Silymarin and vitamin E reduce amiodarone-induced lysosomal phospholipidosis in rats

Livogrit prevents Amiodarone-induced toxicity in experimental model of human liver (HepG2) cells and Caenorhabditis elegans by regulating redox homeostasis

Treatment with cationic amphiphilic drugs like Amiodarone leads to development of phospholipidosis, a type of lysosomal storage disorder characterized by excessive deposition of phospholipids. Such disorder in liver enhances accumulation of drugs and its metabolites, and dysregulates lipid profiles, which subsequently leads to hepatotoxicity. In the present study, we assessed pharmacological effects of herbal medicine, Livogrit, against hepatic phospholipidosis-induced toxicity. Human liver (HepG2) cells and in vivo model of Caenorhabditis elegans (N2 and CF1553 strains) were used to study effect of Livogrit on Amiodarone-induced phospholipidosis. In HepG2 cells, Livogrit treatment displayed enhanced uptake of acidic pH-based stains and reduced phospholipid accumulation, oxidative stress, AST, ALT, cholesterol levels, and gene expression of SCD-1 and LSS. Protein levels of LPLA2 were also normalized. Livogrit treatment restored Pgp functionality which led to decreased cellular accumulation of Amiodarone as observed by UHPLC analysis. In C. elegans, Livogrit prevented ROS generation, fat-6/7 gene overexpression, and lysosomal trapping of Amiodarone in N2 strain. SOD-3::GFP expression in CF1553 strain normalized by Livogrit treatment. Livogrit regulates phospholipidosis by regulation of redox homeostasis, phospholipid anabolism, and Pgp functionality hindered by lysosomal trapping of Amiodarone. Livogrit could be a potential therapeutic intervention for amelioration of drug-induced phospholipidosis and prevent hepatotoxicity.

DUOX1 Gene Missense Mutation Confers Susceptibility on Type 2 Amiodarone-Induced Thyrotoxicosis

Possible triggers and genetic markers involved in pathogenesis of amiodarone-induced thyrotoxicosis (AIT) or amiodarone-induced hypothyroidism (AIH) are currently unknown. This study aimed to analyze the association between polymorphisms in the genes involved in thyroid hormones biosynthesis and metabolism. Thirty-nine consecutive patients with confirmed type 2 amiodarone-induced thyrotoxicosis were enrolled; 39 patients on the same therapy for at least 6 months without thyroid pathology were included as a control group. A comparative study was carried out to determine the distribution and genotypes of polymorphic markers of the (Na)-iodide symporter (NIS) genes (rs7250346, C/G substitution), thyroid stimulating hormone receptor (TSHR) (rs1991517, C/G substitution), thyroid peroxidase (TPO) (rs 732609, A/C substitution), DUOX 1-1 (C/T substitution), DUOX 1-2 (G/T substitution), DUOX 1-3 (C/T substitution), glutathione peroxidase 3 (GPX3) (C/T substitution), glutathione peroxidase 4 (GPX4) (C/T substitution). Statistical analysis was performed using Prism (Version 9.0.0 (86)). This study showed that the risk of AIT2 is 3.18 times higher in the G/T of the DUOX1 gene carriers. This study is the first report of genetic markers associated with amiodarone-related adverse events conducted in humans. The obtained results indicate the necessity for a personalized approach to amiodarone administration.

Role of Silymarin in Cancer Treatment: Facts, Hypotheses, and Questions

The flavonoid silymarin extracted from the seeds of Sylibum marianum is a mixture of 6 flavolignan isomers. The 3 more important isomers are silybin (or silibinin), silydianin, and silychristin. Silybin is functionally the most active of these compounds. This group of flavonoids has been extensively studied and they have been used as hepato-protective substances for the mushroom Amanita phalloides intoxication and mainly chronic liver diseases such as alcoholic cirrhosis and nonalcoholic fatty liver. Hepatitis C progression is not, or slightly, modified by silymarin. Recently, it has also been proposed for SARS COVID-19 infection therapy. The biochemical and molecular mechanisms of action of these substances in cancer are subjects of ongoing research. Paradoxically, many of its identified actions such as antioxidant, promoter of ribosomal synthesis, and mitochondrial membrane stabilization, may seem protumoral at first sight, however, silymarin compounds have clear anticancer effects. Some of them are: decreasing migration through multiple targeting, decreasing hypoxia inducible factor-1α expression, inducing apoptosis in some malignant cells, and inhibiting promitotic signaling among others. Interestingly, the antitumoral activity of silymarin compounds is limited to malignant cells while the nonmalignant cells seem not to be affected. Furthermore, there is a long history of silymarin use in human diseases without toxicity after prolonged administration. The ample distribution and easy accessibility to milk thistle-the source of silymarin compounds, its over the counter availability, the fact that it is a weed, some controversial issues regarding bioavailability, and being a nutraceutical rather than a drug, has somehow led medical professionals to view its anticancer effects with skepticism. This is a fundamental reason why it never achieved bedside status in cancer treatment. However, in spite of all the antitumoral effects, silymarin actually has dual effects and in some cases such as pancreatic cancer it can promote stemness. This review deals with recent investigations to elucidate the molecular actions of this flavonoid in cancer, and to consider the possibility of repurposing it. Particular attention is dedicated to silymarin's dual role in cancer and to some controversies of its real effectiveness.

