Search

Pharmaceuticals are found in the environment but the impact of this contamination on human and animal health is poorly known. The liver could be particularly targeted since a significant number of these drugs are hepatotoxic, in particular via oxidative stress and mitochondrial dysfunction. Notably, the latter events can also be observed in liver diseases linked to obesity, so that the obese liver might be more sensitive to drug toxicity. In this study, we determined the effects of a chronic exposure to low doses of pharmaceuticals in wild-type and obese mice, with a particular focus on mitochondrial function. To this end, wild-type and ob/ob mice were exposed for 4 months to a cocktail of 11 pharmaceuticals provided in drinking water containing 0.01, 0.1, or 1 mg/L of each drug. At the end of the treatment, liver mitochondria were isolated and different parameters were measured. Chronic exposure to the pharmaceuticals reduced mitochondrial respiration driven by succinate and palmitoyl-l-carnitine in wild-type mice and increased antimycin-induced ROS production in ob/ob mice. Hyperglycemia and hepatic histological abnormalities were also observed in treated ob/ob mice. Investigations were also carried out in isolated liver mitochondria incubated with the mixture, or with each individual drug. The mitochondrial effects of the mixture were different from those observed in treated mice and could not be predicted from the results obtained with each drug. Because some of the 11 drugs included in our cocktail can be found in water at relatively high concentrations, our data could be relevant in environmental toxicology. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1375-1389, 2017.

International audience; Mitochondrial dysfunction is a major mechanism whereby different drugs can induce liver injury such as cytolytic hepatitis, microvesicular and/or macrovacuolar steatosis, steatohepatitis, and possibly cholestasis. In the most severe cases, drug-induced mitochondrial dysfunction and liver injury can require liver transplantation or lead to the death of the patient. Moreover, these adverse effects can lead to the withdrawal of drugs from the market, or earlier during clinical trials. Drugs can induce mitochondrial dysfunction by different mechanisms including inhibition of fatty acid oxidation, impairment of oxidative phosphorylation and respiratory chain activity, and alteration of the integrity of the mitochondrial membranes. The present chapter focuses on different drugs for which enough clinical and experimental evidence indicates the potential role of mitochondrial dysfunction in the pathogenesis of liver injury acetaminophen, amiodarone, fialuridine, linezolid, nucleoside reverse transcriptase inhibitors (e.g., stavudine, zidovudine, and didanosine), tamoxifen, tetracycline, troglitazone, and valproic acid. Because drug-induced mitochondrial dysfunction and liver injury are major issues for public health and pharmaceutical companies, mitochondrial liability should be systematically investigated during preclinical safety studies. © 2018 John Wiley and Sons, Inc. All rights reserved.

International audience; Mitochondrial dysfunction can be a major mechanism whereby different drugs can induce adverse effects affecting different tissues such as liver, heart and skeletal muscle. In the most severe cases, drug-induced mitochondrial dysfunction can require a hospitalization, or lead to the death of the patient. Moreover, these adverse effects can lead to the withdrawal of drugs from the market, or earlier during clinical trials. Drugs can induce mitochondrial dysfunction by different mechanisms including inhibition of fatty acid oxidation, impairment of oxidative phosphorylation and respiratory chain activity as well as alteration of the integrity of the mitochondrial membranes. Some drugs also impair mitochondrial function via the production of reactive oxygen species and the generation of reactive metabolites, which can covalently bind to key mitochondrial proteins. The present chapter focuses on different drugs for which enough clinical and experimental evidence indicates the potential role of mitochondrial dysfunction in the pathogenesis of adverse effects such as liver injury, myopathy and cardiotoxicity acetaminophen, amiodarone, doxorubicin, nucleoside reverse transcriptase inhibitors (e.g. stavudine, zidovudine, didanosine), statins (e.g. atorvastatin, cerivastatin, simvastatin) and valproic acid. Notably, these drugs epitomize the diversity of the mechanisms whereby xenobiotics can induce mitochondrial dysfunction and also the variety of the targeted tissues. Other drugs affecting mitochondrial function by similar mechanisms are discussed more briefly in the present chapter. Because drug-induced mitochondrial dysfunction and related adverse events are major issues for public health and pharmaceutical companies, mitochondrial liability should be systematically investigated during preclinical safety studies. © Springer International Publishing AG, part of Springer Nature 2018.

