Pentoxifylline Alleviates Early Brain Injury After Experimental Subarachnoid Hemorrhage in Rats: Possibly via Inhibiting TLR 4/NF-κB Signaling Pathway

Early brain injury (EBI) after subarachnoid hemorrhage (SAH) generally causes significant and lasting damage. Pentoxifylline (PTX), a nonselective phosphodiesterase inhibitor, has shown anti-inflammatory and neuroprotective properties in several brain injury models, but the role of PTX with respect to EBI following SAH remains uncertain. The purpose of this study was to investigate the effects of PTX on EBI after SAH in rats. Adult male Sprauge–Dawley rats were randomly assigned to the sham and SAH groups. PTX (30 or 60 mg/kg) or an equal volume of the administration vehicle (normal saline) was administrated at 30 min intervals following SAH. Neurological scores, brain edema, and neural cell apoptosis were evaluated. In order to explore other mechanisms, changes in the toll-like receptor 4 (TLR4) and the nuclear factor-κB (NF-κB) signaling pathway, in terms of the levels of apoptosis-associated proteins, were also investigated. We found that administration of PTX (60 mg/kg) notably improved neurological function and decreased brain edema at both 24 and 72 h following SAH. Treatment with PTX (60 mg/kg) significantly inhibited the protein expressions of TLR4, NF-κB, MyD88 and the downstream pro-inflammatory cytokines, such as the tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β). PTX also significantly reduced neural cell death and BBB permeability. Our observations may be the first time that PTX has been shown to play a neuroprotective role in EBI after SAH, potentially by suppressing the TLR4/NF-κB inflammation-related pathway in the rat brain.     

Role of autophagy in early brain injury after subarachnoid hemorrhage in rats

Early brain injury (EBI) occurred after aneurismal subarachnoid hemorrhage (SAH) strongly determined the patients’ prognosis. Autophagy was activated in neurons in the acute phase after SAH, while its role in EBI has not been examined. This study was designed to explore the effects of autophagy on EBI post-SAH in rats. A modified endovascular perforating SAH model was established under monitoring of intracranial pressure. Extent of autophagy was regulated by injecting autophagy-regulating drugs (3-methyladenine, wortmannin and rapamycin) 30 min pre-SAH intraventricularly. Simvastatin (20 mg/kg) was prophylactically orally given 14 days before SAH induction. Mortality, neurological scores, brain water content and blood–brain barrier (BBB) permeability were evaluated at 24 h post-SAH. Microtubule-associated protein light chain-3 (LC3 II/I) and beclin-1 were detected for monitoring of autophagy flux. Terminal deoxynucleotidyl transferase-mediated biotinylated UTP nick end labeling, expression of cleaved caspase-3 and cytoplasmic histone-associated DNA fragments were used to detect apoptosis. The results showed that mortality was reduced in rapamycin and simvastatin treated animals. When autophagy was inhibited by 3-methyladenine and wortmannin, the neurological scores were decreased, brain water content and BBB permeability were further aggravated and neuronal apoptosis was increased when compared with the SAH animals. Autophagy was further activated by rapamycin and simvastatin, and apoptosis was inhibited and EBI was ameliorated. The present results indicated that activation of autophagy decreased neuronal apoptosis and ameliorated EBI after SAH. Aiming at autophagy may be a potential effective target for preventing EBI after SAH.     

Enhanced Therapeutic Potential of Nano-Curcumin Against Subarachnoid Hemorrhage-Induced Blood–Brain Barrier Disruption Through Inhibition of Inflammatory Response and Oxidative Stress

