title: Red blood cells upregulate cytoprotective proteins and the labile iron pool in dividing human T cells despite a reduction in oxidative stress.
abstract: We have recently reported that red blood cells (RBC) promote T cell growth and survival by inhibiting activation-induced T cell death. In the present study, we have examined parameters of oxidative stress and intracellular iron in activated T cells and correlated these data with the expression of ferritin, heme oxygenase-1 (HO-1), and the transferrin receptor CD71. T cells growing in the presence of RBC had reduced levels of reactive oxygen species (ROS) and oxidatively modified proteins, suggesting that RBC efficiently counteracted ROS production on the activated T cells. Flow cytometry and immunodetection demonstrated that T cells dividing in the presence of RBC had increased levels of intracellular ferritin rich in L-subunits and HO-1 along with a downmodulation in CD71 expression. Finally, using the fluorescent iron indicator calcein and flow cytometry analysis, we were able to show that a relative amount of the labile iron pool (LIP) was upregulated in T cells growing in the presence of RBC. These findings are consistent with a typical response to iron overload. However, neither heme compounds nor ferric iron reproduced the levels of expansion and survival of T cells induced by intact RBC. Altogether, these data suggest that RBC inhibit apoptosis of activated T cells by a combination of ROS scavenging and upregulation of cytoprotective proteins such as ferritin and HO-1, which may counteract a possible toxic effect of the increased intracellular free iron.
authors.affiliation: Laboratory of Molecular Immunology, Institute for Molecular and Cell Biology (IBMC), Porto, Portugal.
authors.forename: Ana Mafalda
authors.initials: AM
authors.lastname: Fonseca
authors.forename: Carlos F
authors.initials: CF
authors.lastname: Pereira
authors.forename: Graça
authors.initials: G
authors.lastname: Porto
authors.forename: Fernando A
authors.initials: FA
authors.lastname: Arosa
mesh_terms: D015703:Antigens, CD / Q000378:metabolism; D000944:Antigens, Differentiation, B-Lymphocyte / Q000378:metabolism; D015153:Blotting, Western; D002470:Cell Survival; D002478:Cells, Cultured; D004912:Erythrocytes / Q000378:metabolism*; D005293:Ferritins / Q000737:chemistry / Q000378:metabolism; D005434:Flow Cytometry; D005609:Free Radicals; D006418:Heme / Q000737:chemistry; D006419:Heme Oxygenase (Decyclizing) / Q000378:metabolism; D051547:Heme Oxygenase-1; D006801:Humans; D007501:Iron / Q000737:chemistry / Q000378:metabolism*; D008565:Membrane Proteins; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D011233:Precipitin Tests; D017382:Reactive Oxygen Species; D011990:Receptors, Transferrin / Q000378:metabolism; D013601:T-Lymphocytes / Q000378:metabolism*; D013997:Time Factors; D015854:Up-Regulation
chemical_list: D015703:Antigens, CD; D000944:Antigens, Differentiation, B-Lymphocyte; C068126:CD71 antigen; D005609:Free Radicals; D008565:Membrane Proteins; D017382:Reactive Oxygen Species; D011990:Receptors, Transferrin; D006418:Heme; D005293:Ferritins; D007501:Iron; C496541:HMOX1 protein, human; D006419:Heme Oxygenase (Decyclizing); D051547:Heme Oxygenase-1