Zinc and antioxidant vitamin deficiency in patients with severe sickle cell anemia

Endothelial dysfunction in Sickle Cell Disease: Strategies for the treatment

Sickle Cell Anemia (SCA), is an inherited hemoglobinopathy characterized by the presence of an abnormal hemoglobin (HbS), being the most prevalent sickle cell disease (SCD). SCA is characterized by vascular endothelial dysfunction, which contributes significantly to various clinical conditions, including but not limited to pulmonary hypertension, priapism, cutaneous leg ulceration, and stroke. The pathophysiology of endothelial dysfunction (ED) in SCA is a multifaceted process involving a chronic inflammatory and hypercoagulable state. Key factors include hemolysis-associated elements like reduced arginine and nitric oxide (NO) availability, elevated levels of vascular adhesion molecules, the uncoupling effect of NO synthase, heightened arginase activity, an environment characterized by oxidative stress with the production of reactive oxygen and nitrogen species, and occurrences of ischemia-reperfusion injury, along with apolipoprotein A-1 depletion. The urgency for novel interventions addressing ED is evident. Presently, there is a focus on investigating small molecules that disrupt the arginine-nitric oxide pathway, exhibiting anti-inflammatory and antioxidant properties while diminishing levels of cellular and vascular adhesion molecules. In this mini-review article, we delve into the progress made in strategies for treating ED in SCD with the aim of cultivating insights for drug design.

Red Blood Cell Vitamin C Concentration and Its Effect on Deformability in Pediatric Sickle Cell Disease

Red cell rigidity is common in sickle cell disease (SCD). The contribution of oxidative stress on deformability remains unknown. This study investigated red blood cell (RBC) vitamin C concentrations in pediatric SCD (n=43) compared with healthy controls ( n =23) and developed a protocol to raise RBC vitamin C concentrations to measure the effect on deformability. Sickle cell RBC vitamin C concentrations seem low (20.5 μM, SD: 16.2 vs. 51.7 μM, SD: 15.8; P <0.0001). Vitamin C can be successfully loaded into sickle cell RBCs but seems to have minimal effect on deformability. Future studies are needed to understand the clinical implications of vitamin C deficiency in pediatric SCD.

Zinc level and effect of zinc supplementation on growth in a subset of Sudanese children with sickle cell disease

A case-control interventional study was conducted to determine serum zinc levels in children with sickle cell disease (SCD) and to compare them to the levels in normal children and to the levels after 6 months of zinc supplementation. A total of 74 patients and 30 normal children, considered as controls for the zinc levels, were included. The clinical findings, including anthropometric measurements, were obtained. Serum zinc levels at the start and after 6 months, for the patients and at the start for the controls were measured. The mean age at enrolment and diagnosis were 7.5 ± 4.8 years and 5.5 ± 2.4 months, respectively. Male to female ratio was 1:1. Patients showed very low zinc levels at enrolment (0.268 ± 0.146 mg/l), while the controls had a mean zinc level at lower limits of normal (0.542 ± 0.087 mg/l) and a p-value of 0.04. After zinc supplementation, zinc levels in patients increased significantly with a p-value = 0.04. Zinc supplementation had positive effects on weight and height, with a p-value of 0.001 for both. The increase in body mass index and HC were not significant, with p-values of 0.058 and 0.067, respectively. Likewise, zinc supplementation had positive effects on the haematological indices as an increase in haemoglobin levels and a decrease of leucocyte counts, with p = 0.004 and 0.005, while the increase in platelet count was insignificant, p-value = 0.058. Furthermore, zinc supplementation decreased the frequency of hospitalisation significantly. We recommend considering zinc supplementation as one of the standard-of-care interventions in Sudanese children with SCD.

Vitamin C deficiency reveals developmental differences between neonatal and adult hematopoiesis

Hematopoiesis, a process that results in the differentiation of all blood lineages, is essential throughout life. The production of 1x10¹² blood cells per day, including 200x10⁹ erythrocytes, is highly dependent on nutrient consumption. Notably though, the relative requirements for micronutrients during the perinatal period, a critical developmental window for immune cell and erythrocyte differentiation, have not been extensively studied. More specifically, the impact of the vitamin C/ascorbate micronutrient on perinatal as compared to adult hematopoiesis has been difficult to assess in animal models. Even though humans cannot synthesize ascorbate, due to a pseudogenization of the L-gulono-γ-lactone oxidase (GULO) gene, its generation from glucose is an ancestral mammalian trait. Taking advantage of a Gulo^-/- mouse model, we show that ascorbic acid deficiency profoundly impacts perinatal hematopoiesis, resulting in a hypocellular bone marrow (BM) with a significant reduction in hematopoietic stem cells, multipotent progenitors, and hematopoietic progenitors. Furthermore, myeloid progenitors exhibited differential sensitivity to vitamin C levels; common myeloid progenitors and megakaryocyte-erythrocyte progenitors were markedly reduced in Gulo^-/- pups following vitamin C depletion in the dams, whereas granulocyte-myeloid progenitors were spared, and their frequency was even augmented. Notably, hematopoietic cell subsets were rescued by vitamin C repletion. Consistent with these data, peripheral myeloid cells were maintained in ascorbate-deficient Gulo^-/- pups while other lineage-committed hematopoietic cells were decreased. A reduction in B cell numbers was associated with a significantly reduced humoral immune response in ascorbate-depleted Gulo^-/- pups but not adult mice. Erythropoiesis was particularly sensitive to vitamin C deprivation during both the perinatal and adult periods, with ascorbate-deficient Gulo^-/- pups as well as adult mice exhibiting compensatory splenic differentiation. Furthermore, in the pathological context of hemolytic anemia, vitamin C-deficient adult Gulo^-/- mice were not able to sufficiently increase their erythropoietic activity, resulting in a sustained anemia. Thus, vitamin C plays a pivotal role in the maintenance and differentiation of hematopoietic progenitors during the neonatal period and is required throughout life to sustain erythroid differentiation under stress conditions.

Zinc in sickle cell disease: A narrative review

Sickle cell disease (SCD) is an inherited disease caused by hemoglobin S mutated hemoglobin S. It is characterized by chronic hemolysis, intermittent vaso-occlusive crises followed by ischemia-reperfusion, and organ damage. These patients have an increased risk of multiple micronutrient deficiencies, such as zinc. The reduced zinc bioavailability in sickle cell patients may lead to several complications such as growth retardation, delayed wound healing, increased vaso-occlusive crises, and infections. This narrative review aims to analyze the literature concerning the zinc status in SCD and their possible consequences on the patients' clinical evolution. We found in children and adolescents a direct association between zinc insufficiencies/deficiencies with increased disease severity in SCD. Monitoring zinc status in children and adolescent SCD appears essential for reducing disease-associated morbidity and infections. Zinc supplementation is a safe therapeutic modality for treating SCD patients. New research must be carried out, especially for adults, to ensure more remarkable survival for this population.

