The Effects of Cyanate In Vitro on Red Blood Cell Metabolism and Function in Sickle Cell Anemia

Abstract To determine whether diminished activity of the Ca++ extrusion pump could account for the high levels of red blood cell (RBC) Ca++ in sickle cell anemia (SS), we measured calmodulin-sensitive Ca++ ATPase activity in normal and SS RBC. Hemolysates prepared with saponin were compared, since such preparations expressed maximum ATPase activities, exceeding isolated membranes or reconstituted systems of membranes plus cytosol, SS RBC hemolysates had greater Ca++ ATPase activity than normal hemolysates; they exhibited higher Mg++ and Na+ + K+ ATPase activities as well. Assays on density (age) fractions of SS and normal red cells demonstrated that all ATPase activities were highest in low density (young) cells, and activities in SS red cells exceeded those in normals in all fractions studied. Thus, when studied under conditions that maximize enzyme activity, Ca++ ATPase activity, like Mg++ and Na+ + K+ ATPase, is actually increased in SS RBC, probably due to the young red cell population present. The elevated Ca++ levels in these cells are more likely due to an increased Ca++ leak or abnormal calcium binding than to defective extrusion by the ATPase pump.

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Effectiveness of red blood cell exchange, partial manual exchange, and simple transfusion concurrently with iron chelation therapy in reducing iron overload in chronically transfused sickle cell anemia patients

Transfusion ◽

10.1111/trf.13558 ◽

2016 ◽

Vol 56 (7) ◽

pp. 1707-1715 ◽

Cited By ~ 21

Author(s):

Ross M. Fasano ◽

Traci Leong ◽

Megha Kaushal ◽

Eyal Sagiv ◽

Naomi L.C. Luban ◽

...

Keyword(s):

Blood Cell ◽

Iron Overload ◽

Sickle Cell ◽

Sickle Cell Anemia ◽

Red Blood Cell ◽

Chelation Therapy ◽

Iron Chelation ◽

Iron Chelation Therapy

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Red Blood Cell Deformability Demonstrated with the Oxygenscan: Exploring the Association with Hydroxyurea Treatment, Co-Inherited α-Thalassemia, and Frequency of Pain in Children with Sickle Cell Anemia

Blood ◽

10.1182/blood-2019-129836 ◽

2019 ◽

Vol 134 (Supplement_1) ◽

pp. 4834-4834

Author(s):

Amina Nardo-Marino ◽

Jesper Petersen ◽

Andreas Glenthoej ◽

John N. Brewin ◽

Joergen Kurtzhals ◽

...

Keyword(s):

Blood Cell ◽

Sickle Cell ◽

Sickle Cell Anemia ◽

Red Blood Cell ◽

Hemoglobin F ◽

Positive Correlation ◽

King's College ◽

Hydroxyurea Treatment ◽

Pain Frequency ◽

Rbc Deformability

Background Sickle hemoglobin (hemoglobin S, HbS) is a structural variant of adult hemoglobin. HbS polymerizes when oxygen tensions are low, leading to red blood cell (RBC) deformation, so-called "sickling". In sickle cell anemia (SCA), loss of RBC deformability is considered to be a primary factor responsible for vaso-occlusion and hemolysis. Until recently no laboratory tests to measure RBC deformability in SCA have been readily available. Study Aims In this study we examine RBC deformability, measured with the oxygenscan module of the Laser Optical Rotational Red Cell Analyzer (Lorrca) ektacytometer, in children with SCA treated with or without hydroxyurea (HU). Furthermore, we investigate the relationship between RBC deformability and pain frequency, as well as genetic and laboratory measures known to be associated with disease severity in SCA. Methods We included children aged 0-16 years with a confirmed diagnosis of SCA (HbSS) from the pediatric sickle cell clinic at King's College Hospital in London. Children were excluded if they had received any blood transfusions within 3 months of study inclusion. Children on HU were only included if treatment had been initiated >3 months prior to recruitment and the dose was stable. Children and their parents or guardians reported frequency of pain as: daily, weekly, monthly, yearly, or never. Laboratory measurements, including total hemoglobin (hb), hemoglobin F (HbF), and reticulocyte percentage, were performed on the same day as a sample was taken for oxygenscan analysis. Data on co-inheritance of α-thalassemia was recorded if available. EDTA blood samples were kept at approximately 4°C and transported from King's College London to Copenhagen University Hospital (Herlev and Gentofte Hospital), where they were analyzed within 48 hours of sampling using the Lorrca oxygenscan (RR Mechatronics, the Netherlands). The oxygenscan measures RBC deformability expressed as an elongation index (EI) during deoxygenation and reoxygenation, with EImax expressing RBC deformability at normal oxygen concentrations, EImin expressing RBC deformability after deoxygenation, and the point of sickling (POS) expressing the point at which >5% decrease in EI is observed, representing the pO2 at which sickling begins. All statistical analyses were performed in Stata V16.0 (StataCorp. 2019, USA), using the two-sided t-test, one-way ANOVA, and Pearson's correlation when appropriate. Results We included 47 children aged 0-16 years (mean age 7.9 years) in the study, 24 (51%) receiving HU. Children in the HU group presented with significantly higher HbF percentage compared to the non-HU group (15.6% and 10.9%, p=0.03). Children receiving HU had higher EImax and EImin, and lower POS values, compared to children in the non-HU group, although results were not significant (Table 1). There was a positive correlation between HbF and EImax (r= 0.57, p=0.0001) and HbF and EImin (r= 0.56, p=0.0001), and a negative correlation between HbF and POS (r=-0.37, p=0.01), as well as a positive correlation between total hb and EImax (r=0.35, p=0.02). There was no significant correlation between any oxygenscan parameters and reticulocyte percentage. Data on α-thalassemia was available for 23 children. EImax and EImin values were higher in heterozygous children compared to children without co-inherited α-thalassemia, and POS values were lower, but results were not significant (Table 2). We found no significant association between any oxygenscan parameters and pain frequency (Table 3). Conclusion In this study we identified a strong correlation between all oxygenscan parameters and HbF percentage, as has been reported previously. We found higher EImax and EImin and lower POS values in children receiving HU treatment and children with co-inherited heterozygous α-thalassemia, suggesting increased RBC deformability in these children. These results were not significant, however, which may in part be due to lack of power in the study. Also, it is possible that children in the HU group would have presented with lower EImax and EImin and higher POS values prior to HU initiation, with treatment response leading to results similar to those found in the non-HU group. Finally, our results suggest that there is no association between oxygenscan parameters and self-reported frequency of pain in children with SCA. Disclosures No relevant conflicts of interest to declare.

