Mechanisms of methimazole cytotoxicity in isolated rat hepatocytes

Low-dose ketamine improves animals' locomotor activity and decreases brain oxidative stress and inflammation in ammonia-induced neurotoxicity

Ammonium ion (NH4 + ) is the major suspected molecule responsible for neurological complications of hepatic encephalopathy (HE). No specific pharmacological action for NH4 + -induced brain injury exists so far. Excitotoxicity is a well-known phenomenon in the brain of hyperammonemic cases. The hyperactivation of the N-Methyl- d-aspartate (NMDA) receptors by agents such as glutamate, an NH4 + metabolite, could cause excitotoxicity. Excitotoxicity is connected with events such as oxidative stress and neuroinflammation. Hence, utilizing NMDA receptor antagonists could prevent neurological complications of NH4 + neurotoxicity. In the current study, C57BL6/J mice received acetaminophen (APAP; 800 mg/kg, i.p) to induce HE. Hyperammonemic animals were treated with ketamine (0.25, 0.5, and 1 mg/kg, s.c) as an NMDA receptor antagonist. Animals' brain and plasma levels of NH4 + were dramatically high, and animals' locomotor activities were disturbed. Moreover, several markers of oxidative stress were significantly increased in the brain. A significant increase in brain tissue levels of TNF-α, IL-6, and IL-1β was also detected in hyperammonemic animals. It was found that ketamine significantly normalized animals' locomotor activity, improved biomarkers of oxidative stress, and decreased proinflammatory cytokines. The effects of ketamine on oxidative stress biomarkers and inflammation seem to play a key role in its neuroprotective mechanisms in the current study.

The Role of Endoplasmic Reticulum Stress in Cell Injury Induced by Methimazole on Pancreatic Cells

Purpose: Methimazole is an anti-thyroid agent, especially as main therapy option for Graves' disease in children and adults. Drug induced pancreatitis is one of the known adverse effect of methimazole mentioned in case reports. However, the detailed molecular mechanisms of methimazole-induced pancreatitis are still unclear. In this study, the aim is to investigate the adverse effect of methimazole on pancreas cell stress mechanism and apoptosis. Methods: Cytotoxicity was evaluated in human pancreas/duct (PANC-1) cell line. Total oxidant (TOS) and antioxidant status (TAS) for oxidative stress index, glutathione (GSH) level and endoplasmic reticulum (ER) stress biomarkers were evaluated by ELISA. Reactive oxygen species (ROS) levels and apoptosis were evaluated by flow-cytometer. Results: The 30% inhibition rate concentration (IC₃₀) value was determined as 53 mM in PANC1 cells. The exposure concentrations were in the range of 0-40 mM for 48 hours. Methimazole might induce cellular stress conditions. ROS production increases depending on concentration, and this increase shows parallelism with the increase in ER stress biomarkers such as TOS, ERN1 and CASPASE12. Conversely, there was no significant difference between control and exposure groups in terms of apoptosis. Conclusion: In conclusion, methimazole might have triggered the mechanisms of inflammation or autophagy in the pancreatic cells. However, there is still a need for in vitro and in vivo studies including other cellular parameters related to apoptosis.

Mitochondrial dysfunction and oxidative stress are involved in the mechanism of tramadol-induced renal injury

Tramadol (TMDL) is an opioid analgesic widely administered for the management of moderate to severe pain. On the other hand, TMDL is commonly abused in many countries because of its availability and cheap cost. Renal injury is related to high dose or chronic administration of TMDL. No precise mechanism for TMDL-induced renal damage has been identified so far. The current study aimed to evaluate the potential role of oxidative stress and mitochondrial impairment in the pathogenesis of TMDL-induced renal injury. For this purpose, rats were treated with TMDL (40 and 80 ​mg/kg, i.p, 28 consecutive days). A significant increase in serum Cr and BUN was detected in TMDL groups. On the other hand, TMDL (80 ​mg/kg) caused a substantial increase in urine glucose, ALP, protein, and γ-GT levels. Moreover, urine Cr was significantly decreased in TMDL-treated rats (40 and 80 ​mg/kg). Renal histopathological alterations included inflammation, necrosis, and tubular degeneration in the kidney of TMDL-treated animals. Reactive oxygen species (ROS) formation, increased oxidized glutathione (GSSG), lipid peroxidation, and protein carbonylation was increased, whereas total antioxidant capacity and reduced glutathione levels were considerably decreased in TMDL groups. Significant mitochondrial impairment was also detected in the form of mitochondrial depolarization, adenosine-tri-phosphate (ATP) depletion, mitochondrial permeabilization, lipid peroxidation, and decreased mitochondrial dehydrogenase activity in the kidney of TMDL (80 ​mg/kg)-treated animals. These data suggest mitochondrial impairment and oxidative stress as mechanisms involved in the pathogenesis of TMDL-induced renal injury.

