Cytokine toxicity to oligodendrocyte precursors is mediated by iron.
Inflammatory processes play a key role in the pathogenesis of a number of common neurodegenerative disorders such as Alzheimer's disease (AD), Parkinson's disease (PD), and multiple sclerosis (MS). Abnormal iron accumulation is frequently noted in these diseases and compelling evidence exists that iron is involved in inflammatory reactions. Histochemical stains for iron repeatedly demonstrate that oligodendrocytes, under normal conditions, stain more prominently than any other cell type in the brain. Therefore, we examined the hypothesis that cytokine toxicity to oligodendrocytes is iron mediated. Oligodendrocytes in culture were exposed to interferon-gamma (IFN-gamma), interleukin-1beta (IL-1beta), and tumor necrosis factor-alpha (TNF-alpha). Toxicity was observed in a dose-dependent manner for IFN-gamma and TNF-alpha. IL-1beta was not toxic in the concentrations used in this study. The toxic concentration of IFN-gamma, and TNF-alpha was lower if the cells were iron loaded, but iron loading had no effect on the toxicity of IL-1beta. These data provide insight into the controversy regarding the toxicity of cytokines to oligodendrocytes by revealing that iron status of these cells will significantly impact the outcome of cytokine treatment. The exposure of oligodendrocytes to cytokines plus iron decreased mitochondrial membrane potential but activation of caspase 3 is limited. The antioxidant, TPPB, which targets mitochondria, protected the oligodendrocytes from the iron-mediated cytotoxicity, providing further support that mitochondrial dysfunction may underlie the iron-mediated cytokine toxicity. Therapeutic strategies involving anti-inflammatory agents have met with limited success in the treatment of demyelinating disorders. A better understanding of these agents and the contribution of cellular iron status to cytokine toxicity may help develop a more consistent intervention strategy.
Zhang
Xuesheng
X
Department of Neurosurgery, Pennsylvania State University, College of Medicine Hershey, PA 17033, USA.
Haaf
Michael
M
Todorich
Bozho
B
Grosstephan
Erin
E
Schieremberg
Henry
H
Surguladze
Nodar
N
Connor
James R
JR
D000818:Animals; D000831:Animals, Newborn; D000975:Antioxidants / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D053148:Caspase 3; D020169:Caspases / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D016207:Cytokines / Q000276:immunology / Q000378:metabolism* / Q000633:toxicity; D004305:Dose-Response Relationship, Drug; D004660:Encephalitis / Q000276:immunology / Q000378:metabolism* / Q000503:physiopathology; D007371:Interferon-gamma / Q000276:immunology / Q000378:metabolism / Q000633:toxicity; D007375:Interleukin-1 / Q000276:immunology / Q000378:metabolism / Q000633:toxicity; D007501:Iron / Q000378:metabolism* / Q000633:toxicity; D051336:Mitochondrial Membranes / Q000187:drug effects / Q000378:metabolism; D019636:Neurodegenerative Diseases / Q000276:immunology / Q000378:metabolism / Q000503:physiopathology; D009836:Oligodendroglia / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013234:Stem Cells / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology / Q000378:metabolism / Q000633:toxicity
D000975:Antioxidants; D016207:Cytokines; D007375:Interleukin-1; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma; D007501:Iron; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases