A novel MDCKII in vitro model for assessing ABCG2-drug interactions and regulation of ABCG2 transport activity in the caprine mammary gland by environmental pollutants and pesticides

The ABC efflux transporter ABCG2 represents the main route for active secretion of xenobiotics into milk. Thus, ABCG2 regulation by aryl hydrocarbon receptor (AhR) ligands including ubiquitously environmental pollutants is of great toxicological relevance. However, no adequate in vitro model is as yet available to study AhR-dependent ABCG2 regulation in dairy animals. In this study, we therefore systematically investigated the effect of various environmental contaminants and pesticides on ABCG2 efflux activity in MDCKII cells stably expressing mammary ABCG2 from dairy goats. The AhR-agonists TCDD, Aroclor 1254, prochloraz, and iprodione caused a dose- and time-dependent increase in EROD activity. Moreover, TCDD and prochloraz significantly stimulated ABCG2 transport activity through a dose- and time-dependent induction of transporter gene expression. AhR inhibitors like CH 223191 significantly reversed TCDD- and prochloraz-induced stimulation of ABCG2 efflux activity. In contrast, non-AhR activators such as PCB 101 had no significant effect on EROD activity, ABCG2 gene expression or transporter activity. As we identified various anthelmintics including monepantel as potential ABCG2 substrates this regulatory mechanism may result in increased milk residues of potentially harmful xenobiotics. Thus, MDCKII-cABCG2 cells may represent a suitable in vitro model to study mammary ABCG2 secretory activity and its potential regulation by AhR-activating contaminants.     

Palmatine activates AhR and upregulates CYP1A activity in HepG2 cells but not in human hepatocytes

The protoberberine alkaloid palmatine is present in preparations from medicinal plants such as Coptis chinensis and Corydalis yanhusuo. This study examined whether palmatine affects the expression of cytochromes P450 (CYPs) 1A1 and 1A2 in primary cultures of human hepatocytes and human hepatoma HepG2 cells grown as monolayer or spheroids. Gene reporter assays showed that palmatine significantly activated the aryl hydrocarbon receptor (AhR) and increased the activity of CYP1A1 gene promoter in transiently transfected HepG2 cells. In HepG2 monolayer culture, palmatine also significantly increased mRNA and activity levels of CYP1A1, albeit with considerably less potency than 2,3,7,8-tetrachlorodibenzo-p-dioxin, a prototypical CYP1A inducer. On the other hand, CYP1A activity was not significantly elevated by palmatine in HepG2 spheroids. Moreover, palmatine induced mild or negligible changes in CYP1A1 and CYP1A2 mRNA expression without affecting CYP1A activity levels in primary human hepatocytes. It is concluded that palmatine activates the AhR-CYP1A pathway in HepG2 monolayer, while the potential for CYP1A induction is irrelevant in cell systems which are closer to the in vivo situation, i.e. in HepG2 spheroids and primary cultures of human hepatocytes. Possible induction of CYP1A enzymes by palmatine in vivo remains to be investigated.     

Interactions between polymorphisms in the aryl hydrocarbon receptor signalling pathway and exposure to persistent organochlorine pollutants affect human semen quality

Persistent organic pollutants (POPs) may affect male reproductive function. Many dioxin-like POPs exert their effects by activation of the aryl hydrocarbon receptor (AHR) signalling pathway. We analysed whether gene–environment interactions between polymorphisms in AHR (R554K) and AHR repressor (AHRR P185A) and serum levels of markers of POP exposure 1,1-bis-(4-chlorophenyl)-2,2-dichloroethene (p,p′-DDE) and 2,2′,4,4′,5,5′-hexachlorobiphenyl (CB-153) are associated with 21 parameters of male reproductive function in 581 proven-fertile European and Greenlandic men. In Greenlandic men, AHR variants significantly modified the association between serum levels of both p,p′-DDE and CB-153 and inhibin B levels, sperm chromatin integrity, and seminal zinc levels. In the total cohort, interactions between AHRR variants and serum levels of CB-153 were associated with sperm chromatin integrity and the expression of the pro-apoptotic marker protein Fas. The data indicate that susceptibility to adverse effects of POP exposure on male reproductive function is dependent on polymorphisms in genes involved in AHR signalling.     

VitD在降低PM2.5对肺泡上皮细胞毒性中的影响分析

目的分析维生素D(vitamin D, VitD)在降低PM_2.5对肺泡上皮细胞毒性中的影响。 方法采用透射电子显微镜和激光诱导荧光分析对比VitD处理前后,PM_2.5的毒性能力。MMT观察VitD处理前后细胞生存率,分析PM_2.5对A549的毒性影响。 结果VitD作用后的PM_2.5平均粒径减小5.5 nm,颗粒聚结和团聚更为明显,颗粒平均条纹长度增加、弯曲度减小,差异有统计学意义。PM_2.5条纹间距无统计学差异,有明显减小,接近0.06 nm。VitD溶液从PM_2.5解吸3环和4环多环芳香烃(polycyclic aromatic hydrocarbons, PAHs),减少PM_2.5表面附着的致病性PAHs。PM_2.5可引起肺上皮细胞A549生存率明显下降,给予VitD干预后,PM_2.5对A549细胞生存率的抑制改善了54.7%,PM_2.5的生物毒性降低。 结论VitD可减少PM_2.5上吸附的致病性PAHs,抑制其致病活性,减小PM_2.5对肺上皮细胞的毒性。     

Risk of leukemia in relation to exposure to ambient air toxics in pregnancy and early childhood

