Network Pharmacology and Machine Learning Reveal Salidroside's Mechanisms in Idiopathic Pulmonary Fibrosis Treatment

Purpose

Idiopathic pulmonary fibrosis (IPF) is an irreversible respiratory disease. In this study, we evaluated the efficacy of salidroside (SAL), the main component of Rhodiola rosea, in treating IPF.

Methods

The pharmacological effects of SAL against epithelial-mesenchymal transition (EMT) and IPF were assessed through in vivo and in vitro experiments. Targets for SAL in treating IPF were identified from various databases and a PPI network was constructed. Functional analyses of target genes were performed using GO, KEGG, DO, and GSEA. Core target genes were identified using LASSO logistic regression and support vector machine (SVM) analysis, followed by molecular docking simulations. Predicted targets and pathways were validated through Western blotting, qRT-PCR, and IHC.

Results

Our results demonstrated that SAL ameliorated alveolar epithelial cells (AECs) EMT and mitigated bleomycin -induced pulmonary fibrosis. Through network pharmacology, we identified 74 targets for SAL in the treatment of IPF (PFDR<0.05) and analyzed their biological functions. Based on these findings, we further applied machine learning techniques to narrow down 9 core targets (PFDR<0.05). Integrating the results from molecular docking, KEGG, and GSEA analyses, we selected three key targets-IGF1, hypoxia-inducible factor 1-alpha (HIF-1α), and MAPK (PFDR<0.05)-for further investigation. Our study revealed that SAL inhibits the IGF1 signaling pathway, thereby improving AECs senescence and cell cycle arrest. By inhibiting the HIF-1α pathway, SAL alleviates endoplasmic reticulum stress and reduces intracellular ROS accumulation. Moreover, SAL suppresses the activation of the MAPK signaling pathway, leading to a decrease in inflammation markers in AECs and lung tissue.

Conclusion

Experimental results suggest that SAL effectively ameliorates BLM-induced EMT and IPF, likely through the inhibition of IGF1, HIF-1α, and MAPK signaling pathways. This study holds potential translational prospects and may provide new perspectives and insights for the use of traditional Chinese medicine in the treatment of IPF.

Iron homeostasis and post-hemorrhagic hydrocephalus: a review

Iron physiology is regulated by a complex interplay of extracellular transport systems, coordinated transcriptional responses, and iron efflux mechanisms. Dysregulation of iron metabolism can result in defects in myelination, neurotransmitter synthesis, and neuronal maturation. In neonates, germinal matrix-intraventricular hemorrhage (GMH-IVH) causes iron overload as a result of blood breakdown in the ventricles and brain parenchyma which can lead to post-hemorrhagic hydrocephalus (PHH). However, the precise mechanisms by which GMH-IVH results in PHH remain elusive. Understanding the molecular determinants of iron homeostasis in the developing brain may lead to improved therapies. This manuscript reviews the various roles iron has in brain development, characterizes our understanding of iron transport in the developing brain, and describes potential mechanisms by which iron overload may cause PHH and brain injury. We also review novel preclinical treatments for IVH that specifically target iron. Understanding iron handling within the brain and central nervous system may provide a basis for preventative, targeted treatments for iron-mediated pathogenesis of GMH-IVH and PHH.

Advances in Ferritin Physiology and Possible Implications in Bacterial Infection

Due to its advantageous redox properties, iron plays an important role in the metabolism of nearly all life. However, these properties are not only a boon but also the bane of such life forms. Since labile iron results in the generation of reactive oxygen species by Fenton chemistry, iron is stored in a relatively safe form inside of ferritin. Despite the fact that the iron storage protein ferritin has been extensively researched, many of its physiological functions are hitherto unresolved. However, research regarding ferritin's functions is gaining momentum. For example, recent major discoveries on its secretion and distribution mechanisms have been made as well as the paradigm-changing finding of intracellular compartmentalization of ferritin via interaction with nuclear receptor coactivator 4 (NCOA4). In this review, we discuss established knowledge as well as these new findings and the implications they may have for host-pathogen interaction during bacterial infection.

