In utero exposure to benzo[a]pyrene increases adiposity and causes hepatic steatosis in female mice,and glutathione deficiency is protective

Polycyclic aromatic hydrocarbons (PAHs), including benzo[a]pyrene (BaP), are ubiquitous environmental pollutants found in tobacco smoke, air pollution, and grilled foods. Reactive metabolites and reactive oxygen species generated during PAH metabolism are detoxified by reactions involving glutathione (GSH). Early life exposures to tobacco smoke and air pollution have been linked to increased risk of obesity and metabolic syndrome. We investigated the independent and interactive effects of prenatal exposure to BaP and GSH deficiency due to deletion of the modifier subunit of glutamate cysteine ligase (Gclm), the rate-limiting enzyme in GSH synthesis, on adiposity and hepatic steatosis in adult female F1 offspring. We mated Gclm^+/− dams with Gclm^+/− males and treated the pregnant dams with 0, 2, or 10 mg/kg/day BaP in sesame oil by oral gavage daily from gestational day 7 through 16. We analyzed metabolic endpoints in female Gclm^−/− and Gclm^+/+ littermate F1 offspring. Prenatal BaP exposure significantly increased visceral adipose tissue weight, weight gain between 3 weeks and 7.5 months of age, hepatic lipid content measured by oil red O staining, and hepatic fatty acid beta-oxidation gene expression in Gclm^+/+, but not in Gclm^−/−, female offspring. Hepatic expression of lipid biosynthesis and antioxidant genes were decreased and increased, respectively, in Gclm^−/− mice. Our results suggest that reported effects of pre- and peri-natal air pollution and tobacco smoke exposure on obesity may be mediated in part by PAHs. GSH deficiency is protective against the metabolic effects of prenatal BaP exposure.     

Characterization of a gap-junctional intercellular communication (GJIC) assay using cigarette smoke

Inhibition of gap-junctional intercellular communication (GJIC) via exposure to various toxic substances has been implicated in tumor promotion. In the present study, cigarette smoke total particulate matter (TPM), a known inhibitor of GJIC, were used to characterize a new GJIC screening assay in three independent experiments. The main features of this assay were automated fluorescence microscopy combined with non-invasive parachute technique. Rat liver epithelial cells (WB-F344) were stained with the fluorescent dye Calcein AM (acetoxymethyl) and exposed to TPM from the Kentucky Reference Cigarette 2R4F (a blend of Bright and Burley tobaccos) and from two single-tobacco cigarettes (Bright and Burley) for 3 h. Phorbol-12-myristate-13-acetate (TPA) was used as positive control and 0.5% dimethyl sulfoxide (DMSO) as solvent control. The transfer of dye to adjacent cells (percentage of stained cells) was used as a measure of cellular communication. A clear and reproducible dose–response of GJIC inhibition following TPM exposure was seen. Reproducibility and repeatability measurements for the 2R4F cigarette were 3.7% and 6.9%, respectively. The half-maximal effective concentration values were 0.34 ng/ml for TPA, 0.050 mg/ml for the 2R4F, 0.044 mg/ml for the Bright cigarette, and 0.060 mg/ml for the Burley cigarette. The assay was able to discriminate between the two single-tobacco cigarettes (P < 0.0001), and between the single-tobacco cigarettes and the 2R4F (P = 0.0008, 2R4F vs. Burley and P < 0.0001, 2R4F vs. Bright). Thus, this assay can be used to determine the activity of complex mixtures such as cigarette smoke with high throughput and high precision.     

Effects of anthocyanins on the AhR–CYP1A1 signaling pathway in human hepatocytes and human cancer cell lines

