Amifostine Protects Bone Marrow from Benzene-Induced Hematotoxicity in Mice

Benzene is one of the most widely used industrial chemical agents. Long-term benzene exposure causes bone marrow aplasia and leads to a wide range of hematopoietic disorders including aplastic anaemia (AA). There are currently no effective approaches to protect people from benzene-induced hematotoxicity and AA. In addition, current treatments for AA have limitations with short- and long-term risks. Protective agents and new therapeutic approaches, therefore, are needed to prevent and treat the disease. Amifostine is a well-known cytoprotective agent and has been widely used in clinical for protecting normal tissues from the toxic effects of chemotherapy and radiotherapy. The authors utilized an established mouse model to determine the protective effect of amifostine on benzene-induced bone marrow hematotoxicity. Whole-blood cell count, morphological and histopathological alterations in the bone marrow and spleen, as well as the production of inducible toxic oxidative species were examined and compared among the mouse groups. Amifostine treatment in benzene-exposed mice significantly improved blood cell counts, and morphological and histopathological signs of hematotoxicity in the bone marrow as well as in the spleen. Moreover, amifostine prevented benzene-induced bone marrow and spleen cell apoptosis and rescinded the inhibition of cell proliferation induced by benzene exposure. Finally, amifostine significantly inhibited the levels of reactive oxidative species and lipid peroxidation induced by benzene exposure. These data suggest that amifostine appears to have substantial protective effect on benzene-induced bone marrow hematotoxicity.

[Adverse effects of antiepileptic drugs]

Adverse effects of antiepileptic drugs are classified into idiosyncratic adverse effects, pharmacology-related adverse effects and biological effect after modification of seizure frequencies. Pharmacology-related adverse effects include those by administered AED and those by mutual interactions. Stevens-Johnson syndrome, one of the idiosyncratic adverse effects, may be predicted by the intrinsic HLA type (e.g., A*31:01 for CBZ). In epileptic patients after acute encephalitis, cutaneous adverse reactions usually occur in a month after encephalitis, but some patients will tolerate the causative AED by the extremely slow re-introduction. Prevention of pharmacology-related adverse effects needs therapeutic drug monitoring, and slow introduction considering dose-response curves for AEDs. Genotype examination of CYP2C9 and 2C19 can contribute to the safe introduction of PHT.

Type I Interferon Signaling and B Cells Maintain Hemopoiesis duringPneumocystisInfection of the Lung

Loss of CD4 T cells is the hallmark of HIV infection. However, type I IFN-producing plasmacytoid dendritic cells may also be lost. This results in susceptibility to an opportunistic infection such as Pneumocystis pneumonia. In addition, regenerative bone marrow failure resulting in pancytopenia is another common problem in advanced stage AIDS. This may be linked to both the failing immune system and recurrent opportunistic infections. We generated lymphocyte-deficient type I IFN receptor-deficient mice (IFrag-/-) to study the effects on Pneumocystis infection of the lung. When IFrag-/- animals were infected with Pneumocystis they died between days 16 and 21 postinfection with minimal pneumonia but severe anemia due to complete bone marrow failure. This included the loss of uncommitted hemopoietic precursor cells. Bone marrow failure was prevented by the reconstitution of IFrag-/- mice with wild-type lymphocytes, especially B cells. T and B cells lacking type I IFN receptor signaling could only partially prevent bone marrow failure in response to Pneumocystis infection. However, the presence of T and B cells lacking type I IFN signaling resulted in compensatory extramedullary hemopoiesis in the liver and spleen. Lymphocyte support of the regenerative capacity of the bone marrow was provided by both type I IFN-dependent and -independent mechanisms that acted synergistically. Our findings point to the requirement of both type I IFNs and lymphocytes in the regenerative capabilities of the hemopoietic system under the pressure of Pneumocystis infection, but not during steady-state hemopoiesis. This may have implications in the management of pancytopenia in AIDS.