Curcumin and nano-curcumin both exhibit neuroprotective effects in early brain injury (EBI) after experimental subarachnoid hemorrhage (SAH). However, the mechanism that whether curcumin and its nanoparticles affect the blood–brain barrier (BBB) following SAH remains unclear. This study investigated the effect of curcumin and the poly(lactide-co-glycolide) (PLGA)-encapsulated curcumin nanoparticles (Cur-NPs) on BBB disruption and evaluated the possible mechanism underlying BBB dysfunction in EBI using the endovascular perforation rat SAH model. The results indicated that Cur-NPs showed enhanced therapeutic effects than that of curcumin in improving neurological function, reducing brain water content, and Evans blue dye extravasation after SAH. Mechanically, Cur-NPs attenuated BBB dysfunction after SAH by preventing the disruption of tight junction protein (ZO-1, occludin, and claudin-5). Cur-NPs also up-regulated glutamate transporter-1 and attenuated glutamate concentration of cerebrospinal fluid following SAH. Moreover, inhibition of inflammatory response and microglia activation both contributed to Cur-NPs’ protective effects. Additionally, Cur-NPs markedly suppressed SAH-mediated oxidative stress and eventually reversed SAH-induced cell apoptosis in rats. Our findings revealed that the strategy of using Cur-NPs could be a promising way in improving neurological function in EBI after experimental rat SAH.     

Calcitonin increases hepatic hepcidin expression through the BMP6 of kidney in mice

BackgroundOsteoporosis is frequently accompanied by iron disorders. Calcitonin (CT) was approved as a clinical drug to treat osteoporosis. Hepcidin is a peptide hormone that is secreted by the liver and controls body iron homeostasis. Hepcidin deficiency leads to iron overload diseases. This study was aimed at investigating the effect of CT on hepatic hepcidin and the mechanism by which CT modulates hepatic hepcidin pathways and iron metabolism.MethodRT-PCR, Western blot, ELISA and siRNA were used to detect the effect of CT on iron metabolism in vivo and in vitro. In addition, the regulatory signal molecules of hepcidin were measured to explore the molecular mechanism of its regulation.ResultsThe results showed that CT strongly increased hepcidin expression and altered iron homeostasis, after mice were intraperitoneal injection of CT. In response to CT administration, BMP6 level in kidney and the serum BMP6 was increased significantly. The phosphorylation of Smad1/5/8 proteins in liver was increased at 3 h and 6 h. Moreover, the Bmp inhibitor LDN-193,189 pretreatment significantly attenuated the CT-mediated increases in phosphorylated Smad1/5/8 and Hamp1 mRNA levels. Calcitonin receptor (CTR) siRNA transfection significant suppressed the role of CT on BMP6 expression in Caki-1 cells.ConclusionOur results suggest that CT strongly induces hepcidin expression and affected iron metabolism. It will provide a new strategy for the treatment of calcium iron related diseases.     

Elevated Systemic Hepcidin and Iron Depletion in Obese Premenopausal Females

Hepcidin, the body's main regulator of systemic iron homeostasis, is upregulated in response to inflammation and is thought to play a role in the manifestation of iron deficiency (ID) observed in obese populations. We determined systemic hepcidin levels and its association with body mass, inflammation, erythropoiesis, and iron status in premenopausal obese and nonobese women (n = 20/group) matched for hemoglobin (Hb). The obese participants also had liver and abdominal visceral and subcutaneous adipose tissue assessed for tissue iron accumulation and hepcidin mRNA expression. Despite similar Hb levels, the obese women had significantly higher serum hepcidin (88.02 vs. 9.70 ng/ml; P < 0.0001) and serum transferrin receptor (sTfR) (P = 0.001) compared to nonobese. In the obese women hepcidin was not correlated with serum iron (r = ?0.02), transferrin saturation (Tsat) (r = 0.17) or sTfR (r = ?0.12); in the nonobese it was significantly positively correlated with Tsat (r = 0.70) and serum iron (r = 0.58), and inversely with sTfR (r = ?0.63). Detectable iron accumulation in the liver and abdominal adipose tissue of the obese women was minimal. Liver hepcidin mRNA expression was ～700 times greater than adipose tissue production and highly correlated with circulating hepcidin levels (r = 0.61). Serum hepcidin is elevated in obese women despite iron depletion, suggesting that it is responding to inflammation rather than iron status. The source of excess hepcidin appears to be the liver and not adipose tissue. The ID of obesity is predominantly a condition of a true body iron deficit rather than maldistribution of iron due to inflammation. However, these findings suggest inflammation may perpetuate this condition by hepcidin‐mediated inhibition of dietary iron absorption.     