Iron as a therapeutic target in chronic liver disease

It was clearly realized more than 50 years ago that iron deposition in the liver may be a critical factor in the development and progression of liver disease. The recent clarification of ferroptosis as a specific form of regulated hepatocyte death different from apoptosis and the description of ferritinophagy as a specific variation of autophagy prompted detailed investigations on the association of iron and the liver. In this review, we will present a brief discussion of iron absorption and handling by the liver with emphasis on the role of liver macrophages and the significance of the iron regulators hepcidin, transferrin, and ferritin in iron homeostasis. The regulation of ferroptosis by endogenous and exogenous mod-ulators will be examined. Furthermore, the involvement of iron and ferroptosis in various liver diseases including alcoholic and non-alcoholic liver disease, chronic hepatitis B and C, liver fibrosis, and hepatocellular carcinoma (HCC) will be analyzed. Finally, experimental and clinical results following interventions to reduce iron deposition and the promising manipulation of ferroptosis will be presented. Most liver diseases will be benefited by ferroptosis inhibition using exogenous inhibitors with the notable exception of HCC, where induction of ferroptosis is the desired effect. Current evidence mostly stems from in vitro and in vivo experimental studies and the need for well-designed future clinical trials is warranted.

Research on the relationship between serum indoxyl sulfate concentration and iron dynamics index in patients with end-stage kidney disease: a cross-sectional study

Background

Chronic kidney disease (CKD) is frequently associated with renal anemia. Erythropoiesis-stimulating agent-hyporesponsive anemia is often caused by iron deficiency in patients with CKD. We hypothesized that high accumulation of indoxyl sulfate, a uremic toxin, accelerates iron deficiency in patients with CKD. The aim of this study was to clarify whether the accumulation of indoxyl sulfate is a cause of iron deficiency in patients with CKD. Therefore, we investigated the association between serum indoxyl sulfate concentration and iron dynamics in patients with end-stage kidney disease (ESKD).

Methods

We performed a cross-sectional study on 37 non-dialyzed patients with ESKD, who were hospitalized to undergo maintenance hemodialysis treatment at Shirasagi Hospital. Serum indoxyl sulfate concentration, iron dynamics parameters and other laboratory data were measured immediately before the initiation of hemodialysis treatment. Clinical characteristics were obtained from electronic medical records.

Results

The estimated glomerular filtration rate (eGFR) of 37 patients with ESKD was 5.08 (3.78–7.97) mL/min/1.73 m2 (median [range]). Serum ferritin and transferrin saturation (TSAT) were 90 (10–419) ng/mL and 20 (8–59)% (median [range]), respectively. Serum indoxyl sulfate concentration was 62 (11–182) μM (median [range]). Serum indoxyl sulfate concentration was inversely correlated with serum ferritin level (ρ = − 0.422, p = 0.011), but not with TSAT, age, gender, eGFR and c-reactive protein (CRP) in 37 patients. In eight patients taking iron-containing agents, serum indoxyl sulfate concentration was strongly correlated with serum ferritin level (ρ = − 0.796, p = 0.037); however, in 29 patients not taking an iron-containing agent, this correlation was not observed (ρ = − 0.336, p = 0.076). In the multivariate analysis including age, gender, eGFR and CRP, the correlation between serum indoxyl sulfate concentration tended to be, but not significantly correlated with serum ferritin level in 37 patients (regression coefficient = − 54.343, p = 0.137).

Conclusion

Our study suggests that serum accumulation of indoxyl sulfate is one of causes not to increase serum ferritin level in patients with ESKD taking an iron-containing agent. Further clinical study is needed to reveal the appreciable relationship between serum ferritin and serum indoxyl sulfate.

Hypoxia Enhances HIF1α Transcription Activity by Upregulating KDM4A and Mediating H3K9me3, Thus Inducing Ferroptosis Resistance in Cervical Cancer Cells

Objective

Cervical cancer (CC) is a prevalent cancer in women. Hypoxia plays a critical role in CC cell ferroptosis resistance. This study explored the mechanism of hypoxia in CC cell ferroptosis resistance by regulating HIF1α/KDM4A/H3K9me3.

Methods

Cultured SiHa and Hela cells were exposed to CoCl2 and treated with Erastin. Cell viability was detected by MTT assay, and concentrations of iron ion, MDA and GSH were determined using corresponding kits. Expressions of KDM4A, HIF1α, TfR1, DMT1, and H3k9me3 were detected by RT-qPCR, Western blot, and ChIP assay. The correlation of KDM4A and HIF1α was analyzed on Oncomine, UALCAN, and Starbase. CC cells were co-transfected with shKDM4A or/and pcDNA3.1-HIF1α. Iron uptake and release were assessed using the isotopic tracer method. The binding relationship between HIF1α and HRE sequence was verified by dual-luciferase assay.

