Markers of Oxidative Stress Do Not Correlate with Labile Plasma Iron Blood in Patients with Myelodysplastic Syndromes

Background: Modalities of monitoring and clinical impact of post transfusional iron overload in MDS patients remain controversial. Labile Plasma Iron (LPI) is a component of Non-Transferrin Bound Iron (NTBI) that is thought to contribute to oxidative stress in MDS. However, little data support this hypothesis and most studies on LPI have only addressed its ability to produce free radicals in vitro. The aim of this work was to assess LPI and to evaluate the correlation between LPI and plasma and blood markers of peroxidation in MDS patients

Design and Methods: In 67 non-chelated MDS patients, we evaluated: hemoglobin (Hb), indices of iron overload, peroxidation status at inclusion and/or during follow up. The peroxidation status was evaluated by measuring blood Glutathione (GSH) and plasma Advanced Oxidation Protein Products (AOPP). LPI was measured using the Afferix kit. NTBI was measured by a flow cytometry- based assay (FeFlobead) in a subset of patients with high transferrin saturation.

Results: Median age of the 67 patients was 79 years (range 61-93). 38 patients were included at diagnosis of MDS and 29 were included during the disease course (after a median of 50 months, range 3-168, for the latter group). WHO sub-type was: 14 refractory anemia, 22 refractory anemia with ring sideroblasts, 7 refractory cytopenia with mutlilineage dysplasia, 4 5q minus syndrome, 16 refractory anemia with excess of blasts ( RAEB) (type I n=6, Type II n=5, 5 RAEB-t/AML , 3 chronic myelo monocytic leukemia type I, one unclassifiable case. Prognostic score according IPSS was low in 43 patients, Int-1 in 13, Int-2 in 6 and high in 5. 36/67 patients had been transfused and had received a median of 22 packed RBCs (range 2-102). Transfused patients (N=36) were more heavily iron overloaded than non-transfused patients (N=31), as indicated by significantly higher median transferrin (Tf ) saturation (42% versus 62%) (P<0.005) and serum ferritin (SF) values 389microg/L versus 1494)(P<0.0001). A highly significant correlation (r² =0.5, P<0.001) was seen between serum ferritin values and the number of PRBCs. 9/31 (29 %) non transfused and 26/36 (72 %) transfused patients had Tf saturation > 50 %. However, the mean value of LPI was very similar in transfused and non-transfused group (0.34 microM versus 0.38). 8/67pts had LPI levels above limit upper value (≥ 0.4 µM) and their SF was significantly higher than that of other patients(p=0.02). However no significant difference was found between patients with LPI < 0.4 µM and ≥ 0.4 µM, for Tf saturation, blood GSH or AOPP median values. No correlation between LPI and NTBI was seen. GSH and AOPP levels did not statistically differ according (IPSS) groups. 14 patients were studied during follow up, 7 of them after 3 months of iron chelation, and 7 after treatment with EPO. While chelation slightly improved markers of oxidative stress (MAO) (p= NS), EPO induced a very highly significant improvement of MAO-(p= 0.005).

Conclusion: We found no evidence to support LPI pro-oxidant role in vivo. A few patients had an elevated LPI level in this large, moderately transfused, MDS cohort. Utility of LPI in monitoring of post transfusional iron overload remain to be demonstrated. Results obtained following EPO treatment suggest that ineffective erythropoiesis rather than iron overload may be responsible for RBC oxidative stress