Oxidative stress and hepcidin expression in pediatric sickle cell anemia with iron overload

BACKGROUND

Blood transfusion (BT) is essential in treating sickle cell disease (SCD); however, it leads to iron overload (IO) and oxidative stress. We studied the relationship between oxidative stress, iron status parameters, hepcidin mRNA gene expression, and IO in SCD patients.

METHODS

We classified all SCD patients (n = 90) into two groups: Group I, 45 children (s.ferritin ≥ 938 ng/mL) and Group II, 45 children (s.ferritin < 938 ng/mL). A total of 55 children, age and sex matched, participated as a control group. Malondialdehyde (MDA), nitrite, s.iron, s.total iron-binding capacity (sTIBC), transferrin saturation %, s.ferritin, s.hepcidin, and hepcidin mRNA gene expression were assessed.

RESULTS

Among SCD BT-dependent patients (>3 times/year), 63% were from Group I and 37% from Group II, p < .01. The two patient groups had significantly lower s.hepcidin and hepcidin gene expression than controls (p < .001). TIBC, s.iron, s.ferritin, transferrin saturation %, ferritin/hepcidin ratio, and MDA levels were higher among SCD patients than controls (p < .001). Group I had higher mean level of ferritin/hepcidin ratio and MDA than Group II (p < .01). The higher level of MDA and increased frequency of BT were the significant predicting risk factors for IO (p < .05). A receiver-operating characteristic curve indicates that MDA is the outstanding significant biomarker for high level of s.ferritin with subsequent IO progression.

CONCLUSION

MDA may serve as a biomarker of oxidative stress and IO in SCD patients. This result paid attention for urgent initiation of antioxidant and chelation therapy on detecting increased MDA level.

Oxidative status in the β-thalassemia syndromes in Sri Lanka; a cross-sectional survey

In the β-thalassemias, oxidative stress, resulting from chronic hemolysis, globin chain imbalance, iron overload and depleted antioxidant defences, likely contributes to cell death, organ damage, anemia, hypoxia and inflammation. We assessed variations in these parameters in β-thalassemia syndromes in Sri Lanka. Between November 2017 and June 2018, we assessed children and adults attending two thalassemia centres in Sri Lanka: 59 patients with HbE β-thalassemia, 50 β-thalassemia major, 40 β-thalassemia intermedia and 13 HbS β-thalassemia. Median age was 26.0 years (IQR 15.3-38.8), 101 (62.3%) were female and 152 (93.8%) of Sinhalese ethnicity. Methemoglobin, plasma hemoglobin, heme and ferritin were measured as sources of oxidants; plasma total antioxidant capacity, haptoglobin, hemopexin and vitamins C and E assessed antioxidant status; plasma thiobarbituric acid reactive substances and 8-hydroxy-2'-deoxyguanosine assessed oxidative damage; hemoglobin, plasma erythropoietin and transferrin receptor assessed anemia and hypoxia and plasma interleukin-6 and C-reactive protein assessed inflammation. Fruit and vegetable intake was determined by dietary recall. Physical fitness was investigated using the 6-min walk test and measurement of handgrip strength. Oxidant sources were frequently increased and antioxidants depleted, with consequent oxidative damage, anemia, hypoxia and inflammation. Biomarkers were generally most abnormal in HbE β-thalassemia and least abnormal in β-thalassemia intermedia but also varied markedly between individuals with the same thalassemia syndrome. Oxidative stress and damage were also more severe in splenectomized patients and/or those receiving iron chelation therapy. Less than 15% of patients ate fresh fruits or raw vegetables frequently, and plasma vitamins C and E were deficient in 132/160 (82.5%) and 140/160 (87.5%) patients respectively. Overall, physical fitness was poor in all syndromes and was likely due to anemic hypoxia. Studies of antioxidant supplements to improve outcomes in patients with thalassemia should consider individual patient variation in oxidative status both between and within the thalassemia syndromes.

Antioxidant nutrients and hemolysis in sickle cell disease

Hemolysis is one of the main pathophysiological characteristics of sickle cell disease (SCD) and might cause or could be the result of oxidative stress. Antioxidants are studied in SCD due to their potential to ensure redox balance and minimize deleterious effects on erythrocyte membranes. The objective of this systematic review was to evaluate the efficacy of antioxidant nutrient supplementation on reducing hemolysis in SCD patients through randomized clinical trials. We conducted our study according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses and the Cochrane Handbook for Systematic Reviews of Interventions investigating whether antioxidants could improve the hemolytic status of SCD patients. This study included 587 articles published until April 2020. We reduced this pool to 12 articles by excluding duplicates, reviews, comments, and studies with non-human subjects. Omega-3 fatty acids, vitamin A, and zinc were the antioxidants that reportedly improved the indirect hemolysis parameters such as hemoglobin, hematocrit, mean corpuscular volume, or red blood cells. High-dose vitamin C and E supplementation worsened hemolysis, causing increased reticulocytes, lactate dehydrogenase, indirect bilirubin, and haptoglobin. More intervention studies especially high-quality controlled randomized clinical trials are needed to investigate the effects of antioxidant nutrients in reducing hemolysis in SCD.

In Vitro Lymphocyte Functions in Undernourished Children With Sickle Cell Anemia

Background: Children with sickle cell disease (SCD) often suffer from growth deficits and impaired immunity. However, the association between mild to moderate malnutrition and in vitro lymphocyte function has not been well studied. The goal of this study was to investigate the effects of undernutrition on lymphocyte functions in children with SCD. Methods: Weight; height; plasma concentrations of albumin (Alb), prealbumin (PA), transferrin (Tf), retinol-binding protein (RBP), α₁-acid glycoprotein (AGP), C-reactive protein (CRP), and ceruloplasmin (Cp); and lymphocyte proliferation and interleukin (IL)-2 in phytohemagglutinin-treated blood lymphocytes were measured in 90 children with SCD (59 SS, 4 Sβ°, 27 SC hemoglobin genotypes). Results: The mean age of the children included in the analysis was 7.65 years. Four of the 90 children had weight and height below the fifth percentile. A higher percentage of children with HbSS/HbSβ° (61.4%) than of those with HbSC (44%) had ≥2 plasma protein concentrations below normal (Alb <35 g/L, PA <160 mg/L, Tf <2.0 g/L, and RBP ≤20 mg/L). Mean anthropometric measurements, hemoglobin, and hematocrit were lower in children with HbSS/HbSβ° than in those with HbSC (P<0.05). Lymphocyte proliferation was reduced by 20% to 27% in children with HbSS/HbSβ° with undernutrition plus inflammation (AGP >1 g/L, CRP >5 mg/L, Cp >600 mg/L) compared to children with neither. Regardless of inflammatory status, lymphocyte proliferation was reduced by 29% to 49% in children with HbSS/HbSβ° and undernutrition defined by PA or Alb plus RBP (P<0.05) compared to those with RBP within normal range. Neither undernutrition nor inflammation reduced lymphocyte proliferation in children with HbSC. Mean IL-2 activity was reduced by undernutrition, defined as PA <160 mg/L, in both groups. PA, RBP, and hemoglobin concentrations positively correlated with in vitro lymphocyte functions (P<0.05). Conclusion: Undernutrition altered in vitro lymphocyte function in children with the HbSS/HbSβ° genotypes. Dietary supplements may improve the altered functions in these children.

