title: Cell-specific effects of TNF-α and IL-1β on alkaline phosphatase: implication for syndesmophyte formation and vascular calcification.
abstract: Tumor necrosis factor (TNF)-α and interleukin (IL)-1β stimulate tissue non-specific alkaline phosphatase (TNAP) activity and mineralization in cultures of vascular smooth muscle cells (VSMCs). They are, therefore, considered as stimulators of vascular calcification in the context of atherosclerosis and diabetes type 2. In contrast, although ankylosing spondylitis (AS) leads to the formation of syndesmophytes, which are ectopic ossifications from entheses (where ligaments, tendons and capsules are attached to bone), anti-TNF-α therapies fail to block bone formation in this disease. In this context, our aims were to compare the effects of TNF-α and IL-1β on TNAP activity and mineralization in entheseal cells and VSMCs. Organotypic cultures of mouse ankle entheses were treated or not with TNF-α and IL-1β for 5 days. Micro-computed tomography was performed to determine trabecular bone parameters, and histology to assess TNAP activity and mineralization. Human mesenchymal stem cells cultured in pellets in chondrogenic conditions and human VSMCs were also used to determine the effects of cytokines on TNAP activity and expression, measured by quantitative PCR. In organotypic cultures, TNF-α and IL-1β significantly reduced the tibia BV/TV ratio. They also inhibited TNAP activity in entheseal chondrocytes in situ, and in mouse and human chondrocytes in vitro. In contrast, TNF-α stimulated TNAP expression and activity in human VSMCs. These differences were likely due to cell-specific effects of peroxisome proliferator-activated receptor γ (PPARγ), which is inhibited by TNF-α. Indeed, in human chondrocytes and VSMCs, the PPARγ inhibitor GW-9662 displayed the same opposite effects as TNF-α on TNAP expression. In conclusion, whereas TNF-α and IL-1β stimulate TNAP activity in VSMCs, they inhibit it in entheseal cells in situ and on chondrocytes in vitro. The identification of PPARγ as a likely mediator of cytokine effects deserves consideration for future research on the mechanisms of ectopic ossification.
authors.affiliation: Université Lille Nord de France, Lille, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Lencel
authors.forename: Séverine
authors.initials: S
authors.lastname: Delplace
authors.forename: Paul
authors.initials: P
authors.lastname: Pilet
authors.forename: Damien
authors.initials: D
authors.lastname: Leterme
authors.forename: Flore
authors.initials: F
authors.lastname: Miellot
authors.forename: Sophie
authors.initials: S
authors.lastname: Sourice
authors.forename: Axelle
authors.initials: A
authors.lastname: Caudrillier
authors.forename: Pierre
authors.initials: P
authors.lastname: Hardouin
authors.forename: Jérome
authors.initials: J
authors.lastname: Guicheux
authors.forename: David
authors.initials: D
authors.lastname: Magne
mesh_terms: D000125:Achilles Tendon / Q000378:metabolism* / Q000502:physiology; D000328:Adult; D000469:Alkaline Phosphatase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000818:Animals; D000843:Ankle Joint / Q000000981:diagnostic imaging; D001011:Aorta / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D002114:Calcinosis / Q000209:etiology; D002454:Cell Differentiation; D002478:Cells, Cultured; D019902:Chondrocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D020219:Chondrogenesis / Q000502:physiology; D005260:Female; D006801:Humans; D053583:Interleukin-1beta / Q000494:pharmacology*; D007719:Knee Joint / Q000000981:diagnostic imaging; D008297:Male; D059630:Mesenchymal Stem Cells / Q000166:cytology; D051379:Mice; D008810:Mice, Inbred C57BL; D008903:Minerals / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009924:Organ Culture Techniques; D009999:Ossification, Heterotopic / Q000209:etiology; D047495:PPAR gamma / Q000037:antagonists & inhibitors / Q000378:metabolism; D014057:Tomography, X-Ray Computed; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D014652:Vascular Diseases / Q000209:etiology
chemical_list: D053583:Interleukin-1beta; D008903:Minerals; D047495:PPAR gamma; D014409:Tumor Necrosis Factor-alpha; C510878:ALPL protein, mouse; D000469:Alkaline Phosphatase