Detection and profiling of diarrheic marine biotoxins in shellfish by mRNA analysis of exposed Caco-2 cells using qRT-PCR and multiplex magnetic bead-based assays

The mouse bioassay for the detection of marine biotoxins in shellfish products is 40 years old and still in use. A full ban or total replacement of this in vivo test has been postponed because of the fear that current chemical-based detection methods could miss a new emerging toxin. In order to fully replace the mouse bioassay, more efforts are needed in the search for functional assays with specific endpoints. Gene expression elicited by diarrheic shellfish poisons (DSP) in Caco-2 cells allowed us to determine three “DSP profiles”, i.e., OA/DTX, AZA-YTX, and PTX profiles. Twelve marker genes were selected to represent the three profiles. qRT-PCR is relatively cheap and easy, and although its multiplex capacity is limited to 5 genes, this was sufficient to show the three expected profiles. The use of the multiplex magnetic bead-based assay was an even better alternative, allowing the detection of all 12 selected marker genes and 2 reference genes, and resulting in clear profiles with for some genes even higher induction factors than obtained by qRT-PCR. When analyzing blank and contaminated shellfish samples with the multiplex magnetic bead-based assay, the contaminated samples could easily be distinguished from the blank samples, and showed the expected profiles. This work is one step further towards the final replacement of the mouse bioassay. We suggest to combine the neuro-2a bioassay for screening with detection by analytical chemical analyses and with the multiplex magnetic bead-based assay for confirmation of known and unknown toxins.</p

PDE-5 inhibitors in selected herbal supplements from the Ghanaian market for better erectile function as tested by a bioassay

Herbal supplements sold as ‘all natural’ on various markets in Accra (Ghana) and advertised as highly efficacious in treating erectile dysfunction (ED) were bought and analysed by a PDE-5 enzyme inhibition assay. The claimed efficacy of these products could be the result of inherent plant constituents, but also of intentionally added pharmaceuticals. Medically, ED is treated with potent inhibitors of the phosphodiesterase-5 (PDE-5) enzyme, as in the case of sildenafil. To test the efficacy of the Ghanaian supplements, extracts were made and tested using a PDE-Glo phosphodiesterase assay, a luminescent high-throughput screening (HTS) method. Results revealed that about 90% of the selected samples were able to inhibit PDE-5 activity to a high extent. Estimated concentrations in sildenafil equivalents ranged from traces to very high, with 25 samples (62.5%) pointing at daily doses higher than 25 mg sildenafil equivalents and 9 (22.5%) of these at doses higher than the maximal recommended daily intake of 100 mg sildenafil equivalents. Further investigations are needed to confirm if the observed effects are due to inherent plant constituents or merely the result of added synthetic PDE-5 enzyme inhibitors, especially because doses above 100 mg sildenafil equivalents per day may result in severe health risks.</p

Acid condensation products of indole-3-carbinol and their in-vitro (anti)estrogenic, (anti)androgenic and aryl hydrocarbon receptor activities

The objective of the study was to investigate the (anti)estrogenic, (anti)androgenic and aryl hydrocarbon receptor (AhR) agonistic activities of a mixture of acid condensation products of indole-3-carbinol, termed RXM, and to identify the compounds most responsible for the observed effects, using in vitro receptor-reporter gene transcriptional activation bioassays. For this, HPLC-fractions of RXM were prepared and tested. LC-MS/MS analysis was carried out for the identification of some of the acid condensation products. The RXM displayed weak estrogenic and anti-androgenic, and strong AhR agonistic properties. The fraction containing 3,3-diindolylmethane (DIM) displayed a weak estrogenic and relatively strong anti-androgenic activity. DIM was confirmed to be an androgen receptor (hAR) antagonist and a partial estrogen receptor (hERα) agonist. Also the fraction containing the trimer [2-(indol-3-ylmethyl)indol-3-yl]indol-3-ylmethane (LTr1) showed anti-androgenic activities. It was shown for the first time that DIM is not only estrogenic and anti-androgenic, but also possesses anti-estrogenic properties. Though indolo[3,2-b]carbazole (ICZ) is a potent AhR activator and was detected in the RXM, it did not contribute to AhR-agonist activity. Instead, fractions containing the trimers LTr1 and 5,6,11,12,17,18-hexahydrocyclonona[1,2-b:4,5-b′:7,8-b″]tri-indole (CTr), as well as some unidentified compounds showed the highest AhR activation. The fraction, containing the linear trimer LTr1, showed a weak anti-androgenic activity which has not been reported before. The study demonstrates the importance of a bioassay directed approach for identifying compounds that contribute most to the effects of mixtures.</p

Impurities in technical mixtures of chlorinated paraffins show AhR agonist properties as determined by the DR-CALUX bioassay

