Aryl hydrocarbon receptor (AHR) and its heterodimer aryl hydrocarbon nuclear translocator (ARNT) form a ligand-activated transcription complex that regulates expression of the AHR battery of target genes that includes the most important placental biotransformation enzyme cytochrome CYP1A1. Expression, placental localization, and ontogeny of AHR/Ahr and ARNT/Arnt have not been systematically studied in either human or rat placentas. Moreover, induction of such AHR target genes as CYP1A1, CYP1A2, CYP1B1, UGT1A1, and breast cancer resistance protein (BCRP), as well as of AHR, ARNT, and aryl hydrocarbon receptor repressor (AHRR) genes, after exposure to AHR ligands have not been studied in human placental trophoblast cultures. In this article, we show that only CYP1A1 messenger RNA (mRNA), but not CYP1A2, CYP1B1, UGT1A1, BCRP, AHR, ARNT, and AHRR mRNAs, is significantly induced in human term placental trophoblast cultures after exposure to prototype AHR ligands/activators 2,3,7,8-tetrachlorodibenzo-p-dioxin, 3-methylcholanthrene, omeprazole, and β-naphthoflavone. We localized AHR/Ahr and ARNT/Arnt in rat placental trophoblasts throughout gestation and in first trimester and term human placental trophoblast, which comprise the crucial component of the maternal-fetal barrier. We demonstrate that rat Ahr and Cyp1a1 reached highest expression during gestation days 15 and 18, which might indicate different response to Ahr ligands in placental Cyp1a1 induction during rat gestation. We also propose the JEG3 choriocarcinoma cell line as a cellular model for human trophoblast induction studies through AHR. In conclusion, we describe expression and ontogeny of AHR/Ahr and ARNT/Arnt and systematically characterize induction of major AHR target genes in human placental trophoblast forming the placental maternal-fetal morphological and metabolic barrier.

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Aim: Endoglin is a homodimeric transmembrane glycoprotein that has been demonstrated to affect transforming growth factor (TGF-) signaling and endothelial nitric oxide synthase (eNOS) expression by affecting SMAD proteins in vitro. Thus, in this study we stepped forward to elucidate whether endoglin is co-expressed with SMAD2, phosphorylated SMAD2/3 proteins and eNOS in vivo in atherosclerotic lesions in ApoE/LDLR double knockout mice. In addition, we sought whether endoglin expression as well as the expression of SMAD2, phosphorylated SMAD2/3 and eNOS is affected by atorvastatin treatment. Methods: Two-month-old female ApoE/LDLR double knockout mice were divided into two groups. The control group was fed with the western type diet whereas in the atorvastatin group, atorvastatin at dose 100 mg/kg per day was added to the same diet. Immunohistochemical and western blot analysis of endoglin, SMAD2, phosphorylated SMAD2/3 and eNOS expressions in aorta were performed.

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Aim: Transforming growth factor-beta (TGF-) plays important role in atherogenesis via TGF-receptors and Smad proteins, which determine its signaling activity. In this study, we hypothesized, whether non-lipid related effects of atorvastatin, affect both endoglin/ALK-5/Smad2/eNOS and/or endoglin/ALK-1/Smad1/VEGF previously proposed pathways in ApoE/LDLR double knockout mice. Methods: ApoE/LDLR double knockout mice were divided into two groups. The chow group (CHOW) (n 8) was fed with chow diet, while in the atorvastatin group (ATV) (n 8) atorvastatin was added to the chow diet at dose 50 mg/kg/day. Biochemical analyses of lipid profile, lesion area measurement, immunohistochemistry and Western blot analysis of endoglin, ALK-1, 5, phosphorylated and non-phosphorylated forms Smad-1, 2, VEGF and eNOS proteins in mice aorta were performed. Results: Biochemical analysis of blood serum and morphometric analysis of aortic lesion size showed that atorvastatin treatment resulted in a significant increase of cholesterol levels and simultaneously in reduced lesion size in aortic sinus when compared to CHOW mice. Western blot analysis revealed that atorvastatin treatment significantly increase the expressions of endoglin by 102%, ALK-1 by 113%, ALK-5 by 296%, pSmad-1 by 202%, pSmad-2 by 34%, VEGF by 68% and eNOS by 687% as compared with CHOW mice. Immunofluorescence staining revealed endoglin coexpression with all studied markers that were increased by atorvastatin treatment mainly in endothelial cells covering atherosclerotic plaques. Conclusion: This study shows that atorvastatin treatment increases the expression of endoglin, ALK-1, ALK-5, phosphorylated forms of Smad1 and Smad2, VEGF and eNOS and reduces atherosclerotic lesion size beyond its lipid lowering effects. Therefore, we propose that endoglin related receptors and signal transducers might play protective role in atherogenesis.