Amyloid precursor protein mediates monocyte adhesion in AD tissue and apoE(-)/(-) mice

Salivary Aβ Secretion and Altered Oral Microbiome in Mouse Models of AD

BACKGROUND

Beta amyloid (Aβ) peptide containing plaque aggregations in the brain are a hallmark of Alzheimer's Disease (AD). However, Aβ is produced by cell types outside of the brain suggesting that the peptide may serve a broad physiologic purpose.

OBJECTIVE

Based upon our prior work documenting expression of amyloid β precursor protein (APP) in intestinal epithelium we hypothesized that salivary epithelium might also express APP and be a source of Aβ.

METHODS

To begin testing this idea, we compared human age-matched control and AD salivary glands to C57BL/6 wild type, App^NL-G-F , and APP/PS1 mice.

RESULTS

Both male and female AD, App^NL-G-F , and APP/PS1 glands demonstrated robust APP and Aβ immunoreactivity. Female App^NL-G-F mice had significantly higher levels of pilocarpine stimulated Aβ 1-42 compared to both wild type and APP/PS1 mice. No differences in male salivary Aβ levels were detected. No significant differences in total pilocarpine stimulated saliva volumes were observed in any group. Both male and female App^NL-G-F but not APP/PS1 mice demonstrated significant differences in oral microbiome phylum and genus abundance compared to wild type mice. Male, but not female, APP/PS1 and App^NL-G-F mice had significantly thinner molar enamel compared to their wild type counterparts.

CONCLUSION

These data support the idea that oral microbiome changes exist during AD in addition to changes in salivary Aβ and oral health.

Integrated Network and Gene Ontology Analysis Identifies Key Genes and Pathways for Coronary Artery Diseases

BACKGROUND

The prevalence of Coronary Artery Disease (CAD) in developing countries is on the rise, owing to rapidly changing lifestyle. Therefore, it is imperative that the underlying genetic and molecular mechanisms be understood to develop specific treatment strategies. Comprehensive disease network and Gene Ontology (GO) studies aid in prioritizing potential candidate genes for CAD and also give insights into gene function by establishing gene and disease pathway relationships.

METHODS

In the present study, CAD-associated genes were collated from different data sources and protein-protein interaction network was constructed using STRING. Highly interconnected network clusters were inferred and GO analysis was performed.

RESULTS

Interrelation between genes and pathways were analyzed on ClueGO and 38 candidates were identified from 1475 CAD-associated genes, which were significantly enriched in CAD-related pathways such as metabolism and regulation of lipid molecules, platelet activation, macrophage derived foam cell differentiation, and blood coagulation and fibrin clot formation.

DISCUSSION

Integrated network and ontology analysis enables biomarker prioritization for common complex diseases such as CAD. Experimental validation and future studies on the prioritized genes may reveal valuable insights into CAD development mechanism and targeted treatment strategies.

Monocytes in the Peripheral Clearance of Amyloid-β and Alzheimer's Disease

Aging societies have high incidence rates of Alzheimer's disease (AD). AD is diagnosed at later disease stages and has a poor prognosis, and effective drugs and treatments for AD are lacking. The molecular mechanism of AD is not clear, and current research focuses primarily on amyloid-β (Aβ) deposition and tau protein hyperphosphorylation. Aβ deposition is the most frequently hypothesized initiating factor of AD, and Aβ clearance during the pathogenesis of AD may be an optional strategy to suppress AD development. Monocytes play important roles in the peripheral clearance of Aβ. Therefore, the present review summarizes our current knowledge of the potential roles of infiltrating macrophages, circulating monocytes, and Kupffer cells in the peripheral clearance of Aβ in AD.

Herpud1 deficiency could reduce amyloid-β40 expression and thereby suppress homocysteine-induced atherosclerosis by blocking the JNK/AP1 pathway

