α-Mangostin decreases β-amyloid peptides production via modulation of amyloidogenic pathway

Abstract

Aims: β-amyloid (Aβ) aggregation and deposition play a central role in the pathogenic process of Alzheimer's disease (AD). α-Mangostin (α-M), a polyphenolic xanthone, have been shown to dissociate Aβ oligomers. In this study, we further investigated the effect of α-M on Aβ production and its molecular mechanism.

Methods: The Aβ and soluble amyloid precursor protein α (sAPPα) in culture medium of cortical neurons were measured by ELISA. The activities of α-, β-, and γ-secretases were assayed, and the interaction between α-M and β- or γ-secretases was simulated by molecular docking.

Results: α-M significantly decreased Aβ₄₀ and Aβ₄₂ production. α-M did not affect the expression of enzymes involved in nonamyloidogenic and amyloidogenic pathways, but significantly decreased the activities of β-secretase and likely γ-secretase with IC₅₀ 13.22 nmol·L^-1 and 16.98 nmol·L^-1 , respectively. Molecular docking demonstrated that α-M interacted with β-site amyloid precursor protein cleaving enzyme 1 and presenilin 1 to interfere with their active sites.

Conclusions: Our data demonstrate that α-M decreases Aβ production through inhibiting activities of β-secretase and likely γ-secretase in the amyloidogenic pathway. The current data together with previous study indicated that α-M could be a novel neuroprotective agent through intervention of multiple pathological processes of AD.

Keywords: Alzheimer's disease; α-mangostin; β-amyloid; β-secretase; γ-secretase.

Figure 1

α‐M significantly decreased Aβ₄₀, Aβ₄₂ levels in primary cortical neurons. Aβ₄₀ (A), Aβ₄₂ (B), and sAPPα (C) levels were detected in supernatant from cultured cortical neurons incubated with various concentration of α‐M for 24 h. Data represent mean±SEM from at least three independent experiments performed in triplicate. *P<.05, **P<.01, compared with 0 nmol·L⁻¹ of α‐M

Figure 2

The effect of α‐M on mRNA expression of enzymes involved in amyloid precursor protein(APP) metabolism and Aβ degradation in primary cortical neurons. α‐Secretase ADAM9, ADAM10, ADAM17, β‐secretase BACE1, γ‐secretase PS1 and Aβ degrading enzyme neprilysin(NEP) and insulin‐degrading enzyme(IDE) mRNA expression were detected in cultured cortical neurons incubated with various concentration of α‐M for 12 h by quantitative real‐time PCR and was normalized to that of 18 s gene. Data represent mean ± SEM of at least three independent experiments performed in triplicate. *P<.05, **P<.01, compared with 0 nmol·L⁻¹ of α‐M

Figure 3

α‐M did not affect protein expression of secretases and amyloid precursor protein(APP) metabolism in primary cortical neurons. APP (mAPP, imAPP), IDE, BACE1 and PS1 protein expressions were immunoblotted (A) and quantified (B for mAPP, imAPP and mAPP:imAPP ratio, and C for IDE, BACE1, PS1) from cultured cortical neurons incubated with various concentration of α‐M for 24 h. Data represent mean ± SEM of at least three independent experiments

Figure 4

α‐M inhibited β‐secretase and likely γ‐secretase activities. (A) The activities of α‐, β‐ and γ‐secretases were measured from cortical neurons incubated with various concentrations of α‐M for 24 h. *P<.05, **P<.01, compared with 0 nmol·L⁻¹ of α‐M. (B) α‐M inhibited β‐secretase (BACE1) activity by in vitro FRET assay. Data represent mean ± SEM of at least three independent experiments performed in triplicate

Figure 5

Binding mode of α‐M to BACE1. (A) α‐M was docked into crystal structure of BACE1 (PDB ID: 1FKN). The N‐terminal lobe and the C‐terminal lobe of BACE1 are blue and red, respectively. (B) Key hydrogen bonding interactions between α‐M and BACE1 at the catalytic residue Asp32 and at Phe108 of N‐terminal lobe are indicated with green and blue dashed lines

Figure 6

Binding mode of α‐M to PS1. (A) Ribbon diagram of PS1 (PDB ID: 5A63) in complex with α‐M. TM2 and TM6 of PS1 are blue and gray. (B) Interactions between α‐M and residues of PS1