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

Abstract

4732 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 TNF-a production, ATP shortage, and, finally, autophagic cell demise result. We demonstrate that upregulation of the of the NAD+-degrading enzyme poly-(ADP-ribose)-polymerase (PARP) by activated T cells enhances their susceptibility to NAD+ depletion. We relate defective TNF-a production in response to FK866 to impaired SIRT6 activity. Finally, in line with its capacity to interfere with T lymphocyte function and survival, we show that FK866 strikingly reduces the neurological damage and the clinical manifestations of EAE. In conclusion, Nampt inhibitors (and possibly sirtuin inhibitors) could be used to modulate T cell-mediated immune responses and thereby be beneficial in immune-mediated disorders. Disclosures: No relevant conflicts of interest to declare.

A key role for Pre–B cell colony–enhancing factor in experimental hepatitis

“…Specifically, FK866 dose-dependently depleted intracellular NAD þ concentrations in thioglycollate-elicited mouse macrophages and human monocytes, rendering them less responsive to stimulation with LPS. 39 Bruzzone et al 13 investigated the effect of FK866 on T lymphocyte function and demonstrated that activated T lymphocytes specifically undergo a massive NAD þ depletion when treated with FK866. NAD þ depletion inhibits critical T cell functions such as proliferation and IFNc/TNFa production, eventually leading to cell death.…”

“…This leads to functional inactivity of NAD þ -dependent enzymes such as PARP-1 and SIRT-6 that promote cellular activation. 13,14 Numerous studies have described an association between elevated PBEF expression with acute and chronic inflammatory conditions in humans and in mice. PBEF expression is elevated in neutrophils of septic patients preventing neutrophil apoptosis.…”

Sirt6 inhibition delays the onset of experimental autoimmune encephalomyelitis by reducing dendritic cell migration

“…SIRT6 has important roles in physiological and pathological processes, regulating aging, cancer, obesity, insulin resistance, inflammation, and energy metabolism [1]. Regarding immunity and inflammation, our group and others demonstrated that SIRT6 promotes the release of TNFα through its deacetylase activity [2,3]. Moreover, SIRT6-mediated deacylation of TNFα was reported to enhance the release of this cytokine [4].…”

“…Given the role for SIRT6 in lymphocyte and dendritic cell activation [3,9], we evaluated the effect of the SIRT6 inhibitor, compound 1 in a Th1/Th17-driven model of autoimmune disorder of the central nervous system (CNS), such as EAE. In order to investigate the effect of Sirt6 inhibition during the inflammatory phase and to provide the experimental basis for a possible, new therapeutic approach in MS, 1 was administered according to both a "preventive" (i.e., administration before disease onset) and a "therapeutic" (i.e., administration after disease onset) protocol.…”

“…Moreover, SIRT6-mediated deacylation of TNFα was reported to enhance the release of this cytokine [4]. In addition to TNFα, SIRT6 also regulates the secretion of other proinflammatory cytokines, such as IFNγ and IL8 [3,5,6] through the activation of the cation channel TRPM2 [5]. SIRT6 also plays an important role in T lymphocyte biology, since Sirt6KO mice develop lymphopenia [7] and the availability of NAD + for SIRT6 activity is pivotal for the regulation of T cell metabolism during the early and late stages of acute inflammation [8].…”