Mohammad Ali Eghbal

A Review of Molecular Mechanisms Involved in Toxicity of Nanoparticles

In recent decades, the use of nanomaterials has received much attention in industrial and medical fields. However, some reports have mentioned adverse effects of these materials on the biological systems and cellular components. There are several major mechanisms for cytotoxicity of nanoparticles (NPs) such as physicochemical properties, contamination with toxic element, fibrous structure, high surface charge and radical species generation. In this review, a brief key mechanisms involved in toxic effect of NPs are given, followed by the in vitro toxicity assays of NPs and prooxidant effects of several NPs such as carbon nanotubes, titanium dioxide NPs, quantum dots, gold NPs and silver NPs.

Ameliorative Effects of Taurine Against Methimazole-Induced Cytotoxicity in Isolated Rat Hepatocytes

Methimazole is used as an antithyroid drug to control the symptoms of hyperthyroidism and maintain patients in a euthyroid state. Administration of this drug is associated with agranulocytosis and hepatotoxicity, which are the two most significant adverse effects. The present investigation was conducted to study the protective role of taurine against cytotoxicity induced by methimazole and its proposed reactive intermediary metabolite, N-methylthiourea, in an in vitro model of isolated rat hepatocytes. At different points in time, markers such as cell viability, reactive oxygen species (ROS) formation, lipid peroxidation, mitochondrial membrane potential, and hepatocyte glutathione content were evaluated. Treating hepatocytes with methimazole resulted in cytotoxicity characterized by the reduction in cell viability, an increase in ROS formation and lipid peroxidation, mitochondrial membrane potential collapse, and a reduction in cellular glutathione content. Furthermore, a significant amount of oxidized glutathione (GSSG) was formed when rat hepatocytes were treated with methimazole. N-methylthiourea toxicity was accompanied by a reduction in cellular GSH content, but no significant changes in lipid peroxidation, ROS formation, GSSG production, or changes in mitochondrial membrane potential were detected. Administration of taurine (200 μM) effectively reduced the toxic effects of methimazole or its metabolite in isolated rat hepatocytes.

EFFECTS OF ENZYME INDUCTION AND/OR GLUTATHIONE DEPLETION ON METHIMAZOLE-INDUCED HEPATOTOXICITY IN MICE AND THE PROTECTIVE ROLE OF N-ACETYLCYSTEINE

PURPOSEnMethimazole is the most convenient drug used in the management of hyperthyroid patients. However, associated with its clinical use is hepatotoxicity as a life threatening adverse effect. The exact mechanism of methimazole-induced hepatotoxicity is still far from clear and no protective agent has been developed for this toxicity.nnnMETHODSnThis study attempts to evaluate the hepatotoxicity induced by methimazole at different experimental conditions in a mice model. Methimazole-induced hepatotoxicity was investigated in different situations such as enzyme induced and/or glutathione depleted animals.nnnRESULTSnMethimazole (100 mg/kg, i.p) administration caused hepatotoxicity as revealed by increase in serum alanine aminotransferase (ALT) activity as well as pathological changes of the liver. Furthermore, a significant reduction in hepatic glutathione content and an elevation in lipid peroxidation were observed in methimazole-treated mice. Combined administration of L-buthionine sulfoximine (BSO), as a glutathione depletory agent, caused a dramatic change in methimazole-induced hepatotoxicity characterized by hepatic necrosis and a severe elevation of serum ALT activity. Enzyme induction using phenobarbital and/or β-naphtoflavone beforehand, deteriorated methimazole-induced hepatotoxicity in mice. N-acetyl cysteine (300 mg/kg, i.p) administration effectively alleviated hepatotoxic effects of methimazole in both glutathione-depleted and/or enzyme induced animals.nnnCONCLUSIONnThe severe hepatotoxic effects of methimazole in glutathione-depleted animals, reveals the crucial role of glutathione as a cellular defense mechanism against methimazole-induced hepatotoxicity. Furthermore, the more hepatotoxic properties of methimazole in enzyme-induced mice, indicates the role of reactive intermediates in the hepatotoxicity induced by this drug. The protective effects of N-acetylcysteine could be attributed to its radical/reactive metabolite scavenging, and/or antioxidant properties as well as glutathione replenishment activities.