Taurine mitigates cirrhosis-associated heart injury through mitochondrial-dependent and antioxidative mechanisms

Cirrhosis-induced heart injury and cardiomyopathy is a serious consequence of this disease. It has been shown that bile duct ligated (BDL) animals could serve as an appropriate experimental model to investigate heart tissue injury in cirrhosis. The accumulation of cytotoxic chemicals (e.g., bile acids) could also adversely affect the heart tissue. Oxidative stress and mitochondrial impairment are the most prominent mechanisms of bile acid cytotoxicity. Taurine (Tau) is the most abundant non-protein amino acid in the human body. The cardioprotective effects of this amino acid have repeatedly been investigated. In the current study, it was examined whether mitochondrial dysfunction and oxidative stress are involved in the pathogenesis of cirrhosis-induced heart injury. Rats underwent BDL surgery. BDL animals received Tau (50, 100, and 500 mg/kg, i.p.) for 42 consecutive days. A significant increase in oxidative stress biomarkers was detected in the heart tissue of BDL animals. Moreover, it was found that heart tissue mitochondrial indices of functionality were deteriorated in the BDL group. Tau treatment significantly decreased oxidative stress and improved mitochondrial function in the heart tissue of cirrhotic animals. These data provide clues for the involvement of mitochondrial impairment and oxidative stress in the pathogenesis of heart injury in BDL rats. On the other hand, Tau supplementation could serve as an effective ancillary treatment against BDL-associated heart injury. Mitochondrial regulating and antioxidative properties of Tau might play a fundamental role in its mechanism of protective effects in the heart tissue of BDL animals.

Association between genetic polymorphisms of SLCO1B1 and susceptibility to methimazole-induced liver injury

Methimazole (MMI) has been used in the therapy of Grave's disease (GD) since 1954, and drug-induced liver injury (DILI) is one of the most deleterious side effects. Genetic polymorphisms of drug-metabolizing enzymes and drug transporters have been associated with drug-induced hepatotoxicity in many cases. The aim of this study was to investigate genetic susceptibility of the drug-metabolizing enzymes and drug transporters to the MMI-DILI. A total of 44 GD patients with MMI-DILI and 118 GD patients without MMI-DILI development were included in the study. Thirty-three single nucleotide polymorphisms (SNPs) in twenty candidate genes were genotyped. We found that rs12422149 of SLCO2B1, rs2032582_AT of ABCB1, rs2306283 of SLCO1B1 and rs4148323 of UGT1A1 exhibited a significant association with MMI-DILI; however, no significant difference existed after Bonferroni correction. Haplotype analysis showed that the frequency of SLCO1B1*1a (388A521T) was significantly higher in MMI-DILI cases than that in the control group (OR = 2.21, 95% CI = 1.11-4.39, P = 0.023), while the frequency of SLCO1B1*1b (388G521T) was significantly higher in the control group (OR = 0.52, 95% CI = 0.29-0.93, P = 0.028). These results suggested that genetic polymorphisms of SLCO1B1 were associated with susceptibility to MMI-DILI. The genetic polymorphism of SLCO1B1 may be important predisposing factors for MMI-induced hepatotoxicity.

