title: Differential modulation of mitogen driven proliferation and homeostasis driven proliferation of T cells by rapamycin, Ly294002 and chlorophyllin.
abstract: Homeostasis driven proliferation (HDP) of naïve CD4+ T cells depends upon T cell receptor ligation with self-MHC II along with availability of interleukin-7. But the exact nature of downstream signaling events involved in HDP of helper T cells remains elusive. To identify the specific involvement of signaling molecules in HDP, purified CD4+ T cells were treated with either mTOR inhibitor rapamycin or PI3kinase inhibitor Ly294002 or with an antioxidant chlorophyllin (CHL) in vitro. Rapamycin treated cells failed to proliferate, expressed anergic T cell specific transcription factor genes egr-2 and egr-3 and showed diminished IFN-gamma production in response to Con A stimulation in vitro. Although CHL treated cells also failed to proliferate, they showed a normal IFN-gamma production during primary stimulation and did not upregulate egr-2 and egr-3 genes following restimulation in vitro. Ly294002 treated cells failed to express IL-2 and IFN-gamma and did not divide in response to Con A stimulation in vitro. While all these inhibitors significantly inhibited CD4+ T cell proliferation in response to the mitogen in vitro, only CHL treatment could inhibit their HDP in lymphopenic mice. Our results also demonstrate that combined treatment with rapamycin and Ly294002 did not inhibit HDP of CD4+ T cells. Thus, the present study, for the first time, shows a non-essential role of mTOR and PI3kinase during HDP of CD4+ T cells and also describes its possible regulation by an antioxidant.
authors.affiliation: Radiation Biology & Health Sciences Division, Bio-Medical Group, Bhabha Atomic Research Centre, Modular Laboratories, Trombay, Mumbai 400085, India.
authors.forename: Deepak
authors.initials: D
authors.lastname: Sharma
authors.forename: Sandur Santosh
authors.initials: SS
authors.lastname: Kumar
authors.forename: Rashmi
authors.initials: R
authors.lastname: Raghu
authors.forename: Shazia
authors.initials: S
authors.lastname: Khanam
authors.forename: Krishna Balaji
authors.initials: KB
authors.lastname: Sainis
mesh_terms: D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology* / Q000187:drug effects* / Q000276:immunology; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D002735:Chlorophyllides / Q000494:pharmacology*; D002867:Chromones / Q000494:pharmacology*; D003208:Concanavalin A / Q000494:pharmacology; D004347:Drug Interactions; D005786:Gene Expression Regulation / Q000187:drug effects / Q000276:immunology; D006706:Homeostasis; D007166:Immunosuppressive Agents / Q000494:pharmacology; D008213:Lymphocyte Activation / Q000187:drug effects; D051379:Mice; D008807:Mice, Inbred BALB C; D008934:Mitogens; D009025:Morpholines / Q000494:pharmacology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011948:Receptors, Antigen, T-Cell / Q000276:immunology / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology; D020123:Sirolimus / Q000494:pharmacology*
chemical_list: D002735:Chlorophyllides; D002867:Chromones; D007166:Immunosuppressive Agents; D008934:Mitogens; D009025:Morpholines; D011948:Receptors, Antigen, T-Cell; D003208:Concanavalin A; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D019869:Phosphatidylinositol 3-Kinases; C007020:chlorophyllin; D020123:Sirolimus