title: STAT-6 mediates TRAIL induced RANK ligand expression in stromal/preosteoblast cells.
abstract: Receptor activator of nuclear factor kappa-B ligand (RANKL) is a critical osteoclastogenic factor expressed in bone marrow stromal/osteoblast lineage cells. Tumor necrosis factor (TNF) related apoptosis-inducing ligand (TRAIL) levels are elevated in pathologic conditions such as multiple myeloma and inflammatory arthritis, and have been positively correlated with osteolytic markers. Osteoprotegerin (OPG) which inhibits osteoclastogenesis is a decoy receptor for RANKL and also known to interact with TRAIL. Herein, we show that TRAIL increases DR5 and DcR1 receptors but no change in the levels of DR4 and DcR2 expression in human bone marrow derived stromal/preosteoblast (SAKA-T) cell line. We further demonstrated that TRAIL treatment significantly decreased OPG mRNA expression. Interestingly, TRAIL treatment induced RANKL mRNA expression in these cells. In addition, TRAIL significantly increased NF-kB and c-Jun N-terminal kinase (JNK) activity. Human transcription factor array screening by real-time RT-PCR identified TRAIL up-regulation of the signal transducers and activators of the transcription (STAT)-6 expression in SAKA-T cells. TRAIL stimulation induced p-STAT-6 expression in human bone marrow derived primary stromal/preosteoblast cells. Confocal microscopy analysis further revealed p-STAT-6 nuclear localization in SAKA-T cells. Chromatin immunoprecipitation (ChIP) assay confirmed p-STAT-6 binding to the hRANKL gene distal promoter region. In addition, siRNA suppression of STAT-6 expression inhibits TRAIL increased hRANKL gene promoter activity. Thus, our results suggest that TRAIL induces RANKL expression through a STAT-6 dependent transcriptional regulatory mechanism in bone marrow stromal/preosteoblast cells.
authors.affiliation: Charles P. Darby Children's Research Institute, Medical University of South Carolina, Charleston, SC, USA.
authors.forename: Kumaran
authors.initials: K
authors.lastname: Sundaram
authors.affiliation: Charles P. Darby Children's Research Institute, Medical University of South Carolina, Charleston, SC, USA.
authors.forename: Yuvaraj
authors.initials: Y
authors.lastname: Sambandam
authors.affiliation: Department of Radiation Oncology, Medical University of South Carolina, Charleston, SC, USA.
authors.forename: Sundaravadivel
authors.initials: S
authors.lastname: Balasubramanian
authors.affiliation: Charles P. Darby Children's Research Institute, Medical University of South Carolina, Charleston, SC, USA.
authors.forename: Balakrishnan
authors.initials: B
authors.lastname: Pillai
authors.affiliation: Dept. of Microbiology & Immunology, Medical University of South Carolina, Charleston, SC, USA.
authors.forename: Christina
authors.initials: C
authors.lastname: Voelkel-Johnson
authors.affiliation: College of Dental Medicine, Medical University of South Carolina, Charleston, SC, USA.
authors.forename: William L
authors.initials: WL
authors.lastname: Ries
authors.affiliation: Charles P. Darby Children's Research Institute, Medical University of South Carolina, Charleston, SC, USA. Electronic address: reddysv@musc.edu.
authors.forename: Sakamuri V
authors.initials: SV
authors.lastname: Reddy
mesh_terms: D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics; D053245:RANK Ligand / Q000235:genetics* / Q000378:metabolism; D050800:STAT6 Transcription Factor / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D017154:Stromal Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000494:pharmacology*
chemical_list: D016328:NF-kappa B; D053245:RANK Ligand; D050800:STAT6 Transcription Factor; D053221:TNF-Related Apoptosis-Inducing Ligand; D048031:JNK Mitogen-Activated Protein Kinases
keywords: RANK ligand; STAT-6; Stromal/preosteoblasts; TRAIL