Low oxygen tension differentially regulates the expression of placental solute carriers and ABC transporters.

Low oxygen concentration, or hypoxia, is an important physiological regulator of placental function including chemical disposition. Here, we compared the ability of low oxygen tension to alter the expression of solute carriers (SLC) and ABC transporters in two human placental models, namely BeWo cells and term placental explants. We found that exposure to low oxygen concentration differentially regulates transporter expression in BeWo cells, including downregulation of ENT1, OATP4A1, OCTN2, BCRP, and MRP2/3/5, and upregulation of CNT1, OAT4, OATP2B1, SERT, SOAT, and MRP1. Similar upregulation of MRP1 and downregulation of MRP5 and BCRP were observed in explants, whereas uptake transporters were decreased or unchanged. Furthermore, a screening of transcriptional regulators of transporters revealed that hypoxia leads to a decrease in the mRNA levels of aryl hydrocarbon receptor, nuclear factor erythroid 2-related factor 2, and retinoid x receptor alpha in both human placental models. These data suggest that transporter expression is differentially regulated by oxygen concentration across experimental human placental models.

Design and Synthesis of Novel Thiazolo[5,4-d]pyrimidine Derivatives as Potential Angiogenesis Inhibitors.

Vascular endothelial growth factor receptor-2 (VEGFR-2) plays an important role in both vasculogenesis and angiogenesis. Inhibition of VEGFR-2 has been demonstrated as a key method against tumor-associated angiogenesis. Thiazolopyrimidine is an important analog of the purine ring, and we choose the thiazolopyrimidine scaffold as the mother nucleus. Two series of thiazolo[5,4-d]pyrimidine derivatives were synthesized and evaluated for their antiproliferative activity. In HUVEC inhibition assay, compounds 3l (=1-(5-{[2-(4-chlorophenyl)-5-methyl[1,3]thiazolo[5,4-d]pyrimidin-7-yl]amino}pyridin-2-yl)-3-(3,4-dimethylphenyl)urea) and 3m (=1-(5-{[2-(4-chlorophenyl)-5-methyl[1,3]thiazolo[5,4-d]pyrimidin-7-yl]amino}pyridin-2-yl)-3-(4-methoxyphenyl)urea) exhibited the most potent inhibitory effect (IC50 =1.65 and 3.52 µm, respectively). Compound 3l also showed the best potency against VEGFR-2 at 50 µm (98.5 %). These results suggest that further investigation of compound 3l might provide potential angiogenesis inhibitors.

I2-Catalyzed cross dehydrogenative coupling: rapid access to benzoxazinones and quinazolinones.

An efficient and applicable I2-catalyzed intramolecular dehydrogenative C-O/C-N coupling reaction via activating the C-H bond adjacent to the N atom has been developed to provide dozens of substituted benzoxazinones (31 examples) and quinazolinones (5 examples) in good to excellent yields (up to 98%). This one-pot methodology has significant advantages, including a metal-free process, broad substrate scope, high atom economy, and simple operation. This strategy goes through an iminium intermediate followed by nucleophilic attack to provide the desired products.

Down-regulation of the placental BCRP/ABCG2 transporter in response to hypoxia signaling.

INTRODUCTION: The BCRP/ABCG2 efflux transporter protects the developing fetus by limiting the transplacental transfer of drugs and chemicals and prevents the apoptosis of trophoblasts. The purpose of this study was to determine whether hypoxia-related signaling alters placental BCRP expression and function in vitro and in human pregnancies. METHODS: Human BeWo choriocarcinoma cells were treated with the hypoxia mimetic, cobalt chloride (CoCl2), or 3% oxygen for 24-48 h. Activation of HIF-1α signaling and regulation of BCRP was assessed using qPCR, ELISA, western blotting and a fluorescent substrate transport assay. In addition, healthy term placentas from high altitude pregnancies with chronic hypoxia were assessed for BCRP expression. RESULTS: CoCl2 and 3% oxygen increased HIF-1α protein signaling and decreased the mRNA and protein expression of BCRP by 30-75% in BeWo cells. Reduced BCRP expression corresponded with impaired efflux activity during hypoxia as evidenced by accumulation of the substrate Hoechst 33342. A number of transcription factors known to regulate BCRP, including AHR, NRF2 and PPARγ, were also coordinately down-regulated by 3% oxygen in BeWo cells. Moreover, women who gave birth at a high altitude (3100 m) exhibited signs of chronic placental hypoxia, including enhanced protein expression of the HIF-1α target GLUT1, and had reduced BCRP levels in microvillous membranes compared to women at a moderate altitude (1600 m). DISCUSSION: This study provides novel insight into the regulation of the placental BCRP transporter by hypoxia, which may be important for exposure of the fetus to chemicals during early development and in hypoxia-related pregnancy disorders.

2-Substituted 3-methylnaphtho[1,2-b]furan-4,5-diones as novel L-shaped ortho-quinone substrates for NAD(P)H:quinone oxidoreductase (NQO1).

A series of L-shaped ortho-quinone analogs were designed by analyzing the binding mode with NQO1. Metabolic studies demonstrated that compounds 2m, 2n and 2q exhibited higher metabolic rates than ß-lapachone. The docking studies, which supported the rationalization of the metabolic studies, constituted a prospective rational basis for the development of optimized ortho-quinone analogs. Besides, good substrates (2m, 2n and 2r) for NQO1 showed higher selective toxicity than ß-lapachone toward A549 (NQO1-rich) cancer cells versus H596 (NQO1-deficient) cells. Determination of superoxide (O2(•-)) production and in vitro cytotoxicity evaluation in the presence of the NQO1 inhibitor dicoumarol confirmed that the ortho-quinones exerted their antitumor activity through NQO1-mediated ROS production by redox cycling. It was suggested that the L-shaped quinone substrates for NQO1 possessed better specificity and safety than ß-lapachone.