title: Stereoselective sulfoxidation of sulindac sulfide by flavin-containing monooxygenases. Comparison of human liver and kidney microsomes and mammalian enzymes.
abstract: The stereoselective sulfoxidation of the pharmacologically active metabolite of sulindac, sulindac sulfide, was characterized in human liver, kidney, and cDNA-expressed enzymes. Kinetic parameter estimates (pH = 7.4) for sulindac sulfoxide formation in human liver microsomes (N = 4) for R- and S-sulindac sulfoxide were V(max) = 1.5 +/- 0.50 nmol/min/mg, K(m) = 15 +/- 5.1 microM; and V(max) = 1.1 +/- 0.36 nmol/min/mg, K(m) = 16 +/- 6.1 microM, respectively. Kidney microsomes (N = 3) produced parameter estimates (pH = 7.4) of V(max) = 0.9 +/- 0.29 nmol/min/mg, K(m) = 15 +/- 2.9 microM; V(max) = 0.5 +/- 0.21 nmol/min/mg, K(m) = 22 +/- 1.9 microM for R- and S-sulindac sulfoxide, respectively. In human liver and flavin-containing monooxygenase 3 (FMO3) the V(max) for R-sulindac sulfoxide increased 60-70% at pH = 8.5, but for S-sulindac sulfoxide was unchanged. In fourteen liver microsomal preparations, significant correlations occurred between R-sulindac sulfoxide formation and either immunoquantified FMO or nicotine N-oxidation (r = 0.88 and 0.83; P < 0.01). The R- and S-sulindac sulfoxide formation rate also correlated significantly (r = 0.85 and 0.75; P < 0.01) with immunoquantified FMO in thirteen kidney microsomal samples. Mild heat deactivation of microsomes reduced activity by 30-60%, and a loss in stereoselectivity was observed. Methimazole was a potent and nonstereoselective inhibitor of sulfoxidation in liver and kidney microsomes. n-Octylamine and membrane solubilization with lubrol were potent and selective inhibitors of S-sulindac sulfoxide formation. cDNA-expressed CYPs failed to appreciably sulfoxidate sulindac sulfide, and CYP inhibitors were ineffective in suppressing catalytic activity. Purified mini-pig liver FMO1, rabbit lung FMO2, and human cDNA-expressed FMO3 efficiently oxidized sulindac sulfide with a high degree of stereoselectivity towards the R-isomer, but FMO5 lacked catalytic activity. The biotransformation of the sulfide to the sulfoxide is catalyzed predominately by FMOs and may prove to be useful in characterizing FMO activity.
authors.affiliation: Division of Clinical Pharmacology, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
authors.forename: M A
authors.initials: MA
authors.lastname: Hamman
authors.forename: B D
authors.initials: BD
authors.lastname: Haehner-Daniels
authors.forename: S A
authors.initials: SA
authors.lastname: Wrighton
authors.forename: A E
authors.initials: AE
authors.lastname: Rettie
authors.forename: S D
authors.initials: SD
authors.lastname: Hall
mesh_terms: D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000378:metabolism; D001711:Biotransformation; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D007668:Kidney / Q000201:enzymology / Q000378:metabolism*; D008862:Microsomes, Liver / Q000201:enzymology / Q000378:metabolism*; D010105:Oxygenases / Q000378:metabolism*; D011817:Rabbits; D013237:Stereoisomerism; D013467:Sulindac / Q000031:analogs & derivatives* / Q000378:metabolism
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D013467:Sulindac; C025462:sulindac sulfide; D003577:Cytochrome P-450 Enzyme System; D010105:Oxygenases; C020066:dimethylaniline monooxygenase (N-oxide forming)