Methadone induces necrotic-like cell death in SH-SY5Y cells by an impairment of mitochondrial ATP synthesis

Methadone Requires the Co-Activation of μ-Opioid and Toll-Like-4 Receptors to Produce Extracellular DNA Traps in Bone-Marrow-Derived Mast Cells

Methadone is an effective and long-lasting analgesic drug that is also used in medication-assisted treatment for people with opioid use disorders. Although there is evidence that methadone activates μ-opioid and Toll-like-4 receptors (TLR-4s), its effects on distinct immune cells, including mast cells (MCs), are not well characterized. MCs express μ-opioid and Toll-like receptors (TLRs) and constitute an important cell lineage involved in allergy and effective innate immunity responses. In the present study, murine bone-marrow-derived mast cells (BMMCs) were treated with methadone to evaluate cell viability by flow cytometry, cell morphology with immunofluorescence and scanning electron microscopy, reactive oxygen species (ROS) production, and intracellular calcium concentration ([Ca2+]i) increase. We found that exposure of BMMCs to 0.5 mM or 1 mM methadone rapidly induced cell death by forming extracellular DNA traps (ETosis). Methadone-induced cell death depended on ROS formation and [Ca2+]i. Using pharmacological approaches and TLR4-defective BMMC cultures, we found that µ-opioid receptors were necessary for both methadone-induced ROS production and intracellular calcium increase. Remarkably, TLR4 receptors were also involved in methadone-induced ROS production as it did not occur in BMMCs obtained from TLR4-deficient mice. Finally, confocal microscopy images showed a significant co-localization of μ-opioid and TLR4 receptors that increased after methadone treatment. Our results suggest that methadone produces MCETosis by a mechanism requiring a novel crosstalk pathway between μ-opioid and TLR4 receptors.

Effect of fentanyl and remifentanil on neuron damage and oxidative stress during induction neurotoxicity

Opioids can be used for medical and non-medical purposes. Chronic pain such as cancer, as well as the frequent use of such drugs in places such as operating rooms and intensive care units, and in non-medical areas like drug abuse the effects and side effects of these drugs need to be examined in more detail. For this purpose, the effects of fentanyl and remifentanil drugs on neuroinflammation, oxidative stress and cholinesterase metabolism were investigated. Neuron cells (CRL-10742) were used for the evaluation of the toxicity of fentanyl and remifentanil. MTT, PON1 activity and total thiol levels for its effect on oxidative stress, AChE and BChE activities for its effect on the cholinergic system, and TNF, IL-8 and IL-10 gene levels for its neuroinflammation effect were determined. The highest neurotoxic dose of fentanyl and remifentanil was determined as 10 μg/mL. It was observed that the rate of neuron cells in this dose has decreased by up to 61.80% and 56.89%, respectively. The IL-8 gene expression level in both opioids was down-regulated while IL 10 gene level was up-regulated in a dose-dependent manner compared to the control. In our results, the TNF gene expression level differs between the two opioids. In the fentanyl group, it was seen to be up-regulated in a dose-dependent manner compared to the control. Fentanyl and remifentanil showed an inhibitory effect against PON1, while remifentanil showed an increase in total thiol levels. PON1, BChE and total thiol activities showed similarity with MTT.

Chronic exposure to methadone induces activated microglia and astrocyte and cell death in the cerebellum of adult male rats

Methadone is a centrally-acting synthetic opioid analgesic widely used in the methadone maintenance therapy (MMT) programs throughout the world. Considering its neurotoxic effects particularly on the cerebellum, this study aims to address the behavioral and histological alterations in the cerebellar cortex associated with methadone administration. Twenty-four adult male albino rats were randomized into two groups of control and methadone treatment. Methadone was subcutaneously administered (2.5-10 mg/kg) once a day for two consecutive weeks. The functional and structural changes in the cerebellum were compared to the control group. Our data revealed that treating rats with methadone not only induced cerebellar atrophy, but also prompted the actuation of microgliosis, astrogliosis, and apoptotic biomarkers. We further demonstrated that treating rats with methadone increased complexity of astrocyte processes and decreased complexity of microglia processes. Our result showed that methadone impaired motor coordination and locomotor performance and neuromuscular activity. Additionally, relative gene expression of TNF-α, caspase-3 and RIPK3 increased significantly due to methadone. Our findings suggest that methadone administration has a neurodegenerative effect on the cerebellar cortex via dysregulation of microgliosis, astrogliosis, apoptosis, and neuro-inflammation.

Time to initiate randomized controlled clinical trials with methadone in cancer patients

Public media coverage has fueled a demand for methadone as potential cure for cancer itself. Because patients have asked for respective prescriptions, clinical societies issued statements warning against the use of methadone as long as preclinical findings have not been supported by clinical evidence. In fact, not all preclinical data clearly support relevant effects. However, strong epidemiologic data suggest beneficial effects of methadone on cancer. Alternative explanations, namely better safety of methadone or hidden selection bias, seem less likely. This uncertainty can only be resolved by randomized controlled clinical trials. This review discusses all relevant data pertinent to methadone and cancer, uncovers supportive epidemiologic data, and suggests possible study designs.

D,L-Methadone enhances the cytotoxic activity of standard chemotherapeutic agents on pediatric rhabdomyosarcoma

Purpose

In advanced tumor stages, pediatric rhabdomyosarcoma (RMS) shows an intrinsic resistance to standard chemotherapy, which is associated with a dismal prognosis. Alternative therapeutic approaches and optimization of already existent treatment protocols are urgently needed in these conditions. The µ-opioid receptor (OPRM1) agonist, D,L-methadone is frequently used for analgesia in oncological patients. Recent evidence has shown that D,L-methadone in combination with chemotherapeutic agents may enhance their cytotoxic effect against cancer cells. There are no related data in pediatric rhabdomyosarcoma (RMS).