Homocysteine (Hcy) is considered an independent risk factor for various cardiovascular diseases including atherosclerosis which is associated with lipid metabolism, inflammation, and oxidative stress. Results from our previous study suggested that Hcy-induced atherosclerosis could be reversed by Herpud1 knockout which inhibits vascular smooth muscle cell (VSMC) phenotype switching. Here, we aim to investigate more precise mechanisms behind the improvement in Hcy-induced atherosclerosis. Amyloid-β40 (Aβ40), a vital protein in Alzheimer disease (AD), has been regarded as an important component in the atherosclerosis program in recent years due to the biological similarity between AD and atherosclerosis. Thus, we determined to assess the value of Aβ40 in a Herpud1 knockout Hcy-induced atherosclerosis mouse model by measuring Aβ40 expression in tissue and biomarkers of lipid metabolism, inflammation, and oxidative stress in serum. Additionally, since endothelial dysfunction plays a prominent role in atherosclerosis, we tested human umbilical vein endothelial cell (HUVEC) function following Herpud1 silencing in vitro and evaluated JNK/AP1 signaling activation in our models because of its close relationship with Aβ40. As a result, our animal models showed that Herpud1 knockout reduced Aβ40 expression, inflammation, and oxidative stress levels other than lipid metabolism and alleviated atherosclerosis via JNK/AP1 signaling inhibition. Similarly, our cell experiments implied that Hcy-induced Aβ40 elevation and HUVEC dysfunction involving cell proliferation and apoptosis could be restored by Herpud1 silence through restraining JNK/AP1 pathway. Collectively, our study demonstrates that Herpud1 deficiency could reduce Aβ40 expression, thereby suppressing Hcy-induced atherosclerosis by blocking the JNK/AP1 pathway. This may provide novel potential targets for atherosclerosis prevention or treatment.

Probiotics ameliorate intestinal pathophysiology in a mouse model of Alzheimer's disease

Evidence suggests that changes in intestinal microbiota may affect the central nervous system. However, it is unclear whether alteration of intestinal microbiota affects progression of Alzheimer's disease (AD). To understand this, wild-type control (C57BL/6) mice were compared with the App^NL-G-F model of disease. We used probiotic supplementation to manipulate the gut microbiota. Fecal samples were collected for microbiota profiling. To study brain and intestinal inflammation, biochemical and histological analyses were performed. Altered metabolic pathways were examined by quantifying eicosanoid and bile acid profiles in the brain and serum using ultraperformance liquid chromatography-tandem mass spectrometry. We observed that brain pathology was associated with intestinal dysbiosis and increased intestinal inflammation and leakiness in App^NL-G-F mice. Probiotic supplementation significantly decreased intestinal inflammation and gut permeability with minimal effect on amyloid-β, cytokine, or gliosis levels in the brain. Concentrations of several bile acids and prostaglandins were altered in the serum and brain because of AD or probiotic supplementation. Our study characterizes intestinal dysfunction in an AD mouse model and the potential of probiotic intervention to ameliorate this condition.

Partial loss of endothelial nitric oxide leads to increased cerebrovascular beta amyloid

Cerebral amyloid angiopathy (CAA) is present in over half of the elderly population and in 80-90% of Alzheimer's disease (AD) patients. CAA is defined by the deposition of beta amyloid (Aβ) in small cerebral arteries and capillaries. Cardiovascular risk factors are associated with an increased incidence of CAA. We utilized 18-month-old endothelial nitric oxide synthase (eNOS) heterozygous knockout (^+/-) mice, a clinically relevant model of endothelial dysfunction, to examine the role of endothelial nitric oxide (NO) in vascular Aβ accumulation. eNOS^+/- mice had significantly higher vascular levels of Aβ40 (P < 0.05). Aβ42 was not detected. There was no difference in Aβ in brain tissue. Amyloid precursor protein and β-site APP cleavage enzyme 1 protein levels were unaltered, while levels of the α-secretase enzyme, a disintegrin and metalloproteinase 10, were significantly lower in eNOS ^+ /- microvascular tissue (P < 0.05). Insulin degrading enzyme and low-density lipoprotein receptor-related protein 1 were significantly increased in eNOS^+/- microvascular tissue, most likely an adaptive response to locally higher Aβ concentrations. Lastly, catalase and CuZn superoxide dismutase were significantly elevated in eNOS^+/- microvascular tissue (P < 0.05). These data demonstrate decreased availability of endothelial NO leads to increased cerebrovascular concentration of Aβ along with compensatory mechanisms to protect the vasculature.

