Effects Of Excess Iron Research Articles

Abstract TP18: Iron Overload Induces Cognitive Deficits And Autophagy Impairment In The Brains Of Aged Mice In A Sex-Dependent Manner

Iron deposits have been observed in postmortem brain samples from Alzheimer’s disease patients. Different iron overload models have been used to study neurodegeneration in young mice. However, the effects of excess iron with aging, which is a critical factor for Alzheimer’s disease and iron deposition in the brain, remain unexplored. In addition, iron metabolism is regulated by autophagy, a cellular process that degrades intracellular components. Brain autophagy is downregulated with aging and in females, and autophagy impairment occurs in many neurodegenerative disorders. Thus, we hypothesized that sex differences exist in autophagy in the brains of aged mice treated with iron overload. We treated aged (18-20 months) WT mice of both sexes with iron overload (5% ferric citrate, FC, 3 days/week/6 weeks), or a vehicle, by oral gavage. We found that aged females showed impairment in conditioning memory (Fear conditioning), but not aged males. Aged females treated with FC also showed significant increase of iron deposition in their brains, compared with control females. However, we did not find significant differences between control and treated male mice. Furthermore, the brain lysates of aged females treated with iron overload showed increased levels of the early autophagy marker BECLIN1 (in both sexes), and enhanced levels of the autophagy cargo p62 (in both sexes) and the lysosomal marker LAMP1 (only in females), compared with control mice. This suggests that iron overload induces the initial stage of autophagy in both sexes, but impairs late autophagy, mainly in female mice, compared with control mice. Furthermore, in primary culture of cerebral endothelial cells (CEC) isolated from aged mice, we found that CEC treated with ferric citrate exhibit enhanced DNA damage and reduced cell proliferation in a dose-dependent manner. Importantly, CEC derived from female mice showed reduced autophagy flux, compared with male CEC. This suggests that iron overload may be more detrimental in the cerebrovasculature of aged female mice than in males, and this could explain iron overload-induced memory deficiency in aged female mice, but not in males.

Genetic and morphological analysis tolerance to ferrous and ferric forms of iron in rice

An experiment was conducted in the rain out shelter with the objective of analysing the effect of ferric and ferrous iron on rice genotypes and for identifying the tolerant genotypes for iron toxicity. The study was comprised with 12 varieties/genotypes of indica rice, exposed under different concentrations (0, 40 and 80 mg/kg) of two different forms of iron viz., ferrous sulfate (FeSO4) and ferric chloride (FeCl3). Visual scoring scale was used to screen the genotypes and effects of excess iron were examined on different vegetative traits in which root weight and shoot weight were found to be more sensitive to excess iron concentration of both forms. In two different form of iron ferrous form was found toxic than ferric form of iron but high amount of ferric chloride without chelating agent can cause death of plants in hydroponics condition. The soil used for experiments was also analysed to estimate the pH and status of other nutrients in soil. On the basis of visual scoring we identified 4 genotypes tolerant (Dagad deshi, IBD-1, R-RF-127, R-RF 105) and Swarna as susceptible genotype for both form ferrous and ferric iron.

Effects of Excess Iron on the Retina: Insights From Clinical Cases and Animal Models of Iron Disorders.

Iron plays an important role in a wide range of metabolic pathways that are important for neuronal health. Excessive levels of iron, however, can promote toxicity and cell death. An example of an iron overload disorder is hemochromatosis (HH) which is a genetic disorder of iron metabolism in which the body’s ability to regulate iron absorption is altered, resulting in iron build-up and injury in several organs. The retina was traditionally assumed to be protected from high levels of systemic iron overload by the blood-retina barrier. However, recent data shows that expression of genes that are associated with HH can disrupt retinal iron metabolism. Thus, the effects of iron overload on the retina have become an area of research interest, as excessively high levels of iron are implicated in several retinal disorders, most notably age–related macular degeneration. This review is an effort to highlight risk factors for excessive levels of systemic iron build-up in the retina and its potential impact on the eye health. Information is integrated across clinical and preclinical animal studies to provide insights into the effects of systemic iron loading on the retina.