Exploring Innovative Leishmaniasis Treatment: Drug Targets from Pre-Clinical to Clinical Findings

Leishmaniasis is a group of tropical diseases caused by parasitic protozoa belonging to the genus Leishmania. The disease is categorized in cutaneous leishmaniasis (CL), mucocutaneous leishmaniasis (MCL), and visceral leishmaniasis (VL). The conventional treatment is complex and can present high toxicity and therapeutic failures. Thus, there is a continuing need to develop new treatments. In this review, we focus on the novel molecules described in the literature with potential leishmanicidal activity, categorizing them in pre-clinical (in vitro, in vivo), drug repurposing and clinical research.

Qualified method for the estimation of di-18:1 bis(monoacylglycero)phosphate in urine, a noninvasive biomarker to monitor drug-induced phospholipidosis

Aim: Our objective was to develop and qualify a bioanalytical method for the estimation of di-18:1-bis(monoacylglycero)phosphate (di-18:1 BMP) as a urinary biomarker for the assessment of drug-induced phospholipidosis and demonstrate its application in a preclinical study. Methodology/results: di-18:1 BMP was extracted by liquid-liquid extraction using n-butanol and analyzed by LC-MS/MS. The qualified method was selective, precise, robust and accurate across the linearity range (0.2-250 ng/ml). Qualified method was then used to assess chloroquine-induced phospholipidosis in rats dosed at 120 mg/kg for 5 days. A fivefold increase in di-18:1 BMP was observed on Day 5 compared with predose. Conclusion: Di-18:1 BMP can be used as a noninvasive biomarker to assess/screen compounds that could cause drug-induced phospholipidosis in rats.

Effectiveness of amiodarone in treatment of cutaneous leishmaniasis caused by Leishmania major

Development of new chemotherapeutic agents is an essential issue in the treatment and control of a disease. This study aimed to evaluate the anti-leishmanial activity of amiodarone, an antiarrhythmic class III drug, against Leishmania major, the most prevalent etiological agent of cutaneous leishmaniasis in the old world. The proliferation of promastigotes and intracellular amastigotes in the absence or presence of amiodarone was estimated, in an in vitro study. For in vivo study, five weeks after infection of BALB/c mice with L. major, when the lesions appeared at the injection site, the mice were divided into four groups (n = 6 each); treatment was conducted for 28 consecutive days with vehicle, amiodarone at 40 mg/kg orally and glucantime at 60 mg/kg intraperitoneally. Therapy with amiodarone reduced the size of lesions compared to the untreated group after 12 days. Amiodarone decreased the parasite load and inflammatory responses, particularly the macrophages containing amastigotes, and enhanced granulation tissue formation in the dermis and subcutaneous area. The Tumor necrosis factor-α and Interleukin-6 levels were significantly lower in the cell culture supernatants of the inguinal lymph node in the amiodarone treated group compared to the vehicle and untreated groups. Amiodarone significantly increased the activity of glutathione peroxidase in comparison to the vehicle and untreated groups but did not affect the plasma levels of superoxide dismutase, malondialdehyde, adiponectin, and ferric reducing ability of plasma. Therefore, the anti- L. major activity and immunomodulatory effects of amiodarone reduced the parasitic load and enhanced wound healing in cutaneous leishmaniasis in BALB/c mice. Amiodarone reduced the lesion surface area, but it did not cure it completely.

Effects of N-acetyl cysteine, vitamin E and vitamin C on liver glutathione levels following amiodarone treatment in rats

Introduction

Amiodarone, a pharmaceutical extensively used to suppress atrial and ventricular tachyarrhythmias, is also known to cause many side effects on many tissues. N-acetyl-cysteine (NAC), vitamin E and vitamin C are known as antioxidants for their ability to minimize oxidative stress. In the peer-reviewed literature, there is no study reporting on the protective effects of these antioxidant agents against its hepatotoxicity.