Results

Cell viability and GSH were decreased while iron concentration, MDA, KDM4A, and HIF1α levels were increased in hypoxia conditions. The 2-h hypoxia induced ferroptosis resistance. KDM4A and HIF1α were highly-expressed in CC tissues and positively correlated with each other. KDM4A knockdown attenuated cell resistance to Erastin, increased H3K9me3 level in the HIF1α promoter region, and downregulated HIF1α transcription and translation. H3K9me3 level was increased in the HIF1α promoter after hypoxia. HIF1α overexpression abrogated the function of KDM4A knockdown on ferroptosis in hypoxia conditions. Iron uptake/release and TfR1/DMT1 levels were increased after hypoxia. Hypoxia activated HRE sequence in TfR1 and DMT1 promoters.

Conclusion

Hypoxia upregulated KDM4A, enhanced HIF1α transcription, and activated HRE sequence in TfR1 and DMT1 promoters via H3K9me3, thus inducing ferroptosis resistance in CC cells.

CXCL1: Gene, Promoter, Regulation of Expression, mRNA Stability, Regulation of Activity in the Intercellular Space

CXCL1 is one of the most important chemokines, part of a group of chemotactic cytokines involved in the development of many inflammatory diseases. It activates CXCR2 and, at high levels, CXCR1. The expression of CXCL1 is elevated in inflammatory reactions and also has important functions in physiology, including the induction of angiogenesis and recruitment of neutrophils. Due to a lack of reviews that precisely describe the regulation of CXCL1 expression and function, in this paper, we present the mechanisms of CXCL1 expression regulation with a special focus on cancer. We concentrate on the regulation of CXCL1 expression through the regulation of CXCL1 transcription and mRNA stability, including the involvement of NF-κB, p53, the effect of miRNAs and cytokines such as IFN-γ, IL-1β, IL-17, TGF-β and TNF-α. We also describe the mechanisms regulating CXCL1 activity in the extracellular space, including proteolytic processing, CXCL1 dimerization and the influence of the ACKR1/DARC receptor on CXCL1 localization. Finally, we explain the role of CXCL1 in cancer and possible therapeutic approaches directed against this chemokine.

The pyruvate kinase activator mitapivat reduces hemolysis and improves anemia in a β-thalassemia mouse model

Anemia in β-thalassemia is related to ineffective erythropoiesis and reduced red cell survival. Excess free heme and accumulation of unpaired α-globin chains impose substantial oxidative stress on β-thalassemic erythroblasts and erythrocytes, impacting cell metabolism. We hypothesized that increased pyruvate kinase activity induced by mitapivat (AG-348) in the Hbbth3/+ mouse model for β-thalassemia would reduce chronic hemolysis and ineffective erythropoiesis through stimulation of red cell glycolytic metabolism. Oral mitapivat administration ameliorated ineffective erythropoiesis and anemia in Hbbth3/+ mice. Increased ATP, reduced reactive oxygen species production, and reduced markers of mitochondrial dysfunction associated with improved mitochondrial clearance suggested enhanced metabolism following mitapivat administration in β-thalassemia. The amelioration of responsiveness to erythropoietin resulted in reduced soluble erythroferrone, increased liver Hamp expression, and diminished liver iron overload. Mitapivat reduced duodenal Dmt1 expression potentially by activating the pyruvate kinase M2-HIF2α axis, representing a mechanism additional to Hamp in controlling iron absorption and preventing β-thalassemia-related liver iron overload. In ex vivo studies on erythroid precursors from patients with β-thalassemia, mitapivat enhanced erythropoiesis, promoted erythroid maturation, and decreased apoptosis. Overall, pyruvate kinase activation as a treatment modality for β-thalassemia in preclinical model systems had multiple beneficial effects in the erythropoietic compartment and beyond, providing a strong scientific basis for further clinical trials.

FLCN regulates transferrin receptor 1 transport and iron homeostasis

Birt–Hogg–Dubé (BHD) syndrome is a multiorgan disorder caused by inactivation of the folliculin (FLCN) protein. Previously, we identified FLCN as a binding protein of Rab11A, a key regulator of the endocytic recycling pathway. This finding implies that the abnormal localization of specific proteins whose transport requires the FLCN-Rab11A complex may contribute to BHD. Here, we used human kidney-derived HEK293 cells as a model, and we report that FLCN promotes the binding of Rab11A with transferrin receptor 1 (TfR1), which is required for iron uptake through continuous trafficking between the cell surface and the cytoplasm. Loss of FLCN attenuated the Rab11A–TfR1 interaction, resulting in delayed recycling transport of TfR1. This delay caused an iron deficiency condition that induced hypoxia-inducible factor (HIF) activity, which was reversed by iron supplementation. In a Drosophila model of BHD syndrome, we further demonstrated that the phenotype of BHD mutant larvae was substantially rescued by an iron-rich diet. These findings reveal a conserved function of FLCN in iron metabolism and may help to elucidate the mechanisms driving BHD syndrome.