Methods

Antitumor effects of combined D,L-methadone and doxorubicin, carboplatin, and vincristine on RMS cell lines RD and RH30 were analyzed using following outcome data: expression of the OPRM1 receptor (Western blot), cell growth inhibition (MTT assay), cell migration (wound-healing assay), apoptosis induction (caspase-3/7 assay), and reactive oxygen species (ROS) production (flow cytometry).

Results

In both cell lines, OPRM1 expression was significantly increased after combined treatment of D,L-methadone with all three cytotoxic drugs tested, which resulted in suppression of tumor cell growth and increase of apoptosis rates. These effects were mediated by increased ROS production and up-regulation of caspase-3/7 activity. Doxorubicin combined with D,L-methadone significantly reduced cell migration in both cell lines. Carboplatin or vincristine in combination with D,L-methadone had only an impact on cell migration in RH30 cells.

Conclusions

This new therapeutic approach in RMS provides strong antitumor effects in vitro. The combination of standard chemotherapy and D,L-methadone requires further investigation. Especially advanced tumors with a limited effectiveness of conventional treatment regimens seem a potential target of this approach.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00432-022-03945-y.

Mitochondrial Genotoxicity of Hepatitis C Treatment among People Who Inject Drugs

Antiviral nucleoside analogues (ANA) are newly used therapeutics acting against the hepatitis C virus (HCV). This class of drug is well known to exhibit toxicity on mitochondrial DNA (mtDNA). People who inject drugs (PWID) are particularly affected by HCV infection and cumulated mitotoxic drug exposure from HIV treatments (antiretrovirals, ARV) and other illicit drugs. This study aims to explore the impact of direct-acting antiviral (DAA) treatments on mtDNA among PWID. A total of 470 actively injecting heroin users were included. We used quantitative PCR on whole blood to determine the mitochondrial copy number per cell (MCN) and the proportion of mitochondrial DNA deletion (MDD). These parameters were assessed before and after DAA treatment. MDD was significantly increased after HCV treatment, while MCN did not differ. MDD was even greater when subjects were cotreated with ARV. In multivariate analysis, we identified that poly-exposure to DAA and daily heroin injection or regular consumption of methamphetamines were positively associated with high MCN loss while DAA and ARV treatments or methadone use were identified as risk factors for having mtDNA deletion. These observations deserve attention since they were previously associated with premature cell ageing or cell transformation and therefore call for a long-term follow-up.

Morphine dependence and withdrawal-induced changes in mouse Sertoli cell (TM4) line: Evaluation of apoptotic, inflammatory and oxidative stress biomarkers

Chronic morphine exerts deleterious effects on testicular function through either suppression of germ cells or somatic including Sertoli cells, probably through the activation of inflammatory, oxidative, and apoptosis biomarkers. Thus, the present study aimed to investigate whether the damaging effects of morphine dependence were reversed by the spontaneous morphine withdrawal or incubation with methadone and/or naloxone in Sertoli (TM4) cells using an in- vitro cell model of morphine dependence. Morphine dependence in TM4 cells was induced by increasing daily doses of morphine for 10 days and then maintained for two weeks in 5 μM. The cAMP levels were measured for an evaluation of morphine dependence. The cell viability and inflammatory, oxidative, apoptosis biomarkers, and glial cell-derived neurotrophic factor (GDNF) were measured after the end of treatment following the incubation of cells with methadone and naloxone and spontaneous withdrawal from morphine. We found that morphine dependence decreased cell viability, GDNF level and increased the levels of pro-oxidant, pro-inflammatory, and apoptotic biomarkers in TM4 cells, while spontaneous withdrawal from morphine and by naloxone decreased the levels of the biomarkers of pro-inflammatory and apoptotic in TM4 cells. Also, despite the low levels of pro-inflammatory factors following morphine withdrawal by methadone, it increased the cleaved/pro-caspase3 ratio in TM4 cells. This study showed that morphine dependence increased apoptosis probably via oxidative stress and inflammation pathways in TM4 cells. Also, it seems likely that spontaneous and naloxone withdrawal have beneficial consequences in the treatment of morphine dependence than methadone therapy, although they may require longer incubation periods.

The effects of morphine, methadone, and fentanyl on mitochondria: A live cell imaging study

The important role of mitochondria in maintaining normal brain cell function has been demonstrated in several neurodegenerative diseases where mitochondrial dysfunction is a prominent feature. Accumulating evidence indicates that opioids may induce neuronal cell death and inhibit neurogenesis, two factors that are dependent on normal mitochondrial function. The aim of the present study was to examine the effects of morphine, methadone, and fentanyl on MitoTracker-stained mitochondria. Cells from the neuroblastoma/glioma hybrid cell-line NG108-15 were seeded on 96-well cell culture plates and treated with MitoTracker for 30 min prior to opioid treatment. Morphine, methadone, and fentanyl were added at various concentrations and images of mitochondria were acquired every 30 min for four hours using a high-content imaging device. The parameters total mitochondrial area, mitochondrial network, as well as the number and mean area of mitochondrial objects were analyzed using automated image analysis. Methadone and fentanyl, but not morphine, decreased the mitochondrial network, the number of mitochondrial objects, and increased the mean area of mitochondrial objects. Both methadone and fentanyl altered mitochondrial morphology with no effects seen from morphine treatment. These data suggest that methadone and fentanyl impact mitochondrial morphology negatively, which may be associated with neuronal cell death.

