Targeted modification of furan-2-carboxaldehydes into Michael acceptor analogs yielded long-acting hemoglobin modulators with dual antisickling activities

Sickle cell disease (SCD) is the most common genetic disorder, affecting millions of people worldwide. Aromatic aldehydes, which increase the oxygen affinity of human hemoglobin to prevent polymerization of sickle hemoglobin and inhibit red blood cell (RBC) sickling, have been the subject of keen interest for the development of effective treatment against SCD. However, the aldehyde functional group metabolic instability has severly hampered their development, except for voxelotor, which was approved in 2019 for SCD treatment. To improve the metabolic stability of aromatic aldehydes, we designed and synthesized novel molecules by incorporating Michael acceptor reactive centers into the previously clinically studied aromatic aldehyde, 5-hydroxymethylfurfural (5-HMF). Eight such derivatives, referred to as MMA compounds were synthesized and studied for their functional and biological activities. Unlike 5-HMF, which forms Schiff-base interaction with αVal1 nitrogen of hemoglobin, the MMA compounds covalently interacted with βCys93, as evidenced by reverse-phase HPLC and disulfide exchange reaction, explaining their RBC sickling inhibitory activities, which at 2 mM and 5 mM, range from 0% to 21% and 9% to 64%, respectively. Additionally, the MMA compounds showed a second mechanism of sickling inhibition (12%-41% and 13%-62% at 2 mM and 5 mM, respectively) by directly destabilizing the sickle hemoglobin polymer. In vitro studies demonstrated sustained pharmacologic activities of the compounds compared to 5-HMF. These findings hold promise for advancing SCD therapeutics.

A Mutation in DNA Polymerase α Rescues WEE1KO Sensitivity to HU

During DNA replication, the WEE1 kinase is responsible for safeguarding genomic integrity by phosphorylating and thus inhibiting cyclin-dependent kinases (CDKs), which are the driving force of the cell cycle. Consequentially, wee1 mutant plants fail to respond properly to problems arising during DNA replication and are hypersensitive to replication stress. Here, we report the identification of the polα-2 mutant, mutated in the catalytic subunit of DNA polymerase α, as a suppressor mutant of wee1. The mutated protein appears to be less stable, causing a loss of interaction with its subunits and resulting in a prolonged S-phase.

Quail (Coturnix japonica) egg attenuated 2-butoxyethanol-induced enzymatic dysregulation, disseminated thrombosis and hemolytic impairment in female wistar rats

Influence of quail egg on pathologies has increased research interests and series of investigations are currently being done on its influence against these pathologies. The influence of quail egg against 2-butoxyethanol induced hemolysis and disseminated thrombosis was investigated to determine the enzymatic regulations that ensue in the amelioration of deleterious hemolytic and disseminated thrombosis displayed in female Wistar rats. Quail egg was separated into three (3) components (extracts)-quail egg yolk water soluble (QYWS) and fat soluble (QYFS), and albumen extract (QA) and the inorganic and organic compositions were characterized. Depranocytotic assaults was achieved by 250 mg/kg of 2-Butoxyethanol administered for 4 days, the clinical observation revealed a dark purple-red discoloration on the distal tails of the rats and therapeutic applications followed with 1000 mg/kg BWT of QYWS, QYFS and QA, and 15 mg/kg BWT of hydroxyurea. Morphological evaluation, haematological estimations and biochemical evaluations of the influence on the activities of sphingosine kinase-1, RNase, red cell carbonic anhydrase, lactate dehydrogenase, glutathione peroxidase and caspase-3, vis a vis the concentrations of sphingosine-1 phosphate, selenium and zinc (plasma and urine). In vitro anti-inflammatory influence of quail egg components were investigated against hemolysis and key enzymes of inflammation-cycloxygenase, lipoxygenase and β-glucuronidase. The in vitro anti-inflammatory effects of QYWS, QYFS and QA were concentration dependent from 200 to 800 μg/ml against hemolysis and the key enzymes of inflammation. The characterization of inorganic and organic bioactive composition of the yolk and albumen revealed the presence of folic acid, cobalamin, pyridine, riboflavin, ascorbic acid as well as vitamins D and E, selenium, zinc, iron and calcium. These had reflected in the attenuation of the induced hemolytic and disseminated thrombosis by regulations of enzymes linked to the infarction, apoptosis and oxidative stress characterized in sickle cell index.

An Investigation of Structure-Activity Relationships of Azolylacryloyl Derivatives Yielded Potent and Long-Acting Hemoglobin Modulators for Reversing Erythrocyte Sickling

Aromatic aldehydes that bind to sickle hemoglobin (HbS) to increase the protein oxygen affinity and/or directly inhibit HbS polymer formation to prevent the pathological hypoxia-induced HbS polymerization and the subsequent erythrocyte sickling have for several years been studied for the treatment of sickle cell disease (SCD). With the exception of Voxelotor, which was recently approved by the U.S. Food and Drug Administration (FDA) to treat the disease, several other promising antisickling aromatic aldehydes have not fared well in the clinic because of metabolic instability of the aldehyde moiety, which is critical for the pharmacologic activity of these compounds. Over the years, our group has rationally developed analogs of aromatic aldehydes that incorporate a stable Michael addition reactive center that we hypothesized would form covalent interactions with Hb to increase the protein affinity for oxygen and prevent erythrocyte sickling. Although, these compounds have proven to be metabolically stable, unfortunately they showed weak to no antisickling activity. In this study, through additional targeted modifications of our lead Michael addition compounds, we have discovered other novel antisickling agents. These compounds, designated MMA, bind to the α-globin and/or β-globin to increase Hb affinity for oxygen and concomitantly inhibit erythrocyte sickling with significantly enhanced and sustained pharmacologic activities in vitro.

Quantitative prediction of erythrocyte sickling for the development of advanced sickle cell therapies

Sickle cell disease is induced by a mutation that converts normal adult hemoglobin to sickle hemoglobin (HbS) and engenders intracellular polymerization of deoxy-HbS and erythrocyte sickling. Development of anti-sickling therapies requires quantitative understanding of HbS polymerization kinetics under organ-specific conditions, which are difficult to assess with existing experimental techniques. Thus, we developed a kinetic model based on the classical nucleation theory to examine the effectiveness of potential anti-sickling drug candidates. We validated this model by comparing its predictability against prior in vivo and in vitro experimental results. We used the model to quantify the efficacy of sickling inhibitors and obtain results consistent with recent screening assays. Global sensitivity analysis on the kinetic parameters in the model revealed that the solubility, nucleation rate prefactor, and oxygen affinity are quantities that dictate HbS polymerization. This finding provides quantitative guidelines for the discovery of intracellular processes to be targeted by sickling inhibitors.

The effect of the antisickling compound GBT1118 on the permeability of red blood cells from patients with sickle cell anemia

Sickle cell anemia (SCA) is one of the commonest severe inherited disorders. Nevertheless, effective treatments remain inadequate and novel ones are avidly sought. A promising advance has been the design of novel compounds which react with hemoglobin S (HbS) to increase oxygen (O2 ) affinity and reduce sickling. One of these, voxelotor (GBT440), is currently in advanced clinical trials. A structural analogue, GBT1118, was investigated in the current work. As RBC dehydration is important in pathogenesis of SCA, the effect of GBT1118 on RBC cation permeability was also studied. Activities of Psickle , the Gardos channel and the KCl cotransporter (KCC) were all reduced. Gardos channel and KCC activities were also inhibited in RBCs treated with Ca2+ ionophore or the thiol reagent N-ethylmaleimide, indicative of direct effects on these two transport systems. Consistent with its action on RBC membrane transporters, GBT1118 significantly increased RBC hydration. RBC hemolysis was reduced in a nonelectrolyte lysis assay. Further to its direct effects on O2 affinity, GBT1118 was therefore found to reduce RBC shrinkage and fragility. Findings reveal important effects of GBT1118 on protecting sickle cells and suggest that this is approach may represent a useful therapy for amelioration of the clinical complications of SCA.

