Extract of Fructus Cannabis Ameliorates Learning and Memory Impairment Induced by D-Galactose in an Aging Rats Model

Abstract

Hempseed (Cannabis sativa L.) has been used as a health food and folk medicine in China for centuries. In the present study, we sought to define the underlying mechanism by which the extract of Fructus Cannabis (EFC) protects against memory impairment induced by D-galactose in rats. To accelerate aging and induce memory impairment in rats, D-galactose (400 mg/kg) was injected intraperitoneally once daily for 14 weeks. EFC (200 and 400 mg/kg) was simultaneously administered intragastrically once daily in an attempt to slow the aging process. We found that EFC significantly increased the activity of superoxide dismutase, while lowering levels of malondialdehyde in the hippocampus. Moreover, EFC dramatically elevated the organ indices of some organs, including the heart, the liver, the thymus, and the spleen. In addition, EFC improved the behavioral performance of rats treated with D-galactose in the Morris water maze. Furthermore, EFC inhibited the activation of astrocytes and remarkably attenuated phosphorylated tau and suppressed the expression of presenilin 1 in the brain of D-galactose-treated rats. These findings suggested that EFC exhibits beneficial effects on the cognition of aging rats probably by enhancing antioxidant capacity and anti-neuroinflammation, improving immune function, and modulating tau phosphorylation and presenilin expression.

Figure 1

HPLC chromatogram of EFC. (1) n-Hexadecanoic acid, (2) 9,12-octadecadienoic acid (ω6), (3) 9,12,15-octadecatrienoic acid (ω3), and (4) butyl 9,12-octadecadienoate.

Figure 2

Graph of mass spectrometry. (a) 9,12-Octadecadienoic acid (ω6) and (b) 9,12,15-octadecatrienoic acid (ω3).

Figure 3

Effect of EFC on body weight and mean body weight gain in aging rats induced by D-gal. (a) Effect of EFC on body weight. (b) Mean body weight gain at the end of week 14. The results are presented as mean ± SE (n = 8). ^AP < 0.05 as compared to the normal control group. ^BP < 0.05 as compared to the D-gal model group.

Figure 4

Effect of EFC on organ indices in aging rats induced by D-gal. The results are presented as mean ± SE (n = 8). ^aP < 0.05 as compared to the control group. ^bP < 0.05 as compared to the D-gal model group.

Figure 5

Effect of EFC on memory impairment induced by D-gal administration (n = 8 for each group). The Morris water maze test was carried out to access the spatial learning and memory ability of rats. (a) Latencies to find a hidden platform in the water maze during the 5 training days. (b) Mean distance to reach the hidden platform during the 5 training days. (c) Time spent in the target quadrant where the platform was located during training days in the probe test. (d) Numbers of crossings of the exact location of the previous platform during the probe test. (e) The representative traces during the probe test. The results are presented as mean ± SE (n = 8). ^AP < 0.05 as compared to the normal control group. ^BP < 0.05 as compared to the D-gal model group. Statistical differences between groups were analyzed by one-way analysis of variance (ANOVA) followed by Dunnett's test.

Figure 6

Effect of EFC on SOD activity and MDA levels in the brain of aging rats induced by D-galactose. The results are presented as mean ± SE (n = 4). ^aP < 0.05 as compared to the control group. ^bP < 0.05 as compared to the D-gal model group.

Figure 7

Effect of EFC on GFAP expression in the dentate gyrus of hippocampus in D-gal-treated rats measured by immunofluorescence (×100). (a) The images of immunofluorescence staining of GFAP (red), the scale bar represents 100 μm. (b) The bar graph summarizing the number of GFAP-positive cells. All values are expressed as mean ± SE (n = 4), ^AP < 0.05 as compared to the normal control group. ^BP < 0.05 as compared to the D-gal model group.

Figure 8

Effect of EFC on the expression of presenilin 1, total tau, and p-tau in the hippocampus of aging rats induced by D-gal. The relative protein levels between the tested target protein and internal standard GAPDH were calculated and labeled on y-axis. Data are expressed as the mean ± SE (n = 4). ^aP < 0.05 as compared to the normal control group. ^bP < 0.05 as compared to the D-gal model group. The bands are from a representative blot. Lane 1: normal control group; lane 2: D-gal-treated group; lane 3: EFC treatment group; lane 4: D-gal plus EFC (400 mg/kg) treatment group.

Figure 9

Proposed mechanism of the effect of EFC on ameliorating cognitive impairment induced by D-gal. EFC could relieve age-related cognitive impairment by attenuating oxidative stress, improving immune function, and inhibiting the activation of astrocytes as well as attenuating tau phosphorylation and suppressing PS1 expression in the brain of D-gal treated rats.