Effects of huperzine A on amyloid precursor protein processing and β-amyloid generation in human embryonic kidney 293 APP Swedish mutant cells
ABSTRACT The amyloid precursor protein (APP) is cleaved enzymatically by nonamyloidogenic and amyloidogenic pathways. alpha-Secretase (alpha-secretase), cleaves APP within the beta-amyloid (Abeta) sequence, resulting in the release of a secreted fragment of APP (alphaAPPs) and precluding Abeta generation. In this study, we investigated the effects of an acetylcholinesterase inhibitor, huperzine A (Hup A), on APP processing and Abeta generation in human embryonic kidney 293 cells transfected with human APP bearing the Swedish mutation (HEK293 APPsw). Hup A dose dependently (0-10 microM) increased alphaAPPs release and membrane-coupled APP CTF-C83, suggesting increased APP metabolism toward the nonamyloidogenic alpha-secretase pathway. The metalloprotease inhibitor TAPI-2 inhibited the Hup A-induced increase in alphaAPPs release, further suggesting a modulatory effect of Hup A on alpha-secretase activity. The synthesis of full-length APP and cell viability were unchanged after Hup A incubation, whereas the level of Abeta(Total) was significantly decreased, suggesting an inhibitory effect of Hup A on Abeta production. Hup A-induced alphaAPPs release was significantly reduced by the protein kinase C (PKC) inhibitors GF109203X and Calphostin C. These data, together with the finding that the PKCalpha level was enhanced prior to the increase of alphaAPPs secretion, indicate that PKC may be involved in Hup A-induced alphaAPPs secretion by HEK293 APPsw cells. Our data suggest alternative pharmacological mechanisms of Hup A relevant to the treatment of Alzheimer's disease.
- SourceAvailable from: David H Small
[Show abstract] [Hide abstract]
- "Besides the design of new inhibitors with the capacity to block catalytic and peripheral anionic sites of AChE, there is evidence that inhibitors may also influence APP processing. AChE-Is have been shown to alter APP expression and metabolism in cellular (Lahiri et al., 1994; Pakaski et al., 2001; Peng et al., 2006) and animal models (Mori et al., 1995; Zimmermann et al., 2004; Dong et al., 2009), as well in AD-treated patients (Clarke et al., 2001; Basun et al., 2002; Zimmermann et al., 2005). The modulatory effects of AChE-I on APP metabolism have been attributed to their effect on ADAM10/α-secretase (Zimmermann et al., 2004; Peng et al., 2006), BACE1/β-secretase (Lahiri et al., 2007; Fu et al., 2008; Li et al., 2010), and on PS1/Γ-secretase (Silveyra et al., 2011b). "
ABSTRACT: A common feature in the Alzheimer's disease (AD) brain is the presence of acetylcholinesterase (AChE) which is commonly associated with β-amyloid plaques and neurofibrillary tangles (NFT). Although our understanding of the relationship between AChE and the pathological features of AD is incomplete, increasing evidence suggests that both β-amyloid protein (Aβ) and abnormally hyperphosphorylated tau (P-tau) can influence AChE expression. We also review recent findings which suggest the possible role of AChE in the development of a vicious cycle of Aβ and P-tau dysregulation and discuss the limited and temporary effect of therapeutic intervention with AChE inhibitors.Frontiers in Molecular Neuroscience 09/2011; 4:22. DOI:10.3389/fnmol.2011.00022 · 4.08 Impact Factor
[Show abstract] [Hide abstract]
- "HupA has several beneficial effects for AD patients (Wang et al, 2006a) and, in China it is one of the most commonly prescribed drugs for many forms of dementia, including AD (Zhang et al, 2008b). Apart from its well-known inhibitory effect on AChE (Zhu and Giacobini, 1995; Cheng et al, 1996; Cheng and Tang, 1998), HupA is considered to have multiple neuroprotective effects including anti-inflammatory and antioxidant properties (Wang and Tang, 2007; Wang et al, 2008; Zhang et al, 2008a), stimulation of the release of soluble a-secretasederived fragments of APP (sAPPa) (Zhang et al, 2004; Peng et al, 2006; Yan et al, 2007), protection against Ab and glutamate-induced neurotoxicity, and regulation of nerve growth factor (Ved et al, 1997; Tang et al, 2005). "
