Effect of cetiedil, an in vitro antisickling agent, on erythrocyte membrane cation permeability.

Cetiedil has been reported to relieve painful crises in sickle cell anemia and to have antisickling properties in vitro. The drug alters neither oxygen affinity nor the solubility of deoxyhemoglobin S. Because the viscosity of the erythrocyte interior and the kinetics of gelation are dependent on the concentration of hemoglobin, we postulated that cetiedil might inhibit sickling by modifying erythrocyte sodium or potassium movements in a manner that would increase cell water content and thus dilute the cell hemoglobin. The drug has two such effects: it inhibits the specific increase in potassium permeability that follows a rise in cytoplasmic calcium concentration and it causes a rise in passive sodium movements. These effects are further evidence that cell ion and water movements may be important in the process of sickling and suggest a mechanism for the results reported with cetiedil.

An ascorbate-mediated transmembrane-reducing system of the human erythrocyte.

Actively metabolizing human erythrocytes catalyze the extracellular reduction of ferricyanide to ferrocyanide. Because neither of these anions can enter the cell, reducing equivalents generated in the course of glycolysis must in some manner be transferred across the cell membrane, thereby resulting in ferricyanide reduction. Work described in this paper suggests that the transmembrane reduction is effected by ascorbic acid. This compound in its oxidized form (dehydroascorbate) rapidly enters the cell. Here it obtains reducing equivalents which appear to come from NADH made available at the level of glyceraldehyde 3-phosphate dehydrogenase. Once reduced, it leaves the cell as ascorbic acid and accomplishes the non-enzymatic reduction of ferricyanide.

A molecular defect in two families with hemolytic poikilocytic anemia: reduction of high affinity membrane binding sites for ankyrin.

Patients from two families with chronic hemolytic anemia have been studied. The erythrocytes are very fragile and appear microcytic with a great variety of shapes. Clinical evaluation failed to identify traditionally recognized causes of hemolysis. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) showed no significant abnormality of the major polypeptide bands. Erythrocytes spectrin-ankyrin and ankyrin-membrane interactions were analyzed with 125I-labeled spectrin, 125I-labeled ankyrin, and inside-out vesicles. Patients' vesicles bound 125I-spectrin normally. Likewise, patients' spectrin and ankyrin competed normally for the binding sites on control membranes. None of the individual components appeared to have abnormal thermal sensitivity. Ankyrin-stripped, inside-out vesicles prepared from the patients bound less 125I-ankyrin than did vesicles prepared from normals (P less than 0.05 for all corresponding points in the high-affinity region). Scatchard analysis showed the most significant abnormality to be a 50% reduction in the high affinity ankyrin binding sites. Similar experiments were performed with blood from patients with spherocytosis and splenectomized controls, but no abnormalities were detected. The water soluble 43,000-dalton fragments of band 3 (the high-affinity ankyrin binding sites) were prepared from one of the patients and competed normally for 125I-ankyrin binding in solution. This suggests that the primary structural defect is a reduction in the number of high affinity membrane binding sites for ankyrin, and is consistent with an abnormal organization of band 3 in the membrane.

Activation of sickle red blood cell adhesion via integrin-associated protein/CD47-induced signal transduction.

Peripheral human red blood cells (RBCs) are not generally known to become activated and adhesive in response to cell signaling. We show, however, that soluble thrombospondin via integrin-associated protein (IAP; CD47) increases the adhesiveness of sickle RBCs (SS RBCs) by activating signal transduction in the SS RBC. This stimulated adhesion requires occupancy of IAP and shear stress and is mediated by the activation of large G proteins and tyrosine kinases. Reticulocyte-enriched RBCs derived from sickle-cell disease (SCD) patients are most responsive to IAP-induced activation. These studies therefore establish peripheral SS RBCs as signaling cells that respond to a novel synergy between IAP-induced signal transduction and shear stress, suggesting new therapeutic targets in SCD.

Hairy cell leukemia with acquired dyserythropoiesis.

