Evaluation of a microphysiological human placental barrier model for studying placental drug transfer.

Understanding drug transport across the placental barrier is important for assessing the potential fetal drug toxicity and birth defect risks. Current in vivo and in vitro models have structural and functional limitations in evaluating placental drug transfer and toxicity. Microphysiological systems (MPSs) offer more accurate and relevant physiological models of human tissues and organs on a miniature scale for drug development and toxicology testing. MPSs for the placental barrier have been recently explored to study placental drug transfer. We utilized a multilayered hydrogel membrane-based microphysiological model composed of human placental epithelial and endothelial cells to replicate the key structure and function of the human placental barrier. A macroscale human placental barrier model was created using a transwell to compare the results with the microphysiological model. Placental barrier models were characterized by assessing monolayer formation, intercellular junctions, barrier permeability, and their structural integrity. Three small-molecule drugs (glyburide, rifaximin, and caffeine) that are prescribed or taken during pregnancy were studied for their placental transfer. The results showed that all three drugs crossed the placental barrier, with transfer rates in the following order: glyburide (molecular weight, MW = 494 Da) < rifaximin (MW = 785.9 Da) < caffeine (MW = 194.19 Da). Using non-compartmental analysis, we estimated human pharmacokinetic characteristics based on in vitro data from both MPS and transwell models. While further research is needed, our findings suggest that MPS holds potential as an in vitro tool for studying placental drug transfer and predicting fetal exposure, offering insights into pharmacokinetics.

In vivo pharmacokinetic analyses of placental transfer of three drugs of different physicochemical properties in pregnant rats.

Although the use of medication during pregnancy is common, information on exposure to the developing fetus and potential teratogenic effects is often lacking. This study used a rat model to examine the placental transfer of three small-molecule drugs with molecular weights ranging from approximately 300 to 800 Da with different physicochemical properties. Time-mated Sprague Dawley (Hsd:SD) rats aged 11-13 weeks were administered either glyburide, rifaximin, or fentanyl at gestational day 15. Maternal blood, placentae, and fetuses were collected at 5 min, 30 min, 1 h, 4 h, 8 h, 24 h, 48 h, and 96 h post-dose. To characterize the rate and extent of placental drug transfer, we calculated several pharmacokinetic parameters such as maximum concentration (Cmax), time to maximum concentration (Tmax), area under the concentration-time curve (AUC), half-life (t1/2), clearance (CL), and volume of distribution (Vd) for plasma, placenta, and fetus tissues. The results indicated showed that fetal exposure was lowest for glyburide, accounting for only 2.2 % of maternal plasma exposure as measured by their corresponding AUC ratio, followed by rifaximin (37.9 %) and fentanyl (172.4 %). The fetus/placenta AUC ratios were found to be 10.7 % for glyburide, 11.8 % for rifaximin, and 39.1 % for fentanyl. These findings suggest that although the placenta acts as a protective shield for the fetus, the extent of protection varies for different drugs and depends on factors such as molecular weight, lipid solubility, transporter-mediated efflux, and binding to maternal and fetal plasma proteins.

NIEHS/FDA CLARITY-BPA research program update.

Bisphenol A (BPA) is a chemical used in the production of numerous consumer products resulting in potential daily human exposure to this chemical. The FDA previously evaluated the body of BPA toxicology data and determined that BPA is safe at current exposure levels. Although consistent with the assessment of some other regulatory agencies around the world, this determination of BPA safety continues to be debated in scientific and popular publications, resulting in conflicting messages to the public. Thus, the National Toxicology Program (NTP), National Institute of Environmental Health Sciences (NIEHS), and U.S. Food and Drug Administration (FDA) developed a consortium-based research program to link more effectively a variety of hypothesis-based research investigations and guideline-compliant safety testing with BPA. This collaboration is known as the Consortium Linking Academic and Regulatory Insights on BPA Toxicity (CLARITY-BPA). This paper provides a detailed description of the conduct of the study and a midterm update on progress of the CLARITY-BPA research program.