Atherosclerosis is exacerbated by chitinase-3-like-1 in amyloid precursor protein transgenic mice

Although the important role of amyloid precursor protein (APP) in vascular diseases associated with Alzheimer's disease (AD) has been demonstrated, the underlying molecular mechanisms and physiological consequences are unclear. We aimed to evaluate vascular inflammation and atherosclerosis in Swedish mutant of human APP transgenic (APPsw-Tg) and ApoE^-/-/APPsw-Tg mice. We also aimed to explore the mechanisms underlying any changes observed in these mice compared with non-Tg controls. Methods: The transgenic and non-Tg mouse strains were subjected to partial ligation of the left carotid artery to induce atherosclerotic changes, which were measured using histological approaches, immunohistochemistry, quantitative polymerase chain reaction, and gene expression microarrays. Results: Our results showed increased vascular inflammation, arterial wall thickness, and atherosclerosis in APPsw-Tg and ApoE^-/-/APPsw-Tg mice. We further found that the expression of chitinase-3-like-1 (Chi3l1) is increased in the APPsw-Tg mouse artery and Chi3l1 mediates endothelial cell (EC) inflammation and vascular smooth muscle cell (VSMC) activation, which in turn exacerbates atherosclerosis. In addition, using two publicly available microarray datasets from the dorsolateral prefrontal cortex of people with AD and unaffected controls as well as inflamed human umbilical vein endothelial cells, we found that Chi3l1 and associated inflammatory gene were significantly associated with AD, evaluated by co-expression network analysis and functional annotation. Knockdown of Chi3l1 in the arterial endothelium in vivo suppressed the development of atherosclerosis. We also show that microRNA 342-3p (miR-342-3p) inhibits EC inflammation and VSMC activation through directly targeting Chi3l1, and that APPsw increased Chi3l1 expression by reducing miR-342-3p expression in the arterial endothelium, promoting atherosclerosis. Conclusion: Our findings suggest that targeting Chi3l1 might provide new diagnostic and therapeutic strategies for vascular diseases in patients with AD.

APP Regulates Microglial Phenotype in a Mouse Model of Alzheimer's Disease

Prior work suggests that amyloid precursor protein (APP) can function as a proinflammatory receptor on immune cells, such as monocytes and microglia. Therefore, we hypothesized that APP serves this function in microglia during Alzheimer's disease. Although fibrillar amyloid β (Aβ)-stimulated cytokine secretion from both wild-type and APP knock-out (mAPP(-/-)) microglial cultures, oligomeric Aβ was unable to stimulate increased secretion from mAPP(-/-) cells. This was consistent with an ability of oligomeric Aβ to bind APP. Similarly, intracerebroventricular infusions of oligomeric Aβ produced less microgliosis in mAPP(-/-) mice compared with wild-type mice. The mAPP(-/-) mice crossed to an APP/PS1 transgenic mouse line demonstrated reduced microgliosis and cytokine levels and improved memory compared with wild-type mice despite robust fibrillar Aβ plaque deposition. These data define a novel function for microglial APP in regulating their ability to acquire a proinflammatory phenotype during disease.

SIGNIFICANCE STATEMENT

A hallmark of Alzheimer's disease (AD) brains is the accumulation of amyloid β (Aβ) peptide within plaques robustly invested with reactive microglia. This supports the notion that Aβ stimulation of microglial activation is one source of brain inflammatory changes during disease. Aβ is a cleavage product of the ubiquitously expressed amyloid precursor protein (APP) and is able to self-associate into a wide variety of differently sized and structurally distinct multimers. In this study, we demonstrate both in vitro and in vivo that nonfibrillar, oligomeric forms of Aβ are able to interact with the parent APP protein to stimulate microglial activation. This provides a mechanism by which metabolism of APP results in possible autocrine or paracrine Aβ production to drive the microgliosis associated with AD brains.

In-Depth Proteomics Identifies a Role for Autophagy in Controlling Reactive Oxygen Species Mediated Endothelial Permeability

Endothelial cells (ECs) form the inner layer of blood vessels and physically separate the blood from the surrounding tissue. To support tissues with nutrients and oxygen, the endothelial monolayer is semipermeable. When EC permeability is altered, blood vessels are not functional, and this is associated with disease. A comprehensive knowledge of the mechanisms regulating EC permeability is key in developing strategies to target this mechanism in pathologies. Here we have used an in vitro model of human umbilical vein endothelial cells mimicking the formation of a physiologically permeable vessel and performed time-resolved in-depth molecular profiling using stable isotope labeling by amino acids in cell culture mass spectrometry (MS)-proteomics. Autophagy is induced when ECs are assembled into a physiologically permeable monolayer. By using siRNA and drug treatment to block autophagy in combination with functional assays and MS proteomics, we show that ECs require autophagy flux to maintain intracellular reactive oxygen species levels, and this is required to maintain the physiological permeability of the cells.

