|Year : 2012 | Volume
| Issue : 3 | Page : 162-165
A study of CD62P (P-selectin) in β-thalassemia
Samira Z. Sayed1, Basma A. Ali1, Lamiaa H. Ali2, Mohamed H. Mohamed1
1 Department of Pediatrics, Children's Hospital, Minia University, Minia, Egypt
2 Department of Clinical Pathology, Children's Hospital, Minia University, Minia, Egypt
|Date of Submission||23-Feb-2012|
|Date of Acceptance||02-Mar-2012|
|Date of Web Publication||21-Jun-2014|
Basma A. Ali
Department of Pediatric, Children's Hospital, Minia University, Minia 61111
Source of Support: None, Conflict of Interest: None
β-Thalassemia major (β-TM) affects 60 000 births/year worldwide. These patients have to cope with complications of the disease that develop over time. In particular, marked hemostatic changes have been observed in patients with β-TM and β-thalassemia intermedia (β-TI).
Aim of the study
This study aimed to determine the percentage of CD62P (P-selectin) among β-thalassemic patients and to correlate it with the presence and the presence of hemostatic abnormalities.
Patients and methods
Our study included two groups. Group &Igr; included 45 patients with β-thalassemia, which was further subdivided into two subgroups: group Ia included 10 patients with TI and group Ib included 35 patients with TM. Group II included 15 apparently normal children as a control group, age and sex matched to the diseased group. Laboratory investigations were carried out including the following: complete blood count, serum ferritin, bleeding time, clotting time, prothrombin time and concentration, and finally CD62P (P-selectin).
The percentage of CD62P in thalassemic patients was significantly higher than that of the normal controls (P<0.001); in addition, it was higher in patients with TI than TM and in splenectomized patients than nonsplenectomized patients.
The expression of P-selectin, which is a clinical marker of platelet activation, was more prevalent in thalassemic children than the control children, especially those with β-TI, and in splenectomized patients even in the absence of thromboembolic manifestations.
Keywords: CD62P, P-selectin, thalassemia
|How to cite this article:|
Sayed SZ, Ali BA, Ali LH, Mohamed MH. A study of CD62P (P-selectin) in β-thalassemia. Egypt J Haematol 2012;37:162-5
| Introduction|| |
Thalassemia is a congenital hemolytic disease caused by defective globin synthesis, resulting in a decreased quantity of globin chains 1. This disease can be divided into two main subtypes on the basis of the severity of the clinical course: thalassemia major (TM) and thalassemia intermedia (TI) 2. In particular, marked hemostatic changes have been observed in patients with β-TM and β-TI, and also in patients with hemoglobin E thalassemia 3. Many studies have reported that nocturnal hypoxemia, related in part to anemia with platelet and leukocyte activation, which might affect endothelial function, is inversely related to the mean overnight oxygen saturation and there is evidence for increased levels of markers of cellular and endothelial adhesion 4,5. CD62P (P-selectin) exposure is a measure of platelet-granule release on activated platelets 6. P-selectin interactions between platelets stabilize the initial fibrinogen interactions, thereby promoting the formation of a large, stable platelet aggregate 7. Previous studies of cell–cell interactions between activated platelets and erythrocytes have indicated that biochemical communication between these cell types is initiated upon platelet activation, because, without a platelet agonist, erythrocytes cannot promote platelet activation or the recruiting activity of cell-free releasates 8. Many studies have extended the concepts of the role of erythrocytes in thrombogenesis and support the hypothesis that erythrocytes participate actively as signaling cells in thrombogenesis 9.
| Aim of the work|| |
The aim of this study was to determine the percentage of CD62P (P-selectin) among β-thalassemia patients and to correlate its presence with the presence of hemostatic abnormalities.
| Patients and methods|| |
Our study was carried out on 45 patients with β-thalassemia who had regular follow-up in the Pediatric Hematology Outpatient’s Clinic, Minia University Children’s Hospital, and were classified into group &Igr;. They were subdivided into two subgroups: group Ia included 10 patients (22.2%) with TI and group Ib included 35 patients (77.8%) with TM. Another 15 age-matched and sex-matched children were included in a control group and classified into group II. We obtained informed consent from the care giver of every child to be enrolled in the study.
