gms | German Medical Science

Background: There is growing evidence for a dysregulated glucose metabolism of synovial fibroblasts (SF) in rheumatoid arthritis (RA) being a prerequisite for their aggressive phenotype. As yet, little is known about the influence of immune cells on the metabolism of SF although local infiltration of leucocytes constitutes a hallmark in the pathogenesis of RA. In this study, we investigated the effect of T helper (Th) cells on the glucose metabolism and cytokine production of non inflammatory and inflammatory SF in vitro.

Methods: RASF as well as SF from patients with osteoarthritis (OA) were cultured in the presence of a stable glucose isotope (U-13C) and stimulated with culture supernatants (SN) of activated Th cells. Lactate production was measured by proton nuclear magnetic resonance spectroscopy (H-NMR). Secretion of interleukin (IL)-6, IL-8 and matrix metalloprotease (MMP)-3 was quantified by ELISA. The expression of hexokinase (HK)-II, pyruvate kinase (PK)-M2 and pyruvate dehydrogenase (PDH) was analysed by PCR, western blot and immunofluorescence. Janus kinases (JAKs) were blocked by Baricitinib or Tofacitinib, glycolysis was inhibited by 3-Bromopyruvate (3-BP) or Fx11.

Results: In the absence of stimulation, RASF showed a significantly higher lactate production and IL-6 and MMP-3 secretion compared to OASF. Stimulation by Th cell SN strikingly changed the metabolic profile of both RASF and OASF by inducing a shift towards aerobic glycolysis with strongly increased lactate production. In parallel, a significant increase in IL-6 and MMP-3 secretion was induced. Interestingly, Bariticinib and Tofacitinib as well as glycolytic inhibitors significantly reduced both the production of lactate and the secretion of inflammatory cytokines. Finally, perpetual stimulation of non-inflammatory OASF by Th cell SN triggered an inflammatory phenotype characterized by significantly higher amounts of lactate, IL-6 and MMP-3 compared to non- or single stimulated SF.

Conclusion: Chronic stimulation of non-inflammatory SF by activated Th cells provoked an aggressive phenotype with strongly increased glycolytic activity and upregulated secretion of inflammatory cytokines. This was blocked by both JAK- and glycolytic inhibitors. These observations suggest that the Th cell-mediated metabolic switch towards aerobic glycolysis in SF is an important step in the pathogenesis of RA. Targeting this mechanism could provide a new strategy in the therapy of RA.