Tripterygium wilfordii derivative LLDT-8 targets CD2 in the treatment of rheumatoid arthritis

Rheumatoid arthritis (RA), a chronic inflammatory synovitis systemic disease, can lead to joint deformities, loss of function and even death. The pathogenesis of RA may be related to genetics, infection and/or sex hormones; however, detailed accounts of the molecular mechanisms underlying its pathogenesis are lacking. In the present study, the synovial tissues of patients with RA and healthy individuals were analyzed to identify the pathogenic signaling pathways and key candidate genes involved in RA. Gene Ontology (GO), pathway enrichment and protein-protein interaction analysis were further used to identify the differentially expressed genes (DEGs) and their potential roles in RA. Molecular docking was used to screen the potential candidate drugs for management of RA. Small interfering RNA was used for knockdown of the CD2 protein. A Cell Counting Kit-8 assay was used to detect the proliferation of cells. Changes in the levels of inflammatory cytokines were detected using ELISA. A total of 279 DEGs were identified in RA; amongst these genes, 166 and 113 were upregulated and downregulated, respectively. GO analysis revealed that the upregulated DEGs were primarily enriched in the activation of the immune and adaptive immune responses, as well as the inflammatory response. The T-cell surface antigen CD2 (CD2) was identified as the most important hub gene by selecting the most important module from the protein-protein interaction network. Knockout of CD2 reduced the damaging effects of TNF-α on synovial cells. Through in situ screening using computer-aided drug design, the triptolide derivative (5R)-5-hydroxytriptolide (LLDT-8) was determined to have the highest docking score based on the CD2 protein structure. Cell experiments showed that LLDT-8 could inhibit the expression of CD2. Cell proliferation and inflammatory cytokine assays confirmed that CD2 was the direct target of LLDT-8. Together, the results of the present study determined factors involved in the pathogenesis of RA and the important role of CD2 in this process by analyzing the DEGs in the RA process. LLDT-8 inhibited CD2 and may thus be used to treat RA. These candidate genes and signaling pathways may serve as potential targets for the clinical treatment of RA.