Reducing the risk of death induced by aluminum phosphide poisoning: The new therapies

Numerous people suffer from accidental or deliberate exposure to different pesticides when poisoning with aluminum phosphate (AlP) is increasing in the eastern countries. Aluminum phosphate is a conventional insecticide that quickly reacts with water or the moistures in the atmosphere and produces fatal phosphine gas, which absorbs quickly by the body. Oral consumption or inhalation of AlP leads to excessive reaction of the body such as fatigue, vomiting, fever, palpitation, vasodilatory shock, increasing blood pressure, cardiac dysfunction, pulmonary congestion, shortness of breath, and death. The garlic smell from the patient's mouth or exhale is one of the methods to recognize the positioning. Due to the lack of individual antidotes, several supportive treatments are required. The present study focused on the available and new therapies that help reduce the effect of AlP poisoning and the mortality rate. The therapies are divided into the antioxidant-related agent and the other agents. The impacts of each agent on the experimental cases are reported.

Sensing of oxidative stress biomarkers: The cardioprotective effect of taurine & grape seed extract against the poisoning induced by an agricultural pesticide aluminum phosphide

Aluminum phosphide is a well-known hazardous agent used as an agricultural pesticide to protect stored grains from insect damage. However, accidental consumption of a trivial amount of it caused irreversible damage to the human body or even death in acute cases. The present study used taurine and grape seed extract as a natural cardioprotective medicine against aluminum phosphide poisoning by decreasing oxidative stress. The activity of oxidative stress biomarkers (Malondialdehyde, Catalase, Protein carbonyl, and Superoxide dismutase) were evaluated in the cell line model on Human Cardiac Myocyte cells. In the beginning, to clarify the pure impact of aluminum phosphide poison, taurine, and grape seed extract on the human heart cells, their effects on the biomarkers quantity in cell line were measured. Subsequently, the effect of taurine and grape seed extract with various concentrations as a treatment on the oxidative stress biomarkers of the poisoned heart cells were studied. Data analysis reveals that taurine and grape seed extract treatment can successfully diminish the poisoning effect by their antioxidant properties. The oxidative markers values of the poisoned cells were recovered by taurine and grape seed extracts treatment. Taurine (2 g/l) can recover Malondialdehyde, Catalase, Protein carbonyl, and Superoxide dismutase by 56%, 78%, 88%, 78%, when the recovering power of grape seed extract (100 g/l) for the aforementioned enzymes are 56%, 0.71%,74%, 51%, respectively. Therefore, it is clear that the performance of taurine in the recovery of the biomarkers' value is better than grape seed extract.

Study of the cardioprotective effects of crocin on Human Cardiac Myocyte cells and reduction of oxidative stress produced by aluminum phosphide poisoning

OBJECTIVES

The effects of Crocin as a cardioprotective material against Aluminum phosphide poisoning by reducing the oxidative stress is investigated.

METHODS

The level of biomarkers of oxidative stress (Catalase, Superoxide dismutase, Malondialdehyde and Protein carbonyl) were measured in the cell culture model on Human Cardiac Myocyte cells to detect the protective effect of crocin. Initially, to define the pure impact of aluminum phosphide poison and crocin on the heart cells, their effects on the biomarkers quantity in cell line were measured, separately, using the standard related kits. Later the effect of crocin with different concentration as a treatment on the oxidative stress biomarkers of the poisoned heart cells were monitored. Note that in pre-treatment case, the crocin was initially added to the cells before poisoning them. Data were analyzed using the analysis of variance method.

KEY FINDINGS

Results showed that crocin treatment reduced the aluminum phosphide (AlP) poisoning effect significantly. The treatment resulted in substantial deviation in the biomarkers of oxidative stress at the pre- and post-treatment phases for all groups. The oxidative markers values of the poisoned cells were recovered by crocin treatment.

CONCLUSIONS

Crocin is proposed as a potentially powerful antioxidant to treat the cardiotoxicity caused by aluminum phosphide poisoning.

