Effects of colloidal iron overload on renal and hepatic siderosis and the femur in male rats

Functional consequence of Iron dyshomeostasis and ferroptosis in systemic lupus erythematosus and lupus nephritis

Systemic lupus erythematosus (SLE) and its renal manifestation Lupus nephritis (LN) are characterized by a dysregulated immune system, autoantibodies, and injury to the renal parenchyma. Iron accumulation and ferroptosis in the immune effectors and renal tubules are recently identified pathological features in SLE and LN. Ferroptosis is an iron dependent non-apoptotic form of regulated cell death and ferroptosis inhibitors have improved disease outcomes in murine models of SLE, identifying it as a novel druggable target. In this review, we discuss novel mechanisms by which iron accumulation and ferroptosis perpetuate immune cell mediated pathology in SLE/LN. We highlight intra-renal dysregulation of iron metabolism and ferroptosis as an underlying pathogenic mechanism of renal tubular injury. The basic concepts of iron biology and ferroptosis are also discussed to expose the links between iron, cell metabolism and ferroptosis, that identify intracellular pro-ferroptotic enzymes and their protein conjugates as potential targets to improve SLE/LN outcomes.

Animal models of kidney iron overload and ferroptosis: a review of the literature

In recent years, it has been identified that excess iron contributes to the development of various pathologies and their complications. Kidney diseases do not escape the toxic effects of iron, and ferroptosis is identified as a pathophysiological mechanism that could be a therapeutic target to avoid damage or progression of kidney disease. Ferroptosis is cell death associated with iron-dependent oxidative stress. To study the effects of iron overload (IOL) in the kidney, numerous animal models have been developed. The methodological differences between these models should reflect the IOL-generating mechanisms associated with human IOL diseases. A careful choice of animal model should be considered for translational purposes.

Differences in bone microarchitecture between genetic and secondary iron-overload mouse models suggest a role for hepcidin deficiency in iron-related osteoporosis

Iron overload is one of the secondary osteoporosis etiologies. Cellular and molecular mechanisms involved in iron-related osteoporosis are not fully understood.

AIM

The aim of the study was to investigate the respective roles of iron excess and hepcidin, the systemic iron regulator, in the development of iron-related osteoporosis.

MATERIAL AND METHODS

We used mice models with genetic iron overload (GIO) related to hepcidin deficiency (Hfe-/- and Bmp6-/- ) and secondary iron overload (SIO) exhibiting a hepcidin increase secondary to iron excess. Iron concentration and transferrin saturation levels were evaluated in serum and hepatic, spleen, and bone iron concentrations were assessed by ICP-MS and Perl's staining. Gene expression was evaluated by quantitative RT-PCR. Bone micro-architecture was evaluated by micro-CT. The osteoblastic MC3T3 murine cells that are able to mineralize were exposed to iron and/or hepcidin.

RESULTS

Despite an increase of bone iron concentration in all overloaded mice models, bone volume/total volume (BV/TV) and trabecular thickness (Tb.Th) only decreased significantly in GIO, at 12 months for Hfe-/- and from 6 months for Bmp6-/- . Alterations in bone microarchitecture in the Bmp6-/- model were positively correlated with hepcidin levels (BV/TV (ρ = +.481, p < .05) and Tb.Th (ρ = +.690, p < .05). Iron deposits were detected in the bone trabeculae of Hfe-/- and Bmp6-/- mice, while iron deposits were mainly visible in bone marrow macrophages in secondary iron overload. In cell cultures, ferric ammonium citrate exposure abolished the mineralization process for concentrations above 5 μM, with a parallel decrease in osteocalcin, collagen 1, and alkaline phosphatase mRNA levels. Hepcidin supplementation of cells had a rescue effect on the collagen 1 and alkaline phosphatase expression level decrease.

CONCLUSION

Together, these data suggest that iron in excess alone is not sufficient to induce osteoporosis and that low hepcidin levels also contribute to the development of osteoporosis.

REPIN1 regulates iron metabolism and osteoblast apoptosis in osteoporosis

Osteoporosis is not well treated due to the difficulty of finding commonalities between the various types of it. Iron homeostasis is a vital component in supporting biochemical functions, and iron overload is recognized as a common risk factor for osteoporosis. In this research, we found that there is indeed evidence of iron accumulation in the bone tissue of patients with osteoporosis and REPIN1, as an origin specific DNA binding protein, may play a key role in this process. We revealed that sh-Repin1 therapy can rescue bone loss in an iron-overload-induced osteoporosis mouse model. Knockdown of Repin1 can inhibit apoptosis and enhance the resistance of osteoblasts to iron overload toxicity. REPIN1 promoted apoptosis by regulating iron metabolism in osteoblasts. Mechanistically, knockdown of Repin1 decreased the expression of Lcn2, which ameliorated the toxic effects of intracellular iron overload. The anti-iron effect of lentivirus sh-Repin1 was partially reversed or replicated by changing LCN2 expression level via si-RNA or plasmid, which indirectly verified the key regulatory role of LCN2 as a downstream target. Furthermore, the levels of BCL2 and BAX, which play a key role in the mitochondrial apoptosis pathway, were affected. In summary, based on the results of clinical specimens, animal models and in vitro experiments, for the first time, we proved the key role of REPIN1 in iron metabolism-related osteoporosis.

