Objective To observe the neurocyte damage in rat brain slices induced by different levels of manganese, and to estimate the effect of inducible nitric monoxide synthase (iNOS) on the neurocyte damage caused by manganese.
Methods The rat brain slices were prepared and cultured for 15 days with 50% dulbecco's modified Eagle's medium, 25% Hank's balanced salt solution, 24% heat inactivated horse serum, 1% penicillin and streptomycin. Then 0, 25, 100, and 400 μmol/L manganese chloride were added to the rat brain slices culture medium at the 15th day. After manganese exposure for 24 hours, the lactate dehydrogenase (LDH) activity, neurocyte apoptosis, nitric oxide (NO) content, iNOS activity, iNOS mRNA expression, and iNOS protein expression level were detected.
Results Explicit neurocyte damage in the brain slice was observed after 24-hour exposure to manganese at varied doses. With the increase of manganese concentration, the LDH activity was increased to 1.71 and 2.76 times of the control group in the 100 and 400 μmol/L groups respectively. The apoptosis rate and NO content were also increased:The apoptosis rates and NO contents in the groups treated with 25, 100 and 400 μmol/L manganese were 3.31, 4.50, 6.97 and 1.98, 2.79, 4.02 times of the control group, respectively. The iNOS activities in the groups treated with 100 and 400 μmol/L manganese were increased to 2.12 and 2.64 times of the control group respectively. The iNOS mRNA and protein expression levels were also increased:The iNOS mRNA expression levels in the groups treated with 25, 100, and 400μmol/L manganese were 1.27, 1.43, and 1.86 times of the control group; the protein expression levels in the groups treated with 100 and 400 μmol/L manganese were 4.17 and 5.50 times of the control group respectively.
Conclusion Manganese could result in increases of NO content, as well as iNOS mRNA and protein expression levels in rat brain slices, followed by increase of neurocyte apoptosis rate.
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