Hepatoprotective role of berberine against paraquat-induced liver toxicity in rat

Paraquat (PQ) is a herbicide agent commonly used in agricultural applications. Hepatotoxicity is among clinical complications associated with PQ intoxication. Oxidative stress and its subsequent events are major mechanisms identified in PQ-induced liver toxicity. Berberine (BBR) is a natural antioxidant widely investigated for its hepatoprotective effects. The present study designed to evaluate the potential cytoprotective properties of BBR against PQ-induced cytotoxicity in primary cultured rat hepatocytes and in vivo test of liver function enzymes. Cellular and biochemical parameters including lactate dehydrogenase (LDH), cell viability, ROS formation, glutathione (GSH) content, and mitochondrial membrane potential in the PQ-treated hepatocytes were measured, and the mentioned markers were evaluated in the presence of BBR. BBR treatment caused significant decrease in PQ-induced cell death, ROS formation, and LDH release. On the other hand, it was found that BBR inhibits cellular glutathione depletion in PQ-treated hepatocytes. Also, BBR treatment significantly diminished PQ-induced the liver function enzyme elevation. These data mention the potential hepatoprotective effect of BBR with therapeutic capability against PQ-induced liver damage.

Cell junctions and oral health

The oral cavity and its appendices are exposed to considerable environmental and mechanical stress. Cell junctions play a pivotal role in this context. Among those, gap junctions permit the exchange of compounds between cells, thereby controlling processes such as cell growth and differentiation. Tight junctions restrict paracellular transportation and inhibit movement of integral membrane proteins between the different plasma membrane poles. Adherens junctions attach cells one to another and provide a solid backbone for resisting to mechanistical stress. The integrity of oral mucosa, normal tooth development and saliva secretion depend on the proper function of all these types of cell junctions. Furthermore, deregulation of junctional proteins and/or mutations in their genes can alter tissue functioning and may result in various human disorders, including dental and periodontal problems, salivary gland malfunction, hereditary and infectious diseases as well as tumorigenesis. The present manuscript reviews the role of cell junctions in the (patho)physiology of the oral cavity and its appendices, including salivary glands.

Cytoprotective Properties of Carnosine against Isoniazid-Induced Toxicity in Primary Cultured Rat Hepatocytes

Background: Drug-induced liver injury is a critical clinical complication. Hence, finding new and safe protective agents with potential clinical application is of value. Isoniazid (INH) is an antituberculosis agent widely used against Mycobacterium tuberculosis infection in human. On the other hand, hepatotoxicity is a clinical complication associated with isoniazid therapy. Oxidative stress and its associated events are major mechanisms identified for INH-induced liver injury. Carnosine is an endogenously found peptide widely investigated for its hepatoprotective effects. On the other hand, robust antioxidant and cytoprotective effects have been attributed to this peptide. Methods: The current study designed to evaluate the potential cytoprotective properties of carnosine against INH-induced cytotoxicity in drug-exposed primary cultured rat hepatocytes. Primary cultured rat hepatocytes were incubated with INH (1.2 mM). Results: INH treatment caused significant increase in cell death and lactate dehydrogenase (LDH) release. On the other hand, it was found that markers of oxidative stress including reactive oxygen species were significantly increased in INH-treated cells. Cellular glutathione reservoirs were also depleted in INH-treated group. Carnosine treatment (50 and 100 µM) significantly diminished INH-induced oxidative stress and cytotoxicity. Conclusion: These data mention carnosine as a potential protective agent with therapeutic capability against INH hepatotoxicity.

