ABSTRACT
The ability of astrocytes to mediate 17beta-estradiol neuroprotection of spinal motoneurons challenged with AMPA has been evaluated in a co-culture system in which pure motoneurons were pulsed with 20 microM AMPA and then transferred onto an astrocyte layer pretreated for 24 h with 10 nM 17beta-estradiol. Under these conditions, AMPA toxicity was reverted, an effect that was likely related to increased production and release of GDNF, as shown by RT-PCR, Western blot analysis and ELISA assay. In addition, treatment with GDNF during the 24 h that followed the AMPA pulse produced a similar neuroprotective effect, whereas addition of a neutralizing anti-GDNF antibody prevented neuroprotection. These data suggest a role for astrocytes in the neuroprotective effect of 17beta-estradiol against spinal motoneuron death and find strong support in the marked up-regulation of estrogen receptor alpha found in spinal astrocytes of amyotrophic lateral sclerosis patients.
Subject(s)
Amyotrophic Lateral Sclerosis/metabolism , Anterior Horn Cells/metabolism , Astrocytes/metabolism , Estradiol/metabolism , Nerve Degeneration/metabolism , Neuroprotective Agents/metabolism , Adult , Aged , Aged, 80 and over , Amyotrophic Lateral Sclerosis/physiopathology , Animals , Animals, Newborn , Anterior Horn Cells/drug effects , Anterior Horn Cells/pathology , Antibodies/pharmacology , Astrocytes/drug effects , Cell Death/drug effects , Cell Death/physiology , Cell Survival/drug effects , Cell Survival/physiology , Cells, Cultured , Estradiol/pharmacology , Estrogen Receptor alpha/metabolism , Glial Cell Line-Derived Neurotrophic Factor/antagonists & inhibitors , Glial Cell Line-Derived Neurotrophic Factor/metabolism , Humans , Middle Aged , Nerve Degeneration/chemically induced , Nerve Degeneration/drug therapy , Neuroprotective Agents/pharmacology , Neurotoxins/antagonists & inhibitors , Neurotoxins/toxicity , Rats , Rats, Sprague-Dawley , Sex Factors , alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid/antagonists & inhibitors , alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid/toxicityABSTRACT
Primary cultures of rat cortical neurons exposed to toxic concentrations of beta-amyloid peptide (betaAP) begin an unscheduled mitotic cell cycle that does not progress beyond the S phase. To analyze possible signal transduction pathways involved in this effect, the action of betaAP has been studied in SH-SY5Y neuroblastoma cells differentiated by a 7-d exposure to 10 microM retinoic acid. Treatment with the betaAP fragment, betaAP(25-35), (25 microM) for 24, 48, or 72 h caused apoptotic cell death, detected by flow cytometry as a prediploid cell population. Cell cycle analysis showed that betaAP(25-35) modified cell cycle profiles by markedly increasing the number of cells in the S phase and reducing the population of the G2/M area. These effects seem to involve activation of mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK1/2). Inhibition of this pathway by the specific inhibitor PD98059 (2 microM) completely prevented changes of cell cycle distribution induced by betaAP and significantly reduced neuronal death. The data suggest that MAPK cascade can mediate the induction of cell cycle induced by betaAP, thus contributing to the toxicity of the peptide.
