Valproic acid hepatotoxicity in human liver slices

A review: Systematic research approach on toxicity model of liver and kidney in laboratory animals

Therapeutic experiments are commonly performed on laboratory animals to investigate the possible mechanism(s) of action of toxic agents as well as drugs or substances under consideration. The use of toxins in laboratory animal models, including rats, is intended to cause toxicity. This study aimed to investigate different models of hepatotoxicity and nephrotoxicity in laboratory animals to help researchers advance their research goals. The current narrative review used databases such as Medline, Web of Science, Scopus, and Embase and appropriate keywords until June 2021. Nephrotoxicity and hepatotoxicity models derived from some toxic agents such as cisplatin, acetaminophen, doxorubicin, some anticancer drugs, and other materials through various signaling pathways are investigated. To understand the models of renal or hepatotoxicity in laboratory animals, we have provided a list of toxic agents and their toxicity procedures in this review.

A pharmacogenomic method for individualized prediction of drug sensitivity

Using valproic acid as an example, the authors demonstrate that drug response signatures derived from genome-wide expression data can identify individuals likely to respond to a drug, and propose that this method could select optimal populations for clinical trials of new therapies.

Drug response signatures that accurately reflect the cellular response to a drug can be generated from Connectivity Map and publically available gene expression data.

Predictions from the drug response signature for valproic acid correlate with sensitivity to valproic acid in breast cancer cell lines and patient tumors grown in three-dimensional culture and mouse xenografts.

The MATCH algorithm provides an efficient approach for using genome-wide gene expression data to identify a target population for a drug prior to clinical trials.

MATCH can predict drug sensitivity in tumors without knowledge of mechanism of action.

Unlike traditional chemotherapy, targeted cancer therapies are expected to work in only a subset of people with a particular cancer. However, biomarkers of response are not always known before clinical trial initiation. We present MATCH (Merging genomic and pharmacologic Analyses for Therapy CHoice), an algorithm for using genome-wide gene expression data to identify and validate a genomic biomarker of sensitivity (see Figure 1). Our proof-of-principle example is valproic acid (VPA), but we also show that an estrogen blocking drug currently used for breast cancer and a B-RAF inhibitor in trials for melanoma give predictions that correspond to their clinical uses.

We use genome-wide gene expression data from treated and untreated samples from the Connectivity Map to generate a VPA response signature. We validate that the VPA signature can identify treated and untreated cells in an independent data set of normal cells and in independent samples from the Connectivity Map. The AUC for the ROC curve is 0.86. We then apply the VPA signature to publically available data sets from a panel of cancer cell lines and from primary tumor and normal tissue samples. These data suggest that there is a subset of women with breast cancer who will be sensitive to VPA. Finally, we validate that our predictions correlate with sensitivity to VPA in breast cancer cell lines grown in two-dimensional culture, primary breast tumor samples grown in three-dimensional culture, and in vivo mouse breast cancer xenografts. Together, these studies show that MATCH can identify cancer patients most likely to respond to a specific drug treatment.

Identifying the best drug for each cancer patient requires an efficient individualized strategy. We present MATCH (Merging genomic and pharmacologic Analyses for Therapy CHoice), an approach using public genomic resources and drug testing of fresh tumor samples to link drugs to patients. Valproic acid (VPA) is highlighted as a proof-of-principle. In order to predict specific tumor types with high probability of drug sensitivity, we create drug response signatures using publically available gene expression data and assess sensitivity in a data set of >40 cancer types. Next, we evaluate drug sensitivity in matched tumor and normal tissue and exclude cancer types that are no more sensitive than normal tissue. From these analyses, breast tumors are predicted to be sensitive to VPA. A meta-analysis across breast cancer data sets shows that aggressive subtypes are most likely to be sensitive to VPA, but all subtypes have sensitive tumors. MATCH predictions correlate significantly with growth inhibition in cancer cell lines and three-dimensional cultures of fresh tumor samples. MATCH accurately predicts reduction in tumor growth rate following VPA treatment in patient tumor xenografts. MATCH uses genomic analysis with in vitro testing of patient tumors to select optimal drug regimens before clinical trial initiation.