The potential role of mitochondrial impairment in the pathogenesis of imatinib-induced renal injury

Imatinib is a tyrosine kinase inhibitor widely administered against chronic myeloid leukemia. On the other hand, drug-induced kidney proximal tubular injury, electrolytes disturbances, and renal failure is a clinical complication associated with imatinib therapy. There is no precise cellular mechanism(s) for imatinib-induced renal injury. The current investigation aimed to evaluate the role of mitochondrial dysfunction and oxidative stress in the pathogenesis of imatinib nephrotoxicity. Rats received imatinib (50 and 100 mg/kg, oral, 14 consecutive days). Serum and urine biomarkers of renal injury and markers of oxidative stress in the kidney tissue were assessed. Moreover, kidney mitochondria were isolated, and mitochondrial indices, including mitochondrial depolarization, dehydrogenases activity, mitochondrial permeabilization, lipid peroxidation (LPO), mitochondrial glutathione levels, and ATP content were determined. A significant increase in serum (Creatinine; Cr and blood urea nitrogen; BUN) and urine (Glucose, protein, gamma-glutamyl transferase; γ-GT, and alkaline phosphatase; ALP) biomarkers of renal injury, as well as serum electrolytes disturbances (hypokalemia and hypophosphatemia), were evident in imatinib-treated animals. On the other hand, imatinib (100 mg/kg) caused an increase in kidney ROS and LPO. Renal tubular interstitial nephritis, tissue necrosis, and atrophy were evident as tissue histopathological changes in imatinib-treated rats. Mitochondrial parameters were also adversely affected by imatinib administration. These data represent mitochondrial impairment, renal tissue energy crisis, and oxidative stress as possible mechanisms involved in the pathogenesis of imatinib-induced renal injury and serum electrolytes disturbances.

Boldine Supplementation Regulates Mitochondrial Function and Oxidative Stress in a Rat Model of Hepatotoxicity

Background: The xenobiotics-induced liver injury is a clinical complication. Hence, finding new hepatoprotective strategies has clinical value. Oxidative stress and its subsequent complications are major mechanisms involved in xenobiotics-induced hepatotoxicity. Boldine is one of the most potent antioxidant molecules widely investigated for its protective properties in different experimental models. In the current study, the hepatoprotective properties of boldine and its potential mechanisms of hepatoprotection have been investigated. Methods: Rats received thioacetamide (TAA; 200 mg/kg, i.p) as a model of acute liver injury. Boldine (5, 10, 1nd 20 mg/kg; 24 hours intervals; oral) was administered as the hepatoprotective agent. Results: Liver injury was evident in TAA-treated animals (48 hours after TAA exposure) as a severe increase in serum level of liver injury biomarkers and histopathological alterations. Moreover, markers of oxidative stress were increased in liver tissue of TAA-treated rats. Assessment of mitochondrial indices of functionality revealed a significant decrease in mitochondrial dehydrogenases activity, the collapse of mitochondrial membrane potential, mitochondrial swelling and depletion of ATP content. It was found that boldine supplementation mitigated liver tissue markers of oxidative stress and improved mitochondrial indices of functionality in TAA-treated animals. Conclusion: The hepatoprotective properties of boldine might primarily rely on antioxidant and mitochondria protecting effects of this alkaloid.

Methimazole-Induced Aplastic Anemia with Concomitant Hepatitis in a Young Filipina with Graves' Disease

A 34-year-old female Filipino with Graves' disease on methimazole came in due to fever, sore throat and jaundice. She was initially diagnosed with methimazole-induced agranulocytosis and drug-induced liver injury. She was treated with intravenous broad-spectrum antibiotic and granulocyte colony stimulating factor. On day 4 of admission, she developed pancytopenia and was managed as methimazole-induced aplastic anemia. She was started on steroid therapy and received 1 unit of packed red blood cell. The jaundice also increased, hence, she was given ursodeoxycholic acid. On day 9 of admission, with the consideration of "lineage steal phenomenon," biopsy was done and eltrombopag was started. Patient was discharged stable at 12th hospital day. This case presents 3 rare life-threatening complications of methimazole namely: agranulocytosis, aplastic anemia and hepatitis.