International audience; Mitochondrial liability of drugs and other xenobiotics is a major issue for patients because such toxicity can damage different tissues and organs such as liver, heart, and muscle. Drug-induced mitochondrial toxicity is also a major concern for pharmaceutical industries. Indeed, it is now acknowledged that such mechanism of toxicity can induce severe, and sometimes fatal, liver injury which can lead to the interruption of clinical trials, or drug withdrawal after marketing, such as in the case of troglitazone. Therefore, drug-induced mitochondrial dysfunction is increasingly sought after by pharmaceutical companies by using reliable in vitro assays in order to discard potential mitochondrion-toxic drugs during drug discovery stage. This chapter presents the in vitro methods used to identify potential mitochondrion-toxic drugs. To this end, different types of biological materials are used such as isolated mouse liver mitochondria and the human hepatic HepaRG® cell line, which expresses the main enzymes and transcription factors involved in drug metabolism. The in vitro method we discussed allows to investigate several key mitochondrial parameters such as oxygen consumption, transmembrane potential, respiratory chain complex activities, and mtDNA levels. These investigations are able to detect not only direct and acute mitochondrial alterations due to parent drugs but also indirect and chronic mitochondrial liability that can be induced by secondary metabolites. Hence, it could be used to detect potential drug-induced mitochondrial liability and to understand the involved mechanisms. © 2018, Springer Science+Business Media, LLC, part of Springer Nature.

International audience; Drug-induced liver injury (DILI) in humans is difficult to predict using classical in vitro cytotoxicity screening and regulatory animal studies. This explains why numerous compounds are stopped during clinical trials or withdrawn from the market due to hepatotoxicity. Thus, it is important to improve early prediction of DILI in human. In the present study, we hypothesized that this goal could be achieved by investigating drug-induced mitochondrial dysfunction as this toxic effect is a major mechanism of DILI. To this end, we developed a high-throughput screening platform using isolated mouse liver mitochondria. Our broad spectrum multiparametric assay was designed to detect the global mitochondrial membrane permeabilization (swelling), inner membrane permeabilization (transmembrane potential), outer membrane permeabilization (cytochrome c release) and alteration of mitochondrial respiration driven by succinate or malate/glutamate. A pool of 124 chemicals (mainly drugs) was selected, including 87 with documented DILI and 37 without reported clinical hepatotoxicity. Our screening assay revealed an excellent sensitivity for clinical outcome of DILI (94 or 92% depending on cut-off) and a high positive predictive value (89 or 82%). A highly significant relationship between drug-induced mitochondrial toxicity and DILI occurrence in patients was calculated (P

International audience; Numerous investigations have shown that mitochondrial dysfunction is a major mechanism of drug-induced liver injury, which involves the parent drug or a reactive metabolite generated through cytochromes P450. Depending of their nature and their severity, the mitochondrial alterations are able to induce mild to fulminant hepatic cytolysis and steatosis (lipid accumulation), which can have different clinical and pathological features. Microvesicular steatosis, a potentially severe liver lesion usually associated with liver failure and profound hypoglycemia, is due to a major inhibition of mitochondrial fatty acid oxidation (FAO). Macrovacuolar steatosis, a relatively benign liver lesion in the short term, can be induced not only by a moderate reduction of mitochondrial FAO but also by an increased hepatic de novo lipid synthesis and a decreased secretion of VLDL-associated triglycerides. Moreover, recent investigations suggest that some drugs could favor lipid deposition in the liver through primary alterations of white adipose tissue (WAT) homeostasis. If the treatment is not interrupted, steatosis can evolve toward steatohepatitis, which is characterized not only by lipid accumulation but also by necroinflammation and fibrosis. Although the mechanisms involved in this aggravation are not fully characterized, it appears that overproduction of reactive oxygen species by the damaged mitochondria could play a salient role. Numerous factors could favor drug-induced mitochondrial and metabolic toxicity, such as the structure of the parent molecule, genetic predispositions (in particular those involving mitochondrial enzymes), alcohol intoxication, hepatitis virus C infection, and obesity. In obese and diabetic patients, some drugs may induce acute liver injury more frequently while others may worsen the pre-existent steatosis (or steatohepatitis).