DMT1 Expression and Iron Levels at the Crossroads Between Aging and Neurodegeneration

Iron homeostasis is an essential prerequisite for metabolic and neurological functions throughout the healthy human life, with a dynamic interplay between intracellular and systemic iron metabolism. The development of different neurodegenerative diseases is associated with alterations of the intracellular transport of iron and heavy metals, principally mediated by Divalent Metal Transporter 1 (DMT1), responsible for Non-Transferrin Bound Iron transport (NTBI). In addition, DMT1 regulation and its compartmentalization in specific brain regions play important roles during aging. This review highlights the contribution of DMT1 to the physiological exchange and distribution of body iron and heavy metals during aging and neurodegenerative diseases. DMT1 also mediates the crosstalk between central nervous system and peripheral tissues, by systemic diffusion through the Blood Brain Barrier (BBB), with the involvement of peripheral iron homeostasis in association with inflammation. In conclusion, a survey about the role of DMT1 and iron will illustrate the complex panel of interrelationship with aging, neurodegeneration and neuroinflammation.

Hypoxia induces copper stable isotope fractionation in hepatocellular carcinoma, in a HIF-independent manner

Hepatocellular carcinoma (HCC) is the most frequent type of primary liver cancer, with increasing incidence worldwide. The unrestrained proliferation of tumour cells leads to tumour hypoxia which in turn promotes cancer aggressiveness. While changes in the concentration of copper (Cu) have long been observed upon cancerization, we have recently reported that the isotopic composition of copper is also altered in several types of cancer. In particular, we showed that in hepatocellular carcinoma, tumour tissue contains heavier copper compared to the surrounding parenchyma. However, the reasons behind such isotopic signature remained elusive. Here we show that hypoxia causes heavy copper enrichment in several human cell lines. We also demonstrate that this effect of hypoxia is pH, HIF-1 and -2 independent. Our data identify a previously unrecognized cellular process associated with hypoxia, and suggests that in vivo tumour hypoxia determines copper isotope fractionation in HCC and other solid cancers.

The mechanisms of systemic iron homeostasis and etiology, diagnosis, and treatment of hereditary hemochromatosis

Hereditary hemochromatosis (HH) is a group of genetic iron overload disorders that manifest with various symptoms, including hepatic dysfunction, diabetes, and cardiomyopathy. Classic HH type 1, which is common in Caucasians, is caused by bi-allelic mutations of HFE. Severe types of HH are caused by either bi-allelic mutations of HFE2 that encodes hemojuvelin (type 2A) or HAMP that encodes hepcidin (type 2B). HH type 3, which is of intermediate severity, is caused by bi-allelic mutations of TFR2 that encodes transferrin receptor 2. Mutations of SLC40A1 that encodes ferroportin, the only cellular iron exporter, causes either HH type 4A (loss-of-function mutations) or HH type 4B (gain-of-function mutations). Studies on these gene products uncovered a part of the mechanisms of the systemic iron regulation; HFE, hemojuvelin, and TFR2 are involved in iron sensing and stimulating hepcidin expression, and hepcidin downregulates the expression of ferroportin of the target cells. Phlebotomy is the standard treatment for HH, and early initiation of the treatment is essential for preventing irreversible organ damage. However, because of the rarity and difficulty in making the genetic diagnosis, a large proportion of patients with non-HFE HH might have been undiagnosed; therefore, awareness of this disorder is important.

A universal fluorogenic switch for Fe(ii) ion based on N-oxide chemistry permits the visualization of intracellular redox equilibrium shift towards labile iron in hypoxic tumor cells