Adaptation of a microbead assay for the easy evaluation of traditional anti-sickling medicines: application to DREPANOSTAT and FACA

CONTEXT

Sickle cell disease is a common inherited blood disorder affecting millions of people worldwide. Due to lack of progress in drug discovery for a suitable treatment, sufferers often turn to traditional medicines that take advantage of the plant extracts activity used by traditional healers.

OBJECTIVE

This study optimizes an anti-sickling screening test to identify preparations capable of reverting sickle cells back to the morphology of normal red blood cells. We focused on the miniaturization and practicability of the assay, so that it can be adapted to the laboratory conditions commonly found in less developed countries.

MATERIALS AND METHODS

We tested two traditional anti-sickling herbal medicines, FACA^® and DREPANOSTAT^®, composed of Zanthoxylum zanthoxyloides (Lam.) Zepern. & Timler (Rutaceae) and Calotropis procera (Aiton) Dryand. (Apocynaceae) at screening concentrations of hydroethanol extracts from 0.2 to 1 mg/mL. Potential bioactive molecules present in the extracts were profiled using Ultra High Performance Liquid Chromatography coupled with High Resolution Mass Spectrometry (UHPLC-HRMS/MS) method, identified through HRMS, MS/MS spectra and in silico fragmentation tools.

RESULTS

Hydroethanol extracts of FACA^® and DREPANOSTAT^® showed low anti-sickling activity, inhibiting less than 10% of the sickling process. The UHPLC-HRMS/MS profiles identified 28 compounds (18 in FACA^® and 15 in DREPANOSTAT^®, including common compounds) among which l-phenylalanine is already described as potential anti-sickling agent. When used as positive control, 7 mg/mL phenylalanine reduced the sickled RBC to 52%.

DISCUSSION AND CONCLUSIONS

This assay has been optimized for the easy screening of plant extracts or extracted compounds from bioassay guided fractionation, valuable to laboratories from less developed countries.

Rational modification of vanillin derivatives to stereospecifically destabilize sickle hemoglobin polymer formation

Increasing the affinity of hemoglobin for oxygen represents a feasible and promising therapeutic approach for sickle cell disease by mitigating the primary pathophysiological event, i.e. the hypoxia-induced polymerization of sickle hemoglobin (Hb S) and the concomitant erythrocyte sickling. Investigations on a novel synthetic antisickling agent, SAJ-310, with improved and sustained antisickling activity have previously been reported. To further enhance the biological effects of SAJ-310, a structure-based approach was employed to modify this compound to specifically inhibit Hb S polymer formation through interactions which perturb the Hb S polymer-stabilizing αF-helix, in addition to primarily increasing the oxygen affinity of hemoglobin. Three compounds, TD-7, TD-8 and TD-9, were synthesized and studied for their interactions with hemoglobin at the atomic level, as well as their functional and antisickling activities in vitro. X-ray crystallographic studies with liganded hemoglobin in complex with TD-7 showed the predicted mode of binding, although the interaction with the αF-helix was not as strong as expected. These findings provide important insights and guidance towards the development of molecules that would be expected to bind and make stronger interactions with the αF-helix, resulting in more efficacious novel therapeutics for sickle cell disease.

Prevalence and incidence of congenital anomalies amongst babies born to women with sickle cell disease and exposed to hydroxyurea during pregnancy: a systematic review protocol

REVIEW QUESTION/OBJECTIVE

What is the prevalence and incidence of congenital anomalies among babies born to women with sickle cell disease (SCD) and who have been exposed to hydroxyurea (HU) therapy at any time in their pregnancy?The objective of this review is to identify the proportion of babies born with congenital anomalies among babies born to mothers with SCD who have been exposed to HU therapy at any point during pregnancy and to describe the specific types of congenital anomalies encountered.

Design, Synthesis, and Biological Evaluation of Ester and Ether Derivatives of Antisickling Agent 5-HMF for the Treatment of Sickle Cell Disease

Candidate drugs to counter intracellular polymerization of deoxygenated sickle hemoglobin (Hb S) continue to represent a promising approach to mitigating the primary cause of the pathophysiology associated with sickle cell disease (SCD). One such compound is the naturally occurring antisickling agent, 5-hydroxymethyl-2-furfural (5-HMF), which has been studied in the clinic for the treatment of SCD. As part of our efforts to develop novel efficacious drugs with improved pharmacologic properties, we structurally modified 5-HMF into 12 ether and ester derivatives. The choice of 5-HMF as a pharmacophore was influenced by a combination of its demonstrated attractive hemoglobin modifying and antisickling properties, well-known safety profiles, and its reported nontoxic major metabolites. The derivatives were investigated for their time- and/or dose-dependent effects on important antisickling parameters, such as modification of hemoglobin, corresponding changes in oxygen affinity, and inhibition of red blood cell sickling. The novel test compounds bound and modified Hb and concomitantly increased the protein affinity for oxygen. Five of the derivatives exhibited 1.5- to 4.0-fold higher antisickling effects than 5-HMF. The binding mode of the compounds with Hb was confirmed by X-ray crystallography and, in part, helps explain their observed biochemical properties. Our findings, in addition to the potential therapeutic application, provide valuable insights and potential guidance for further modifications of these (and similar) compounds to enhance their pharmacologic properties.

Reactivation of Fetal Hemoglobin for Treating β-Thalassemia and Sickle Cell Disease

Reactivation of fetal hemoglobin (HbF) in adult hematopoietic cells has the potential for great clinical benefit in patients bearing deleterious mutations in the β-globin gene, such as β-thalassemia and sickle cell disease (SCD), since increasing the production of HbF can compensate for underproduction of β-globin chains (in β-thalassemia) and it can also disrupt sickle hemoglobin polymerization (in SCD). Thus for the past few decades, concerted efforts have been made to identify an effective way to induce the synthesis of HbF in adult erythroid cells for potential therapeutic relief from the effects of these β-globinopathies. Chemical inducers of HbF as well as a number of transcription factors that are able to reactivate HbF synthesis in vitro and in vivo in adult erythroid cells have been identified. However, there has been only limited success in attempts to manipulate either the drugs or regulatory proteins, and in only a fraction of patients, and there is wide variation in individual response to these drugs or transcription factors. These studies highlight the importance for understanding the molecular mechanisms underlying hemoglobin switching so that future studies can be designed to treat these disorders.

Elevated sphingosine-1-phosphate promotes sickling and sickle cell disease progression

Sphingosine-1-phosphate (S1P) is a bioactive lipid that regulates multicellular functions through interactions with its receptors on cell surfaces. S1P is enriched and stored in erythrocytes; however, it is not clear whether alterations in S1P are involved in the prevalent and debilitating hemolytic disorder sickle cell disease (SCD). Here, using metabolomic screening, we found that S1P is highly elevated in the blood of mice and humans with SCD. In murine models of SCD, we demonstrated that elevated erythrocyte sphingosine kinase 1 (SPHK1) underlies sickling and disease progression by increasing S1P levels in the blood. Additionally, we observed elevated SPHK1 activity in erythrocytes and increased S1P in blood collected from patients with SCD and demonstrated a direct impact of elevated SPHK1-mediated production of S1P on sickling that was independent of S1P receptor activation in isolated erythrocytes. Together, our findings provide insights into erythrocyte pathophysiology, revealing that a SPHK1-mediated elevation of S1P contributes to sickling and promotes disease progression, and highlight potential therapeutic opportunities for SCD.

