Involvement of nicotinic acetylcholine receptor in the proliferation of mouse induced pluripotent stem cells

α7nAChR activation in AT2 cells promotes alveolar regeneration through WNT7B signaling in acute lung injury

Reducing inflammatory damage and improving alveolar epithelium regeneration are two key approaches to promoting lung repair in acute lung injury/acute respiratory distress syndrome (ALI/ARDS). Stimulation of cholinergic α7 nicotinic acetylcholine receptor (α7nAChR, coded by Chrna7) signaling could dampen lung inflammatory injury. However, whether activation of α7nAChR in alveolar type II (AT2) cells promotes alveolar epithelial injury repair and underlying mechanisms is elusive. Here, we found that α7nAChR was expressed on AT2 cells and was upregulated in response to LPS-induced ALI. Meanwhile, deletion of Chrna7 in AT2 cells impeded lung repair process and worsened lung inflammation in ALI. Using in vivo AT2 lineage-labeled mice and ex vivo AT2 cell-derived alveolar organoids, we demonstrated that activation of α7nAChR expressed on AT2 cells improved alveolar regeneration by promoting AT2 cells to proliferate and subsequently differentiate toward alveolar type I cells. Then, we screened out the WNT7B signaling pathway by the RNA-Seq analysis of in vivo AT2 lineage-labeled cells and further confirmed its indispensability for α7nAChR activation-mediated alveolar epithelial proliferation and differentiation. Thus, we have identified a potentially unrecognized pathway in which cholinergic α7nAChR signaling determines alveolar regeneration and repair, which might provide us a novel therapeutic target for combating ALI.

Treatment with lysophosphatidic acid prevents microglial activation and depression-like behaviours in a murine model of neuropsychiatric systemic lupus erythematosus

Neuropsychiatric systemic lupus erythematosus (NPSLE) is an incurable disease characterised by neuropsychiatric symptoms, particularly depression. Novel therapeutic options for NPSLE are urgently needed. Several previous reports have suggested that both microglial activation and impaired neurogenesis may be involved in the progression of depression. In contrast, the administration of lysophosphatidic acid (LPA) ameliorates depression and anxiety. Therefore, in the present study, we determined whether treatment with LPA affects microglial activation, impaired neurogenesis, and abnormal behaviour in MRL/lpr mice. In both tail suspension test and forced swim test, the MRL/lpr mice exhibited a significant increase in total immobility time compared with MRL/+ mice. Treatment with LPA significantly suppressed the prolonged immobility time in MRL/lpr mice. In contrast, pretreatment with ki16425 (a specific antagonist of LPA receptor 1 and 3) significantly reversed the effects of LPA. Furthermore, MRL/lpr mice exhibited impairments in spatial working memory and visual cognitive memory, which were suppressed by LPA treatment. The expression levels of TMEM119, CD68, GFAP, and caspase-3 in the hippocampus and prefrontal cortex of MRL/lpr mice were significantly higher than those in MRL/+ mice. Treatment with LPA inhibited these increases in MRL/lpr mice. Pretreatment with ki16425 reversed LPA-mediated inhibition of microglial activation. The quantity of sodium fluorescein that leaked into the brain tissues in MRL/lpr mice were significantly higher than that in MRL/+ mice. Treatment with LPA tended to decrease the sodium fluorescein leakage. These findings suggest that treatment with LPA may regulate microglial activation, which is important in the pathogenesis of NPSLE, as well as blood-brain-barrier weakening and abnormal behaviour.

Expression of Chrna9 is regulated by Tbx3 in undifferentiated pluripotent stem cells

