Mycobacterium tuberculosis has diminished capacity to counteract redox stress induced by elevated levels of endogenous superoxide

Abstract

Mycobacterium tuberculosis (Mtb) has evolved protective and detoxification mechanisms to maintain cytoplasmic redox balance in response to exogenous oxidative stress encountered inside host phagocytes. In contrast, little is known about the dynamic response of this pathogen to endogenous oxidative stress generated within Mtb. Using a noninvasive and specific biosensor of cytoplasmic redox state of Mtb, we for first time discovered a surprisingly high sensitivity of this pathogen to perturbation in redox homeostasis induced by elevated endogenous reactive oxygen species (ROS). We synthesized a series of hydroquinone-based small molecule ROS generators and found that ATD-3169 permeated mycobacteria to reliably enhance endogenous ROS including superoxide radicals. When Mtb strains including multidrug-resistant (MDR) and extensively drug-resistant (XDR) patient isolates were exposed to this compound, a dose-dependent, long-lasting, and irreversible oxidative shift in intramycobacterial redox potential was detected. Dynamic redox potential measurements revealed that Mtb had diminished capacity to restore cytoplasmic redox balance in comparison with Mycobacterium smegmatis (Msm), a fast growing nonpathogenic mycobacterial species. Accordingly, Mtb strains were extremely susceptible to inhibition by ATD-3169 but not Msm, suggesting a functional linkage between dynamic redox changes and survival. Microarray analysis showed major realignment of pathways involved in redox homeostasis, central metabolism, DNA repair, and cell wall lipid biosynthesis in response to ATD-3169, all consistent with enhanced endogenous ROS contributing to lethality induced by this compound. This work provides empirical evidence that the cytoplasmic redox poise of Mtb is uniquely sensitive to manipulation in steady-state endogenous ROS levels, thus revealing the importance of targeting intramycobacterial redox metabolism for controlling TB infection.

Thiol activated prodrugs of sulfur dioxide (SO2) as MRSA inhibitors

“…S3). 22 [27][28][29][30][31][32][33][34][35]. Consistent with previous observations that both nitro groups were necessary for decomposition, we found that 9j-9l gave 1 mol of SO 2 per mol of compound (Table 2, entries 36-38).…”

“…Induction of redox stress through enhancement of reactive oxygen species (ROS) 29,35 or reactive nitrogen species (RNS) has been considered as a possible mechanism for developing new anti-bacterials. [36][37][38][39] Ours is the first report of MRSA being sensitive to sulfur dioxide, a reactive sulfur species.…”

Targeting Mycobacterium tuberculosis Sensitivity to Thiol Stress at Acidic pH Kills the Bacterium and Potentiates Antibiotics

“…Recent studies have shown that increases in endogenous ROS can have significant and detrimental results on Mtb growth and viability in vitro and during infection (Vilcheze, et al, 2013) (Tyagi, et al, 2015). To measure intracellular ROS formation in Mtb, the fluorescent dye CellROX green was employed (Saini, et al, 2016).…”

Acidic pH-dependent depletion ofMycobacterium tuberculosisthiol pools potentiates antibiotics and oxidizing agents

“…The transcriptional profiling data and potentiation of oxidation agents suggests that AC2P36 may promote the accumulation of intracellular reactive oxygen species (ROS). Recent studies have shown that increases in endogenous ROS can have significant and detrimental results on Mtb growth and viability in vitro and during infection (Vilcheze, et al, 2013) (Tyagi, et al, 2015). To measure intracellular ROS formation in Mtb, the fluorescent dye CellROX green was employed (Saini, et al, 2016).…”