Novel angiotensin receptor blocker, azilsartan induces oxidative stress and NFkB-mediated apoptosis in hepatocellular carcinoma cell line HepG2

Overexpression of renin angiotensin system (RAS) components and nuclear factor-kappa B (NF-kB) has a key role in various cancers. Blockade of RAS and NF-kB pathway has been suggested to reduce cancer cell proliferation. This study aimed to investigate the role of angiotensin II and NF-kB pathway in liver hepatocellular carcinoma cell line (HepG2) proliferation by using azilsartan (as a novel Ag II antagonist) and Bay 11-7082 (as NF-kB inhibitor). HepG2 cells were treated with different concentrations of azilsartan and Bay 11-7082. Cytotoxicity was determined after 24, 48, and 72?h by MTT assay. Reactive oxygen spices (ROS) generation and cytochrome c release were measured following azilsartan and Bay11- 7082 treatment. Apoptosis was analyzed qualitatively by DAPI staining and quantitatively through flow cytometry methodologies and Bax and Bcl-2 mRNA and protein levels were assessed by real time PCR and ELISA methods, respectively. The cytotoxic effects of different concentration of azilsartan and Bay11- 7082 on HepG2 cells were observed as a reduction in cell viability, increased ROS formation, cytochrome c release and apoptosis induction. These effects were found to correlate with a shift in Bax level and a downward trend in the expression of Bcl-2. These findings suggest that azilsartan and Bay11- 7082 in combination or alone have strong potential as an agent for prevention or treatment of liver cancer after further studies.

Protective effects of coenzyme Q10 nanoparticles on dichlorvos-induced hepatotoxicity and mitochondrial/lysosomal injury

Development of biocompatible antioxidant nanoparticles for xenobiotic-induced liver disease treatment by oral or parenteral administration is of great interest in medicine. In the current study, we demonstrate the protective effects of coenzyme Q10 nanoparticles (CoQ10-NPs) on hepatotoxicity induced by dichlorvos (DDVP) as an organophosphate. Although CoQ10 is an efficient antioxidant, its poor bioavailability has limited the applications of this useful agent. First, CoQ10-NPs were prepared then characterized using dynamic light scattering (DLS) and transmission electron microscopy (TEM). In DDVP-treated and non-treated hepatocytes in the presence of CoQ10-NPs, cell viability, the level of reactive oxygen species (ROS), lipid peroxidation (LPO), mitochondrial membrane potential (MMP), lysosome membrane integrity, and cellular glutathione (GSH) content were measured. The prepared CoQ10-NPs were mono-dispersed and had narrow size distribution with average diameter of 54 nm. In the in vivo study, we evaluated the enzymes, which are involved in the antioxidant system for maintenance of normal liver function. In comparison to nonparticulate CoQ10, the CoQ10-NPs efficiently decreased the ROS formation, lipid peroxidation and cell death. Also, particulate form of CoQ10 improved MMP, GSH level and lysosome membrane integrity. In the in vivo, study, we revealed that CoQ10-NPs were better hepatoprotective than its nonparticulate form (P < .05). Altogether, we propose that the CoQ10-NPs have potential capability to be used as a therapeutic and prophylactic agent for poisoning that is induced by organophosphate agents, especially in the case of DDVP. Furthermore, these positive remarks make this nanoparticle amenable for the treatment of xenobiotic-induced liver diseases.

Betanin reduces organophosphate induced cytotoxicity in primary hepatocyte via an anti-oxidative and mitochondrial dependent pathway

Organophosphates (OP) are potent pesticide commonly utilized in agricultural and domestic use. However, plentitude of data represent their side effects in different body tissues. We attempted to study whether betanin (a natural pigment) is able to mitigate some OPs-induced hepatotoxicity in primary rat hepatocytes. Cell viability, lactate dehydrogenase (LDH) leakage, reactive oxygen species (ROS) formation, lipid peroxidation (LPO), glutathione (GSH) depletion and mitochondrial depolarization were tested as toxicity markers. The outcomes revealed that betanin (25μM) significantly increased cell viability, plummeted ROS formation and LPO, restored cellular GSH reservoirs and protected mitochondria after chlorpyrifos (CPF) (300μM), diazinon (DZN) (600μM) and dichlrovos (DDVP) (400μM) treatment. Taken together, all data suggests the potential protective role of betanin in OPs-induced hepatotoxicity in which the mechanism appears to be inhibition of ROS formation and mitochondrial protection.

