Functionality of aryl hydrocarbon receptors (AhR1 and AhR2) of white sturgeon (Acipenser transmontanus) and implications for the risk assessment of dioxin-like compounds

ABSTRACT: Worldwide, populations of sturgeons are endangered, and it is hypothesized that anthropogenic chemicals, including dioxin-like compounds (DLCs), might be contributing to the observed declines in populations. DLCs elicit their toxic action through activation of the aryl hydrocarbon receptor (AhR), which is believed to regulate most, if not all, adverse effects associated with exposure to these chemicals. Currently, risk assessment of DLCs in fishes uses toxic equivalency factors (TEFs) developed for the World Health Organization (WHO) that are based on studies of embryo-lethality with salmonids. However, there is a lack of knowledge of the sensitivity of sturgeons to DLCs, and it is uncertain whether TEFs developed by the WHO are protective of these fishes. Sturgeons are evolutionarily distinct from salmonids, and the AhRs of sturgeons differ from those of salmonids. Therefore, this study investigated the sensitivity of white sturgeon (Acipenser transmontanus) to DLCs in vitro via the use of luciferase reporter gene assays using COS-7 cells transfected with AhR1 or AhR2 of white sturgeon. Specifically, activation and relative potencies (RePs) of 2,3,7,8-tetrachloro-dibenzo-p-dioxin (TCDD), 2,3,4,7,8-pentachlorodibenzofuran, 2,3,7,8-tetrachloro-dibenzofuran, 3,3′,4,4′,5-pentachlorobiphenyl, 3,3′,4,4′-tetrachlorobiphenyl, and 2,3,3′,4,4′-pentachlorobiphenyl were determined for each AhR. It was demonstrated that white sturgeon expresses AhR1s and AhR2s that are both activated by DLCs with EC 50 values for 2,3,7,8-TCDD that are lower than those of any other AhR of vertebrates tested to date. Both AhRs of white sturgeon had RePs for polychlorinated dibenzofurans more similar to TEFs for birds, while RePs for polychlorinated biphenyls were most similar to TEFs for fishes. Measured concentrations of select DLCs in tissues of white sturgeon from British Columbia, Canada, were used to calculate toxic equivalents (TEQs) by use of TEFs for fishes used by the WHO and TCDD equivalents (TCDD-EQs) via the use of RePs for AhR2 of white sturgeon as determined by transfected COS-7 cells. TCDD-EQs calculated for endangered populations of white sturgeon were approximately 10-fold greater than TEQs and were within ranges known to cause adverse effects in other fishes, including other species of sturgeons. Therefore, TEFs used by the WHO might not adequately protect white sturgeon, illuminating the need for additional investigation into the sensitivity of these fish to DLCs

Identification of Tetrapeptides from a Mixture Based Positional Scanning Library That Can Restore nM Full Agonist Function of the L106P, I69T, I102S, A219V, C271Y, and C271R Human Melanocortin-4 Polymorphic Receptors (hMC4Rs)

Human obesity has been linked to genetic factors and single nucleotide polymorphisms (SNPs). Melanocortin-4 receptor (MC4R) SNPs have been associated with up to 6% frequency in morbidly obese children and adults. A potential therapy for individuals possessing such genetic modifications is the identification of molecules that can restore proper receptor signaling and function. These compounds could serve as personalized medications improving quality of life issues as well as alleviating diseases symptoms associated with obesity including type 2 diabetes. Several hMC4 SNP receptors have been pharmacologically characterized in vitro to have a decreased, or a lack of response, to endogenous agonists such as α-, β-, and γ2-melanocyte stimulating hormones (MSH) and adrenocorticotropin hormone (ACTH). Herein we report the use of a mixture based positional scanning combinatorial tetrapeptide library to discover molecules with nM full agonist potency and efficacy to the L106P, I69T, I102S, A219V, C271Y, and C271R hMC4Rs. The most potent compounds at all these hMC4R SNPs include Ac-His-(pI)DPhe-Tic-(pNO2)DPhe-NH2, Ac-His-(pCl)DPhe-Tic-(pNO2)DPhe-NH2, Ac-His-(pCl)DPhe-Arg-(pI)Phe-NH2, and Ac-Arg-(pCl)DPhe-Tic-(pNO2)DPhe-NH2, revealing new ligand pharmacophore models for melanocortin receptor drug design strategies

Physical and psychological attributes of fatigue in female heart transplant recipients.

BackgroundThe attributes of fatigue after orthotopic heart transplantation (OHT) are poorly understood. We conducted this study to assess the prevalence, severity and correlates of fatigue among female OHT survivors.MethodsFifty women (age 54.7 +/- 13.0 years) from a single heart transplant center, who underwent OHT 5.1 +/- 4.4 (mean +/- SD) years earlier, completed a battery of questionnaires including the Profile of Mood States-fatigue sub-scale to assess levels of fatigue, the Beck Depression Inventory to measure depression, and the Short Form-36 to measure functional status and mental health. Demographic and clinical data were obtained from self-reports and medical chart reviews.ResultsWomen reported mean scores of 15.7 +/- 6.8 (range 3 to 27), 13.2 +/- 8.2 (range 0 to 38), 37.2 +/- 10.8 (range 22 to 62) and 41.5 +/- 11.2 (range 17 to 60) for fatigue, depression, functional status and mental health, respectively. Univariate analyses revealed that sociodemographic and clinical variables (e.g., age, employment status, anemia, renal insufficiency) were significantly related to fatigue (p < 0.001). Likewise, depression, functional status and mental health were also significantly related to fatigue (p < 0.001). In a multivariate model, age (adjusted R(2) = 0.23, p < 0.001), anemia (adjusted R(2) = 0.39, p < 0.001), functional status (adjusted R(2) = 0.60, p < 0.001) and depression (adjusted R(2) = 0.69, p < 0.001) were significant predictors of fatigue. The model explained 69% of the variance in fatigue (p < 0.001).ConclusionsFatigue is common in women after OHT and is associated with both physiologic and psychologic factors. Clinicians should evaluate all female recipients for symptoms of fatigue, especially those with anemia, renal insufficiency, poor functional status and depression. Other potential mediators of fatigue, such as the denervated donor heart and type of immunosuppressive regimen, may also play a role and require further study

Physical and psychological attributes of fatigue in female heart transplant recipients.