Quercetin protects against iron overload-induced osteoporosis through activating the Nrf2/HO-1 pathway

AIMS

Eucommia is the tree bark of Eucommia japonica, family Eucommiaceae. In traditional Chinese medicine, Eucommia is often used to treat osteoporosis. Quercetin (QUE), a major flavonoid extract of Eucommia japonica, has been reported to have anti-osteoporosis effects. However, there are no studies reporting the mechanism of QUE in the treatment of iron overload-induced osteoporosis. This study set out to investigate the therapeutic effects of QUE against iron overload-induced bone loss and its potential molecular mechanisms.

MATERIALS AND METHODS

In vitro, MC3T3-E1 cells were used to study the effects of QUE on osteogenic differentiation, anti-apoptosis and anti-oxidative stress damage in an iron overload environment (FAC 200 μM). In vivo, we constructed an iron overload mouse model by injecting iron dextrose intraperitoneally and assessed the osteoprotective effects of QUE by Micro-CT and histological analysis.

KEY FINDINGS

In vitro, we found that QUE increased the ALP activity of MC3T3-E1 cells in iron overload environment, promoted the formation of bone mineralized nodules and upregulated the expression of Runx2 and Osterix. In addition, QUE was able to reduce FAC-induced apoptosis and ROS production, down-regulated the expression of Caspase3 and Bax, and up-regulated the expression of Bcl-2. In further studies, we found that QUE activated the Nrf2/HO-1 signaling pathway and attenuated FAC-induced oxidative stress damage. The results of the in vivo study showed that QUE was able to reduce iron deposition induced by iron dextrose and attenuate bone loss.

SIGNIFICANCE

Our results suggested that QUE protects against iron overload-induced osteoporosis by activating the Nrf2/HO-1 signaling pathway.

Iron overload impairs renal function and is associated with vascular calcification in rat aorta

Vascular calcification (VC) has been associated with a risk of cardiovascular diseases. Iron may play a critical role in progressive VC. Therefore, we investigated the effects of iron overload on the aorta of rats. A rat model of iron overload was established by intraperitoneal injection of Iron-Dextran. The levels of iron, calcium, and ALP activity were detected. Von Kossa staining and Perl's staining were conducted. The expression of iron metabolism-related and calcification related factors were examined in the aortic tissue of rats. The results showed serum and aortic tissue iron were increased induced by iron overload and excessive iron induced hepatic and renal damage. In iron overload rats, the expression of divalent metal transporter 1 (DMT1) and hepcidin were higher, but ferroportin1 (FPN1) was lower. Von Kossa staining demonstrated calcium deposition in the aorta of iron overload rats. The calcium content and ALP activity in serum and aortic tissue were increased and iron level in aortic tissue highly correlated with calcium content and ALP activity. The expressions of the osteogenic markers were increased while a decrease of Alpha-smooth muscle actin (α-SMA) in the aortic tissue of iron overload rats. IL-24 was increased during the calcification process induced by iron. Overall, we demonstrated excessive iron accumulation in the aortic tissue and induced organs damage. The iron metabolism-related factors were significantly changed during iron overload. Moreover, we found that iron overload leads to calcium deposition in aorta, playing a key role in the pathological process of VC by mediating osteoblast differentiation factors.

Ferric ammonium citrate (FAC)-induced inhibition of osteoblast proliferation/differentiation and its reversal by soybean-derived peptides (SDP)

Ferric citrate has been used to treat hyperphosphatemia, a prevalent symptom in patients with chronic kidney disease while ferric ammonium citrate (FAC), a more dissolvable format, is widely used as food additive. However, excess iron is associated with osteoporosis. Dietary soybean products have been shown to prevent the progression of osteoporosis. In this study, a group of peptides, referred as P3, was identified from the enzymolysis of soybean protein isolates, and its biological functions were investigated. The results showed that MC3T3-E1 cell cycle progression from G0/G1 to S phase was accelerated by P3 treatment. MC3T3-E1 cell proliferation was enhanced by P3 via ERK1/2 activation. Importantly, P3 treatment abolished the antiproliferative effect of FAC on MC3T3-E1 cell. In addition, P3 treatment increased the expression of ALP, COL-1, OCN, consequently promoting the differentiation and mineralization of MC3T3-E1 cells via activation of p38 MAPK pathway. Consequently, P3 treatment was able to reverse the inhibitory effect of FAC on osteoblasts differentiation and mineralization. Our findings suggest P3, as a dietary supplement, has a potential therapeutic function to attenuate the adverse effects of FAC on bone metabolism and to prevent osteoporosis progression.

The Role of the Trabecular Bone Score in the Assessment of Osteoarticular Disorders in Patients with HFE-Hemochromatosis: A Single-Center Study from Poland

Type 1 hereditary hemochromatosis (HH) is an autosomal, recessive genetic entity with systemic iron overload. Iron homeostasis disorders develop as a result of HFE gene mutations, which are associated with hepcidin arthropathy or osteoporosis and may cause permanent disability in HH patients despite a properly conducted treatment with phlebotomies. In this study, selected parameters of calcium and phosphate metabolism were analyzed in combination with the assessment of bone mineral density (BMD) disorders in patients from northern Poland with clinically overt HFE-HH. BMD was determined by a dual-energy X-ray absorptiometry (DXA) test with the use of the trabecular bone score (TBS) function. The study included 29 HH patients (mean age = 53.14 years) who were compared with 20 healthy volunteers. A significantly lower TBS parameter and serum 25-OH-D3 concentration, a higher concentration of intact parathormone and more a frequent occurrence of joint pain were found in HH patients compared with the control group. In HH patients, the diagnosis of liver cirrhosis was associated with lower serum 25-OH-D3 and osteocalcin concentrations. In HH, DXA with the TBS option is a valuable tool in the early assessment of the bone microarchitecture and fracture risk. A supplementation of vitamin D, monitoring its concentration, should be considered especially in HH patients with liver damage and liver cirrhosis.