Clinical and hematological effects of hydroxyurea therapy in sickle cell patients: a single-center experience in Brazil

CONTEXT AND OBJECTIVES Sickle cell disease (SCD) is the most common genetic disorder among people of African descent, affecting approximately 3,500 newborns each year in Brazil. Hydroxyurea (HU) is the only effective drug to treating patients with SCD, thereby reducing morbidity and mortality. The objective was to analyze the effects of HU on SCD patients at our institution. DESIGN AND SETTING Retrospective study conducted at a sickle cell centre in Ribeirão Preto, São Paulo, Brazil. METHODS We analyzed clinical and laboratory data on 37 patients. The hematological parameters and clinical events that occurred during the year before and the first year of treatment with HU were analyzed. The mean dose of HU was 24.5 ± 5.5 mg/kg/day. RESULTS There were rises in three parameters: hemoglobin (8.3 g/dl to 9.0 g/dl, P = 0.0003), fetal hemoglobin (HbF) (2.6% to 19.8%, P < 0.0001) and mean cell volume MCV (89 to 105 fl, P = 0.001); and reductions in the numbers of leukocytes (10,050/µl to 5,700/µl, P < 0.0001), neutrophils (6,200/µl to 3,400/µl, P = 0.001), platelets (459,000/µl to 373,000/µl, P = 0.0002), painful crises (1.86 to 0.81, P = 0.0014), acute chest syndromes (0.35 to 0.08, P = 0.0045), infections (1.03 to 0.5, P = 0.047), hospitalizations (1.63 to 0.53, P = 0.0013) and transfusions (1.23 to 0.1, P = 0.0051). CONCLUSION The patients presented clinical and hematological improvements, with an increase in HbF and a reduction in the infection rate, which had not been addressed in most previous studies.

Solenostemon monostachyus, Ipomoea involucrata and Carica papaya seed oil versus Glutathione, or Vernonia amygdalina: methanolic extracts of novel plants for the management of sickle cell anemia disease

BACKGROUND

Sickle cell disease (SCD) is a genetic disease caused by an individual inheriting an allele for sickle cell hemoglobin from both parents and is associated with unusually large numbers of immature blood cells, containing many long, thin, crescent-shaped erythrocytes. It is a disease prevalent throughout many populations. The use of medicinal plants and nutrition in managing SCD is gaining increasing attention.

METHODS

The antisickling effects of Solenostemon monostachyus (SolMon), Carica papaya seed oil (Cari-oil) and Ipomoea involucrata (Ipocrata) in male (HbSSM) and female (HbSSF) human sickle cell blood was examined in vitro and compared with controls, or cells treated with glutathione or an antisickling plant (Vernonia amygdalina; VerMyg).

RESULTS

Levels of sickle blood cells were significantly reduced (P < 0.05) in all the plant-extract treated SCD patients' blood compared with that of untreated SCD patients. RBCs in SolMon, Ipocrata, and Cari-oil treated samples were significantly higher (P < 0.05) compared with VerMyg-treated samples. The Fe(2+)/Fe(3+) ratio was significantly reduced (P < 0.05) in all plant extract-treated HbSSM samples compared with controls. Hemoglobin concentration was significantly increased (P < 0.05) by SolMon treatment in HbSSF compared with VerMyg. Sickle cell polymerization inhibition exhibited by SolMon was significantly higher (P < 0.05) compared with that of VerMyg in HbSSF blood. Sickle cell polymerization inhibition in SolMon and Ipocrata were significantly higher (P < 0.05) compared with VerMyg in HbSSM blood. All plant extracts significantly reduced (P < 0.05) lactate dehydrogenase activity in both HbSSM and HbSSF-treated blood. Catalase activity was significantly increased (P < 0.05) in HbSSF blood treated with Ipocrata compared with glutathione. Cari-oil treated HbSSM and HbSSF blood had significantly increased (P < 0.05) peroxidase activity compared with controls.

CONCLUSIONS

Methanolic extracts from S. monostachyus, C. papaya seed oil and I. involucrata exhibited particular antisickling properties coupled with the potential to reduce stress in sickle cell patients. Each plant individually or in combination may be useful for the management of sickle cell disease.

Crystallographic analysis of human hemoglobin elucidates the structural basis of the potent and dual antisickling activity of pyridyl derivatives of vanillin

Vanillin has previously been studied clinically as an antisickling agent to treat sickle-cell disease. In vitro investigations with pyridyl derivatives of vanillin, including INN-312 and INN-298, showed as much as a 90-fold increase in antisickling activity compared with vanillin. The compounds preferentially bind to and modify sickle hemoglobin (Hb S) to increase the affinity of Hb for oxygen. INN-312 also led to a considerable increase in the solubility of deoxygenated Hb S under completely deoxygenated conditions. Crystallographic studies of normal human Hb with INN-312 and INN-298 showed that the compounds form Schiff-base adducts with the N-terminus of the α-subunits to constrain the liganded (or relaxed-state) Hb conformation relative to the unliganded (or tense-state) Hb conformation. Interestingly, while INN-298 binds and directs its meta-positioned pyridine-methoxy moiety (relative to the aldehyde moiety) further down the central water cavity of the protein, that of INN-312, which is ortho to the aldehyde, extends towards the surface of the protein. These studies suggest that these compounds may act to prevent sickling of SS cells by increasing the fraction of the soluble high-affinity Hb S and/or by stereospecific inhibition of deoxygenated Hb S polymerization.

Advances in sickle cell disease treatment: from drug discovery until the patient monitoring

Sickle cell disease (SCD) is one of the most prevalent hematological diseases in the world. Despite the immense progress in molecular knowledge about SCD in last years few therapeutical sources are currently available. Nowadays the treatment is performed mainly with drugs such as hydroxyurea or other fetal hemoglobin inducers and chelating agents. This review summarizes current knowledge about the treatment and the advancements in drug design in order to discover more effective and safe drugs. Patient monitoring methods in SCD are also discussed.

In vivo pharmaco-proteomic analysis of hydroxyurea induced changes in the sickle red blood cell membrane proteome

Hydroxyurea (HU) is an effective drug for the treatment of sickle cell disease (SCD). The main clinical benefit of HU is thought to derive from its capacity to increase fetal hemoglobin (HbF) production. However, other effects leading to clinical benefit, such as improved blood rheology, have been suggested. In order to understand HU-induced changes at the proteomic level, we profiled sickle RBC membranes from of HU-treated and untreated patients. Our previous in vitro profiling studies on sickle RBC membranes identified a significant increase in predominantly anti-oxidant enzymes, protein repair and degradation components and a few RBC cytoskeletal proteins. In the present study, using 2D-DIGE (Two-Dimensional Difference In-Gel Electrophoresis) and tandem mass spectrometry, we detected 32 different proteins that significantly changed in abundance in the HU treatment group. The proteins that significantly increased in abundance were mostly membrane skeletal components involved in the regulation of RBC shape and flexibility, and those showing a significant decrease were components of the protein repair and degradation machinery. RBC palmitoylated membrane protein 55 (p55) is significantly increased in abundance at low (in vitro) and high (in vivo) concentrations of HU. Palmitoylated p55 may be an important target of HU-dependent regulation of the sickle RBC membrane, consistent with our earlier in vitro studies.

