Effects Of General Cistanosides Mediated Specific Androgen Receptors On Synaptic Proteins And Cognitive Function in SAMP8 Mice Ⅱ

2 results

2. 1 Effect of GCs on learning and memory in mice 

After 30 days of GC administration, the escape latency of the positioning and navigation experiment gradually decreased with the increase of experimental days, and the downward trend was the most significant. Compared with the Model group, the escape latency of the GCs group was significantly reduced on the 4th and 5th days (P ＜ 0. 05); compared with the GCs group, the escape latency of the GCs + F group was increased on the 4th and 5th days. , the escape latency of the GCs + ICI group was significantly reduced on the 4th and 5th days (P ＜ 0. 05), but there was no significant difference from 1 to 3 d (P ＞ 0. 05). see picture 1.

Figure 1 Escape latency of each group in the positioning navigation experiment

Note: Compared with the Model group, * P < 0. 05; Compared with the GCs group, # P < 0. 05

Figure 2 Number of platform crossings for each group in the space exploration experiment

Note: Compared with the Model group, * P < 0. 05; Compared with the GCs group, # P < 0. 05

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In the space exploration experiment, compared with the Model group, the number of platform crossings in the GCs group was significantly increased (P ＜ 0. 05); compared with the GCs group, the GCs + F group was decreased in the number of platform crossings (P ＜ 0. 05) , the GCs +ICI group increased (P ＜ 0. 05). See Figure 2. The swimming trajectory chart showed that the swimming trajectory of the mice in the Model group was disorganized and irregular, and the percentage of time spent in the target quadrant was the lowest (P < 0. 05). Compared with the Model group, the swimming trajectories of mice in the GCs group were more concentrated, with most of them located in the quadrant of the platform, and the animals spent the largest percentage of time staying in the target quadrant (P ＜ 0. 05); compared with the GCs group, the crossing of the GCs + F group The number of platforms decreased (P ＜ 0. 05), but increased in the GCs + ICI group (P ＜ 0. 05). See Figure 3.

2. 2. The effect of GCs on the protein expression of SYN, PSD-95, and BDNF in the mouse hippocampus. 

Compared with the Model group, the protein expression of SYN, PSD-95, and BDNF in the GCs group was significantly increased (P ＜ 0. 05); compared with the Model group, Compared with group, the expression of PSD-95 protein in the GCs + F group and the GCs + ICI group was significantly decreased (P ＜ 0. 05); the expression of SYN protein in the GCs + F group was significantly increased (P ＜ 0. 05) ; The protein expression of BDNF in the GCs + F group and GCs + ICI group was significantly reduced (P ＜0. 05). See Figure 4.

Figure 3 Swimming trajectories of each group in the space exploration experiment

Note: A: Model group, B: GCs group, C: GCs + F group, D: GCs + ICI group, E: F group, F: ICI group

Figure 4 Western blot detection of PSD-95, SYN, and BDNF protein expression in the hippocampus of each group

Note: A: SYN protein expression, B: BDNF protein expression, C: PSD-95 protein expression.

Compared with the Model group, * P < 0. 05; Compared with the GCs group, # P < 0. 05

2. 3 GCs on mouse hippocampus tissue

Effects on SYN, PSD-95, and BDNF mＲNA expression Compared with the Model group, the GCs group had significantly higher expression levels of SYN, PSD-95, and BDNF mＲNA (P＜0. 05); compared with the GCs group, the GCs + F group, the mRNA expression level of PSD-95 in the GCs + ICI group was significantly decreased (P ＜ 0. 05); the mRNA expression of SYN in the GCs + F group was significantly increased (P ＜ 0. 05); the GCs + F group, GCs + The mRNA expression of BDNF in the ICI group was significantly reduced (P ＜ 0. 05). See Figure 5.