The protective mechanism of resveratrol against hepatic injury induced by iron overload in mice

Excessive iron deposition can produce toxicity. Liver, as the main storage site of iron, is more vulnerable to excessive iron than other organs. Many studies have found that Resveratrol (RES) can effectively eliminate oxygen free radicals and resist lipid peroxide damage. However, studies investigating the mechanism of how RES prevents liver injury induced by iron overload are few. This study aims to observe the protective effect of RES on liver injury induced by iron overload in mice. Mice, except for the control group, received an intraperitoneal injection of iron dextran (50 mg/kg) every morning. The L-RES and H-RES groups received intragastric administration of low- and high-concentration RES solutions (20 or 50 mg/kg). The deferoxamine (DFO) group was intraperitoneally injected with DFO (50 mg/kg), while the control and iron overload groups were intraperitoneally injected with the same amount of normal saline every afternoon. Two weeks after continuous administration, iron-overloaded mice treated with high and low doses of RES significantly improved liver injury (GOT and GPT) and decreased LDH activity and MDA content and increased SOD and GSH activities (P < 0.01). Morphological tests showed that RES treatment can reduce liver iron deposition and improve liver pathological changes in iron-overloaded mice. Furthermore, RES treatment caused a significant decrease in Ft expression (P < 0.01). In conclusion, RES can alleviate liver injury in iron-overloaded mice. The mechanism may be related to improve the antioxidant capacity and reduce excess iron in the liver.

Protective effects of grape seed proanthocyanidins against iron overload-induced renal oxidative damage in rats

BACKGROUND

Excessive exposure to iron can cause kidney damage, and chelating drugs such as deferoxamine and deferiprone have limited usefulness in treating iron poisoning. This study was designed to investigate the protective effects of grape seed proanthocyanidins (GSPAs) against iron overload induced nephrotoxicity in rats. The roles of GSPAs in chelating iron, antioxidant activity, renal function, pathological section, and apoptosis-related gene expression were assessed.

METHODS

Newly weaned male Sprague-Dawley rats aged 21 days (weight, 65 ± 5 g) were randomly divided into four groups containing 10 rats each: normal control (negative) group, iron overload (positive) group, GSPAs group, and GSPAs + iron overload (test) group. Iron dextran injections (2.5 mg⋅ kg^-1) and GSPAs (25 mg⋅ kg^-1) were intraperitoneally and intragastrically administered to rats daily for 7 weeks, respectively. Measurements included red blood cell (RBC) count and hemoglobin (Hb) level, serum total iron-binding capacity (TIBC), renal iron content, glutathione peroxidase (GSH-Px) activity, superoxide dismutase (SOD) activity, malondialdehyde (MDA) content, total antioxidant activity (T-AOC), creatinine (CR) and blood urea nitrogen (BUN) levels, pathological changes, and apoptotic Fas, Bax expressions in the kidney tissue. Differences among the dietary groups were determined using one-way analysis of variance with post-hoc Tukey's test. P < 0.05 was considered statistically significant.

RESULTS

RBC count, Hb level, renal iron content, MDA content, CR and BUN levels, and Fas, Bax expressions significantly increased in the positive group than in the negative group; contrarily, TIBC, GSH-Px activity, and T-AOC significantly decreased in the positive group than in the negative group (P < 0.05). Although not statistically significant, SOD activity was slightly reduced in the positive group than in the negative group. Inflammatory cell infiltration and fibrous tissue proliferation were observed in the kidney tissue of the rats in the positive group; in contrast, the rats exhibited better recovery when GSPAs were used instead of iron alone. Compared with the positive group, RBC counts, Hb levels, renal iron contents, the MDA content, CR and BUN levels, and Fas, Bax expressions significantly decreased, whereas the TIBC, the GSH-Px and SOD activities as well as T-AOC significantly increased in the test group rats (P < 0.05). There were no significant differences in the RBC counts, Hb levels, TIBC, renal iron contents, the SOD activity and MDA content, CR and BUN levels, and Fas expression between the GSPAs and negative groups. The GSH-Px activity and T-AOC were significantly increased whereas Bax expression was significantly decreased in the GSPAs group rats than in the negative group rats (P < 0.05). The rats in the GSPAs, test, and negative groups displayed glomeruli and tubules with a clear structure; further, the epithelial cells in the renal tubules were neatly arranged.

CONCLUSIONS

GSPAs have protective effects on nephrotoxicity in rats with iron overload. Thus, further investigation of GSPAs as a new and natural phytochemo-preventive agent against iron overload is warranted.

A Wearable Iron-Based Implant as an Intramedullary Nail in Tibial Shaft Fracture of Sheep

A stable repaired fracture is the key factor responsible for the recovery of a damaged bone. The iron-based implant is one of the biodegradable metals that have been proven safe as a fracture fixation device. The objective of our experimental approach was to examine the potential of the iron-based implant as a biodegradable metal in tibia shaft fracture in sheep chronically. The samples used for this experiment were iron-based and stainless steel implants. Each had a diameter of 5 mm. These samples were analyzed through 3 phases which are material characterization, in vitro and in vivo examination. The samples were examined using a scanning electron microscope with energy dispersive spectrometer and X-ray diffraction. Based on the analysis carried out, the samples contained 90,02% and 60,81% Fe for iron-based implant and stainless implant, respectively. Both implants maintained high viability when being in contact with calf pulmonary artery endothelial cells, indicating that both implants had a minimum response to the cell in a hemocytometer and methyl tetrazolium (MTT) assay. The systemic effect of the implants was observed using hematology and blood chemistry examination. Data collection also shows that both implants also had a minimum response to the erythrocytes, leucocytes, blood chemistry, and blood mineral during the period of observation. Therefore, it could be concluded that the iron-based implant is tolerable for a period of 9 months. It also has the potential to be used as a biodegradable orthopedic implant.

