Iron Overload Injury Research Articles

A Ce-MOF@polydopamine composite nanozyme as an efficient scavenger for reactive oxygen species and iron in thalassemia disease therapy.

Patients with β-thalassemia are prone to complications such as cardiovascular diseases and secretory gland injury due to iron overload (IO) and reactive oxygen species (ROS) production caused by blood transfusions. Simultaneously scavenging ROS and eliminating IO using nanomedicine remains challenging. Herein, we designed a dual-functional Ce-based metal-organic framework@polydopamine (Ce-MOF@PDA) composite that integrates oxidative stress reduction and IO elimination and evaluated its protective effect on IO injury in thalassemia. Using Ce-MOF with multiple active sites as the core, dopamine, which can coordinate iron ions, was modified on the surface of Ce-MOF and spontaneously polymerized to obtain PDA with iron elimination ability. Dopamine modification also adjusted the Ce3+/Ce4+ ratio to further enhance the catalytic activity for scavenging ROS. Ce-MOF@PDA exhibited multiple nanozyme activities, such as superoxide dismutase- and catalase-like activities, and decreased iron-mediated oxidative stress levels in vitro. Furthermore, the serum ferritin levels and iron concentrations in the liver of IO mice were reduced following treatment with Ce-MOF@PDA, and the fecal clearance ability was comparable to that of deferoxamine. These results indicate that Ce-MOF@PDA can eliminate IO while scavenging ROS and reduce tissue damage caused by oxidative stress. Therefore, the Ce-MOF@PDA nanozyme is a promising therapeutic nanomedicine for treating thalassemia IO.

Luteoloside protects the vascular endothelium against iron overload injury via the ROS/ADMA/DDAH II/eNOS/NO pathway.

Iron overload injury is considered to be a part of blood stasis syndrome of arthralgia in traditional Chinese medicine. Its primary therapies include clearing heat and detoxification, activating blood circulation, and removing blood stasis. Lonicera japonica flos (LJF) has long been known as an excellent antipyretic and antidote. Luteoloside (Lut) is one of the main components of LJF and exhibits antioxidant, anti-inflammatory, and cytoprotective properties. However, the protection of Lut against iron overload injury and its underlying mechanisms remain unclear. Therefore, HUVECs were exposed to 50 μmol·L-1 iron dextran for 48 h to establish an iron overload damage model and the effects of Lut were assessed. Our results showed that 20 μmol·L-1 Lut not only increased cell viability and weakened LDH activity, but also significantly up-regulated DDAHⅡ expression and activity, increased p-eNOS/eNOS ratio and NO content, and reduced ADMA content in HUVECs exposed to iron overload. Furthermore, Lut significantly attenuated intracellular/mitochondrial ROS generation, improved SOD, CAT, and GSH-Px activities, reduced MDA content, maintained MMP, inhibited mPTP opening, prevented cyt c from mitochondria released into cytoplasm, reduced cleaved-caspase3 expression, and ultimately decreased cell apoptosis induced by iron overload. The effects of Lut were similar to those of L-arginine (an ADMA competitive substrate), cyclosporin A (a mPTP blocker agent), and edaravone (a free radical scavenger) as positive controls. However, addition of pAD/DDAH II-shRNA adenovirus reversed the above beneficial effects of Lut. In conclusion, Lut can protect HUVECs against iron overload injury via the ROS/ADMA/DDAH II/eNOS/NO pathway. The mitochondria are the target organelles of Lut's protective effects.

