Cigarette smoke interacts with amiodarone toxicity in Saccharomyces cerevisiae.

Amiodarone (AMD) is an antiarrhythmic drug prescribed to treat ventricular tachycardia and fibrillation. However, it causes an unpredictable toxicity (idiosyncratic), which may depend on co-exposure to pollutants. AMD toxicity involves calcium homeostasis alteration and oxidative stress, which are also affected by cigarette smoke (CS). We investigated the interaction of CS-condensate (CSC), phenanthrene, and benzo(a)pyrene with AMD toxicity on Saccharomyces cerevisiae. AMD toxicity was reduced by CSC or phenanthrene. Benzo(a)pyrene mildly decreased AMD toxicity on the wild-type strain, but not on the catalase-CTT1 mutant. This latter and other mutants in glucose receptor-GPR1 or calcium transporter-PMR1 showed lower antagonistic effect to AMD by CSC or phenanthrene relative to the wild type, suggesting roles of oxidative stress, calcium homeostasis, and hexose-sensing in this interaction.

Dose-dependent interaction of two heavy metals with amiodarone toxicity in Saccharomyces cerevisiae.

Amiodarone (AMD) is an antiarrhythmic drug that induces idiosyncratic toxicity. Environmental pollutants, including heavy metals, could interact with its toxicity by affecting pharmacokinetics and pharmacodynamics. Other levels of interaction could exist in yeast, such as oxidative stress and the general stress response. In this study, we investigated the interaction of mercury chloride (HgCl2) and cadmium chloride (CdCl2) with AMD toxicity on Saccharomyces cerevisiae. Interaction type - synergistic, additive, or antagonistic - was determined by median drug effect analysis using "CompuSyn". HgCl2 potentiated AMD toxicity at high doses (≥ 71.4 µm, which yielded more than 60% inhibition). CdCl2 acted similarly at high doses (≥ 57.9 µm). An antagonistic effect appeared at lower doses with both heavy metals (≤ 49.4 µm for HgCl2 and AMD; ≤ 18.9 µm for CdCl2 and AMD). The threshold concentrations (HgCl2 or CdCl2 combined with AMD) that switched the interaction from antagonistic to additive, and then to synergistic, were decreased in the yeast strain mutant in catalase (CTT1), suggesting an important role for this enzyme. Moreover, mutation of the nutrient sensing receptor gene GPR1 caused the synergistic interaction of CdCl2, but not HgCl2, with AMD to occur at the lowest tested concentrations (1.2 µm). The reverse was obtained with the mutant strain in calcium-manganese transporter gene PMR1, where the synergistic interaction of HgCl2 with AMD occurred at concentrations (20.7 µm) lower than that of the wild type (71.4 µm). These results demonstrated a dose-dependent interaction between the two heavy metals with AMD toxicity, and the involvement of oxidative stress, calcium homeostasis, and nutrient sensing in the observed interaction.

N-acetylcysteine potentiates diclofenac toxicity in Saccharomyces cerevisiae: stronger potentiation in ABC transporter mutant strains.

Diclofenac (DCF) adverse reactions involve diverse mechanisms in different models. We recently demonstrated that DCF-induced toxicity in HepaRG decreases as they express DCF-metabolizing enzymes. DCF metabolism promotes toxicity in Saccharomyces cerevisiae expressing heterologous cytochromes-P450. N-Acetylcysteine (NAC) is used to treat diverse medical conditions due to its multiple properties (antioxidant, metal chelator, thiol-disulfide disruption). The latter property accounts for its mucolytic effects and broadens its potential molecular targets to signal transduction proteins, ABC transporters and others. Interaction of NAC with DCF effects depends on the experimental model. This study aims to investigate NAC/DCF interaction and the involvement of ABC transporters in wild type and mutant Saccharomyces cerevisiae. DCF inhibited yeast growth in a dose- and time-dependent manner and the cells started adapting to DCF 24-h post-treatment. NAC potentiated DCF-induced toxicity if added prior or parallel to DCF. Pretreatment with NAC increased its potentiation effect and compromised cells adaption to DCF. Post-treatment with NAC potentiated DCF toxicity without compromising adaptation. Moreover, mutant strains in ABC transporters Pdr5, Yor1, Bpt1 or Pdr15, were more sensitive to DCF; while mutant strains in Pdr5, Vmr1 or Pdr12 were more sensitive to NAC/DCF interaction. DCF ± NAC elicited on the mutant strain in Yap1, an oxidative stress-related protein, the same effects as on the wild type. Therefore, oxidative stress does not seem to be key actor in DCF toxicity in our model. Our hypothesis is that NAC potentiation effect is at least due to its ability to disrupt disulfide bridge in proteins required to overcome DCF toxicity in yeast.