Reduction in inflammation and the expression of amyloid precursor protein and other proteins related to Alzheimer's disease following gastric bypass surgery

OBJECTIVE

Obesity and type 2 diabetes are associated with an increase in the incidence and prevalence of Alzheimer's disease (AD) and an impaired cognitive function. Because peripheral blood mononuclear cells (MNC) express amyloid precursor protein (APP), the precursor of β-amyloid, which forms the pathognomonic plaques in the brain, we hypothesized that APP expression diminishes after the marked caloric restriction and weight loss associated with Roux-en-Y gastric bypass (RYGB) surgery.

RESEARCH DESIGN AND METHODS

Fifteen type 2 diabetic patients with morbid obesity (body mass index, 52.1 ± 13 kg/m(2)) underwent RYGB, and the expression of inflammatory and AD-related genes was examined before and after 6 months in plasma and in MNC.

RESULTS

Body mass index fell to 40.4 ± 11.1 kg/m(2) at 6 months after RYGB. There was a significant fall in plasma concentrations of glucose and insulin and in homeostasis model of assessment for insulin resistance. The expression of APP mRNA fell by 31 ± 9%, and that of protein fell by 36 ± 14%. In addition, there was a reduction in the expression of other AD-related genes including presinilin-2, ADAM-9, GSK-3β, PICALM, SORL-1, and clusterin (P < 0.05 for all). Additionally, the expression of c-Fos, a subunit of the proinflammatory transcription factor AP-1, was also suppressed after RYGB. These changes occurred in parallel with reductions in other proinflammatory mediators including C-reactive protein and monocyte chemoattractant protein-1.

CONCLUSIONS

Thus, the reversal of the proinflammatory state of obesity is associated with a concomitant reduction in the expression of APP and other AD-related genes in MNC. We conclude that obesity and caloric intake modulate the expression of APP in MNC. If indeed, this effect also occurs in the brain, this may have implications for the pathogenesis and the treatment of AD. It is relevant that cognitive function has been shown to improve with weight loss following bariatric surgery.

Increased EID1 nuclear translocation impairs synaptic plasticity and memory function associated with pathogenesis of Alzheimer's disease

Though loss of function in CBP/p300, a family of CREB-binding proteins, has been causally associated with a variety of human neurological disorders, such as Rubinstein-Taybi syndrome, Huntington's disease and drug addiction, the role of EP300 interacting inhibitor of differentiation 1 (EID1), a CBP/p300 inhibitory protein, in modulating neurological functions remains completely unknown. Through the examination of EID1 expression and cellular distribution, we discovered that there is a significant increase of EID1 nuclear translocation in the cortical neurons of Alzheimer's disease (AD) patient brains compared to that of control brains. To study the potential effects of EID1 on neurological functions associated with learning and memory, we generated a transgenic mouse model with a neuron-specific expression of human EID1 gene in the brain. Overexpression of EID1 led to an increase in its nuclear localization in neurons mimicking that seen in human AD brains. The transgenic mice had a disrupted neurofilament organization and increase of astrogliosis in the cortex and hippocampus. Furthermore, we demonstrated that overexpression of EID1 reduced hippocampal long-term potentiation and impaired spatial learning and memory function in the transgenic mice. Our results indicated that the negative effects of extra nuclear EID1 in transgenic mouse brains are likely due to its inhibitory function on CBP/p300 mediated histone and p53 acetylation, thus affecting the expression of downstream genes involved in the maintenance of neuronal structure and function. Together, our data raise the possibility that alteration of EID1 expression, particularly the increase of EID1 nuclear localization that inhibits CBP/p300 activity in neuronal cells, may play an important role in AD pathogenesis.

