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1.
Nicotine consumed upon smoking affects numerous physiological processes through nicotinic acetylcholine receptors, which mediate cholinergic regulation by the neuronal and endogenous acetylcholine. Consequently, nicotinic receptors are expressed in many non-excitable tissues including the blood. In spite of the documented effect of nicotine on hematopoiesis, little is known about the expression and role of nicotinic receptors in the course of blood cell differentiation. The aim of the present study was to investigate whether and how nicotinic receptors are involved in the development of myeloid and erythroid cells within the bone marrow. The presence of nicotinic receptors containing alpha4(beta2) and alpha7 subunits in the bone marrow cells of C57Bl/6 mice was shown by the binding of [125I]-alpha-bungarotoxin or [3H]-Epibatidine and by flow cytometry with subunit-specific antibodies or fluorescein-labeled alpha-cobratoxin. Both TER119+ (erythroid) and CD16+CD43med (myeloid) progenitor cells bound more alpha4-specific antibodies than their mature forms, while the binding of alpha-cobratoxin and alpha7-specific antibodies was also high in mature cells. According to morphological analysis, either the absence of alpha7-containing nicotinic receptors in knockout mice or their desensitization in mice chronically treated with nicotine decreased the number of myeloid and erythroid progenitors and junior cells. In contrast, the absence of beta2-containing receptors favored myelocyte generation and erythroid cell maturation. It is concluded that the development of both myeloid and erythroid cell lineages is regulated by endogenous cholinergic ligands and can be affected by nicotine through alpha7- and alpha4beta2-containing nicotinic receptors, which play different roles in the course of the cell maturation.  相似文献   

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3.
Kim SJ  Kim JE  Ko BH  Moon IS 《Molecules and cells》2004,17(2):242-247
Carbofuran (CF), an anticholinesterase carbamate, is one of the most widely used N-methylcarbamate esters in insect and nematode control. Despite its serious adverse health effects on wildlife and humans, cellular and molecular studies of the damage of CF to CNS neurons are very limited. We have examined the cytotoxic effects of CF on cultured rat cortical cells, and the expression of the alpha7 subunit of the nicotinic acetylcholine receptor (alpha7 nAChR) in hippocampal neurons. CF was cytotoxic with an IC50 approximately 730 and approximately 640 microm when assessed by the lactate dehydrogenase (LDH) assay and propidium iodide (PI) staining, respectively, 3 days after treatment. CF induced DNA fragmentation and exposure of phosphatidyl serine (PS) on the cell surface. Surface labeling of the alpha7 nAChR with Alexa Fluor 488-conjugated alpha-bungarotoxin (alphaBgt) revealed a significant decrease in the density of the subunits in treated (500 microm CF) hippocampal neurons. Our data indicate that CF induces neuronal death by apoptosis and down-regulates nAChRs.  相似文献   

4.
Disruption of neuronal signaling by soluble β-amyloid has been implicated in deficits in short-term recall in the early stages of Alzheimer's disease. One potential target for β-amyloid is the synapse, with evidence for differential interaction with both pre- and post-synaptic elements. Our previous work revealed an agonist-like action of soluble β-amyloid (pM to nM) on isolated pre-synaptic terminals to increase [Ca2+]i, with apparent involvement of pre-synaptic nicotinic receptors. To directly establish the role of nicotinic receptors in pre-synaptic Ca2+ regulation, we investigated the pre-synaptic action of β-amyloid on terminals isolated from mice harboring either β2 or α7 nicotinic receptor null mutants (knockouts). Average pre-synaptic responses to β-amyloid in hippocampal terminals of α7 knockout mice were unchanged, whereas responses in hippocampal terminals from β2 knockout mice were strongly attenuated. In contrast, pre-synaptic responses to soluble β-amyloid were strongly attenuated in cortical terminals from α7 knockout mice but were moderately attenuated in cortical terminals from β2 knockout mice. The latter responses, having distinct kinetics, were completely blocked by α-bungarotoxin. The use of receptor null mutants thus permitted direct demonstration of the involvement of specific nicotinic receptors in pre-synaptic Ca2+ regulation by soluble β-amyloid, and also indicated differential neuromodulation by β-amyloid of synapses in hippocampus and cortex.  相似文献   