Icariin protects against iron overload-induced bone loss via suppressing oxidative stress

Iron overload is common in patients with diseases such as hemoglobinopathies, hereditary hemochromatosis or elderly men and postmenopausal women. This disorder is frequently associated with bone loss and recently has been considered as an independent risk factor for osteoporosis. By excess reactive oxygen species (ROS) production through Fenton reaction, iron could induce osteoblast apoptosis, inhibit osteoblast osteogenic differentiation. Moreover, Iron could also promote osteoclasts differentiation and bone absorption. The goal of the study is to investigate whether icariin could reverse iron overload-induced bone loss in vitro and in vivo. Icariin is the major active ingredient of Herba Epimedii and has antioxidant, antiosteoporosis functions. In the current study, we demonstrated that oral administration of icariin significantly prevented bone loss in iron overloaded mice. Icariin could protect against iron overload-induced mitochondrial membrane potential dysfunction and ROS production, promote osteoblast survival and reverse the reduction of Runx2, alkaline phosphatase, and osteopontin expression induced by iron overload. Icariin also inhibited osteoclasts differentiation and function. Moreover, we also found that icariin remarkably reduced iron accumulation in bone marrow, suggesting that icariin has the ability to regulate systemic iron metabolism in vivo. These results indicated that icariin could be a potential natural resource for developing medicines to prevent or treat iron overload-induced osteoporosis.

Cardiovascular, liver, and renal toxicity associated with an intravenous ferric carboxymaltose similar versus the originator compound

Background

Ferric carboxymaltose (FCM) is a stable, non-dextran-based intravenous iron complex used to treat iron deficiency of various etiologies. As FCM is a nonbiological complex drug and cannot be fully characterized by physicochemical analyses, it is important to demonstrate in nonclinical models that FCM similars (FCMS) have similar biodistribution.

Materials and methods

A total of 30 nonanemic rats were treated weekly with 40 mg iron/kg body weight intravenous FCM, FCMS, or isotonic saline (controls) for 4 weeks. Blood pressure, liver enzymes, and renal function were evaluated. In liver, heart, and kidney tissue, markers for oxidative stress (malondialdehyde to assess lipid peroxidation and antioxidant enzymes) and inflammation (TNFα and IL6) were measured. Iron deposits were localized.

Results

The FCMS-treated group had significantly lower blood pressure, higher liver enzymes, increased proteinuria, and reduced creatinine clearance versus the FCM and control groups by day 29. Serum iron and transferrin saturation were significantly higher with FCMS versus FCM or controls. Iron deposition was altered in FCMS-treated animals, with decreased ferritin deposits and iron deposition outside the physiological storage compartments. Markers for lipid peroxidation and antioxidant-enzyme activity were significantly increased after FCMS administration versus FCM and controls, as were inflammatory markers.

Conclusion

Results from this blinded nonclinical study demonstrated significant differences between the originator FCM and this FCMS.

Wnt5a is a key target for the pro-osteogenic effects of iron chelation on osteoblast progenitors

Iron overload due to hemochromatosis or chronic blood transfusions has been associated with the development of osteoporosis. However, the impact of changes in iron homeostasis on osteoblast functions and the underlying mechanisms are poorly defined. Since Wnt signaling is a critical regulator of bone remodeling, we aimed to analyze the effects of iron overload and iron deficiency on osteoblast function, and further define the role of Wnt signaling in these processes. Therefore, bone marrow stromal cells were isolated from wild-type mice and differentiated towards osteoblasts. Exposure of the cells to iron dose-dependently attenuated osteoblast differentiation in terms of mineralization and osteogenic gene expression, whereas iron chelation with deferoxamine promoted osteogenic differentiation in a time- and dose-dependent manner up to 3-fold. Similar results were obtained for human bone marrow stromal cells. To elucidate whether the pro-osteogenic effect of deferoxamine is mediated via Wnt signaling, we performed a Wnt profiler array of deferoxamine-treated osteoblasts. Wnt5a was amongst the most highly induced genes. Further analysis revealed a time- and dose-dependent induction of Wnt5a being up-regulated 2-fold after 48 h at 50 μM deferoxamine. Pathway analysis using specific inhibitors revealed that deferoxamine utilized the phosphatidylinositol-3-kinase and nuclear factor of activated T cell pathways to induce Wnt5a expression. Finally, we confirmed the requirement of Wnt5a in the deferoxamine-mediated osteoblast-promoting effects by analyzing the matrix mineralization of Wnt5a-deficient cells. The promoting effect of deferoxamine on matrix mineralization in wild-type cells was completely abolished in Wnt5a^-/- cells. Thus, these data demonstrate that Wnt5a is critical for the pro-osteogenic effects of iron chelation using deferoxamine.

The role of S-methylisothiourea hemisulfate as inducible nitric oxide synthase inhibitor against kidney iron deposition in iron overload rats

Background:

Iron dextran is in common use to maintain iron stores. However, it is potentially toxic and may lead to iron deposition (ID) and impair functions of organs. Iron overload can regulate the expression of inducible nitric oxide synthase (iNOS) in some cells that has an important role in tissue destruction. S-methylisothiourea hemisulfate (SMT) is a direct inhibitor of iNOS, and this study was designed to investigate the effect of SMT against kidney ID in iron overload rats.