Serum levels of copper, zinc and disease severity scores in sickle cell disease patients in Benin City, Nigeria

BACKGROUND

Micronutrient deficiency is recognized in sickle cell anaemia (SCA) but it is not known for certain whether changes in zinc, copper and copper-to-zinc ratio are associated with Sickle cell disease severity scores.

OBJECTIVE

To compare serum levels of copper, zinc and copper-to-zinc ratio in SCA subjects with control group and correlate the variables with objective disease severity scores.

METHODS

Serum copper and zinc were determined in 100 SCA patients and 50 controls using kits supplied by Centronic, Germany. Unpaired Students't-test was used to compare the variables between SCA patients in steady clinical state, vaso-occlusive crisis and controls, while Spearman correlation coefficient was used to associate the parameters with disease severity scores.

RESULTS

Serum copper level was higher (P=0.008) in SCA patients than controls, while serum zinc level was lower (P<0.001) in SCA patients than controls. The copper/zinc ratio was higher (P<0.001) in SCA patients than controls. Significantly higher (P<0.001) copper and lower (P<0.001) zinc levels were observed in patients in vaso-occlusive crisis than in steady clinical state. Zinc correlated inversely (r=-0.2743; P=0.006) while copper-to-zinc ratio correlated positively with disease severity scores.

CONCLUSION

Copper-to-zinc ratio may be an indicator of disease severity in SCA patients.

Zinc for Infection Prevention in Sickle Cell Anemia (ZIPS): study protocol for a randomized placebo-controlled trial in Ugandan children with sickle cell anemia

BACKGROUND

Sickle cell anemia (SCA) is the most common inherited hemoglobinopathy worldwide. Infection is a major cause of illness and death in children with SCA, especially in sub-Saharan Africa where an estimated 50-90% of affected children die before their fifth birthday. Interventions to reduce the incidence and severity of infections are needed urgently. A high proportion of adults and children with SCA are zinc-deficient, and zinc deficiency leads to impaired immunity and an increased risk of infection. Zinc supplementation has been shown to decrease the risk of infection in adolescents and adults, but there are no data on the effectiveness of zinc for prevention of infection in children < 5 years of age with SCA.

METHODS/DESIGN

The study will be a randomized, placebo-controlled, double-blind clinical trial in which 250 Ugandan children 1.00-4.99 years of age with SCA will receive daily zinc supplementation (10 mg oral dispersible tablet) or identical placebo for 12 months.

DISCUSSION

If this trial shows a reduction in severe or invasive infection incidence, it would be the basis for a multi-site, multi-country clinical trial to assess real-world safety and efficacy of zinc in African children with SCA. Since zinc is safe, inexpensive, and easy to administer, this trial has the potential to improve the health of hundreds of thousands of African children with SCA through reduction of infection-related morbidity and mortality.

TRIAL REGISTRATION

Clinicaltrials.gov, NCT03528434. Registered on May 17, 2018 Protocol Version: 1.0. Date: Dec 11, 2017 Sponsor: Indiana University. Sponsor's protocol identifier, 1712339562.

Red Blood Cell and Serum Magnesium Levels Among Children and Adolescents With Sickle Cell Anemia

Patients with sickle cell anemia (SCA) can acquire many biochemical abnormalities, including altered magnesium levels. However, the roles of magnesium in the pathogenesis and management of SCA need to be determined. The aim of this work was to evaluate magnesium levels among pediatric patients with SCA in Basra, Iraq. The study employed a case-control design and examined 87 patients with SCA (3-15 years old) who had attended the Basra Center for Hereditary Blood Diseases while in a steady state and 90 apparently healthy control subjects. Complete blood count, red blood cell (RBC), and serum magnesium, calcium, potassium, sodium, zinc, and copper levels were measured in all subjects. The results revealed significantly lower RBC and serum magnesium levels among the patients with SCA (3.62 ± 0.42 and 1.35 ± 0.19 mg/dL, respectively) than those among the control subjects (4.47 ± 0.55 and 1.87 ± 0.27 mg/dL, respectively). In addition, compared to the control subjects, the patients with SCA had significantly lower serum levels of potassium, sodium, and zinc; significantly higher serum levels of copper; and significantly higher Ca/Mg and Na/Mg ratios. Among the SCA patients, the RBC magnesium level was significantly negatively associated with the frequencies of vaso-occlusive crises (r = - 0.423, P < 0.001) and disease-related hospitalization (r = - 0.225, P < 0.05). To conclude, the RBC magnesium level, but not the serum magnesium level, is significantly associated with vaso-occlusive crises and hospitalization. Therefore, screening and management of low RBC magnesium levels in SCA patients are required.

Albumin, copper, manganese and cobalt levels in children suffering from sickle cell anemia at Kasumbalesa, in Democratic Republic of Congo

Background

Sickle Cell Anemia (SCA) is characterized by high levels of oxidative stress markers and low levels of antioxidant capacity. Antioxidant defence mechanisms against the harmful effects of ROS requires cellular and extracellular enzymes. These enzymes requires micronutrient for complete activity. Information on micronutrients such as manganese, cobalt and copper in SCA population was poorly documented in the literature.

Methods

Plasma copper, manganese, cobalt and albumin concentrations determined by atomic absorption spectrophotometry were compared between two groups of children: 76 with SCA (Hb-SS) and 76 without SCA (controls). This study was conducted in the Muhona Hospital of Kasumbalesa, which is situated in a rural and low in resources.

Results

The mean age was 10.0 years (SD = 5.4) in SCA children and 9.2 years (SD = 4.7) in the control group. The levels of cobalt, manganese, copper and albumin were not different between the two groups (p > 0.05).

Conclusion

In our study, albumin, manganese, cobalt and copper values did not differ between SCA children in steady state and Hb-AA children. The lack of differences in plasma elemental concentrations between the two groups in context of increased demands in the SCA group, may represent adequate compensatory intake or elemental dyshomeostasis in the SCA group.

