scholarly journals Impairment of amyloid precursor protein alpha-processing in cerebral microvessels of type 1 diabetic mice

2017 ◽  
Vol 39 (6) ◽  
pp. 1085-1098
Author(s):  
Tongrong He ◽  
Ruohan Sun ◽  
Anantha VR Santhanam ◽  
Livius V d'Uscio ◽  
Tong Lu ◽  
...  
Keyword(s):  
Amyloid Precursor Protein ◽  
Precursor Protein ◽  
Local Concentration ◽  
Microvascular Endothelium ◽  
Cerebral Microvessels ◽  
Protein Levels ◽  
Enhanced Production ◽  
Amyloidogenic Processing

The mechanisms underlying dysfunction of cerebral microvasculature induced by type 1 diabetes (T1D) are not fully understood. We hypothesized that in cerebral microvascular endothelium, α-processing of amyloid precursor protein (APP) is impaired by T1D. In cerebral microvessels derived from streptozotocin (STZ)-induced T1D mice protein levels of APP and its α-processing enzyme, a disintegrin and metalloprotease 10 (ADAM10) were significantly decreased, along with down-regulation of adenylate cyclase 3 (AC3) and enhanced production of thromboxane A2 (TXA2). In vitro studies in human brain microvascular endothelial cells (BMECs) revealed that knockdown of AC3 significantly suppressed ADAM10 protein levels, and that activation of TXA2 receptor decreased APP expression. Furthermore, levels of soluble APPα (sAPPα, a product of α-processing of APP) were significantly reduced in hippocampus of T1D mice. In contrast, amyloidogenic processing of APP was not affected by T1D in both cerebral microvessels and hippocampus. Most notably, studies in endothelial specific APP knockout mice established that genetic inactivation of APP in endothelium was sufficient to significantly reduce sAPPα levels in the hippocampus. In aggregate, our findings suggest that T1D impairs non-amyloidogenic processing of APP in cerebral microvessels. This may exert detrimental effect on local concentration of neuroprotective molecule, sAPPα, in the hippocampus.

scholarly journals Nitrous Oxide Plus Isoflurane Induces Apoptosis and Increases β-Amyloid Protein Levels

2009 ◽  
Vol 111 (4) ◽  
pp. 741-752 ◽  
Author(s):  
Yu Zhen ◽  
Yuanlin Dong ◽  
Xu Wu ◽  
Zhipeng Xu ◽  
Yan Lu ◽  
...  
Keyword(s):  
Nitrous Oxide ◽  
Amyloid Precursor Protein ◽  
Caspase 3 ◽  
Precursor Protein ◽  
Primary Neurons ◽  
Gamma Secretase ◽  
Protein Levels ◽  
Secretase Inhibitor

Background Some anesthetics have been suggested to induce neurotoxicity, including promotion of Alzheimer's disease neuropathogenesis. Nitrous oxide and isoflurane are common anesthetics. The authors set out to assess the effects of nitrous oxide and/or isoflurane on apoptosis and beta-amyloid (Abeta) levels in H4 human neuroglioma cells and primary neurons from naïve mice. Methods The cells or neurons were exposed to 70% nitrous oxide and/or 1% isoflurane for 6 h. The cells or neurons and conditioned media were harvested at the end of the treatment. Caspase-3 activation, apoptosis, processing of amyloid precursor protein, and Abeta levels were determined. Results Treatment with a combination of 70% nitrous oxide and 1% isoflurane for 6 h induced caspase-3 activation and apoptosis in H4 naïve cells and primary neurons from naïve mice. The 70% nitrous oxide plus 1% isoflurane, but neither alone, for 6 h induced caspase-3 activation and apoptosis, and increased levels of beta-site amyloid precursor protein-cleaving enzyme and Abeta in H4-amyloid precursor protein cells. In addition, the nitrous oxide plus isoflurane-induced Abeta generation was reduced by a broad caspase inhibitor, Z-VAD. Finally, the nitrous oxide plus isoflurane-induced caspase-3 activation was attenuated by gamma-secretase inhibitor L-685,458, but potentiated by exogenously added Abeta. Conclusion These results suggest that the common anesthetics nitrous oxide plus isoflurane may promote neurotoxicity by inducing apoptosis and increasing Abeta levels. The generated Abeta may further potentiate apoptosis to form another round of apoptosis and Abeta generation. More studies, especially the in vivo confirmation of these in vitro findings, are needed.

