Halcrow PW, Kumar N, Hao E, Khan N, Meucci O, Geiger JD. Mu opioid receptor-mediated release of endolysosome iron increases levels of mitochondrial iron, reactive oxygen species, and cell death.
NEUROIMMUNE PHARMACOLOGY AND THERAPEUTICS 2023;
2:19-35. [PMID:
37027339 PMCID:
PMC10070011 DOI:
10.1515/nipt-2022-0013]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Accepted: 09/01/2022] [Indexed: 11/15/2022]
Abstract
Objectives
Opioids including morphine and DAMGO activate mu-opioid receptors (MOR), increase intracellular reactive oxygen species (ROS) levels, and induce cell death. Ferrous iron (Fe2+) through Fenton-like chemistry increases ROS levels and endolysosomes are "master regulators of iron metabolism" and contain readily-releasable Fe2+ stores. However, mechanisms underlying opioid-induced changes in endolysosome iron homeostasis and downstream-signaling events remain unclear.
Methods
We used SH-SY5Y neuroblastoma cells, flow cytometry, and confocal microscopy to measure Fe2+ and ROS levels and cell death.
Results
Morphine and DAMGO de-acidified endolysosomes, decreased endolysosome Fe2+ levels, increased cytosol and mitochondria Fe2+ and ROS levels, depolarized mitochondrial membrane potential, and induced cell death; effects blocked by the nonselective MOR antagonist naloxone and the selective MOR antagonist β-funaltrexamine (β-FNA). Deferoxamine, an endolysosome-iron chelator, inhibited opioid agonist-induced increases in cytosolic and mitochondrial Fe2+ and ROS. Opioid-induced efflux of endolysosome Fe2+ and subsequent Fe2+ accumulation in mitochondria were blocked by the endolysosome-resident two-pore channel inhibitor NED-19 and the mitochondrial permeability transition pore inhibitor TRO.
Conclusions
Opioid agonist-induced increases in cytosolic and mitochondrial Fe2+ and ROS as well as cell death appear downstream of endolysosome de-acidification and Fe2+ efflux from the endolysosome iron pool that is sufficient to affect other organelles.
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