Deferasirox decreases age-associated iron accumulation in the aging F344XBN rat heart and liver

Targeting Ferroptosis: A Novel Strategy for the Treatment of Atherosclerosis

Since ferroptosis was reported in 2012, its application prospects in various diseases have been widely considered, initially as a treatment direction for tumors. Recent studies have shown that ferroptosis is closely related to the occurrence and development of atherosclerosis. The primary mechanism is to affect the occurrence and development of atherosclerosis through intracellular iron homeostasis, ROS and lipid peroxide production and metabolism, and a variety of intracellular signaling pathways. Inhibition of ferroptosis is effective in inhibiting the development of atherosclerosis, and it can bring a new direction for treating atherosclerosis. In this review, we discuss the mechanism of ferroptosis and focus on the relationship between ferroptosis and atherosclerosis, summarize the different types of ferroptosis inhibitors that have been widely studied, and discuss some issues worthy of attention in the treatment of atherosclerosis by targeting ferroptosis.

Cardiac iron metabolism during aging - Role of inflammation and proteolysis

Iron is the most abundant trace element in the human body. Since iron can switch between its 2-valent and 3-valent form it is essential in various physiological processes such as energy production, proliferation or DNA synthesis. Especially high metabolic organs such as the heart rely on iron-associated iron-sulfur and heme proteins. However, due to switches in iron oxidation state, iron overload exhibits high toxicity through formation of reactive oxygen species, underlining the importance of balanced iron levels. Growing evidence demonstrates disturbance of this balance during aging. While age-associated cardiovascular diseases are often related to iron deficiency, in physiological aging cardiac iron accumulates. To understand these changes, we focused on inflammation and proteolysis, two hallmarks of aging, and their role in iron metabolism. Via the IL-6-hepcidin axis, inflammation and iron status are strongly connected often resulting in anemia accompanied by infiltration of macrophages. This tight connection between anemia and inflammation highlights the importance of the macrophage iron metabolism during inflammation. Age-related decrease in proteolytic activity additionally affects iron balance due to impaired degradation of iron metabolism proteins. Therefore, this review accentuates alterations in iron metabolism during aging with regards to inflammation and proteolysis to draw attention to their implications and associations.

Light and heavy ferritin chain expression in the liver and kidneys of Wistar rats: aging, sex differences, and impact of gonadectomy

Ferritin is the main intracellular storage of iron. Animal studies show that female liver and kidney express more ferritin and accumulate more iron than male. However, no study so far has investigated sex and age differences in light (FtL) and heavy (FtH) ferritin chain expression. To address this, we relied on specific antibodies and immunochemical methods to analyse the expression of both ferritin chains in the liver and kidney of 3-month and 2-year-old male and female Wistar rats. To see how sex hormones may affect expression we also studied adult animals gonadectomised at the age of 10 weeks. FtL and FtH were more expressed in both organs of female rats, while gonadectomy increased the expression in males and decreased it in females, which suggests that it is stimulated by female and inhibited by male steroid hormones. Normal kidney ferritin distribution and change with aging warrant more attention in studies of (patho) physiological and toxicological processes.

Therapeutic Potential of Cerium Oxide Nanoparticles for the Treatment of Peritonitis Induced by Polymicrobial Insult in Sprague-Dawley Rats

OBJECTIVES

Peritonitis is a life-threatening disease that is associated with high mortality. The purpose of this study was to determine if cerium oxide nanoparticles can be used to diminish intra-abdominal infection-induced mortality and systemic inflammatory response syndrome in the laboratory rat.

DESIGN

Randomized, controlled animal study and cell culture study.

SETTING

University research laboratory.

SUBJECTS

Male Sprague-Dawley rats aged 12 weeks, RAW 246.7 macrophage cell line.

INTERVENTIONS

Intra-abdominal infection or peritonitis was induced by intraperitoneal injection of cecal material (600 mg/kg in 5% sterile dextrose water at a dosage of 5 mL/kg) obtained from healthy donors. Rats in control and peritonitis groups received 200 μL of sterile deionized water IV via the tail vein, whereas rats in cerium oxide-only group and peritonitis+cerium oxide group received cerium oxide nanoparticles (0.5 mg/kg) IV at the time of polymicrobial injection. Survival rate was monitored for 14 days, while in other experiments, animals were killed at 3 and 18 hours after induction of peritonitis for biochemical analysis.