5.
The ideal antiserum for immunohistochemical (IHC) applications contains monospecific high-affinity antibodies with little nonspecific adherence to sections. Many commercially available antibodies are “affinity” purified, but it is unknown if they meet “hard” specificity criteria, such as absence of staining in tissues genetically deficient for the antigen or a staining pattern that is identical to that of an antibody raised against a different epitope on the same protein. Reviewers, therefore, often require additional characterization. Although the affinity-purified antibodies used in our study on the distribution of muscarinic receptors produced selective staining patterns on sections, few passed the preabsorption test, and none produced bands of the anticipated size on Western blots. More importantly, none showed a difference in staining pattern on sections or Western blots between wild-type and knockout mice. Because these antibodies were used in most studies published thus far, our findings cast doubts on the validity of the extant body of morphological knowledge of the whole family of muscarinic receptors. We formulate requirements that antibody-specification data sheets should meet and propose that journals for which IHC is a core technique facilitate consumer rating of antibodies. “Certified” antibodies could avoid fruitless and costly validation assays and should become the standard of commercial suppliers. (J Histochem Cytochem 56:1099–1111, 2008)  相似文献   

6.
In complex tissues where multiple subtypes of nicotinic acetylcholine receptors (nAChRs) are expressed, immunohistochemistry has been the most popular tool for investigation of nAChR subunit distribution. However, recent studies with nAChR subunit knockout mice demonstrated that a large panel of antibodies is unsuitable. Thus, we aimed to develop a histochemical method for selective labeling of α7 nAChR with neurotoxins, utilizing α7 nAChR-transfected cells, dorsal root ganglia (DRG) and spinal cord from wild-type and knockout mouse. The specificity of Alexa Fluor 488-conjugated α-bungarotoxin (Alexa-αBgt) was demonstrated in binding to α7-transfected cells inhibited by long-chain α-cobratoxin (CTX), but not short-chain α-neurotoxin II (NTII). In contrast, binding to Torpedo muscle-type nAChRs and to motor end plates in mouse tongue sections was prevented by both CTX and NTII. In tissue sections of DRG, expressing all neuronal nAChR subunits, only CTX precluded Alexa-αBgt labeling of neurons, with no staining for α7 nAChR knockout tissue. It proved that α7 nAChRs are the major αBgt-binding sites in mouse DRG. Corresponding results were obtained for terminals in the spinal cord. Thus, we present a protocol utilizing Alexa-αBgt and non-labeled CTX/NTII that allows specific histochemical detection of α7 nAChR with a spatial resolution at the level of single axon terminals.  相似文献   

7.
Commercially available angiotensin II AT2 receptor antibodies are widely employed for receptor localization and quantification, but they have not been adequately validated. In this study, we characterized three commercially available AT2 receptor antibodies: 2818-1 from Epitomics, sc-9040 from Santa Cruz Biotechnology, Inc., and AAR-012 from Alomone Labs. Using western blot analysis the immunostaining patterns observed were different for every antibody tested, and in most cases consisted of multiple immunoreactive bands. Identical immunoreactive patterns were present in wild-type and AT2 receptor knockout mice not expressing the target protein. In the mouse brain, immunocytochemical studies revealed very different cellular immunoreactivity for each antibody tested. While the 2818-1 antibody reacted only with endothelial cells in small parenchymal arteries, the sc-9040 antibody reacted only with ependymal cells lining the cerebral ventricles, and the AAR-012 antibody reacted only with multiple neuronal cell bodies in the cerebral cortex. Moreover, the immunoreactivities were identical in brain tissue from wild-type or AT2 receptor knockout mice. Furthermore, in both mice and rat tissue extracts, there was no correlation between the observed immunoreactivity and the presence or absence of AT2 receptor binding or gene expression. We conclude that none of these commercially available AT2 receptor antibodies tested met the criteria for specificity. In the absence of full antibody characterization, competitive radioligand binding and determination of mRNA expression remain the only reliable approaches to study AT2 receptor expression.  相似文献   

