Proinflammatory profile of autoimmune CD8+ T cells relies on increased LDHA activity and aerobic glycolysis.

OBJECTIVES CD8+ T cells (CD8) contribute to rheumatoid arthritis (RA) by releasing pro-inflammatory and cytolytic mediators, even in a challenging hypoxic and nutrient-poor microenvironment like the synovial membrane (SM). Here we explore the mechanisms through which RA CD8 meet their metabolic demands. METHODS Purified blood CD8 from RA, PsA, SpA and control individuals, and from RA SM were stimulated in media containing 13 C-labeled metabolic substrates in the presence or absence of metabolic inhibitors under normoxia or hypoxia. The production of metabolic intermediates was quantified by 1 H nuclear magnetic resonance. The expression of metabolic enzymes, transcription factors and immune effector molecules was assessed at mRNA and protein levels. Functional studies were performed. RESULTS Blood RA CD8 met their metabolic demands through aerobic glycolysis (uniformly 13 C-enriched lactate in RA: 2.6 to 3.7-fold higher than SpA, PsA and controls, p<0.01) and glutaminolysis. Overexpression of Warburg effect-linked enzymes in all RA CD8 subsets maintained this metabolic profile, conferring RA CD8 the capacity to proliferate under hypoxia and low glucose conditions. LDHA was overexpressed at mRNA (n=6/group, p<0.03) and protein (RA n=17, controls n=9, p<0.05) levels in all RA subsets. Inhibition of LDHA with FX11 reduced lipogenesis, migration, proliferation and effector functions in RA CD8, while increasing ROS production 1.5-fold (p<0.03). Under FX11, RA CD8 lost their capacity to induce healthy B cells to develop a pro-inflammatory phenotype. Similar metabolic alterations were observed in SM RA CD8. CONCLUSION Remodeling glucose and glutamine metabolism in RA CD8 by targeting LDHA activity can reduce their deleterious inflammatory and cytolytic contribution to autoimmunity.