Treatment with nerve growth factor decreases expression of divalent metal transporter 1 and transferrin receptor in PC12 cells

Hepatocyte growth factor protects PC12 cells against OGD/R-induced injury by reducing iron

In the light of hepatocyte growth factor (HGF) the inhibiting role on the expression of hepcidin, we hypothesized that HGF might be able to reduce cell and tissue iron by increasing ferroportin 1 (Fpn1) content and Fpn1-mediated iron release from cells and tissues. The hypothesized ability of HGF to reduce iron might be one of the mechanisms associated with its neuroprotective action under the conditions of ischemia/reperfusion (I/R). Here, we investigated the effects of HGF on the expression of hepcidin as well as transferrin receptor 1 (TfR1), divalent metal transporter 1 (DMT1), Fpn1, ferritin and iron regulatory proteins (IRPs) in oxygen-glucose deprivation and reoxygenation (OGD/R)-treated PC12 cells by real-time PCR and Western blot analysis. We demonstrated that HGF could completely reverse the OGD/R-induced reduction in Fpn1 and IRP1 expression and increase in ferritin light chain protein and hepcidin mRNA levels in PC12 cells. It was concluded that HGF protects PC12 cells against OGD/R-induced injury mainly by reducing cell iron contents via the up-regulation of Fpn1 and increased Fpn1-mediated iron export from cells. Our findings suggested that HGF may also be able to ameliorate OGD/R or I/R-induced overloading of brain iron by promoting Fpn1 expression.

Brain-derived neurotrophic factor and glial cell line-derived neurotrophic factor inhibit ferrous iron influx via divalent metal transporter 1 and iron regulatory protein 1 regulation in ventral mesencephalic neurons

Iron accumulation is observed in the substantia nigra of patients with Parkinson's disease. However, it is unknown whether neurotrophic factors, brain-derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF) participate in the modulation of neuronal iron metabolism. Here, we investigated the effects and underlying mechanisms of BDNF and GDNF on the iron influx process in primary cultured ventral mesencephalic neurons. 6-hydroxydopamine-induced enhanced ferrous iron influx via improper up-regulation of divalent metal transporter 1 with iron responsive element (DMT1+IRE) was consistently relieved by BDNF and GDNF. Both the mRNA and protein levels of DMT1+IRE were down-regulated by BDNF or GDNF treatment alone. We further demonstrated the involvement of iron regulatory protein 1 (IRP1) in BDNF- and GDNF-induced DMT1+IRE expression. Extracellular-regulated kinase 1/2 (ERK1/2) and Akt were activated and participated in these processes. Inhibition of ERK1/2 and Akt phosphorylation abolished the down-regulation of IRP1 and DMT1+IRE induced by BDNF and GDNF. Taken together, these results show that BDNF and GDNF ameliorate iron accumulation via the ERK/Akt pathway, followed by inhibition of IRP1 and DMT1+IRE expression, which may provide new targets for the neuroprotective effects of these neurotrophic factors.

Plutonium uptake and distribution in mammalian cells: molecular vs. polymeric plutonium

PURPOSE

To study the cellular responses to molecular and polymeric forms of plutonium using PC12 cells derived from a rat pheochromocytoma.

MATERIALS AND METHODS

Serum starved PC12 cells were exposed to polymeric and molecular forms of plutonium for 3 h. Cells were washed with 10 mM ethylene glycol tetraacetic acid (EGTA), 100 mM NaCl at pH 7.4 to remove surface sorbed plutonium. Localization of plutonium in individual cell was quantitatively analyzed by synchrotron X-ray fluorescence (XRF) microscopy.

RESULTS

Molecular plutonium complexes introduced to cell growth media in the form of nitrilotriacetic acid (NTA), citrate, or transferrin complexes were taken up by PC12 cells, and mostly colocalized with iron within the cells. Aged polymeric plutonium prepared separately was not internalized by PC12 cells but it was always found on the cell surface as big agglomerates; however, polymeric plutonium formed in situ was mostly found within the cells as agglomerates.

CONCLUSIONS

PC12 cells can differentiate molecular and polymeric forms of plutonium. Molecular plutonium is taken up by PC12 cells and mostly co-localizes with iron but aged polymeric plutonium is not internalized by the cells.

