title: PKA-induced receptor activator of NF-kappaB ligand (RANKL) expression in vascular cells mediates osteoclastogenesis but not matrix calcification.
abstract: Vascular calcification is a predictor of cardiovascular mortality and is prevalent in patients with atherosclerosis and chronic renal disease. It resembles skeletal osteogenesis, and many bone cells as well as bone-related factors involved in both formation and resorption have been localized in calcified arteries. Previously, we showed that aortic medial cells undergo osteoblastic differentiation and matrix calcification both spontaneously and in response to PKA agonists. The PKA signaling pathway is also involved in regulating bone resorption in skeletal tissue by stimulating osteoblast-production of osteoclast regulating cytokines, including receptor-activator of nuclear κB ligand (RANKL) and interleukins. Therefore, we investigated whether PKA activators regulate osteoclastogenesis in aortic smooth muscle cells (SMC). Treatment of murine SMC with the PKA agonist forskolin stimulated RANKL expression at both mRNA and protein levels. Forskolin also stimulated expression of interleukin-6 but not osteoprotegerin (OPG), an inhibitor of RANKL. Consistent with these results, osteoclastic differentiation was induced when monocytic preosteoclasts (RAW264.7) were cocultured with forskolin-treated aortic SMC. Oxidized phospholipids also slightly induced RANKL expression in T lymphocytes, another potential source of RANKL in the vasculature. Because previous studies have shown that RANKL treatment alone induces matrix calcification of valvular and vascular cells, we next examined whether RANKL mediates forskolin-induced matrix calcification by aortic SMC. RANKL inhibition with OPG had little or no effect on osteoblastic differentiation and matrix calcification of aortic SMC. These findings suggest that, as in skeletal tissues, PKA activation induces bone resorptive factors in the vasculature and that aortic SMC calcification specifically induced by PKA, is not mediated by RANKL.
authors.affiliation: Department of Physiological Science, University of California, Los Angeles, California 90095, USA.
authors.forename: Wendy
authors.initials: W
authors.lastname: Tseng
authors.forename: Lucia S
authors.initials: LS
authors.lastname: Graham
authors.forename: Yifan
authors.initials: Y
authors.lastname: Geng
authors.forename: Aneela
authors.initials: A
authors.lastname: Reddy
authors.forename: Jinxiu
authors.initials: J
authors.lastname: Lu
authors.forename: Rita B
authors.initials: RB
authors.lastname: Effros
authors.forename: Linda
authors.initials: L
authors.lastname: Demer
authors.forename: Yin
authors.initials: Y
authors.lastname: Tintut
mesh_terms: D000818:Animals; D001011:Aorta / Q000378:metabolism* / Q000473:pathology; D001018:Aortic Diseases / Q000378:metabolism* / Q000473:pathology; D002114:Calcinosis / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D002454:Cell Differentiation / Q000187:drug effects / Q000235:genetics; D002460:Cell Line; D005576:Colforsin / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism*; D016207:Cytokines / Q000096:biosynthesis* / Q000235:genetics; D005109:Extracellular Matrix / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D005786:Gene Expression Regulation; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism; D051379:Mice; D009131:Muscle, Smooth, Vascular / Q000378:metabolism* / Q000473:pathology; D032389:Myocytes, Smooth Muscle / Q000378:metabolism* / Q000473:pathology; D010006:Osteoblasts / Q000378:metabolism / Q000473:pathology; D010010:Osteoclasts / Q000378:metabolism* / Q000473:pathology; D010743:Phospholipids / Q000235:genetics / Q000378:metabolism; D053245:RANK Ligand / Q000096:biosynthesis* / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis; D013601:T-Lymphocytes / Q000378:metabolism / Q000473:pathology
chemical_list: D016207:Cytokines; C508600:IL6 protein, human; D015850:Interleukin-6; D010743:Phospholipids; D053245:RANK Ligand; D012333:RNA, Messenger; C505688:TNFSF11 protein, human; C505689:Tnfsf11 protein, mouse; C025940:bone resorption factor; D005576:Colforsin; D017868:Cyclic AMP-Dependent Protein Kinases