Metallothionein expression prevents apoptosis. II: Evaluation of the role of metallothionein expression on the chemotherapy-induced apoptosis during the treatment of acute leukemia.

Metallothioneins (MT) are low molecular weight cysteine-rich proteins, present in a wide variety of eukaryotes. Although their physiological function is not entirely understood, recently it was found that in vitro human MTs (hMTs) expression prevents apoptosis. In the present study, the apoptosis preventing effect of hMTs is evaluated in vivo, in order to correlate the apoptotic effect of chemotherapy during the treatment of acute leukemia with the expression of hMTs. The expression of hMTs was studied immunocytochemically in bone marrow smears and peripheral blood cytocentrifugations of 47 children with acute leukemia at diagnosis and during treatment. Apoptosis was quantitatively studied in peripheral blood samples during the induction therapy. Eighteen cases were found to be positive for hMTs expression at diagnosis and the mean apoptosis curve of these cases showed maximal effect on the second day of treatment, the apoptotic action of chemotherapy being completed on the tenth day. The mean apoptosis curve of the hMTs negative cases (29 cases) showed maximal effect on the first day of treatment and the apoptotic action of chemotherapy was completed on the sixth day. When considering the day on which the maximal apoptotic effect appeared and the day on which the apoptotic action of treatment was completed, the results indicated retardation of the chemotherapy-induced apoptosis dependent on hMTs expression, as a result of resistance to treatment. Furthermore, the study of hMTs expression during treatment, showed that although the apoptotic action of chemotherapy eliminates blast cells, a cell population positive for hMTs survived and increased during treatment, since they were able to escape apoptotic cell death. These findings, indicated that in vivo, hMTs constitute a cellular protective mechanism preventing chemotherapy-induced apoptosis, thus regulating the response of patients to treatment.

The presurgical management with erythrocytapheresis of a patient with a high-oxygen-affinity, unstable Hb variant (Hb Bryn Mawr).

BACKGROUND: Hemoglobin (Hb) Bryn Mawr is an unstable Hb variant resulting in congenital hemolytic anemia. This variant Hb also has an increased affinity for oxygen. The perioperative transfusion management of this disorder is described, and the first genomic analysis of this Hb variant is given. CASE REPORT: An 11-year-old boy, heterozygous for Hb Bryn Mawr, was referred for cholecystectomy. Sequence analysis of genomic DNA confirmed that the patients was heterozygous for a T-->C transition in the codon for amino acid 85, causing a substitution of serine for phenylalanine in the beta-globin chain. On the basis of whole-blood O2 dissociation studies, projected tissue O2 delivery would have been suboptimal during general anesthesia; therefore, a partial red cell exchange transfusion was performed to lower variant Hb and prevent tissue hypoxia during surgery. The red cell mass to be exchanged (50%) was determined from the calculated increase in O2 delivery capacity required to maintain an O2 extraction of 4 to 5 mL of O2 per dL of whole blood. The p50 of whole blood from the patients immediately after the exchange transfusion was 16.0 torr. At the time of surgery, the p50 was normal (25.9 torr). The patient's whole blood 2,3 DPG levels were 4.70 mmol per mL of red cells (before transfusion) (normal range = 4.8 +/- 0.3 mmol/mL red cells), 4.07 mmol per mL of red cells (immediately after transfusion), and 4.55 mmol per mL of red cells (48 hours after transfusion). CONCLUSION: This patient with Hb Bryn Mawr was prepared for surgery with a partial exchange transfusion to prevent tissue hypoxia during anesthesia. Decreased 2,3 DPG levels immediately after transfusion resulted in increased O2 affinity of whole blood; however, 48 hours after exchange transfusion, a normal p50 (due to both removal of variant Hb and regeneration of 2,3, DPG) was observed. Partial exchange transfusion is useful in the preoperative management of patients with Hb variants characterized by increased O2 affinity.

Different hematological phenotypes caused by the interaction of triplicated alpha-globin genes and heterozygous beta-thalassemia.

The pathophysiology and clinical severity of beta-thalassemia are related to the degree of alpha/non-alpha-chain imbalance. A triplicated alpha-globin gene locus can exacerbate effects of excess alpha-chains caused by a defective beta-globin gene, although this is not observed in all cases. Extensive studies on this condition are lacking. We report a group of 17 patients who are heterozygous for both the alpha alpha alpha(anti-3.7) allele and a mutation in the beta-globin gene cluster. Their clinical phenotypes varied: six had mild anemia with microcytosis and hypochromia, while 11 had more severe anemia with splenomegaly requiring splenectomy (three cases) and blood transfusions (four cases). Different phenotypes were also evident in the presence of the same beta-thalassemia mutation: in one family, two individuals had the same alpha- and beta-globin genotypes but presented with different hematologic phenotypes. In addition, the complex interaction involving a triplicated alpha-globin gene, beta39- and delta+27-thalassemia mutations is studied in a family with two siblings presenting with hemolytic anemia, normal Hb A2 and increased Hb F. Analysis of this series of patients suggests that additional genetic determinants play a role in modulating phenotypic expression in individuals with identical alpha- and beta-globin genotypes. Interaction with a triplicated alpha-gene can play a role in the clinical presentation of patients with defective beta-globin gene expression and should be considered in the diagnosis of atypical cases.

Hb Osler [beta 145(HC2)Tyr-->Asp] results from posttranslational modification.

We studied two members of an African American family with erythrocytosis. An abnormal hemoglobin variant with an electrophoretic pattern on cellulose acetate similar to Hb J was identified. The oxygen dissociation curve using whole blood was biphasic, dramatically left-shifted, and hyperbolic. Sequence analysis of DNA from the proband showed heterozygosity for a T-->A change at the first position of codon 145 in the beta-globin gene which results in the substitution of an asparagine residue for normal tyrosine. The second cycle of C-terminal amino acid sequence analysis of a mixture of alpha- and beta-globin chains showed tyrosine, aspartic acid, and small amounts of asparagine. Collectively, these results indicate the existence of a mutation at codon 145 of the beta-globin gene which encodes for asparagine instead of tyrosine, and that asparagine then undergoes a partial posttranslational deamidation to aspartic acid. This amino acid substitution corresponds to Hb Osler, which is a high oxygen affinity hemoglobin variant, initially described to be caused by a substitution of Tyr-->Asp at beta 145. Posttranslational amino acid modification may constitute an important component in the pathophysiology of hemoglobinopathies.

Neurologic complications of treatment of childhood acute immune thrombocytopenic purpura with intravenously administered immunoglobulin G.

We studied the incidence, associated morbidity, and impact on health care charges of neurologic complications in 38 children with acute immune thrombocytopenic purpura (ITP) treated with intravenously administered IgG. Thirteen patients (34%) had transient neurologic complications, manifested by severe headache, nausea, and, rarely, aseptic meningitis. Computed tomography was performed in nine patients. Twelve patients were hospitalized longer than was required for their ITP alone. Neurologic complications caused by the IgG preparations used in the treatment of childhood ITP occur more frequently than has previously been suggested and may substantially increase the cost of treatment.