Vascular phenotype of amyloid precursor protein-deficient mice

Association of angiogenesis-associated genes with atherosclerotic plaque progression, intraplaque hemorrhage, and immune infiltration

Mounting evidence suggests that intraplaque angiogenesis is associated with the progression of atherosclerotic plaques and the development of intraplaque hemorrhage. The specificity of intraplaque immune cell infiltration may be associated with abnormalities in the structure and function of the nascent capillaries. Here, we analyzed expression levels of angiogenesis-associated genes in early and advanced carotid atheromatous plaque tissues as well as in stable and intraplaque hemorrhage plaques. Expression profiles of advanced arterial plaques based on angiogenesis-associated genes were classified into subtypes by performing a consensus clustering analysis. The correlation between the immune microenvironment of plaques and expression of angiogenesis-associated genes was also explored using the single sample gene set enrichment analysis method and the CIBERSORT algorithm. We identified hub angiogenesis-associated genes showing similar expression patterns throughout plaque adverse progression, and constructed a prediction model using the random forest algorithm. Receiver operating curves were constructed to evaluate efficacy in identification of intraplaque hemorrhage in a plaque. Our results suggest that heterogeneity of angiogenesis-related genes may promote the malignant development of plaques and cause plaque rupture. In conclusion, we propose a model based on expression of angiogenesis-related genes to predict the risk of plaque rupture.

Spatiotemporal insights of APP function

The amyloid-β precursor protein (APP) is a ubiquitous protein with a strong genetic link to Alzheimer's disease. Although the protein was identified more than forty years ago, its physiological function is still unclear. In recent years, advances in technology have allowed researchers to tackle APP functions in greater depth. In this review, we discuss the latest research pertaining to APP functions from development to aging. We also address the different roles that APP could play in specific types of cells of the central and peripheral nervous system and in other organs of the body. We argue that, until we fully identify the functions of APP in space and time, we will be missing important pieces of the puzzle to solve its pathological implication in Alzheimer's disease and beyond.

Altered stress hormone levels affect in vivo vascular function in the hAPP23+/- overexpressing mouse model of Alzheimer's disease

Alzheimer's disease (AD) has long been considered a brain-specific dementia syndrome. However, in recent decades, the occurrence of cardiovascular (CV) disease in the progression of AD has been confirmed by increasing epidemiological evidence. In this study, we conducted an in-depth cardiovascular characterization of a humanized amyloid precursor protein (APP) overexpressing mouse model (hAPP23+/-), which overexpresses the Swedish mutation (KM670/671NL). At the age of 6 mo, hAPP23+/- mice had a lower survival, lower body weight, and increased corticosterone and VMA levels compared with C57BL/6 littermates. Systolic blood pressure was increased in hAPP23+/- animals compared with C57BL/6 littermates, but diastolic blood pressure was not statistically different. Pulse pressure remained unchanged but abdominal and carotid pulse-wave velocity (aPWV and cPWV) were increased in hAPP23+/- compared with C57BL/6 mice. Echocardiography showed no differences in systolic or diastolic cardiac function. Ex vivo evaluation of vascular function showed decreased adreno receptor dependent vasoconstriction of hAPP23+/- aortic segments, although the isobaric biomechanics of the aortic wall were similar to C57BL/6 aortic segments. In conclusion, hAPP23+/- mice exhibited high serum corticosterone levels, elevated systolic blood pressure, and increased arterial stiffness in vivo. However, ex vivo aortic stiffness of hAPP23+/- aortic segments was not changed and vascular reactivity to α1-adrenoceptor stimulation was attenuated. These findings highlight the need for more frequent assessment of circulating stress hormone levels and PWV measurements in daily clinical practice for people at risk of AD.NEW & NOTEWORTHY We showed that male amyloid precursor protein (APP) transgenic mice have higher circulating stress hormone levels. As a result, higher systolic blood pressure and pulse-wave velocity were measured in vivo in addition to a smaller α-adrenergic receptor-dependent contraction upon ex vivo stimulation with phenylephrine. Our findings highlight the need for more frequent assessment of circulating stress hormone levels and PWV measurements in daily clinical practice for people at risk of Alzheimer's disease.

New Insights Into Blood-Brain Barrier Maintenance: The Homeostatic Role of β-Amyloid Precursor Protein in Cerebral Vasculature

Cerebrovascular homeostasis is maintained by the blood-brain barrier (BBB), a highly selective structure that separates the peripheral blood circulation from the brain and protects the central nervous system (CNS). Dysregulation of BBB function is the precursor of several neurodegenerative diseases including Alzheimer’s disease (AD) and cerebral amyloid angiopathy (CAA), both related to β-amyloid (Aβ) accumulation and deposition. The origin of BBB dysfunction before and/or during CAA and AD onset is not known. Several studies raise the possibility that vascular dysfunction could be an early step in these diseases and could even precede significant Aβ deposition. Though accumulation of neuron-derived Aβ peptides is considered the primary influence driving AD and CAA pathogenesis, recent studies highlighted the importance of the physiological role of the β-amyloid precursor protein (APP) in endothelial cell homeostasis, suggesting a potential role of this protein in maintaining vascular stability. In this review, we will discuss the physiological function of APP and its cleavage products in the vascular endothelium. We further suggest how loss of APP homeostatic regulation in the brain vasculature could lead toward pathological outcomes in neurodegenerative disorders.