Dyserythropoiesis, a qualitative abnormality of erythrocyte production, is described in a patient with hairy cell leukemia (leukemic reticuloendotheliosis). The development of a second population of circulating RBCs with a mean corpuscular volume of 154 cu mu suggests the emergence of an abnormal clone of marrow erythrocyte precursors.

Toxoplasma gondii and the compromised host. Antibody response in the absence of clinical manifestations of disease.

Toxoplasmosis is a well-described opportunistic infection in immunocompromised hosts. Meningoencephalitis, myocarditis, and pneumonitis are the most frequent clinical manifestations of disease. Because of difficulties both with isolation of the organism and with its identification in tissue, most laboratories rely on serological techniques for diagnosis of acute disease. The most widely available and commonly employed serological method is the indirect fluorescent antibody test (IFA). We recently encountered an immunocompromised patient with an undefined hematologic malignant neoplasm who had an IFA titer greater than 1:100,000 without clinical evidence of active toxoplasmosis. Although his dye test titer and direct agglutination titer were also elevated, he had negative double-sandwich-IgM enzyme-linked immunosorbent assay titers. Immunoperoxidase staining of the tissues failed to demonstrate trophozoites. This case demonstrates that elevated toxoplasma IFA titers may occur in patients at high risk for opportunistic infection but who do not manifest overt clinical toxoplasmosis.

Hemolysis caused by factor VIII concentrates.

Immune hemolytic anemia is a recognized complication of the use of factor VIII concentrates. Hemolysis is obscured often by the presence of active bleeding. Where hemolysis has been demonstrated, red blood cell (RBC) destruction has been attributed to anti-A antibodies found in the transfused material. We present two episodes of hemolysis associated with the use of factor VIII concentrate. In the first, a high titer of "immune" anti-A (1:256) was present in the factor VIII. In the second, the patient's RBCs were group B, and the hemolysis was caused by anti-B antibody in the factor VIII concentrate. In addition, the antibody titer in the material that was received was much lower than previously described. The RBC destruction presumably occurred because of the massive dosage of factor VIII concentrate administered on order to overcome a factor VIII inhibitor.

Hemoglobin-based oxygen carrier preserves submaximal exercise capacity in humans.

OBJECTIVE: The objective of this study was to evaluate the exercise capacity of subjects given an autologous transfusion or a polymerized bovine hemoglobin solution to define the pharmacodynamics and pharmacokinetics of a new hemoglobin-based oxygen carrier (HBOC-201). METHODS: Six normal healthy male subjects (ages 25 to 45 years) participated in this randomized, single-blind, two-way crossover study, which took place at Upjohn Research Clinics in Kalamazoo, Mich. A radial artery catheter was inserted in each subject before serial cardiac output and pulmonary function tests and phlebotomy of 15% blood volume (750 ml plus another 250 ml for study laboratories yields 1000 ml, or about 150 gm human hemoglobin). This was followed by isovolemic hemodilution with Ringer's lactate plus an autologous blood transfusion (or HBOC-201) and 1 week later 45 gm bovine hemoglobin of HBOC-201 (or autologous transfusion). Bicycle exercise stress tests to anaerobic threshold (approximately 65% of predicted maximum aerobic capacity) were done before phlebotomy and at approximately 45 minutes after the autologous transfusion or HBOC-201 infusion. RESULTS: Subjects had similar exercise and diffusion capacity but lower lactate levels (for up to 24 hours) during HBOC-201 (which paralleled plasma HBOC-201 levels) than during autologous transfusion periods. Oxygen use (uptake) and carbon dioxide production at rest were greater during the HBOC-201 infusion than during the autologous transfusion period. The half-life of HBOC-201 was about 23 hours. CONCLUSIONS: Exercise capacity and diffusion capacity were similar after HBOC-201 and autologous transfusion. HBOC-201 resulted in greater oxygen (or uptake) and carbon dioxide production and lower lactate levels compared with autologous transfusion. Under the conditions of the study, the physiologic effects of 1 gm bovine hemoglobin of HBOC-201 were similar to 3 gm human hemoglobin from autologous transfusion.

A single-dose pharmacokinetic study of the antisickling agent cetiedil.