Iron (Fe) species play a number of biologically and pathologically important roles. In particular, iron is a key element in oxygen sensing in living tissue where its metabolism is intimately linked with oxygen metabolism. Regulation of redox balance of labile iron species to prevent the generation of iron-catalyzed reactive oxygen species (ROS) is critical to survival. However, studies on the redox homeostasis of iron species are challenging because of a lack of a redox-state-specific detection method for iron, in particular, labile Fe2+. In this study, a universal fluorogenic switching system is established, which is responsive to Fe2+ ion based on a unique N-oxide chemistry in which dialkylarylamine N-oxide is selectively deoxygenized by Fe2+ to generate various fluorescent probes of Fe2+-CoNox-1 (blue), FluNox-1 (green), and SiRhoNox-1 (red). All the probes exhibited fluorescence enhancement against Fe2+ with high selectivity both in cuvette and in living cells. Among the probes, SiRhoNox-1 showed an excellent fluorescence response with respect to both reaction rate and off/on signal contrast. Imaging studies were performed showing the intracellular redox equilibrium shift towards labile iron in response to reduced oxygen tension in living cells and 3D tumor spheroids using SiRhoNox-1, and it was found that the hypoxia induction of labile Fe2+ is independent of iron uptake, hypoxia-induced signaling, and hypoxia-activated enzymes. The present studies demonstrate the feasibility of developing sensitive and specific fluorescent probes for Fe2+ with refined photophysical characteristics that enable their broad application in the study of iron in various physiological and pathological conditions.

Ferrous Iron Up-regulation in Fibroblasts of Patients with Beta Propeller Protein-Associated Neurodegeneration (BPAN)

Mutations in WDR45 gene, coding for a beta-propeller protein, have been found in patients affected by Neurodegeneration with Brain Iron Accumulation, NBIA5 (also known as BPAN). BPAN is a movement disorder with Non Transferrin Bound Iron (NTBI) accumulation in the basal ganglia as common hallmark between NBIA classes (Hayflick et al., 2013). WDR45 has been predicted to have a role in autophagy, while the impairment of iron metabolism in the different NBIA subclasses has not currently been clarified. We found the up-regulation of the ferrous iron transporter (-)IRE/Divalent Metal Transporter1 and down-regulation of Transferrin receptor in the fibroblasts of two BPAN affected patients with splicing mutations 235+1G>A (BPAN1) and 517_519ΔVal 173 (BPAN2). The BPAN patients showed a concomitant increase of intracellular ferrous iron after starvation. An altered pattern of iron transporters with iron overload is highlighted in BPAN human fibroblasts, supporting for a role of DMT1 in NBIA. We here present a novel element, about iron accumulation, to the existing knowledge in field of NBIA. Attention is focused to a starvation-dependent iron overload, possibly accounting for iron accumulation in the basal ganglia. Further investigation could clarify iron regulation in BPAN.

Brusatol inhibits HIF-1 signaling pathway and suppresses glucose uptake under hypoxic conditions in HCT116 cells

Hypoxia-inducible factor-1 (HIF-1) is an important transcription factor that induces adaptive responses upon low oxygen conditions in human cancers and triggers off a poor prognostic outcome of conventional treatments. In this study, we discovered for the first time that brusatol (BRU), a quassinoid extracted from Brucea Esters, has the capability to inhibit HIF-1 signaling pathway. We found that BRU concentration-dependently down-regulated HIF-1α protein levels under hypoxia or CoCl₂-induced mimic hypoxia in HCT116 cells without causing significant cytotoxicity. Besides, the transactivation activity of HIF-1 was suppressed by BRU under hypoxic conditions, as well as the expression of HIF-1 target genes, including VEGF, GLUT1, HK2 and LDHA. In addition, BRU can also decrease glucose consumption under hypoxia through inhibition of HIF-1 signaling pathway. Further studies revealed that the inhibitory effect of BRU on HIF-1 signaling pathway might be attributed to promoting degradation of HIF-1α. Interestingly, intracellular reactive oxygen species (ROS) levels and mitochondrial ROS level were both decreased by BRU treatment, indicating the involvment of mitochondrial ROS regulation in the action of BRU. Taken together, these results provided clear evidence for BRU-mediated HIF-1α regulation and suggested its therapeutic potential in colon tumors.

Iron Regulatory Protein 1 Suppresses Hypoxia-Induced Iron Uptake Proteins Expression and Decreases Iron Levels in HepG2 Cells

