Context: Rheumatoid arthritis (RA) is an autoimmune disease with the aberrant differentiation of T helper 17 (Th17) cells. Pyruvate kinase M2 (PKM2), a key enzyme of glycolysis, was associated with Th17 cell differentiation.
Aim: To investigate the potential therapeutic effects of triptolide (TP) in collagen-induced arthritis (CIA) and Th17 cell differentiation, and elucidated the underlying mechanisms.
Methods: PKM2 expression and IL-17A production in peripheral blood of RA patients were detected by RT-qPCR or ELISA. Flow cytometry and ELISA were employed to assess the effect of Th17 cell differentiation by TP. PKM2 expression and other glycolysis-related factors were detected using RT-qPCR and Western Blot. PKM2 specific inhibitor Compound 3 K was used to verify the mechanisms. Male DBA/1J mice were divided into control, model, and TP (60 μg/kg) groups to assess the anti-arthritis effect, Th17 cell differentiation and PKM2 expression.
Results: PKM2 expression positively correlated with IL-17A production in RA patients. PKM2 expression was increased upon Th17 cell differentiation. Down-regulating PKM2 expression could strongly reduce Th17 cell differentiation. Molecular docking analysis predicted that TP targeted PKM2. TP treatment significantly reduced Th17 cell differentiation, PKM2 expression, pyruvate, and lactate production. In addition, compared with down-regulating PKM2 alone (Compound 3 K treatment), co-treatment with TP and Compound 3 K further significantly decreased PKM2-mediated glycolysis and Th17 cell differentiation. In CIA mice, TP repressed the PKM2-mediated glycolysis and attenuated joint inflammation.
Conclusion: TP inhibited Th17 cell differentiation through the inhibition of PKM2-mediated glycolysis. We highlight a novel strategy for the use of TP in RA treatment.
Keywords: Immunometabolism; PKM2; Th17; rheumatoid arthritis; triptolide.