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

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.

Methadone Potentiates the Cytotoxicity of Temozolomide by Impairing Calcium Homeostasis and Dysregulation of PARP in Glioblastoma Cells

Methadone is commonly used as an alternative to morphine in patients with pain associated with glioblastoma and other cancers. Although concomitant administration of methadone and cytostatics is relatively common, the effect of methadone on the efficacy of cytostatic drugs has not been well studied until recently. Moreover, the mechanism behind the effect of methadone on temozolomide efficacy has not been investigated in previous studies, or this effect has been automatically attributed to opioid receptors. Our findings indicate that methadone potentiates the effect of temozolomide on rat C6 glioblastoma cells and on human U251 and T98G glioblastoma cells and increases cell mortality by approximately 50% via a mechanism of action independent of opioid receptors. Our data suggest that methadone acts by affecting mitochondrial potential, the level of oxidative stress, intracellular Ca²⁺ concentration and possibly intracellular ATP levels. Significant effects were also observed on DNA integrity and on cleavage and expression of the DNA repair protein PARP-1. None of these effects were attributed to the activation of opioid receptors and Toll-like receptor 4. Our results provide an alternative perspective on the mechanism of action of methadone in combination with temozolomide and a potential strategy for the treatment of glioblastoma cell resistance to temozolomide.

Mapping the Evidence for Opioid-Mediated Changes in Malignancy and Chemotherapeutic Efficacy: Protocol for a Scoping Review

BACKGROUND

Numerous reports contend opioids can augment or inhibit malignancy. At present, there is no consensus on the risk or benefit posed by opioids on malignancy or chemotherapeutic activity. Distinguishing the consequences of opioid use from pain and its management is challenging. Additionally, opioid concentration data is often lacking in clinical studies. A scoping review approach inclusive of preclinical and clinical data will improve our understanding of the risk-benefit relationship concerning commonly prescribed opioids and cancer and cancer treatment.

OBJECTIVE

The aim of the study is to map diverse studies spanning from preclinical to clinical regarding opioids with malignancy and its treatment.

METHODS

This scoping review will use the Arksey six stages framework to (1) identify the research question; (2) identify relevant studies; (3) select studies meeting criteria; (4) extract and chart data; (5) collate, summarize, and report results; and (6) conduct expert consultation. An initial pilot study was undertaken to (1) parameterize the extent and scale of existing data for an evidence review, (2) identify key factors to be extracted in systematic charting efforts, and (3) assess opioid concentration as a variable for its relevance to the central hypothesis. Six databases will be searched with no filters: MEDLINE, Embase, CINAHL Complete, Cochrane Library, Biological Sciences Collection, and International Pharmaceutical Abstracts. Trial registries will include ClinicalTrials.gov, Cochrane CENTRAL, International Standard Randomised Controlled Trial Number Registry, European Union Clinical Trials Register, and World Health Organization International Clinical Trials Registry. Eligibility criteria will include preclinical and clinical study data on opioids effects on tumor growth or survival, or alteration on the antineoplastic activity of chemotherapeutics. We will chart data on (1) opioid concentration from human subjects with cancer, yielding a "physiologic range" to better interpret available preclinical data; (2) patterns of opioid exposure with disease and treatment-related patient outcomes; and (3) the influence of opioids on cancer cell survival, as well as opioid-related changes to cancer cell susceptibility for chemotherapeutics.

RESULTS

This scoping review will present results in narrative forms as well as with the use of tables and diagrams. Initiated in February 2021 at the University of Utah, this protocol is anticipated to generate a scoping review by August 2023. The results of the scoping review will be disseminated through scientific conference proceedings and presentations, stakeholder meetings, and by publication in a peer-reviewed journal.

CONCLUSIONS

The findings of this scoping review will provide a comprehensive description of the consequences of prescription opioids on malignancy and its treatment. By incorporating preclinical and clinical data, this scoping review will invite novel comparisons across study types that could inform new basic, translational, and clinical studies regarding risks and benefits of opioid use among patients with cancer.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

PRR1-10.2196/38167.

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.

Efficacy of D,L-methadone in the treatment of glioblastoma in vitro

AIM

Recently, D,L-methadone has been put forward as adjuvant treatment in glioblastoma (GBM).

METHODS

We analyzed the μ-opioid receptor expression in a set of GBM cell lines and investigated the efficacy of D,L-methadone alone and in combination with temozolomide (TMZ). Results & conclusion: Expression of the μ-opioid receptor was similar in the tested cell lines. High concentrations of D,L-methadone induced apoptosis in all cell lines and showed treatment interaction with TMZ. However, in lower dosages, reflecting clinically attainable concentrations, D,L-methadone alone showed no efficacy, and induced even higher proliferation in one specific cell line. Also, no interaction with TMZ was observed. These results suggest caution to the premature use of D,L-methadone in the treatment of GBM patients.