Myocardial iron quantification using T2-prepared SSFP parametric images at 3 Tesla

Background Quantification of myocardial iron overload is critical for the management of patients with hemochromatosis. The effects of excess iron over T2 and T2* relaxation times are well known and both measures strongly correlate with iron concentration. Due to its lower sensitivity to B0 inhomogeneities, T2 has theoretical advantages over T2*, but the latter became the clinical standard as it can be easily obtained in a fast one breath-hold ECG gated multi-echo GRE sequence. T2* is especially challenging at 3T due to greater B0 inhomogeneities at higher field strengths. We aimed to validate a recently developed T2-prepared SSFP sequence that quantifies myocardial T2 times at 3T, compared to standard GRE based multi-echo T2* times at 1.5T. Methods A total of 15 normal volunteers and 7 chronic anemia patients (with a myocardial T2* measure <20 ms in the last 2 years, five of these on iron chelating therapy) were prospectively enrolled. Myocardial T2* and T2 times were quantified in the same day, the former using a breath-hold multi-echo GRE sequence at 1.5T (Symphony, Siemens, Erlangen, Germany) and the latter using a recently developed T2 mapping technique based on a breath-hold T2-prepared SSFP sequence at 3T (Verio, Siemens, Erlangen, Germany). All ROIs were placed at mid-interventricular septum, carefully avoiding the blood pool (Figure 1). All analyses were blinded. Results All patients had regular heart rhythm and all MRI exams showed diagnostic image quality. Volunteers and patients had significantly different mean myocardial T2* (27.2 ms +/- 3.9 vs. 15.4 ms +/- 6.3 p<0.05 respectively) and T2 times (44.9 ms +/- 2.2 vs. 37.9 ms +/- 6.6 p<0.05 respectively). 3T T2 times strongly correlated with 1.5T T2* times (r=0.91 and Figure 2). C-statistic of 3T T2 times for the prediction of a 1.5T T2* <20 ms was 0.97. Using the 3T T2 cut-off of 40 ms and the standard 1.5T T2* of 20 ms, sensitivity and specificity for 3T T2 were 80% and 100% respectively.

Myocardial iron quantification using modified Look-Locker inversion recovery (MOLLI) T1 mapping at 3 Tesla

Background Quantification of myocardial iron overload is critical for the management of patients with hemochromatosis. The effects of excess iron on T1 and T2* relaxation times correlate directly with tissue iron concentration. T2* became the clinical standard at 1.5T as it can be easily obtained in a fast one breath-hold ECG gated multi-echo GRE sequence. At 3T, however, T2* quantification can be limited by pronounced susceptibility artifacts and signal sampling restraints due to shorter T2* times at higher iron concentrations . Since myocardial T1 time is up to thirty times longer than T2*, it can be quantified with short echo-time inversionrecovery sequences even at high iron concentrations, and is less sensitive to susceptibility artifacts. We aimed to validate a recently developed modified LookLocker inversion recovery (MOLLI) sequence to quantify myocardial T1 in healthy controls and patients with iron overload at 3T, comparing to standard GRE based multi-echo T2* times at 1.5T. Methods A total of 15 normal volunteers and 7 chronic anemia patients (with a myocardial T2* measure <20 ms at 1.5T in the last 2 years, five of these on iron chelating therapy) were prospectively enrolled. Myocardial T2* and T1 times were quantified in the same day, the former using a breath-hold multi-echo GRE sequence at 1.5T (Symphony, Siemens, Erlangen, Germany) and the latter using the T1 mapping -MOLLI sequence at 3T (Verio, Siemens, Erlangen, Germany). All ROIs were placed at mid-interventricular septum, carefully avoiding the blood pool (Fig 1). All analyses were blinded. Results All patients had regular heart rhythm and all MRI exams showed diagnostic image quality. Volunteers and patients had significantly different mean myocardial T2* (27.2 ms +/- 3.9 vs. 15.4 ms +/- 6.3 p<0.05 respectively) and T1 times 1175.7 ms +/- 22.8 vs. 952.1 ms +/- 173.2 p<0.05 respectively). 3T T1 times strongly correlated with 1.5T T2* times (r=0.95 and Fig 2). Using the 3T T1 cut-off of 1130 ms, sensitivity and specificity for 3T

Comparing qualitative and quantitative spectroscopic techniques for the detection of the effect of direct iron loading of mammalian cell cultures.