Hepcidin, an antimicrobial peptide is downregulated in ceruloplasmin-deficient mice

Hepcidin, a principle regulator of iron metabolism, is synthesized by the liver. Contradictory results have been reported on the regulation of hepcidin expression in response to serum transferrin saturation and liver iron content. In the present study, we explore the expression of murine hepcidin mRNA and further analyze the relationship between liver hepcidin mRNA expression, liver iron stores, and serum iron level utilizing ceruloplasmin gene knockout mice. We find that hepcidin expression correlates significantly with serum transferrin saturation, whereas there is a negative correlation of hepcidin expression with liver tissue iron level.     

Effect of exposure to 50 Hz magnetic field with or without insulin on blood–brain barrier permeability in streptozotocin‐induced diabetic rats

We investigated the effect of long‐term exposure to modulation magnetic field (MF), insulin, and their combination on blood–brain barrier (BBB) permeability in a diabetic rat model. Fifty‐three rats were randomly assigned to one of six groups: sham, exposed to no MF; MF, exposed to MF; diabetes mellitus (DM), DM induced with streptozotocin (STZ); DM plus MF (DMMF); DM plus insulin therapy (DMI); and DM plus insulin therapy plus MF (DMIMF). All the rats underwent Evans blue (EB) measurement to evaluate the BBB 30 days after the beginning of experiments. The rats in MF, DMMF, and DMIMF groups were exposed to MF (B = 5 mT) for 165 min every day for 30 days. Mean arterial blood pressure (MABP), body mass, and serum glucose level of the study rats were recorded. The extravasation of brain EB of the MF, DM, DMMF, DMI, and DMIMF groups was higher than that of the sham group and the extravasation of right hemisphere of the DMIMF group was highest (P < 0.05). The post‐procedure body mass of the sham and MF groups were significantly higher than those of the DM and DMMF groups (P < 0.05). In the DM, DMMF, DMI, and DMIMF groups, the baseline glucose was significantly lower than the post‐procedure glucose (P < 0.05). DM and MF increase BBB permeability; in combination, they cause more increase in BBB permeability, and insulin decreases their effect on BBB. Improved glucose metabolism may prevent body mass loss and the hypoglycemic effect of MF. DM increases MABP but MF causes no additional effect. Bioelectromagnetics 31:262–269, 2010. © 2009 Wiley‐Liss, Inc.     

Role of duodenal iron transporters and hepcidin in patients with alcoholic liver disease

Patients with alcoholic liver disease (ALD) often display disturbed iron indices. Hepcidin, a key regulator of iron metabolism, has been shown to be down‐regulated by alcohol in cell lines and animal models. This down‐regulation led to increased duodenal iron transport and absorption in animals. In this study, we investigated gene expression of duodenal iron transport molecules and hepcidin in three groups of patients with ALD (with anaemia, with iron overload and without iron overload) and controls. Expression of DMT1, FPN1, DCYTB, HEPH, HFE and TFR1 was measured in duodenal biopsies by using real‐time PCR and Western blot. Serum hepcidin levels were measured by using ELISA. Serum hepcidin was decreased in patients with ALD. At the mRNA level, expressions of DMT1, FPN1 and TFR1 genes were significantly increased in ALD. This pattern was even more pronounced in the subgroups of patients without iron overload and with anaemia. Protein expression of FPN1 paralleled the increase at the mRNA level in the group of patients with ALD. Serum ferritin was negatively correlated with DMT1 mRNA. The down‐regulation of hepcidin expression leading to up‐regulation of iron transporters expression in the duodenum seems to explain iron metabolism disturbances in ALD. Alcohol consumption very probably causes suppression of hepcidin expression in patients with ALD.     

