Elevated serum and bronchoalveolar lavage fluid levels of interleukin 8 and granulocyte colony-stimulating factor associated with the acute chest syndrome in patients with sickle cell disease

Acute chest syndrome of sickle cell disease: genetics, risk factors, prognosis and management

IntroductionSickle cell disease, one of the world's most prevalent Mendelian disorders, is a chronic hemolytic anemia punctuated by acute vasoocclusive events. Both hemolysis and vasoocclusion lead to irreversible organ damage and failure. Among the many sub-phenotypes of sickle cell disease is the acute chest syndrome (ACS) characterized by combinations of chest pain, cough, dyspnea, fever, abnormal lung exam, leukocytosis, hypoxia, and new radiographic opacities. ACS is a major cause of morbidity and mortality.Area coveredWe briefly review the diagnosis, epidemiology, etiology, and current treatments for ACS and focus on understanding and estimating the risks for developing this complication, how prognosis and outcomes might be improved and the genetic elements that might impact the risk of ACS.Expert opinionThe clinical heterogeneity of ACS has hindered our understanding of risk stratification. Lacking controlled clinical trials most treatment is based on expert opinion. Fetal hemoglobin levels and coexistent α thalassemia affect the incidence of ACS; other genetic associations are tenuous. Transfusions, whose use not innocuous, should be targeted to the severity and likelihood of ACS progression. Stable, non-hypoxic patients with favorable hematologic and radiographic findings usually do not need transfusion; severe progressive ACS is best managed with exchange transfusion.

Acute chest syndrome in sickle cell anaemia: higher serum levels of interleukin-8 and highly sensitive C-reactive proteins are associated with impaired lung function

BACKGROUND

Sickle cell anaemia (SCA) is a chronic inflammatory disorder with multiple organ manifestations including acute and long-term pulmonary dysfunction.

AIMS/OBJECTIVES

To assess lung function of children with SCA and determine the possible role of acute chest syndrome (ACS), serum inflammatory cytokines, highly sensitive C-reactive protein (hs-CRP), leucocytes and 25-hydroxyvitamin D on the development of impaired lung function.

SUBJECTS AND METHODS

Lung function of 76 children with SCA was determined by spirometer and classified into normal or impaired. Sociodemographic, clinical, haematological, biochemical and immunological data of the two groups were compared by univariate and multivariate analyses.

RESULTS

Fifty (65.8%) patients had impaired lung function, comprising of 30.3%, 3.9% and 31.6% with restrictive, obstructive and mixed disease patterns, respectively. Children with previous ACS were 3.6 times more likely to have impaired lung function than those without ACS (82.1% vs 56.3%, p = 0.02, OR 3.6, 95% CI 1.2-10.8). Interleukin (IL)-8 and hs-CRP were significantly higher in patients with impaired lung function (p = 0.02 and <0.001, respectively). Using logistic regression, previous ACS (OR 5.8, 95% CI 1.1-5.8, p = 0.03) and higher serum IL-8 levels (OR 3.0, 95% CI 1.0-8.0, p = 0.02) independently predicted the presence of abnormal lung function.

CONCLUSIONS

Lung dysfunction, predominantly restrictive pattern, is common in SCA and is associated with previous ACS and alterations in immunological markers, especially serum IL-8 and hs-CRP.

ABBREVIATIONS

ACS: acute chest syndrome; CBT: chronic blood transfusion; ELISA: enzyme-linked immunosorbent assay; FEV₁: forced expiratory volume in 1 s; FVC: forced vital capacity; HPLC: high-density liquid chromatography; hs-CRP: highly sensitive C-reactive proteins; HU: hydroxyurea; IL: Interleukin; PEFR: peak expiratory flow rate; SEM: standard error of the mean; TLC: total lung capacity; 25-OHD: 25-hydroxyvitamin D; VOC: vaso-occlusive crisis; WGH: Wesley Guild Hospital.