Methadone-mediated sensitization of glioblastoma cells is drug and cell line dependent

PURPOSE

D,L-methadone (MET), an analgesic drug used for pain treatment and opiate addiction, has achieved attention from oncologists and social media as possible chemoensitizing agent in cancer therapy, notably brain cancer (glioblastoma multiforme, GBM). MET has been reported to enhance doxorubicin-induced cytotoxicity in GBM cells via activation of the µ-opioid receptor (MOR). Here, we extended this work and quantified the toxic effect of MET in comparison to other opioids alone and in combination with doxorubicin and the clinically more relevant alkylating drug temozolomide (TMZ), using a set of GBM cell lines and primary GBM cells.

METHODS

MOR expression in GBM cells was investigated by immunofluorescence and immunoblotting. Resistance to drugs alone and in combination with anticancer drugs was assessed by MTT assays. Concentration effect curves were fitted by nonlinear regression analysis and IC50 values were calculated. Apoptosis and necrosis rates were determined by annexin V/propidium iodide (PI)-flow cytometry.

RESULTS

MET alone was cytotoxic in all GBM cell lines and primary GBM cells at high micromolar concentrations (IC50 ~ 60-130 µM), observed both in the metabolic MTT assay and by quantifying apoptosis and necrosis, while morphine and oxycodone were not cytotoxic in this concentration range. Naloxone was not able to block MET-induced cytotoxicity, indicating that cell death-inducing effects of MET are not MOR-dependent. We recorded doxorubicin and TMZ concentration- response curves in combination with fixed MET concentrations. MET enhanced doxorubicin-induced cytotoxicity in only one cell line, and in primary cells it was observed only in a particular MET concentration range. In all assays, MET was not effective in sensitizing cells to TMZ. In two cell lines, MET even decreased the cell's sensitivity to TMZ.

CONCLUSION

MET was found to be cytotoxic in GBM cells in vitro only at high, clinically not relevant concentrations, where it was effective in inducing apoptosis and necrosis. Sensitizing effects were only observed in combination with doxorubicin, but not with TMZ, and are dependent on cell line and the applied drug concentration. Therefore, our findings do not support the use of MET in the treatment of GBM in combination with TMZ, as no sensitizing effect of MET was observed.

Repeated Administration of Clinically Relevant Doses of the Prescription Opioids Tramadol and Tapentadol Causes Lung, Cardiac, and Brain Toxicity in Wistar Rats

Tramadol and tapentadol, two structurally related synthetic opioid analgesics, are widely prescribed due to the enhanced therapeutic profiles resulting from the synergistic combination between μ-opioid receptor (MOR) activation and monoamine reuptake inhibition. However, the number of adverse reactions has been growing along with their increasing use and misuse. The potential toxicological mechanisms for these drugs are not completely understood, especially for tapentadol, owing to its shorter market history. Therefore, in the present study, we aimed to comparatively assess the putative lung, cardiac, and brain cortex toxicological damage elicited by the repeated exposure to therapeutic doses of both prescription opioids. To this purpose, male Wistar rats were intraperitoneally injected with single daily doses of 10, 25, and 50 mg/kg tramadol or tapentadol, corresponding to a standard analgesic dose, an intermediate dose, and the maximum recommended daily dose, respectively, for 14 consecutive days. Such treatment was found to lead mainly to lipid peroxidation and inflammation in lung and brain cortex tissues, as shown through augmented thiobarbituric acid reactive substances (TBARS), as well as to increased serum inflammation biomarkers, such as C reactive protein (CRP) and tumor necrosis factor-α (TNF-α). Cardiomyocyte integrity was also shown to be affected, since both opioids incremented serum lactate dehydrogenase (LDH) and α-hydroxybutyrate dehydrogenase (α-HBDH) activities, while tapentadol was associated with increased serum creatine kinase muscle brain (CK-MB) isoform activity. In turn, the analysis of metabolic parameters in brain cortex tissue revealed increased lactate concentration upon exposure to both drugs, as well as augmented LDH and creatine kinase (CK) activities following tapentadol treatment. In addition, pneumo- and cardiotoxicity biomarkers were quantified at the gene level, while neurotoxicity biomarkers were quantified both at the gene and protein levels; changes in their expression correlate with the oxidative stress, inflammatory, metabolic, and histopathological changes that were detected. Hematoxylin and eosin (H & E) staining revealed several histopathological alterations, including alveolar collapse and destruction in lung sections, inflammatory infiltrates, altered cardiomyocytes and loss of striation in heart sections, degenerated neurons, and accumulation of glial and microglial cells in brain cortex sections. In turn, Masson's trichrome staining confirmed fibrous tissue deposition in cardiac tissue. Taken as a whole, these results show that the repeated administration of both prescription opioids extends the dose range for which toxicological injury is observed to lower therapeutic doses. They also reinforce previous assumptions that tramadol and tapentadol are not devoid of toxicological risk even at clinical doses.

