Dataset Information

Alpha7 Nicotinic Acetylcholine Receptor Mediates Nicotine-induced Apoptosis and Cell Cycle Arrest of Hepatocellular Carcinoma HepG2 Cells.

ABSTRACT: Purpose: The cytotoxic properties upon treatment with nicotine have been reported in several studies, but the underlying mechanisms remain not fully defined. The alpha7 nicotinic acetylcholine receptor (?7nAChR) is one of the important nicotinic receptors, which nicotine partly by binding to this receptor exerts its effects. The current study aimed to investigates the influences of nicotine on cellular proliferative and apoptotic activities and tried to determine the involvement of ?7nAChR in these functions. Methods: Human hepatocellular carcinoma (HepG2) cell line was used to determine the individual or combined effects of treatments with nicotine (10 ?M) and specific siRNA (100 nM) targeting ?7nAChR expression. The MTT assay, DAPI staining assay, and flow cytometry assay were applied to measure the cell viability, apoptosis and cell cycle progression of the cells, respectively. In addition, the changes in the mRNA level of the genes were assessed by qRT-PCR. Results: Compared to control groups, the cells treated with nicotine exhibited significant dosedependent decreases in cell viability (log IC50 = -5.12±0.15). Furthermore, nicotine induced apoptosis and cell cycle arrest especially at G2/M Phase. The qRT-PCR revealed that nicotine increased the mRNA levels of ?7nAChR as well as caspase-3 and suppressed the expression of cyclin B1. Treatment with ?7-siRNA abolished these effects of nicotine. Conclusion: These experiments determined that upregulation of ?7nAChR by nicotine inhibits HepG2 cells proliferation and induces their apoptosis. These effects blocked by treatment with ?7-siRNA, which indicates the involvement of ?7nAChR pathways in these processes.

SUBMITTER: Hajiasgharzadeh K

PROVIDER: S-EPMC6983989 | biostudies-literature | 2020 Jan

REPOSITORIES: biostudies-literature

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Alpha7 Nicotinic Acetylcholine Receptor Mediates Nicotine-induced Apoptosis and Cell Cycle Arrest of Hepatocellular Carcinoma HepG2 Cells.

Hajiasgharzadeh Khalil K Somi Mohammad Hossein MH Mansoori Behzad B Doustvandi Mohammad Amin MA Vahidian Fatemeh F Alizadeh Mohsen M Mokhtarzadeh Ahad A Shanehbandi Dariush D Baradaran Behzad B

Advanced pharmaceutical bulletin 20191211 1

<i><b>Purpose:</b></i> The cytotoxic properties upon treatment with nicotine have been reported in several studies, but the underlying mechanisms remain not fully defined. The alpha7 nicotinic acetylcholine receptor (α7nAChR) is one of the important nicotinic receptors, which nicotine partly by binding to this receptor exerts its effects. The current study aimed to investigates the influences of nicotine on cellular proliferative and apoptotic activities and tried to determine the involvement of ...[more]

PMID: 32002363

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Project description:BackgroundCigarette smoking adversely affects endochondral ossification during the course of skeletal growth. Among a plethora of cigarette chemicals, nicotine is one of the primary candidate compounds responsible for the cause of smoking-induced delayed skeletal growth. However, the possible mechanism of delayed skeletal growth caused by nicotine remains unclarified. In the last decade, localization of neuronal nicotinic acetylcholine receptor (nAChR), a specific receptor of nicotine, has been widely detected in non-excitable cells. Therefore, we hypothesized that nicotine affect growth plate chondrocytes directly and specifically through nAChR to delay skeletal growth.Methodology/principal findingsWe investigated the effect of nicotine on human growth plate chondrocytes, a major component of endochondral ossification. The chondrocytes were derived from extra human fingers. Nicotine inhibited matrix synthesis and hypertrophic differentiation in human growth plate chondrocytes in suspension culture in a concentration-dependent manner. Both human and murine growth plate chondrocytes expressed alpha7 nAChR, which constitutes functional homopentameric receptors. Methyllycaconitine (MLA), a specific antagonist of alpha7 nAChR, reversed the inhibition of matrix synthesis and functional calcium signal by nicotine in human growth plate chondrocytes in vitro. To study the effect of nicotine on growth plate in vivo, ovulation-controlled pregnant alpha7 nAChR +/- mice were given drinking water with or without nicotine during pregnancy, and skeletal growth of their fetuses was observed. Maternal nicotine exposure resulted in delayed skeletal growth of alpha7 nAChR +/+ fetuses but not in alpha7 nAChR -/- fetuses, implying that skeletal growth retardation by nicotine is specifically mediated via fetal alpha7 nAChR.Conclusions/significanceThese results suggest that nicotine, from cigarette smoking, acts directly on growth plate chondrocytes to decrease matrix synthesis, suppress hypertrophic differentiation via alpha7 nAChR, leading to delayed skeletal growth.