Sickle cell disease: Classification of clinical complications and approaches to preventive and therapeutic management

Sickle cell disease (SCD) is an inherited disorder of hemoglobin structure that has no established cure in adult patients. Cure has been achieved in selected children with sickle cell anemia (SCA) using allogeneic bone marrow transplantation or cord blood transplantation. SCD is essentially a triumvirate of (1) pain syndromes, (2) anemia and its sequelae and (3) organ failure, including infection. Pain, however, is the hallmark of SCD and dominates its clinical picture throughout the life of the patients. The prevalence of these complications varies with age from infancy through adult life. However, pain, infections and anemia requiring blood transfusion occur throughout the life span of affected patients. The overall medical care of patients with SCD in developed countries has improved such that their life expectancy has almost doubled since 1951. Currently, there are at least five major approaches for the general management of SCD and its complications. These include (i) symptomatic management, (ii) supportive management, (iii) preventive management, (iv) abortive management, and (v) curative therapy.

Granulocyte-CSF links destructive inflammation and comorbidities in obstructive lung disease

Chronic obstructive pulmonary disease (COPD) is an incurable inflammatory lung disease that afflicts millions of people worldwide, and it is the fourth leading cause of death. Systemic comorbidities affecting the heart, skeletal muscle, bone, and metabolism are major contributors to morbidity and mortality. Given the surprising finding in large prospective clinical biomarker studies that peripheral white blood cell count is more closely associated with disease than inflammatory biomarkers, we probed the role of blood growth factors. Using the SHIP-1-deficient COPD mouse model, which manifests a syndrome of destructive lung disease and a complex of comorbid pathologies, we have identified a critical and unexpected role for granulocyte-CSF (G-CSF) in linking these conditions. Deletion of G-CSF greatly reduced airway inflammation and lung tissue destruction, and attenuated systemic inflammation, right heart hypertrophy, loss of fat reserves, and bone osteoporosis. In human clinical translational studies, bronchoalveolar lavage fluid of patients with COPD demonstrated elevated G-CSF levels. These studies suggest that G-CSF may play a central and unforeseen pathogenic role in COPD and its complex comorbidities, and identify G-CSF and its regulators as potential therapeutic targets.

Amelioration of inflammation and tissue damage in sickle cell model mice by Nrf2 activation

Sickle cell disease (SCD) is an inherited disorder caused by a point mutation in the β-globin gene, leading to the production of abnormally shaped red blood cells. Sickle cells are prone to hemolysis and thereby release free heme into plasma, causing oxidative stress and inflammation that in turn result in damage to multiple organs. The transcription factor Nrf2 (nuclear factor erythroid 2-related factor 2) is a master regulator of the antioxidant cell-defense system. Here we show that constitutive Nrf2 activation by ablation of its negative regulator Keap1 (kelch-like ECH-associated protein 1) significantly improves symptoms in SCD model mice. SCD mice exhibit severe liver damage and lung inflammation associated with high expression levels of proinflammatory cytokines and adhesion molecules compared with normal mice. Importantly, these symptoms subsided after Nrf2 activation. Although hemolysis and stress erythropoiesis did not change substantially in the Nrf2-activated SCD mice, Nrf2 promoted the elimination of plasma heme released by sickle cells' hemolysis and thereby reduced oxidative stress and inflammation, demonstrating that Nrf2 activation reduces organ damage and segregates inflammation from prevention of hemolysis in SCD mice. Furthermore, administration of the Nrf2 inducer CDDO-Im (2-cyano-3, 12 dioxooleana-1, 9 diene-28-imidazolide) also relieved inflammation and organ failure in SCD mice. These results support the contention that Nrf2 induction may be an important means to protect organs from the pathophysiology of sickle cell-induced damage.

Red blood cell alloimmunization is influenced by recipient inflammatory state at time of transfusion in patients with sickle cell disease