Mechanisms of methimazole cytotoxicity in isolated rat hepatocytes

Abstract Methimazole is an antithyroid drug widely used in the treatment of hyperthyroidism. Administration of this drug, often in a chronic manner, is associated with several adverse drug reactions in humans, including life-threatening hepatotoxicity. This study attempted to investigate the cytotoxic mechanism(s) of methimazole toward isolated rat hepatocytes. In addition, the role of proposed methimazole intermediary metabolites, such as N-methylthiourea and glyoxal, in the toxicity induced by this drug was evaluated. Isolated hepatocytes were prepared by the collagenase enzyme perfusion method. Cells were treated with methimazole, N-methylthiourea, and other chemicals and markers, such as cell viability, mitochondrial membrane potential (MMP), reactive oxygen species (ROS) formation, lipid peroxidation (LPO), and cellular glutathione (GSH) content, were measured. Methimazole-induced cytotoxicity was accompanied by collapse in MMP, increase in ROS formation, and LPO. Further, methimazole caused reduction in GSH reservoirs, and the cytotoxic effect of the drug was much more severe in GSH-depleted cells. N-methylthiourea caused toxicity in lower concentrations than methimazole and reduced hepatocytes glutathione content. The specific flavin-containing monooxygenase inhibitor, N,N-dimethylaniline, attenuated toxicity induced by N-methylthiourea. Administration of glyoxal trapping agents, such as metformin, hydralazine, or N-acetyl cysteine, effectively prevented methimazole toxicity in intact or GSH-depleted rat hepatocytes. This study indicates that methimazole reactive metabolites are responsible for the cytotoxicity induced by this drug, but the role of glyoxal as a metabolite, which causes ROS formation, LPO, and mitochondrial injury, is predominant because the glyoxal-trapping agents diminished these adverse effects.

An Overview on the Proposed Mechanisms of Antithyroid Drugs-Induced Liver Injury

Drug-induced liver injury (DILI) is a major problem for pharmaceutical industry and drug development. Mechanisms of DILI are many and varied. Elucidating the mechanisms of DILI will allow clinicians to prevent liver failure, need for liver transplantation, and death induced by drugs. Methimazole and propylthiouracil (PTU) are two convenient antithyroid agents which their administration is accompanied by hepatotoxicity as a deleterious side effect. Although several cases of antithyroid drugs-induced liver injury are reported, there is no clear idea about the mechanism(s) of hepatotoxicity induced by these medications. Different mechanisms such as reactive metabolites formation, oxidative stress induction, intracellular targets dysfunction, and immune-mediated toxicity are postulated to be involved in antithyroid agents-induced hepatic damage. Due to the idiosyncratic nature of antithyroid drugs-induced hepatotoxicity, it is impossible to draw a specific conclusion about the mechanisms of liver injury. However, it seems that reactive metabolite formation and immune-mediated toxicity have a great role in antithyroids liver toxicity, especially those caused by methimazole. This review attempted to discuss different mechanisms proposed to be involved in the hepatic injury induced by antithyroid drugs.

Protective effect of NAC against malathion-induced oxidative stress in freshly isolated rat hepatocytes

PURPOSEnInduction of oxidative stress by Organophosphate compounds (OPs) has been previously reported. In the present work, the mechanism of protective effects of N-acetylcysteine as a glutathion (GSH) prodrug against malathion-induced cell toxicity was investigated. In this work, freshly isolated rat hepatocytes were used to determine the effect of NAC on malathion-induced cytotoxicity, formation of reactive oxygen species (ROS) and mitochondrial dysfunction.nnnMETHODSnRat hepatocytes were isolated using collagenase perfusion and then cell viability, mitchondrial membrane potential (MMP) and ROS formation were determined using trypan blue exclusion, Rhodamine 123 fluorescence and fluorogenic probe, 2, 7 -dichlorofluorescin diacetate (DCFH-DA), respectively.nnnRESULTSnDespite the protective effect of NAC on malathion-induced cell toxicity and MMP dysfunction, its efficacy against ROS formation was not adequate to completely protect the cells.nnnCONCLUSIONnCytotoxic effects of malathion regardless of its cholinergic feature, is started with gradual free radical production but, the main factor that causes cell death, is mitochondrial dysfunction, so that reduction of ROS formation alone is not sufficient for cell survival, and the maintenance of mitochondrial integrity through different mechanisms is the most ameliorative factor specially at high levels of cell damage, as NAC seemed to protect cells with various fashions apart from ROS scavenging in concentrations higher than malathions LC50.

Cytoprotective Effects of Organosulfur Compounds against Methimazole-Induced Toxicity in Isolated Rat Hepatocytes

PURPOSEnMethimazole is a drug widely used in hyperthyroidism. However, life threatening hepatotoxicity has been associated with its clinical use. No protective agent has been found to be effective against methimazole induced hepatotoxicity yet. Hence, the capacity of organosulfur compounds to protect rat hepatocytes against cytotoxic effects of methimazole and its proposed toxic metabolite, N-methylthiourea was evaluated.nnnMETHODSnHepatocytes were prepared by the method of collagenase enzyme perfusion via portal vein. Cells were treated with different concentrations of methimazole, N methylthiourea, and organosulfur chemicals. Cell death, protein carbonylation, reactive oxygen species formation, lipid peroxidation, and mitochondrial depolarization were assessed as toxicity markers and the role of organosulfurs administration on them was investigated.nnnRESULTSnMethimazole caused a decrease in cellular glutathione content, mitochondrial membrane potential (ΔΨm) collapse, and protein carbonylation. In addition, an increase in reactive oxygen species (ROS) formation and lipid peroxidation was observed. Treating hepatocytes with N methylthiourea caused a reduction in hepatocytes glutathione reservoirs and an elevation in carbonylated proteins, but no significant ROS formation, lipid peroxidation, or mitochondrial depolarization was observed. N-acetyl cysteine, allylmercaptan, and diallyldisulfide attenuated cell death and prevented ROS formation and lipid peroxidation caused by methimazole. Furthermore, organosulfur compounds diminished methimazole induced mitochondrial damage and reduced the carbonylated proteins. In addition, these chemicals showed protective effects against cell death and protein carbonylation induced by methimazole metabolite.nnnCONCLUSIONnOrganosulfur chemicals extend their protective effects against methimazole-induced toxicity by attenuating oxidative stress caused by this drug and preventing the adverse effects of methimazole and/or its metabolite (s) on subcellular components such as mitochondria.