Mechanistic Approach for Thioridazine-Induced Hepatotoxicity and Potential Benefits of Melatonin and/or Coenzyme Q10 on Freshly Isolated Rat Hepatocytes

Thioridazine (TZ) is used mainly in the treatment of schizophrenia. However, hepatotoxicity as a life-threatening adverse effect is associated with its clinical use. In this context, we examined the cytotoxic mechanisms of TZ on freshly isolated rat hepatocytes to better understanding of the pathogenesis of TZ-induced hepatotoxicity. Hepatocytes were prepared by the method of collagenase enzyme perfusion via the portal vein. The level of parameters such as cell death, reactive oxygen species (ROS) formation, lipid peroxidation (LPO), mitochondrial membrane potential (MMP), lysosomal membrane integrity and cellular glutathione (GSH) content in TZ-treated and non-treated hepatocytes were determined and the mentioned markers were assessed in the presence of Coenzyme Q10 and/or melatonin. Results showed that TZ caused an increase in ROS formation as well as induction of LPO and GSH depletion. Moreover, mitochondria and lysosomes seem to be targets of TZ-induced toxicity. The administration of Coenzyme Q10 and/or melatonin efficiently decreased the rate of ROS formation, LPO and improved cell viability, MMP, GSH level and lysosome membrane integrity. This study proposes the possible protective role of Coenzyme Q10 and/or melatonin against TZ-induced cellular injury probably through their radical scavenging properties and their effects on mitochondria and lysosomes.

Venlafaxine-Induced Cytotoxicity Towards Isolated Rat Hepatocytes Involves Oxidative Stress and Mitochondrial/Lysosomal Dysfunction

Purpose: Depression is a public disorder worldwide. Despite the widespread use of venlafaxine in the treatment of depression, it has been associated with the incidence of toxicities. Hence, the goal of the current investigation was to evaluate the mechanisms of venlafaxine-induced cell death in the model of the freshly isolated rat hepatocytes. Methods: Collagenase-perfused rat hepatocytes were treated with venlafaxine and other agents. Cell damage, reactive oxygen species (ROS) formation, lipid peroxidation, mitochondrial membrane potential decline, lysosomal damage, glutathione (GSH) level were analyzed. Moreover, rat liver mitochondria were isolated through differential centrifugation to assess respiratory chain functionality. Results: Our results demonstrated that venlafaxine could induce ROS formation followed by lipid peroxidation, cellular GSH content depletion, elevated GSSG level, loss of lysosmal membrane integrity, MMP collapse and finally cell death in a concentration-dependent manner. N-acetyl cysteine, taurine and quercetine significantly decreased the aforementioned venlafaxine-induced cellular events. Also, radical scavenger (butylatedhydroxytoluene and α-tocopherol), CYP2E1 inhibitor (4-methylpyrazole), lysosomotropic agents (methylamine and chloroquine), ATP generators (L-gluthamine and fructose) and mitochondrial pore sealing agents (trifluoperazine and L-carnitine) considerably reduced cytotoxicity, ROS generation and lysosomal leakage following venlafaxine treatment. Mitochondrion dysfunction was concomitant with the blockade of the electron transfer complexes II and IV of the mitochondrial respiratory system. Conclusion: Therefore, our data indicate that venlafaxine induces oxidative stress towards hepatocytes and our findings provide evidence to propose that mitochondria and lysosomes are of the primary targets in venlafaxine-mediated cell damage.