Differential sensitivity of metabolically competent and non-competent HepaRG cells to apoptosis induced by diclofenac combined or not with TNF-α.

The role of reactive metabolites and inflammatory stress has been largely evoked in idiosyncratic hepatotoxicity of diclofenac (DCF); however mechanisms remain poorly understood. We aimed to evaluate the influence of liver cell phenotype on the hepatotoxicity of DCF combined or not with TNF-α using differentiated and undifferentiated HepaRG cells, and for comparison, HepG2 cells. Our results demonstrate that after a 24h-treatment metabolizing HepaRG cells were less sensitive to DCF than their undifferentiated non-metabolizing counterparts as shown by lower oxidative and endoplasmic reticulum stress responses and lower activation of caspase 9. Differentiated HepaRG cells were also less sensitive than HepG2 cells. Their lower sensitivity to DCF was related to their high content in glutathione transferases. DCF-induced apoptotic effects were potentiated by TNF-α only in death receptor-expressing differentiated HepaRG and HepG2 cells and were associated with marked activation of caspase 8. TNF-α co-treatment did not aggravate DCF-induced cholestatic features. Altogether, our results demonstrate that (i) lower sensitivity to DCF of differentiated HepaRG cells compared to their non-metabolically active counterparts was related to their high detoxifying capacity, giving support to the higher sensitivity of nonhepatic tissues than liver to this drug; (ii) TNF-α-potentiation of DCF cytotoxicity occurred only in death receptor-expressing cells.

Impact of inflammation on chlorpromazine-induced cytotoxicity and cholestatic features in HepaRG cells.

Several factors are thought to be implicated in the occurrence of idiosyncratic adverse drug reactions. The present work aimed to question as to whether inflammation is a determinant factor in hepatic lesions induced by chlorpromazine (CPZ) using the human HepaRG cell line. An inflammation state was induced by a 24-hour exposure to proinflammatory cytokines interleukin-6 (IL-6) and IL-1ß; then the cells were simultaneously treated with CPZ and/or cytokine for 24 hours or daily for 5 days. The inflammatory response was assessed by induction of C-reactive protein and IL-8 transcripts and proteins as well as inhibition of CPZ metabolism and down-regulation of cytochrome 3A4 (CYP3A4) and CYP1A2 transcripts, two major cytochrome P450 (P450) enzymes involved in its metabolism. Most effects of cotreatments with cytokines and CPZ were amplified or only observed after five daily treatments; they mainly included increased cytotoxicity and overexpression of oxidative stress-related genes, decreased Na(+)-taurocholate cotransporting polypeptide mRNA levels and activity, a key transporter involved in bile acids uptake, and deregulation of several other transporters. However, CPZ-induced inhibition of taurocholic acid efflux and pericanalicular F-actin distribution were not affected. In addition, a time-dependent induction of phospholipidosis was noticed in CPZ-treated cells, without obvious influence of the inflammatory stress. In summary, our results show that an inflammatory state induced by proinflammatory cytokines increased cytotoxicity and enhanced some cholestatic features induced by the idiosyncratic drug CPZ in HepaRG cells. These changes, together with inhibition of P450 activities, could have important consequences if extrapolated to the in vivo situation.

Different dose-dependent mechanisms are involved in early cyclosporine a-induced cholestatic effects in hepaRG cells.

Mechanisms involved in drug-induced cholestasis in humans remain poorly understood. Although cyclosporine A (CsA) and tacrolimus (FK506) share similar immunosuppressive properties, only CsA is known to cause dose-dependent cholestasis. Here, we have investigated the mechanisms implicated in early cholestatic effects of CsA using the differentiated human HepaRG cell line. Inhibition of efflux and uptake of taurocholate was evidenced as early as 15 min and 1 h respectively after addition of 10µM CsA; it peaked at around 2 h and was reversible. These early effects were associated with generation of oxidative stress and deregulation of cPKC pathway. At higher CsA concentrations (≥50µM) alterations of efflux and uptake activities were enhanced and became irreversible, pericanalicular F-actin microfilaments were disorganized and bile canaliculi were constricted. These changes were associated with induction of endoplasmic reticulum stress that preceded generation of oxidative stress. Concentration-dependent changes were observed on total bile acid disposition, which were characterized by an increase and a decrease in culture medium and cells, respectively, after a 24-h treatment with CsA. Accordingly, genes encoding hepatobiliary transporters and bile acid synthesis enzymes were differently deregulated depending on CsA concentration. By contrast, FK506 induced limited effects only at 25-50µM and did not alter bile canaliculi. Our data demonstrate involvement of different concentration-dependent mechanisms in CsA-induced cholestasis and point out a critical role of endoplasmic reticulum stress in the occurrence of the major cholestatic features.