Potent Iron Chelator Research Articles

Targeting the Metastasis Suppressor, NDRG1, Using Novel Iron Chelators: Regulation of Stress Fiber-Mediated Tumor Cell Migration via Modulation of the ROCK1/pMLC2 Signaling Pathway

The iron-regulated metastasis suppressor, N-myc downstream-regulated gene 1 (NDRG1), is up-regulated by cellular iron depletion mediated by iron chelators and can inhibit cancer cell migration. However, the mechanism of how NDRG1 achieves this effect remains unclear. In this study, we implemented established and newly constructed NDRG1 overexpression and knockdown models using the DU145, HT29, and HCT116 cancer cell lines to investigate the molecular basis by which NDRG1 exerts its inhibitory effect on cell migration. Using these models, we demonstrated that NDRG1 overexpression inhibits cell migration by preventing actin-filament polymerization, stress fiber assembly and formation. In contrast, NDRG1 knockdown had the opposite effect. Moreover, we identified that NDRG1 inhibited an important regulatory pathway mediated by the Rho-associated, coiled-coil containing protein kinase 1 (ROCK1)/phosphorylated myosin light chain 2 (pMLC2) pathway that modulates stress fiber assembly. The phosphorylation of MLC2 is a key process in inducing stress fiber contraction, and this was shown to be markedly decreased or increased by NDRG1 overexpression or knockdown, respectively. The mechanism involved in the inhibition of MLC2 phosphorylation by NDRG1 was mediated by a significant (P < 0.001) decrease in ROCK1 expression that is a key kinase involved in MLC2 phosphorylation. Considering that NDRG1 is up-regulated after cellular iron depletion, novel thiosemicarbazone iron chelators (e.g., di-2-pyridylketone 4,4-dimethyl-3-thiosemicarbazone) were demonstrated to inhibit ROCK1/pMLC2-modulated actin-filament polymerization, stress fiber assembly, and formation via a mechanism involving NDRG1. These results highlight the role of the ROCK1/pMLC2 pathway in the NDRG1-mediated antimetastatic signaling network and the therapeutic potential of iron chelators at inhibiting metastasis.

Human apo-lactoferrin as a physiological mimetic of hypoxia stabilizes hypoxia-inducible factor-1 alpha

Apo-form of human lactoferrin (LF) is a potent iron chelator, this feature being similar to the iron-binding properties of a synthetic chelator desferoxamine (DFO). The latter stabilizes the principal adaptive transcriptional hypoxia-inducible factor-1 alpha (HIF-1α). Since DFO is known as a pharmacological mimetic of hypoxia it was decided to test whether apo-LF is able to perform as such. Mice either injected intraperitoneally or given per os apo-LF displayed HIF-1α in liver, lungs, heart, brain, spleen and kidneys, as judged by results of Western blotting. Similar administration of iron-saturated LF (75 mg/kg) did not bring forth such effect. Synthesis of erythropoietin and ceruloplasmin became increased in the first case, which is explained by the respective genes being targets for HIF-1α. Apo-LF, but not Fe-LF, injected intraperitoneally to hypoxia low-resistant mice 24 h before animals were subjected to normobaric hypoxia with hypercapnia caused a significant increase of life-time by 40 %. The results obtained show that, like DFO, apo-LF performs as a normoxic mimetic of hypoxia, capable of stabilizing HIF-1α. Protective features of LF and DFO and their pharmacological properties involving HIF-1α are discussed.

ChemInform Abstract: Spectaflavoside A, a New Potent Iron Chelating Dimeric Flavonol Glycoside from the Rhizomes of Zingiber spectabile Griff.

