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.