There are few established causes of leukemia, the most common type of cancer in children. Studies in adults suggest a role for specific environmental agents, but little is known about any effect from exposures in pregnancy to toxics in ambient air. In our case–control study, we ascertained 69 cases of acute lymphoblastic leukemia (ALL) and 46 cases of acute myeloid leukemia (AML) from California Cancer Registry records of children <age 6, and 19,209 controls from California birth records within 2 km (1.3 miles) (ALL) and 6 km (3.8 miles) (AML) of an air toxics monitoring station between 1990 and 2007. Information on air toxics exposures was taken from community air monitors. We used logistic regression to estimate the risk of leukemia associated with one interquartile range increase in air toxic exposure. Risk of ALL was elevated with 3^rd trimester exposure to polycyclic aromatic hydrocarbons (OR = 1.16, 95% CI 1.04, 1.29), arsenic (OR = 1.33, 95% CI 1.02, 1.73), benzene (OR = 1.50, 95% CI 1.08, 2.09), and three other toxics related to fuel combustion. Risk of AML was increased with 3rd trimester exposure to chloroform (OR = 1.30, 95% CI 1.00, 1.69), benzene (1.75, 95% CI 1.04, 2.93), and two other traffic-related toxics. During the child's first year, exposure to butadiene, ortho-xylene, and toluene increased risk for AML and exposure to selenium increased risk for ALL. Benzene is an established cause of leukemia in adults; this study supports that ambient exposures to this and other chemicals in pregnancy and early life may also increase leukemia risk in children.     

Aryl hydrocarbon receptor signaling,toxicity, and gene expression responses to mono‐methylchrysenes

Polycyclic aromatic hydrocarbons (PAHs) comprise a large family of toxic compounds that come from natural and anthropogenic sources. Chrysene is a PAH with multiple effects, but the toxic potentials of mono‐methylchrysenes are less characterized. A comparison of chrysene and six mono‐methylchrysenes was performed using assays for cytotoxicity, human aryl hydrocarbon receptor (AhR) reporter gene signaling, and AhR‐regulated target gene and protein expression. Sulforhodamine B and trypan blue dye binding assays revealed these chrysenes to be similar in their cytotoxic effects on HepG2 cells. A yeast‐based reporter assay detecting human AhR‐mediated gene expression identified 4‐methylchrysene as being six times more potent and 5‐methylchrysene about one‐third as potent as chrysene. Other methylchrysenes were more similar to chrysene in the ability to act as AhR ligands. The mono‐methylchrysenes all strongly induced CYP1A1 mRNA and protein and moderately induced CYP1B1 expression in HepG2 cells. Levels of CYP1A2 mRNA were induced at higher concentrations of the chrysenes, but protein expression was not significantly altered. The PCR‐based gene expression and immunoblotting analyses indicated induced expression differences across the chrysene members were similar to each other. Overall, the effects of methylated chrysenes were comparable to unsubstituted chrysene, suggesting members of this group may be considered approximately equivalent in their effects. © 2019 Wiley Periodicals, Inc.     

Improvement in Mechanical and Thermal Properties of Transparent Semi‐Aromatic Polyimide by Crosslinking

Both the formation of insoluble salt for aliphatic diamines and the poor reactivity for aliphatic dianhydrides result in semi‐aromatic polyimide (SAPI) with low molecular weight and, thereby, in highly brittle SAPI films in nature. To solve the above problems, a cyclic‐olefin copolymer synthesized from norbornene and maleic anhydride is used as the third monomer (crosslinking agent) to prepare the crosslinked SAPI (cSAPI) films. The relative viscosity of the precursor solution of cSAPI is increased with the loading of cyclic‐olefin copolymer, giving rise to the improvement in mechanical and thermal properties of cSAPI films. The tensile modulus, tensile strength, and elongation at break of cSAPI film with 5 wt% cyclic‐olefin copolymer are increased to 4.49 GPa, 137 MPa, and 14.9% from 3.57 GPa, 111 MPa, and 7.6%, respectively, compared to those of the baseline SAPI film. Meanwhile, the glass transition temperature of cSAPI films is increased to 282 from 270 °C of the SAPI film, which is advantageous to better meet the requirement for high‐temperature manufacturing processes such as lead‐free solder reflowing. In addition, all cSAPI films exhibit good optical transparency in the entire visible region.     

Chemical state of heterocyclic aromatic amines in grilled beef: Evaluation by in vitro digestion model and comparison of alkaline hydrolysis and organic solvent for extraction

During grilling of the roast beef the following heterocyclic aromatic amines were found: IQ = 200.6 ng 100 g⁻¹, MeIQx = 719.8 ng 100 g⁻¹, MeIQ = 532.9 ng 100 g⁻¹, 4.8-diMeIQx = 755.4 ng 100 g⁻¹, norharmane = 507.0 ng 100 g⁻¹, harmane = 1952.6 ng 100 g⁻¹, Phe-P 1 = 263.7 ng 100 g⁻¹, Trp-P 2 = 559.2 ng 100 g⁻¹, PhIP = 1179.8 ng 100 g⁻¹ and AαC = 51.7 ng 100 g⁻¹. Their content was tested by using the method based on alkaline hydrolysis of the sample and the method based on solvent extraction of the grilled meat samples at different temperatures (without hydrolysis). The study showed that the heterocyclic aromatic amines produced during the grilling of beef are in a free form and chemically or physico-chemically bonded. The chemical forms of HAA formed in food have never been studied. For the purpose of the partial confirmation that HAA may be chemically or physico-chemically bonded, grilled beef samples were digested in vitro in model segments of the human digestive tract. Digestive enzymes, particularly proteolytic enzymes caused a statistically significant increase of free HAA determined by using solvent extraction without prior chemical hydrolysis of the sample.