Protective Roles of N-acetyl Cysteine and/or Taurine against Sumatriptan-Induced Hepatotoxicity

Purpose: Triptans are the drug category mostly prescribed for abortive treatment of migraine. Most recent cases of liver toxicity induced by triptans have been described, but the mechanisms of liver toxicity of these medications have not been clear. Methods: In the present study, we obtained LC₅₀ using dose-response curve and investigated cell viability, free radical generation, lipid peroxide production, mitochondrial injury, lysosomal membrane damage and the cellular glutathione level as toxicity markers as well as the beneficial effects of taurine and/or N-acetyl cysteine in the sumatriptan-treated rat parenchymal hepatocytes using accelerated method of cytotoxicity mechanism screening. Results: It was revealed that liver toxicity induced by sumatriptan in in freshly isolated parenchymal hepatocytes is dose-dependent. Sumatriptan caused significant free radical generation followed by lipid peroxide formation, mitochondrial injury as well as lysosomal damage. Moreover, sumatriptan reduced cellular glutathione content. Taurine and N-acetyl cysteine were able to protect hepatocytes against sumatriptan-induced harmful effects. Conclusion: It is concluded that sumatriptan causes oxidative stress in hepatocytes and the decreased hepatocytes glutathione has a key role in the sumatriptan-induced harmful effects. Also, N-acetyl cysteine and/or taurine could be used as treatments in sumatriptan-induced side effects.

Role of renin-angiotensin system in liver diseases: an outline on the potential therapeutic points of intervention

The current review aimed to outline the functions of the renin angiotensin system (RAS) in the context of the oxidative stress-associated liver disease. Areas covered: Angiotensin II (Ang II) as the major effector peptide of the RAS is a pro-oxidant and fibrogenic cytokine. Mechanistically, NADPH oxidase (NOX) is a multicomponent enzyme complex that is able to generate reactive oxygen species (ROS) as a downstream signaling pathway of Ang II which is expressed in liver. Ang II has a detrimental role in the pathogenesis of chronic liver disease through possessing pro-oxidant, fibrogenic, and pro-inflammatory impact in the liver. The alternative axis (ACE2/Ang(1-7)/mas) of the RAS serves as an anti-inflammatory, antioxidant and anti-fibrotic component of the RAS. Expert commentary: In summary, the use of alternative axis inhibitors accompanying with ACE2/ Ang(1-7)/mas axis activation is a promising new strategy serving as a novel therapeutic option to prevent and treat chronic liver diseases.

Triazole rizatriptan Induces Liver Toxicity through Lysosomal/Mitochondrial Dysfunction

Background: Triptans are used as antimigraine agents. Some cases of hepatotoxicity by triptans have been reported. However, the exact mechanism of triptan-induced hepatotoxicity is not clear yet. Methods: In this study, the cytotoxic effects of rizatriptan were investigated in freshly isolated rat hepatocytes using accelerated cytotoxicity mechanism screening. We designed experiments to evaluate toxicity markers, such as cell death, reactive oxygen species (ROS) formation, lipid peroxidation, mitochondrial membrane potential, lysosomal membrane integrity and the amount of reduced and oxidized glutathione in the rizatriptan-treated hepatocytes. Results: Cytotoxicity caused by rizatriptan in rat hepatocytes was concentration-dependent. An increase in ROS formation accompanied by a significant rise in lipid peroxidation, mitochondrial depolarization and loss of lysosomal membrane integrity was observed. Cellular glutathione reservoirs were decreased and a significant amount of oxidized glutathione was formed. All the aforementioned rizatriptan-induced cellular events were significantly (p<0.05) prevented by ROS scavengers, antioxidants, endocytosis inhibitors and adenosine triphosphate (ATP) generators. Also, the present results demonstrated that CYP450 is involved in rizatriptan-induced oxidative stress and cytotoxicity mechanism and different CYP450 inducers had different effects on the toxicity. Conclusion: It is suggested that the adverse effect of rizatriptan towards hepatocytes is mediated by oxidative stress and the hepatocytes lysosomes and mitochondria play an important role in rizatriptan-induced cell injury.