The studied groups were subjected to thorough history taking, clinical examination, and laboratory investigations including complete blood count by Sysmex (Sysmex Corporation, Kobe, Japan), serum ferritin by ELISA (reference normal range is 18–323 ng/ml) 10, bleeding time (BT) and clotting time (CT) 11, prothrombin time (PT) and prothrombin concentration (PC) 12, liver enzymes and serum bilirubin, and finally CD62P by flow cytometry 13.
The standard computer program SPSS for Windows, release 13.0 (SPSS Inc., Chicago, Illinois, USA), was used for data entry and analysis 14.
| Results|| |
[Table 1] shows that the percentage of CD62P in β-thalassemic patients was significantly higher than that in the controls (P<0.001). However, there were no statistically significant differences between the β-thalassemic patients and the controls in the other hemostatic markers. Comparison of β-thalassemia subtypes indicated that the percentage of CD62P was significantly higher among patients with TI than that among patients with TM (P=0.01). Furthermore, BT and CT were higher among the patients with β-TI than the patients with β-TM, but the differences were statistically insignificant (P=0.6 and 0.5, respectively). However, the platelet count and PC were higher among the patients with β-TM than patients with β-TI, but the differences were statistically insignificant. Finally, serum ferritin was significantly higher in patients with TM than those with TI (P=0.003) [Table 2] and [Table 3]. Comparison of splenectomized patients and nonsplenectomized patients showed that the frequency of transfusion was significantly lower among the splenectomized than the nonsplenectomized patients (P=0.04). However, the platelet counts and the percentage of CD62P were significantly higher in splenectomized than in nonsplenectomized patients (P=0.001 and <0.001, respectively). [Figure 1] shows that there was a moderately positive significant correlation between CD62P and platelet count in group I (r=0.5, P=0.004). In the β-thalassemia subgroups, there was a fairly positive insignificant association between platelet counts and the level of CD62P among patients with β-TM (r=0.3, P=0.3), whereas there was a moderately positive significant association between platelet counts and the level of CD62P among patients with β-TI (r=0.6, P<0.001) [Figure 2] and [Figure 3].
|Figure 1: Correlation between CD62P and the platelet count in group I (r=0.5, P=0.004). Grades of r: 0.00–0.24 (weak or no association), 0.25–0.49 (fair association), 0.50–0.74 (moderate association), and ≥0.75 (strong association).|
Click here to view
|Figure 2: Correlation between CD62P and the platelet count in group Ib (β-thalassemia major patients) (r=0.3, P=0.3).|
Click here to view
|Figure 3: Correlation between CD62P and the platelet count in group Ia (β-thalassemia intermedia patients) (r=0.6, P=0.0001).|
Click here to view
|Table 1: Comparison between β-thalassemic patients and the control group in the percentage of CD62P and some hemostatic markers|
Click here to view
|Table 2: Comparison between Group Ia (β-thalassemia intermedia) and group Ib (β-thalassemia major) patients in the percentage of CD62P, serum ferritin, and some hemostatic parameters|
Click here to view
|Table 3: Comparison between splenectomized and nonsplenectomized patients in some clinical and laboratory data in thalassemia major patients|
Click here to view
| Discussion|| |
The life expectancy of β-thalassemia patients has improved markedly over the last few years; however, they still have many complications because of their chronic disease 2. Thrombosis is a major complication in patients with β-TM or TI 15. Thrombotic events can continue and can result in severe physical or mental debilitation or even death 16.
CD62P (P-selectin) is a cell adhesion molecule and CD antigen; its expression on activated platelets appears not to be simply to aid leukocyte and/or endothelial adhesion. There is evidence that it is also important for interplatelet aggregation, thus leading to the formation of large and stable platelet aggregates 6. The expression of P-selectin at the surface of the platelet is considered as a clinical marker of activation, easily detectable by flow cytometry 7.
