Aging and amyloid β oligomers enhance TLR4 expression, LPS-induced Ca2+ responses, and neuron cell death in cultured rat hippocampal neurons

Abstract

BackgroundToll-like receptors (TLRs) are transmembrane pattern-recognition receptors of the innate immune system recognizing diverse pathogen-derived and tissue damage-related ligands. It has been suggested that TLR signaling contributes to the pathogenesis of age-related, neurodegenerative diseases, including Alzheimer’s disease (AD). AD is associated to oligomers of the amyloid β peptide (Aβo) that cause intracellular Ca2+ dishomeostasis and neuron cell death in rat hippocampal neurons. Here we assessed the interplay between inflammation and Aβo in long-term cultures of rat hippocampal neurons, an in vitro model of neuron aging and/or senescence.MethodsCa2+ imaging and immunofluorescence against annexin V and TLR4 were applied in short- and long-term cultures of rat hippocampal neurons to test the effects of TLR4-agonist LPS and Aβo on cytosolic [Ca2+] and on apoptosis as well as on expression of TLR4.ResultsLPS increases cytosolic [Ca2+] and promotes apoptosis in rat hippocampal neurons in long-term culture considered aged and/or senescent neurons, but not in short-term cultured neurons considered young neurons. TLR4 antagonist CAY10614 prevents both effects. TLR4 expression in rat hippocampal neurons is significantly larger in aged hippocampal cultures. Treatment of aged hippocampal cultures with Aβo increases TLR4 expression and enhances LPS-induced Ca2+ responses and neuron cell death.ConclusionsAging and amyloid β oligomers, the neurotoxin involved in Alzheimer’s disease, enhance TLR4 expression as well as LPS-induced Ca2+ responses and neuron cell death in rat hippocampal neurons aged in vitro.Electronic supplementary materialThe online version of this article (doi:10.1186/s12974-017-0802-0) contains supplementary material, which is available to authorized users.

The Nootropic Drug Α-Glyceryl-Phosphoryl-Ethanolamine Exerts Neuroprotective Effects in Human Hippocampal Cells

“…As a final step, the cytoprotective properties of the compound were tested in a model of aged neurons, i.e., adult hippocampal cells maintained for 21 DIV [25]. Moderate but detectable levels of common markers of DNA damage were found in these neuronal cells, thus confirming the validity of the cellular model.…”

“…As a final step, the putative cytoprotective properties of the compound were tested in a model of aged neurons. To mimic cellular aging, the hippocampal cells were maintained for 21 days in vitro (DIV) [25].…”

“…To establish the aging model, adult hippocampal neurons were maintained in culture for 21 DIV (days in vitro) [25,43]. Cells were cultured in the presence of PBS or GPE (5, 50, and 500 µM).…”

Acetylcholine suppresses microglial inflammatory response via αnAChR to protect hippocampal neurons

“…There is evidence to indicate LPS promotes rat hippocampal neuronal apoptosis by increasing cytosolic [Ca 2+ ] when neurons are cultured long-term (> 18 days, regarded as aged neurons), but does not exert an effect on short-term cultured neurons (< 9 days, regarded as young or mature neurone) (Calvo-Rodríguez et al, 2017). The preliminary data reported here shows that LPS has no significant detrimental effect on enriched seven-day-old hippocampal neurons in the absence of microglia, while it demonstrates that apoptosis of hippocampal neurons was elicited when LPS was applied to neuron-microglia co-cultures.…”

Autophagy and Cell Death in Alzheimer’s, Parkinson’s and Prion Diseases

“…The products of post-translational protein modifications in AD, PD and PrD favour apoptosis and necroptosis over AUT by (a) increasing the activation of apoptosis (e.g. by increasing MITO membrane permeability) and necroptosis, by chronic activation of TRL4 and TNFα receptors [216][217][218][219][220][221][222][223][224][225][226][227][228][229][230][231][232][233][234], (b) promoting moderate to high increases in cytosolic ROS concentrations and (c) attenuating AUT [42,62,[235][236][237][238][239][240]. In contrast to PD and AD, PrP SC -infected cells are more likely to respond with necroptosis and then apoptosis.…”