ALBERT

Description: Introduction: Recent evidence suggests that coagulation activation is involved in the pathogenesis of progressive organ failure in Sickle Cell Anemia (SCA). In addition, generation of neutrophil extracellular traps (NETosis), one of the components of immunothrombosis, has been associated with the pathogenesis of both venous thromboembolism and SCA. NETosis is a complex process that involves the orchestrated participation of several proteins such as peptidyl arginine deaminase (PADI4), neutrophil elastase (ELANE) and myeloperoxidase (MPO). PADI4 mediates histone citrulination, an essential step for NETosis. Accordingly, its inhibition has been recently cited as a potential therapeutic strategy for diseases in which NETosis are thought to play a relevant pathogenic role such as SCA. Although attractive, investment in PADI4 inhibitors in SCA requires gathering of more convincing evidences of the role of this enzyme in its pathogenesis. Herein, we used two cohorts of patients to investigate the expression of NETosis regulators (PADI4, ELANE and MPO) in SCA at steady state and during acute crisis, and to assess whether PADI4 activity is increased in any of these states. Methods: patients were recruited from two different centers in Brazil. Whole blood samples were obtained from patients from cohort 1 at steady state or during acute crisis (within 24 hours from admission). mRNA was obtained from granulocytes isolated by Ficoll gradient and gene expression of PADI4, ELANE, and MPO were measured by qPCR. In patients from cohort 2, PADI4 and MPO activity were measured in samples obtained within 24 hours from admission and after patient discharge (convalescence) using commercial kits in serum (MPO, Myeloperoxidase activity assay kit; ab105136) and plasma (PADI4, PAD4 Inhibitor Screening Assay Kit; Cayman chemical). Healthy individuals from the same geographic region were used as controls for each cohort, independently Results: In total, 54 steady state patients, 27 acute crisis and 40 healthy volunteers were evaluated for mRNA expression of NETosis regulators. Patients in acute crisis expressed higher levels of PADI4, MPO and ELANE compared to both healthy volunteers and patients in steady-state. Furthermore, plasma activity of PADI4 was higher in acute crisis when compared to healthy individuals (7.36x106 vs 5.24x106; P= 0.002), with no decrease after discharge (median of 13.5 days after admission) (7.36x106vs 7.41x106; P= 0.004). No differences were observed in serum MPO activity during acute crisis. Conclusion: we demonstrate that the mRNA expression of NETosis regulators, including PADI4, is increased in SCA; and that this increase is associated with higher levels of PADI4 activity in plasma during acute crisis. These results support the concept of PADI4 inhibition as a therapeutic strategy for acute episodes of SCA, and warrant additional studies in this area. Disclosures No relevant conflicts of interest to declare.

Description: Background: Sickle cell anemia (SCA) is characterized by chronic hemolysis and endothelial dysfunction (ED). Plasma hemoglobin (pHb) and its heme component released from intravascular hemolysis (IH) are among the most important factors contributing to ED. Unfortunately, the importance of IH to the development of an ED and the effects of hydroxyurea therapy on IH and ED in SCA remains unclear. Aims: We evaluated plasma levels of IH and ED markers among Brazilian SCA patients not receiving hydroxyurea therapy (HbSS), and compared with those of hydroxyurea-treated SCA patients (HbSS_HU) and healthy controls (HbAA). Methods: A cross-sectional study of 60 SCA consenting patients (32 HbSS and 28 HbSS_HU; 19-42 years) in steady state, who are being followed up at the Blood Center, Pernambuco (HEMOPE) and 32 HbAA controls. The IH markers were serum Lactate Dehydrogenase [LDH] and total heme measured by enzymatic colorimetric tests, and pHb measured by enzyme-linked immunosorbent assay (ELISA). The ED markers were plasma von Willebrand factor (vWF:Ag) and vWF ristocetin cofactor activity (vWF:Rco) levels measured by the latex enhanced immunoassay. The other ED markers were the antigen of vWF-cleaving protease (ADAMTS13:Ag), thrombospondin-1 and endothelin-1 levels measured by ELISA, and ADAMTS13 Activity (ADAMTS13:Act) measured by FRETS-VWF73 method. The study was approved by the Ethics Committee of the State University of Campinas and HEMOPE under protocol No: 1.863.428. Data were analyzed using GraphPad Prism 6. Results: The pHb and LDH were significantly increased in HbSS than HbSS_HU patients (Figures 1A and 1B). Plasma levels of vWF:Ag, vWF:Rco, serum levels of total heme, thrombospondin-1 and endothelin-1 were significantly increased in HbSS and HbSS_HU patients compared to HbAA controls (Figures 1C and 2A, 2B, 2E, 2F), while serum level of thrombospondin-1 level was elevated in HbSS than HbSS_HU patients (Figure 2E). Similarly, ADAMTS13:Ag levels and ADAMTS13 activity were significantly lower in HbSS and HbSS_HU patients than HbAA controls, while ADAMTS13 activity levels were significantly elevated in HbSS_HU patients compared to HbSS patients (Figure 2D). In HbSS_HU patients, the ADAMTS13:Act was negatively correlated with heme and LDH [r = -0.47, p = 0.013; and r = -0.44, p = 0.023 respectively]. In additional, heme was positively correlated with vWF:Ag and LDH [(r = 0.47, p = 0.017) and (r = 0.56, p = 0.003) respectively]. In HbSS patients, LDH and pHb were positively correlated (r = 0.44, p = 0.014). Conclusions: Hydroxyurea therapy was associated with a reduced levels of LDH, pHb and thrombospondin-1 levels, and increased levels of ADAMTS13 activity in SCA patients. Increased ADAMTS13 activity levels may be attributed to reduction of pHb and thrombospondin-1 levels because previous invitro studies have shown that thrombospondin-1 or pHb are bound to vWF. Thus, vWF is restrained from ADAMTS13 activity and cleavage, and hyperreactive vWF might accumulate as a consequence of inhibition of ADAMTS13 activity. Increased thrombospondin-1, pHb and hyperreactive vWF levels are proposed to participate in sickle cell adhesion and promote thrombotic complications. Therefore, our results demonstrate an additional clinical benefit for the use of hydroxyurea in these patients. Disclosures No relevant conflicts of interest to declare.

