Genetic Inactivation of ZCCHC6 Suppresses Interleukin‐6 Expression and Reduces the Severity of Experimental Osteoarthritis in Mice.
ANIMAL experimentation; CARTILAGE; CARTILAGE cells; DACTINOMYCIN; DNA-binding proteins; GENE expression; GENETIC aspects; IN vivo studies; INTERLEUKINS; MICE; MICRORNA; OSTEOARTHRITIS; PREVENTION; SEQUENCE analysis; SEVERITY of illness index; SYNOVITIS; TRANSCRIPTION factors
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 ZCCHC6 (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 ZCCHC6 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 ZCCHC6 in human chondrocytes was knocked down using small interfering RNAs. IL‐6 transcript stability was determined by actinomycin D chase, and 3′‐uridylation of microRNAs 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: ZCCHC6 was markedly up‐regulated in damaged cartilage from human OA patients and from wild‐type mice with surgically induced OA. Overexpression of ZCCHC6 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 ZCCHC6 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 ZCCHC6 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 ZCCHC6 as a novel therapeutic target to inhibit disease pathogenesis. [ABSTRACT FROM AUTHOR]
Ansari Mohammad Y; Khan Nazir M; Ahmad Nashrah; Green Jonathan; Novak Kimberly; Haqqi Tariq M
Arthritis & Rheumatology
2019
2019-04
<a href="http://doi.org/10.1002/art.40751" target="_blank" rel="noreferrer noopener">10.1002/art.40751</a>
Coordinate down-regulation of cartilage matrix gene expression in Bcl-2 deficient chondrocytes is associated with decreased SOX9 expression and decreased mRNA stability.
Aggrecans; Animals; C-Type; Cell Line; Chondrocytes/*physiology; Collagen Type II/genetics/metabolism; Dactinomycin; Down-Regulation; Extracellular Matrix Proteins/analysis/genetics/*metabolism; Gene Expression Regulation; Glycoproteins/analysis/genetics/*metabolism; High Mobility Group Proteins/genetics/*metabolism; Lectins; Matrilin Proteins; Messenger/analysis/biosynthesis; Polymerase Chain Reaction/methods; Proteoglycans/genetics/metabolism; Proto-Oncogene Proteins c-bcl-2/deficiency/genetics/*physiology; Rats; RNA; RNA Stability; Signal Transduction; SOX9 Transcription Factor; Transcription Factors/genetics/*metabolism; Transfection
The anti-apoptotic protein Bcl-2 has been shown to function in roles unrelated to apoptosis in a variety of cell types. We have previously reported that loss of Bcl-2 expression alters chondrocyte morphology and modulates aggrecan expression via an apoptosis-independent pathway. Here we show that Bcl-2 is required for chondrocytes to maintain expression of a variety of cartilage-specific matrix proteins. Using quantitative, real-time PCR, we demonstrate that Bcl-2-deficient chondrocytes coordinately down-regulate genes coding for hyaline cartilage matrix proteins including collagen II, collagen IX, aggrecan, and link protein. The decrease in steady-state level of these mRNA transcripts results, in part, from decreased mRNA stability in Bcl-2-deficient chondrocytes. Transcriptional regulation is also likely involved because chondrocytes with decreased Bcl-2 levels show decreased expression of SOX9, a transcription factor necessary for expressing the major cartilage matrix proteins. In contrast, chondrocytes constitutively expressing Bcl-2 have a stable phenotype when subjected to loss of serum factor signaling. These cells maintain high levels of SOX9, as well as the SOX9 targets collagen II and aggrecan. These results suggest that Bcl-2 is involved in a pathway important for maintaining a stable chondrocyte phenotype.
Kinkel Mary D; Horton Walter E Jr
Journal of cellular biochemistry
2003
2003-04
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1002/jcb.10442" target="_blank" rel="noreferrer noopener">10.1002/jcb.10442</a>