Precision-cut tissue chips as an in vitro toxicology system

Precision-cut tissue slices mimic specific organ toxicity because normal cellular heterogeneity and organ architecture are retained. To optimize the use of the smaller tissues of the mouse and to establish easy assays for tissue viability, a tissue chip based system was used to generate large numbers of samples from a single organ. Iodoacetamide (IAM) was used as a model toxicant and assays for intracellular potassium (normalized to DNA content) were used to establish viability and toxicant susceptibility. Thereafter, assays that were more rapid and specific were pursued. Lysates from tissues incubated in 6-carboxyfluorescein fluoresced proportionately to concentrations of IAM, indicating disruption of cellular membranes. Similarly, FURA-2, a probe applied to lysates to measure calcium levels, fluoresced proportionately to IAM dosage. Monobromobimane, a fluorescent sulfhydryl probe, displayed a decrease in fluorescent intensity at higher IAM challenge-a finding confirmed with an absorbance assay with Ellman's reagent. Importantly, the number of samples per organ/mouse was increased at least threefold and a significant time reduction per analysis was realized.

Effect of cold and warm ischaemia on drug metabolism in isolated hepatocytes and slices from human and monkey liver

1. The influence of short-term cold storage in University of Wisconsin organ preservation solution (UW) on the ability to metabolize lidocaine, testosterone and 7-ethoxycoumarin in isolated human and cynomolgus monkey (Macaca fascicularis) hepatocytes and liver slices has been investigated. 2. The human liver tissue was obtained from two different sources, i.e. healthy liver tissue from patients undergoing partial hepatectomy because of metastases of colorectal carcinoma (PH livers) and donor tissue remaining as surgical waste after reduced size or split liver transplantation (Tx livers). Tx livers were perfused in situ with ice-cold UW avoiding warm ischaemia. This in contrast with PH livers, where the operation caused warm ischaemia for 5-90 min. 3. Liver slices and hepatocytes from cynomolgus monkey liver showed comparable metabolic rates for the substrates tested, indicating that all hepatocytes in the slice are participating in the biotransformation of the substrates. These monkey liver preparations can be stored up to 18 h with only a slight loss of their metabolic capacity. 4. Liver slices and isolated hepatocytes from the Tx livers as well as isolated cells from the PH livers could also be stored up to 18 h without losing metabolic capacity. However, for liver slices prepared from PH livers cold storage is not recommended, because metabolic function was reduced by approximately 40% after 18 h.

Comparison of five incubation systems for rat liver slices using functional and viability parameters

Precision-cut liver slices are presently used for various research objects, e.g. to study metabolism, transport, and toxicity of xenobiotics. Various incubation systems are presently employed, but a systematic comparison between these incubation systems with respect to preservation of slice function has not been performed yet. Therefore, we started a comparative study to evaluate five of these systems: the shaken flask (an Erlenmeyer in a shaking water bath), the stirred-well (24-well culture plate equipped with grids and magnetic stirrers), rocker platform (6-well culture plate with Netwell insert rocked on a platform), the roller system (dynamic organ culture rolled on an insert in a glass vial), and the 6-well shaker (6-well culture plate in a shaking water bath). The liver slices were incubated in these incubation systems for 0.5, 1.5, and 24.5 h and subsequently subjected to viability and metabolic function tests. The viability of the incubated liver slices was evaluated by: potassium content, MTT assay, energy charge, histomorphology, and LDH leakage. Their metabolic functions were studied by determination of the metabolism of lidocaine, testosterone, and antipyrine. Up to 1.5 h of incubation all five incubation systems gave similar results with respect to viability and metabolic function of the liver slices. However, after 24 h, the shaken flask, the rocker platform, and the 6-well shaker incubation systems appeared to be superior to the stirred well and the roller incubation systems.

Precision-cut tissue slices: applications in pharmacology and toxicology

Almost a decade has passed since the first paper describing the isolation and maintenance of precision-cut liver slices produced using a mechanical tissue slicer was published (1). Although tissue slices of various organs have been employed as an in vitro system for several decades, the lack of reproducibility within the slices and the relatively limited viability of the tissue preparations has prevented a widespread acceptance of the technique. The production of an automated slicer, capable of reproducibly producing relatively thin slices of tissue, as well as the development of a dynamic organ culture system, overcame several of these obstacles. Since that time, significant advances in the methods to produce and culture tissue slices have been made, as well as the application of the technique to several other organs, including kidney, lung and heart. This review will i) summarize the historical use of tissue slices prior to the development of the precision-cut tissue slice system; ii) briefly analyze current methods to produce precision-cut liver, kidney, lung and heart slices; and iii) discuss the applications of this powerful in vitro system to the disciplines of pharmacology and toxicology.