Project description:BACKGROUND: Nicotinic acetylcholine (Ach) receptors are ligand-gated pentameric ion channels whose main function is to transmit signals for the neurotransmitter Ach in peripheral and central nervous system. However, the alpha7 nicotinic receptor has been recently found in several non-neuronal cells and described as an important regulator of cellular function. Nicotine and ACh have been recently reported to inhibit tumor necrosis factor-alpha (TNF-alpha) production in human macrophages as well as in mouse microglial cultures. In the present study, we investigated whether the stimulation of alpha7 nicotinic receptor by the specific agonist nicotine could affect the functional state of activated microglia by promoting and/or inhibiting the release of other important pro-inflammatory and lipid mediator such as prostaglandin E2. METHODS: Expression of alpha7 nicotinic receptor in rat microglial cell was examined by RT-PCR, immunofluorescence staining and Western blot. The functional effects of alpha7 receptor activation were analyzed in resting or lipopolysaccharide (LPS) stimulated microglial cells pre-treated with nicotine. Culture media were assayed for the levels of tumor necrosis factor, interleukin-1beta, nitric oxide, interleukin-10 and prostaglandin E2. Total RNA was assayed by RT-PCR for the expression of COX-2 mRNA. RESULTS: Rat microglial cells express alpha7 nicotinic receptor, and its activation by nicotine dose-dependently reduces the LPS-induced release of TNF-alpha, but has little or no effect on nitric oxide, interleukin-10 and interleukin-1beta. By contrast, nicotine enhances the expression of cyclooxygenase-2 and the synthesis of one of its major products, prostaglandin E2. CONCLUSIONS: Since prostaglandin E2 modulates several macrophage and lymphocyte functions, which are instrumental for inflammatory resolution, our study further supports the existence of a brain cholinergic anti-inflammatory pathway mediated by alpha7 nicotinic receptor that could be potentially exploited for novel treatments of several neuropathologies in which local inflammation, sustained by activated microglia, plays a crucial role.

Project description:We and others have shown that one of the mechanisms of growth regulation of small cell lung cancer cell lines and cultured pulmonary neuroendocrine cells is by the binding of agonists to the alpha7 neuronal nicotinic acetylcholine receptor. In addition, we have shown that the nicotine-derived carcinogenic nitrosamine, 4(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), is a high affinity agonist for the alpha7 nicotinic acetylcholine receptor. In the present study, our goal was to determine the extent of alpha7 mRNA and protein expression in the human lung.Experiments were done using reverse transcription polymerase chain reaction (RT-PCR), a nuclease protection assay and western blotting using membrane proteins.We detected mRNA for the neuronal nicotinic acetylcholine receptor alpha7 receptor in seven small cell lung cancer (SCLC) cell lines, in two pulmonary adenocarcinoma cell lines, in cultured normal human small airway epithelial cells (SAEC), one carcinoid cell line, three squamous cell lines and tissue samples from nine patients with various types of lung cancer. A nuclease protection assay showed prominent levels of alpha7 in the NCI-H82 SCLC cell line while alpha7 was not detected in SAEC, suggesting that alpha7 mRNA levels may be higher in SCLC compared to normal cells. Using a specific antibody to the alpha7 nicotinic receptor, protein expression of alpha7 was determined. All SCLC cell lines except NCI-H187 expressed protein for the alpha7 receptor. In the non-SCLC cells and normal cells that express the alpha7 nAChR mRNA, only in SAEC, A549 and NCI-H226 was expression of the alpha7 nicotinic receptor protein shown. When NCI-H69 SCLC cell line was exposed to 100 pm NNK, protein expression of the alpha7 receptor was increased at 60 and 150 min.Expression of mRNA for the neuronal nicotinic acetylcholine receptor alpha7 seems to be ubiquitously expressed in all human lung cancer cell lines tested (except for NCI-H441) as well as normal lung cells. The alpha7 nicotinic receptor protein is expressed in fewer cell lines, and the tobacco carcinogen NNK increases alpha7 nicotinic receptor protein levels.

Dataset Information

Alpha7 Nicotinic Acetylcholine Receptor Mediates Nicotine-induced Apoptosis and Cell Cycle Arrest of Hepatocellular Carcinoma HepG2 Cells.

Publications

Alpha7 Nicotinic Acetylcholine Receptor Mediates Nicotine-induced Apoptosis and Cell Cycle Arrest of Hepatocellular Carcinoma HepG2 Cells.

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