Downregulation of lncRNA ITSN1-2 correlates with decreased disease risk and activity of rheumatoid arthritis (RA), and reduces RA fibroblast-like synoviocytes proliferation and inflammation via inhibiting NOD2/RIP2 signaling pathway.

This study aimed to investigate the effect of lnc-ITSN1-2 knockdown on cell proliferation, apoptosis, inflammation and mRNA expression patterns in rheumatoid arthritis (RA) fibroblast-like synoviocytes (FLS), and the correlation of its synovium tissue expression with disease risk, inflammatory cytokines and disease activity of RA. Control shRNA plasmids and lnc-ITSN1-2 shRNA plasmids were transfected into RA FLS, and then cell proliferation, apoptosis, inflammatory cytokines expressions were evaluated. Subsequently, mRNA sequencing and bioinformatics analyses were conducted, and rescue experiment of nucleotide-binding oligomerization domain 2 (NOD2) mRNA overexpression on alleviating the functions of Inc-ITSN1-2 was performed. Additionally, lnc-ITSN1-2 and NOD2 mRNA expressions in synovial tissue in 30 RA patients and 15 controls were measured. Lnc-ITSN1-2 expression was increased in RA FLS compared with normal FLS. Lnc-ITSN1-2 knockdown inhibited RA FLS proliferation and inflammation while promoted RA FLS apoptosis. mRNA sequencing and bioinformatics analyses revealed 144 upregulated and 98 downregulated genes by lnc-ITSN1-2 knockdown, which were enriched in regulating inflammatory responses and cytokines related pathways. NOD2 was selected for rescue experiment, which disclosed that upregulating NOD2 alleviated the effect of lnc-ITSN1-2 knockdown on cell proliferation, apoptosis and inflammation in RA FLS. In addition, synovial tissue lnc-ITSN1-2 positively associated with NOD2 mRNA, and both of them positively correlated with disease risk, inflammation and activity of RA. Downregulation of lnc-ITSN1-2 correlates with decreased disease risk and activity of RA, and reduces RA FLS proliferation and inflammation via regulating NOD2/RIP2 signaling pathway.