Mycobacterium tuberculosisCatalase and Peroxidase Activities and Resistance to Oxidative Killing in Human Monocytes In Vitro

Abstract

Mycobacterium tuberculosis has a relatively high resistance to killing by hydrogen peroxide and organic peroxides. Resistance may be mediated by mycobacterial catalase-peroxidase (KatG) and possibly by alkyl hydroperoxide reductase (AhpC). To determine the interrelationship between sensitivity to H2O2, catalase and peroxidase activities, and bacillary growth rates measured both intracellularly in human monocytes and in culture medium, we examined one laboratory strain, two clinical isolates, and three recombinant strains of M. tuberculosis with differing levels of KatG and AhpC. Five of the mycobacterial strains had intracellular doubling times of 27 to 32 h, while one KatG-deficient clinical isolate (ATCC 35825) doubled in ∼76 h. Killing of mycobacteria by exogenously added H2O2 was more pronounced for intracellular bacilli than for those bacilli derived from disrupted monocytes. Strains with no detectable KatG expression or catalase activity were relatively sensitive to killing (43 to 67% killing) by exogenous H2O2. However, once even minimal catalase activity was present, mycobacterial catalase activity over a 10-fold range (0.56 to 6.2 U/mg) was associated with survival of 85% of the bacilli. Peroxidase activity levels correlated significantly with resistance of the mycobacterial strains to H2O2-mediated killing. An endogenous oxidative burst induction by 4β-phorbol 12β-myristate 13α-acetate treatment of infected monocytes reduced the viability of the KatG null strain (H37Rv Inhr) but not the KatG-overexpressing strain [H37Rv(pMH59)]. These results suggest that mycobacterial resistance to oxidative metabolites (including H2O2 and other peroxides) may be an important mechanism of bacillary survival within the host phagocyte.

Mycobacterium tuberculosis secretory proteins CFP‐10, ESAT‐6 and the CFP10:ESAT6 complex inhibit lipopolysaccharide‐induced NF‐κB transactivation by downregulation of reactive oxidative species (ROS) production

“…M. tuberculosis unlike other intracellular bacteria like Escherichia coli and Salmonella typhimurium are not Secretory proteins on ROS production N Ganguly et al equipped to produce Oxy R, a critical component of oxidative stress response. Mtb does possess a host of components to potentially deal with ROS or oxidative stress, such as catalase peroxidase, KatG [47][48][49] and two superoxide dismutase proteins, SodA and SodC. 50 ROS is known to activate the transcription factor NF-kB that leads to transcription of genes.…”

Emergence of an effective adaptive cell mediated immune response toMycobacterium lepraeis not impaired in reactive oxygen intermediate-deficient mice

“…Furthermore, M. tuberculosis is even more resistant to ROI than M. leprae. In addition to its uptake generating little respiratory burst, M. tuberculosis possesses several cell wall components that inhibit ROI production (Chan et al, 1989(Chan et al, , 1991Wadee & Clara, 1989;Brozna et al, 1991;Yuan et al, 1995), and it has a functional catalase (Middlebrook, 1954;Manca et al, 1999) as well as superoxide dismutases (Jackett et al, 1978;Piddington et al, 2001). RNI, in contrast, are crucial for the control of virulent M. tuberculosis infection in mice, as NOS2-deficient conditions lead to increased bacillary burden, augmented granulomatous response and shortened survival time (Chan et al, 1995;Adams et al, 1997;MacMicking et al, 1997;Flynn et al, 1998).…”

The gene controls sensitivity of the bacterium to hydrogen peroxide

“…Resistance to H 2 O 2 is thought to be controlled by the katG gene [8] which encodes the mycobacterial catalase-peroxidase and ahpC gene which encodes a homologue of the alkyl hydroperoxide reductase [9]. Previous work [19] demonstrated that M. tuberculosis strains with no detectable expression of katG gene were more susceptible to the killing effect of H 2 O 2 . Sensitivity to isoniazid (isonicotinic acid hydrazide INH) was directly related to the expression of the katG gene which is required for activation of the drug [8].…”