Chronic dietary iron overload affects hepatic iron metabolism and cognitive behavior in Wistar rats

BACKGROUND

Iron accumulation in organs affects iron metabolism, leading to deleterious effects on the body. Previously, it was studied that high dietary iron in various forms and concentrations influences iron metabolism, resulting in iron accumulation in the liver and spleen and cognitive impairment. However, the actual mechanism and impact of long-term exposure to high dietary iron remain unknown. As a result, we postulated that iron overload caused by chronic exposure to excessive dietary iron supplementation would play a role in iron dyshomeostasis and inflammation in the liver and brain of Wistar rats.

METHODS

Animals were segregated into control, low iron (FAC-Ferric Ammonium Citrate 5000 ppm), and high iron dose group (FAC 20,000 ppm). The outcome of dietary iron overload on Wistar rats was evaluated in terms of body weight, biochemical markers, histological examination of liver and brain tissue, and cognitive-behavioral studies. Also, gene expression of rat brain tissue involving iron transporters Dmt1, TfR1, iron storage protein Fpn1, inflammatory markers Nf-kB, Tnf-α, Il-6, and hepcidin was performed.

RESULTS

Our data indicate that excess iron supplementation for 30 weeks leads to decreased body weight, increased serum iron levels, and decreased RBC levels in iron fed Wistar rats. Morris water maze (MWM) studies after 30 weeks showed increased escape latency in the high iron dose group compared with the control group. Histological studies of the high iron dose group showed an iron accumulation in the liver and brain loss of cellular architecture, and cellular degeneration was observed. Excess iron treatment showed upregulation of the Dmt1 gene in iron metabolism and a remarkable increase in the Nf-kB gene in rat brain tissue.

CONCLUSION

The results show chronic excess iron supplementation leads to iron accumulation in the liver, leading to inflammation in Wistar rats.

Progressive in vivo development of resistance to cefiderocol in Pseudomonas aeruginosa

We report in vivo development of cefiderocol (FDC) resistance among four sequential Pseudomonas aeruginosa clinical isolates ST244 recovered from a single patient, without exposure to FDC, which raises concern about the effectiveness of this novel drug. The first recovered P. aeruginosa isolate (P-01) was susceptible to FDC (2 μg/mL), albeit this MIC value was higher than that of a wild-type P. aeruginosa (0.12-0.25 μg/ml). The subsequent isolated strains (P-02, P-03, P-04) displayed increasing levels of FDC MICs (8, 16, and 64 μg/ml, respectively). Those isolates also showed variable and gradual increasing levels of resistance to most β-lactams tested in this study. Surprisingly, no acquired β-lactamase was identified in any of those isolates. Whole-genome sequence analysis suggested that this resistance was driven by multifactorial mechanisms including mutational changes in iron transporter proteins associated with FDC uptake, ampC gene overproduction, and mexAB-oprM overexpression. These findings highlight that a susceptibility testing to FDC must be performed prior to any prescription.

Effect of zinc depletion/repletion on intestinal iron absorption and iron status in rats

Iron and zinc deficiencies likely coexist in general population. We have previously demonstrated that zinc treatment induces while zinc deficiency inhibits iron absorption in intestinal cell culture models, but this needs to be tested in vivo. In the present study we assessed intestinal iron absorption, iron status (haemoglobin), red blood cell number, plasma ferritin, transferrin receptor, hepcidin) and tissue iron levels in zinc depleted, replete and pair fed control rats. Zinc depletion led to reduction in body weight, tissue zinc levels, intestinal iron absorption, protein and mRNA expression of iron transporters, the divalent metal ion transporter-1, hephaestin and ferroportin, but elevated the intestinal and liver tissue iron levels compared with the pair fed control rats. Zinc repletion led to a significant weight gain compared to zinc deficient rats and normalized the iron absorption, iron transporter expression, tissue iron levels to that of pair fed control rats. Surprisingly, haemoglobin levels and red blood cell number reduced significantly in zinc repleted rats, which could be due to rapid weight gain. Together, these results indicate that whole body zinc status has profound influence on growth, intestinal absorption and systemic utilization of iron, mediated via modulation of iron transporter expression.