Comparative metabolism and toxicity of dichlorobenzenes in Sprague-Dawley, Fischer-344 and human liver slices

1. Precision-cut liver slices, prepared from Sprague-Dawley and Fischer-344 rats and donated human liver tissue, were used to identify differences in 1,2-dichlorobenzene (1,2-DCB), 1,3-dichlorobenzene (1,3-DCB) and 1,4-dichlorobenzene (1,4-DCB) metabolism and how it may relate to toxicity. 2. Rat and human liver slices were incubated with 1 mM of either dichlorobenzene to determine metabolism and toxicity, at 2 and 6 h of organ culture. 3. The human liver slices metabolised the dichlorobenzenes to a greater extent than those from either of the rat strains. Liver slices from the Fischer-344 strain had a higher metabolic rate than the slices from the Sprague-Dawley rat strain. 4. The metabolic rate of dichlorobenzene isomers did not consistently correlate with its toxicity. For example, human slices did not exhibit any hepatoxicity, even though they metabolised these compounds to a greater extent than either rat strain. 5. Cross species covalent binding did not correlate with toxicity endpoints measured in this study. 6. The phase two metabolite profiles for each of the isomers in human and rat slices were similar in that the glutathione-cysteine conjugate was the major metabolite. 7. The use of an in vitro system which utilises human liver slices might provide an important bridge between animal derived data and the human situation.

The hepatotoxicities of endotoxin and ethanol comparisons in vitro using the precision-cut rat liver slice model

Using the precision-cut rat liver slice model, the in vitro toxicities of endotoxin and ethanol, independently and in combination, were evaluated. Hepatotoxicity was assessed by two measures: the leakage of LDH from slice to medium and the ability of slices to reduce a tetrazolium compound, MTT. Ethanol, in concentrations of 1% and greater, exhibited a time and dose dependent hepatotoxicity; MTT reductive capacity was more profoundly affected than LDH leakage. Endotoxin (0.1 to 100 micrograms/ml), however, had only a modest effect on MTT reduction and did not perturb LDH leakage. When combined in vitro, the toxicities of 2% ethanol and various concentrations of endotoxin were additive. Slices prepared from the livers of rats injected ip with endotoxin one day previously sustained considerably more injury (compared to normal rat liver slices) upon subsequent in vitro exposure to either endotoxin or ethanol. Prior in vivo exposure to ethanol, however, did not affect the subsequent in vitro toxicity of endotoxin. Thus, while endotoxin exhibits only subtle toxic effects upon liver slices in vitro, exposure to endotoxin in vivo renders the liver more susceptible to subsequent direct injury by endotoxin or ethanol.

Culture of precision-cut liver slices: effect of some peroxisome proliferators

Precision-cut rat liver slices were prepared with a Krumdieck tissue slicer and cultured in three standard hepatocyte culture media. Rat liver slices cultured in either RPMI 1640 medium or Williams Medium E could be maintained in culture for up to 72 hr. In contrast, Leibovitz's L-15 medium was unsatisfactory in that slice viability, assessed either by morphological examination or by measurement of enzyme activities, could not be maintained for periods greater than 24 hr. As a measure of functional viability liver slices were cultured with some known rodent peroxisome proliferators, namely clofibric acid, nafenopin, ciprofibrate and Wy-14,643. The peroxisome proliferators induced both palmitoyl CoA oxidation and carnitine acetyltransferase activities in 48- and 72-hr slice cultures. Ultrastructural examination of liver slices cultured with either ciprofibrate or Wy-14,643 for 72 hr revealed an increase in the number of peroxisomes. These results demonstrate that rat liver slices may be maintained in culture for up to 72 hr, and that they respond in a similar manner to rat primary hepatocyte cultures to some peroxisome proliferators. Precision-cut liver slices may therefore be a useful alternative in vitro system to hepatocyte cultures for screening compounds for effects on enzyme activities and for assessing species differences in response.