Sickle cell disease (SCD) patients are at increased risk of red blood cell (RBC) alloimmunization. Recipient inflammatory state at time of transfusion has been shown to regulate alloimmunization in murine models, but evidence is lacking in SCD patients. We retrospectively studied a cohort of alloimmunized SCD patients to determine the influence of pro-inflammatory SCD-related complications at time of transfusion on alloimmunization. For each transfusion, the presence of pro-inflammatory state, degree of RBC antigen matching, unit age, storage solution and alloantibody detection date were ascertained. Transfusion-associated pro-inflammatory events were compared between transfusions resulting and not resulting in new alloantibodies. Univariate analysis and multivariate logistic regression were performed. Fifty-two patients received 3166 pre-storage leuco-reduced transfusions of which 128 resulted in alloantibodies. Transfusions during inflammatory events were associated with increased alloantibody risk on univariate and multivariate analysis; acute chest syndrome and vaso-occlusive crisis showed strongest associations with alloimmunization. Increased antigen matching demonstrated a protective effect on alloimmunization (univariate and multivariate analysis). Although an association was seen between citrate-phosphate-dextrose (adenine) stored units and alloimmunization on univariate analysis, no effect was found on multivariate analysis. Identifying recipient pro-inflammatory states at time of transfusion that promote alloimmunization can impact RBC unit selection decisions for SCD patients at risk for alloimmunization.

Beyond the definitions of the phenotypic complications of sickle cell disease: an update on management

The sickle hemoglobin is an abnormal hemoglobin due to point mutation (GAG → GTG) in exon 1 of the β globin gene resulting in the substitution of glutamic acid by valine at position 6 of the β globin polypeptide chain. Although the molecular lesion is a single-point mutation, the sickle gene is pleiotropic in nature causing multiple phenotypic expressions that constitute the various complications of sickle cell disease in general and sickle cell anemia in particular. The disease itself is chronic in nature but many of its complications are acute such as the recurrent acute painful crises (its hallmark), acute chest syndrome, and priapism. These complications vary considerably among patients, in the same patient with time, among countries and with age and sex. To date, there is no well-established consensus among providers on the management of the complications of sickle cell disease due in part to lack of evidence and in part to differences in the experience of providers. It is the aim of this paper to review available current approaches to manage the major complications of sickle cell disease. We hope that this will establish another preliminary forum among providers that may eventually lead the way to better outcomes.

Red blood cell alloimmunization in sickle cell disease: prevalence in 2010

BACKGROUND

Transfusion of red blood cells (RBCs) is frequently required for care of individuals with sickle cell disease (SCD). Alloimmunization rates are high and may be reduced by matching for RBC antigens that can cause alloimmunization.

STUDY DESIGN AND METHODS

During the PROACTIVE Feasibility Study, patients with SCD age 2 years or older admitted for pain without acute chest syndrome were enrolled for possible randomization to preventive blood transfusion or standard care. Transfusion and antibody histories were obtained at each site, and antibody screening was done, to assess transfusion burden and alloimmunization prevalence. Participating sites were surveyed regarding antigen matching practice.

RESULTS

A total of 237 patients (169 SS, 42 SC, 15 Sβ(0) -thalassemia, 11 Sβ(+) -thalassemia), 118 males and 119 females, were enrolled. Mean age was 19.3 years (range, 2.0-68.0); there were 122 children and 115 adults. A total of 75.8% had received at least a single transfusion of RBCs before the study. Thirty-four patients (14.4%) had a history of at least one alloantibody and 17 of these had more than one. When surveyed, 19 sites (83% of responders) reported antigen matching to at least include C, E, and K for transfusion of all patients with SCD.

CONCLUSION

Though antigen typing before transfusion of people with SCD and providing antigen-negative units is now widely employed by sickle cell centers, the alloimmunization rate remains quite high in contemporary sickle cell populations and may be due in large part to transfusions received at institutions not providing extended matching.

Refining the value of secretory phospholipase A2 as a predictor of acute chest syndrome in sickle cell disease: results of a feasibility study (PROACTIVE)

Acute chest syndrome (ACS) is defined as fever, respiratory symptoms and a new pulmonary infiltrate in an individual with sickle cell disease (SCD). Nearly half of ACS episodes occur in SCD patients already hospitalized, potentially permitting pre-emptive therapy in high-risk patients. Simple transfusion of red blood cells may abort ACS if given to patients hospitalized for pain who develop fever and elevated levels of secretory phospholipase A2 (sPLA2). In a feasibility study (PROACTIVE; ClinicalTrials.gov NCT00951808), patients hospitalized for pain who developed fever and elevated sPLA2 were eligible for randomization to transfusion or observation; all others were enrolled in an observational arm. Of 237 enrolled, only 10 were randomized; one of the four to receive transfusion had delayed treatment. Of 233 subjects receiving standard care, 22 developed ACS. A threshold level of sPLA2 ≥ 48 ng/ml gave optimal sensitivity (73%), specificity (71%) and accuracy (71%), but a positive predictive value of only 24%. The predictive value of sPLA2 was improved in adults and patients with chest or back pain, lower haemoglobin concentration and higher white blood cell counts, and in those receiving less than two-thirds maintenance fluids. The hurdles identified in PROACTIVE should facilitate design of a larger, definitive, phase 3 randomized controlled trial.

