Phosphatidic Acid Promoting the Generation of Interleukin‐17A Producing Double‐Negative T Cells by Enhancing mTORC1 Signaling in Lupus

Abstract

ObjectivesTo investigate the role and intracellular regulatory mechanisms of double negative T (DNT) cells in the pathogenesis of systemic lupus erythematosus (SLE).MethodsDNT cells were assessed in murine models, SLE patients and controls using flow cytometry (FCM). DNT cells from either resiquimod (R848) or vehicle‐treated C57BL/6 (B6) mice were cultured with B cells from R848‐treated mice to explore functions. Differential mTOR pathway signaling in DNT cells measured using FCM and qPCR was validated by rapamycin inhibition. Candidate lipid metabolites detected using LC‐ESI‐MS/MS were functionally assessed in DNT cell cultures.ResultsDNT cells were markedly increased in both spontaneous and induced mouse lupus models and in SLE patients. Expanded DNT cells from R848‐treated B6 mice produced elevated IL‐17A and IgG with increased germinal center B (GCB) cells. Expansion of DNT cells associated with activation of mTORC1 pathway that both IL‐17A levels and the number of DNT cells exhibited dose‐dependent reduction with rapamycin treatment. Lipidomics studies revealed differential patterns of lipid metabolites in T cells of R848‐treated mice. Among candidate metabolites, elevated phosphatidic acid (PA) that was partially controlled by phospholipase D2, increased the expression of the mTORC1 downstream target p‐S6, and positively expanded IL‐17A‐producing DNT cells. Similarly, elevated proportions of circulating DNT cells in SLE patients correlated with disease activity and proteinuria, and IL‐17A secretion was elevated after in vitro PA stimulation.ConclusionsThe accumulation of PA in T cells could activate the mTORC1 pathway, promoting DNT cell expansion and IL‐17A secretion, resulting in GCB cell abnormalities in lupus.image