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- Hammoud, Hayma, et al.
(författare)
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Insulin differentially modulates GABA signalling in hippocampal neurons and, in an age-dependent manner, normalizes GABA-activated currents in the tg-APPSwe mouse model of Alzheimer's disease
- 2021
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Ingår i: Acta Physiologica. - : John Wiley & Sons. - 1748-1708 .- 1748-1716. ; 232:2
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Tidskriftsartikel (refereegranskat)abstract
- AimWe examined if tonic γ‐aminobutyric acid (GABA)‐activated currents in primary hippocampal neurons were modulated by insulin in wild‐type and tg‐APPSwe mice, an Alzheimer’s disease (AD) model.MethodsGABA‐activated currents were recorded in dentate gyrus (DG) granule cells and CA3 pyramidal neurons in hippocampal brain slices, from 8‐10 weeks old (young) wild‐type mice and in dorsal DG granule cells in adult, 5‐6 and 10‐12 (aged) months old wild‐type and tg‐APPSwe mice, in the absence or presence of insulin, by whole‐cell patch‐clamp electrophysiology.ResultsIn young mice, insulin (1 nM) enhanced the total spontaneous inhibitory postsynaptic current (sIPSCT) density in both dorsal and ventral DG granule cells. The extrasynaptic current density was only increased by insulin in dorsal CA3 pyramidal neurons. In absence of action potentials, insulin enhanced DG granule cells and dorsal CA3 pyramidal neurons miniature IPSCT (mIPSCT) frequency, consistent with insulin regulation of presynaptic GABA release. sIPSCT densities in DG granule cells were similar in wild‐type and tg‐APPSwe mice at 5‐6 months but significantly decreased in aged tg‐APPSwe mice where insulin normalized currents to wild‐type levels. The extrasynaptic current density was increased in tg‐APPSwe mice relative to wild‐type littermates but, only in aged tg‐APPSwe mice did insulin decrease and normalize the current.ConclusionInsulin effects on GABA signalling in hippocampal neurons are selective while multifaceted and context‐based. Not only is the response to insulin related to cell‐type, hippocampal axis‐location, age of animals and disease but also to the subtype of neuronal inhibition involved, synaptic or extrasynaptic GABAA receptors‐activated currents.
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| 3. |
- Hammoud, Hayma
(författare)
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Insulin promotes GABA signalling modulation in both the mouse hippocampus and human CD4+ T cells
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Gamma-aminobutyric acid (GABA) is the most common inhibitory neurotransmitter in the adult mammalian brain, where it mediates several biological functions. Rapid inhibition is predominantly mediated by the activation of GABA-A receptors that are ubiquitously expressed across the central nervous system in a cell-, circuit-, or region-specific manner. This work contains four studies where GABA signalling and the modulatory effects of insulin are examined.In paper I, we used the patch-clamp technique to record synaptic and extrasynaptic GABA-A receptor-activated tonic currents from the granule cells of the dentate gyrus (DG) and CA3 pyramidal neurons along the dorsoventral axis of the mouse hippocampus. The results suggested cell type-specific variations in the inhibitory tone along the longitudinal hippocampal axis. In paper II, we analyzed both cell types in the mouse hippocampus and aimed to determine the effects of insulin on GABA signalling along the dorsoventral axis in the wild-type and Alzheimer’s disease animal model, tg-APPSwe mice. Physiological concentration of insulin modulated GABAergic synaptic and extrasynaptic tonic currents based on neuronal subtype and position along the axis in young wild-type mice. Furthermore, insulin normalized GABA-activated currents in aged tg-APPSwe mice to levels similar to those recorded in wild-type mice.In addition to the brain, GABA is present in blood and acts as a signalling molecule in immune cells. We show in paper III that GABA modulated cytokine release and the proliferation of activated CD4+ T cells isolated from normal individuals. These effects were differentially regulated by extracellular glucose concentration; the effects decreased as extracellular glucose concentration increased. GABA also modulated the expression of several genes and metabolism-related proteins in activated CD4+ T cells. Furthermore, insulin treatment increased the expression of the rho2 subunit of GABA-A receptors in activated CD4+ T cells and further enhanced the GABA effects. In paper IV, we observed that GABA inhibited the proliferation and altered cytokine release in a glucose concentration-dependent manner in activated CD4+ T cells isolated from type I diabetic patients. The findings of papers III and IV indicated a subset of samples called “non-responders”, wherein GABA did not affect the proliferation of activated CD4+ T cells but increased the release of a number of cytokines.The findings in my thesis increase the understanding of the modulatory effects of insulin on GABA signalling when GABA functions as a neurotransmitter and as an immunoregulatory molecule.
