Melatonin decreases the oxidative stress produced by 2,4-dichlorophenoxyacetic acid in rat cerebellar granule cells.

2,4-Dichlorophenoxyacetic acid (2,4-D) is one of the most widely used herbicides due to its relatively moderate toxicity and to its biodegradability in the soil. In toxic concentrations, 2,4-D displays strong neurotoxicity, partly due to generation of free radicals. Since melatonin has remarkable antioxidant properties, the objective of this study was to assess to what extent it was effective in preventing the 2,4-D effect on redox balance of rat cerebellar granule cells (CGC) in vitro. Cellular viability, generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS), reduced glutathione (GSH) levels, and the activities of the antioxidant enzymes Cu/Zn-superoxide dismutase (Cu/Zn-SOD), Mn-SOD, selenium-glutathione peroxidase (Se-GPx) and catalase (CAT) were measured in CGC exposed to 2,4-D and/or melatonin for 48 h. In CGC cultures exposed to 2,4-D, cell viability, GSH levels and CAT activity decreased significantly whereas ROS generation and Se-GPx activities were augmented. Except for Se-GPx activity, all these changes were counteracted by the concomitant addition of 0.1 or 0.5 mM melatonin. In addition, incubation of CGC with melatonin alone resulted in augmentation of cell viability, GSH levels and Se-GPx activity. RNS generation and SOD activity remained unaffected by either treatment. Since melatonin was able to counteract most of redox changes produced by 2,4-D in CGC in culture, the experimental evidence reported further support the efficacy of melatonin to act as a neuroprotector.

Dopamine-beta-hydroxylase immunohistochemical study in the locus coeruleus of neonate rats exposed to 2,4-dichlorophenoxyacetic acid through mother's milk.

Dopamine-beta-hydroxylase (DbetaH), the enzyme that synthesizes noradrenaline from dopamine, was studied in the locus coeruleus (LC) of neonate rats exposed to 2,4-dichlorophenoxyacetic acid (2,4-D) through lactation for 14 days (from PND 9 to 22). Pups (22 days old) were anesthetized and fixed by transcardiac perfusion. Control and treated serial sections from brain stem--which correspond with the LC according to the Paxinos and Watson atlas--were simultaneously processed by an immunohistochemistry method for the DbetaH detection. Using an image analysis system, the immunostaining optical density (OD) was measured as an estimation of the enzyme content, and an OD significant decrease in the LC of 2,4-D-exposed animals was observed. As tyrosine hydroxylase levels in the LC are regulated by serotonin and in a previous study we demonstrated that this neurotransmitter was increased in 2,4-D-exposed pups, an indirect effect through serotonergic inhibition could be involved in the decreased DbetaH synthesis in the LC of these pups.