␥-Secretase, exhibiting characteristics of aspartyl protease, mediates the intramembranous proteolysis of -amyloid precursor protein (APP) and Notch, and it is considered to be a prime pharmacological target in the development of therapeutics for Alzheimer's disease (AD). To identify compounds that block ␥-secretase-mediated proteolysis, we used a highly sensitive cell-based reporter gene assay for ␥-secretase in which Gal4/VP16-tagged C99-APP was expressed as the immediate substrate of ␥-secretase, and Gal4/VP16-tagged APP intracellular domain released by the ␥-secretase cleavage then activated the expression of the Gal4-driven luciferase reporter gene. Using this reporter assay, we demonstrated that the newly synthesized (hydroxyethyl)urea peptidomimetics, which contain unnatural amino acid moieties at positions P1Ј and/or P3Ј, can effectively inhibit ␥-secretase activity and significantly reduce A production. The ␥-secretase-dependent S3 cleavage of Notch was also consistently blocked by these (hydroxyethyl)ureas as evidenced by the decreased generation of the Notch intracellular domain, a prerequisite for the activation of Notch signaling. The inhibition of Notch signaling by active Jia compounds efficiently promotes the neuronal differentiation of neuroblastoma cells, intervening in tumorigenesis and the malignancy of neuroblastomas. Our results suggest that (hydroxyethyl)urea peptidomimetics containing unnatural amino acid substitutions could represent a novel class of ␥-secretase inhibitors with enhanced stability, providing the basis for the further development of effective therapeutics for AD and neuroblastomas.␥-Secretase catalyzes the final proteolytic step in the generation of A (the principal constituent of senile plaques in the AD brain), and it has thus been regarded as a prime therapeutic target for AD. Mounting evidence from pharmacological studies, mutagenesis, affinity labeling, and biochemical isolation strongly suggests that ␥-secretase is an aspartyl protease and that the active site of ␥-secretase is located at the interface of the presenilin (PS) heterodimer (Wolfe and Haass, 2001). The heterodimeric PS consisting of an ϳ30-kDa N-terminal fragment (NTF) and a ϳ20-kDa C-terminal fragment (CTF) is thought to be the active form of PS (Capell et al., 1998). Peptidomimetics that mimic the
PurposeWe sought to imitate angiographic cerebral circulation time (CCT) and create a similar index from baseline CT perfusion (CTP) to better predict vasospasm in patients with subarachnoid hemorrhage (SAH).MethodsForty-one SAH patients with available DSA and CTP were retrospectively included. The vasospasm group was comprised of patients with deterioration in conscious functioning and newly developed luminal narrowing; remaining cases were classified as the control group. The angiography CCT (XA-CCT) was defined as the difference in TTP (time to peak) between the selected arterial ROIs and the superior sagittal sinus (SSS). Four arterial ROIs were selected to generate four corresponding XA-CCTs: the right and left anterior cerebral arteries (XA-CCTRA2 and XA-CCTLA2) and right- and left-middle cerebral arteries (XA-CCTRM2 and XA-CCTLM2). The CCTs from CTP (CT-CCT) were defined as the differences in TTP from the corresponding arterial ROIs and the SSS. Correlations of the different CCTs were calculated and diagnostic accuracy in predicting vasospasm was evaluated.ResultsIntra-class correlations ranged from 0.96 to 0.98. The correlations of XA-CCTRA2, XA-CCTRM2, XA-CCTLA2, and XA-CCTLM2 with the corresponding CT-CCTs were 0.64, 0.65, 0.53, and 0.68, respectively. All CCTs were significantly prolonged in the vasospasm group (5.8–6.4 s) except for XA-CCTLA2. CT-CCTA2 of 5.62 was the optimal cut-off value for detecting vasospasm with a sensitivity of 84.2% and specificity 82.4%ConclusionCT-CCTs can be used to interpret cerebral flow without deconvolution algorithms, and outperform both MTT and TTP in predicting vasospasm risk. This finding may help facilitate management of patients with SAH.
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