TRAF3 mediates neuronal apoptosis in early brain injury following subarachnoid hemorrhage via targeting TAK1-dependent MAPKs and NF-κB pathways

Neuronal apoptosis has an important role in early brain injury (EBI) following subarachnoid hemorrhage (SAH). TRAF3 was reported as a promising therapeutic target for stroke management, which covered several neuronal apoptosis signaling cascades. Hence, the present study is aimed to determine whether downregulation of TRAF3 could be neuroprotective in SAH-induced EBI. An in vivo SAH model in mice was established by endovascular perforation. Meanwhile, primary cultured cortical neurons of mice treated with oxygen hemoglobin were applied to mimic SAH in vitro. Our results demonstrated that TRAF3 protein expression increased and expressed in neurons both in vivo and in vitro SAH models. TRAF3 siRNA reversed neuronal loss and improved neurological deficits in SAH mice, and reduced cell death in SAH primary neurons. Mechanistically, we found that TRAF3 directly binds to TAK1 and potentiates phosphorylation and activation of TAK1, which further enhances the activation of NF-κB and MAPKs pathways to induce neuronal apoptosis. Importantly, TRAF3 expression was elevated following SAH in human brain tissue and was mainly expressed in neurons. Taken together, our study demonstrates that TRAF3 is an upstream regulator of MAPKs and NF-κB pathways in SAH-induced EBI via its interaction with and activation of TAK1. Furthermore, the TRAF3 may serve as a novel therapeutic target in SAH-induced EBI.Subject terms: Apoptosis, Neuro-vascular interactions     

Eupatilin alleviates inflammatory response after subarachnoid hemorrhage by inhibition of TLR4/MyD88/NF-κB axis

Early brain injury (EBI) is associated with the adverse prognosis of subarachnoid hemorrhage (SAH) patients. The key bioactive component of the Chinese herbal medicine Artemisia asiatica Nakai (Asteraceae) is eupatilin. Recent research reports that eupatilin suppresses inflammatory responses induced by intracranial hemorrhage. This work is performed to validate whether eupatilin can attenuate EBI and deciphers its mechanism. A SAH rat model was established by intravascular perforation in vivo. At 6 h after SAH in rats, 10 mg/kg eupatilin was injected into the rats via the caudal vein. A Sham group was set as the control. In vitro, BV2 microglia was treated with 10 μM Oxyhemoglobin (OxyHb) for 24 h, followed by 50 μM eupatilin treatment for 24 h. The SAH grade, brain water content, neurological score, and blood-brain barrier (BBB) permeability of the rats were measured 24 h later. The content of proinflammatory factors was detected via enzyme-linked immunosorbent assay. Western blot analysis was conducted to analyze the expression levels of TLR4/MyD88/NF-κB pathway-associated proteins. In vivo, eupatilin administration alleviated neurological injury, and decreased brain edema and BBB injury after SAH in rats. Eupatilin markedly reduced the levels of interleukin-1β (IL-1β), IL-6, and tumor necrosis factor-α (TNF-α), and suppressed the expression levels of MyD88, TLR4, and p-NF-κB p65 in the SAH rats' cerebral tissues. Eupatilin treatment also reduced the levels of IL-1β, IL-6, and TNF-α, and repressed the expression levels of MyD88, TLR4, and p-NF-κB p65 in OxyHb-induced BV2 microglia. Additionally, pyrrolidine dithiocarbamate or resatorvid enhanced the suppressive effects of eupatilin on OxyHb-induced inflammatory responses in BV2 microglia. Eupatilin ameliorates SAH-induced EBI via modulating the TLR4/MyD88/NF-κB pathway in rat model.     

Hepcidin Treatment Modulates the Expression of Divalent Metal Transporter-1, Ceruloplasmin,and Ferroportin-1 in the Rat Cerebral Cortex and Hippocampus

