Protective effect of pine pollen on lipopolysaccharide-induced learning and memory impairment in mice / 中国基层医药

ABSTRACT

Objective:To investigate the protective effect of pine pollen on lipopolysaccharide (LPS)-induced learning and memory impairments in mice and the underlying mechanism.Methods:Sixty mice were randomly divided into four groups ( n = 15/group) normal control, model, low-dose pine pollen (500 mg/kg) and high-dose pine pollen (1 000 mg/kg). Mouse models of learning and memory impairment were established by lateral ventricle injection of LPS. The learning and memory abilities of mice were determined by the Morris water maze test. Superoxide dismutase (SOD) activity and glutathione (GSH) and malondialdehyde (MDA) levels in the hippocampus of mice were measured. Interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), dopamine (DA), and norepinephrine (NE) levels in the hippocampus were also determined. Results:The latency in the passive avoidance test in the model group was significantly shorter than that in the normal control group [(134.80 ± 33.89) s vs. (282.20 ± 17.43) s, t = 4.23, P < 0.01]. The number of errors in the model group was significantly higher than that in the normal control group [(4.00 ± 1.58) vs. (1.20 ± 1.30) times, t = 2.85, P < 0.01]. The latency in the passive avoidance test in the low-dose pine pollen (500 mg/kg) and high-dose pine pollen (1000 mg/kg) groups was significantly longer than that in the normal control group [(189.40 ± 27.21) s or (213.40 ± 21.26) s vs. (134.80 ± 33.89) s, t = 3.21, 4.38, all P < 0.05]. The number of errors in the low-dose pine pollen (500 mg/kg) and high-dose pine pollen (1 000 mg/kg) groups was significantly lower than that in the normal control group [(1.60 ± 1.44) times or (1.40 ± 1.44) times vs. (4.00 ± 1.58) times, t = 5.12, 6.42, both P < 0.05]. SOD activity and GSH, DA and NE levels in the hippocampus in the model group were significantly decreased compared with the normal control group [SOD (7.59 ± 1.77) kU/g vs. (39.90 ± 6.37) kU/g; GSH (3.49 ± 0.13) mmol/g vs. (6.37 ± 0.14) mmol/g; DA (418.42 ± 2.57) ng/L vs. (586.37 ± 3.64) ng/L; NE (187.20 ± 5.41) ng/L vs. (298.42 ± 2.32) ng/L, t = 3.67, 8.23, 2.23, 3.65, all P < 0.05]. MDA, IL-6 and TNF-α levels in the hippocampus in the normal control group were significantly higher than those in the model group [MDA (8.79 ± 0.82) mmol/g vs. (2.62 ± 0.16) mmol/g, IL-6 (48.07 ± 5.56) ng/L vs. (18.76 ± 1.42) ng/L, TNF-α (87.20 ± 4.31) ng/L vs. (22.42 ± 3.39) ng/L, t = 7.45, 2.67, 4.35, P < 0.05 or P < 0.01]. SOD activity, GSH, DA and NE levels in the hippocampus in the low-dose pine pollen (500 mg/kg) and high-dose pine pollen (1 000 mg/kg) groups were significantly higher than those in the model group [SOD (18.80 ± 2.39) kU/g, (28.70 ± 2.36) kU/g vs. (7.59 ± 1.77) kU/g, GSH (5.04 ± 0.36) mmol/g, (5.45 ± 0.17) mmol/g vs. (3.49 ± 0.13) mmol/g, DA (488.37 ± 3.46) ng/L, (506.29 ± 5.72) ng/L vs. (418.42 ± 2.57) ng/L, NE (225.65 ± 3.72) ng/L, (239.76 ± 5.58) ng/L vs. (187.20 ± 5.41) ng/L, t = 4.56 or 6.71, t = 4.65 or 5.32, t = 4.73 or 6.72, t = 3.84 or 5.63, P < 0.05 or P < 0.01]. MDA, IL-6 and TNF-α levels in the hippocampus in the low-dose pine pollen (500 mg/kg) and high-dose pine pollen (1 000 mg/kg) groups were significantly lower than those in the model group [MDA (5.72 ± 0.47) mmol/g, (3.77 ± 0.23) mmol /g vs. (8.79 ± 0.82) mmol/g, IL-6 (28.42 ± 3.54) ng/L, (23.43 ± 5.62) ng/L vs. (48.07 ± 5.56) ng/L, TNF-α (48.87 ± 4.82) ng/L, (39.65 ± 6.69) ng/L vs. (87.20 ± 4.31) ng/L, t = 6.31 or 7.28, t = 3.46 or 6.31, t = 4.28 or 3.57, P < 0.05 or P < 0.01]. Conclusion:Pine pollen can improve LPS-induced learning and memory impairments possibly through up-regulating the levels of monoamine neurotransmitters DA and NE and inhibiting the levels of oxidative stress and inflammatory reaction in the hippocampus of mice.