Increased oxidative-modifications of cytosolic proteins in 3,4-methylenedioxymethamphetamine (MDMA, ecstasy)-exposed rat liver

Contributing roles of mitochondrial dysfunction and hepatocyte apoptosis in liver diseases through oxidative stress, post-translational modifications, inflammation, and intestinal barrier dysfunction

This review provides an update on recent findings from basic, translational, and clinical studies on the molecular mechanisms of mitochondrial dysfunction and apoptosis of hepatocytes in multiple liver diseases, including but not limited to alcohol-associated liver disease (ALD), metabolic dysfunction-associated steatotic liver disease (MASLD), and drug-induced liver injury (DILI). While the ethanol-inducible cytochrome P450-2E1 (CYP2E1) is mainly responsible for oxidizing binge alcohol via the microsomal ethanol oxidizing system, it is also responsible for metabolizing many xenobiotics, including pollutants, chemicals, drugs, and specific diets abundant in n-6 fatty acids, into toxic metabolites in many organs, including the liver, causing pathological insults through organelles such as mitochondria and endoplasmic reticula. Oxidative imbalances (oxidative stress) in mitochondria promote the covalent modifications of lipids, proteins, and nucleic acids through enzymatic and non-enzymatic mechanisms. Excessive changes stimulate various post-translational modifications (PTMs) of mitochondrial proteins, transcription factors, and histones. Increased PTMs of mitochondrial proteins inactivate many enzymes involved in the reduction of oxidative species, fatty acid metabolism, and mitophagy pathways, leading to mitochondrial dysfunction, energy depletion, and apoptosis. Unique from other organelles, mitochondria control many signaling cascades involved in bioenergetics (fat metabolism), inflammation, and apoptosis/necrosis of hepatocytes. When mitochondrial homeostasis is shifted, these pathways become altered or shut down, likely contributing to the death of hepatocytes with activation of inflammation and hepatic stellate cells, causing liver fibrosis and cirrhosis. This review will encapsulate how mitochondrial dysfunction contributes to hepatocyte apoptosis in several types of liver diseases in order to provide recommendations for targeted therapeutics.

The ameliorating effects of Vitamin E on hepatotoxicity of ecstasy

Background:

The production of stress oxidative condition in body which is caused by consumption of ecstasy (3,4-methylenedioxymethamphetamine [MDMA]) leads to a liver damage. As an antioxidant, Vitamin E can protect cells and tissues against the deleterious effects of free radicals. This study evaluates the protective effects of Vitamin E on MDMA induced liver toxicity.

Materials and Methods:

Twenty-eight male albino mice were randomly assigned to four equal groups. Group 1 received saline (control), Group 2 received MDMA and saline, Group 3 received MDMA, and Vitamin E and Group 4 received Vitamin E. MDMA was injected with single daily dose, three sequential days/week for 5 weeks. At the end of the period, blood samples were collected for a biochemical analysis and then the mice were sacrificed by cervical dislocation for histopathological and biochemical examinations of liver.

Results:

The administration of Vitamin E attenuated the increased levels of alanine transaminase, aspartate transaminase, and alkaline phosphatase enzymes in serum. Vitamin E treatments significantly restored endogenous antioxidant enzymes (reduced glutathione and superoxide dismutase enzyme) activities as compared with MDMA-treated animals. Histological examination of liver revealed significant morphological tissue injuries in hepatocytes after MDMA being used, but in coadministration of vitamin E and MDMA, these morphological alterations reduced.

Conclusion:

The study showed that MDMA administration has adverse effects on the liver. Vitamin E lessened the deleterious impact considerably.

Peroxiredoxins in inflammatory liver diseases and ischemic/reperfusion injury in liver transplantation

Peroxiredoxins (Prxs) belong to the superfamily of thiol-dependent peroxidases, and remove reactive oxygen species (ROS) and other oxidative stress products. The expression and activity of Prxs can be substantially affected by stimuli from the microenvironment, and in turn regulate cytokine secretion in the context of inflammation in both peroxidase-dependent and -independent pathways. Prxs translocate to mitochondria and are hyperoxidized during acute liver damage, and attenuate intracellular ROS accumulation through their peroxidase activity. In particularly, Prx1 modulates the microenvironment in liver injuries by reducing adhesion molecule expression in vascular endothelial cells and inhibiting the inflammatory response and adhesion of macrophages. Prxs have potent prosurvival effects against ROS in ischemic/reperfusion (I/R) injury, but Prxs released from necrotic cells increase secretion of inflammatory cytokines by macrophages through TLR2 and 4 activation, which promotes cell death. Prxs can be used as biomarkers to evaluate I/R injury and predict graft survival in liver transplantation. Prxs are modulated in various types of chronic hepatitis and hepatosteatosis, and mediate disease progression. Alcohol administration increases oxidization and inactivation of Prxs in mice because of oxidative stress. In conclusion, Prxs are essential mediators and biomarkers in inflammatory liver diseases and I/R injury.

