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Humanin (HN) and its derivatives, such as Colivelin (CLN), suppress neuronal death induced by insults related to Alzheimer's disease (AD) by activating STAT3 in vitro. They also ameliorate functional memory impairment of mice induced by anticholinergic drugs or soluble toxic amyloid-β (Aβ) in vivo when either is directly administered into the cerebral ventricle or intraperitoneally injected. However, the mechanism underlying the in vivo effect remains uncharacterized. In addition, from the standpoint of clinical application, drug delivery methods that are less invasive and specific to the central nervous system (CNS) should be developed. In this study, we show that intranasally (i.n.) administered CLN can be successfully transferred to CNS via the olfactory bulb. Using several behavioral tests, we have demonstrated that i.n. administered CLN ameliorates memory impairment of AD models in a dose-responsive manner. Attenuation of AD-related memory impairment by HN derivatives such as CLN appears to be correlated with an increase in STAT3 phosphorylation levels in the septohippocampal region, suggesting that anti-AD activities of HN derivatives may be mediated by activation of STAT3 in vivo as they are in vitro. We further demonstrate that CLN treatment inhibits an Aβ induced decrease in the number of choline acetyltransferase (ChAT)-positive neurons in the medial septum. Combined with the finding that HN derivatives upregulate mRNA expression of neuronal ChAT and vesicular acetylcholine transporter (VAChT) in vitro, it is assumed that CLN may ameliorate memory impairment of AD models by supporting cholinergic neurotransmission, which is at least partly mediated by STAT3-mediated transcriptional upregulation of ChAT and VAChT.Neuropsychopharmacology (2008) 33, 2020–2032; doi:10.1038/sj.npp.1301591; published online 10 October 2007 [ABSTRACT FROM AUTHOR]

Alzheimer's disease (AD) is the most common cause of dementia. Humanin (HN) is a short bioactive peptide abolishing neuronal cell death induced by various familial AD (FAD)-causative genes and amyloid-β (Aβ) in vitro. It has been shown that HN suppresses memory impairment of mice induced by intracerebroventricular administration of Aβ. To potentiate the neuroprotective effect of HN, we synthesized a hybrid peptide named Colivelin composed of activity-dependent neurotrophic factor (ADNF) C-terminally fused to AGA-(C8R)HNG17, a potent HN derivative. Colivelin completely suppresses death induced by overexpressed FAD-causative genes and Aβ-43 at a concentration of 100 fM, whereas AGA-(CSR)HNG17 does so at a concentration of 10 pM. Colivelin-induced neuroprotection has been confirmed to occur via two neuroprotective pathways: one mediated by Ca2+/calmodulin-dependent protein kinase IV, triggered by ADNF, and one mediated by signal transducer and activator of transcription 3, triggered by HN. In vivo animal studies have further indicated that intracerebroventricular administration of Colivelin not only completely suppresses impairment in spatial working memory induced by repetitive intracerebroventricular injection of Aβ25-35 or Aβ1-42, but also it antagonizes neuronal loss in the CA1 region of hippocampus induced by hippocampal injection of Aβ1-42. In addition, intraperitoneally administered Colivelin suppresses memory impairment caused by a muscarinic acetylcholine receptor antagonist, 3-quinuclidinyl benzilate, indicating that a substantial portion of intraperitoneally administered Colivelin passes through the blood-brain barrier and suppresses functional memory deficit. Thus, Colivelin might serve as a novel drug candidate for treatment of AD. [ABSTRACT FROM AUTHOR]

APP, amyloid beta precursor protein, is linked to the onset of Alzheimer's disease (AD). We have here found that transforming growth factor beta2 (TGFbeta2), but not TGFbeta1, binds to APP. The binding affinity of TGFbeta2 to APP is lower than the binding affinity of TGFbeta2 to the TGFbeta receptor. On binding to APP, TGFbeta2 activates an APP-mediated death pathway via heterotrimeric G protein G(o), c-Jun N-terminal kinase, NADPH oxidase, and caspase 3 and/or related caspases. Overall degrees of TGFbeta2-induced death are larger in cells expressing a familial AD-related mutant APP than in those expressing wild-type APP. Consequently, superphysiological concentrations of TGFbeta2 induce neuronal death in primary cortical neurons, whose one allele of the APP gene is knocked in with the V642I mutation. Combined with the finding indicated by several earlier reports that both neural and glial expression of TGFbeta2 was upregulated in AD brains, it is speculated that TGFbeta2 may contribute to the development of AD-related neuronal cell death.

