TY - JOUR
T1 - A comparative study of the redox-cycling of a quinone (rifamycin S) and a quinonimine (rifabutin) antibiotic by rat liver microsomes
AU - Rao, D. N.Ramakrishna
AU - Cederbaum, Arthur I.
N1 - Funding Information:
These studies were supported by USPHS Grant AA-09460 from The National Institute on Alcohol Abuse and Alcoholism. We thank Ms. Pilar Visco Cenizal for typing the manuscript.
PY - 1997
Y1 - 1997
N2 - Rifamycin S and rifabutin are clinical drugs used to treat tuberculosis and leprosy. The formation of reactive oxygen species during the redox- cycling of rifamycin S (quinone) and rifabutin (quinonimine) was evaluated. The semiquinone (or semiquinonimine) and hydroquinone (or hydroquinonimine) formed during the reduction of the parent molecules by microsomal electron transfer in the presence of nicotinamide-adenine dinucleotide phosphate, reduced (NADPH) or nicotinamide-adenine dinucleotide, reduced (NADH) reoxidizes in air to generate superoxide radical and hydrogen peroxide. In the presence of added iron, hydroxyl radicals, formed by the Fenton reaction, were detected using 5,5-dimethyl-pyrroline-N-oxide as the spin-trap. Rifamycin S, a quinone, redox cycles more efficiently than rifabutin, a quinonimine, as approximately five times the concentration of hydroxyl radical adduct of 5,5'-dimethyl-l-pyroline-N-oxide (DMPO) was detected, when compared with rifabutin. The NADPH-dependent microsomal production of hydroxyl radical in the presence of rifamycin S was somewhat higher than the NADH-rifamycin S system with most into chelators. However, with rifabutin, NADH-dependent microsomal production of hydroxyl radical was higher than that found with the NADPH-rifabutin system. An exception was the iron chelator, diethylene-triamine-pentacetic acid (DTPA), in which NADPH-dependent rates exceeded the rates with NADH with both antibiotics. Rat liver sub- mitochondrial particles also generated hydroxyl radical in the presence of NADH and either rifamycin S or rifabutin. The electron transport chain inhibitors such as rotenone and antimycin A enhanced the signal intensity of DMPO-OH, suggesting NADH dehydrogenase (complex I) as the major component involved in the reduction of rifamycin S. Rifamycin S was shown to be readily reduced to rifamycin SV, the corresponding hydroquinone by Fe(II); under similar conditions Fe(II) did not reduce rifabutin. Using optical spectroscopy, we determined that rifamycin S forms a complex with Fe(II). The stoichiometry of the complex was Fe(rifamycin S), in phosphate buffer at pH 7.4. Rifabutin did not form a detectable complex with Fe(II). The redox cycling of rifamycin S and rifabutin did not cause microsomal lipid peroxidation. In fact, the Fe:ATP induced lipid peroxidation was completely inhibited by these two molecules. These results indicate that rifamycin S and rifabutin can interact with rat liver microsomes to undergo redox-cycling, with the subsequent production of hydroxyl radicals when iron complexes are present. Compared to NADPH, NADH is almost as effective (rifamycin S) or even more effective (rifabutin) in promoting these interactions. These interactions may play a role in the hepatotoxicity associated with the use of these antibiotics.
AB - Rifamycin S and rifabutin are clinical drugs used to treat tuberculosis and leprosy. The formation of reactive oxygen species during the redox- cycling of rifamycin S (quinone) and rifabutin (quinonimine) was evaluated. The semiquinone (or semiquinonimine) and hydroquinone (or hydroquinonimine) formed during the reduction of the parent molecules by microsomal electron transfer in the presence of nicotinamide-adenine dinucleotide phosphate, reduced (NADPH) or nicotinamide-adenine dinucleotide, reduced (NADH) reoxidizes in air to generate superoxide radical and hydrogen peroxide. In the presence of added iron, hydroxyl radicals, formed by the Fenton reaction, were detected using 5,5-dimethyl-pyrroline-N-oxide as the spin-trap. Rifamycin S, a quinone, redox cycles more efficiently than rifabutin, a quinonimine, as approximately five times the concentration of hydroxyl radical adduct of 5,5'-dimethyl-l-pyroline-N-oxide (DMPO) was detected, when compared with rifabutin. The NADPH-dependent microsomal production of hydroxyl radical in the presence of rifamycin S was somewhat higher than the NADH-rifamycin S system with most into chelators. However, with rifabutin, NADH-dependent microsomal production of hydroxyl radical was higher than that found with the NADPH-rifabutin system. An exception was the iron chelator, diethylene-triamine-pentacetic acid (DTPA), in which NADPH-dependent rates exceeded the rates with NADH with both antibiotics. Rat liver sub- mitochondrial particles also generated hydroxyl radical in the presence of NADH and either rifamycin S or rifabutin. The electron transport chain inhibitors such as rotenone and antimycin A enhanced the signal intensity of DMPO-OH, suggesting NADH dehydrogenase (complex I) as the major component involved in the reduction of rifamycin S. Rifamycin S was shown to be readily reduced to rifamycin SV, the corresponding hydroquinone by Fe(II); under similar conditions Fe(II) did not reduce rifabutin. Using optical spectroscopy, we determined that rifamycin S forms a complex with Fe(II). The stoichiometry of the complex was Fe(rifamycin S), in phosphate buffer at pH 7.4. Rifabutin did not form a detectable complex with Fe(II). The redox cycling of rifamycin S and rifabutin did not cause microsomal lipid peroxidation. In fact, the Fe:ATP induced lipid peroxidation was completely inhibited by these two molecules. These results indicate that rifamycin S and rifabutin can interact with rat liver microsomes to undergo redox-cycling, with the subsequent production of hydroxyl radicals when iron complexes are present. Compared to NADPH, NADH is almost as effective (rifamycin S) or even more effective (rifabutin) in promoting these interactions. These interactions may play a role in the hepatotoxicity associated with the use of these antibiotics.
KW - Free radicals
KW - Hydroxyl Radical
KW - Rat Liver Microsomes
KW - Redox Cycling
KW - Rifabutin
KW - Rifamycin S
UR - http://www.scopus.com/inward/record.url?scp=0031024633&partnerID=8YFLogxK
U2 - 10.1016/S0891-5849(96)00335-8
DO - 10.1016/S0891-5849(96)00335-8
M3 - Article
C2 - 8981035
AN - SCOPUS:0031024633
SN - 0891-5849
VL - 22
SP - 439
EP - 446
JO - Free Radical Biology and Medicine
JF - Free Radical Biology and Medicine
IS - 3
ER -