Inositol 1,4,5-triphosphate receptor-sensitive Ca(2+) release, store-operated Ca(2+) entry, and cAMP responsive element binding protein phosphorylation in developing cortical cells following exposure to polychlorinated biphenyls.
The present study assessed intracellular Ca(2+) signaling pathways sensitive to polychlorinated biphenyls (PCBs), xenobiotics that perturb neural development and plasticity. Mobilization of intracellular Ca(2+) stores after acute exposure to a PCB mixture, Aroclor 1254 (A1254), as well as selected PCB congeners, was studied in P0 rat cortical neuronal culture using fluorescence microscopy. Ca(2+) responses to A1254 progressed from a transient intracellular Ca(2+) increase (lasting 3--5 min) at 1 to 2 microM (0.3-0.6 ppm) to a Ca(2+) transient with store-operated Ca(2+) influx and later disturbances of basal Ca(2+) concentration; this latter pattern occurred more often with 10 to 20 microM (3--6 ppm) A1254. Thapsigargin, xestospongin C, and carbachol/Ca(2+)-free buffer blocked significantly the PCB-induced Ca(2+) transient, whereas both ryanodine (to deplete ryanodine-sensitive stores) and the L-type Ca(2+) channel blocker nifedipine were without effect on the A1254 initial Ca(2+) transient. Both thapsigargin and xestospongin also blocked latent elevations (at 0.5 h) in Ca(2+), disturbances that depend upon extracellular Ca(2+) entry via ion channels. Two possible consequences were explored. Phosphorylation of cAMP responsive element binding protein, a Ca(2+)-activated nuclear transcription factor (CREB), occurred in an A1254 concentration-dependent manner and persisted at least 1 h. Cell viability following a 24-h exposure to A1254 (2-20 microM) was decreased at 20 microM, but only in cells cultured >6 days. This cell death did not occur via an apoptotic mechanism. These results indicate that Ca(2+) disturbances following PCB exposure are associated with 1) discrete alterations in IP(3) receptor-mediated signals and 2) activation of downstream events that impact developing cortical cells.
Inglefield
J R
JR
Neurotoxicology Division, National Health and Environmental Effects Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, USA.
Mundy
W R
WR
Shafer
T J
TJ
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects*; D020013:Calcium Signaling / Q000187:drug effects*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D003593:Cytoplasm / Q000187:drug effects / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D053496:Inositol 1,4,5-Trisphosphate Receptors; D019579:Neocortex / Q000166:cytology / Q000254:growth & development / Q000378:metabolism*; D010766:Phosphorylation; D011078:Polychlorinated Biphenyls / Q000494:pharmacology*; D051381:Rats; D018160:Receptors, Cytoplasmic and Nuclear / Q000187:drug effects*
D015220:Calcium Channels; D017362:Cyclic AMP Response Element-Binding Protein; D053496:Inositol 1,4,5-Trisphosphate Receptors; D018160:Receptors, Cytoplasmic and Nuclear; D011078:Polychlorinated Biphenyls; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases; D002118:Calcium