Early detection of cardiac involvement in thalassemia: From bench to bedside perspective

Myocardial siderosis is known as the major cause of death in thalassemia major(TM) patients since it can lead to iron overload cardiomyopathy.Although this condition can be prevented if timely effective intensive chelation is given to patients,the mortality rate of iron overload cardiomyopathy still remains high due to late detection of this condition.Various direct and indirect methods of iron assessment,including serum ferritin level,echocardiogram,non-transferrin-bound iron,cardiac magnetic resonance T2*,heart rate variability,and liver biopsy and myocardial biopsy,have been proposed for early detection of cardiac iron overload in TM patients.However,controversial evidence and limitations of their use in clinical practice exist.In this review article,all of these iron assessment methods that have been proposed or used to directly or indirectly determine the cardiac iron status in TM reported from both basic and clinical studies are comprehensively summarized and presented.Since there has been growing evidence in the past decades that cardiac magnetic resonance imaging as well as cardiac autonomic status known as the heart rate variability can provide early detection of cardiac involvement in TM patients,these two methods are also presented and discussed.The existing controversy regarding the assessment of cardiac involvement in thalassemia is also discussed.

Iron-chelating and anti-lipid peroxidation properties of 1-(N-acetyl-6-aminohexyl)-3-hydroxy-2-methylpyridin-4-one(CM1)in longterm iron loading β-thalassemic mice

Objective:To evaluate the iron—chelating properties and free—radical scavenging activities of1-(N-acetyl-6-aminohexyl)-3-hydroxy-2-methyIpyridin—4-one(CM1) treatment in chronic iron-loaded β-thalassemic(BKO) mice.Methods:The BKO mice were fed with a ferrocene-rich diet and were orally administered with CM1|50 mg/(kg·day)| for 6 months.Blood levels of non-transferrin hound iron,labile plasma iron.ferritin(Ft) and malondialdehyde were determined.Results:The BKO mice were fed with an iron diet for 8 months which resulted in iron overload.Interestingly,the mice showed a decrease in the non—transferrin bound iron,labile plasma iron and malondialdehyde levels,but not the Ft levels after continuous CM1 treatment.Conclusions:CM1 could be an effective oral iron chelator that can reduce iron overload and lipid peroxidation in chronic iron overload β—thalassemic mice.

Combined treatment of 3-hydroxypyridine-4-one derivatives and green tea extract to induce hepcidin expression in iron-overloaded b-thalassemic mice

Objective:To evaluate the efficacy of deferiprone(DFP),1-(N-acetyl-6-aminohexyl)-3-hydroxy-2-methylpyridin-4-one(CM1)or green tea extract(GTE)in enhancing expression of hepatic hepcidin1(Hamp1)m RNA and relieving iron overload in b-globin knockout thalassemic mice.Methods:The b-globin knockout thalassemic mice were fed with a ferrocenesupplemented diet for 2 months and oral administration of deionized water,DFP(50 mg/kg),CM1(50 mg/kg),GTE(50 mg epigallocatechin 3-gallate equivalent/kg),GTE along with DFP(50 mg/kg),and GTE along with CM1(50 mg/kg)every day for 3months.Levels of hepatic Hamp1 m RNA,plasma non-transferrin bound iron,plasma alanine aminotransferase activity and tissue iron content were determined.Results:All chelation treatments could reduce plasma non-transferrin bound iron concentrations.Additionally,hepatic Hamp1 m RNA expression was significantly upregulated in the mice in a GTE+DFP combined treatment,correlating with a decrease in the plasma alanine aminotransferase activity and tissue iron deposition.Conclusions:The GTE+DFP treatment could ameliorate iron overload and liver oxidative damage in non-transfusion dependent b-thalassemic mice,by chelating toxic iron in plasma and tissues,and increasing hepcidin expression to inhibit duodenal iron absorption and iron release from hepatocytes and macrophages in the spleen.There is probably an advantage in giving GTE with DFP when treating patients with iron overload.