Kidney Iron Deposition By R2* Is Associated with Hemolysis and Urinary Iron

Introduction Kidney iron deposition has been described in hemolytic disorders including mechanical valves, paroxysmal nocturnal hematuria, and sickle cell disease (Roberts & Morrow, Circulation 1966; Leonardi & Ruol, Blood 1960). Circulating plasma hemoglobin is filtered at the glomerulus and reabsorbed via the megalin cubulin system in the proximal and distal tubules (Gburek et al, J Am Soc Nephrol 2002). On MRI, this manifests as signal loss on gradient and spin echo sequences in the cortex of the kidney with complete sparing of the medulla (Jeong et al, Radiographics 2002). The signal darkening is quantified by the parameter R2*, which has been shown to be directly proportional to tissue iron in the liver and heart. Kidney R2* has previously been demonstrated to rise proportionally to lactate dehydrogenase (LDH) in chronically transfused sickle cell disease (SCD) patients (Wood et al, Br J Haematol 2016; Schein et al, J Magn Reson Imaging 2008), but LDH is not a specific marker of hemolysis, and chronically transfused patients could potentially deposit iron in the kidney through other mechanisms. Therefore, we characterized the relationship between kidney R2*, urinary iron and markers of hemolysis in non-transfused SCD patients. Methods Sixty-five non-transfused SCD patients were recruited to the study, which was approved by the Institutional Review Board of Children's Hospital Los Angeles. Following medical history and physical exam, subjects completed blood and urine testing, and then abdominal MRI for assessment of somatic iron stores. R2* measurements were collected using multiple gradient echo pulse sequences on 1.5 Tesla magnets. Statistical analysis was performed using JMP® Pro, Version 14.0.0 (SAS Institute Inc., Cary, NC, 2018). Results Subjects were generally adults with a mean age of 32 years. Nearly three quarters of subjects had homozygous sickle cell disease, while a quarter had SC disease or S-Beta thalassemia, and one subject had sickle cell trait. Most subjects were anemic, and all subjects had elevated markers of hemolysis. Fifty-four percent of subjects had an elevated kidney R2* level (≥34 Hz). On univariate analysis, kidney R2* was associated with urinary iron (R2=0.52, p<0.0001), LDH (R2=0.33, p<0.0001), plasma hemoglobin (R2=0.18, p=0.0007), and hemoglobin (R2=0.08, p=0.02), but it was not associated with reticulocyte count. On multivariate analysis, kidney R2* was associated with urinary iron and LDH (Figure 1). No association was found between R2* values of the kidney, liver, and pancreas. Discussion Our study supports previous findings that kidney R2* is associated with intravascular hemolysis, as measured by plasma hemoglobin and LDH, and inversely by hemoglobin (Kato et al, Blood 2006). The stronger association with urinary iron reinforces the concept that kidney R2* reflects filtered iron, which is insufficiently reabsorbed due to proximal and distal tubular injury in iron overload (van Raaij et al, Am J Physiol Renal Physiol 2019). Urinary iron is also elevated in diabetic nephropathy (Van et al, J Am Soc Nephrol 2017) and nephrotic syndrome (Niel et al, Blood 2011). These data raise important questions regarding the possible role of iron in sickle related renal disease. Disclosures Coates: apo pharma: Consultancy, Honoraria, Speakers Bureau; vifor: Consultancy, Honoraria; agios pharma: Consultancy, Honoraria; celgene: Consultancy, Honoraria, Other: steering committee of clinical study. Wood:National Institutes of Health: Research Funding; Philips Healthcare: Research Funding; BluebirdBio: Consultancy; Celgene: Consultancy; Apopharma: Consultancy; WorldcareClinical: Consultancy; BiomedInformatics: Consultancy; Imago Biosciences: Consultancy.

Iron-overload injury and cardiomyopathy in acquired and genetic models is attenuated by resveratrol therapy.

Iron-overload cardiomyopathy is a prevalent cause of heart failure on a world-wide basis and is a major cause of mortality and morbidity in patients with secondary iron-overload and genetic hemochromatosis. We investigated the therapeutic effects of resveratrol in acquired and genetic models of iron-overload cardiomyopathy. Murine iron-overload models showed cardiac iron-overload, increased oxidative stress, altered Ca2+ homeostasis and myocardial fibrosis resulting in heart disease. Iron-overload increased nuclear and acetylated levels of FOXO1 with corresponding inverse changes in SIRT1 levels in the heart corrected by resveratrol therapy. Resveratrol, reduced the pathological remodeling and improved cardiac function in murine models of acquired and genetic iron-overload at varying stages of iron-overload. Echocardiography and hemodynamic analysis revealed a complete normalization of iron-overload mediated diastolic and systolic dysfunction in response to resveratrol therapy. Myocardial SERCA2a levels were reduced in iron-overloaded hearts and resveratrol therapy restored SERCA2a levels and corrected altered Ca2+ homeostasis. Iron-mediated pro-oxidant and pro-fibrotic effects in human and murine cardiomyocytes and cardiofibroblasts were suppressed by resveratrol which correlated with reduction in iron-induced myocardial oxidative stress and myocardial fibrosis. Resveratrol represents a clinically and economically feasible therapeutic intervention to reduce the global burden from iron-overload cardiomyopathy at early and chronic stages of iron-overload.