Elevated iron levels are considered to play a role in the neurodegenerative mechanisms that underlie Alzheimer's and Parkinson's disease. The linkage between hepcidin (Hepc) and ferroportin-1 (FPN1), the divalent metal transporter 1 (DMT1), and ceruloplasmin (CP) in the brain is unknown. To discern the role of Hepc in regulating the expression of these proteins, we investigated FPN1, DMT1, and CP protein and mRNA expression in the brain after the intracerebroventricular injection of Hepc. Our results show that after Hepc injection, expression of FPN1 mRNA and FPN1 protein was inhibited in the cerebral cortex and hippocampus. Furthermore, we showed a clear change of DMT1 and CP protein and mRNA levels in the brain. The immunohistochemical analysis revealed an increase of DMT1 and a decrease of CP levels. Semi-quantitative analysis using PCR methods showed an increase of DMT1(+IRE) mRNA, and a decrease of DMT1(−IRE) mRNA and CP mRNA levels. Since alterations in iron levels in the brain are causally linked to degenerative conditions such as Alzheimer's disease, an improved understanding of the regulation of iron transport protein expression such as FPN1, DMT1, and CP could lead to novel strategies for treatments.     

Plasma hepcidin correlates positively with interleukin-6 in patients undergoing pulmonary endarterectomy

Hepcidin, a recently discovered antimicrobial peptide synthesized in the liver, was identified to be the key mediator of iron metabolism and distribution. Despite our knowledge of hepcidin increased in recent years, there are only limited data on hepcidin regulation during systemic inflammatory response in human subjects. In a prospective study, the time course of plasma hepcidin was analyzed in relations to six inflammatory parameters - plasma cytokines and acute-phase proteins in patients undergoing uncomplicated pulmonary endarterectomy. Twenty-four patients (males, aged 52.6+/-10.2 years, treated with pulmonary endarterectomy in a deep hypothermic circulatory arrest) were enrolled into study. Hepcidin, interleukin (IL)-6, IL-8, tumor necrosis factor-alpha, C-reactive protein, alpha(1)-antitrypsin and ceruloplasmin arterial concentrations were measured before surgery and repeatedly within 120 h post-operatively. Hemodynamic parameters, hematocrit and markers of iron metabolism were followed up. In a postoperative period, hepcidin increased from preoperative level 8.9 ng/ml (6.2-10.7) (median and interquartile range) to maximum 16.4 ng/ml (14.1-18.7) measured 72 h after the end of surgery. Maximum post-operative concentrations of hepcidin correlated positively with maximum IL-6 levels. Both hepcidin and IL-6 maximum concentrations correlated positively with extracorporeal circulation time. In conclusions, the study demonstrated that plasma hepcidin is a positive acute-phase reactant in relation to an uncomplicated large cardiac surgery. Hepcidin increase was related to IL-6 concentrations and to the duration of surgical procedure. Our clinical findings are in conformity with recent experimental studies defining hepcidin as a type II acute-phase protein.     

Decreased Serum Hepcidin Concentration Correlates with Brain Iron Deposition in Patients with HBV-Related Cirrhosis

Purpose

Excessive brain iron accumulation contributes to cognitive impairments in hepatitis B virus (HBV)-related cirrhotic patients. The underlying mechanism remains unclear. Hepcidin, a liver-produced, 25-aminoacid peptide, is the major regulator of systemic iron metabolism. Abnormal hepcidin level is a key factor in some body iron accumulation or deficiency disorders, especially in those associated with liver diseases. Our study was aimed to explore the relationship between brain iron content in patients with HBV-related cirrhosis and serum hepcidin level.

Methods

Seventy HBV-related cirrhotic patients and forty age- sex-matched healthy controls were enrolled. Brain iron content was quantified by susceptibility weighted phase imaging technique. Serum hepcidin as well as serum iron, serum transferrin, ferritin, soluble transferrin receptor, total iron binding capacity, and transferrin saturation were tested in thirty cirrhotic patients and nineteen healthy controls. Pearson correlation analysis was performed to investigate correlation between brain iron concentrations and serum hepcidin, or other iron parameters.

Results

Cirrhotic patients had increased brain iron accumulation compared to controls in the left red nuclear, the bilateral substantia nigra, the bilateral thalamus, the right caudate, and the right putamen. Cirrhotic patients had significantly decreased serum hepcidin concentration, as well as lower serum transferring level, lower total iron binding capacity and higher transferrin saturation, compared to controls. Serum hepcidin level negatively correlated with the iron content in the right caudate, while serum ferritin level positively correlated with the iron content in the bilateral putamen in cirrhotic patients.

