Selective ORAI1 Inhibition Ameliorates Autoimmune Central Nervous System Inflammation by Suppressing Effector but Not Regulatory T Cell Function

Abstract

The function of CD4+ T cells is dependent on Ca2+ influx through Ca2+ release-activated Ca2+ (CRAC) channels formed by ORAI proteins. To investigate the role of ORAI1 in pro-inflammatory Th1 and Th17 cells and autoimmune diseases, we genetically and pharmacologically modulated ORAI1 function. Immunization of mice lacking Orai1 in T cells with MOG peptide resulted in attenuated severity of experimental autoimmune encephalomyelitis (EAE). The numbers of T cells and innate immune cells in the CNS of ORAI1-deficient animals were strongly reduced along with almost completely abolished production of IL-17, IFN-γ and GM-CSF despite only partially reduced Ca2+ influx. In Th1 and Th17 cells differentiated in vitro, ORAI1 was required for cytokine production but not the expression of Th1- and Th17-specific transcription factors T-bet and RORγt. The differentiation and function of induced iTreg cells, by contrast, was independent of ORAI1. Importantly, induced genetic deletion of Orai1 in adoptively transferred, MOG-specific T cells was able to halt EAE progression after disease onset. Likewise, treatment of wild-type mice with a selective CRAC channel inhibitor after EAE onset ameliorated disease. Genetic deletion of Orai1 and pharmacological ORAI1 inhibition reduced the leukocyte numbers in the CNS and attenuated Th1/Th17 cell-mediated cytokine production. In human CD4+ T cells, CRAC channel inhibition reduced the expression of IL-17, IFN-γ and other cytokines in a dose-dependent manner. Taken together, these findings support the conclusion that Th1 and Th17 cell function is particularly dependent on CRAC channels, which could be exploited as a therapeutic approach to T cell-mediated autoimmune diseases.

ORAI2 modulates store-operated calcium entry and T cell-mediated immunity

“…Orai2 −/− effector T cells had SOCE comparable to WT cells, whereas deletion of Orai1 resulted in a >60% reduction of SOCE (Supplementary Fig. 4a,b) consistent with results in Orai1 −/− (refs 22, 25, 26, 32) and Orai1 R93W mice24. The smaller effect of Orai2 deletion in effector T cells is in line with its reduced expression in effector T cells.…”

“…Orai2 −/− mice were born at normal Mendelian ratios without gross morphological or histological abnormalities. To determine the role of ORAI1 and ORAI2 in T cells, we analysed T cells from Orai1 fl/fl Cd4cre mice that lack Orai1 in all T cells25, Orai2 −/− mice, and Orai1 fl/fl Orai2 −/− Cd4cre mice, whose T cells lack both ORAI proteins. When SOCE was induced by depletion of ER Ca 2+ stores with thapsigargin, which inhibits sarcoplasmic/endoplasmic Ca 2+ ATPases, ablation of Orai1 reduced SOCE in naive CD4 + and CD8 + T cells by ∼30–50% (Fig.…”

Tobacco Smoke Constituents Trigger Cytoplasmic Calcium Release

“…Furthermore, deranged Ca 2+ homeostasis has been linked to autoimmune disease, asthma, and cancer, further suggesting that tobacco-induced Ca 2+ release may be an important biomarker of exposure. [27][28][29] In addition to observing an increase in Ca 2+ with common tobacco products (Fig. 1), we also observed increases in Fluo-4 fluorescence following 1-NH2-naphthalene, formaldehyde, nicotine, or NNK (Fig.…”

The Role of Calcium–Calcineurin–NFAT Signaling Pathway in Health and Autoimmune Diseases

“…In accordance with this, immunization of mice deficient in Orai1 in T cells with MOG peptide yields to improvement of EAE severity. These mice are shown to have almost completely suppressed the production of IL-17A, IFNγ, and granulocyte macrophage-colony stimulating factor (GM-CSF) (133), suggesting that CRAC channels, including STIM and Orai1, modulate Th1 and Th17 responses and could therefore be a therapeutic target of EAE.…”