MEASUREMENTS AND MAIN RESULTS

Administration of a single dose (0.5 mg/kg) of cerium oxide nanoparticles IV to rats in the peritonitis group significantly improved survival rates and functioned to restore core body temperature toward baseline. Treatment-induced increases in animal survivability were associated with reduced systemic and hepatic oxidative stress, diminished serum cytokines, and chemokine levels. Changes in serum inflammatory markers with treatment were accompanied by decreased monocyte and lymphocyte extravasation into the peritoneal cavity along with decreased infiltration of macrophages into liver. In the heart, treatment diminished extracellular signal-regulated kinase 1/2 mitogen-activated protein kinase-Stat-3 signaling and attenuated endothelial expression of P-selectin and vascular cell adhesion molecule-1.

CONCLUSIONS

Cerium oxide nanoparticles attenuate the systemic inflammatory response associated with peritonitis, suggesting potential use as a novel therapeutic agent for the treatment of severe intra-abdominal infection.

The Effects of Aging on Indices of Oxidative Stress and Apoptosis in the Female Fischer 344/Nnia X Brown Norway/BiNia Rat Heart

Oxidative-nitrosative stress may play a role in age-associated cardiovascular disease as implied by recent studies.However, limited research has been conducted using aged female rodent models. In this study, we examined hearts obtained from 6-, 26-, and 30-month old female Fischer 344/Nnia x Brown Norway/BiNia (F344xBN) rats in order to examine how aging affects levels of cardiac oxidative-nitrosative stress and apoptosis. Oxidative (superoxide anion and 4-HNE) and nitrosative (protein nitrosylation) stress markers were increased 180 ± 17 %, 110 ± 3 %, and 14 ± 2 %, respectively in 30-month hearts compared to the hearts of 6-month female rats. Coincident with these changes in oxidative-nitrosative stress, aging was also found to be associated with increases in the number of Tdt-mediated dUTP nick labeling (TUNEL)-positive cardiomyocytes, alterations in the Bax/Bcl-2 ratio, and elevated cleavage of caspase-3. Regression analysis demonstrates significant correlation in the age-associated changes markers of oxidative–nitrosative stress with changes in apoptotic signaling. The findings from this descriptive study imply that age-associated increases in mitochondrial-mediated apoptosis may be associated with the increase in oxidative-nitrosative stress in the aging F344xBN female heart.

Aging-dependent changes in rat heart mitochondrial glutaredoxins--Implications for redox regulation

Clinical and animal studies have documented that hearts of the elderly are more susceptible to ischemia/reperfusion damage compared to young adults. Recently we found that aging-dependent increase in susceptibility of cardiomyocytes to apoptosis was attributable to decrease in cytosolic glutaredoxin 1 (Grx1) and concomitant decrease in NF-κB-mediated expression of anti-apoptotic proteins. Besides primary localization in the cytosol, Grx1 also exists in the mitochondrial intermembrane space (IMS). In contrast, Grx2 is confined to the mitochondrial matrix. Here we report that Grx1 is decreased by 50–60% in the IMS, but Grx2 is increased by 1.4–2.6 fold in the matrix of heart mitochondria from elderly rats. Determination of in situ activities of the Grx isozymes from both subsarcolemmal (SSM) and interfibrillar (IFM) mitochondria revealed that Grx1 was fully active in the IMS. However, Grx2 was mostly in an inactive form in the matrix, consistent with reversible sequestration of the active-site cysteines of two Grx2 molecules in complex with an iron–sulfur cluster. Our quantitative evaluations of the active/inactive ratio for Grx2 suggest that levels of dimeric Grx2 complex with iron–sulfur clusters are increased in SSM and IFM in the hearts of elderly rats. We found that the inactive Grx2 can be fully reactivated by sodium dithionite or exogenous superoxide production mediated by xanthine oxidase. However, treatment with rotenone, which generates intramitochondrial superoxide through inhibition of mitochondrial respiratory chain Complex I, did not lead to Grx2 activation. These findings suggest that insufficient ROS accumulates in the vicinity of dimeric Grx2 to activate it in situ.

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Glutaredoxins play key roles in cellular redox regulation, which is sensitive to aging-dependent dysregulation.

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Grx1 is diminished in the intermembrane space of mitochondria from aged heart; matrix Grx2 is increased but mostly in an inactive form.

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The inactive Grx2 is selectively activated by superoxide.

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Mitochondrial glutaredoxin changes may contribute to dysregulation of redox homeostasis during aging.

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Changes in in situ activities of heart mitochondrial Grx1 and Grx2 with aging provide mechanistic insights for future studies.

Correlation between iron stores and QTc dispersion in chronic ambulatory peritoneal dialysis patients

AIM

We aimed to investigate the QT dispersion and corrected QT (QTc) dispersion which are suggested as the signals of ventricular arrhythmias, in patients on maintenance CAPD and to evaluate the correlation between iron stores and these electrocardiographic parameters.

MATERIALS AND METHOD

Fifty-eight patients on maintenance CAPD and 19 healthy age- and sex-matched adults without cardiac disease were included. The PD patients were divided into two groups according to whether their computerized measurements of QTc dispersion were longer than 65 ms.