Pulmonary complications of sickle cell disease

The pulmonary complications of sickle cell disease are a major cause of morbidity and mortality in affected patients. The acute chest syndrome (ACS) is a leading cause of death in patients with sickle cell disease and has a multifactorial etiology. Hydroxyurea (HU), stem cell transplantation (SCT) and chronic transfusions are known to prevent the recurrence of ACS. Careful management of patients admitted for pain crises and surgery including use of incentive spirometry is critical in preventing this complication. Pulmonary hypertension is well known to be associated with sickle cell disease and patients with pulmonary hypertension have increased mortality. Asthma is also commonly seen in patients with sickle cell disease and is associated with a more complicated course. Chronic lung disease develops in a significant proportion of patients with sickle cell disease.

How I treat acute chest syndrome in children with sickle cell disease

Acute chest syndrome describes new respiratory symptoms and findings, often severe and progressive, in a child with sickle cell disease and a new pulmonary infiltrate. It may be community-acquired or arise in children hospitalized for pain or other complications. Recognized etiologies include infection, most commonly with atypical bacteria, and pulmonary fat embolism (PFE); the cause is often obscure and may be multifactorial. Initiation of therapy should be based on clinical findings. Management includes macrolide antibiotics, supplemental oxygen, modest hydration and often simple transfusion. Partial exchange transfusion should be reserved for children with only mild anemia (Hb > 9 g/dL) but deteriorating respiratory status. Therapy with corticosteroids may be of value; safety, efficacy and optimal dosing strategy need prospective appraisal in a clinical trial. On recovery, treatment with hydroxyurea should be discussed to reduce the likelihood of recurrent episodes.

Association between Duffy antigen receptor for chemokines expression and levels of inflammation markers in sickle cell anemia patients

Since inflammation plays a prominent role in the pathogenesis of sickle cell anemia (SCA) and Duffy antigen receptor for chemokines (DARC) modulates the function of inflammatory processes, we analyzed the relationship between the erythrocyte DARC phenotype and clinical expression of SCA. DARC locus was genotyped in 212 SS adult patients followed by the sickle cell center of Guadeloupe (French West Indies). After patients' stratification according to RBC DARC expression, the prevalence of renal disease, leg ulcers, priapism and osteonecrosis was compared between patient groups as well as hematological variables and plasma levels of chemokines. Duffy-positive patients exhibited higher counts of white blood cells (9.95+/-2.36 vs 8.88+/-2.32 10(9)/L, p=0.0066), polynuclear neutrophils (5.1+/-1.73 vs 4.51+/-1.71 10(9)/L, p=0.0227), higher plasma levels of IL-8 (4.46+/-1.22 vs 1.47+/-0.5 pg/mL, p=0.0202) and RANTES (27.8+/-4.3 vs 18.1+/-2.3 ng/mL, p=0.04) than Duffy-negative patients. No association was detected between RBC expression of DARC and the studied complications.

Effect of interleukin-8 and RANTES on the Gardos channel activity in sickle human red blood cells: role of the Duffy antigen receptor for chemokines

We investigated the effects of the chemokines IL-8 and RANTES on the activity of the Gardos channel (GC) of sickle red blood cells (SSRBCs). SSRBCs expressing the Duffy antigen receptor for chemokines (DARC) incubated under oxygenated conditions exhibit GC activation. The deoxygenation-stimulated K(+) loss via the GC is activated by the chemokines in the Duffy-positive SSRBCs. The percentage of cells with high density is 17 times higher in the Duffy-positive group. These findings are consistent with a greater susceptibility of Duffy-positive SSRBCs to inflammatory chemokines leading to GC activation and cellular dehydration and suggest a coupling, promoted by the sickling process, between DARC and the GC.

