Estrogenicity and androgenicity screening of PCB sulfate monoesters in human breast cancer MCF-7 cells

Abstract

Recent studies identified PCB sulfate esters as a major product of PCB metabolism. Since hydroxy-PCBs (HO-PCBs), the immediate precursors of PCB sulfates and important contributors to PCB toxicity, were shown to have estrogenic activity, we investigated the estrogenicity/androgenicty of a series of PCB sulfate metabolites. We synthesized the five possible structural sulfate monoester metabolites of PCB 3, a congener shown to be biotransformed to sulfates, a sulfate ester of the paint-specific congener PCB 11, and sulfate monoesters of two HO-PCBs reported to interact with sulfotransferases (PCB 39, no ortho chlorines, and PCB 53, 3 ortho chlorines). We tested these PCB sulfates and 4’-HO-PCB 3 as positive control for estrogenic, androgenic, anti-estrogenic and anti-androgenic activity in the E- and A-screen with human breast cancer MCF7 derived cells at 100 μM – 1 pM concentrations. Only 4’-HO-PCB 3 was highly cytotoxic at 100 μM. We observed structure-activity relationships: compounds with a sulfate group in the chlorine-containing ring of PCB 3 (2PCB 3 and 3PCB 3 sulfate) showed no interaction with the estrogen (ER) and androgen (AR) receptor. The 4’-HO-PCB 3 and its sulfate ester had the highest estrogenic effect, but at 100 fold different concentrations, i.e. 1 μM and 100 μM, respectively. Four of the PCB sulfates were estrogenic (2’PCB 3, 4’PCB 3, 4PCB 39, 4PCB 53 sulfates; at 100 μM). These sulfates and 3’PCB 3 sulfate also exhibited anti-estrogenic activity, but at nM and pM concentrations. The 4’PCB 3 sulfate (para-para’ substituted) had the strongest androgenic activity, followed by 3’PCB 3, 4PCB 53, 4PCB11, and 4PCB 39 sulfates and the 4’HO-PCB 3. In contrast, anti-androgenicity was only observed with the two compounds that have the sulfate group in ortho- or meta- position in the second ring (2’PCB 3 and 3’PCB 3 sulfate). No dose-response was observed in any screen, but, with exception of estrogenic activity (only seen at 100 μM), endocrine activity was often displayed at several concentrations and even at 1 pM concentration. These data suggest that sulfation of HO-PCBs is indeed reducing their cytotoxicity and estrogenicity, but may produce other endocrine disruptive activities at very low concentrations.

Hundreds of Unrecognized Halogenated Contaminants Discovered in Polar Bear Serum

“…Forc lasses showing increasing trends,all individual homologs within the class were tested and had similar increasing trends ( Figure 5) and comparable doubling times ( Figure S17). [21] Considering regulatory restrictions and controls implemented for the past 1-2 decades,t he detected stable PCB metabolite trends and increasing PFSAs for the past 3d ecades in polar bears are worth further study.T he presence of these substances in blood means they could disrupt normal physiology,a sr elated OH-PCBs, [22] PFSAs [23] and 4-OH-HpCS [17] bind to serum proteins and can thereby disrupt hormone homeostasis.SO 4 -PCBs bind to estrogen and androgen receptors, [24] and the new chlorinated aromatics (Class 3.1-3.4) may be bioactivated to reactive intermediates (e.g. As shown for most classes of substances discovered, the method benefited tremendously from HPLC to separate isomeric homologs or congeners prior to mass spectral characterization.…”

“…Thecontamination of top predator polar bears suggests exposure to the same contaminants in the underlying marine foodweb,a nd the mouse study provides evidence that other mammals,i ncluding people,m ay be exposed to the 5novel classes of PCB metabolites.The novel PCB metabolites described here may have been missed in previous studies of serum due to ah istoric reliance on GCbased techniques that require silica gel clean-up steps, derivatization, and use of strong acids or bases for sample preparation. [21] Considering regulatory restrictions and controls implemented for the past 1-2 decades,t he detected stable PCB metabolite trends and increasing PFSAs for the past 3d ecades in polar bears are worth further study.T he presence of these substances in blood means they could disrupt normal physiology,a sr elated OH-PCBs, [22] PFSAs [23] and 4-OH-HpCS [17] bind to serum proteins and can thereby disrupt hormone homeostasis.SO 4 -PCBs bind to estrogen and androgen receptors, [24] and the new chlorinated aromatics (Class 3.1-3.4) may be bioactivated to reactive intermediates (e.g. epoxides), just as PCBs.…”

Thyroid-disrupting chemicals and brain development: an update

“…On the other hand, one PCB metabolite (PCB104) exhibits both, AR antagonistic and ER agonist properties ( 315 ). PCBs may also induce estrogenicity indirectly through inhibition of the estrogen sulfotransferase ( 316 ).…”

The potential disruption of estrogen and androgen homeostasis and adipocyte differentiation by metabolites of common airborne polychlorinated biphenyls

“…OH-PCBs interfere with the thyroid hormone system and estrogen and androgen sulfotransferases [60][61][62]. OH-PCBs are known to be cytotoxic, suppress thyroid hormone receptor and have estrogenic activity; their sulfation to PCB-sulfates reduced their activity as estrogen receptors [63,64]. There is a correlation between PCB 11, and its metabolite 4-OH-PCB 11, and mitochondrial oxidative stress [52].…”

“…Research on human breast cancer MCF-7 cells has indicated that high concentrations of 2'-PCB 3, 4'-PCB 3, 4'-PCB 39, and 4'-PCB 53 sulfates resulted in estrogenic effects, and 4'-PCB 3, 3'-PCB 3, 4'-PCB 53, 4-PCB11, and 4-PCB 39 sulfates and the 4'-OH-PCB 3 had androgenic effects [209]. PCB sulfates have also proved to be ligands of human transthyretin and could influence thyroid hormone homeostasis [36].…”