ChemInformVolume 43, Issue 41 Natural Products ChemInform Abstract: Spectaflavoside A, a New Potent Iron Chelating Dimeric Flavonol Glycoside from the Rhizomes of Zingiber spectabile Griff. Yasodha Sivasothy, Yasodha Sivasothy Dep. Chem., Fac. Sci., Univ. Malaya, 50603 Kuala Lumpur, Malay.Search for more papers by this authorA. Hamid A. Hadi, A. Hamid A. Hadi Dep. Chem., Fac. Sci., Univ. Malaya, 50603 Kuala Lumpur, Malay.Search for more papers by this authorKhalit Mohamad, Khalit Mohamad Dep. Chem., Fac. Sci., Univ. Malaya, 50603 Kuala Lumpur, Malay.Search for more papers by this authorKok Hoong Leong, Kok Hoong Leong Dep. Chem., Fac. Sci., Univ. Malaya, 50603 Kuala Lumpur, Malay.Search for more papers by this authorHalijah Ibrahim, Halijah Ibrahim Dep. Chem., Fac. Sci., Univ. Malaya, 50603 Kuala Lumpur, Malay.Search for more papers by this authorShaida Fariza Sulaiman, Shaida Fariza Sulaiman Dep. Chem., Fac. Sci., Univ. Malaya, 50603 Kuala Lumpur, Malay.Search for more papers by this authorKheng Leong Ooi, Kheng Leong Ooi Dep. Chem., Fac. Sci., Univ. Malaya, 50603 Kuala Lumpur, Malay.Search for more papers by this authorKhalijah Awang, Khalijah Awang Dep. Chem., Fac. Sci., Univ. Malaya, 50603 Kuala Lumpur, Malay.Search for more papers by this author Yasodha Sivasothy, Yasodha Sivasothy Dep. Chem., Fac. Sci., Univ. Malaya, 50603 Kuala Lumpur, Malay.Search for more papers by this authorA. Hamid A. Hadi, A. Hamid A. Hadi Dep. Chem., Fac. Sci., Univ. Malaya, 50603 Kuala Lumpur, Malay.Search for more papers by this authorKhalit Mohamad, Khalit Mohamad Dep. Chem., Fac. Sci., Univ. Malaya, 50603 Kuala Lumpur, Malay.Search for more papers by this authorKok Hoong Leong, Kok Hoong Leong Dep. Chem., Fac. Sci., Univ. Malaya, 50603 Kuala Lumpur, Malay.Search for more papers by this authorHalijah Ibrahim, Halijah Ibrahim Dep. Chem., Fac. Sci., Univ. Malaya, 50603 Kuala Lumpur, Malay.Search for more papers by this authorShaida Fariza Sulaiman, Shaida Fariza Sulaiman Dep. Chem., Fac. Sci., Univ. Malaya, 50603 Kuala Lumpur, Malay.Search for more papers by this authorKheng Leong Ooi, Kheng Leong Ooi Dep. Chem., Fac. Sci., Univ. Malaya, 50603 Kuala Lumpur, Malay.Search for more papers by this authorKhalijah Awang, Khalijah Awang Dep. Chem., Fac. Sci., Univ. Malaya, 50603 Kuala Lumpur, Malay.Search for more papers by this author First published: 13 September 2012 https://doi.org/10.1002/chin.201241204Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume43, Issue41October 9, 2012 RelatedInformation

Ulcerated hemosiderinic dyschromia and iron deposits within lower limbs treated with a topical application of biological chelator

The ulcerative haemosiderinic dyschromia of chronic venous insufficiency is difficult to heal and presents a high accumulation of iron. Lactoferrin, a potent natural iron chelator, could help to scar this ulcerative haemosi - derinic dyschromia. The objective of this study was to determine whether the topical application of a liposomal gel with Lactoferrin favors scarring/degradation of the brown colored spot typical of ulcerative haemosiderinic dyschromia. Nine patients with severe chronic venous insufficiency and ulcerative haemosiderinic dyschromia (CEAP-C6), with a natural evolution of over 12 months, were included in the study. Hemo chromatosis gene mutations were investigated. The levels of serum ferritin, transferrin saturation and blood cell counts were analyzed. The presence of hemosiderin was investigated through periulcerous and ulcer fundus biopsies carried out at baseline and 30 days after treatment with Lactoferrin. The severity of the injuries (CEAP classification) was evaluated at the beginning of and throughout the whole 3-month treatment period. No patient had received compression treatment during the three months previous to this therapy. Significant improvement in these injuries, with a reduction in the dimensions of the brown spot (9 of 9) at Day 90, and complete scarring with a closure time ranging from 15 to 180 days (7 of 9) were observed. The use of topical lactoferrin is a non-invasive therapeutic tool that favors clearance of hemosiderinic dyschromia and scarring of the ulcer. The success of this study was not influenced either by the hemochromatosis genetics or the iron metabolism profile observed.

