Session Title: Rheumatoid Arthritis - Animal Models I
Session Type: Abstract Submissions (ACR)
Background/Purpose: Many of the signaling pathways activated in inflammation have a profound effect on cell metabolism. However, little is known about metabolome in rheumatoid arthritis (RA), particularly in fibroblast-like synoviocytes (FLS). The shift from ATP generation through oxidative phosphorylation to glycolysis has been implicated not only in tumor cells growth but also in immune cell function upon activation. To determine the role of glycolysis in arthritis, we examined glucose metabolism in FLS and evaluated whether this pathway could play a role in inflammation and joint damage.
Methods: The glucose profile of FLS cells was determined by 1H-MRS. Analysis of FLS oxygen consumption/extracellular acidification after LPS stimulation used Seahorse technology. FLS function using the glycolysis inhibitor 2-Deoxy-D-glucose (2-DG) in medium and platelet derived growth factor (PDGF) stimulated cells was evaluated by measuring 1) migration of cultured FLS monolayers (scratch assay); 2) proliferation using an MTT assay; and 3) protein expression by ELISA. For arthritis experiments, mice were injected with K/BxN sera on day 0. The glycolysis inhibitor bromopyruvate (BrPa; 5mg/kg) was injected daily i.p. beginning on day 0 after serum administration. Clinical arthritis scores were serially assessed. Joint histology was evaluated using a semiquantitative scoring system.
Results: One-dimensional 1H MRS spectra of aqueous extracts revealed 39.8±5.2% higher intracellular lactate accumulation in RA FLS compared with osteoarthritis (OA) FLS (p<0.01) indicating increased glycolytic rate. Of interest, FLS also displayed an unusual mitochondrial response, decreasing mitochondrial respiration (pmol O2/min) and increasing extracellular acidification (mpH/min) by 49.6±10.2% and 44±8.6% respectively after LPS stimulation. Glycolysis regulated key FLS functions that might contribute to cartilage damage in RA. For example, glycolysis inhibition with 2-DG (10 mM) reduced MMP3 and IL-6 secretion by 68±5.2% and 75±4.3%, respectively (p<0.01). Proliferation was reduced by 79±7.2% and migration by 63±15% (p<0.05). Finally, glycolysis inhibition by BrPa significantly decreased arthritis severity. Day 8 scores were 11.6±1.5 and 2±0.6 (P<0.01) for vehicle and BrPa-treated mice, respectively. Joint histology scores for vehicle and BrPa-treated mice for inflammation were 2.3±1.1 and 0.25±0.35 (p<0.01), bone erosion scores were 1.8±1.2 and 0.12±0.35 (p<0.01), and cartilage damage scores were 2.1±0.83 and 0.88±0.35 (p<0.01), respectively.
Conclusion: The metabolic profile in RA FLS suggests that glucose metabolism is abnormal and has shifted to ATP generation through oxidative phosphorylation to glycolysis. Blocking this pathway with a glycolysis inhibitor suppressed inflammatory arthritis in mice as well as the aggressive behavior of cultured RA FLS, including proliferation, cytokine secretion and cell migration. These data suggest that glycolysis inhibition may be disease modifying by directly modulating synoviocyte mediated functions and could be an effective strategy for arthritis.
G. S. Firestein,
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/targeting-glycolysis-in-rheumatoid-arthritis/