Granulocyte colony-stimulating factor (G-CSF) administration in individuals with sickle cell disease: time for a moratorium?

Granulocyte colony-stimulating factor (G-CSF) is used commonly in an attempt to reduce the duration of neutropenia and hospitalization in patients undergoing chemotherapy and to obtain hematopoietic stem cells (HSC) for transplantation applications. Despite the relative safety of administration of G-CSF in most individuals, including subjects with sickle cell trait, severe and life-threatening complications have been reported when used in individuals with sickle cell disease (SCD), including those who were asymptomatic and undiagnosed prior to administration. The administration of G-CSF has now been reported in a total of 11 individuals with SCD. Seven developed severe adverse events, including vaso-occlusive episodes, acute chest syndrome, multi-organ system failure and death. Precautions, including minimizing the peak white blood cell count, dividing or reducing the G-CSF dose and red blood cell transfusions to reduce sickle hemoglobin (HbS) levels, have been employed with no consistent benefit. These reported data indicate that administration of G-CSF in individuals with SCD should be undertaken only in the absence of alternatives and after full disclosure of the risks involved. Unless further data demonstrate safety, routine usage of G-CSF in individuals with SCD should be avoided.

Airway hyperreactivity detected by methacholine challenge in children with sickle cell disease

Recent studies have emphasized the presence of airway hyperreactivity (AHR) in children with sickle cell disease (SCD). However, various tests for the detection of AHR have yielded distinctly different results in these patients. This study identified AHR via a methacholine challenge test (MCT) in a group of children with SCD (31 patients; age range, 6-16 years). The results of pulmonary function tests (PFTs) in patients with SCD and age-matched controls (30 healthy children) were investigated and compared. A positive methacholine challenge result was noted in 25 patients (77.5%). We found that when compared with controls, the children with SCD had lower forced vital capacity (FVC) and forced expiratory volume in 1 sec (FEV(1)) and that both their forced expiratory flow at 25-75% of the FVC (FEF(25-75)) and their FEV(1)/FVC ratio were not statistically significantly different from those of the controls. The statistically significant differences remained after treatment with a bronchodilator agent, but the changes in the FVC, FEV(1), and FEF(25-75) in response to bronchodilator treatment did not differ with statistical significance between the two groups. There was a negative correlation between the number of ACS attacks and the percent predicted of the FEV(1) and the FEV(1)/FVC ratio. We found that the MCT reveals a high incidence of AHR in patients with SCD, regardless of whether those individuals have ACS.

Temporal relationship of asthma to acute chest syndrome in sickle cell disease

Acute chest syndrome (ACS) is an important cause of mortality and morbidity in children with sickle cell disease (SCD). An association between asthma and ACS has been reported. Our aims were to determine whether asthma was more common in SCD children than controls and the relationship of the timing of the SCD children's first ACS episode to a diagnosis of asthma. One hundred and sixty-five SCD children median age 8.2 (range 0.3-17.3) years and 151 similar ethnic origin and aged controls were prospectively recruited into the study and a detailed history was taken from all of the children to determine if they were taking anti-asthma medication. The medical records of the SCD children were examined to assess whether they had an ACS episode, the age this episode occurred and when any diagnosis of asthma had been made. A similar proportion of the SCD children and controls were taking anti-asthma medication (7% and 9%). Thirty-three SCD children had at least one ACS episode. More of the children who had an ACS compared to those who had not were taking anti-asthma medication (P = 0.02). The ACS children had been diagnosed as asthmatic at a median of 3.5 (range 0.5-7) years prior to their first ACS episode. In conclusion, these results suggest asthma exacerbations may predispose to ACS episodes.

Impact of acute chest syndrome on lung function of children with sickle cell disease

OBJECTIVE

To test the hypothesis that children with sickle cell disease (SCD) who experienced an acute chest syndrome (ACS) hospitalization episode would have worse lung function than children with SCD without ACS episodes.