Aim

We investigated the oxidative effects of NAC, vitamins E and C on liver tissue after amiodarone treatment.

Material and methods

Rats were randomly assigned to: control; amiodarone group; amiodarone + NAC treated group; amiodarone + Vit. E group and amiodarone + Vit. C group. Liver tissues were isolated from animals and total glutathione levels were measured.

Results

In all time intervals, the level of glutathione increased. When all time intervals were compared, the amiodarone group revealed the lowest levels. The antioxidant co-administered group was studied; the glutathione levels were statistically significantly higher than the sole amiodarone group. When vitamins E, C or N-acetyl cysteine were examined, there was no statistically significant difference among them.

Conclusions

In this study we found that hepatotoxicity capacity of amiodarone may be reduced by taking up antioxidants. In addition, the effect documented here may be reproducible and may be applied to clinical settings.

Involvement of oxidative stress and impaired lysosomal degradation in amiodarone-induced schwannopathy

Amiodarone hydrochloride (AMD), an anti-arrhythmic agent, has been shown to cause peripheral neuropathy; however, its pathogenesis remains unknown. We examined the toxic effects of AMD on an immortalized adult rat Schwann cell line, IFRS1, and cocultures of IFRS1 cells and adult rat dorsal root ganglion neurons or nerve growth factor-primed PC12 cells. Treatment with AMD (1, 5, and 10 μm) induced time- and dose-dependent cell death, accumulation of phospholipids and neutral lipids, upregulation of the expression of gangliosides, and oxidative stress (increased nuclear factor E2-related factor in nuclear extracts and reduced GSH/GSSG ratios) in IFRS1 cells. It also induced the upregulation of LC3-II and p62 expression, with phosphorylation of p62, suggesting that deficient autolysosomal degradation is involved in AMD-induced IFRS1 cell death. Furthermore, treatment of the cocultures with AMD induced detachment of IFRS1 cells from neurite networks in a time- and dose-dependent manner. These findings suggest that AMD-induced lysosomal storage accompanied by enhanced oxidative stress and impaired lysosomal degradation in Schwann cells might be a cause of demyelination in the peripheral nervous system.

Effects of 2,3-Dehydrosilybin and Its Galloyl Ester and Methyl Ether Derivatives on Human Umbilical Vein Endothelial Cells

The effects in vitro of 2,3-dehydrosilybin and several galloyl esters and methyl ethers on the viability, proliferation, and migration of human umbilical vein endothelial cells (HUVECs) were evaluated. The monogalloyl esters were synthesized by a chemoselective esterification method or by Steglich esterification of suitably protected 2,3-dehydrosilybin (1) with protected gallic acid. 2,3-Dehydrosilybin (1) displayed more potent cytotoxic, antiproliferative, and antimigratory activities (IC50 12.0, 5.4, and 12.2 μM, respectively) than silybin. The methylated derivatives were less active, with the least potent being 3,7-di-O-methyl-2,3-dehydrosilybin (6). On the other hand, galloylation at C-7 OH and C-23 OH markedly increased the cytotoxicity and the effects on the proliferation and migration of HUVECs. The most active derivative was 7-O-galloyl-2,3-dehydrosilybin (13; IC50 value of 3.4, 1.6, and 4.7 μM in the cytotoxicity, inhibition of proliferation, and antimigratory assays, respectively). Overall, this preliminary structure-activity relationship study demonstrated the importance of a 2,3-double bond, a C-7 OH group, and a galloyl moiety in enhancing the activity of flavonolignans toward HUVECs.

Dysregulation of protein degradation pathways may mediate the liver injury and phospholipidosis associated with a cationic amphiphilic antibiotic drug

A large number of antibiotics are known to cause drug-induced liver injury in the clinic; however, interpreting clinical risk is not straightforward owing to a lack of predictivity of the toxicity by standard preclinical species and a poor understanding of the mechanisms of toxicity. An example is PF-04287881, a novel ketolide antibiotic that caused elevations in liver function tests in Phase I clinical studies. In this study, a mouse diversity panel (MDP), comprised of 34 genetically diverse, inbred mouse strains, was utilized to model the toxicity observed with PF-04287881 treatment and investigate potential mechanisms that may mediate the liver response. Significant elevations in serum alanine aminotransferase (ALT) levels in PF-04287881-treated animals relative to vehicle-treated controls were observed in the majority (88%) of strains tested following a seven day exposure. The average fold elevation in ALT varied by genetic background and correlated with microscopic findings of hepatocellular hypertrophy, hepatocellular single cell necrosis, and Kupffer cell vacuolation (confirmed as phospholipidosis) in the liver. Global liver mRNA expression was evaluated in a subset of four strains to identify transcript and pathway differences that distinguish susceptible mice from resistant mice in the context of PF-04287881 treatment. The protein ubiquitination pathway was highly enriched among genes associated with PF-04287881-induced hepatocellular necrosis. Expression changes associated with PF-04287881-induced phospholipidosis included genes involved in drug transport, phospholipid metabolism, and lysosomal function. The findings suggest that perturbations in genes involved in protein degradation leading to accumulation of oxidized proteins may mediate the liver injury induced by this drug.