In vitro and in vivo evaluation of the mechanisms of citalopram-induced hepatotoxicity

Even though citalopram is commonly used in psychiatry, there are several reports on its toxic effects. So, the current study was designed to elucidate the mechanisms of cytotoxic effects of in vitro and in vivo citalopram treatment on liver and the following cytolethal events. For in vitro experiments, freshly isolated rat hepatocytes were exposed to citalopram along with/without various agents. To do in vivo studies liver function enzyme assays and histological examination were performed. In the in vitro experiments, citalopram (500 µM) exposure demonstrated cell death, a marked elevation in ROS formation, mitochondrial potential collapse, lysosomal membrane leakiness, glutathione (GSH) depletion and lipid peroxidation. In vivo biochemistry panel assays for liver enzymes function (AST, ALT and GGTP) and histological examination confirmed citalopram (20 mg/kg)-induced damage. citalopram-induced oxidative stress cytotoxicity markers were significantly prevented by antioxidants, ROS scavengers, MPT pore sealing agents, endocytosis inhibitors, ATP generators and CYP inhibitors. Either enzyme induction or GSH depletion were concomitant with augmented citalopram-induced damage both in vivo and in vitro which were considerably ameliorated with antioxidants and CYP inhibitors. In conclusion, it is suggested that citalopram hepatotoxicity might be a result of oxidative hazard leading to mitochondrial/lysosomal toxic connection and disorders in biochemical markers which were supported by histomorphological studies.

Improvement of Liver Cell Therapy in Rats by Dietary Stearic Acid

BACKGROUND

Stearic acid is known as a potent anti-inflammatory lipid. This fatty acid has profound and diverse effects on liver metabolism. The aim of this study was to investigate the effect of stearic acid on markers of hepatocyte transplantation in rats with acetaminophen (APAP)-induced liver damage.

METHODS

Wistar rats were randomly assigned to 10-day treatment. Stearic acid was administered to the rats with APAP-induced liver damage. The isolated liver cells were infused intraperitoneally into rats. Blood samples were obtained to evaluate the changes in the serum liver enzymes, including activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT) and alkaline phosphatase (ALP) and the level of serum albumin. To assess the engraftment of infused hepatocytes, rats were euthanized, and the liver DNA was used for PCR using sex-determining region Y (SRY) primers.

RESULTS

The levels of AST, ALT and ALP in the serum of rats with APAP-induced liver injury were significantly increased and returned to the levels in control group by day six. The APAP-induced decrease in albumin was significantly improved in rats through cell therapy, when compared with that in the APAP-alone treated rats. SRY PCR analysis showed the presence of the transplanted cells in the liver of transplanted rats.

CONCLUSION

Stearic acid-rich diet in combination with cell therapy accelerates the recovering of hepatic dysfunction in a rat model of liver injury.

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.

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

PURPOSE

Amitriptyline, 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.

METHODS

Markers 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.

RESULTS

Present 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.

CONCLUSION

Our 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.

Involvement of oxidative stress and mitochondrial/lysosomal cross-talk in olanzapine cytotoxicity in freshly isolated rat hepatocytes

1. Olanzapine (OLZ) is a widely used atypical antipsychotic agent for the treatment of schizophrenia and other disorders. Serious hepatotoxicity and elevated liver enzymes have been reported in patients receiving OLZ. However, the cellular and molecular mechanisms of the OLZ hepatotoxicity are unknown. 2. In this study, the cytotoxic effect of OLZ on freshly isolated rat hepatocytes was assessed. Our results showed that the cytotoxicity of OLZ in hepatocytes is mediated by overproduction of reactive oxygen species (ROS), mitochondrial potential collapse, lysosomal membrane leakiness, GSH depletion and lipid peroxidation preceding cell lysis. All the aforementioned OLZ-induced cellular events were significantly (p < 0.05) prevented by ROS scavengers, antioxidants, endocytosis inhibitors and adenosine triphosphate generators. Also, the present results demonstrated that CYP450 is involved in OLZ-induced oxidative stress and cytotoxicity mechanism. 3. It is concluded that OLZ hepatotoxicity is associated with both mitochondrial/lysosomal involvement following the initiation of oxidative stress in hepatocytes.

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 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.

