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Background A 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. Objective To investigate potential effect of exogenous trivalent iron ions on neuronal activity in human neuroblastoma (SH-SY5Y) cells and tau hyperphosphorylation and aggregation. Methods SH-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). Results After 24 h of FeCl3 exposure, the cell survival rate of SH-SY5Y cells among all groups was statistically different (F=8.63, P<0.01). The cell survival rates in the 200 and 400 mg·L−1 groups were 80.1% and 68.7% of the control group, respectively (P<0.05). Compared with the control group, the nuclei of the 200 mg·L−1 FeCl3 group were mainly yellowish-brown after iron staining and the positive cell rate was up-regulated by 12.9% (P<0.01). After 24 h of FeCl3 exposure , the p-tau (Ser396) protein expression was statistically different among all groups (F=11.6, P<0.01). Compared with the control group, the p-tau protein expression level of SH-SY5Y cells in the 200 mg·L−1 group was up-regulated by 72.7% (P<0.01). After FeCl3-treated SH-SY5Y cells with tau overexpression for 24 h, the p-tau (Ser396) protein expression was statistically different among all groups (F=27.8, P<0.01). Compared with the tau group, the p-tau (Ser396) protein expression level of SH-SY5Y cells in the tau + 200 mg·L−1 group was up-regulated by 44.6% (P<0.05). Compared with the tauR3 group, the fluorescence intensities in the 84 and 96 h tauR3 + FeCl3 groups were up-regulated by 49.9% and 53.7% (P<0.01) respectively. After 96 h of coincubation, compared with the tauR3 group, FeCl3 + tauR3 aggravated tau aggregation and formed fiber deposition under TEM. Conclusion Exogenous trivalent iron ions may inhibit SH-SY5Y cell viability, promote the phosphorylation of tau in SH-SY5Y cells transfected with tau-P301L plasmid, and aggravate tauR3 aggregation and fiber production.
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Alzheimer's disease （AD） is a neurodegenerative disease. With the acceleration of aging process， the number of AD patients increases year by year. This threatens the health and even life of patients， and causes heavy economic burden and mental pressure to patients， families and society. In traditional Chinese medicine （TCM）， AD belongs to the category of dementia， and tonifying kidney is the main treatment. Based on the basic theory of TCM and combined with clinical manifestations of AD， AD is closely correlated with liver and spleen. Therefore， "simultaneous regulation of three Yin" of liver， spleen and kidney will be an important way for the prevention and treatment of AD. Hei Xiaoyaosan， a representative prescription of "simultaneous regulation of three Yin" of liver， spleen and kidney， has theoretical， experimental and clinical basis in preventing and treating AD. Modern studies have shown that neurofibrillary tangle formed by tau hyperphosphorylation is a main pathological feature of AD， and trimethylamine oxide （TMAO） is closely related to tau hyperphosphorylation. Therefore， regulating TMAO metabolism to inhibit tau hyperphosphorylation is a new target for the prevention and treatment of AD. On the basis of the above theory and previous studies， this paper put forward the hypothesis that Hei Xiaoyaosan regulates the trimethylamine（TMA）/heparin monooxygenase 3（FMO3）/TMAO metabolic pathway of intestinal flora through "simultaneous regulation of three Yin" of liver， spleen and kidney， and then inhibits tau hyperphosphorylation in brain hippocampus， thereby protecting nerve cells， improving learning and memory， and preventing AD. This paper explored the role and mechanism of Hei Xiaoyaosan in the prevention and treatment of AD from the perspective of inhibiting tau hyperphosphorylation by regulating the TMA/FMO3/TMAO metabolic pathway of intestinal flora， which provided new ideas and strategies for in-depth study of Hei Xiaoyaosan in the prevention and treatment of AD.
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Objective To study the role and mechanism of A2AR activation in tau hyperphosphorylation after brain injury.Methods SD rats were cultured with no specific pathogen level.SH-SY5Y was cultured.The rats were treated with CGS21680 solution and DMSO and SH-SY5Y respectively.The CGS21680 solution and sb216763, H-89, or Only add ZM241385, the control group plus DMSO, compared with each group tau hyperphosphorylation.Results The phosphorylation level of tau protein in SH-SY5Y cells was significantly higher than that in the control group (P<0.05).The phosphorylation level of tau protein in the primary hippocampal neurons of rats was significantly higher than that of the control group (P<0.05).The levels of tau protein phosphorylation in group 2 and group 3 were significantly higher than those in control group (P<0.05).The expression of tau in group 4 and group 5 was statistically significant (P<0.05)There was no significant difference in phosphorylation level between the two groups.Conclusion A2AR activation can activate kinase A and GSK-3β after brain injury, leading to tau hyperphosphorylation.
