In Vitro Activation of Human Adrenergic Receptors and Trace Amine-Associated Receptor 1 by Phenethylamine Analogues Present in Food Supplements.

Pre-workout supplements are popular among sport athletes and overweight individuals. Phenethylamines (PEAs) and alkylamines (AA) are widely present in these supplements. Although the health effects of these analogues are not well understood yet, they are hypothesised to be agonists of adrenergic (ADR) and trace amine-associated receptors (TAARs). Therefore, we aimed to pharmacologically characterise these compounds by investigating their activating properties of ADRs and TAAR1 in vitro. The potency and efficacy of the selected PEAs and AAs was studied by using cell lines overexpressing human ADRα1A/α1B/α1D/α2a/α2B/ß1/ß2 or TAAR1. Concentration-response relationships are expressed as percentages of the maximal signal obtained by the full ADR agonist adrenaline or the full TAAR1 agonist phenethylamine. Multiple PEAs activated ADRs (EC50 = 34 nM-690 µM; Emax = 8-105%). Almost all PEAs activated TAAR1 (EC50 = 1.8-92 µM; Emax = 40-104%). Our results reveal the pharmacological profile of PEAs and AAs that are often used in food supplements. Several PEAs have strong agonistic properties on multiple receptors and resemble potencies of the endogenous ligands, indicating that they might further stimulate the already activated sympathetic nervous system in exercising athletes via multiple mechanisms. The use of supplements containing one, or a combination of, PEA(s) may pose a health risk for their consumers.

Perfluoroalkyl substances (PFASs) decrease the expression of recombination-activating genes (RAG1 and RAG2) in human B lymphoma Namalwa cells.

Per- and polyfluoroalkyl substances (PFASs) are omnipresent and have been shown to induce a wide range of adverse effects, including hepatotoxicity, developmental toxicity and immunotoxicity. So far, little information is available about the mechanisms underlying the toxicity of PFASs, including those related to their immunotoxicity. Reported immunotoxic effects of PFASs include decreased antibody responses in experimental animals and humans, indicating that PFASs may, among others, affect B cell function. In the present study, we first assessed the effects of PFOA on the transcriptome of the human Namalwa B cell line using RNA seq analysis. Gene expression changes, analyzed using Ingenuity Pathway Analysis, pointed to various cellular processes affected by PFOA, including 'B cell development' and 'Primary immunodeficiency signaling'. Interestingly, PFOA decreased the expression of RAG1 and RAG2, genes involved in immunoglobulin and T cell receptor V(D)J recombination. As a next step, time- and concentration-dependent changes in the expression of RAG1 and RAG2 upon exposure to PFOA, PFNA, PFHxS and PFOS were studied through RT-qPCR analysis. Analysis with the concentration-response modeling software PROAST resulted in the following potency ranking: PFNA > PFOA > PFOS > PFHxS. Altogether, the present in vitro study provides insights into the effects of selected PFASs on B cells, identifying RAG1 and RAG2 expression as possible relevant targets that may play a role in the immunotoxicity of PFASs.

Comparison of gene expression and biotransformation activity of HepaRG cells under static and dynamic culture conditions.

Flow conditions have been shown to be important in improving longevity and functionality of primary hepatocytes, but the impact of flow on HepaRG cells is largely unknown. We studied the expression of genes encoding CYP enzymes and transporter proteins and CYP1 and CYP3A4 activity during 8 weeks of culture in HepaRG cells cultured under static conditions (conventional 24-/96-well plate culture with common bicarbonate/CO2 buffering) and under flow conditions in an organ-on-chip (OOC) device. Since the OOC-device is a closed system, bicarbonate/CO2 buffering was not possible, requiring application of another buffering agent, such as HEPES. In order to disentangle the effects of HEPES from the effects of flow, we also applied HEPES-supplemented medium in static cultures and studied gene expression and CYP activity. We found that cells cultured under flow conditions in the OOC-device, as well as cells cultured under static conditions with HEPES-supplemented medium, showed more stable gene expression levels. Furthermore, only cells cultured in the OOC-device showed relatively high baseline CYP1 activity, and their gene expression levels of selected CYPs and transporters were most similar to gene expression levels in human primary hepatocytes. However, there was a decrease in baseline CYP3A4 activity under flow conditions compared to HepaRG cells cultured under static conditions. Altogether, the present study shows that HepaRG cells cultured in the OOC-device were more stable than in static cultures, being a promising in vitro model to study hepatoxicity of chemicals upon chronic exposure.

Development of a villi-like micropatterned porous membrane for intestinal magnesium and calcium uptake studies.

Intestinal enterocytes are key players in the absorption of magnesium (Mg2+) and calcium (Ca2+). Understanding the exact molecular mechanisms by which their absorption behavior is regulated could greatly improve treatment strategies for stimulating intestinal absorption in diseases with Mg2+ and/or Ca2+ deficiency. However, such studies are hampered by the lack of in vitro intestinal cell models mimicking the mechanical and physiological properties of the gut. In this study we develop an in vitro gut model based on porous micropatterned membranes with villi-like surface topography and mechanical properties closely mimicking that of intestinal tissue. These membranes are prepared via phase separation micromolding using poly-ε-caprolactone/poly-lactic-glycolic acid (PCL/PLGA) polymer blend and can facilitate cellular differentiation of Caco-2 cells similar to native enterocytes. In fact, cells cultured on these micropatterned membranes form a brush border of microvilli with spatial differences in morphology and tight junction formation along the villous-base axis. Moreover, cells cultured on our membranes show a 2-fold increased alkaline phosphatase activity at the end of differentiation. Finally, we demonstrate that cells cultured on our micropatterned membranes have a 4- and 1.5-fold increased uptake of 25Mg and 45Ca, respectively, compared to non-patterned membranes. These results indicate that the new membranes can mimic the intestinal environment and therefore can have a great impact on mineral uptake in vitro. STATEMENT OF SIGNIFICANCE: This study presents the development of an in vitro gut model consisting of villi-like PCL/PLGA micropatterned membranes. These membranes are prepared via phase separation micromolding (PSµM), a technique which allows tailoring of the membrane surface topography combined with membrane porosity and interconnectivity which are important parameters for membranes used for in vitro transport studies. The culture of Caco-2 cells on these micropatterned membranes shows that they facilitate cellular differentiation similar to gut enterocytes. Our data indicate that mimicking the 3D geometry of the gut is very important for improving the physiological relevance of in vitro gut models. In the future, our micropatterned membranes with segment-specific geometries, in combination with isotopic measurements, would be applied to perform detailed ion uptake and transport studies.