Study of embryotoxicity of Fusarium mycotoxin butenolide using a whole rat embryo culture model.

Butenolide, a mycotoxin elaborated by several toxigenic Fusarium species, has been implicated as an etiological factor of Kashin-Beck disease and it is always detected in food from endemic Kashin-Beck disease areas. Although butenolide is considered as a potential health risk to humans and animals, its toxicity targets and mechanism of action have not been fully understood and the knowledge of its developmental toxicity is absent. The present study investigated butenolide embryotoxicity via an in vitro whole embryo culture system using rat embryos. Embryos exposed to butenolide at a concentration of 0.625 mg/L showed and differentiation similar to that of the control embryos (=no observed adverse effect concentration; NOAECwec). The embryonic growth and differentiation were affected, represented as reduced crown-rump length and head length, and decreased number of somites from 1.25 mg/L. Total morphological scores decreased significantly at the concentration of butenolide of 2.5 mg/L. All embryos were malformed at 3.75 mg/L and above (=ICMaxWEC), presenting growth retardation with flexion failure and irregular somite differentiation. The IC503T3 of butenolide as calculated from the balb/c 3T3 cytotoxicity test is 6.45 mg/L. Our study shows that butenolide exerts detrimental effects on embryo development in vitro by inducing growth retardation and differentiation inhibition, and the embryotoxicity effect of butenolide should be treated with caution.

Chlorpyrifos induces delayed cytotoxicity after withdrawal in primary hippocampal neurons through extracellular signal-regulated kinase inhibition.

In this study, the delayed effect and related mechanism after chlorpyrifos (CPF) withdrawal was studied in primary rat hippocampal neurons. The results showed that 10 muM CPF induced no detectable cytotoxicity during 96 h continuous exposure while its withdrawal after 48 h exposure induced evident cytotoxicity, as indexed by decreased methyl thiazolyl tetrazolium (MTT) metabolism, increased loss of neurons immunostained by neuron-specific enolase (NSE) antibody, and the increased terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling (TUNEL) positive cell rate in the following 24 h and 48 h incubation in the absence of CPF. Extracellular signal-related kinase (ERK)1/2 activation by phosphorylation was observed and persisted during CPF exposure. However, CPF withdrawal after 48 h exposure led to inhibition of ERK1/2 phosphorylation. Carbacol and nerve growth factor (NGF), which are ERK1/2 activators, protected the neurons after CPF withdrawal, while atropine and PD98059, which are ERK1/2 inhibitors, exacerbated the cytotoxicity, indicating the involvement of inhibition of ERK1/2 phosphorylation in CPF-induced delayed cytotoxicity. In conclusion, CPF withdrawal after exposure induced delayed cytotoxicity in cultured neurons. Inhibition of ERK1/2 phosphorylation was found to be related to the delayed cytotoxicity. This finding may provide a new insight into the toxicological mechanism of organophosphorus pesticides, especially chronic organophosphate-induced neuropsychiatric disorder characterized by delayed occurrence.

Chronic organophosphate (OP)-induced neuropsychiatric disorder is a withdrawal syndrome.

Chronic organophosphate-induced neuropsychiatric disorder is a less well-characterized syndrome, which is usually delay-occurred, persists long and is similar to the symptom of cholinergic deficit, its mechanism is unclear. The characteristics of chronic organophosphate-induced neuropsychiatric disorder are somewhat opposite to the direct action of OP pesticide, since withdrawal effect is usually opposite to the original effect of a drug, hypothesis that chronic organophosphate-induced neuropsychiatric disorder is a kind of withdrawal syndrome is suggested.

Toxic effects of Fusarium mycotoxin butenolide on rat myocardium and primary culture of cardiac myocytes.

