TY - JOUR
T1 - Altered NADH/NAD+ ratio mediates coresistance to isoniazid and ethionamide in mycobacteria
AU - Vilchèze, Catherine
AU - Weisbrod, Torin R.
AU - Chen, Bing
AU - Kremer, Laurent
AU - Hazbón, Manzour H.
AU - Wang, Feng
AU - Alland, David
AU - Sacchettini, James C.
AU - Jacobs, William R.
PY - 2005/2
Y1 - 2005/2
N2 - The front-line antituberculosis drug isoniazid (INH) and the related drug ethionamide (ETH) are prodrugs that upon activation inhibit the synthesis of mycolic acids, leading to bactericidal activity. Coresistance to INH and ETH can be mediated by dominant mutations in the target gene inhA, encoding an enoyl-ACP reductase, or by recessive mutations in ndh, encoding a type II NADH dehydrogenase (NdhII). To address the mechanism of resistance mediated by the latter, we have isolated novel ndh mutants of Mycobacterium smegmatis and Mycobacterium bovis BCG. The M. smegmatis ndh mutants were highly resistant to INH and ETH, while the M. bovis BCG mutants had low-level resistance to INH and ETH. All mutants had defects in NdhII activity resulting in an increase in intracellular NADH/NAD+ ratios. Increasing NADH levels were shown to protect InhA against inhibition by the INH-NAD adduct formed upon INH activation. We conclude that ndh mutations mediate a novel mechanism of resistance by increasing the NADH cellular concentration, which competitively inhibits the binding of INH-NAD or ETH-NAD adduct to InhA.
AB - The front-line antituberculosis drug isoniazid (INH) and the related drug ethionamide (ETH) are prodrugs that upon activation inhibit the synthesis of mycolic acids, leading to bactericidal activity. Coresistance to INH and ETH can be mediated by dominant mutations in the target gene inhA, encoding an enoyl-ACP reductase, or by recessive mutations in ndh, encoding a type II NADH dehydrogenase (NdhII). To address the mechanism of resistance mediated by the latter, we have isolated novel ndh mutants of Mycobacterium smegmatis and Mycobacterium bovis BCG. The M. smegmatis ndh mutants were highly resistant to INH and ETH, while the M. bovis BCG mutants had low-level resistance to INH and ETH. All mutants had defects in NdhII activity resulting in an increase in intracellular NADH/NAD+ ratios. Increasing NADH levels were shown to protect InhA against inhibition by the INH-NAD adduct formed upon INH activation. We conclude that ndh mutations mediate a novel mechanism of resistance by increasing the NADH cellular concentration, which competitively inhibits the binding of INH-NAD or ETH-NAD adduct to InhA.
UR - http://www.scopus.com/inward/record.url?scp=12944255779&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=12944255779&partnerID=8YFLogxK
U2 - 10.1128/AAC.49.2.708-720.2005
DO - 10.1128/AAC.49.2.708-720.2005
M3 - Article
C2 - 15673755
AN - SCOPUS:12944255779
SN - 0066-4804
VL - 49
SP - 708
EP - 720
JO - Antimicrobial agents and chemotherapy
JF - Antimicrobial agents and chemotherapy
IS - 2
ER -