Objective: To investigate the effect of manganese chloride (MnCl₂) or 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP) on the neurobehavioral and histopathology in C57BL/6 mice and provide evidence for the diagnosis, treatment and prevention of manganism. Methods: Adult male C57BL/6 mice were treated with MnCl₂ and MPTP respectively by intraperitoneal injection at the doses of 5, 10, 20mg Mn/kg and 30mg MPTP/kg. Controls were injected equivalent normal saline. All animals were administrated 5 times a week for 4 consecutive weeks and sacrificed after behavior tests on the fifth week. Balance ability, anxiety and depression level and cognitive function were tested respectively by vertical pole test, open field locomotion test and Morris swim task. The neuron pathological changes of striatum and substantia nigra were examined through HE-staining pathological section by using optical microscope. Results: Compared with the control group, the high dose of MnCl₂ reduced body weight obviously (P<0.01) . The results of vertical pole test showed that MnCl₂ and MPTP lengthened the pole-climbing time and turnaround time. Open field locomotion test showed that movement distance, stand-up time and central field time were decreased after the exposure of MnCl₂ or MPTP. In the Morris swim task, the escape latency time increased and the target quadrant activity time decreased significantly after the injection of MPTP as well as high-dose MnCl₂, comparing with controls (P<0.05) . Moreover, the escape latency time of high dose MnCl₂ prolonged prominently comparing with MPTP grou (P<0.05) . The results of histopathology showed that acidophilic changes elevated in MnCl₂ and MPTP group, comparing with controls. Furthermore, in striatum the oxyphil cells number increased in MnCl₂ high-dose group comparing with MPTP group (P<0.01) . On the contrary, there were more oxyphil cells in MPTP group comparing with MnCl₂ groups in substantia nigra (P<0.01) . Conclusion Both manganese and MPTP can induce the impairment of dopaminergic neural system, but the symptons and injured location of manganism are inconsistent with PD models induced by MPTP.

Objective: To investigate the effect of manganese chloride (MnCl₂) or 1-methyl-4-phenylpyridinium (MPP ⁺) on oxidative stress and autophagy in human neuroblastomaSK-N-SH cells and the mechanism of the neurotoxicity of manganese. Methods: SK-N-SH cells were treated with MnCl₂ or MPP⁺ at doses of 0.062 5, 0.125, 0.25, 0.5, 1.0, and 2.0 mmol/L for 24 hours, and MTT assay was used to measure cell viability. The cells weretreated with MnCl₂ or MPP⁺ at doses of 0.125, 0.25, and 0.5 mmol/L for 24 hours, and flow cytometry was used to measure the content of reactive oxygen species (ROS) in cells, a laser scanning confocal microscope was used to observe autophagosome in cells, and Western blot was used to measure the expression of autophagy-related proteins P62 and LC3-II/LC3-I. Results: Compared with the control group, the 0.0625-2.0 mmol/L MnCl₂ and 0.125-2.0 mmol/L MPP ⁺ treatment groups had significant reductions in the viability of SK-N-SH cells, and the 0.25-2.0 mmol/L MnCl₂ treatment groups had significantly lower viability than the groups treated with the same doses of MPP⁺ (all P<0.05) . Compared with the control group, the 0.125-0.25 mmol/L MnCl₂ and 0.125-0.5 mmol/L MPP⁺ treatment groups had significant increases in the content of ROS, and the 0.25-0.5 mmol/L MPP⁺ treatment groups had significantly higher content of ROS than the groups treated with the same doses of MnCl₂ (all P<0.05) . Compared with the control group, the 0.25-0.5 mmol/L MnCl₂ andMPP⁺ treatment groups had significant increases in autophagy-related proteins LC3-II/LC3-I and significant reductions in P62 expression; the 0.125-0.5 mmol/L MPP⁺ treatment groups had significantly higher LC3-II/LC3-I than the groups treated with the same doses of MnCl₂, and the 0.125 and 0.25 mmol/L MPP ⁺ treatment groups had significantly lower P62 expression than the groups treated with the same doses of MnCl₂ (all P<0.05) . Conclusion Both MnCl₂ and MPP⁺ can induce oxidative stress and autophagy in SK-N-SH cells, and MPP⁺ has a significantly greater inductive effect on autophagy of SK-N-SH cells than MnCl₂.

Objective: To investigate the role of lysosomes in manganese-induced toxicity in human neuroblastoma SK-N-SH cells. Methods: SK-N-SH cells were treated with MnCl₂ at doses of 0.062 5, 0.125, 0.25, 0.5, 1.0, 2.0 and 4.0 mmol/L for 24 h, and the cell viability was detected by MTT assay. Cells were treated with MnCl₂ at doses of 0.125, 0.25, 0.5 and 1.0mmol/L for 24 h, and lysosomes labeled with lysotracker red were observed by laser confocal microscopy, the expression levels of LAMP1 and CTSD were detected by western blot, and CTSD activity was detected by Cathepsin D Activity Fluorometric Assay Kit. Results: Compared with the control group, the survival rates of SK-N-SH cells were decreased significantly in the 0.5-4.0 mmol/L MnCl₂ treatment groups (P<0.01) , the relative fluorescence intensities of 0.5 and 1.0 mmol/L MnCl₂ treatment groups were increased (P<0.01) . Compared with the control group, the 0.125-0.5 mmol/L MnCl₂ treatment groups had significant increase in the the expression of LAMP1 (P<0.01) . Compared with the control group, the expression of m-CTSD was significantly increased at the does of 0.125-0.25 mmol/L MnCl₂, while it was decreased at the does of 1.0 mmol/L (P<0.01) . Otherwise, it wasn’t observed significant difference of the activity of CTSD between different MnCl₂ treatment groups. Conclusion MnCl₂ could cause cytotoxicity in SK-N-SH cells. Lysosomes may play a normal function at low doses of manganese, but they may be damaged at high doses of manganese. As an organelle that can degradate substrates in autophagy, lysosomes participate in the neurotoxic mechanism of manganese.