It was reported that nicotinic acetylcholine receptor (nAChR)-mediated signaling pathways affect the proliferation and differentiation of pluripotent stem cells. However, detail expression profiles of nAChR genes were unrevealed in these cells. In this study, we comprehensively investigated the gene expression of α subunit of nAChRs (Chrna) during differentiation and induction of pluripotent stem cells. Mouse embryonic stem (ES) cells expressed multiple Chrna genes (Chrna3-5, 7 and 9) in undifferentiated status. Among them, Chrna9 was markedly down-regulated upon the differentiation into mesenchymal cell lineage. In mouse tissues and cells, Chrna9 was mainly expressed in testes, ES cells and embryonal F9 teratocarcinoma stem cells. Expression of Chrna9 gene was acutely reduced during differentiation of ES and F9 cells within 24 h. In contrast, Chrna9 expression was increased in induced pluripotent stem cells established from mouse embryonic fibroblast. It was shown by the reporter assays that T element-like sequence in the promoter region of Chrna9 gene is important for its activities in ES cells. Chrna9 was markedly reduced by siRNA-mediated knockdown of Tbx3, a pluripotency-related transcription factor of the T-box gene family. These results indicate that Chrna9 is a nAChR gene that are transcriptionally regulated by Tbx3 in undifferentiated pluripotent cells.

Multiple Roles for Cholinergic Signaling from the Perspective of Stem Cell Function

Stem cells have extensive proliferative potential and the ability to differentiate into one or more mature cell types. The mechanisms by which stem cells accomplish self-renewal provide fundamental insight into the origin and design of multicellular organisms. These pathways allow the repair of damage and extend organismal life beyond that of component cells, and they probably preceded the evolution of complex metazoans. Understanding the true nature of stem cells can only come from discovering how they are regulated. The concept that stem cells are controlled by particular microenvironments, also known as niches, has been widely accepted. Technical advances now allow characterization of the zones that maintain and control stem cell activity in several organs, including the brain, skin, and gut. Cholinergic neurons release acetylcholine (ACh) that mediates chemical transmission via ACh receptors such as nicotinic and muscarinic receptors. Although the cholinergic system is composed of organized nerve cells, the system is also involved in mammalian non-neuronal cells, including stem cells, embryonic stem cells, epithelial cells, and endothelial cells. Thus, cholinergic signaling plays a pivotal role in controlling their behaviors. Studies regarding this signal are beginning to unify our understanding of stem cell regulation at the cellular and molecular levels, and they are expected to advance efforts to control stem cells therapeutically. The present article reviews recent findings about cholinergic signaling that is essential to control stem cell function in a cholinergic niche.

Mining the effect of the neonicotinoids imidacloprid and clothianidin on the chemical homeostasis and energy equilibrium of primary mouse neural stem/progenitor cells using metabolomics

The projection of plant protection products' (PPPs) toxicity to non-target organisms at early stages of their development is challenging and demanding. Recent developments in bioanalytics, however, have facilitated the study of fluctuations in the metabolism of biological systems in response to treatments with bioactives and the discovery of corresponding toxicity biomarkers. Neonicotinoids are improved insecticides that target nicotinic acetylocholine receptors (nAChR) in insects which are similar to mammals. Nonetheless, they have sparked controversy due to effects on non-target organisms. Within this context, mammalian cell cultures represent ideal systems for the development of robust models for the dissection of PPPs' toxicity. Thus, we have investigated the toxicity of imidacloprid, clothianidin, and their mixture on primary mouse (Mus musculus) neural stem/progenitor (NSPCs) and mouse neuroblastoma-derived Neuro-2a (N2a) cells, and the undergoing metabolic changes applying metabolomics. Results revealed that NSPCs, which in vitro resemble those that reside in the postnatal and adult central nervous system, are five to seven-fold more sensitive than N2a to the applied insecticides. The energy equilibrium of NSPCs was substantially altered, as it is indicated by fluctuations of metabolites involved in energy production (e.g. glucose, lactate), Krebs cycle intermediates, and fatty acids, which are important components of cell membranes. Such evidence plausibly suggests a switch of cells' energy-producing mechanism to the direct metabolism of glucose to lactate in response to insecticides. The developed pipeline could be further exploited in the discovery of unintended effects of PPPs at early steps of development and for regulatory purposes.

