Targeting bioenergetics prevents CD4 T cell–mediated activation of synovial fibroblasts in rheumatoid arthritis

Abstract

Objectives We investigated the reciprocal relationship linking fibroblast-like synoviocytes (FLS) and T lymphocytes in the inflamed RA synovium and subsequently targeted cellular metabolic pathways in FLS to identify key molecular players in joint inflammation. Methods RA FLS were cultured with CD4 T cells or T cell conditioned medium (CD4CM); proliferation, expression of adhesion molecules and intracellular cytokines were examined by flow cytometry. FLS invasiveness and secreted cytokines were measured by transwell matrigel invasion chambers and ELISA, while metabolic profiles were determined by extracellular Seahorse flux analysis. Gene expression was quantified by real-time quantitative RT-PCR. Results Our results showed mutual activation between CD4 T cells and FLS, which resulted in increased proliferation and expression of intercellular adhesion molecule 1 and vascular cell adhesion molecule 1 by both CD4 T cells and FLS. Furthermore, interaction between CD4 T cells and FLS resulted in an increased frequency of TNF-α+, IFN-γ+ and IL-17A+ CD4 T cells and augmented TNF-α, IFN-γ, IL-17A, IL-6, IL-8 and VEGF secretion. Moreover, CD4CM promoted invasiveness and boosted glycolysis in FLS while downregulating oxidative phosphorylation, effects paralleled by increased glucose transporters GLUT1 and GLUT3; key glycolytic enzymes GSK3A, HK2, LDHA and PFKFB3; angiogenic factor VEGF and MMP-3 and MMP-9. Importantly, these effects were reversed by the glycolytic inhibitor 2-DG and AMP analogue 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR). Conclusion This study demonstrates that CD4 T cells elicit an aggressive phenotype in FLS, which subsequently upregulate glycolysis to meet the increased metabolic demand. Accordingly, 2-DG and AICAR prevent this activation, suggesting that glycolytic manipulation could have clinical implications for RA treatment.

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

“…*p < 0.05, Wilcoxon signed-rank test. 3-BrPa, 3-bromopyruvate Th cells [26]. In contrast to these findings, we demonstrate here that the migratory capacities of OASF and RASF are significantly reduced under stimulation with ThCM and also under stimulation with inflammatory cytokines, especially when applied in combination.…”

“…In a recent study, Petrasca and colleagues demonstrated that Th cells promoted the aggressive phenotype in RASF by boosting glycolysis-confirmed here with our data-and this effect could be reversed by 2-deoxy-D-glucose (2-DG) or by the AMP analogue 5-aminoimidazole-4-carboxamide ribonucleotide [26]. An abrogation of the aggressive phenotype of RASF by 2-DG, a non-metabolizable glucose analogue which blocks glycolysis downstream of HK2, has also been described by others [19], and 2-DG has been shown to be effective in reducing the severity of arthritis in a mouse model [55].…”

“…The interaction between Th17 cells and SF has been described as a key mechanism for the development of synovial tissue inflammation [25]. Interaction and reciprocal activation of Th cells and RASF have recently been shown to induce and amplify inflammatory responses and to result in a metabolic shift towards glycolysis in SF to meet the increased metabolic demand [26]. On the other hand, interaction with Th cells induces immunosuppressive functions of SF, a capacity that has been shown to be reduced in RASF compared to OASF [27,28].…”

Metabolic Fitness of T Cells in Autoimmune Disease

“…The inflamed synovial lesions exclusively contain memory and effector T cells and these cells are exposed to metabolic cues imposed by the tissue environment. Besides having to share energy resources, lesional T cells will receive metabolic signals from neighboring cell populations, which are highly metabolically active [18]. A dominant metabolite encountered in the inflamed joint is lactate [19,20], a breakdown product of glucose, produced by metabolically active stromal cells, endothelial cells and invading immune cells.…”

Metabolic Control of Autoimmunity and Tissue Inflammation in Rheumatoid Arthritis

“…Heterozygous deletion of GLUT3 correlates directly with expression levels of GLUT3 and influences glycolysis rates in the human immune system ( 46 ), but the frequency of the GLUT3 copy number variant is not different among RA, multiple sclerosis and heathy control, providing no evidence for RA protection in deletion of GLUT3 ( 46 ), the study of which demonstrated GLUT3 is not necessary for glucose transfer in patients with RA. However, another study showed the mutual activation between CD4 + T cells and FLS, which resulted in increased proliferation and expression of glucose transporters GLUT1 and GLUT3 in FLS ( 47 ). In rat Arthritis model, arthritic rats showed cachexia, reduced adipocyte size, and downregulated GLUT4 in adipocyte membranes ( 48 ).…”