Protective effects of Mangifera indica L extract (Vimang), and its major component mangiferin, on iron-induced oxidative damage to rat serum and liver

In vivo preventive effects of a Mangifera indica L extract (Vimang) or its major component mangiferin on iron overload injury have been studied in rats given respectively, 50, 100, 250 mg kg −1 body weight of Vimang, or 40 mg kg −1 body weight of mangiferin, for 7 days prior to, and for 7 days following the administration of toxic amounts of iron-dextran. Both Vimang or mangiferin treatment prevented iron overload in serum as well as liver oxidative stress, decreased serum and liver lipid peroxidation, serum GPx activity, and increased serum and liver GSH, serum SOD and the animals overall antioxidant condition. Serum iron concentration was decreased although at higher doses, Vimang tended to increase it; percent tranferrin saturation, liver weight/body mass ratios, liver iron content was decreased. Treatment increased serum iron-binding capacity and decreased serum levels of aspartate-amine transferase (ASAT) and alanine-amine transferase (ALAT), as well as the number of abnormal Kupffer cells in iron-loaded livers. It is suggested that besides acting as antioxidants, Vimang extract or its mangiferin component decrease liver iron by increasing its excretion. Complementing earlier in vitro results from our group, it appears possible to support the hypothesis that Vimang and mangiferin present therapeutically useful effects in iron overload related diseases.

Iron toxicity and chelation therapy.

Iron is an essential mineral for normal cellular physiology, but an excess can result in cell injury. Iron in low-molecular-weight forms may play a catalytic role in the initiation of free radical reactions. The resulting oxyradicals have the potential to damage cellular lipids, nucleic acids, proteins, and carbohydrates; the result is wide-ranging impairment in cellular function and integrity. The rate of free radical production must overwhelm the cytoprotective defenses of cells before injury occurs. There is substantial evidence that iron overload in experimental animals can result in oxidative damage to lipids in vivo, once the concentration of iron exceeds a threshold level. In the liver, this lipid peroxidation is associated with impairment of membrane-dependent functions of mitochondria and lysosomes. Iron overload impairs hepatic mitochondrial respiration primarily through a decrease in cytochrome C oxidase activity, and hepatocellular calcium homeostasis may be compromised through damage to mitochondrial and microsomal calcium sequestration. DNA has also been reported to be a target of iron-induced damage, and this may have consequences in regard to malignant transformation. Mitochondrial respiratory enzymes and plasma membrane enzymes such as sodium-potassium-adenosine triphosphatase (Na(+) + K(+)-ATPase) may be key targets of damage by non-transferrin-bound iron in cardiac myocytes. Levels of some antioxidants are decreased during iron overload, a finding suggestive of ongoing oxidative stress. Reduced cellular levels of ATP, lysosomal fragility, impaired cellular calcium homeostasis, and damage to DNA all may contribute to cellular injury in iron overload. Evidence is accumulating that free-radical production is increased in patients with iron overload. Iron-loaded patients have elevated plasma levels of thiobarbituric acid reactants and increased hepatic levels of aldehyde-protein adducts, indicating lipid peroxidation. Hepatic DNA of iron-loaded patients shows evidence of damage, including mutations of the tumor suppressor gene p53. Although phlebotomy therapy is effective in removing excess iron in hereditary hemochromatosis, chelation therapy is required in the treatment of many patients who have combined secondary and transfusional iron overload due to disorders in erythropoiesis. In patients with beta-thalassemia who undergo regular transfusions, deferoxamine treatment has been shown to be effective in preventing iron-induced tissue injury and in prolonging life expectancy. The use of the oral chelator deferiprone remains controversial, and work is continuing on the development of new orally effective iron chelators.

Relationship Between Free Iron Level and Rat Liver Mitochondrial Dysfunction in Experimental Dietary Iron Overload

The concentration of total iron in the hepatic tissue and mitochondria from rats fed a 2.5% carbonyl iron supplemented diet progressively increased up to 40 days, then reached nearly a steady-state. By contrast the level of free iron (desferrioxamine-chelatable) exhibited a transient but significant increase at 40 days of treatment, only in this period of treatment the induction of lipid peroxidation and the resulting mitochondrial abnormalities in calcium transport was observed too. The enhancement of the energy dissipating mitochondrial calcium cycling was found to be associated with a significant decrease of endogenous mitochondrial ATP content. As to the pathophysiological mechanism for hepatocellular injury in iron overload, these results indicated that the transit pool of free iron may play a critical role in initiating organelle dysfunctions, at least in this experimental model of iron overload.

