title: Retinoic acid regulates cell cycle progression and cell differentiation in human monocytic THP-1 cells.
abstract: All-trans-retinoic acid (RA), a natural metabolite of retinol, carries out most of the biological activities of vitamin A and is required for normal growth, cell differentiation, and immune functions. In the present studies, THP-1 human monocytes were used to investigate the mechanisms by which RA may regulate progression through the G1/S phase of the cell cycle. Physiological concentrations of all-trans-RA reduced the levels of cyclin E mRNA by 6 h and reduced cyclin E protein in a dose- and time-dependent manner. Similar reductions were observed for the retinoic acid receptor RARalpha and RXRalpha proteins. Concomitantly, RA increased the level of the cyclin-dependent kinase inhibitor p27 (Kip-1). The levels of retinoblastoma mRNA and protein (pRb) were also increased, while the proportion of hyperphosphorylated (phosphoserine 807/811) pRb was markedly reduced. Overall, RA increased the functionality of pRb as an inhibitor of cell cycle progression. Furthermore, RA reduced the binding activity of the transcription factor E2F to its core DNA element. Retinoic acid-induced changes in cell cycle-related proteins occurred in 4-6 h, including reduced cyclin E expression in bromodeoxyuridine (BrdU)-labeled cells, before the onset of cell differentiation as indicated by an increase in the percentage of G1 phase cells and a reduction in S phase cells at 24 h. The expression of CD11b, a cell surface marker of macrophage-like differentiation was increased by RA, as was phagocytic activity. The multiple effects of RA on cell cycle progression may help to explain its well-documented ability to induce the differentiation of THP-1 cells, and thereby to enhance macrophage-like immune functions.
authors.affiliation: Department of Nutritional Sciences and Huck Institute for Life Sciences, Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: Qiuyan
authors.initials: Q
authors.lastname: Chen
authors.forename: A Catharine
authors.initials: AC
authors.lastname: Ross
mesh_terms: D039481:CD11b Antigen / Q000235:genetics / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology*; D018797:Cell Cycle Proteins / Q000187:drug effects / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects / Q000235:genetics*; D002460:Cell Line; D019927:Cyclin E / Q000235:genetics / Q000378:metabolism; D050760:Cyclin-Dependent Kinase Inhibitor p27; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000187:drug effects / Q000235:genetics; D050684:E2F Transcription Factors; D016193:G1 Phase / Q000187:drug effects / Q000235:genetics; D005786:Gene Expression Regulation / Q000187:drug effects / Q000235:genetics; D018816:Genes, cdc / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D009000:Monocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects / Q000235:genetics; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D011930:Reaction Time / Q000187:drug effects / Q000235:genetics; D018168:Receptors, Retinoic Acid / Q000187:drug effects / Q000378:metabolism; D016160:Retinoblastoma Protein / Q000235:genetics / Q000378:metabolism; D000072482:Retinoic Acid Receptor alpha; D047488:Retinoid X Receptors; D016196:S Phase / Q000187:drug effects / Q000235:genetics; D014157:Transcription Factors / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D014212:Tretinoin / Q000378:metabolism* / Q000494:pharmacology; D025521:Tumor Suppressor Proteins / Q000187:drug effects / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics
chemical_list: D039481:CD11b Antigen; D018797:Cell Cycle Proteins; D019927:Cyclin E; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; C000607071:RARA protein, human; D012333:RNA, Messenger; D018168:Receptors, Retinoic Acid; D016160:Retinoblastoma Protein; D000072482:Retinoic Acid Receptor alpha; D047488:Retinoid X Receptors; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D014212:Tretinoin