The adenine nucleotide translocator (ANT) is a mitochondrial bi-functional protein, which catalyzes the exchange of ADP and ATP between cytosol and mitochondria and participates in many models of mitochondrial apoptosis. The human adenine nucleotide translocator sub-family is composed of four isoforms, namely ANT1-4, encoded by four nuclear genes, whose expression is highly regulated. Previous studies have revealed that ANTI and 3 induce mitochondrial apoptosis, whereas ANT2 is anti-apoptotic. However, the role of the recently identified isoform ANT4 in the apoptotic pathway has not yet been elucidated. Here, we investigated the effects of stable heterologous expression of the ANT4 on proliferation, mitochondrial respiration and cell death in human cancer cells, using ANT3 as a control of pro-apoptotic isoform. As expected, ANT3 enhanced mitochondria-mediated apoptosis in response to lonidamine, a mitochondriotoxic chemotherapeutic drug, and staurosporine, a protein kinase inhibitor. Our results also indicate that the pro-apoptotic effect of ANT3 was accompanied by decreased rate of cell proliferation, alteration in the mitochondrial network topology, and decreased reactive oxygen species production. Of note, we demonstrate for the first time that ANT4 enhanced cell growth without impacting mitochondria] network or respiration. Moreover, ANT4 differentially regulated the intracellular levels of hydrogen peroxide without affecting superoxide anion levels. Finally, stable ANT4 overexpression protected cancer cells from lonidamine and staurosporine apoptosis in a manner independent of Bcl-2 expression. These data highlight a hitherto undefined cytoprotective activity of ANT4, and provide a novel dichotomy in the human ANT isoform sub-family with ANT1 and 3 isoforms functioning as pro-apoptotic while ANT2 and 4 isoforms render cells resistant to death inducing stimuli. (C) 2010 Elsevier Ltd. All rights reserved.

Mitochondrial Dysfunction and Diseases (H Jaeschke, Section Editor); International audience; Drug-induced inhibition of mitochondrial fatty acid β-oxidation (mtFAO) is a key mechanism whereby drugs can induce steatosis. The type and severity of this liver lesion is dependent on the residual mtFAO flux. Indeed, a severe inhibition of mtFAO leads to microvesicular steatosis, hypoglycemia and liver failure, which can be favored by genetic predispositions. In contrast, moderate impairment of mtFAO can cause macrovacuolar steatosis, which is by itself a benign lesion. In the long-term, however, macrovacuolar steatosis can progress with some drugs to steatohepatitis. Interestingly, drugs that are more likely to cause steatohepatitis are those impairing the mitochondrial respiratory chain (MRC) activity. Indeed, MRC impairment favors not only hepatic fat accretion but also oxidative stress and lipid peroxidation. Drugs inhibiting mtFAO could be more toxic in obese patients with preexisting nonalcoholic fatty liver disease (NAFLD) since higher mtFAO is a key metabolic adaptation to curb fat accretion during NAFLD.

International audience; Dengue viruses belong to the Flavivirus family and are responsible for hemorrhagic fever in Human. Dengue virus infection triggers apoptosis especially through the expression of the small membrane (M) protein. Using isolated mitochondria, we found that synthetic peptides containing the C-terminus part of the M ectodomain caused apoptosis-related mitochondrial membrane permeabilization (MMP) events. These events include matrix swelling and the dissipation of the mitochondrial transmembrane potential (DeltaPsi(m)). Protein M Flavivirus sequence alignments and helical wheel projections reveal a conserved distribution of charged residues. Moreover, when combined to the cell penetrating HIV-1 Tat peptide transduction domain (Tat-PTD), this sequence triggers a caspase-dependent cell death associated with DeltaPsi(m) loss and cytochrome c release. Mutational approaches coupled to functional screening on isolated mitochondria resulted in the selection of a protein M derived sequence containing nine residues with potent MMP-inducing properties on isolated mitochondria. A chimeric peptide composed of a Tat-PTD linked to the 9-mer entity triggers MMP and cell death. Finally, local administration of this chimeric peptide induces growth inhibition of xenograft prostate PC3 tumors in immuno-compromised mice, and significantly enhances animal survival. Together, these findings support the notion of using viral genomes as valuable sources to discover mitochondria-targeted sequences that may lead to the development of new anticancer compounds.

