Cerebrovascular deposition of amyloid beta-protein (Abeta) is a common pathological feature of Alzheimer's disease and related disorders. In particular, the Dutch E22Q and Iowa D23N mutations in Abeta cause familial cerebrovascular amyloidosis with abundant diffuse amyloid plaque deposits. Both of these charge-altering mutations enhance the fibrillogenic and pathogenic properties of Abeta in vitro. Here, we describe the generation of several transgenic mouse lines (Tg-SwDI) expressing human neuronal Abeta precursor protein (AbetaPP) harboring the Swedish K670N/M671L and vasculotropic Dutch/Iowa E693Q/D694N mutations under the control of the mouse Thy1.2 promoter. Tg-SwDI mice expressed transgenic human AbetaPP only in the brain, but at levels below those of endogenous mouse AbetaPP. Despite the paucity of human AbetaPP expression, quantitative enzyme-linked immunosorbent assay measurements revealed that Tg-SwDI mice developed early-onset and robust accumulation of Abeta in the brain with high association with isolated cerebral microvessels. Tg-SwDI mice exhibited striking perivascular/vascular Abeta deposits that markedly increased with age. The vascular Abeta accumulations were fibrillar, exhibiting strong thioflavin S staining, and occasionally presented signs of microhemorrhage. In addition, numerous largely diffuse, plaque-like structures were observed starting at 3 months of age. In vivo transport studies demonstrated that Dutch/Iowa mutant Abeta was more readily retained in the brain compared with wild-type Abeta. These results with Tg-SwDI mice demonstrate that overexpression of human AbetaPP is not required for early-onset and robust accumulation of both vascular and parenchymal Abeta in mouse brain.

Alzheimer's disease (AD) is characterized by three primary pathologies in the brain: amyloid plaques, neurofibrillary tangles, and neuron loss. Mouse models have been useful for studying components of AD but are limited in their ability to fully recapitulate all pathologies. We crossed the APPSwDI transgenic mouse, which develops amyloid ␤ (A␤)-protein deposits only, with a nitric oxide synthase 2 (NOS2) knock-out mouse, which develops no AD-like pathology. APPSwDI/NOS2 Ϫ/Ϫ mice displayed impaired spatial memory compared with the APPSwDI mice, yet they have unaltered levels of A␤. APPSwDI mice do not show tau pathology, whereas APPSwDI/NOS2 Ϫ/Ϫ mice displayed extensive tau pathology associated with regions of dense microvascular amyloid deposition. Also, APPSwDI mice do not have any neuron loss, whereas the APPSwDI/NOS2 Ϫ/Ϫ mice have significant neuron loss in the hippocampus and subiculum. Neuropeptide Y neurons have been shown to be particularly vulnerable in AD. These neurons appear to be particularly vulnerable in the APPSwDI/ NOS2Ϫ/Ϫ mice as we observe a dramatic reduction in the number of NPY neurons in the hippocampus and subiculum. These data show that removal of NOS2 from an APP transgenic mouse results in development of a much greater spectrum of AD-like pathology and behavioral impairments.

Increasing evidence indicates that cerebrovascular dysfunction plays a pathogenic role in Alzheimer's dementia (AD). Amyloid-β (Aβ), a peptide central to the pathogenesis of AD, has profound vascular effects mediated, for the most part, by reactive oxygen species produced by the enzyme NADPH oxidase. The mechanisms linking Aβ to NADPH oxidase-dependent vascular oxidative stress have not been identified, however. We report that the scavenger receptor CD36, a membrane glycoprotein that binds Aβ, is essential for the vascular oxidative stress and neurovascular dysfunction induced by Aβ 1-40 . Thus, topical application of Aβ 1-40 onto the somatosensory cortex attenuates the increase in cerebral blood flow elicited by neural activity or by endothelium-dependent vasodilators in WT mice but not in CD36-null mice (CD36 0/0 ). The cerebrovascular effects of infusion of Aβ 1-40 into cerebral arteries are not observed in mice pretreated with CD36 blocking antibodies or in CD36 0/0 mice. Furthermore, CD36 deficiency prevents the neurovascular dysfunction observed in transgenic mice overexpressing the Swedish mutation of the amyloid precursor protein Tg2576 despite elevated levels of brain Aβ 1-40 . CD36 is also required for the vascular oxidative stress induced by exogenous Aβ 1-40 or observed in Tg2576 mice. These observations establish CD36 as a key link between Aβ 1-40 and the NADPH oxidase-dependent vascular oxidative stress underlying the neurovascular dysfunction and suggest that CD36 is a potential therapeutical target to counteract the cerebrovascular dysfunction associated with Aβ.Alzheimer's disease | functional hyperemia | Nox2 | receptor for advanced glycation end-products T here is increasing evidence that vascular factors play a significant role in the pathogenesis of Alzheimer's dementia (AD) (1, 2). Whereas the structure of cerebral blood vessels is altered in AD, cerebral blood flow (CBF) is reduced even in the early stages of the disease (3). Epidemiological studies have shown that cerebrovascular diseases and AD share similar risk factors, suggesting a pathogenic commonality (4). Furthermore, small ischemic lesions amplify the cognitive dysfunction linked to amyloid plaques and neurofibrillary tangles, the neuropathological hallmarks of AD (5, 6). These observations have suggested an interaction between vascular insufficiency and the clinical expression of AD, raising the possibility that cerebrovascular dysfunction promotes the disease process underlying the dementia (1, 4, 7).Amyloid-β (Aβ), the amyloid precursor protein (APP)-derived peptide central to AD pathogenesis, has profound cerebrovascular effects that disrupt the brain's blood supply and render the brain more vulnerable to injury (3). The survival of the brain depends on continuous and well-regulated delivery of blood to ensure that its energy requirements are met and that deleterious metabolic byproducts are cleared from the neuronal microenvironment (8). Consequently, sophisticated vascular control mechanisms ensure that the brain receives a...