STUDY DESIGN

Forced expiratory volume in 1 second (FEV(1)); forced vital capacity (FVC); FEV(1)/FVC ratio; peak expiratory flow (PEF); forced expiratory flow at 25% (FEF(25)), 50% (FEF(50)), and 75% (FEF(75)) of FVC; airway resistance (Raw); and lung volumes were compared in 20 children with ACS and 20 aged-matched children without ACS (median age, 11 years; range, 6 to 16 years). Fourteen age-matched pairs were assessed before and after bronchodilator use.

RESULTS

The mean Raw (P = .03), TLC (P = .01), and RV (P = .003) were significantly higher in the group with ACS than in the group without ACS. There were no significant differences in the changes in lung function test results in response to bronchodilator administration between the 2 groups, but the children with ACS had a lower FEF(25) (P = .04) and FEF(75) (P = .03) pre-bronchodilator use and a lower mean FEV(1)/FVC ratio (P = .03) and FEF(75) (P = .03) post-bronchodilator use.

CONCLUSIONS

Children with SCD who experienced an ACS hospitalization episode had significant differences in lung function compared with those who did not experience ACS episodes. Our results are compatible with the hypothesis that ACS episodes predispose children to increased airway obstruction.

Red blood cell blood group antigens: structure and function

Red blood cell (RBC) blood group antigens are polymorphic, inherited, carbohydrate or protein structures located on the extracellular surface of the RBC membrane. They contribute to the architecture of the RBC membrane, and their individual function(s) are being slowly revealed. The biological qualities assigned to these RBC membrane structures are based on observed physiological alteration in RBCs that lack the component, by documenting similarities in its protein sequence (predicted from the nucleotide sequence of the gene) to proteins of known function and by extrapolation to identified functional homologues in other cells. The varied roles of RBC antigens include membrane structural integrity, the transport of molecules through the membrane, as receptors for extracellular ligands, adhesion molecules, enzymes, complement components and regulators, and in glycocalyx formation.

Human CD34(+) and CD34(+)CD38(-) hematopoietic progenitors in sickle cell disease differ phenotypically and functionally from normal and suggest distinct subpopulations that generate F cells

OBJECTIVE

Sickle cell disease (SCD) is remarkable for stress erythropoiesis. We investigated the progenitor populations contributing to erythroid stress.

MATERIALS AND METHODS

We characterized hematopoietic progenitor cells in sickle bone marrow and sickle peripheral blood from patients with SCD compared to those in normal bone marrow.

RESULTS

There were increased proportions of sickle bone marrow and sickle peripheral blood CD34(+) cells that coexpressed glycophorin A (GlyA), normally expressed late during erythroid differentiation when CD34 is down-regulated. Remarkably, increased numbers of CD34(+)CD38(-) hematopoietic progenitor cells from sickle bone marrow (p < 0.03) and sickle peripheral blood (p < 0.004) coexpressed GlyA, compared to normal bone marrow CD34(+)CD38(-) hematopoietic progenitor cells. At a molecular level, even the sickle bone marrow and sickle peripheral blood CD34(+)CD38(-) hematopoietic progenitor cells not expressing GlyA by fluorescence-activated cell sorting or reverse transcriptase-polymerase chain reaction expressed the erythroid-specific gene GATA-1, unlike normal bone marrow, suggesting desynchronized erythroid gene expression in the SCD hematopoietic progenitor cells. We also generated red blood cells in vitro from GlyA(+) and GlyA(-)CD34(+) cells. GlyA(+)CD34(+) produced more F cells (p < 0.02) and had lower clonogenicity (p < 0.01) and erythroid expansion potential. Increased F cells were generated only from sickle CD34(+) hematopoietic progenitor cells (p < 0.04), as occurs in vivo.

CONCLUSION

Stress erythropoiesis in SCD has been postulated to accelerate erythropoiesis and production of F cells. Thus, CD34(+)CD38(-) expressing GlyA may represent the "stress progenitor" population. This is the first study characterizing CD34(+) and CD34(+)CD38(-) hematopoietic progenitor cells in sickle bone marrow, comparing them to sickle peripheral blood and normal bone marrow and using them to generate sickle red blood cells that recapitulate F cell production observed in vivo. We identified a unique population of GlyA(+)CD34(+) cells in SCD, which is in an accelerated erythroid differentiation pathway, has not down-regulated CD34 antigen expression, and predominantly generates F cells.

