We have previously shown that CD4+ T cells from B6.Sle1.Sle2.Sle3 (TC) lupus mice and patients present a high cellular metabolism, and a treatment combining 2-deoxyglucose (2DG), which inhibits glucose metabolism, and metformin, which inhibits oxygen consumption, normalized lupus T cell functions in vitro and reverted disease in mice. We obtained similar results with B6.lpr mice, another model of lupus, and showed that a continuous treatment is required to maintain the beneficial effect of metabolic inhibitors. Further, we investigated the relative roles of glucose oxidation and pyruvate reduction into lactate in this process.. Treatments of TC mice with either 2DG or metformin were sufficient to prevent autoimmune activation, while their combination was necessary to reverse the process. Treatment of TC mice with dichloroacetate (DCA), an inhibitor of lactate production, failed to effectively prevent or reverse autoimmune pathology. In vitro, CD4+ T cell activation upregulated the expression of genes that favor oxidative phosphorylation. Blocking glucose oxidation inhibited both IFNγ and IL-17 production, which could not be achieved by blocking pyruvate reduction. Overall, our data shows that targeting glucose oxidation is required to prevent or reverse lupus development in mice, which cannot be achieved by simply targeting the pyruvate-lactate conversion.

The K/BxN mouse is a spontaneous model of arthritis driven by T cell receptor transgenic CD4+ T cells from the KRN strain that are activated by glucose-6-phosphate isomerase (GPI) peptides presented by the H-2g7 allele from the NOD strain. It is a model of autoimmune seropositive arthritis because the production of anti-GPI IgG is necessary and sufficient for joint pathology. The production of high levels of anti-GPI IgG requires on the expansion of CD4+ follicular helper T (Tfh) cells. The metabolic requirements of this expansion have never been characterized. Based on the therapeutic effects of the combination of metformin and 2-deoxyglucose (2DG) in lupus models that normalized the expansion of effector CD4+ T cells. We showed that the CD4+ T cells and to a lesser extent, the B cells from K/BxN mice are more metabolically active than the KRN controls. Accordingly, preventive inhibition of glycolysis with 2DG significantly reduced joint inflammation and the activation of both adaptive and innate immune cells, as well as the production of pathogenic autoantibodies. However, contrary to the lupus-prone mice, the addition of metformin had little beneficial effect, suggesting that glycolysis is the major driver of immune activation in this model. We propose that K/BxN mice are another model in which autoreactive Tfh cells are highly glycolytic and that their function can be limited by inhibiting glucose metabolism.

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We report a novel model of lupus-associated cardiovascular pathology accelerated by the TLR7 agonist R848 in lupus-prone B6.Sle1.Sle2.Sle3 (TC) mice. R848-treated TC mice but not non-autoimmune C57BL/6 (B6) controls developed microvascular inflammation and myocytolysis with intracellular vacuolization. This histopathology was similar to antibody-mediated rejection after heart transplant, although it did not involve complement. The TC or B6 recipients of serum or splenocytes from R848-treated TC mice developed a reactive cardiomyocyte hypertrophy, which also presents spontaneously in old TC mice as well as in TC.Rag-/- mice that lack B and T cells. Each of these cardiovascular lesions correspond to abnormalities that have been reported in lupus patients. Lymphoid and non-lymphoid immune cells as well as soluble factors contribute to lupus-associated cardiovascular lesions in TC mice, which can now be dissected using this model with and without R848 treatment.

Estrogen-related receptor gamma (Esrrg) is a murine lupus susceptibility gene associated with T cell activation. Here, we report that Esrrg controls regulatory T cells (Treg) through mitochondria homeostasis. Esrrg deficiency impaired the maintenance and function of Treg cells, leading to global T cell activation and autoimmunity in aged mice. Further, Esrrg-deficient Treg cells presented an impaired differentiation into follicular Treg (Tfr) cells that enhanced follicular helper T cells (Tfh) responses. Mechanistically, Esrrg-deficient Treg cells presented with dysregulated mitochondria with decreased oxygen consumption as well as ATP and NAD + production. In addition, Esrrg-deficient Treg cells exhibited decreased phosphatidylinositol and TGF-β signaling pathways and increased mTORC1 activation. We found that the expression of human ESRRG, which is high in Treg cells, was lower in CD4 + T cells from lupus patients than in healthy controls.Finally, knocking down ESRRG in Jurkat T cells decreased their metabolism. Together, our results reveal a critical role of Esrrg in the maintenance and metabolism of Treg cells, which may provide a genetic link between lupus pathogenesis and mitochondrial dysfunction in T cells.