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Hippocampal hyperphosphorylated tau-induced deficiency is rescued by L-type calcium channel blockade.

ABSTRACT: Aging and Alzheimer's disease are associated with chronic elevations in neuronal calcium influx via L-type calcium channels. The hippocampus, a primary memory encoding structure in the brain, is more vulnerable to calcium dysregulation in Alzheimer's disease. Recent research has suggested a link between L-type calcium channels and tau hyperphosphorylation. However, the precise mechanism of L-type calcium channel-mediated tau toxicity is not understood. In this study, we seeded a human tau pseudophosphorylated at 14 amino acid sites in rat hippocampal cornu ammonis 1 region to mimic soluble pretangle tau. Impaired spatial learning was observed in human tau pseudophosphorylated at 14 amino acid sites-infused rats as early as 1-3 months and worsened at 9-10 months post-infusion. Rats infused with wild-type human tau exhibited milder behavioural deficiency only at 9-10 months post-infusion. No tangles or plaques were observed in all time points examined in both human tau pseudophosphorylated at 14 amino acid sites and human tau-infused brains. However, human tau pseudophosphorylated at 14 amino acid sites-infused hippocampus exhibited a higher amount of tau phosphorylation at S262 and S356 than the human tau-infused rats at 3 months post-infusion, paralleling the behavioural deficiency observed in human tau pseudophosphorylated at 14 amino acid sites-infused rats. Neuroinflammation indexed by increased Iba1 in the cornu ammonis 1 was observed in human tau pseudophosphorylated at 14 amino acid sites-infused rats at 1-3 but not 9 months post-infusion. Spatial learning deficiency in human tau pseudophosphorylated at 14 amino acid sites-infused rats at 1-3 months post-infusion was paralleled by decreased neuronal excitability, impaired NMDA receptor-dependent long-term potentiation and augmented L-type calcium channel-dependent long-term potentiation at the cornu ammonis 1 synapses. L-type calcium channel expression was elevated in the soma of the cornu ammonis 1 neurons in human tau pseudophosphorylated at 14 amino acid sites-infused rats. Chronic L-type calcium channel blockade with nimodipine injections for 6 weeks normalized neuronal excitability and synaptic plasticity and rescued spatial learning deficiency in human tau pseudophosphorylated at 14 amino acid sites-infused rats. The early onset of L-type calcium channel-mediated pretangle tau pathology and rectification by nimodipine in our model have significant implications for preclinical Alzheimer's disease prevention and intervention.

SUBMITTER: Crossley CA

PROVIDER: S-EPMC10984573 | biostudies-literature | 2024

REPOSITORIES: biostudies-literature

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Hippocampal hyperphosphorylated tau-induced deficiency is rescued by L-type calcium channel blockade.

Crossley Chelsea A CA Omoluabi Tamunotonye T Torraville Sarah E SE Duraid Sarah S Maziar Aida A Hasan Zia Z Rajani Vishaal V Ando Kanae K Hell Johannes W JW Yuan Qi Q

Brain communications 20240320 2

Aging and Alzheimer's disease are associated with chronic elevations in neuronal calcium influx <i>via</i> L-type calcium channels. The hippocampus, a primary memory encoding structure in the brain, is more vulnerable to calcium dysregulation in Alzheimer's disease. Recent research has suggested a link between L-type calcium channels and tau hyperphosphorylation. However, the precise mechanism of L-type calcium channel-mediated tau toxicity is not understood. In this study, we seeded a human tau ...[more]