Conclusions

Decreased serum hepcidin level correlated with excessive iron accumulation in the basal ganglia in HBV-related cirrhotic patients. Our results indicated that systemic iron overload underlined regional brain iron repletion. Serum hepcidin may be a clinical biomarker for brain iron deposition in cirrhotic patients, which may have therapeutic potential.     

Expression of the peptide hormone hepcidin increases in cardiomyocytes under myocarditis and myocardial infarction

The micronutrient iron is an essential component that plays a role in many crucial metabolic reactions. The peptide hormone hepcidin is thought to play a central role in iron homeostasis and its expression is induced by iron overloading and inflammation. Recently, hepcidin has been reported to be expressed also in the heart; however, the kinetics of altered hepcidin expression in diseases of the heart remain unknown. In this study, we examined cardiac expression of hepcidin in rat experimental autoimmune myocarditis (EAM), human myocarditis and rat acute myocardial infarction (AMI). In rat EAM and AMI hearts, hepcidin was expressed in cardiomyocytes; ferroportin, which is a cellular iron exporter bound by hepcidin, was also expressed in various cells. Analysis of the time course of the hepcidin to cytochrome oxidase subunit 6a (Cox6a)2 expression ratio showed that it abruptly increased more than 100-fold in hearts in the very early phase of EAM and in infarcted areas 1 day after MI. The hepcidin/Cox6a2 expression ratio correlated significantly with that of interleukin-6/γ-actin in both EAM and AMI hearts (r=0.781, P<.0001 and r=0.563, P=.0003). In human hearts with histological myocarditis, the ratio was significantly higher than in those without myocarditis (0.0400±0.0195 versus 0.0032±0.0017, P=.0045). Hepcidin is strongly induced in cardiomyocytes under myocarditis and MI, conditions in which inflammatory cytokine levels increase and may play an important role in iron homeostasis and free radical generation.     

Molecular analysis of increased iron status in moderately exercised rats

Although iron plays a critical role in exercise, the regulatory mechanism of iron metabolism remains poorly understood. The aims of the present study were to investigate the effects of different intensity exercise on body iron status and the regulatory mechanism of duodenal iron absorption. Thirty female Sprague-Dawley rats (90–100 g) were randomly divided into three groups: a control group (remained sedentary, CG), a moderately exercised group (swam 1.5 h/day, MG) and a strenuously exercised group (swam with different load, SG). Serum iron status, serum ferritin and Hct were examined after 10 weeks of swimming. Western blot was performed to detect the expression of iron transport proteins: divalent metal transporter1 (DMT1) and ferroportin 1 (FPN1) in duodenal epithelium. The expression of hepcidin mRNA in liver was examined by RT-PCR. The results showed: (1) the body iron status in MG was kept at a high level compared to that of CG and SG, (2) Western blot showed DMT1 with iron responsive element (IRE) and FPN1 in duodenal epithelium which were higher in MG than that of CG and (3) the expression of hepatic hepcidin mRNA was down regulated in MG (p < 0.05). The data suggested that moderate exercise improved iron status and that was likely regulated by increased DMT1 with IRE and FPN1 expression. Hepcidin signaling pathway may involve in the regulation of duodenal iron absorption proteins. Xiang Lin Duan and Yan Zhong Chang share Senior Authorship     

Exercise-Induced Changes in Iron Status and Hepcidin Response in Female Runners

Background and Aims

Exercise-induced iron deficiency is a common finding in endurance athletes. It has been suggested recently that hepcidin may be an important mediator in this process.

Objective

To determine hepcidin levels and markers of iron status during long-term exercise training in female runners with depleted and normal iron stores.

Methods

Fourteen runners were divided into two groups according to iron status. Blood samples were taken during a period of eight weeks at baseline, after training and after ten days’ recovery phase.

