The Alginate Immobilization of Metabolic Enzymes Platform Retrofits an Estrogen Receptor Transactivation Assay With Metabolic Competence

The U.S. EPA Endocrine Disruptor Screening Program utilizes data across the ToxCast/Tox21 high-throughput screening (HTS) programs to evaluate the biological effects of potential endocrine active substances. A potential limitation to the use of in vitro assay data in regulatory decision-making is the lack of coverage for xenobiotic metabolic processes. Both hepatic- and peripheral-tissue metabolism can yield metabolites that exhibit greater activity than the parent compound (bioactivation) or are inactive (bioinactivation) for a given biological target. Interpretation of biological effect data for both putative endocrine active substances, as well as other chemicals, screened in HTS assays may benefit from the addition of xenobiotic metabolic capabilities to decrease the uncertainty in predicting potential hazards to human health. The objective of this study was to develop an approach to retrofit existing HTS assays with hepatic metabolism. The Alginate Immobilization of Metabolic Enzymes (AIME) platform encapsulates hepatic S9 fractions in alginate microspheres attached to 96-well peg lids. Functional characterization across a panel of reference substrates for phase I cytochrome P450 enzymes revealed substrate depletion with expected metabolite accumulation. Performance of the AIME method in the VM7Luc estrogen receptor transactivation assay was evaluated across 15 reference chemicals and 48 test chemicals that yield metabolites previously identified as estrogen receptor active or inactive. The results demonstrate the utility of applying the AIME method for identification of false-positive and false-negative target assay effects, reprioritization of hazard based on metabolism-dependent bioactivity, and enhanced in vivo concordance with the rodent uterotrophic bioassay. Integration of the AIME metabolism method may prove useful for future biochemical and cell-based HTS applications.

Monoassociation with bacterial isolates reveals the role of colonization, community complexity and abundance on locomotor behavior in larval zebrafish

Background

Across taxa, animals with depleted intestinal microbiomes show disrupted behavioral phenotypes. Axenic (i.e., microbe-free) mice, zebrafish, and fruit flies exhibit increased locomotor behavior, or hyperactivity. The mechanism through which bacteria interact with host cells to trigger normal neurobehavioral development in larval zebrafish is not well understood. Here, we monoassociated zebrafish with either one of six different zebrafish-associated bacteria, mixtures of these host-associates, or with an environmental bacterial isolate.

Results

As predicted, the axenic cohort was hyperactive. Monoassociation with three different host-associated bacterial species, as well as with the mixtures, resulted in control-like locomotor behavior. Monoassociation with one host-associate and the environmental isolate resulted in the hyperactive phenotype characteristic of axenic larvae, while monoassociation with two other host-associated bacteria partially blocked this phenotype. Furthermore, we found an inverse relationship between the total concentration of bacteria per larvae and locomotor behavior. Lastly, in the axenic and associated cohorts, but not in the larvae with complex communities, we detected unexpected bacteria, some of which may be present as facultative predators.

Conclusions

These data support a growing body of evidence that individual species of bacteria can have different effects on host behavior, potentially related to their success at intestinal colonization. Specific to the zebrafish model, our results suggest that differences in the composition of microbes in fish facilities could affect the results of behavioral assays within pharmacological and toxicological studies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s42523-020-00069-x.

0157 The Relationship Between Reaction Time, Insomnia Severity, Sleepiness, and Dysfunctional Beliefs About Sleep

Introduction

Poor sleep quality has adverse effects ranging from decreased focus to increased work-related injuries. The Perceptual Vigilance Task (PVT), a measure of reaction time (RT) used to assess alertness is commonly used in sleep research. This study focuses on the relationship between dysfunctional sleep-related cognitions (Dysfunctional Beliefs and Attitudes About Sleep Scale [DBAS]), insomnia severity (Insomnia Severity Index [ISI]), and sleepiness (Epworth Sleepiness Scale [ESS]) and their association to PVT RT.

Methods

162 participants were recruited from East Carolina University. Inclusion criteria: right-handed adults; exclusion criteria: history of brain injury, seizure disorder, or vision impairment. Age range 18–39 (M = 20.15; SD = 3.01); 81 (49.1%) females.

Results

ISI was correlated with PVT RT for inter-stimulus interval delay times of 1000ms r(162) = .155, p =.05, 2000ms r(162) = .204, p = .009, 5000ms r(162) =.164, p = .04, and 6000ms r(162) = .181, p = .02. DBAS was correlated with PVT RT for delay times of 2000ms r(162) = .204, p =.021, 3000ms r(162) = .160, p = .04, 4000ms r(162) = .170, p = .03, 6000ms r(162) = .171, p = .030, 7000ms r(162) = .219, p =.005, and 8000ms r(162) = .158 p = .045. ESS was not correlated with PVT. A regression was calculated to predict reaction time at 7000ms delay based on the DBAS (F(1,151) = 2.51, p = .01), with an R2 of .12.

Conclusion

There is a diminishing association found between insomnia severity and RT during inter-stimulus delay times (>6000ms). Dysfunctional beliefs about sleep correlate with RT through 8000ms delay, eventually predicting RT. Regardless of severity of sleep disturbance, sleep-related bias may affect subjective feelings of wakefulness and objective levels of alertness (e.g., one who believes they are not obtaining sufficient sleep may act accordingly).

Support

N/A

Triclosan-Selected Host-Associated Microbiota Perform Xenobiotic Biotransformations in Larval Zebrafish

Microbiota regulate important physiologic processes during early host development. They also biotransform xenobiotics and serve as key intermediaries for chemical exposure. Antimicrobial agents in the environment may disrupt these complex interactions and alter key metabolic functions provided by host-associated microbiota. To examine the role of microbiota in xenobiotic metabolism, we exposed zebrafish larvae to the antimicrobial agent triclosan. Conventionally colonized (CC), microbe-free axenic (AX), or axenic colonized on day 1 (AC1) zebrafish were exposed to 0.16-0.30 µM triclosan or vehicle on days 1, 6, 7, 8, and 9 days post fertilization (dpf). After 6 and 10 dpf, host-associated microbial community structure and putative function were assessed by 16S rRNA gene sequencing. At 10 dpf, triclosan exposure selected for bacterial taxa, including Rheinheimera. Triclosan-selected microbes were predicted to be enriched in pathways related to mechanisms of antibiotic resistance, sulfonation, oxidative stress, and drug metabolism. Furthermore, at 10 dpf, colonized zebrafish contained 2.5-3 times more triclosan relative to AX larvae. Nontargeted chemical analysis revealed that, relative to AX larvae, both cohorts of colonized larvae showed elevations in 23 chemical features, including parent triclosan and putative triclosan sulfate. Taken together, these data suggest that triclosan exposure selects for microbes that harbor the capacity to biotransform triclosan into chemical metabolites with unknown toxicity profiles. More broadly, these data support the concept that microbiota modify the toxicokinetics of xenobiotic exposure.