Inflammation in sickle cell disease

The primary β-globin gene mutation that causes sickle cell disease (SCD) has significant pathophysiological consequences that result in hemolytic events and the induction of the inflammatory processes that ultimately lead to vaso-occlusion. In addition to their role in the initiation of the acute painful vaso-occlusive episodes that are characteristic of SCD, inflammatory processes are also key components of many of the complications of the disease including autosplenectomy, acute chest syndrome, pulmonary hypertension, leg ulcers, nephropathy and stroke. We, herein, discuss the events that trigger inflammation in the disease, as well as the mechanisms, inflammatory molecules and cells that propagate these inflammatory processes. Given the central role that inflammation plays in SCD pathophysiology, many of the therapeutic approaches currently under pre-clinical and clinical development for the treatment of SCD endeavor to counter aspects or specific molecules of these inflammatory processes and it is possible that, in the future, we will see anti-inflammatory drugs being used either together with, or in place of, hydroxyurea in those SCD patients for whom hematopoietic stem cell transplants and evolving gene therapies are not a viable option.

Impact of zinc on sexual maturation of female sickle cell anemia (SCA) children in Enugu, Southeast Nigeria

Adolescence is an important developmental period of childhood. Good health and adequate nutrition consisting major food constituents and trace elements like zinc are fundamental for optimal sexual maturation. To determine the relationship between zinc levels and pattern of breast and pubic hair development, as well as menarcheal age of female SCA children aged 6-18 years and their matched controls with hemoglobin genotype AA. Cross sectional, case-control study. Information on biodata, age at menarche, medical and drug history as well as 24-hour dietary recall was documented using interviewer administered questionnaire. Sexual maturation was assessed using Tanner staging and zinc levels determined using Atomic absorption spectrophotometer. Eighty-one subjects were compared with 81 controls. There was significant delay in the mean age of attainment of various Tanner stages of breast and pubic hair in the subjects. Mean age of 14.81 ± 1.07 years at menarche in subjects was significantly higher than 12.62 ± 1.18 years in controls (p = 0.001). Serum zinc of 58.01 ± 10.58 µg/dl in subjects was significantly lower than 68.37 ± 8.67 µg/dl in controls (p = 0.001). Serum zinc levels were found to have a significant positive relationship with stages of sexual maturation and mean age at menarche. Reduced serum zinc in children with SCA was associated with delayed sexual maturation.

Assessment of some indicators of oxidative stress in nigerian sickle cell anemic patients

Background:

Oxidative stress, the imbalance between the productive of reactive species and antioxidant defences notably plays an important role in the pathogenesis of sickle cell disease. Generating the necessary data about oxidative stress in patients with sickle cell anemia (SCA) would help in developing cost-effective and accessible treatment interventions of SCA in resource-poor countries.

Aim:

The aim of this study is to evaluate the levels plasma lipid peroxidation product, malondialdehyde (MDA), serum nitric oxide (NO), and total antioxidant activity (TAOA) as indicators of oxidative stress in sickle cell individuals.

Materials and Methods:

In this pilot study, 52 patients; homozygous (Hb SS) sickle cell patients confirmed by cellulose electrophoresis and 20 age- and sex-matched healthy (Hb AA) controls were subjected to analysis of NO, MDA, and TAOA. The plasma MDA was measured by a thiobarbituric reaction, (NO) was evaluated by the method described by Guevara et al. using Griess reagent and the TAOA of serum was determined by the method of Koracevic et al.

Results:

The results showed a statistically significant decrease and increase in baseline levels of NO and MDA, respectively, in Hb SS group when compared with the control Hb AA (P = 0.000 and 95% confidence interval [CI] of 0.10–0.18 and −9.67–−5.57, respectively). A slight decrease in the TAOA level between the groups was observed although not statistically significant (P = 0.15 95% CI was −0.28–2.90).

Conclusion:

The results showed of imbalance between oxidant and antioxidant status in patients with SCA. Antioxidant supplementation may be a cheap assessable intervention for in sickle cell individuals (in the steady state or in crisis) to prevent further oxidative damage to the erythrocytes.

Evaluation of Serum Zinc and Antioxidant Vitamins in Adolescent Homozygous Sickle Cell Patients in Wardha, District of Central India

INTRODUCTION

Sickle cell anaemia is a condition characterized by haemolytic and vaso-occlusive crisis. Previous studies in different part of the world have reported deficiency of zinc, vitamin C and E but the role of their supplementation in sickle cell disease remains question. Nutritional factors may contribute to clinical manifestation in rural population of developing countries specially in adolescent age group. Thus, the present study was designed in rural population of Wardha district of Maharashtra in adolescent sickle cell homozygous patients in view to evaluate serum zinc and antioxidant vitamins C and E.

AIM

To evaluate the serum zinc and antioxidant vitamins C and E in cases of adolescent homozygous sickle cell disease.

MATERIALS AND METHODS

The study includes adolescent (between 10-20 years) individuals in two groups of 33 each. Group A included confirmed cases of Sickle Cell Disease (SCD) and Group B included age and sex matched normal healthy controls. Serum zinc, vitamins C and E were analysed in all the subjects of both the groups. Data were expressed as Mean±SD; unpaired t-test was used to compare the two groups. Statistical significance was decided by calculating the p-value.

RESULTS

Serum levels of zinc and antioxidant vitamins E and C were significantly low in sickle cell anaemia patients when compared to normal health controls (p-value<0.001).

CONCLUSION

Our study shows that the adolescent patients with SCD have significant low levels of zinc and significantly low antioxidant vitamins C and E, which may contribute to some of the manifestations of sickle cell disease.

Gum Arabic as novel anti-oxidant agent in sickle cell anemia, phase II trial

Background

Sickle cell anemia patients suffer from oxidative stress due to chronic inflammation and self-oxidation of sickle hemoglobin (Hb S). Chronic oxidative stress contributes to endothelial dysfunction, inflammation and multiple organ damage in sickle cell disease (SCD). Thus, antioxidant medication may favorably influence the disease. Gum Arabic (GA), edible, dried, gummy exudates from Acacia Senegal tree, has been claimed to act as an anti-oxidant and cytoprotective agent, protecting against experimental hepatic, renal and cardiac toxicities in rats. We hypothesized that regular intake of GA increases anti-oxidant capacity and reduce oxidative stress.

Methods

Forty-seven patients (5–42 years) carrying hemoglobin SS were recruited. Patients received 30 g/day GA for 12 weeks. Total anti-oxidant capacity (TAC), malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) levels were measured by spectrophotometric methods before and after GA intake. Complete blood count was measured by sysmex.

Results

Gum Arabic significantly increased TAC level P < 0.001and decreased the oxidative markers MDA (P < 0.05) and H₂O₂ (P < 0.005).

Conclusions

GA has potent anti- oxidative properties in sickle cell anemia. The anti-oxidant effect of GA may thus favorably influence the clinical condition of this and further diseases characterized by oxidative stress.

Trial registration

ClinicalTrials.gov Identifier: NCT02467257. Registered 3rd June 2015. Retrospective registration.

Nutrient Insufficiencies/Deficiencies in Children With Sickle Cell Disease and Its Association With Increased Disease Severity

BACKGROUND

Sickle cell disease (SCD) is characteristically described as a disease of hemolytic anemia and vaso-occlusive crises (VOCs). However, patients suffer from a multitude of other problems including impaired development, chronic pain, and increased susceptibility to infection. Nutritional deficiency has been implicated as a contributor to these issues.

