title: Sodium arsenite retards proliferation of PHA-activated T cells by delaying the production and secretion of IL-2.
abstract: Arsenic is a metalloid that commonly contaminates drinking water, and is a known human carcinogen. It has been shown that peripheral blood mononuclear cells (PBMCs) from healthy donors treated in vitro with NaAsO(2) and stimulated with phytohemagglutinin (PHA) show a lower proliferation than nontreated cells. We reported previously a reduction in the secretion of IL-2 in NaAsO(2)-treated PBMCs stimulated with PHA, an observation that might explain, in part, the reduction in proliferation. Since arsenic induces cytoskeleton alterations, which in turn may affect protein transport of the cell, we assumed that NaAsO(2) induced an accumulation of IL-2 inside the cells, and thus a reduction in the secretion of IL-2. In order to demonstrate this hypothesis, we assessed the intracellular IL-2 at the single cell level by flow cytometry, and unexpectedly found a reduction in the percentage of IL-2 producing T cells in the presence of NaAsO(2). We tracked the proliferation of T cells by using the 5,6-carboxyfluorescein diacetate succinimidyl ester (CFSE) dye and found that NaAsO(2) slows down the entrance to cell division and delays the proliferation of cells that have already entered the cell cycle. Nevertheless, the expression of the activation molecules, CD25 and CD69, was unaltered. Assessment of the intracellular and secreted IL-2 in kinetic experiments showed that in fact, NaAsO(2) delays the production of IL-2, given that a recovery of both intracellular and secreted IL-2 was detected at 72 h. Evaluation of the cell cycle showed a higher proportion of cells in G(0)/G(1) and a lower proportion in G(2)/M in the presence of NaAsO(2). We thus conclude that NaAsO(2) reduces proliferation of T cells by delaying the production and secretion of IL-2, thus blocking T cells in G(1); as a consequence, the entry to cell cycle and the rounds of cell division are retarded, and a lower proliferation of T cells is hence observed.
authors.affiliation: Departamento de Inmunología y Enfermedades Infecciosas, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Apartado Postal 70228, CU, Mexico City CP 04510, Mexico.
authors.forename: Georgina
authors.initials: G
authors.lastname: Galicia
authors.forename: Rosario
authors.initials: R
authors.lastname: Leyva
authors.forename: Eda Patricia
authors.initials: EP
authors.lastname: Tenorio
authors.forename: Patricia
authors.initials: P
authors.lastname: Ostrosky-Wegman
authors.forename: Rafael
authors.initials: R
authors.lastname: Saavedra
mesh_terms: D000328:Adult; D018053:Arsenites / Q000633:toxicity*; D002273:Carcinogens / Q000633:toxicity*; D002453:Cell Cycle / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002469:Cell Separation; D002470:Cell Survival / Q000187:drug effects; D003470:Culture Media; D005434:Flow Cytometry; D005452:Fluoresceins; D005455:Fluorescent Antibody Technique; D005456:Fluorescent Dyes; D006801:Humans; D066298:In Vitro Techniques; D007376:Interleukin-2 / Q000096:biosynthesis*; D008297:Male; D010835:Phytohemagglutinins / Q000037:antagonists & inhibitors* / Q000494:pharmacology*; D017670:Sodium Compounds / Q000633:toxicity*; D013347:Subcellular Fractions / Q000737:chemistry / Q000378:metabolism; D013388:Succinimides; D013601:T-Lymphocytes / Q000187:drug effects* / Q000378:metabolism*; D013936:Thymidine / Q000378:metabolism
chemical_list: C087165:5-(6)-carboxyfluorescein diacetate succinimidyl ester; D018053:Arsenites; D002273:Carcinogens; D003470:Culture Media; D005452:Fluoresceins; D005456:Fluorescent Dyes; D007376:Interleukin-2; D010835:Phytohemagglutinins; D017670:Sodium Compounds; D013388:Succinimides; C017947:sodium arsenite; D013936:Thymidine