Adult rat liver slices as a model for studying the hepatotoxicity of vincaalkaloids

Synchrotron Radiation FTIR Microspectroscopy Study of Biomolecular Alterations in Vincristine-Treated WRL68 Cells at the Single-Cell Level

The toxic effect of vincristine on hepatocytes has rarely been studied. Synchrotron radiation-based Fourier transform infrared (SR-FTIR) microspectroscopy is a novel technique for investigating drug-cell interaction systems. In this research, the biomolecular alterations in WRL68 cells induced by vincristine treatment were investigated by SR-FTIR microspectroscopy and were further analyzed by multivariate statistical analysis and semiquantitative methods, including principal component analysis (PCA), orthogonal partial least square-discriminant analysis (OPLS-DA), and the peak area ratios of several characteristic IR bands. In vincristine-treated WRL68 cells, alterations in lipid structures and the presence of more long-chain fatty acids were found. A decrease in protein α-helical content relative to β-sheet structures in vincristine-treated WRL68 cells was identified. The nucleic acid content was decreased relative to that of lipids and proteins in WRL68 cells treated with vincristine. These results provide important information about the toxic effect of vincristine on normal liver cells. This research also provides a new approach to reveal the biomolecular alterations in drug-treated hepatocytes by combining SR-FTIR with multivariate statistical analysis and semiquantitative methods.

Vinblastine-Loaded Nanoparticles with Enhanced Tumor-Targeting Efficiency and Decreasing Toxicity: Developed by One-Step Molecular Imprinting Process

Molecularly imprinted polymers have exhibited good performance as carriers on drug loading and sustained release. In this paper, vinblastine (VBL)-loaded polymeric nanoparticles (VBL-NPs) were prepared by a one-step molecular imprinting process, avoiding the waste and incomplete removal of the template, and evaluated as targeting carriers for VBL delivery after modification. Using acryloyl amino acid comonomers and disulfide cross-linkers, VBL-NPs were synthesized and then conjugated with poly(ethylene glycol)-folate. The dynamic size of the obtained VBL-NPs-PEG-FA was 258.3 nm (PDI = 0.250), and the encapsulation efficiency was 45.82 ± 1.45%. The nanoparticles of VBL-NPs-PEG-FA were able to completely release VBL during 48 h under a mimic tumor intracellular condition (pH 4.5, 10 mM glutathione (GSH)), displaying significant redox responsiveness, whereas the release rates were much slower in the mimic body liquid (pH 7.4, 2 μM GSH) and tumor extracellular environment (pH 6.5, 2 μM GSH). Furthermore, the carriers NPs-PEG-FA, prepared without VBL, showed satisfactory intrinsic hemocompatibility, cellular compatibility, and tumor-targeting properties: they could rapidly and efficiently accumulate to folate receptor positive Hela cells and then internalized via receptor-mediated endocytosis, and the retention in tumor tissues could last for over 48 h. Interestingly, VBL-NPs-PEG-FA could evidently increase the accumulation of VBL in tumor tissues while decreasing the distribution of VBL in organs, exert similar anticancer efficacy against Hela tumors in the xenograft model of nude mice to VBL injection, and significantly improve the abnormality of liver and spleen observed in VBL injection. VBL-NPs-PEG-FA has the potential to be the delivery carrier for VBL by enhancing the tumor-targeting efficacy of VBL and decreasing toxicity to normal tissues.

Viability, function and morphological integrity of precision-cut liver slices during prolonged incubation: Effects of culture medium