RESULTS

Although QT interval was statistically significantly shorter in control group (34 ± 28 vs. 43 ± 34 ms; p < 0.05), there was no significant difference in regards to the QTc, QT dispersion and QTc dispersion between two groups. PD patients with QTc dispersion longer than 65 ms had higher levels of serum ferritin (p = 0.038) and transferrin saturation (TSAT; p = 0.022) than the others. QTc dispersion were positively correlated with ferritin (r = 0.469, p < 0.01) and TSAT (r = 0.430, p < 0.01) in CAPD patients.

CONCLUSION

Although prolonged QTc, QT dispersion and QTc dispersion were suggested as the markers of ventricular arrhythmias we did not find any significant difference in regards to these parameters between control patients and CAPD patients. But the high body iron stores in these patients increase the risk of increased QT dispersion. The concern over iron overload in dialysis patients is not only because of its oxidative toxicity, but also its precipitation of arrhythmias, which may be measured by the surrogate marker of QTc dispersion.

Elevated serum levels of cell death circulating biomarkers, M30 and M65, in patients with β-thalassemia major

Deposition of iron in visceral organs, mainly in the liver, causes tissue damage in β-thalassemia major (β-TM) patients. Keratin 18 (K18) represents one of the major caspase substrates during apoptosis of hepatocytes. To better characterize the hepatic apoptosis and/or necrosis in β-thal patients, the circulating levels of M65 (soluble intact K18) and M30 (the caspases-generated K18 fragment) were measured in 40 β-TM patients and compared with 40 healthy controls. The ratio of M30/M65 (caspase-cleaved to total K18) was also determined in thalassemic and normal subjects. Results of the ELISA assays revealed that the serum levels of hepatocyte death markers, M65 and M30, were significantly increased in β-thal patients compared to healthy controls (p <0.0001). M30 serum levels were also positively correlated with the serum levels of liver transaminases including aspartate aminotransferase (AST) (r = 0.337, p = 0.047) and alanine aminotransferase (ALT) (r =0.391, p = 0.02).

Dietary iron concentration may influence aging process by altering oxidative stress in tissues of adult rats

Iron is an essential element. However, in its free form, iron participates in redox-reactions, leading to the production of free radicals that increase oxidative stress and the risk of damaging processes. Living organisms have an efficient mechanism that regulates iron absorption according to their iron content to protect against oxidative damage. The effects of restricted and enriched-iron diets on oxidative stress and aging biomarkers were investigated. Adult Wistar rats were fed diets containing 10, 35 or 350 mg/kg iron (adult restricted-iron, adult control-iron and adult enriched-iron groups, respectively) for 78 days. Rats aged two months were included as a young control group. Young control group showed higher hemoglobin and hematocrit values, lower levels of iron and lower levels of MDA or carbonyl in the major studied tissues than the adult control group. Restricted-iron diet reduced iron concentrations in skeletal muscle and oxidative damage in the majority of tissues and also increased weight loss. Enriched-iron diet increased hematocrit values, serum iron, gamma-glutamyl transferase, iron concentrations and oxidative stress in the majority of tissues. As expected, young rats showed higher mRNA levels of heart and hepatic L-Ferritin (Ftl) and kidneys SMP30 as well as lower mRNA levels of hepatic Hamp and interleukin-1 beta (Il1b) and also lower levels of liver protein ferritin. Restricted-iron adult rats showed an increase in heart Ftl mRNA and the enriched-iron adult rats showed an increase in liver nuclear factor erythroid derived 2 like 2 (Nfe2l2) and Il1b mRNAs and in gut divalent metal transporter-1 mRNA (Slc11a2) relative to the control adult group. These results suggest that iron supplementation in adult rats may accelerate aging process by increasing oxidative stress while iron restriction may retards it. However, iron restriction may also impair other physiological processes that are not associated with aging.

Impaired iron status in aging research

Aging is associated with disturbances in iron metabolism and storage. During the last decade, remarkable progress has been made toward understanding their cellular and molecular mechanisms in aging and age-associated diseases using both cultured cells and animal models. The field has moved beyond descriptive studies to potential intervention studies focusing on iron chelation and removal. However, some findings remain controversial and inconsistent. This review summarizes important features of iron dyshomeostasis in aging research with a particular emphasis on current knowledge of the mechanisms underlying age-associated disorders in rodent models.

