Abstract
BackgroundChronic neuroinflammation and calcium (Ca+2) dysregulation are both components of Alzheimer’s disease. Prolonged neuroinflammation produces elevation of pro-inflammatory cytokines and reactive oxygen species which can alter neuronal Ca+2 homeostasis via L-type voltage-dependent Ca+2 channels (L-VDCCs) and ryanodine receptors (RyRs). Chronic neuroinflammation also leads to deficits in spatial memory, which may be related to Ca+2 dysregulation.MethodsThe studies herein use an in vivo model of chronic neuroinflammation: rats were infused intraventricularly with a continuous small dose of lipopolysaccharide (LPS) or artificial cerebrospinal fluid (aCSF) for 28 days. The rats were treated with the L-VDCC antagonist nimodipine or the RyR antagonist dantrolene.ResultsLPS-infused rats had significant memory deficits in the Morris water maze, and this deficit was ameliorated by treatment with nimodipine. Synaptosomes from LPS-infused rats had increased Ca+2 uptake, which was reduced by a blockade of L-VDCCs either in vivo or ex vivo.ConclusionsTaken together, these data indicate that Ca+2 dysregulation during chronic neuroinflammation is partially dependent on increases in L-VDCC function. However, blockade of the RyRs also slightly improved spatial memory of the LPS-infused rats, demonstrating that other Ca+2 channels are dysregulated during chronic neuroinflammation. Ca+2-dependent immediate early gene expression was reduced in LPS-infused rats treated with dantrolene or nimodipine, indicating normalized synaptic function that may underlie improvements in spatial memory. Pro-inflammatory markers are also reduced in LPS-infused rats treated with either drug. Overall, these data suggest that Ca+2 dysregulation via L-VDCCs and RyRs play a crucial role in memory deficits resulting from chronic neuroinflammation.
Highlights
Chronic neuroinflammation is a component of normal aging and may contribute to age-related cognitive decline as well as neurodegenerative disorders such as Alzheimer’s disease (AD; [1])
These data indicate that LPS-induced spatial memory deficits in the Morris water maze (MWM) can be reversed by blockade of L-type voltage-dependent Ca+2 channels (L-VDCCs), while blockade of ryanodine receptors (RyRs) only confers a minor improvement
LPS + vehicle rats were significantly impaired compared to Blockade of L-VDCCs or RyRs during chronic neuroinflammation reduces aberrant expression of activity-regulated cytoskeletonassociated protein (Arc) Due to the spatial memory improvements we observed in LPS-infused rats treated with drugs that normalize or reduce intracellular Ca+2 concentration, we examined levels of the immediate early genes (IEGs) Arc, which is Ca+2 dependent
Summary
Chronic neuroinflammation is a component of normal aging and may contribute to age-related cognitive decline as well as neurodegenerative disorders such as Alzheimer’s disease (AD; [1]). Chronic neuroinflammation in young rats impairs performance in a variety of memory tasks [5] and such memory impairments are associated with long-term potentiation (LTP) deficits [6]. Epidemiological studies have shown that the use of L-type voltage-dependent. Chronic neuroinflammation and calcium (Ca+2) dysregulation are both components of Alzheimer’s disease. Prolonged neuroinflammation produces elevation of pro-inflammatory cytokines and reactive oxygen species which can alter neuronal Ca+2 homeostasis via L-type voltage-dependent Ca+2 channels (L-VDCCs) and ryanodine receptors (RyRs). Chronic neuroinflammation leads to deficits in spatial memory, which may be related to Ca+2 dysregulation
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