Presence Of Fumonisin B1 Research Articles

Prevalence of Fumonisin Contamination in Corn and Corn-based Feeds in Taiwan

The purpose of this study was to investigate the prevalence of fumonisin contamination in corn and corn-based feeds in Taiwan. A total of 233 samples was collected from 8 feed mill factories located in four different regions in Taiwan. The presence of fumonisin B1 (FB1) and B2 (FB2) was determined by thin layer chromatograph, while the total fumonisin content was determined using immuno-affinity column cleanup and fluorometer quantitation. Our results showed that 55 samples of swine feeds had the highest percentage of incidence of FB1 and FB2 (41.8% and 41.8%, respectively), followed by 66 samples of duck feeds (40.9% and 37.8%). However, the percentage of incidence of FB1 and FB2 was much lower in 43 samples of broiler feeds (23.2% and 13.9%) and 69 samples of corn (17.3% and 10.1%). Corn and duck feeds were found to have a significant higher level of means of total fumonisins (5.4±1.5 and 5.8±0.6 ppm, respectively) than swine feeds (2.9±0.4 ppm) and broiler feeds (3.0±0.5 ppm). Comparing fumonisins distribution in different regions, the highest percentage of FB1 incidence (39.2%) was found in the eastern region of Taiwan, and total fumonisins level (4.5±0.7 ppm) was significantly higher than other regions. However, the highest percentage of FB2 incidence (32.0%) was found in the central region of Taiwan. Trimonthly analysis of data showed that both high percentage of FB1 and FB2 incidence (39.3% and 37.7%) and total concentration of fumonisin (5.7±0.4 ppm) were found in the period of Jan. to Mar., The incidence and concentration were significantly higher than other trimothly periods. These results indicate that fumonisin B mycotoxins are both widespread and persistent in feed-grade corn and corn-based feeds in Taiwan. (Asian-Aust. J. Anim. Sci. 2002. Vol 15, No. 4 : 610-614)

Process Outgrowth of Oligodendrocytes Is Promoted by Interaction of Fyn Kinase with the Cytoskeletal Protein Tau

Fyn kinase plays an important role during myelination and has been shown to promote morphological differentiation of cultured oligodendrocytes. We analyzed the downstream targets of Fyn kinase in oligodendrocytes. Because process outgrowth and wrapping of axons involve cytoskeletal rearrangement, we focused on cytoskeletal proteins linked to Fyn. Here we demonstrate that Fyn binds to the cytoskeletal proteins Tau and alpha-Tubulin in oligodendrocytes. Tau interacts with the Fyn SH3 domain whereas alpha-Tubulin binds to the Fyn SH2 and SH3 domains. To study the function of the Fyn-Tau interaction in oligodendrocytes, we designed a Tau deletion mutant that would compete with endogenous Tau-Fyn binding in transfected cells. The mutant Tau protein binds to the Fyn SH3 domain but lacks the microtubuli interaction domain and thus cannot bind to microtubuli. In the presence of the mutant Tau protein, a reduction of the process number and process length in oligodendroglial cells was observed. This effect is likely to be caused by interference with the Fyn-Tau-microtubuli cascade rather than inactivation of the kinase, because Fyn bound to the mutant Tau retains activity. A similar inhibition of process outgrowth was observed when oliogodendroglial cells were cultured in the presence of Fumonisin B1, an inhibitor of sphingolipid synthesis that prevents the formation of rafts. Because ligation of the cell adhesion molecule F3 on oligodendrocytes leads to activation of Fyn kinase localized in rafts, these findings suggest that recruitment of Tau and Tubulin to activated Fyn kinase in rafts is an important step in the initiation of myelination.

Ceramide generation occurring during 7beta-hydroxycholesterol- and 7-ketocholesterol-induced apoptosis is caspase independent and is not required to trigger cell death.

Biological activities of oxysterols seem tightly regulated. Therefore, the ability to induce cell death of structurally related oxysterols, such as those oxidized at C7(7alpha-, 7beta-hydroxycholesterol, and 7-ketocholesterol), was investigated on U937 cells at different times of treatment in a concentration range of 5-80 microg/ml. Whereas all oxysterols accumulate inside the cells, strong inhibition of cell growth and increased permeability to propidium iodide were observed only with 7beta-hydroxycholesterol and 7-ketocholesterol, which trigger an apoptotic process characterized by the occurrence of cells with fragmented and/or condensed nuclei, and by various cellular dysfunctions: loss of mitochondrial transmembrane potential, cytosolic release of cytochrome c, activation of caspase-9 and -3 with subsequent enhanced activity of caspase-3, degradation of poly(ADP-ribose) polymerase, and increased accumulation of cellular C16 : 0 and C24 : 1 ceramide species. This ceramide generation is not attributed to caspase activation since inhibition of 7beta-hydroxycholesterol- and 7-ketocholesterol-induced apoptosis by Z-VAD-fmk (100 microM), a broad spectrum caspase inhibitor, did not reduce C16 : 0 and C24 : 1 ceramide species accumulation. Conversely, when U937 cells were treated with 7beta-hydroxycholesterol and 7-ketocholesterol in the presence of fumonisin B1 (100 microM), a specific inhibitor of ceramide synthase, C16 : 0 and C24 : 1 ceramide species production was completely abrogated whereas apoptosis was not prevented. Noteworthy, 7alpha-hydroxycholesterol induced only a slight inhibition of cell growth. Collectively, these results are consistent with the notion that the alpha or beta hydroxyl radical position of oxysterols oxidized at C7 plays a key role in the induction of the apoptotic process. In addition, our findings demonstrate that 7beta-hydroxycholesterol- and 7-ketocholesterol-induced apoptosis involve the mitochondrial signal transduction pathway and they suggest that C16 : 0 and C24 : 1 ceramide species generated through ceramide synthase play a minor role in the commitment of 7beta-hydroxycholesterol- and 7-ketocholesterol-induced cell death.

