Effects of hydroxyurea on cytotoxicity, inflammation and oxidative stress markers in neutrophils of patients with sickle cell anemia: dose-effect relationship

Abstract

Introduction Although the efficacy of hydroxyurea (HU) in inhibiting erythrocyte sickling has been well demonstrated, the action of this drug on human neutrophils and the mechanism by which it improves the manifestations of the disease have not been studied thoroughly. We aimed to investigate the cell viability, along with inflammatory and oxidative markers in the neutrophils of sickle cell anemia (SCA) patients and the effects of HU therapy on these cells, by evaluating the dose-responsiveness. Methods In the present study, 101 patients (45 men and 56 women, aged 18–69 years) with SCA were divided into groups according to the use or not of HU: the SS group (without HU treatment, n = 47) and the SSHU group (under HU treatment, n = 54). The SSHU group was further stratified into subgroups according to the daily dose of the drug that patients already used: SSHU - 0.5 g (n = 19); SSHU - 1 g (n = 26) and SSHU - 1.5–2 g (n = 9). A control group (AA) comprised 50 healthy individuals. Neutrophils isolated from whole blood were analyzed using Trypan Blue, monoiodotyrosine (MTT) and lactate dehydrogenase (LDH) toxicity assays. Myeloperoxidase (MPO), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) activities and concentrations of interleukin 10 (IL-10), tumor necrosis factor alpha (TNF-α) and malonaldehyde (MDA) were also measured. Results Neutrophils from SCA patients showed membrane fragility and a significant decrease in cell viability when analyzed by Trypan Blue ( p < 0.05), MTT ( p < 0.001) and LDH ( p = 0.011), compared to the AA group. Levels of inflammatory (MPO, TNF-α, and IL-10) and oxidative markers (SOD, GSH-Px, and MDA) were also altered ( p < 0.05) in these cells, showing a significant difference in the SSHU-1g and SSHU - 1.5–2 g groups, compared to the SS group. Treatment with HU reverted the levels of all markers to concentrations similar to those in healthy individuals in a positive dose-effect relationship. Conclusion The HU did not generate a cytotoxic effect on neutrophils in SCA patients, but it modulated their oxidative and inflammatory mechanisms, promoting cytoprotection with a positive dose-effect.

Iron Chelation Reduces DNA Damage in Sickle Cell Anemia

“…23 The effects of HU on the hematological parameters revealed that it could result in higher levels of hemoglobin, hematocrit, and mean corpuscular volume (MCV) and a decline in leukocyte and neutrophil numbers. 24 Further, a significant increase was observed in the activity of the LDH enzyme in the SCA group as compared to the control group. All the HU-treated groups demonstrated a significant decline in LDH levels in comparison to the SCA group.…”

“…All the HU-treated groups demonstrated a significant decline in LDH levels in comparison to the SCA group. 24 It was noted that SCA patients had significantly higher leukocyte and neutrophil counts and that HU resulted in not only an increased concentration of HbF but also a decreased number of these cells. 24 …”

“… 24 It was noted that SCA patients had significantly higher leukocyte and neutrophil counts and that HU resulted in not only an increased concentration of HbF but also a decreased number of these cells. 24 …”

“…All the HU-treated groups demonstrated a significant decline in LDH levels in comparison to the SCA group. 24 It was noted that SCA patients had significantly higher leukocyte and neutrophil counts and that HU resulted in not only an increased concentration of HbF but also a decreased number of these cells. 24 The results of another study that compared the treatment with either HU or chronic transfusion therapy indicated that the HU group presented a significantly higher HbF percentage than the other group.…”

Prognostic factors associated with COVID-19 related severity in sickle cell disease

“…HCW employment has not been previously reported as a risk factor in SCD ICU admission but has been associated with COVID-19 morbidity in the general US population as well as comprehensive meta-analysis [13] , [14] .. HU use has been reported to reduce morbidity in SCD in one report [1] but not others [10] , [21] . It is biologically plausible that HU might decrease morbidity from COVID-19 infection due to reduction of coagulation and neutrophil and endothelial cell activation [26] , [27] , [28] . Finally, the level of immature granulocytes has not been previously reported as a risk factor in SCD ICU admission, but is associated with disease severity and ICU admission in the general population [15] , [17] .…”