Nitric oxide inhibition decreases bleomycin-detectable iron in spleen, bone marrow cells and heart but not in liver in exercise rats

Iron and zinc homeostases in female rats with physically active and sedentary lifestyles

To determine the effects of repeated physical activity on iron and zinc homeostases in a living system, we quantified blood and tissue levels of these two metals in sedentary and physically active Long-Evans rats. At post-natal day (PND) 22, female rats were assigned to either a sedentary or an active treatment group (n = 10/group). The physically active rats increased their use of a commercially-constructed stainless steel wire wheel so that, by the end of the study (PND 101), they were running an average of 512.8 ± 31.9 (mean ± standard error) min/night. After euthanization, plasma and aliquots of liver, lung, heart, and gastrocnemius muscle were obtained. Following digestion, non-heme iron and zinc concentrations in plasma and tissues were measured using inductively coupled plasma optical emission spectroscopy. Concentrations of both non-heme iron and zinc in plasma and liver were significantly decreased among the physically active rats relative to the sedentary animals. In the lung, both metals were increased in concentration among the physically active animals but the change in zinc did not reach significance. Similarly, tissue non-heme iron and zinc levels were both increased in heart and muscle from the physically active group. It is concluded that repeated physical activity in an animal model can be associated with a translocation of both iron and zinc from sites of storage (e.g. liver) to tissues with increased metabolism (e.g. the lung, heart, and skeletal muscle).

Cyclophosphamide induces a significant increase in iron content in the liver and spleen of mice

Objective:

Oxidative stress is one of the major mechanisms of cyclophosphamide (CPX)-induced toxicities. However, it is unknown how CPX induces oxidative stress. Based on the available information, we speculated that CPX could increase iron content in the tissues and then induce oxidative stress.

Method:

We tested this hypothesis by investigating the effects of CPX on iron and ferritin contents, expression of transferrin receptor 1 (TfR1), ferroportin 1 (Fpn1), iron regulatory proteins (IRPs), hepcidin, and nuclear factor erythroid 2-related factor-2 (Nrf2) in the liver and spleen, and also on reticulocyte count, immature reticulocyte fraction, and hemoglobin (Hb) in the blood in c57/B6 mouse.

Results:

We demonstrated that CPX could induce a significant increase in iron contents and ferritin expression in the liver and spleen, notably inhibit erythropoiesis and Hb synthesis and lead to a reduction in iron usage. The reduced expression in TfR1 and Fpn1 is a secondary effect of CPX-induced iron accumulation in the liver and spleen and also partly associated with the suppressed IRP/iron-responsive element system, upregulation of hepcidin, and downregulation of Nrf2.

Conclusions:

The reduced iron usage is one of the causes for iron overload in the liver and spleen and the increased tissue iron might be one of the mechanisms for CPX to induce oxidative stress and toxicities.

Cystathionine β-synthase (CBS) deficiency suppresses erythropoiesis by disrupting expression of heme biosynthetic enzymes and transporter

The reduced iron usage induced by the suppression of erythropoiesis is a major cause of the systemic iron overload in CBS knockout (CBS^−/−) mice. However, the relevant mechanisms are unknown. Here, we examined changes in granulocyte/erythroid cell ratios, iron content, and expression of iron-metabolism proteins, including; two key enzymes involved in the heme biosynthetic pathway, ALAS2 (delta-aminolevulinate synthase 2) and FECH (ferrochelatase), a heme exporter from the cytosol and mitochondria, FLVCR (feline leukemia virus subgroup C cellular receptor) as well as EPO (erythropoietin), EPOR (erythropoietin receptor) and HIF-2α (hypoxia inducible factor-2 subunit α), in the blood, bone marrow or liver of CBS^−/− (homozygous), CBS^+/− (heterozygous) and CBS^+/+ (Wild Type) mice. Our findings demonstrate that CBS deficiency can induce a significant reduction in the expression of ALAS2, FECH, FLVCR, HIF-2α, EPO, and EPOR as well as an increase in interleukin-6 (IL-6), hepcidin and iron content in the blood, bone marrow or liver of mice. We conclude that the suppression of erythropoiesis is mainly due to the CBS deficiency-induced disruption in the expression of heme biosynthetic enzymes and heme-transporter.

Tissue iron is negatively correlated with TERC or TERT mRNA expression: A heterochronic parabiosis study in mice

To test the hypothesis that iron accumulation in tissues with age is a key harmful factor for the development of aging, we established heterochronic parabiosis-pairings and investigated changes in serum iron, the expression of major iron transport proteins and iron contents, as well as telomerase reverse transcriptase (TERT), telomerase RNA component (TERC), and telomere length in the liver, kidney and heart of Y-O(O) (old pairing with young), Y-O(Y) (young pairing with old), O-O (pairings between two old) and Y-Y (pairings between two young) mice. We demonstrated that the reduced serum iron, increased iron and reduced expression of TERT and TERC in the tissues of aged mice are reversible by exposure to a younger mouse’s circulation. All of these measurements in young mice are reversible by exposure to an older mouse’s circulation. Correlation analysis showed that tissue iron is negatively correlated with TERT and TERC expression in the liver, kidney and heart of parabiotic mice. These findings provide new evidence for the key role of iron in aging and also imply the existence of rejuvenating factors in young serum with an anti-ageing role that act by reversing the impaired activity of iron metabolism in old mice.

