To investigate the changes of extracellular regulated protein kinases (Erk)1/2, phospho-Erk1/2, matrix metalloproteinases (MMP)-2 and MMP-9 in rats with experimental chronic fluorosis and the role of chondroitin sulfate in treatment of rat with experimental chronic fluorosis.

Using a group design and cell culture methods, the SH-SY5Y cells were divided into control group (culture medium with 0.0 mmol/L fluoride ion), fluoride group (fluoride ion: 4.0 mmol/L) and chondroitin sulfate group (fluoride ion: 4.0 mmol/L, chondroitin sulfate: 0.4 g/L). The ultrastructural changes of the SH-SY5Y cells were observed through electron microscope after 24 h treatment. The SH-SY5Y cells were cultured for 72 h, the number of cells survived in three groups were detected after stained by trypan blue. Fifteen clean grade SD rats with body weight of 100-120 g were divided into control group (tap water: fluorine content less than 0.5 mg/L), fluoride group (fluoride ion: 10.0 mg/L) and chondroitin sulfate group (fluoride ion: 10.0 mg/L, the rats were performed intraperitoneal injection with 0.66 mg/kg chondroitin sulfate for 5 days after intaking fluoride for 90 days) on the basis of random number table. Five rats were in each group, and the experiment was carried out for 95 days. The capability of learning and memory of rats were tested by Morris water maze test; the expression of phospho-Erk1/2, Erk1/2, MMP-2 and MMP-9 protein in brain tissue was detected by Western blotting; the expression of phospho-Erk1/2, MMP-2 and MMP-9 in hippocampus CA2 area of brain was detected by immunohistochemistry.

More vesicles and swelling of mitochondria or endoplasmic reticulum were observed in SH-SY5Y cell treated with fluoride through electron microscope, but relatively less in chondroitin sulfate group. Survival rate and amount of SH-SY5Y treated with chondroitin sulfate [(92 ± 23)% and (7.83 ± 1.38) × 10⁶/ml] were significantly higher than that of fluoride group [(55 ± 2)%, (2.19 ± 1.26) × 10⁶/ml, P < 0.05]. Animal experiment results showed that most rats in control group and chondroitin sulfate group used spatial direct search strategy, and the amount of this search strategy (2.20 ± 1.09, 3.40 ± 1.34) was more than that in fluoride group (0.40 ± 0.54, P < 0.05). The expression of phospho-Erk1/2 in brain tissue of rats in fluoride group (3.26 ± 0.88) was significantly higher than that in control group (1.53 ± 0.28) and chondroitin sulfate group (2.36 ± 0.87, P < 0.05) . Immunohistochemistry results showed that average gray value of phospho-Erk1/2 in chondroitin sulfate group (220.20 ± 3.09) was significantly higher than that of the control group and the fluoride group (100.00 ± 0.00, 130.98 ± 1.27, P < 0.05). The average gray value of MMP-2 in the fluoride group (294.52 ± 5.18) was significantly higher than that in control group and chondroitin sulfate group (100.00 ± 0.00, 117.95 ± 1.55, P < 0.05). The average gray value of MMP-9 protein of the fluoride group (993.64 ± 3.66) and the chondroitin sulfate group (1 167.30 ± 2.39) was significantly higher than that of control group (100.00 ± 0.00, P < 0.05).

Erk1/2 pathway possibly maintains the stability of cell survival by regulating the expression of MMP-2 and MMP-9. Chondroitin sulfate can protective nerve cells and reduce the nervous damage caused by fluorosis to some certain extent.

Fluorine; Chondroitin sulfate; Erk1/2; MMP-2; MMP-9