Cetiedil citrate is an antisickling agent shown to be effective in reducing the severity and duration of acute sickle cell crisis. With the use of a sensitive GC/MS assay, the pharmacokinetic profile of cetiedil was studied in normal men and in men with sickle cell anemia who were not in crisis at the time of study. A peak cetiedil concentration of 70 to 200 ng/ml was found immediately after a 30-minute drug infusion. The plasma level then gradually declined to approximately 10 ng/ml during a 3-hour distributive phase. Computer analysis of the data was most consistent with a three-compartment model. No pharmacokinetic differences were found between the normal men and the subjects with sickle cell. Because the cetiedil plasma levels achieved during this in vivo study are well below concentrations that exhibit antisickling activity in vitro, additional clinical studies will be necessary before an optimal dosing regimen can be established.

Hydroxyurea and sickle cell anemia. Clinical utility of a myelosuppressive "switching" agent. The Multicenter Study of Hydroxyurea in Sickle Cell Anemia.

Painful crises in patients with sickle cell anemia are caused by vaso-occlusion and infarction. Occlusion of blood vessels depends on (at least) their diameter, the deformability of red cells, and the adhesion of blood cells to endothelium. Deoxygenated sickle cells are rigid because they contain linear polymers of hemoglobin S (Hb S); polymerization is highly concentration dependent, and dilution of Hb S by a nonsickling hemoglobin such as fetal hemoglobin (Hb F) would be expected to lead ultimately to a decrease in the frequency of painful crises. It might also be expected to decrease the severity of anemia, although the pathogenesis of anemia in sickle cell anemia (SS disease) is not clearly understood. Reversion to production of fetal rather than adult hemoglobin became practical with the discovery that HU was an orally effective and relatively safe "switching agent." Preliminary dose-ranging studies led to a double-blind randomized controlled clinical trial, the Multicenter Study of Hydroxyurea in Sickle Cell Anemia (MSH), designed to test whether patients treated with HU would have fewer crises than patients treated with placebo. The MSH was not designed to assess the mechanism(s) by which a beneficial effect might be achieved, but it was hoped that observations made during the study might illuminate that question. The 2 MSH treatment groups were similar to each other and were representative of African-American patients with relatively severe disease. The trial was closed earlier than expected, after demonstration that median crisis rate was reduced by almost 50% (2.5 versus 4.5 crises per year) in patients assigned to HU therapy. Hospitalizations, episodes of chest syndrome, and numbers of transfusions were also lower in patients treated with HU. Eight patients died during the trial, and treatment was stopped in 53. There were no instances of alarming toxicity. Patients varied widely in their maximum tolerated doses, but it was not clear that all were taking their prescribed treatments. When crisis frequency was compared with various clinical and laboratory measurements, pretreatment crisis rate and treatment with HU were clearly related to crisis rate during treatment. Pretreatment laboratory measurements were not associated with crisis rates during the study in either treatment group. It was not clear that clinical improvement was associated with an increase in Hb F. Crisis rates of the 2 treatment groups became different within 3 months. Mean corpuscular volumes (MCVs) and the proportion of Hb F containing red cells (F cells) rose, and neutrophil and reticulocyte counts fell, within 7 weeks. When patients were compared on the basis of 2-year crisis rates, those with lower crisis rates had higher F-cell counts and MCVs and lower neutrophil counts. Neutrophil, monocyte, reticulocyte, and platelet counts were directly associated, and F cells and MCV were inversely associated, with crisis rates in 3-month periods. In multivariable analyses, there was strong evidence of independent association of lower neutrophil counts with lower crisis rates. F-cell counts were associated with crisis rate only in the first 3 months of treatment; MCV showed an association over longer periods of time. Overall, the evidence that decreased neutrophil counts played a role in reducing crisis rates was strong. Increased F cells or MCV and evidence of cytoreduction by HU were also associated with decreased crisis rates, but no definitive statement can be made regarding the mechanism of action of HU because the study was not designed to address that question. Future studies should be designed to explore the mechanism of action of HU, to identify the optimal dosage regimen, and to study the effect of HU when combined with other antisickling agents.

