Interleukin-6 counteracts therapy-induced cellular oxidative stress in multiple myeloma by up-regulating manganese superoxide dismutase

Charles O Brown; Kelley Salem; Brett A Wagner; Soumen Bera; Neeraj Singh; Ajit Tiwari; Amit Choudhury; Garry R Buettner; Apollina Goel

doi:10.1042/BJ20112019

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Interleukin-6 counteracts therapy-induced cellular oxidative stress in multiple myeloma by up-regulating manganese superoxide dismutase

Journal article

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Interleukin-6 counteracts therapy-induced cellular oxidative stress in multiple myeloma by up-regulating manganese superoxide dismutase

Charles O Brown, Kelley Salem, Brett A Wagner, Soumen Bera, Neeraj Singh, Ajit Tiwari, Amit Choudhury, Garry R Buettner and Apollina Goel

Biochemical journal, Vol.444(Pt 3), pp.515-527

06/15/2012

DOI: 10.1042/BJ20112019

PMCID: PMC3365439

PMID: 22471522

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Abstract

IL (interleukin)-6, an established growth factor for multiple myeloma cells, induces myeloma therapy resistance, but the resistance mechanisms remain unclear. The present study determines the role of IL-6 in re-establishing intracellular redox homoeostasis in the context of myeloma therapy. IL-6 treatment increased myeloma cell resistance to agents that induce oxidative stress, including IR (ionizing radiation) and Dex (dexamethasone). Relative to IR alone, myeloma cells treated with IL-6 plus IR demonstrated reduced annexin/propidium iodide staining, caspase 3 activation, PARP [poly(ADP-ribose) polymerase] cleavage and mitochondrial membrane depolarization with increased clonogenic survival. IL-6 combined with IR or Dex increased early intracellular pro-oxidant levels that were causally related to activation of NF-κB (nuclear factor κB) as determined by the ability of N -acetylcysteine to suppress both pro-oxidant levels and NF-κB activation. In myeloma cells, upon combination with hydrogen peroxide treatment, relative to TNF (tumour necrosis factor)-α, IL-6 induced an early perturbation in reduced glutathione level and increased NF-κB-dependent MnSOD (manganese superoxide dismutase) expression. Furthermore, knockdown of MnSOD suppressed the IL-6-induced myeloma cell resistance to radiation. MitoSOX Red staining showed that IL-6 treatment attenuated late mitochondrial oxidant production in irradiated myeloma cells. The present study provides evidence that increases in MnSOD expression mediate IL-6-induced resistance to Dex and radiation in myeloma cells. The results of the present study indicate that inhibition of antioxidant pathways could enhance myeloma cell responses to radiotherapy and/or chemotherapy.

Dex, dexamethasone

TNF, tumour necrosis factor

E+, ethidium cation

KD, knockdown

H2DCF-DA, 2′,7′-dichlorodihydrofluorescein diacetate

CF, cleaved fragment

MM, multiple myeloma

NAC, N-acetylcysteine

manganese superoxide dismutase (MnSOD)

interleukin-6

BM, bone marrow

RLU, relative luciferase units

IR, ionizing radiation

DHE, dihydroethidium

JC-1, 5,5′,6,6′-tetrachloro-1,1′,3,3′-tetraethylbenzimidazolylcarbocyanine iodide

MFI, mean fluorescence intensity

2-OH-E+, 2-hydroxyethidium

GPx, glutathione peroxidase

ROS, reactive oxygen species

IκB, inhibitor of NF-κB

qPCR, quantitative PCR

ICCM, irradiated cell conditioned medium

NSF, normalized survival fraction

dexamethasone

Z-VAD-FMK, benzyloxycarbonyl-Val-Ala-DL-Asp-fluoromethylketone

multiple myeloma

shRNA, small hairpin RNA

PI, propidium iodide

MnSOD, manganese superoxide dismutase

NBD, NEMO (NF-κB essential modulator)-binding domain

PEG–SOD, poly(ethylene glycol)-conjugated superoxide dismutase

SOD, superoxide dismutase

NF-κB, nuclear factor-κB

Z-LEHD-FMK, benzyloxycarbonyl-Leu-Glu-His-DL-Asp-fluoromethylketone

MOI, multiplicity of infection

IL, interleukin

radiation therapy

MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide

nuclear factor κB (NF-κB)

PARP, poly(ADP-ribose) polymerase

Details

Title: Subtitle: Interleukin-6 counteracts therapy-induced cellular oxidative stress in multiple myeloma by up-regulating manganese superoxide dismutase
Creators: Charles O Brown - Free Radical and Radiation Biology Program, Department of Radiation Oncology, University of Iowa, Iowa City, IA 52242, U.S.A
Kelley Salem - Free Radical and Radiation Biology Program, Department of Radiation Oncology, University of Iowa, Iowa City, IA 52242, U.S.A
Brett A Wagner - Free Radical and Radiation Biology Program, Department of Radiation Oncology, University of Iowa, Iowa City, IA 52242, U.S.A
Soumen Bera - Free Radical and Radiation Biology Program, Department of Radiation Oncology, University of Iowa, Iowa City, IA 52242, U.S.A
Neeraj Singh - Free Radical and Radiation Biology Program, Department of Radiation Oncology, University of Iowa, Iowa City, IA 52242, U.S.A
Ajit Tiwari - †Department of Anatomy and Cell Biology, The Holden Comprehensive Cancer Center, University of Iowa, Iowa City, IA 52242, U.S.A
Amit Choudhury - †Department of Anatomy and Cell Biology, The Holden Comprehensive Cancer Center, University of Iowa, Iowa City, IA 52242, U.S.A
Garry R Buettner - Free Radical and Radiation Biology Program, Department of Radiation Oncology, University of Iowa, Iowa City, IA 52242, U.S.A
Apollina Goel - Free Radical and Radiation Biology Program, Department of Radiation Oncology, University of Iowa, Iowa City, IA 52242, U.S.A
Resource Type: Journal article
Publication Details: Biochemical journal, Vol.444(Pt 3), pp.515-527
DOI: 10.1042/BJ20112019
PMID: 22471522
PMCID: PMC3365439
NLM abbreviation: Biochem J
ISSN: 0264-6021
eISSN: 1470-8728
Publisher: Portland Press Ltd
Alternative title: IL-6-mediated redox regulation of multiple myeloma
Language: English
Date published: 06/15/2012
Academic Unit: Radiation Oncology
Record Identifier: 9984047739502771

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