Iron overload augments diseases of the liver and microorganism infection as well as deregulates the immune system. In vitro analysis of the effects of iron loading and its chelation involves determining the amount of iron constituting overload, which metal sources and cell lines to use and reliable assay methods. The uptake of 500 microM FeSO4 or FeEDTA by CEMss, U937 or leukocytes was confirmed by inductively coupled plasma-atomic emission spectroscopy (ICP-AES). Excess iron increased CEMss viability (assessed by MTT, XTT, Trypan- and Alamar Blue) by an average of 18% (P = 0.034). Flow cytometry indicated dye-viable cells to be undergoing apotosis/necrosis while still confirming an increase (9%, P < 0.001) in excess iron-induced viability. The iron chelator desferioxamine (DFO) when added in addition to Fe, reversed the effects of excess iron (and vice versa) and had detrimental effects when used on its own (33% inhibition of viability as measured by dyes and 10.85%; P = 0.0427 assessed by flow cytometry). The 4 dyes demonstrated different levels of sensitivity in detecting the influence of iron or DFO but gave a related, qualitative picture while flow cytometry and ICP-AES data was more quantitative.

Alterations in the structure, physicochemical properties, and pH of hepatocyte lysosomes in experimental iron overload.

While hemochromatosis is characterized by sequestration of iron-protein complexes in hepatocyte lysosomes, little is known about the effects of excess iron on these organelles. Therefore, we studied the effects of experimental iron overload on hepatocyte lysosomal structure, physicochemical properties, and function in rats fed carbonyl iron. A sixfold increase (P less than 0.0001) in hepatic iron and a fivefold increase in lysosomal iron (P less than 0.01) was observed after iron loading; as a result, hepatocyte lysosomes became enlarged and misshapen. These lysosomes displayed increased (P less than 0.0001) fragility; moreover, the fluidity of lysosomal membranes isolated from livers of iron-loaded rats was decreased (P less than 0.0003) as measured by fluorescence polarization. Malondialdehyde, an end product of lipid peroxidation, was increased by 73% (P less than 0.008) in lysosomal membranes isolated from livers of iron-overloaded rats. While amounts of several individual fatty acids in isolated lysosomal membranes were altered after iron overload, cholesterol/phospholipid ratios, lipid/protein ratios, double-bond index, and total saturated and unsaturated fatty acids remained unchanged. The pH of lysosomes in hepatocytes isolated from livers of iron-loaded rats and measured by digitized video microscopy was increased (control, 4.70 +/- 0.05; iron overload, 5.21 +/- 0.10; P less than 0.01). Our results demonstrate that experimental iron overload causes marked alterations in hepatocyte lysosomal morphology, an increase in lysosomal membrane fragility, a decrease in lysosomal membrane fluidity, and an increase in intralysosomal pH. Iron-catalyzed lipid peroxidation is likely the mechanism of these structural, physicochemical, and functional disturbances.

Iron regulation of ferritin gene expression

Ferritin is a ubiquitous iron-storage protein found in the cells of animals, plants, molds, and bacteria which it protects from toxic intracellular levels of iron. Ferritin stores iron within a hollow protein shell formed by subunits of two types, H and L. The 5' untranslated regions of the two subunit mRNAs contain an almost identical 28-nucleotide sequence which regulates translation by binding to a specific cell sap protein. When cell iron level is low, this repressor protein obstructs translation of stored ferritin mRNAs, whereas increased iron levels release this protein, thus permitting extensive ferritin subunit synthesis to respond rapidly. Similar motifs in the 3' untranslated region of transferrin receptor mRNA interact with this protein to regulate breakdown of the mRNA and thus change the receptor population. Finally, transcription of the H and L genes can be independently increased by iron and other factors. In the case of iron, synthesis of the L-mRNA is increased preferentially since ferritin shells with a preponderance of L-subunits store iron more efficiently. Thus regulation of ferritin synthesis at the translational and transcriptional levels and by transferrin receptor mRNA abundance at the level of breakdown provide a coordinated mechanism for protecting cells against the effects of excess iron.

Tolerance of rice cultivars to iron toxicity

Abstract Iron toxicity is an important growth‐limiting factor for flooded rice production in various parts of the world, including Brazil. Data related to the reaction of rice cultivars to iron concentrations are limited, especially for large numbers of cultivars. Forty rice cultivars were grown in a greenhouse in nutrient solutions containing 0.09, 0.89, and 1.78 mM Fe (5, 50 and 100 ppm Fe). The effects of excess iron were measured on plant height, root length, and root and shoot dry weight. Root and shoot dry weight were found to be more sensitive to excess iron concentration. Based on dry matter yield, reduction of shoots at higher Fe concentrations compared to the optimum or control treatment, rice cultivars were classified as tolerant, moderately tolerant, moderately susceptible or susceptible. The effect of Fe concentrations on concentrations and contents of other nutrient was also investigated. Higher concentration of Fe in the nutrient solution exerted an inhibiting effect on the concentrations and contents of almost all macro and micronutrients.