8.
Aberrant amyloid β (Aβ) production plays a causal role in Alzheimer disease pathogenesis. A major cellular pathway for Aβ generation is the activity-dependent endocytosis and proteolytic cleavage of the amyloid precursor protein (APP). However, the molecules controlling activity-dependent APP trafficking in neurons are less defined. Mints are adaptor proteins that directly interact with the endocytic sorting motif of APP and are functionally important in regulating APP endocytosis and Aβ production. We analyzed neuronal cultures from control and Mint knockout neurons that were treated with either glutamate or tetrodotoxin to stimulate an increase or decrease in neuronal activity, respectively. We found that neuronal activation by glutamate increased APP endocytosis, followed by elevated APP insertion into the cell surface, stabilizing APP at the plasma membrane. Conversely, suppression of neuronal activity by tetrodotoxin decreased APP endocytosis and insertion. Interestingly, we found that activity-dependent APP trafficking and Aβ generation were blocked in Mint knockout neurons. We showed that wild-type Mint1 can rescue APP internalization and insertion in Mint knockout neurons. In addition, we found that Mint overexpression increased excitatory synaptic activity and that APP was internalized predominantly to endosomes associated with APP processing. We demonstrated that presenilin 1 (PS1) endocytosis requires interaction with the PDZ domains of Mint1 and that this interaction facilitates activity-dependent colocalization of APP and PS1. These findings demonstrate that Mints are necessary for activity-induced APP and PS1 trafficking and provide insight into the cellular fate of APP in endocytic pathways essential for Aβ production.  相似文献   

9.
We examined the mechanism by which lithium chloride (LiCl) attenuates the impaired learning capability and memory function of dual-transgenic APP/PS1 mice. Six- or 12-month-old APP/PS1 and wild-type (WT) mice were randomized into four groups, namely WT, WT+Li (100 mg LiCl/kg body weight, gavage once daily), APP/PS1 and APP/PS1+Li. Primary rat hippocampal neurons were exposed to β-amyloid peptide oligomers (AβOs), LiCl and/or XAV939 (inhibitor of Wnt/β-catenin) or transfected with small interfering RNA against the β-catenin gene. In the cerebral zone of APP/PS1 mice, the level of Aβ was increased and those of α7 nicotinic acetylcholine receptors (nAChR), phosphor-GSK3β (ser9), β-catenin and cyclin D1 (protein and/or mRNA levels) reduced. Two-month treatment with LiCl at ages of 4 or 10 months weakened all of these effects. Similar expression variations were observed for these proteins in primary neurons exposed to AβOs, and these effects were attenuated by LiCl and aggravated by XAV939. Inhibition of β-catenin expression lowered the level of α7 nAChR protein in these cells. LiCl attenuates the impaired learning capability and memory function of APP/PS1 mice via a mechanism that might involve elevation of the level of α7 nAChR as a result of altered Wnt/β-catenin signalling.  相似文献   

10.
Nicotine elicits dopamine release by stimulating nicotinic acetylcholine receptors (nAChRs) on dopaminergic neurons. However, a modulation of these neurons by endogenous acetylcholine has not been described. We recorded, in vivo, the spontaneous activity of dopaminergic neurons in the VTA of anaesthetized wt and nAChR knockout mice and their response to nicotine injections. Deleting alpha7 or beta2 subunits modified the spontaneous firing patterns, demonstrating their direct stimulation by endogenous acetylcholine. Quantitative analysis further revealed four principal modes of firing, each depending on the expression of particular nAChR subunits and presenting unique responses to nicotine. The prominent role of the beta2 subunit was further confirmed by its selective lentiviral reexpression in the VTA. These data suggest a hierarchical control of dopaminergic neuron firing patterns by nAChRs: activation of beta2*-nAChR switches cells from a resting to an excited state, whereas activation of alpha7*-nAChRs finely tunes the latter state but only once beta2*-nAChRs have been activated.  相似文献   

11.
A new subunit, beta 2, of the neuronal nicotinic receptor family has been identified. This subunit has the structural features of a non-agonist-binding subunit. We provide evidence that beta 2 can substitute for the muscle beta 1 subunit to form a functional nicotinic receptor in Xenopus oocytes. Expression studies performed in oocytes have demonstrated that three different neuronal nicotinic acetylcholine receptors can be formed by the pairwise injection of beta 2 mRNA and each of the neuronal alpha subunit mRNAs. The beta 2 gene is expressed in PC12 cells and in areas of the central nervous system where the alpha 2, alpha 3, and alpha 4 genes are expressed. These results lead us to propose that the nervous system expresses diverse forms of neuronal nicotinic acetylcholine receptors by combining beta 2 subunits with different agonist-binding alpha subunits.  相似文献   

