title: Ceramide synthase inhibition by fumonisin B1 treatment activates sphingolipid-metabolizing systems in mouse liver.
abstract: Sphingolipids are important components of cell structure and cell signaling. Both external and internal stimuli can alter levels of cellular sphingolipids by regulating enzyme activities associated with sphingolipid metabolism. Fumonisin B1, mycotoxin produced by Fusarium verticillioides, is a reportedly specific inhibitor of ceramide synthase. In order to test our hypothesis whether ceramide synthase inhibition by fumonisin B1 alters other sphingolipid-metabolizing enzymes, we investigated the changes in free sphingoid bases and sphingomyelin (SM) and activities of key enzymes for their metabolism, sphingomyelinase (SMase), serine palmitoyltransferase (SPT), and sphingosine kinase (SPHK) in mouse liver. The hepatic free sphingoid bases increased significantly following five daily treatments with fumonisin B1 in mice. The activity of acidic SMase was enhanced by fumonisin B1, accompanied with a decrease in liver SM content. The expression and activities of SPT and SPHK1 in liver increased significantly following fumonisin B1 treatment. Another hepatotoxicant acetaminophen caused liver regeneration similar to fumonisin B1 but did not produce similar effects on liver sphingolipid-metabolizing enzymes, suggesting that activation of sphingolipid metabolism was not a consequence of hepatocyte regeneration. Data suggest that ceramide synthase inhibition by fumonisin B1 treatment stimulates sphingolipid-metabolizing systems to maintain a balance of cellular sphingolipids.
authors.affiliation: Department of Physiology and Pharmacology, College of Veterinary Medicine, The University of Georgia, Athens, Georgia 30602-7389, USA. qhe@cydexinc.com
authors.forename: Quanren
authors.initials: Q
authors.lastname: He
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Suzuki
authors.forename: Neelesh
authors.initials: N
authors.lastname: Sharma
authors.forename: Raghubir P
authors.initials: RP
authors.lastname: Sharma
mesh_terms: D000818:Animals; D056486:Chemical and Drug Induced Liver Injury / Q000201:enzymology / Q000209:etiology; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000633:toxicity*; D005260:Female; D037341:Fumonisins / Q000633:toxicity*; D007279:Injections, Subcutaneous; D007527:Isoenzymes; D008099:Liver / Q000187:drug effects* / Q000201:enzymology; D051379:Mice; D008810:Mice, Inbred C57BL; D009183:Mycotoxins / Q000633:toxicity*; D010088:Oxidoreductases / Q000037:antagonists & inhibitors*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000096:biosynthesis / Q000235:genetics; D051102:Serine C-Palmitoyltransferase / Q000096:biosynthesis / Q000235:genetics; D013107:Sphingolipids / Q000378:metabolism*; D013108:Sphingomyelin Phosphodiesterase / Q000096:biosynthesis / Q000235:genetics; D013109:Sphingomyelins / Q000378:metabolism; D000099157:Sphingosine Kinase
chemical_list: D004791:Enzyme Inhibitors; D037341:Fumonisins; D007527:Isoenzymes; D009183:Mycotoxins; D010088:Oxidoreductases; D017853:Phosphotransferases (Alcohol Group Acceptor); D051102:Serine C-Palmitoyltransferase; D013107:Sphingolipids; D013108:Sphingomyelin Phosphodiesterase; D013109:Sphingomyelins; D000099157:Sphingosine Kinase; C056933:fumonisin B1; C108138:dihydroceramide desaturase