BackgroundThe attributes of fatigue after orthotopic heart transplantation (OHT) are poorly understood. We conducted this study to assess the prevalence, severity and correlates of fatigue among female OHT survivors.MethodsFifty women (age 54.7 +/- 13.0 years) from a single heart transplant center, who underwent OHT 5.1 +/- 4.4 (mean +/- SD) years earlier, completed a battery of questionnaires including the Profile of Mood States-fatigue sub-scale to assess levels of fatigue, the Beck Depression Inventory to measure depression, and the Short Form-36 to measure functional status and mental health. Demographic and clinical data were obtained from self-reports and medical chart reviews.ResultsWomen reported mean scores of 15.7 +/- 6.8 (range 3 to 27), 13.2 +/- 8.2 (range 0 to 38), 37.2 +/- 10.8 (range 22 to 62) and 41.5 +/- 11.2 (range 17 to 60) for fatigue, depression, functional status and mental health, respectively. Univariate analyses revealed that sociodemographic and clinical variables (e.g., age, employment status, anemia, renal insufficiency) were significantly related to fatigue (p < 0.001). Likewise, depression, functional status and mental health were also significantly related to fatigue (p < 0.001). In a multivariate model, age (adjusted R(2) = 0.23, p < 0.001), anemia (adjusted R(2) = 0.39, p < 0.001), functional status (adjusted R(2) = 0.60, p < 0.001) and depression (adjusted R(2) = 0.69, p < 0.001) were significant predictors of fatigue. The model explained 69% of the variance in fatigue (p < 0.001).ConclusionsFatigue is common in women after OHT and is associated with both physiologic and psychologic factors. Clinicians should evaluate all female recipients for symptoms of fatigue, especially those with anemia, renal insufficiency, poor functional status and depression. Other potential mediators of fatigue, such as the denervated donor heart and type of immunosuppressive regimen, may also play a role and require further study

Data from: In silico site-directed mutagenesis informs species-specific predictions of chemical susceptibility derived from the Sequence Alignment to Predict Across Species Susceptibility (SeqAPASS) tool

Chemical hazard assessment requires extrapolation of information from model organisms to all species of concern. The Sequence Alignment to Predict Across Species Susceptibility (SeqAPASS) tool was developed as a rapid, cost effective method to aid cross-species extrapolation of susceptibility to chemicals acting on specific protein targets through evaluation of protein structural similarities and differences. The greatest resolution for extrapolation of chemical susceptibility across species involves comparisons of individual amino acid residues at key positions involved in protein-chemical interactions. However, a lack of understanding of whether specific amino acid substitutions among species at key positions in proteins affect interaction with chemicals made manual interpretation of alignments time consuming and potentially inconsistent. Therefore, this study used in silico site-directed mutagenesis coupled with docking simulations of computational models for acetylcholinesterase (AChE) and ecdysone receptor (EcR) to investigate how specific amino acid substitutions impact protein-chemical interaction. This study found that computationally derived substitutions in identities of key amino acids caused no change in protein-chemical interaction if residues share the same side chain functional properties and have comparable molecular dimensions, while differences in these characteristics can change protein-chemical interaction. These findings were considered in the development of capabilities for automatically generated species-specific predictions of chemical susceptibility in SeqAPASS. These predictions for AChE and EcR were shown to agree with SeqAPASS predictions comparing the primary sequence and functional domain sequence of proteins for more than 90 % of the investigated species, but also identified dramatic species-specific differences in chemical susceptibility that align with results from standard toxicity tests. These results provide a compelling line-of-evidence for use of SeqAPASS in deriving screening level, species-specific, susceptibility predictions across broad taxonomic groups for application to human and ecological hazard assessment

A Cross-species Quantitative Adverse Outcome Pathway for Activation of the Aryl Hydrocarbon Receptor Leading to Early Life Stage Mortality in Birds and Fishes

Dioxin-like compounds (DLCs) elicit adverse effects through activation of the aryl hydrocarbon receptor (AHR). Prior investigations demonstrated that sensitivity to activation of AHR1 in an in vitro AHR transactivation assay is predictive of early life stage mortality among birds. The present study investigated the link between sensitivity to activation of AHR1s and AHR2s and early life stage mortality among fishes. A significant, linear relationship was demonstrated between sensitivity to activation of AHR2 and early life stage mortality among nine fishes, while no relationship was found for AHR1. The slope and <i>y</i>-intercept for the linear relationship between sensitivity to activation of AHR1 and early life stage mortality in birds was not statistically different from the same relationship for AHR2 in fishes. Data for fishes and birds across DLCs were expanded into four significant, linear regression models describing the relationship between sensitivity to activation of AHR and the dose to cause early life stage mortality of 0%, 10%, 50%, or 100%. These four relationships were combined to form a quantitative adverse outcome pathway which can predict dose–response curves of early life stage mortality for DLCs to any bird or fish from species- and chemical-specific responses in an in vitro AHR transactivation assay