orrigendum to “The fourth isoform of the adenine nucleotide ranslocator inhibits mitochondrial apoptosis in cancer cells” Int. J. Biochem. Cell Biol. 42 (2010) 623–629] indy Gallernea,2, Zahia Touata,1, Zhi Xiong Chenb, Cecile Martela,2, Eleonore Mayolaa,2, ssama Sharaf el deina,2, Nelly Buronc,3, Morgane Le Brasa, Etienne Jacototc,4, nnie Borgne-Sanchezc,3, Antoinette Lemoined, Christophe Lemairea,2, Shazib Pervaizb, atherine Brennera,∗,2

International audience; The Trans-activator protein (Tat) of human immunodeficiency virus (HIV) is a pleiotropic protein involved in different aspects of AIDS pathogenesis. As a number of viral proteins Tat is suspected to disturb mitochondrial function. We prepared pure synthetic full-length Tat by native chemical ligation (NCL), and Tat peptides, to evaluate their direct effects on isolated mitochondria. Submicromolar doses of synthetic Tat cause a rapid dissipation of the mitochondrial transmembrane potential (ΔΨ(m)) as well as cytochrome c release in mitochondria isolated from mouse liver, heart, and brain. Accordingly, Tat decreases substrate oxidation by mitochondria isolated from these tissues, with oxygen uptake being initially restored by adding cytochrome c. The anion-channel inhibitor 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) protects isolated mitochondria against Tat-induced mitochondrial membrane permeabilization (MMP), whereas ruthenium red, a ryanodine receptor blocker, does not. Pharmacologic inhibitors of the permeability transition pore, Bax/Bak inhibitors, and recombinant Bcl-2 and Bcl-XL proteins do not reduce Tat-induced MMP. We finally observed that Tat inhibits cytochrome c oxidase (COX) activity in disrupted mitochondria isolated from liver, heart, and brain of both mouse and human samples, making it the first described viral protein to be a potential COX inhibitor.

The phosphatidylinositol 3-kinase subunit PI3K is frequently mutated in human cancers and therefore represents an interesting therapeutic target. Cancer resistance to therapies is often related to expression of anti-apoptotic Bcl-2 family members which negatively regulate mitochondrial cell death. We investigated the influence of PI3K mutations on Bcl-2 family proteins both at the cellular and mitochondrial level. We used human breast epithelial cell lines with an endogenous “knock-in” PI3K mutation (HME-1 cells harbouring the H1047R activating mutation) from which we purified the mitochondria to homogeneity (95%). We first characterized these mitochondria for their sensitivity to reference compounds (Calcium, t-Bid) on 3 parameters: swelling, m loss and cytochrome c release. Mitochondrial preparations from wild-type and mutated HME-1 were analysed for their protein pattern in Bcl-2 family members. We observed accumulation of anti-apoptotic (Bcl-xl and Bcl-2) and pro-apoptotic (Bad) proteins in mitochondria isolated from PI3K mutated cells. We showed that the excess of anti-apoptotic proteins at the mitochondria does not change their sensitivity to the Bcl-2 family inhibitor, ABT-737. Investigations with PI3K-inhibitors are currently undergoing to determine the mitochondrial on-target biomarker for drug development. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr LB-14.

Current limitations of chemotherapy include toxicity on healthy tissues and multidrug resistance on malignant cells. A number of recent anti-cancer strategies are targeting the mitochondrial apoptotic machinery to induce tumor cell death. In this study, we set up protocols to isolate mitochondria from various origins with high purity, quality and functionality. We analyzed the effect of putative Bcl-2 inhibitors on both healthy and tumor isolated mitochondria. We measured mitochondrial membrane permeabilization (swelling), mitochondrial transmembrane potential (ΔΨm) and mitochondrial outer membrane permeabilization (MOMP) in both isolated healthy and tumoral cell mitochondria. Like t-Bid and some BH3 peptides, the molecule ABT-737 was found to present a tumor-specific mitochondrio-toxicity, while compounds like HA-14.1, YC-137, Chelerythrine, Gossypol, TW-37 or EM20-25 did not. We thus demonstrated that ABT-737 can induce a relatively large and targeted MOMP triggering the release of apoptotic proteins from tumoral cell mitochondria (Cytochrome c, Smac/Diablo and Omi/HtrA2 but not AIF) however without any mitochondrial swelling. Furthermore, ABT-737 addition to isolated tumoral cell mitochondria induced specific Bax/Bak channel formation by oligomerizing monomeric Bax and/or Bak already inserted in the mitochondrial membrane. We also provided evidence that tumoral cell mitochondria can be either resistant or sensitive to ABT-737-induced MOMP, depending on their origin and interactions between pro- and anti-apoptotic proteins. Finally, this method based on MOMP is an interesting screening tool, tailored for identifying Bcl-2 antagonists with selective toxicity profile against tumoral cell mitochondria but devoid of toxicity against healthy mitochondria. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1021.