Materials and Methods:

24 Wistar rats (male and female) were randomly assigned to two groups. Iron overloading was performed by iron dextran 100 mg/kg/day every other day for 2 weeks. In addition, during the study, groups 1 and 2 received vehicle and SMT (10 mg/kg, ip), respectively. Finally, blood samples were obtained, and the kidneys were prepared for histopathological procedures.

Results:

SMT significantly reduced the serum levels of creatinine and blood urea nitrogen. However, SMT did not alter the serum levels of iron and nitrite, and the kidney tissue level of nitrite. Co-administration of SMT with iron dextran did not attenuate the ID in the kidney.

Conclusion:

SMT, as a specific iNOS inhibitor, could not protect the kidney from ID while it attenuated the serum levels of kidney function biomarkers.

Iron overload inhibits osteogenic commitment and differentiation of mesenchymal stem cells via the induction of ferritin

Osteogenic differentiation of multipotent mesenchymal stem cells (MSCs) plays a crucial role in bone remodeling. Numerous studies have described the deleterious effect of iron overload on bone density and microarchitecture. Excess iron decreases osteoblast activity, leading to impaired extracellular matrix (ECM) mineralization. Additionally, iron overload facilitates osteoclast differentiation and bone resorption. These processes contribute to iron overload-associated bone loss. In this study we investigated the effect of iron on osteogenic differentiation of human bone marrow MSCs (BMSCs), the third player in bone remodeling. We induced osteogenic differentiation of BMSCs in the presence or absence of iron (0-50μmol/L) and examined ECM mineralization, Ca content of the ECM, mRNA and protein expressions of the osteogenic transcription factor runt-related transcription factor 2 (Runx2), and its targets osteocalcin (OCN) and alkaline phosphatase (ALP). Iron dose-dependently attenuated ECM mineralization and decreased the expressions of Runx2 and OCN. Iron accomplished complete inhibition of osteogenic differentiation of BMSCs at 50μmol/L concentration. We demonstrated that in response to iron BMSCs upregulated the expression of ferritin. Administration of exogenous ferritin mimicked the anti-osteogenic effect of iron, and blocked the upregulation of Runx2, OCN and ALP. Iron overload in mice was associated with elevated ferritin and decreased Runx2 mRNA levels in compact bone osteoprogenitor cells. The inhibitory effect of iron is specific toward osteogenic differentiation of MSCs as neither chondrogenesis nor adipogenesis were influenced by excess iron. We concluded that iron and ferritin specifically inhibit osteogenic commitment and differentiation of BMSCs both in vitro and in vivo.

Decreased Bone Formation Explains Osteoporosis in a Genetic Mouse Model of Hemochromatosiss

Osteoporosis may complicate iron overload diseases such as genetic hemochromatosis. However, molecular mechanisms involved in the iron-related osteoporosis remains poorly understood. Recent in vitro studies support a role of osteoblast impairment in iron-related osteoporosis. Our aim was to analyse the impact of excess iron in Hfe-/- mice on osteoblast activity and on bone microarchitecture. We studied the bone formation rate, a dynamic parameter reflecting osteoblast activity, and the bone phenotype of Hfe-/- male mice, a mouse model of human hemochromatosis, by using histomorphometry. Hfe-/- animals were sacrificed at 6 months and compared to controls. We found that bone contains excess iron associated with increased hepatic iron concentration in Hfe-/- mice. We have shown that animals with iron overload have decreased bone formation rate, suggesting a direct impact of iron excess on active osteoblasts number. For bone mass parameters, we showed that iron deposition was associated with bone loss by producing microarchitectural impairment with a decreased tendency in bone trabecular volume and trabecular number. A disorganization of trabecular network was found with marrow spaces increased, which was confirmed by enhanced trabecular separation and star volume of marrow spaces. These microarchitectural changes led to a loss of connectivity and complexity in the trabecular network, which was confirmed by decreased interconnectivity index and increased Minkowski's fractal dimension. Our results suggest for the first time in a genetic hemochromatosis mouse model, that iron overload decreases bone formation and leads to alterations in bone mass and microarchitecture. These observations support a negative effect of iron on osteoblast recruitment and/or function, which may contribute to iron-related osteoporosis.

Effects of dietary resveratrol on excess-iron-induced bone loss via antioxidative character

Estrogen deficiency has been considered to be a major cause of osteoporosis, but recent epidemiological evidence and mechanistic studies have indicated that aging and the associated increase in reactive oxygen species (ROS) are the proximal pathogenic factors. Through ROS-mediated reactions, iron can induce disequilibrium of oxidation and antioxidation and can cause bone loss in mice. Therefore, we investigated the effects of resveratrol (RES) on bone mineral density, bone microstructure and the osteoblast functions under iron-overload conditions. Excess iron disrupted the antioxidant/prooxidant equilibrium of the mice and induced the defect and the lesion of the bone trabecula as well as disequilibrium between bone formation and bone resorption in iron-overload mice. Oral administration of RES significantly prevented bone loss in the osteoporotic mice. RES reversed the reduction of Runx2, OCN and type I collagen from excess iron; up-regulated the level of FOXO1; and maintained the antioxidant/prooxidant equilibrium in the mice. RES also reduced the ratio of OPG/RANKL in MC3T3-E1 cells and in mice and significantly inhibited subsequent osteoclastogenesis. These results provide new insights into the antiosteoporosis mechanisms of RES through antioxidative effects, suggesting that RES can be considered a potential natural resource for developing medicines or dietary supplements to prevent and treat osteoporosis.

