Increasing evidence suggests that the elevation of ␤-amyloid (A␤) peptides in the brain is central to the pathogenesis of Alzheimer's disease (AD). Our recent studies have demonstrated that nobiletin, a polymethoxylated flavone from citrus peels, enhances cAMP/protein kinase A/extracellular signalregulated kinase/cAMP response element-binding protein signaling in cultured hippocampal neurons and ameliorates A␤-induced memory impairment in AD model rats. For the first time, we report that this natural compound improves memory deficits in amyloid precursor protein (APP) transgenic mice that overexpress human APP695 harboring the double Swedish and London mutations [APP-SL 7-5 transgenic (Tg) mice]. Our enzyme-linked immunosorbent assay (ELISA) also showed that administration of nobiletin to the transgenic mice for 4 months markedly reduced quantity of guanidine-soluble A␤ 1-40 and A␤ 1-42 in the brain. Furthermore, consistent with the results of ELISA, by immunohistochemistry with anti-A␤ antibody, it was evidently shown that the administration of nobiletin decreased the A␤ burden and plaques in the hippocampus of APP-SL 7-5 Tg mice. These findings suggest that this natural compound has potential to become a novel drug for fundamental treatment of AD.

Cancer chemotherapy targeted to angiogenic vessels is expected to cause indirect tumor regression through the damage of the neovasculature without the induction of drug resistance. To develop a tool for neovasculaturespeci®c drug delivery, we isolated novel peptides homing to angiogenic vessels formed by a dorsal air sac method from a phage-displayed peptide library. Three distinct phage clones that markedly accumulated in murine tumor xenografts presented PRPGAPLAGSWPGTS-, DRWRPALPVVLFPLH-or ASSSYPLIHWRPWARpeptide respectively. After the determination of the epitope sequences of these peptides, we modi®ed liposomes with epitope penta-peptides. Liposome modi®ed with APRPG-peptide showed high accumulation in murine tumor xenografts, and APRPG-modi®ed liposome encapsulating adriamycin eectively suppressed experimental tumor growth. Finally, speci®c binding of APRPG-modi®ed liposome to human umbilical endothelial cells, and that of PRP-containing peptide to angiogenic vessels in human tumors, i.e., islet cell tumor and glioblastoma, were demonstrated. The present study indicates the usefulness of APRPG-peptide as a tool for anti-neovascular therapy, a novel modality of cancer treatment.

Two major C-terminal variants ending at Val40 and Ala42 constitute the majority of amyloid ␤-protein (A␤), which undergoes postsecretory aggregation and deposition in the Alzheimer disease (AD) brain. To probe the differential pathobiology of the two A␤ variants, we used an in vivo paradigm in which freshly solubilized A␤1-40 or A␤1-42 was injected into rat brains, followed by examination using Congo red birefringence, A␤ immunohistochemistry, and electron microscopy. In the rat brain, soluble A␤ 1-40 and A␤1-42 formed aggregates, and the A␤1-40 but not the A␤1-42 aggregates showed Congo red birefringence. Electron microscopy revealed that the A␤1-40 aggregates contained fibrillar structures similar to the amyloid fibrils of AD, whereas the A␤1-42 aggregates contained nonfibrillar amorphous material. Preincubation of A␤1-42 solution in vitro led to the formation of birefringent aggregates, and after injection of the preincubated A␤1-42, the aggregates remained birefringent in the rat brain. Thus, a factor or factors might exist in the rat brain that inhibit the fibrillar assembly of soluble A␤1-42. To analyze the postsecretory processing of A␤, we used the same in vivo paradigm and showed that A␤1-40 and A␤1-42 were processed at their N termini to yield variants starting at pyroglutamate, and at their C termini to yield variants ending at Val40 and at Val39. Thus the normal rat brain could produce enzymes that mediate the conversion of A␤ 1-40/1-42 into processed variants similar to those in AD. This experimental paradigm may facilitate efforts to elucidate mechanisms of A␤ deposition evolving into amyloid plaques in AD.

Gangliosides, GM3 and GM1, are suggested to accelerate the deposition of the amyloid beta-protein as amyloid angiopathy and senile plaques, respectively, in the Alzheimer brain. We investigated the profile of amyloid deposition in the brains of transgenic mice expressing a mutant amyloid precursor protein with a disrupted GM2 synthase gene, in which GM3 accumulates whereas GM1 is lacking. These mice showed a significantly increased level of deposited amyloid beta-protein in the vascular tissues. Furthermore, formation of severe dyshoric-form amyloid angiopathy, in which amyloid extended from the blood vessel walls deeply into the surrounding parenchyma was observed. Our results indicate that the expression of gangliosides is a critical determinant for the amyloid pathology in the Alzheimer brain.