PubMed · 8908985
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A D Nieuw. 1996. Death.. https://pubmed.ncbi.nlm.nih.gov/8908985/
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In this report, we have tested the hypothesis that brain-derived neurotrophic factor (BDNF) is an anterograde neurotrophic factor in the CNS and have focused on central noradrenergic neurons that synthesize BDNF. Double-label immunocytochemistry for BDNF and dopamine-beta-hydroxylase (DBH), a marker for noradrenergic neurons, demonstrated that BDNF is partially localized to noradrenergic nerve fibers and terminals in the adult rat brain. To test the functional importance of this anterograde BDNF, we analyzed transgenic mice carrying a DBH-BDNF minigene. Increased synthesis of BDNF in noradrenergic neurons of DBH-BDNF mice caused elevated TrkB tyrosine kinase activation throughout postnatal life in the neocortex, a noradrenergic target region. This afferently regulated increase in TrkB receptor activity led to long-lasting alterations in cortical morphology. To determine whether noradrenergic neuron-expressed BDNF also anterogradely regulated neuronal survival, we examined a second noradrenergic target, neonatal facial motoneurons. One week after axotomy, 72% of facial motoneurons were lost in control animals, whereas only 30-35% were lost in DBH-BDNF transgenic mice. Altogether, these results indicate that BDNF is anterogradely transported to fibers and terminals of noradrenergic neurons, that anterogradely secreted BDNF causes activation of TrkB in target regions, and that this secretion has functional consequences for target neuron survival and differentiation. This presynaptic secretion of BDNF may provide a cellular mechanism for modulating neural circuitry, in either the developing or mature nervous system.
Several lines of evidence suggest that neurotrophin administration may be of some therapeutic benefit in the treatment of peripheral neuropathy. However, a third of sensory neurons do not express receptors for the neurotrophins. These neurons are of small diameter and can be identified by the binding of the lectin IB4 and the expression of the enzyme thiamine monophosphatase (TMP). Here we show that these neurons express the receptor components for glial-derived neurotrophic factor (GDNF) signaling (RET, GFRalpha-1, and GFRalpha-2). In lumbar dorsal root ganglia, virtually all IB4-labeled cells express RET mRNA, and the majority of these cells (79%) also express GFRalpha-1, GFRalpha-2, or GFRalpha-1 plus GFRalpha-2. GDNF, but not nerve growth factor (NGF), can prevent several axotomy-induced changes in these neurons, including the downregulation of IB4 binding, TMP activity, and somatostatin expression. GDNF also prevents the slowing of conduction velocity that normally occurs after axotomy in a population of small diameter DRG cells and the A-fiber sprouting into lamina II of the dorsal horn. GDNF therefore may be useful in the treatment of peripheral neuropathies and may protect peripheral neurons that are refractory to neurotrophin treatment.
The complete remission (CR) rate after intensive chemotherapy for acute myelogenous leukemia (AML) remains low in elderly patients, mainly because of a higher infectious mortality rate related to neutropenia and an increased incidence of adverse prognostic factors. Granulocyte-macrophage colony-stimulating factor (GM-CSF) has been shown to potentially recruit leukemic blasts into cell cycle and improve cytotoxic effects when given during chemotherapy, and to shorten the duration of neutropenia when administered after chemotherapy. Two hundred forty patients aged 55 to 75 years who had newly diagnosed AML were randomly assigned to receive placebo or Escherichia coli-derived GM-CSF (5 micrograms/kg/d by 6-hour intravenous infusion) starting during induction chemotherapy on day 1 and continued through and after chemotherapy until recovery of neutrophils, or evidence of regrowth of leukemia, or up to day 28. Induction chemotherapy consisted of idarubicin (8 mg/m2/d on days 1 to 5) and cytarabine (100 mg/m2/d on days 1 to 7). The study drug was not administered subsequent to the induction course. Patients who achieved a CR received continuous maintenance therapy for 1 year with four quarterly reinduction courses; in the 55- to 64-year age subgroup, patients were randomly assigned to receive or not a consolidation course before maintenance therapy. The CR rate was similar in the GM-CSF and placebo groups (63% and 60.5%, respectively; P = .79). The mortality, rate of resistant disease, and rate of regrowth of leukemia were also similar in both groups. The time to neutrophil recovery was shorter in patients who received GM-CSF (24 v 29 days; P = .0001), but the incidence and characteristics of infectious events were not different. The 2-year disease-free survival (DFS) rate was significantly improved in the GM-CSF group (48% v 21% in the placebo group; P = .003). This effect was highly significant in the cohort of patients aged 55 to 64, but only marginal in patients >/=65 years of age. There was a trend toward a longer overall survival (OS) in the GM-CSF group (P = .082). In summary, the administration of GM-CSF, concomitantly with chemotherapy and thereafter during induction course in AML, shortened the time to neutrophil recovery, but did not improve the CR rate in patients aged 55 to 75. Nonetheless, DFS and OS were significantly prolonged in patients aged 55 to 64 treated with GM-CSF. These results are promising and further evaluation of myeloid growth factors in AML is warranted.