[Mechanism of polyphyllin Ⅱ in improving DEHP-induced learning and memory impairment via targeting CK2b and...

This study aimed to explore the effect and mechanism of polyphyllin Ⅱ in improving di(2-ethylhexyl)phthalate(DEHP)-induced learning and memory impairment. In the experiment, male C57BL/6 mice were randomly divided into five groups: a control group, a model group(exposed to 5 mg·kg~(-1) DEHP), and polyphyllin Ⅱ groups(5 mg·kg~(-1) DEHP + 0.5 mg·kg~(-1) polyphyllin Ⅱ, DEHP + 1 mg·kg~(-1) polyphyllin Ⅱ, and DEHP + 2 mg·kg~(-1) polyphyllin Ⅱ). The learning and memory function of mice was tested using the Morris water maze. The hippocampal neuron structure was detected by Nissl staining. The expression of casein kinase Ⅱ subunit beta(CK2b), protein kinase B(Akt)-cAMP response element binding protein(CREB) pathway-related proteins, as well as postsynaptic density protein 95(PSD95) and synapsin 1 was determined by immunofluorescence and Western blot. The brain-derived neurotrophic factor(BDNF) expression was measured by enzyme-linked immunosorbent assay(ELISA). The results showed that compared with the control group, DEHP induced learning and memory impairment, as well as hippocampal neuronal apoptosis in mice. Additionally, DEHP downregulated CK2b, inhibited the Akt-CREB pathway, and downregulated the PSD95, synapsin1, and BDNF expression. After polyphyllin Ⅱ administration, DEHP-induced learning and memory impairment was significantly improved, with inhibited hippocampal neuronal apoptosis, restored CK2b expression, reactivated Akt-CREB pathway, as well as restored expression of PSD95, synapsin1, and BDNF. Furthermore, the surface plasmon resonance(SPR) experiment of N2a cells demonstrated that polyphyllin Ⅱ targeted CK2b and stabilized its expression. After using siRNA to inhibit CK2b, the neuroprotective effect of polyphyllin Ⅱ was also significantly inhibited, and neuronal apoptosis was reinduced. In conclusion, polyphyllin Ⅱ can ameliorate DEHP-induced learning and memory impairment, with its potential mechanism involving the Akt-CREB pathway activation via CK2b upregulation, which leads to restored PSD95 and synapsin1 expression, and synaptic plasticity, as well as inhibited neuronal apoptosis, ultimately exerting a neuroprotective effect. This study suggests that polyphyllin Ⅱ possesses a neuroprotective effect and has potential application value in improving cognitive impairment.