Mechanism of valproic acid-induced Fanconi syndrome involves mitochondrial dysfunction and oxidative stress in rat kidney

AIM

Drug-induced kidney proximal tubular injury and renal failure (Fanconi syndrome; FS) is a clinical complication. Valproic acid (VPA) is among the FS-inducing drugs. The current investigation was designed to evaluate the role of mitochondrial dysfunction and oxidative stress in VPA-induced renal injury.

METHODS

Animals received VPA (250 and 500 mg/kg, i.p., 15 consecutive days). Serum biomarkers of kidney injury and markers of oxidative stress were assessed. Moreover, kidney mitochondria were isolated and mitochondrial indices, including succinate dehydrogenase activity (SDA), mitochondrial depolarization, mitochondrial permeability transition pore (MPP), reactive oxygen species (ROS), lipid peroxidation (LPO), mitochondrial glutathione, and ATP were determined.

RESULTS

Valproic acid-treated animals developed biochemical evidence of FS as judged by elevated serum gamma-glutamyl transferase (γ-GT), alkaline phosphatase (ALP), creatinine (Cr), and blood urea nitrogen (BUN) along with hypokalaemia, hypophosphataemia, and a decrease in serum uric acid. VPA caused an increase in kidney ROS and LPO. Renal GSH reservoirs were depleted and tissue antioxidant capacity decreased in VPA-treated animals. Renal tubular interstitial nephritis, tissue necrosis, and atrophy were also evident in VPA-treated rats. Mitochondrial parameters including SDA, MMP, GSH, ATP and MPP were decreased and mitochondrial ROS and LPO were increased with VPA treatment. It was found that carnitine (100 mg/kg, i.p.) mitigated VPA adverse effects towards the kidney.

CONCLUSIONS

These data suggest that mitochondrial dysfunction and oxidative stress contributed to the VPA-induced FS. On the other hand, carnitine could be considered a potentially safe and effective therapeutic option in attenuating VPA-induced renal injury.

Sulfasalazine induces mitochondrial dysfunction and renal injury

Sulfasalazine is a commonly used drug for the treatment of rheumatoid arthritis and inflammatory bowel disease. There are several cases of renal injury encompass sulfasalazine administration in humans. The mechanism of sulfasalazine adverse effects toward kidneys is obscure. Oxidative stress and its consequences seem to play a role in the sulfasalazine-induced renal injury. The current investigation was designed to investigate the effect of sulfasalazine on kidney mitochondria. Rats received sulfasalazine (400 and 600 mg/kg/day, oral) for 14 consecutive days. Afterward, kidney mitochondria were isolated and assessed. Sulfasalazine-induced renal injury was biochemically evident by the increase in serum blood urea nitrogen (BUN), gamma-glutamyl transferase (γ-GT), and creatinine (Cr). Histopathological presentations of the kidney in sulfasalazine-treated animals revealed by interstitial inflammation, tubular atrophy, and tissue necrosis. Markers of oxidative stress including an increase in reactive oxygen species (ROS) and lipid peroxidation (LPO), a defect in tissue antioxidant capacity, and glutathione (GSH) depletion were also detected in the kidney of sulfasalazine-treated groups. Decreased mitochondrial succinate dehydrogenase activity (SDA), mitochondrial depolarization, mitochondrial GSH depletion, increase in mitochondrial ROS, LPO, and mitochondrial swelling were also evident in sulfasalazine-treated groups. Current data suggested that oxidative stress and mitochondrial injury might be involved in the mechanism of sulfasalazine-induced renal injury.