Toxicity evaluation of bisphenol A administered by gavage to Sprague Dawley rats from gestation day 6 through postnatal day 90.

Bisphenol A (BPA) is a high production volume industrial chemical to which there is widespread human oral exposure. Guideline studies used to set regulatory limits detected adverse effects only at doses well above human exposures and established a no-observed-adverse-effect level (NOAEL) of 5 mg/kg body weight (bw)/day. However, many reported animal studies link BPA to potentially adverse effects on multiple organ systems at doses below the NOAEL. The primary goals of the subchronic study reported here were to identify adverse effects induced by orally (gavage) administered BPA below the NOAEL, to characterize the dose response for such effects and to determine doses for a subsequent chronic study. Sprague Dawley rat dams were dosed daily from gestation day 6 until the start of labor, and their pups were directly dosed from day 1 after birth to termination. The primary focus was on seven equally spaced BPA doses (2.5-2700 µg/kg bw/day). Also included were a naïve control, two doses of ethinyl estradiol (EE2) to demonstrate the estrogen responsiveness of the animal model, and two high BPA doses (100,000 and 300,000 µg/kg bw/day) expected from guideline studies to produce adverse effects. Clear adverse effects of BPA, including depressed gestational and postnatal body weight gain, effects on the ovary (increased cystic follicles, depleted corpora lutea, and antral follicles), and serum hormones (increased serum estradiol and prolactin and decreased progesterone), were observed only at the two high doses of BPA. BPA-induced effects partially overlapped those induced by EE2, consistent with the known weak estrogenic activity of BPA.

Pharmacokinetic distribution of 67Cu(II)2[3,5-diisopropyl(carboxy-14C)salicylate]4 among murine tissues.

Non-toxic doses of tetrakis-mu-3,5-diisopropylsalicylatodicopper(II) [Cu(II)2(3,5-DIPS)4] have been found to have anti-inflammatory, analgesic, anti-ulcer, anti-colitis, anti-convulsant, anti-cancer, anti-mutagenic, anti-carcinogenic, and anti-diabetic activities and, in addition, facilitates recovery from lethal irradiation and ischemia-reperfusion injuries. The goal of this research was to determine the time-dependent tissue distribution and persistence of 67Cu and the 14C labeled salicylate ligand, carboxy-14C-3, 5-diisopropylsalicylate [3,5-DIP(carboxy-14C)S], following subcutaneous administration of a 50 micromole per kilogram of body mass dose of double labeled tetrakis-mu-3,5-diisopropyl[carboxy-14C]salicylatodiaquo [67Cu]dicopper(II) 67Cu(II)4[3,5-DIP(carboxy-14C)S]4. This compound was administered to nine groups of six 20 gram female C57BL/6 mice and blood, liver, kidney, intestine, lung, thymus, femur, muscle, spleen, and brain tissues removed and analyzed for 67Cu and 14C at 0.5, 1, 3, 6, 12, 24, 48, 72, and 96 hours after treatment. These data were then analyzed using a pharmacokinetic model simulation program. Both 67Cu and 14C were found in all tissues as well as urine and feces at 0.5 hour after administration. As anticipated, 67Cu entered the liver storage pool; it was conserved by the kidneys, and subsequently underwent release in maintaining 67Cu levels in all other tissues. While the presence of 67Cu correlated with the presence of the salicylate ligand, 3,5-DIP (carboxy-14C)S, early in the course of this experiment, the ligand was lost via ligand exchange and could not be measured in blood, kidney, intestine, lung, thymus, spleen, and brain after 24 hours following administration. However, 3,5-DIP(carboxy-14C)S persisted in liver, femur, and muscle throughout the 5-day period of study. It is suggested that marked lipophilicity accounts for its very rapid distribution to all tissues wherein it undergoes ligand exchange as 67Cu is incorporated into Cu-dependent enzymes and proteins and persists in tissues based upon physiological demand for Cu in meeting normal biochemical requirements.