Glial toxicity of CdCl2 in zebrafish brain

Cadmium (cd) is known as a potent toxic metal and a significant aquatic and terrestrial environmental pollutant. In this study was verified the ability of cadmium chloride (CdCl2) to induce cytotoxic effects on the brain of zebrafish through the detection of the expression of glial fibrillary acidic protein (GFAP), astroglial marker. It was also carried out a staining method with methasol fast blue for the evaluation of the myelin integrity. Specimens of adult zebrafish were exposed for 16 days to 1.0 mg/L of CdCl2, a concentration of cadmium observed at some sites affected by industrial pollution, and the brains were analyzed after 2,7 and 16 days of exposure. By western blotting experiments a decrease in the levels of GFAP was observed after 2 days in the order of 40% compared with the control. This decrease arrived to be 50% after 16 days. A reduction of GFAP positive fibers was revealed by ABC technique in the brain of the fishes treated compared to that of the controls, in all three times tested, with a progressive trend. After 2 days of treatment was observed a reduction in the level of positivity at ventricular and pial surface. The affected areas were the midbrain and the medulla oblongata. A reduced immunoreactivity was also found after 7 days in the cerebellum, medulla oblongata and ependima, while after 16 days in addition to the cerebellum and the medulla oblongata a low expression of the protein was observed also in the telencephalon. The methasol fast blue staining showed a reduction of affinity to the dye after 7 and 16 days of exposure in neurons axons of medulla oblongata, optic tectum and cerebellum. These data confirm the toxic action performed by cadmium in the brain, highlighting the effects on macroglial cells, key components for the function of SNC. The toxic role of cadmium on myelin integrity was already showed as well as the impairment of this in GFAP null models, so the deconstruction of astroglial processes could be the link between cadmium and myelin diseases