Continuing treatment with Salvia miltiorrhiza injection attenuates myocardial fibrosis in chronic iron-overloaded mice

Iron overload cardiomyopathy results from iron accumulation in the myocardium that is closely linked to iron-mediated myocardial fibrosis. Salvia miltiorrhiza (SM, also known as Danshen), a traditional Chinese medicinal herb, has been widely used for hundreds of years to treat cardiovascular diseases. Here, we investigated the effect and potential mechanism of SM on myocardial fibrosis induced by chronic iron overload (CIO) in mice. Kunming male mice (8 weeks old) were randomized to six groups of 10 animals each: control (CONT), CIO, low-dose SM (L-SM), high-dose SM (H-SM), verapamil (VRP) and deferoxamine (DFO) groups. Normal saline was injected in the CONT group. Mice in the other five groups were treated with iron dextran at 50 mg/kg per day intraperitoneally for 7 weeks, and those in the latter four groups also received corresponding daily treatments, including 3 g/kg or 6 g/kg of SM, 100 mg/kg of VRP, or 100 mg/kg of DFO. The iron deposition was estimated histologically using Prussian blue staining. Myocardial fibrosis was determined by Masson's trichrome staining and hydroxyproline (Hyp) quantitative assay. Superoxide dismutase (SOD) activity, malondialdehyde (MDA) content and protein expression levels of type I collagen (COL I), type I collagen (COL III), transforming growth factor-β1 (TGF-β1) and matrix metalloproteinase-9 (MMP-9) were analyzed to investigate the mechanisms underlying the effects of SM against iron-overloaded fibrosis. Treatment of chronic iron-overloaded mice with SM dose-dependently reduced iron deposition levels, fibrotic area percentage, Hyp content, expression levels of COL I and COL III, as well as upregulated the expression of TGF- β1 and MMP-9 proteins in the heart. Moreover, SM treatment decreased MDA content and increased SOD activity. In conclusion, SM exerted activities against cardiac fibrosis induced by CIO, which may be attributed to its inhibition of iron deposition, as well as collagen metabolism and oxidative stress.

Hepcidin deficiency undermines bone load-bearing capacity through inducing iron overload

Osteoporosis is one of the leading disorders among aged people. Bone loss results from a number of physiological alterations, such as estrogen decline and aging. Meanwhile, iron overload has been recognized as a risk factor for bone loss. Systemic iron homeostasis is fundamentally governed by the hepcidin-ferroportin regulatory axis, where hepcidin is the key regulator. Hepcidin deficiency could induce a few disorders, of which iron overload is the most representative phenotype. However, there was little investigation of the effects of hepcidin deficiency on bone metabolism. To this end, hepcidin-deficient (Hamp1(-/-)) mice were employed to address this issue. Our results revealed that significant iron overload was induced in Hamp1(-/-) mice. Importantly, significant decreases of maximal loading and maximal bending stress were found in Hamp1(-/-) mice relative to wildtype (WT) mice. Moreover, the levels of the C-telopeptide of type I collagen (CTX-1) increased in Hamp1(-/-) mice. Therefore, hepcidin deficiency resulted in a marked reduction of bone load-bearing capacity likely through enhancing bone resorption, suggesting a direct correlation between hepcidin deficiency and bone loss. Targeting hepcidin or the pathway it modulates may thus represent a therapeutic for osteopenia or osteoporosis.

Danshen (Salvia miltiorrhiza) injection suppresses kidney injury induced by iron overload in mice

Objectives

Excessive iron can accumulate in the kidney and induce tissue damage. Danshen (Salvia miltiorrhiza) injection is a traditional Chinese medicinal preparation used for preventing and treating chronic renal failure. The aim of the present study was to evaluate the effects of treatment with Danshen injection on iron overload-induced kidney damage.

Methods

Mice were mock-treated with saline (control group) or given a single dose of iron dextran without treatment (iron overload group, 50 mg/kg/day for 2 weeks) or with daily treatments of low-dose Danshen (3 g/kg/day), high-dose Danshen (6 g/kg/day) or deferoxamine (100 mg/kg/day).

Results

Treatment of iron-overloaded mice with Danshen injection led to significant improvements of body weight and decreased iron levels in the kidney. Danshen injection treatment also reduced concentrations of blood urea nitrogen, creatinine and malondialdehyde and enhanced glutathione peroxidase and superoxide dismutase activities. Histopathological examinations showed that Danshen injection ameliorated pathological changes and reduced iron deposition in kidneys of iron overloaded mice. Furthermore, the treatment was demonstrated to suppress apoptosis in nephrocytes.

Conclusions

These results indicated that Danshen injection exerted significant renal protective effects in iron-overloaded mice, which were closely associated with the decrease of iron deposition and suppression of lipid peroxidation and apoptosis in the kidney.

Mechanism of protective effects of Danshen against iron overload-induced injury in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Danshen (Salvia miltiorrhiza) has been widely prescribed in traditional folk medicine for treatment of hepatic and cardiovascular diseases in China and other Asian countries for several hundred years.

MATERIALS AND METHODS

Sixty male mice were randomly divided into five groups: control, iron overload, low-dose Danshen (L-Danshen, 3g/kg/day), high-dose Danshen (H-Danshen, 6g/kg/day) and deferoxamine (DFO) groups (n=12 per group). Iron dextran was injected intraperitoneally (i.p.) at 50mg/kg body weight/day to establish the iron overload model. While control mice received saline, mice of the treated groups simultaneously received (i.p.) injections of L-Danshen, H-Danshen or DFO daily for 2 weeks. At the end of the experiment, changes in alanine aminotransferase (ALT) and aspartate aminotransferase (AST), glutathione peroxidase (GSH-Px), superoxide desmutase (SOD) and malondialdehyde (MDA) were measured, and histological changes were observed by Prussian blue or hematoxylin and eosin staining of the liver. Apoptosis was detected by terminal-deoxynucleotidyl transferase mediated nick end labeling.

