Nrf2/ARE Signaling Directly Regulates SOX9 to Potentially Alter Age-Dependent Cartilage Degeneration

Antioxidants

Thomas Pufe¹  Claudius Conrads¹  Prathyusha Pavanram¹  Rainer Beckmann¹  Athanassios Fragoulis¹  Christoph Jan Wruck¹  Holger Jahr¹  Yusuke Kubo¹  Sven Nebelung²  Michael Wolf³ 

[1] Department of Anatomy and Cell Biology, Uniklinik RWTH Aachen, Wendlingweg 2, D-52074 Aachen, Germany;Department of Diagnostic and Interventional Radiology, Uniklinik RWTH Aachen, Pauwelsstraße 30, D-52074 Aachen, Germany;Department of Orthodontics, Uniklinik RWTH Aachen, Pauwelsstraße 30, D-52074 Aachen, Germany;

关键词: SOX9;    Nrf2;    antioxidant response element;    Keap1;    osteoarthritis;   

DOI  :  10.3390/antiox11020263

来源: DOAJ

【 摘 要 】

Oxidative stress is implicated in osteoarthritis, and nuclear factor erythroid 2–related factor 2 (Nrf2)/antioxidant response element (ARE) pathway maintains redox homeostasis. We investigated whether Nrf2/ARE signaling controls SOX9. SOX9 expression in human C-28/I2 chondrocytes was measured by RT–qPCR after shRNA-mediated knockdown of Nrf2 or its antagonist the Kelch-like erythroid cell-derived protein with cap ‘‘n’’ collar homology-associated protein 1 (Keap1). To verify whether Nrf2 transcriptionally regulates SOX9, putative ARE-binding sites in the proximal SOX9 promoter region were inactivated, cloned into pGL3, and co-transfected with phRL–TK for dual-luciferase assays. SOX9 promoter activities without and with Nrf2-inducer methysticin were compared. Sox9 expression in articular chondrocytes was correlated to cartilage thickness and degeneration in wild-type (WT) and Nrf2-knockout mice. Nrf2-specific RNAi significantly decreased SOX9 expression, whereas Keap1-specific RNAi increased it. Putative ARE sites (ARE₁, ARE₂) were identified in the SOX9 promoter region. ARE₂ mutagenesis significantly reduced SOX9 promoter activity, but ARE₁ excision did not. Functional ARE₂ site was essential for methysticin-mediated induction of SOX9 promoter activity. Young Nrf2-knockout mice revealed significantly lower Sox9-positive chondrocytes, and old Nrf2-knockout animals showed thinner cartilage and more cartilage degeneration. Our results suggest Nrf2 directly regulates SOX9 in articular cartilage, and Nrf2-loss can develop mild osteoarthritis at old age. Pharmacological Nrf2 induction may hold the potential to diminish age-dependent cartilage degeneration through improving SOX9 expression.

【 授权许可】

Unknown