Ceruloplasmin expression and its role in iron transport in C6 cells

Iron-induced cellular in vitro neurotoxic responses in rat C6 cell line

Iron is an essential metal critical for normal cellular and biochemical function and it is used as a cofactor in many vital biological pathways within the brain. However, accumulation of excess iron in brain is commonly associated with several neurodegenerative and neurotoxic adverse effects. Chronic exposure of iron leads to an increased risk for several neurodegenerative diseases. The exact mechanism of iron-induced neurotoxicity is still unclear. Therefore, our study aimed to investigate the mechanism of neurotoxic and neurodegenerative effects through in vitro exposure of ferrous sulphate in rat C6 cell line. The findings of our study have indicated that ferrous sulphate exposure may lead to induction of molecular markers of neuronal inflammation, apoptotic neuronal cell death, amyloid-beta and hyperphosphorylated tau levels. This study provides a basic mechanistic understanding of signaling pathway and biomarkers involved during iron-induced neurotoxicity.

Brain Ceruloplasmin Expression After Experimental Intracerebral Hemorrhage and Protection Against Iron-Induced Brain Injury

Ceruloplasmin (CP) is an essential ferroxidase that is involved in maintaining iron homeostasis by oxidizing toxic ferrous iron (Fe²⁺) to less-toxic ferric iron (Fe³⁺). CP has been well studied in many neurodegenerative diseases, but there has not been an in-depth investigation in intracerebral hemorrhage (ICH). This research investigated brain CP expression in rats after ICH and the effect of CP on Fe²⁺-induced brain injury. This study had two parts: first, rats had injection of autologous blood into the right basal ganglia and the time course of CP expression in the brain examined (protein and mRNA). Second, rats had an injection of either Fe²⁺ in saline, Fe²⁺ plus CP in saline, or saline alone into the right basal ganglia. All rats in the second part had T2-weighted magnetic resonance imaging, and behavioral tests before the brains were harvested for immunohistochemistry and Western blotting. We found that CP was expressed on neurons and astrocytes in both cortex and basal ganglia after ICH. The time course showed that ICH induced CP expression increased from 4 h to 7 days, peaking at day 3. Whether the brain itself can produce CP was confirmed by RT-PCR. Exogenous CP reduced Fe²⁺-induced T2 lesions, blood-brain barrier disruption, brain cell death, and neurological deficits. These results suggest a role of CP in potentially reducing ICH-induced brain injury.

Serum Copper Homeostasis in Hypertensive Intracerebral Hemorrhage and its Clinical Significance

This study was to investigate the alterations of serum copper homeostasis after hypertensive intracerebral hemorrhage (ICH), which is not yet clear. We recruited 85 hypertensive ICH patients and determined their serum levels of total copper (TCu), small molecule copper (SMC), and ceruloplasmin (Cp). Sera from 32 healthy persons and 12 primary hypertension patients were collected and analyzed as well. Serum TCu levels in ICH patients were tested at three time points (on admission, day 3, and day 7) and found to be higher than that in hypertension patients (p < 0.05). The serum SMC levels in hypertension patients and ICH patients at three time points were higher than that in healthy controls (p < 0.05). Higher serum SMC levels on days 3 and 7 were associated with death in the hospital. Additionally, higher serum SMC levels on the seventh day were associated with poor outcome at discharge. High serum Cp levels on admission, as well as low serum Cp levels on the seventh day, were associated with death in the hospital (p = 0.002 and p = 0.034, respectively). Our findings indicated that declines in serum Cp and increases in serum SMC are correlated with lethal or poor outcome in hypertensive ICH patients, possibly as a result of contributions to secondary injury of brain after hemorrhage due to impairment of iron transport and enhanced oxidative stress.

Nifedipine Increases Iron Content in WKPT-0293 Cl.2 Cells via Up-Regulating Iron Influx Proteins

