Lack of efflux of diglycolic acid from proximal tubule cells leads to its accumulation and to toxicity of diethylene glycol

Human and rat renal proximal tubule in vitro models for ADME applications

The kidney is a major organ dictating excretion rates of chemicals and their metabolites from the body and thus renal clearance is frequently a major component of pharmaco-(toxico)-kinetic profiles. Within the nephron, the proximal tubule is the major site for xenobiotic reabsorption from glomerular filtrate and xenobiotic secretion from the blood into the lumen via the expression of multiple inward (lumen to interstitium) and outward transport systems (interstitium to lumen). While there exist several human proximal tubular cell culture options that could be utilized for modelling the proximal tubule component of renal clearance, they do not necessarily represent the full complement of xenobiotic transport processes of their in vivo counterparts. Here, we review available human and rat renal proximal tubule in vitro models, including subcellular fractions, immortalized cell lines, primary cell cultures, induced pluripotent stem cell (iPSC)-derived models and also consider more organotypic cell culture environments such as microporous growth supports, organoids and microfluidic systems. This review focuses on expression levels and function of human and rat renal transporters and phase I and II metabolizing enzymes in these models in order to critically assess their usefulness and to identify potential solutions to overcome identified limitations.

A perfused iPSC-derived proximal tubule model for predicting drug-induced kidney injury

The kidney is frequently exposed to high levels of drugs and their metabolites, which can injure the kidney and the proximal tubule (PT) in particular. In order to detect nephrotoxicity early during drug development, relevant in vitro models are essential. Here, we introduce a robust and versatile cell culture insert-based iPSC-derived PT model, which can be maintained in a microphysiological system for at least ten days. We demonstrate the model's ability to predict drug-induced PT injury using polymyxin B, cyclosporin A, and cisplatin, and observe that perfusion distinctly impacts our model's response to xenobiotics. We observe that the upregulation of metallothioneins that is described in vivo after treatment with these drugs is reliably detected in dynamic, but not static in vitro PT models. Finally, we use our model to alleviate polymyxin-induced nephrotoxicity by supplementing the antioxidant curcumin. Together, these findings illustrate that our perfused iPSC-derived PT model is versatile and well-suited for in vitro studies investigating nephrotoxicity and its prevention. Reliable and user-friendly in vitro models like this enable the early detection of nephrotoxic potential, thereby minimizing adverse effects and reducing drug attrition.

Rapid Determination of Trace Ethylene Glycol and Diethylene Glycol in Propylene Glycol-Contained Syrups by Ultrahigh-Performance Supercritical Fluid Chromatography-Mass Spectrometry after Precolumn Derivatization

Ethylene glycol (EG) and diethylene glycol (DEG) are two contaminants known to cause a variety of human health problems, when ingested in certain amounts, they can cause adverse effects such as nephrotoxicity, neurotoxicity and even death. They are widely found in propylene glycol, which is commonly used as a base for pharmaceutical syrups. The aim of this study was to develop an analytical method for the evaluation of EG and DEG in commercially available pediatric syrups. In this study, a fast, simple and reliable ultrahigh performance supercritical fluid chromatography-electrospray ionization-mass spectrometry (UHPSFC-ESI-MS) method was developed. The work involved the evaluation of three derivatization reagents for UHPSFC-ESI-MS. Benzoyl chloride was finally selected as the optimal derivatization reagent. Compared with an approach without derivatization, the present method achieved the separation and detection of EG and DEG efficiently, sensitively and rapidly, and analysis of EG and DEG in syrup formulations was realized within 7 min. The linear determination coefficients of EG and DEG in the concentration range of 0.25-25.0 μg/mL were greater than 0.999. The limits of detection for EG and DEG were 0.02 μg/mL and 0.07 μg/mL, respectively, and the limits of quantification were 0.09 μg/mL and 0.25 μg/mL, respectively. The recovery rates of DEG and EG ranged from 85.5%-108.1% and 86.7%-117.2%, respectively. The absolute values of the matrix effects in the three types of syrups considered were all less than 10%. Meanwhile, a gas chromatography-hydrogen flame ionization detection method was established for cross-testing of the analytical results. In 10 batches of syrup formulations, DEG was not detected by either method. The presence of EG was detected by UHPSFC-ESI-MS in only three batches, none of which exceeded 90.23 parts per million (ppm), with a mean absolute error of 5.95 ppm between the two sets of results. The developed UHPSFC-ESI-MS method was rapid, simple, efficient, sensitive and accurate for the determination of EG and DEG in genuine syrup formulations.

Thrombotic Microangiopathy and Acute Tubular Injury After Diethylene Glycol Ingestion: A Kidney Biopsy Teaching Case

We present a rare and unusual case of thrombotic microangiopathy (TMA) in a patient who ingested chafing fuel containing diethylene glycol. The patient showed a typical clinical course of initial gastrointestinal symptoms followed by acute kidney injury (AKI) and peripheral sensorimotor neuropathy. A kidney biopsy showed TMA and diffuse acute tubular injury. Diethylene glycol is widely used as a solvent in numerous consumer products, including brake fluid, antifreeze, chafing fuel, and artificial fog solutions. Diethylene glycol has been implemented in mass poisonings, and the incidence of AKI in diethylene glycol poisonings is linked to high-mortality rates. TMA, a pathologic lesion observed in a wide spectrum of diseases, is triggered by endothelial injury. Our case shows that TMA should be considered as a possible life-threatening complication in the setting of acute diethylene glycol poisoning. Direct toxic injury to endothelial cells by diethylene glycol is a possible mechanism. It is therefore plausible that patients with a genetic predisposition to endothelial injury may develop TMA following diethylene glycol exposure.