Preliminary in vitro antisickilng properties of crude juice extracts of Persia Americana, Citrus sinensis, Carica papaya and Ciklavit®

The antisickling properties of crude juice extracts of the edible portions of three commonly consumed tropical fruits namely Persia americana, Citrus sinensis, and Carica papaya were investigated in vitro alongside a new drug preparation called Ciklavit® that has antisickling activity. Four different solvent extracts of the crude juice of each fruit including aqueous, acidic, alkaline and alcoholic extracts were prepared and their antisickling effects on sickle cell trait (HbAS) and sickle cell disease (HbSS) blood samples checked alongside Ciklavit®. Blood samples were stabilized using normal saline and the antisickling effects were checked by counting the number of sickle cells remaining after incubation of the blood samples with the crude fruit extracts and Ciklavit® for twenty-four hours. The results showed that Ciklavit® produced a sustained reduction in the number of sickle cells in both HbAS and HbSS blood samples. Also the alkaline and alcoholic extracts of P. americana and C. papaya produced significant reduction in the number of sickle cells.

Antisickling activity of anthocyanins from Bombax pentadrum, Ficus capensis and Ziziphus mucronata: photodegradation effect

AIM OF THE STUDY

A survey was conducted in Lubumbashi city (Democratic Republic of Congo) in order to: (a) identify medicinal plants used by traditional healers in the management of sickle cell anaemia, (b) verify their antisickling activity in vitro, (c) determine the most active plants, and (d) verify if anthocyanins are responsible of the bioactivity and study their photodegradation effect.

MATERIALS AND METHODS

The Emmel test was used in vitro, for the antisickling activity assays of aqueous and ethanolic extracts of different parts of these plants when a UV lamp and solar irradiations were used to induce the photodegradation effect.

RESULTS

The survey revealed that 13 medicinal plants are used in the treatment of drepanocytosis among which 12 plants exhibited the in vitro antisickling activity for at least one of the used parts or extracts. These plants are Bombax pentadrum, Bougainvillea sp., Byarsocarpus orientalis, Dalberigia bochmintaub, Diplorrhynbchus condolocarpus, Euphorbia heterophylla, Ficus capensis, Harungana madagascariensis, Parinari mobola, Pothmania witfchidii, Syzygium guineense, Temnocalys verdickii and Ziziphus mucronata of which four (Bombax pentadrum, Ficus capensis, Parinari mobola and Ziziphus mucronata) revealed a high antisickling activity. The biological activity of three of these plants is due to anthocyanins. The antisickling activity and photodegradation effect of anthocyanins extracts were studied and minimal concentration of normalization determined. The biological activity of Bombax pentadrum anthocyanins decreased to half of its value after 40 min of irradiation under a lamp emitting at a wavelength of 365 nm and after about 10h of solar irradiation. For Ziziphus mucronata and Ficus capensis, the antisickling activity decreased to half after about 6h under a lamp exposition and after about 50h of solar exposition.

CONCLUSION

In vitro Antisickling activity justifies the use of these plants by traditional healers and this activity would be due to anthocyanins. But these natural pigments are instable towards UV-Visible irradiations. The conservation of these plants should then be performed in a shield from the sun radiation.

Pharmaco-proteomic study of hydroxyurea-induced modifications in the sickle red blood cell membrane proteome

Hydroxyurea (HU) is an effective oral drug for the management of homozygous sickle cell anemia (SS) in part because it increases fetal hemoglobin (HbF) levels within sickle red blood cells (RBCs) and thus reduces sickling. However, results from the Multicenter Study of HU suggested that clinical symptoms often improved before a significant increase in HbF levels occurred. This indicated that HU may be acting through the modification of additional cellular mechanisms that are yet to be identified. Hence, in this study, we focused on the analysis of the sickle RBC membrane proteome +/- HU treatment. 2D-DIGE (Two Dimensional Difference In-Gel Electrophoresis) technology and tandem mass spectrometry has been used to determine quantitative differences between sickle cell membrane proteins in the presence and absence of a clinically relevant concentration of HU. In vitro protein profiling of 13 sickle RBC membrane samples +/- 50 muM HU identified 10 statistically significant protein spots. Of these, the most remarkable class of proteins to show a statistically significant increase was the anti-oxidant enzymes-catalase, thioredoxin peroxidase and biliver-din reductase and the chaperonin containing TCP1 complex assisting in the folding of RBC cytoskeletal proteins. Interestingly, catalase immunoblots showed an increase in the acidic forms of the enzyme within sickle RBC membranes on incubation with 50 muM HU. We further identified this modification in catalase to be phosphorylation and demonstrated that HU exposed SS RBC membranes showed a 2-fold increase in tyrosine phosphorylation of catalase as compared to counterparts not exposed to HU. These results present an attractive model for HU-induced post-translational modification and potential activation of catalase in mature sickle RBCs. These findings also identify protein targets of HU other than fetal hemoglobin and enhance the understanding of the drug mechanism.

[Effect of Morinda lucida Benth. (Rubiaceae) and Newbouldia leavis P. Beauv. (Bignoniaceae) on sickling of red blood cells]

The purpose of this study was to evaluate the In vitro anti-sickling activity of two plants widely used for treatment of sickle cell disease in Togo, i.e., Morinda lucida et Newbouldia leavis. A concentration-dependent decrease in the rate of sickling was observed after incubation of red blood cells with plant extracts and 2% sodium metabisulfite as compared to incubation with 0.9% NaCl. On samples with a SS blood genotype the inhibition rate of Morinda lucida was 17.30% at a concentration of 1 mg/ml and 92.31% at a concentration of 30 mg/ml. On samples with an AS blood genotype, the inhibition rate of Morinda lucida 48.10% at a concentration of 1 mg/ml and 99.34% at a concentration of 30 mg/ml. Using Newbouldia leavis the inhibition rates at concentrations of 1 mg/ml and 30 mg/ml were 15.66% and 90.42% respectively on samples with a SS blood genotype and 64.03% and 99.02% respectively on samples with an AS blood genotype. The study protocol appeared to be adequate for both SS and AS blood genotypes since the Pearson correlation coefficient between rates measured on the two types of samples was 0.92 for Newuboulida and 0.89 for Morinda. These findings show that these two plants have clear-cut in vitro anti-sickling activity and support their use in traditional medicine.

Investigational agents for sickle cell disease

Developments in the treatment of sickle cell disease (SCD) have not kept pace with advances in understanding the pathophysiology of this haemoglobinopathy. Drugs undergoing preclinical and clinical assessment for the therapy of these globin gene disorders are discussed in this article. Beginning with investigational agents for treatment of SCD as a whole, the discussion proceeds to drugs being developed for specific manifestations or iatrogenic complications. Despite being licensed in the USA, the prototype antisickling agent, hydroxycarbamide, has not attained worldwide clinical use because of concerns about long-term toxicity. The less toxic decitabine, which (as with hydroxycarbamide) increases fetal haemoglobin level, cannot be administered orally; therefore, the search continues for effective and safe antisickling drugs that can be taken orally. The naturally occurring benzaldehyde 5-hydroxymethyl-2-furfural has shown promising antisickling properties in vitro, and when administered to transgenic sickle mice. These effects are surpassed by the new synthetic pyridyl derivatives of benzaldehyde. Studies in humans with SCD are required to assess the clinical efficacy of these benzaldehydes. Niprisan, another antisickling agent with significant clinical efficacy and an attractive safety profile, is undergoing further development. The prospects of antiadhesion therapy in SCD are demonstrated by a recombinant protein containing the Fc fragment of IgG fused to the natural ligand for selectins: the conjugate significantly inhibited blood vessel occlusion in transgenic sickle mice. Whereas the orally administrable iron-chelating agent deferasirox is likely to increasingly take the place of desferioxamine (which can only be given parenterally), effective treatment of priapism in SCD remains a distressing challenge.