Amyloid precursor protein expression modulates intestine immune phenotype

Amyloid precursor protein (APP) is widely expressed across many tissue and cell types. Proteolytic processing of the protein gives rise to a plethora of protein fragments with varied biological activities. Although a large amount of data has been generated describing the metabolism of the protein in neurons, its role in regulating the phenotype of other cells remains unclear. Based upon prior work demonstrating that APP regulates the activation phenotype of monocytic lineage cells, we hypothesized that APP can regulate macrophage activation phenotype in tissues other than brain. Ileums of the small intestines from C57BL6/J wild type and APP(-/-) mice were compared as a representative tissue normally associated with abundant macrophage infiltration. APP(-/-) intestines demonstrated diminished CD68 immunoreactivity compared to wild type mice. This correlated with significantly less cyclooxygenase-2 (cox-2), CD68, CD40, CD11c, and βIII-tubulin protein levels. Peritoneal macrophages from APP(-/-) mice demonstrated decreased in vitro migratory ability compared to wild type cells and diminished basal KC cytokine secretion. Whereas, APP(-/-) intestinal macrophages had an increase in basal KC cytokine secretion compared to wild type cells. Conversely, there was a significant decrease in multiple cytokine levels in APP(-/-) compared to wild type ileums. Finally, APP(-/-) mice demonstrated impaired absorption and increased motility compared to wild type mice. These data demonstrate the APP expression regulates immune cell secretions and phenotype and intestinal function. This data set describes a novel function for this protein or its metabolites that may be relevant not only for Alzheimer's disease but a range of immune-related disorders.

HIV-1 Tat-induced cerebrovascular toxicity is enhanced in mice with amyloid deposits

HIV-1-infected brains are characterized by elevated depositions of amyloid beta (Aβ); however, the interactions between Aβ and HIV-1 are poorly understood. In the present study, we administered specific HIV-1 protein Tat into the cerebral vasculature of 50-52-week-old double transgenic (B6C3-Tg) mice that express a chimeric mouse/human amyloid precursor protein (Mo/HuAPP695swe) and a mutant human presenilin 1 (PS1-dE9) and are characterized by increased Aβ depositions in the brain. Exposure to Tat increased permeability across cerebral capillaries, enhanced disruption of zonula occludens (ZO)-1 tight junction protein, and elevated brain expression of matrix metalloproteinase-9 (MMP-9) in B6C3-Tg mice as compared with age-matched littermate controls. These changes were associated with increased leukocyte attachment and their transcapillary migration. The majority of Tat-induced effects were attenuated by treatment with a specific Rho inhibitor, hydroxyfasudil. The results of animal experiments were reproduced in cultured brain endothelial cells exposed to Aβ and/or Tat. The present data indicate that increased brain levels of Aβ can enhance vascular toxicity and proinflammatory responses induced by HIV-1 protein Tat.

Insulin suppresses the expression of amyloid precursor protein, presenilins, and glycogen synthase kinase-3beta in peripheral blood mononuclear cells

OBJECTIVE

Our objective was to determine whether peripheral blood mononuclear cells express amyloid precursor protein (APP) and other mediators involved in the pathogenesis of Alzheimer's disease and whether their expression is suppressed by insulin.

RESEARCH DESIGN AND METHODS

Ten obese type 2 diabetic patients were infused with insulin (2 U/h with 100 ml 5% dextrose/h) for 4 h. Patients were also infused with 5% dextrose/h or normal physiological saline for 4 h, respectively, on two other days as controls. Blood samples were obtained at 0, 2, 4, and 6 h.

RESULTS

Insulin infusion significantly suppressed the expression of APP, presenilin-1, presenilin-2, and glycogen synthase kinase-3β in peripheral blood mononuclear cells. Dextrose and saline infusions did not alter these indices. Insulin infusion also caused significant parallel reductions in nuclear factor-κB binding activity and plasma concentrations of serum amyloid A and intercellular adhesion molecule-1.

CONCLUSIONS

A low dose infusion of insulin suppresses APP, presenilin-1, presenilin-2, and glycogen synthase kinase-3β, key proteins involved in the pathogenesis of Alzheimer's disease, in parallel with exerting its other antiinflammatory effects.

Lack of alpha-synuclein modulates microglial phenotype in vitro

Alpha (α)-synuclein neuronal effects are continually being defined although its role in regulating glial phenotypes remains unclear. An ability to regulate microglial activation was investigated using primary cultures from wild type and α-synuclein deficient mice (Snca-/-). Snca-/- microglia demonstrated increased secretion of the cytokine tumor necrosis factor-alpha (TNF-α), impaired phagocytic ability, elevated prostaglandin levels, and increased protein levels of key enzymes in lipid-mediated signaling events, cytosolic phospholipase (cPLA(2)), cyclooxygenase-2 (Cox-2) and phospholipase D2 (PLD2) when compared to wild type cells. Increased cytokine secretion and cPLA(2) and Cox-2 levels in Snca-/- microglia were partially attenuated by inhibiting PLD-dependent signaling with n-butanol treatment.

