Silencing the expression of connexin 43 decreases inflammation and joint destruction in experimental arthritis

Abstract

The objective of the present study was to determine whether the expression of connexin 43 (Cx43) effected on inflammatory conditions in rat fibroblast-like synoviocytes (FLS) and on rat model of rheumatoid arthritis (RA). The expression of Cx43 in rat FLS stimulated with lipopolysaccharide (LPS) was confirmed by real-time reverse transcriptase polymerase chain reaction (RT-PCR). The effects of small-interfering RNA targeting Cx43 (siCx43) on pro-inflammatory cytokines and chemokine were assessed by real-time RT-PCR and enzyme-linked immunosorbent assay (ELISA). The therapeutic and side effects of siCx43 in a rat model of collagen-induced arthritis (CIA) were examined by in vivo electroporation method. LPS markedly enhanced Cx43 gene expression in rat FLS, with transfection of siCx43 suppressing the over-expression of pro-inflammatory cytokines and the chemokine. Treatment of CIA rats with siCx43 significantly ameliorated paw swelling, and significantly reduced histological arthritis scores and radiographic scores. In histological appearance of rat ankle joints, siCx43 treatment significantly decreased the number of tartrate-resistant acid phosphatase (TRAP)-positive (osteoclast-like) cells. These findings indicated that siCx43 had anti-inflammatory effects in rat FLS and efficiently inhibited the development of CIA. Cx43 may play an important role in the pathophysiology of RA, and may be a potential target molecule for novel RA therapies. Keywords: connexin 43; gap junction; pro-inflammatory cytokine; rheumatoid arthritis; collagen-induced arthritis Rheumatoid arthritis (RA) is one of the most common articular diseases, characterized by hyperproliferation of synovial cells and bone destruction. Pro-inflammatory cytokines and chemokines, including tumor necrosis factor (TNF)-a, interleukin (IL)-6, IL-1b, and stromal cell-derived factor 1 (CXCL12), have been associated with the progression of RA and may play pathogenic roles in the establishment of rheumatoid synovitis. 1,2Biological preparations targeting these pro-inflammatory cytokines are widely used clinically in the treatment of RA.3 However, there are caveats in using the biological preparations, including risk of infections such as tuberculosis, high cost, and individual variations in efficacy.4 Therefore, further investigations are needed to achieve remission of arthritis.Gap junctions are cell-cell communication channels, consisting of multimeric proteins called connexins, that allow the exchange of ions, second messengers, and metabolites between adjacent cells.5 To date, 21 human genes encoding connexins have been identified. The most widely expressed connexin gene is connexin 43 (Cx43), a protein expressed in the synovial cells and tissue.6 Cx43 plays an important role in the regulation of various immune processes. 7 In the nervous system, silencing of Cx43 downregulates the inflammatory response. 8,9 These reports suggest that Cx43 may be involved in RA pathophysiology, and that inhibition of Cx43 may decrease synovitis in RA.Therefore, we ...

Identification of shoulder osteoarthritis biomarkers: comparison between shoulders with and without osteoarthritis

“…12 As such, Cx43 might be a target in which pharmacological agents can block the gap protein and slow or halt the progression of OA in the shoulder. A study by Tsuchida et al 51 showed in a rat model of rheumatoid arthritis that inhibition of Cx43 protected against the development of inflammation and joint destruction. Increased Cx43 in osteoarthritic joints has biological plausibility considering that increased mechanical load can lead to both the degradation of joints and an increase in Cx43.…”

Regulation of Hemichannels and Gap Junction Channels by Cytokines in Antigen-Presenting Cells

“…In addition, immunofluorescence analysis of bones shows that most cells presented Panx3 at the growth plate [29], suggesting that OCs might express this protein. Finally, Cx43, forming either GJCs or HCs, is involved in the development of rheumatoid arthritis because silencing Cx43 in rat lower limbs reduces the number of OCs and delays the onset of this disease [174]. This suggests that Cx43 expression by OCs might contribute to the development of this disease and might be a relevant target for its treatment.…”

Expression of Connexin 43 in Synovial Tissue of Patients With Rheumatoid Arthritis

“…We also showed that the expression of Cx43 was enhanced in synovial tissue from rats with the collagen-induced arthritis (CIA) model of RA. 17 In this study, we demonstrated that the expression of Cx43 in RASFs was significantly enhanced by TNF-a stimulation and that high levels of Cx43 expression was associated with infiltration of inflammatory cells into synovial tissue of RA patients. These findings suggest that increased expression of Cx43 may be involved in the pathogenesis of RA synovitis.…”