Effect of red cell exchange transfusion on plasma levels of inflammatory mediators in sickle cell patients with acute chest syndrome

Red cell exchange transfusion is the recommended therapy for patients with sickle cell disease (SCD) who have severe, progressive acute chest syndrome (ACS). A double-volume red cell exchange transfusion decreases the percentage of hemoglobin S (Hgb S) containing red blood cells to less than 20%, improving vascular perfusion. We speculated that reduction of pro-inflammatory mediators might also contribute to the therapeutic effect of an exchange transfusion. We measured white blood cell count (WBC), absolute neutrophil count (ANC), platelet concentration as well as plasma levels of interleukin-1alpha (IL-1alpha), interleukin-1beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha), interleukin-8 (IL-8), and soluble vascular cell adhesion molecule-1 (sVCAM-1) in 8 sickle cell patients with 9 episodes of ACS who received a manual, double-volume exchange transfusion. Six patients with SCD seen during a routine clinic visit were used as controls. The mean number of hospitalization days was 6, with an average of 2 days in the intensive care unit. All patients recovered without complication. Sickle cell patients with ACS had a higher WBC and ANC at baseline but lower sVCAM-1 levels compared to controls. TNF-alpha, IL-1alpha, IL-1beta, and IL-8 levels were not significantly different from controls. WBC, ANC, platelet, and sVCAM-1 measurements were significantly decreased immediately post-exchange in patients with ACS; however, this effect was not persistent as levels trended towards pre-exchange values by 24 hr post-exchange. Due to wide inter-individual variability, a consistent pattern was not seen for TNF-alpha, IL-1alpha, IL-1beta, or IL-8. We conclude that in sickle cell patients with ACS, a manual, double-volume exchange transfusion lowers WBC, ANC, platelets, and sVCAM-1 levels, but the effect is short-lived.

Enhanced pulmonary and systemic response to endotoxin in transgenic sickle mice

Some suggest that sickle cell disease (SCD) is associated with a "proinflammatory state" that predisposes patients to acute chest syndrome in the setting of triggering factors. Conflicting data emerged when inflammation markers in SCD were compared with healthy individuals. Therefore, we examined transgenic sickle and control mice at baseline and with endotoxin (LPS) intraperitoneal injection to determine whether a proinflammatory state truly exists. At baseline, sickle mice had elevated levels of circulating leukocytes and soluble vascular cell adhesion molecule 1 (sVCAM-1). No other differences were observed at baseline or in response to saline. However, LPS challenge was associated with significant increases in mortality (p<0.05), airway tone (p<0.03), serum and bronchoalveolar lavage levels of cytokines tumor necrosis factor-alpha (p<0.03), interleukin-1beta (p<0.02), and sVCAM-1 (p<0.01) in sickle mice compared with control subjects. Furthermore, 4 hours after LPS, microarray analysis identified 413 genes differentially expressed in the sickle mice (n=5) compared with only 7 in the control subjects (n=5). No difference in lung parenchyma was observed by light microscopy. This enhanced response to LPS suggests that the sickle red blood cell confers a subclinical "proinflammatory state." This enhanced response to inflammatory insult, particularly by adhesion molecules such as sVCAM-1, could play a role in the increased susceptibility to pulmonary dysfunction that has been observed clinically in SCD.

Spontaneous circulation of myeloid-lymphoid-initiating cells and SCID-repopulating cells in sickle cell crisis