Cerebral microvascular amyloid ␤ protein (A␤) deposition and associated neuroinflammation is increasingly recognized as an important component leading to cognitive impairment in Alzheimer's disease and related cerebral amyloid angiopathy disorders. Transgenic mice expressing the vasculotropic Dutch/Iowa (E693Q/D694N) mutant human A␤ precursor protein in brain (Tg-SwDI) accumulate abundant cerebral microvascular fibrillar amyloid deposits and exhibit robust neuroinflammation. In the present study, we investigated the effect of the anti-inflammatory drug minocycline on A␤ accumulation, neuroinflammation, and behavioral deficits in Tg-SwDI mice. Twelve-month-old mice were treated with saline or minocycline by intraperitoneal injection every other day for a total of 4 weeks. During the final week of treatment, the mice were tested for impaired learning and memory. Brains were then harvested for biochemical and immunohistochemical analysis. Minocycline treatment did not alter the cerebral deposition of A␤ or the restriction of fibrillar amyloid to the cerebral microvasculature. Similarly, minocycline-treated Tg-SwDI mice exhibited no change in the levels of total A␤, the ratios of A␤40 and A␤42, or the amounts of soluble, insoluble, or oligomeric A␤ compared with the saline-treated control Tg-SwDI mice. In contrast, the numbers of activated microglia and levels of interleukin-6 were significantly reduced in minocycline-treated Tg-SwDI mice compared with saline-treated Tg-SwDI mice. In addition, there was a significant improvement in behavioral performance of the minocycline-treated Tg-SwDI mice. These finding suggest that anti-inflammatory treatment targeted for cerebral microvascular amyloid-induced microglial activation can improve cognitive deficits without altering the accumulation and distribution of A␤.

Background and Purpose Accumulation of amyloid-β in cerebral blood vessels occurs in familial and sporadic forms of cerebral amyloid angiopathy and is a prominent feature of Alzheimer disease. However, the functional correlates of the vascular pathology induced by cerebral amyloid angiopathy and the mechanisms involved have not been fully established. Methods We used male transgenic mice expressing the Swedish, Iowa, and Dutch mutations of the amyloid precursor protein (Tg-SwDI) to examine the effect of cerebral amyloid angiopathy on cerebrovascular structure and function. Somatosensory cortex cerebral blood flow was monitored by laser-Doppler flowmetry in anesthetized Tg-SwDI mice and wild-type littermates equipped with a cranial window. Results Tg-SwDI mice exhibited reductions in cerebral blood flow responses to whisker stimulation, endothelium-dependent vasodilators, or hypercapnia at 3 months when compared with wild-type mice, whereas the response to adenosine was not attenuated. However, at 18 and 24 months, all cerebrovascular responses were markedly reduced. At this time, there was evidence of cerebrovascular amyloid deposition, smooth muscle fragmentation, and pericyte loss. Neocortical superfusion with the free radical scavenger manganic(I–II)meso-tetrakis(4-benzoic acid) porphyrin rescued endothelium-dependent responses and functional hyperemia completely at 3 months but only partially at 18 months. Conclusions Tg-SwDI mice exhibit a profound age-dependent cerebrovascular dysfunction, involving multiple regulatory mechanisms. Early in the disease process, oxidative stress is responsible for most of the vascular dysfunction, but with advancing disease structural alterations of the vasomotor apparatus also play a role. Early therapeutic interventions are likely to have the best chance to counteract the deleterious vascular effects of cerebral amyloid angiopathy.