Aplastic anemia: recent advances in pathogenesis and treatment

Review of lithium effects on brain and blood

Clinicians have long used lithium to treat manic depression. They have also observed that lithium causes granulocytosis and lymphopenia while it enhances immunological activities of monocytes and lymphocytes. In fact, clinicians have long used lithium to treat granulocytopenia resulting from radiation and chemotherapy, to boost immunoglobulins after vaccination, and to enhance natural killer activity. Recent studies revealed a mechanism that ties together these disparate effects of lithium. Lithium acts through multiple pathways to inhibit glycogen synthetase kinase-3beta (GSK3 beta). This enzyme phosphorylates and inhibits nuclear factors that turn on cell growth and protection programs, including the nuclear factor of activated T cells (NFAT) and WNT/beta-catenin. In animals, lithium upregulates neurotrophins, including brain-derived neurotrophic factor (BDNF), nerve growth factor, neurotrophin-3 (NT3), as well as receptors to these growth factors in brain. Lithium also stimulates proliferation of stem cells, including bone marrow and neural stem cells in the subventricular zone, striatum, and forebrain. The stimulation of endogenous neural stem cells may explain why lithium increases brain cell density and volume in patients with bipolar disorders. Lithium also increases brain concentrations of the neuronal markers n-acetyl-aspartate and myoinositol. Lithium also remarkably protects neurons against glutamate, seizures, and apoptosis due to a wide variety of neurotoxins. The effective dose range for lithium is 0.6-1.0 mM in serum and >1.5 mM may be toxic. Serum lithium levels of 1.5-2.0 mM may have mild and reversible toxic effects on kidney, liver, heart, and glands. Serum levels of >2 mM may be associated with neurological symptoms, including cerebellar dysfunction. Prolonged lithium intoxication >2 mM can cause permanent brain damage. Lithium has low mutagenic and carcinogenic risk. Lithium is still the most effective therapy for depression. It "cures" a third of the patients with manic depression, improves the lives of about a third, and is ineffective in about a third. Recent studies suggest that some anticonvulsants (i.e., valproate, carbamapazine, and lamotrigene) may be useful in patients that do not respond to lithium. Lithium has been reported to be beneficial in animal models of brain injury, stroke, Alzheimer's, Huntington's, and Parkinson's diseases, amyotrophic lateral sclerosis (ALS), spinal cord injury, and other conditions. Clinical trials assessing the effects of lithium are under way. A recent clinical trial suggests that lithium stops the progression of ALS.

Pathogenic and host range determinants of the feline aplastic anemia retrovirus

Feline leukemia virus (FeLV) C-Sarma (or FSC) is a prototype of subgroup C FeLVs, which induce fatal aplastic anemia in outbred specific-pathogen-free (SPF) cats. FeLV C isolates also possess an extended host range in vitro, including an ability, unique among FeLVs, to replicate in guinea pig cells. To identify the viral determinants responsible for the pathogenicity and host range of FSC we constructed a series of proviral DNAs by exchanging gene fragments between FSC and FeLV-61E (or F6A), the latter of which is minimally pathogenic and whose host range in vitro is restricted to feline cells. Transfer of an 886-base-pair (bp) fragment of FSC, encompassing the codons for 73 amino acids at the 3' end of pol (the integrase/endonuclease gene) and the codons for 241 amino acids of the N-terminal portion of env [the extracellular glycoprotein (gp70) gene], into the F6A genome was sufficient to confer onto chimeric viruses the ability to induce fatal aplastic anemia in SPF cats. In contrast, no chimera lacking this sequence induced disease. When assayed in vitro, all chimeric viruses containing the 886-bp fragment of FSC acquired the ability to replicate in heterologous cells, including dog and guinea pig cells. Thus, the pathogenic and the host range determinants of the feline aplastic anemia retrovirus colocalize to a 3' pol-5' env region of the FSC genome and likely reside within a region encoding 241 amino acid residues of the N terminus of the extracellular glycoprotein.

Effect of androgens on the response to antithymocyte globulin in patients with aplastic anaemia

30 patients with aplastic anaemia (18/30 with severe aplastic anaemia) were prospectively randomized to be treated with 100 mg/kg ATG with or without the oral androgen Methenolone (3 mg/kg). 15 of 30 patients responded. Among the 15 patients receiving ATG plus androgen, 11 patients (73%) responded, including 8 complete and 3 partial responses. 4 of the 15 patients (31%) receiving ATG only responded, including 2 complete and 2 partial responses. The difference in response rate was statistically significant (p = 0.01). The survival rate in the total population of 30 patients was 64%. The survival rate in the group receiving ATG plus androgen was 87%; in the group receiving ATG only it was 43%. The difference in survival rates between both groups did not reach statistical significance (p = 0.15). Toxicity of ATG and androgens was considerable but manageable. These data support the result of the recent European reevaluation of a large pool of patients by the EBMT (39), that androgens in addition to ATG increase survival in patients with aplastic anaemia. They are, however, in contradiction to a controlled American study showing no benefit of a combined treatment with androgens as compared to ATG only. Further controlled studies on a larger number of patients are indicated to determine the therapeutic efficacy of androgens in addition to immunosuppression in aplastic anaemia.

Bone biopsy in haematological disorders

Bone marrow biopsies are now widely used in the investigation and follow-up of many diseases. Semi-thin sections of 8216 undecalcified biopsies of patients with haematological disorders were studied. Observations were made on the cytopenias and the myelodysplastic syndromes, the acute leukaemias the myeloproliferative disorders, Hodgkin's disease and the malignant lymphomas including multiple myeloma, hairy cell leukaemia and angioimmunoblastic lymphadenopathy. Bone marrow biopsies are essential for the differential diagnosis of most cytopenias and for the early recognition of fibrosis which most frequently occurred as a consequence of megakaryocytic proliferation in the myeloproliferative disorders. Different patterns of bone marrow involvement were found in the lymphoproliferative disorders and both their type and extent constituted factors of prognostic significance. A survey of the literature is given and the conclusion is drawn that bone marrow biopsies provide indispensible information for the diagnostic evaluation and the follow-up of patients with haematological disorders.