Uptake of ferrous iron by cultured rat astrocytes

Abstract

Astrocytes are considered to play an important role in iron homeostasis of the brain, yet the mechanisms involved in the uptake of iron into astrocytes remain elusive. To investigate the uptake of iron into astrocytes, we have applied ferric ammonium citrate (FAC) to rat astrocyte-rich primary cultures. These cultures express the mRNAs of two membrane-bound ferric reductases, Dcytb and SDR2, and reduce extracellular ferric iron (100 muM) with a rate of 3.2 +/- 0.4 nmol/(hr x mg). This reduction rate is substantially lower than the rate of cellular iron accumulation from 100 muM FAC [24.7 +/- 8.9 nmol/(hr x mg)], which suggests that iron accumulation from FAC does at best partially depend on extracellular ferric reduction. Nonetheless, when the iron in FAC was almost completely reduced by an excess of exogenous ascorbate, astrocytes accumulated iron in a time- and concentration-dependent manner with specific iron accumulation rates that increased linearly for concentrations of up to 100 muM ferrous iron. This accumulation was attenuated by lowering the incubation temperature, by the presence of ferrous iron chelators, or by lowering the pH from 7.4 to 6.8. These data indicate that, in addition to the DMT1-mediated uptake of ferrous iron, astrocytes can accumulate ferric and ferrous iron by mechanisms that are independent of DMT1 or transferrin.

Effects of Iron Chelators, Iron Salts, and Iron Oxide Nanoparticles on the Proliferation and the Iron Content of Oligodendroglial OLN-93 Cells

“…Since ferrous iron is quickly oxidised to ferric iron in physiological media [40,41], the iron applied as FeCl 2 or FAS to OLN-93 cells is likely to become quickly oxidised to ferric iron that subsequently may bind to transferrin. Alternatively, a DMT1-independent ferrous iron uptake [41] or a ferric iron uptake perhaps via b-integrin-mobilferrin or by a trivalent cation-specific transporter [42,43] could contribute to the observed iron accumulation in OLN-93 cells from low molecular weight iron. The ability of OLN-93 cells to accumulate efficiently extracellular iron from various iron sources may reflect the ability of oligodendrocyte precursors to accumulate iron by multiple mechanisms.…”

Differential Effect of Nimodipine in Attenuating Iron-Induced Toxicity in Brain- and Blood–Brain Barrier-Associated Cell Types

“…to ferrous (Fe 2? ) iron, thereby increasing astrocytic NTBI uptake [40]. In addition, astrocytes express transferrin receptors, contain ferritin [41], and express ceruloplasmin, an iron efflux protein [42].…”

Hyperspectral fluorescence imaging for cellular iron mapping in thein vitromodel of Parkinson’s disease

“…10,11 Also, this hyperspectral signal imaging provides the location with quantity of iron which was not offered from colorimetric ferrozine-based assay. Using this intensity measurement, we can relatively quantify the intensity differences between sample groups without cell lysis (Fig.…”

“…Most previous quantification studies depended on the colorimetric ferrozine-based assay using cell lysates. 10,11 With a matter of concern, cellular iron level is influenced by microscopic changes in temperature or pH and may be changed by the physiological state of the cells with various chemicals. 11 Moreover, the previous methods have limitations to observe the location of iron and have difficulty analyzing the amount of iron in the intracellular organelles.…”

“…10,11 With a matter of concern, cellular iron level is influenced by microscopic changes in temperature or pH and may be changed by the physiological state of the cells with various chemicals. 11 Moreover, the previous methods have limitations to observe the location of iron and have difficulty analyzing the amount of iron in the intracellular organelles. An analytical technique with high-resolution imaging is needed for the visualization and quantification of cellular iron elevation as the pathology of PD progresses.…”