Transferrin receptor (TfR1) and divalent metal transporter 1 (DMT1) are important proteins for cellular iron uptake, and both are regulated transcriptionally through the binding of hypoxia-inducible factor 1 (HIF-1) to hypoxia-responsive elements (HREs) under hypoxic conditions. These proteins are also regulated post-transcriptionally through the binding of iron regulatory protein 1 (IRP1) to iron-responsive elements (IREs) located in the mRNA untranslated region (UTR) to control cellular iron homeostasis. In iron-deficient cells, IRP1-IRE interactions stabilize TfR1 and DMT1 mRNAs, enhancing iron uptake. However, little is known about the impact of IRP1 on the regulation of cellular iron homeostasis under hypoxia. Thus, to investigate the role of IRP1 in hypoxic condition, overexpression and knockdown assays were performed using HepG2 cells. The overexpression of IRP1 suppressed the hypoxia-induced increase in TfR1 and DMT1 (+IRE) expression and reduced the stability of TfR1 and DMT1 (+IRE) mRNAs under hypoxia, whereas IRP1 knockdown further increased the hypoxia-induced expression of both proteins, preventing the decrease in IRE-dependent luciferase activity induced by hypoxia. Under hypoxic conditions, ferrous iron uptake, the labile iron pool (LIP), and total intracellular iron reduced when IRP1 was overexpressed and further increased when IRP1 was knocked down. IRP1 expression declined and TfR1/DMT1 (+IRE) expression increased with the time of hypoxia prolonged, whereas the binding of IRP1 to the IRE of TfR1/DMT1 mRNA maintained. In summary, IRP1 suppressed TfR1/DMT1 (+IRE) expression, limited the cellular iron content and decreased lactate dehydrogenase (LDH) release induced by hypoxia.

Iron entry in neurons and astrocytes: a link with synaptic activity

Iron plays a fundamental role in the development of the central nervous system (CNS) as well as in several neuronal functions including synaptic plasticity. Accordingly, neuronal iron supply is tightly controlled: it depends not only on transferrin-bound iron but also on non-transferrin-bound iron (NTBI), which represents a relevant quote of the iron physiologically present in the cerebrospinal fluid (CSF). Different calcium permeable channels as well as the divalent metal transporter 1 (DMT1) have been proposed to sustain NTBI entry in neurons and astrocytes even though it remains an open issue. In both cases, it emerges that the control of iron entry is tightly linked to synaptic activity. The iron-induced oxidative tone can, in physiological conditions, positively influence the calcium levels and thus the synaptic plasticity. On the other hand, an excess of iron, with the ensuing uncontrolled production of reactive oxygen species (ROS), is detrimental for neuronal survival. A protective mechanism can be played by astrocytes that, more resistant to oxidative stress, can uptake iron, thereby buffering its concentration in the synaptic environment. This competence is potentiated when astrocytes undergo activation during neuroinflammation and neurodegenerative processes. In this minireview we focus on the mechanisms responsible for NTBI entry in neurons and astrocytes and on how they can be modulated during synaptic activity. Finally, we speculate on the relevance they may have in both physiological and pathological conditions.

α-tocopherol supplementation prevents lead acetate and hypoxia-induced hepatic dysfunction

OBJECTIVE

Lead (Pb) is a long-known poison of environment and industrial origin. Its prolonged exposure affects cellular material and alters cellular genetics and produces oxidative damages. In this study, we investigated the exposure of chronic sustained hypoxia or lead acetate alone or in combination with or without supplementation of α-tocopherol on hepatic oxidative and nitrosative stress in rats.

MATERIALS AND METHODS

The rats weighing 165 ± 5 g were exposed to chronic sustained hypoxia (10% oxygen) or lead acetate (25 mg/kg of body weight, intraperitoneally) alone or in combination with or without supplementation of α-tocopherol (10 mg/100 g b.wt, intramuscularly). The body weight of all the rats was recorded on the day 1 of the treatment and the day of sacrifice. Serum lipid profile was estimated by using a biochemical analyzer. Oxidant and enzymatic antioxidants status was evaluated by using spectrophotometer. Serum levels of hypoxia inducible factor-1 alpha (HIF-1α) and vascular endothelial growth factor (VEGF) were measured by using ELISA technique. Histopathological assessments of hepatic tissue were also done.

RESULTS

Exposure of both lead and hypoxia showed decreased body weight, altered serum lipid profile, oxidant and enzymatic antioxidants status, serum HIF-1α and VEGF concentrations. Simultaneous α-tocopherol supplementation showed beneficial effects to all these alterations. Histopathological observations also showed hepatic degenerative changes after lead or hypoxia exposure either alone or in combination, but remarkable improvement has been noticed after α-tocopherol supplementation.

CONCLUSION

Supplementation of α-tocopherol is beneficial to counter both lead acetate and hypoxia induced hepatic cytotoxicities possibly by reducing oxidative and nitrosative stress.