Pulmonary hypertension and cor pulmonale in the sickle hemoglobinopathies.

Although pulmonary hypertension is frequently mentioned as a complication of the sicklemic state, careful review of the medical literature revealed only a single subject in whom cardiac catheterization data substantiated this diagnosis. In two additional patients, both clinical and autopsy findings of pulmonary vascular disease and cor pulmonale were described, although no hemodynamic studies had been performed. We have therefore detailed the clinical history, cardiac catheterization results, and autopsy findings in three previously undescribed patients. These three patients, along with the three case reports culled from the medical literature, from the substance of this review. Pulmonary hypertension should be suspected in patients with sickle hemoglobinopathy in whom either fixed dyspnea or unexplained syncope develops. Early in the course of the disease, right heart catheterization remains the only way to establish the diagnosis with certainty. Noninvasive studies such as chest x-ray, electrocardiography, and echocardiography tend to be nondiagnostic until late in the course of right ventricular failure. Although specific therapy has yet to be defined, the ominous prognosis of this complication of sickle hemoglobinopathy supports the application of experimental modalities such as continuous oxygen therapy, partial exchange transfusion, or even limited phlebotomy.

Cetiedil inhibition of calmodulin-stimulated enzyme activity.

Cetiedil, an in vitro anti-sickling agent, inhibited calmodulin-stimulated cyclic 3':5'-nucleotide phosphodiesterase (EC 3.1.4.17) and Ca2+-ATPase (ATP phosphohydrolase, EC 3.6.1.3) activities. The drug had no effect on basal enzyme activities in the absence of calmodulin. The inhibition of phosphodiesterase was competitive with respect to the concentrations of both cAMP and calmodulin. Cetiedil did not inhibit calmodulin-stimulated enzyme activities by acting as a calcium chelator, since increasing the concentration of calcium did not reverse the inhibitory effect.

Pappenheimer bodies. An additional cause for a spurious platelet count.

A 67-year-old woman who had sideroblastic anemia had a spuriously elevated platelet count due primarily to Pappenheimer bodies. The platelet count on an electrooptical instrument was falsely elevated. The true platelet count was determined by phase microscopy using lysed whole blood and by the peripheral blood smear. There appear to have been no previous reports of falsely elevated platelet counts due to Pappenheimer bodies. Other causes of spuriously elevated platelet counts are reviewed. The reasons for the spurious counts are discussed.

Effects of cognitive coping skills training on coping strategies and experimental pain sensitivity in African American adults with sickle cell disease.

The present study examined whether training in cognitive coping skills would enhance pain coping strategies and alter pain perception in adults with sickle cell disease (SCD). Sixty-four African Americans with SCD were randomly assigned to either a cognitive coping skills condition (three 45-min sessions in which patients were trained to use 6 cognitive coping strategies) or a disease-education control condition (three 45-min didactic-discussion sessions about SCD). Pain sensitivity to calibrated noxious stimulation was measured at pre- and posttesting, as were cognitive coping strategies, clinical pain, and health behaviors. Results indicated that, compared with the randomly assigned control condition, brief training in cognitive coping skills resulted in increased coping attempts, decreased negative thinking, and lower tendency to report pain during laboratory-induced noxious stimulation.

Follow-up of coping skills training in adults with sickle cell disease: analysis of daily pain and coping practice diaries.

This study examined the 3-month follow-up effects of a pain coping skills intervention in African American adults with sickle cell disease. Sixty-seven participants were randomly assigned to either a coping skills condition or a disease-education control condition. Multivariate analyses applied to summary measures of coping, laboratory pain perception, and clinical measures indicated that participants in the coping intervention reported significantly lower laboratory pain and significantly higher coping attempts at 3-month follow-up in comparison with the control condition. Multilevel random effects models applied to prospective daily diaries of daily pain, health care contacts, and coping practice indicated that on pain days when participants practiced their strategies, they had less major health care contacts in comparison with days when they did not use strategies.

A phase I/II study of polymerized bovine hemoglobin in adult patients with sickle cell disease not in crisis at the time of study.

