concanavalin-a and sodium-arsenite

Aging is associated with immune dysfunction and conditions such as inflamm-aging and immunosuppression. Arsenic, an environmental contaminant distributed worldwide, affects the immune system. This study tested the hypothesis that arsenic has distinct effects on T cell proliferation and the production of cytokines by activated T cells. Murine splenocytes from young (2 months) and aged (24-26 months) C57BL/6 mice were exposed to arsenite (As(3+)), the most toxic form of inorganic arsenic, and stimulated with concanavalin A (Con A) or anti-CD3 antibody. T cell proliferation decreased significantly in response to Con A and anti-CD3 at subtoxic doses of arsenite in splenocytes from both young and aged mice. Arsenite, added concurrently with Con A or anti-CD3, significantly inhibited the production of interleukin-2 (IL-2), interferon-γ (IFN-γ), and interleukin-4 (IL-4) by splenocytes from young mice and significantly reduced the production of IL-10 by splenocytes from aged mice. In contrast, the production of IL-2 and IL-4 by splenocytes from aged mice was only slightly affected by arsenite. The results show that arsenic exposure reduces the immune response in splenocytes. Moreover, this effect may be influenced by aging.

Topics: Aging; Animals; Arsenites; CD3 Complex; Cell Proliferation; Cells, Cultured; Concanavalin A; Cytokines; Dose-Response Relationship, Drug; Enzyme Inhibitors; Immune Tolerance; Male; Mice; Sodium Compounds; Spleen; Th1 Cells; Th2 Cells

This study examined the effects of sodium arsenite treatment on free [Ca(2+)]i and cell death in mitogen-activated murine lymphocytes. The main findings of this study were that simultaneous sodium arsenite treatment inhibited PHA- but not Con A-induced T cell proliferation, induced a higher increase in free [Ca(2+)]i and an early increase in the proportion of dead cells in PHA than in Con A activated cells. Sodium arsenite pre-treatment reduced both PHA- and Con A-induced T-cell proliferation. Phorbol myristate ester (PMA) did not prevent the inhibitory effects of both sodium arsenite treatments, suggesting that sodium arsenite did not significantly decreased PKC activation or that its effects occurred on events parallel to PKC activation. Both PHA and Con A increased free [Ca(2+)]i after stimulation, yet the effect was more pronounced in mitogen-activated cells simultaneously treated with sodium arsenite and particularly in those activated with PHA. The increase in free [Ca(2+)]i was in agreement with the early cell death induced by sodium arsenite in PHA-activated cells, a finding consistent with the inhibitory effects on PHA-induced proliferation. Sodium arsenite-induced cell death occurred faster in PHA-activated cells. Further studies are needed to ascertain the relationships between the effects of sodium arsenite on free [Ca(2+)]i levels and the type of cell death induced by sodium arsenite and their relevance for the proliferative response of T cells.

Topics: Animals; Arsenites; Calcium; Cell Death; Cell Division; Concanavalin A; Enzyme Inhibitors; Female; Flow Cytometry; Lymphocyte Activation; Mice; Mice, Inbred C57BL; Phytohemagglutinins; Sodium Compounds; T-Lymphocytes; Tetradecanoylphorbol Acetate

A portion of our research involves the investigation of biomarkers as preclinical indicators of toxic stress. Stemming from this effort, we report three unique proteins that phosphorylate and synthesize during the S-phase of lymphoma cells following chemical insult. Mouse lymphoma cell nuclei were physically sorted (using a fluorescence activated cell sorter) from partitions of the cell cycle and specific nuclear proteins in each partition were examined by gel microelectrophoresis. The changes in [32P]-incorporation by stress proteins (SPs) were examined in each of seven partitions following administration of sodium arsenite. Four SPs [80,000-84,000 relative molecular mass (Mr)], designated 'c','b','x', and 'y', underwent significant alterations in [32P]-labeling and each exhibited varying degrees of differential [32P]-incorporation in partition 3 of G1 phase, all five partitions of S-phase, and partition 1 of G2 phase of the cell cycle. Three other predominantly S-phase SPs (designated S1, S2 and S3) were phosphorylated after sodium arsenite treatment. Stress protein S1 was labeled exclusively in S-phase, while proteins S2 and S3 were labeled only in partition 3 of G1 and S-phase. Stress protein S1 possessed an identical isoelectric point, molecular mass, distribution of polypeptide fragments and immunochemical determinants as S-phase SPs found previously in mouse spleen (X') and mouse liver (LP-S). The identical biochemical characteristics of these three S-phase (SPs), found in diverse tissue types, suggest they are homologous.

Topics: Animals; Arsenic; Arsenites; Cell Nucleus; Concanavalin A; Electrophoresis, Gel, Two-Dimensional; Heat-Shock Proteins; Isoelectric Point; Isoproterenol; Liver; Lymphoma; Mice; Molecular Weight; Nuclear Proteins; Peptide Mapping; Phenobarbital; Phosphorus Radioisotopes; S Phase; Sodium Compounds; Spleen; Tumor Cells, Cultured