Multifunctional Opioid-Derived Hybrids in Neuropathic Pain: Preclinical Evidence, Ideas and Challenges

When the first- and second-line therapeutics used to treat neuropathic pain (NP) fail to induce efficient analgesia—which is estimated to relate to more than half of the patients—opioid drugs are prescribed. Still, the pathological changes following the nerve tissue injury, i.a. pronociceptive neuropeptide systems activation, oppose the analgesic effects of opiates, enforcing the use of relatively high therapeutic doses in order to obtain satisfying pain relief. In parallel, the repeated use of opioid agonists is associated with burdensome adverse effects due to compensatory mechanisms that arise thereafter. Rational design of hybrid drugs, in which opioid ligands are combined with other pharmacophores that block the antiopioid action of pronociceptive systems, delivers the opportunity to ameliorate the NP-oriented opioid treatment via addressing neuropathological mechanisms shared both by NP and repeated exposition to opioids. Therewith, the new dually acting drugs, tailored for the specificity of NP, can gain in efficacy under nerve injury conditions and have an improved safety profile as compared to selective opioid agonists. The current review presents the latest ideas on opioid-comprising hybrid drugs designed to treat painful neuropathy, with focus on their biological action, as well as limitations and challenges related to this therapeutic approach.

Assessing Cell Viability Effects of Opioids in Primary Cortical Cells from Rat

Although the number of studies that have examined the impact of opioids on cell viability is very limited, it has clearly shown that opioids commonly used in the clinic can both decrease neurogenesis and induce cell death. These negative effects induced by opioids are worrying and there is a need for further in-depth investigations addressing the impact of opioids on cell function and cell viability. A useful in vitro approach for studying the effects of opioids on cellular function and viability is using primary cortical cell cultures obtained from embryonic day 17 (E17) rat embryos. These cell cultures contain both neurons and glial cells that provide a more physiologically relevant culture condition when compared to the use of various commercially available cell lines. The primary cortical cells can be cultivated in 96-well plates, treated with various concentrations of opioids, and cell viability functions such as mitochondrial function and membrane integrity can easily be assessed using specific colorimetric assays.

Impact of Opioid Use in Hematological Malignancies: Clinical, Immunological and Concomitant Aspects

Opioid agents play a unique role in pain and symptom management for cancer patients. Research shows that opiate use, especially when associated with underlying cancer, has significant effects on hematological parameters. These changes may lead to greater risk for immunosuppression, tumor growth and progression of metastatic processes. The aim of this review is to explore the effects of opiates on various metabolic and biological processes, as well as the hematopoietic system, especially in cancer patients. Our findings demonstrate that the tumor-promoting effects of opiates remain contradictory, as both growth-promoting and anti-tumor effects have been observed. However, available data suggest that opiates can facilitate the proliferation and migration of tumor cells, and understanding of this process on cancer treatment is tremendously important.

Suppressor capacity of copper nanoparticles biosynthesized using Crocus sativus L. leaf aqueous extract on methadone-induced cell death in adrenal phaeochromocytoma (PC12) cell line

In this research, we prepared and formulated a neuroprotective supplement (copper nanoparticles in aqueous medium utilizing Crocus sativus L. Leaf aqueous extract) for determining its potential against methadone-induced cell death in PC12. The results of chemical characterization tests i.e., FE-SEM, FT-IR, XRD, EDX, TEM, and UV–Vis spectroscopy revealed that the study showed that copper nanoparticles were synthesized in the perfect way possible. In the TEM and FE-SEM images, the copper nanoparticles were in the mean size of 27.5 nm with the spherical shape. In the biological part of the present research, the Rat inflammatory cytokine assay kit was used to measure the concentrations of inflammatory cytokines. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) test was used to show DNA fragmentation and apoptosis. Caspase-3 activity was assessed by the caspase activity colorimetric assay kit and mitochondrial membrane potential was studied by Rhodamine123 fluorescence dye. Also, the cell viability of PC12 was measured by trypan blue assay. Copper nanoparticles-treated cell cutlers significantly (p ≤ 0.01) decreased the inflammatory cytokines concentrations, caspase-3 activity, and DNA fragmentation and they raised the cell viability and mitochondrial membrane potential in the high concentration of methadone-treated PC12 cells. The best result of neuroprotective properties was seen in the high dose of copper nanoparticles i.e., 4 µg. According to the above results, copper nanoparticles containing C. sativus leaf aqueous extract can be used in peripheral nervous system treatment as a neuroprotective promoter and central nervous system after approving in the clinical trial studies in humans.

Against Repurposing Methadone for Glioblastoma Therapy

Methadone, which is used as maintenance medication for outpatient treatment of opioid dependence or as an analgesic drug, has been suggested by preclinical in vitro and mouse studies to induce cell death and sensitivity to chemo- or radiotherapy in leukemia, glioblastoma, and carcinoma cells. These data together with episodical public reports on long-term surviving cancer patients who use methadone led to a hype of methadone as an anti-cancer drug in social and public media. However, clinical evidence for a tumoricidal effect of methadone is missing and prospective clinical trials, except in colorectal cancer, are not envisaged because of the limited preclinical data available. The present article reviews the pharmacokinetics, potential molecular targets, as well as the evidence for a tumoricidal effect of methadone in view of the therapeutically achievable doses in the brain. Moreover, it provides original in vitro data showing that methadone at clinically relevant concentrations fails to impair clonogenicity or radioresistance of glioblastoma cells.