Mycotoxin toxicosis has been implicated in the etiopathogenesis of Keshan disease (KD), an endemic cardiomyopathy prevailing in some regions of China. Butenolide (4-acetamido-4-hydroxy-2-butenoic acid gamma-lactone, CAS No. 16275-44-8), a mycotoxin produced by several Fusarium species such as Fusarium tricinctum and Fusarium graminearum, is frequently detected from the cereals in the endemic areas of KD. The present study is undertaken to investigate whether this mycotoxin can induce myocardial damage. Exposure of primary culture of cardiac myocytes to butenolide resulted in significant cytotoxicity, manifested by changes in cell morphology and decreases in cell viability. Consistent with the in vitro findings, distinct myocardial toxicity in vivo was observed after administration of rats by gavage with butenolide (10 and 20 mg/kg/day) for 2 months, and the myocardial injuries were characterized by focal necrosis of myocardium and fragmentation of myofiber. Butenolide also induced significant oxidative damage to the myocardium in vitro evidenced by a concentration-dependent lipid peroxidation in the myocardial homogenates, whereas antioxidants superoxide dismutase (SOD), N-acetylcysteine (NAC) and glutathione (GSH) provided significant protections against this oxidative effect. Taken together, these results clearly reveal that butenolide possesses the potential to induce myocardial toxicity. The present findings may reinforce the hypothesis that toxicosis by mycotoxins is one of the etiological factors for KD.

The oxidative damage of butenolide to isolated erythrocyte membranes.

Butenolide (CAS No. 16275-44-8), a mycotoxin produced by several Fusarium species, has been shown to be a potential risk factor for animal and human health. This study was undertaken to investigate the potential oxidative damage of butenolide to biomembranes in vitro using the erythrocyte membrane model. Following exposure of isolated rat erythrocyte membranes to butenolide, the extent of oxidative damage was assessed by measuring lipid peroxidation, -SH groups content, Ca2+/Mg2+-ATPase and Na+/K+-ATPase activities, and conformational changes in membrane proteins. It was observed that butenolide resulted in a significant lipid peroxidation, revealed by a concentration-dependent increase in the level of thiobarbituric acid reactive substances (TBARS). Similarly, this toxin induced a concentration-dependent decrease in the content of membrane total -SH groups, as well as free -SH groups. Membrane-bound enzymes were also impaired by the toxin, demonstrated by the marked inhibition of the activities of Na+/K+-ATPase and Ca2+/Mg2+-ATPase. Conformational changes in membrane proteins were determined using electron paramagnetic resonance (EPR) spin labeling. Butenolide caused an increase in the ratio of weakly to strongly immobilized components (W/S ratio) in a manner of concentration-dependent, indicating conformational changes in membrane proteins occurred. In conclusion, these findings indicate that butenolide is capable of inducing significant oxidative damage to membrane lipids and proteins.

Depletion of intracellular glutathione mediates butenolide-induced cytotoxicity in HepG2 cells.

Butenolide, 4-acetamido-4-hydroxy-2-butenoic acid gamma-lactone is one of the mycotoxins produced by Fusarium species which are often found on cereal grains and animal feeds throughout the world. It has been implicated as the etiology of some diseases both in animals and in humans. Though butenolide represents a potential threat to animal and human heath, there are few studies on its toxicity so far, especially on the toxic mechanisms. In this study, we investigated the cytotoxicity of butenolide on HepG2 cells and its possible mechanism from the viewpoint of oxidative stress. Butenolide reduced cell viability in a concentration- and time-dependent manner. A rapid depletion of intracellular glutathione (GSH) was observed after exposure cells to butenolide, concomitantly an increase in intracellular reactive oxygen species (ROS) production prior to cell death, indicating that oxidative stress was involved in butenolide cytotoxicity. To elucidate the role of GSH in the cytotoxicity of butenolide, intracellular GSH content was modulated before exposure to butenolide. l-buthionine-[S,R]-sulfoximine (BSO), a well-known inhibitor of GSH synthesis, aggravated butenolide-induced GSH depletion, ROS production and the loss in cell viability; in contrast, GSH depletion and ROS production was strongly inhibited, and the loss in cell viability was completely abrogated by thiol-containing compounds GSH, N-acetylcysteine (NAC) and dithiothreitol (DTT). Furthermore, a ROS scavenger catalase obviously abated ROS production and cytotoxicity induced by butenolide. Together, these results clearly demonstrate that oxidative stress plays an important role in butenolide cytotoxicity, and intracellular GSH depletion may be an original trigger of the onset of butenolide cytotoxicity.