Involvement of oxidative stress in subacute toxicity induced by fumonisin B1 in broiler chicks.

Fumonisin B1 (FB1) is a mycotoxin produced by Fusarium spp. It has been reported to be a potential cause of liver cancer in rats and esophageal cancer in humans. The underlying mechanisms of FB1 toxicity are thought to be related to the inhibition of ceramide synthase, causing an accumulation of sphingosine (SO) and sphinganine (SA), which in turn may cause tissue functional impairment and the development of oxidative stress. Therefore, in this study, we investigate the effects of an FB1-contaminated diet on markers of oxidative stress in chick liver. A total of 24 male broiler chicks (Cobb 500) were fed a standard control diet or a diet contaminated with FB1 (100mg/kg) for 21 days, starting on postnatal day one. The feed and animals were weighed on days 0, 7, 14 and 21 to estimate the feed conversion ratio, and at 21 days, the liver weight and liver relative weight were determined. At the end of the experiment, samples of blood and liver were collected. The blood was used to quantify the SA/SO ratio, and the liver was used to determine the activity of antioxidant enzymes superoxide dismutase (SOD), catalase (CAT) and glutathione-S-transferase (GST); ascorbic acid levels (VitC), non-protein thiol (NPSH) levels and TBARS content were also determined. The FB1 diet increased the liver weight, liver relative weight, feed conversion and SA/SO ratio. Furthermore, hepatic TBARS levels, Vit C content and CAT activity were also increased. Conversely, the activities of SOD, GST and NPSH levels, in the liver were not altered by the mycotoxin-contaminated diet. In summary, we showed that subacute exposure of broiler chicks to FB1 induced liver oxidative stress concomitantly with SA/SO accumulation.

Cysteinyl leukotriene receptor (CysLT) antagonists decrease pentylenetetrazol-induced seizures and blood-brain barrier dysfunction.

Current evidence suggests that inflammation plays a role in the pathophysiology of seizures. In line with this view, selected pro-inflammatory arachidonic acid derivatives have been reported to facilitate seizures. Kainate-induced seizures are accompanied by leukotriene formation, and are reduced by inhibitors of LOX/COX pathway. Moreover, LTD4 receptor blockade and LTD4 synthesis inhibition suppress pentylenetetrazol (PTZ)-induced kindling and pilocarpine-induced recurrent seizures. Although there is convincing evidence supporting that blood-brain-barrier (BBB) dysfunction facilitates seizures, no study has investigated whether the anticonvulsant effect of montelukast is associated with its ability to maintain BBB integrity. In this study we investigated whether montelukast and other CysLT receptor antagonists decrease PTZ-induced seizures, as well as whether these antagonists preserve BBB during PTZ-induced seizures. Adult male albino Swiss mice were stereotaxically implanted with a cannula into the right lateral ventricle, and two electrodes were placed over the parietal cortex along with a ground lead positioned over the nasal sinus for electroencephalography (EEG) recording. The effects of montelukast (0.03 or 0.3 µmol/1 µL, i.c.v.), pranlukast (1 or 3 µmol/1 µL, i.c.v.), Bay u-9773 (0.3, 3 or 30 nmol/1 µL, i.c.v.), in the presence or absence of the agonist LTD4 (0.2, 2, 6 or 20 pmol/1 µL, i.c.v.), on PTZ (1.8 µmol/2 µL)-induced seizures and BBB permeability disruption were determined. The animals were injected with the antagonists, agonist or vehicle 30 min before PTZ, and monitored for additional 30 min for the appearance of seizures by electrographic and behavioral methods. BBB permeability was assessed by sodium fluorescein method and by confocal microscopy for CD45 and IgG immunoreactivity. Bay-u9973 (3 and 30 nmol), montelukast (0.03 and 0.3 µmol) and pranlukast (1 and 3 µmol), increased the latency to generalized seizures and decreased the mean amplitude of EEG recordings during seizures. LTD4 (0.2 and 2 pmol) reverted the anticonvulsant effect of montelukast (0.3 µmol). Montelukast (0.03 and 0.3 µmol) prevented PTZ-induced BBB disruption, an effect that was reversed by LTD4 at the dose of 6 pmol, but not at the doses 0.2 and 2 pmol. Moreover, the doses of LTD4 (0.2 and 2 pmol) that reverted the effect of montelukast on seizures did not alter montelukast-induced protection of BBB, dissociating BBB protection and anticonvulsant activity. Confocal microscopy analysis revealed that 1. PTZ increased the number of CD45+ and double-immunofluorescence staining for CD45 and IgG cells in the cerebral cortex, indicating BBB leakage with leukocyte infiltration; 2. while LTD4 (6 pmol) potentiated, montelukast decreased the effect of PTZ on leukocyte migration and BBB, assessed by double-immunofluorescence staining for CD45 and IgG cells in the cannulated hemisphere. Our data do not allow us ruling out that mechanisms unrelated and related to BBB protection may co-exist, resulting in decreased seizure susceptibility by montelukast. Notwithstanding, they suggest that CysLT1 receptors may be a suitable target for anticonvulsant development.