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Hydrolyzed fumonisins HFB 1 and HFB 2 are acylated in vitro and in vivo by ceramide synthase to form cytotoxic N ‐acyl‐metabolites
Author(s) -
Seiferlein Michaela,
Humpf HansUlrich,
Voss Kenneth A.,
Sullards M. Cameron,
Allegood Jeremy C.,
Wang Elaine,
Merrill Alfred H.
Publication year - 2007
Publication title -
molecular nutrition and food research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.495
H-Index - 131
eISSN - 1613-4133
pISSN - 1613-4125
DOI - 10.1002/mnfr.200700118
Subject(s) - ceramide synthase , acylation , ceramide , in vivo , biochemistry , chemistry , in vitro , fumonisin b1 , microsome , enzyme , biology , mycotoxin , apoptosis , microbiology and biotechnology , catalysis , food science
Fumonisins B 1 and B 2 (FB 1 and FB 2 ) are the most abundant members of the fumonisins ‐ mycotoxins that are produced by Fusarium verticillioides and are natural inhibitors of ceramide synthase. Their hydrolyzed forms, HFB 1 and HFB 2 (also called AP 1 and AP 2 ) are found in some foods, and they are not only inhibitors of ceramide synthase but also undergo acylation by this enzyme. This study characterized the conversion of HFB 1 and HFB 2 by ceramide synthase to their respective N‐ acylated metabolites using rat liver microsomes and palmitoyl‐CoA or nervonoyl‐CoA as cosubstrates, and examined animals that had been dosed with hydrolyzed fumonisins to ascertain if acylation occurs in vivo . Using an HPLC‐MS/MS method that allowed the sensitive and selective detection of the acylation products, both HFB 1 and HFB 2 were found to be metabolized in vitro to nervonoyl‐ or palmitoyl‐HFB 1 and ‐HFB 2 ( i. e . C 24:1 ‐HFB 1/2 and C 16 ‐HFB 1/2 , respectively). The apparent v max was considerably higher for formation of C 24:1 HFB 1 (157 pmol/min/mg protein) than for formation of C 16 HFB 1 (8.7 pmol/min/mg protein). The acylation products also inhibited ceramide synthase and significantly reduced the number of viable cells in an in vitro [3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT)] assay using a human colonic cell line (HT29). Furthermore, HPLC‐MS/MS analysis of tissues from rats given intraperitoneal doses of HFB 1 confirmed that formation of N‐ acyl‐HFB 1 occurs in vivo to produce metabolites with fatty acids of various chain lengths. The contribution of acylated HFB 1 and HFB 2 metabolites to fumonisin toxicity in vivo warrants further investigation.