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Published on: May 15, 2019
D,L-Methadone causes leukemic cell apoptosis via an OPRM1-triggered increase in IP3R-mediated ER Ca2+ release and
JungKwon Lee1,2, Jesusa L Rosales1, Hee-Guk Byun2
1Department of Cell Biology and Anatomy, Arnie Charbonneau Cancer, Alberta Children's Hospital Research Institutes, Cumming School of Medicine, University of Calgary, Calgary, AB, T2N 4N1, Canada.
Abstract:
The search continues for improved therapy for acute lymphoblastic leukemia (aLL), the most common malignancy in children. Recently, D,L-methadone was put forth as sensitizer for aLL chemotherapy. However, the specific target of D,L-methadone in leukemic cells and the mechanism by which it induces leukemic cell apoptosis remain to be defined. Here, we demonstrate that D,L-methadone induces leukemic cell apoptosis through activation of the mu1 subtype of opioid receptors (OPRM1). D,L-Methadone evokes IP3R-mediated ER Ca2+ release that is inhibited by OPRM1 loss. In addition, the rate of Ca2+ extrusion following D,L-methadone treatment is reduced, but is accelerated by loss of OPRM1. These D,L-methadone effects cause a lethal rise in [Ca2+]i that is again inhibited by OPRM1 loss, which then prevents D,L-methadone-induced apoptosis that is associated with activation of calpain-1, truncation of Bid, cytochrome C release, and proteolysis of caspase-3/12. Chelating intracellular Ca2+ with BAPTA-AM reverses D,L-methadone-induced apoptosis, establishing a link between the rise in [Ca2+]i and D,L-methadone-induced apoptosis. Altogether, our findings point to OPRM1 as a specific target of D,L-methadone in leukemic cells, and that OPRM1 activation by D,L-methadone disrupts IP3R-mediated ER Ca2+ release and rate of Ca2+ efflux, causing a rise in [Ca2+]i that upregulates the calpain-1-Bid-cytochrome C-caspase-3/12 apoptotic pathway.
Insights
D,L-methadone induces apoptosis in acute lymphoblastic leukemia (aLL) cells by activating mu1 opioid receptors (OPRM1). This mechanism involves calcium release and disruption of calcium extrusion, leading to cell death via the calpain-1 pathway.
Area of Science:
- Oncology
- Pharmacology
- Cell Biology
Background:
- Acute lymphoblastic leukemia (aLL) remains a significant pediatric malignancy requiring novel therapeutic strategies.
- D,L-methadone has emerged as a potential sensitizer for aLL chemotherapy, but its cellular targets and mechanisms of action are not fully understood.
Purpose of the Study:
- To elucidate the specific molecular target and mechanism by which D,L-methadone induces apoptosis in aLL cells.
- To investigate the role of opioid receptors and intracellular calcium signaling in D,L-methadone's anti-leukemic effects.
Main Methods:
- Investigated D,L-methadone's effects on aLL cell apoptosis.
- Utilized OPRM1 knockout models to assess receptor dependency.
- Monitored intracellular calcium ([Ca2+]i) dynamics, including ER Ca2+ release and Ca2+ extrusion.
- Analyzed key proteins in the apoptotic cascade (calpain-1, Bid, cytochrome C, caspase-3/12).
Main Results:
- D,L-methadone-induced apoptosis is mediated by the activation of the mu1 subtype of opioid receptors (OPRM1).
- D,L-methadone disrupts inositol trisphosphate receptor (IP3R)-mediated ER Ca2+ release and reduces Ca2+ extrusion rates.
- These calcium dysregulations lead to a lethal rise in intracellular calcium, activating the calpain-1/Bid/cytochrome C/caspase-3/12 apoptotic pathway.
Conclusions:
- OPRM1 is identified as a specific target of D,L-methadone in aLL cells.
- D,L-methadone's pro-apoptotic effects are dependent on OPRM1 activation and subsequent intracellular calcium overload.
- These findings provide a mechanistic basis for D,L-methadone as a potential sensitizer in aLL therapy.
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