Increase of aerobic glycolysis mediated by activated T helper cells drives synovial fibroblasts towards an inflammatory phenotype: new targets for therapy?

Abstract

Background A dysregulated glucose metabolism in synovial fibroblasts (SF) has been associated with their aggressive phenotype in rheumatoid arthritis (RA). Even though T helper (Th) cells are key effector cells in the propagation and exacerbation of synovitis in RA, little is known about their influence on the metabolism of SF. Thus, this study investigates the effect of Th cells on the glucose metabolism and phenotype of SF and how this is influenced by the blockade of cytokines, janus kinases (JAKs) and glycolysis. Methods SF from patients with RA or osteoarthritis (OA) were cultured in the presence of a stable glucose isotopomer ([U-13C]-glucose) and stimulated with the conditioned media of activated Th cells (ThCM). Glucose consumption and lactate production were measured by proton nuclear magnetic resonance (1H NMR) spectroscopy. Cytokine secretion was quantified by ELISA. The expression of glycolytic enzymes was analysed by PCR, western blot and immunofluorescence. JAKs were blocked using either baricitinib or tofacitinib and glycolysis by using either 3-bromopyruvate or FX11. Results Quiescent RASF produced significantly higher levels of lactate, interleukin (IL)-6 and matrix metalloproteinase (MMP) 3 than OASF. Stimulation by ThCM clearly changed the metabolic profile of both RASF and OASF by inducing a shift towards aerobic glycolysis with strongly increased lactate production together with a rise in IL-6 and MMP3 secretion. Interestingly, chronic stimulation of OASF by ThCM triggered an inflammatory phenotype with significantly increased glycolytic activity compared to unstimulated, singly stimulated or re-stimulated OASF. Finally, in contrast to cytokine-neutralizing biologics, inhibition of JAKs or glycolytic enzymes both significantly reduced lactate production and cytokine secretion by Th cell-stimulated SF. Conclusions Soluble mediators released by Th cells drive SF towards a glycolytic and pro-inflammatory phenotype. Targeting of JAKs or glycolytic enzymes both potently modulate SF’s glucose metabolism and decrease the release of IL-6 and MMP3. Thus, manipulation of glycolytic pathways could represent a new therapeutic strategy to decrease the pro-inflammatory phenotype of SF.

Targeting of Janus Kinases Limits Pro-Inflammatory but Also Immunosuppressive Circuits in the Crosstalk between Synovial Fibroblasts and Lymphocytes

“…Furthermore, we have previously shown that chronic stimulation of SF not only resulted in the development of an "inflammatory memory", but also in that of a "glycolytic memory". On top of an enhanced secretion of IL-6 and MMP3, repeated stimulation of SF with ThCM triggered a significantly increased glycolytic activity as compared to unstimulated, singly stimulated or even restimulated SF [40]. A dysregulated glucose metabolism in SF has been suggested to play a critical role in the pathogenesis of RA [59] and tofacitinib has been shown to suppress the glycolytic activity of RASF [37].…”

“…An inflammatory microenvironment not only induces a shift in SF phenotype towards inflammation and cartilage and bone destruction, but also leads to the imprinting of this aggressive phenotype, attributed at least in part to epigenetic modifications [20,57]. Remarkably, a pro-inflammatory memory has been described for SF primed by an inflammatory stimulus [58], and chronic stimulation of SF by ThCM triggered a significantly enhanced inflammatory memory response as compared to a single or even a second stimulation [40]. Hence, to be effective, any therapeutic option should be able to suppress the pro-inflammatory memory response of chronically activated SF.…”

“…In a previous study, we showed that chronic stimulation of SF by soluble factors released by activated Th cells resulted in a significantly enhanced inflammatory response as compared to a single or a second stimulation [40]. This might be important as RA treatment with these targeted drugs is normally initiated when arthritis is already ongoing for months to years.…”

Fibroblast Memory in Development, Homeostasis and Disease

“…Likewise, fibroblast metabolic and inflammatory memory seem to be closely associated. While metabolic memory in FLS and retinal pericytes is able to induce a persistent proinflammatory phenotype, activated T cells have been shown to reprogram fibroblast metabolism in inflammatory rheumatoid arthritis [ 90 , 112 ]. The way in which positional memory confers site-specific fibroblast behaviours and links to other environmental adaptations is largely unknown.…”

“…Loss of Cav-1 causes CAF metabolic reprogramming to aerobic glycolysis, mitochondrial dysfunction and increased autophagy/mitophagy, which propagates to neighbouring CAFs and promotes the anabolic growth of adjacent cancer cells [ 111 ]. Notably, in rheumatoid arthritis, T helper cells have been shown to reprogramme fibroblasts to a glycolytic phenotype [ 112 ], suggesting that fibroblast metabolic reprogramming is a common feature in cancer and inflammatory diseases. Similarly, this phenotype can be further induced and maintained by autocrine TGF-β signalling and is able to spread to adjacent fibroblasts through paracrine signalling [ 111 ].…”