Preventive effects of dietary walnuts on high-fat-induced hepatic fat accumulation, oxidative stress and apoptosis in mice

We hypothesized that dietary walnut would prevent high-fat-diet (HFD)-induced hepatic apoptosis based on its antioxidant properties. Male C57BL/6J mice were fed a rodent chow or HFD (45% energy-derived)±walnuts (21.5% energy-derived) for 6 weeks. Liver histological and biochemical analyses revealed significantly elevated fat accumulation in mice fed HFD compared to mice fed the chow or HFD±walnuts. Walnut supplementation prevented HFD-mediated alteration of the levels of key proteins in lipid homeostasis such as Sirt1, AMPK and FAS, leading to decreased fat accumulation. In addition, walnut supplementation to HFD significantly decreased the hepatic levels of cytochrome P450-2E1, nitrated proteins and lipid peroxidation. Furthermore, walnut supplementation decreased the activated cell-death-associated p-JNK and p-p38K accompanied with increased hepatocyte apoptosis in HFD group. The beneficial effects of dietary walnut likely result, at least partially, from its antioxidant ingredients and attenuating HFD-induced hepatic steatosis, nitroxidative stress and apoptosis.

"Ecstasy" toxicity to adolescent rats following an acute low binge dose

BACKGROUND

3,4-Methylenedioxymethamphetamine (MDMA or "ecstasy") is a worldwide drug of abuse commonly used by adolescents. Most reports focus on MDMA's neurotoxicity and use high doses in adult animals, meanwhile studies in adolescents are scarce. We aimed to assess in rats the acute MDMA toxicity to the brain and peripheral organs using a binge dose scheme that tries to simulate human adolescent abuse.

METHODS

Adolescent rats (postnatal day 40) received three 5 mg/kg doses of MDMA (estimated equivalent to two/three pills in a 50 kg adolescent), intraperitoneally, every 2 h, while controls received saline. After 24 h animal sacrifice took place and collection of brain areas (cerebellum, hippocampus, frontal cortex and striatum) and peripheral organs (liver, heart and kidneys) occurred.

RESULTS

Significant hyperthermia was observed after the second and third MDMA doses, with mean increases of 1 °C as it occurs in the human scenario. MDMA promoted ATP levels fall in the frontal cortex. No brain oxidative stress-related changes were observed after MDMA. MDMA-treated rat organs revealed significant histological tissue alterations including vascular congestion, but no signs of apoptosis or necrosis were found, which was corroborated by the lack of changes in plasma biomarkers and tissue caspases. In peripheral organs, MDMA did not affect significantly protein carbonylation, glutathione, or ATP levels, but liver presented a higher vulnerability as MDMA promoted an increase in quinoprotein levels.

CONCLUSIONS

Adolescent rats exposed to a moderate MDMA dose, presented hyperthermia and acute tissue damage to peripheral organs without signs of brain oxidative stress.

Mitochondrial dysfunction and cell death in neurodegenerative diseases through nitroxidative stress

Mitochondria are important for providing cellular energy ATP through the oxidative phosphorylation pathway. They are also critical in regulating many cellular functions including the fatty acid oxidation, the metabolism of glutamate and urea, the anti-oxidant defense, and the apoptosis pathway. Mitochondria are an important source of reactive oxygen species leaked from the electron transport chain while they are susceptible to oxidative damage, leading to mitochondrial dysfunction and tissue injury. In fact, impaired mitochondrial function is commonly observed in many types of neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, Huntington's disease, alcoholic dementia, brain ischemia-reperfusion related injury, and others, although many of these neurological disorders have unique etiological factors. Mitochondrial dysfunction under many pathological conditions is likely to be promoted by increased nitroxidative stress, which can stimulate post-translational modifications (PTMs) of mitochondrial proteins and/or oxidative damage to mitochondrial DNA and lipids. Furthermore, recent studies have demonstrated that various antioxidants, including naturally occurring flavonoids and polyphenols as well as synthetic compounds, can block the formation of reactive oxygen and/or nitrogen species, and thus ultimately prevent the PTMs of many proteins with improved disease conditions. Therefore, the present review is aimed to describe the recent research developments in the molecular mechanisms for mitochondrial dysfunction and tissue injury in neurodegenerative diseases and discuss translational research opportunities.