Anthocyanins are plant pigments occurring in flowers and berry fruits. Since a phenomenon of food–drug interactions is increasingly emerging, we examined the effects of 21 major anthocyanins and the extracts from 3 food supplements containing anthocyanins on the aryl hydrocarbon receptor (AhR)–cytochrome P450 CYP1A1 signaling pathway in human hepatocytes and human hepatic HepG2 and intestinal LS174T cancer cells. Pelargonidin-3-O-rutinoside (PEL-2) and cyanidin-3,5-O-diglucoside (CYA-3) dose-dependently activated AhR, as revealed by gene reporter assay. PEL-2 and CYA-3 induced CYP1A1 mRNA but not protein in HepG2 and LS174T cells. Neither compounds induced CYP1A1 mRNA and protein in four different primary human hepatocytes cultures. The effects of PEL-2 and CYA-3 on AhR occurred by ligand-dependent and ligand-independent mechanisms, respectively, as demonstrated by ligand binding assay. In a direct enzyme inhibition assay, none of the antocyanins tested inhibited the CYP1A1 marker activity to less than 50% even at 100 μM concentration. PEL-2 and CYA-3 at 100 μM inhibited CYP1A1 to 79% and 65%, respectively. In conclusion, with exception of PEL-2 and CYA-3, there were no effects of 19 major anthocyanins and 3 food supplements containing anthocyanins on AhR–CYP1A1 signaling, implying zero potential of these compounds for food–drug interactions with respect to AhR–CYP1A1 pathway.     

Two new aromatic acids from Clerodendrum formicarum Gürke (Lamiaceae) of Cameroon

The ethanolic extract of the leaves of Clerodendrum formicarum, a Lameacious plant of Cameroon, afforded two new salicylic acid derivatives named formoic acids A and B along with four known constituents which have been obtained for the first time from this source. They include flemingipanic acid, martynoside, verbascoside, and seguinoside K. Structures of all the isolated constituents have been elucidated with the aid of 1D and 2D NMR spectroscopic techniques.     

New aromatic esters from Galinsoga parviflora

Galinosoates A–C (1–3), new aromatic esters, have been isolated from the n-hexane soluble fraction of Galinsoga parviflora. Their structures were assigned from the spectral data including IR, HR-EI-MS, 1D and 2D NMR.     

The tryptophan derivative 6-formylindolo[3,2-b]carbazole,FICZ, a dynamic mediator of endogenous aryl hydrocarbon receptor signaling,balances cell growth and differentiation

Abstract

The aryl hydrocarbon receptor (AHR) is not essential to survival, but does act as a key regulator of many normal physiological events. The role of this receptor in toxicological processes has been studied extensively, primarily employing the high-affinity ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). However, regulation of physiological responses by endogenous AHR ligands remains to be elucidated. Here, we review developments in this field, with a focus on 6-formylindolo[3,2-b]carbazole (FICZ), the endogenous ligand with the highest affinity to the receptor reported to date. The binding of FICZ to different isoforms of the AHR seems to be evolutionarily well conserved and there is a feedback loop that controls AHR activity through metabolic degradation of FICZ via the highly inducible cytochrome P450 1A1. Several investigations provide strong evidence that FICZ plays a critical role in normal physiological processes and can ameliorate immune diseases with remarkable efficiency. Low levels of FICZ are pro-inflammatory, providing resistance to pathogenic bacteria, stimulating the anti-tumor functions, and promoting the differentiation of cancer cells by repressing genes in cancer stem cells. In contrast, at high concentrations FICZ behaves in a manner similar to TCDD, exhibiting toxicity toward fish and bird embryos, immune suppression, and activation of cancer progression. The findings are indicative of a dual role for endogenously activated AHR in barrier tissues, aiding clearance of infections and suppressing immunity to terminate a vicious cycle that might otherwise lead to disease. There is not much support for the AHR ligand-specific immune responses proposed, the differences between FICZ and TCDD in this context appear to be explained by the rapid metabolism of FICZ.     

对《中国药典》2010年版附录芳香第一胺类鉴别试验方法的改进

目的:改进《中国药典》2010年版附录芳香第一胺鉴别试验方法,避免假阳性结果。方法:在滴加碱性β-萘酚试液前加入脲溶液中和多余的亚硝酸,避免多余的亚硝酸与β-萘酚反应生成猩红色的1-亚硝基-2-萘酚而干扰鉴别试验现象的观察。结果:脲溶液可以有效中和反应过程中多余的亚硝酸,使反应后的溶液颜色不再干扰沉淀颜色的辨识。结论:本方法可以避免鉴别试验出现假阳性结果。