Nobiletin, a flavone from Citrus depressa, induces gene expression and increases the protein level and activity of neprilysin in SK-N-SH cells

Abstract

Neprilysin (NEP) is one of the candidate amyloid β protein (Aβ) degrading enzymes affecting brain Aβ clearance. This enzyme declines in the brain with age, which leads to the increased Aβ deposition in Alzheimer's disease (AD). Pharmacological activation of NEP during the aging process, therefore, represents a potential strategy to prevent the development of AD. To examine the influence of nobiletin on neprilysin activity, we measured cellular NEP activity in SK-N-SH cells. Moreover, NEP expression was examined by using reverse transcription - polymerase chain reaction and Western blotting. Measurement of cellular NEP activity showed that nobiletin stimulated this in a dose- and time-dependent manner in SK-N-SH cells. Moreover, nobiletin increased the expression of NEP mRNA, and then the levels of NEP protein, also in a dose- and time-dependent manner. Our findings showed that nobiletin promoted NEP gene and protein expression, resulting in enhancement of cellular NEP activity in SK-N-SH cells. This compound could be a novel Aβ-degrading compound for use in the development of disease-modifying drugs to prevent and (or) cure AD.

Nobiletin Reduces Intracellular and Extracellular β-Amyloid in iPS Cell-Derived Alzheimer’s Disease Model Neurons

“…In this study, whether nobiletin directly up-regulates neprilysin gene expression remains unclear. Previously, we showed that nobiletin evokes PKA/ERK/CREB signaling 23) and CRE-dependent transcription, 16) thus increasing the gene expression of the CREB-binding protein (CBP), 25) c-Fos, 24) c-jun, and Fra1 (data not shown) in PC12 and PC12D cells. In recent years, a number of studies have implicated epigenetic modifications in the expression of neprilysin.…”

“…The extraction, isolation, and purification of nobiletin were performed as previously described. 16,25) The purity of purified nobiletin was confirmed by HPLC and 1 H-and 13 C-NMR. 16) The obtained nobiletin was dissolved in dimethyl sulfoxide (DMSO) (Sigma-Aldrich Co., LLC, St. Louis, MO, U.S.A.) at a concentration of 100 mM and stored at −20°C.…”

“…Furthermore, nobiletin elevates the expression of memory-and transcription-related genes in PC12 and PC12D cells. 24,25) Interestingly, we recently found that nobiletin also enhances the expression of the neprilysin gene and protein, as well as the activity of the enzyme, in the human neuroblastoma cell line, SK-N-SH. 26) In the present study, we examined whether nobiletin promotes Aβ degradation in vitro.…”

The Multifunctional Effects of Nobiletin and Its Metabolites In Vivo and In Vitro

“…Neprilysin (NEP) is one of the enzymes for degrading A β . NOB has been showed to upregulate the expression of NEP in a time and dose dependent manner in SK-N-SH cells [ 15 ] ( Table 1 ). The beneficial effects of NOB on memory-improving in various animal models and against pathological characteristics of AD have been comprehensively reviewed [ 16 ].…”

Amyloid-clearing proteins and their epigenetic regulation as a therapeutic target in Alzheimer’s disease

“…(Melzig and Janka, 2003; Ayoub and Melzig, 2006; Kiss et al, 2006; Deng et al, 2014; Fujiwara et al, 2014). Green tea catechins were shown to be preventive in AD animal models via up-regulation of NEP (Lim et al, 2013).…”