PMID: 38562310

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Project description:Objective: L-type calcium channels (LTCC) homeostatically regulate calcium on a beat by beat basis, but also provide Ca that over long time scales may contribute to transcriptional regulation. We previously showed that sustained LTCC blockade (CCB) elicits LTCC remodeling in ventricular cardiac myocytes (CM). Here we hypothesize that sustained CCB has broad effects on the expression of genes involved in calcium handling. Methods and Results: Therefore, we subjected adult mice to sustained CCB for 24 hours and performed gene expression profiling. In comparison to vehicle-only control animals, 231 genes were up-regulated, and 111 genes were down-regulated by sustained LTCC blockade (p <0.01). Gene ontology analysis suggested that the CaMKIIdelta signaling pathway was up-regulated in these cells. Unexpectedly, phosphorylation of phospholamban (PLN) at threonine17 (Thr17), an index of CaMKIIdelta activity, was not changed by sustained CCB; however, the degree of phosphorylation of the neighboring PLN-Ser16 substrate site for PKA was significantly reduced by sustained CCB compared to control. Gene expression profiling suggested no change in PKA, but it showed that protein phosphatase 2A (PP2A) mRNA increased, and immunoblots demonstrated that PP2Ac-alpha protein was significantly increased by sustained CCB. Consistent with elevated PP2Ac-alpha protein expression LTCC exhibited decreased phosphorylation of the C-terminal Ser1928 PKA substrate site. Conclusions: We conclude that sustained CCB elicits a spectrum of transcriptional events, including compensatory up-regulation of LTCC and PP2Ac-alpha. Although this study is restricted to mouse, these results suggest the new hypothesis that clinically-relevant sustained LTCC blockade in humans results in changes in gene regulation in the heart. Keywords: L-type calcium channel, calcium channel blockade, verapamil Female and male ICR mice (12-14 weeks age) weighing between 25 and 30 grams were anesthetized with a ketamine/xylazine mixture ( i.p.) allowing the subcutaneous implantation of miniosmotic pumps (Alzet, model 2001). The pumps were filled with either verapamil or vehicle (0.02% ascorbic acid). Control animals carried mini-pumps with vehicle and control animals were investigated in parallel with each set of experimental animals. Mini pumps delivered verapamil at 3.6 mg/kg/day for 24 (RNA)-48 (protein) hours. After treatment animals were anesthetized and weighed. Hearts were excised, rinsed, blotted dry, weighed, and then frozen on dry ice and the stored at -80oC until studied. Animals were anesthetized and euthanized according to animal protocols approved by the University of Kentucky Institutional Animal Care and Use Committee. This investigation conforms with the Guide for the Care and Use of Laboratory Animals published by the US National Institutes of Health (NIH Publication NO. 85-23, revised 1996). Left ventricular free wall from female mice was rapidly excised and either snap frozen at -80oC or used immediately for RNA isolation. Three VER treated mice and 3 vehicle treated mice were used to generate RNA for microarray. Total RNA was isolated using the RNAqueous -4PCR kit (Ambion) and quantitated spectrophotometrically at 260nm. Contaminating genomic DNA was eliminated by DNase treatment (Ambion). RNA quality was assessed using the Agilent 2100 Bioanalyzer. Microarray data was obtained using the Affymetrix 430 V2 GeneChip (representing 45,101 probe sets), in accordance with the manufacturer’s specifications.

Project description:PurposeHuman hypothalamic hamartomas (HHs) are associated with gelastic seizures, intrinsically epileptogenic, and notoriously refractory to medical therapy. We previously reported that the L-type calcium channel antagonist nifedipine blocks spontaneous firing and γ-aminobutyric acid (GABA)(A)-induced depolarization of single cells in HH tissue slices. In this study, we examined whether blocking L-type calcium channels attenuates emergent activity of HH neuronal networks.MethodsA high-density multielectrode array was used to record extracellular signals from surgically resected HH tissue slices. High-frequency oscillations (HFOs, ripples and fast ripples), field potentials, and multiunit activity (MUA) were studied (1) under normal and provoked [4-aminopyridine (4-AP)] conditions; and (2) following nifedipine treatment.Key findingsSpontaneous activity occurred during normal artificial cerebrospinal fluid (aCSF) conditions. Nifedipine reduced the total number and duration of HFOs, abolished the association of HFOs with field potentials, and increased the inter-HFO burst intervals. Notably, the number of active regions was decreased by 45 ± 9% (mean ± SEM) after nifedipine treatment. When considering electrodes that detected activity, nifedipine increased MUA in 58% of electrodes and reduced the number of field potentials in 67% of electrodes. Provocation with 4-AP increased the number of events and, as the number of electrodes that detected activity increased 248 ± 62%, promoted tissue-wide propagation of activity. During provocation with 4-AP, nifedipine effectively reduced HFOs, the association of HFOs with field potentials, field potentials, MUA, and the number of active regions, and limited propagation.SignificanceThis is the first study to report (1) the presence of HFOs in human subcortical epileptic brain tissue in vitro; (2) the modulation of "pathologic" high-frequency oscillations (i.e., fast ripples) in human epileptic tissue by L-type calcium channel blockers; and (3) the modulation of network physiology and synchrony of emergent activity in human epileptic tissue following blockade of L-type calcium channels. Attenuation of activity in HH tissue during normal and provoked conditions supports a potential therapeutic usefulness of L-type calcium channel blockers in epileptic patients with HH.

Dataset Information

Hippocampal hyperphosphorylated tau-induced deficiency is rescued by L-type calcium channel blockade.

Publications

Hippocampal hyperphosphorylated tau-induced deficiency is rescued by L-type calcium channel blockade.

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