![]() ![]() † p < 0.05 relative to PCB-95 alone.The growth of Ag dendrites induced by the Ag ion migration between Ag-4Pd alloy wire couples immersed in pure water under bias was observed, and its failure mode leading to a short circuit was investigated. * p < 0.05, and ** p < 0.01 relative to vehicle control. Transfection with the endogenous Wnt2 antagonist Wif blocked PCB-95 effects on dendritic length (–, without, +, with FLA365) ( F) and branching ( G) in 9-DIV hippocampal neurons co-transfected with MAP2B-EGFP (–, without, +, with Wif) (mean ± SE n = 30 neurons). ( E) PCB-95 increased Wnt2 mRNA in hippocampal neurons as determined by qPCR, and this effect was blocked by 10-µM FLA365 (mean ± SE n = 3 per condition). Expression of dnCREB or CREB shRNA inhibited PCB-95 effects on dendritic length ( C) and branching ( D) in 9-DIV hippocampal neurons co-transfected with MAP2B-EGFP (mean ± SE n = 30 neurons). ( B) Densitometry of blots probed for pCREB normalized to total CREB presented as percent of control (mean ± SE n = 3). ( A) Representative Western blot illustrating increased pCREB in hippocampal neurons (7 DIV) stimulated with BIC (20 µM, 30 min) or PCB-95 (200 nM). * p < 0.05 relative to vehicle control.ĬREB and Wnt2 activity are required for PCB-95–induced dendritic growth. Data are presented as mean ± SE ( n = 10–12 neurons from three independent dissections). Acute exposure to PCB-95 increased the frequency and amplitude of spontaneous Ca 2+ transients in soma and distal dendrites. Bar graphs at the right summarize Ca 2+ transient responses > 2× mean normalized to baseline fluorescence. ( C) 4CmC (100 µM) which activates RyR1 and RyR2, but not RyR3, was used to confirm the block of Ca 2+ channel activity. ![]() ![]() Neurons pretreated with ryanodine (500 µM, 1 hr) to block all RyR channel activity essentially negated the stimulatory actions of PCB-95 (lower two traces). ( B) Representative Ca 2+ transient activity captured from soma and distal dendrites of Fluo-4–loaded hippocampal neurons at 7 DIV before and after perfusion of PCB-95 (200 nM) (upper two traces). ( A) Representative Ca 2+ transient activity captured from soma and distal dendrites of Fluo-4–loaded hippocampal neurons at 7 DIV with perfusion of DMSO (0.01%) vehicle. Ryanodine blocks amplification of spontaneous Ca 2+ oscillations triggered by acute PCB-95 exposure. Our findings identify PCBs as candidate environmental risk factors for neurodevelopmental disorders, especially in children with heritable deficits in calcium signaling associated with autism. RyR activity contributes to dynamic remodeling of dendritic architecture in response to NDL PCBs via CaMKI-CREB-Wnt2 signaling in rats. Antagonism of γ-aminobutyric acid (GABA) receptors with bicuculline (BIC) phenocopied the dendrite-promoting effects of PCB-95, and pharmacological antagonism or siRNA knockdown of RyR blocked BIC-induced dendritic growth in dissociated and slice cultures of hippocampal neurons. Blocking CaMKK, CaMKIα/γ, MEK/ERK, CREB, or Wnt2 prevented PCB-95-induced dendritic growth. As determined by Western blotting and quantitative polymerase chain reaction, PCB-95 also activated CREB and up-regulated Wnt2. We tested the hypothesis that the CaMKI-CREB-Wnt2 signaling pathway couples NDL PCB-enhanced RyR activity to dendritic arborization.Ĭa(2+) imaging of dissociated cultures of primary rat hippocampal neurons indicated that PCB-95 (2,2',3,5'6-pentachlorobiphenyl a potent RyR potentiator), enhanced synchronized Ca(2+) oscillations in somata and dendrites that were blocked by ryanodine. RyRs regulate the spatiotemporal dynamics of intracellular Ca(2+) signals, but whether RyRs promote dendritic growth via modulation of this signaling pathway is not known. Activity-dependent dendritic growth, which is a critical determinant of neuronal connectivity in the developing brain, is mediated by calcium ion (Ca(2+))-dependent activation of Ca(2+)/calmodulin kinase-I (CaMKI), which triggers cAMP response element binding protein (CREB)-dependent Wnt2 transcription. Non-dioxin-like (NDL) polychlorinated biphenyls (PCBs) promote dendritic growth in hippocampal neurons via ryanodine receptor (RyR)-dependent mechanisms however, downstream signaling events that link enhanced RyR activity to dendritic growth are unknown. ![]()
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