Attenuated atherogenesis in apolipoprotein E-deficient mice lacking amyloid precursor protein

OBJECTIVE

Recent evidence suggests that amyloid precursor protein (APP) is overexpressed in atherosclerosis-prone regions of mouse aorta. We therefore investigated in the present study whether APP has a role in the progression and composition of atherosclerotic plaques.

METHODS AND RESULTS

Apolipoprotein E-deficient (apoE(-/-)) mice were crossbred with animals lacking APP (APP(-/-)). After 16 weeks on a Western-type diet, apoE(-/-) and APP(-/-)/apoE(-/-) mice showed similar cholesterol levels. However, atherosclerotic plaque size was significantly reduced in the distal thoracic aorta (90% reduction) and abdominal aorta (75% reduction) of APP(-/-)/apoE(-/-) mice as compared to apoE(-/-). Plaques at the level of the aortic valves were not different in size, but showed a more stable phenotype in APP(-/-)/apoE(-/-) mice, as indicated by a reduced macrophage content, an increased amount of collagen and a thicker fibrous cap.

CONCLUSION

Our findings provide evidence that lack of APP attenuates atherogenesis and leads to plaque stability.

Tyr(682) in the intracellular domain of APP regulates amyloidogenic APP processing in vivo

BACKGROUND

The pathogenesis of Alzheimer's disease is attributed to misfolding of Amyloid-β (Aβ) peptides. Aβ is generated during amyloidogenic processing of Aβ-precursor protein (APP). Another characteristic of the AD brain is increased phosphorylation of APP amino acid Tyr(682). Tyr(682) is part of the Y(682)ENPTY(687) motif, a docking site for interaction with cytosolic proteins that regulate APP metabolism and signaling. For example, normal Aβ generation and secretion are dependent upon Tyr(682) in vitro. However, physiological functions of Tyr(682) are unknown.

METHODOLOGY/PRINCIPAL FINDINGS

To this end, we have generated an APP Y682G knock-in (KI) mouse to help dissect the role of APP Tyr(682) in vivo. We have analyzed proteolytic products from both the amyloidogenic and non-amyloidogenic processing of APP and measure a profound shift towards non-amyloidogenic processing in APP KI mice. In addition, we demonstrate the essential nature of amino acid Tyr(682) for the APP/Fe65 interaction in vivo.

CONCLUSIONS/SIGNIFICANCE

Together, these observations point to an essential role of APP intracellular domain for normal APP processing and function in vivo, and provide rationale for further studies into physiological functions associated with this important phosphorylation site.

Amyloid precursor protein mediates a tyrosine kinase-dependent activation response in endothelial cells

Amyloid precursor protein (APP) is a ubiquitously expressed type 1 integral membrane protein. It has the ability to bind numerous extracellular matrix components and propagate signaling responses via its cytoplasmic phospho-tyrosine, (682)YENPTY(687), binding motif. We recently demonstrated increased protein levels of APP, phosphorylated APP (Tyr682), and beta-amyloid (Abeta) in brain vasculature of atherosclerotic and Alzheimer's disease (AD) tissue colocalizing primarily within the endothelial layer. This study demonstrates similar APP changes in peripheral vasculature from human and mouse apoE(-/-) aorta, suggesting that APP-related changes are not restricted to brain vasculature. Therefore, primary mouse aortic endothelial cells and human umbilical vein endothelial cells were used as a model system to examine the function of APP in endothelial cells. APP multimerization with an anti-N-terminal APP antibody, 22C11, to simulate ligand binding stimulated an Src kinase family-dependent increase in protein phospho-tyrosine levels, APP phosphorylation, and Abeta secretion. Furthermore, APP multimerization stimulated increased protein levels of the proinflammatory proteins, cyclooxygenase-2 and vascular cell adhesion molecule-1 also in an Src kinase family-dependent manner. Endothelial APP was also involved in mediating monocytic cell adhesion. Collectively, these data demonstrate that endothelial APP regulates immune cell adhesion and stimulates a tyrosine kinase-dependent response driving acquisition of a reactive endothelial phenotype. These APP-mediated events may serve as therapeutic targets for intervention in progressive vascular changes common to cerebrovascular disease and AD.