The use of an insuflon device for the administration of G-CSF in pediatric cancer patients

In pediatric oncology, granulocyte colony-stimulating factor (G-CSF) is applied with the aim of shortening neutropenic periods after chemotherapy and for mobilization of peripheral blood stem cells for apheresis procedures. G-CSF is administered, subcutaneously or intravenously, on a daily basis. An insuflon device for the administration of G-CSF was used in 29 patients for 93 G-CSF periods. Retrospective evaluation shows that this administration route is feasible, safe and preferred by young children rather than by teenagers with cancer.

Five years of experience with hydroxyurea in children and young adults with sickle cell disease

The short-term beneficial effect of hydroxyurea (HU) in sickle cell disease (SCD) has been proven by randomized studies in children and adults. The Belgian registry of HU-treated SCD patients was created to evaluate its long-term efficacy and toxicity. The median follow-up of the 93 patients registered is 3.5 years; clinical and laboratory data have been obtained for 82 patients at 1 year, 61 at 2 years, 44 at 3 years, 33 at 4 years, and 22 after 5 years. On HU, the number of hospitalizations and days hospitalized dropped significantly. Analysis of the 22 patients with a minimum of 5 years of follow-up confirm a significant difference in the number of hospitalizations (P =.0002) and days in the hospital (P <.01), throughout the treatment when compared to prior to HU therapy. The probabilities of not experiencing any event or any vaso-occlusive crisis requiring hospitalization during the 5 years of treatment were, respectively, 47% and 55%. On HU, the rate per 100 patient-years of severe events was estimated to be 3.5% for acute chest syndrome, 1.2% for aplastic crisis, 0.4% for splenic sequestration; it was 0% for the 9 patients with a history of stroke or transient ischemic attack followed for an average of 4 years. No important adverse effect occurred. Long-term chronic treatment with HU for patients with SCD appears feasible, effective, and devoid of any major toxicity; in patients with a history of stroke, HU may be a valid alternative to chronic transfusion support. (Blood. 2001;97:3628-3632)

Granulocyte colony-stimulating factor given to donors before apheresis does not prevent aplasia in patients treated with donor leukocyte infusion for recurrent chronic myeloid leukemia after bone marrow transplantation

We conducted 2 sequential studies of donor leukocyte infusion (DLI) in 26 patients with chronic myeloid leukemia in hematologic relapse after unmodified allogeneic bone marrow transplantation. In the first study, cells for DLI were collected from 13 donors who were not treated with granulocyte colony-stimulating factor (G-CSF) (group 1). In the second study, cells were collected from 13 donors who received G-CSF before apheresis (group 2) in an attempt to avoid aplasia after DLI. Patients in group 2 received 550-fold more CD34+ cells than those in group 1. We found no significant difference in the incidence (31% versus 22%), onset time (41 vs. 48 days), or duration (15 vs. 14 days) of cytopenia after DLI in the 2 groups. G-CSF given to donors before collection of cells did not prevent aplasia. These findings support the hypothesis that the pathogenesis of aplasia after DLI is not restricted to the destruction of recipient hematopoietic cells but also involves failure of donor hematopoiesis by undefined mechanisms.

Bone marrow stem cell protection from chemotherapy by low--molecular-weight compounds

The stem cells of the bone marrow have the capacity for both self-renewal and derivation of all the blood cell lineages. Consequently, toxicity to these cells can result in neutropenia, agranulocytosis, thrombocytopenia, pancytopenia, or aplastic anemia. Many anticancer drugs adversely affect the bone marrow, and neutropenia is a common limiting factor in dose escalation. In this review, we discuss agents that appear to have potential as bone marrow sparing agents. Computerized catalogs of the National Library of Medicine and Medline were searched for reports on low-molecular-weight compounds that detailed effects on the hematopoietic progenitor cells. The most promising agents are the endogenous peptides p-glutamic acid-glutamic acid-aspartic acid-cysteine-lysine and acetyl-serine-aspartic acid-lysine-proline, and the exogenous compounds amifostine and ammonium trichloro[dioxoethylene-O,O']tellurate, but several others are also discussed. These compounds preserve stem cell function in the presence of antineoplastic drugs of diverse pharmacological classes, and they do so by various mechanisms of action. Their present status in clinical practice is also detailed. More needs to be learned about their mechanisms of action and therapeutic potential, but the results are encouraging for some of these compounds and more clinical trials should be expected.