Identification of hepatic phospholipidosis inducers in sandwich-cultured rat hepatocytes, a physiologically relevant model, reveals altered basolateral uptake and biliary excretion of anionic probe substrates

Drug-induced phospholipidosis (PLD) is characterized by phospholipid accumulation within the lysosomes of affected tissues, resulting in lysosomal enlargement and laminar body inclusions. Numerous adverse effects and toxicities have been linked to PLD-inducing drugs, but it remains unknown whether drug-induced PLD represents a distinct toxicity or cellular adaptation. In silico and immortalized cellular models have been used to evaluate the PLD potential of new drugs, but these systems have some limitations. The aims of this study were to determine whether primary sandwich-cultured hepatocytes (SCH) can serve as a sensitive and selective model to evaluate hepatic drug-induced PLD, and to evaluate the impact of PLD on the uptake and biliary excretion of probe substrates, taurocholate (TC) and rosuvastatin (RSV). Rat SCH were cultured for 48 h with prototypic hepatic PLD-inducing drugs, amiodarone (AMD), chloroquine (CHQ), desipramine (DES), and azithromycin (AZI), as well as the renal PLD inducer gentamicin (GTM). LysoTracker Red localization and transmission electron microscopy indicated enlarged lysosomal compartments and laminar body inclusions in SCH treated with AMD, CHQ, DES, and AZI, but not GTM, relative to control. PLD resulted in a 51-92% decrease in the in vitro biliary clearance of both TC and RSV; the biliary excretion index significantly decreased for TC from 88 to 35-73%. These data suggested that PLD significantly reduced both organic anion transporting polypeptide-mediated uptake, and bile salt export pump-mediated biliary transport processes. The current study demonstrates that the rat SCH system is a promising model to study hepatic PLD in vitro. Altered hepatic transport of anionic substrates secondary to drug-induced PLD is a novel finding.

Ameliorative effect of grapefruit juice on amiodarone-induced cytogenetic and testicular damage in albino rats

OBJECTIVE

To evaluate the ameliorative role of grapefruit juice on the cytogenetic and testicular damage induced by the antiarrythmic drug amiodarone in albino rats.

METHODS

Animals were divided into four groups. Group I was considered as control. Group II was given grapefruit juice at a dose level of 27 mL/kg body weight. Group III was orally administered amiodarone (18 mg/kg body weight) daily for 5 weeks. Animals were sacrificed after 5 weeks of treatment. Bone marrow was collected from the femurs for analysis of chromosomal aberrations and mitotic indices. Testes were removed and stained with H&E for histological examination. Sperms were collected from epidedymis for detection of sperm head abnormalities. Comet assay was used to detect DNA damage.

RESULTS

Amiodarone treatment caused a significant increase in the percentage of chromosomal aberrations, decreased the mitotic index and increased DNA damage. The testis showed many histopathological alterations, inhibition of spermatogenesis and morphometric changes. The number of sperm head abnormalities was increased. Treating animals with amiodarone and grapefruit juice caused a reduction in chromosomal aberrations, mitotic index, DNA damage and testicular alterations caused by amiodarone.

CONCLUSIONS

The results of this study indicated that grapefruit juice ameliorates the cytotoxicty and testicular alterations induced by amiodarone in albino rats and this is may be due to the potent antioxidant effects of its components.

May toxicity of amiodarone be prevented by antioxidants? A cell-culture study

BACKGROUND

Atrial Fibrillation is the most common arrhythmia encountered following cardiac surgery. The most commonly administered drug used in treatment and prophylaxis is amiodarone which has several toxic effects on major organ functions. There are few clinical data concerning prevention of toxic effects and there is no routinely suggested agent. The aim of this study is to document the cytotoxic effects of amiodarone on cell culture media and compare the cytoprotective effects of commonly used antioxidant agents.

