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Genetic Inactivation of ZCCHC 6 Suppresses Interleukin‐6 Expression and Reduces the Severity of Experimental Osteoarthritis in Mice
Author(s) -
Ansari Mohammad Y.,
Khan Nazir M.,
Ahmad Nashrah,
Green Jonathan,
Novak Kimberly,
Haqqi Tariq M.
Publication year - 2019
Publication title -
arthritis and rheumatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.106
H-Index - 314
eISSN - 2326-5205
pISSN - 2326-5191
DOI - 10.1002/art.40751
Subject(s) - gene knockdown , pathogenesis , small interfering rna , cytokine , cartilage , gene expression , gene silencing , microbiology and biotechnology , interleukin , osteoarthritis , chemistry , biology , rna , cancer research , gene , immunology , medicine , pathology , biochemistry , anatomy , alternative medicine
Objective Cytokine expression is tightly regulated posttranscriptionally, but high levels of interleukin‐6 ( IL ‐6) in patients with osteoarthritis ( OA ) indicate that regulatory mechanisms are disrupted in this disorder. The enzyme ZCCHC 6 (zinc‐finger CCHC domain–containing protein 6; TUT ‐7) has been implicated in posttranscriptional regulation of inflammatory cytokine expression, but its role in OA pathogenesis is unknown. The present study was undertaken to investigate whether ZCCHC 6 directs the expression of IL ‐6 and influences OA pathogenesis in vivo. Methods Human and mouse chondrocytes were stimulated with recombinant IL ‐1β. Expression of ZCCHC 6 in human chondrocytes was knocked down using small interfering RNA s. IL ‐6 transcript stability was determined by actinomycin D chase, and 3′‐uridylation of micro RNA s was determined by deep sequencing. Zcchc6 −/− mice were produced by gene targeting. OA was surgically induced in the knee joints of mice, and disease severity was scored using a semiquantitative grading system. Results ZCCHC 6 was markedly up‐regulated in damaged cartilage from human OA patients and from wild‐type mice with surgically induced OA . Overexpression of ZCCHC 6 induced the expression of IL ‐6, and its knockdown reduced IL ‐6 transcript stability and IL ‐1β–induced IL ‐6 expression in chondrocytes. Reintroduction of Zcchc6 in Zcchc6 −/− mouse chondrocytes rescued the IL ‐1β–induced IL ‐6 expression. Knockdown of ZCCHC 6 reduced the population of micro‐ RNA 26b (miR‐26b) with 3′‐uridylation by 60%. Zcchc6 −/− mice with surgically induced OA produced low levels of IL ‐6 and exhibited reduced cartilage damage and synovitis in the joints. Conclusion These findings indicate that ZCCHC 6 enhances IL ‐6 expression in chondrocytes through transcript stabilization and by uridylating miR‐26b, which abrogates repression of IL ‐6. Inhibition of IL ‐6 expression and significantly reduced OA severity in Zcchc6 −/− mice identify ZCCHC 6 as a novel therapeutic target to inhibit disease pathogenesis.