Multi-faced neuroprotective effects of Ginsenoside Rg1 in an Alzheimer mouse model - PubMed (original) (raw)

Multi-faced neuroprotective effects of Ginsenoside Rg1 in an Alzheimer mouse model

Fang Fang et al. Biochim Biophys Acta. 2012 Feb.

Abstract

There has been no extensive characterization of the effects of Ginsenoside Rg1, a pharmacological active component purified from the nature product ginseng, in an Alzheimer's disease mouse model. The well-characterized transgenic Alzheimer disease (AD) mice over expressing amyloid precursor protein (APP)/Aβ (Tg mAPP) and nontransgenic (nonTg) littermates at age of 6 and 9 months were treated with Rg 1 for three months via intraperitoneal injection. Mice were then evaluated for changes in amyloid pathology, neuropathology and behavior. Tg mAPP treated with Rg1 showed a significant reduction of cerebral Aβ levels, reversal of certain neuropathological changes, and preservation of spatial learning and memory, as compared to vehicle-treated mice. Rg1 treatment inhibited activity of γ-secretase in both Tg mAPP mice and B103-APP cells, indicating the involvement of Rg1 in APP regulation pathway. Furthermore, administration of Rg1 enhanced PKA/CREB pathway activation in mAPP mice and in cultured cortical neurons exposed to Aβ or glutamate-mediated synaptic stress. Most importantly, the beneficial effects on attenuation of cerebral Aβ accumulation, improvement in neuropathological and behavioral changes can be extended to the aged mAPP mice, even to 12-13 months old mice that had extensive amyloid pathology and severe neuropathological and cognitive malfunction. These studies indicate that Rg1 has profound multi-faced and neuroprotective effects in an AD mouse model. Rg1 induces neuroprotection through ameliorating amyloid pathology, modulating APP process, improving cognition, and activating PKA/CREB signaling. These findings provide a new perspective for the treatment of AD and demonstrate potential for a new class of drugs for AD treatment.

PubMed Disclaimer

Figures

Fig. 1

Effect of Rg1 on Aβ accumulation. Panels A and B. ELISA used for the measurement of Aβ 40 (left) and Aβ 42 (right) in the hippocampus of 9 (A) and 12-13 (B) month old Tg mAPP mice injected intraperitoneally with Rg1 (10mg/kg) daily continuously for 3 month or with vehicle. Aβ 40 and Aβ 42 levels were significantly decreased in Rg1 injection group as compared to vehicle. Panel C. Immunostaining for Aβ plaque using Aβ antibody (3D6) in 9 month old Tg mAPP mice injected with Rg1 or vehicle. Representative sections showed Aβ deposits from Tg mAPP mice injected with Rg1(left) or with vehicle (right). Panel D. Quantification of area (percentage) occupied by Aβ plaques in the indicated Tg mice. N = 5-6 mice per group. Scale bar 30 μm.

Fig. 2

Effect of Rg1 on γ-secretase activity in the brain of Tg mAPP mice and nonTg mice. Panel A. Densitometry of APP C-terminal fragment cleavage by gamma secretase (APP-CTF-γ) from indicated Tg mice at age of 12-13 m. Decreased γ-secretase activity in the cerebral cortex assessed by APP-CTF- γ from membrane-associated APP in Tg mAPP mice injected with Rg1 as compared to Tg mAPP mice injected with vehicle. Panel B. Representative Western blots of brain extracts for full length APP, APP-CTF-γ and β-actin in the indicated mice. Rg1 did not affect total APP expression, whereas the cleavage products of APP-CTF-γ generated from membrane-bound APP were diminished in Rg1-treated mAPP mice. N = 3-5 mice per group.

Fig. 3. Effect of Rg1 on γ-secretase activity in neuronal cells expressing wt APP

Panel A. Aβ ELISA used for measurement of Aβ1-40 and Aβ1-42 levels in the supernatant of cultured neuronal cells (B103) stably expressed wild-type APP (wtAPP) in the presence of Rg1 (5 and 10μM) or vehicle for 48 hours. Panel B. Representative Western blots of cultured B103-wtAPP cells for APP and APP-CTF-γ, showing decreased APP-CTF-γ generated from membrane associated APP because of reduced γ-secretase activity in cultured B103-wtAPP cells treated with 5μM or 10μM Rg1 for 48 hours. Panels C-D. Densitometry of APP (C) and APP-CTF-γ (D) immunoreactive bands in cells with and without treatment of Rg1. (*P<0.01, #P<0.05 compared to those from vehicle-treated B103-wtAPP cells).

