NAD hydrolysis by the tuberculosis necrotizing toxin induces lethal oxidative stress in macrophages

Academic Article

Abstract

  • Mycobacterium tuberculosis (Mtb) kills infected macrophages through necroptosis, a programmed cell death that enhances mycobacterial replication and dissemination. The tuberculosis necrotizing toxin (TNT) is the major cytotoxicity factor of Mtb in macrophages and induces necroptosis by NAD+ hydrolysis. Here, we show that the catalytic activity of TNT triggers the production of reactive oxygen species (ROS) in Mtb-infected macrophages causing cell death and promoting mycobacterial replication. TNT induces ROS formation both by activating necroptosis and by a necroptosis-independent mechanism. Most of the detected ROS originate in mitochondria as a consequence of opening the mitochondrial permeability transition pore. However, a significant part of ROS is produced by mechanisms independent of TNT and necroptosis. Expressing only the tnt gene in Jurkat T-cells also induces lethal ROS formation indicating that these molecular mechanisms are not restricted to macrophages. Both the antioxidant N-acetyl-cysteine and replenishment of NAD+ by providing nicotinamide reduce ROS levels in Mtb-infected macrophages, protect them from cell death, and restrict mycobacterial replication. Our results indicate that a host-directed therapy combining replenishment of NAD+ with inhibition of necroptosis and/or antioxidants might improve the health status of TB patients and augment antibacterial TB chemotherapy.
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    Digital Object Identifier (doi)

    Author List

  • Pajuelo D; Gonzalez-Juarbe N; Niederweis M
  • Volume

  • 22
  • Issue

  • 1