RESULTS

Treatment of iron overloaded mice with either low or high doses of Danshen not only significantly attenuated the hepatic dysfunction (ALT/AST levels), decreased the content of MDA and increased the activities of GSH-Px and SOD, it also suppressed apoptosis in hepatocytes. Histopathological examination showed that treatment with Danshen reduced iron deposition and ameliorated pathological changes in the liver of iron overloaded mice.

CONCLUSIONS

Danshen demonstrated significant protective effects in the liver of iron overloaded mice, which were at least partly due to the decrease of iron deposition and inhibition of lipid peroxidation and hepatocyte apoptosis.

A comparison of the biological activities of human osteoblast hFOB1.19 between iron excess and iron deficiency

Bone metabolism has a close relationship with iron homeostasis. To examine the effects of iron excess and iron deficiency on the biological activities of osteoblast in vitro, human osteoblast cells (hFOB1.19) were incubated in a medium supplemented with 0-200 μmol/L ferric ammonium citrate and 0-20 μmol/L deferoxamine. The intracellular iron was measured by a confocal laser scanning microscope. Proliferation of osteoblasts was evaluated by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide assay. Apoptotic cells were detected using annexin intervention V/PI staining with a flow cytometry. Alkaline phosphatase (ALP) activity was measured using an ALP assay kit. The number of calcified nodules and mineral area was evaluated by von Kossa staining assay. The expressions of type I collagen and osteocalcin of cultured osteoblasts were detected by reverse transcriptase polymerase chain reaction and Western blot. Intracellular reactive oxygen species (ROS) was measured using the oxidation-sensitive dye 2,7-dichlorofluorescin diacetate by flow cytometry. The results indicated that excessive iron inhibited osteoblast activity in a concentration-dependent manner. Low iron concentrations, in contrast, produced a biphasic manner on osteoblasts: mild low iron promoted osteoblast activity, but serious low iron inhibited osteoblast activity. Osteogenesis was optimal in certain iron concentrations. The mechanism underlying biological activity invoked by excessive iron may be attributed to increased intracellular ROS levels.

Ferric ion could facilitate osteoclast differentiation and bone resorption through the production of reactive oxygen species

Iron overload is widely regarded as a risk factor for osteoporosis. It has been demonstrated that iron can inhibit osteoblast differentiation. However, the effects of iron on osteoclast differentiation and bone resorption remain controversial. In this study, we found that ferric ion promoted Receptor Activator of Nuclear Factor κ B Ligand (RANKL)-induced osteoclast (OC) formation in both RAW264.7 cells and bone marrow-derived macrophages (BMMs), and this effect was accompanied by elevated levels of reactive oxygen species (ROS) and oxidative stress. Moreover, this effect was attenuated by the administration of antioxidant N-acetyl-L-cysteine (NAC). Therefore, we conclude that ferric ion can promote osteoclast differentiation and bone resorption through the production of ROS.

Does iron inhibit calcification during atherosclerosis?

Oxidative stress has been implicated in the etiology of atherosclerosis and even held responsible for plaque calcification. Transition metals such as iron aggravate oxidative stress. To understand the relation between calcium and iron in atherosclerotic lesions, a sensitive technique is required that is quantitatively accurate and avoids isolation of plaques or staining/fixing tissue, because these processes introduce contaminants and redistribute elements within the tissue. In this study, the three ion-beam techniques of scanning transmission ion microscopy, Rutherford backscattering spectrometry, and particle-induced X-ray emission have been combined in conjunction with a high-energy (MeV) proton microprobe to map the spatial distribution of the elements and quantify them simultaneously in atherosclerotic rabbit arteries. The results show that iron and calcium within the atherosclerotic lesions exhibit a highly significant spatial inverse correlation. It may be that iron accelerates the progression of atherosclerotic lesion development, but suppresses calcification. Alternatively, calcification could be a defense mechanism against atherosclerotic progression by excluding iron.

Iron homeostasis in osteoporosis and its clinical implications

Osteoporosis has until now been considered to be a disease associated with abnormal calcium metabolism. However, an increasing number of clinical observations strongly suggest the association of iron overload with bone diseases, particularly in osteoporosis in menopausal women. The recent identification of hepcidin sheds new light into the crucial role of iron homeostasis in bone metabolism. Decreasing iron overload in cell studies as well as in animal experiments has been shown to improve bone cell metabolism and growth in vitro and in vivo. In view of the significant iron overload found in the aging population, especially in females, the therapeutic potential of lowering iron overload for the treatment of osteoporosis is suggested.

Effect of hepcidin on intracellular calcium in human osteoblasts

Hepcidin is known to increase intracellular iron through binding to and degrading ferroportin, which is a transmembrane protein that transports iron from the intracellular to the outside. However, it is not clear whether hepcidin has a similar effect on intracellular calcium. Here, we investigated the influence of hepcidin on intracellular calcium in human osteoblasts, with or without high environmental iron concentrations. Our data showed that hepcidin (<100 nmol/L) could increase intracellular calcium, and this effect was more significant when cells were exposed to high environmental iron concentrations. To further explore its underlying mechanisms, we pretreated human osteoblasts with Nimodipine, a L-type calcium channel blocker, and Dantrolene, a ryanodine receptor antagonist to inhibit abnormal calcium release from the sarco-endoplasmic reticulum. These treatments had not resulted in any alteration of intracellular calcium in human osteoblasts. Thus, these findings indicate that the increase of intracellular calcium induced by hepcidin is probably due to calcium release from endoplasmic reticulum, which is triggered by calcium influx.