The only curative therapy for sickle cell disease (SCD) is allogeneic hematopoietic stem cell (HSC) transplantation. Gene therapy approaches for autologous HSC transplantation are being developed. Although earlier engraftment is seen when cells from GCSF-mobilized blood are transplanted than when bone marrow is transplanted, administration of GCSF to patients with SCD can cause significant morbidity. We tested whether primitive hematopoietic progenitors are spontaneously mobilized in the blood of patients with SCD during acute crisis (AC-SCD patients). The frequency of myeloid-lymphoid-initiating cells (ML-ICs) and SCID-repopulating cells (SRCs) was significantly higher in blood from AC-SCD patients than in blood from patients with steady-state SCD or from normal donors. The presence of SRCs in peripheral blood was not associated with detection of long-term culture-initiating cells, consistent with the notion that SRCs are more primitive than long-term culture-initiating cells. As ML-ICs and SRCs were both detected in blood of AC-SCD patients only, these assays may both measure primitive progenitors. The frequency of ML-ICs also correlated with increases in stem cell factor, GCSF, and IL-8 levels in AC-SCD compared with steady-state SCD and normal-donor sera. Because significant numbers of ML-ICs and SRCs are mobilized in the blood without exogenous cytokine treatment during acute crisis of SCD, collection of peripheral blood progenitors during crisis may yield a source of autologous HSCs suitable for ex-vivo correction by gene therapy approaches and subsequent transplantation.

Gene expression profiles of microvascular endothelial cells after stimuli implicated in the pathogenesis of vasoocclusion

Altered gene expression in endothelial cells interacting with sickle red blood cells (RBC) and other blood components, in particular the pro-inflammatory cytokines, is an essential step in the pathogenesis of vasoocclusive crises in sickle cell disease (SCD). Using cDNA arrays, we monitored gene expression profiles of human lung microvascular endothelial cells (HMVEC-L) after stimuli that are likely involved in the pathogenesis of vasoocclusion. We detected increased expression of multiple genes in HMVEC-L after their exposure to pro-inflammatory cytokines TNFalpha and IL-1beta and to RBC with increased external exposure of phosphatidylserine and RBC from a patient with SC hemoglobin. While some of these genes have previously been implicated in vascular damage, many represent new targets for investigation of the pathogenesis of vasoocclusion in SCD.

Sickle cell anaemia: progress in pathogenesis and treatment

The phenotypic expression of sickle cell anaemia varies greatly among patients and longitudinally in the same patient. It influences all aspects of the life of affected individuals including social interactions, intimate relationships, family relations, peer interactions, education, employment, spirituality and religiosity. The clinical manifestations of sickle cell anaemia are protean and fall into three major categories: anaemia and its sequelae;pain and related issues; andorgan failure including infection. Recent studies on the pathogenesis of sickle cell anaemia have centred on the sequence of events that occur between polymerisation of deoxy haemoglobin (Hb) S and vaso-occlusion. Cellular dehydration, inflammatory response and reperfusion injury seem to be important pathophysiological mechanisms. Management of sickle cell anaemia continues to be primarily palliative in nature, including supportive, symptomatic and preventative approaches to therapy. Empowerment and education are the major aspects of supportive care. Symptomatic management includes pain management, blood transfusion and treatment of organ failure. Pain managment should follow certain priniciples that include assessment, individualisation of therapy and proper utilisation of opioid and nonopioid analgesics in order to acheive adequate pain relief. Blood selected for transfusion should be leuko-reduced and phenotypically matched for the C, E and Kell antigens. Exchange transfusion is indicated in patients who are transfused chronically in order to prevent or delay the onset of iron-overload. Acute chest syndrome is the most common form of organ failure and its management should be agressive, including adequate ventilation, multiple antibacterials and simple or exchange blood transfusion depending on its severity. Preventitive therapy includes prophylactic penicillin in infants and children, blood transfusion (preferably exchange transfusion) in patients with stroke, and hydroxyurea in patients with frequent acute painful episodes. Bone marrow and cord blood transplantation have been successful modalities of curative therapy in selected children with sickle cell anaemia. Newer approaches to preventative therapy include cellular rehydration with agents that inhibit the Gardos channel or the KCl co-transport channel. Curative gene therapy continues to be investigational at the level of the test tube and transgenic mouse models.

Interleukin-8 receptor antagonists in pulmonary diseases

Inflammatory cells are thought to be instrumental in the pathophysiology of pulmonary diseases, and control of their recruitment and activation in the lung would appear to be an attractive strategy for therapeutic intervention. Interleukin-8 and related CXC chemokines are involved in the function of neutrophils and T cells, and have been implicated in several lung diseases. Small-molecule antagonists of the interleukin-8 receptors have been identified, which may help elucidate the role of interleukin-8 and related chemokines in the pathophysiology of lung diseases.