In Vivo and In Vitro Studies on the Antioxidant Activity of Aloin Compared to Doxorubicin in Rats

Abstract Strategy, Management and Health Policy Enabling Technology, Genomics, Proteomics Preclinical Research Preclinical Development Toxicology, Formulation Drug Delivery, Pharmacokinetics Clinical Development Phases I‐III Regulatory, Quality, Manufacturing Postmarketing Phase IV In the present study, the cardiotoxicity of aloin, a naturally occurring anthraquinone glycoside with antiproliferative activity was compared with doxorubicin, a cardiotoxic anthracyline drug, in rats. The antioxidant and iron‐chelating activities of aloin and doxorubicin in vitro were also evaluated. Rats treated with aloin (50 mg/kg body weight, intramuscular)) twice weekly over 2 weeks showed no signs of cardiotoxicity as assessed by an absence of changes in relative heart weight, serum level of heart function enzymes, and a lack of degeneration in the myocardium of the left ventricle. Acute doxorubicin administration (30 mg/kg body weight, intraperitoneal) to rats produced severe cardiotoxicity as supported by biochemical and histological studies. Aloin did not induce oxidative stress or enhance the endogenous antioxidant defense system in the heart. In vitro antioxidant tests showed that aloin, in contrast to doxorubicin, had substantial antioxidant activity represented by scavenging of 1,1‐diphenyl 2‐picrylhydrazyl and nitric oxide· radicals, inhibition of lipid peroxidation, and ferric‐reducing antioxidant activity in addition to iron chelating potential. Ventricular inducible nitric oxide synthase protein expression was unaffected by either aloin and doxorubicin treatments. In conclusion, repeated aloin treatment, in contrast to that of doxorubicin, failed to produce oxidative stress‐induced cardiotoxicity in the rats.

Spectaflavoside A, a new potent iron chelating dimeric flavonol glycoside from the rhizomes of Zingiber spectabile Griff.

The rhizomes of Zingiber spectabile yielded a new dimeric flavonol glycoside for which the name kaempferol-3-O-(4″-O-acetyl)-α-l-rhamnopyranoside-(I-6,II-8)-kaempferol-3-O-(4″-O-acetyl)-α-l-rhamnopyranoside; spectaflavoside A (1) was proposed, along with kaempferol and its four acetylrhamnosides (2–6), demethoxycurcumin (7) and curcumin (8). The structure of spectaflavoside A was elucidated by spectroscopic methods including, 1D and 2D NMR techniques. This is the first report on the occurrence of a dimeric flavonol glycoside in the Zingiberaceae and the second in nature. Spectaflavoside A was found to be a potent iron chelating agent.

Antifungal and Antioxidant Activities of Piptostigma calophyllum, Uvariodendron calophyllum and Uvariodendron molundense Growing in Cameroon

Fungal infections have substantially increased in number and severity in the last two decades and are generally associated with free radical generation. In a search for plant-derived antifungal and antioxidant agents, ethanolic extracts from Uvariodendron molundense, Uvariodendron calophyllum, and Piptostigma calophyllum (Annonaceace) were investigated for their antifungal activity against yeasts and moulds, using the agar well diffusion/dilution and the broth microdilution methods and their antioxidant activity, using the DPPH radical scavenging and the metal chelating techniques. Extracts were screened for their phytochemical content. The yield of extraction ranged from 3.72 to 9.51%. All the extracts showed antifungal activity with MIC values ranging 1.30 mg/mL against C. glabrata to 36 mg/mL against Aspergillus fumigatus and Aspergillus flavus. The most potent extract was that of the twigs of U. molundense. The leaf extract of P. calophyllum showed the highest antioxidant activity with a SC50 of 0.2 mg/mL. The extracts showed potent iron chelation, the most active having an IC50 of 3.07 mg/mL. Tannins, phenols, and glycosides were found to be commonly present in all the extracts. The results achieved support further investigation of these plants for antifungal and antioxidant agents.

