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Fig. 6 | Particle and Fibre Toxicology

Fig. 6

From: Silica nanoparticles induce neurodegeneration-like changes in behavior, neuropathology, and affect synapse through MAPK activation

Fig. 6

Effects of NP on synapse. After the mice were intranasally instilled with either vehicle (sterile PBS, control group) or NP in PBS (8 mg/kg, NP group) once per day for 81 days, the mice were sacrificed and the frontal cortex and hippocampus of the brains were harvested, followed by isolation of the synaptosome fraction. a An FM dye assay was performed to measure endocytosis and exocytosis in the synaptosome fraction from the frontal cortex and the hippocampus. Endocytosis was determined by the change in fluorescence intensity in the first step (Fendo), while exocytosis was calculated using the change in fluorescence intensity in the second step with the equation (Fendo - Fexo)/Fendo. Data were normalized to the control group at each step and analyzed with unpaired Student’s t-tests (n = 8). b The effect of JNK and ERK inhibitors on endocytosis and exocytosis were evaluated using an FM dye assay. Primary neuronal cultures were treated with pharmacological inhibitors against JNK (JNKi) or ERK (U0126) for 1 h before NP exposure (48 h). Endocytosis and exocytosis levels were then determined/calculated as described in Methods section. Data were normalized to the control group at each step and analyzed by one-way ANOVA followed by Tukey’s Post hoc test (n = 4). Scale bar: 20 μm. c Representative images showing synapsin I and synaptophysin protein expression in 14-day primary cortical neuron cultures exposed to NP for 48 h (n = 3 independent batches of primary culture of cortical neurons). A total of 5 cells were imaged on each cover slip. Scale bar: 20 μm. d Western blot analysis of synapsin I and synaptophysin protein expression in the frontal cortex and hippocampus synaptosome fractions. Band intensity was normalized to that of α-tubulin and analyzed using unpaired Student’s t-tests (n=8). * p < 0.05, ** p < 0.01, *** p < 0.001, **** p < 0.0001, compared to the control; ### p < 0.001, compared to the NP group

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