The results of the present study showed that the percentage of CD62P in thalassemic patients, either intermedia or major, was significantly higher when compared with the normal controls. Our result was in agreement with the results obtained by Eldor et al. 16 and Taher et al. 15, who reported that there were increased fractions of platelets carrying the activation markers CD62P by flow cytometric studies in β-thalassemic patients. Taher et al. 15 reported that the higher level of CD62P among thalassemic patients may be attributed to platelet activation caused by increased platelet aggregation and the abnormalities in morphological platelets detected by an electron microscope. Moreover, there were abnormal red blood cells (RBCs) with increased aggregability, which in turn increased platelet activation and thrombin activation. Moreover, the procoagulant effect of the thalassemic RBCs might be a result of the following mechanism: Oxidation of B and Y hemoglobin subunits leads to the formation of hemichromes, whose rate of formation determines the rate of hemolysis 17. Hemichromes bind to or modify various components of the mature red-cell membrane, such as protein band 3, protein 4.1, ankyrin, and spectrin. After precipitation of hemichromes, heme disintegrates and toxic non-transferrin-bound iron species are released. The resulting free iron catalyzes the formation of reactive oxygen species. Iron-dependent oxidation of membrane proteins and the formation of red-cell ‘senescence’ antigens such as phosphatidylserine cause thalassemic red cells to become rigid and deformed and to aggregate, resulting in the activation of the platelet and coagulation system 17.
In the current study, it was also found that the percentage of CD62P in patients with TI was significantly higher than that in patients with TM. Our result was in agreement with the results obtained by Chen et al. 18, who had found that RBCs from thalassemic patients show enhanced cohesiveness and aggregability. RBC aggregation and the size of thalassemic RBCs were reduced to the normal range after the patients had received a blood transfusion. They confirmed this observation by in-vitro testing, where a reduction in aggregation was found with the addition of normal RBCs to thalassemic RBCs; these findings could explain why patients with β-TI who did not receive regular transfusion had a higher level of CD62P than those with TM who were receiving regular transfusions. In terms of the other hemostatic parameters, there were insignificant differences between the thalassemic patients and the controls in BT, CT, PT, PC, and platelets. Also, there was an insignificant difference between patients with TM and minor in terms of the platelet count, BT, CT, and PC.
In terms of the percentage of CD62P in splenectomized patients, our results showed that it was significantly higher when compared with nonsplenectomized patients. This result was in agreement with the result obtained by Eldor et al. 16 and Taher et al. 15. This could be attributed to the presence of high platelet counts and/or an increased number of abnormal RBCs, resulting in the activation of the coagulation system. This is supported by the fact that repeated transfusions decrease the risk of thrombosis significantly 19.
Furthermore, our results showed that there was no association between a history of thromboembolic manifestations and the percentage of CD62P. Although the percentage of CD62P was significantly increased in our thalassemic patients, either intermedia or major, when compared with the normal controls, none of our patients had a history of thromboembolic manifestations. Our result was in agreement with the results obtained by Eldor et al. 16, who reported that markers of platelet activation were persistently and consistently elevated in most thalassemic patients even in the absence of overt thromboembolic events. The presence of this high percentage of CD62P in thalassemic patients even in the absence of overt thromboembolic events indicates that thrombosis is largely a subclinical process in thalassemia and requires precipitating factors to produce thrombosis.
