Hydrogen peroxide and methyl mercury are primary stimuli of eicosanoid release in human platelets

Possible role of serotoninergic system in the neurobehavioral impairment induced by acute methylmercury exposure in zebrafish (Danio rerio)

Adult zebrafish were treated acutely with methylmercury (1.0 or 5.0 μg g(-1), i.p.) and, 24h after treatment, were tested in two behavioral models of anxiety, the novel tank and the light/dark preference tests. At the smaller dose, methylmercury produced a marked anxiogenic profile in both tests, while the greater dose produced hyperlocomotion in the novel tank test. These effects were accompanied by a decrease in extracellular levels of serotonin, and an increase in extracellular levels of tryptamine-4,5-dione, a partially oxidized metabolite of serotonin. A marked increase in the formation of malondialdehyde, a marker of oxidative stress, accompanied these parameters. It is suggested that methylmercury-induced oxidative stress produced mitochondrial dysfunction and originated tryptamine-4,5-dione, which could have further inhibited tryptophan hydroxylase. These results underscore the importance of assessing acute, low-level neurobehavioral effects of methylmercury.

Effect of cytochrome P-450 inhibitors econazole, bifonazole and clotrimazole on prostanoid formation

1. The present study was carried out to clarify the effect of the imidazole antimycotics econazole, bifonazole and clotrimazole on prostanoid biosynthesis. Osteoblast-like MC3T3-E1 cells stimulated by endothelin-1, melittin, ionomycin or arachidonic acid showed diminished prostaglandin E(2) (PGE(2)) production upon pretreatment with econazole. Following pretreatment with bifonazole, stimulation with ionomycin or arachidonic acid also resulted in decreased PGE(2) formation. Clotrimazole inhibited ionomycin but not arachidonic acid stimulated PGE(2) synthesis in MC3T3-E1 cells. 2. The results observed in osteoblast-like UMR-106 cells pretreated with econazole, bifonazole or clotrimazole and stimulated by arachidonic acid were similar with the exception of clotrimazole which was a more effective inhibitor of PGE(2) biosynthesis than in MC3T3-E1 cells. 3. Upon treatment with arachidonic acid thromboxane B(2) (TXB(2)) production in human platelets was abolished completely at concentrations of the three imidazole antimycotics higher than 5 microM (IC(50)<1 microM). 4. These data were confirmed by a direct assay using purified ram seminal vesicle prostaglandin H(2) synthase-1 (PGHS-1), which clearly showed inhibitory properties of econazole (IC(50) 4.7+/-2.3 microM), bifonazole (IC(50) 9.4+/-0.8 microM) and clotrimazole (IC(50) 4.4+/-0.6 microM). 5. Summarizing, these results indicate an inhibitory effect of econazole, bifonazole and clotrimazole on PGHS-1, varying in its potency dependent on the cell system used. In addition TXB(2) formation is affected at doses even lower than those needed to suppress PGE(2) biosynthesis.