Iron Efflux from Astrocytes Plays a Role in Remyelination
ABSTRACT How iron is delivered to the CNS for myelination is not well understood. We assessed whether astrocytes can provide iron to cells in the CNS for remyelination. To study this we generated a conditional deletion of the iron efflux transporter ferroportin (Fpn) in astrocytes, and induced focal demyelination in the mouse spinal cord dorsal column by microinjection of lysophosphatidylcholine (LPC). Remyelination assessed by electron microscopy was reduced in astrocyte-specific Fpn knock-out mice compared with wild-type controls, as was proliferation of oligodendrocyte precursor cells (OPCs). Cell culture work showed that lack of iron reduces the ability of microglia to express cytokines (TNF-α and IL-1β) involved in remyelination. Furthermore, astrocytes in culture express high levels of FGF-2 in response to IL-1β, and IGF-1 in response to TNF-α stimulation. FGF-2 and IGF-1 are known to be important for myelination. Reduction in IL-1β and IGF-1 were also seen in astrocyte-specific Fpn knock-out mice after LPC-induced demyelination. These data suggest that iron efflux from astrocytes plays a role in remyelination by either direct effects on OPCs or indirectly by affecting glial activation.
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ABSTRACT: The expression of Ferroportin (Fpn) was examined at different time points in rats following focal cerebral ischemia treated with or without the traditional Chinese medicine Naotaifang. Initially, rats were randomly divided into 2, 6, 12, 24 and 72 h groups following middle cerebral artery occlusion (MCAO) and the mRNA and protein level of Fpn was detected by immunohistochemistry and reverse transcription polymerase chain reaction (RT‑PCR) at the above time points. Secondly, the rats were randomly divided into five groups as follows: Sham surgery group, model group, low‑dose group (3 g/kg NTE), medium dose group (9 g/kg NTE) and the high‑dose group (27 g/kg NTE). After 3 days of corresponding therapy by intragastric administration once a day, the regional cerebral ischemia model was reproduced by the MCAO suture method. On the third day, the neurological behavior of the rats was analyzed by neurobehavioral assessment. Fpn in the hippocampal CA2 region was measured by immunohistochemistry and the mRNA level of Fpn was detected by RT‑PCR. Expression of Fpn in the hippocampal CA2 region reached a peak 12 h after surgery (P<0.05, compared with the model group). The high‑dose group (27 g/kg NTE) exhibited a lower neurological behavior score (P<0.05) and a higher level of expression of Fpn at the mRNA and protein level compared with the sham surgery group and model group (P<0.05). Dysregulation of intracellular iron balance is possibly a new mechanism underlying cerebral ischemia. NTE can protect the neuronal population in the hippocampal CA2 region by adjusting the expression of Fpn to balance iron levels following cerebral ischemia.Molecular Medicine Reports 02/2015; DOI:10.3892/mmr.2015.3309 · 1.48 Impact Factor
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ABSTRACT: Iron accumulation occurs in the CNS in multiple sclerosis (MS) and in experimental autoimmune encephalomyelitis (EAE). However, the mechanisms underlying such iron accumulation are not fully understood. We studied the expression and cellular localization of molecules involved in cellular iron influx, storage, and efflux. This was assessed in two mouse models of EAE: relapsing-remitting (RR-EAE) and chronic (CH-EAE). The expression of molecules involved in iron homeostasis was assessed at the onset, peak, remission/progressive and late stages of the disease. We provide several lines of evidence for iron accumulation in the EAE spinal cord which increases with disease progression and duration, is worse in CH-EAE, and is localized in macrophages and microglia. We also provide evidence that there is a disruption of the iron efflux mechanism in macrophages/microglia that underlie the iron accumulation seen in these cells. Macrophages/microglia also lack expression of the ferroxidases (ceruloplasmin and hephaestin) which have antioxidant effects. In contrast, astrocytes which do not accumulate iron, show robust expression of several iron influx and efflux proteins and the ferroxidase ceruloplasmin which detoxifies ferrous iron. Astrocytes therefore are capable of efficiently recycling iron from sites of EAE lesions likely into the circulation. We also provide evidence of marked dysregulation of mitochondrial function and energy metabolism genes, as well as of NADPH oxidase genes in the EAE spinal cord. This data provides the basis for the selective iron accumulation in macrophage/microglia and further evidence of severe mitochondrial dysfunction in EAE. It may provide insights into processes underling iron accumulation in MS and other neurodegenerative diseases in which iron accumulation occurs. Copyright © 2015 Elsevier Inc. All rights reserved.Neurobiology of Disease 02/2015; DOI:10.1016/j.nbd.2015.02.001 · 5.20 Impact Factor
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ABSTRACT: Controversy exists regarding the association between Iron Deficiency Anemia (IDA), iron status, and Febrile Convulsion (FC) during childhood. In this article, a systematic review and meta-analysis is conducted in order to determine possible association and the degree of association between these statuses and FC. To identify all studies related to IDA and FC, various references such as MEDLINE (PubMed), Embase (OVID), Web of sciences (Thomson Reuters) and Google scholar were searched (up until 15 January 2013). Heterogeneity was assessed using the Q statistic, Tau 2 , and I 2 . Additionally, subgroup analyses were performed. The outcome of primary interest was the overall Odds Ratio (OR) of FC for IDA and standard mean differences (SMD) of ferritin level. In total, 21 articles were considered to assess the association between IDA and FC. Anemia was more prevalent among the FC patients compared with the controls and the overall OR was 1.52 (95% CI=1.03 to 2.25). In addition, the pooled OR for 17 studies performed in the populations with low and moderate prevalence of anemia was 2.04 (95% CI=1.46 to 2.85). Furthermore, 12 studies assessed the association between the ferritin level and FC. The overall SMD was -0.02 with a 95% CI of -0.09 to 0.06. Besides, the pooled SMD of ferritin was -0.57 (95% CI=-0.7 to -0.46) in 6 studies reporting no difference between the FC and the control group with respect to temperature. IDA was associated with a moderate increased risk of FC in children, particularly in the areas with low and moderate prevalence of anemia.Iranian Journal of Medical Sciences 11/2014; 39(6).