Organoids for Drug Discovery and Personalized Medicine

A wide variety of organs are in a dynamic state, continuously undergoing renewal as a result of constant growth and differentiation. Stem cells are required during these dynamic events for continuous tissue maintenance within the organs. In a steady state of production and loss of cells within these tissues, new cells are constantly formed by differentiation from stem cells. Today, organoids derived from either adult stem cells or pluripotent stem cells can be grown to resemble various organs. As they are similar to their original organs, organoids hold great promise for use in medical research and the development of new treatments. Furthermore, they have already been utilized in the clinic, enabling personalized medicine for inflammatory bowel disease. In this review, I provide an update on current organoid technology and summarize the application of organoids in basic research, disease modeling, drug development, personalized treatment, and regenerative medicine.

The Coordinated Activities of nAChR and Wnt Signaling Regulate Intestinal Stem Cell Function in Mice

Cholinergic signaling, which modulates cell activities via nicotinic and muscarinic acetylcholine receptors (n- and mAChRs) in response to internal or external stimuli, has been demonstrated in mammalian non-neuronal cells that synthesize acetylcholine (ACh). One of the major pathways of excitatory transmission in the enteric nervous system (ENS) is mediated by cholinergic transmission, with the transmitter ACh producing excitatory potentials in postsynaptic effector cells. In addition to ACh-synthesizing and ACh-metabolizing elements in the ENS, the presence of non-neuronal ACh machinery has been reported in epithelial cells of the small and large intestines of rats and humans. However, little is known about how non-neuronal ACh controls physiological function in the intestine. Here, experiments using crypt-villus organoids that lack nerve and immune cells in culture suggest that endogenous ACh is synthesized in the intestinal epithelium to drive organoid growth and differentiation through activation of nAChRs. Treatment of organoids with nicotine enhanced cell growth and the expression of marker genes for stem and epithelial cells. On the other hand, the nAChR antagonist mecamylamine strongly inhibited the growth and differentiation of organoids, suggesting the involvement of nAChRs in the regulation of proliferation and differentiation of Lgr5-positive stem cells. More specifically, RNA sequencing analysis revealed that Wnt5a expression was dramatically upregulated after nicotine treatment, and Wnt5a rescued organoid growth and differentiation in response to mecamylamine. Taken together, our results indicate that coordinated activities of nAChR and Wnt signaling maintain Lgr5-positive stem cell activity and balanced differentiation. Furthermore, we could clearly separate the two groups, neuronal ACh in the ENS and non-neuronal ACh in the intestinal epithelium. Dysfunction of the non-neuronal cholinergic system is involved in the pathogenesis of disease. The data will increase our understanding of the cholinergic properties of non-neuronal cells and lead to optimization of drug therapy.

Non-neuronal acetylcholine involved in reproduction in mammals and honeybees

Bacteria and archaea synthesize acetylcholine (ACh). Thus, it can be postulated that ACh was created by nature roughly three billion years ago. Therefore, the wide expression of ACh in nature (i.e., in bacteria, archaea, unicellular organisms, plants, fungi, non-vertebrates and vertebrates and in the abundance of non-neuronal cells of mammals) is not surprising. The term non-neuronal ACh and non-neuronal cholinergic system have been introduced to describe the auto- and paracrine, that is, local regulatory actions of ACh in cells not innervated by neuronal cholinergic fibers and to communicate among themselves. In this way non-neuronal ACh binds to the nicotinic or muscarinic receptors expressed on these local and migrating cells and modulates basic cells functions such as proliferation, differentiation, migration and the transport of ions and water. The present article is focused to the effects of non-neuronal ACh linked to reproduction; data on the expression and function of the non-neuronal cholinergic system in the following topics are summarized: (i) Sperm, granulosa cells, oocytes; (ii) Auxiliary systems (ovary, oviduct, placenta); (iii) Embryonic stem cells as first step for reproduction of a new individual after fertilization; (iv) Larval food as an example of reproduction in insects (honeybees) and adverse effects of the neonicotinoids, a class of world-wide applied insecticides. The review article will show that non-neuronal ACh is substantially involved in the regulation of reproduction in mammals and also non-mammals like insects (honeybees). There is a need to learn more about this biological role of ACh. In particular, we have to consider that insecticides like the neonicotinoids, but also carbamates and organophosphorus pesticides, interfere with the non-neuronal cholinergic system thus compromising for example the breeding of honeybees. But it is possible that other species may also be adversely affected as well, a mechanism which may contribute to the observed decline in biodiversity. This is an article for the special issue XVth International Symposium on Cholinergic Mechanisms.