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.

Role for cAMP-protein kinase A signalling in augmented neutrophil adhesion and chemotaxis in sickle cell disease

The significance of the leukocyte in sickle cell disease (SCD) pathophysiology is becoming increasingly recognised; we sought to examine whether the chemotactic properties of neutrophils of SCD individuals may be altered and, further, to better understand the signalling events that mediate altered SCD neutrophil function. Adhesion to immobilised fibronectin (FN) and chemotaxis of control and SCD neutrophils were assessed using in vitro static adhesion assays and 96-well chemotaxis chamber assays. Adhesion assays confirmed a significantly higher basal adhesion of SCD neutrophils to FN, compared with control neutrophils. Chemotaxis assays established, for the first time, that SCD neutrophils demonstrate greater spontaneous migration and, also, augmented migration in response to IL-8, when compared with control neutrophils. Co-incubation of SCD neutrophils with KT5720 (an inhibitor of PKA) abrogated increased basal SCD neutrophil adhesion, spontaneous chemotaxis and IL-8-stimulated chemotaxis. Stimulation of SCD neutrophils with IL-8 also significantly augmented SCD neutrophil adhesion to FN with a concomitant increase in cAMP levels and this increase in adhesion was abolished by KT5720. Interestingly, the adhesive properties of neutrophils from SCD individuals on hydroxyurea therapy were not significantly altered and results indicate that a reduction in intracellular cAMP may contribute to lower the adhesive properties of these cells. Data indicate that up-regulated cAMP signalling plays a significant role in the altered adhesive and migratory properties in SCD neutrophils. Such alterations may have important implications for the pathophysiology of the disease and the cAMP-PKA pathway may represent a therapeutic target for the abrogation of altered leukocyte function.

Tunable Delocalization of Unpaired Electrons of Nitroxide Radicals for Sickle-Cell Disease Drug Improvements

Hydroxyurea is a drug recently approved to treat sickle cell diseases. Hydroxyurea benefits the patients by increasing the level of fetal hemoglobin via a nitroxide radical pathway. Here, we report an unpaired-electron-delocalization approach to tune the stability of nitroxide radicals. In this approach, the substitution by an unsaturated alkyl group containing conjugated C=C double bonds for the hydrogen on the nitrogen atom attached to the hydroxyl of hydroxyurea can significantly increase its ability to generate nitroxide radical. Furthermore, the increase can be remarkably enhanced by increasing the number of conjugated C=C double bonds. For a hydroxyurea derivative that contains two conjugated C=C double bonds, the reaction rate to generate its radical is 118 times faster than that of hydroxyurea, and for a hydroxyurea derivative containing 20 conjugated C=C double bonds, the reaction rate to form its radical is 238 times faster than that of hydroxyurea. For this reason, hydroxyurea derivatives with conjugated C=C double bonds may constitute new potential drugs for the treatment of sickle-cell diseases.

Adherent leukocytes capture sickle erythrocytes in an in vitro flow model of vaso-occlusion

Recent in vivo studies suggest that adherent leukocytes bind RBCs and contribute to the microvascular pathology that characterizes sickle cell disease (SCD). A parallel-plate flow assay was used: to investigate the capture of RBCs by adherent neutrophils, monocytes, and T-lymphocytes; to examine whether RBC capture is elevated in patients with SCD; and to determine whether hydroxyurea (HU) therapy affects these interactions. Four measures of cell-cell adhesion were used: adhesion of leukocytes to TNF-alpha-treated human umbilical vein endothelial cells (HUVECs), percent of adherent leukocytes that captured RBCs, number of RBCs captured per interacting leukocyte, and duration of RBC capture. Leukocyte subpopulations from sickle patients were more adherent to activated ECs and captured more RBCs per interacting leukocyte than the corresponding subpopulations from healthy controls. While HU did not affect leukocyte adhesion to activated ECs, it reduced the proportion of adherent leukocytes that captured RBCs, as well as the number of RBCs captured per neutrophil. T-lymphocytes demonstrated elevated adhesion in all measures, and may be the leukocyte subpopulation whose behavior is most altered in SCD. Our findings suggest that neutrophils, monocytes, and T-lymphocytes could all be involved in adhesive interactions with autologous RBCs in patients with SCD.

In vitro antidrepanocytary actvity (anti-sickle cell anemia) of some congolese plants

Thirty aqueous and ethanolic extracts from 13 congolese plants were evaluated for their antidrepanocytary activity. Twelve of these plants, Alchornea cordifolia, Afromomum albo violaceum, Annona senegalensis, Cymbopogon densiflorus, Bridelia ferruginea, Ceiba pentandra, Morinda lucida, Hymenocardia acida, Coleus kilimandcharis, Dacryodes edulis, Caloncoba welwithsii, and Vinga unguiculata exhibited significant activities, thus, supporting the claims of the traditional healers and suggesting a possible correlation between the chemical composition of these plants and their uses in traditional medicine.

Effects of hydroxyurea on malaria, parasite growth and adhesion in experimental models

We recently raised concern over using hydroxyurea (HU) in the treatment of sickle cell disease in areas endemic for malaria, becauseit up-regulates the endothelial surface expression of ICAM-1, a major receptor for Plasmodium falciparum-infected erythrocytes in the brain. Using human in vitro models of cerebral malaria, we evaluated the interaction of HU with parasites and demonstrated that HU pretreatment increased the number of infected red blood cells adhering to the endothelium, but did not increase endothelial apoptosis. Moreover, using an experimental cerebral malaria model, HU pretreatment was found to prevent significantly mice from developing neurological syndrome by inhibiting parasite growth, opening potential therapeutic avenues.

Role of cyclic nucleotides in fetal hemoglobin induction in cultured CD34+ cells

OBJECTIVE

In vivo, several drugs have been shown to increase fetal hemoglobin (HbF), including 5-azacytidine (AZA), sodium butyrate (SB), and hydroxyurea (HU). Studies in K562 cells suggest that cyclic guanosine monophosphate (cGMP) is required for HbF induction; however, the role of cyclic nucleotides in HbF induction in primary erythroid cultures has not been established.

METHODS

CD34-selected peripheral blood monocytes cultured in a semi-solid serum-free system that mimics in vivo F-cell production are utilized to explore the role of cyclic adenosine monophosphate (cAMP) and cGMP in HbF induction in response to HU, AZA, and SB.

RESULTS

In serum-free CD34 cultures, HU, SB, and AZA all markedly stimulate FNRBC production up to 30-fold, associated with induction of gamma-globin mRNA and total HbF protein. Guanylate cyclase inhibition results in only minimal blunting of HbF induction by each agent. In contrast, adenylate cyclase inhibition markedly reduces HU, SB, and AZA-mediated FNRBC induction and gamma-globin mRNA induction. The adenylate cyclase activator forskolin modestly induces FNRBC production and augments the action of standard induction agents. HU, AZA, and SB, however, fail to significantly stimulate adenylate cyclase themselves.