Predictors of osteoclast activity in patients with sickle cell disease

BACKGROUND

Bone changes are common in sickle cell disease, but the pathogenesis is not fully understood. Tartrate-resistant acid phosphatase (TRACP) type 5b is produced by bone-resorbing osteoclasts. In other forms of hemolytic anemia, increased iron stores are associated with osteoporosis. We hypothesized that transfusional iron overload would be associated with increased osteoclast activity in patients with sickle cell disease.

DESIGN AND METHODS

We examined tartrate-resistant acid phosphatase 5b concentrations in patients with sickle cell disease and normal controls of similar age and sex distribution at steady state. Serum tartrate-resistant acid phosphatase 5b concentration was measured using an immunocapture enzyme assay and plasma concentrations of other cytokines were assayed using the Bio-Plex suspension array system. Tricuspid regurgitation velocity, an indirect measure of systolic pulmonary artery pressure, was determined by echocardiography.

RESULTS

Tartrate-resistant acid phosphatase 5b concentrations were higher in 58 adults with sickle cell disease than in 22 controls (medians of 4.4 versus 2.4 U/L, respectively; P=0.0001). Among the patients with sickle cell disease, tartrate-resistant acid phosphatase 5b independently correlated with blood urea nitrogen (standardized beta=0.40, P=0.003), interleukin-8 (standardized beta=0.30, P=0.020), and chemokine C-C motif ligand 5 (standardized beta=-0.28, P=0.031) concentrations, but not with serum ferritin concentration. Frequent blood transfusions (>10 units in life time) were not associated with higher tartrate-resistant acid phosphatase 5b levels in multivariate analysis. There were strong correlations among tartrate-resistant acid phosphatase 5b, alkaline phosphatase and tricuspid regurgitation velocity (r>0.35, P<0.001).

CONCLUSIONS

Patients with sickle cell disease have increased osteoclast activity as reflected by serum tartrate-resistant acid phosphatase 5b concentrations. Our results may support a potential role of inflammation rather than increased iron stores in stimulating osteoclast activity in sickle cell disease. The positive relationships among tartrate-resistant acid phosphatase 5b, alkaline phosphatase and tricuspid regurgitation velocity raise the possibility of a common pathway in the pulmonary and bone complications of sickle cell disease.

Bone loss caused by iron overload in a murine model: importance of oxidative stress

Osteoporosis is a frequent problem in disorders characterized by iron overload, such as the thalassemias and hereditary hemochromatosis. The exact role of iron in the development of osteoporosis in these disorders is not established. To define the effect of iron excess in bone, we generated an iron-overloaded mouse by injecting iron dextran at 2 doses into C57/BL6 mice for 2 months. Compared with the placebo group, iron-overloaded mice exhibited dose-dependent increased tissue iron content, changes in bone composition, and trabecular and cortical thinning of bone accompanied by increased bone resorption. Iron-overloaded mice had increased reactive oxygen species and elevated serum tumor necrosis factor-α and interleukin-6 concentrations that correlated with severity of iron overload. Treatment of iron-overloaded mice with the antioxidant N-acetyl-L-cysteine prevented the development of trabecular but not cortical bone abnormalities. This is the first study to demonstrate that iron overload in mice results in increased bone resorption and oxidative stress, leading to changes in bone microarchitecture and material properties and thus bone loss.

Excess iron inhibits osteoblast metabolism

Hemochromatosis is an iron overload disorder associated with osteopenia and osteoporosis. To learn more about the effects of iron on bone cells, we examined the effects of ferric ion on the proliferation, differentiation, and mineralization of two types of cultured osteoblasts, the cell line MC3T3-E1 and rat calvarial osteoblast-like (ROB) cells. We used ferric ammonium citrate (FAC) as a donor of ferric ion, and FAC inhibited the proliferation of MC3T3-E1 cells in a dose-dependent manner. FAC (0.1-1 microg/ml) inhibited indices of osteoblast differentiation, such as the expression of type I collagen (mRNA and protein), the activity of alkaline phosphatase, and the deposition of calcium by osteoblasts. These results suggest that iron overload might give rise to osteoporosis by inhibiting osteoblast proliferation and differentiation.

Neuroprotection by Spirulina platensis protean extract and phycocyanin against iron-induced toxicity in SH-SY5Y neuroblastoma cells

We investigated the effect of Spirulina platensis protean extract and the biliprotein phycocyanin isolated from this microalga, on the activities of the antioxidant enzymes SOD, CAT, GPx, and GR, lipid peroxidation inhibitory activity and glutathione levels after the iron induced oxidative stress in SH-SY5Y neuroblastoma cells. Iron is one of the most important agents that produce oxidative stress and decline of neuronal functions. S. platensis protean extract and phycocyanin exert the antioxidant activity by protecting the activity of the cellular antioxidant enzymes total GPx, GPx-Se and GR and by increasing reduced glutathione in cells against oxidative stress induced by iron. These results suggested that S. platensis protean extract is a powerful antioxidant through a mechanism related to antioxidant activity, capable of interfering with radical-mediated cell death. S. platensis may be useful in diseases known to be aggravated by reactive oxygen species and in the development of novel treatments for neurodegenerative disorders as long as iron has been implicated in the neuropathology of several neurodegenerative disorders such as Alzheimer's or Parkinson diseases.