Plant growth promoting bacteria for combating salinity stress in plants - Recent developments and prospects: A review

Soil salinity has emerged as a great threat to the agricultural ecosystems throughout the globe. Many continents of the globe are affected by salinity and crop productivity is severely affected. Anthropogenic activities leading to the degradation of agricultural land have also accelerated the rate of salinization in arid and semi-arid regions. Several approaches are being evaluated for remediating saline soil and restoring their productivity. Amongst these, utilization of plant growth promoting bacteria (PGPB) has been marked as a promising tool. This greener approach is suitable for simultaneous reclamation of saline soil and improving the productivity. Salt-tolerant PGPB utilize numerous mechanisms that affect physiological, biochemical, and molecular responses in plants to cope with salt stress. These mechanisms include osmotic adjustment by ion homeostasis and osmolyte accumulation, protection from free radicals by the formation of free radicals scavenging enzymes, oxidative stress responses and maintenance of growth parameters by the synthesis of phytohormones and other metabolites. As salt-tolerant PGPB elicit better plant survival under salinity, they are the potential candidates for enhancing agricultural productivity. The present review focuses on the various mechanisms used by PGPB to improve plant health under salinity. Recent developments and prospects to facilitate better understanding on the functioning of PGPB for ameliorating salt stress in plants are emphasized.

The hypoferremic response to acute inflammation is maintained in thalassemia mice even under parenteral iron loading

Background

Hepcidin controls iron homeostasis by inducing the degradation of the iron efflux protein, ferroportin (FPN1), and subsequently reducing serum iron levels. Hepcidin expression is influenced by multiple factors, including iron stores, ineffective erythropoiesis, and inflammation. However, the interactions between these factors under thalassemic condition remain unclear. This study aimed to determine the hypoferremic and transcriptional responses of iron homeostasis to acute inflammatory induction by lipopolysaccharide (LPS) in thalassemic (Hbb^th3/+) mice with/without parenteral iron loading with iron dextran.

Methods

Wild type and Hbb^th3/+ mice were intramuscularly injected with 5 mg of iron dextran once daily for two consecutive days. After a 2-week equilibration, acute inflammation was induced by an intraperitoneal injection of a single dose of 1 µg/g body weight of LPS. Control groups for both iron loading and acute inflammation received equal volume(s) of saline solution. Blood and tissue samples were collected at 6 hours after LPS (or saline) injection. Iron parameters and mRNA expression of hepcidin as well as genes involved in iron transport and metabolism in wild type and Hbb^th3/+ mice were analyzed and compared by Kruskal–Wallis test with pairwise Mann–Whitney U test.

Results

We found the inductive effects of LPS on liver IL-6 mRNA expression to be more pronounced under parenteral iron loading. Upon LPS administration, splenic erythroferrone (ERFE) mRNA levels were reduced only in iron-treated mice, whereas, liver bone morphogenetic protein 6 (BMP6) mRNA levels were decreased under both control and parenteral iron loading conditions. Despite the altered expression of the aforementioned hepcidin regulators, the stimulatory effect of LPS on hepcidin mRNA expression was blunt in iron-treated Hbb^th3/+ mice. Contrary to the blunted hepcidin response, LPS treatment suppressed FPN1 mRNA expression in the liver, spleen, and duodenum, as well as reduced serum iron levels of Hbb^th3/+ mice with parenteral iron loading.

Conclusion

Our study suggests that a hypoferremic response to LPS-induced acute inflammation is maintained in thalassemic mice with parenteral iron loading in a hepcidin-independent manner.

Iron homeostasis in a mouse model of thalassemia intermedia is altered between adolescence and adulthood

Background

Iron overload is one of common complications of β-thalassemia. Systemic iron homeostasis is regulated by iron-regulatory hormone, hepcidin, which inhibits intestinal iron absorption and iron recycling by reticuloendothelial system. In addition, body iron status and requirement can be altered with age. In adolescence, iron requirement is increased due to blood volume expansion and growth spurt. Heterozygous β-globin knockout mice (Hbb^th3/+; BKO) is a mouse model of thalassemia widely used to study iron homeostasis under this pathological condition. However, effects of age on iron homeostasis, particularly the expression of genes involved in hemoglobin metabolism as well as erythroid regulators in the spleen, during adolescence have not been explored in this mouse model.

Methods

Iron parameters as well as the mRNA expression of hepcidin and genes involved in iron transport and metabolism in wildtype (WT) and BKO mice during adolescence (6–7 weeks old) and adulthood (16–20 weeks old) were analyzed and compared by 2-way ANOVA.

Results

The transition of adolescence to adulthood was associated with reductions in duodenal iron transporter mRNA expression and serum iron levels of both WT and BKO mice. Erythrocyte parameters in BKO mice remained abnormal in both age groups despite persistent induction of genes involved in hemoglobin metabolism in the spleen and progressively increased extramedullary erythropiesis. In BKO mice, adulthood was associated with increased liver hepcidin and ferroportin mRNA expression along with splenic erythroferrone mRNA suppression compared to adolescence.

Conclusion

Our results demonstrate that iron homeostasis in a mouse model of thalassemia intermedia is altered between adolescence and adulthood. The present study underscores the importance of the age of thalassemic mice in the study of molecular or pathophysiological changes under thalassemic condition.