PROCEDURE

We reported the nutrition status with respect to vitamin D, zinc, B6, B12, folate, and homocysteine serum levels in Canadian children with SCD (n = 91). We also tested for associations between nutrients and markers of disease severity and growth.

RESULTS

Almost half the sample (42%) had multiple nutrient insufficiencies/deficiencies, and a further 27% had a single insufficiency/deficiency. The most common insufficiency/deficiency was zinc in 57% followed by calcidiol (25 dihydroxyvitamin D (25(OH)D)) (52%). Sixteen percent of patients had low vitamin B6 levels, while folate, calcitriol (1,25(OH)D), and homocysteine levels were normal. Increased number of vitamin insufficiencies/deficiencies was associated with increasing disease severity (P = 0.018). Zinc insufficiency/deficiency was significantly associated with an increased number of home pain crises (P = 0.001) and an increased incidence of hospitalizations for VOCs (P = 0.01).

CONCLUSIONS

Our findings show that patients with SCD commonly have multiple nutrient insufficiencies/deficiencies and support the growing evidence for the link between low zinc and increased VOC. It also indicates that increased nutrient insufficiencies/deficiencies are associated with increased disease severity in SCD. Prospective studies with larger samples are needed to further elucidate the relationship between nutrient deficiencies and SCD, and to determine whether nutrient supplementation can improve the disease course.

Oxidant-antioxidant status in Egyptian children with sickle cell anemia: a single center based study

OBJECTIVE

the present study was conducted to investigate the oxidant-antioxidant status in Egyptian children with sickle cell anemia.

METHODS

the serum levels of total antioxidant capacity (TAO), paraoxonase (PON), vitamin E, nitrite, and malondialdehyde (MDA) were measured in 40 steady state children with homozygous sickle cell anemia (24 males and 16 females) and 20 apparently healthy age- and gender-matched controls.

RESULTS

mean serum TAO, PON, vitamin E, and nitrite levels were significantly lower in the group with sickle cell anemia, whereas mean serum MDA was significantly higher in these children compared to controls. No significant differences in mean levels of TAO, PON, nitrite, vitamin E, and MDA were found in sickle cell anemia patients receiving hydroxyurea when compared with those not receiving hydroxyurea. A significant negative correlation between serum nitrite and the occurrence of vaso-occlusive crises (VOC) was observed (r=-0.3, p=0.04). PON level was found to be positively correlated with patients' weight and BMI (r=-0.4, p=0.01; r=-0.7, p<0.001, respectively), but not with frequency of VOC. The area under the curve of serum nitrite in predicting occurrence of VOC was 0.782, versus 0.701 for PON, and 0.650 for TAO (p=0.006). Serum MDA was not correlated with nitrite, PON, TAO, or vitamin E levels. No significant correlations were detected between serum nitrite and hemoglobin or antioxidant enzymes.

CONCLUSION

children with sickle cell anemia have chronic oxidative stress that may result in increased VOC, and decreased serum nitrite may be associated with increases in VOC frequency. A novel finding in this study is the decrease in PON level in these patients, which is an interesting subject for further research.

Docosahexaenoic and eicosapentaenoic acid supplementation does not exacerbate oxidative stress or intravascular haemolysis in homozygous sickle cell patients

We investigated whether or not Omega-3 long-chain polyunsaturated fatty acid (omega-3 LCPUFA) supplementation exacerbates oxidative stress in homozygous sickle cell patients aged 2 to 14 years. Depending on their age, they received between one and three omega-3 (277.8mg DHA and 39.0mg EPA/capsule) or placebo (high oleic acid sunflower seed oil) capsules for one year. Supplementation increased significantly the levels of the two fatty acids in red cell phosphatidylcholine and phosphatidylethanolamine (p<0.001). The patients who received omega-3 LCPUFA compared with their placebo-taking counterparts had a higher concentration of plasma vitamin E at one year (14.3±2.8 versus 12.3±2.8µmol/l; p<0.001). The two groups had comparable concentrations of the vitamin at six month intervention (10.8±2.2 versus 10.7±2.9µmol/l; p>0.05) and baseline (10.7±3.1 versus 10.7±2.8µmol/l; p>0.05). After six month of intervention, the patients on omega 3 fatty acids had lower GPx-1 (33.5±13.4 versus 46.6 ±17.6, p<0.01) and Cu/Zn-SOD (1070±600 versus 1470±690 p<0.05) activities than at baseline. GPx-1 (33.5±17.6IU/g Hb versus 43.7±13.2IU/g Hb; p<0.01) and Cu/Zn-SOD (1070±600IU/g Hb versus 1360±920IU/g Hb; p>0.05) activities were reduced in the omega 3 compared with the placebo at six month intervention. There was no difference in the activity of either of the enzymes between baseline and six month intervention in the placebo group (p>0.05). This study demonstrates; DHA and EPA supplementation, rather than exacerbating the inherent oxidative stress associated with the disease, seems to provide an antioxidant protection. Hence, it will be safe to provide omega-3 LCPUFA to sickle cell patients to help ameliorate vaso-occlusive and haemolytic crises and membrane fatty acid abnormality.

Erythrocyte NADPH oxidase activity modulated by Rac GTPases, PKC, and plasma cytokines contributes to oxidative stress in sickle cell disease

Chronic inflammation has emerged as an important pathogenic mechanism in sickle cell disease (SCD). One component of this inflammatory response is oxidant stress mediated by reactive oxygen species (ROS) generated by leukocytes, endothelial cells, plasma enzymes, and sickle red blood cells (RBC). Sickle RBC ROS generation has been attributed to sickle hemoglobin auto-oxidation and Fenton chemistry reactions catalyzed by denatured heme moieties bound to the RBC membrane. In this study, we demonstrate that a significant part of ROS production in sickle cells is mediated enzymatically by NADPH oxidase, which is regulated by protein kinase C, Rac GTPase, and intracellular Ca(2+) signaling within the sickle RBC. Moreover, plasma from patients with SCD and isolated cytokines, such as transforming growth factor β1 and endothelin-1, enhance RBC NADPH oxidase activity and increase ROS generation. ROS-mediated damage to RBC membrane components is known to contribute to erythrocyte rigidity and fragility in SCD. Erythrocyte ROS generation, hemolysis, vaso-occlusion, and the inflammatory response to tissue damage may therefore act in a positive-feedback loop to drive the pathophysiology of sickle cell disease. These findings suggest a novel pathogenic mechanism in SCD and may offer new therapeutic targets to counteract inflammation and RBC rigidity and fragility in SCD.

