title: Interferon-gamma sensitizes the human salivary gland cell line, HSG, to tumor necrosis factor-alpha induced activation of dual apoptotic pathways.
abstract: Activated immune cells secrete proinflammatory cytokines such as tumor necrosis factor alpha (TNF-alpha), interferon-gamma (IFN-gamma) and Fas ligand (FasL) and these cytokines have been reported to induce apoptosis in numerous cell types. Apoptotic cell death has been associated with the progression of numerous autoimmune diseases. Proinflammatory cytokines are reportedly involved in apoptosis in the salivary glands of patients with Sjögren's syndrome (SS); an autoimmune disorder characterized by the destruction of salivary and lachrymal glands. In this study, we used the HSG cell line to determine if exposure to proinflammatory cytokines induces apoptosis in human salivary gland cells. In addition, we identified the mediators controlling the apoptotic process in response to TNF alpha and IFN gamma. TNF-alpha and IFN-gamma induced apoptosis in HSG cells and resulted in the activation of caspase 8 and the "death receptor" pathway. We further determined that caspase 9 and the "mitochondrial" pathway was also activated. Induction of the intrinsic and extrinsic pathways in HSG cells resulted in substrate cleavage by effector caspases, in particular the cleavage of alpha II spectrin, an autoantigen in Sjögren's syndrome. Our results suggest that HSG cells provide a model system to study processes regulating proinflammatory cytokine-induced apoptotic cell death.
authors.affiliation: Program in Microbiology and Immunology, Wright State University Boonshoft School of Medicine, 3640 Colonel Glenn Highway, 042 Biological Sciences Building, Dayton, Ohio 45435, USA.
authors.forename: Kashmira
authors.initials: K
authors.lastname: Kulkarni
authors.forename: Kaisa
authors.initials: K
authors.lastname: Selesniemi
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Brown
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D051023:BH3 Interacting Domain Death Agonist Protein / Q000378:metabolism; D053148:Caspase 3 / Q000378:metabolism; D053453:Caspase 9 / Q000378:metabolism; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology*; D008954:Models, Biological; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D012469:Salivary Glands / Q000166:cytology* / Q000187:drug effects*; D013049:Spectrin / Q000378:metabolism; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000378:metabolism
chemical_list: D051023:BH3 Interacting Domain Death Agonist Protein; D019253:Proto-Oncogene Proteins c-bcl-2; D014409:Tumor Necrosis Factor-alpha; D051636:X-Linked Inhibitor of Apoptosis Protein; D013049:Spectrin; D007371:Interferon-gamma; D011065:Poly(ADP-ribose) Polymerases; D053148:Caspase 3; D053453:Caspase 9