Fumonisin B1influenced the effects of arachidonic acid, prostaglandins E2 and A2 on cell cycle progression, apoptosis induction, tyrosine- and CDC2-kinase activity in oesophageal cancer cells

In a previous study, we showed that, of a group of lipids including arachidonic acid (AA), prostaglandins E2 (PGE2) and A2 (PGA2), PGA2 had the most marked effect on the inhibition of cell growth, activation of tyrosine kinase activity, lowering of the number of G1-phase cells, and induction of p53 levels in oesophageal carcinoma (WHCO3) cells17. No significant effects by the three lipids were seen in normal monkey kidney cells. In the present study, the effects of the inhibitor of ceramide synthesis, fumonisin B1(FB1), a metabolite ofFusarium verticillioides (=F.moniliforme) which is implicated in the high incidence of oesophageal cancer, were determined on AA, PGE2 and PGA2 WHCO3 treated cells. In the presence of FB1, the lipid-enhanced tyrosine kinase activity was lowered. Flow cytometric and morphological studies showed that FB1lowered the marked apoptosis induced by especially PGA2. FB1, however, in combination with AA, PGE2 or PGA2 increased the number of G2/M cells. AA⪢PGE2⪢PGA2 alone decreased CDC2-kinase activity, but, in the presence of FB1, CDC2-kinase activity was significantly increased. The PGA2- and AA-induced p53 levels were lowered in the presence of FB1. We concluded that FB1diminished the cytotoxic effects of the lipids on oesophageal tumour cells.

The Role of Sphingolipids in the Maintenance of Fibroblast Morphology: THE INHIBITION OF PROTRUSIONAL ACTIVITY, CELL SPREADING, AND CYTOKINESIS INDUCED BY FUMONISIN B1 CAN BE REVERSED BY GANGLIOSIDE GM3

Previous studies demonstrated that inhibition of sphingolipid synthesis by the mycotoxin fumonisin B1 (FB1) disrupts axonal growth in cultured hippocampal neurons (Harel, R., and Futerman, A. H. (1993) J. Biol. Chem. 268, 14476-14481) by affecting the formation or stabilization of axonal branches (Schwarz, A., Rapaport, E., Hirschberg, K., and Futerman, A.H. (1995) J. Biol. Chem. 270, 10990-10998). We now demonstrate that long term incubation with FB1 affects fibroblast morphology and proliferation. Incubation of Swiss 3T3 cells with FB1 resulted in a decrease in synthesis of ganglioside GM3, the major glycosphingolipid in 3T3 fibroblasts and of sphingomyelin. The projected cell area of FB1-treated cells was approximately 45% less than control cells. FB1 had no affect on the organization of microtubules or intermediate filaments, but fewer actin-rich stress fibers were observed, and there was a loss of actin-rich lamellipodia at the leading edge. Three other processes involving the actin cytoskeleton, cytokinesis, microvilli formation, and the formation of long processes induced by protein kinase inhibitors, were all disrupted by FB1. All the effects of FB1 on cell morphology could be reversed by addition of ganglioside GM3 even in the presence of FB1, whereas the bioactive intermediates, sphinganine, sphingosine, and ceramide, were without effect. Finally, FB1 blocked cell proliferation and DNA synthesis in a reversible manner, although ganglioside GM3 could not reverse the effects of FB1 on cell proliferation. Together, these data suggest that ongoing sphingolipid synthesis is required for the assembly of both new membrane and of the underlying cytoskeleton.