12.
Currently, there are no effective therapies to ameliorate the pathological progression of Alzheimer's disease (AD). Evidence suggests that environmental factors may contribute to AD. Notably, dietary nutrients are suggested to play a key role in mediating mechanisms associated with brain function. Choline is a B‐like vitamin nutrient found in common foods that is important in various cell functions. It serves as a methyl donor and as a precursor for production of cell membranes. Choline is also the precursor for acetylcholine, a neurotransmitter which activates the alpha7 nicotinic acetylcholine receptor (α7nAchR), and also acts as an agonist for the Sigma‐1 R (σ1R). These receptors regulate CNS immune response, and their dysregulation contributes to AD pathogenesis. Here, we tested whether dietary choline supplementation throughout life reduces AD‐like pathology and rescues memory deficits in the APP/PS1 mouse model of AD. We exposed female APP/PS1 and NonTg mice to either a control choline (1.1 g/kg choline chloride) or a choline‐supplemented diet (5.0 g/kg choline chloride) from 2.5 to 10 months of age. Mice were tested in the Morris water maze to assess spatial memory followed by neuropathological evaluation. Lifelong choline supplementation significantly reduced amyloid‐β plaque load and improved spatial memory in APP/PS1 mice. Mechanistically, these changes were linked to a decrease of the amyloidogenic processing of APP, reductions in disease‐associated microglial activation, and a downregulation of the α7nAch and σ1 receptors. Our results demonstrate that lifelong choline supplementation produces profound benefits and suggest that simply modifying diet throughout life may reduce AD pathology.  相似文献   

13.
Nicotinic acetylcholine receptors play important roles in numerous cognitive processes as well as in several debilitating central nervous system (CNS) disorders. In order to fully elucidate the diverse roles of nicotinic acetylcholine receptors in CNS function and dysfunction, a detailed knowledge of their cellular and subcellular localizations is essential. To date, methods to precisely localize nicotinic acetylcholine receptors in the CNS have predominantly relied on the use of anti-receptor subunit antibodies. Although data obtained by immunohistology and immunoblotting are generally in accordance with ligand binding studies, some discrepancies remain, in particular with electrophysiological findings. In this context, nicotinic acetylcholine receptor subunit-deficient mice should be ideal tools for testing the specificity of subunit-directed antibodies. Here, we used standard protocols for immunohistochemistry and western blotting to examine the antibodies raised against the alpha3-, alpha4-, alpha7-, beta2-, and beta4-nicotinic acetylcholine receptor subunits on brain tissues of the respective knock-out mice. Unexpectedly, for each of the antibodies tested, immunoreactivity was the same in wild-type and knock-out mice. These data imply that, under commonly used conditions, these antibodies are not suited for immunolocalization. Thus, particular caution should be exerted with regards to the experimental approach used to visualize nicotinic acetylcholine receptors in the brain.  相似文献   

14.
Deficits of cortical nicotinic acetylcholine receptors (nAChRs) have been observed in Alzheimer's disease (AD) by receptor binding assays. Little is known about the receptor subunit specificity influenced by AD, and it might be of importance for therapeutic strategies. In the present study, the protein levels of nAChR alpha3, alpha4, alpha7, and beta2 subunits were investigated using western blot analysis on postmortem brains of patients with AD and age-matched controls. The results showed that in human postmortem brain samples, bands with molecular masses of 52, 42, and 50 kDa were detected by anti-alpha4, anti-alpha7, and anti-beta2 antibodies, respectively. When anti-alpha3 antibody was used, one major band of 49 kDa and two minor bands of 70 and 38 kDa were detected. In AD patients, as compared with age-matched controls, the alpha4 subunit was reduced significantly by approximately 35 and 47% in the hippocampus and temporal cortex, respectively. A significant reduction of 25% in the alpha3 subunit was also observed in the hippocampus and a 29% reduction in the temporal cortex. For the alpha7 subunit, the protein level was reduced significantly by 36% in the hippocampus of AD patients, but no significant change was detected in the temporal cortex. In neither the hippocampus nor the temporal cortex was a significant difference observed in the beta2 subunit between AD patients and controls. These results reveal brain region-specific changes in the protein levels of the nAChR alpha3, alpha4, and alpha7 subunits in AD.  相似文献   