BACKGROUND: The painful episodes of sickle cell disease (SCD) involve vaso-occlusion and impaired oxygen delivery. HBOC-201, a hemoglobin-based oxygen carrier, has been shown to support oxygen delivery in animal studies and to be safe and well tolerated in normal human volunteers. Therefore, we speculated that it might have a therapeutic role in SCD. METHODS: Eighteen adults with SCD who were asymptomatic at the time of study were enrolled in a Phase I/II single-blind, placebo-controlled, dose-escalation study of HBOC-201. The primary purpose was to assess the safety of the material in this patient population. In addition, as a surrogate marker of efficacy, each subject underwent a variety of exercise tests before and after HBOC-201 was given. RESULTS: All HBOC-201 infusions were well tolerated by the study subjects and no evidence of toxicity was noted. In addition, there was a significant difference in heart rate response to the identical aerobic exercise workload when the study subjects who received HBOC-201 were compared to the subjects who received placebo (p = 0.0061). CONCLUSIONS: HBOC-201 was safely administered to patients with SCD who were not in crisis at the time of study. Furthermore, following infusion of the study material, subjects with SCD performed the identical aerobic exercise-induced workload with an increase in heart rate that was significantly less than the increase observed in the subjects who received an infusion of the saline placebo. These safety and surrogate efficacy data support the notion that HBOC-201 could have efficacy as a treatment for the vasoocclusive episodes of SCD.

Case report: splenic sequestration and multiorgan failure as the presenting manifestation of hemoglobin SC disease.

Acute splenic sequestration, a well recognized complication of the various sickle cell syndromes, is characterized by increasing splenomegaly and a sudden fall in hemoglobin concentration. In this article, the authors describe a 21-year-old woman with previously undiagnosed hemoglobin SC disease whose initial presentation was that of acute, severe splenic sequestration. Despite the severity of her illness, prompt diagnosis and appropriate therapy led to a complete recovery. The splenic sequestration in this case was apparently exacerbated by a recent hepatitis B infection. To date, this presentation of hemoglobin SC disease has not been described in the medical literature.

Case report: splenomegaly and splenic sequestration in an adult with sickle cell anemia.

Splenomegaly in adult patients with homozygous sickle cell anemia (HbSS) is uncommon and splenic sequestration crises are rare. This paper describes a patient with HbSS who, at the age of 24, began to experience acute splenic sequestration crises. These episodes occurred with sufficient frequency and severity to warrant splenectomy. This case is presented to emphasize that, although rare, splenomegaly can persist in adults with homozygous HbSS and can be associated with severe and even life-threatening splenic sequestration. The incidence of splenomegaly in adults with HbSS and the factors linked to it will be discussed and the published reports of splenic sequestration crises in this patient population reviewed. It appears that high hemoglobin F (HbF) levels and alpha-thalassemia may be important etiologic factors in causing persistence of splenomegaly and predisposing patients to splenic sequestration crises.

Bone marrow necrosis in sickle cell disease: a description of three cases and a review of the literature.

Bone marrow necrosis (BMN) ranges from a localized to a widespread generalized process. Most often seen in patients with leukemia and other malignant conditions, generalized BMN has also been observed in patients with sickle cell disease (SCD), where it is almost certainly a consequence of blood vessel occlusion. Activation of the clotting system seems to play a role in this clinical setting. Systemic fat embolism and acute multi-organ failure syndrome can also complicate BMN in patients with SCD. We describe here 3 cases of BMN associated with SCD. Each patient exhibited an unusually severe vaso-occlusive crisis accompanied by persistent fever, a high level of serum lactate dehydrogenase, leukoerythroblastosis, and large numbers of nucleated red cells. Despite such suggestive clinical features, diagnosis of BMN still requires a bone marrow biopsy. Particularly in patients with SCD, the early institution of transfusion therapy can be life-saving. The ominous prognosis ascribed to generalized BMN seems to reflect the poor outcome of such underlying conditions as leukemia; however, the prognosis of generalized BMN is not so poor in association with SCD and other nonmalignant states.