RESUMEN
In Alzheimer's disease (AD) more than 50% of the patients are affected by capillary cerebral amyloid-angiopathy (capCAA), which is characterized by localized hypoxia, neuro-inflammation and loss of blood-brain barrier (BBB) function. Moreover, AD patients with or without capCAA display increased vessel number, indicating a reactivation of the angiogenic program. The molecular mechanism(s) responsible for BBB dysfunction and angiogenesis in capCAA is still unclear, preventing a full understanding of disease pathophysiology. The Liver X receptor (LXR) family, consisting of LXRα and LXRß, was reported to inhibit angiogenesis and particularly LXRα was shown to secure BBB stability, suggesting a major role in vascular function. In this study, we unravel the regulatory mechanism exerted by LXRα to preserve BBB integrity in human brain endothelial cells (BECs) and investigate its role during pathological conditions. We report that LXRα ensures BECs identity via constitutive inhibition of the transcription factor SNAI2. Accordingly, deletion of brain endothelial LXRα is associated with impaired DLL4-NOTCH signalling, a critical signalling pathway involved in vessel sprouting. A similar response was observed when BECs were exposed to hypoxia, with concomitant LXRα decrease and SNAI2 increase. In support of our cell-based observations, we report a general increase in vascular SNAI2 in the occipital cortex of AD patients with and without capCAA. Importantly, SNAI2 strongly associated with vascular amyloid-beta deposition and angiopoietin-like 4, a marker for hypoxia. In hypoxic capCAA vessels, the expression of LXRα may decrease leading to an increased expression of SNAI2, and consequently BECs de-differentiation and sprouting. Our findings indicate that LXRα is essential for BECs identity, thereby securing BBB stability and preventing aberrant angiogenesis. These results uncover a novel molecular pathway essential for BBB identity and vascular homeostasis providing new insights on the vascular pathology affecting AD patients.
Asunto(s)
Enfermedad de Alzheimer , Angiopatía Amiloide Cerebral , Humanos , Enfermedad de Alzheimer/metabolismo , Péptidos beta-Amiloides/metabolismo , Barrera Hematoencefálica/metabolismo , Angiopatía Amiloide Cerebral/complicaciones , Angiopatía Amiloide Cerebral/metabolismo , Angiopatía Amiloide Cerebral/patología , Células Endoteliales/metabolismo , Hipoxia/metabolismo , Receptores X del Hígado/genética , Receptores X del Hígado/metabolismo , Factores de Transcripción de la Familia Snail/genética , Factores de Transcripción de la Familia Snail/metabolismoRESUMEN
Alzheimer's disease (AD) is the most common form of dementia affecting millions of people worldwide. While different immunotherapies are imminent, currently only disease-modifying medications are available and a cure is lacking. Over the past decade, immunological interfaces of the central nervous system (CNS) and their role in neurodegenerative diseases received increasing attention. Specifically, emerging evidence shows that subsets of circulating CD8+ T cells cross the brain barriers and associate with AD pathology. To gain more insight into how the adaptive immune system is involved in disease pathogenesis, we here provide a comprehensive overview of the contribution of T cells to AD pathology, incorporating changes at the brain barriers. In addition, we review studies that provide translation of these findings by targeting T cells to combat AD pathology and cognitive decline. Importantly, these data show that immunological changes in AD are not confined to the CNS and that AD-associated systemic immune changes appear to affect brain homeostasis.
Asunto(s)
Enfermedad de Alzheimer , Encéfalo , Linfocitos T CD8-positivos/patología , Humanos , Sistema Inmunológico/patologíaRESUMEN
The blood-brain barrier (BBB) is indispensable for the maintenance of brain homeostasis and proper neuronal functioning. Dysfunction of the BBB significantly contributes to the pathogenesis of neuroinflammatory and neurodegenerative diseases like stroke, multiple sclerosis (MS), and Alzheimer's disease (AD). The neuroinflammatory environment that characterizes these disorders propagates chronic impaired function of the BBB, processes that will be discussed in this review. Limiting dysfunction of the BBB may be an attractive target for treatment of neurological disorders. To date, no current treatments are directly targeting the function of the BBB. In this review, we will specifically discuss the potential protective role of nuclear liver X receptors (LXRs) as a promising therapeutic target to reverse or prevent BBB impairment in neurological diseases.
Asunto(s)
Barrera Hematoencefálica/inmunología , Receptores X del Hígado/metabolismo , Animales , Humanos , Enfermedades Neurodegenerativas/metabolismo , Neuroinmunomodulación/fisiología , Neuroprotección/fisiologíaRESUMEN
Alzheimer's disease (AD) is the most common form of dementia, affecting millions of people worldwide. One of the prominent causative factors of AD pathogenesis is cerebral vascular dysfunction, which results in diminished cerebral perfusion. Moreover, due to the loss of the protective function of the blood-brain barrier (BBB), impaired clearance of excess neurotoxic amyloid beta (Aß) occurs, causing vascular perturbation and diminished cognitive functioning. The relationship between the prevalence of AD and vascular risk factors is complex and not fully understood. In this review we illustrate the vascular risk factors, their effects on BBB function and their contributions to the onset of AD. Additionally, we discuss the underlying factors that may lead to altered neurovascular function and/or cerebral hypoperfusion in AD.