Background
In addition to the typical signs of skin damage, long-term arsenic exposure is often accompanied by signs and symptoms of neurobehavioral abnormalities.
Objective
To investigate potential intervention effect of sciadopitysin on senescence of neurons induced by sodium arsenite in rats and possible underlying mediating effect of cell cycle-related transcription factor E2F1.
Methods
SH-SY5Y cells were treated with 4 μmol·L−1 sodium arsenite for 24 h and intervened with 50 μg·mL−1 Ginkgo biloba extract (EGb761) or four major biflavonoids in Ginkgo biloba leaves (isoginkgetin, bilobetin, sciadopitysin, and ginkgetin) for 24 h respectively. Then, cell viability was measured by CCK-8 assay. Thirty-two 180-200 g SPF rats were randomly divided into a control group, an arsenic treatment group (10 mg·L−1), a Ginkgo biloba extract intervention group (10 mg·kg−1), and a sciadopitysin intervention group (10 mg·kg−1), 8 rats in each group, half male and half female. The rats were treated with sodium arsenite by free drinking water for 3 consecutive months, and the intervention treatment was conducted after 2 months of poisoning with drug intake by gavage for 1 month. HE staining was used to detect structural changes in the hippocampus, while Nissl's staining was used to detect changes in hippocampal morphology and neuron numbers. Moreover, senescence-associated β galactosidase (SA-β-gal) staining and Western blotting were used to detect senescence of hippocampal neurons and the expression level of E2F1, respectively.
Results
Compared to the arsenic treatment group, EGb761 and the four biflavonoids in Ginkgo biloba leaves effectively antagonized the inhibitory effect of sodium arsenite on cell viability (all Ps＜0.05), and sciadopitysin showed better restoration of cellular viability than Ginkgo biloba extract (P＜0.05). The results of HE staining and Nissl's staining showed that the hippocampal neurons in the arsenic treatment group were reduced in cell count and the synaptic structure was abnormal, with swelling, nuclear shrinkage, and vacuole, compared with the control group. The results of SA-β-gal staining showed that the number of senescent cells in the arsenic treatment group (15.75±3.01) was significantly increased compared with the control group (2.88±0.84) (P＜0.05); the numbers of senescent cells in the Ginkgo biloba extract group (9.38±1.92) and the sciadopitysin treatment group (7.75±2.38) were significantly decreased compared with the arsenic treatment group (all Ps＜0.05). The results of Western blotting showed that compared with the control group, the expression of E2F1 protein in hippocampus of the arsenic treatment group was significantly decreased (1.00±0.17 vs. 0.65±0.19, P<0.05); compared with the arsenic treatment group, the protein expression level of E2F1 in hippocampus of the sciadopitysin treatment group (0.89±0.18) was significantly recovered (P<0.05); compared withGinkgo biloba extract (0.68±0.19), sciadopitysin had a better recovery effect on E2F1 expression level (0.89±0.18) (P＜0.05). The results of correlation analysis showed that the E2F1 protein expression level was negatively correlated with the positive rate of SA-β-gal staining in hippocampal neurons (r=−0.518,P＜0.05).
Conclusion
Sciadopitysin is an effective component of Ginkgo biloba extract. It can effectively inhibit the senescence of hippocampal neurons induced by sodium arsenite, and E2F1 may play an important mediating role.
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