Pharmacoepigenomics of opiates and methadone maintenance treatment: current data and perspectives

Current treatments of opioid addiction include primarily maintenance medications such as methadone. Chronic exposure to opiate and/or long-lasting maintenance treatment induce modulations of gene expression in brain and peripheral tissues. There is increasing evidence that epigenetic modifications underlie these modulations. This review summarizes published results on opioid-induced epigenetic changes in animal models and in patients. The epigenetic modifications observed with other drugs of abuse often used by opiate abusers are also outlined. Specific methadone maintenance treatment induced epigenetic modifications at different treatment stages may be combined with the ones resulting from patients’ substance use history. Therefore, research comparing groups of addicts with similar history and substances use disorders but contrasting for well-characterized treatment phenotypes should be encouraged.

Modulating cancer cell survival by targeting intracellular cholesterol transport

Background:

Demand for cholesterol is high in certain cancers making them potentially sensitive to therapeutic strategies targeting cellular cholesterol homoeostasis. A potential approach involves disruption of intracellular cholesterol transport, which occurs in Niemann–Pick disease as a result of acid sphingomyelinase (ASM) deficiency. Hence, a class of lysosomotropic compounds that were identified as functional ASM inhibitors (FIASMAs) might exhibit chemotherapeutic activity by disrupting cancer cell cholesterol homoeostasis.

Methods:

Here, the chemotherapeutic utility of ASM inhibition was investigated. The effect of FIASMAs on intracellular cholesterol levels, cholesterol homoeostasis, cellular endocytosis and signalling cascades were investigated. The in vivo efficacy of ASM inhibition was demonstrated using melanoma xenografts and a nanoparticle formulation was developed to overcome dose-limiting CNS-associated side effects of certain FIASMAs.

Results:

Functional ASM inhibitors inhibited intracellular cholesterol transport leading to disruption of autophagic flux, cellular endocytosis and receptor tyrosine kinase signalling. Consequently, major oncogenic signalling cascades on which cancer cells were reliant for survival were inhibited. Two tested ASM inhibitors, perphenazine and fluphenazine that are also clinically used as antipsychotics, were effective in inhibiting xenografted tumour growth. Nanoliposomal encapsulation of the perphenazine enhanced its chemotherapeutic efficacy while decreasing CNS-associated side effects.

Conclusions:

This study suggests that disruption of intracellular cholesterol transport by targeting ASM could be utilised as a potential chemotherapeutic approach for treating cancer.

A possible biomarker for methadone related deaths

Methadone (MTH) concentrations in those dying of MTH toxicity totally overlap concentrations where the presence of MTH is only an incidental finding, making it very difficult to make distinctions in actual cases. A biomarker, be it anatomical or biochemical for MTH toxicity is badly needed, particularly if that markers were known to disrupt effective ventilation. Because the brainstem houses the regulatory centers for cardiorespiratory-control enters, it would seem to be the most likely anatomical site to seek abnormalities in cardiorespiratory control.

OBJECTIVE

To locate and describe the cells of nucleus of the solitary tract (TS)(NTS) in human brainstem and determine if neuronal cell death, either necrotic or apoptotic, within the TS of humans is more common in deaths due directly to MTH toxicity than with in the solitary tract itself.

DESIGN, SETTING, PARTICIPANTS

This was a single cohort study of MTH related decedents autopsied at a large university hospital. Each decedent had a recent history of non medical/illicit MTH use and had been pronounced dead in the field, prior to ever reaching the hospital. Complete autopsy and complete toxicology testing were performed on the formalin fixed brains of each individual. Multiple blocks were prepared of the area of interest, namely the tissue lying immediately between the inferior and the super colliculi. This volume, by definition, would have included the area of the Rostral Ventrolateral Medulla (RVLM), the location of the TS. Immunohistochemistry studies utilizing caspase-9 reaction (a protease enzyme involved in the process of preprogrammed death) were performed in order to estimate the degree and proportion of neuronal apoptosis, and also access the degree of classical necrosis within the NTS.

MAIN OUTCOMES AND MEASURES

The primary outcome measure was the presence or absence of neuronal apoptosis and/or necrosis within the NTS.

RESULTS

Cells displaying evidence of early apoptosis and advanced apoptosis, consisting primarily of nuclear fragmentation, admixed with other neurons displaying the features of classic necrosis were found. Evidence of classic necrosis was identifiable in most of the controls, though minor degrees of apoptosis were identifiable with Caspase staining and quantitative image analysis of immunohistochemical stains.

