Angelica polysaccharide ameliorates memory impairment in Alzheimer's disease rat through activating BDNF/TrkB/CREB pathway

Abstract

This study aimed to investigate the effect of Angelica sinensis polysaccharides (ASP) on Alzheimer’s disease (AD) and its underlying mechanisms. In our study, we build the AD model by injecting Aβ_25–35. Morris water maze (MWM) was applied to investigate learning and memory. Moreover, neurotransmitters, free radical, and inflammatory factors were also measured. Pathological change and neuronal death in hippocampus CA1, CA3, and DG region were detected by HE staining and Nissl staining. The neuronal apoptosis was detected by TUNEL. The expressions of caspase-3, Bcl-2 and Bax were measured by immunohistochemistry and Western blot. The expressions of BDNF, TrkB, p-Akt, Akt, p-CREB, and CREB were measured by Western blot. Our results showed that ASP could ameliorate spatial learning and memory deficiency in AD rats. ASP decreased AchE level and increased the levels of Ach and chAT in AD rats. ASP could increase the activity of SOD and CAT, decrease MDA activity, and inhibit the expression levels of inflammatory factors and neurons apoptosis in AD rats. Pathological change of hippocampus CA1, CA3, and DG region was ameliorated by ASP. In addition, the effects of ASP were reversed by K252a (TrkB inhibitor). Our study demonstrated that ASP could ameliorate memory impairment in AD rat through activating BDNF/TrkB/CREB pathway.

Impact statement: The present study demonstrated that ASP could ameliorate memory impairment through regulation of the balance of neurotransmitters, free radical metabolism, inflammation, and neurons apoptosis. Moreover, the mechanism of ASP on memory impairment may be related to BDNF/TrkB/CREB pathway in AD. Our research provides an innovatively regulatory mechanism about the ASP in AD rat and points a new way to the treatment of AD.

Keywords: Alzheimer’s disease; Angelica sinensis polysaccharides; Aβ25-35; BDNF/TrkB/CREB pathway; inflammatory factors; neurotransmitters.

Figure 1.

ASP ameliorated spatial learning and memory deficiency in AD rats. (a) Escape latency time of rats in each group. (b) Time spent in the target quadrant during the MWM probe test. (c) Number of times the rat crossed platform position during the MWM probe test. Data were presented as mean ± standard deviation with repeated for three times. *P < 0.05, vs. Sham group; ^#P < 0.05, vs. Model group.

Figure 2.

ASP regulated the balance of neurotransmitters in AD rats. (a) The activity of Ach in each group. (b) The activity of AchE in each group. (c) The activity of chAT in each group. Data were presented as mean ± standard deviation with repeated for three times. *P < 0.05, vs. Sham group; ^#P < 0.05, vs. Model group.

Figure 3.

ASP decreased the free radical metabolism and inhibited the expressions of inflammatory factors in AD rats. (a) The content of SOD, CAT, and MDA in each group. (b) The levels of IL-1β, IL-6, and TNF-α in each group. Data were presented as mean ± standard deviation with repeated for three times. *P < 0.05, vs. Sham group; ^#P < 0.05, vs. Model group.

Figure 4.

ASP decreased hippocampus neurons damage in AD rats. (a) Pathological change of hippocampus CA1, CA3, and DG region were detected by HE staining (× 400). (b) Neuronal death in hippocampus CA1, CA3, and DG region was examined by Nissl staining (× 400). Data were presented as mean ± standard deviation with repeated for three times. *P < 0.05, vs. Sham group; ^#P < 0.05, vs. Model group. (A color version of this figure is available in the online journal.)

Figure 5.

ASP inhibited neuronal apoptosis in AD rats. (a) The neuronal apoptosis was detected by TUNEL. (b) The expressions of caspase-3, Bcl-2 and Bax were measured by immunohistochemistry. (c) The expressions of caspase-3, Bcl-2 and Bax were measured by Western blot. (d) Ratios of Western blot products relative to Bcl-2 and Bax. Data were presented as mean ± standard deviation with repeated for three times. Scale bar = 50 μm, arrows stand for positive cells. *P < 0.05, vs. Sham group; ^#P < 0.05, vs. Model group. (A color version of this figure is available in the online journal.)

Figure 6.

The expressions of BDNF, TrkB, p-Akt, Akt, p-CREB and CREB were measured by Western blot. Data were presented as mean ± standard deviation with repeated for three times. *P < 0.05, vs. Sham group; ^#P < 0.05, vs. Model group.

Figure 7.

ASP protected Aβ_25–35-induced AD by activating BDNF/TrkB/CREB pathway in rats. (a) The expressions of BDNF, TrkB, p-Akt and p-CREB were measured by Western blot. (b) The activity of Ach, AchE, and chAT was detected in each group. (c) The content of SOD, CAT, and MDA was detected in each group. (d) The levels of IL-1β, IL-6, and TNF-α were measured in each group. (e) The neuronal apoptosis was detected by TUNEL. (f) The expressions of caspase-3, Bcl-2 and Bax were measured by Western blot. (g) Ratios of Western blot products relative to Bcl-2 and Bax. Data were presented as mean ± standard deviation with repeated for three times. Scale bar = 50 μm. *P < 0.05, vs. Model group; ^#P < 0.05, vs. ASP group. (A color version of this figure is available in the online journal.)