Activation of the extrinsic apoptotic pathway by TNF-alpha in human salivary gland (HSG) cells in vitro, suggests a role for the TNF receptor (TNF-R) and intercellular adhesion molecule-1 (ICAM-1) in Sjögren's syndrome-associated autoimmune sialadenitis.
Studies suggest that apoptosis plays a major role in destruction of salivary glands in Sjögren's syndrome. We hypothesise that apoptosis results in the exposure of cryptic T cell epitopes and an autoimmune response which is pathway-specific.


OBJECTIVE
To activate the extrinsic or intrinsic apoptotic pathway to examine morphology, adhesion molecules, markers of antigen processing, and autoantigens on apoptotic bodies in vitro.


METHODS
Tumor necrosis factor-alpha (TNF-alpha) or staurosporine, a protein kinase inhibitor, was used to trigger the extrinsic or intrinsic apoptotic pathway in a Human Salivary Gland cell line (HSG), in vitro. Activated genes were profiled by cDNA array. Apoptotic bodies were visualised using light and SEM. Proteins were evaluated by immunofluorescence and confirmed by functional binding assays with Jurkat lymphocytes.


RESULTS
TNF-alpha-triggered extrinsic apoptosis resulted in "sticky" aggregated, apoptotic bodies which displayed cleaved alpha-fodrin autoantigen. In contrast, intrinsic apoptosis induced by staurosporine, resulted in dispersed cell blebs which were alpha-fodrin-negative. cDNA arrays revealed that TNF-alpha, but not staurosporine, upregulated transcriptional expression of Intercellular Adhesion Molecule-1 (ICAM-1) and Macrophage Inflammatory Protein-3 (CCL20).


CONCLUSIONS
The apoptotic pathway controls morphological, structural and functional properties of apoptotic bodies. Collectively, TNF-alpha-dependent activation of the extrinsic apoptotic pathway leads to upregulation of ICAM-1 and CCL20 in HSG in vitro. This suggests that pathogenesis in Sjögren's syndrome may involve a TNF-controlled cross-talk between apoptotic ductal and CCL20-attracted dendritic cells via the CD137/CD137L signalling pathway.
Wang
Yan
Y
Department of Oral Biology, University of Missouri-Kansas City School of Dentistry, 650 E 25th Street, Kansas City, MO 64108, United States.
Shnyra
Alexander
A
Africa
Charlene
C
Warholic
Christopher
C
McArthur
Carole
C
D017209:Apoptosis / Q000276:immunology*; D001323:Autoantibodies / Q000276:immunology; D001327:Autoimmune Diseases / Q000276:immunology*; D002460:Cell Line; D054418:Chemokine CCL20 / Q000096:biosynthesis; D003713:Dendritic Cells / Q000276:immunology; D020869:Gene Expression Profiling; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000276:immunology*; D019169:Jurkat Cells; D020411:Oligonucleotide Array Sequence Analysis; D020239:Receptor Cross-Talk; D018124:Receptors, Tumor Necrosis Factor / Q000276:immunology*; D012469:Salivary Glands / Q000166:cytology / Q000276:immunology*; D012793:Sialadenitis / Q000276:immunology*; D015398:Signal Transduction; D012859:Sjogren's Syndrome / Q000276:immunology*; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000276:immunology; D053261:Tumor Necrosis Factor Receptor Superfamily, Member 9 / Q000096:biosynthesis / Q000276:immunology; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology
D001323:Autoantibodies; C108355:CCL20 protein, human; D054418:Chemokine CCL20; D018124:Receptors, Tumor Necrosis Factor; D053221:TNF-Related Apoptosis-Inducing Ligand; C505714:TNFRSF9 protein, human; D053261:Tumor Necrosis Factor Receptor Superfamily, Member 9; D014409:Tumor Necrosis Factor-alpha; D018799:Intercellular Adhesion Molecule-1