Abstract
Background In living systems iron appears predominantly associated with proteins (including transferrin in the plasma, and ferritin in the cells). However, when the binding capacity of these proteins is exceeded, the iron in the plasma begins to appear in the form of low molecular weight complexes called NTBI (Not-Transferrin Bound Iron), whose chemical composition is heterogeneous and thought to consist of several circulating isoforms, that is Fe (III) bound to albumin and citrate and potentially to acetate, malate and phosphate. The fraction of redox-active and chelatable NTBI is designated Labile Plasma Iron (LPI). It has been shown that these complexes, in particular LPI, are able to selectively penetrate cardiomyocytes and pancreatic islet cells promoting the formation of Reactive Oxygen Species (ROS) overriding the cellular antioxidant machineries and causing oxidative damage. The aim of our study was to quantify NTBI and LPI fractions on sera from 55 Thalassemia Transfusion Dependent patients (29 females and 26 males) under chelation treatment as monotherapy or in different combinations referred to our Center.
Material and Methods Blood samples were drawn after a short period of washout that is 12 hours for Deferiprone (DFP) and 24 hours for Desferoxiammine (DFO) and/or Deferasirox (DFX).
In each patient LPI was detected in 500 ml of serum using the FeROS™ kit (kindly provided by Aferrix Ltd., Israel) that measures the iron-specific redox activity. A reducing agent (ascorbic acid) and an oxidizing agent (atmospheric O2) cause labile iron in the tested sample to generate ROS via the Fenton reaction. The ROS are detected by an oxidation-sensitive probe (DHR) that becomes fluorescent when oxidized. With this assay an index of eLPI (enhanced/extractable LPI), that reflects the total NTBI levels, is provided by the use of a mobilizing agent.
One-way analysis of variance (ANOVA) was performed to compare means of LPI for different types of chelation treatment. Furthermore, data were studied in terms of correlation (Pearson's r) and association (Odds Ratio) for different LPI levels. LPI was categorized into two classes: <0.2 Units equal to 0 and ≥0.2 Units equal to 1.
Results A statistically significant difference was found for LPI means of different types of chelation treatment (p-value < 0.005, Table 1). Furthermore, no statistically significant correlation was found among eLPI and LPI with age and serum ferritin. Association among eLPI and LPI with cirrhosis, diabetes and cardiopathy was studied, and no statistical significance was found (OR 0.7, 95% CI 0.07-9.3, p-value 0.7; OR 1.2, 95% CI 0.2 -14.4, p-value 0.81; OR 2.6, 95% CI 0.3 - 132.8; p-value 0.37, respectively), even if, it was observed that cardiopathy is more common (83.3%) for high (≥ 0.2 Units) LPI values versus low (<0.2 Units) LPI values.
Discussion The results of this preliminary study showed that patients treated with DFX have lower LPI levels than other chelation treatments. In addition, for future analyses, it is to take into consideration that data could be indicative of an association between higher LPI values and heart disease. LPI and eLPI parameters when used together with other markers of iron overload (transferrin, ferritin, MRI heart-liver) can provide a convenient and immediate measure of chelation efficacy and are useful tool for monitoring treatment and patient compliance.
One-way analysis of variance of LPI for different types of chelation treatment
No relevant conflicts of interest to declare.
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