International audience; Current limitations of chemotherapy include toxicity on healthy tissues and multidrug resistance of malignant cells. A number of recent anti-cancer strategies aim at targeting the mitochondrial apoptotic machinery to induce tumor cell death. In this study, we set up protocols to purify functional mitochondria from various human cell lines to analyze the effect of peptidic and xenobiotic compounds described to harbour either Bcl-2 inhibition properties or toxic effects related to mitochondria. Mitochondrial inner and outer membrane permeabilization were systematically investigated in cancer cell mitochondria versus non-cancerous mitochondria. The truncated (t-) Bid protein, synthetic BH3 peptides from Bim and Bak, and the small molecule ABT-737 induced a tumor-specific and OMP-restricted mitochondrio-toxicity, while compounds like HA-14.1, YC-137, Chelerythrine, Gossypol, TW-37 or EM20-25 did not. We found that ABT-737 can induce the Bax-dependent release of apoptotic proteins (cytochrome c, Smac/Diablo and Omi/HtrA2 but not AIF) from various but not all cancer cell mitochondria. Furthermore, ABT-737 addition to isolated cancer cell mitochondria induced oligomerization of Bax and/or Bak monomers already inserted in the mitochondrial membrane. Finally immunoprecipatations indicated that ABT-737 induces Bax, Bak and Bim desequestration from Bcl-2 and Bcl-xL but not from Mcl-1L. This study investigates for the first time the mechanism of action of ABT-737 as a single agent on isolated cancer cell mitochondria. Hence, this method based on MOMP (mitochondrial outer membrane permeabilization) is an interesting screening tool, tailored for identifying Bcl-2 antagonists with selective toxicity profile against cancer cell mitochondria but devoid of toxicity against healthy mitochondria.

In many pathological conditions, a sudden lack of energy, accompanied by an increased reactive oxygen (ROS) level and calcium overload, accelerates cell death with necrotic features. As the mitochondrion is the main source of cellular ATP and ROS, it has become an attractive therapeutic target for human pathology such as cardiac, neuronal and hepatic ischemia-reperfusion injury. In this context, we and others have shown that pharmacological modulation of ANT can prevent three acute pathologies in mice1 and recently, we hypothesized that activation of ANT might be an innovative strategy for cardioprotection. Here, we present the design and the implementation of enzymatic, cellular and subcellular assays and their optimization for the screening of modulators of ANT (i.e. inhibitors and/or activators). We miniaturized the ADP/ATP exchange measurement in cardiac interfibrillar and subsarcolemmal isolated mitochondria from rat heart, evaluated its robustness (Z-factor) in 96 well-microtiter plates and screened an in silico-generated library of ANT-potential ligands and small molecules, i.e. about 100 molecules. Cytotoxicity was evaluated in rat H9c2 and human HT29 cell lines and non-cytotoxic compounds (i.e. with LD50 >200 μM) were selected for further studies. To confirm potential hits activity directly on ANT, we purified the native protein from rat hearts in the presence of Triton X-100, confirmed its purity by western-blot and incorporated it into small unilamellar vesicles (100 nm of diameter) as described.2 Validation of a novel ANT-containing proteoliposome bioluminescent assay is currently on-going to develop a method to quantify the ability of molecules to modulate ADP/ATP exchange efficacy in dose-response and calculate EC50. If robust, this assay will be adapted to our high throughput screening platform. For a therapeutic perspective, identified molecules will be evaluated for their toxicity, druggability, and for their ability to influence the disease outcome in animal models as a prerequisite for future clinical studies.