Dataset Information

Microglial cell response in α7 nicotinic acetylcholine receptor-deficient mice after systemic infection with Escherichia coli.

ABSTRACT:

Background

Development of neurodegeneration in older people has been associated with microglial cell activation triggered by systemic infection. We hypothesize that α7 nicotinic acetylcholine receptor (α7nAChR) plays an important role in regulation of this process.

Methods

8- to 10-week-old male wild-type (WT) and α7nAChR knock-out (α7nAChR^-/-) mice were intraperitoneally inoculated with live Escherichia (E.) coli or saline. After inoculation, all mice were treated with ceftriaxone (an antimicrobial drug) at 12 and 24 h and killed at 2 or 3 days. The microglial response was characterized by immunohistochemical staining with an ionized calcium-binding adaptor molecule 1 (Iba-1) antibody and flow cytometry. To quantify inflammatory response, mRNA expression of pro- and anti-inflammatory mediators was measured in brain and spleen.

Results

We observed no differences in Iba-1 positive cell number or morphology and flow cytometry (CD11b, CD45 and CD14) of microglial cells between WT and α7nAChR^-/- mice after systemic infection. Infected α7nAChR^-/- mice showed significantly higher mRNA expression in brain for tumor necrosis factor alpha (TNF-α) at day 2 and 3, interleukin 6 (IL-6) at day 2 and monocyte chemotactic protein 1 (MCP-1) and suppressor of cytokine signaling 1 (SOCS1) at day 3, there was significantly lower mRNA expression in brain for mitogen-activated protein kinase 1 (MAPK1) at day 2 and 3, high-mobility group 1 (HMGB-1) and CD11b at day 2, and deubiquitinase protein A20 (A20) at day 3 compared to infected WT mice.

Interpretation

Loss of function of α7nAChR during systemic infection led to an increased expression of TNF-α and IL-6 in brain after systemic infection with E. coli, but not to distinct differences in microglial cell number or morphological activation of microglia.

SUBMITTER: Hoogland ICM

PROVIDER: S-EPMC9006549 | biostudies-literature | 2022 Apr

REPOSITORIES: biostudies-literature

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Publications

Microglial cell response in α7 nicotinic acetylcholine receptor-deficient mice after systemic infection with Escherichia coli.

Hoogland Inge C M ICM Yik Jutka J Westhoff Dunja D Engelen-Lee Joo-Yeon JY Valls Seron Merche M Man Wing Kit WK Houben-Weerts Judith H P M JHPM Tanck Michael W T MWT van Westerloo David J DJ van der Poll Tom T van Gool Willem A WA van de Beek Diederik D

Journal of neuroinflammation 20220412 1

<h4>Background</h4>Development of neurodegeneration in older people has been associated with microglial cell activation triggered by systemic infection. We hypothesize that α7 nicotinic acetylcholine receptor (α7nAChR) plays an important role in regulation of this process.<h4>Methods</h4>8- to 10-week-old male wild-type (WT) and α7nAChR knock-out (α7nAChR<sup>-/-</sup>) mice were intraperitoneally inoculated with live Escherichia (E.) coli or saline. After inoculation, all mice were treated with ...[more]