CONCLUSIONS

In human CD34(+) cultures, cAMP production is required for full induction of HbF by HU, SB, and AZA, while perturbation of cGMP production has only minimal effects. These findings are in marked contrast to data in K562 cells where cGMP production is critical for HbF induction while cAMP stimulation blunts HbF response, and suggest that these agents may share a common induction pathway.

Pathophysiologically based drug treatment of sickle cell disease

Sickle cell disease is a systemic disorder that is caused by a mutation (Glu6Val) in the gene that encodes beta globin. The sickle hemoglobin molecule (HbS) is a tetramer of two alpha-globin chains and two sickle beta-globin chains, and has the tendency to polymerize when deoxygenated. HbS facilitates abnormal interactions between the sickle erythrocyte and leukocytes and endothelial cells, which trigger a complex pathobiology. This multifaceted pathophysiology provides the opportunity to interrupt the disease at multiple sites, including polymerization of HbS, erythrocyte density and cell-cell interactions. For example, it is possible to induce higher concentrations of fetal hemoglobin, which disrupts the pathology-initiating step of HbS polymerization. Furthermore, it is possible to improve the hydration of sickle erythrocytes and it might be feasible to counteract the endothelial, inflammatory and oxidative abnormalities of sickle cell disease. A therapeutic approach that targets several sites of pathobiology might be most promising.

Effect of intracellular magnesium and oxygen tension on K+-Cl- cotransport in normal and sickle human red cells

In red cells from normal individuals (HbA cells), the K+-Cl- cotransporter (KCC) is inactivated by low O2 tension whilst in those from sickle cell patients (HbS cells), it remains fully active. Changes in free intracellular [Mg2+] have been proposed as a mechanism. In HbA cells, KCC activity was stimulated by Mg2+ depletion and inhibited by Mg2+ loading but the effect of O2 was independent of Mg2+. At all [Mg2+]is, the transporter was stimulated in oxygenated cells, minimally active in deoxygenated ones. By contrast, the stimulatory effects of O2 was abolished by inhibitors of protein (de)phosphorylation. HbS cells had elevated KCC activity, which was of similar magnitude in oxygenated and deoxygenated cells, regardless of Mg2+ clamping. In deoxygenated cells, the antisickling agent dimethyl adipimidate inhibited sickling, Psickle and KCC. Results indicate a role for protein phosphorylation in O2 dependence of KCC, with different activities of the relevant enzymes in HbA and HbS cells, probably dependent on Hb.

Insights into elevated distortion product otoacoustic emissions in sickle cell disease: Comparisons of hydroxyurea-treated and non-treated young children

Distortion product otoacoustic emissions (DPOAEs) were examined in 15 normal-hearing African-American children between the ages of 6 and 14 years with homozygous sickle cell disease (SCD), who were on a regimen of hydroxyurea (HDU), a drug that reduces inflammatory processes and symptoms of SCD; a matched group of 15 African-American children with homozygous SCD not on HDU; and 15 African-American children with normal hemoglobin. DPOAEs were evoked by 13 primary tone pairs with f2 frequencies ranging from 1000 to 4500 Hz. Increased DPOAE amplitudes, believed to be a precursor of eventual hearing loss, were evident in children with SCD who were not receiving HDU. Those taking HDU had DPOAE amplitudes similar to normal controls. These findings suggest that HDU, in addition to reducing symptoms of SCD, may play a role in inhibiting or preventing cochlear pathology and hearing loss in individuals with SCD.

Modulation of erythrocyte arginase activity in sickle cell disease patients during hydroxyurea therapy

An elevated erythrocyte arginase activity with a corresponding decrease in nitric oxide (NO) level has been implicated in the pathophysiology of sickle cell disease (SCD). Recent studies have shown that hydroxyurea (HU) increases the production of NO, which increases the soluble guanylate cyclase activity and fetal haemoglobin (HbF) synthesis. To study the effects of HU on the arginase and nitric oxide synthase (NOS) activities in SCD patients, we compared levels of arginase activity and NO metabolites in red blood cells and plasma, respectively, from 23 patients with SCD (HbSS) receiving HU therapy, with those of 12 SCD patients not receiving HU treatment. Patients on HU therapy showed significantly lower arginase activity than that of HbSS patients not on HU therapy (1.36+/-0.2 U/10(8) cells vs. 3.31+/-0.29 U/10(8) cells). NOS activity was higher in patients on HU therapy than in untreated patients (0.72+/-0.4 nmol/ml/min vs. 0.35+/-0.15 nmol/ml/min, P<0.05). Among the HU-treated patients, the decreased level of arginase activity correlated (r=0.71) with HbF level as well as the mean corpuscular haemoglobin content. These data suggest that one of the beneficial effects of HU in vivo may involve the regulation of arginase activity and a concomitant induction of NOS activity, which may lead to an increased production of NO. The outcome of this study may lead to the development of improved NO-based treatments for SCD.

Effect of hydroxyurea on the deformability of the red blood cell membrane in patients with sickle cell anemia

Sickle cell disease is characterized by vaso-occlusive episodes, mainly in the small vessels, resulting in tissue ischemia, multi-organ failure, and, occasionally, death. Hydroxyurea (HU) is an agent with important and effective role in the treatment of patients suffering from this disease. The purpose of this study was to estimate the effect of HU on the deformability of the red blood cell's membrane (RBCM) in an effort to possibly improve the rheological properties of the RBCs of patients with sickle cell anemia (SCA), as well as to investigate the mechanical and rheological properties of these cells using micropipette and filtration techniques. The rigidity index, IR, which is a measure of cell rigidity and the elastic shear modulus, mu, which is a measure of cell's membrane deformability (CMd), of the RBCs from normal subjects, used as normal controls, were found significantly lower as compared to those of patients with SCA, regardless the treatment with HU. Patients under treatment with HU exhibited values better than those of untreated patients, in both, IR as well as mu, although still worse than the values of normal controls.

Effects of hydroxyurea treatment on cerebral oxygenation in adult patients with sickle cell disease: an open-label pilot study

BACKGROUND

In patients with sickle cell disease (SCD), cerebral oxygen saturation (rSO(2)) has been reported to be below normal and to increase after red blood cell transfusion.

OBJECTIVE

This study was designed to determine the effects of long-term and short-term hydroxyurea (HU) treatment on cerebral oxygenation in patients with SCD.

METHODS

This open-label pilot study was conducted at the Department of Anesthesiology and the Center for Sickle Cell Disease, College of Medicine, Howard University, Washington, DC. Adult African American outpatients with SCD and hemoglobin (Hb) genotype HbSS (homozygous sickle Hb) who were receiving long-term (>6 months) HU treatment (15-30 mg/kg . d PO) or who had never received this treatment (control group) were enrolled. Patients in the treated and control groups were matched for age, sex, race, and Hb genotype. Cerebral oximetry (near-infrared spectroscopy) was performed to determine rSO(2) index. In a separate analysis to determine the effects of short-term HU treatment on cerebral oxygenation, hospitalized patients with SCD and vaso-occlusive crisis (VOC)receiving long-term therapy with HU were enrolled. We performed cerebral and pulse (fingernail) oximetry to determine rSO (2)index and arterial oxygen saturation (SpO(2)) after the administration of a single oral dose of HU (500-mg tablet) alone and again after dosing concomitantly with inhaled oxygen.

