ABSTRACT
Acetylcholinesterase (AChE) hydrolyzes acetylcholine at cholinergic synapses, and which has various isoforms of AChE, i.e. AChER, AChEH and AChET, deriving from single gene. AChEH exists as a glycophosphatidylinositol (GPI)-linked dimer (G2), presents mainly in plasma membrane of mammalian erythrocyte. Transgenic mice with ACHE gene depletion were employed here to investigate the possible role of AChE in blood cell formation. ACHE knock-out mice were found to suffer normocytic anemia. In erythrocyte of ACHE-/- mice, the amount of hemoglobin, especially α-globin, was found to be markedly reduced. In addition, the number of erythrocyte and hematocrit of ACHE-/- mice were significantly lowered. To probe the role of AChE isoforms in erythroid differentiation, erythroblast-like cells (TF-1) over-expressed with different AChE isoforms were induced to differentiate by erythropoietin (EPO): this differentiation induced the expression of each AChE isoform. Only in the TF-1â¯cells over-expressed with AChEH, the EPO-induced transcriptions and protein expressions of α- and ß-globins could be significantly enhanced, which therefore suggested that AChEH might regulate the responsiveness of TF-1â¯cells to EPO. The alternation of EPO-induced downstream signaling might be accounted by association of AChE with EPO receptor in cell surface. The findings indicated the significance of AChE in erythroblast maturation, which provided an insight in elucidating possible mechanisms in regulating erythropoiesis.
Subject(s)
Acetylcholinesterase/metabolism , Receptors, Erythropoietin/metabolism , Acetylcholinesterase/chemistry , Acetylcholinesterase/immunology , Animals , Antibodies/immunology , Cell Differentiation , Cell Line , Dimerization , Erythroblasts/cytology , Erythroblasts/metabolism , Erythropoietin/pharmacology , Gene Expression/drug effects , Hemoglobins/metabolism , Humans , Mice , Mice, Knockout , Receptors, Erythropoietin/immunologyABSTRACT
Acetylcholinesterase (AChE) hydrolyzes the neurotransmitter acetylcholine in neurons. However, AChE has been proposed to also have nonneuronal functions in different cell types. Here, we report that AChE is expressed in melanocytes and melanoma cells, and that the tetrameric (G4) form is the major AChE isoform in these cells. During melanogenesis of B16F10 murine melanoma cells, AChE levels decreased markedly. The differentiation of melanoma cells led to (i) an increase in melanin and tyrosinase, (ii) a change in intracellular cAMP levels, and (iii) a decrease in microphthalmia-associated transcription factor (MITF). We hypothesized that the regulation of AChE during melanogenesis is mediated by two transcription factors: cAMP-response element-binding protein (CREB) and MITF. In melanoma cells, exogenous cAMP suppressed AChE expression and the promoter activity of the ACHE gene. This suppression was mediated by a cAMP-response element (CRE) located on the ACHE promoter, as mutation of CRE relieved the suppression. In melanoma, MITF overexpression induced ACHE transcription, and mutation of an E-box site in human ACHE promoter blocked this induction. An AChE inhibitor greatly enhanced acetylcholine-mediated responses of melanogenic gene expression levels in vitro; however, this enhancement was not observed in the presence of agonists of the muscarinic acetylcholine receptor. These results indicate that ACHE transcription is regulated by cAMP-dependent signaling during melanogenesis of B16F10 cells, and the effect of this enzyme on melanin production suggests that it has a potential role in skin pigmentation.
Subject(s)
Acetylcholinesterase/metabolism , Melanins/biosynthesis , Melanoma, Experimental/metabolism , Microphthalmia-Associated Transcription Factor/physiology , Up-Regulation/physiology , Acetylcholine/metabolism , Acetylcholinesterase/genetics , Animals , Cell Differentiation , Cell Line, Tumor , Cyclic AMP/metabolism , Cyclic AMP Response Element-Binding Protein/physiology , Gene Expression Regulation, Enzymologic/physiology , Melanins/metabolism , Melanocytes/cytology , Melanocytes/metabolism , Melanoma, Experimental/enzymology , Melanoma, Experimental/pathology , Mice , Monophenol Monooxygenase/metabolism , Promoter Regions, GeneticABSTRACT
Astragali Radix (AR), a Chinese materia medica (CMM) known as Huangqi, is an important medicine prescribed in herbal composite formulae (Fufang) by Traditional Chinese medicine (TCM) practitioners for thousands of years. According to the literature, AR is suggested for patients suffering from “Qi”- and “Blood”-deficiencies, and its clinical effects are reported to be related to anti-cancer cell proliferation, anti-oxidation, relief of complications in cardiovascular diseases, etc. The underlying cell signaling pathways involved in the regulation of these various diseases are presented here to support the mechanisms of action of AR. There are two botanical sources recorded in China Pharmacopoeia (CP, 2015): Astragalus membranaceus (Fisch.) Bge. Var. mongohlicus, (Bge.) Hsiao, and Astragalus membranaceus (Fisch.) Bge. (Fam. Leguminosae), whose extracts of dried roots are processed via homogenization-assisted negative pressure cavitation extraction. Geographic factors and extraction methods have impacts on the pharmaceutical and chemical profiles of AR. Therefore, the levels of the major bioactive constituents of AR, including polysaccharides, saponins, and flavonoids, may not be consistent in different batches of extract, and the pharmaceutical efficacy of these bioactive ingredients may vary depending on the source. Therefore, the present review mainly focuses on the consistency of the available sources of AR and extracts and on the investigation of the biological functions and mechanisms of action of AR and of its major bioactive constituents. Furthermore, it will also include a discussion of the most popular AR composite formulae to further elucidate their chemical and biological profiles and understand the pharmaceutical value of AR.