Abstract TP486: Role of Beta-Site Amyloid Precursor Protein-Cleaving Enzyme 2 in the Metabolism of Amyloid Precursor Protein in Human Brain Microvascular Endothelial Cells

Stroke ◽  
2020 ◽  
Vol 51 (Suppl_1) ◽  
Author(s):  
Tongrong He ◽  
Zvonimir S Katusic
Keyword(s):  
Protein Expression ◽  
Amyloid Precursor Protein ◽  
Precursor Protein ◽  
Protective Function ◽  
Protein Levels ◽  
Genetic Inactivation ◽  
Amyloidogenic Processing ◽  
Protein Expressions ◽  
App Metabolism

Under physiological conditions, β-site amyloid precursor protein (APP)-cleaving enzyme 2 (BACE2) cleaves APP within Aβ sequence thereby functioning like a α-secretase. However, BACE2 could also function as a conditional β-secretase during aging, contributing to Alzheimer’s disease pathogenesis. To date the physiological functions of BACE2 in endothelium are largely unknown. The present study is therefore designed to investigate the role of BACE2 in APP metabolism in human BMECs. Cultured human BMECs (passage 5-6 or passage 22) were treated with BACE2siRNA (30 nM, for 3 days), levels of soluble APPα (sAPPα, a neurotrophic product of non-amyloidogenic processing of APP) and Aβ40 in the supernatant were measured. In human BMECs (passage 5-6), genetic inactivation of BACE2 significantly decreased production of sAPPα (n=12, P<0.05), but had no effect on production of Aβ40 (n=9, P>0.05). BACE2siRNA treatment significantly suppressed APP protein expression (n=7, P<0.05), but augmented protein levels of BACE1 (n=7, P<0.05). Genetic inactivation of BACE2 did not change protein levels of mature ADAM10 (n=7, P>0.05). Thus, reduced sAPPα secretion by BACE2siRNA treatment is likely caused not only by decreased α-secretase-like function of BACE2, but also by reduced APP expression. We further examined the effects of BACE2siRNA in senescent human BMECs. In cultured human BMECs (passage 22), protein expressions of senescent markers (p 21Cip1 and p 16INK4a ) were significantly increased (n=4, P<0.05). Genetic inactivation of BACE2 in senescent human BMECs also significantly suppressed secretion of sAPPα (n=8, P<0.05), but did not affect Aβ40 production (n=8, P>0.05). BACE2-siRNA treatment significantly inhibited protein expressions of APP and mature ADAM10 (n=7, P<0.05), but did not change BACE1 protein expression (n=7, P>0.05). Thus in senescent human BMECs, reduced APP expression and impaired α-processing may play important roles in the decreased sAPPα production. Since our previous studies have demonstrated that endothelial production of sAPPα significantly contributes to the sAPPα content in the hippocampus, our current findings suggests that inhibition of BACE2 could impair protective function of sAPPα in the hippocampus.

scholarly journals Role of prostacyclin signaling in endothelial production of soluble amyloid precursor protein-α in cerebral microvessels

2016 ◽  
Vol 37 (1) ◽  
pp. 106-122 ◽  
Author(s):  
Tongrong He ◽  
Anantha Vijay R Santhanam ◽  
Tong Lu ◽  
Livius V d'Uscio ◽  
Zvonimir S Katusic
Keyword(s):  
Endothelial Cells ◽  
Amyloid Precursor Protein ◽  
Precursor Protein ◽  
Microvascular Endothelial Cells ◽  
Brain Microvascular Endothelial Cells ◽  
Cerebral Microvessels ◽  
Protein Levels ◽  
Selective Agonist ◽  
Ip Receptor

We tested hypothesis that activation of the prostacyclin (PGI2) receptor (IP receptor) signaling pathway in cerebral microvessels plays an important role in the metabolism of amyloid precursor protein (APP). In human brain microvascular endothelial cells activation of IP receptor with the stable analogue of PGI2, iloprost, stimulated expression of amyloid precursor protein and a disintegrin and metalloprotease 10 (ADAM10), resulting in an increased production of the neuroprotective and anticoagulant molecule, soluble APPα (sAPPα). Selective agonist of IP receptor, cicaprost, and adenylyl cyclase activator, forskolin, also enhanced expression of amyloid precursor protein and ADAM10. Notably, in cerebral microvessels of IP receptor knockout mice, protein levels of APP and ADAM10 were reduced. In addition, iloprost increased protein levels of peroxisome proliferator-activated receptor δ (PPARδ) in human brain microvascular endothelial cells. PPARδ-siRNA abolished iloprost-augmented protein expression of ADAM10. In contrast, GW501516 (a selective agonist of PPARδ) upregulated ADAM10 and increased production of sAPPα. Genetic deletion of endothelial PPARδ (ePPARδ−/−) in mice significantly reduced cerebral microvascular expression of ADAM10 and production of sAPPα. In vivo treatment with GW501516 increased sAPPα content in hippocampus of wild type mice but not in hippocampus of ePPARδ−/− mice. Our findings identified previously unrecognized role of IP-PPARδ signal transduction pathway in the production of sAPPα in cerebral microvasculature.