Antioxidant vitamins C and E supplementation increases markers of haemolysis in sickle cell anaemia patients: a randomized, double-blind, placebo-controlled trial

Erythrocytes from sickle cell anaemia (SCA) patients continuously produce larger amounts of pro-oxidants than normal cells. Oxidative stress seems to primarily affect the membrane and results in haemolysis. The use of antioxidants in vitro reduces the generation of pro-oxidants. To evaluate the impact of vitamins C (VitC) and E (VitE) supplementation in SCA patients, patients over 18 years were randomly assigned to receive VitC 1400 mg + VitE 800 mg per day or placebo orally for 180 d. Eighty-three patients were enrolled (44 vitamins, 39 placebo), median age 27 (18-68) years, 64% female. There were no significant differences between the two groups regarding clinical complications or baseline laboratorial tests. Sixty percent of the patients were VitC deficient, 70% were VitE deficient. Supplementation significantly increased serum VitC and E. However, no significant changes in haemoglobin levels were observed, and, unexpectedly, there was a significant increase in haemolytic markers with vitamin supplementation. In conclusion, VitC + VitE supplementation did not improve anaemia and, surprisingly, increased markers of haemolysis in patients with SCA and S-β(0) -thalassaemia. The exact mechanisms to explain this findings and their clinical significance remain to be determined.

Targeting NADPH oxidase decreases oxidative stress in the transgenic sickle cell mouse penis

INTRODUCTION

Sickle cell disease (SCD) is a state of chronic vasculopathy characterized by endothelial dysfunction and increased oxidative stress, but the sources and mechanisms responsible for reactive oxygen species (ROS) production in the penis are unknown.

AIMS

We evaluated whether SCD activates NADPH oxidase, induces endothelial nitric oxide synthase (eNOS) uncoupling, and decreases antioxidants in the SCD mouse penis. We further tested the hypothesis that targeting NADPH oxidase decreases oxidative stress in the SCD mouse penis.

METHODS

SCD transgenic (sickle) mice were used as an animal model of SCD. Hemizygous (hemi) mice served as controls. Mice received an NADPH oxidase inhibitor apocynin (10 mM in drinking water) or vehicle. Penes were excised at baseline for molecular studies. Markers of oxidative stress (4-hydroxy-2-nonenal [HNE]), sources of ROS (eNOS uncoupling and NADPH oxidase subunits p67(phox) , p47(phox) , and gp91(phox) ), and enzymatic antioxidants (superoxide dismutase [SOD]1, SOD2, catalase, and glutathione peroxidase-1 [GPx1]) were measured by Western blot in penes.

MAIN OUTCOME MEASURES

Sources of ROS, oxidative stress, and enzymatic antioxidants in the SCD penis.

RESULTS

Relative to hemi mice, SCD increased (P<0.05) protein expression of NADPH oxidase subunits p67(phox) , p47(phox) , and gp91(phox) , 4-HNE-modified proteins, induced eNOS uncoupling, and reduced Gpx1 expression in the penis. Apocynin treatment of sickle mice reversed (P<0.05) the abnormalities in protein expressions of p47(phox) , gp91(phox) (but not p67(phox) ) and 4-HNE, but only slightly (P>0.05) prevented eNOS uncoupling in the penis. Apocynin treatment of hemi mice did not affect any of these parameters.

CONCLUSION

NADPH oxidase and eNOS uncoupling are sources of oxidative stress in the SCD penis; decreased GPx1 further contributes to oxidative stress. Inhibition of NADPH oxidase upregulation decreases oxidative stress, implying a major role for NADPH oxidase as a ROS source and a potential target for improving vascular function in the SCD mouse penis.

Nocturnal haemoglobin oxygen saturation variability is associated with vitamin C deficiency in Tanzanian children with sickle cell anaemia

Aim

To compare pulse oximetry in children with sickle cell anaemia (SCA) and controls and test the hypothesis that vitamin C deficiency (VCD; <11.4 μmol/L) is associated with nocturnal haemoglobin oxygen desaturation in SCA.

Methods

We undertook nocturnal and daytime pulse oximetry in 23 children with SCA (median age 8 years) with known steady-state plasma vitamin C concentrations and 18 siblings (median 7 years).

Results

Median nocturnal delta 12 s index (delta12 s), a measure of haemoglobin oxygen saturation (SpO₂) variability, was 0.38 (interquartile range 0.28–0.51) in SCA and 0.35 (0.23–0.48) in controls, with 9/23 and 6/18, respectively, having a delta12 s >0.4, compatible with obstructive sleep apnoea (OSA). Eleven of twenty-three with SCA had VCD; logged vitamin C concentrations showed a 66% decrease per 0.1 unit increase in delta12 s ([95% CI −86%, −15%]; p = 0.023) and delta12 s >0.4 was associated with VCD (odds ratio 8.75 [1.24–61.7], p = 0.029). Daytime and mean nocturnal SpO₂ were lower in SCA but there was no association with vitamin C.

Conclusion

Obstructive sleep apnoea (OSA), detected from nocturnal haemoglobin oxygen saturation variability, is common in Tanzanian children and associated with vitamin C Deficiency in SCA. The direction of causality could be determined by comparing OSA treatment with vitamin C supplementation.

Sickle cell disease serum induces NADPH enzyme subunit expression and oxidant production in leukocytes

Oxidative stress plays a significant role in sickle cell disease (SCD), contributing to haemolysis, vaso-occlusive processes and endothelial dysfunction. To study the effects that the serum of SCD individuals has on the oxidative state of blood cells, sera were pooled from control individuals, steady-state SCD patients and SCD patients on hydroxyurea therapy (SCDHU), and their effects on markers of oxidative stress and damage in neutrophils isolated from healthy individuals observed. Incubation of control neutrophils, but not platelets nor red blood cells, with SCD serum (10% v/v; 2 hours) significantly augmented their production of reactive oxygen species (ROS). Increased ROS production in SCD serum-incubated neutrophils was associated with increased superoxide anion generation, apoptosis and increased nicotinamide adenine dinucleotide phosphate oxidase subunit expression. Although serum from SCDHU individuals also induced ROS generation in neutrophils, its oxidative capacity appeared to be lower. Results suggest that factors in the serum of SCD individuals contribute to ROS generation and oxidative damage in leukocytes.

Relationship between Painful Crisis and Serum Zinc Level in Children with Sickle Cell Anaemia

Sickle cell anaemia (SCA) is associated with zinc deficiency; zinc supplementation may ameliorate some of its clinical manifestations including the relief of painful crisis. Subjects and Methods. Serum zinc levels were determined in 71 children with SCA and painful crisis and in equal numbers in steady state. Seventy-one children with AA genotype acted as controls. Qualitative assessment of zinc content of 24-hour dietary recall and the last meal consumed before blood was drawn was taken. Serum zinc was determined using atomic absorption spectrophotometer. Haemoglobin concentration and packed cell volume (PCV) were determined using standard methods. Results. The mean serum zinc concentration in the study was less than international reference range. The controls had significantly higher serum zinc concentrations than the SCA group (42.7 ± 13.6 versus 32.3 ± 14.0 μg/dL, P < .000); this difference was due to the significantly lower values of serum zinc in SCA with painful crisis compared with the remaining two groups F = 30.9, P<.000. There was a positive correlation between serum zinc and haemoglobin concentration only in the control group (r = 0.4; P = .001). Conclusion. The serum zinc levels in this study were low. Painful crisis in SCA may exert greater demand for zinc utilization in children with SCA thereby resulting in lower serum levels.