Antimutagenic effects of vitamin E on oncology and non oncology hospital nurses by comet assay

Vitamin E is a natural antioxidant and its most common biologically active form is α-tocopherol. The antiproliferative effects of α-tocopherol have been previously demonstrated. In this study the antimutagenic effects of vitamin E on oncology and non oncology hospital nurses was investigated. A total of 138 female nurses from oncology and non oncology hospitals participated in the study. They received 200 mg/day vitamin E for 2 weeks. The urine samples before and after intake of vitamin E were collected and the nucleus of urothelial cells were evaluated with comet assay. The length of epithelial cells nuclei correlated with increased fracture rate of DNA. Nucleolus length of urine epithelial cells of all nursing staff before and after vitamin E treatment were measured and the data were evaluated by student t-test and SPSS. Our study showed that 20% of nursing staff have apoptosis and DNA fracture in the nucleolus of their urine epithelial cells and DNA damage in the urothelial cells of exposed nurses was significantly higher than the control group (P<0.05).The antimutagenic activity of vitamin E had significant effects on oncology hospital nurses effectively in repairing DNA damage and decreasing their nucleus length in urine epithelial cells.We propose that the higher therapeutic doses of vitamin E and increasing the length of treatment period will be effective against DNA strand breakage and may have more effect on oncology nurses.

Mechanisms of trazodone-induced cytotoxicity and the protective effects of melatonin and/or taurine toward freshly isolated rat hepatocytes

It has been reported that the bioactive intermediate metabolites of trazodone might cause hepatotoxicity. This study was designed to investigate the exact mechanism of hepatocellular injury induced by trazodone as well as the protective effects of taurine and/or melatonin against this toxicity. Freshly isolated rat hepatocytes were used. Trazodone was cytotoxic and caused cell death with LC50 of 300 µm within 2 h. Trazodone caused an increase in reactive oxygen species (ROS) formation, malondialdehyde accumulation, depletion of intracellular reduced glutathione (GSH), rise of oxidized glutathione disulfide (GSSG), and a decrease in mitochondrial membrane potential, which confirms the role of oxidative stress in trazodone-induced cytotoxicity. Preincubation of hepatocytes with taurine prevented ROS formation, lipid peroxidation, depletion of intracellular reduced GSH, and increase of oxidized GSSG. Taurine could also protect mitochondria against trazodone-induced toxicity. Administration of melatonin reduced the toxic effects of trazodone in isolated rat hepatocytes.

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.

Biological evaluation of a siliconized analog of clofibrate (silafibrate) in rodents

Silicon is the element very similar to carbon, and bioactive siliconized compounds have therefore received much attention. Siliconization of a compound enhances its biological activities. In the present study the hypolipidemic effect and toxicity of clofibrate and its siliconized analog, silafibrate, were compared. The experiments were performed in hypercholesterolemicWistar rats. Animals received high fat diet with 62.75% normal chow, 2% cholesterol, 0.25% cholic acid, 15% lard oil, 10% wheat flour and 10% sucrose.Silafibrate(40 mg/kg/day) produced a predominant reduction in the serum levels of total cholesterol (28.4%, p < 0.001), triglycerides (62%, p < 0.0001) and low-density lipoproteins (27%, p < 0.001) being more effective than the reference drug clofibrate (20%, 40%, 14.5%; p < 0.05). Similarly, it increased the total antioxidant levels in serum by 40% (p < 0.05). Simultaneously, treatment with silafibrate also reduced the malondialdehyde(MDA) concentration by 41% (p < 0.05). LD50 of silafibrate, given orally,was greater than 2000 mg/kg body weight inalbino mice while LD50 for clofibrate was calculated to be 1220 mg/kg. Thirty-day subacute toxicity was also evaluated with oral daily dose at 25, 50 and 100 mg/kg body weight in Wistarrats. No significant changes in body weight, food intake, behavior, mortality, hematology, blood biochemistry, vital organ weight were detected. The results of this study indicate that the effectiveness and safety of thehypolipidemic drug, clofibrate, were enhanced remarkably by replacing chlorine atom in its phenoxy ring with trimethylsilyl.

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.

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

PURPOSE

Induction 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.

METHODS

Rat 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.