Effects of iron oxide nanoparticles: cytotoxicity, genotoxicity, developmental toxicity, and neurotoxicity

Iron oxide nanoparticles (ION) with superparamagnetic properties hold great promise for use in various biomedical applications; specific examples include use as contrast agents for magnetic resonance imaging, in targeted drug delivery, and for induced hyperthermia cancer treatments. Increasing potential applications raise concerns over their potential effects on human health. Nevertheless, very little is currently known about the toxicity associated with exposure to these nanoparticles at different levels of biological organization. This article provides an overview of recent studies evaluating ION cytotoxicity, genotoxicity, developmental toxicity and neurotoxicity. Although the results of these studies are sometimes controversial, they generally indicate that surface coatings and particle size seem to be crucial for the observed ION-induced effects, as they are critical determinants of cellular responses and intensity of effects, and influence potential mechanisms of toxicity. The studies also suggest that some ION are safe for certain biomedical applications, while other uses need to be considered more carefully. Overall, the available studies provide insufficient evidence to fully assess the potential risks for human health related to ION exposure. Additional research in this area is required including studies on potential long-term effects.

Quercetin attenuates chronic ethanol hepatotoxicity: implication of "free" iron uptake and release

Emerging evidence has displayed that oxygen free radicals especially ones promoted by "free" iron play an important role in the development of alcoholic liver disease (ALD). Naturally-occurring quercetin has been reported to prevent ALD and iron overload-induced damage aside from the "free" iron. The purpose was to explore the potential mechanisms by which quercetin arrests alcohol-induced "free" iron disorder. Chronic alcohol (30% of total calories) or iron (0.2%)-fed adult male C57BL/J mice for 15 weeks resulted in significantly elevated levels of hepatic iron, labile iron pool-Fe and serum non-transferrin bound iron, accompanied with sustained oxidative damage. The hepatotoxicity was further exacerbated by ethanol and iron. Quercetin (100 mg/kg. body weight) alleviated the detrimental effects induced by ethanol and/or iron. The expressions of divalent metal transporter 1, zinc transporter member 14, mucolipin 1, transferrin receptor 1 (TfR1) and ferritin were up-regulated by ethanol and/or iron, which were partially normalized by quercetin. Quercetin prevented ethanol-induced hepatotoxicity, which may be partially attributed to the alleviated disorder of bound iron and "free" iron. The significant suppression of ethanol-stimulated molecules for "free" iron uptake and release may contribute to the hepatoprotective effect of quercetin, although TfR1-mediated physiological pathway of iron uptake also played a role.

Retinal iron homeostasis in health and disease

Iron is essential for life, but excess iron can be toxic. As a potent free radical creator, iron generates hydroxyl radicals leading to significant oxidative stress. Since iron is not excreted from the body, it accumulates with age in tissues, including the retina, predisposing to age-related oxidative insult. Both hereditary and acquired retinal diseases are associated with increased iron levels. For example, retinal degenerations have been found in hereditary iron overload disorders, like aceruloplasminemia, Friedreich's ataxia, and pantothenate kinase-associated neurodegeneration. Similarly, mice with targeted mutation of the iron exporter ceruloplasmin and its homolog hephaestin showed age-related retinal iron accumulation and retinal degeneration with features resembling human age-related macular degeneration (AMD). Post mortem AMD eyes have increased levels of iron in retina compared to age-matched healthy donors. Iron accumulation in AMD is likely to result, in part, from inflammation, hypoxia, and oxidative stress, all of which can cause iron dysregulation. Fortunately, it has been demonstrated by in vitro and in vivo studies that iron in the retinal pigment epithelium (RPE) and retina is chelatable. Iron chelation protects photoreceptors and retinal pigment epithelial cells (RPE) in a variety of mouse models. This has therapeutic potential for diminishing iron-induced oxidative damage to prevent or treat AMD.

Manganese homeostasis and transport

The review addresses issues pertinent to Mn accumulation and its mechanisms of transport, its neurotoxicity and mechanisms of neurodegeneration. The role of mitochondria and glia in this process is emphasized. We also discuss gene x environment interactions, focusing on the interplay between genes linked to Parkinson's disease (PD) and sensitivity to Mn.

1B/(-)IRE DMT1 expression during brain ischemia contributes to cell death mediated by NF-κB/RelA acetylation at Lys310

