Fumonisin- and AAL-Toxin-Induced Disruption of Sphingolipid Metabolism with Accumulation of Free Sphingoid Bases

Abstract

Fumonisins (FB) and AAL-toxin are sphingoid-like compounds produced by several species of fungi associated with plant diseases. In animal cells, both fumonisins produced by Fusarium moniliforme and AAL-toxin produced by Alternaria alternata f. sp. lycopersici inhibit ceramide synthesis, an early biochemical event in the animal diseases associated with consumption of f. moniliforme-contaminated corn. In duckweed (Lemna pausicostata Heglem. 6746), tomato plants (Lycopersicon esculentum Mill), and tobacco callus (Nicotiana fabacum cv Wisconsin), pure FB1 or AAL-toxin caused a marked elevation of phytosphingosine and sphinganine, sphingoid bases normally present in low concentrations. The relative increases were quite different in the three plant systems. Nonetheless, disruption of sphingolipid metabolism was clearly a common feature in plants exposed to FB, or AAL-toxin. Resistant varieties of tomato (AsclAsc) were much less sensitive to toxin-induced increases in free sphinganine. Because free sphingoid bases are precursors to plant "ceramides," their accumulation suggests that the primary biochemical lesion is inhibition of de novo ceramide synthesis and reacylation of free sphingoid bases. Thus, in plants the disease symptoms associated with A. alternata and F. moniliforme infection may be due to disruption of sphingolipid metabolism.

Fumonisins in Maize: Can We Reduce Their Occurrence?

“…Although pigs are unusually sensitive to trichothecene mycotoxins produced by Fusarium species, they appear to be considerably less sensitive than horses to fumonisins. Survey data and feeding experiments suggest that pigs consuming naturally contaminated feeds containing approximately 100 µg of fumonisins per g (FB 1 and FB 2 ) are at risk for PPE (29). To our knowledge, however, this lung disease has not yet been produced by oral dosage with pure fumonisins.…”

“…This reaction results in the removal of the primary amine group from the fumonisin molecule. Lu et al (28) reported that treatment of FB 1 with fructose under these conditions resulted in a significant reduction in detectable FB 1 . More importantly, when a diet containing the product of the FB 1 -fructose reaction was fed to rats, it was not toxic and did not result in cancer initiation (28).…”

“…Research has shown that Ca(OH) 2 treatment can reduce detectable FB 1 concentrations (37,40,54), but there are conflicting reports about the toxicity of the hydrolyzed end products. Murphy et al (37) found that the hydrolyzed fumonisin may be nearly as toxic as unaltered FB 1 . Similar results were reported by Park et al (40), but these workers found that a modified nixtamalization process resulted in some detoxification.…”

“…Several commercially available enzymes have been tested for their ability to detoxify fumonisins (37). None of these products significantly reduced recovery of FB 1 . Ammoniation, tested as a detoxification method for other mycotoxins (particularly aflatoxins), may successfully detoxify the fumonisins when combined with high temperature (41).…”

“…lycopersici in tomato (12). In addition, purified fumonisins at low (10 -6 M) concentrations have been shown to cause necrosis and other symptoms in maize seedlings, tomato seedlings, and other plants (1,12,23).…”