Figure 5 RT-PCR detection of PSD-95, SYN, and BDNF mＲNA expression in the hippocampus of each group Note: A: SYN mＲNA expression, B: PSD-95 mＲNA expression, C: BDNF mＲNA expression. Compared with the Model group, * P < 0. 05; Compared with the GCs group, # P < 0. 05

3 Discussion

There is no protoplasmic connection between neurons in structure, and they only rely on synaptic contact to transmit information. Abnormal changes in synaptic structure and function will affect the effective transmission of information between neurons, so it is generally believed that AD cognitive dysfunction is Closely related to pathological changes in synapses [6]. Synaptic plasticity mainly refers to the structural and functional modification of synaptic connections, including the increase or decrease in the number of synapses and changes in physiological functions. Synaptic plasticity is the basis of learning and memory, and its reduction is one of the main pathogenic factors of AD cognitive dysfunction. Previous studies have shown that GCs can regulate synaptic plasticity through multiple mechanisms to improve cognitive function. It is worth noting that GCs can also increase androgen levels in animals, and testosterone can improve AD cognitive dysfunction [7]. Therefore, it is speculated that GCs may improve cognitive function by exerting androgen-like effects.

This study found that GCs can significantly shorten the escape latency of SAMP8 mice and increase the number of platform crossings, suggesting that GCs can improve the cognitive dysfunction of SAMP8 mice; and giving animals flutamide (AR antagonist) can block the effect of GCs on SAMP8 mice. The effect on cognitive function in mice suggests that after administration of flutamide, the complete combination of GCs and ARＲ may be blocked and the effect cannot be exerted, that is, GCs may exert its effects by specifically mediating ARＲ.

Under physiological conditions, testosterone can aromatize into dihydrotestosterone (DHT) and estradiol (E2) in the body. In this experiment, the administration of fulvestrant (ER antagonist) to animals can significantly improve the cognitive dysfunction of SAMP8 mice. The reason may be that fulvestrant blocks the specific binding of E2 and ER in the body, resulting in the dissociation of E2 in the body. E2 levels increase and accumulate, inhibiting the metabolism of testosterone to E2. On the contrary, the aromatization of testosterone into DHT compensatory increases, and the combination with ARＲ increases, thereby significantly improving the cognitive dysfunction of SAMP8 mice. This result further verifies that GCs may Acts by mediating specific ARＲ.

It is well known that cognitive dysfunction in AD patients is closely related to synaptic plasticity. Previous studies have shown that the expression of synapse-related proteins SYN, PSD-95, and BDNF in AD model animals is significantly reduced [8].

The results of this experiment showed that after administration of GCs, the expression of synapse-related proteins SYN, PSD-95, and BDNF increased, suggesting that GCs can improve synaptic plasticity. Studies have shown that BDNF can interact with neurotrophin receptors, affecting the release of vesicles and neurotransmitters, thereby affecting learning and cognitive functions [9]. The results of this experiment found that compared with the GCs group, the expression of BDNF was reduced in the GCs+F group and GCs+ICI group, suggesting that GCs may mediate ARＲ's participation in the above process to affect learning and cognitive functions. Synaptophysin (SYN) is a calcium-binding protein located on the synaptic vesicle membrane.

It exists in the central and peripheral nerve terminals of almost all animals, and may participate in the formation of synaptic vesicle-specific channels, and is also related to the transport of vesicles and the release of neurotransmitters [10]. Postsynaptic density protein (PSD-95) is located in the postsynaptic membrane and is responsible for receiving neurotransmitters released from the presynaptic and involved in regulating synaptic signal transmission and synaptic plasticity. Therefore, SYN and PSD-95 are considered It is a marker for evaluating synaptic activity and functional plasticity [11]. The results of this experiment found that compared with the GCs group, the expression of SYN increased and the expression of PSD-95 decreased after animals were given flutamide, suggesting that GCs may specifically mediate AR to regulate the postsynaptic membrane, but not the presynaptic membrane. The effect does not specifically mediate ARＲ. Compared with the GCs group, the expression levels of BDNF and PSD-95 decreased after the animals were given fulvestrant, and the decrease was more significant than that of the GCs + F group, which further verified that GCs may play a role by mediating specific ARＲ.

In summary, GCs may mediate specific ARＲ to regulate synaptic plasticity, thereby improving AD cognitive dysfunction, which will provide new ideas for the use of GCs in the prevention and treatment of AD.

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