Lipocalin-2 induces cardiomyocyte apoptosis by increasing intracellular iron accumulation

Our objective was to determine whether lipocalin-2 (Lcn2) regulates cardiomyocyte apoptosis, the mechanisms involved, and the functional significance. Emerging evidence suggests that Lcn2 is a proinflammatory adipokine associated with insulin resistance and obesity-related complications, such as heart failure. Here, we used both primary neonatal rat cardiomyocytes and H9c2 cells and demonstrated for the first time that Lcn2 directly induced cardiomyocyte apoptosis, an important component of cardiac remodeling leading to heart failure. This was shown by detection of DNA fragmentation using TUNEL assay, phosphatidylserine exposure using flow cytometry to detect annexin V-positive cells, caspase-3 activity using enzymatic assay and immunofluorescence, and Western blotting for the detection of cleaved caspase-3. We also observed that Lcn2 caused translocation of the proapoptotic protein Bax to mitochondria and disruption of mitochondrial membrane potential. Using transient transfection of GFP-Bax, we confirmed that Lcn2 induced co-localization of Bax with MitoTracker® dye. Importantly, we used the fluorescent probe Phen Green SK to demonstrate an increase in intracellular iron in response to Lcn2, and depleting intracellular iron using an iron chelator prevented Lcn2-induced cardiomyocyte apoptosis. Administration of recombinant Lcn2 to mice for 14 days increased cardiomyocyte apoptosis as well as an acute inflammatory response with compensatory changes in cardiac functional parameters. In conclusion, Lcn2-induced cardiomyocyte apoptosis is of physiological significance and occurs via a mechanism involving elevated intracellular iron levels and Bax translocation.

On improvement in ejection fraction with iron chelation in thalassemia major and the risk of future heart failure

BACKGROUND

Trials of iron chelator regimens have increased the treatment options for cardiac siderosis in beta-thalassemia major (TM) patients. Treatment effects with improved left ventricular (LV) ejection fraction (EF) have been observed in patients without overt heart failure, but it is unclear whether these changes are clinically meaningful.

METHODS

This retrospective study of a UK database of TM patients modelled the change in EF between serial scans measured by cardiovascular magnetic resonance (CMR) to the relative risk (RR) of future development of heart failure over 1 year. Patients were divided into 2 strata by baseline LVEF of 56-62% (below normal for TM) and 63-70% (lower half of the normal range for TM).

RESULTS

A total of 315 patients with 754 CMR scans were analyzed. A 1% absolute increase in EF from baseline was associated with a statistically significant reduction in the risk of future development of heart failure for both the lower EF stratum (EF 56-62%, RR 0.818, p < 0.001) and the higher EF stratum (EF 63-70%, RR 0.893 p = 0.001).

CONCLUSION

These data show that during treatment with iron chelators for cardiac siderosis, small increases in LVEF in TM patients are associated with a significantly reduced risk of the development of heart failure. Thus the iron chelator induced improvements in LVEF of 2.6% to 3.1% that have been observed in randomized controlled trials, are associated with risk reductions of 25.5% to 46.4% for the development of heart failure over 12 months, which is clinically meaningful. In cardiac iron overload, heart mitochondrial dysfunction and its relief by iron chelation may underlie the changes in LV function.

Deferasirox protects against iron-induced hepatic injury in Mongolian gerbil

Iron overload is associated with an increased risk of liver complications including fibrosis, cirrhosis, and hepatocellular carcinoma. Deferasirox is a new oral chelator with high iron-binding potency and selectivity. Here we investigate the ability of deferasirox to remove excessive hepatic iron and prevent iron-induced hepatic injury. Adult male Mongolian gerbils were divided into 3 groups (n=5/group)-control, iron overload (100 mg iron-dextran/kg body weight/5 days; intraperitoneal for 10 weeks), and iron overload followed by deferasirox treatment (100 mg deferasirox/kg body weight/d; pulse oral for 1 or 3 months). Compared with the nontreated iron overload group, deferasirox reduced hepatic iron concentration by 44% after 3 months of treatment (P<0.05). Histological analysis of hepatic tissue from the iron overloaded group detected frequent iron deposition, evidence of hepatic damage, and an accumulation of lipid vacuoles. Iron deposition was significantly diminished with deferasirox treatment, and no evidence of lipid accumulation was observed. Immunoblotting demonstrated that iron overload caused approximately 2-fold increase in hepatic ferritin expression (P<0.05), which was 48% lower after 3 months of deferasirox treatment (P<0.05). Deferasirox treatment also was associated with reduced hepatic protein oxidation, superoxide abundance, and cell death. The percentage of terminal deoxynucleotidyl transferase dUTP nick end labeling positive cells in the deferasirox-treated livers was 41% lower than that of iron overloaded group (P<0.05). Similarly, an iron-related increase in the expression of Bax/Bcl2, Bad, and caspase-3 were significantly lower after deferasirox treatment. These findings suggest that deferasirox may confer protection against iron-induced hepatic toxicity.