METHODS

L929 mouse fibroblast cell line was cultured and 100,000 cells/well-plate were obtained. First group of cells were treated with increasing concentrations of amiodarone (20 to 180 μM) alone. Second and third group of cells were incubated with one-fold equimolar dose of vitamin C and N-acetyl cysteine prior to amiodarone exposure. The viability of cells were measured by MTT assay and the cytoprotective effect of each agent was compared.

RESULTS

The cytotoxicity of amiodarone was significant with concentrations of 100 μM and more. The viabilities of both vitamin C and N-acetyl cysteine treated cells were higher compared to untreated cells.

CONCLUSIONS

Vitamin C and N-acetyl cysteine are commonly used in the clinical setting for different purposes in context of their known antioxidant actions. Their role in prevention of amiodarone induced cytotoxicity is not fully documented. The study fully demonstrates the cytoprotective role of both agents in amiodarone induced cytotoxicity on cell culture media; more pronounced with vitamin C in some concentrations. The findings may be projectile for further clinical studies.

Amiodarone exposure during modest inflammation induces idiosyncrasy-like liver injury in rats: role of tumor necrosis factor-alpha

Amiodarone [2-butyl-3-(3′,5′-diiodo-4’α-diethylaminoethoxybenzoyl)-benzofuran] (AMD), a class III antiarrhythmic drug, is known to cause idiosyncratic hepatotoxic reactions in human patients. One hypothesis for the etiology of idiosyncratic adverse drug reactions is that a concurrent inflammatory stress results in decreased threshold for drug toxicity. To explore this hypothesis in an animal model, male Sprague-Dawley rats were treated with nonhepatotoxic doses of AMD or its vehicle and with saline vehicle or lipopolysaccharide (LPS) to induce low-level inflammation. Elevated alanine aminotransferase (ALT), aspartate aminotransferase, alkaline phosphatase, and gamma-glutamyltransferase activities as well as increased total bile acid concentrations in serum and midzonal hepatocellular necrosis were observed only in AMD/LPS-cotreated rats. The time interval between AMD and LPS administration was critical: AMD injected 16 h before LPS led to liver injury, whereas AMD injected 2–12 h before LPS failed to cause this response. The increase in ALT activity in AMD/LPS cotreatment showed a clear dose-response relationship with AMD as well as LPS. The metabolism and hepatic accumulation of AMD were not affected by LPS coexposure. Serum concentration of tumor necrosis factor-alpha (TNF) was significantly increased by LPS and was slightly prolonged by AMD. In Hepac1c7 cells, addition of TNF potentiated the cytotoxicity of both AMD and its primary metabolite, mono-N-desethylamiodarone. In vivo inhibition of TNF signaling by etanercept attenuated the AMD/LPS-induced liver injury in rats. In summary, AMD treatment during modest inflammation induced severe hepatotoxicity in rats, and TNF contributed to the induction of liver injury in this animal model of idiosyncratic AMD-induced liver injury.

Individual organelle pH determinations of magnetically enriched endocytic organelles via laser-induced fluorescence detection

The analysis of biotransformations that occur in lysosomes and other endocytic organelles is critical to studies on intracellular degradation, nutrient recycling, and lysosomal storage disorders. Such analyses require bioactive organelle preparations that are devoid of other contaminating organelles. Commonly used differential centrifugation techniques produce impure fractions and may not be compatible with microscale separation platforms. Density gradient centrifugation procedures reduce the level of impurities but may compromise bioactivity. Here we report on simple magnetic setup and a procedure that produce highly enriched bioactive organelles based on their magnetic capture as they traveled through open tubes. Following capture, in-line laser-induced fluorecence detection (LIF) determined for the first time the pH of each magnetically retained individual endocytic organelle. Unlike bulk measurements, this method was suitable to describe the distributions of pH values in endocytic organelles from L6 rat myoblasts treated with dextran-coated iron oxide nanoparticles (for magnetic retention) and fluorescein/TMRM-conjugated dextran (for pH measurements by LIF). Their individual pH values ranged from 4 to 6, which is typical of bioactive endocytic organelles. These analytical procedures are of high relevance to evaluate lysosomal-related degradation pathways in aging, storage disorders, and drug development.

The effect of vitamin C on amiodarone-induced toxicity in rat thymocytes

Although, the antiarrhythmic effect of amiodarone (AMD) is well characterized, the mechanism of its toxicity on extracardiac tissues is still poorly understood. Several antioxidants have been shown to prevent AMD-induced toxicity by antioxidant and/or non-antioxidant mechanisms. In the current study, we evaluated the possible protective effect, in vitro, of vitamin C on AMD-induced toxicity in rat thymocytes. Rat thymocytes were cultured with increasing AMD concentrations (1–20 μM) with or without vitamin C (1000 μg/ml), for 24 hours. Cells treatment with AMD resulted in a concentration-dependent increase of hypodiploid cells and a significant decrease in cellular glutathione content. Vitamin C combined with AMD significantly decreased the proportion of hypodiploid cells and markedly increased the cellular glutathione content, compared with AMD treatment alone. These results suggest that treatment with vitamin C may prevent AMD-induced toxicity in rat thymocytes by restoring cellular glutathione content.