Precision-cut liver slices (PCLS) are an ex vivo model for metabolism and toxicity studies. However, data on the maintenance of the morphological integrity of the various cell types in the slices during prolonged incubation are lacking. Therefore, our aims were to characterize morphological and functional changes in rat PCLS during five days of incubation in a rich medium, RegeneMed®, and a standard medium, Williams' Medium E. Although cells of all types in the slices remain viable, profound changes in morphology were observed, which were more prominent in RegeneMed®. Slices underwent notable fibrosis, bile duct proliferation and fat deposition. Slice thickness increased, resulting in necrotic areas, while slice diameter decreased, possibly indicating cell migration. An increased proliferation of parenchymal and non-parenchymal cells (NPCs) was observed. Glycogen, albumin and Cyp3a1 were maintained albeit to a different level in two media. In conclusion, both hepatocytes and NPCs remain viable and functional, enabling five-day toxicity studies. Tissue remodeling and formation of a new capsule-like cell lining around the slices are evident after 3–4 days. The differences in effects between media emphasize the importance of media selection and of the recognition of morphological changes in PCLS, when interpreting results from toxicological or pharmacological studies.

Liver slices in in vitro pharmacotoxicology with special reference to the use of human liver tissue

In the early years of research in in vitro pharmacotoxicology liver slices have been used. After a decline in the application of slices in favour of the use of isolated hepatocytes and the isolated perfused liver preparation, the development of the Krumdieck slicer in the 1980s led to a ;comeback' of the technique. This review will focus on the use of human liver, with special reference to the comparison of slices with isolated hepatocytes in in vitro pharmacotoxicology. In addition, an overview on the predictive value of these in vitro systems for drug disposition and toxicity in vivo will be given. Preservation techniques for liver slices and hepatocytes will also be discussed. These techniques ensure an efficient utilization of the scarce human material. For long-term storage of liver slices and hepatocytes, cryopreservation seems most promising. However, cryopreservation is still in its infancy, and reports mainly deal with drug metabolism studies after cryopreservation. Drug toxicity, metabolism and transport data determined in slices and isolated hepatocytes, from both human and animal liver showed good correlation with the corresponding parameters measured in vivo. Therefore, the results obtained in such studies may give rise to more in-depth research on the mechanisms of pharmactoxicology in the human liver.

Preparation and incubation of precision-cut liver and intestinal slices for application in drug metabolism and toxicity studies

Precision-cut tissue slices (PCTS) are viable ex vivo explants of tissue with a reproducible, well defined thickness. They represent a mini-model of the organ under study and contain all cells of the tissue in their natural environment, leaving intercellular and cell-matrix interactions intact, and are therefore highly appropriate for studying multicellular processes. PCTS are mainly used to study the metabolism and toxicity of xenobiotics, but they are suitable for many other purposes. Here we describe the protocols to prepare and incubate rat and human liver and intestinal slices. Slices are prepared from fresh liver by making a cylindrical core using a drill with a hollow bit, from which slices are cut with a specially designed tissue slicer. Intestinal tissue is embedded in cylinders of agarose before slicing. Slices remain viable for 24 h (intestine) and up to 96 h (liver) when incubated in 6- or 12-well plates under 95% O(2)/5% CO(2) atmosphere.

Development of highly functional long-term culture method of liver slice embedded in agarose gel for bioartificial liver

It is difficult to a produce highly functional bioartificial liver (BAL) using only hepatocytes, because it is believed that liver-specific three-dimensional structure is necessary to maintain high function for BAL. But it is difficult to construct a culture system with liver-specific three-dimensional structure in vitro. To realize a highly functional culture system with liver-specific three-dimensional structure, we developed a culture system using liver slices that keep liver-specific architecture, such as liver lobule and hepatic microvascular system. Liver slices were embedded in agarose gel to maintain them under a moist and three-dimensional environment. We examined the viability and function of liver slices by using various shapes of agarose gel. Liver slices were cultured 1) under stationary condition (control), 2) directly embedded in gel, and 3) embedded in cylindrical gel for good drainage of medium and ventilation of air. The viability and function of the incubated liver slices were evaluated by LDH leakage, histomorphology, and immunohistochemistry. At 10 days, the morphological condition and function of liver slices embedded in cylindrical gel were maintained better than liver slices directly embedded in gel or in the stationary condition. We suggest that high functionality and morphological condition of liver slices could be maintained by embedding in cylindrical gel. In the future, it is possible that this method could be used to develop a highly functional bioartificial liver.