15.
Autoimmune diseases involving nicotinic receptors   总被引:1,自引:0,他引:1  
The antibody-mediated autoimmune response to alpha1 muscle nicotinic acetylcholine receptors that causes myasthenia gravis is one of the best characterized autoimmune diseases. Antibody-mediated autoimmune responses to neuronal nicotinic receptors are just beginning to be discovered and characterized. One of these causes dysautonomia through antibodies to alpha 3 nicotinic receptors of autonomic ganglia. Another causes pemphigus through antibodies to alpha 9 nicotinic receptors in skin. Other autoimmune responses to nicotinic receptors may be discovered as the many functional roles of nicotinic receptors are revealed.  相似文献   

16.
Molecular studies of the neuronal nicotinic acetylcholine receptor family   总被引:16,自引:0,他引:16  
Nicotinic acetylcholine receptors on neurons are part of a gene family that includes nicotinic acetylcholine receptors on skeletal muscles and neuronal alpha bungarotoxin-binding proteins that in many species, unlike receptors, do not have an acetylcholine-regulated cation channel. This gene superfamily of ligand-gated receptors also includes receptors for glycine and gamma-aminobutyric acid. Rapid progress on neuronal nicotinic receptors has recently been possible using monoclonal antibodies as probes for receptor proteins and cDNAs as probes for receptor genes. These studies are the primary focus of this review, although other aspects of these receptors are also considered. In birds and mammals, there are subtypes of neuronal nicotinic receptors. All of these receptors differ from nicotinic receptors of muscle pharmacologically (none bind alpha bungarotoxin, and some have very high affinity for nicotine), structurally (having only two types of subunits rather than four), and, in some cases, in functional role (some are located presynaptically). However, there are amino acid sequence homologies between the subunits of these receptors that suggest the location of important functional domains. Sequence homologies also suggest that the subunits of the proteins of this family all evolved from a common ancestral protein subunit. The ligand-gated ion channel characteristic of this superfamily is formed from multiple copies of homologous subunits. Conserved domains responsible for strong stereospecific association of the subunits are probably a fundamental organizing principle of the superfamily. Whereas the structure of muscle-type nicotinic receptors appears to have been established by the time of elasmobranchs and has evolved quite conservatively since then, the evolution of neuronal-type nicotinic receptors appears to be in more rapid flux. Certainly, the studies of these receptors are in rapid flux, with the availability of monoclonal antibody probes for localizing, purifying, and characterizing the proteins, and cDNA probes for determining sequences, localizing mRNAs, expressing functional receptors, and studying genetic regulation. The role of nicotinic receptors in neuromuscular transmission is well understood, but the role of nicotinic receptors in brain function is not. The current deluge of data using antibodies and cDNAs is beginning to come together nicely to describe the structure of these receptors. Soon, these techniques may combine with others to better reveal the functional roles of neuronal nicotinic receptors.  相似文献   

17.
Recent evidence reveals a crucial role for acetylcholine and its receptors in the regulation of inflammation, particularly of nicotinic acetylcholine receptor α7 (Chrna7) and muscarinic acetylcholine receptor 3 (Chrm3). Immunohistochemistry is a key tool for their cellular localization in functional tissues. We evaluated nine different commercially available antibodies on back skin tissue from wild-type (Wt) and gene-deficient (KO) mice. In the immunohistochemical analysis, we focused on key AChR-ligand sensitive skin cells (mast cells, nerve fibers and keratinocytes). All five antibodies tested for Chrm3 and the first three Chrna7 antibodies stained positive in both Wt and respective KO skin. With the 4th antibody (ab23832) nerve fibers were unlabeled in the KO mice. By western blot analysis, this antibody detected bands in both Wt and Chrna7 KO skin and brain. qRT-PCR revealed mRNA amplification with a primer set for the undeleted region in both Wt and KO mice, but none with a primer set for the deleted region in KO mice. By 2D electrophoresis, we found β-actin and β-enolase cross reactivity, which was confirmed by double immunolabeling. In view of the present results, the tested antibodies are not suitable for immunolocalization in skin and suggest thorough control of antibody specificity is required if histomorphometry is intended.  相似文献   