CONCLUSIONS

and Relevance: Our study shows that neurons, primarily along the TS, but occasionally in other cell nuclei (even controls) are vulnerable, both to direct MTH toxicity (via apoptosis) and indirectly (via hypoxia leading to classical cell necrosis). When MTH is found to be present in significant concentrations, but apoptotic lesions are absent, it would be reasonable to assume that MTH was not primarily the cause of cardiorespiratory arrest.

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.

Chronic opioid therapy in long-term cancer survivors

PURPOSE

Long-term cancer survivors develop special health issues and specific needs. Chronic pain, whether the consequence of their cancer or as a side effect of treatment, is one of their most prevalent concerns.

METHODS

We conducted a review of the English-language literature on long-term cancer survivorship and chronic opioid therapy, with the objective of determining the efficacy, safety and tolerability in this group of patients. Practical management recommendations are made on the basis of this review.

RESULTS

Pain syndromes encountered in the long-term cancer survivors are diverse. Opioid receptor pathways possess complex and pleiotropic functions and continuous over-activation may lead to de novo endocrinopathies, immunosuppression, neurocognitive impairment, or cell cycle disturbances with potential clinical connotations. However, there are insufficient data to support evidence-based decision making with respect to patient selection, doses, administration, monitoring and follow-up. Data about long-term treatment effectiveness and safety are limited and often aggravated by the overlapping of several diseases prevalent among long-term cancer survivors, as well as chronic opiate-induced toxicity.

CONCLUSIONS

Chronic opioid therapy is frequent in long-term cancer survivors, and may negatively affect the immune system, and produce health problems such as endocrinopathies, osteoporosis, neurological or cardiopulmonary effects, alterations of cell cycle kinetics, abuse and addiction. This review highlights the need for specialized teams to treat chronic pain in long-term cancer survivors from an integrative perspective.

Contribution of inorganic polyphosphate towards regulation of mitochondrial free calcium

BACKGROUND

Calcium signaling plays a key role in the regulation of multiple processes in mammalian mitochondria, from cellular bioenergetics to the induction of stress-induced cell death. While the total concentration of calcium inside the mitochondria can increase by several orders of magnitude, the concentration of bioavailable free calcium in mitochondria is maintained within the micromolar range by the mitochondrial calcium buffering system. This calcium buffering system involves the participation of inorganic phosphate. However, the mechanisms of its function are not yet understood. Specifically, it is not clear how calcium-orthophosphate interactions, which normally lead to formation of insoluble precipitates, are capable to dynamically regulate free calcium concentration. Here we test the hypothesis that inorganic polyphosphate, which is a polymerized form of orthophosphate, is capable to from soluble complexes with calcium, playing a significant role in the regulation of the mitochondrial free calcium concentration.

METHODS

We used confocal fluorescence microscopy to measure the relative levels of mitochondrial free calcium in cultured hepatoma cells (HepG2) with variable levels of inorganic polyphosphate (polyP).

RESULTS

The depletion of polyP leads to the significantly lower levels of mitochondrial free calcium concentration under conditions of pathological calcium overload. These results are coherent with previous observations showing that inorganic polyphosphate (polyP) can inhibit calcium-phosphate precipitation and, thus, increase the amount of free calcium.

CONCLUSIONS

Inorganic polyphosphate plays an important role in the regulation of mitochondrial free calcium, leading to its significant increase.

GENERAL SIGNIFICANCE

Inorganic polyphosphate is a previously unrecognized integral component of the mitochondrial calcium buffering system.

Caspase-activated DNase is necessary and sufficient for oligonucleosomal DNA breakdown, but not for chromatin disassembly during caspase-dependent apoptosis of LN-18 glioblastoma cells

