title: Estrogen attenuates glutamate-induced cell death by inhibiting Ca2+ influx through L-type voltage-gated Ca2+ channels.
abstract: Estrogen-mediated neuroprotection is observed in neurodegenerative disease and neurotrauma models; however, determining a mechanism for these effects has been difficult. We propose that estrogen may limit cell death in the nervous system tissue by inhibiting increases in intracellular free Ca(2+). Here, we present data using VSC 4.1 cell line, a ventral spinal motoneuron and neuroblastoma hybrid cell line. Treatment with 1 mM glutamate for 24 h induced apoptosis. When cells were pre-treated with 100 nM 17beta-estradiol (estrogen) for 1 h and then co-treated with glutamate, apoptotic death was significantly attenuated. Estrogen also prevented glutamate-mediated changes in resting membrane potential and membrane capacitance. Treatment with either 17 alpha-estradiol or cell impermeable estrogen did not mimic the findings seen with estrogen. Glutamate treatment significantly increased both intracellular free Ca(2+) and the activities of downstream proteases such as calpain and caspase-3. Estrogen attenuated both the increases in intracellular free Ca(2+) and protease activities. In order to determine the pathway responsible for estrogen-mediated inhibition of these increases in intracellular free Ca(2+), cells were treated with several Ca(2+) entry inhibitors, but only the L-type Ca(2+) channel blocker nifedipine demonstrated cytoprotective effects comparable to estrogen. To expand these findings, cells were treated with the L-type Ca(2+) channel agonist FPL 64176, which increased both cell death and intracellular free Ca(2+), and estrogen inhibited both effects. From these observations, we conclude that estrogen limits glutamate-induced cell death in VSC 4.1 cells through effects on L-type Ca(2+) channels, inhibiting Ca(2+) influx as well as activation of the pro-apoptotic proteases calpain and caspase-3.
authors.affiliation: Division of Neurology, Department of Neurosciences, Medical University of South Carolina, 96 Jonathan Lucas Street, Charleston, SC 29425, USA.
authors.forename: Eric A
authors.initials: EA
authors.lastname: Sribnick
authors.forename: Angelo M
authors.initials: AM
authors.lastname: Del Re
authors.forename: Swapan K
authors.initials: SK
authors.lastname: Ray
authors.forename: John J
authors.initials: JJ
authors.lastname: Woodward
authors.forename: Naren L
authors.initials: NL
authors.lastname: Banik
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002118:Calcium / Q000378:metabolism*; D002120:Calcium Channel Agonists / Q000008:administration & dosage; D020746:Calcium Channels, L-Type / Q000378:metabolism*; D002154:Calpain / Q000378:metabolism; D053148:Caspase 3 / Q000378:metabolism; D002460:Cell Line; D002468:Cell Physiological Phenomena / Q000187:drug effects; D025802:Electric Capacitance; D004958:Estradiol / Q000008:administration & dosage; D004967:Estrogens / Q000008:administration & dosage*; D018698:Glutamic Acid / Q000633:toxicity*; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D018696:Neuroprotective Agents / Q000008:administration & dosage*; D011758:Pyrroles / Q000008:administration & dosage; D051381:Rats
chemical_list: D002120:Calcium Channel Agonists; D020746:Calcium Channels, L-Type; D004967:Estrogens; D018696:Neuroprotective Agents; D011758:Pyrroles; C071658:FPL 64176; D018698:Glutamic Acid; D004958:Estradiol; D002154:Calpain; D053148:Caspase 3; D002118:Calcium