ABSTRACT: Huperzine A (HupA) is a reversible and selective inhibitor of acetylcholinesterase (AChE), and it has multiple targets when used for Alzheimer's disease (AD) therapy. In this study, we searched for new mechanisms by which HupA could activate Wnt signaling and reduce amyloidosis in AD brain. A nasal gel containing HupA was prepared. No obvious toxicity of intranasal administration of HupA was found in mice. HupA was administered intranasally to β-amyloid (Aβ) precursor protein and presenilin-1 double-transgenic mice for 4 months. We observed an increase in ADAM10 and a decrease in BACE1 and APP695 protein levels and, subsequently, a reduction in Aβ levels and Aβ burden were present in HupA-treated mouse brain, suggesting that HupA enhances the nonamyloidogenic APP cleavage pathway. Importantly, our results further showed that HupA inhibited GSK3α/β activity, and enhanced the β-catenin level in the transgenic mouse brain and in SH-SY5Y cells overexpressing Swedish mutation APP, suggesting that the neuroprotective effect of HupA is not related simply to its AChE inhibition and antioxidation, but also involves other mechanisms, including targeting of the Wnt/β-catenin signaling pathway in AD brain.Neuropsychopharmacology: official publication of the American College of Neuropsychopharmacology 02/2011; 36(5):1073-89. DOI:10.1038/npp.2010.245 · 7.83 Impact Factor
[Show abstract] [Hide abstract]
- "Western blot was performed as previously reported (Peng et al., 2006). TBS-brain homogenates were used to detect αAPPs, C3, and iNOS levels, while TBS-T brain homogenates were used to examine total APP, CD68, F4/80 and synaptophysin levels. "
ABSTRACT: Complement factor C3 is the central component of the complement system and a key inflammatory protein activated in Alzheimer's disease (AD). Previous studies demonstrated that inhibition of C3 by overexpression of soluble complement receptor-related protein y in an AD mouse model led to reduced microgliosis, increased amyloid beta (Abeta) plaque burden, and neurodegeneration. To further address the role of C3 in AD pathology, we generated a complement C3-deficient amyloid precursor protein (APP) transgenic AD mouse model (APP;C3(-/-)). Brains were analyzed at 8, 12, and 17 months of age by immunohistochemical and biochemical methods and compared with age-matched APP transgenic mice. At younger ages (8-12 months), no significant neuropathological differences were observed between the two transgenic lines. In contrast, at 17 months of age, APP;C3(-/-) mice showed significant changes of up to twofold increased total Abeta and fibrillar amyloid plaque burden in midfrontal cortex and hippocampus, which correlated with (1) significantly increased Tris-buffered saline (TBS)-insoluble Abeta(42) levels and reduced TBS-soluble Abeta(42) and Abeta(40) levels in brain homogenates, (2) a trend for increased Abeta levels in the plasma, (3) a significant loss of neuronal-specific nuclear protein-positive neurons in the hippocampus, and (4) differential activation of microglia toward a more alternative phenotype (e.g., significantly increased CD45-positive microglia, increased brain levels of interleukins 4 and 10, and reduced levels of CD68, F4/80, inducible nitric oxide synthase, and tumor necrosis factor). Our results suggest a beneficial role for complement C3 in plaque clearance and neuronal health as well as in modulation of the microglia phenotype.The Journal of Neuroscience : The Official Journal of the Society for Neuroscience 07/2008; 28(25):6333-41. DOI:10.1523/JNEUROSCI.0829-08.2008 · 6.75 Impact Factor