The molecular mechanisms responsible for increasing iron and neurodegeneration in brain ischemia are an interesting area of research which could open new therapeutic approaches. Previous evidence has shown that activation of nuclear factor kappa B (NF-κB) through RelA acetylation on Lys310 is the prerequisite for p50/RelA-mediated apoptosis in cellular and animal models of brain ischemia. We hypothesized that the increase of iron through a NF-κB-regulated 1B isoform of the divalent metal transporter-1 (1B/DMT1) might contribute to post-ischemic neuronal damage. Both in mice subjected to transient middle cerebral artery occlusion (MCAO) and in neuronally differentiated SK-N-SH cells exposed to oxygen-glucose-deprivation (OGD), 1A/DMT1 was only barely expressed while the 1B/DMT1 without iron-response-element (−IRE) protein and mRNA were early up-regulated. Either OGD or over-expression of 1B/(−)IRE DMT1 isoform significantly increased iron uptake, as detected by total reflection X-ray fluorescence, and iron-dependent cell death. Iron chelation by deferoxamine treatment or (−)IRE DMT1 RNA silencing displayed significant neuroprotection against OGD which concomitantly decreased intracellular iron levels. We found evidence that 1B/(−)IRE DMT1 was a target gene for RelA activation and acetylation on Lys310 residue during ischemia. Chromatin immunoprecipitation analysis of the 1B/DMT1 promoter showed there was increased interaction with RelA and acetylation of H3 histone during OGD exposure of cortical neurons. Over-expression of wild-type RelA increased 1B/DMT1 promoter-luciferase activity, the (−)IRE DMT1 protein, as well as neuronal death. Expression of the acetylation-resistant RelA-K310R construct, which carried a mutation from lysine 310 to arginine, but not the acetyl-mimic mutant RelA-K310Q, down-regulated the 1B/DMT1 promoter, consequently offering neuroprotection. Our data showed that 1B/(−)IRE DMT1 expression and intracellular iron influx are early downstream responses to NF-κB/RelA activation and acetylation during brain ischemia and contribute to the pathogenesis of stroke-induced neuronal damage.

Expression of divalent metal transporter 1 in primary hippocampal neurons: reconsidering its role in non-transferrin-bound iron influx

The divalent metal transporter 1 (DMT1) is the best characterized Fe²⁺ transporter involved in cellular iron uptake in mammals. Four possible isoforms have been identified as a result of alternative promoter (DMT1-1A and DMT1-1B) and alternative splicing involving the C-terminus and producing transcripts with or without an iron responsive element [DMT1-IRE⁺ and DMT1-IRE⁻, respectively]. Despite the general importance of DMT1 in controlling iron homeostasis, the distribution and the role of the transporter in the CNS is still controversial. In this study, we characterize the expression of DMT1 in hippocampal neurons and astrocytes. We found that the main isoform endogenously expressed is DMT1-1B/IRE⁺, which shows cytoplasmic distribution, colocalization with late endosome/lysosome markers and iron regulation, as expected from the presence of an iron responsive element. Our results also show that DMT1-1B/IRE⁺ isoform does not sustain iron entry, even after its neuronal over-expression. Overall, our results argue against a physiological role of the endogenous DMT1 in neuronal iron uptake but do not exclude that, under pathological conditions, the expression of other DMT1 isoforms might contribute to iron overload.

Effect of hypoxia on the expression of iron regulatory proteins 1 and the mechanisms involved

Iron is essential for many biological processes, including oxygen delivery, and its supply is tightly regulated. Iron regulatory proteins (IRPs, IRP1 and IRP2) are master regulators of cellular iron metabolism. Hypoxia triggers a broad range of gene responses that are primarily mediated by hypoxia-inducible factor-1 (HIF-1). In this study, we have shown that hypoxia could not only upregulate the expression of hypoxia inducible factor-1 but also downregulate the expression of IRP1. However, the molecular mechanisms that govern the IRP1 response to hypoxia are not known. Herein we suggested that HIF/HRE system was an essential link between IRP1 and hypoxia. The HRE of IRP1 5'-regulation regions could combine with HIF-1 in vitro. Dual-luciferase reporter assay showed that IRP1 was directly downregulated by HIF/HRE system.

Iron and mechanisms of neurotoxicity

The accumulation of transition metals (e.g., copper, zinc, and iron) and the dysregulation of their metabolism are a hallmark in the pathogenesis of several neurodegenerative diseases. This paper will be focused on the mechanism of neurotoxicity mediated by iron. This metal progressively accumulates in the brain both during normal aging and neurodegenerative processes. High iron concentrations in the brain have been consistently observed in Alzheimer's (AD) and Parkinson's (PD) diseases. In this connection, metalloneurobiology has become extremely important in establishing the role of iron in the onset and progression of neurodegenerative diseases. Neurons have developed several protective mechanisms against oxidative stress, among them, the activation of cellular signaling pathways. The final response will depend on the identity, intensity, and persistence of the oxidative insult. The characterization of the mechanisms mediating the effects of iron-induced increase in neuronal dysfunction and death is central to understanding the pathology of a number of neurodegenerative disorders.