title: Impact of progestins on estrogen-induced neuroprotection: synergy by progesterone and 19-norprogesterone and antagonism by medroxyprogesterone acetate.
abstract: Estrogen replacement therapy is associated with improvement of cognitive deficits and reduced incidence of Alzheimer's disease. To compare the impact of therapeutically relevant progestins on estrogen-induced neuroprotection, we treated primary hippocampal neuron cultures with 17beta-E2 and progestin, alone and in combination, 48 h before glutamate insult. Estrogen, progesterone, and 19-norprogesterone, alone or in combination, protected against glutamate toxicity. In contrast, medroxyprogesterone acetate (MPA) failed to protect against glutamate toxicity. Not only was MPA an ineffective neuroprotectant but it attenuated the estrogen- induced neuroprotection when coadministered. We addressed the role of MAPK activation in neuroprotection by ovarian steroids. Estrogen and all three progestins tested, alone or in combination, activated MAPK, indicating another mechanism of protection. Bcl-2 expression has been shown to prevent cell death and is up-regulated by 17beta-E2. Progesterone and 19-norprogesterone, alone or in combination with estrogen, increased Bcl-2 expression. In contrast, MPA blocked estrogen-induced Bcl-2 expression when coadministered. These results may have important implications for the effective use of hormone replacement therapy in the maintenance of neuronal function during menopause and aging and for protection against neurodegenerative diseases such as Alzheimer's disease.
authors.affiliation: Department of Molecular Pharmacology and Toxicology, Pharmaceutical Sciences Center, University of Southern California, Los Angeles, CA 90033, USA. rbrinton@hsc.usc.edu
authors.forename: Jon
authors.initials: J
authors.lastname: Nilsen
authors.forename: Roberta Diaz
authors.initials: RD
authors.lastname: Brinton
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology; D002478:Cells, Cultured; D004357:Drug Synergism; D004789:Enzyme Activation / Q000187:drug effects; D004958:Estradiol / Q000494:pharmacology*; D018698:Glutamic Acid / Q000494:pharmacology; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects*; D017258:Medroxyprogesterone Acetate / Q000494:pharmacology*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009474:Neurons / Q000187:drug effects; D018696:Neuroprotective Agents / Q000494:pharmacology*; D009498:Neurotoxins / Q000494:pharmacology; D009653:Norprogesterones / Q000494:pharmacology*; D011374:Progesterone / Q000494:pharmacology*; D045167:Progesterone Congeners / Q000494:pharmacology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D018696:Neuroprotective Agents; D009498:Neurotoxins; D009653:Norprogesterones; D045167:Progesterone Congeners; D019253:Proto-Oncogene Proteins c-bcl-2; C030703:19-norprogesterone; D018698:Glutamic Acid; D011374:Progesterone; D004958:Estradiol; D017258:Medroxyprogesterone Acetate; D020928:Mitogen-Activated Protein Kinases