The Role of Nutrition in Sickle Cell Disease

Finding a widely available cure for sickle cell anemia (HbSS) still remains a challenge one hundred years after its discovery as a genetically inherited disease. However, growing interest in the nutritional problems of the disease has created a body of literature from researchers seeking nutritional alternatives as a means of decreasing morbidity and improving quality of life among HbSS patients. This review demonstrates that over the past 30 years the role of protein/energy deficiency in HbSS has been more clearly defined via direct measurements, leading to the concept of a relative shortage of nutrients for growth and development, despite apparently adequate dietary intakes. Although there is still a paucity of data supporting the efficacy of macronutrient supplementation, it is becoming clearer that recommended dietary allowances (RDAs) for the general population are insufficient for the sickle cell patient. A similar shortage is likely to be true for micronutrient deficiencies, including recent findings of vitamin D deficiency that may be associated with incomplete ossification and bone disease, which are well known complications of HbSS disease. We conclude that there is need for more effort and resources to be dedicated to research (including supplementation studies of larger sample size) aimed at establishing specific RDAs for HbSS patients, much like the specific RDAs developed for pregnancy and growth within the general population.

Characterization of S-glutathionyl hemoglobin in homozygous sickle cell disease

S-glutathionyl hemoglobin is a proposed biomarker of oxidative stress but has not been measured in sickle cell disease patients. Unlike the S-glutathionyl adduct of normal adult hemoglobin, S-glutathionyl sickle hemoglobin (HbSSG) cannot be directly measured by capillary isoelectric focusing, because it coelutes with fetal hemoglobin (HbF). This suggests that HbF, measured in sickle cell patients with or without hydroxyurea therapy, might contain endogenous HbSSG. As S-glutathionyl hemoglobin can form during sample storage, HbSSG could falsely elevate HbF levels in stored samples. We measured HbSSG based on the quantitative difference in the heterogeneous HbF/HbSSG peak before and after hemolysates were treated with dithiothreitol. Paired t tests showed that dithiothreitol reduced HbF/HbSSG in blood from pediatric sickle cell patients (n=25, mean decrease+/-SD=1.0%+/-0.6, P<0.05) but not in normal infants (n=25). Higher HbF levels in hydroxyurea-treated patients (n=5) were not attributable to HbSSG. HbSSG increased significantly within 1 day in samples stored at -20 degrees C but was unchanged in samples stored 60 days at-70 degrees C. We conclude that blood from sickle cell patients contained up to 2.2% HbSSG, and that endogenous HbSSG is a minor interferent in the measurement of HbF in fresh blood but a major interferent in improperly stored samples.

Nutritional deficiencies in iron overloaded patients with hemoglobinopathies

One of the hallmarks of both sickle cell disease (SCD) and thalassemia major (TM) is accelerated oxidative damage. Decreased antioxidant levels and increased oxidant stress biomarkers are found in both diseases. Although isolated vitamin deficiencies have been reported in TM and nontransfused SCD patients, a comprehensive evaluation of vitamin and trace mineral levels has never been performed in chronically transfused SCD or TM patients. As vitamins and trace minerals may be consumed as a result of chronic oxidative stress; we hypothesized that levels of these compounds would correlate with surrogates of iron overload, hemolysis, and inflammation in chronically transfused patients. Using a convenience sample of our group of chronically transfused patients we studied 43 patients with SCD (17 male, 26 female) and 24 patients with TM (13 male and 11 female). The age range for our patients varied from 1.5 to 31.4 years. Levels of vitamins A, thiamin, B6, B12, C, D, E as well as selenium, zinc, copper, and ceruloplasmin were measured. We found that 40-75% of the patients were deficient in A, C, D and selenium and 28-38% of the patients had low levels of B vitamins and folate. There was little association with iron overload, hemolysis, or inflammation. Although the precise mechanism of these deficiencies is unclear, they may contribute to the morbidity of chronically transfused hemoglobinopathy patients.

Oxidative process in erythrocytes of individuals with hemoglobin S

The understanding of the oxidative stress mechanisms helps to explain many of the processes of cellular lesion and death, especially those related to the hemolytic diseases. Sickle cell anemia, thalassemias and G6-PD deficiency are among the more frequent genetic anomalies accompanied by oxidative stress. In the sickle cells, one of the factors that predisposes to the hemolytic process is the oxidative degradation of the hemoglobin S due to its deoxigenation leading to hemichrome formation and precipitation as Heinz bodies. The oxidative stress contributes to the sickle process and shortening of the erythrocyte survival. Here we analyzed the oxidative process in erythrocytes of patients with two different genotypes for HbS (AS and SS). Units of blood from donors of the Center of Hematology and Hemotherapy of Paraná (HEMEPAR), from normal individuals (AA) and from heterozygote individuals (AS), and venous blood collected from patients with sickle cell anemia (SS) were analyzed. In order to evaluate the protective action of the vitamins C and E in oxidative stress, erythrocytes were treated with antioxidant substances, vitamin C and vitamin E, and then treated with the oxidant tert-butilhydroperoxide (TBHP). The oxidative action induced by TBHP was observed in erythrocytes AA<AS<SS, by the increase in the content of Heinz bodies, methemoglobin, hemolysis, GSH depletion and lowering activities of the enzymes G6-PD and GR. The protective actions of the vitamins C and E for the oxidative stress induced by TBHP were observed for the erythrocytes in the lowering Heinz bodies, methemoglobin, hemolysis, and partial recovery of GSH more efficiently in AS and SS erythrocytes. Recovery was not observed in the levels of the activities of the enzymes G6-PD and GR, under the vitamins actions. The results obtained confirmed the higher susceptibility of the sickle erythrocyte to oxidation which necessitates precaution in the transfusion adequacy of AS erythrocytes. On the other hand, the protective effect of the vitamins C and E over the oxidative stress observed in erythrocytes AS and SS open perspectives for their use for treatment of patients with sickle cell anemias, as well as in the preservation of transfusional erythrocyte bag units.