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Objective To investigate the effect of melatonin(MT)on tau hyperphosphorylation in hippocampus of mice with exposure to lead(Pb)at early development stage and its possible mechanism.Methods Healthy C57BL/6 mice were randomly divided into four groups:control group(received normal water),lead exposure group(exposed to 0.2% Pb acetate from postnatal day 1(PND 1)to PND 21 through drinking water),MT group(received 50 mg/mL MT through drinking water since 12-month-old for 3 months)and MT combined with lead exposure group(exposed to 0.2% Pb acetate from PND 1 to PND 21 and then given 50 mg/mL MT since 12-month-old for 3 months through drinking water).The Pb levels in the blood and hippocampus were determined by graphite furnace atomic absorption spectrometry.Morris water maze was used to detect the spatial learning and memory.The phosphorylation level of tau and the protein level of GRP78 and CHOP in hippocampus were detected by Western blotting.Results Compared with the control group,the Pb levels in the blood and hippocampus were significantly increased in lead exposure group(P<0.05),while MT treatment did not affect the Pb levels both in the blood and hippocampus.In the lead exposure group,the phosphorylation level of tau in the hippocampus was significantly increased compared with control group(P<0.01),and after treatment with MT,the phosphorylation level of tau in MT combined with lead exposure group was significantly decreased compared with the lead exposure group(P<0.05).Furthermore,the expression of GRP78 and CHOP in the hippocampus was significantly higher in lead exposure group than in control group(P<0.05),and after treatment with MT,the expression levels of GRP78 and CHOP were lower than those of the control group.Conclusion MT can ameliorate the phosphorylation level of tau in the hippocampus and defects of learning and memory in C57BL/6 mice with exposure to lead at early development stage,and this may be related with the modulation of endoplasmic reticulum stress.
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OBJECTIVE: To investigate the regulating effects and its possible mechanism of safflower yellow (SY) on tau protein hyperphosphorylation in SH-SY 5Y cell induced by okadaic acid (OA). METHODS: Cell viability was measured by MTT colorimetric method. The cell apoptosis was determined with Hoechst 33342 after SH-SY 5Y cell were treated with SY. To determined the phos-phorylated tau protein of p-tau (T205), p-tau(S199) sites, and total GSK-3β, PP2A in SH-SY 5Y cell were determined using Western blotting. RESULTS: SY significantly increased survival rates of SH-SY5Y cell damaged by OA. Hoechst 33342 showed that SY decreased the apoptosis of SH-SY5Y cells. Western blotting analysis showed that tau protein content was increased compared to control group at p-tau (T205), p-tau (S199) sites. However, SY treatment significantly reduced tau protein content at p-tau (T205) and p-tau (S199) sites. PP2A content was significantly suppressed by OA, significantly increased by SY, GSK-3β content was significantly increased by OA and significantly decreased by SY. CONCLUSION: These results suggest that safflower yellow may have neuroprotective effect on OA-induced SH-SY 5Y cells injury, which may be associated with tau hyperphosphorylation at the enzyme level by activation of tau kinases or by a decline in the activities of tau phosphatases.
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<p><b>OBJECTIVE</b>To study the effect of chronic noise exposure on expression of N-methyl-D-aspartic acid receptor 2B (NR2B) and tau phosphorylation in hippocampus of rats.</p><p><b>METHODS</b>Twenty-four male SD rats were divided in control group and chronic noise exposure group. NR2B expression and tau phosphorylation in hippocampus of rats were detected after chronic noise exposure (100 dB SPL white noise, 4 h/d×30d) and their mechanisms underlying neuronal apoptosis in hippocampus of rats with TUNEL staining.</p><p><b>RESULTS</b>The NR2B expression decreased significantly after chronic noise exposure which resulted in tau hyperphosphorylation and neural apoptosis in hippocampus of rats. Immunohistochemistry showed that the tau hyperphosphorylation was most prominent in dentate gyrus (DG) and CA1 region of rat hippocampus.</p><p><b>CONCLUSION</b>The abnormality of neurotransmitter system, especially Glu and NR2B containing NMDA receptor, and tau hyperphosphorylation in hippocampus of rats, may play a role in chronic noise-induced neural apoptosis and cognition impairment.</p>