[The development of immune-mediated aplastic anemia in mice can be blocked by cimetidine]

OBJECTIVE

To investigate the effect of H(2) receptor antagonist cimetidine on the development of immune-mediated aplastic anemia (AA) in mice.

METHODS

The immune-mediated aplastic anemia mice model was induced by irradiation and half-matched allogeneic lymphocytes transfusion (ALT). The mice were divided into 3 groups: the irradiation alone control group, the irradiation + ALT group (AA group) and the irradiation + ALT + cimetidine group. In cimetidine group, each mouse was intraperitoneally injected cimetidine at different doses once a day for 8 days. On day 14, the bone marrow histology was examined.

RESULTS

In 0.5 mg, 1.0 mg and 2.0 mg x (10g)(-1) x d(-1) cimetidine groups, the percentages of hematopoietic tissue volume in bone marrow were (46.58 +/- 20.41)%, (51.88 +/- 24.94)% and (59.12 +/- 32.48)%, respectively, and all much higher than that in AA group [(19.99 +/- 10.98)%, P < 0.01], but were not different from that in irradiated control group [(53.81 +/- 31.72)%, P > 0.05].

CONCLUSION

The development of immune-mediated aplastic anemia in irradiated mice by half-matched allogeneic lymphocytes transfusion was blocked by H(2) receptor antagonist cimetidine.

Monitoring patients taking oral carbonic anhydrase inhibitors

Although no prospective studies have been done and no recommendations can be reasonably evidenced based, we believe that our "alternative views" are reason-able, taking into account the serious nature of aplastic anemia and its more favorable prognosis when this disorder is treated early. Because aplastic anemia represents only about one half of possible CAl blood dyscrasias, early recognition of non-aplastic anemia dyscrasias alone Justifies hematologic screening.

[Detection of parvovirus B19 in patients of the Zulia State blood bank with different hematological alterations]

PURPOSE

To assess the seroprevalence of IgG and IgM specific for parvovirus B19 (B19) and its association with aplastic crisis developing in patients with different haematological disorders.

PATIENTS AND METHODS

Fifty-three serum samples were evaluated, 24 from patients with aplastic crisis and 29 from others without such crises, all of them suffering from different haematological diseases diagnosed at the University Hospital of Maracaibo and the Zulia State Blood Bank, in Venezuela; 15 samples from healthy blood donors were examined as well. Indirect immunofluorescence technique was used in the study. Lymphocyte subsets were quantified in 10 of the patients with aplastic crisis by means of cytofluorometry. Serum proteins were assessed by electrophoresis in all samples. The statistical analysis was performed according to Student's t test and chi square, by applying the statix 4.0 and SAS programmes.

RESULTS

Positive IgG was found in 20 of the 24 patients with aplastic crisis (83.3%), 20 of the 29 without crisis (68.9%) and 7 of the 15 healthy controls (46.6%). Positive IgM was found only in 2 of the 24 patients with aplastic crisis (8.3%). Both the patients without aplastic crises and the control groups were negative for PB19 IgM. The average CD4 and CD8 T lymphocyte count and the CD4-CD8 index in the patients studied were 454 CD4 cells/microL, 1,006 CD8 cells/microL and 0.5%, significantly different from the control group, whose figures were 860 CD4 cells/microL, 546 CD8 cells/microL and 1.6%. The average B lymphocyte count of the patients (628 cells/microL) was higher than that of the control group (349 cells/microL). The average NK cell count in the patient was 174 cells/microL, slightly below the control group (221 cells/microL). Mild beta-globulin decrease was found in the electrophoretic study of the serum proteins of the patients, along with significant increase of the total protein and the gammaglobulin fraction with regard to the control group.

CONCLUSIONS

Higher PB19 IgG seropositivity was seen in the patients with aplastic crisis with respect to the control group, suggesting wider exposition to the virus among them with regard to the healthy population. Specific PB19 IgM was detected in 2 patients with immunodeficiency and aplastic crisis. A significant decrease of the CD4 and CD8 T-lymphocyte subsets, along with decreased CD4-CD8 quotient, were found in the aplastic crisis group, and an impairment of the immune response to the viral challenge can be inferred form this. The alterations of the serum proteins, together with the increased B lymphocytes, might suggest a polyclonal activation of these cells. The absence of other known lymphotropic viruses in most of the patients studied (50) show that the alterations found here are related to recent or past B19 infection.