The Protective and Restorative Effects of Growth Hormone and Insulin-Like Growth Factor-1 on Methadone-Induced Toxicity In Vitro

Evidence to date suggests that opioids such as methadone may be associated with cognitive impairment. Growth hormone (GH) and insulin-like growth factor-1 (IGF-1) are suggested to be neuroprotective and procognitive in the brain and may therefore counteract these effects. This study aims to explore the protective and restorative effects of GH and IGF-1 in methadone-treated cell cultures. Primary cortical cell cultures were harvested from rat fetuses and grown for seven days in vitro. To examine the protective effects, methadone was co-treated with or without GH or IGF-1 for three consecutive days. To examine the restorative effects, methadone was added for the first 24 h, washed, and later treated with GH or IGF-1 for 48 h. At the end of each experiment, mitochondrial function and membrane integrity were evaluated. The results revealed that GH had protective effects in the membrane integrity assay and that both GH and IGF-1 effectively recovered mitochondrial function and membrane integrity in cells pretreated with methadone. The overall conclusion of the present study is that GH, but not IGF-1, protects primary cortical cells against methadone-induced toxicity, and that both GH and IGF-1 have a restorative effect on cells pretreated with methadone.

Methadone for Pain Management in Children with Cancer

Methadone is a synthetic opioid with unique pharmacodynamic and pharmacokinetic properties. It is effective in treating both nociceptive and neuropathic pain, which commonly co-exist in children with cancer. Upon reviewing the literature describing the use of methadone in pediatric oncology patients, publications are limited in number and low in quality of evidence; nevertheless, there is support for the safety and efficacy of methadone in treating pain in children with cancer, particularly when pain is refractory to conventional treatment. Although the risk of life-threatening arrhythmia is commonly cited as an argument against the use of methadone, our review of the literature did not support this finding in children. Further evaluation with prospective studies is warranted to develop evidence-based recommendations for the use of methadone in pediatric oncology.

Delay-Dependent Impairments in Memory and Motor Functions After Acute Methadone Overdose in Rats

Methadone is used as a substitution drug for the treatment of opioid dependence and chronic pain. Despite its widespread use and availability, there is a serious concern with respect to the relative safety of methadone. The purpose of this study was to characterize how acute methadone overdose affects the cognitive and motor performance of naïve healthy rats. The methadone overdose was induced by administering an acute toxic dose of methadone (15 mg/kg; ip; the equivalent dose of 80% of LD50) to adolescent rats. Resuscitation using a ventilator pump along with a single dose of naloxone (2 mg/kg; ip) was administered following the occurrence of apnea. The animals which were successfully resuscitated divided randomly into three apnea groups that evaluated either on day 1, 5, or 10 post-resuscitation (M/N-Day 1, M/N-Day 5, and M/N-Day 10 groups) in the Y-maze and novel object memory recognition tasks as well as pole and rotarod tests. The data revealed that a single toxic dose of methadone had an adverse effect on spontaneous behavior. In addition, Recognition memory impairment was observed in the M/N-Day 1, 5, and 10 groups after methadone-induced apnea. Further, descending time in the M/N-Day 5 group increased significantly in comparison with its respective Saline control group. The overall results indicate that acute methadone-overdose-induced apnea produced delay-dependent cognitive and motor impairment. We suggest that methadone poisoning should be considered as a possible cause of delayed neurological disorders, which might be transient, in some types of memory or motor performance in naïve healthy rats.

Mitochondrial impairments contribute to spatial learning and memory dysfunction induced by chronic tramadol administration in rat: Protective effect of physical exercise

Despite the worldwide use of tramadol, few studies have been conducted about its effects on memory and mitochondrial function, and controversial results have been reported. Recently, there has been an increasing interest in physical exercise as a protective approach to neuronal and cognitive impairments. Therefore, the aim of this study was to investigate the effects of physical exercise on spatial learning and memory and brain mitochondrial function in tramadol-treated rats. After completion of 2-week (short-term) and 4-week (long-term) treadmill exercise regimens, male Wistar rats received tramadol (20, 40, 80mg/kg/day) intraperitoneally for 30days. Then spatial learning and memory was assessed by Morris water maze test (MWM). Moreover, brain mitochondrial function was evaluated by determination of mitochondrial reactive oxygen species (ROS) level, mitochondrial membrane potential (MMP), mitochondrial swelling and cytochrome c release from mitochondria. Chronic administration of tramadol impaired spatial learning and memory as well as brain mitochondrial function as indicated by increased ROS level, MMP collapse, increased mitochondrial swelling and cytochrome c release from mitochondria. Conversely, treadmill exercise significantly attenuated the impairments of spatial learning and memory and brain mitochondrial dysfunction induced by tramadol. The results revealed that chronic tramadol treatment caused memory impairments through induction of brain mitochondrial dysfunction. Furthermore, pre-exposure to physical exercise markedly mitigated these impairments through its positive effects on brain mitochondrial function.

The Effects of Fentanyl on Hepatic Mitochondrial Function

BACKGROUND

Remifentanil interferes with hepatic mitochondrial function. The aim of the present study was to evaluate whether hepatic mitochondrial function is affected by fentanyl, a more widely used opioid than remifentanil.

METHODS

Human hepatoma HepG2 cells were exposed to fentanyl or pretreated with naloxone (an opioid receptor antagonist) or 5-hydroxydecanoate (5-HD, an inhibitor of mitochondrial adenosine triphosphate (ATP)-sensitive potassium [mitoKATP] channels), followed by incubation with fentanyl. Mitochondrial function and metabolism were then analyzed.

RESULTS

Fentanyl marginally reduced maximal mitochondrial complex-specific respiration rates using exogenous substrates (decrease in medians: 11%-18%; P = 0.003-0.001) but did not affect basal cellular respiration rates (P = 0.834). The effect on stimulated respiration was prevented by preincubation with naloxone or 5-HD. Fentanyl reduced cellular ATP content in a dose-dependent manner (P < 0.001), an effect that was not significantly prevented by 5-HD and not explained by increased total ATPase concentration. However, in vitro ATPase activity of recombinant human permeability glycoprotein (an ATP-dependent drug efflux transporter) was significantly stimulated by fentanyl (P = 0.004).