Cystathionine β-synthase is required for body iron homeostasis

Cystathionine β-synthase (CBS) catalyzes the transsulfuration pathway and contributes, among other functions, to the generation of hydrogen sulfide. In view of the exceptionally high expression of CBS in the liver and the common interleukin-6 pathway used in the regulatory systems of hydrogen sulfide and hepcidin, we speculate that CBS is involved in body iron homeostasis. We found that CBS knockout (CBS^-/- ) mice exhibited anemia and a significant increase in iron content in the serum, liver, spleen, and heart, along with severe damage to the liver, displaying a hemochromatosis-like phenotype. A high level of hepatic and serum hepcidin was also found. A major cause of the systemic iron overload is the reduced iron usage due to suppressed erythropoiesis, which is consistent with an increase in interleukin-6 and reduced expression of erythropoietin. Importantly, in the liver, absence of CBS caused both a reduction in the transcriptional factor nuclear factor erythroid 2-related factor-2 and an up-regulation of hepcidin that led to a decrease in the iron export protein ferroportin 1. The resulting suppression of iron export exacerbates iron retention, causing damage to hepatocytes. Finally, administration of CBS-overexpressing adenovirus into CBS mutant mice could partially reverse the iron-related phenotype.

CONCLUSION

Our findings point to a critical role of CBS in iron homeostasis of the body, and the liver in particular; it is likely that a hemochromatosis-like phenotype in patients can be induced by aberration not only in the expression of key molecules in the hepcidin pathway but also of those related to CBS. (Hepatology 2018;67:21-35).

Ghrelin is Negatively Correlated with Iron in the Serum in Human and Mice

BACKGROUND/AIMS

The studies in the patients with iron deficiency anemia (IDA) implied the existence of the association of ghrelin with iron or hepcidin levels in the plasma under the pathophysiological conditions. We hypothesized that fasting may be able to affect iron metabolism via ghrelin under the physiological conditions.

METHODS

We investigated the effects of fasting on serum ghrelin and iron contents in healthy volunteers (23-31 years) and C57BL/6 male mice (8-week-olds) under the physiological conditions.

RESULTS

Fasting induced a significant elevation in both total ghrelin and acylated ghrelin and a reduction in iron levels in the serum of both human and mice. Correlation analysis demonstrated that total ghrelin or acylated ghrelin is negatively correlated with iron in the serum in human and mice.

CONCLUSION

Ghrelin has a role to reduce serum iron under the conditions of fasting.

Fasting up-regulates ferroportin 1 expression via a Ghrelin/GHSR/MAPK signaling pathway

The significant positive correlation between ghrelin and iron and hepcidin levels in the plasma of children with iron deficiency anemia prompted us to hypothesize that ghrelin may affect iron metabolism. Here, we investigated the effects of fasting or ghrelin on the expression of hepcidin, ferroportin 1 (Fpn1), transferrin receptor 1 (TfR1), ferritin light chain (Ft-L) proteins, and ghrelin, and also hormone secretagogue receptor 1 alpha (GHSR1α) and ghrelin O-acyltransferase (GOAT) mRNAs in the spleen and/or macrophage. We demonstrated that fasting induces a significant increase in the expression of ghrelin, GHSR1α, GOAT, and hepcidin mRNAs, as well as Ft-L and Fpn1 but not TfR1 proteins in the spleens of mice in vivo. Similar to the effects of fasting on the spleen, ghrelin induced a significant increase in the expression of Ft-L and Fpn1 but not TfR1 proteins in macrophages in vitro. In addition, ghrelin was found to induce a significant enhancement in phosphorylation of ERK as well as translocation of pERK from the cytosol to nuclei. Furthermore, the increased pERK and Fpn1 induced by ghrelin was demonstrated to be preventable by pre-treatment with either GHSR1α antagonist or pERK inhibitor. Our findings support the hypothesis that fasting upregulates Fpn1 expression, probably via a ghrelin/GHSR/MAPK signaling pathway.

Long-term aerobic exercise increases redox-active iron through nitric oxide in rat hippocampus