FLT-3 ligand provides hematopoietic protection from total body irradiation in rabbits

Several hematopoietic cytokines have been investigated for their potential to provide protection from the lethal consequences of bone marrow aplasia after total body irradiation (TBI). Some can increase the dose of irradiation tolerated by the animals; none allow endogenous recovery after doses such as administered in clinical blood or marrow transplantation. We tested the radioprotective potential of FLT-3 ligand, an early acting hematopoietic cytokine, alone and in combination with a late acting cytokine, granulocyte-colony stimulating factor (G-CSF). Adult outbred New Zealand White rabbits were submitted to TBI of 1,200 or 1,400 cGy by a Co60 source. Recombinant human (rh) FLT-3 ligand at a dose of 500 microg/kg and/or rhG-CSF at a dose of 10 microg/kg were administered for 14 days subcutaneously daily, beginning either 2 days before or the day after TBI. All control animals given no growth factors died of aplasia at day 10 (range, 5 to 16). All 8 animals given G-CSF had severe aplasia and 7 died at day 8 (range, 5 to 10); 1 animal survived, with G-CSF being administered before TBI. In contrast, 11 of 12 animals given FLT-3 ligand, with or without G-CSF, survived. Radioprotection was best in the group given FLT-3 ligand together with G-CSF before TBI. In these animals median platelet counts were never <10 x 10(9)/L and median white blood cell counts never <0.5 x 10(9)/L. These data show that hematopoietic recovery can occur after 1,400 cGy TBI in rabbits, if protected by FLT-3 ligand, and suggest a radioprotective clinical potential of this cytokine.

The new anticonvulsant drugs. Implications for avoidance of adverse effects

Several new antiepileptic drugs offer a worthwhile alternative when standard antiepileptic drugs have failed. Suggestions have been made to improve the risk-benefit ratio of the new antiepileptic agents. More specifically, vigabatrin, which is a very useful and well tolerated new antiepileptic drug for refractory partial epilepsy, should be started at a low dosage of 0.5 g/day with increments of 0.5 g/day every week. Daily dosages exceeding 3 g/day should be restricted to patients with improvement. If necessary, the daily dosage of vigabatrin should be withdrawn slowly, i.e. by not more than 1 g/week. Lamotrigine is also a beneficial new drug for refractory partial and generalized seizures. However, the drug is associated with rash. In patients also receiving valproic acid (sodium valproate) [which inhibits the metabolism of lamotrigine], the incidence of rash can be reduced by slow titration of 25mg every other day for the first week and 25mg per day for the second week. Rare hypersensitivity reactions, e.g. Stevens-Johnson syndrome, remain a problem. The risk-benefit ratio of felbamate has recently been compromised by fatal aplastic anaemia and fatal liver disease in a number of patients. In general, patients should be withdrawn from felbamate, if possible, until further clarification of its definitive risk-benefit ratio. Finally, gabapentin is a very safe add-on medication. Its remarkably low potential to cause adverse effects makes it a welcome addition for the treatment of refractory partial epilepsy.

Age-dependent amelioration of hypoplastic anemia in Ws/Ws rats with a small deletion at the kinase domain of c-kit

The white-spotting (Ws) locus of rats represents a 12-base deletion of the c-kit receptor tyrosine kinase. Homozygous Ws/Ws rats are deficient in melanocytes, mast cells, and erythrocytes. Although mice possessing two mutant alleles at the c-kit (W) locus, such as mice of W/Wv genotype, show severe anemia even in adult age, the anemia of Ws/Ws rats remarkably ameliorated with age. We investigated the mechanism of the age-dependent amelioration. Bone marrow cells of Ws/Ws rats did not form macroscopic colonies in the spleen of irradiated rats, and the concentration of burst-forming unit-erythroid in the marrow of Ws/Ws rats was comparable with that of +/+ rats. Therefore, the increase in morphologically identifiable erythroid precursors in the marrow of Ws/Ws rats was attributed to the increased concentration of colony-forming unit-erythroid (CFU-E). Furthermore, the increase in CFU-E appeared to result from the increased concentration of erythropoietin (EPO). Because injections of relatively low doses of EPO cured the slight anemia that remained in adult Ws/Ws rats, CFU-E and/or its immediate precursors of Ws/Ws rats appeared to be more sensitive to EPO than those of W/Wv mice, in which a huge dose of EPO was necessary to cure the anemia.

