Molecular interaction of PCB180 to human serum albumin: insights from spectroscopic and molecular modelling studies

Levels, tissue distribution and isomer stereoselectivity of Dechlorane Plus in humans: A critical review

Exposure of human tissues to Dechlorane Plus (DP) has raised public concern because of the multiple health threats it may pose to humans. Therefore, it is important to summarize the main findings of previous studies on DP in human tissues and to provide potential guidance for future studies. In this paper, DP levels in different populations and human tissues worldwide since 2009 were systematically reviewed. DP levels in human tissues of workers in e-waste dismantling sites in Guangdong Province, China (median 190 ng·g-1 lw in serum) and DP manufacturing plants in Jiangsu Province, China (mean 857 ng·g-1 lw in whole-blood) are the highest reported worldwide. DP levels in tissues of the general population in recent studies are close to those of residents near e-waste dismantling sites, which should be of concern. DP levels in different human tissues were found to be positively correlated with a pattern of blood > breast milk > adipose tissue. The distribution of DP in different human tissues is mainly lipid-driven and may also be influenced by the interaction of DP with proteins such as human serum albumin. Most of the past studies determined the isomer stereoselectivity of DP in human tissues only by comparing the composition of DP in commercial DP products and human tissues, which lacks evidence of mechanism. Recently, a significantly different affinity of DP isomers for proteins was found, which seems to confirm the isomer selectivity of DP in human tissues. We simulated the binding of DP to human serum albumin and DP to thyroid hormone receptor β by molecular docking and found differences in the binding behavior of syn-DP and anti-DP to the selected proteins. Molecular docking seems to be a feasible approach for future studies to predict and reveal the mechanisms of DP behavior and health effects in human tissues.

Sulfation of Lower Chlorinated Polychlorinated Biphenyls Increases Their Affinity for the Major Drug-Binding Sites of Human Serum Albumin

The disposition of toxicants is often affected by their binding to serum proteins, of which the most abundant in humans is serum albumin (HSA). There is increasing interest in the toxicities of environmentally persistent polychlorinated biphenyls (PCBs) with lower numbers of chlorine atoms (LC-PCBs) due to their presence in both indoor and outdoor air. PCB sulfates derived from metabolic hydroxylation and sulfation of LC-PCBs have been implicated in endocrine disruption due to high affinity-binding to the thyroxine-carrying protein, transthyretin. Interactions of these sulfated metabolites of LC-PCBs with HSA, however, have not been previously explored. We have now determined the relative HSA-binding affinities for a group of LC-PCBs and their hydroxylated and sulfated derivatives by selective displacement of the fluorescent probes 5-dimethylamino-1-naphthalenesulfonamide and dansyl-l-proline from the two major drug-binding sites on HSA (previously designated as Site I and Site II). Values for half-maximal displacement of the probes indicated that the relative binding affinities were generally PCB sulfate ≥ OH-PCB > PCB, although this affinity was site- and congener-selective. Moreover, specificity for Site II increased as the numbers of chlorine atoms increased. Thus, hydroxylation and sulfation of LC-PCBs result in selective interactions with HSA which may affect their overall retention and toxicity.

Modeling techniques and fluorescence imaging investigation of the interactions of an anthraquinone derivative with HSA and ctDNA

A new anthraquinone derivative (AORha) was synthesized. Its interactions with human serum albumin (HSA) and calf thymus DNA (ctDNA) were investigated by fluorescence spectroscopy, UV-visible absorption spectroscopy and molecular modeling. Cell viability assay and cell imaging experiment were performed using cervical cancer cells (HepG2 cells). The fluorescence results revealed that the quenching mechanism was static quenching. At different temperatures (290, 300, 310 K), the binding constants (K) and the number of binding sites (n) were determined, respectively. The positive ΔH and ΔS values showed that the binding of AORha with HSA was hydrophobic force, which was identical with the molecular docking result. Studying the fluorescence spectra, UV spectra and molecular modeling also verified that the binding mode of AORha and ctDNA might be intercalative. When HepG2 cells were treated with AORha, the fluorescence became brighter and turned green, which could be used for bioimaging.