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- Jin, Zhe, et al.
(författare)
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GABA-mediated inhibition of human CD4+ T cell functions is enhanced by insulin but impaired by high glucose levels.
- 2024
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Ingår i: EBioMedicine. - 2352-3964. ; 105, s. 105217-
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: γ-aminobutyric acid (GABA), known as the main inhibitory neurotransmitter in the brain, exerts immunomodulatory functions by interaction with immune cells, including T cells. Metabolic programs of T cells are closely linked to their effector functions including proliferation, differentiation, and cytokine production. The physiological molecules glucose and insulin may provide environmental cues and guidance, but whether they coordinate to regulate GABA-mediated T cell immunomodulation is still being examined.METHODS: CD4+ T cells that were isolated from blood samples from healthy individuals and from patients with type 1 diabetes (T1D) were activated in vitro. We carried out metabolic assays, multiple proximity extension assay (PEA), ELISA, qPCR, immunoblotting, immunofluorescence staining, flow cytometry analysis, MS-based proteomics, as well as electrophysiology and live-cell Ca2+ imaging.FINDINGS: We demonstrate that GABA-mediated reduction of metabolic activity and the release of inflammatory proteins, including IFNγ and IL-10, were abolished in human CD4+ T cells from healthy individuals and patients with T1D when the glucose concentration was elevated above levels typically observed in healthy people. Insulin increased GABAA receptor-subunit ρ2 expression, enhanced the GABAA receptors-mediated currents and Ca2+ influx. GABA decreased, whereas insulin sustained, hexokinase activity and glycolysis in a glucose concentration-dependent manner.INTERPRETATION: These findings support that metabolic factors, such as glucose and insulin, influence the GABA-mediated immunomodulation of human primary T cells effector functions.FUNDING: The Swedish Children's Diabetes Foundation, The Swedish Diabetes Foundation, The Swedish Research Council 2018-02952, EXODIAB, The Ernfors Foundation, The Thurings Foundation and the Science for Life Laboratory.
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- Netsyk, Olga, et al.
(författare)
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Tonic GABA-activated synaptic and extrasynaptic currents in dentate gyrus granule cells and CA3 pyramidal neurons along the mouse hippocampal dorsoventral axis
- 2020
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Ingår i: Hippocampus. - UK : John Wiley & Sons. - 1050-9631 .- 1098-1063. ; 30:11, s. 1146-1157
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Tidskriftsartikel (refereegranskat)abstract
- The hippocampus is a medial temporal lobe structure in the brain and is widely studied for its role in memory and learning, in particular, spacial memory and emotional responses. It was thought to be a homogenous structure but emerging evidence shows differentiation along the dorsoventral axis and even microdomains for functional and cellular markers. We have examined in two cell‐types of the hippocampal projection neurons, the dentate gyrus (DG) granule cells and CA3 pyramidal neurons, if the GABA‐activated tonic current density varied between the dorsal (septal) and the ventral (temporal) poles of the male mouse hippocampus. Tonic synaptic currents, arising from spontaneous and miniature inhibitory postsynaptic currents (sIPSC, mIPSC), and extrasynaptic tonic currents were evaluated. The results revealed different levels of sIPSC but not mIPSC density between the dorsal and ventral hippocampal neurons for both the DG granule cells and the CA3 pyramidal neurons. The extrasynaptic tonic current density was larger in the DG granule cells as compared to the CA3 pyramidal neurons but did not vary between the dorsal and ventral regions. IPSC bursting was observed in both cell‐types in the ventral hippocampus but was more common in the CA3 pyramidal neurons. Only in the dorsal DG granule cells was the level of the sIPSC and mIPSC density similar. The results indicate that the tonic GABAergic inhibition is particularly strong in the ventral hippocampal DG granule cells and enhanced in the dorsal as compared to the ventral hippocampal CA3 pyramidal neurons.
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