Search

Background: Neurotoxicity induced by the amyloid beta (Aβ) peptide is one of the most important pathological mechanisms of Alzheimer's disease (AD). Activation of the adaptive IRE1α-XBP1 pathway contributes to the pathogenesis of AD, making it a potential target for AD therapeutics. However, the mechanism of IRE1α-XBP1 pathway involvement in AD is unclear. We, therefore, investigated the effect of the IRE1α-XBP1 axis in an in vitro AD model and explored its potential mechanism. Methods: The human neuroblastoma cell line, SH-SY5Y, was used. Cells were treated with Aβ25–35, with or without 4μ8c, an inhibitor of IRE1α. Cells were collected and analyzed by Western blotting, quantitative real-time PCR, electron microscopy, fluorescence microscopy, calcium imaging, and other biochemical assays. Results: Aβ-exposed SH-SY5Y cells showed an increased expression of XBP1s and p-IRE1α. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and calcium imaging analysis showed that the IRE1α inhibitor, 4μ8c, reduced Aβ-induced cytotoxicity. Increased levels of ATP, restoration of mitochondrial membrane potential, and decreased production of mitochondrial reactive oxygen species after Aβ treatment in the presence of 4μ8c showed that inhibiting the IRE1α-XBP1 axis effectively mitigated Aβ-induced mitochondrial dysfunction in SH-SY5Y cells. Furthermore, Aβ treatment increased the expression and interaction of IP3R, Grp75, and vdac1 and led to an increased endoplasmic reticulum (ER)–mitochondria association, malfunction of mitochondria-associated ER-membranes (MAMs), and mitochondrial dysfunction. These deficits were rescued by inhibiting the IRE1α-XBP1 axis. Conclusion: These findings demonstrate that Aβ peptide induces the activation of the IRE1α-XBP1 axis, which may aggravate cytotoxicity and mitochondrial impairment in SH-SY5Y cells by targeting MAMs. Inhibition of the IRE1α-XBP1 axis provides the protection against Aβ-induced injury in SH-SY5Y cells and may, therefore, be a new treatment strategy. [ABSTRACT FROM AUTHOR]

Mitochondrial dysfunction plays a key role in the pathogenesis and progression of Alzheimer's Disease (AD). Our previous studies showed that over expression of AD‐associated mutant β‐amyloid precursor protein (APP) led to abnormalities of mitochondrial biogenesis and mitophagy, leading to mitochondrial dysfunction. However, the mechanism remains unclear. In this study, we investigated the effect of orexin‐A on mitochondrial biogenesis, mitophagy and mitochondrial structure in overexpression of AD‐associated mutant APP cells. We used 20E2 cells as the AD cell model. 20E2 cells were treated with orexin‐A (50, 100 nmol/L). The effect of different concentrations of orexin‐A on cell activity was detected by MTT. As compared with the non‐treated 20E2 cells, orexin‐A‐treated 20E2 cells showed increased expression of APP, decreased cell viability and decreased adenosine triphosphate (ATP) level, decreased levels of regulatory proteins of mitochondrial biogenesis (peroxisome proliferator‐activated receptor gamma coactivator 1‐alpha [PGC‐1α], nuclear respiratory factor 1/2 [NRF1/2], mitochondrial transcription factor A [TFAM]), increased levels of regulatory proteins of mitophagy (Parkin, PTEN‐induced putative kinase 1 [PINK1], microtubule‐associated protein light chain 3 II/I [LC3‐II/LC3‐I]) and decreased p62 level, with damaged mitochondrial structure. Orexin‐A may reduce mitochondrial biogenesis, enhance mitophagy and damage mitochondrial structure in AD. [ABSTRACT FROM AUTHOR]

Mitochondrial dysfunction is a prominent feature of Alzheimer's disease (AD). As vascular endothelial growth factor (VEGF) has been shown to be protective in AD, the aim of this study was to investigate the effects of VEGF on mitochondrial function in models of AD. Adeno associated virus (AAV)-VEGF was injected into the hippocampus of APP/PS1 mice. Cognitive function was assessed in these mice with use of the Morris water maze (MWM) and β-amyloid (Aβ) levels in the hippocampus were also measured. Cell viability and reactive oxygen species (ROS) levels were determined in the SH-SY5Y cells treated with Aβ25–35 which served as a cell model of AD. Transmission electron microscopy (TEM) was used to evaluate structural changes in mitochondria and mitochondrial DNA (mtDNA) copy number and mitochondrial membrane potential (MMP) were also recorded. Finally, we investigated the effects of VEGF upon mitochondrial biogenesis, autophagy and mitochondrial autophagy (mitophagy) as determined both in vivo and in vitro with western blots. VEGF treated mice showed improvements in spatial learning and memory along with reduced Aβ levels. VEGF protected SH-SY5Y cells against Aβ25–35 induced neurotoxicity as demonstrated by increased cell viability and decreased ROS production. Associated with these effects were improvements in mitochondrial structure and function, and increased numbers of mitochondria resulting from stimulation of mitochondrial biogenesis. VEGF alleviates Aβ related patholoy in models of AD. In part, these beneficial effects of VEGF result from protection of mitochondria and stimulation of mitochondrial biogenesis. [ABSTRACT FROM AUTHOR]

• Orexin-A aggravated cognitive deficit in APP/PS1 mice. • Orexin-A promoted Aβ accumulation in APP/PS1 mice. • Orexin-A aggravated mitochondrial impairment in APP/PS1 mice. • Orexin-A aggravated mitochondrial impairment in Aβ-treated SH-SY5Y cells. Alzheimer's disease (AD) is a progressive neurodegenerative disease which is characterized by the accumulation of amyloid-β peptide (Aβ). Orexin-A is a neuropeptide which has been reported to participate in the pathogenesis of AD. Thus, we aimed to investigate the possible mechanism by which Orexin-A acts in AD. APP/PS1 transgenic mice, an animal model of AD, were intracerebroventricularly injected with Orexin-A. Aβ-treated SH-SY5Y cells were used as a cell model of AD and treated with Orexin-A. The Morris water maze test, fluorescence microscopy, enzyme-linked immunosorbent assay (ELISA), electron microscopy, real-time PCR, and other biochemical assays were conducted. The Morris water maze test showed that Orexin-A aggravated cognitive deficit in APP/PS1 mice. Using thioflavine-S staining and ELISA, we found that Orexin-A promoted Aβ accumulation in APP/PS1 mice. By evaluating mitochondrial morphology, cytochrome c oxidase activity, ATP level, mitochondrial DNA copy number, and reactive oxygen species, we found that Orexin-A aggravated mitochondrial impairment in APP/PS1 mice and Aβ-treated SH-SY5Y cells. Our results indicate that Orexin-A exacerbates AD by inducing mitochondrial impairment. This is a new mechanism that explains how Orexin-A participates in the pathogenesis of AD. [ABSTRACT FROM AUTHOR]