Chlorinated paraffins (CPs) are produced at more than one million tons per year. Technical CPs mixtures may contain impurities, which end up in consumer products. In the present study, 17 technical CPs mixtures were investigated for the potential occurrence of potential impurities. By applying the DR-CALUX bioassay, 3 out of 17 technical mixtures were shown to elicit responses at 4 h exposure time, but much lower at 48 h. Constitutional defined CPs materials did not show responses. Subsequently different groups of known AhR-agonists and compounds suspected to be present in technical CPs mixtures were investigated. Benzene, (poly)chlorobenzene, non-dioxin like polychlorinated naphthalenes (PCNs), and three-ringed polyaromatic hydrocarbons (PAHs) did not result in a significant response at 4 h or 48 h. TCDD, non-ortho PCBs, dioxin-like PCNs, four or five ringed PAHs and their chlorinated analogues resulted in a significant response. TCDD and the non-ortho PCBs showed the highest potency and stability, while dioxin-like PCNs, PAHs, and the chlorinated PAHs were clearly inactivated (metabolized) at longer incubation. Altogether, the present findings substantiate that AhR-mediated responses of CPs technical mixtures in the DR-CALUX bioassay are caused by impurities, most likely some intermediate stable AhR-agonists such as dioxin-like PCNs or (chlorinated) PAHs. The current study shows that impurities in CPs technical mixtures need to be investigated for assessing the safety of technical CPs mixtures.</p

Presence and risks of polycyclic aromatic hydrocarbons, dioxins and dioxin-like PCBs in dietary plant supplements as elucidated by a combined DR CALUX® bioassay and GC-HRMS based approach

Plant-based dietary supplements may contain undesirable contaminants such as polycyclic aromatic hydrocarbons, dioxins and dioxin-like polychlorinated biphenyls (dl-PCBs) due to the sources of raw materials or processing methods used. The presence of these contaminants in a series of herbal supplements sold on the Ghanaian market for improving sexual performance was examined using the DR CALUX® bioassay in combination with GC-HRMS analysis. Overall, cell responses at 4 and 48 h exposure to extracts prepared without an acid-silica clean-up were relatively higher than the responses obtained from extracts prepared with an acid-silica clean-up. This indicated that the 40 supplements contained only low levels of stable aryl hydrocarbon receptor (AhR) agonists like polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dl-PCBs, while some contained substantial amounts of less stable AhR-agonists. Ten supplements selected for confirmation with GC-HRMS analysis contained PCDD/Fs and dl-PCBs at levels ranging from 0.01 to 0.19 pg toxic equivalent (TEQ)/g only, while the level of the sum of 4 polycyclic aromatic hydrocarbons (Σ4PAHs) representing less stable AhR agonists, ranged from not detected (ND) to 25.5 ng/g. These concentrations were in line with the responses observed in the DR CALUX® bioassay. The concentration of PCDD/Fs and dl-PCBs corresponded to estimated daily intakes (EDIs) ranging from 0.01 to 1.20 pg TEQ/day, or 0.001 to 0.12 pg TEQ/kg bw/week for a 70 kg bw consumer, which was below the established tolerable weekly intake (TWI) of 2 pg TEQ/kg bw/week, thus indicating low concern for consumers’ health. Similarly, the EDIs based on the detected Σ4PAHs in supplements ranged from 7.2 to 111 ng/day, or 0.1 to 1.6 ng/kg bw/day, which corresponded to MOE values above 10,000, indicating a low health concern

Microsphere Peptide-Based Immunoassay for the Detection of Recombinant Bovine Somatotropin in Injection Preparations

The use of peptides in immunoassays can be favored over the use of the full protein when more cost effective or less toxic approaches are needed, or when access to the full protein is lacking. Due to restricted access to recombinant bovine somatotropin (rbST), a protein enhancing growth and lactating performances of livestock, which use has been banned in the EU, Canada and Australia (amongst others), we developed a peptide-based biorecognition assay on an imaging planar array analyzer. For this, we identified the rbST epitope that is responsible for binding to the rbST-targeting monoclonal antibody 4H12 (MAb 4H12) to be115 DLEEGILALMR125 . This linear peptide was synthesized and coupled to microspheres, after which it was tested in a biorecognition competitive inhibition assay format. We observed IC50 values of approximately 0.11 µg mL−1, which are lower than observed for the full rbST protein (IC50 = 0.20 µg mL−1 ). Importantly, there was no binding with the scrambled peptide. Preliminary results of directly coupled peptides in a microsphere biorecognition assay for detection of rbST are presented. Real-life applicability for detection of somatotropins (STs) in injection preparations of bovine-, porcine-and equine ST are shown. This newly developed immunoassay strongly supports future developments of peptide-based immunoassays to circumvent the limited access to the full protein

Glyceollins and dehydroglyceollins isolated from soybean act as SERMs and ER subtype-selective phytoestrogens