Nifedipine was reported to enhance urinary iron excretion in iron overloaded mice. However, it remains unknown how nifedipine stimulates urinary iron excretion in the kidney. We speculated that nifedipine might inhibit the TfR1/ DMT1 (transferrin receptor 1/divalent metal transporter1)-mediated iron uptake by proximal tubule cells in addition to blocking L-type Ca2+ channels, leading to an increase in iron in lumen-fluid and then urinary iron excretion. To test this hypothesis, we investigated the effects of nifedipine on iron content and expression of TfR1, DMT1 and ferroportin1 (Fpn1) in WKPT-0293 Cl.2 cells of the S1 segment of the proximal tubule in rats, using a graphite furnace atomic absorption spectrophotometer and Western blot analysis, respectively. We demonstrated for the first time that nifedipine significantly enhanced iron content as well as TfR1 and DMT1 expression and had no effect on Fpn1 levels in the cells. We also found that ferric ammonium citrate decreased TfR1 levels, increased Fpn1 expression and had no effect on DMT1 content, while co-treatment with nifedipine and FAC increase TfR1 and DMT1 expression and also had no effect on Fpn1 levels. These findings suggest that the nifedipine-induced increase in cell iron may mainly be due to the corresponding increase in TfR1 and DMT1 expression and also imply that the effects of nifedipine on iron transport in proximal tubule cells can not explain the increase in urinary iron excretion.

Ceruloplasmin is regulated by copper and lactational hormones in PMC42-LA mammary epithelial cell culture models

Ceruloplasmin (Cp) is a multicopper ferroxidase that is considered to be an important source of copper in milk for normal neonatal development. We investigated the expression, subcellular localization and secretion of Cp in PMC42-LA cell culture models representative of resting, lactating and suckled human mammary epithelia. Both secreted Cp (sCp) and plasma membrane associated glycosylphosphatidylinositol-linked Cp (GPI-Cp) were expressed in PMC42-LA cells. In all three epithelial models (resting, lactating and suckled), the expression and secretion of copper-bound, ferroxidase active, Cp (holo-Cp) was dependent on media copper concentration. In low copper (bathocuproinedisulphonic acid/d-penicillamine treated models) there was greater than a 2-fold decrease in holo-Cp expression and secretion, which was mirrored by a 2-fold increase in the expression and secretion of copper-free Cp protein (apo-Cp). Cell surface biotinylation studies revealed that the state of PMC42-LA cell differentiation (functionality), and the level of extracellular copper, had no significant effect on the level of plasma membrane bound GPI-Cp. Quantitative real time PCR analyses determined that there was no significant (P > 0.05) difference in Cp mRNA levels across all copper conditions investigated (0, 5, 50 μM). However, there was a significant (P < 0.05) increase (∼2-fold) in Cp mRNA in both the lactating and suckled models in comparison to the resting model. Furthermore, the Cp mRNA increase in response to PMC42-LA differentiation corresponded with more secreted Cp protein, both apo and holo forms, indicating a link between function and Cp requirement. Our results provide significant insight on the regulation of Cp expression and secretion in lactation and copper incorporation into milk.

Fluorescence-guided surgery for brain tumors

5-aminolevulinic acid-induced protoporphyrin IX fluorescence was authorized in the EU for visualization of tumor tissue during surgery for WHO grade III and IV gliomas in 2007. It facilitates tumor identification and doubles the number of gross total resections that can be achieved in these tumors. The growing acceptance of fluorescence-guided surgery in malignant gliomas brings forward a substantial yield of data on many types of intracranial lesions. The following review summarizes the main findings of these publications and illustrates the limitations, caveats and future perspectives of 5-aminolevulinic acid-induced fluorescence in malignant glioma as well as in other brain neoplasms.

Age-dependent expression of duodenal cytochrome b, divalent metal transporter 1, ferroportin 1, and hephaestin in the duodenum of rats

BACKGROUND AND AIM

The body's requirement for iron is different at different developmental stages. However, the molecular mechanisms of age-dependent iron metabolism are poorly understood. In the present study, we investigated the expression of iron transport proteins in the duodenum of Sprague-Dawley rats at five different age stages.

METHODS

Male Sprague-Dawley rats at postnatal week (PNW) 1, 3, 12, 44, and 88 were employed in the study. Serum iron status and tissue non-heme iron concentrations in the spleen, liver, bone marrow, heart, kidney, duodenal epithelium, and gastrocnemius were examined at each age stage. The expression of duodenal cytochrome b (DcytB), divalent metal transporter 1 (DMT1), ferroportin 1 (FPN1), hephaestin, and hepcidin were measured by real-time polymerase chain reaction or Western blot.

RESULTS

The levels of serum iron and transferrin saturation were higher in the rats at PNW1 and 3 than in those at PNW12, 44, and 88. Non-heme iron contents decreased from PNW1 to PNW3 and then increased thereafter. Duodenal DcytB, DMT1, and FPN1 increased to the highest level at PNW3 and then decreased from PNW12 to 88. The hepatic hepcidin mRNA level decreased to the lowest level at PNW3 and then increased with age.