Iron Deprivation Suppresses Hepatocellular Carcinoma Growth in Experimental Studies

Hepatocellular carcinoma (HCC) is the third most common cause of cancer-related death, and iron overload is a significant risk factor in the development of HCC. In this study, we investigated the potential application of depriving iron by a novel iron chelator, thiosemicarbazone-24 (TSC24), in HCC treatment. Two HCC cell lines and HFE knockout (HFE(-/-)) mice were used to determine iron chelation efficiency of TSC24. The anticancer effects of TSC24 on HCC were analyzed in vitro and in athymic xenograft mouse models. Treatment with TSC24 significantly decreased the cellular iron concentration in hepatoma cells and the serum iron concentration in HFE(-/-) mice by blocking iron uptake and interfering with normal regulation of iron levels. Moreover, the viability of HCC cell lines was reduced by TSC24. Confirming the mechanism of the agent, this decrease in viability could be partially rescued by addition of exogenous iron. TSC24 also suppressed tumor growth in athymic mice bearing human HCC xenografts in a concentration-dependent manner, without apparent toxicity in parallel with a decrease in the serum iron level. Further studies revealed that TSC24 efficiently triggered cell-cycle arrest and apoptosis in Hep3B and HepG2 cell lines. TSC24 is a potent iron chelator that suppresses human HCC tumor growth by disrupting iron homeostasis, reducing available iron, and triggering cell-cycle arrest and apoptosis, without apparent host toxicity at effective doses. Thus, TSC24 shows great potential for the treatment of HCC.

Trypanosoma cruzi: Desferrioxamine decreases mortality and parasitemia in infected mice through a trypanostatic effect

Desferrioxamine (DFO) is a potent iron chelator that is also known to modulate inflammation and act as an efficient antioxidant under normal conditions and under oxidative stress. Many in vitro and in vivo studies have shown the efficacy of DFO in the treatment of viral, bacterial and protozoan infections. DFO is known to reduce the intensity of Trypanosoma cruzi infections in mice even during a course of therapy that is not effective in maintaining anaemia or low iron levels. To further clarify these findings, we investigated the action of DFO on mouse T. cruzi infection outcomes and the direct impact of DFO on parasites.Infected animals treated with DFO (5mg/animal/day) for 35days, beginning 14days prior to infection, presented lower parasitemia and lower cumulative mortality rate. No significant effect was observed on iron metabolism markers, erythrograms, leukograms or lymphocyte subsets.In the rapid method for testing in vivo T. cruzi susceptibility, DFO also induced lower parasitemia.In regard to its direct impact on parasites, DFO slightly inhibited the growth of amastigotes and trypomastigotes in fibroblast culture. Trypan blue staining showed no effects of DFO on parasite viability, and only minor apoptosis in trypomastigotes was observed. Nevertheless, a clear decrease in parasite mobility was detected.In conclusion, the beneficial actions of DFO on mice T. cruzi infection seem to be independent of host iron metabolism and free of significant haematological side effects. Through direct action on the parasite, DFO has more effective trypanostatic than trypanocidal properties.

Dopamine D2/D3 Agonists with Potent Iron Chelation, Antioxidant and Neuroprotective Properties: Potential Implication in Symptomatic and Neuroprotective Treatment of Parkinson’s Disease

Grey matters! D-390 (shown) is a dopamine D2/D3 receptor agonist that chelates iron and possesses antioxidant activity. This compound exhibited efficacious activity in an animal model of Parkinson's disease, indicating blood–brain barrier penetration. In a mouse MPTP neuroprotection model, D-390 exhibited significant neuroprotection, indicating its possible therapeutic application in both the symptomatic and neuroprotective treatment of Parkinson's disease.

A mechanism for the effect of alginate on the gut microflora

IntroductionAlginates are hydrocolloids produced by brown seaweeds which are commonly used as gelling and thickening agents in the food industry. In addition in the pharmaceutical industry they are found in...

The iron chelator Dp44mT inhibits the proliferation of cancer cells but fails to protect from doxorubicin-induced cardiotoxicity in spontaneously hypertensive rats