Functional roles of protein nitration in acute and chronic liver diseases

Nitric oxide, when combined with superoxide, produces peroxynitrite, which is known to be an important mediator for a number of diseases including various liver diseases. Peroxynitrite can modify tyrosine residue(s) of many proteins resulting in protein nitration, which may alter structure and function of each target protein. Various proteomics and immunological methods including mass spectrometry combined with both high pressure liquid chromatography and 2D PAGE have been employed to identify and characterize nitrated proteins from pathological tissue samples to determine their roles. However, these methods contain a few technical problems such as low efficiencies with the detection of a limited number of nitrated proteins and labor intensiveness. Therefore, a systematic approach to efficiently identify nitrated proteins and characterize their functional roles is likely to shed new insights into understanding of the mechanisms of hepatic disease pathophysiology and subsequent development of new therapeutics. The aims of this review are to briefly describe the mechanisms of hepatic diseases. In addition, we specifically describe a systematic approach to efficiently identify nitrated proteins to study their causal roles or functional consequences in promoting acute and chronic liver diseases including alcoholic and nonalcoholic fatty liver diseases. We finally discuss translational research applications by analyzing nitrated proteins in evaluating the efficacies of potentially beneficial agents to prevent or treat various diseases in the liver and other tissues.

A reconsideration and response to Parrott AC (2013) "Human psychobiology of MDMA or 'Ecstasy': an overview of 25 years of empirical research"

Parrott recently published a review of literature on MDMA/ecstasy. This commentary is a response to the content and tenor of his review, which mischaracterizes the literature through misstatement and omission of contrary findings, and fails to address the central controversies in the literature. The review makes several erroneous statements concerning MDMA-assisted psychotherapy, such as incorrect statements about research design and other statements that are baseless or contradicted by the literature. Though it critiques an attempt by other authors to characterize the risks of MDMA, the review fails to produce a competing model of risk assessment, and does not discuss potential benefits. Parrott does not represent an even-handed review of the literature, but instead recites dated misconceptions about neurotoxicity concerns involving the recreational drug ecstasy, which do not relate directly to the use of pure MDMA in a therapeutic setting. Unchallenged, Parrott's report may deter researchers from further investigating an innovative treatment that in early clinical trials has demonstrated lasting benefits for people with chronic, treatment-resistant post-traumatic stress disorder.

Pentoxifylline Protects the Rat Liver Against Fibrosis and Apoptosis Induced by Acute Administration of 3,4-Methylenedioxymethamphetamine (MDMA or Ecstasy)

OBJECTIVE(S)

3,4-Methylenedioxymethamphetamine (MDMA) is one of the most popular drugs of abuse in the world with hallucinogenic properties that has been shown to induce apoptosis in liver cells. The present study aimed to investigate the effects of pentoxifylline (PTX) on liver damage induced by acute administration of MDMA in Wistar rat.

MATERIALS AND METHODS

Animals were administered with saline or MDMA (7.5 mg/kg, IP) 3 times with 2 hr intervals. PTX (200 mg kg, IP), was administered simultaneously with last injection of MDMA in experimental group.

RESULTS

The concomitant administration of pentoxifylline and MDMA decreased liver injury including apoptosis, fibrosis and hepatocytes damages.

CONCLUSION

Our results showed for the first time that PTX treatment diminishes the extent of apoptosis and fibrosis caused by MDMA in rat liver.