Adult hippocampus is highly vulnerable to iron-induced oxidative stress. Aerobic exercise has been proposed to reduce oxidative stress but the findings in the hippocampus are conflicting. This study aimed to observe the changes of redox-active iron and concomitant regulation of cellular iron homeostasis in the hippocampus by aerobic exercise, and possible regulatory effect of nitric oxide (NO). A randomized controlled study was designed in the rats with swimming exercise treatment (for 3 months) and/or an unselective inhibitor of NO synthase (NOS) (L-NAME) treatment. The results from the bleomycin-detectable iron assay showed additional redox-active iron in the hippocampus by exercise treatment. The results from nonheme iron content assay, combined with the redox-active iron content, showed increased storage iron content by exercise treatment. NOx (nitrate plus nitrite) assay showed increased NOx content by exercise treatment. The results from the Western blot assay showed decreased ferroportin expression, no changes of TfR1 and DMT1 expressions, increased IRP1 and IRP2 expression, increased expressions of eNOS and nNOS rather than iNOS. In these effects of exercise treatment, the increased redox-active iron content, storage iron content, IRP1 and IRP2 expressions were completely reversed by L-NAME treatment, and decreased ferroportin expression was in part reversed by L-NAME. L-NAME treatment completely inhibited increased NOx and both eNOS and nNOS expression in the hippocampus. Our findings suggest that aerobic exercise could increase the redox-active iron in the hippocampus, indicating an increase in the capacity to generate hydroxyl radicals through the Fenton reactions, and aerobic exercise-induced iron accumulation in the hippocampus might mainly result from the role of the endogenous NO.

Effects of grape seed polyphenols on oxidative damage in liver tissue of acutely and chronically exercised rats

The objective of the present study was to investigate the effects of grape seed extract (GSE) supplementation on oxidative stress and antioxidant defense markers in liver tissue of acutely and chronically exercised rats. Rats were randomly assigned to six groups: Control (C), Control Chronic Exercise (CE), Control Acute Exercise (AE), GSE-supplemented Control (GC), GSE-supplemented Chronic Exercise(GCE) and GSE-supplemented Acute Exercise (GAE). Rats in the chronic exercise groups were subjected to a six-week treadmill running and in the acute exercise groups performed an exhaustive running. Rats in the GSE supplemented groups received GSE (100 mg.kg(-1) .day(-1) ) in drinking water for 6 weeks. Liver tissues of the rats were taken for the analysis of malondialdehyde (MDA), nitric oxide (NO) levels and total antioxidant activity (AOA) and xanthine oxidase (XO) activities. MDA levels decreased with GSE supplementation in control groups but increased in acute and chronic exercise groups compared to their non-supplemented control. NO levels increased with GSE supplementation. XO activities were higher in AE group compared to the CE group. AOA decreased with GSE supplementation. In conclusion, while acute exercise triggers oxidative stress, chronic exercise has protective role against oxidative stress. GSE has a limited antioxidant effect on exercise-induced oxidative stress in liver tissue.

Changes of iron stores and duodenal transepithelial iron transfer during regular exercise in rats

It is unclear whether regular exercise depletes body iron stores and how exercise regulates iron absorption. In this study, growing female Sprague-Dawley rats were fed a high-iron diet (300 mg iron/kg) and subjected to swimming for 1, 3, or 12 months. Their body weight, liver nonheme iron content (NHI), spleen NHI, blood hemoglobin (Hb) concentration, hematocrit (Hct), and kinetics of 59Fe transfer across isolated duodenal segments were then compared with sedentary controls. The main results were as follows: exercise for 1 month enhanced the transepithelial 59Fe transfer and increased liver NHI content and Hb concentration; exercise for 3 months inhibited transepithelial 59Fe transfer without affecting the liver and spleen NHI content, Hb concentration, and Hct; exercise for 12 months did not affect these parameters as compared with the corresponding sedentary controls; and the changes in transepithelial iron transfer were not associated with basolateral iron transfer. Our findings demonstrated that chronic, regular exercise in growing rats with a high dietary iron content does not deplete iron stores in the liver and spleen and may possibly enhance or inhibit duodenal iron absorption and even maintain duodenal iron absorption at the sedentary level, at least, in part depending on growth.

Identification of transcriptionally regulated genes in response to cellular iron availability in rat hippocampus

The present study was attempted to identify transcriptionally regulated genes of the normal neurocytes responsive to iron availability. Postnatal rat hippocampus cells were primarily cultured either under the iron-loaded or depleted conditions. These cultured cells were applied for the generation of subtracted complementary DNA libraries by the suppression subtraction hybridization (SSH) and for the subsequent identification of differentially expressed transcripts by reverse Northern blot. The differentially expressed genes were chosen to perform sequencing, and then some of them were performed by Northern blot analysis for observation of their expression in the hippocampus of rats with the different iron status. The results indicated that five unique transcripts were strong candidates for differential expression in cellular iron repletion, one of them is a novel sequence (GenBank No. AF 433878), while 26 unique transcripts were strong candidates for differential expression in cellular iron deprivation, one of them is a novel sequence (GenBank No. AY 912101). The revealed known genes responsive to iron availability were previously unknown to respond to iron availability, or have not been determined in the brain, have not even been currently determined in their physiological and biological functions. Interestingly, the proteins encoded by most of the known genes are either directly pointed to or indirectly associated with the molecules that play important, even key roles in cellular signal transduction and the cell cycle. These findings lead to the important suggestion that the cellular responses to iron availability involve extensive transcriptional regulation and cellular signal transduction. Therefore, iron may serve as a signal, which directly and/or indirectly regulates or modulates cell functions.

Molecular analysis of increased iron status in moderately exercised rats

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