Estrogenic and AhR activities in dissolved phase and suspended solids from wastewater treatment plants.
ABSTRACT The distribution of estrogen receptor (ERalpha) and Aryl Hydrocarbon Receptor (AhR) activities between the dissolved phase and suspended solids were investigated during wastewater treatment. Three wastewater treatment plants with different treatment technologies (waste stabilization ponds (WSPs), trickling filters (TFs) and activated sludge supplemented with a biofilter system (ASB)) were sampled. Estrogenic and AhR activities were detected in both phases in influents and effluents. Estrogenic and AhR activities in wastewater influents ranged from 41.8 to 79 ng/L E(2) Eq. and from 37.9 to 115.5 ng/L TCDD Eq. in the dissolved phase and from 5.5 to 88.6 ng/g E(2) Eq. and from 15 to 700 ng/g TCDD Eq. in the suspended solids. For both activities, WSP showed greater or similar removal efficiency than ASB and both were much more efficient than TF which had the lowest removal efficiency. Moreover, our data indicate that the efficiency of removal of ER and AhR activities from the suspended solid phase was mainly due to removal of suspended solids. Indeed, ER and AhR activities were detected in the effluent suspended solid phase indicating that suspended solids, which are usually not considered in these types of studies, contribute to environmental contamination by endocrine disrupting compounds and should therefore be routinely assessed for a better estimation of the ER and AhR activities released in the environment.
Article: Ivermectin induces P-glycoprotein expression and function through mRNA stabilization in murine hepatocyte cell line.[show abstract] [hide abstract]
ABSTRACT: Ivermectin is widely used in human and veterinary medicine for the control of helminth infections. Ivermectin is known to interact with P-glycoprotein (P-gp/MDR1), being a good substrate and a potent inhibitor, however, the influence of ivermectin on the expression of the transporter has not been investigated. Expression of P-glycoprotein was investigated in cultured mouse hepatocytes acutely exposed to ivermectin. The two P-glycoprotein murine isoforms, Mdr1a and Mdr1b, mRNA levels were assessed by real-time RT-PCR. Ivermectin induced a clear time- and concentration-dependent up-regulation of Mdr1a and Mdr1b mRNA levels (as early as a 12-h exposure and up to 2.5-fold at 10μM). Moreover, ivermectin-treated cells displayed enhanced cellular efflux of the P-glycoprotein substrate calcein that was inhibited by the P-glycoprotein blocker valspodar, providing evidence that the ivermectin-induced P-glycoprotein was functional. The mechanisms underlying these effects were investigated. Ivermectin-mediated Mdr1 mRNA induction was independent of the two nuclear receptors CAR and PXR, which are known to be involved in drug transporters regulation. Moreover, by using reporter cell lines that detects specific ligand-activated transcription factors, we showed that ivermectin did not displayed CAR, PXR or AhR ligand activities. However, studies with actinomycin D revealed that the half-life of Mdr1a and Mdr1b mRNA were significantly prolonged by two-fold in ivermectin-treated cells suggesting a post-transcriptional mode of ivermectin regulation. This study demonstrates for the first time that ivermectin induces P-glycoprotein overexpression through post-transcriptional mRNA stabilization, thus offering insight into the mechanism of reduced therapeutic efficacy and development of ivermectin-resistant parasites.Biochemical pharmacology 01/2012; 83(2):269-78. · 4.25 Impact Factor