Alteration of striatal tetrahydrobiopterin in iron-induced unilateral model of Parkinson's disease.

It has been suggested that transition metal ions such as iron can produce an oxidative injuries to nigrostriatal dopaminergic neurons, like Parkinson's disease (PD) and subsequent compensative increase of tetrahydrobiopterin (BH4) during the disease progression induces the aggravation of dopaminergic neurodegeneration in striatum. It had been established that the direct administration of BH4 into neuron would induce the neuronal toxicity in vitro. To elucidate a role of BH4 in pathogenesis in the PD in vivo, we assessed the changes of dopamine (DA) and BH4 at striatum in unilateral intranigral iron infused PD rat model. The ipsistriatal DA and BH4 levels were significantly increased at 0.5 to 1 d and were continually depleting during 2 to 7 d after intranigral iron infusion. The turnover rate of BH4 was higher than that of DA in early phase. However, the expression level of GTP-cyclohydrolase I mRNA in striatum was steadily increased after iron administration. These results suggest that the accumulation of intranigral iron leads to generation of oxidative stress which damage to dopaminergic neurons and causes increased release of BH4 in the dopaminergic neuron. The degenerating dopaminergic neurons decrease the synthesis and release of both BH4 and DA in vivo that are relevance to the progression of PD. Based on these data, we propose that the increase of BH4 can deteriorate the disease progression in early phase of PD, and the inhibition of BH4 increase could be a strategy for PD treatment.

Effect of 835 MHz radiofrequency radiation exposure on calcium binding proteins in the hippocampus of the mouse brain.

Worldwide expansion of mobile phones and electromagnetic field (EMF) exposure has raised question of their possible biological effects on the brain and nervous system. Radiofrequency (RF) radiation might alter intracellular signaling pathways through changes in calcium (Ca(2+)) permeability across cell membranes. Changes in the expression of calcium binding proteins (CaBP) like calbindin D28-k (CB) and calretinin (CR) could indicate impaired Ca(2+)homeostasis due to EMF exposure. CB and CR expression were measured with immunohistochemistry in the hippocampus of mice after EMF exposure at 835 MHz for different exposure times and absorption rates, 1 h/day for 5 days at a specific absorption rate (SAR)=1.6 W/kg, 1 h/day for 5 days at SAR=4.0 W/kg, 5 h/day for 1 day at SAR=1.6 W/kg, 5 h/day for 1 day at SAR=4.0 W/kg, daily exposure for 1 month at SAR=1.6 W/kg. Body weights did not change significantly. CB immunoreactivity (IR) displayed moderate staining of cells in the cornu ammonis (CA) areas and prominently stained granule cells. CR IR revealed prominently stained pyramidal cells with dendrites running perpendicularly in the CA area. Exposure for 1 month produced almost complete loss of pyramidal cells in the CA1 area. CaBP differences could cause changes in cellular Ca(2+)levels, which could have deleterious effect on normal hippocampal functions concerned with neuronal connectivity and integration.