Human superoxide dismutase 1 attenuates quinoneimine metabolite formation from mefenamic acid.

Mefenamic acid (MFA), one of the nonsteroidal anti-inflammatory drugs (NSAIDs), sometimes causes liver injury. Quinoneimines formed by cytochrome P450 (CYP)-mediated oxidation of MFA are considered to be causal metabolites of the toxicity and are detoxified by glutathione conjugation. A previous study reported that NAD(P)H:quinone oxidoreductase 1 (NQO1) can reduce the quinoneimines, but NQO1 is scarcely expressed in the human liver. The purpose is to identify enzyme(s) responsible for the decrease in MFA-quinoneimine formation in the human liver. The formation of MFA-quinoneimine by recombinant CYP1A2 and CYP2C9 was significantly decreased by the addition of human liver cytosol, and the extent of the decrease in the metabolite formed by CYP1A2 was larger than that by CYP2C9. By column chromatography, superoxide dismutase 1 (SOD1) was identified from the human liver cytosol as an enzyme decreasing MFA-quinoneimine formation. Addition of recombinant SOD1 into the reaction mixture decreased the formation of MFA-quinoneimine from MFA by recombinant CYP1A2. By a structure-activity relationship study, we found that SOD1 decreased the formation of quinoneimines from flufenamic acid and tolfenamic acid, but did not affect those produced from acetaminophen, amodiaquine, diclofenac, and lapatinib. Thus, SOD1 may selectively decrease the quinoneimine formation from fenamate-class NSAIDs. To examine whether SOD1 can attenuate cytotoxicity caused by MFA, siRNA for SOD1 was transfected into CYP1A2-overexpressed HepG2 cells. The leakage of lactate dehydrogenase caused by MFA treatment was significantly increased by knockdown of SOD1. In conclusion, we found that SOD1 can serve as a detoxification enzyme for quinoneimines to protect from drug-induced toxicity.

Cytochrome P450-mediated bioactivation of mefenamic acid to quinoneimine intermediates and inactivation by human glutathione S-transferases.

Mefenamic acid (MFA) has been associated with rare but severe cases of hepatotoxicity, nephrotoxicity, gastrointestinal toxicity, and hypersensitivity reactions that are believed to result from the formation of reactive metabolites. Although formation of protein-reactive acylating metabolites by phase II metabolism has been well-studied and proposed to be the cause of these toxic side effects, the oxidative bioactivation of MFA has not yet been competely characterized. In the present study, the oxidative bioactivation of MFA was studied using human liver microsomes (HLM) and recombinant human P450 enzymes. In addition to the major metabolite 3'-OH-methyl-MFA, resulting from the benzylic hydroxylation by CYP2C9, 4'-hydroxy-MFA and 5-hydroxy-MFA were identified as metabolites resulting from oxidative metabolism of both aromatic rings of MFA. In the presence of GSH, three GSH conjugates were formed that appeared to result from GSH conjugation of the two quinoneimines formed by further oxidation of 4'-hydroxy-MFA and 5-hydroxy-MFA. The major GSH conjugate was identified as 4'-OH-5'-glutathionyl-MFA and was formed at the highest activity by CYP1A2 and to a lesser extent by CYP2C9 and CYP3A4. Two minor GSH conjugates resulted from secondary oxidation of 5-hydroxy-MFA and were formed at the highest activity by CYP1A2 and to a lesser extent by CYP3A4. Additionally, the ability of seven human glutathione S-transferases (hGSTs) to catalyze the GSH conjugation of the quinoneimines formed by P450s was also investigated. The highest increase of total GSH conjugation was observed with hGSTP1-1, followed by hepatic hGSTs hGSTA2-2 and hGSTM1-1. The results of this study show that, next to phase II metabolites, reactive quinoneimines formed by oxidative bioactivation might also contribute to the idiosyncratic toxicity of MFA.

Valoración doble-ciega cruzada de la eficacia y tolerancia de etodolac vs. piroxicam en tratamiento de la dismenorrea primaria / Valorization double-blind crassway of eficacy and tolerance of etodolac versus piroxican in the treatment of dysminorrhea primary

Objetivo: Verificar la eficacia de etodolac por vía oral comparado con piroxicam en el tratamiento de la dismenorrea primaria. Material y métodos: Se seleccionaron 31 adolescentes de un colegio de clase social media, con edades entre 10-24 años, con ciclos regulares y una menarquía de un año de evolución. Antecedentes de dismenorrea moderada a severa. Se descartó embarazo o masas pélvicas o uso de anticonceptivos. Se solicitó ecografía pélvica previa, cuadro hemático, parcial de orina, glicemia, proteinas totales. El estudio se diseño en forma doble-ciega-cruzada, durante 4 meses donde la paciente tenía la oportunidad de recibir la medicación en forma alterna en dos ocasiones. En un cuestionário tanto personal como por los investigadores se evaluó la eficacia y tolerancia de los 2 productos. Para la valoración de significancia se utilizó la prueba de Kruskal-Wallis. Resultados: Edad de la menarquia: fue de 12,8 años, ciclos de 29,8 ñ 3,2 y duración de 4-5 días. La dismenorrea (leve) se presentó en 9,6 por ciento. Grado II (moderada), 58,1 por ciento y grado III (severa), 32,2 por ciento. En forma aleatoria el 48,4 por ciento recibió tratamiento con etodolac y 51,6 por ciento, piroxicam. La mejoría en la intensidad del dolor fue del 29,4 por ciento para etodolac y para el piroxicam, 32,5 por ciento, sin evidencia de diferencias estadísticamente significativas. Los exámenes paraclínicos previos estuvieron dentro de limites normales. Los efectos secundarios fueron mínimos, sin obligar a suspender la medicación durante los 4 días de tratamiento. Conclusión: Estos resultados nos permiten afirmar que tanto el etodolac como el piroxicam son eficaces en el tratamiento de la dismenorrea primaria. Los efectos secundarios fueron minimos

Mepirizole, a non-steroidal antiinflammatory compound, its ulcerogenicity and inhibitory action on lesions induced by acidic antiinflammatory agents in the rat stomach.

Gastric lesions were produced in rats by the administration for 2 weeks of 300 mg/kg/day of mepirizole, a basic non-steroidal antiinflammatory compound. Although the single administration of 200 mg/kg of mepirizole had no effect, the addition of water-immersion stress for one hour induced lesions not only in the corpus but also in the pyloric antrum. The administration of 250 mg/kg of mefenamic acid, an acidic non-steroidal antiinflammatory compound (insufficient for producing gastric lesions at this dose alone) with the addition of one hour of water-immersion stress induced gastric lesions. The addition of 200 mg/kg of mepirizole reduced the ulcer index from 8.1 to 4.7 in the corpus and from 4 to 0.5 in the pyloric antrum. It is suggested that basic antiinflammatory compounds inhibit gastric lesions induced by combination of acidic antiinflammatory compounds and water-immersion stress.