Humanin (HN) is a 24-amino acid peptide that protects neuronal cells from death caused by Alzheimer's disease (AD)-related genes and amyloid-beta (Abeta). Multiple studies have revealed its biochemical and neuroprotective characteristics in vitro; however, little has been known regarding whether HN is effective in vivo in AD model systems. We examined the effect of S14G-HN, a 1,000-fold more potent derivative of HN in vitro, on amnesia induced by Abeta25-35 in mice. The Y-maze test revealed that at least 50 pmol of S14G-HN by intracerebroventricular injection prevented Abeta-induced impairment of short-term/spatial working memory; however, 5 nmol of S14A-HN, a neuroprotection-defective mutant in vitro, did not prevent Abeta-induced amnesia. These results are in agreement with the structure-function correlation shown previously in vitro. In the water-finding task, S14G-HN prevented prolongation of finding latency (the time to find water) observed in Abeta-amnesic mice, indicating that S14G-HN also blocked Abeta-induced impairment of latent learning. In accordance with these observations, immunohistochemical analysis showed that S14G-HN sustained the number of cholinergic neurons in the basal forebrain and the striata nearly to the normal level. Furthermore, genistein, a specific inhibitor of tyrosine kinases, blocked recovery from scopolamine-induced amnesia by S14G-HN, suggesting that certain tyrosine kinase(s) are involved in the inhibitory function of S14G-HN in vivo. Taking these findings together, we conclude that S14G-HN has rescue activity against memory impairment caused by AD-related insults in vivo by activating the same intracellular neuroprotective machinery as elucidated previously in vitro., (Copyright (c) 2005 Wiley-Liss, Inc.)

The biological function of full-length amyloid-beta protein precursor (AbetaPP), the precursor of Abeta, is not fully understood. Multiple laboratories have reported that antibody binding to cell surface AbetaPP causes neuronal cell death. Here we examined whether induced dimerization of the cytoplasmic domain of AbetaPP (AbetaPPCD) triggers neuronal cell death. In neurohybrid cells expressing fusion constructs of the epidermal growth factor (EGF) receptor with AbetaPPCD (EGFR/AbetaPP hybrids), EGF drastically enhanced neuronal cell death in a manner sensitive to acetyl-l-aspartyl-l-glutamyl-l-valyl-l-aspartyl-aldehyde (Ac-DEVD-CHO; DEVD), GSH-ethyl ester (GEE), and pertussis toxin (PTX). Dominant-negative apoptosis signal-regulating kinase 1 (ASK1) blocked this neuronal cell death, but not alpha-synuclein-induced cell death. Constitutively active ASK1 (caASK1) caused DEVD/GEE-sensitive cell death in a manner resistant to PTX and sensitive to Humanin, which also suppressed neuronal cell death by EGFR/AbetaPP hybrid. ASK1 formed a complex with AbetaPPCD via JIP-1b, the c-Jun N-terminal kinase (JNK)-interacting protein. EGFR/AbetaPP hybrid-induced and caASK1-induced neuronal cell deaths were specifically blocked by SP600125 (anthra[1,9-cd]pyrazol-6(2H)-one), a specific JNK inhibitor. Combined with our earlier study, these data indicate that dimerization of AbetaPPCD triggers ASK1/JNK-mediated neuronal cell death. We also noticed a potential role of ASK1/JNK in sustaining the activity of this mechanism after initial activation by AbetaPP, which allows for the achievement of cell death by short-term anti-AbetaPP antibody treatment. Understanding the function of AbetaPPCD and its downstream pathway should lead to effective anti-Alzheimer's disease therapeutics.