PMID: 35413868

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Project description:BackgroundRecently, analysis of bone from knockout mice identified muscarinic acetylcholine receptor subtype M3 (mAChR M3) and nicotinic acetylcholine receptor (nAChR) subunit α2 as positive regulator of bone mass accrual whereas of male mice deficient for α7-nAChR (α7KO) did not reveal impact in regulation of bone remodeling. Since female sex hormones are involved in fair coordination of osteoblast bone formation and osteoclast bone degradation we assigned the current study to analyze bone strength, composition and microarchitecture of female α7KO compared to their corresponding wild-type mice (α7WT).MethodsVertebrae and long bones of female 16-week-old α7KO (n = 10) and α7WT (n = 8) were extracted and analyzed by means of histological, radiological, biomechanical, cell- and molecular methods as well as time of flight secondary ion mass spectrometry (ToF-SIMS) and transmission electron microscopy (TEM).ResultsBone of female α7KO revealed a significant increase in bending stiffness (p < 0.05) and cortical thickness (p < 0.05) compared to α7WT, whereas gene expression of osteoclast marker cathepsin K was declined. ToF-SIMS analysis detected a decrease in trabecular calcium content and an increase in C4H6N(+) (p < 0.05) and C4H8N(+) (p < 0.001) collagen fragments whereas a loss of osteoid was found by means of TEM.ConclusionsOur results on female α7KO bone identified differences in bone strength and composition. In addition, we could demonstrate that α7-nAChRs are involved in regulation of bone remodelling. In contrast to mAChR M3 and nAChR subunit α2 the α7-nAChR favours reduction of bone strength thereby showing similar effects as α7β2-nAChR in male mice. nAChR are able to form heteropentameric receptors containing α- and β-subunits as well as the subunits α7 can be arranged as homopentameric cation channel. The different effects of homopentameric and heteropentameric α7-nAChR on bone need to be analysed in future studies as well as gender effects of cholinergic receptors on bone homeostasis.

Project description:PurposeThe α7 nicotinic acetylcholine receptor (nAChR) is widely expressed in the nervous system, including in the inner retinal neurons in all species studied to date. Although reductions in the expression of α7 nAChRs are thought to contribute to the memory and visual deficits reported in Alzheimer's disease (AD) and schizophrenia , the α7 nAChR knockout (KO) mouse is viable and has only slight visual dysfunction. The absence of a major phenotypic abnormality may be attributable to developmental mechanisms that serve to compensate for α7 nAChR loss. We hypothesized that the upregulation of genes encoding other nAChR subunits or muscarinic acetylcholine receptor (mAChR) subtypes during development partially accounts for the absence of major deficiencies in the α7 nAChR KO mouse. The purpose of this study was to determine whether the deletion of the α7 nAChR subunit in a mouse model resulted in changes in the regulation of other cholinergic receptors or other ion channels in an α7 nAChR KO mouse when compared to a wild-type (WT) mouse.MethodsTo examine gene expression changes, we employed a quantitative real-time polymerase chain reaction (qPCR) using whole retina RNA extracts as well as RNA extracted from selected regions of the retina. These extracts were collected using laser capture microdissection (LCM). The presence of acetylcholine receptor (AChR) subunit and subtype proteins was determined via western blotting. To determine any differences in the number and distribution of choline acetyltransferase (ChAT) amacrine cells, we employed wholemount and vertical immunohistochemistry (IHC) and cell counting. Additionally, in both WT and α7 nAChR KO mouse retinas, the distribution of the nAChR subunit and mAChR subtype proteins were determined via IHC for those KO mice that experienced mRNA changes.ResultsIn the whole retina, there was a statistically significant upregulation of α2, α9, α10, β4, nAChR subunit, and m1 and m4 mAChR subtype transcripts in the α7 nAChR KO mice. However, the retinal layers showed complex patterns of transcript expression. In the ganglion cell layer (GCL), m2 and m4 mAChR subtype transcripts were significantly upregulated, while β3 and β4 nAChR subunit transcripts were significantly downregulated. In the inner portion of the inner nuclear layer (iINL), α2, α9, β4, nAChR subunit, and m3 and m4 mAChR subtype transcripts were significantly downregulated. In the outer portion of the inner nuclear layer (oINL), β2, β4, and m4 AChR subunit transcripts were significantly upregulated. Western blot experiments confirmed the protein expression of α3-α5 and α9-containing nAChR subunits and m1-m2 mAChR subtypes in mouse retinas. IHC results supported many of the mRNA changes observed. Finally, this is the first report of α9 and α10 nAChR subunit expressions in the retina of any species.ConclusionsRather than a simple upregulation of a single AChR subunit or subtype, the absence of the α7 nAChR in the KO mice was associated with complex layer-specific changes in the expression of AChR subunits and subtypes.

Dataset Information

Microglial cell response in α7 nicotinic acetylcholine receptor-deficient mice after systemic infection with Escherichia coli.

Background

Methods

Results

Interpretation

Publications

Microglial cell response in α7 nicotinic acetylcholine receptor-deficient mice after systemic infection with Escherichia coli.

Similar Datasets

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