CONCLUSIONS

Our data suggest that fentanyl reduces stimulated mitochondrial respiration of cultured human hepatocytes by a mechanism that is blocked by a mitoKATP channel antagonist. Increased energy requirements for fentanyl efflux transport may offer an explanation for the substantial decrease in cellular ATP concentration.

Methadone enhances human influenza A virus replication

Growing evidence has indicated that opioids enhance replication of human immunodeficiency virus and hepatitis C virus in target cells. However, it is unknown whether opioids can enhance replication of other clinically important viral pathogens. In this study, the interaction of opioid agonists and human influenza A/WSN/33 (H1N1) virus was examined in human lung epithelial A549 cells. Cells were exposed to morphine, methadone or buprenorphine followed by human H1N1 viral infection. Exposure to methadone differentially enhanced viral propagation, consistent with an increase in virus adsorption, susceptibility to virus infection and viral protein synthesis. In contrast, morphine or buprenorphine did not alter H1N1 replication. Because A549 cells do not express opioid receptors, methadone-enhanced H1N1 replication in human lung cells may not be mediated through these receptors. The interaction of methadone and H1N1 virus was also examined in adult mice. Treatment with methadone significantly increased H1N1 viral replication in lungs. Our data suggest that use of methadone facilitates influenza A viral infection in lungs and might raise concerns regarding the possible consequence of an increased risk of serious influenza A virus infection in people who receive treatment in methadone maintenance programs.

Overall Survival among Cancer Patients Undergoing Opioid Rotation to Methadone Compared to Other Opioids

BACKGROUND

Methadone has been associated with lower overall survival (OS) in patients with chronic pain. There are no data available on the association of methadone with OS in cancer patients.

OBJECTIVE

Our aim was to compare the OS in cancer outpatients undergoing opioid rotation (OR) to methadone and other strong opioids.

DESIGN

Demographics, symptoms, and morphine equivalent daily dose (MEDD) were collected in patients who underwent OR from strong opioids to either methadone or other strong opioids and returned for a follow-up within six weeks.

SETTING/SUBJECTS

Nine hundred thirty-eight consecutive outpatients to the supportive care center of a tertiary cancer center were reviewed.

MEASUREMENTS

Kaplan-Meier curves were used to evaluate survival.

RESULTS

Of a total of 164 eligible patients, 54/76 patients who underwent OR to methadone and 48/88 patients who underwent OR to other opioids returned for a follow-up visit. The median age was 56 years, 54% were male, and 87% had advanced cancer. There were no significant differences between the two groups in patient characteristics, performance status, MEDD, and pain scores. The Kaplan-Meier curves revealed no significant difference in median OS between all patients undergoing OR to methadone and other opioids [3.75 months (95% confidence interval, CI, 2.30-6.46) vs. 2.62 months (95% CI 1.74-4.33); p = 0.35] and also among those who returned for a follow-up following an OR to methadone and other opioids [5.15 months (95% CI 3.64-7.41) vs. 5.90 months (95% CI 2.62-9.28); p = 0.89].

CONCLUSIONS

We observed no significant difference in OS in cancer patients in methadone group compared to other opioids.

Growth hormone is protective against acute methadone-induced toxicity by modulating the NMDA receptor complex

Human growth hormone (GH) displays promising protective effects in the central nervous system after damage caused by various insults. Current evidence suggests that these effects may involve N-methyl-d-aspartate (NMDA) receptor function, a receptor that also is believed to play a role in opioid-induced neurotoxicity. The aims of the present study were to examine the acute toxic effects of methadone, an opioid receptor agonist and NMDA receptor antagonist, as well as to evaluate the protective properties of recombinant human GH (rhGH) on methadone-induced toxicity. Primary cortical cell cultures from embryonic day 17 rats were grown for 7days in vitro. Cells were treated with methadone for 24h and the 50% lethal dose was calculated and later used for protection studies with rhGH. Cellular toxicity was determined by measuring mitochondrial activity, lactate dehydrogenase release, and caspase activation. Furthermore, the mRNA expression levels of NMDA receptor subunits were investigated following methadone and rhGH treatment using quantitative PCR (qPCR) analysis. A significant protective effect was observed with rhGH treatment on methadone-induced mitochondrial dysfunction and in methadone-induced LDH release. Furthermore, methadone significantly increased caspase-3 and -7 activation but rhGH was unable to inhibit this effect. The mRNA expression of the NMDA receptor subunit GluN1, GluN2a, and GluN2b increased following methadone treatment, as assessed by qPCR, and rhGH treatment effectively normalized this expression to control levels. We have demonstrated that rhGH can rescue cells from methadone-induced toxicity by maintaining mitochondrial function, cellular integrity, and NMDA receptor complex expression.

Comparative study of the neurotoxicological effects of tramadol and tapentadol in SH-SY5Y cells

Opioid therapy and abuse are increasing, justifying the need to study their toxicity and underlying mechanisms. Given opioid pharmacodynamics at the central nervous system, the analysis of toxic effects in neuronal models gains particular relevance. The aim of this study was to compare the toxicological effects of acute exposure to tramadol and tapentadol in the undifferentiated human SH-SY5Y neuroblastoma cell line. Upon exposure to tramadol and tapentadol concentrations up to 600μM, cell toxicity was assessed through evaluation of oxidative stress, mitochondrial and metabolic alterations, as well as cell viability and death mechanisms through necrosis or apoptosis, and related signalling. Tapentadol was observed to trigger much more prominent toxic effects than tramadol, ultimately leading to energy deficit and cell death. Cell death was shown to predominantly occur through necrosis, with no alterations in membrane potential or in cytochrome c release. Both drugs were shown to stimulate glucose uptake and to cause ATP depletion, due to changes in the expression of energy metabolism enzymes. The toxicity mechanisms in such a neuronal model are relevant to understand adverse reactions to these opioids and to contribute to dose adjustment in order to avoid neurological damage.