Calcium and zinc decrease intracellular iron by decreasing transport during iron repletion in an in vitro model

PURPOSE

Iron is an essential micronutrient that participates in a number of vital reactions and its absorption may be altered by various nutritional factors such as other micronutrients. Our hypothesis is that iron absorption is decreased because of the interactions with zinc and calcium. We evaluated the interaction between calcium and zinc on iron uptake and transport, intracellular Fe and Zn levels and mRNA expression of DMT1, ferroportin, Zip4 and ZnT1 in an in vitro model.

METHODS

Caco-2 cells were cultivated with 1 mM Ca; 10 or 30 µM Zn and/or 10, 20 or 30 µM Fe for 24 h.

RESULTS

Intracellular Fe decreased in cells incubated with 30 µM Zn or with the mix Ca/10 µM Zn/Fe. Zn mostly increased under Ca, Zn and Fe treatment. DMT1 mRNA expression decreased when intracellular Fe increased. Ferroportin expression displayed no change in cells cultured with different Fe concentrations. The mix of Ca, Zn and Fe increased DMT1 and ferroportin expression mainly under high Zn concentration. Zip4 expression was mostly augmented by Ca and Fe; however, ZnT1 showed no change in all conditions studied. Fe uptake was higher in all the conditions studied compared to control cells; however, Fe transport increased only in cells incubated with Fe alone. In all the other conditions, Fe transport was lower than that in control cells.

CONCLUSIONS

The present findings suggest that Ca and Zn interfere with iron metabolism. This interference is through an increase in ferroportin activity, which results in a diminished net iron absorption.

Maternal protein restriction depresses the duodenal expression of iron transporters and serum iron level in male weaning piglets

To investigate the effects of maternal dietary protein restriction on offspring Fe metabolism, twenty-four second-parity Landrace×Yorkshire sows were randomly allocated to standard-protein (SP) and low-protein (LP) groups. The SP sows were fed diets containing 15 and 18 % crude protein throughout pregnancy and lactation, respectively, whereas the LP sows were subjected to 50 % dietary protein restriction. Offspring birth weight was not affected, but the body weight at weaning (P=0·06) and average daily gain (P=0·01) of the female piglets were significantly decreased. Serum Fe level in the LP piglets was markedly decreased at weaning, especially in males (P=0·03). Serum ferritin level (P=0·08) tended to be lower, yet serum transferrin was greatly higher (P=0·01) in male weaning piglets of the LP group. Duodenal expression of the divalent metal transporter 1 (DMT1) and ferroportin (FPN) was surprisingly reduced (P<0·05) at the level of protein, but not at the mRNA level, in male weaning piglets of the LP group. Male weaning piglets born to the LP sows exhibited higher hepatic hepcidin levels (P=0·09), lower hepatic expression of transferrin (P<0·01) and transferrin receptor 1 (P<0·05) at the level of mRNA. However, no significant differences were observed for hepatic Fe storage, ferritin, transferrin and transferrin receptor 1 protein expression in male weaning piglets of the two groups. These results indicate that maternal protein restriction during pregnancy and lactation influences growth of female offspring at weaning, reduces duodenal expression of Fe transporters (DMT1 and FPN) and decreases serum Fe level in male weaning piglets.

Brain Iron Metabolism Dysfunction in Parkinson's Disease

Dysfunction of iron metabolism, which includes its uptake, storage, and release, plays a key role in neurodegenerative disorders, including Parkinson's disease (PD), Alzheimer's disease, and Huntington's disease. Understanding how iron accumulates in the substantia nigra (SN) and why it specifically targets dopaminergic (DAergic) neurons is particularly warranted for PD, as this knowledge may provide new therapeutic avenues for a more targeted neurotherapeutic strategy for this disease. In this review, we begin with a brief introduction describing brain iron metabolism and its regulation. We then provide a detailed description of how iron accumulates specifically in the SN and why DAergic neurons are especially vulnerable to iron in PD. Furthermore, we focus on the possible mechanisms involved in iron-induced cell death of DAergic neurons in the SN. Finally, we present evidence in support that iron chelation represents a plausable therapeutic strategy for PD.

Liver iron transport

The liver plays a central role in iron metabolism. It is the major storage site for iron and also expresses a complex range of molecules which are involved in iron transport and regulation of iron homeostasis. An increasing number of genes associated with hepatic iron transport or regulation have been identified. These include transferrin receptors (TFR1 and 2), a ferrireductase (STEAP3), the transporters divalent metal transporter-1 (DMT1) and ferroportin (FPN) as well as the haemochromatosis protein, HFE and haemojuvelin (HJV), which are signalling molecules. Many of these genes also participate in iron regulatory pathways which focus on the hepatic peptide hepcidin. However, we are still only beginning to understand the complex interactions between liver iron transport and iron homeostasis. This review outlines our current knowledge of molecules of iron metabolism and their roles in iron transport and regulation of iron homeostasis.