Fumonisin B1 induces protein kinase C translocation via direct interaction with diacylglycerol binding site

Fumonisins are carcinogenic to rats and are suspected human carcinogens. However, the mechanism(s) of carcinogenesis of fumonisin B1 (FB1) is poorly understood. Multiple signal transduction pathways such as protein kinase C (PKC) have been shown to play an important role in carcinogenesis. This study was undertaken to evaluate whether FBI affects PKC activation. Similar to tumor-promoting phorbol ester, phorbol 12-myristate-13-acetate (PMA), PKC is also catalytically activated by FB1. Protein kinase C activity and its redistribution in response to FB1 were determined in rat cerebrocortical slices. Cytosolic and membranous PKC activities were determined by histone phosphorylation in the presence of [γ32P]ATP, phosphatidyl-l-serine, PMA, and Ca 2+. Distribution of γPKC isozyme in the presence of FB1 was also assessed by immunoblotting using affinity purified anti-peptide antibodies. Similar to PMA, FB1 added in vitro to rat cerebrocortical slices facilitated PKC translocation from cytosol to membrane in a concentration-dependant manner. This FB1-induced PKC translocation was inhibited by incubation with the inactive 4α-phorbol 12,13-didecanoate. The effects of FB1 and PMA were neither additive nor synergistic. In addition, PMA and FB1-induced PKC enzyme redistribution were inhibited by pretreating tissues with sphingosine. A concentration-related FB1 attenuation of specific phorbol dibutyrate, [3H]PDBu, binding was also observed when cortical membranes were incubated with either PMA or sphingosine. This is the first report of FB1-induced PKC translocation via a direct action on the diacylglycerol site that also binds phorbol esters. Because phorbol esters are well known tumor promoters, we provide a plausible cellular mechanism to explain the carcinogenicity of FB1.

Hierarchy of mechanisms involved in generating Na/K-ATPase polarity in MDCK epithelial cells.

We have studied mechanisms involved in generating a polarized distribution of Na/K-ATPase in the basal-lateral membrane of two clones of MDCK II cells. Both clones exhibit polarized distributions of marker proteins of the apical and basal-lateral membranes, including Na/K-ATPase, at steady state. Newly synthesized Na/K-ATPase, however, is delivered from the Golgi complex to both apical and basal-lateral membranes of one clone (II/J), and to the basal-lateral membrane of the other clone (II/G); Na/K-ATPase is selectively retained in the basal-lateral membrane resulting in the generation of complete cell surface polarity in both clones. Another basal-lateral membrane protein, E-cadherin, is sorted to the basal-lateral membrane in both MDCK clones, demonstrating that there is not a general sorting defect for basal-lateral membrane proteins in clone II/J cells. A glycosyl-phosphatidylinositol (GPI)-anchored protein (GP-2) and a glycosphingolipid (glucosylceramide, GlcCer) are preferentially transported to the apical membrane in clone II/G cells, but, in clone II/J cells, GP-2 and GlcCer are delivered equally to both apical and basal-lateral membranes, similar to Na/K-ATPase. To examine this apparent inter-relationship between sorting of GlcCer, GP-2 and Na/K-ATPase, sphingolipid synthesis was inhibited in clone II/G cells with the fungal metabolite, Fumonisin B1 (FB1). In the presence of FB1, GP-2 and Na/K-ATPase are delivered to both apical and basal-lateral membranes, similar to clone II/J cells; FB1 had no effect on sorting of E-cadherin to the basal-lateral membrane of II/G cells. Addition of exogenous ceramide, to circumvent the FB1 block, restored GP-2 and Na/K-ATPase sorting to the apical and basal-lateral membranes, respectively. These results show that the generation of complete cell surface polarity of Na/K-ATPase involves a hierarchy of sorting mechanisms in the Golgi complex and plasma membrane, and that Na/K-ATPase sorting in the Golgi complex of MDCK cells may be regulated by exclusion from an apical pathway(s). These results also provide new insights into sorting pathways for other apical and basal-lateral membrane proteins.

Pharmacokinetic fate and pathological effects of 14C-fumonisin B1 in laying hens.

Presence of fumonisin B1 (FB1), a major metabolite of Fusarium moniliforme, in corn is of great concern to both human and animal health because of its wide range of toxicity. The pharmacokinetics of FB1 was studied in laying hens following oral and intravenous administration of 14C-labelled FB1. After iv dosing (2.0 mg = 23.68 kBq/kg bw) plasma radioactivity underwent a very rapid bi-exponential decline (t1/2 alpha = 2.5 +/- 0.3 min; t1/2 beta = 48.8 +/- 11.2 min) with negligible levels measured after 4-6 hr. Mean value for the apparent volume of distribution at steady state (Vdss) was 18.27 ml/kg, apparent volume of central compartment (Vd beta) was 82.20 ml/kg and plasma clearance was 1.18 ml/min/kg. At 24 hr post-dosing only trace residues were present in liver, kidney, and cecum. When dosed by the oral route (2.0 mg = 47.36 kBq/kg bw), systemic absorption of fumonisin appeared to be poor (F = 0.71 +/- 0.5%) with peak plasma concentrations of only 40-145 dpm/ml (equivalent to 28-103 ng FB1 and/or metabolites per ml) between 1.5 and 2.5 hr. At 24 hr post-dosing only trace amounts were present in crop, liver, kidney, small intestine, and cecum. In both orally and iv dosed birds almost all (97.7 +/- 3.73%) of the radioactivity was recovered in excreta by the end of the 24 hr experiment period and no residues were found in eggs laid during the 24 hr post-dosing period.(ABSTRACT TRUNCATED AT 250 WORDS)