Exacerbated liver injury of antithyroid drugs in endotoxin-treated mice

Drug-induced liver injury is a major concern in clinical studies as well as in post-marketing surveillance. Previous evidence suggested that drug exposure during periods of inflammation could increase an individual's susceptibility to drug hepatoxicity. The antithyroid drugs, methimazole (MMI) and propylthiouracil (PTU) can cause adverse reactions in patients, with liver as a usual target. We tested the hypothesis that MMI and PTU could be rendered hepatotoxic in animals undergoing a modest inflammation. Mice were treated with a nonhepatotoxic dose of LPS (100 µg/kg, i.p) or its vehicle. Nonhepatotoxic doses of MMI (10, 25 and 50 mg/kg, oral) and PTU (10, 25 and 50 mg/kg, oral) were administered two hours after LPS treatment. It was found that liver injury was evident only in animals received both drug and LPS, as estimated by increases in serum alanine aminotransferase (ALT), lactate dehydrogenase (LDH), aspartate aminotransferase (AST), and TNF-α. An increase in liver myeloperoxidase (MPO) enzyme activity and tissue lipid peroxidation (LPO) in addition of liver glutathione (GSH) depletion were also detected in LPS and antithyroid drugs cotreated animals. Furthermore, histopathological changes including, endotheliitis, fatty changes, severe inflammatory cells infiltration (hepatitis) and sinusoidal congestion were detected in liver tissue. Methyl palmitate (2 g/kg, i.v, 44 hours before LPS), as a macrophage suppressor, significantly alleviated antithyroids hepatotoxicity in LPS-treated animals. The results indicate a synergistic liver injury from antithyroid drugs and bacterial lipopolysaccharide coexposure.

An extremely high dietary iodide supply forestalls severe hypothyroidism in Na+/I- symporter (NIS) knockout mice

The sodium/iodide symporter (NIS) mediates active iodide (I⁻) accumulation in the thyroid, the first step in thyroid hormone (TH) biosynthesis. Mutations in the SLC5A5 gene encoding NIS that result in a non-functional protein lead to congenital hypothyroidism due to I⁻ transport defect (ITD). ITD is a rare autosomal disorder that, if not treated promptly in infancy, can cause mental retardation, as the TH decrease results in improper development of the nervous system. However, in some patients, hypothyroidism has been ameliorated by unusually large amounts of dietary I⁻. Here we report the first NIS knockout (KO) mouse model, obtained by targeting exons 6 and 7 of the Slc5a5 gene. In NIS KO mice, in the thyroid, stomach, and salivary gland, NIS is absent, and hence there is no active accumulation of the NIS substrate pertechnetate (^99mTcO₄⁻). NIS KO mice showed undetectable serum T₄ and very low serum T₃ levels when fed a diet supplying the minimum I⁻ requirement for rodents. These hypothyroid mice displayed oxidative stress in the thyroid, but not in the brown adipose tissue or liver. Feeding the mice a high-I⁻ diet partially rescued TH biosynthesis, demonstrating that, at high I⁻ concentrations, I⁻ enters the thyroid through routes other than NIS.

Effects of methimazole on Drosophila glucolipid metabolism in vitro and in vivo

Methimazole (MMI) is an antithyroid agent widely used in the treatment of hyperthyroidism, and metabolized by cytochrome P450 enzymes and flavin-containing monooxygenases in mammals. However, drug overdose and the inadequate detoxification of the metabolite(s) are responsible for hepatocellular damage and organ dysfunction. Depending on the desired properties, Drosophila melanogaster has recently emerged as an ideal model organism for the study of human diseases. Here we investigated the changes in metabolic profiles and mRNA expressions related to glucolipid metabolism in response to treatment with MMI in Drosophila. Remarkable loss of lifespan occurred in fruit flies fed on the diets containing 10 or 30mM MMI compared to unsupplemented controls. To examine whether MMI affects glucolipid metabolism in vitro and in vivo, fruit flies were fed diets containing 30mM MMI for two weeks and Drosophila S2 cells were incubated with 300μM MMI for 48h. Measurements of metabolites showed that triglyceride content dramatically decreased (30.56% in vivo and 18.13% in vitro), and glycogen content significantly increased (10.7% in vivo and 126.8% in vitro). Quantitative analyses indicated that mRNA expression levels of Dmfmo1, s6k, dilp2, acc and dilp5 genes involved in metabolic homeostasis were remarkably down-regulated in vivo and in vitro. Meanwhile, the addition of MMI could significantly reduce the lipid droplet content in S2 cells by approximately 25% compared to control subjects. These data may provide a biological basis for the study of MMI on disease symptoms and complications, and discovery of therapeutic treatments.

