Numerous studies demonstrate inflammatory proteins in the brain and microcirculation in Alzheimer's disease (AD) and implicate inflammation in disease pathogenesis. However, emerging literature suggests that neuroinflammation can also be neuroprotective. The chemokine RANTES has been implicated in neurodegenerative diseases including AD. The objectives of this study are to determine the expression of RANTES in AD microvessels, its regulation in endothelial cells and its effects on neuronal survival. Our data show elevated expression of RANTES in the cerebral microcirculation of AD patients. Treatment of neurons in vitro with RANTES results in an increase in cell survival and a neuroprotective effect against the toxicity of thrombin and sodium nitroprusside. Oxidative stress upregulates RANTES expression in rat brain endothelial cells. Developing strategies to augment neuroprotection and diminish inflammatory activation of multifunctional mediators such as RANTES holds promise for the development of novel neuroprotective therapeutics in AD.

Considerable evidence implicates hypoxia and vascular inflammation in Alzheimer's disease (AD). Thrombin, a multifunctional inflammatory mediator, is demonstrable in the brains of AD patients both in the vessel walls and senile plaques. Hypoxia-inducible factor 1α (HIF-1α), a key regulator of the cellular response to hypoxia, is also upregulated in the vasculature of human AD brains. The objective of this study is to investigate inflammatory protein expression in the cerebrovasculature of transgenic AD mice and to explore the role of thrombin as a mediator of cerebrovascular inflammation and oxidative stress in AD and in hypoxia-induced changes in brain endothelial cells. Immunofluorescent analysis of the cerebrovasculature in AD mice demonstrates significant (p < 0.01–0.001) increases in thrombin, HIF-1α, interleukin-6 (IL-6), monocyte chemoattractant protein-1 (MCP-1), matrix metalloproteinases (MMPs), and reactive oxygen species (ROS) compared to controls. Administration of the thrombin inhibitor dabigatran (100 mg/kg) to AD mice for 34 weeks significantly decreases expression of inflammatory proteins and ROS. Exposure of cultured brain endothelial cells to hypoxia for 6 h causes an upregulation of thrombin, HIF-1α, MCP-1, IL-6, and MMP2 and ROS. Treatment of endothelial cells with the dabigatran (1 nM) reduces ROS generation and inflammatory protein expression (p < 0.01–0.001). The data demonstrate that inhibition of thrombin in culture blocks the increase in inflammatory protein expression and ROS generation evoked by hypoxia. Also, administration of dabigatran to transgenic AD mice diminishes ROS levels in brain and reduces cerebrovascular expression of inflammatory proteins. Taken together, these results suggest that inhibiting thrombin generation could have therapeutic value in AD and other disorders where hypoxia, inflammation, and oxidative stress are involved.

No disease-modifying therapies are currently available for Alzheimer's disease (AD), a neurodegenerative disorder that affects more than 36 million people worldwide. Although cardiovascular risk factors such as hypertension and diabetes are increasingly implicated as contributing to the development of AD, the mechanisms whereby these factors influence pathological processes in the AD brain have not been defined. Here we propose, for the first time, vascular activation as a relevant mechanism in AD pathogenesis. We explore this hypothesis in two transgenic AD animal models: AD2576APPSwe (AD2576) and LaFerla 3xTg (3xTgAD) mice using the vascular activation inhibitor sunitinib. Our data show that in both AD animal models, the cerebrovasculature is activated and overexpresses amyloid beta, thrombin, tumor necrosis factor alpha, interleukin-1 beta, interleukin-6, and matrix metalloproteinase 9. Oral administration of sunitinib significantly reduces vascular expression of these proteins. Furthermore, sunitinib improves cognitive function, as assessed by several behavioral paradigms, in both AD animal models. Finally, oxidant injury of brain endothelial cells in culture, resulting in expression of inflammatory proteins, is mitigated by sunitinib. The current data, as well as published studies showing cerebrovascular activation in human AD, support further exploration of vascular-based mechanisms in AD pathogenesis. New thinking about AD pathogenesis and novel, effective treatments are urgently needed. Identification of "vascular activation" as a heretofore unexplored target could stimulate translational investigations in this newly defined area, leading to innovative therapeutic approaches for the treatment of this devastating disease.