In vitro investigation of the molecular mechanisms of hepatotoxicity

Uncovering the toxicity mechanisms of a series of carboxylic acids in liver cells through computational and experimental approaches

Hepatotoxicity poses a significant concern in drug design due to the potential liver damage that can be caused by new drugs. Among common manifestations of hepatotoxic damage is lipid accumulation in hepatic tissue, resulting in liver steatosis or phospholipidosis. Carboxylic derivatives are prone to interfere with fatty acid metabolism and cause lipid accumulation in hepatocytes. This study investigates the toxic behaviour of 24 structurally related carboxylic acids in hepatocytes, specifically their ability to cause accumulation of fatty acids and phospholipids. Using high-content screening (HCS) assays, we identified two distinct lipid accumulation patterns. Subsequently, we developed structure-activity relationship (SAR) and quantitative structure-activity relationship (QSAR) models to determine relevant molecular substructures and descriptors contributing to these adverse effects. Additionally, we calculated physicochemical properties associated with lipid accumulation in hepatocytes and examined their correlation with our chemical structure characteristics. To assess the applicability of our findings to a wide range of chemical compounds, we employed two external datasets to evaluate the distribution of our QSAR descriptors. Our study highlights the significance of subtle molecular structural variations in triggering hepatotoxicity, such as the presence of nitrogen or the specific arrangement of substitutions within the carbon chain. By employing our comprehensive approach, we pinpointed specific molecules and elucidated their mechanisms of toxicity, thus offering valuable insights to guide future toxicology investigations.

Calcium imaging: a technique to monitor calcium dynamics in biological systems

Calcium ion (Ca2+) is a multifaceted signaling molecule that acts as an important second messenger. During the course of evolution, plants and animals have developed Ca2+ signaling in order to respond against diverse stimuli, to regulate a large number of physiological and developmental pathways. Our understanding of Ca2+ signaling and its components in physiological phenomena ranging from lower to higher organisms, and from single cell to multiple tissues has grown exponentially. The generation of Ca2+ transients or signatures for various stress factor is a well-known mechanism adopted in plant and animal systems. However, the decoding of such remarkable signatures is an uphill task and is always an interesting goal for the scientific community. In the past few decades, studies on the concentration and dynamics of intracellular Ca2+ are significantly increasing and have become a trend in modern biology. The advancement in approaches from Ca2+ binding dyes to in vivo Ca2+ imaging through the use of Ca2+ biosensors to achieve spatio-temporal resolution in micro and milliseconds range, provide us phenomenal opportunities to study live cell Ca2+ imaging or dynamics. Here, we describe the usage, improvement and advancement of Ca2+ based dyes, genetically encoded probes and sensors to achieve extraordinary Ca2+ imaging in plants and animals.

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General Cytotoxicity Assessment by Means of the MTT Assay

Cytotoxicity assays were among the first in vitro bioassay methods used to predict toxicity of substances to various tissues. In vitro cytotoxicity testing provides a crucial means for safety assessment and screening, and for ranking compounds. The choice of using a particular cytotoxicity assay technology may be influenced by specific research goals. As such, four main classes of assays are used to monitor the response of cultured cells after treatment with potential toxicants. These methods measure viability, cell membrane integrity, cell proliferation, and metabolic activity. In this chapter, we focus on the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide tetrazolium reduction colorimetric assay to evaluate detrimental intracellular effects on metabolic activity. This assay is well-characterized, simple to use and remains popular in several laboratories worldwide.

Kinetic and density functional theory (DFT) studies of in vitro reactions of acrylamide with the thiols: captopril, l-cysteine, and glutathione

In vitro kinetic studies with DFT computations to explain the potential of acrylamide metabolism/toxicity with thiols in vivo.

In vitro studies on the reaction rates of acrylamide with the key body-fluid thiols l-cysteine, glutathione, and captopril

The mechanisms of interactions of acrylamide with l-cysteine, glutathione and captopril were studied in vitro. Experimental second order rate constants calculated at 303 K were 0.34 ± 0.02, 0.18 ± 0.02, and 0.13 ± 0.01 dm3 mol−1 s−1 for l-cysteine, glutathione, and captopril, respectively, potentially involving inter- and intra-molecular H-bonding in the acrylamide-glutathione complex.