Caspase-dependent apoptosis is a controlled type of cell death characterized by oligonucleosomal DNA breakdown and major nuclear morphological alterations. Other kinds of cell death do not share these highly distinctive traits because caspase-activated DNase (DFF40/CAD) remains inactive. Here, we report that human glioblastoma multiforme-derived LN-18 cells do not hydrolyze DNA into oligonucleosomal fragments after apoptotic insult. Furthermore, their chromatin remains packaged into a single mass, with no signs of nuclear fragmentation. However, ultrastructural analysis reveals that nuclear disassembly occurs, although compacted chromatin does not localize into apoptotic nuclear bodies. Caspases become properly activated, and ICAD, the inhibitor of DFF40/CAD, is correctly processed. Using cell-free in vitro assays, we show that chromatin from isolated nuclei of LN-18 cells is suitable for hydrolysis into oligonuclesomal fragments by staurosporine-pretreated SH-SY5Y cytoplasms. However, staurosporine-pretreated LN-18 cytoplasms do not induce DNA laddering in isolated nuclei from either LN-18 or SH-SY5Y cells because LN-18 cells express lower amounts of DFF40/CAD. DFF40/CAD overexpression makes LN-18 cells fully competent to degrade their DNA into oligonucleosome-sized fragments, and yet they remain unable to arrange their chromatin into nuclear clumps after apoptotic insult. Indeed, isolated nuclei from LN-18 cells were resistant to undergoing apoptotic nuclear morphology in vitro. The use of LN-18 cells has uncovered a previously unsuspected cellular model, whereby a caspase-dependent chromatin package is DFF40/CAD-independent, and DFF40/CAD-mediated double-strand DNA fragmentation does not warrant the distribution of the chromatin into apoptotic nuclear bodies. The studies highlight a not-yet reported DFF40/CAD-independent mechanism driving conformational nuclear changes during caspase-dependent cell death.

Chromatin collapse during caspase-dependent apoptotic cell death requires DNA fragmentation factor, 40-kDa subunit-/caspase-activated deoxyribonuclease-mediated 3'-OH single-strand DNA breaks

Apoptotic nuclear morphology and oligonucleosomal double-strand DNA fragments (also known as DNA ladder) are considered the hallmarks of apoptotic cell death. From a classic point of view, these two processes occur concomitantly. Once activated, DNA fragmentation factor, 40-kDa subunit (DFF40)/caspase-activated DNase (CAD) endonuclease hydrolyzes the DNA into oligonucleosomal-size pieces, facilitating the chromatin package. However, the dogma that the apoptotic nuclear morphology depends on DNA fragmentation has been questioned. Here, we use different cellular models, including MEF CAD(-/-) cells, to unravel the mechanism by which DFF40/CAD influences chromatin condensation and nuclear collapse during apoptosis. Upon apoptotic insult, SK-N-AS cells display caspase-dependent apoptotic nuclear alterations in the absence of internucleosomal DNA degradation. The overexpression of a wild-type form of DFF40/CAD endonuclease, but not of different catalytic-null mutants, restores the cellular ability to degrade the chromatin into oligonucleosomal-length fragments. We show that apoptotic nuclear collapse requires a 3'-OH endonucleolytic activity even though the internucleosomal DNA degradation is impaired. Moreover, alkaline unwinding electrophoresis and In Situ End-Labeling (ISEL)/In Situ Nick Translation (ISNT) assays reveal that the apoptotic DNA damage observed in the DNA ladder-deficient SK-N-AS cells is characterized by the presence of single-strand nicks/breaks. Apoptotic single-strand breaks can be impaired by DFF40/CAD knockdown, abrogating nuclear collapse and disassembly. In conclusion, the highest order of chromatin compaction observed in the later steps of caspase-dependent apoptosis relies on DFF40/CAD-mediated DNA damage by generating 3'-OH ends in single-strand rather than double-strand DNA nicks/breaks.

TPEN induces apoptosis independently of zinc chelator activity in a model of acute lymphoblastic leukemia and ex vivo acute leukemia cells through oxidative stress and mitochondria caspase-3- and AIF-dependent pathways

Acute lymphoblastic leukemia is still an incurable disease with resistance to therapy developing in the majority of patients. We investigated the effect of TPEN, an intracellular zinc chelator, in Jurkat and in ex vivo acute lymphoblastic leukemia (ALL) cells resistant to chemotherapy. Changes of nuclei morphology, reactive oxygen species generation, presence of hypodiploid cells, phosphatidylserine translocation, mitochondrial membrane depolarization, immunohistochemical identification of cell death signalling molecules, and pharmacological inhibition were assayed to detect the apoptotic cell death pathways. We found that TPEN induces apoptosis in both types of cells by a molecular oxidative stress pathway involving O(2)(•-) > H(2)O(2) >> NF-κB (JNK/c-Jun) >p53> loss ΔΨ(m)> caspase-3, AIF > chromatin condensation/DNA fragmentation. Interestingly, TPEN induced apoptosis independently of glucose; leukemic cells are therefore devoid of survival capacity by metabolic resistance to treatment. Most importantly, TPEN cytotoxic effect can eventually be regulated by the antioxidant N-acetyl-cysteine and zinc ions. Our data suggest that TPEN can be used as a potential therapeutic prooxidant agent against refractory leukemia. These data contribute to understanding the importance of oxidative stress in the treatment of ALL.

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.