Results

Of 14 runners, 7 were iron deficient at baseline and 10 after training. Hepcidin was lower at recovery compared with baseline (p<0.05). The mean cell haemoglobin content, haemoglobin content per reticulocyte and total iron binding capacity all decreased, whereas soluble transferrin receptor and hypochromic red cells increased after training and recovery (p<0.05 for all).

Conclusion

The prevalence of depleted iron stores was 71% at the end of the training phase. Hepcidin and iron stores decreased during long-term running training and did not recover after ten days, regardless of baseline iron status.     

Molecular mechanisms of iron homeostasis

Iron metabolism in mammals requires a complex and tightly regulated molecular network. The classical view of iron metabolism has been challenged over the past ten years by the discovery of several new proteins, mostly Fe (II) iron transporters, enzymes with ferro-oxydase (hephaestin or ceruloplasmin) or ferri-reductase (Dcytb) activity or regulatory proteins like HFE and hepcidin. Furthermore, a new transferrin receptor has been identified, mostly expressed in the liver, and the ability of the megalin-cubilin complex to internalise the urinary Fe (III)-transferrin complex in renal tubular cells has been highlighted. Intestinal iron absorption by mature duodenal enterocytes requires Fe (III) iron reduction by Dcytb and Fe (II) iron transport through apical membranes by the iron transporter Nramp2/DMT1. This is followed by iron transfer to the baso-lateral side, export by ferroportin and oxidation into Fe (III) by hephaestin prior to binding to plasma transferrin. Macrophages play also an important role in iron delivery to plasma transferrin through phagocytosis of senescent red blood cell, heme catabolism and recycling of iron. Iron egress from macrophages is probably also mediated by ferroportin and patients with heterozygous ferroportin mutations develop progressive iron overload in liver macrophages. Iron homeostasis at the level of the organism is based on a tight control of intestinal iron absorption and efficient recycling of iron by macrophages. Signalling between iron stores in the liver and both duodenal enterocytes and macrophages is mediated by hepcidin, a circulating peptide synthesized by the liver and secreted into the plasma. Hepcidin expression is stimulated in response to iron overload or inflammation, and down regulated by anemia and hypoxia. Hepcidin deficiency leads to iron overload and hepcidin overexpression to anemia. Hepcidin synthesis in response to iron overload seems to be controlled by the HFE molecule. Patients with hereditary hemochromatosis due to HFE mutation have impaired hepcidin synthesis and forced expression of an hepcidin transgene in HFE deficient mice prevents iron overload. These results open new therapeutic perspectives, especially with the possibility to use hepcidin or antagonists for the treatment of iron overload disorders.     

Melatonin Attenuates Early Brain Injury via the Melatonin Receptor/Sirt1/NF-κB Signaling Pathway Following Subarachnoid Hemorrhage in Mice

Melatonin (Mel) has been reported to alleviate early brain injury (EBI) following subarachnoid hemorrhage (SAH). The activation of silent information regulator 1 (Sirt1), a histone deacetylase, has been suggested to be beneficial in SAH. However, the precise role of Sirt1 in Mel-mediated protection against EBI following SAH has not been elucidated. The present study aims to evaluate the role of melatonin receptor/Sirt1/nuclear factor-kappa B (NF-κB) in this process. The endovascular perforation SAH model was used in male C57BL/6J mice, and melatonin was administrated intraperitoneally (150 mg/kg). The mortality, SAH grade, neurological score, brain water content, and neuronal apoptosis were evaluated. The expression of Sirt1, acetylated-NF-κB (Ac-NF-κB), Bcl-2, and Bax were detected by western blot. To study the underlying mechanisms, melatonin receptor (MR) antagonist luzindole and Sirt1 small interfering RNA (siRNA) were administrated to different groups. The results suggest that Mel improved the neurological deficits and reduced the brain water content and neuronal apoptosis. In addition, Mel enhanced the expression of Sirt1 and Bcl-2 and decreased the expression of Ac-NF-κB and Bax. However, the protective effects of Mel were abolished by luzindole or Sirt1 siRNA. In conclusion, our results demonstrate that Mel attenuates EBI following SAH via the MR/Sirt1/NF-κB signaling pathway.