlorophenyl)-ethylene (p,p'-DDE).

METHODS

The study included 338 males from Greenland (Inuit's), Sweden, Warsaw (Poland) and Kharkiv (Ukraine). The AhR transactivity of serum extracts alone (AhRag) and competitive AhR activity (AhRcomp) upon co-exposure with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) were determined in the lipophilic serum fraction containing the POPs using the AhR mediated luciferase reporter Hepa1.12cR cell assay.

RESULTS

The European groups showed higher median level of AhR-TEQ (TCDD toxic equivalents) compared to the Inuit's, whereas higher incidence of Inuits sample further induced AhRcomp activity. Neither AhRag nor AhR-TEQ were correlated to CB-153 or p,p'-DDE for any of the study groups. Multiple regressions showed a significant heterogeneity of association between the CB-153 and the AhRcomp across the study groups, and accordingly a negative association between AhRcomp and CB-153 was found for the Kharkiv group.

CONCLUSION

No consistent correlation between AhR activities and two POP markers was found. Although the difference of AhRag between European and Inuit men could not be explained by CB-153 or p,p'-DDE levels alone, we believe that the variation of AhR serum activity reflects different pattern of POP exposure, genetics and/or life style factors.