Cu,Zn Superoxide Dismutase ofMycobacterium tuberculosisContributes to Survival in Activated Macrophages That Are Generating an Oxidative Burst

Abstract

Macrophages produce reactive oxygen species and reactive nitrogen species that have potent antimicrobial activity. Resistance to killing by macrophages is critical to the virulence of Mycobacterium tuberculosis. M. tuberculosis has two genes encoding superoxide dismutase proteins, sodA and sodC. SodC is a Cu,Zn superoxide dismutase responsible for only a minor portion of the superoxide dismutase activity of M. tuberculosis. However, SodC has a lipoprotein binding motif, which suggests that it may be anchored in the membrane to protect M. tuberculosis from reactive oxygen intermediates at the bacterial surface. To examine the role of the Cu,Zn superoxide dismutase in protecting M. tuberculosis from the toxic effects of exogenously generated reactive oxygen species, we constructed a null mutation in the sodC gene. In this report, we show that the M. tuberculosis sodC mutant is readily killed by superoxide generated externally, while the isogenic parental M. tuberculosis is unaffected under these conditions. Furthermore, the sodC mutant has enhanced susceptibility to killing by gamma interferon (IFN-␥)-activated murine peritoneal macrophages producing oxidative burst products but is unaffected by macrophages not activated by IFN-␥ or by macrophages from respiratory burst-deficient mice. These observations establish that the Cu,Zn superoxide dismutase contributes to the resistance of M. tuberculosis against oxidative burst products generated by activated macrophages.

Expression of Th1-mediated immunity in mouse lungs induces aMycobacterium tuberculosistranscription pattern characteristic of nonreplicating persistence

“…mice (36), or not more susceptible at all (R.J.N., unpublished results). In addition, the knowledge that sodC null mutants are not defective in the ability to grow in guinea pigs (37) or in mice (38) suggests the possibility that superoxide dismutases may not play an essential role in the protection of M. tuberculosis against host immunity.…”

Role of KatG catalase‐peroxidase in mycobacterial pathogenesis: countering the phagocyte oxidative burst

“…We considered the possibility that the potential impact of phagocyte NADPH oxidase on MTB might be masked by bacterial mechanisms for evasion or detoxification of the oxidative burst. One obvious candidate is the SOD-KatG pathway for conversion of O 2 -◊ to water and molecular oxygen, which was shown previously to be important for MTB survival in ROS-producing macrophages (Manca et al, 1999;Piddington et al, 2001). Here, we show that, although KatG catalase-peroxidase was important for survival of MTB in wild-type C57Bl/6 mice and in NOS2 -/-mice, which are capable of generating an oxidative burst, it was dispensable for survival in gp91 Phox-/-mice, which cannot produce an oxidative burst.…”

“…MTB produces two SODs: an iron-dependent enzyme (SodA) and a copper/zinc-dependent enzyme (SodC). Deletion of the sodC gene in the MTB chromosome resulted in hypersensitivity to O 2 -◊ and hydrogen peroxide (H 2 O 2 ) in vitro (Dussurget et al ., 2001;Piddington et al ., 2001), and impaired survival in murine macrophages generating a respiratory burst (Piddington et al ., 2001), but did not attenuate virulence in guinea pigs (Dussurget et al ., 2001) or mice (Piddington et al ., 2001). Attempts to delete the sodA gene in MTB have so far been unsuccessful, suggesting that SodA activity might be essential for bacterial survival.…”

Enhanced Oxidative Stress Resistance through Activation of a Zinc Deficiency Transcription Factor inBrachypodium distachyon

“…Leaves were treated with either paraquat or copper sulfate (Fig. 8F) and incubated with NBT, followed by extraction, solubilization, and detection of formazan at 570 nm (Piddington et al, 2001). When normalized to leaf mass, extracts of BdbZIP10o/e leaf samples showed a marked reduction in signal compared with wild-type controls, consistent with decreased production of ROS during oxidative stress.…”