Mechanism of protection of lobenzarit against paracetamol-induced toxicity in rat hepatocytes

• Published in: European journal of pharmacology Vol. 293; no. 4; pp. 301 - 308
• Main Authors: Remirez, Diadelis, Commandeur, Jan N.M., Groot, Ed, Vermeulen, Nico P.E.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 07.12.1995; Elsevier
• Subjects: Acetaminophen - antagonists & inhibitors; Acetaminophen - toxicity; Animals; Biological and medical sciences; Cells, Cultured; Chemoprotection; Cytochrome P-450 CYP2E1; Cytochrome P-450 Enzyme System - metabolism; Drug toxicity and drugs side effects treatment; Glutathione - metabolism; Glutathione Transferase - metabolism; Hepatotoxicity; Isoenzymes - metabolism; L-Lactate Dehydrogenase - metabolism; Lipid Peroxidation; Liver - drug effects; Liver - enzymology; Lobenzarit; Male; Medical sciences; Microsomes, Liver - drug effects; Mixed Function Oxygenases - metabolism; Molecular mechanism; ortho-Aminobenzoates - administration & dosage; ortho-Aminobenzoates - pharmacology; Paracetamol; Pharmacology. Drug treatments; Rats; Rats, Wistar; Toxicity: digestive system; Lobenzarit; Paracetamol; Chemoprotection; Hepatotoxicity; Molecular mechanism; Rat; Hepatoprotector; Toxicity; Liver; Rodentia; In vitro; Prevention; Vertebrata; Mammalia; Analgesic; Cytoprotector; Hepatocyte; Animal; Mechanism of action
• ISSN: 0926-6917; 0014-2999
• DOI: 10.1016/0926-6917(95)90049-7

The protective effects of lobenzarit, an antioxidative agent and antirheumatic drug, on the cytotoxicity of paracetamol in rat hepatocytes were studied, as well as the inhibitory effects of lobenzarit on cytochrome P-450s and glutathione S-transferases (GSTs) in rat liver. Paracetamol was selected as a model toxin, since it is known to be bioactivated by specific cytochrome P-450s presumably to N-acetyl- p-benzoquinoneimine, a reactive metabolite which upon overdasage of paracetamol causes protein and non-protein thiol depletion, lipid peroxidation and cytotoxicity measurable as LDH leakage. At concentrations of lobenzarit of 0.2 and 0.3 mM, added 30 min before paracetamol, the drug prevented paracetamol-induced leakage of lactate dehydrogenase (LDH) almost completely and lipid peroxidation (LPO) and depletion of glutathione (GSH) substantially and also the formation of the 3-glutathionyl conjugate of paracetamol. However, at a concentration of 0.05 mM lobenzarit did not protect anymore against the paracetamol toxicity. When added to the hepatocytes 1 h and 2 h before paracetamol, 0.05 and 0.2 and 0.3 mM concentrations of lobenzarit did not protect against the cytotoxicity induced by paracetamol either. Lobenzarit did not inhibit cytochromes P-450 1A1/1A2, 2B1/2B2 abd 2E1 which were measured as ethoxyresorufin O-deethylation (EROD) activity in β-naphthoflavone-induced rat liver microsomes, as pentoxyresorufin de-pentylation (PROD) activity in phenobarbital-induced microsomes and as p-nitrophenol hydroxylation (PNPH) activity in pyrazol-induced microsomes. Lobenzarit did not show inhibition of glutathione S-transferase (GST) activity towards 1-chloro-2,4-dinitrobenzene (CDNB) in cytosol from liver of rats treated with phenobarbital, pyrazol and β-naphthoflavone either. It is concluded that the cytoprotective effect of lobenzarit is most likely due to its antioxidant effects and/or to its ability to stimulate GSH reductase.