Expression patterns of antioxidant genes in human SH-SY5Y cells after treatment with methadone

The expression levels of nine antioxidant genes in SH-SY5Y cells exposed to methadone (final concentrations 1-20µM) were investigated. Based on this study the genes could be categorized on three different groups. The number of down-regulated genes were increased as a function of exposure time (P=0.004). The methadone associated mRNA alterations were modulated by N-acetyl-cysteine. These findings suggested that different pathways for regulation of antioxidant genes could be active after exposing of SH-SY5Y cells to methadone; and also suggested that methadone might act by inducing the reactive oxygen species.

On the mechanism underlying ethanol-induced mitochondrial dynamic disruption and autophagy response

We have explored the mechanisms underlying ethanol-induced mitochondrial dynamics disruption and mitophagy. Ethanol increases mitochondrial fission in a concentration-dependent manner through Drp1 mitochondrial translocation and OPA1 proteolytic cleavage. ARPE-19 (a human retinal pigment epithelial cell line) cells challenged with ethanol showed mitochondrial potential disruptions mediated by alterations in mitochondrial complex IV protein level and increases in mitochondrial reactive oxygen species production. In addition, ethanol activated the canonical autophagic pathway, as denoted by autophagosome formation and autophagy regulator elements including Beclin1, ATG5-ATG12 and P-S6 kinase. Likewise, autophagy inhibition dramatically increased mitochondrial fission and cell death, whereas autophagy stimulation rendered the opposite results, placing autophagy as a cytoprotective response aimed to remove damaged mitochondria. Interestingly, although ethanol induced mitochondrial Bax translocation, this episode was associated to cell death rather than mitochondrial fission or autophagy responses. Thus, Bax required 600 mM ethanol to migrate to mitochondria, a concentration that resulted in cell death. Furthermore, mouse embryonic fibroblasts lacking this protein respond to ethanol by undergoing mitochondrial fission and autophagy but not cytotoxicity. Finally, by using the specific mitochondrial-targeted scavenger MitoQ, we revealed mitochondria as the main source of reactive oxygen species that trigger autophagy activation. These findings suggest that cells respond to ethanol activating mitochondrial fission machinery by Drp1 and OPA1 rather than bax, in a manner that stimulates cytoprotective autophagy through mitochondrial ROS.

Long-term methadone intake and genotoxicity in addicted patients

Background:

It is well known that contact with some physical, chemical or biological compounds can increase the incidence of mutation. Among these compounds, are pharmaceuticals that meet long duration of use and potentially could be misused and taken more than the ordered dosage.

Objectives:

The aim of this study was to evaluate mutagenic effect of methadone in addicted patients referred to Imam Khomeini Hospital in Ahvaz by single cell gel electrophoresis technic or comet assay.

Patients and Methods:

In this study, 90 subjects were divided into dichromate treated group, no treated healthy volunteers group and test group. Each group included 30 subjects. Screening was performed according to questionnaire and qualified subjects were entered the study. Blood samples were collected and lymphocytes were isolated, mixed with low melting point agarose for slide preparation according to standard method. Slides were analyzed using fluorescence microscope and comet patterns were assessed.

Results:

The mutagenicity index in addicted group was robustly higher than healthy volunteers. Fortunately, this significant difference was lower than positive control.

Conclusions:

Genome instability in addicted patients was demonstrated in this study. Controversially, considering incoherent results of previous studies and our data, more studies in longer duration of methadone use are needed to elucidate the consequence.

The role of anesthetic drugs in liver apoptosis

CONTEXT

The modern practice of anesthesia is highly dependent ona group of anesthetic drugs which many of them are metabolized in the liver.

EVIDENCE ACQUISITION

The liver, of course, usually tolerates this burden. However, this is not always an unbroken rule. Anesthetic induced apoptosis has gained great concern during the last years; especially considering the neurologic system.

RESULTS

However, we have evidence that there is some concern regarding their effects on the liver cells. Fortunately not all the anesthetics are blamed and even some could be used safely, based on the available evidence.

CONCLUSIONS

Besides, there are some novel agents, yet under research, which could affect the future of anesthetic agents' fate regarding their hepatic effects.

3-Nitropropionic acid induces autophagy by forming mitochondrial permeability transition pores rather than activating the mitochondrial fission pathway

BACKGROUND AND PURPOSE

Huntington's disease is a neurodegenerative process associated with mitochondrial alterations. Inhibitors of the electron-transport channel complex II, such as 3-nitropropionic acid (3NP), are used to study the molecular and cellular pathways involved in this disease. We studied the effect of 3NP on mitochondrial morphology and its involvement in macrophagy.

EXPERIMENTAL APPROACH

Pharmacological and biochemical methods were used to characterize the effects of 3NP on autophagy and mitochondrial morphology. SH-SY5Y cells were transfected with GFP-LC3, GFP-Drp1 or GFP-Bax to ascertain their role and intracellular localization after 3NP treatment using confocal microscopy.

