Pharmacologic inhibition of glycolysis prevents the development of lupus by altering the gut microbiome in mice

Gut Expansion of a Human Lupus Pathobiont is Associated With Autoantibody Production and T Cell Dysregulation

OBJECTIVE

The mechanisms by which the gut microbiome contributes to lupus pathogenesis remain poorly understood. The anaerobe Ruminococcus gnavus (RG) expands in patients with lupus in association with flares. The goal of this study was to determine the mechanisms by which candidate pathobiont lipoglycan-producing RG2 may contribute to autoimmunity and to identify factors promoting its expansion.

METHODS

The consequences of RG colonization or depletion were evaluated in the B6.Sle1.Sle2.Sle3 triple congenic (TC) lupus model by flow cytometry and enzyme-linked immunosorbent assay. RG lysates were tested on Treg cells in vitro. Fecal microbiota transfers evaluated the contribution of the microbiome origin from lupus or control donors and dietary tryptophan. RG1 and RG2 growth and metabolome were evaluated in response to tryptophan in vitro.

RESULTS

Only RG2 stably colonized TC mice, in which it induced autoantibody production and T cell activation. Depletion of anaerobes had the opposite effect, with an increased Treg frequency. RG2 induced Treg apoptosis in cocultures with dendritic cells. RG is present in TC microbiota, from which it is amplified by tryptophan. The combination of TC microbiota and high dietary tryptophan induced autoimmune activation and intestinal inflammation in healthy control mice. Finally, tryptophan enhanced RG2 growth and production of immunomodulatory metabolites.

CONCLUSION

RG2 contributes to autoimmune activation, at least by inducing Treg apoptosis. The expansion of this pathobiont is promoted by host genetic factors and tryptophan metabolism. Thus, targeted RG2 depletion may improve disease outcomes in patients with lupus.

Microbiota transfer early after birth modulates genetic susceptibility to chronic arthritis in mice

Genetics is central to the susceptibility or resistance to autoimmunity, and mounting evidence indicates that the intestinal microbiota also plays an essential role. In murine arthritis models, short-chain fat acid supplementation reduces disease severity by modulating tryptophan-metabolizing bacteria. Common microbiota transfer methods modulate arthritis severity, however, they are not practical for chronic models such as pristane-induced arthritis (PIA). PIA-resistant (HIII) and PIA-susceptible (LIII) mice harbor diverse intestinal microbiomes, which might be implicated in their divergent susceptibility. To investigate this hypothesis, we used cross-fostering to stably transfer the microbiota. In this study, we show that extreme susceptibility to arthritis can be modulated by early microbiota transfer, with long-lasting effects. HIII and LIII pups were cross-fostered and injected with pristane after weaning. PIA severity in cross-fostered LIII mice was significantly reduced in the chronic phase. Metagenomic analyses showed that HIII and LIII microbiomes were partly shifted by cross-fostering. Microbial groups whose abundance was associated with either HIII or LIII mice presented similar composition in cross-fostered mice of the opposite strains, suggesting a role in PIA susceptibility. Identification of bacterial groups that modulate chronic arthritis will contribute novel insights on the pathogenesis of human rheumatoid arthritis and targets for replication and functional studies.

The role of gut microbiota in different murine models of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disorder characterized by immune system dysfunction that can lead to serious health issues and mortality. Recent investigations highlight the role of gut microbiota alterations in modulating inflammation and disease severity in SLE. This review specifically summaries the variations in gut microbiota composition across various murine models of lupus. By focusing on these differences, we aim to elucidate the intricate relationship between gut microbiota dysbiosis and the development and progression of SLE in preclinical settings.

Glutaminolysis promotes the function of follicular helper T cells in lupus-prone mice

Glutamine metabolism is essential for T cell activation and functions. The inhibition of glutaminolysis impairs Th17 cell differentiation and alters Th1 cell functions. There is evidence for an active glutaminolysis in the immune cells of lupus patients. Treatment of lupus-prone mice with glutaminolysis inhibitors ameliorated disease in association with a reduced frequency of Th17 cells. This study was performed to determine the role of glutaminolysis in murine Tfh cells, a critical subset of helper CD4 + T cells in lupus that provide help to autoreactive B cells to produce autoantibodies. We showed that lupus Tfh present a high level of glutamine metabolism. The pharmacological inhibition of glutaminolysis with DON had little effect on the Tfh cells of healthy mice, but it reduced the expression of the critical costimulatory molecule ICOS on lupus Tfh cells, in association with a reduction of autoantibody production, germinal center B cell dynamics, as well as a reduction of the frequency of atypical age-related B cells and plasma cells. Accordingly, profound transcriptomic and metabolic changes, including an inhibition of glycolysis, were induced in lupus Tfh cells by DON, while healthy Tfh cells showed little changes. The T cell-specific inhibition of glutaminolysis by deletion of the gene encoding for the glutaminase enzyme GLS1 largely phenocopied the effects of DON on Tfh cells and B cells in an autoimmune genetic background with little effect in a congenic control background. These results were confirmed in an induced model of lupus. Finally, we showed that T cell-specific Gls1 deletion impaired T- dependent humoral responses in autoimmune mice as well as their Tfh response to a viral infection. Overall, these results demonstrated a greater intrinsic requirement of lupus Tfh cells for their helper functions, and they suggest that targeting glutaminolysis may be beneficial to treat lupus.

