- Andrographolide reduces cognitive impairment in young and mature AbetaPPswe/PS-1 mice Molecular Neurodegeneration 2014, 9:61 doi:10.1186/1750-1326-9-61
ANDRO decreases Aβ depositions in young AβPPswe/PS-1 mice
Previous studies have suggested that amyloid levels in AD patients and mouse models are related to cognitive impairment ; the effects of Aβ oligomers are thought to be the cause of synaptic function impairment in the postsynaptic region [23-25]. Under this condition, young (7-month-old) and mature (12-month-old) AβPPswe/PS-1 mice were treated with ANDRO for 4 weeks, and then the amounts of Aβ aggregates present in their brains were analyzed. A more detailed analysis of amyloid plaques in the cortical layers and hippocampi were measured in 7-month-old AβPPswe/PS-1 mice (Figure 1a and b). These data show a significant reduction in amyloid plaques in cortical layers I-IV [F(7,3) = 2,68, p < 0,05], whereas we did not observe changes in layers V [F(15,3) = 3,15, p = NS] and VI [F(17,3) = 2,38, p = NS] with ANDRO treatment (Figure 1b) [F(4,4) = 0,1077, p = NS]. Additionally, we detected a reduction in the ThS burden in the hippocampus (Figure 1b) [F(12,3) = 3,15, p < 0,05]. Then, to analyze a probable change in the levels of Aβ oligomers in the hippocampi of 7-month-old AβPPswe/PS-1 mice treated with ANDRO, we evaluated the levels of Aβ oligomers in hippocampi by slot blot using the A11 antibody without finding any significant changes (Figure 1b). These results indicate that ANDRO treatment causes a reduction in the overall amount of Aβ plaques, but not Aβ oligomers, in young animals. In this context, we performed a detailed analysis of the plaque size distribution. The aggregate size distribution, which is presented as a cumulative frequency plot, demonstrates that AβPPswe/PS-1 mice treated with ANDRO shifted their plaque size distribution toward a smaller plaque size from cortex (Figure 1c). To further analyze the effect of ANDRO treatment on amyloid plaques, we performed an analysis of the different amyloid plaques, which were categorized by maturation stages according to their morphology as follows : type 1, plaques displaying a reticular appearance without a central dense core; type 2, plaques displaying a dense core surrounded by fibrillar material in the shape of a corona (type 2a) or radiating from the center (type 2b) or plaques displaying a dense core lacking any surrounding material (type 2c) (Figure 1d). The analysis of type 2a [F(1,3) = 1,5, p = NS]and 2c[F(1,3) = 3,1, p = NS]plaques in the whole brains of 7-month-old AβPPswe/PS-1 mice treated with ANDRO indicated no significant differences in relation to controls. In contrast, the number of type 2b plaques significantly decreased in the brains of ANDRO-treated AβPPswe/PS-1 young mice (Figure 1d) [F(2,3) = 5,13, p < 0,05]. The number of immature plaques (type 1) increased significantly with ANDRO treatment, demonstrating that ANDRO treatment affects amyloid plaque maturation [F(2,3) = 13,54, p < 0,05].
- Biochemical Journal Immediate Publication. Published on 25 Nov 2014 as manuscript BJ20140207
Andrographolide activates the canonical Wnt signalling pathway by a mechanism that implicates the non-ATP competitive inhibition of GSK-3β: Auto regulation of GSK-3β in vivo
Wnt/β-catenin signalling is an important pathway that regulates multiple biological processes including cell adhesion and cell fate determination during animal development and in the adult nervous system regulates the structure and function of synapses. Wnt signalling dysfunction is associated with several neurodegenerative diseases such as schizophrenia and Alzheimer´s disease. The use of natural compounds is an interesting strategy in the search of drugs with therapeutic potential to activate this signalling pathway. Here, we report that andrographolide (ANDRO), a component of Andrographis paniculata, is a potent activator of Wnt signalling. Our results indicate that ANDRO activates this pathway inducing the transcription of Wnt target genes by a mechanism that by-passes Wnt ligand binding to its receptor. In vitro kinase assays demonstrate that ANDRO inhibits Glycogen synthase kinase-3 (GSK-3β) by a non-ATP competitive, substrate competitive mode of action. In silico analyses suggest that ANDRO interacts with the substrate binding site of GSK-3β. Finally, we demonstrated that the increase seen on the levels of GSK-3β phosphorylated at Ser9 are a result of an auto-regulatory mechanism of the kinase in vivo, although not by activation of the phosphatase PP1. Our results suggest that ANDRO could be used as a potential therapeutic for disorders caused by Wnt signaling dysfunction such as neurogenerative diseases.