Calcium channels and iron uptake into the heart

Iron overload can lead to iron deposits in many tissues,particularly in the heart.It has also been shown to be associated with elevated oxidative stress in tissues.Elevated cardiac iron deposits can lead to iron overload cardiomyopathy,a condition which provokes mortality due to heart failure in iron-overloaded patients.Currently,the mechanism of iron uptake into cardiomyocytes is still not clearly understood.Growing evidence suggests L-type Ca2+channels(LTCCs)as a possible pathway for ferrous iron(Fe2+)uptake into cardiomyocytes under iron overload conditions.Nevertheless,controversy still exists since some findings on pharmacological interventions and those using different cell types do not support LTCC’s role as a portal for iron uptake in cardiac cells.Recently,T-type Ca2+channels (TTCC)have been shown to play an important role in the diseased heart.Although TTCC and iron uptake in cardiomyocytes has not been investigated greatly,a recent finding indicated that TTCC could be an important portal in thalassemic hearts.In this review,comprehensive findings collected from previous studies as well as a discussion of the controversy regarding iron uptake mechanisms into cardiomyocytes via calcium channels are presented with the hope that understanding the cellular iron uptake mechanism in cardiomyocytes will lead to improved treatment and prevention strategies,particularly in iron-overloaded patients.

Evaluation of a novel oral iron chelator 1-(N-acetyl-6-aminohexyl)-3-hydroxypyridin-4-one (CM1) for treatment of iron overload in mice

Desferrioxamine (DFO), deferiprone (DFP) and deferasirox (DFX) are promising effective iron chelators for the treatment of iron overload in b-thalassemia patients;nonetheless, their side effects have also been reported. 3-Hydroxypyridinone derivatives are being developed as a safer new chelator and in combined chelation therapy. We evaluated the iron-chelating activity of 1-(N-acetyl-6-aminohexyl)-3-hydroxypyridin-4-one (CM1) in iron-loaded C57BL6 mice. The feeding of a ferrocene-supplemented diet (Fe diet) to mice resulted in iron overload, detectable plasma nontransferrin-bound iron (NTBI) and labile plasma iron (LPI), and increases of red cell membrane iron, plasma malondialdehyde (MDA) and excessive tissue iron deposits. Like DFP, the CM1 lowered the levels of the membrane non-heme iron, the NTBI and LPI (p < 0.05) and the MDA after 3 months of treatment. Administration of the Fe diet and the Fe diet along with the chelators did not change the morphology of the liver and heart. Numerous iron accumulations were observed in the liver and spleen tissues of the Fe dietfed mice, whereas the CM1 reduced such iron deposition. Thus, 1-(N-acetyl-6-aminohexyl)-3-hydro- xypyridin-4-one (CM1) can be considered a candidate bidentate oral iron chelator and is effective in the removal of toxic irons in blood compartment and tissues. The effectiveness and toxicity of the CM1 need to be investigated extensively in thalassemia mice and patients with iron overload.

Efficacy of 1-(N-acetyl-6-aminohexyl)-3-hydroxypyridin-4-one (CM1) in treatment of iron-loaded hepatocyte cultures

Excessive iron is toxic to cells and organelles, where it can generate harmful reactive oxygen species (ROS) resulting in oxidative tissue damage. Liver is the major organ for iron storage and redox active iron in this tissue can cause fibrosis and cirrhosis in β-thalassemia patients. Desferrioxamine (DFO), deferiprone (DFP) and deferasirox (DFX) are clinically approved iron chelators used for the treatment of patients with iron overload, but none of these chelators are completely free of side effects. In this study we report the properties of a new iron chelator 1-(N-acetyl-6-aminohexyl)-3-hydroxypyridin-4-one (CM1). The labile iron pool (LIP) content was measured by using a calcein fluorescence technique and the lipidperoxidation products were quantified using the thiobarbituric acid reactive substances (TBARS) method. The cytotoxicity of CM1 was also examined with the (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. CM1 was demonstrated to reduce iron-induced redox damage and to decrease the levels of the intracellular iron pool in hepatocytes. CM1 is a potentially useful iron-chelating agent which has potential to ameliorate liver iron overload and ROS-induced lipid peroxidation. CM1 is currently under investigation for oral efficacy.