Catastrophic NAD+ Depletion in Activated T Lymphocytes through Nampt Inhibition Reduces Demyelination and Disability in EAE

Abstract

Nicotinamide phosphoribosyltransferase (Nampt) inhibitors such as FK866 are potent inhibitors of NAD+ synthesis that show promise for the treatment of different forms of cancer. Based on Nampt upregulation in activated T lymphocytes and on preliminary reports of lymphopenia in FK866 treated patients, we have investigated FK866 for its capacity to interfere with T lymphocyte function and survival. Intracellular pyridine nucleotides, ATP, mitochondrial function, viability, proliferation, activation markers and cytokine secretion were assessed in resting and in activated human T lymphocytes. In addition, we used experimental autoimmune encephalomyelitis (EAE) as a model of T-cell mediated autoimmune disease to assess FK866 efficacy in vivo. We show that activated, but not resting, T lymphocytes undergo massive NAD+ depletion upon FK866-mediated Nampt inhibition. As a consequence, impaired proliferation, reduced IFN-γ and TNF-α production, and finally autophagic cell demise result. We demonstrate that upregulation of the NAD+-degrading enzyme poly-(ADP-ribose)-polymerase (PARP) by activated T cells enhances their susceptibility to NAD+ depletion. In addition, we relate defective IFN-γ and TNF-α production in response to FK866 to impaired Sirt6 activity. Finally, we show that FK866 strikingly reduces the neurological damage and the clinical manifestations of EAE. In conclusion, Nampt inhibitors (and possibly Sirt6 inhibitors) could be used to modulate T cell-mediated immune responses and thereby be beneficial in immune-mediated disorders.

Basic leucine zipper transcription factor, ATF-like (BATF) regulates epigenetically and energetically effector CD8 T-cell differentiation via Sirt1 expression

“…NAD + -consuming enzymes such as Sirt1 and Parp1 use NAD + as a substrate, and their inhibitors increase NAD + levels in activated T cells (25). Treatment with the Sirt1 inhibitors nicotinamide (Nam) and Sirtinol, but not with the Parp1 inhibitor 6-(5H)-phenanthridinone (PHE), increased the viability of Batf gfp/gfp CD8 T cells to Batf +/+ CD8 T-cell levels (Fig.…”

Targeting cancer metabolism: a therapeutic window opens

“…Small molecule inhibitors of PFK2FB3 have been NAMPT inhibition in cells has an effect primarily on the cytosolic (rather than the mitochondrial) NAD + pool 121 . NAMPT inhibition can also be toxic to lymphocytes 122 , suggesting that use of NAMPT inhibitors in patients might be limited by immunosuppression. Mild lymphopenia was observed in early trials of NAMPT inhibitors, but thrombocytopenia was the dose limiting toxicity 123 .…”

Sirtuins and inflammation: Friends or foes?

“…It is noteworthy however that nicotinamide, the prototypic sirtuin inhibitor, 18 displays anti-inflammatory properties both in vitro and in vivo [49], [73]. Although nicotinamide may represent a general inhibitor for all NAD-consuming reactions, we and others have been able to confirm the potential beneficial role of sirtuin inhibitors as antiinflammatory compounds both in vitro and in vivo [49], [50], although these observations need to be further extended to more clinically relevant settings.…”

“…In contrast to the anti-inflammatory role generally attributed to sirtuins, we and others have recently reported a possible positive regulatory role for SIRT6 in the induction of proinflammatory cytokine expression, in both innate and adaptive immune cells [49], [50]. In…”

“…A c c e p t e d M a n u s c r i p t 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 13 these studies, reduction of intracellular NAD levels, obtained by inhibiting the enzymatic activity of Nampt, led to reduced secretion of selected cytokines (such as TNFIL-6 and/or IFN) by immune cells, while leaving other pro-inflammatory mediators (such as CCL5/Rantes) unaffected [49], [50]. Surprisingly, several sirtuin inhibitors could reproduce these effects, suggesting therefore that the NAD-sirtuin axis could also represent a positive regulatory loop required for adequate cytokine secretion.…”