Seven prenylated 6a-hydroxy-pterocapans and five prenylated 6a,11a-pterocarpenes with different kinds of prenylation were purified from an ethanolic extract of fungus-treated soybean sprouts. The activity of these compounds toward both human estrogen receptors (hERα and hERβ) was determined in a yeast bioassay and the activity toward hERα was additionally tested in an U2-OS based hERα CALUX bioassay. In the yeast bioassay, compounds with chain prenylation showed in general an agonistic mode of action toward hERα, whereas furan and pyran prenylation led to an antagonistic mode of action. Five of these antagonistic compounds had an agonistic mode of action in the U2-OS based hERα CALUX bioassay, implying that these compounds can act as SERMs. The yeast bioassay also identified 8 ER subtype-selective compounds, with either an antagonistic mode of action or no response toward hERα and an agonistic mode of action toward hERβ. The ER subtype-selective compounds were characterized by 6a-hydroxy-pterocarpan or 6a,11a-pterocarpene backbone structure. It is suggested that either the extra D-ring or the increase in length to 12-13.5 Å of these compounds is responsible for an agonistic mode of action toward hERβ and, thereby, inducing ER subtype-selective behavior.</p

Quantitative in vitro-to-in vivo extrapolation (QIVIVE) of estrogenic and anti-androgenic potencies of BPA and BADGE analogues

The goal of the present study was to obtain an in vivo relevant prioritization method for the endocrine potencies of different polycarbonate monomers, by combining in vitro bioassay data with physiologically based kinetic (PBK) modelling. PBK models were developed for a selection of monomers, including bisphenol A (BPA), two bisphenol F (BPF) isomers and four different bisphenol A diglycidyl ethers (BADGEs), using in vitro input data. With these models, the plasma concentrations of the compounds were simulated, providing means to estimate the dose levels at which the in vitro endocrine effect concentrations are reached. The results revealed that, whereas the in vitro relative potencies of different BADGEs (predominantly anti-androgenic effects) can be up to fourfold higher than BPA, the estimated in vivo potencies based on the oral equivalent doses are one to two orders of magnitude lower than BPA because of fast detoxification of the BADGEs. In contrast, the relative potencies of 2,2-BPF and 4,4-BPF increase when accounting for the in vivo availability. 4,4-BPF is estimated to be fivefold more potent than BPA in humans in vivo in inducing estrogenic effects and both 2,2-BPF and 4,4-BPF are estimated to be, respectively, 7 and 11-fold more potent in inducing anti-androgenic effects. These relative potencies were considered to be first-tier estimates, particularly given that the potential influence of intestinal metabolism on the in vivo availability was not accounted for. Overall, it can be concluded that both 2,2-BPF and 4,4-BPF are priority compounds

Marine biotoxins and associated outbreaks following seafood consumption : Prevention and surveillance in the 21st century

Marine biotoxins are mostly produced by phytoplankton. Proliferation of algae producing marine biotoxins, also known as harmful algal bloom (HAB), occurs worldwide. Such event depends on environmental conditions, including temperature, water pH/salinity, current patterns and anthropogenic nutrient input. Marine biotoxins can accumulate in seafood products and as such present a threat to consumers.This paper reviews and compiles up-to-date literature on reported human intoxications following exposure to marine biotoxins through seafood consumption. The review includes a discussion about prevention of such outbreaks and surveillance programs to identify possible limitations and approaches for limiting the impact of HABs on human health. It is concluded that marine biotoxins represent a threat to human health as thousands of poisonings following consumption of seafood contaminated with marine biotoxins were reported in the 21st century, emphasizing the need for carrying on/developing surveillance programs to detect the presence of HABs, and for development, validation and implementation of sensitive high-throughput methods for detecting these biotoxins in seafood to protect consumers. Regarding the possible presence of unknown toxins and general lack of standards for many known toxins, in vitro effect-based bioassays may play an important role in the monitoring for biotoxins

Whole genome mRNA transcriptomics analysis reveals different modes of action of the diarrheic shellfish poisons okadaic acid and dinophysis toxin-1 versus azaspiracid-1 in Caco-2 cells

A study with DNA microarrays was performed to investigate the effects of two diarrhetic and one azaspiracid shellfish poison, okadaic acid (OA), dinophysistoxin-1 (DTX-1) and azaspiracid-1 (AZA-1) respectively, on the whole-genome mRNA expression of undifferentiated intestinal Caco-2 cells. Previously, the most responding genes were used to develop a dedicated array tube test to screen shellfish samples on the presence of these toxins. In the present study the whole genome mRNA expression was analyzed in order to reveal modes of action and obtain hints on potential biomarkers suitable to be used in alternative bioassays. Effects on key genes in the most affected pathways and processes were confirmed by qPCR. OA and DTX-1 induced almost identical effects on mRNA expression, which strongly indicates that OA and DTX-1induce similar toxic effects. Biological interpretation of the microarray data indicates that both compounds induce hypoxia related pathways/processes, the unfolded protein response (UPR) and endoplasmic reticulum (ER) stress. The gene expression profile of AZA-1 is different and shows increased mRNA expression of genes involved in cholesterol synthesis and glycolysis, suggesting a different mode of action for this toxin. Future studies should reveal whether identified pathways provide suitable biomarkers for rapid detection of DSPs in shellfish.</p