Increased iron levels correlate with the selective nigral dopaminergic neuron degeneration in Parkinson's disease

The staging of Lewy-related pathology in sporadic Parkinson's disease (PD) reveals that many brain nuclei are affected in PD during different stages, except the ventral tegmental area (VTA), which is close related to the substantia nigra (SN) and enriched in dopamine (DA) neurons. Why DA neurons are selectively degenerated in the SN of PD is far from known. In the present study, we observed that the number of tyrosine hydroxylase immunoreactive neurons decreased and iron-staining positive cells increased in the SN, but not in the VTA, in the chronic 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated PD mice. Increased expression of divalent metal transporter 1 and decreased expression of ferroportin 1 might associate with this increased nigral iron levels. Lipofuscin granular aggregations and upregulation of alpha-synuclein (α-synuclein) were also observed only in the SN. These results suggest that increased iron levels associate with the selective degeneration of DA neurons in the SN. The intracellular regulation mechanisms for the iron transporters may be different in the SN and VTA under the same conditions. Moreover, the lipofuscin granular aggregations and upregulation of α-synuclein were also involved in the selective degeneration of dopaminergic neurons in the SN.

Docosahexaenoic Acid Enhances Iron Uptake by Modulating Iron Transporters and Accelerates Apoptotic Death in PC12 Cells

The effect of docosahexaenoic acid (DHA; 22:6 n-3) on Fe(2+)-mediated and/or H(2)O(2)-mediated oxidative stress (OS) was investigated in a PC12 pheochromocytoma cell line in the presence or absence of 50 ng/ml nerve growth factor (NGF). DHA-supplemented cells showed enhanced Fe(2+)-induced cell damage as evident by increased lipid peroxides formation (10-fold) and reduced neutral red (NR) dye uptake in a NGF-independent fashion. DHA caused a nearly 10-fold increase in free iron uptake in NGF-treated cells and doubled iron uptake in nondifferentiated cells. DHA-enrichment induced an elevation in the transferrin receptor protein in the nondifferentiated cells whereas NGF-treatment led to a substantial increase in the ubiquitous divalent metal ion transporter 1 (DMT-1) as detected by mRNA levels using qRT-PCR. The mechanism of action of DHA to accelerate cell death may be associated with the externalization of amino-phosphoglycerides (PG) species of which, increased ethanolamine plasmalogen levels, may be essential for cell rescue as noted in NGF-treated PC12 cells.

Anoxia tolerance in turtles: Metabolic regulation and gene expression

Freshwater turtles of the Trachemys and Chrysemys genera are champion facultative anaerobes able to survive for several months without oxygen during winter hibernation in cold water. They have been widely used as models to identify and understand the molecular mechanisms of natural anoxia tolerance and the molecular basis of the hypoxic/ischemic injuries that occur in oxygen-sensitive systems and underlie medical problems such as heart attack and stroke. Peter L. Lutz spent much of his career investigating turtle anaerobiosis with a particular focus on the mechanisms of brain ion homeostasis and neurotransmitter responses to anoxia exposure and the mechanisms that suppress brain ion channel function and neuronal excitability during anaerobiosis. Our interests intersected over the mechanisms of metabolic rate depression which is key to long term anoxia survival. Studies in my lab have shown that a key mechanism of metabolic arrest is reversible protein phosphorylation which provides coordinated suppression of the rates of multiple ATP-producing, ATP-utilizing and related cellular processes to allow organisms to enter a stable hypometabolic state. Anoxia tolerance is also supported by selective gene expression as revealed by recent studies using cDNA library and DNA array screening. New studies with both adult T. scripta elegans and hatchling C. picta marginata have identified prominent groups of genes that are up-regulated under anoxia in turtle organs, in several cases suggesting aspects of cell function and metabolic regulation that have not previously been associated with anaerobiosis. These groups of anoxia-responsive genes include mitochondrially-encoded subunits of electron transport chain proteins, iron storage proteins, antioxidant enzymes, serine protease inhibitors, transmembrane solute carriers, neurotransmitter receptors and transporters, and shock proteins.