Inhibition of Gata4 and Tbx5 by Nicotine-Mediated DNA Methylation in Myocardial Differentiation

Maternal nicotine exposure causes alteration of gene expression and cardiovascular programming. The discovery of nicotine-medicated regulation in cardiogenesis is of major importance for the study of cardiac defects. The present study investigated the effect of nicotine on cardiac gene expression and epigenetic regulation during myocardial differentiation. Persistent nicotine exposure selectively inhibited expression of two cardiac genes, Tbx5 and Gata4, by promoter DNA hypermethylation. The nicotine-induced suppression on cardiac differentiation was restored by general nicotinic acetylcholine receptor inhibition. Consistent results of Tbx5 and Gata4 gene suppression and cardiac function impairment with decreased left ventricular ejection fraction were obtained from in vivo studies in offspring. Our results present a direct repressive effect of nicotine on myocardial differentiation by regulating cardiac gene suppression via promoter DNA hypermethylation, contributing to the etiology of smoking-associated cardiac defects.

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Nicotine downregulates Tbx5 and Gata4 during in vitro and in vivo cardiogenesis

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Nicotine causes diminished cardiac differentiation and impaired cardiac function

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Nicotine causes Tbx5 and Gata4 gene suppression via promoter DNA hypermethylation

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nAChR antagonist restores nicotine-induced gene suppression and DNA methylation

Nicotine exposure during differentiation causes inhibition of N-myc expression

Background

The ability of chemicals to disrupt neonatal development can be studied using embryonic stem cells (ESC). One such chemical is nicotine. Prenatal nicotine exposure is known to affect postnatal lung function, although the mechanisms by which it has this effect are not clear. Since fibroblasts are a critical component of the developing lung, providing structure and secreting paracrine factors that are essential to epithelialization, this study focuses on the differentiation of ESC into fibroblasts using a directed differentiation protocol.

Methods

Fibroblasts obtained from non-human primate ESC (nhpESC) differentiation were analyzed by immunohistochemistry, immunostaining, Affymetrix gene expression array, qPCR, and immunoblotting.

Results

Results of these analyses demonstrated that although nhpESCs differentiate into fibroblasts in the presence of nicotine and appear normal by some measures, including H&E and SMA staining, they have an altered gene expression profile. Network analysis of expression changes demonstrated an over-representation of cell-cycle related genes with downregulation of N-myc as a central regulator in the pathway. Further investigation demonstrated that cells differentiated in the presence of nicotine had decreased N-myc mRNA and protein expression and longer doubling times, a biological effect consistent with downregulation of N-myc.

Conclusions

This study is the first to use primate ESC to demonstrate that nicotine can affect cellular differentiation from pluripotency into fibroblasts, and in particular, mediate N-myc expression in differentiating ESCs. Given the crucial role of fibroblasts throughout the body, this has important implications for the effect of cigarette smoke exposure on human development not only in the lung, but in organogenesis in general.

Effect of prenatal exposure to nicotine on kidney glomerular mass and AT1R expression in genetically diverse strains of rats

Prenatal exposure to maternal cigarette smoking in humans or nicotine in experimental animals is associated with elevated blood pressure in the offspring. This effect may be limited to genetically vulnerable individuals and related to alterations in the kidneys. Here we investigated whether prenatal exposure to nicotine (PEN) alters kidney morphology and gene expression, and whether these effects differ between two genetically distant strains, i.e. spontaneously hypertensive (SHR) and Brown Norway (BN) rats. The results showed that, in SHR but not in BN offspring, PEN decreases kidney glomerular mass and increases renal expression of the angiotensin II type 1b receptor gene; the latter is not mediated through changes in DNA methylation of the proximal promoter of this gene. The results also showed that PEN alters expression of multiple genes involved in the kidney nervous system function, with mostly opposite effects being seen in SHR and BN. These results suggest that, in genetically vulnerable individuals, PEN leads to morphological and molecular changes in the kidneys that may contribute to fetal programming of hypertension.