Cytotoxicity effects of amiodarone on cultured cells

Amiodarone is a potent anti-arrhythmic drug used for the treatment of cardiac arrhythmias. Although, the effects of amiodarone are well characterized on post-ischemic heart and cardiomyocytes, its toxicity on extra-cardiac tissues is still poorly understood. To this aim, we have monitored the cytotoxicity effects of this drug on three cultured cell lines including hepatocytes (HepG2), epithelial cells (EAhy 926) and renal cells (Vero). We have investigated the effects of amiodarone on (i) cell viabilities, (ii) heat shock protein expressions (Hsp 70) as a parameter of protective and adaptive response and (iii) oxidative damage.Our results clearly showed that amiodarone inhibits cell proliferation, induces an over-expression of Hsp 70 and generates significant amount of reactive oxygen species as measured by lipid peroxidation occurrence. However, toxicity of amiodarone was significantly higher in renal and epithelial cells than in hepatocytes. Vitamin E supplement restores the major part of cell mortalities induced by amiodarone showing that oxidative damage is the predominant toxic effect of the drug.Except its toxicity for the cardiac system, our findings demonstrated that amiodarone can target other tissues. Therefore, kidneys present a high sensibility to this drug which may limit its use with subjects suffering from renal disorders.

Molecular mechanisms of silybin and 2,3-dehydrosilybin antiradical activity--role of individual hydroxyl groups

The flavonolignans silybin (1) and 2,3-dehydrosilybin (2) are important natural compounds with multiple biological activities operating at various cell levels. Many of these effects are connected with their radical-scavenging activities. The molecular mechanisms of the antioxidant activity of these compounds and even the functional groups responsible for this activity are not yet well known. Their mechanism can be inferred from the structures of the dimeric products obtained from radical-mediated reactions of selectively methylated derivatives of 1 and 2. The radical oxidation of 1 methylated at 7-OH and 2 methylated at both 3-OH and 7-OH yields C-C and C-O dimers that enable the molecular mechanism of their E-ring interaction with radicals to be elucidated and shows the importance of the 20-OH group in this respect. The pivotal role of the 3-OH group in the radical-scavenging activity of 2 was confirmed through the formation of another type of dimer from its selectively methylated derivative.

A toxicogenomics approach for early assessment of potential non-genotoxic hepatocarcinogenicity of chemicals in rats

For assessing carcinogenicity in animals, it is difficult and costly, an alternative strategy has been desired. We explored the possibility of applying a toxicogenomics approach by using comprehensive gene expression data in rat liver treated with various compounds. As prototypic non-genotoxic hepatocarcinogens, thioacetamide (TAA) and methapyrilene (MP) were selected and 349 commonly changed genes were extracted by statistical analysis. Taking both compounds as positive with six compounds, acetaminophen, aspirin, phenylbutazone, rifampicin, alpha-naphthylisothiocyanate, and amiodarone as negative, prediction analysis of microarray (PAM) was performed. By training and 10-fold cross validation, a classifier containing 112 probe sets that gave an overall success rate of 95% was obtained. The validity of the present discriminator was checked for 30 chemicals. The PAM score showed characteristic time-dependent increases by treatment with several non-genotoxic hepatocarcinogens, including TAA, MP, coumarin, ethionine and WY-14643, while almost all of the non-carcinogenic samples were correctly predicted. Measurement of hepatic glutathione content suggested that MP and TAA cause glutathione depletion followed by a protective increase, but the protective response is exhausted during repeated administration. Therefore, the presently obtained PAM classifier could predict potential non-genotoxic hepatocarcinogenesis within 24 h after single dose and the inevitable pseudo-positives could be eliminated by checking data of repeated administrations up to 28 days. Tests for carcinogenicity using rats takes at least 2 years, while the present work suggests the possibility of lowering the time to 28 days with high precision, at least for a category of non-genotoxic hepatocarcinogens causing oxidative stress.