Glycolysis inhibition functionally reprograms T follicular helper cells and reverses lupus

Systemic lupus erythematosus (SLE) is an autoimmune disease in which the production of pathogenic autoantibodies depends on T follicular helper (T FH ) cells. This study was designed to investigate the mechanisms by which inhibition of glycolysis with 2-deoxy-d-glucose (2DG) reduces the expansion of T FH cells and the associated autoantibody production in lupus-prone mice. Integrated cellular, transcriptomic, epigenetic and metabolic analyses showed that 2DG reversed the enhanced cell expansion and effector functions, as well as mitochondrial and lysosomal defects in lupus T FH cells, which include an increased chaperone-mediated autophagy induced by TLR7 activation. Importantly, adoptive transfer of 2DG-reprogrammed T FH cells protected lupus-prone mice from disease progression. Orthologs of genes responsive to 2DG in murine lupus T FH cells were overexpressed in the T FH cells of SLE patients, suggesting a therapeutic potential of targeting glycolysis to eliminate aberrant T FH cells and curb the production of autoantibodies inducing tissue damage.

Intersection of the microbiome and immune metabolism in lupus

Systemic lupus erythematosus is a complex autoimmune disease resulting from a dysregulation of the immune system that involves gut dysbiosis and an altered host cellular metabolism. This review highlights novel insights and expands on the interactions between the gut microbiome and the host immune metabolism in lupus. Pathobionts, invasive pathogens, and even commensal microbes, when in dysbiosis, can all trigger and modulate immune responses through metabolic reprogramming. Changes in the microbiota's global composition or individual taxa may trigger a cascade of metabolic changes in immune cells that may, in turn, reprogram their functions. Factors contributing to dysbiosis include changes in intestinal hypoxia, competition for glucose, and limited availability of essential nutrients, such as tryptophan and metal ions, all of which can be driven by host metabolism changes. Conversely, the accumulation of some host metabolites, such as itaconate, succinate, and free fatty acids, could further influence the microbial composition and immune responses. Overall, mounting evidence supports a bidirectional relationship between host immunometabolism and the microbiota in lupus pathogenesis.

Dietary tryptophan and genetic susceptibility expand gut microbiota that promote systemic autoimmune activation

Tryptophan modulates disease activity and the composition of microbiota in the B6.Sle1.Sle2.Sle3 (TC) mouse model of lupus. To directly test the effect of tryptophan on the gut microbiome, we transplanted fecal samples from TC and B6 control mice into germ-free or antibiotic-treated non-autoimmune B6 mice that were fed with a high or low tryptophan diet. The recipient mice with TC microbiota and high tryptophan diet had higher levels of immune activation, autoantibody production and intestinal inflammation. A bloom of Ruminococcus gnavus (Rg), a bacterium associated with disease flares in lupus patients, only emerged in the recipients of TC microbiota fed with high tryptophan. Rg depletion in TC mice decreased autoantibody production and increased the frequency of regulatory T cells. Conversely, TC mice colonized with Rg showed higher autoimmune activation. Overall, these results suggest that the interplay of genetic and tryptophan can influence the pathogenesis of lupus through the gut microbiota.

Metabolic Modulators in Cardiovascular Complications of Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a multifactorial disorder with contributions from hormones, genetics, and the environment, predominantly affecting young women. Cardiovascular disease is the primary cause of mortality in SLE, and hypertension is more prevalent among SLE patients. The dysregulation of both innate and adaptive immune cells in SLE, along with their infiltration into kidney and vascular tissues, is a pivotal factor contributing to the cardiovascular complications associated with SLE. The activation, proliferation, and differentiation of CD4+ T cells are intricately governed by cellular metabolism. Numerous metabolic inhibitors have been identified to target critical nodes in T cell metabolism. This review explores the existing evidence and knowledge gaps concerning whether the beneficial effects of metabolic modulators on autoimmunity, hypertension, endothelial dysfunction, and renal injury in lupus result from the restoration of a balanced immune system. The inhibition of glycolysis, mitochondrial metabolism, or mTORC1 has been found to improve endothelial dysfunction and prevent the development of hypertension in mouse models of SLE. Nevertheless, limited information is available regarding the potential vasculo-protective effects of drugs that act on immunometabolism in SLE patients.