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Determinants of Inter-Procedure Interval in Patients with Sickle Cell Anemia Enrolled a Chronic Red Blood Cell Exchange Program

Blood ◽

10.1182/blood.v124.21.4284.4284 ◽

2014 ◽

Vol 124 (21) ◽

pp. 4284-4284

Author(s):

Alecia C. Nero ◽

Theresa Nguyen Kinard ◽

Beverley Adams-Huet ◽

Karen Matevosyan ◽

Ravindra Sarode

Keyword(s):

Blood Cell ◽

Multiple Regression ◽

Sickle Cell ◽

Sickle Cell Anemia ◽

Red Blood Cell ◽

Small Sample ◽

Blood Type ◽

Acute Chest Syndrome ◽

Intractable Pain ◽

Post Procedure

Abstract Background: Sickle cell anemia (SCA) is a genetically inherited disorder that can lead to severe sequelae in any organ system. The most clinically devastating complications, e.g. stroke, are managed with chronic red blood cell (RBC) transfusions as curing the underlying SCA is often not an option. Chronic RBC exchange (RBCx), is an effective alternative to simple transfusions and often performed every 4-5 weeks. Isovolemic Hemodilution-Red Blood Cell Exchange (IHD-RBCx) is a modified RBCx method used at UT Southwestern Medical Center (UTSW) and increases the time interval between transfusions, i.e. inter-procedure interval (IPI), up to 9 weeks while maintaining the desired hemoglobin S targets at safe levels. This minimizes the overall lifetime procedures and blood exposures. The standard operating procedure for IHD-RBCx is published (Matevosyan et al, 2012). However, we observed IPI variability between patients in this chronic IHD-RBCx program. We sought to analyze hematologic characteristics in a cohort of adult SCA patients that may be associated with this noted variability. Methods: This IRB approved cross-sectional study evaluated medical and blood bank records of adult patients with SCA, i.e. hemoglobin SS or Sβ0 thalassemia genotypes, undergoing chronic IHD-RBCx at UTSW adult hospital sites between January 1, 2012 and December 31, 2013. Excluded participants were those with autoimmune disease, non-compliance with IHD-RBCx leading to delays > 7 days, or use of hydroxyurea or steroids within four months of the study period. Patients with < 5 exchanges were excluded as several procedures are needed to determine baseline IPIs. The primary indication for IHD-RBCx was secondary stroke prevention. Three subjects had alternative indications (i.e. recurrent severe acute chest syndrome that failed hydroxyurea therapy, intractable pain and severe anemia ineligible for iron chelation due to end-stage renal disease). Median values during the 2 year study were determined for the IPI, laboratory, and RBC properties for use in subsequent analyses. Correlation and multiple regression analyses were performed to determine variables predictive of IPI. Results: Twenty-four SCA patients in this chronic IHD-RBCx transfusion program met inclusion criteria of which 14 (58.3%) were female with age range 18-41 years. Three subjects had incomplete data. The median number of packed RBC (pRBC) units per IHD-RBCx was 8 (range: 6-11 units). The median volume per unit of pRBCs was 304.5 mL (range: 298.8-326.5 mL) with average age of the pRBCs 5.8 days ± 0.7 days. The median IPI was 55.8 days (range: 36.0-65.5 days). The strongest correlation with IPI was the change from the mid to post-procedure hemoglobin and hematocrit values, r=0.56, p=0.005 and r=0.57, p=0.003, respectively. Participants with documented direct antiglobulin test positivity (n=7), compared to those who remained negative (n=16), had 4.9 days increased IPI. This difference was not statistically significant, p=0.19. ABO differences in blood type also did not show statistical significant differences. However, A+ subjects had a 58 day interval compared to 51, 52, 53 days for B+, O+, O- respectively (Figure). In multiple regression models, log blood urea nitrogen (BUN) and post-procedure white blood cell count (WBC) were found to be independent predictors of IPI, beta=-11.3, p=0.04 and -2.1, p=0.03 respectively, with adjusted R2=0.31. Conclusions: Chronic IHD-RBCx effectively treats severe SCA complications. Discontinuing transfusions lead to repeat stroke events or the recurrence of disease manifestations making chronic transfusion programs an indefinite therapy. Outside of the expected correlation between the IPI and hemoglobin/hematocrit, WBC and BUN were found to have negative associations with IPIs. The decrease in WBCs is likely due to the direct clearing effect by the operating system. The association between BUN and IPI may imply relationship with renal function. Interestingly, association with creatinine was not statistically significant. The study is limited by the small sample size. Future studies of similar cohorts should prospectively evaluate target mechanisms which may lead to interventions that can minimize lifetime blood exposures given the growing demands for continued RBCx in severe SCA. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

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