KEY RESULTS

Untreated SH-SY5Y cells presented a long, tubular and filamentous net of mitochondria. After 3NP (5 mM) treatment, mitochondria became shorter and rounder. 3NP induced formation of mitochondrial permeability transition pores, both in cell cultures and in isolated liver mitochondria, and this process was inhibited by cyclosporin A. Participation of the mitochondrial fission pathway was excluded because 3NP did not induce translocation of the dynamin-related protein 1 (Drp1) to the mitochondria. The Drp1 inhibitor Mdivi-1 did not affect the observed changes in mitochondrial morphology. Finally, scavengers of reactive oxygen species failed to prevent mitochondrial alterations, while cyclosporin A, but not Mdivi-1, prevented the generation of ROS.

CONCLUSIONS AND IMPLICATIONS

There was a direct correlation between formation of mitochondrial permeability transition pores and autophagy induced by 3NP treatment. Activation of autophagy preceded the apoptotic process and was mediated, at least partly, by formation of reactive oxygen species and mitochondrial permeability transition pores.

Pharmacological Characterization of the Mechanisms Involved in Delayed Calcium Deregulation in SH-SY5Y Cells Challenged with Methadone

Previously, we have shown that SH-SY5Y cells exposed to high concentrations of methadone died due to a necrotic-like cell death mechanism related to delayed calcium deregulation (DCD). In this study, we show that, in terms of their Ca²⁺ responses to 0.5 mM methadone, SH-SY5Y cells can be pooled into four different groups. In a broad pharmacological survey, the relevance of different Ca²⁺-related mechanisms on methadone-induced DCD was investigated including extracellular calcium, L-type Ca²⁺ channels, μ-opioid receptor, mitochondrial inner membrane potential, mitochondrial ATP synthesis, mitochondrial Ca²⁺/2Na⁺-exchanger, reactive oxygen species, and mitochondrial permeability transition. Only those compounds targeting mitochondria such as oligomycin, FCCP, CGP 37157, and cyclosporine A were able to amend methadone-induced Ca²⁺ dyshomeostasis suggesting that methadone induces DCD by modulating the ability of mitochondria to handle Ca²⁺. Consistently, mitochondria became dramatically shorter and rounder in the presence of methadone. Furthermore, analysis of oxygen uptake by isolated rat liver mitochondria suggested that methadone affected mitochondrial Ca²⁺ uptake in a respiratory substrate-dependent way. We conclude that methadone causes failure of intracellular Ca²⁺ homeostasis, and this effect is associated with morphological and functional changes of mitochondria. Likely, this mechanism contributes to degenerative side effects associated with methadone treatment.

Minocycline exerts uncoupling and inhibiting effects on mitochondrial respiration through adenine nucleotide translocase inhibition

The present study was aimed to provide a better understanding of the mitochondria-targeted actions of minocycline (MC), a second-generation tetracycline which has cytoprotective effects. Although the specific mechanisms underlying its activity remained elusive, considerable amounts of data indicated mitochondria as the primary pharmacological target of MC. Previous reports have shown that MC affects the oxygen-uptake rate by isolated mitochondria in different respiratory states. Here, we report on the effect of MC, in the range 50-200μM, on mitochondrial respiration. State 3 respiration titration with carboxyatractyloside revealed that MC inhibits the adenine nucleotide translocase. Furthermore, we analyze MC channel-forming capacity in the lipid membrane bilayer. Our results confirmed the crucial role of Δψ and showed a dependence on Ca(2+) for MC to have an effect on mitochondria. Our data also indicated that outer and inner mitochondrial membranes contribute differently to this effect, involving the presence of Δψ (the inner membrane) and VDAC (the outer membrane). Data from three isosmotic media indicate that MC does not increase the permeability of the inner membrane to protons or potassium. In addition, by using mitoplasts and ruthenium red, we showed that Ca(2+) uptake is not involved in the MC effect, suggesting involvement of VDAC in the MC interaction with the outer membrane. Our data contribute to unravel the mechanisms behind the mitochondria-targeted activity of the cytoprotective drug MC.

Methadone induces CAD degradation and AIF-mediated necrotic-like cell death in neuroblastoma cells

Methadone (d,l-methadone hydrochloride) is a full-opioid agonist, originally developed as a substitution for heroin or other opiates abusers. Nowadays methadone is also being applied as long-lasting analgesics in cancer, and it is proposed as a promising agent for leukemia therapy. Previously, we have demonstrated that high concentrations of methadone (0.5mM) induced necrotic-like cell death in SH-SY5Y cells. The pathway involved is caspase-independent but involves impairment of mitochondrial ATP synthesis and mitochondrial cytochrome c release. However, the downstream mitochondrial pathways remained unclear. Here, we studied the participation of apoptosis inducing factor (AIF) in methadone-induced cell death. Methadone resulted in a translocation of AIF from mitochondria to the nucleus. Translocation was inhibited by cyclosporine A, but not by lack of Bax protein. Therefore the effect seems mediated by the formation of the mitochondrial transition pore, but is apparently independent of Bax. Furthermore, methadone-treated SH-SY5Y nuclei show characteristics that are typical for stage I nuclear condensation. Methadone did not induce degradation of DNA into oligonucleosomal fragments or into high molecular weight DNA fragments. Absence of DNA fragmentation coincided with a considerable decrease in the levels of the caspase-actived endonuclase DNase and its chaperone-inhibitor ICAD. In conclusion, our results provide mechanistic insights into the molecular mechanisms that underlie methadone-induced cell death. This knowledge may prove useful to develop novel strategies to prevent toxic side-effects of methadone thereby sustaining its use as therapeutical agent against tumors.