scholarly journals Ubiquilin-1 Is a Molecular Chaperone for the Amyloid Precursor Protein

2011 ◽  
Vol 286 (41) ◽  
pp. 35689-35698 ◽  
Author(s):  
Emily S. Stieren ◽  
Amina El Ayadi ◽  
Yao Xiao ◽  
Efraín Siller ◽  
Megan L. Landsverk ◽  
...  
Keyword(s):  
Amyloid Precursor Protein ◽  
Molecular Chaperone ◽  
Late Onset ◽  
Precursor Protein ◽  
Common Denominator ◽  
Nucleotide Polymorphisms ◽  
Protein Levels ◽  
Bona Fide ◽  
Complex Forms

Alzheimer disease (AD) is associated with extracellular deposition of proteolytic fragments of amyloid precursor protein (APP). Although mutations in APP and proteases that mediate its processing are known to result in familial, early onset forms of AD, the mechanisms underlying the more common sporadic, yet genetically complex forms of the disease are still unclear. Four single-nucleotide polymorphisms within the ubiquilin-1 gene have been shown to be genetically associated with AD, implicating its gene product in the pathogenesis of late onset AD. However, genetic linkage between ubiquilin-1 and AD has not been confirmed in studies examining different populations. Here we show that regardless of genotype, ubiquilin-1 protein levels are significantly decreased in late onset AD patient brains, suggesting that diminished ubiquilin function may be a common denominator in AD progression. Our interrogation of putative ubiquilin-1 activities based on sequence similarities to proteins involved in cellular quality control showed that ubiquilin-1 can be biochemically defined as a bona fide molecular chaperone and that this activity is capable of preventing the aggregation of amyloid precursor protein both in vitro and in live neurons. Furthermore, we show that reduced activity of ubiquilin-1 results in augmented production of pathogenic amyloid precursor protein fragments as well as increased neuronal death. Our results support the notion that ubiquilin-1 chaperone activity is necessary to regulate the production of APP and its fragments and that diminished ubiquilin-1 levels may contribute to AD pathogenesis.

scholarly journals Gleevec Increases Levels of the Amyloid Precursor Protein Intracellular Domain and of the Amyloid-β–degrading Enzyme Neprilysin

2007 ◽  
Vol 18 (9) ◽  
pp. 3591-3600 ◽  
Author(s):  
Yvonne S. Eisele ◽  
Matthias Baumann ◽  
Bert Klebl ◽  
Christina Nordhammer ◽  
Mathias Jucker ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Amyloid Precursor Protein ◽  
Kinase Inhibitor ◽  
Amyloid Β ◽  
Precursor Protein ◽  
Intracellular Domain ◽  
Degrading Enzyme ◽  
Protein Levels

Amyloid-β (Aβ) deposition is a major pathological hallmark of Alzheimer's disease. Gleevec, a known tyrosine kinase inhibitor, has been shown to lower Aβ secretion, and it is considered a potential basis for novel therapies for Alzheimer's disease. Here, we show that Gleevec decreases Aβ levels without the inhibition of Notch cleavage by a mechanism distinct from γ-secretase inhibition. Gleevec does not influence γ-secretase activity in vitro; however, treatment of cell lines leads to a dose-dependent increase in the amyloid precursor protein intracellular domain (AICD), whereas secreted Aβ is decreased. This effect is observed even in presence of a potent γ-secretase inhibitor, suggesting that Gleevec does not activate AICD generation but instead may slow down AICD turnover. Concomitant with the increase in AICD, Gleevec leads to elevated mRNA and protein levels of the Aβ-degrading enzyme neprilysin, a potential target gene of AICD-regulated transcription. Thus, the Gleevec mediated-increase in neprilysin expression may involve enhanced AICD signaling. The finding that Gleevec elevates neprilysin levels suggests that its Aβ-lowering effect may be caused by increased Aβ-degradation.

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