Inhibition of Kupffer cell activity induces hepatic triglyceride synthesis in fasted rats, independent of lipopolysaccharide challenge

BACKGROUND

Lipopolysaccharides (LPS), cleared from the blood by Kupffer cells, induce hypertriglyceridemia.

AIMS

To test the hypothesis that GdCl(3), through inhibition of large Kupffer cell activity, modulates LPS-induced hyperlipidemia in rats.

METHODS

Male Wistar rats received a single intravenous injection of GdCl(3)(10 mg/kg) or saline, 24 h before intraperitoneal LPS (1.5 mg/kg) administration. Serum and hepatic lipids as well as activity of key enzymes controlling fatty acid synthesis and esterification in liver tissue were measured. The incorporation of labeled precursors into lipids was assessed in cultured precision-cut liver slices.

RESULTS

GdCl(3) does not prevent hypertriglyceridemia occurring in LPS-treated rats. Surprisingly, GdCl(3) per se is able to promote triglycerides accumulation in the liver tissue, an effect related to an increase in hepatic fatty acid esterification. Such an effect also occurs in rats receiving a dietary supplementation with glycine (5%) known to inhibit Kupffer cell secretory capacity.

CONCLUSIONS

Large Kupffer cell inhibition does not prevent LPS-induced hypertriglyceridemia and even leads to a metabolic shift of fatty acids towards their esterification and accumulation in the liver tissue, suggesting that Kupffer cells play a role in the regulation of lipid metabolism of the adjacent hepatocytes, independent of any inflammatory stimulus.

Modulation of paracetamol metabolism by Kupffer cells: a study on rat liver slices

Recent studies support the hypothesis that non parenchymal cells (mainly macrophages) may play a role in the metabolism and cellular effects of paracetamol. In order to investigate this hypothesis, male Wistar rats were intravenously injected with either 7.5 mg/kg gadolinium chloride (Gd+) or NaCl 0.9% (Gd-). The treatment with GdCl3 decreased the number and the function of Kupffer cells in liver tissue, as assessed by the histological examination of the liver after colloidal carbon injection in the portal vein. Precision-cut liver slices (PCLS) were prepared from both groups of rats and cultured for 8h in Waymouth's medium in the presence and absence of 5 mM paracetamol. Interestingly, PCLS obtained from Gd+ rats exhibited a lower release of tumor necrosis factor (TNF-alpha) and a better viability than PCLS from control (Gd-) rats. Incubation with paracetamol led to a decreased glycogen level in liver slices from Gd+ or Gd-, without modifying neither liver morphology nor ATP level nor LDH release. A higher proportion of paracetamol glucuronide, was secreted from the slices obtained from Gd+ rats. These data suggest that Kupffer cells could affect the viability of PCLS in culture and are involved in the regulation of phase II metabolism in the adjacent hepatocytes. We propose that PCLS in culture is a suitable model to elucidate the biochemical mechanism underlying the modulation of metabolism occurring through hepatocytes-Kupffer cells interactions.

Thermic transition and glycolytic capacity as critical events in the survival of rat liver slices after overnight cold hypoxic preservation

Cellular survival and hypoxia-reoxygenation injury in overnight cold-preserved liver slices (+/-20 h at 4 degrees C) were investigated. Increased cell death after overnight cold hypoxia depended more on temperature than on the reoxygenation process itself. Fructose (at 50 mM) added before the onset of hypoxia improved survival at the end of 20 h of cold hypoxia over Krebs- or glucose-treated slices. Such a protective effect by fructose was also seen during the normothermic (37 degrees C) reoxygenation of previously cold hypoxic-preserved slices, but only in the absence and not in the presence of tert-butyl hydroperoxide, a model compound widely used to induce an oxidative stress. The protection by fructose was equivalent to that observed when liver slices were incubated in the University of Wisconsin solution (UW). Finally, the morphological study of haematoxylin and eosin (H & E)-stained slices has shown cytoplasmic vacuoles during the reoxygenation step, which were more pronounced in UW-treated than in fructose-treated slices.

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.