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Identification of P-glycoprotein (P-gp, Abcb1) inhibitors in contaminated freshwater sediments

P-glycoprotein (P-gp, ABCB1) is an important part of the multixenobiotic resistance (MXR) defense system in aquatic organisms. The main goal of this study was identification of P-gp inhibitors in contaminated sediments using the effect-directed analysis (EDA) approach. After complex array of fractionations, chemical and biological analysis, we have identified novel fish Pgp inhibitors that include nonionic surfactants, including alcohol polyethoxylates (LAEOs) and polypropylene glycols (PPGs). These detergents can modulate toxicity of other xenobiotics present in complex environmental samples with the potential to cause adverse effects in fish.

Identification of P-glycoprotein (P-gp, Abcb1) inhibitors in contaminated freshwater sediments

EDA approach to identify novel Pgp inhibitors

P-glycoprotein (P-gp, ABCB1) is an important part of the multixenobiotic resistance (MXR) defense system in aquatic organisms. The main goal of this study was identification of P-gp inhibitors in contaminated sediments using the effect-directed analysis (EDA) approach. The samples were collected from the Gorjak creek (Zagreb, Croatia), a recipient of wastewater effluents from the pharmaceutical industry. Sediment samples were extracted and fractionated using two-tiered approach. Resulting non-polar, medium polar and polar fractions were tested on the inhibition of P-gp activity using P-gp overexpressing PLHC-1/dox cells and calcein-AM as model substrate. The obtained EC50 values - up to 757 μg/g, expressed in toxicity equivalents of model P-gp inhibitor cyclosporine A - revealed high inhibitory potential of polar fractions of investigated sediments and clearly reflected the impact of pharmaceutical wastewater. P-gp specific ATPase assay and the cytotoxicity modulation experiments with colchicine indicated that most of the observed P-gp inhibition was due to the presence of non-competitive inhibitors. A detailed chemical analysis by ultrahigh-performance liquid chromatography-quadrupole/time-of-flight mass spectrometry (UPLC-QToFMS) revealed nonionic surfactants, including alcohol polyethoxylates (LAEOs) and polypropylene glycols (PPGs), as the major components of the most active sub-fractions. Testing of several LAEO and PPG commercial mixtures confirmed their potential to inhibit the fish P-glycoprotein and modulate toxicity of other xenobiotics present in complex environmental samples.

Division for Marine and Environmental Research

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