title: Nitric oxide cooperates with glucocorticoids in thymic epithelial cell-mediated apoptosis of double positive thymocytes.
abstract: T cell development in the thymus is controlled by thymic epithelial cells (TE). While it is accepted that TE interact with maturing T cells, the mechanisms by which they trigger 'death by neglect' of double-positive (DP) thymocytes are poorly understood. We and others have demonstrated a role for TE-derived glucocorticoids (GCs) in this process. We have studied TE-induced apoptosis using an in vitro system based on co-culturing a thymic epithelial cell line (TEC) with DP thymic lymphoma cells or thymocytes (DP thymic cells). Here, we demonstrate that nitric oxide (NO*) is also involved in this death process. The inducible nitric oxide synthase (iNOS) inhibitors N(G)-methyl-L-arginine and 1,4-PBIT attenuated TEC-induced apoptosis of DP thymic cells. Co-cultivation of TEC with DP thymic cells increased the expression of iNOS in TEC. A concomitant increase in NO* was detected by staining with DAF-FM diacetate. Moreover, the iNOS-regulating cytokines IL-1alpha, IL-1beta and IFNgamma were up-regulated upon interaction of TEC with DP thymic cells. Neutralizing IL-1R or IFNgamma reduced TEC-induced apoptosis of DP thymic cells. Cardinally, NO* synergizes with GCs in eliciting apoptosis of DP thymic cells. Our data indicate that a cross-talk between DP thymic cells and TEC is required for proper induction of iNOS-up-regulating cytokines with a subsequent increase in iNOS expression and NO* production in TEC. NO*, in turn, cooperates with GCs in promoting death by neglect. We suggest that NO* together with GCs fine-tune the T cell selection process.
authors.affiliation: Department of Immunology, The Lautenberg Center for General and Tumor Immunology, Institute of Medical Research, The Hebrew University-Hadassah Medical School, Jerusalem, Israel.
authors.forename: Orly
authors.initials: O
authors.lastname: Cohen
authors.forename: Shlomit
authors.initials: S
authors.lastname: Kfir-Erenfeld
authors.forename: Rachel
authors.initials: R
authors.lastname: Spokoini
authors.forename: Yael
authors.initials: Y
authors.lastname: Zilberman
authors.forename: Eitan
authors.initials: E
authors.lastname: Yefenof
authors.forename: Ronit Vogt
authors.initials: RV
authors.lastname: Sionov
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000276:immunology*; D018920:Coculture Techniques; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism; D005938:Glucocorticoids / Q000276:immunology* / Q000378:metabolism; D006727:Hormone Antagonists / Q000494:pharmacology; D007371:Interferon-gamma / Q000276:immunology / Q000378:metabolism; D053582:Interleukin-1alpha / Q000276:immunology / Q000378:metabolism; D053583:Interleukin-1beta / Q000276:immunology / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D015735:Mifepristone / Q000494:pharmacology; D009569:Nitric Oxide / Q000276:immunology* / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000037:antagonists & inhibitors / Q000276:immunology* / Q000378:metabolism; D011965:Receptors, Glucocorticoid / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism; D013890:Thiourea / Q000031:analogs & derivatives / Q000494:pharmacology; D013950:Thymus Gland / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects / Q000276:immunology; D019323:omega-N-Methylarginine / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D005938:Glucocorticoids; D006727:Hormone Antagonists; D053582:Interleukin-1alpha; D053583:Interleukin-1beta; D011965:Receptors, Glucocorticoid; C118852:S,S'-1,4-phenylene-bis(1,2-ethanediyl)bis-isothiourea; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D015735:Mifepristone; D007371:Interferon-gamma; D052247:Nitric Oxide Synthase Type II; D013890:Thiourea