Mohammed I Rasool1, Ahsan F Bairam2, Katsuhisa Kurogi3, Ming-Cheh Liu4. 1. Department of Pharmacology, College of Pharmacy and Pharmaceutical Sciences, University of Toledo Health Science Campus, Toledo, USA; Department of Pharmacology and Toxicology, College of Pharmacy, University of Karbala, Karbala, Iraq. 2. Department of Pharmacology, College of Pharmacy and Pharmaceutical Sciences, University of Toledo Health Science Campus, Toledo, USA; Department of Pharmacology and Toxicology, College of Pharmacy, University of Kufa, Kufa, Iraq. 3. Department of Pharmacology, College of Pharmacy and Pharmaceutical Sciences, University of Toledo Health Science Campus, Toledo, USA; Biochemistry and Applied Biosciences, University of Miyazaki, Miyazaki, Japan. 4. Department of Pharmacology, College of Pharmacy and Pharmaceutical Sciences, University of Toledo Health Science Campus, Toledo, USA. Electronic address: ming.liu@utoledo.edu.
Abstract
BACKGROUND: Previous studies have demonstrated that sulfate conjugation is involved in the metabolism of the active metabolite of tramadol, O-desmethyltramadol (O-DMT). The current study aimed to systematically identify the human cytosolic sulfotransferases (SULTs) that are capable of mediating the sulfation of O-DMT. METHODS: The sulfation of O-DMT under metabolic conditions was demonstrated using HepG2 hepatoma cells and Caco-2 human colon carcinoma cells. O-DMT-sulfating activity of thirteen known human SULTs and four human organ specimens was examined using an established sulfotransferase assay. pH-Dependency and kinetic parameters were also analyzed using, respectively, buffers at different pHs and varying O-DMT concentrations in the assays. RESULTS: Of the thirteen human SULTs tested, only SULT1A3 and SULT1C4 were found to display O-DMT-sulfating activity, with different pH-dependency profiles. Kinetic analysis revealed that SULT1C4 was 60 times more catalytically efficient in mediating the sulfation of O-DMT than SULT1A3 at respective optimal pH. Of the four human organ specimens tested, the cytosol prepared from the small intestine showed much higher O-DMT-sulfating activity than cytosols prepared from liver, lung, and kidney. Both cultured HepG2 and Caco-2 cells were shown to be capable of sulfating O-DMT and releasing sulfated O-DMT into cultured media. CONCLUSION: SULT1A3 and SULT1C4 were the major SULTs responsible for the sulfation of O-DMT. Collectively, the results obtained provided a molecular basis underlying the sulfation of O-DMT and contributed to a better understanding about the pharmacokinetics and pharmacodynamics of tramadol in humans.
BACKGROUND: Previous studies have demonstrated that sulfate conjugation is involved in the metabolism of the active metabolite of tramadol, O-desmethyltramadol (O-DMT). The current study aimed to systematically identify the human cytosolic sulfotransferases (SULTs) that are capable of mediating the sulfation of O-DMT. METHODS: The sulfation of O-DMT under metabolic conditions was demonstrated using HepG2 hepatoma cells and Caco-2 humancolon carcinoma cells. O-DMT-sulfating activity of thirteen known human SULTs and four human organ specimens was examined using an established sulfotransferase assay. pH-Dependency and kinetic parameters were also analyzed using, respectively, buffers at different pHs and varying O-DMT concentrations in the assays. RESULTS: Of the thirteen human SULTs tested, only SULT1A3 and SULT1C4 were found to display O-DMT-sulfating activity, with different pH-dependency profiles. Kinetic analysis revealed that SULT1C4 was 60 times more catalytically efficient in mediating the sulfation of O-DMT than SULT1A3 at respective optimal pH. Of the four human organ specimens tested, the cytosol prepared from the small intestine showed much higher O-DMT-sulfating activity than cytosols prepared from liver, lung, and kidney. Both cultured HepG2 and Caco-2 cells were shown to be capable of sulfating O-DMT and releasing sulfated O-DMT into cultured media. CONCLUSION:SULT1A3 and SULT1C4 were the major SULTs responsible for the sulfation of O-DMT. Collectively, the results obtained provided a molecular basis underlying the sulfation of O-DMT and contributed to a better understanding about the pharmacokinetics and pharmacodynamics of tramadol in humans.
Authors: Ahsan F Bairam; Mohammed I Rasool; Fatemah A Alherz; Maryam S Abunnaja; Amal A El Daibani; Katsuhisa Kurogi; Ming-Cheh Liu Journal: Arch Biochem Biophys Date: 2018-04-26 Impact factor: 4.013
Authors: Sarah Dubaisi; Hailin Fang; Joseph A Caruso; Roger Gaedigk; Carrie A Vyhlidal; Thomas A Kocarek; Melissa Runge-Morris Journal: Drug Metab Dispos Date: 2020-04-17 Impact factor: 3.922
Authors: Tania E Perez Jimenez; Butch Kukanich; Hyun Joo; Katrina L Mealey; Tamara L Grubb; Stephen A Greene; Michael H Court Journal: Drug Metab Dispos Date: 2018-10-26 Impact factor: 3.922