Protective Effects of N-acetylcysteine Against the Statins Cytotoxicity in Freshly Isolated Rat Hepatocytes

PURPOSEnHepatotoxicity is one of the most important side effects of the statins therapy as lipid-lowering agents. However, the mechanism(s) of hepatotoxicity induced by these drugs is not clearly understood yet, and no hepatoprotective agent has been developed against this complication.nnnMETHODSnThe protective effect of N-acetylcysteine (NAC) against statins-induced cytotoxicity was evaluated by using freshly isolated rat hepatocytes. Hepatocytes were prepared by the method of collagenase enzyme perfusion via portal vein. This technique is based on liver perfusion with collagenase after removal of calcium ion (Ca2+) with a chelator (ethylene glycol tetra acetic acid (EGTA) 0.5 mM). The level of parameters such as cell death, ROS formation, lipid peroxidation, mitochondrial membrane potential (MMP) in the statins-treated hepatocytes were determined. Additionally, the mentioned markers were assessed in the presence of NAC.nnnRESULTSnIncubation of hepatocytes with the statins resulted in cytotoxicity characterized by an elevation in cell death, increasing ROS generation and consequently lipid peroxidation and impairment of mitochondrial function. Administration of NAC caused reduction in amount of ROS formation, lipid peroxidation and finally, cell viability and mitochondrial membrane potential (MMP) were improved.nnnCONCLUSIONnThis study confirms that oxidative stress and consequently mitochondrial dysfunction is one of the mechanisms underlying the statins-induced liver injury and treating hepatocytes by NAC (200 μM) attenuates this cytotoxicity.

Cytoprotective Effects of Melatonin Against Amitriptyline-Induced Toxicity in Isolated Rat Hepatocytes

PURPOSEnAmitriptyline, one of the commonly used tricyclic antidepressants, caused rare but severe hepatotoxicity in patients who received it continuously. Previous findings showed that the intermediate metabolites of amitriptyline produced by CYP450 are involved in hepatic injury. Melatonin is an antiaging and antioxidant hormone synthesized from pineal gland. The aim of present study was to evaluate the protective role of melatonin in an in vitro model of isolated rat hepatocytes.nnnMETHODSnMarkers such as cell viability, reactive oxygen species formation, lipid peroxidation, mitochondrial membrane potential, and hepatocytes glutathione content were evaluated every 60 minutes for 180 minutes.nnnRESULTSnPresent results indicated that administration of 1mM of melatonin effectively reduced the cell death, ROS formation and lipid peroxidation, mitochondrial membrane potential collapse, and reduced cellular glutathione content caused by amitriptyline.nnnCONCLUSIONnOur results indicated that melatonin is an effective antioxidant in preventing amitriptyline-induced hepatotoxicity. We recommend further in vivo animal and clinical trial studies on the hepatoprotective effects of melatonin in patients receiving amitriptyline.

Anti-cancer effects of citalopram on hepatocellular carcinoma cells occur via cytochrome C release and the activation of NF-kB

BACKGROUNDnEvidence has been provided of the anti-proliferative activity of citalopram against some cancer cells.nnnOBJECTIVEnThe apoptotic impact of citalopram, an antidepressant, against liver hepatocellular carcinoma cell line HepG2 was investigated in relation to the oxidative pathway and nuclear factor (NF)κB activation.nnnMETHODnThe cytotoxic effects of citalopram on HepG2 cells were determined by MTT assay. Reactive oxygen species (ROS) formation and cytochrome c release were measured following treatment with citalopram. Apoptosis analysis and Bax and Bcl--2 mRNA and protein levels were also determined.nnnRESULTSnThe cytotoxic effects of different concentrations of citalopram on HepG2 cells were observed as a reduction in cell viability and an increase in ROS formation. Citalopram caused an increase in mitochondrial Bax levels and a decrease in Bcl2 levels and also caused cytochrome c release. Moreover, DAPI staining and flow cytometry assays revealed citalopram-induced apoptosis in HepG2 cells. Oxidant scavengers and Bay 11-7082 (an irreversible inhibitor of NFκB activation) prevented the citalopram-associated cell death, increased BAX and decreased Bcl2.nnnCONCLUSIONnOutcomes from current study suggest that citalopram might exhibit apoptotic effect against hepatocellular carcinoma cell line by induction of cell death through cytochrome c release and ROS-dependent activation of NFκB.