Zinc supplementation decreases oxidative stress, incidence of infection, and generation of inflammatory cytokines in sickle cell disease patients

Zinc deficiency is common in adult sickle-cell disease (SCD) patients. We previously demonstrated that zinc supplementation to adult SCD patients decreased the incidences of infections and hospital admissions. We hypothesize that zinc supplementation improves T-helper cell function and decreases vascular endothelial cell activation, oxidative stress, and nuclear factor-kappa B (NF-kappaB)-DNA binding in mononuclear cells (MNCs) in SCD patients. To test this hypothesis, 36 SCD patients were recruited and randomly divided into 2 groups. One group (n = 18) received 25-mg zinc orally thrice a day for 3 months. The other group (n = 18) received placebo. The results indicate that the zinc-supplemented group had decreased incidence of infections compared with the placebo group. After zinc supplementation, red blood cell, hemoglobin (Hb), hematocrit, (Hct), plasma zinc, and antioxidant power increased; plasma nitrite and nitrate (NOx), lipid peroxidation products, DNA oxidation products, and soluble vascular cell adhesion molecule-1 decreased in the zinc-supplemented group, compared with the placebo group. Zinc-supplemented patients exhibited significant decreases in lipopolysaccharide-induced tumor necrosis factor-alpha (TNF-alpha) and IL-1beta mRNAs, and TNF-induced nuclear factor of kappaB-DNA binding in MNCs, compared with the placebo group. Ex vivo addition of zinc to MNCs isolated from the placebo subjects decreased TNF-alpha and IL-1beta mRNAs. Zinc supplementation also increased relative levels of IL-2 and IL-2Ralpha mRNAs in phytohemagglutinin-p-stimulated MNCs. These results suggest that zinc supplementation may be beneficial to SCD patients.

C-reactive protein and interleukin-6 are decreased in transgenic sickle cell mice fed a high protein diet

Sickle cell disease is associated with hypermetabolism and a consequent shortage of substrates for normal growth and healthy immune response. The protein:energy ratio is a major determinant of dietary adequacy; the requirement for optimal growth of control mice is 20% of energy from dietary protein. This study investigated the efficacy of increased dietary protein for improving weight gain and reducing inflammation in the Berkeley sickle cell mouse model (S). The study examined the effect of diet on weight gain and circulating levels of 2 inflammatory proteins, C-reactive protein (CRP), and cytokine interleukin-6 (IL-6). Male C57BL/6 (C) control (n = 8) and S mice (n = 8) were randomized at weaning to 40 d of isoenergetic diets containing 20% (normal) and 35% (high) of energy from protein (C20, C35, S20, S35), replacing dextrin. Rate of weight gain was calculated and plasma CRP and IL-6 concentrations determined by ELISA. Liver mRNA expression of these proteins was measured by real-time PCR and L-arginase by colorimetric assay. S35 mice tended to gain weight more rapidly than S20 mice (P = 0.06) and more rapidly than C35 mice (P < 0.01). Circulating CRP and IL-6 levels were also lower in S35 mice than in S20 mice (P < 0.05), as was liver CRP mRNA expression (P < 0.01). These results demonstrate that introducing a high protein diet at weaning attenuates the steady-state inflammation in this S mouse model. Dietary L-arginine availability was investigated as a possible mechanism for increased nitric oxide production and consequent reduced inflammation.

Sickle cell disease vasculopathy: a state of nitric oxide resistance

Sickle cell disease (SCD) is a hereditary hemoglobinopathy characterized by microvascular vaso-occlusion with erythrocytes containing polymerized sickle (S) hemoglobin, erythrocyte hemolysis, vasculopathy, and both acute and chronic multiorgan injury. It is associated with steady state increases in plasma cell-free hemoglobin and overproduction of reactive oxygen species (ROS). Hereditary and acquired hemolytic conditions release into plasma hemoglobin and other erythrocyte components that scavenge endothelium-derived NO and metabolize its precursor arginine, impairing NO homeostasis. Overproduction of ROS, such as superoxide, by enzymatic (xanthine oxidase, NADPH oxidase, uncoupled eNOS) and nonenzymatic pathways (Fenton chemistry), promotes intravascular oxidant stress that can likewise disrupt NO homeostasis. The synergistic bioinactivation of NO by dioxygenation and oxidation reactions with cell-free plasma hemoglobin and ROS, respectively, is discussed as a mechanism for NO resistance in SCD vasculopathy. Human physiological and transgenic animal studies provide experimental evidence of cardiovascular and pulmonary resistance to NO donors and reduced NO bioavailability that is associated with vasoconstriction, decreased blood flow, platelet activation, increased endothelin-1 expression, and end-organ injury. Emerging epidemiological data now suggest that chronic intravascular hemolysis is associated with certain clinical complications: pulmonary hypertension, cutaneous leg ulcerations, priapism, and possibly stroke. New therapeutic strategies to limit intravascular hemolysis and ROS generation and increase NO bioavailability are discussed.

Sickle cell disease: role of reactive oxygen and nitrogen metabolites

1. Sickle cell disease (SCD) is an inherited disorder of haemoglobin synthesis that is associated with significant morbidity and mortality due to sequelae of episodic vaso-occlusive events: pain crises and multiorgan damage. The microvascular responses to the initiation, progression and resolution of vaso-occlusive events are consistent with an inflammatory phenotype as suggested by activation of multiple cell types, an oxidatively stressed environment and endothelial cell dysfunction. 2. Decreased anti-oxidant defences in SCD patients and mice are accompanied by activation of enzymatic (NADPH oxidase, xanthine oxidase) and non-enzymatic (sickle haemoglobin auto-oxidation) sources of reactive oxygen species. The resultant oxidative stress leads to dysfunction/activation of arteriolar and venular endothelial cells, resulting in impaired vasomotor function and blood cell-endothelial cell adhesion. 3. Changes in substrate and cofactor availability for endothelial cell nitric oxide synthase may underlie reactive oxygen- and nitrogen-induced events that contribute to SCD-induced vasculopathy. 4. The emerging role of reactive oxygen and nitrogen species in the pathogenesis of SCD provides a platform for the development of novel agents to treat this painful and lethal disease.

Effect of zinc upon human and murine cell viability and differentiation

Most zinc studies show its benefits or changes that coincide with its deficiency, but some have reported damages by supplements. In this work, the effects of zinc in different cell lines (U-937, human monocytes, and murine bone marrow cells) were analyzed. The cells were put in their specific culture medium either alone or with a stimulant [1-phorbol 12-myristate 13-acetate (PMA) for U-937 and monocytes, granulocyte macrophage colony stimulating factor (GM-CSF) for bone marrow cells]. These preparations, with or without zinc (0.05 to 1.0 mM), were incubated and microscopically analyzed on days 3, 9, and 11. The viability of all cells cultivated with 0.05 and 0.1 mM of zinc was similar to that of the controls without zinc (90%). With 1.0 mM of zinc, the viability diminished (p < 0.005) to 80% in U-937 and to 50% in monocytes and bone marrow cells; the number of cells increased in the three lines, but there was no differentiation. We conclude that the effects observed with different doses of zinc vary not only among the different species but also according to the time the cells were exposed to the metal. The same doses of zinc can have either a stimulatory or an inhibitory effect.