Dual inhibition of glutaminolysis and autophagy suppresses proliferation of Rheumatoid arthritis fibroblast-like synoviocytes and mitigates arthritis in SKG mice

Recent evidence highlights the critical role of immune metabolism in the pathogenesis of rheumatoid arthritis (RA). We previously demonstrated that glutaminase 1 (GLS1), a key enzyme in glutamine metabolism, is upregulated in fibroblast-like synoviocytes from RA patients (RA-FLS) and that GLS1 inhibition exerts an antiproliferative effect on RA-FLS. Glutaminolysis has also been shown to suppress autophagy, raising the possibilitiy that inhibiting glutaminolysis may enhance autophagy. Given this interplay, we hypothesized that dual inhibition of glutaminolysis and autophagy could synergistically suppress RA-FLS proliferation. This study aimed to investigate the effects of combining autophagy and glutaminolysis inhibition on RA-FLS and arthritis in SKG mice. We utilized chloroquine (CQ) as an autophagy inhibitor and compound 968 (C968), a GLS1 inhibitor, to suppress glutaminolysis. Treatment with C968 upregulated LC3B and ATG5 expression and increased LC3-II protein levels in RA-FLS, indicative of enhanced autophagy. Furthermore, C968 promoted autophagosome formation in RA-FLS. These findings confirm that glutaminolysis inhibition enhances autophagy in RA-FLS. The combination of C968 and CQ significantly inhibited RA-FLS proliferation and increased apoptotic cell death. Moreover, C968-CQ co-treatment markedly alleviated arthritis severity in SKG mice. Our findings suggest that concurrent suppression of glutaminolysis and autophagy represents a promising therapeutic strategy for RA.