Fig. 4

Effect of Rg1 on neuropathological findings in Tg mAPP mice. AChE activity was determined histochemically in the entorhinal cortex of the indicated mice groups at 12-13 months of age. Quantification of density of AChE-positive neurites in the entorhinal cortex of hippocampus in the indicated Tg mice (* P < 0.01 vs. other groups of mice, n = 4-6 mice/group). Representative images for AChE staining in the entorhinal cortex of the indicated mice are shown in the lower panel. Scale bar=5 μm.

Fig. 5

Effect of Rg1 on spatial learning/memory in Tg mAPP mice. Spatial/learning memory was tested with the radial arm water maze at 9-10 months (left) and 12-13 months (right) of age in the indicated groups of mice (n=5-8 male mice /group). Trials 1-4 denote acquisition trials and trial 5 denotes retention trial. Tg mAPP mice injected with Rg1 showed improved spatial learning memory as compared to Tg mAPP mice injected with vehicle. *P < 0.01, # P < 0.05 vs. Tg mAPP+ vehicle.

Fig. 6

Rg1 activation of PKA and p-CREB pathway. Panel A. PKA activity was determined in brain extracts of the indicated Tg mice treated with Rg1 or vehicle for three months (started at 9 months old), respectively. Panel B. ELISA was performed to measure levels of phosphor- and total-CREB in the cortex of the indicated Tg mice. The bar graphs of Figure 6B represented fold-increased phosphor-CREB normalized to total of CREB. There was no significant change in the total of CREB. * p<0.05 vs. vehicle-treated nonTg mice and #P<0.05 vs. vehicle-treated Tg mAPP mice. Panel C. Ginsenoside Rg1 attenuated the decrease in PKA activity induced by oligomeric Aβ1-42. The cultured cortical neurons were preincubated with ginsenoside Rg1 (0, 2.5, 5, 10 μM) for 1 hour, and then oligomeric Aβ1-42 (5 μM) or vehicle was added to the cells. Two hours later, PKA activity in cell lysates was measured and data were expressed as fold-increased compared to vehicle-treated cells. Results are shown as the mean ± SEM. *P < 0.05, #P < 0.01 vs. neurons with 5.0 μM Aβ1-42 treatment. Panel D. Modulation of glutamate-stimulated CREB phosphorylation by oligomeric Aβ1-42. Phosphorylation is stimulated strongly by treatment with 50 μM glutamate (Glut) for 15 min. Pretreatment with 5 μM Aβ for 2 h results in a decrease in pCREB /T-CREB. This effect is opposed by the preincubation of 2.5/5/10 μM ginsenoside Rg1 (Rg1-Aβ-Glut). Data are shown as the mean ± SEM. #P < 0.01 vs. neurons with 5.0μM Aβ1-42 treatment. Studies were repeated at least three times.

References

1. Attele AS, Wu JA, Yuan CS. Ginseng pharmacology: multiple constituents and multiple actions. Biochemical pharmacology. 1999;58:1685–1693. -PubMed
1. Cheng Y, Shen LH, Zhang JT. Anti-amnestic and anti-aging effects of ginsenoside Rg1 and Rb1 and its mechanism of action. Acta pharmacologica Sinica. 2005;26:143–149. -PubMed
1. Fu LM, Li JT. A systematic review of single Chinese herbs for Alzheimer's disease treatment. Evid Based Complement Alternat Med. 2009 -PMC -PubMed
1. C DH, Zhang JT, Chen Cf, Liu GZ. The chemistry, metabolism and biological activities of ginseng. Chemical Industry Press; Beijing: 2006.
1. Hu SQ, Yu HM, Liu TS, Yang DJ, Chen XZ, He CJ. Neuroprotective effects of water extracts of American Ginseng on SH-SY5Y cells apoptosis induced by Abeta25-35. Zhong yao cai = Zhongyaocai = Journal of Chinese medicinal materials. 2008;31:1373–1377. -PubMed

Multi-faced neuroprotective effects of Ginsenoside Rg1 in an Alzheimer mouse model - PubMed (original) (raw)