Prevention of Hepatocyte Injury and Lipid Peroxidation by Iron Chelators and α–Tocopherol in Isolated Iron–Loaded Rat Hepatocytes

These experiments were performed to characterize the relationship between lipid peroxidation and hepatocyte viability in iron overload. Hepatocytes were isolated from rats with chronic dietary iron overload and the effects of in vitro iron chelation on lipid peroxidation, cell viability and ultrastructure were studied over a 4-hr incubation period. Cell viability was significantly reduced at 3 and 4 hr in iron-loaded hepatocytes compared with controls and was preceded by an increase in iron-dependent lipid peroxidation. Similarly, extensive degenerative ultrastructural changes were observed in iron-loaded hepatocytes compared with controls after 4 hr of incubation. In vitro iron chelation with either deferoxamine or apotransferrin protected against lipid peroxidation, loss of viability and ultrastructural damage in iron-loaded hepatocytes. The addition of an antioxidant, alpha-tocopherol, also protected against lipid peroxidation and preserved cell viability over a 4-hr incubation. The protective effects of iron chelators and alpha-tocopherol support a strong association between iron-dependent lipid peroxidation and hepatocellular injury in iron overload.

Lipid peroxidation and associated hepatic organelle dysfunction in iron overload

Iron overload can have serious health consequences. Since humans lack an effective means to excrete excess iron, overload can result from an increased absorption of dietary iron or from parenteral administration of iron. When the iron burden exceeds the body's capacity for safe storage, the result is widespread damage to the liver, heart and joints, and the pancreas and other endocrine organs. Clear evidece is now available that iron overload leads to lipid peroxidation in experimental animals, if sufficiently high levels of iron are achieved. In contrast, there is a paucity of data regarding lipid peroxidation in patients with iron overload. Data from experiments using an animal model of dietary iron overload support the concept that iron overload results in an increase in an hepatic cytosolic pool of low molecular weight iron which is catalytically active in stimulating lipid peroxidation. Lipid peroxidation is associated with hepatic mitochondrial and microsomal dysfunction in experimental iron overload, and lipid peroxidation may underlie the increased lysosomal fragility that has been detected in homogenates of liver samples from both iron-loaded human subjects and experimental animals. Some current hypotheses focus on the possibility that the demonstrated functional abnormalities in organelles of the iron-loaded liver may play a pathogenic role in hepatocellular injury and eventual fibrosis. The recent demonstration that hepatic fibronosis is produced in animals with long-term dietary iron overload with allow this model to be used to further investigate the relationship between lipid peroxidation and hepatic injury in iron overload.

Iron-induced peroxidative injury to isolated rat hepatic mitochondria

Peroxidative injury to the mitochondrial inner membrane with resultant defects in oxidative metabolism may be partially responsible for hepatocellular injury in iron overload. We examined the effects of iron-induced lipid peroxidation in vitro on hepatic mitochondrial morphology and function and determined if various inhibitors of free-radical-mediated injury could be protective. Normal rat liver mitochondria were prepared by differential centrifugation and were incubated with 1, 2, and 3 μM Fe 2+, NADPH, and with and without oxygen radical scavengers, iron chelators, and antioxidants. There was a direct linear relationship between the concentration of added iron and the degree of lipid peroxidation as measured by malondialdehyde (MDA) production ( r =.85). With 3 μM Fe 2+ there was a decrease in the respiratory control ratio (RCR) for all four substrates tested; this decrease in RCR was due to a decrease in the state 3 respiratory rate for all substrates, with no changes in the state 4 respiratory rate for glutamate, β-hydroxybutyrate, or succinate. Oxygen radical scavengers failed to prevent iron-induced lipid peroxidation or to protect against associated mitochondrial dysfunction. Iron chelators and antioxidants prevented MDA formation and mitochondrial function was maintained. Iron-induced lipid peroxidation in vitro produces an irreversible inhibitory defect in mitochondrial electron transport that may be specific at complex IV (cytochrome oxidase).