Description: Introduction: Sickle cell anemia (SCA) is a chronic inflammatory disease with heterogeneous clinical features and the reasons for the heterogeneity of the clinical manifestations has not been fully elucidated. New mediators of the pathogenesis of SCA described recently include the formation of Neutrophil Extracellular Traps (NETs), which may contribute to the amplification of inflammation via the production of pro-inflammatory mediators. Peptidylarginine Deiminase 4 (PADI4) is a critical regulator of NETosis by mediating histone citrullination, an essential step for the generation of NETs. There appears to be a relationship between PADI4 gene polymorphisms and the pathophysiology of other inflammatory diseases in which NETosis seems to be relevant. Our aim was to investigate the association of PADI4 gene polymorphisms [rs874881(G〉C), rs1748033(T〉C), rs11203366(G〉A), rs11203367 (T 〉C), rs2240340 (T〉C)], which have been previously associated with increased PADI4 mRNA stability and with some clinical manifestations in cohorts of SCA patients. Methods: The study included 194 SCA patients (93 males and 101 females with mean age 33.29 ± 9.54 years) being followed up at the Hematology and Hemotherapy Foundation of Pernambuco (HEMOPE), Recife, Brazil. PADI4 gene polymorphisms were performed by Polymerase Chain Reaction (PCR) and their products were sequenced using the Big Dye Terminator Cycle Sequencing Ready Reaction Kit v3.1 (Applied Biosystems, CA, USA). These results obtained were compared with the clinical data obtained from the patients' records. Ethical approval was obtained from Ethics Committee of HEMOPE and all patients gave informed consent. Results: The frequencies of the genotypes found were as follows: rs874881 (22.2% GG, 50.5% GC, 27.3% CC); rs1748033 (17% TT, 42.3% TC, 40.7% CC); rs11203366 (21.1% GG, 50% GA, 28.9% AA); rs11203367 (20.6% TT, 49.5% TC, 29.9% CC); rs2240340 (24.7% TT, 46.4% TC, 28.9% CC). The distribution of the genotypes was in accordance with the Hardy-Weinberg equilibrium (p 〉 0.05). Twenty-four patients (12.4%) presented with a history of acute chest syndrome (ACS), 27 (13.9%) with stroke, 168 (86.6%) with vaso-occlusive crisis (VOC), and 81 (47.8%) with leg ulcers (LU). No association was observed between the polymorphisms studied and the history of LU, VOC and stroke in the patients (p 〉 0.05). However, for rs 874881 and 1748033 with the G and T alleles, respectively, were associated with a higher risk of ACS (OR: 2.96, p = 0.02 and OR: 4.75, p = 0.01, respectively). Conclusion: In the present study, we found an association between the wild type alleles (rs874881G and rs1748033T) and a history of ACS in our cohort of SCA patients. There is need for future studies on these polymorphisms in larger cohorts of SCA patients to affirm this association. Disclosures No relevant conflicts of interest to declare.