Protective effects of GM-CSF in experimental neonatal hypothyroidism

Hypothyroidism induced by methimazole (MMI), has a negative impact on the postnatal development. Neonatal Granulocyte Macrophage-Colony Stimulating Factor [GM-CSF; 50μg/kg, intramuscular injection at postnatal day (PND) 17] had been tested to ameliorate the effects of MMI [0.05%, (weight per volume; w/v), intraperitoneal injection at PND 15]-induced hypothyroidism in Wistar rats. The hypothyroid conditions due to the administration of MMI produced inhibitory effects on neonatal serum thyroxine (T4), 3,5,3'-triiodothyronine (T3), neutrophil count in bone marrow and blood, cerebellar glutathione (GSH) and acetylcholinesterase (AchE), although it induced stimulatory actions on serum thyrotropin (TSH), growth hormone (GH), insulin growth factor-II (IGF-II), tumor necrosis factor alpha (TNF-α), and cerebellar malondialdehyde (MDA) at PND 19. The treatment with GM-CSF could reverse the depressing and stimulating effects of MMI on these markers except for cerebellar AchE where its enhancement was non-significant (P>0.05) at tested PND. Thus, neonatal GM-CSF may be responsible for suppressing autoimmune responses and preventing hypothyroidism.

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.

Mitigation of Methimazole-Induced Hepatic Injury by Taurine in Mice

Methimazole is the most widely prescribed antithyroid medication in humans. However, hepatotoxicity is a deleterious adverse effect associated with methimazole administration. No specific protective agent has been developed against this complication yet. This study was designed to investigate the role of taurine as a hepatoprotective agent against methimazole-induced liver injury in mice. Different reactive metabolites were proposed to be responsible for methimazole hepatotoxicity. Hence, methimazole-induced liver injury was investigated in intact and/or enzyme-induced animals in the current investigation. Animals were treated with methimazole (200 mg/kg, by gavage), and hepatic injury induced by this drug was investigated in intact and/or enzyme-induced groups. Markers such as lipid peroxidation, hepatic glutathione content, alanine aminotransferase (ALT) and alkaline phosphatase (ALP) in plasma, and histopathological changes in the liver of animals were monitored after drug administration. Methimazole caused liver injury as revealed by increased plasma ALT. Furthermore, a significant amount of lipid peroxidation was detected in the drug-treated animals, and hepatic glutathione reservoirs were depleted. Methimazole-induced hepatotoxicity was more severe in enzyme-induced mice. The above-mentioned alterations in hepatotoxicity markers were endorsed by significant histopathological changes in the liver. Taurine administration (1 g/kg, i.p.) effectively alleviated methimazole-induced liver injury in both intact and/or enzyme-induced animals.

Factors affecting drug-induced liver injury: antithyroid drugs as instances

Methimazole and propylthiouracil have been used in the management of hyperthyroidism for more than half a century. However, hepatotoxicity is one of the most deleterious side effects associated with these medications. The mechanism(s) of hepatic injury induced by antithyroid agents is not fully recognized yet. Furthermore, there are no specific tools for predicting the occurrence of hepatotoxicity induced by these drugs. The purpose of this article is to give an overview on possible susceptibility factors in liver injury induced by antithyroid agents. Age, gender, metabolism characteristics, alcohol consumption, underlying diseases, immunologic mechanisms, and drug interactions are involved in enhancing antithyroid drugs-induced hepatic damage. An outline on the clinically used treatments for antithyroid drugs-induced hepatotoxicity and the potential therapeutic strategies found to be effective against this complication are also discussed.

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

PURPOSE

Hepatotoxicity 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.

METHODS

The 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.

RESULTS

Incubation 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.

CONCLUSION

This 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.

Effects of Enzyme Induction and/or Glutathione Depletion on Methimazole-Induced Hepatotoxicity in Mice and the Protective Role of N-Acetylcysteine

PURPOSE

Methimazole 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.

METHODS

This 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.

RESULTS

Methimazole (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.

CONCLUSION

The 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.

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

PURPOSE

Methimazole 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.

METHODS

Hepatocytes 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.

RESULTS

Methimazole 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.

CONCLUSION

Organosulfur 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.