Drug-induced aplastic anemia: pathogenesis and clinical aspects

Drug-induced aplastic anemia is one of the few life-threatening reactions to drugs. Although the majority of reported cases have been associated with chloramphenicol, many drugs have the potential to be toxic to the bone marrow. There are two distinct types of toxicity with differing pathogenic mechanisms--a dose-related reversible marrow aplasia and a dose-independent idiosyncratic aplasia with a high mortality. These two forms of marrow suppression may be difficult to distinguish. The pathogenesis of idiosyncratic marrow aplasia is not well understood. Various studies have demonstrated biochemical, immune, pharmacokinetic, and genetic defects that could affect hematopoietic stem cells. The clinical significance of the reported experimental findings is not established. The prognosis of drug-induced aplastic anemia is similar to that of idiopathic aplastic anemia. Patients with this condition respond to bone marrow transplantation or immunosuppressive therapy in a manner similar to patients with idiopathic marrow aplasia. Many questions regarding drug-induced aplastic anemia remain to be answered; little progress has been made in the last decade.

Autologous bone marrow infusion following high dose chemotherapy of the canine transmissible venereal tumor (TVT)

The present study was undertaken to evaluate infusion of cryopreserved autologous bone marrow following supralethal chemotherapy in canines bearing a solid tumor thought to be moderately sensitive to cytotoxic agents. Initial studies in 5 dogs established a combination of busulfan (Bu) 3 mg/kg X 2 days and cyclophosphamide (Cy) 50 mg/kg on day 3 to produce bone marrow lethality within 14 days (high dose regime). Bu 1 mg/kg, Cy 20 mg/kg produced tolerable toxicity (low dose regime). Eight pairs of dogs were challenged with 3 X 10(8) transmissible venereal tumor cells. Measurable progressive tumor growth occurred in all instances. Marrow aspirated from the femoral shafts of the animals was cryopreserved in 10% DMSO. One dog of each pair received the high dose Bu + Cy regime followed in 30 h by marrow infusion and his partner received the low dose regime without marrow. Tumors were measured serially for at least 2 months. Infusion of marrow resulted in evidence of hematologic recovery within 2 weeks following the high dose regime. Tumor responses occurred in both groups when compared to 8 untreated tumor challenged controls. High dose animals had greater initial responses than low dosed dogs but long term responses were not significantly different. Eight dogs rechallenged with tumor cells after initial successful therapy failed to develop tumors. It was concluded that: a) cryopreserved autologous bone marrow infusion was effective in protecting tumor bearing canines from otherwise lethal chemotherapy; b) the transmissible venereal tumor of canines responded to both high and low dose regimes; c) the rescue of dogs by stored autologous marrow did not offer additional benefits in tumor control over a standard regime; d) chemotherapy treated dogs resisted tumor rechallenge. This model may offer a large animal system to study the autologous marrow rescue concept during controlled periods of tumor evolution.

Chrysotherapy-induced aplastic anemia: a case report

A case of gold-induced aplastic anemia occurring in a 58-year-old male with rheumatoid arthritis who received a total dose of 635 mg of gold sodium thiomalate over a 16-week period is reported. The clinical features, treatment, prevention and pathogenesis of gold-induced aplastic anemia are reviewed. The ability to predict patients in whom this hematologic effect may occur is discussed. Chrysotherapy is beneficial in the treatment of rheumatoid arthritis, but gold-induced aplastic anemia may be fatal. Absolute identification of patients at risk of having this hematologic side effect is not possible, but dosage reduction and intense monitoring of laboratory and clinical signs may prevent its occurrence.