RESULTS

The study enrolled 11 patients in the HU group (6 women, 5 men; mean [SD] age, 37 [8] years) and 20 controls (8 women, 12 men; mean [SD] age, 35 [6] years). Mean (SD) rSO(2) index was significantly increased (but still low) in patients receiving long-term HU treatment compared with controls (46.1% [6.6%] vs 41.2% [7.6%]; P< 0.025). Hb concentration (9.6 [1.4] g/dL vs 8.5 [1.2] g/dL; P< 0.027), hematocrit (28% [3%] vs 24% [4%]; P < 0.028), and mean corpuscular volume (102% [7%] vs 89% [8%]; P < 0.027) also were significantly higher in the HU group compared with controls. In 8 patients with SCD and VOC (6 men, 2 women; mean [SD] age, 28 [5] years), single-dose HU, either alone or in combination with inhaled oxygen, did not significantly affect cerebral oxygenation, and SpO(2) failed to correlate with rSO(2) index in these patients.

CONCLUSIONS

The results of this open-label pilot study in patients with SCD suggest that the low cerebral oxygenation in these patients is significantly improved but not normalized with long-term HU treatment. A single dose of HU, either alone or in combination with inhaled oxygen, did not appear to influence cerebral oxygenation in patients with VOC.

Effects of a pharmacologically-induced shift of hemoglobin-oxygen dissociation on myocardial energetics during ischemia in patients with coronary artery disease

BACKGROUND

Conventional strategies to treat myocardial ischemia include interventions that reduce oxygen demand and/or increase myocardial blood flow. Animal experiments suggest that right-shifting the hemoglobin-oxygen dissociation curve may also attenuate the metabolic consequences of myocardial ischemia. We evaluated whether exercise-induced myocardial ischemia can be alleviated in subjects with coronary artery disease (CAD) by enhancing oxygen release with an allosteric modifier of hemoglobin's affinity for oxygen (RSR13).

METHODS AND RESULTS

Seven subjects with CAD underwent a randomized, double-blind, cross-over study of the metabolic consequences of RSR13 administration on myocardial ischemia. Myocardial high-energy phosphates were quantified with 31P nuclear magnetic resonance (NMR) spectroscopy before, during, and after isometric handgrip-exercise. Subjects underwent NMR studies at baseline and on two separate occasions following the infusion of RSR13 (100 mg/kg) or placebo. RSR13 infusion significantly increased mean p50 by 8.1 +/- 2.7 mmHg at the end of the infusion, and it was still elevated by 4.9 +/- 3.3 mmHg after the completion of the treadmill tests while placebo had no effect. The myocardial creatine-phosphate (PCr) to adenosine-triphosphate (ATP) ratio decreased during handgrip-exercise in the baseline studies (from 1.39 +/- 0.23 before exercise to 0.95 +/- 0.21 during handgrip-exercise, p = 0.0001) and in the placebo studies (from 1.29 +/- 0.16 to 0.98 +/- 0.37, p = 0.06) but not during administration of RSR13 (from 1.28 +/- 0.18 to 1.02 +/- 0.24, p = 0.12). However, the mean values of cardiac PCr/ATP during handgrip-exercise did not differ significantly among the three measurements (baseline, placebo, RSR13).

CONCLUSIONS

A single infusion of RSR13 to subjects with CAD increased mean p50 by 4.9-8.1 mmHg but did not significantly alter myocardial PCr/ATP during exercise. This is the largest right-shift in hemoglobin-oxygen binding affinity achieved in CAD subjects, and it did not provide clear evidence of protection from cardiac ischemia.

Structural basis for the potent antisickling effect of a novel class of five-membered heterocyclic aldehydic compounds

Naturally occurring five-membered heterocyclic aldehydes, including 5-hydroxymethyl-2-furfural, increase the oxygen affinity of hemoglobin (Hb) and strongly inhibit the sickling of homozygous sickle red blood (SS) cells. X-ray studies of Hb complexed with these compounds indicate that they form Schiff base adducts in a symmetrical fashion with the N-terminal alphaVal1 nitrogens of Hb. Interestingly, two cocrystal types were isolated during crystallization experiments with deoxygenated Hb (deoxyHb): one crystal type was composed of the low-affinity or tense (T) state Hb quaternary structure; the other crystal type was composed of high-affinity or relaxed state Hb (with a R2 quaternary structure). The R2 crystal appears to be formed as a result of the aldehydes binding to fully or partially ligated Hb in the deoxyHb solution. Repeated attempts to crystallize the compounds with liganded Hb failed, except on rare occasions when very few R state crystals were obtained. Oxygen equilibrium, high performance liquid chromatography (HPLC), antisickling, and X-ray studies suggest that the examined heterocyclic aldehydes may be acting to prevent polymerization of sickle hemoglobin (HbS) by binding to and stabilizing liganded Hb in the form of R2 and/or various relaxed state Hbs, as well as binding to and destabilizing unliganded T state Hb. The proposed mechanism may provide a general model for the antisickling effects of aldehyde containing small molecules that bind to N-terminal alphaVal1 nitrogens of Hb. The examined compounds also represent a new class of potentially therapeutic agents for treating sickle cell disease (SCD).

A recombinant human hemoglobin with anti-sickling properties greater than fetal hemoglobin

A new recombinant, human anti-sickling beta-globin polypeptide designated beta(AS3) (betaGly(16) --> Asp/betaGlu(22) --> Ala/betaThr(87) --> Gln) was designed to increase affinity for alpha-globin. The amino acid substitutions at beta22 and beta87 are located at axial and lateral contacts of the sickle hemoglobin (HbS) polymers and strongly inhibit deoxy-HbS polymerization. The beta16 substitution confers the recombinant beta-globin subunit (beta(AS3)) with a competitive advantage over beta(S) for interaction with the alpha-globin polypeptide. Transgenic mouse lines that synthesize high levels of HbAS3 (alpha(2)beta(AS3)(2)) were established, and recombinant HbAS3 was purified from hemolysates and then characterized. HbAS3 binds oxygen cooperatively and has an oxygen affinity that is comparable with fetal hemoglobin. Delay time experiments demonstrate that HbAS3 is a potent inhibitor of HbS polymerization. Subunit competition studies confirm that beta(AS3) has a distinct advantage over beta(S) for dimerization with alpha-globin. When equal amounts of beta(S)- and beta(AS3)-globin monomers compete for limiting alpha-globin chains up to 82% of the tetramers formed is HbAS3. Knock-out transgenic mice that express exclusively human HbAS3 were produced. When these mice were bred with knock-out transgenic sickle mice the beta(AS3) polypeptides corrected all hematological parameters and organ pathology associated with the disease. Expression of beta(AS3)-globin should effectively lower the concentration of HbS in erythrocytes of patients with sickle cell disease, especially in the 30% percent of these individuals who coinherit alpha-thalassemia. Therefore, constructs expressing the beta(AS3)-globin gene may be suitable for future clinical trials for sickle cell disease.