Primary hepatocytes: current understanding of the regulation of metabolic enzymes and transporter proteins, and pharmaceutical practice for the use of hepatocytes in metabolism, enzyme induction, transporter, clearance, and hepatotoxicity studies

This review brings you up-to-date with the hepatocyte research on: 1) in vitro-in vivo correlations of metabolism and clearance; 2) CYP enzyme induction, regulation, and cross-talk using human hepatocytes and hepatocyte-like cell lines; 3) the function and regulation of hepatic transporters and models used to elucidate their role in drug clearance; 4) mechanisms and examples of idiosyncratic and intrinsic hepatotoxicity; and 5) alternative cell systems to primary human hepatocytes. We also report pharmaceutical perspectives of these topics and compare methods and interpretations for the drug development process.

Metabolism of acrylamide to glycidamide and their cytotoxicity in isolated rat hepatocytes: protective effects of GSH precursors

Acrylamide (AA) is a widely studied industrial chemical that is neurotoxic, mutagenic to somatic and germ cells, and carcinogenic in rodents. The recent discovery of AA at ppm levels in a wide variety of commonly consumed foods has energized research efforts worldwide to define toxicity and prevention. Metabolism and cytotoxicity of AA and its epoxide glycidamide (GA) were studied in the hepatocytes freshly isolated from male Sprague-Dawley rats. The isolated hepatocytes metabolized AA to GA. The formation of GA followed Michaelis-Menten kinetic parameters yielded apparent Km = 0.477 +/- 0.100 and 0.263 +/- 0.016 mM, Vmax = 6.5 +/- 2.1 and 26.4 +/- 3.0 nmol/h/10(6) cells, and CLint = 14 +/- 5 and 100 +/- 12 microl/h/10(6) cells for the hepatocytes from untreated and acetone-treated rats, respectively. There were lower Km and marked increases in Vmax (four-fold) and in CLint (sevenfold) in acetone-treated rat hepatocytes. The data suggest that CYP2E1 played a major role in metabolizing AA to more toxic GA. Both AA and GA induced a concentration- and time-dependent glutathione (GSH) depletion of the hepatocytes. From decreasing rates of GSH contents in hepatocytes, the parameters of glutathione S-transferase (GST) in hepatocytes to AA and GA were calculated to be Km = 1.4 and 1.5 mM, Vmax = 21 and 33 nmol/h/10(6) cells, and CLint = 15 and 23 microl/h/10(6) cells, respectively. GA 1.5-times more readily depleted GSH content than AA. GA decreased the viability of hepatocytes at 3 mM, but AA did not. These data indicate that GA is more toxic than AA as assessed by intracellular GSH depletion and loss of viability of hepatocytes. GSH precursors such as N-acetylcysteine and methionine provided significant anti-cytotoxic effects on the decrease of GSH content and cell viability of hepatocytes induced by GA and AA.

Cytoprotective actions of estrogens against tert-butyl hydroperoxide-induced toxicity in hepatocytes

Estrogens are effective antioxidants in diverse biological systems. Despite their antioxidant activities, it is not known yet whether estrogens prevent or alleviate liver toxicity induced by oxidative stress. In the present work, we studied this possibility by examining in vitro the protective potential of different estrogen compounds (17beta-estradiol, 2-hydroxyestradiol, and diethylstilbestrol) against tert-butyl hydroperoxide-induced hepatocyte damage. Various parameters such as cell viability, lipid peroxidation, adenine nucleotide content, and thiol status were measured as an index of cytotoxicity. The protective effects of estrogens were compared to those of the iron chelator deferoxamine. The molecules tested prevented oxidant-induced cell death differently, showing variable degrees of protection. Deferoxamine was the most potent agent, followed by diethylstilbestrol and 2-hydroxyestradiol, 17beta-estradiol being the least efficient. The inhibitory effects on lipid and thiol oxidations paralleled the effects on cell viability. The molecules also reduced the oxidant-induced ATP depletion, except for 17beta-estradiol which had no effect on the decreased ATP levels. Our results suggest that the mechanisms of the preventive actions of estrogens may be related not only to their antioxidant activity against free radicals, but also and to a lesser extent to the maintenance of the normal redox status of the cell, which partially recovers the intracellular GSH levels.