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BackgroundA large amount of iron deposition in the brain can cause neuronal damage by inducing oxidative stress, neuroinflammation, and abnormal mitochondrial function. In addition, iron deposition is also reported to be closely related to the pathogenesis of Alzheimer's disease (AD). The neurofibrillary tangles aggregated by tau hyperphosphorylation are one of the important pathological features of AD. ObjectiveTo investigate potential effect of exogenous trivalent iron ions on neuronal activity in human neuroblastoma (SH-SY5Y) cells and tau hyperphosphorylation and aggregation. MethodsSH-SY5Y cells were treated with ferric chloride (FeCl3) at four concentrations (10, 100, 200, and 400 mg·L−1). Cell survival rate was then detected by CCK8 assay. Intracellular iron content was determined prussian blue (Perl's) by iron staining after 24 h exposure to FeCl3 at 10 or 200 mg·L−1. Transfection of tau-P301L plasmid was conducted to construct an AD-like cell model for tau overexpression. The differences in the expression of the phosphorylated tau (p-tau) protein in SH-SY5Y cells and SH-SY5Y cells with tau overexpression were detected by Western blotting after 24 h exposure to FeCl3 at 10 and 200 mg·L−1. After dilution with phosphate buffered saline (PBS), FeCl3, human tauR3, and FeCl3 + tauR3 were incubated at 37℃, and the fluorescence intensity reflecting tau aggregation level was measured by thioflavin T(ThT) method at 12, 24, 36, 48, 60, 72, 84, and 96 h, respectively. Meanwhile, after 96 h coincubation of FeCl3 and tauR3, the fibers formed by tau aggregation were observed under a transmission electron microscope (TEM). ResultsAfter 24 h of FeCl3 exposure, the cell survival rate of SH-SY5Y cells among all groups was statistically different (F=8.63, P |