The iron chelator Dp44mT is a potent topoisomerase IIα inhibitor with novel anticancer activity. Doxorubicin (Dox), the current front-line therapy for breast cancer, induces a dose-limiting cardiotoxicity, in part through an iron-mediated pathway. We tested the hypothesis that Dp44mT can improve clinical outcomes of treatment with Dox by alleviating cardiotoxicity. The general cardiac and renal toxicities induced by Dox were investigated in the presence and absence of Dp44mT. The iron chelating cardioprotectant Dexrazoxane (Drz), which is approved for this indication, was used as a positive control. In vitro studies were carried out with H9c2 rat cardiomyocytes and in vivo studies were performed using spontaneously hypertensive rats. Testing of the GI(50) profile of Dp44mT in the NCI-60 panel confirmed activity against breast cancer cells. An acute, toxic dose of Dox caused the predicted cellular and cardiac toxicities, such as cell death and DNA damage in vitro and elevated cardiac troponin T levels, tissue damage, and apoptosis in vivo. Dp44mT alone caused insignificant changes in hematological and biochemical indices in rats, indicating that Dp44mT is not significantly cardiotoxic as a single agent. In contrast to Drz, Dp44mT failed to mitigate Dox-induced cardiotoxicity in vivo. We conclude that although Dp44mT is a potent iron chelator, it is unlikely to be an appropriate cardioprotectant against Dox-induced toxicity. However, it should continue to be evaluated as a potential anticancer agent as it has a novel mechanism for inhibiting the growth of a broad range of malignant cell types while exhibiting very low intrinsic toxicity to healthy tissues.

Iron-chelating backbone coupled with monoamine oxidase inhibitory moiety as novel pluripotential therapeutic agents for Alzheimer’s disease: a tribute to Moussa Youdim

It is for these authors a great privilege to dedicate this review article to Moussa Youdim, who is one of the most imperative pharmacologists and pioneer investigators in the search and development of novel therapeutics for neurodegenerative diseases. 40 years ago, Moussa Youdim has started studying brain iron, catecholamine receptor and monoamine oxidase (MAO)-A and -B functions. Although Moussa Youdim succeeded in exploring the novel anti-Parkinsonian, selective MAO-B inhibitor drug, rasagiline (Azilect, Teva Pharmaceutical Co.), he did not stop searching for superior therapeutic approaches for neurodegenerative disorders. To date, Moussa Youdim and his research group are designing and synthesizing pluripotential drug candidates possessing diverse pharmacological properties that can act on multiple targets and pathological features ascribed to Parkinson's disease, Alzheimer's disease (AD) and amyotrophic lateral sclerosis. One such example is the multimodal non-toxic, brain-permeable iron-chelating compound, M30 (5-[N-methyl-N-propargylaminomethyl]-8-hydroxyquinoline), which amalgamates the propargyl moiety of rasagiline with the backbone of the potent iron chelator, VK28. This review discusses the multiple effects of several leading compounds of this series, concerning their neuroprotective/neurorestorative molecular mechanisms in vivo and in vitro, with a special focus on the pathological features ascribed to AD, including antioxidant and iron chelating activities, regulation of amyloid precursor protein and amyloid β peptide expression processing, activation of pro-survival signaling pathways and regulation of cell cycle and neurite outgrowth.

Caffeic acid inhibits the formation of 1-hydroxyethyl radical in the reaction mixture of rat liver microsomes with ethanol partly through its metal chelating activity

Effect of caffeic acid on the formation of 1-hydroxyethyl radicals via the microsomal ethanol-oxidizing system pathway was examined. The electron spin resonance spin trapping showed that 1-hydroxyethyl radicals form in the control reaction mixture which contained 0.17 M ethanol, 1 mg protein/ml rat river microsomes, 0.1 M α-(4-pyridyl-1-oxide)-N-tert-butylnitrone, 5 mM nicotinamide adenine dinucleotide phosphate and 30 mM phosphate buffer (pH 7.4). When the electron spin resonance spectra of the control reaction mixtures with caffeic acid were measured, caffeic acid inhibited the formation of 1-hydroxyethyl radicals in a concentration dependent manner. Gallic acid, dopamine, l-dopa, chlorogenic acid and catechin also inhibited the formation of 1-hydroxyethyl radicals. Above results indicated that the catechol moiety is essential to the inhibitory effect. Caffeic acid seems to chelate of iron ion at the catechol moiety. Indeed, the inhibitory effect by caffeic acid was greatly diminished in the presence of desferrioxamine, a potent iron chelator which removes iron ion in the Fe (III)-caffeic acid complex. Since Fe (III)-desferrioxamine complex is active for the 1-hydroxyethyl radicals formation, caffeic acid inhibits the formation of 1-hydroxyethyl radicals in the reaction mixture partly through its metal chelating activity.

