kely intracellular signaling partners by which β1-integrins support orbitofrontal cortical function and connectivity with the basolateral amygdala.Characterizing the pharmacokinetic properties of drug candidates represents an essential task during drug development. In the past, liver microsomes and primary suspended hepatocytes have been extensively used for this purpose, but their relatively short stability limits the applicability of such in vitro systems for drug compounds with low metabolic turnover. In the present study, we used 3D primary human hepatocyte spheroids to predict the hepatic clearance of seven drugs with low to intermediate clearance in humans. Our results indicate that hepatocyte spheroids maintain their in vivo like phenotype during prolonged incubations allowing to monitor the depletion of parent drug for seven days. In contrast, attempts to increase the relative metabolic capacity by pooling hepatocyte spheroids resulted in an immediate fusion of the spheroids followed by hepatocellular de-differentiation processes, demonstrating limited applicability of the pooling approach for quantitative pharmacokinetic studies. The hepatic clearance values obtained from incubations with individual spheroids were in close correlation with the clinical reference data with six out of seven drug compounds being predicted within a three-fold deviation and average fold and absolute average fold errors of 0.57 and 1.74, respectively. In conclusion, the hepatocyte spheroid model enables accurate hepatic clearance predictions for slowly metabolized drug compounds and represents a valuable tool for determining the pharmacokinetic properties of new drug candidates as well as for mechanistic pharmacokinetic studies. Significance Statement Traditional in vitro systems often fail to predict the hepatic clearance of slowly metabolized drug compounds. The current study demonstrates the ability of primary human hepatocyte spheroids to provide accurate projections on the hepatic clearance of drug compounds with low and intermediate clearance.Pyrazinamide (PZA) is an important component of a standard combination therapy against tuberculosis. However, PZA is hepatotoxic and the underlying mechanisms are poorly understood. Biotransformation of PZA in the liver was primarily suggested behind its hepatoxicity. This review summarizes the knowledge of the key enzymes involved in PZA metabolism and discusses their contributions to PZA hepatotoxicity. Significance Statement This review outlines the current understanding of PZA metabolism and hepatotoxicity. This work also highlights the gaps in this field, which can be used to guide the future studies on PZA-induced liver injury.Anticancer drug, irinotecan shows serious dose-limiting gastrointestinal toxicity regardless of intravenous dosing. Although enzymes and transporters involved in irinotecan disposition are known, quantitative contributions of these mechanisms in complex in vivo disposition of irinotecan are poorly understood. We explained intestinal disposition and toxicity of irinotecan by integrating i) in vitro metabolism and transport data of rinotecan and its metabolites, ii) ex vivo gut microbial activation of the toxic metabolite, SN-38, and iii) the tissue protein abundance data of enzymes and transporters relevant to irinotecan and its metabolites. Integration of in vitro kinetics data with the tissue enzyme and transporter abundance predicted that carboxylesterase (CES) mediated hydrolysis of irinotecan is the rate-limiting process in the liver, where the toxic metabolite formed is rapidly deactivated by glucuronidation. In contrast, the poor SN-38 glucuronidation rate as compared to its efficient formation by CES2 ransporters. The results of this study explain the characteristic intestinal exposure and toxicity of irinotecan. Quantitative tissue-specific in vitro to in vivo extrapolation approach presented in this study can be extended to cancer cells.Exposure to the environmental pollutant cadmium is ubiquitous as it is present in cigarette smoke and the food supply. Over time, cadmium enters and accumulates in the kidneys where it causes tubular injury. The breast cancer resistance protein (BCRP, ABCG2) is an efflux transporter that mediates the urinary secretion of pharmaceuticals and toxins. TheABCG2 genetic variant Q141K exhibits altered membrane trafficking which results in reduced efflux of BCRP substrates. Here, we sought to 1) evaluate the in vitro and in vivo ability of BCRP to transport cadmium and protect kidney cells from toxicity, and 2) determine whether this protection is impaired by the Q141K variant. Cadmium concentrations, cellular stress, and toxicity were quantified in HEK293 cells expressing an empty vector (EV), BCRP wild-type (WT), or variant (Q141K) gene. Treatment with CdCl2 resulted in greater accumulation of cadmium and apoptosis in EV cells relative to WT cells. Exposure to CdCl2 induced expression of stress-related genes and proteins including MT-1A/2A, NQO1, and HO-1 to a higher extent in EV cells compared to WT cells. Notably, the Q141K variant protected against CdCl2-induced activation of stress genes and cytotoxicity, but this protection was to a lesser magnitude than observed with WT BCRP. Lastly, concentrations of cadmium in the kidneys of Bcrp KO mice were 40% higher than in WT mice, confirming that cadmium is an in vivo substrate of BCRP. learn more In conclusion, BCRP prevents the accumulation of cadmium and protects against toxicity, a response that is impaired by the Q141K variant. Significance Statement The BCRP transporter lowers cellular accumulation of the toxic heavy metal cadmium. This protective function is partially attenuated by the Q141K genetic variant in the ABCG2 gene.Cytochrome P450 1A2 (CYP1A2) as one of the most important CYP isoforms is involved in the biotransformation of many important endogenous and exogenous substances. CYP1A2 plays an important role in the development of many diseases because it is involved in the biotransformation of precancerous substances and poisons. Although the generation of Cyp1a2 knockout (KO) mouse model has been reported, there are still no relevant rat models for the study of CYP1A2-mediated pharmacokinetics and diseases. In this report, CYP1A2 KO rat model was established successfully by using CRISPR/Cas9 without any detectable off-target effect. Compared with wild-type rats, this model showed a loss of CYP1A2 protein expression in the liver. The results of pharmacokinetics in vivo and incubation in vitro of specific substrates of CYP1A2 confirmed the lack of function of CYP1A2 in KO rats. In further studies of potential compensatory effects, we found that CYP1A1 was significantly up-regulated, and CYP2E1, CYP3A2 and LXRβ were down-regulated in KO rats.