Moreover, we found that there was a moderately positive significant association between the platelet count and the percentage of CD62P in thalassemic patients, either major or intermedia. This could be attributed to the fact that the increased platelet count may lead to clumping of platelets in the circulation and increased platelet coagulant effect, resulting in the increase in the percentage of CD62P. Finally, we also found that there was a fairly insignificant association between the platelet count and the percentage of CD62P among patients with TM, but there was a moderately positive significant association between platelet count and the percentage of CD62P among patients with TI. This could be attributed to the increased number of abnormal RBCs, which were higher in TI because of infrequent transfusions, resulting in higher activation of the platelets.
| Conclusion|| |
The presence of a high percentage of CD62P in β-thalassemic patients, especially those with β-TI, and in splenectomized patients even in the absence of overt thromboembolic events indicates that thrombosis is largely a subclinical process in β-thalassemia. Therefore, the expression of P-selectin at the surface of the platelet was considered as a clinical marker of activation, easily detectable by flow cytometry.
| References|| |
|1.||Rund D, Rachmilewitz E. Beta-thalassemia. N Engl J Med. 2005;353:1135–1146 |
|2.||Borgna-Pignatti C, Rugolotto S, De Stefano P, Zhao H, Cappellini MD, Del Vecchio GC, et al. Survival and complications in patients with thalassemia major treated with transfusion and deferoxamine. Haematologica. 2004;89:1117–1119 |
|3.||Amiram E, Eliezer A. The hypercoagulable state in thalassemia. Blood. 2002;99:36–43 |
|4.||Kirkham FJ, Datta AK. Hypoxic adaptation during development: relation to pattern of neurological presentation and cognitive disability. Dev Sci. 2006;9:411–427 |
|5.||Inwald DP. Platelet and leukocyte activation in childhood sickle cell disease: association with nocturnal hypoxaemia. Br J Haematol. 2000;111:474–481 |
|6.||Berman CL, Yeo EL, Wencel-Drake JD, Furie BC, Ginsberg MH, Furie BA. Platelet alpha granule membrane protein that is associated with the plasma membrane after activation: characterization and subcellular localization of platelet activation-dependent granule-external membrane protein. J Clin Invest. 1986;78:130–137 |
|7.||Merten M, Thiagarajan P. P-selectin expression on platelets determines size and stability of platelet aggregates. Circ J. 2000;102:1931–1936 |
|8.||Schmidtke DW, Diamond SL. Direct observation of membrane tethers formed during neutrophil attachment to platelets or P-selectin under physiological flow. J Cell Biol. 2000;149:719–730 |
|9.||Marcus AJGallin J, Snyderman R. Platelets: their role in hemostasis, thrombosis and inflammation. Inflammation: basic principles and clinical correlates. 1999 Philadelphia, PA Lippincott Williams & Wilkins:77–95 |
|10.||Young DS Effects of preanalytical variables on clinical laboratory test. 1977;242nd ed. Washington, DC AACC Press:152–154 |
|11.||Lanzkowsky P. Thalassemias. Manual of pediatric hematology and oncology. 2005;7:181–200 |
|12.||Thomas SL. Cosensus of DGKL and VDGH for interim reference interval on enzymes in serum. J Lab Med. 2005;29:301–308 |
|13.||Semenov AV, Romanov YA, Loktionova SA. Production of soluble P-selectin by platelets and endothelial cells. Biochemistry (Mosc). 1999;64:1326–1335 |
|14.||Daniel WW Biostatistics: a foundation for analysis in the health science. 19956th ed. New York John Wiley and Sons Inc. |
|15.||Taher A, Otrock K, Uthman I, Cappellinni M. Thalassemia and hypercoagulability. Blood Rev. 2008;22:283–292 |
|16.||Eldor A, Elietec A, Rachmilurite EA. The hypercoagulable State in thalassemia. Blood. 2002;99:36–43 |
|17.||Ruf A, Pick M, Deutsch V, Patscheke H, Goldfarb A, Rachmilewitz EA. In-vivo platelet activation correlates with red cell anionic phospholipid exposure in patients with beta-thalassaemia major. Br J Haematol. 1997;98:51–56 |
|18.||Chen S, Eldor A, Barshtein G, Zhang S, Goldfarb A, Rachmilewitz E. Enhanced aggregability of red blood cells of beta-thalassemia major patients. Am J Physiol. 1996;270:1951–1956 |
|19.||Cappellini M, Taher A, Ismaeel H. Thalassemia intermedia. Blood Cells Mol Dis. 2006;37:12–20 |
[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3]