Assessment of the Antioxidant and Reactive Oxygen Species Scavenging Activity of Methanolic Extract of Caesalpinia crista Leaf

“Oxidative stress” is initiated by reactive oxygen species (ROS), which are responsible for majority of the diseases. However, antioxidants with ROS scavenging ability may have great relevance in the prevention of oxidative stress. The present study was undertaken, using a 70% methanolic extract of Caesalpinia crista leaves, to examine different in vitro tests in diversified fields including total antioxidant activity, scavenging activities for various ROS, iron chelating activity and phenolic and flavonoid contents. Total antioxidant activity was evaluated as trolox equivalent antioxidant capacity value of 0.546 ± 0.014. The extract was investigated for different ROS scavenging activities and IC50 values were found to be 0.44 ± 0.1 mg/ml, 24.9 ± 0.98 μg/ml, 33.72 ± 0.85 μg/ml, 61.13 ± 3.24 μg/mL and 170.51 ± 4.68 μg/mL for hydroxyl, superoxide, nitric oxide, singlet oxygen and hypochlorous acid, respectively; however, no significant results were obtained in scavenging of hydrogen peroxide and peroxynitrite anion. The extract was found to be a potent iron chelator with IC50 = 279.85 ± 4.72 μg/mL. The plant extract (100 mg) yielded 50.23 ± 0.003 mg/mL gallic acid equivalent phenolic content and 106.83 ± 0.0003 mg/mL quercetin equivalent flavonoid content. In the in vivo experiments, the extract treatment showed significant increase in the level of superoxide dismutase, catalase, glutathione-S-transferase and reduced glutathione. In a word, it may be concluded that 70% methanol extract of C. crista leaves acts as an antioxidant and ROS scavenger; which may be due to the presence of phenolic and flavonoid compounds.

In vitro interactions of coumarins with iron

Coumarins are a large group of natural substances with diverse pharmacological properties that may predetermine some of them for the prevention and/or treatment of cardiovascular diseases and also other pathologies. Free iron participates in the production of reactive oxygen species (ROS) and plays an important role in the pathogenesis of cardiovascular diseases. Therefore, chelation of iron may attenuate some ROS consequences, but on the other hand, reduction of ferric ions to ferrous ones is unfavourable and leads to intensification of ROS production. In this study, we have examined the interaction of iron with coumarins which has been rarely analyzed. A series of naturally occurring and chemically synthesized 4-methylcoumarins were analyzed for their ferrous and total iron-chelating properties and compared with standard iron chelator deferoxamine. The iron chelation activity was assessed by a simple spectrophotometric approach based on the specific indicator for ferrous ions – ferrozine. The methodology was also extended for the measurement of total iron. Among the tested coumarins, ortho-dihydroxyderivatives were the most potent iron chelators and 7,8-dihydroxy-4-methylcoumarin even reached the efficiency of deferoxamine in neutral pH. However, these ortho-dihydroxycoumarins did not bind iron firmly in acidic conditions (e.g., in acute myocardial infarction) and, moreover, they reduced ferric ions that could lead to intensification of the Fenton chemistry. Other tested coumarins did not substantially chelate iron with the exception of ortho-diacetoxycoumarins. Conclusively, the use of iron-chelating coumarins in acidic conditions may be disadvantageous in contrast to neutral conditions.

Therapeutic potential of iron chelators in diseases associated with iron mismanagement

A considerable array of diseases are now recognized to be associated with misplacement of iron. Excessive deposits of the metal in sensitive tissue sites can result in formation of destructive hydroxyl radicals as well as in stimulation of growth of neoplastic and microbial cell invaders. To counteract potential iron damage, hosts employ the iron chelators, transferrin and lactoferrin. These proteins have been recently developed into pharmaceutical products. Additionally, a variety of low molecular mass iron chelators are being used/tested to treat whole body iron loading, and specific diseases for which the metal is a known or suspected risk factor.