RESULTS

Despite 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.

CONCLUSION

Cytotoxic 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 malathion's LC50.

Biochemical evidence on the potential role of organophosphates in hepatic glucose metabolism toward insulin resistance through inflammatory signaling and free radical pathways

Several studies show that organophosphate pesticides exert several effects on glucose homeostasis. The current study investigates the influence of subchronic exposure to malathion (MT) on hepatic gluconeogenesis in relation to acetyl cholinesterase (AChE) inhibition, oxidative stress and inflammatory response in the rat. MT was administered by gavage at doses of 25, 50 and 100 mg/kg for 32 days. Fasting hyperglycemia was seen in line with an increased activity of hepatic phosphoenolpyruvate carboxykinase, glucose 6-phosphatase and tumor necrosis factor α. In addition to the impaired glucose tolerance and inhibition of AChE in a dose-dependent manner, there were significant increases in hepatic lipid peroxidation, carbonyl groups and 8-deoxyguanosine as the biomarkers of reactive oxygen species–mediated damage to lipid, protein and DNA, respectively. Altered quality of the liver in glucose production especially gluconeogenesis could be a compensatory mechanism against MT toxicity or even result in tissue damage. MT-induced insulin resistance in the liver occurs through oxidative and inflammatory signaling pathways.

The protective effects of garlic extract against acetaminophen-induced oxidative stress and glutathione depletion

Acetaminophen, the most commonly sold over-the-counter antipyretic analgesic, is capable of causing severe and sometimes fatal hepatic damage in humans and experimental animals. The incidence of liver injury due to acetaminophen overdose, either with suicidal intent or by accident, is increasing. Garlic is among those medicinal plants famous for its different health protective effects. In this study, the protective effects of garlic extract on acute acetaminophen-induced liver injury were investigated using freshly isolated rat hepatocytes. The hepatocytes were isolated from Sprague-Dawley male rats by a two step collagenase model. Formation of Reactive Oxygen Species (ROS) and Glutathione (GSH) depletion were studied after addition of acetaminophen to cell suspensions. The effects of garlic extract on prevention of ROS formation as well as GSH depletion was investigated and compared with the effects of N-Acetyl Cysteine (NAC) as the standard treatment. Reactive oxygen species formation was assessed by a spectrofluorometry method and garlic extract was shown to be as effective as NAC in decreasing ROS formation induced by acetaminophen. Glutathione (GSH) levels of hepatocytes were determined using HPLC. Garlic extract was effective in preventing GSH depletion significantly (p < 0.05). It is concluded that garlic extract has an antioxidant effect and can protect hepatocytes from GSH depletion following NAPQI production.

Hydrogen peroxide supports hepatocyte P450 catalysed xenobiotic/drug metabolic activation to form cytotoxic reactive intermediates

1. A H2O2 generating system markedly increased the cytotoxicity of catechols, hydroquinone, in isolated hepatocytes, but not in P450 inhibited hepatocytes. 2. H2O2 or NADPH supported microsomal catalysed GSH conjugate formation with catechols or hydroquinone. Cytochrome P450 inhibitors inhibited conjugate formation. However, superoxide dismutase inhibited NADPH, but did not affect H2O2 supported GSH conjugate formation. The conjugate formed with dihydrocaffeic acid was identified as a mono-GSH conjugate indicating that the o-quinone was the major metabolite formed. 3. Dopamine (a catecholamine) induced cytotoxicity was prevented by inhibitors of monoamine oxidase (MAO) or P450, but was markedly increased by hepatocyte catalase inhibition or NAD(P)H:quinone oxidoreductase inhibition. This suggests that H2O2 formed by the mitochondrial metabolism of monoamine oxidase then oxidised dopamine to cytotoxic o-quinone catalysed by P450. Dihydrocaffeic acid cytotoxicity was also increased by the monoamine oxidase substrate tyramine. 4. It is concluded that polyphenolics are oxidised by H2O2/P450 in hepatocytes to form quinone metabolites.