Hydroxyurea downregulates endothelin-1 gene expression and upregulates ICAM-1 gene expression in cultured human endothelial cells

The clinical efficacy of oral hydroxyurea (HU) in adults and children with sickle cell anemia (SCA) cannot solely be explained by its ability to enhance fetal hemoglobin (HbF) expression. Since increased adherence of sickle red blood cells to vascular endothelium is a possible contributing factor to vaso-occlusive crisis (VOC), we explored the effect of HU on human endothelial cell (EC) lines (TrHBMEC and EA-hy 926). We demonstrated that HU, in a dose-dependent and reversible manner, significantly decreased (up to three-fold) the release of endothelin-1 (ET-1), a vasoconstrictor peptide through downregulation (up to three-fold) of ET-1 gene expression. This finding is of therapeutic relevance as SCA patients exhibit elevated serum levels of ET-1 during episodes of VOC and levels correlate with disease severity. Unexpectedly, HU upregulated (up to three-fold) the expression of membrane-bound intercellular cell adhesion molecule 1 (mbICAM-1) and its soluble form (sICAM-1) with a parallel increase in ICAM-1 mRNA expression. Although ICAM-1 does not appear to be involved in the sickle cell adhesion to vascular endothelium, it may exacerbate vaso-occlusion by promoting leukocyte adhesion. The HU-induced increase in mbICAM-1 may appear inconsistent with the clinical benefits confered by HU. However, both the increase in sICAM-1- and HU-induced leukocyte reduction in patients, may counteract the potentially detrimental effect of elevated mbICAM-1 expression. Also HU reduces the expression of vascular cell adhesion molecule (VCAM-1) on EC. Since HU reduces the very late antigen 4-positive reticulocytes in SCA patients, a ligand for VCAM-1, HU-induced downregulation of VCAM-1 on EC will very likely decrease the reticulocyte-endothelium adhesion. Thus, HU, apart from inducing HbF expression in the red cell, also affects the expression profile of EC compartment.

LC/MS/NMR analysis of isomeric divanilloylquinic acids from the root bark of Fagara zanthoxyloides Lam

Gradient HPLC coupled to DAD/UV, MS/MS and NMR has been applied to the rapid structure determination of three new isomeric divanilloylquinic acids from Fagara zanthoxyloides collected in Burkina Faso: 3,4-O-divanilloylquinic acid, 3,5-O-divanilloylquinic acid and 4,5-O-divanilloylquinic acid. Furthermore these new compounds named burkinabins A-C could play a useful role in sickle cell disease, as the active agents of Fagara zanthoxyloïdes are said to be unidentified aromatic compounds with carboxylic acid grouping (Adesanya, S.A., Sofowora, A., 1983. Biological standardisation of Zanthoxylum roots for antisickling activity. Planta Med. 48, 27-33).

Effects of hydroxyurea on the membrane of erythrocytes and platelets in sickle cell anemia

BACKGROUND AND OBJECTIVES

Adhesion molecules on the surface of erythrocytes, leukocytes and platelets are involved in vascular occlusion in sickle cell anemia. Hydroxyurea treatment of sickle cell anemia patients leads to clinical improvement and reduces the incidence of vaso-occlusive episodes. It has been previously demonstrated that hydroxyurea treatment also reduces the expression of adhesion molecules on the surface of erythrocytes. Phosphatidylserine (PS) exposure on the surface of erythrocytes has been considered to be the main determinant of altered erythrocyte adhesion in sickle cell anemia. In this study we examine the expression of PS on the surface of erythrocytes and platelets of sickle cell anemia patients before and during treatment with hydroxyurea.

DESIGN AND METHODS

Blood samples from 15 sickle cell anemia patients were analyzed before and during treatment with hydroxyurea. The profile of PS expression was examined by flow cytometry.

RESULTS

Hydroxyurea was effective, as determined by the patients clinical improvement and increased hemoglobin (8.3 vs 9.1 g/dL, p< 0.005), F cells (15.9% vs 37.1%, p< 0.005) and mean corpuscular volume ( 82 fL vs 101 fL, p< 0.005). PS expression on the surface of erythrocytes and platelets decreased from 6.27% to 2.96% (p< 0.005) and from 13.5% to 4.7% (p< 0.005), respectively.

INTERPRETATION AND CONCLUSIONS

Hydroxyurea treatment reduces PS expression on the surface of erythrocytes and platelets, thus contributing to the favorable effects of this therapy.

Anti-sickling potential of a Nigerian herbal formula (ajawaron HF) and the major plant component (Cissus populnea L. CPK)

The anti-sickling activities of the extracts of the roots of a plant Cissus populnea L. (CPK) (a major constituent of a herbal formula Ajawaron HF used in the management of sickle cell disease in south-west Nigeria) has been examined. Phytochemical examination of the extract showed the presence of anthraquinone derivatives, steroidal glycosides and cardiac glycosides. Alkaloids and tannins were completely absent in the CPK extracts. Evaluation of the anti-sickling activity involved the use of both positive (p-hydroxybenzoic acid, 5 microg/mL) and negative control (normal saline) for each set of experiments aimed at the inhibition of sodium metabisulphite-induced sickling of the HbSS red blood cells obtained from confirmed non-crisis state sickle-cell patients. The chloroform and water partitioned fractions of the cold methanol extracts of CPK exhibited a 62.2% and 52.9% inhibition of sickling, respectively, at 180 min. The herbal formula (HF) aqueous extract showed the highest anti-sickling activity on a weight by weight basis of all the extracts and fractions tested, giving a 71.4% inhibition of sickling at the end of 180 min incubation when compared with the normal saline control. The maximum percentage inhibition of sickling exhibited by the p-hydroxybenzoic acid control was 46.0% at 90 min incubation.

Effect of fetal hemoglobin-stimulating medicines on the interaction of DNA and protein of important erythroid regulatory elements

β-Thalassemia is the most common single gene disorder in the world, which is caused by the imbalance between α-globin chain and β-globin chain synthesis. Several medicines, such as 5-azacytidine, hydroxyurea, cytarabine, vinblatine, butyrate, and myleran, have been shown to be able to reactivate γ-globin chain synthesis during the adult stage, and some of them (5-azacytidine, hydroxyurea, myleran, and butyrate) have been used clinically to treat thalas semia and sickle cell disease. Much research efforts are focusing on the determination of the underlying mechanisms of medicine action. In this experiment, as an effort to probe the underlying mechanism of medicine action, we used ligation-mediated polymerase chain reaction and in vivo footprinting methods to study the DNA-protein interaction at critical erythroid regulatory elements after hydroxyurea or myleran administration to mice. Our results showed that the patterns of in vivo footprints at both the hypersensitive site 2 of the locus control region and the β-globin gene promoter were changed after medicine treatment. We proposed based on these results that the medicines' administration might result in a change in the interaction between trans-acting factors and cis-acting elements at these regions. These changes might influence the assembly of the transcription complex and, lastly, influence the expression of the β-globin gene.Key words: hydroxyurea, in vivo footprinting, ligation-mediated PCR, LCR, β-globin.

Urease enhances the formation of iron nitrosyl hemoglobin in the presence of hydroxyurea

Although it has been shown that hydroxyurea (HU) therapy produces measurable amounts of nitric oxide (NO) metabolites, including iron nitrosyl hemoglobin (HbNO) in patients with sickle cell disease, the in vivo mechanism for formation of these is not known. Much in vitro data and some in vivo data indicates that HU is the NO donor, but other studies suggest a role for nitric oxide synthase (NOS). In this study, we confirm that the NO-forming reactions of HU with hemoglobin (Hb) or other blood constituents is too slow to account for NO production measured in vivo. We hypothesize that, in vivo, HU is partially metabolized to hydroxylamine (HA), which quickly reacts with Hb to form methemoglobin (metHb) and HbNO. We show that addition of urease, which converts HU to HA, to a mixture of blood and HU, greatly enhances HbNO formation.