Neutrophil gelatinase-associated lipocalin (NGAL/Lcn2) is upregulated in gastric mucosa infected with Helicobacter pylori

Helicobacter pylori infection is one of the most significant risk factors for gastric cancer. The infection is established early in life and persists lifelong leading to a sustained chronic inflammation. Iron is essential for most living organisms. Bacteria use several mechanisms to acquire iron from their hosts, including the synthesis of the potent iron chelators known as siderophores. Hosts cells may express the siderophore-binding protein neutrophil gelatinase-associated lipocalin (NGAL/lipocalin-2 (Lcn2)) in response to infection, thus preventing bacterial iron uptake. We have characterized here the pattern of expression of NGAL/Lcn2 in gastric mucosa (45 non-neoplastic and 38 neoplastic tissue samples) and explored the connection between NGAL/Lcn2 expression and H. pylori infection. Immunohistochemical analysis showed high NGAL/Lcn2 expression in normal and gastritis-affected mucosa compared to low expression in intestinal metaplasia, dysplasia, and gastric cancer. In normal and gastritis-affected mucosa (n=36 tissue samples), NGAL/Lcn2 was more frequently seen in epithelial cells located at the neck and base of the glands in H. pylori-positive cases than in similar epithelial cells of noninfected cases (Fisher's exact test, p=0.04). In conclusion, the high expression of NGAL/Lcn2 in normal and gastritis-affected mucosa infected with H. pylori suggests that NGAL/Lcn2 is upregulated locally in response to this bacterial infection. It is discussed whether this may have a causal relation to the development of gastric cancer.

ARPE-19 retinal pigment epitheliaL CELLS are highly resistant to oxidative stress and exercise strict control over their lysosomal redox-active iron

Normal retinal pigment epithelial (RPE) cells are postmitotic, long-lived and basically not replaced. Daily, they phagocytose substantial amounts of lipid-rich material (photoreceptor outer segment discs), and they do so in the most oxygenated part of the body – the retina. One would imagine that this state of affairs should be associated with a rapid formation of the age pigment lipofuscin (LF). However, LF accumulation is slow and reaches significant amounts only late in life when, if substantial, it often coincides with or causes age-related macular degeneration. LF formation occurs inside the lysosomal compartment as a result of iron-catalyzed peroxidation and polymerization. This process requires phagocytosed or autophagocytosed material under degradation, but also the presence of redox-active low mass iron and hydrogen peroxide. To gain some information on how RPE cells are able to evade LF formation, we investigated the response of immortalized human RPE cells (ARPE-19) to oxidative stress with/without the protection of a strong iron-chelator. The cells were found to be extremely resistant to hydrogen peroxide-induced lysosomal rupture and ensuing cell death. This marked resistance to oxidative stress was not explained by enhanced degradation of hydrogen peroxide, but to a certain extent further increased by the potent lipophilic iron chelator SIH. The cells were also able to survive, and even replicate, at high concentrations of SIH and showed a high degree of basal autophagic flux. We hypothesize that RPE cells have a highly developed capacity to keep lysosomal iron in a non-redox-active form, perhaps by pronounced autophagy of iron-binding proteins in combination with an ability to rapidly relocate low mass iron from the lysosomal compartment.

The influence of iron loading and iron chelation on the proliferation and telomerase activity of human peripheral blood mononuclear cells.

Iron is an essential trace element in cell proliferation. Several investigations demonstrate that iron deprivation inhibits cell proliferation. However, the impact of iron on telomerase activity of activated lymphocytes remains unexplained to date. In this study, the effect of iron on the proliferation and telomerase activity of lymphocytes stimulated by phytohemagglutinin (PHA) were investigated. Iron loading was performed by incubating peripheral blood mononuclear cells in 500microM FeSO4.7H2O for 24 h and iron chelation was done by exposing cells to desferrioxamine, a potent iron chelator. The effects of silymarin, a flavonoid with both antioxidant and iron chelating activities, on the proliferation and telomerase activity of PHA-activated lymphocytes were also compared with desferrioxamine. Proliferation and telomerase activity were assessed using BrdU incorporation assay and Telomeric Repeat Amplification Protocol (TRAP), respectively. The proliferations of lymphocytes were significantly inhibited by 10 and 20 microg/ml desferrioxamine in a dose dependent manner, while iron loading recovered suppressed cell proliferation to the normal level. Silymarin at 20 microg/ml significantly increased the proliferation of lymphocytes in both normal and iron-treated conditions. Telomerase activity of lymphocytes was markedly increased by iron treatment and suppressed by desferrioxamine. Conversely, iron treatment had no effect on the telomerase activity of lymphocytes incubated with silymarin. Iron plays a significant role in the proliferation and telomerase activity of lymphocytes. The effects of silymarin on the proliferation and telomerase activity of lymphocytes were completely different from those of desferrioxamine, suggesting that the immunomodulatory effect of silymarin is probably not associated with its iron chelating activity.