CONCLUSION

Our findings showed that age had a significant effect on body iron status. The increased duodenal DcytB, DMT1, and FPN1 expression can enhance intestinal iron absorption to meet the high iron requirements in infants. Hepcidin or enterocyte iron levels may be involved in the regulation of age-dependent FPN1, DMT1, and DcytB expression in the duodenum.

Sex differences in iron status and hepcidin expression in rats

Studies have shown that men and women exhibit significant differences regarding iron status. However, the effects of sex on iron accumulation and distribution are not well established. In this study, female and male Sprague-Dawley rats were killed at 4 months of age. Blood samples were analyzed to determine the red blood cell (RBC) count, hemoglobin (Hb) concentration, hematocrit (Hct), and mean red blood cell volume (MCV). The serum samples were analyzed to determine the concentrations of serum iron (SI), transferrin saturation (TS), ferritin, soluble transferrin receptor (sTfR), and erythropoietin (EPO). The tissue nonheme iron concentrations were measured in the liver, spleen, bone marrow, kidney, heart, gastrocnemius, duodenal epithelium, lung, pallium, cerebellum, hippocampus, and striatum. Hepatic hepcidin expression was detected by real-time PCR analysis. The synthesis of ferroportin 1 (FPN1) in the liver, spleen, kidney, and bone marrow was determined by Western blot analysis. The synthesis of duodenal cytochrome B561 (DcytB), divalent metal transporter 1 (DMT1), FPN1, hephaestin (HP) in the duodenal epithelium was also measured by Western blot analysis. The results showed that the RBC, Hb, and Hct in male rats were higher than those in female rats. The SI and plasma TS levels were lower in male rats than in female rats. The levels of serum ferritin and sTfR were higher in male rats than in female rats. The EPO levels in male rats were lower than that in female rats. The nonheme iron contents in the liver, spleen, bone marrow, and kidney in male rats were also lower (56.7, 73.2, 60.6, and 61.4 % of female rats, respectively). Nonheme iron concentrations in the heart, gastrocnemius, duodenal epithelium, lung, and brain were similar in rats of both sexes. A moderate decrease in hepatic hepcidin mRNA content was also observed in male rats (to 56.0 % of female rats). The levels of FPN1 protein in the liver, spleen, and kidney were higher in male rats than in female rats. There was no significant change in FPN1 expression in bone marrow. Significant difference was also not found in DcytB, DMT1, FPN1, and HP protein levels in the duodenal epithelium between male and female rats. These data suggest that iron is distributed differently in male and female rats. This difference in iron distribution may be associated with the difference in the hepcidin level.

Role of hepcidin in murine brain iron metabolism

Brain iron homeostasis is maintained by a balance of both iron uptake and release, and accumulating evidence has revealed that brain iron concentrations increase with aging. Hepcidin, an iron regulatory hormone produced by hepatocytes in response to inflammatory stimuli, iron, and hypoxia, has been shown to be the long-sought hormone responsible for the regulation of body iron balance and recycling in mammals. In this study, we report that hepcidin is widely expressed in the murine brain. In cerebral cortex, hippocampus and striatum, hepcidin mRNA levels increased with aging. Injection of hepcidin into the lateral cerebral ventricle resulted in decreased Fpn1 protein levels in cerebral cortex, hippocampus, and striatum. Additionally, treatment of primary cultured neurons with hepcidin caused decreased neuronal iron release and Fpn1 protein levels. Together, our data provide further evidence that hepcidin may be involved in the regulation of brain iron metabolism.

Brain iron metabolism: neurobiology and neurochemistry

New findings obtained during the past years, especially the discovery of mutations in the genes associated with brain iron metabolism, have provided key insights into the homeostatic mechanisms of brain iron metabolism and the pathological mechanisms responsible for neurodegenerative diseases. The accumulated evidence demonstrates that misregulation in brain iron metabolism is one of the initial causes for neuronal death in some neurodegenerative disorders. The errors in brain iron metabolism found in these disorders have a multifactorial pathogenesis, including genetic and nongenetic factors. The disturbances of iron metabolism might occur at multiple levels, including iron uptake and release, storage, intracellular metabolism and regulation. It is the increased brain iron that triggers a cascade of deleterious events, leading to neuronal death in these diseases. In the article, the recent advances in studies on neurochemistry and neuropathophysiology of brain iron metabolism were reviewed.