Amiodarone reversibly decreases sodium-iodide symporter mRNA expression at therapeutic concentrations and induces antioxidant responses at supraphysiological concentrations in cultured human thyroid follicles

CONTEXT

Amiodarone, a potent antiarrhythmic, iodine-containing agent, is a highly active oxidant exerting cytotoxic effects on thyrocytes at pharmacological concentrations. Patients receiving amiodarone usually remain euthyroid, but occasionally develop thyroid dysfunction. Although there is a general consensus that amiodarone-associated hypothyroidism is iodine induced, the destructive mechanism of thyroid follicles in amiodarone-induced thyrotoxicosis remains unknown.

OBJECTIVE

To elucidate the mechanism by which amiodarone elicits thyroid dysfunction.

DESIGN

Human thyroid follicles were cultured with thyroid-stimulating hormone (TSH) and amiodarone at therapeutic (1-2 microM) and pharmacological (10-20 microM) concentrations, and the drug-induced effect on whole human gene expression was analyzed by cDNA microarray. Microarray data were confirmed by real-time PCR and Western blot.

MAIN OUTCOMES

Amiodarone at 1-2 muM decreased the expression level of the sodium-iodide symporter (NIS) to nearly half, but did not affect genes participating in thyroid hormonogenesis (thyroid peroxidase, thyroglobulin, pendrin, and NADPH oxidase). Higher concentrations (10-20 microM) decreased the expression of all these genes, accompanied by increased expression of antioxidant proteins such as heme oxygenase 1 and ferritin. When thyroid follicles obtained from a patient with Graves' disease who had been treated with amiodarone were cultured in amiodarone-free medium, TSH-induced thyroid function was intact, suggesting that amiodarone at a maintenance dose did not elicit any cytotoxic effect on thyrocytes. The ultrastructural features of cultured thyroid follicles were compatible with these in vitro findings.

CONCLUSION

These in vitro and ex vivo findings suggest that patients taking maintenance doses of amiodarone usually remain euthyroid, probably due to escape from the Wolff-Chaikoff effect mediated by decreased expression of NIS mRNA. Further, amiodarone is not cytotoxic for thyrocytes at therapeutic concentrations but elicits cytotoxicity through oxidant activity at supraphysiological concentrations. We speculate that when amiodarone-induced prooxidant activity somehow exceeds the endogenous antioxidant capacity, the thyroid follicles will be destroyed and amiodarone-induced destructive thyrotoxicosis may develop.

An updated systematic review of the pharmacology of silymarin

BACKGROUND

Recent years have seen an explosion of scientific papers that deal with drugs from the fruits of milk thistle and its active substances silymarin (standardized mixture of flavonolignanes), thus justifying an updated systematic review.

METHODS

Electronic databases identified silymarin, silibinin, silicristin or milk thistle as descriptors in >700 papers (34% published in last 5 years; 92% dealt with animal pharmacological). Only papers adequately reporting on experimental conditions, dosing, variables tested and statistics were analysed.

RESULTS

Silymarin was found to modify specifically the functions related to various transporters and receptors located in the cell membranes; that is, organic anion uptake transporter peptides (OATP), ABC transporters (P-gp), bile salt export pump, as well as TNF-alpha-dependent and possibly selectin-dependent phenomena. In the cytoplasm, some antioxidant properties and the inhibition of the lipoxygenase pathway seem quite selective and could concur to the antitoxic effects. Some effects like the inhibition of inducible nitric-oxide synthase, of nuclear factor kappa B, and reduction of collagen synthesis are indicative of DNA/RNA-mediated effects. Several studies using 'in vitro' and 'in vivo' cancer models suggest a potential of silymarin in such diseases. Topical and systemic silymarin has skin protective properties against UV-induced damage in epidermis and causes an up-regulation of tumour-suppressor genes p53- and p21CIP1. There were no data on hepatic viral replication, viremia or spontaneous tumours in the data examined.

CONCLUSIONS

Data presented here do not solve the question about the complex mechanism(s) of action of the medicinal herbal drug silymarin. Silymarin may be a natural multi-functional and multi-target drug.

Drug-induced mitochondrial toxicity

Mitochondria play a critical role in generating most of the cell's energy as ATP. They are also involved in other metabolic processes such as urea generation, haem synthesis and fatty acid beta-oxidation. Disruption of mitochondrial function by drugs can result in cell death by necrosis or can signal cell death by apoptosis (e.g., following cytochrome c release). Drugs that injure mitochondria usually do so by inhibiting respiratory complexes of the electron chain; inhibiting or uncoupling oxidative phosphorylation; inducing mitochondrial oxidative stress; or inhibiting DNA replication, transcription or translation. It is important to test for mitochondrial toxicity early in drug development as impairment of mitochondrial function can induce various pathological conditions that are life threatening or can increase the progression of existing mitochondrial diseases.