18.
The distribution of neuronal and non-neuronal mRNAs for alpha7 and alpha4 nicotinic acetylcholine receptor subunits was investigated in Triturus carnifex tissues using the in situ hybridization approach. The findings reveal a composite pattern of expression only partially overlapping for the two subunits; subunit alpha7 seems to be expressed widely throughout nervous, gastrointestinal and skin tissues, while alpha4 is present in a restricted number of cells of nervous and gastrointestinal tissue. We also found a specific pattern for each subunit; alpha7 and alpha4 associated exclusively to the epidermal glands and hypophysis, respectively; this is probably due to alternative roles that nicotinic acetylcholine receptors play in regulating physiological functions of non-neuronal amphibian tissues, rather than as mere neurotransmitters in the nervous system.  相似文献   

19.
We have proposed the novel concept that the macrophage ubiquitin-proteasome pathway functions as a key regulator of Lipopolysaccharide (LPS)-induced inflammation signaling. These findings suggest that proteasome-associated protease subunits X, Y, and Z are replaced by LMP subunits after LPS treatment of RAW 264.7 cells. The objective here was to determine the contribution of selective LMP proteasomal subunits to LPS-induced nitric oxide (NO) and TNF-α production in primary murine macrophages. Accordingly, thioglycollate-elicited macrophages from LMP7, LMP2, LMP10 (MECL-1), and LMP7/MECL-1 double knockout mice were stimulated in vitro with LPS, and were found to generate markedly reduced NO levels compared to wild-type (WT) mice, whereas TNF-α levels responses were essentially unaltered relative to wild-type responses. The recent studies suggest that the TRIF/TRAM pathway is defective in LMP knockouts which may explain why iNOS/NO are not robustly induced in LPS-treated macrophages from knockouts. Treating these macrophages with IFN-γ and LPS, however, reverses this defect, leading to robust NO induction. TNF-α is induced by LPS in the LMP knockout macrophages because IκB and IRAK are degraded normally via the MyD88 pathway. Collectively, these findings strongly support the concept that LMP7/MECL-1 proteasomes subunits actively function to regulate LPS-induced NO production by affecting the TRIF/TRAM pathway.  相似文献   

20.
Prenatal stress in humans is associated with psychiatric problems in offspring such as anxiety, depression, and schizophrenia. These same illnesses are also associated with neuronal nicotinic acetylcholine receptor (nAChR) dysfunction. Despite the known associations between prenatal stress exposure and offspring mental illness, and between mental illness and nAChR dysfunction, it is not known whether prenatal stress exposure impacts neuronal nAChRs. Thus, we tested the hypothesis that maternal stress alters the development of hippocampal alpha4 beta2 (α4β2?) and alpha7 (α7?) nicotinic receptor levels in adult offspring. Female Sprague‐Dawley rats experienced unpredictable variable stressors two to three times daily during the last week of gestation. At weaning (21 days) the offspring of prenatally stressed (PS) and nonstressed (NS) dams were assigned to same‐sex PS or NS groups. In young adulthood (56 days), the brains of offspring were collected and adjacent sections processed for quantitative autoradiography using [125I]‐epibatidine (α4β2* nicotinic receptor‐selective) and [125I]‐α‐bungarotoxin (α‐BTX; α7* nicotinic receptor‐selective) ligands. We found that PS significantly increased hippocampal α4β2* nAChRs of males and females in all subfields analyzed. In contrast, only females showed a trend toward PS‐induced increases in α7* nAChRs in the dentate gyrus. Interestingly, NS females displayed a significant left‐biased lateralization of α7* nAChRs in the laconosum moleculare of area CA1, whereas PS females did not, suggesting that PS interfered with normal lateralization patterns of α7* nAChRs during development. Taken together, our results suggest that PS impacts the development of hippocampal nAChRs, which may be an important link between PS exposure and risk for neuropsychiatric illness. © 2013 Wiley Periodicals, Inc. Develop Neurobiol 73:806–814, 2013  相似文献   

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