Molecular evaluation of a new highly sensitive aryl hydrocarbon receptor in ostriches

Abstract

A 1,000-fold difference has been reported in dioxin sensitivity between avian species. This difference is because the 2 amino acids in the type 1 aryl hydrocarbon receptor (AhR1), at positions 325 and 381, correspond to Leu324 and Ser380 in chickens. The chicken had been reported to be the only avian species to possess a sensitive form of AhR1. This is the first study to reveal that the ostrich (Struthio camelus), a nonchicken species, also has a pair of amino acids (Ile-325 and Ser-381) that show high ligand affinity. However, the alignment of the AhR1 cDNA sequence showed that the AhR sequence in the ostrich was different than that of other avian species even though the critical amino acids were observed at positions 325 and 381. Ostrich AhR1 was also evaluated in a heterologous expression study. Ostrich AhR1 showed very high transcriptional activity of the cytochrome P450 1A5 (CYP1A5) gene in African Green Monkey Cercopithecus aethiops kidney cells (COS-7) treated with Sudan III. In primary cultures of ostrich kidney cells, CYP1A5 expression was induced by Sudan III at a lower (or almost identical) concentration to that observed in the chicken. The present study revealed a new AhR ligand sensitive avian species (i.e., the ostrich).

Dioxin Sensitivity-Related Two Critical Amino Acids of Arylhydrocarbon Receptor May Not Correlate with the Taxonomy or Phylogeny in Avian Species

“…In the ostrich, multiple amino acid changes were found throughout the ligand-binding domain, compared with other avian species. This ostrich AhR1 was reported to possess high transactivation ability in our previous study, similar to chicken AhR1 [11]. …”

“…The dioxin concentration required to induce these types of toxicity varies significantly between birds [3]. The large difference in dioxin sensitivity among avian species is reported to be dependent on the arylhydrocarbon receptor (AhR) protein [11, 17], which has a role in the induction of toxicity [10, 21, 27]. …”

Catbirds are the New Chickens: High Sensitivity to a Dioxin-like Compound in a Wildlife Species

“…Currently, 5% (5/100) of species with published AHR1 LBD sequences are identified as having a type 1 AHR1 LBD. ,, The three type 1 species that have been tested for sensitivity to embryotoxic effects of DLCs in vivo (chicken, catbird, and starling) were all confirmed as highly sensitive. In vitro evidence supports that a fourth type 1 species, the ostrich ( Struthio camelus ), is also highly sensitive . The ruby-throated hummingbird ( Archilochus colubris ), which is another North American wildlife species, is also predicted to be highly sensitive to DLCs although to test its sensitivity in vivo is more challenging.…”

“…In vitro evidence supports that a fourth type 1 species, the ostrich (Struthio camelus), is also highly sensitive. 39 The ruby-throated hummingbird (Archilochus colubris), which is another North American wildlife species, is also predicted to be highly sensitive to DLCs although to test its sensitivity in vivo is more challenging. Approximately 10,000 species of birds exist worldwide, 40 but the AHR1 type is only known for ∼1% of species.…”

Identification of Modulators of the C. elegans Aryl Hydrocarbon Receptor and Characterization of Transcriptomic and Metabolic AhR-1 Profiles

“…We used this cell line from the Green Monkey Chlorocebus sabeus as: (1) no commercial C. elegans cell line is currently used; and (2) the use of primary neurons from the nematode would be difficult considering the small number of cells expressing ahr-1. Cos-7 cells are widely used for AhR screening experiments of different species [36][37][38].…”