Effect of Amiodarone on Phospholipid Content and Composition in Heart, Lung, Kidney and Skeletal Muscle: Relationship to Alteration of Thyroid Function

To investigate the effect of chronic amiodarone treatment on tissue phospholipids, a marker of amiodarone-induced toxicity, and to test the hypothesis that tissue phospholipids changes are related to amiodarone-induced effects on thyroid function, male Wistar rats were treated with amiodarone and tissue phospholipid content and fractions were assessed. Twenty-six animals were allocated to 4 groups: (i) group 1 received amiodarone, 20 mg/kg per day, for 3 weeks (n = 6); (ii) group 2 received amiodarone for 5 weeks (n = 6); (iii) group 3 received drug for 6 weeks (n = 6), and (iv) group 4 (control group) received the diluent for 6 weeks (n = 8). Total phospholipid content of lung, kidney and skeletal muscle but not heart was increased after 3 weeks of amiodarone treatment. With longer durations of treatment, the phospholipid content was significantly (p < 0.05) reduced in all four organs. The proportion of phospholipids in different classes was modified by amiodarone treatment with the most consistent changes across different tissues being reductions in phosphatidylethanolamine and increases in phosphatidylserine. Serum thyroxine concentration was significantly (p < 0.05) reduced at 5 weeks of treatment and thereafter. There was a significant correlation between serum thyroxine and total phospholipid concentration in heart (r = 0.555; p < 0.05) and lung (r = 0.502; p < 0.05). For heart, there was a significant correlation between serum thyroxine and the distribution of phospholipid classes, mainly for phosphatidylserine even after considering amiodarone dose. The same was found in the lung. In the kidney and skeletal muscle, there was a significant (p < 0.05) correlation between serum thyroxine and the proportion of phospholipids in phosphatidylcholine and sphingomyelin. In conclusion, this study presents the novel finding of a biphasic tissue phospholipid response to amiodarone characterized by a short term increase in phospholipids in lung, kidney and skeletal muscle but not the heart followed by a long term decline in phospholipids in all four organs that is likely due to a direct action of amiodarone on phospholipid metabolism and potentially the result of amiodarone-induced reduction in thyroid function.

Silybin and silymarin--new effects and applications

This article aims to review critically literature published mainly within this millennium on the new and emerging applications of silymarin, the polyphenolic fraction from the seeds of Silybum marianum and its main component silybin. Silymarin and silybin used so far mostly as hepatoprotectants were shown to have other interesting activities as e.g., anticancer and canceroprotective. These activities were demonstrated in a large variety of illnesses of different organs as e.g., prostate, lungs, CNS, kidneys, pancreas and others. Besides the cytoprotective activity of silybin mediated by its antioxidative and radical-scavenging properties also new activities based on the specific receptor interaction were discovered--e.g., inhibition and modulation of drug transporters, P-glycoproteins, estrogenic receptors, nuclear receptors and some others. New derivatives of silybin open new ways to its therapeutic applications. Pharmacology dealing with optically pure silybin diastereomers may suggest new mechanisms of its action.

α-Tocopherol influences the lipid membrane affinity of desipramine in a pH-dependent manner

Phopholipidosis is a lipid storage disorder caused by cationic amphiphilic drugs (CADs) characterized by the lysosomal accumulation of phospholipids and drug. alpha-Tocopherol (alpha-Toc) has a reversible effect on phospholipidosis in rats and cell culture. We studied the influence of alpha-Toc on the partitioning of the CAD desipramine in a liposome/buffer system using equilibrium dialysis with the following lipid compositions: egg phosphatidylcholine (PhC) or wheat germ phosphatidylinositol (PhI) or a combination of PhC, PhI and cholesterol, containing between 1.5 and 20% (mol per mol total lipids) of alpha-Toc, alpha-tocopherol acetate (alpha-TocAc), 2,2,5,7,8-pentamethyl-6-chromanol (PMC) or cholesterol. alpha-Toc (1.5%) enhanced the partition coefficient of neutral desipramine by up to 1.1 log units while it had no influence on the partitioning of the ionized compound. In the PhC liposome system, at pH 7.4 logD increased with increasing alpha-Toc concentrations but was unchanged at pH 4.5. Similar effects were found with PMC while alpha-TocAc or cholesterol, between 1.5 and 20%, had no influence on the partitioning of desipramine. From these results we postulate that in vivo, alpha-Toc could mediate a redistribution of CADs from lysosomal membranes (pH approximately 4.5) to membranes and lipoproteins at physiological pH.