Reduction of pro‐inflammatory effector functions through remodeling of fatty acid metabolism in CD8 ⁺ T‐cells from rheumatoid arthritis patients

Objectives RA CD8+ T-cells (CD8) maintain their effector pro-inflammatory phenotype by changing their metabolism towards aerobic glycolysis. However, their massive energetic and biosynthetic needs may require additional substrates to furnish this high demand. Since systemic alterations in lipid metabolism have been reported in RA patients, we explored the role of fatty acid (FA) metabolism in CD8 to identify potential targets to curb their pro-inflammatory potential. Methods The expression of FA metabolism-related genes was analyzed for total and CD8-subsets from RA patients and healthy controls (CNT). Peripheral-blood CD8 were isolated from RA, PsA, SpA patients under different therapies (DMARD, biologicals, JAK-inhibitors) and CNT and were TCR-stimulated with or without FA metabolism inhibitors. We quantified the expression of the main FA transporters, lipid uptake, intracellular content of (un-)saturated FA, cytokine production, activation, proliferation, and capacity to inhibit tumor cell growth. Results The CD8 gene expression profile of FA metabolism-related genes was significantly different between untreated RA patients and CNT. RA patients with a good clinical response after 6 months MTX therapy significantly increased the expression of FA metabolism-related genes. Cell-surface expression of FA transporters FABP4 and GPR84 and FA-uptake was higher in effector and memory CD8 of RA patients than for CNT. In vitro blockade of FA metabolism significantly impaired CD8 effector functions. Conclusions RA CD8 present an altered FA-metabolism which can be potential therapeutic targets to control their pro-inflammatory profile, especially by targeting the transport and oxidation of free FAs which are abundant in the serum and synovial fluid of patients. ### Competing Interest Statement MMSC: Scientific support: Novartis, Pfizer. HML: Scientific funding: Abbvie, Novartis, Pfizer, Roche; Consulting fees and honoraria: Abbvie, AstraZeneca, Actelion, Amgen, Bayer Vital, Boehringer Ingelheim, BMS, Celgene, GlaxoSmithKline (GSK), Galapagos, Janssen, Elli Lilly, Medac, MSD, Novartis, Pfizer, Roche, Sanofi, UCB; Travel support: Abbvie, AstraZeneca, Boehriner Ingelheim, BMS, Celgene, GSK, Gilead, Janssen, Elli Lilly, MSD, Novartis, Pfizer, Roche, Sanofi, UCB; Data safety monitoring and/or advisory board: Abbvie, AstraZeneca, Amgen, Boehriner Ingelheim, BMS, Celgene, GSK, Gilead, Janssen, Elli Lilly, Medac, MSD, Novartis, Pfizer, Roche, Sanofi, UCB ### Funding Statement This work was supported by an internal grant from the Heidelberg Medical School to H-M Lorenz, and a grant from the German Research Foundation (Deutsche Forschungsgesellschaft) to M.M. Souto-Carneiro (SO 1402/1-1). F.V. Kraus was supported by an Add-On Fellowship of the Joachim Herz Foundation. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The study was approved by the Institutional Ethics Committee of Heidelberg University, and is registred under case numbers S-096/2016 and S-969/2020. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors. All data produced in the present work are contained in the manuscript.