Nitric oxide signaling is recruited as a compensatory mechanism for sustaining synaptic plasticity in Alzheimer's disease mice.
Synaptic plasticity deficits are increasingly recognized as causing the memory impairments which define Alzheimer's disease (AD). In AD mouse models, evidence of abnormal synaptic function is present before the onset of cognitive deficits, and presents as increased synaptic depression revealed only when synaptic homeostasis is challenged, such as with suppression of ryanodine receptor (RyR)-evoked calcium signaling. Otherwise, at early disease stages, the synaptic physiology phenotype appears normal. This suggests compensatory mechanisms are recruited to maintain a functionally normal net output of the hippocampal circuit. A candidate calcium-regulated synaptic modulator is nitric oxide (NO), which acts presynaptically to boost vesicle release and glutamatergic transmission. Here we tested whether there is a feedforward cycle between the increased RyR calcium release seen in presymptomatic AD mice and aberrant NO signaling which augments synaptic plasticity. Using a combination of electrophysiological approaches, two-photon calcium imaging, and protein biochemistry in hippocampal tissue from presymptomatic 3xTg-AD and NonTg mice, we show that blocking NO synthesis results in markedly augmented synaptic depression mediated through presynaptic mechanisms in 3xTg-AD mice. Additionally, blocking NO reduces the augmented synaptically evoked dendritic calcium release mediated by enhanced RyR calcium release. This is accompanied by increased nNOS levels in the AD mice and is reversed upon normalization of RyR-evoked calcium release with chronic dantrolene treatment. Thus, recruitment of NO is serving a compensatory role to boost synaptic transmission and plasticity during early AD stages. However, NO's dual role in neuroprotection and neurodegeneration may convert to maladaptive functions as the disease progresses.
Department of Neuroscience, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois 60064.
Shreaya
S
Chakroborty
University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15216, and.
Joyce
J
Kim
University of Pittsburgh, Department of Neuroscience, Pittsburgh, Pennsylvania 15260.
Corinne
C
Schneider
Department of Neuroscience, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois 60064.
Anthony R
AR
West
Department of Neuroscience, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois 60064, grace.stutzmann@rosalindfranklin.edu.
Grace E
GE
Stutzmann
D000544:Alzheimer Disease / Q000473:pathology*; D016564:Amyloid beta-Protein Precursor / Q000235:genetics; D000818:Animals; D004195:Disease Models, Animal; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000235:genetics / Q000502:physiology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000235:genetics*; D006624:Hippocampus / Q000473:pathology / Q000503:physiopathology; D006801:Humans; D066298:In Vitro Techniques; D051379:Mice; D008822:Mice, Transgenic; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009473:Neuronal Plasticity / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D009569:Nitric Oxide / Q000378:metabolism*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D053764:Presenilin-1 / Q000235:genetics; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism; D026423:S-Nitroso-N-Acetylpenicillamine / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D016875:tau Proteins / Q000235:genetics
D016564:Amyloid beta-Protein Precursor; D004791:Enzyme Inhibitors; D020030:Nitric Oxide Donors; C508853:PSEN1 protein, human; D053764:Presenilin-1; D019837:Ryanodine Receptor Calcium Release Channel; D016875:tau Proteins; D009569:Nitric Oxide; D026423:S-Nitroso-N-Acetylpenicillamine; D019331:NG-Nitroarginine Methyl Ester
calcium; homeostasis; nitric oxide; ryanodine receptor; synaptic depression; synaptic plasticity