An insight into the hepatocellular death induced by amphetamines, individually and in combination: the involvement of necrosis and apoptosis

The liver is a vulnerable target for amphetamine toxicity, but the mechanisms involved in the drug's hepatotoxicity remain poorly understood. The purpose of the current research was to characterize the mode of death elicited by four amphetamines and to evaluate whether their combination triggered similar mechanisms in immortalized human HepG2 cells. The obtained data revealed a time- and temperature-dependent mortality of HepG2 cells exposed to 3,4-methylenedioxymethamphetamine (MDMA, ecstasy; 1.3 mM), methamphetamine (3 mM), 4-methylthioamphetamine (0.5 mM) and D-amphetamine (1.7 mM), alone or combined (1.6 mM mixture). At physiological temperature (37 °C), 24-h exposures caused HepG2 death preferentially by apoptosis, while a rise to 40.5 °C favoured necrosis. ATP levels remained unaltered when the drugs where tested at normothermia, but incubation at 40.5 °C provoked marked ATP depletion for all treatments. Further investigations on the apoptotic mechanisms triggered by the drugs (alone or combined) showed a decline in BCL-2 and BCL- XL mRNA levels, with concurrent upregulation of BAX, BIM, PUMA and BID genes. Elevation of Bax, cleaved Bid, Puma, Bak and Bim protein levels was also seen. To the best of our knowledge, Puma, Bim and Bak have never been linked with the toxicity induced by amphetamines. Time-dependent caspase-3/-7 activation, but not mitochondrial membrane potential (∆ψm) disruption, also mediated amphetamine-induced apoptosis. The cell dismantling was confirmed by poly(ADP-ribose)polymerase proteolysis. Overall, for all evaluated parameters, no relevant differences were detected between individual amphetamines and the mixture (all tested at equieffective cytotoxic concentrations), suggesting that the mode of action of the amphetamines in combination does not deviate from the mode of action of the drugs individually, when eliciting HepG2 cell death.

Increased nitroxidative stress promotes mitochondrial dysfunction in alcoholic and nonalcoholic fatty liver disease

Increased nitroxidative stress causes mitochondrial dysfunctions through oxidative modifications of mitochondrial DNA, lipids, and proteins. Persistent mitochondrial dysfunction sensitizes the target cells/organs to other pathological risk factors and thus ultimately contributes to the development of more severe disease states in alcoholic and nonalcoholic fatty liver disease. The incidences of nonalcoholic fatty liver disease continuously increase due to high prevalence of metabolic syndrome including hyperlipidemia, hypercholesterolemia, obesity, insulin resistance, and diabetes. Many mitochondrial proteins including the enzymes involved in fat oxidation and energy supply could be oxidatively modified (including S-nitrosylation/nitration) under increased nitroxidative stress and thus inactivated, leading to increased fat accumulation and ATP depletion. To demonstrate the underlying mechanism(s) of mitochondrial dysfunction, we employed a redox proteomics approach using biotin-N-maleimide (biotin-NM) as a sensitive biotin-switch probe to identify oxidized Cys residues of mitochondrial proteins in the experimental models of alcoholic and acute liver disease. The aims of this paper are to briefly describe the mechanisms, functional consequences, and detection methods of mitochondrial dysfunction. We also describe advantages and limitations of the Cys-targeted redox proteomics method with alternative approaches. Finally, we discuss various applications of this method in studying oxidatively modified mitochondrial proteins in extrahepatic tissues or different subcellular organelles and translational research.

Evaluation of Bcl-2 Family Gene Expression in Hippocampus of 3, 4-methylenedioxymethamphetamine Treated Rats

OBJECTIVE

3,4-methylenedioxymethamphetamine (MDMA) is an illicit, recreational drug that causes cellular death and neurotoxicity. This study evaluates the effects of different doses of MDMA on the expression of apoptosis-related proteins and genes in the hippocampus of adult rats.

MATERIALS AND METHODS

In this expremental study,a total of 20 male Sprague Dawley rats (200-250 g ) were treated with MDMA (0, 5, 10, 20 mg/kg i.p. twice daily) for 7 days. Seven days after the last administration of MDMA, the rats were killed. Bax and Bcl-2 genes in addition to protein expressions were detected by western blot and reverse transcriptionpolymerase chain reaction (RT-PCR).Results were analyzed using one-way ANOVA and p≤0.05 was considered statistically significant.

RESULTS

Our results showed that MDMA caused dose dependent up-regulation of Bax and down-regulation of Bcl-2 in the hippocampus. There was a significant alteration in bcl-2 and bax genes density.

CONCLUSION

Changes in apoptosis-related proteins and respective genes relating to Bax and Bcl-2 might be involved in the molecular mechanism of MDMA-induced apoptosis.