FRI0076 LACTATE/SLC5A12-induced metabolic signalling network: a new target in rheumatoid arthritis
Authors: V Pucino, J Smith, D Cucchi, K Blighe, M Bombardieri, C Pitzalis, C Mauro
Journal: Annals of the Rheumatic Diseases (2017)

<h3>Background</h3> RA is a systemic-autoimmune-disease characterized by chronic inflammation of the synovial-joints. Up to 30–40% of patients do not respond to treatment and current biomarkers are largely insensitive at predicting disease progression and response to treatment. It is well recognised that RA-synovitis is a heterogeneous pathology with different histological phenotypes i.e. lymphoid-(L), myeloid-(M) and fibroid-(F). As a result of inflammation the RA synovial microenvironment is hypoxic and acidic partly due to the accumulation of lactate, the end product of anaerobic glycolysis. Exposure of CD4<sup>+</sup> T cells to lactate inhibits their migratory capabilities and induces their shift toward a Th17 phenotype<sup>1,2</sup>. These effects are mediated via the interaction of lactate with its transporter SLC5A12, which is expressed on the CD4<sup>+</sup> T cell surface<sup>1,2</sup>. <h3>Objectives</h3> To characterize whether the newly identified lactate/SLC5A12-induced metabolic signalling pathway can be harnessed in the stratification of RA patients in the different histological phenotypes and to modulate inflammatory responses <i>in vitro</i> and <i>in vivo</i>. <h3>Methods</h3> RA peripheral blood cells, RA synovial tissues (ST, 21 lymphoid and 8 myeloid) and mononuclear cells from tonsil of patients undergoing tonsillectomy were included in the analysis. RNA sequencing of RA-ST was performed and data analysed for the expression of metabolic genes. SLC5A12 expression and IL17 production was performed by flow-cytometry. Cytokines and transcription factors mRNA relative expression was evaluated by RT-PCR. Seahorse and western blot analysis was performed for the evaluation of metabolic pathways. Transwell plates were used for migration assays. Human-glucose-6-phosphate-isomerase (hG6PI) induced arthritis model was used to evaluate the impact of anti-SLC5A12 on the clinical and histological score. <h3>Results</h3> We showed that: i) the expression of SLC5A12 is up-regulated by CD4<sup>+</sup> T cells upon inflammation; ii) SLC5A12 is up-regulated in anti-CD3 stimulated RA CD4<sup>+</sup> T cells cultured in autologous synovial fluid; iii) the lactate/SLC5A12 induced metabolic pathway is differentially activated in RA patients with distinctive synovial "pathotypes"; iv) SLC5A12 antibody reduces lactate-induced pro-inflammatory cytokines, limits Th17 and follicular helper T cell differentiation, reverses lactate impaired CD4<sup>+</sup> T cell migration and restores lactate-mediated inhibition of glycolysis <i>in vitro</i>; v) antibody-mediated blockade of SLC5A12 ameliorates the clinical course in human-glucose-6-phosphate-isomerase (hG6PI)-induced arthritis. <h3>Conclusions</h3> Targeting lactate/SLC5A12-induced metabolic signalling pathway may provide a novel therapeutic strategy to reduce inflammation in RA patients. <h3>References</h3> Haas R. et al. PLoS Biology 2015. Pucino V. et al. Eur J Immunol 2017. <h3>Acknowledgements</h3> This work is supported by a fellowship from the Arthritis Research UK (ARUK) to V.P. by a fellowship from the British Heart Foundation, a project grant from the CARIPLO Foundation, a Proof of Concept award from Queen Mary Inno-vation, Ltd., to C.M. and MRC ARUK founded project "The Pathobiology of Early Arthritis Cohort (PEAC)" to C.P. <h3>Disclosure of Interest</h3> None declared